Publications

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Umbra is a new Sandia-developed modeling and simulation framework. The Umbra framework allows users to quickly build models and simulations for intelligent system development, analysis, experimentation, and control and supports tradeoff analyses of complex robotic systems, device, and component concepts. Umbra links together heterogeneous collections of modeling tools. The models in Umbra include 3D geometry and physics models of robots, devices and their environments. Model components can be built with varying levels of fidelity and readily switched to allow models built with low fidelity for conceptual analysis to be gradually converted to high fidelity models for later phase detailed analysis. Within control environments, the models can be readily replaced with actual control elements. This paper describes Umbra at a functional level and describes issues that Sandia uses Umbra to address.

The construction of inverse states in a finite field F{sub P{sub P{alpha}}} enables the organization of the mass scale by associating particle states with residue class designations. With the assumption of perfect flatness ({Omega}total = 1.0), this approach leads to the derivation of a cosmic seesaw congruence which unifies the concepts of space and mass. The law of quadratic reciprocity profoundly constrains the subgroup structure of the multiplicative group of units F{sub P{sub {alpha}}}* defined by the field. Four specific outcomes of this organization are (1) a reduction in the computational complexity of the mass state distribution by a factor of {approximately}10{sup 30}, (2) the extension of the genetic divisor concept to the classification of subgroup orders, (3) the derivation of a simple numerical test for any prospective mass number based on the order of the integer, and (4) the identification of direct biological analogies to taxonomy and regulatory networks characteristic of cellular metabolism, tumor suppression, immunology, and evolution. It is generally concluded that the organizing principle legislated by the alliance of quadratic reciprocity with the cosmic seesaw creates a universal optimized structure that functions in the regulation of a broad range of complex phenomena.

This report describes the use of PorSalsa, a parallel-processing, finite-element-based, unstructured-grid code for the simulation of subsurface nonisothermal two-phase, two component flow through heterogeneous porous materials. PorSalsa can also model the advective-dispersive transport of any number of species. General source term and transport coefficient implementation greatly expands possible applications. Spatially heterogeneous flow and transport data are accommodated via a flexible interface. Discretization methods include both Galerkin and control volume finite element methods, with various options for weighting of nonlinear coefficients. Time integration includes both first and second-order predictor/corrector methods with automatic time step selection. Parallel processing is accomplished by domain decomposition and message passing, using MPI, enabling seamless execution on single computers, networked clusters, and massively parallel computers.

Arithmetic conditions relating particle masses can be defined on the basis of (1) the supersymmetric conservation of congruence and (2) the observed characteristics of particle reactions and stabilities. Stated in the form of common divisors, these relations can be interpreted as expressions of genetic elements that represent specific particle characteristics. In order to illustrate this concept, it is shown that the pion triplet ({pi}{sup {+-}}, {pi}{sup 0}) can be associated with the existence of a greatest common divisor d{sub 0{+-}} in a way that can account for both the highly similar physical properties of these particles and the observed {pi}{sup {+-}}/{pi}{sup 0} mass splitting. These results support the conclusion that a corresponding statement holds generally for all particle multiplets. Classification of the respective physical states is achieved by assignment of the common divisors to residue classes in a finite field F{sub P{sub {alpha}}} and the existence of the multiplicative group of units F{sub P{sub {alpha}}} enables the corresponding mass parameters to be associated with a rich subgroup structure. The existence of inverse states in F{sub P{sub {alpha}}} allows relationships connecting particle mass values to be conveniently expressed in a form in which the genetic divisor structure is prominent. An example is given in which the masses of two neutral mesons (K{degree} {r_arrow} {pi}{degree}) are related to the properties of the electron (e), a charged lepton. Physically, since this relationship reflects the cascade decay K{degree} {r_arrow} {pi}{degree} + {pi}{degree}/{pi}{degree} {r_arrow} e{sup +} + e{sup {minus}}, in which a neutral kaon is converted into four charged leptons, it enables the genetic divisor concept, through the intrinsic algebraic structure of the field, to provide a theoretical basis for the conservation of both electric charge and lepton number. It is further shown that the fundamental source of supersymmetry can be expressed in terms of hierarchical relationships between odd and even order subgroups of F{sub P{sub {alpha}}}, an outcome that automatically reflects itself in the phenomenon of fermion/boson pairing of individual particle systems. Accordingly, supersymmetry is best represented as a group rather than a particle property. The status of the Higgs subgroup of order 4 is singular; it is isolated from the hierarchical pattern and communicates globally to the mass scale through the seesaw congruence by (1) fusing the concepts of mass and space and (2) specifying the generators of the physical masses.

The stress of scandium dideuteride, ScD{sub 2}, thin films is investigated during each stage of vacuum processing including metal deposition via evaporation, reaction and cooldown. ScD{sub 2} films with thin Cr underlayers are fabricated on three different substrate materials: molybdenum-alumina cermet, single crystal sapphire and quartz. In all experiments, the evaporated Cr and Sc metal is relatively stress-free. However, reaction of scandium metal with deuterium at elevated temperature to form a stoichiometric dideuteride phase leads to a large compressive in-plane film stress. Compression during hydriding results from an increased atomic density compared with the as-deposited metal film. After reaction with deuterium, samples are cooled to ambient temperature, and a tensile stress develops due to mismatched coefficients of thermal expansion (CTE) of the substrate-film couple. The residual film stress and the propensity for films to crack during cooldown depends principally on the substrate material when using identical process parameters. Films deposited onto quartz substrates show evidence of stress relief during cooldown due to a large CTE misfit; this is correlated with crack nucleation and propagation within films. All ScD{sub 2} layers remain in a state of tension when cooled to 30 C. An in-situ, laser-based, wafer curvature sensor is designed and implemented for studies of ScD{sub 2} film stress during processing. This instrument uses a two-dimensional array of laser beams to noninvasively monitor stress during sample rotation and with samples stationary. Film stress is monitored by scattering light off the backside of substrates, i.e., side opposite of the deposition flux.

An experiment to measure surface pressure data on a series of three stainless steel simulated parachute ribbons was conducted. During the first phase of the test, unsteady pressure measurements were made on the windward and leeward sides of the ribbons to determine the statistical properties of the surface pressures. Particle Image Velocimetry (PIV) measurements were simultaneously made to establish the velocity field in the wake of the ribbons and its correlation with the pressure measurements. In the second phase of the test, steady-state pressure measurements were made to establish the pressure distributions. In the third phase, the stainless steel ribbons were replaced with nylon ribbons and PIV measurements were made in the wake. A detailed error analysis indicates that the accuracy of the pressure measurements was very good. However, an anomaly in the flow field caused the wake behind the stainless steel ribbons to establish itself in a stable manner on one side of the model. This same stability was not present for the nylon ribbon model although an average of the wake velocity data indicated an apparent 2{degree} upwash in the wind tunnel flow field. Since flow angularity upstream of the model was not measured, the use of the data for code validation is not recommended without a second experiment to establish that upstream boundary condition.

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In support of two major SNL programs, the Long-term Inflow and Structural Test (LIST) program and the Blade Manufacturing Initiative (BMI), three Micon 65/13M wind turbines have been erected at the USDA Agriculture Research Service (ARS) center in Bushland, Texas. The inflow and structural response of these turbines are being monitored with an array of 60 instruments: 34 to characterize the inflow, 19 to characterize structural response and 7 to characterize the time-varying state of the turbine. The primary characterization of the inflow into the LIST turbine relies upon an array of five sonic anemometers. Primary characterization of the structural response of the turbine uses several sets of strain gauges to measure bending loads on the blades and the tower and two accelerometers to measure the motion of the nacelle. Data are sampled at a rate of 30 Hz using a newly developed data acquisition system. The system features a time-synchronized continuous data stream and telemetered data from the turbine rotor. This paper documents the instruments and infrastructure that have been developed to monitor these turbines and their inflow.

Numerical methods may require derivatives of functions whose values are known only on irregularly spaced calculation points. This document presents and quantifies the performance of Moving Least-Squares (MLS), a method of derivative evaluation on irregularly spaced points that has a number of inherent advantages. The user selects both the spatial dimension of the problem and order of the highest conserved moment. The accuracy of calculations is maintained on highly irregularly spaced points. Not required are creation of additional calculation points or interpolation of the calculation points onto a regular grid. Implementation of the method requires the use of only a relatively small number of calculation points. The method is fast, robust and provides smooth results even as the order of the derivative increases.

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Meso-scale manufacturing processes are bridging the gap between silicon-based MEMS processes and conventional miniature machining. These processes can fabricate two and three-dimensional parts having micron size features in traditional materials such as stainless steels, rare earth magnets, ceramics, and glass. Meso-scale processes that are currently available include, focused ion beam sputtering, micro-milling, micro-turning, excimer laser ablation, femtosecond laser ablation, and micro electro discharge machining. These meso-scale processes employ subtractive machining technologies (i.e., material removal), unlike LIGA, which is an additive meso-scale process. Meso-scale processes have different material capabilities and machining performance specifications. Machining performance specifications of interest include minimum feature size, feature tolerance, feature location accuracy, surface finish, and material removal rate. Sandia National Laboratories is developing meso-scale mechanical components and actuators which require meso-scale parts fabricated in a variety of materials. Subtractive meso-scale manufacturing processes expand the functionality of meso-scale components and complement silicon based MEMS and LIGA technologies.

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This technical report presents the initial proposal and renewable proposals for an LDRD project whose intended goal was to enable applications to take full advantage of the hardware available on Sandia's current and future massively parallel supercomputers by analyzing various ways of combining distributed-memory and shared-memory programming models. Despite Sandia's enormous success with distributed-memory parallel machines and the message-passing programming model, clusters of shared-memory processors appeared to be the massively parallel architecture of the future at the time this project was proposed. They had hoped to analyze various hybrid programming models for their effectiveness and characterize the types of application to which each model was well-suited. The report presents the initial research proposal and subsequent continuation proposals that highlight the proposed work and summarize the accomplishments.

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This paper studies the implementation of polar format, synthetic aperture radar image formation in modern Field Programmable Gate Arrays (FPGA's). The polar format algorithm is described in rough terms and each of the processing steps is mapped to FPGA logic. This FPGA logic is analyzed with respect to throughput and circuit size for compatibility with airborne image formation.

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New algorithms are proposed for the modification of a mixed hexahedra-tetrahedra element mesh to maintain compatibility by the insertion of pyramid elements. Several methods for generation of the pyramids are presented involving local tetrahedral transformations and/or node insertion near the hex/tet interface. Local smoothing and topological operations improve the quality of the transition region. Results show superior performance of the resulting elements in a commercial finite-element code over non-conforming interface conditions. © 2001 Elsevier Science B.V. All rights reserved.

The progress in the fabrication of high voltage GaN and AlGaN rectifiers, GaN/AlGaN HBT and GaN MOSFET is reviewed. Improvements in epitaxial layer quality are studied. The advances in fabrication techniques that led to the improvement of device performance are discussed.

Heavy ion beam transport through the containment chamber plays a crucial role in all heavy ion fusion (HIF) scenarios. Here, several parameters are used to characterize the operating space for HIF beams; transport modes are assessed in relation to evolving target/accelerator requirements; results of recent relevant experiments and simulations of HIF transport are summarized; and relevant instabilities are reviewed. All transport options still exist, including (1) vacuum ballistic transport, (2) neutralized ballistic transport, and (3) channel-like transport. Presently, the European HIF program favors vacuum ballistic transport, while the US HIF program favors neutralized ballistic transport with channel-like transport as an alternate approach. Further transport research is needed to clearly guide selection of the most attractive, integrated HIF system. © 2001 Published by Elsevier Science B.V.

We have studied the reversible pressure induced structural transition (primitive cubic to polymeric monoclinic) of Na2CsC60 and the superconductivity in both phases. We have established that the single carbon-carbon bonded polymeric phase of Na2CsC60 is superconducting with an ambient pressure transition temperature about 3 K lower than that for the primitive cubic phase. We believe that an analogous lowering of the transition temperature in the corresponding phase of Na2RbC60 either leads to a very low transition temperature or to a total absence of superconductivity. © 2001 Elsevier Science B.V.

It is shown that the combination of pulse-front slant, k-vector tilt, and crystal birefringence often permits exact matching of both phase and group velocities for three-wave mixing in birefringent crystals. This exact match makes possible more-efficient mixing of short light pulses, and it permits efficient mixing of chirped or broadband light. I analyze this process and present examples. © 2001 Optical Society of America.

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Real-time measurements of stress evolution during the deposition of Volmer-Weber thin films reveal a complex interplay between mechanisms for stress generation and stress relaxation. We observed a generic stress evolution from compressive to tensile, then back to compressive stress as the film thickened, in amorphous and polycrystalline Ge and Si, as well as in polycrystalline Ag, Al, and Ti. Direct measurements of stress relaxation during growth interrupts demonstrate that the generic behavior occurs even in the absence of stress relaxation. When relaxation did occur, the mechanism depended sensitively on whether the film was continuous or discontinuous, on the process conditions, and on the film/substrate interfacial strength. For Ag films, interfacial shear dominated the early relaxation behavior, whereas this mechanism was negligible in Al films due to the much stronger bonding at the Al/SiO2 interface. For amorphous Ge, selective relaxation of tensile stress was observed only at elevated temperatures, consistent with surface-diffusion-based mechanisms. In all the films studied here, stress relaxation was suppressed after the films became continuous. © 2001 American Institute of Physics.

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Ab initio barriers to concerted downward transport of Cu atoms range from 0.66 to 0.85 eV, when kinks on adjacent Cu(1 1 1) terraces are close. The lowest of these permits mound decay to proceed much faster, at 300-340 K, than when terraces are farther apart, and decay is limited by formation of Cu adatoms and their passage over an island-edge "Schwoebel barrier." © 2001 Published by Elsevier Science B.V.

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This paper documents work performed to convert scanned range data to CAD solid model representation. The work successfully developed surface fitting algorithms for quadric surfaces (e.g. plane, cone, cylinder, and sphere), and a segmentation algorithm based entirely on surface type, rather than on a differential metric like Gaussian curvature. Extraction of all CAD-required parameters for quadric surface representation was completed. Approximate face boundaries derived from the original point cloud were constructed. Work to extrapolate surfaces, compute exact edges and solid connectivity was begun, but left incomplete due to funding reductions. The surface fitting algorithms are robust in the face of noise and degenerate surface forms.

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As part of a project with SEMATECH, detailed chemical reaction mechanisms have been developed that describe the gas-phase and surface chemistry occurring during the fluorocarbon plasma etching of silicon dioxide and related materials. The fluorocarbons examined are C{sub 2}F{sub 6}, CHF{sub 3} and C{sub 4}F{sub 8}, while the materials studied are silicon dioxide, silicon, photoresist, and silica-based low-k dielectrics. These systems were examined at different levels, ranging from in-depth treatment of C{sub 2}F{sub 6} plasma etch of oxide, to a fairly cursory examination of C{sub 4}F{sub 8} etch of the low-k dielectric. Simulations using these reaction mechanisms and AURORA, a zero-dimensional model, compare favorably with etch rates measured in three different experimental reactors, plus extensive diagnostic absolute density measurements of electron and negative ions, relative density measurements of CF, CF{sub 2}, SiF and SiF{sub 2} radicals, ion current densities, and mass spectrometric measurements of relative ion densities.

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As computers become faster, have more memory, and use multiple parallel processors, large, complex codes that more accurately simulate physical phenomena have emerged to utilize this capability. Most problems can benefit from this approach and many require it. But not all! There are problems for which simpler methods on more modest computers still work. The trick is to identify those problems, write the codes, and make their implementation sufficiently simple that they can be used conveniently by those who could profit from them. A Simple Plasma Code has been written with this philosophy in mind. It retains just enough physics to allow realistic simulations to be formulated and run quickly, even on a personal computer. This paper describes the physical model, its numerical implementation, and presents a sample simulation.

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Window and free surface interfaces perturb the flow in compression wave experiments. The velocity of these interfaces is routinely measured in shock-compression experiments using interferometry (i.e., VISAR). Interface perturbations often must be accounted for before meaningful material property results can be obtained. For shockless experiments when stress is a single valued function of strain, the governing equations of motion are hyperbolic and can be numerically integrated forward or backward in either time or space with assured stability. Using the VISAR results as ''initial conditions'' the flow fields are integrated backward in space to the interior of the specimen where the VISAR interface has not perturbed the flow at earlier times and results can be interpreted as if the interface had not been present. This provides a rather exact correction for free surface perturbations. The method can also be applied to window interfaces by selecting the appropriate initial conditions. Applications include interpreting Z-accelerator ramp wave experiments. The method applies to multiple layers and multiple reverberations. For an elastic-plastic material model the flow is dissipative and the governing equations are parabolic. When the parabolic terms are small, the equations also can be successfully integrated backward in space. This is verified by using a traditional elastic-plastic wave propagation code with a backward-derived stress history as the boundary condition for a forward calculation. Calculated free surface histories match the starting VISAR record verifying that the backward method produced an accurate solution to the governing equations. With our cooperation, workers at Los Alamos have successfully applied the Sandia-developed backward technique for the time-dependent quasielastic material model and are analyzing stress histories at a spall plane using the VISAR free surface velocity measurement from a ''pullback'' experiment.

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Superresolution concepts offer the potential of resolution beyond the classical limit. This great promise has not generally been realized. In this study we investigate the potential application of superresolution concepts to synthetic aperture radar. The analytical basis for superresolution theory is discussed. The application of the concept to synthetic aperture radar is investigated as an operator inversion problem. Generally, the operator inversion problem is ill posed. A criterion for judging superresolution processing of an image is presented.

This report is a supplement to ''The Unique Signal Concept for Detonation Safety in Nuclear Weapons,'' SAND91-1269, which provides a prerequisite fundamental background on the unique signal (UQS) concept. The UQS is one of the key constituents of Enhanced Nuclear Detonation Safety (ENDS), as outlined in Section 1 of that report. There have been many documents written over the past quarter of a century describing various aspects of the UQS, but none of these emphasized the mathematical approaches that help explain why the UQS is effective in resisting inadvertent pre-arming, even in abnormal environments and how UQS implementations can be quantitatively assessed. The intent of this report is to describe various pertinent mathematical methodologies (many of which have not been previously reported) without duplicating, any more than necessary, background information available in other reports. Mathematical UQS analysis is needed because of quantitative requirements associated with ENDS, and because limited comparisons of various implementation approaches can be quantified under mathematical modeling assumptions. Some of the mathematics-based results shown in this report are presented to explain: (1) The reasons that the UQS methodology can provide greater protection against accident environments than could combinational techniques (Sections 2.1 through 2.4); (2) The reason that the probability of inadvertently duplicating a UQS comprising n bivalued events cannot be estimated as low as (1/2) inches (Section 2.4); (3) The value of, and the Sandia National Laboratories policy on independent sequential communication of UQS events (Section 3.4); and (4) The care that must be exercised if any signal processing is necessary (Section 4). There are also numerous examples (e.g., in Appendices A and B) of ill-advised deviations from UQS methodology that can seriously degrade safety. These examples help demonstrate that the UQS methodology should not be compromised.

Dual control volume molecular dynamics was employed to study the flux of methane through channels of thin silicalite membranes. The DCANIS force field was analyzed to describe the adsorption isotherms of methane and ethane in silicalite. The alkane parameters and silicalite parameters were determined by fiiting the DCANIS force field to single-component vapor-liquid coexistence curves (VLCC) and adsorption isotherms respectively. The adsorption layers on the surfaces of thin silicalite membranes showed a sifnificant resistance to the flux of methane. The results depicted the insensitivity of permeance to both the average pressure and pressure drop.

For highly cross-linked polymer networks bonded to a solid surface, the effect of interfacial bond density and system size on interfacial fracture is studied using molecular dynamics simulations. Results for tensile and shear mode simulations are given. The correspondence between the stress-strain curve and the sequence of molecular deformations is obtained. The failure strain for a fully bonded surface is equal to the strain necessary to make taut the average of the minimal paths through the network from a bonded site on the bottom solid surface to a bonded site on the top surface. At fractional interfacial bond densities, cavities form above the nonbonded surface, yielding an inhomogeneous strain profile and a smaller failure strain. The failure strain and stress are linearly proportional to the number of bonds at the interface except in the tensile mode when number of bonds is so few that van der Waals interactions dominate. The failure mode is successfully constructed to be interracial by limiting the interfacial bond density to be less than the bulk bond density.

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Advanced thin-film processing and packaging technologies are employed in the fabrication of new planar thin-film multijunction thermal converters (MJTCs). The processing, packaging, and design features build on experience gained from prior NIST demonstrations of thin-film converters and are optimized for improved sensitivity, bandwidth, manufacturability, and reliability.

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This case study describes a success in technology transfer out of Sandia National Laboratories that resulted in commercialization supporting both the laboratories' national security mission and economic development. This case exemplifies how the process of technology innovation stretches from national legislation to laboratory management to entrepreneurs, and then out into the community where the technology must be developed and commercialized if innovation is to occur. Two things emerged from the research for this case study that have implications for technology transfer and commercialization from other national laboratories and may also be relevant to technology commercialization out of other federal laboratories and universities. The first is the very clear theme that partnerships were critical to the ultimate successful commercialization of the technology--partnerships between public and private research groups as well as between business development groups. The second involves identifiable factors that played a role in moving the process forward to successful commercialization. All of the factors, with two significant exceptions, focused on technology and business development directly related to creating research and business partnerships. The two exceptions, a technology with significant market applications, and entrepreneurs willing and able to take the risks and accomplish the hard work of technology innovation, were initiating requirements for the process.

The Sandia Photovoltaic Program conducted research in crystalline-silicon solar cells between 1986 and 2000 for the U.S. Department of Energy. This period saw rapid improvements in the fundamental understanding of c-Si materials and devices, improvements in c-Si PV manufacturing and control, and a rapid expansion of c-Si PV manufacturing capacity. Crystalline-silicon technology has provided the basis for PV to emerge as a serious option for global energy needs. The c-Si cell research at Sandia examined c-Si materials, devices, processing, and process integration. This report summarizes research conducted in this program over the past 15 years.

Despite the end of the Cold War, the US and Russia continue to maintain their ICBMs and many SLBMs in a highly alerted state--they are technically prepared to launch the missiles within minutes of a command decision to do so. Some analysts argue that, particularly in light of the distressed condition of the Russian military, these high alert conditions are tantamount to standing on the edge of a nuclear cliff from which we should now step back. They have proposed various bilateral ''de-alerting'' measures, to be taken prior to and outside the context of the formal strategic arms reduction treaty (START) process. This paper identifies several criteria for a stable de-alerting regime, but fails to find de-alerting measures that convincingly satisfy the criteria. However, some de-alerting measures have promise as de-activation measures for systems due for elimination under the START II and prospective START III treaties. Moreover, once these systems are deactivated, a considerable part of the perceived need to keep nuclear forces on high alert as a survivability hedge will be reduced. At the same time, the U.S. and Russia could consider building on their earlier cooperative actions to reduce the risk of inadvertent nuclear war by enhancing their communications links and possibly joining in efforts to improve early warning systems.

The authors have developed novel metal-assisted texturing processes that have led to optically favorable surfaces for solar cells. Large area ({approximately} 200 cm{sup 2}) uniform texturing has been achieved. The physical dimensions of the chamber limited texturing of even larger wafers. Surface contamination and residual RIE-induced damage were removed by incorporation of a complete RCA clean process followed by wet-chemical etching treatments. RIE-textured solar cells with optimized profiles providing performance comparable to the random, wet-chemically etched cells have been demonstrated. A majority of the texture profiles exhibit an enhanced IQE response in the near IR region.using scanning electron microscope measurements, they carried out a detailed analysis of the microstructure of random RIE-textured surfaces. The random microstructure represents a superposition of sub-{micro}m grating structures with a wide distribution of periods, depths, and profiles as determined by the SEM measurements. These structures were modeled using GSOLVER{trademark} software for periodic patterns. The enhanced IR response from random, RIE-textured surfaces is attributed to enhanced coupling of light into the transmitted diffraction orders. These obliquely propagating diffraction orders generate electron-hole pairs closer to the surface, thus, reducing bulk recombination losses relative to a non-scattering, planar surface with identical hemispherical reflection. The optimized texture and damage removal processes have been applied to large area (100--132 cm{sup 2}) multi-crystalline wafers. initial results have demonstrated improved performance relative to planar, control wafers. However, the texture and solar cell fabrication processes require further optimization in the RCA clean, DRE treatments, and emitter formation in order to fully realize the benefits of the low-reflection ({approximately}1-2%) textured surfaces.

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We have used selective AlGaAs oxidation, dry-etching, and high-gain semiconductor laser simulation to create new in-plane lasers with interconnecting passive waveguides for use in high-density photonic circuits and future integration of photonics with electronics. Selective oxidation and doping of semiconductor heterostructures have made vertical cavity surface emitting lasers (VCSELs) into the world's most efficient low-power lasers. We apply oxidation technology to improve edge-emitting lasers and photonic-crystal waveguides, making them suitable for monolithic integrated microsystems. Two types of lasers are investigated: (1) a ridge laser with resonant coupling to an output waveguide; (2) a selectively-oxidized laser with a low active volume and potentially sub-milliAmp threshold current. Emphasis is on development of high-performance lasers suited for monolithic integration with photonic circuit elements.

Ion implantation of O and Al were used to form nanometer-size precipitates of NiO or Al{sub 2}O{sub 3} in the near-surface of Ni. The yield strengths of the treated layers were determined by nanoindentation testing in conjunction with finite-element modeling. The strengths range up to {approximately}5 GPa, substantially above values for hard bearing steels. These results agree quantitatively with predictions of dispersion-hardening theory based on the precipitate microstructures observed by transmission electron microscopy. Such surface hardening by ion implantation may be beneficial for Ni components in micro-electromechanical systems.

An effort is underway at Sandia National Laboratories to develop a library of algorithms to search for potential interactions between surfaces represented by analytic and discretized topological entities. This effort is also developing algorithms to determine forces due to these interactions for transient dynamics applications. This document describes the Application Programming Interface (API) for the ACME (Algorithms for Contact in a Multiphysics Environment) library.

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The type of polymeric material used in the manufacturing of tubing determines its strength, elasticity, and durability. Tubing made of polymeric material is commonly used for analytical work because it is readily available, inexpensive and can be relatively inert. Polymeric tubing is used in many sampling applications for explosive compounds. A major concern is the uptake of the explosive compounds into or onto the tubing during sampling. Because of the reactive nature of explosives, it is important that as little of the detectable explosive as possible is lost by tubing uptake. It is also important that nothing leaches out of the tubing to interfere with the detection of explosives. High Performance Liquid Chromatography (HPLC) is commonly used for the analysis of trace levels of explosive compounds in the range of parts per billion (ppb) to parts per million (ppm). This study attempts to determine which types of polymers are most conducive to sampling applications where large volumes of dilute explosive solutions are collected through a length of tubing for analysis. This was determined by analyzing the amount of explosive lost from solution per cm{sup 2} of tubing in solution. It was determined that tubing made of polyethylene, teflon, polypropylene, or KYNAR{reg_sign} is recommended for dilute trinitrotoluene (TNT) solution analyses. Tubing made of polypropylene, PHARMED{reg_sign}, KYNAR{reg_sign}, or polyethylene is recommended for analyses involving dilute explosive solutions of RDX. Tubing made from polyurethane, TYGON{reg_sign}, nylon, vinyl, gum rubber, or reinforced PVC are not recommended because they leach contaminants into solution that may interfere with HPLC analysis of explosive peaks.

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The next major performance plateau for high-speed, long-haul networks is at 10 Gbps. Data visualization, high performance network storage, and Massively Parallel Processing (MPP) demand these (and higher) communication rates. MPP-to-MPP distributed processing applications and MPP-to-Network File Store applications already require single conversation communication rates in the range of 10 to 100 Gbps. MPP-to-Visualization Station applications can already utilize communication rates in the 1 to 10 Gbps range. This LDRD project examined some of the building blocks necessary for developing a 10 to 100 Gbps computer network architecture. These included technology areas such as, OS Bypass, Dense Wavelength Division Multiplexing (DWDM), IP switching and routing, Optical Amplifiers, Inverse Multiplexing of ATM, data encryption, and data compression; standards bodies activities in the ATM Forum and the Optical Internetworking Forum (OIF); and proof-of-principle laboratory prototypes. This work has not only advanced the body of knowledge in the aforementioned areas, but has generally facilitated the rapid maturation of high-speed networking and communication technology by: (1) participating in the development of pertinent standards, and (2) by promoting informal (and formal) collaboration with industrial developers of high speed communication equipment.

The NEWPEP thermochemical code is a computer program that has been developed to help predict the performance of a user generated propellant system. Sandia has used the program to model the use of different oxidizer/fuel combinations. The program has been adapted to fit Sandia's need by expanding the programs combustion species database and the ingredient list. This paper provides the user with a thorough set of operating instructions.

Several years ago Sandia National Laboratories developed a prototype interior robot [1] that could navigate autonomously inside a large complex building to aid and test interior intrusion detection systems. Recently the Department of Energy Office of Safeguards and Security has supported the development of a vehicle that will perform limited security functions autonomously in a structured exterior environment. The goal of the first phase of this project was to demonstrate the feasibility of an exterior robotic vehicle for security applications by using converted interior robot technology, if applicable. An existing teleoperational test bed vehicle with remote driving controls was modified and integrated with a newly developed command driving station and navigation system hardware and software to form the Robotic Security Vehicle (RSV) system. The RSV, also called the Sandia Mobile Autonomous Navigator (SANDMAN), has been successfully used to demonstrate that teleoperated security vehicles which can perform limited autonomous functions are viable and have the potential to decrease security manpower requirements and improve system capabilities.

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This report provides a brief summary of the characteristics of contemporary high-power microwave sources. The focus is on their physical and operational characteristics and regions of application rather than their theory of operation. Magnetrons, linear beam tubes, split-cavity oscillators, virtual cathode oscillators, gyrotrons, free-electron lasers, and orbitron microwave masers are described. Power supply requirements and engineering issues of the application of HPM devices are addressed.

In support of the Cassini Mission Final Safety Analysis Report (FSAR), Sandia National Laboratories (SNL) was requested by Lockheed Martin Corporation (LMC) to investigate for various scenarios, the distribution of aerosol and particulate mass in a stabilized buoyant plume created as a result of a fireball explosion. The information obtained from these calculations is to provide background information for the radiological consequence analysis of the FSAR. Specifically, the information is used to investigate the mass distribution within the ''cap and stem'' portions of the initial fireball plume, a modeling feature included in the SATRAP module in the LMC SPARRC code. The investigation includes variation of the plume energy and the application of several meteorological conditions for a total of seven sensitivity case studies. For each of the case studies, the calculations were performed for two configurations of particle mass in the plume (total mass and plutonium mass).

The DAKOTA (Design Analysis Kit for Optimization and Terascale Applications) toolkit provides a flexible and extensible interface between simulation codes and iterative analysis methods. DAKOTA contains algorithms for optimization with gradient and nongradient-based methods; uncertainty quantification with sampling, analytic reliability, and stochastic finite element methods; parameter estimation with nonlinear least squares methods; and sensitivity analysis with design of experiments and parameter study methods. These capabilities may be used on their own or as components within advanced strategies such as surrogate-based optimization, mixed integer nonlinear programming, or optimization under uncertainty. By employing object-oriented design to implement abstractions of the key components required for iterative systems analyses, the DAKOTA toolkit provides a flexible and extensible problem-solving environment for design and performance analysis of computational models on high performance computers. This report serves as a reference manual for the commands specification for the DAKOTA software, providing input overviews, option descriptions, and example specifications.

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Steady and oscillatory shear 3-D simulations of electro- and magnetorheology in uniaxial and biaxial fields are presented, and compared to the predictions of the chain model. These large scale simulations are three dimensional, and include the effect of Brownian motion. In the absence of thermal fluctuations, the expected shear thinning viscosity is observed in steady shear, and a striped phase is seen to rapidly form in a uniaxial field, with a shear slip zone in each sheet. However, as the influence of Brownian motion increases, the fluid stress decreases, especially at lower Mason numbers, and the striped phase eventually disappears, even when the fluid stress is still high. In a biaxial field, an opposite trend is seen, where Brownian motion decreases the stress most significantly at higher Mason numbers. To account for the uniaxial steady shear data we propose a microscopic chain model of the role played by thermal fluctuations on the rheology of ER and MR fluids that delineates the regimes where an applied field can impact the fluid viscosity, and gives an analytical prediction for the thermal effect. In oscillatory shear, a striped phase again appears in a uniaxial field, at strain amplitudes greater than ∼0.15, and the presence of a shear slip zone creates strong stress nonlinearities at low strain amplitudes. In a biaxial field, a shear slip zone is not created, and so the stress nonlinearities develop only at expected strain amplitudes. The nonlinear dynamics of these systems is shown to be in good agreement with the Kinetic Chain Model.

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In this study, twelve embedded atom method (EAM) function sets were tested for their ability to predict liquid/vapor surface tension. Testing was carried out in the isochoric-isothermal (NVT) ensemble with a Berendsen thermostat. It was shown that the use of charge gradient corrections in conjunction with appropriate EAM functions provide surface property predictions in excellent agreement with experiment for solid and liquid metals.

A method for decomposing a volume with a prescribed quadrilateral surface mesh, into a hexahedral-dominated mesh is proposed. With this method, known as Hex-Morphing (H-Morph), an initial tetrahedral mesh is provided. Tetrahedra are transformed and combined starting from the boundary and working towards the interior of the volume. The quadrilateral faces of the hexahedra are treated as internal surfaces, which can be recovered using constrained triangulation techniques. Implementation details of the edge and face recovery process are included. Examples and performance of the H-Morph algorithm are also presented.

Remarkable materials ordered at the nano scale emerge when a sol-gel solution becomes co-organized with a surfactant. At sufficiently high concentration, the surfactant forms crystalline or liquid-crystalline arrays of micelles in the presence of the sol-gel, and as gelation proceeds the arrays become locked into the gel. Recent experiments demonstrate that the degree of order in the resulting mesoporous ceramic phase can be enhanced and controlled by continuous dip coating in which the solution, initially dilute, evolves through the critical micelle concentration by steady-state evaporation. The long-range order and microstructural orientation in these films suggest that the propagation of a critical-micelle-concentration transition front, with large physico-chemical gradients, promotes oriented self assembly of surfactant aggregates. This "steep-gradient" view is supported by results from unsteady evaporation of aerosols of similar solutions, in which internally well-ordered but complex particles are formed.

Remarkable materials ordered at the nano scale emerge when a sol-gel solution becomes co-organized with a surfactant. At sufficiently high concentration, the surfactant forms crystalline or liquid-crystalline arrays of micelles in the presence of the sol-gel, and as gelation proceeds the arrays become locked into the gel. Recent experiments demonstrate that the degree of order in the resulting mesoporous ceramic phase can be enhanced and controlled by continuous dip coating in which the solution, initially dilute, evolves through the critical micelle concentration by steady-state evaporation. The long-range order and microstructural orientation in these films suggest that the propagation of a critical-micelle-concentration transition front, with large physico-chemical gradients, promotes oriented self assembly of surfactant aggregates. This "steep-gradient" view is supported by results from unsteady evaporation of aerosols of similar solutions, in which internally well-ordered but complex particles are formed.

We have demonstrated the dc and rf characteristics of a novel p-n-p GaAs/InGaAsN/GaAs double heterojunction bipolar transistor. This device has near ideal current-voltage (I-V) characteristics with a current gain greater than 45. The smaller bandgap energy of the InGaAsN base has led to a device turn-on voltage that is 0.27 V lower than in a comparable p-n-p AlGaAs/GaAs heterojunction bipolar transistor. This device has shown f T and f MAX values of 12 GHz. In addition, the aluminum-free emitter structure eliminates issues typically associated with AlGaAs.

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Contaminant release scenarios proposed for the Waste Isolation Pilot Plant (WIPP) repository suggest that the Culebra Dolomite member of the Rustler Formation could be an important radionuclide release path. This thin, vuggy, highly fractured unit is the most transmissive geologic unit overlying the WIPP. Many of the samples obtained from drill cores in the Culebra exhibit fractures that are lined with iron-oxyhydroxide-rich and clay-rich mineral coatings. The coatings are mineralogically distinct from the rock matrix, and may have sorptive characteristics that are different from a clay-poor dolomite matrix. Where locally abundant, such coatings could affect advective/diffusive exchange between matrix blocks and fractures and the accessible mineral surface area available for radionuclide adsorption. Clay minerals are present in the matrix and as fracture coatings in the samples from all the drill core locations examined in this study. Visual examination of rock sample surfaces in the H -19b7 core suggests that at least 7% of the total fracture surface area is coated with iron oxhydroxides or clays. In the samples from H-19b7, the amount of clay disseminated in the matrix varies from <1% to {approx}12 % by weight, and generally increases with stratigraphic height within the unit. In a suite of samples obtained from 12 other locations in the vicinity of the WIPP site, matrix samples from the Culebra contain 0.6--7% clay. These samples were taken from the more transmissive lower two-thirds of the unit (Culebra Units 2-4) which was considered to be the accessible portion of the unit in the WIPP Compliance Certification Application (CCA). Clay minerals also occur as clay-rich laminae and partings with the geometries of primary sedimentary structures and dissolution residues. Such partings are the loci of bedding plane fractures, and have the heaviest clay coatings found in the unit. Crosscutting fractures also commonly exhibit clay mineral coatings, but these are generally discontinuous and much thinner.

The restructuring of the U.S. power industry will surely lead to a greater dependence on computers and communications to allow appropriate information sharing for management and control of the power grid. This report describes the operating environment for system operations that control the bulk power system as it exists today including the role NERC plays in this process. Some high-level functional requirements for new approaches to control of the grid are listed followed by a description of the next research steps that are needed to identify specific information management functions.

Intelligent agents and multi-agent systems promise to take information management for real-time control of the power grid to a new level. This report presents our concept for intelligent agents to mediate and coordinate communications between Control Areas and Security Coordinators for real-time control of the power grid. An appendix describes the organizations and publications that deal with agent technologies.

Magnesium vanadates are potentially important catalytic materials for the conversion of alkanes to alkenes via oxidative dehydrogenation. However, little is known about the active sites at which the catalytic reactions take place. It may be possible to obtain a significant increase in the catalytic efficiency if the effects of certain material properties on the surface reactions could be quantified and optimized through the use of appropriate preparation techniques. Given that surface reactivity is often dependent upon surface structure and that the atomic level structure of the active sites in these catalysts is virtually unknown, we desire thin film samples consisting of a single magnesium vanadate phase and a well defined crystallographic orientation in order to reduce complexity and simplify the study of active sites. This report describes the use of reactive RF sputter deposition to fabricate very highly oriented, stoichiometric Mg{sub 3}(VO{sub 4}){sub 2} thin films, and subsequent studies of the reactivity of these films under reaction conditions typically found during oxidative dehydrogenation. We demonstrate that the synthesis methods employed do in fact result in stoichiometric films with the desired crystallographic orientation, and that the chemical behavior of the films closely approximates that of bulk, high surface area Mg{sub 3}(VO{sub 4}){sub 2} powders. We further use these films to demonstrate the effects of oxygen vacancies on chemical behavior, demonstrate that surface composition can vary significantly under reaction conditions, and obtain the first evidence for structure sensitivity in Mg{sub 3}(VO{sub 4}){sub 2} catalysts.

Consider a system of rigid bodies with multiple concurrent contacts. The multi-rigid-body contact problem is to predict the accelerations of the bodies and the normal friction loads acting at the contacts. This paper presents theoretical results for the multi-rigid-body contact problem under the assumptions that one or more contacts occur over locally planar, finite regions and that friction forces are consistent with the maximum work inequality. Existence and uniqueness results are presented for this problem under mild assumptions on the system inputs. In addition, the performance of two different time-stepping methods for integrating the dynamics are compared on two simple multi-body systems.

In this study, the erosion rates of four reconstituted sediments in both rectangular and circular sample tubes have been determined as a function of density and shear stress by means of a high shear stress sediment erosion flume at Sandia National Laboratories. This was done to determine if circular cores used in field sampling would provide the same results found using the existing technology of rectangular cores. Two samples were natural, cohesive sediments retrieved from different sites in the Boston Harbor identified as Open Cell and Mid Channel. The other two sediments were medium and coarse grain, non-cohesive quartz sediments. For each sediment type, erosion tests were performed with both rectangular and circular core tubes. For all cores, bulk density was determined as a function of depth and consolidation time. Sediments were eroded to determine erosion rates as a function of density and shear stress for both types of core tubes used. No measurable difference was found between the two core types.

Sandia National Laboratories has sponsored an LDRD (Laboratory Directed Research and Development) project to investigate and develop micro-chemical sensors for in-situ monitoring of subsurface contaminants. As part of this project, a literature search has been conducted to survey available technologies and identify the most promising methods for sensing and monitoring subsurface contaminants of interest. Specific sensor technologies are categorized into several broad groups, and these groups are then evaluated for use in subsurface, long-term applications. This report introduces the background and specific scope of the problem being addressed by this LDRD project, and it provides a summary of the advantages and disadvantages of each sensor technology identified from the literature search.

Atomistic simulations of the growth of helium bubbles in metals are performed. The metal is represented by embedded atom method potentials for palladium. The helium bubbles are treated via an expanding repulsive spherical potential within the metal lattice. The simulations predict bubble pressures that decrease monotonically with increasing helium to metal ratios. The swelling of the material associated with the bubble growth is also computed. It is found that the rate of swelling increases with increasing helium to metal ratio consistent with experimental observations on the swelling of metal tritides. Finally, the detailed defect structure due to the bubble growth was investigated. Dislocation networks are observed to form that connect the bubbles. Unlike early model assumptions, prismatic loops between the bubbles are not retained. These predictions are compared to available experimental evidence.

This suggested practices manual examines the requirements of the National Electrical Code (NEC) as they apply to photovoltaic (PV) power systems. The design requirements for the balance of systems components in a PV system are addressed, including conductor selection and sizing, overcurrent protection ratings and location, and disconnect ratings and location. PV array, battery, charge controller, and inverter sizing and selection are not covered, as these items are the responsibility of the system designer, and they in turn determine the items in this manual. Stand-alone, hybrid, and utility-interactive PV systems are all covered.

Current copper backplane technology has reached the technical limits of clock speed and width for systems requiring multiple boards. Currently, bus technology such as VME and PCI (types of buses) will face severe limitations are the bus speed approaches 100 MHz. At this speed, the physical length limit of an unterminated bus is barely three inches. Terminating the bus enables much higher clock rates but at drastically higher power cost. Sandia has developed high bandwidth parallel optical interconnects that can provide over 40 Gbps throughput between circuit boards in a system. Based on Sandia's unique VCSEL (Vertical Cavity Surface Emitting Laser) technology, these devices are compatible with CMOS (Complementary Metal Oxide Semiconductor) chips and have single channel bandwidth in excess of 20 GHz. In this project, we are researching the use of this interconnect scheme as the physical layer of a greater ATM (Asynchronous Transfer Mode) based backplane. There are several advantages to this technology including small board space, lower power and non-contact communication. This technology is also easily expandable to meet future bandwidth requirements in excess of 160 Gbps sometimes referred to as UTOPIA 6. ATM over optical backplane will enable automatic switching of wide high-speed circuits between boards in a system. In the first year we developed integrated VCSELs and receivers, identified fiber ribbon based interconnect scheme and a high level architecture. In the second year, we implemented the physical layer in the form of a PCI computer peripheral card. A description of future work including super computer networking deployment and protocol processing is included.

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Surface and groundwater resources do not recognize political boundaries. Where nature and boundary cross, tension over shared water resources can erupt. Such tension is exacerbated in regions where demand approaches or exceeds sustainable supplies of water. Establishing equitable management strategies can help prevent and resolve conflict over shared water resources. This paper describes a methodology for addressing transboundary water issues predicated on the integration of monitoring and modeling within a framework of cooperation. Cooperative monitoring begins with agreement by international scientists and/or policy makers on transboundary monitoring goals and strategies; it leads to the process of obtaining and sharing agreed-upon information among parties with the purpose of providing verifiable and secure data. Cooperative modeling is the process by which the parties jointly interpret the data, forecast future events and trends, and quantify cause and effect relationships. Together, cooperative monitoring and modeling allow for the development and assessment of alternative management and remediation strategies that could form the basis of regional watershed agreements or treaties. An example of how this multifaceted approach might be used to manage a shared water resource is presented for the Kura River basin in the Caucasus.

This report summarizes experimental and test results from a two year LDRD project entitled Real Time Error Correction Using Electromagnetic Bearing Spindles. This project was designed to explore various control schemes for levitating magnetic bearings with the goal of obtaining high precision location of the spindle and exceptionally high rotational speeds. As part of this work, several adaptive control schemes were devised, analyzed, and implemented on an experimental magnetic bearing system. Measured results, which indicated precision positional control of the spindle was possible, agreed reasonably well with simulations. Testing also indicated that the magnetic bearing systems were capable of very high rotational speeds but were still not immune to traditional structural dynamic limitations caused by spindle flexibility effects.

This report describes the results of a study on stationary energy storage technologies for a range of applications that were categorized according to storage duration (discharge time): long or short. The study was funded by the U.S. Department of Energy through the Energy Storage Systems Program. A wide variety of storage technologies were analyzed according to performance capabilities, cost projects, and readiness to serve these many applications, and the advantages and disadvantages of each are presented.

The structural dynamics modeling of engineering structures must accommodate the energy dissipation due to microslip in mechanical joints. Given the nature of current hardware and software environments, this will require the development of constitutive models for joints that both adequately reproduce the important physics and lend themselves to efficient computational processes. The exploration of the properties of mechanical joints--either through fine resolution finite element modeling or through experiment--is itself an area of research, but some qualitative behavior appears to be established. The work presented here is the presentation of a formulation of idealized elements due to Iwan, that appears capable of reproducing the important joint properties as they are now understood. Further, methods for selecting parameters for that model by joining the results from experiments in regimes of small and large load are developed. The significance of this work is that a reduced order model is presented that is capable of reproducing the important qualitative properties of mechanical joints using only a small number of parameters.

Event tree analysis and Monte Carlo-based discrete event simulation have been used in risk assessment studies for many years. This report details how features of these two methods can be combined with concepts from object-oriented analysis to develop a new risk assessment methodology with some of the best features of each. The resultant Object-Based Event Scenarios Tree (OBEST) methodology enables an analyst to rapidly construct realistic models for scenarios for which an a priori discovery of event ordering is either cumbersome or impossible (especially those that exhibit inconsistent or variable event ordering, which are difficult to represent in an event tree analysis). Each scenario produced by OBEST is automatically associated with a likelihood estimate because probabilistic branching is integral to the object model definition. The OBEST method uses a recursive algorithm to solve the object model and identify all possible scenarios and their associated probabilities. Since scenario likelihoods are developed directly by the solution algorithm, they need not be computed by statistical inference based on Monte Carlo observations (as required by some discrete event simulation methods). Thus, OBEST is not only much more computationally efficient than these simulation methods, but it also discovers scenarios that have extremely low probabilities as a natural analytical result--scenarios that would likely be missed by a Monte Carlo-based method. This report documents the OBEST methodology, the demonstration software that implements it, and provides example OBEST models for several different application domains, including interactions among failing interdependent infrastructure systems, circuit analysis for fire risk evaluation in nuclear power plants, and aviation safety studies.

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Two-phase flow and transport of reactants and products in the air cathode of proton exchange membrane (PEM) fuel cells is studied analytically and numerically. Single- and two-phase regimes of water distribution and transport are classified by a threshold current density corresponding to first appearance of liquid water at the membrane/cathode interface. When the cell operates above the threshold current density, liquid water appears and a two-phase zone forms within the porous cathode. A two-phase, multicomponent mixture model in conjunction with a finite-volume-based computational fluid dynamics (CFD) technique is applied to simulate the cathode operation in this regime. The model is able to handle the situation where a single-phase region co-exists with a two-phase zone in the air cathode. For the first time, the polarization curve as well as water and oxygen concentration distributions encompassing both single- and two-phase regimes of the air cathode are presented. Capillary action is found to be the dominant mechanism for water transport inside the two-phase zone of the hydrophilic structure. The liquid water saturation within the cathode is predicted to reach 6.3% at 1.4 A cm-2 for dry inlet air.

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The effect of polymer architecture on macroscopic properties were investigated using the self-consistent integral equation theory. Using several types of polyolefin polymers, the results obtained using the self consistent polymer reference interaction site model (PRISM) and molecular dynamics (MD) simulations were compared. The results from the two methods were then compared with experimental X ray scattering data.

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We report first-principles total energy calculations of interaction of nitrogen in silicon with silicon self-interstitials. Substitutional nitrogen captures a silicon interstitial with 3.5 eV binding energy forming a (100) split interstitial ground-state geometry, with the nitrogen forming three bonds. The low-energy migration path is through a bond bridge state having two bonds. Fast diffusion of nitrogen occurs through a pure interstitialcy mechanism: the nitrogen never has less than two bonds. Near-zero formation energy of the nitrogen interstitialcy with respect to the substitutional rationalizes the low solubility of substitutional nitrogen in silicon. © 2001 American Institute of Physics.

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A wave-optical model that is coupled to a microscopic gain theory is used to investigate lateral mode behavior in group-III nitride quantum-well lasers. Beam filamentation due to self-focusing in the gain medium is found to limit fundamental-mode output to narrow stripe lasers or to operation close to lasing threshold. Differences between nitride and conventional near-infrared semiconductor lasers arise because of band structure differences, in particular, the presence of a strong quantum-confined Stark effect in the former. Increasing mirror reflectivities in plane-plane resonators to reduce lasing threshold current tends to exacerbate the filamentation problem. On the other hand, a negative-branch unstable resonator is found to mitigate filament effects, enabling fundamental-mode operation far above threshold in broad-area lasers.

Under ultrahigh vacuum conditions at 300 K, the applied electric field and/or resulting current from an STM tip creates nanoscale voids at the interface between an epitaxial, 7.0 angstroms thick Al2O3 film and a Ni3Al(1 1 1) substrate. This phenomenon is independent of tip polarity. Constant current (1 nA) images obtained at +0.1 V bias and +2.0 V bias voltage (sample positive) reveal that voids are within the metal at the interface and, when small, are capped by the oxide film. Void size increases with time of exposure. The rate of void growth increases with applied bias/field and tunneling current, and increases significantly for field strengths >5 MV/cm, well below the dielectric breakdown threshold of 12±1 MV/cm. Slower rates of void growth are, however, observed at lower applied field strengths. Continued growth of voids, to approximately 30 angstroms deep and approximately 500 angstroms wide, leads to the eventual failure of the oxide overlayer. Density functional theory calculations suggest a reduction-oxidation mechanism: interfacial metal atoms are oxidized via transport into the oxide, while oxide surface Al cations are reduced to admetal species which rapidly diffuse away. This is found to be exothermic in model calculations, regardless of the details of the oxide film structure; thus, the barriers to void formation are kinetic rather than thermodynamic. We discuss our results in terms of mechanisms for the localized pitting corrosion of aluminum, as our results suggest nanovoid formation requires just electric field and current, which are ubiquitous in environmental conditions.

Parameters in the heat conduction equation are frequently modeled as temperature dependent. Thermal conductivity, volumetric heat capacity, convection coefficients, emissivity, and volumetric source terms are parameters that may depend on temperature. Many applications, such as parameter estimation, optimal experimental design, optimization, and uncertainty analysis, require sensitivity to the parameters describing temperature-dependent properties. A general procedure to compute the sensitivity of the temperature field to model parameters for nonlinear heat conduction is studied. Parameters are modeled as arbitrary functions of temperature. Sensitivity equations are implemented in an unstructured grid, element-based numerical solver. The objectives of this study are to describe the methodology to derive sensitivity equations for the temperature-dependent parameters and present demonstration calculations. In addition to a verification problem, the design of an experiment to estimate temperature variable thermal properties is discussed.

The goal of this project is to predict the drawdown that will be observed in specific piezometers placed in the MIU-2 borehole due to pumping at a single location in the MIU-3 borehole. These predictions will be in the form of distributions obtained through multiple forward runs of a well-test model. Specifically, two distributions will be created for each pumping location--piezometer location pair: (1) the distribution of the times to 1.0 meter of drawdown and (2) the distribution of the drawdown predicted after 12 days of pumping at a discharge rates of 25, 50, 75 and 100 l/hr. Each of the steps in the pumping rate lasts for 3 days (259,200 seconds). This report is based on results that were presented at the Tono Geoscience Center on January 27th, 2000, which was approximately one week prior to the beginning of the interference tests. Hydraulic conductivity (K), specific storage (S{sub s}) and the length of the pathway (L{sub p}) are the input parameters to the well-test analysis model. Specific values of these input parameters are uncertain. This parameter uncertainty is accounted for in the modeling by drawing individual parameter values from distributions defined for each input parameter. For the initial set of runs, the fracture system is assumed to behave as an infinite, homogeneous, isotropic aquifer. These assumptions correspond to conceptualizing the aquifer as having Theis behavior and producing radial flow to the pumping well. A second conceptual model is also used in the drawdown calculations. This conceptual model considers that the fracture system may cause groundwater to move to the pumping well in a more linear (non-radial) manner. The effects of this conceptual model on the drawdown values are examined by casting the flow dimension (F{sub d}) of the fracture pathways as an uncertain variable between 1.0 (purely linear flow) and 2.0 (completely radial flow).

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Geostatistical simulation is used to extrapolate data derived from site characterization activities at the MIU site into information describing the three-dimensional distribution of hydraulic conductivity at the site and the uncertainty in the estimates of hydraulic conductivity. This process is demonstrated for six different data sets representing incrementally increasing amounts of characterization data. Short horizontal ranges characterize the spatial variability of both the rock types (facies) and the hydraulic conductivity measurements. For each of the six data sets, 50 geostatistical realizations of the facies and 50 realizations of the hydraulic conductivity are combined to produce 50 final realizations of the hydraulic conductivity distribution. Analysis of these final realizations indicates that the mean hydraulic conductivity value increases with the addition of site characterization data. The average hydraulic conductivity as a function of elevation changes from a uniform profile to a profile showing relatively high hydraulic conductivity values near the top and bottom of the simulation domain. Three-dimensional uncertainty maps show the highest amount of uncertainty in the hydraulic conductivity distribution near the top and bottom of the model. These upper and lower areas of high uncertainty are interpreted to be due to the unconformity at the top of the granitic rocks and the Tsukyoshi fault respectively.

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In this report, computable global bounds on errors due to the use of various mathematical models of physical phenomena are derived. The procedure involves identifying a so-called fine model among a class of models of certain events and then using that model as a datum with respect to which coarser models can be compared. The error inherent in a coarse model, compared to the fine datum, can be bounded by residual functionals unambiguously defined by solutions of the coarse model. Whenever there exist hierarchical classes of models in which levels of sophistication of various coarse models can be defined, an adaptive modeling strategy can be implemented to control modeling error. In the present work, the class of models is within those embodied in nonlinear continuum mechanics.

Ground mobile robots are much in the mind of defense planners at this time, being considered for a significant variety of missions with a diversity ranging from logistics supply to reconnaissance and surveillance. While there has been a very large amount of basic research funded in the last quarter century devoted to mobile robots and their supporting component technologies, little of this science base has been fully developed and deployed--notable exceptions being NASA's Mars rover and several terrestrial derivatives. The material in this paper was developed as a first exemplary step in the development of a more systematic approach to the R and D of ground mobile robots.

The overall objectives of this program are to (1) develop rapid and low-cost processes for manufacturing that can improve yield, throughput, and performance of silicon photovoltaic devices, (2) design and fabricate high-efficiency solar cells on promising low-cost materials, and (3) improve the fundamental understanding of advanced photovoltaic devices. Several rapid and potentially low-cost technologies are described in this report that were developed and applied toward the fabrication of high-efficiency silicon solar cells.

It is critically important, for the sake of credible computational predictions, that model-validation experiments be designed, conducted, and analyzed in ways that provide for measuring predictive capability. I first develop a conceptual framework for designing and conducting a suite of physical experiments and calculations (ranging from phenomenological to integral levels), then analyzing the results first to (statistically) measure predictive capability in the experimental situations then to provide a basis for inferring the uncertainty of a computational-model prediction of system or component performance in an application environment or configuration that cannot or will not be tested. Several attendant issues are discussed in general, then illustrated via a simple linear model and a shock physics example. The primary messages I wish to convey are: (1) The only way to measure predictive capability is via suites of experiments and corresponding computations in testable environments and configurations; (2) Any measurement of predictive capability is a function of experimental data and hence is statistical in nature; (3) A critical inferential link is required to connect observed prediction errors in experimental contexts to bounds on prediction errors in untested applications. Such a connection may require extrapolating both the computational model and the observed extra-model variability (the prediction errors: nature minus model); (4) Model validation is not binary. Passing a validation test does not mean that the model can be used as a surrogate for nature; (5) Model validation experiments should be designed and conducted in ways that permit a realistic estimate of prediction errors, or extra-model variability, in application environments; (6) Code uncertainty-propagation analyses do not (and cannot) characterize prediction error (nature vs. computational prediction); (7) There are trade-offs between model complexity and the ability to measure a computer model's predictive capability that need to be addressed in any particular application; and (8) Adequate quantification of predictive capability, even in greatly simplified situations, can require a substantial number of model-validation experiments.

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A model is developed for the forces acting on a micrometer-size particle (dust) suspended within a plasma sheath. The significant forces acting on a single particle are gravity, neutral gas drag, electric field, and the ion wind due to ion flow to the electrode. It is shown that an instability in the small-amplitude dust oscillation might exist if the conditions are appropriate. In such a case the forcing term due to the ion wind exceeds the damping of the gas drag. The basic physical cause for the instability is that the ion wind force can be a decreasing function of the relative ion-particle velocity. However it seems very unlikely the appropriate conditions for instability are present in typical dusty plasmas.

In this paper the development of a gridless method to solve compressible flow problems is discussed. The governing evolution equations for velocity divergence {delta}, vorticity {omega}, density {rho}, and temperature T are obtained from the primitive variable Navier-Stokes equations. Simplifications to the equations resulting from assumptions of ideal gas behavior, adiabatic flow, and/or constant viscosity coefficients are given. A general solution technique is outlined with some discussion regarding alternative approaches. Two radial flow model problems are considered which are solved using both a finite difference method and a compressible particle method. The first of these is an isentropic inviscid 1D spherical flow which initially has a Gaussian temperature distribution with zero velocity everywhere. The second problem is an isentropic inviscid 2D radial flow which has an initial vorticity distribution with constant temperature everywhere. Results from the finite difference and compressible particle calculations are compared in each case. A summary of the results obtained herein is given along with recommendations for continuing the work.

A FORTRAN computer code has been written to calculate the heat transfer properties at the wetted perimeter of a coolant channel when provided the bulk water conditions. This computer code is titled FILM-30 and the code calculates its heat transfer properties by using the following correlations: (1) Sieder-Tate: forced convection, (2) Bergles-Rohsenow: onset to nucleate boiling, (3) Bergles-Rohsenow: partially developed nucleate boiling, (4) Araki: fully developed nucleate boiling, (5) Tong-75: critical heat flux (CHF), and (6) Marshall-98: transition boiling. FILM-30 produces output files that provide the heat flux and heat transfer coefficient at the wetted perimeter as a function of temperature. To validate FILM-30, the calculated heat transfer properties were used in finite element analyses to predict internal temperatures for a water-cooled copper mockup under one-sided heating from a rastered electron beam. These predicted temperatures were compared with the measured temperatures from the author's 1994 and 1998 heat transfer experiments. There was excellent agreement between the predicted and experimentally measured temperatures, which confirmed the accuracy of FILM-30 within the experimental range of the tests. FILM-30 can accurately predict the CHF and transition boiling regimes, which is an important advantage over current heat transfer codes. Consequently, FILM-30 is ideal for predicting heat transfer properties for applications that feature high heat fluxes produced by one-sided heating.

Smoke can cause interruptions and upsets in active electronics. Because nuclear power plants are replacing analog with digital instrumentation and control systems, qualification guidelines for new systems are being reviewed for severe environments such as smoke and electromagnetic interference. Active digital systems, individual components, and active circuits have been exposed to smoke in a program sponsored by the U.S. Nuclear Regulatory Commission. The circuits and systems were all monitored during the smoke exposure, indicating any immediate effects of the smoke. The major effect of smoke has been to increase leakage currents (through circuit bridging across contacts and leads) and to cause momentary upsets and failures in digital systems. This report summarizes two previous reports and presents new results from conformal coating, memory chip, and hard drive tests. The report describes practices for mitigation of smoke damage through digital system design, fire barriers, ventilation, fire suppressants, and post fire procedures.

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We describe a technique, based on shear force microscopy, that allows one to detect shear forces in a chosen direction at the nanometer scale. The lateral direction of an oscillating probe tip is determined by selecting which of the four quadrants are excited on the piezo driver. The shear forces depend directly on this lateral direction if structural anisotropies are present, as confirmed with polydiacetylene monolayers. © 2001 American Institute of Physics.

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Thin films of polymethylmethacrylate (PMMA) doped with perylene provide selective, robust and easily prepared optical sensor films for NO2 gas with suitable response times for materials aging applications. The materials are readily formed as 200 nm thin spin cast films on glass from chlorobenzene solution. The fluorescence emission of the films (λmax = 442 nm) is quenched upon exposure to NO2 gas through an irreversible reaction forming non-fluorescent nitroperylene. Infrared, UV-VIS and fluorescence spectroscopies confirmed the presence of the nitro adduct in the films. In other atmospheres examined, such as air and 1000 ppm concentrations of SO2, CO, Cl2 and NH3, the films exhibited no loss of fluorescence intensity over a period of days to weeks. Response curves were obtained for 1000, 100 and 10 ppm NO2 at room temperature with equilibration times varying from hours to weeks. The response curves were fit using a numerical solution to the coupled diffusion and a nonlinear chemical reaction problem assuming that the situation is reaction limiting. The forward reaction constant fitted to experimental data was kf to approximately 0.06 (ppm min)-1.

Abstract not provided.

Two experiments have been performed to measure the effects of pulsed radiation loads on the front of small tubular structures, using as an energy source the X-ray fluence produced by a Z-pinch at the Sandia National Laboratories Z Facility. The project had two major goals: to establish the feasibility of using the Z machine to study the phenomenology associated with debris generation and propagation down tubular structures with partitions; and to use the resultant experimental data to validate numerical hydrocodes (shock physics codes) so that we have confidence in their use in analyzing these types of situations. Two tubular aluminum structures (5 and 10 cm long and 1 cm inside diameter) were prepared, with aluminum partitions located at the front, halfway down the pipe, and at the rear. Interferometry (VISARs) provided multiple velocity histories for all of the partitions. In both experiments, the first barrier, which was exposed directly to the x-ray fluence, was launched into the pipe at a velocity of ∼2 km/s, accelerating to give a mean velocity of ∼ 2.6 km/s. Loss of plate integrity is inferred from the dispersed launch of the second partition at ∼1 km/s. Wall shocks propagating at 4.5 km/s were inferred. Post-test metallography showed evidence of melting and partial vaporization of the plates, and turbulent mixing with material from the walls. Calculations qualitatively agree with the observed results, but slightly overpredict debris velocity, possibly due to overestimates of total energy fluence. An application for this work is the study of techniques for line-of-sight shock and debris mitigation on high-power pulsed power facilities such as Z and its follow-on machines. © 2001 Elsevier Science Ltd. All rights reserved.

Fluid mechanics research related to fire is reviewed with a focus on canonical flows, multiphysics coupling aspects, and experimental and numerical techniques. Fire is a low-speed, chemically reacting flow in which buoyancy plays an important role. Fire research has focused on two canonical flows, the reacting boundary layer and the reacting free plume. There is rich, multilateral, bidirectional coupling among fluid mechanics and scalar transport, combustion, and radiation. There is only a limited experimental fluid mechanics database for fire owing to measurement difficulties in the harsh environment and to the focus within the fire community on thermal/chemical consequences. Increasingly, computational fluid dynamics techniques are being used to provide engineering guidance on thermal/chemical consequences and to study fire phenomenology.

Steady shear simulations of electrorheology (ER) and magnetorheology (MR) in a uniaxiai field are presented. These large scale simulations are three dimensional, and include the effect of Brownian motion. In the absence of thermal fluctuations, the expected shear thinning viscosity is observed and a striped phase is seen to rapidly form in a uniaxiai field, with a shear slip zone in each sheet. However, as the influence of Brownian motion increases, the fiuid stress decreases, especially at lower Mason numbers, and the striped phase eventually disappears, even when the fluid stress is still high. To account for the uniaxiai steady shear data we propose a microscopic chain model of the role played by thermal fluctuations on the rheology of ER and MR fluids that delineates the regimes where an applied field can impact the fluid viscosity, and gives an analytical prediction for the thermal affect. ©2000 The American Physical Society.

A series of fine-grained porous alumina samples, with and without a liquid phase, were fabricated in compositions matched closely to commercially available alumina used as microelectronic substrates. Hertzian indentation on monolithic specimens of the glass-containing samples produced a greater quasi-ductile stress-strain response compared with that observed in the pure alumina. Maximum residual indentation depths, determined from surface profilometry, correlated with the stress-strain results. Moreover, microstructural observations from bonded interface specimens revealed significantly more damage in the form of microcracking and under extreme loading, pore collapse, in the glass-containing specimens. The absence of the typical twin faulting mechanism observed for larger-grained alumina suggests that the damage mechanism for quasi-ductility in these fine-grained porous aluminas was derived from the pores acting as a stress concentrator and the grain boundary glass phase providing a weak path for short crack propagation.

The Long-term Inflow and Structural Test (LIST) program is collecting long-term, continuous inflow and structural response data to characterize the extreme loads on wind turbines. A heavily instrumented Micon 65/13M turbine with SERI 8m blades is being used as the primary test turbine for this test series. This turbine is located in Bushland, TX, a test site that exposes the turbine to a wind regime that is representative of a Great Plains commercial site. The turbine and its inflow are being characterized with 60 measurements: 34 to characterize the inflow, 19 to characterize structural response, and 7 to characterize the time-varying state of the turbine. In a companion paper, Sutherland, Jones and Neal1 give a detailed description of the turbine, the site and the instrumentation. In this paper, a preliminary analysis of the structural and inflow data is presented. Particular attention is paid to the determination of the various structural loads on the turbine. Long-term fatigue spectra are also presented.

Chemically prepared Pb(Zr0.95Ti0.05)O3 (PZT 95/5) ceramics were fabricated with a range of different porosity levels, while grain size was held constant, by systematic additions of added organic pore former (Avicel). Use of Avicel in amounts ranging from 0 to 4.0 wt% resulted in fired ceramic densities that ranged from 97.3% to 82.3%. Hydrostatic-pressure-induced ferroelectric (FE) to antiferroelectric (AFE) phase transformations were substantially more diffuse and occurred at lower hydrostatic pressures with increasing porosity. An ∼12 MPa decrease in hydrostatic transformation pressure per volume percent added porosity was observed. The decrease in transformation pressure with decreasing density was quantitatively consistent with the calculated macroscopic stress required to achieve a specific volumetric macrostrain (0.40%). This strain was equivalent to experimentally measured macrostrain for FE-to-AFE transformation. The macroscopic stress levels were calculated using measured bulk modulus values that decreased from 84 to 46 GPa as density decreased from 97.3% to 82.3%. Good agreement between calculated and measured values of FE-to-AFE transformation stress was obtained for ceramics fired at 1275° and 1345°C.

The wavelength variation of the second-order nonlinear coefficients of KNbO3, KH2PO4 and LiB3O5 crystals was discussed. The second-order nonlinear coefficients were measured using optical parametric amplification and second-harmonic generation over a wide range of wavelengths for the crystals. The results showed that Miller scaling was a useful approximation for the crystals.

We compare frequency doubling of broadband light in a single nonlinear crystal with doubling in five crystals with intercrystal temporal walk-off compensation and with doubling in five crystals adjusted for offset phase-matching frequencies. Using a plane-wave dispersive numerical model of frequency doubling, we study the bandwidth of the second harmonic and the conversion efficiency as functions of crystal length and fundamental irradiance. For low irradiance, the offset phase-matching arrangement has lower efficiency than a single crystal of the same total length but gives a broader second-harmonic bandwidth. The walk-off-compensated arrangement gives both higher conversion efficiency and broader bandwidth than a single crystal. At high irradiance, both multicrystal arrangements improve on the single-crystal efficiency while maintaining a broad bandwidth. © 2001 Optical Society of America.

A kinetic, three-dimensional Monte Carlo model for simulating grain growth in the presence of mobile pores is presented. The model was used to study grain growth and pore migration by surface diffusion in an idealized geometry that ensures constant driving force for grain growth. The driving forces, pore size, and pore mobilities were varied to study their effects on grain-boundary mobility and grain growth. The simulations captured a variety of complex behaviors, including reduced grain-boundary velocity due to pore drag that has been predicted by analytical theories. The model is capable of treating far more complex geometries, including polycrystals. We present the capabilities of this model and discuss its limitations.

The Long-term Inflow and Structural Test (LIST) program is collecting long-term, continuous inflow and structural response data to characterize the extreme loads on wind turbines. A heavily instrumented Micon 65/13M turbine with SERI 8-m blades is being used as the first test turbine for this program. This turbine and its two sister turbines are located in Bushland, TX, a test site that exposes the turbines to a wind regime that is representative of a Great Plains commercial site. The turbines and their inflow are being characterized with 60 measurements: 34 to characterize the inflow, 19 to characterize structural response, and 7 to characterize the time-varying state of the turbine. The primary characterization of the inflow into the LIST turbine relies upon an array of five sonic anemometers. Primary characterization of the structural response of the turbine uses several sets of strain gauges to measure bending loads on the blades and the tower and two accelerometers to measure the motion of the nacelle. Data from the various instruments are sampled at a rate of 30 Hz using a newly developed data acquisition system that features a time-synchronized continuous data stream that is telemetered from the turbine rotor. The data, taken continuously, are automatically divided into 10-minute segments and archived for analysis. Preliminary data are presented to illustrate the operation of the turbine and the data acquisition and analysis system.

This paper describes a system, which acquires 3D data and tracks an eleven degree of freedom human model in real-time. Using four cameras we create a time-varying volumetric image (a visual hull) of anything moving in the space observed by all four cameras. The sensor is currently operating in a volume of approximately 500,000 voxels (1.5 inch cubes) at a rate of 25 Hz. The system is able to track the upper body dynamics of a human (x,y position of the body, a torso rotation, and four rotations per arm). Both data acquisition and tracking occur on one computer at a rate of 16 Hz. We also developed a calibration procedure, which allows the system to be moved and be recalibrated quickly. Furthermore we display in real-time, either the data overlaid with the joint locations or a human avatar. Lastly our system has been implemented to perform crane gesture recognition.

A new instrument to accurately and verifiably measure mechanical properties across an entire MEMS wafer is under development. We have modified the optics on a conventional microelectronics probe station to enable three-dimensional imaging while maintaining the full working distance of a long working distance objective. This allows standard probes or probe cards to be used. We have proceeded to map out mechanical properties of polycrystalline silicon along a wafer column by the Interferometry for Material Property Measurement (IMaP) methodology. From interferograms of simple actuated cantilevers, out-of-plane deflection profiles at the nanometer scale are obtained. These are analyzed by integrated software routines that extract basic mechanical properties such as cantilever curvature and Young's modulus. Non-idealities such as support post compliance and beam take off angle are simultaneously quantified. Curvature and residual stress are found to depend on wafer position. Although deflections of cantilevers varied across the wafer, Young's modulus E - 161 GPa is independent of wafer position as expected. This result is achieved because the non-idealities have been taken into account.

A low toxicity, high performance, hypergolic, bipropellant system is desired to replace conventional nitrogen tetroxide (NTO) and hydrazine propulsion systems. Hydrogen peroxide exothermically decomposes to water, and oxygen, making it an ideal oxidizer for more environmentally friendly propulsion systems. Unfortunately, the choice of fuel for such systems is not as clear. Many factors such as ignition delay, performance, toxicity, storability, and cost must be considered. Numerous candidate fuels and fuel/catalyst mixtures were screened using a simple laboratory setup and visual observation. A mixture of ethanolamine and 1% copper (II) chloride was found to rapidly ignite with 90% hydrogen peroxide. Hydrogen peroxide and ethanolamine are much less toxic than NTO and hydrazine. Hydrogen peroxide and ethanolamine have a calculated specific impulse of 245 seconds compared to 284 seconds for NTO and monomethyl hydrazine. A low-freezing blend of furfuryl alcohol (47.5%), ethanolamine (47.5%), and copper (II) chloride (5%) was successfully test fired in a small rocket engine with both 90% and 99% hydrogen peroxide. Hypergolic ignition of this mixture was achieved with 70% hydrogen peroxide. Our quest for a non-toxic hypergol began by researching the literature. Most current low freezing points, exhibit good performance, and are non-toxic compared to hydrazines.1 Unfortunately, hypergolic ignition was only achieved after adding a large amount (>10%) of manganese based catalyst.2-4 Metallic catalysts are toxic and impair performance, so low concentrations are desired. In addition, an insoluble catalyst may not remain in uniform suspension, converting a hypergolic fuel into one with inconsistent age related performance. We wanted to find a fuel that was hypergolic by itself, or that could be made so with a much smaller addition of metallic catalyst.

International standards for wind turbine certification depend on finding long-term fatigue load distributions that are conservative with respect to the state of knowledge for a given system. Statistical models of loads for fatigue application are described and demonstrated using flap and edge blade-bending data from a commercial turbine in complex terrain. Distributions of rainflow-counted range data for each ten-minute segment are characterized by parameters related to their first three statistical moments (mean, coefficient of variation, and skewness). Quadratic Weibull distribution functions based on these three moments are shown to match the measured load distributions if the non-damaging low-amplitude ranges are first eliminated. The moments are mapped to the wind conditions with a two-dimensional regression over ten-minute average wind speed and turbulence intensity. With this mapping, the short-term distribution of ranges is known for any combination of average wind speed and turbulence intensity. The long-term distribution of ranges is determined by integrating over the annual distribution of input conditions. First, we study long-term loads derived by integration over wind speed distribution alone, using standard-specified turbulence levels. Next, we perform this integration over both wind speed and turbulence distribution for the example site. Results are compared between standard-driven and site-driven load estimates. Finally, using statistics based on the regression of the statistical moments over the input conditions, the uncertainty (due to the limited data set) in the long-term load distribution is represented by 95% confidence bounds on predicted loads.

Helium-cooled, refractory heat exchangers are now under consideration for first wall and divertor applications. These refractory devices take advantage of high temperature operation with large delta-Ts to effectively handle high heat fluxes. The high temperature helium can then be used in a gas turbine for high-efficiency power conversion. Over the last five years, heat removal with helium was shown to increase dramatically by using porous metal to provide a very large effective surface area for heat transfer in a small volume. Last year, the thermal performance of a bare-copper, dual-channel, helium-cooled, porous metal divertor mock-up was evaluated on the 30 kW Electron Beam Test System at Sandia National Laboratories. The module survived a maximum absorbed heat flux of 34.6 MW/m2 and reached a maximum surface temperature of 593 °C for uniform power loading of 3 kW absorbed on a 2-cm2 area. An impressive 10 kW of power was absorbed on an area of 24 cm2. Recently, a similar dual-module, helium-cooled heat exchanger made almost entirely of tungsten was designed and fabricated by Thermacore, Inc. and tested at Sandia. A complete flow test of each channel was performed to determine the actual pressure drop characteristics. Each channel was equipped with delta-P transducers and platinum resistance temperature devices (RTDs) for independent calorimetry. One mass flow meter monitored the total flow to the heat exchanger, while a second monitored flow in only one of the channels. The thermal response of each tungsten module was obtained for heat fluxes in excess of 5 MW/m2 using 50 °C helium at 4 MPa. Fatigue cycles were also performed to assess the fracture toughness of the tungsten modules. A description of the module design and new results on flow instabilities are also presented.

A unified set of high-temperature-hohlraum models has been developed. For a simple hohlraum, (Formula presented) where (Formula presented) is the total power radiated by the source, (Formula presented) is the source area, (Formula presented) is the area of the cavity wall excluding the source and holes in the wall, (Formula presented) is the area of the holes, σ is the Stefan-Boltzmann constant, (Formula presented) is the radiation brightness temperature, (Formula presented) is the hohlraum volume, and c is the speed of light. The wall albedo (Formula presented) where (Formula presented) is the brightness temperature of area (Formula presented) The net power radiated by the source (Formula presented) which suggests that for laser-driven hohlraums the conversion efficiency (Formula presented) be defined as (Formula presented) The characteristic time required to change (Formula presented) in response to a change in (Formula presented) is (Formula presented) Using this model, (Formula presented) (Formula presented) and (Formula presented) can be expressed in terms of quantities directly measurable in a hohlraum experiment. For a steady-state hohlraum that encloses a convex capsule, (Formula presented) where (Formula presented) is the capsule albedo, (Formula presented) is the capsule area, (Formula presented) and (Formula presented) is the brightness temperature of the radiation that drives the capsule. According to this relation, the capsule-coupling efficiency of the baseline National Ignition Facility hohlraum is 15–23 % higher than predicted by previous analytic expressions. A model of a hohlraum that encloses a z pinch is also presented. © 2001 The American Physical Society.

In manufacturing, the conceptual design and detailed design stages are typically regarded as sequential and distinct. Decisions made in conceptual design are often made with little information as to how they would affect detailed design or manufacturing process specification. Many possibilities and unknowns exist in conceptual design where ideas about product shape and functionality are changing rapidly. Few if any tools exist to aid in this difficult, amorphous stage in contrast to the many CAD and analysis tools for detailed design where much more is known about the final product. The Materials Process Design Environment (MPDE) is a collaborative problem solving environment (CPSE) that was developed so geographically dispersed designers in both the conceptual and detailed stage can work together and understand the impacts of their design decisions on functionality, cost and manufacturability.

Abstract not provided.

Adhesively-bonded joints of LaRC™ PETI-5, a phenylethynyl-terminated polyimide, with chromic acid anodized titanium were fabricated and debonded interfacially. The adhesive-substrate failure surfaces were investigated using several surface analysis techniques. From Auger spectroscopy, field emission scanning electron microscopy, and atomic force microscopy studies, polymer appears to he penetrating the pores of the anodized substrate to a depth of approximately 100 nm. From X-ray photoelectron spectroscopy data, the polymer penetrating the pores appears to be in electrical contact with the titanium oxide, leading to differential charging. These analyses confirm that the polymer is becoming mechanically interlocked within the substrate surface.

Hypersonic transitional flows over a flat plate and a sharp cone are studied using four turbulence models: the one-equation eddy viscosity transport model of Spalart-Allmaras, a low Reynolds number κ-ε model, the Menter κ-ω model, and the Wilcox κ-ω model. A framework is presented for the assessment of turbulence models that includes documentation procedures, solution accuracy, model sensitivity, and model validation. The accuracy of the simulations is addressed, and the sensitivities of the models to grid refinement, freestream turbulence levels, and wall y+ spacing are presented. The flat plate skin friction results are compared to the well-established laminar and turbulent correlations of Van Driest. Correlations for the sharp cone are discussed in detail. These correlations, along with recent experimental data, are used to judge the validity of the simulation results for skin friction and surface heating on the sharp cone. The Spalart-Allmaras performs the best with regards to model sensitivity and model accuracy, while the Menter κ-ω model also performs well for these zero pressure gradient boundary layer flows. © 2001 American Institute of Aeronautics & Astronautics.

The development of microsystems that merge biological materials with microfabricated structures is highly dependent on the successful interfacial interactions between these innately incompatible materials. Surface passivation of semiconductor and glass surfaces with thin organic films can attenuate the adhesion of proteins and cells that lead to biofilm formation and biofouling of fluidic structures. We have examined the adhesion of glial cells and serum albumin proteins to microfabricated glass and semiconductor surfaces coated with self-assembled monolayers (SAM) of octadecyltrimethoxysilane (OTMS) and N-(triethoxysilylpropyl)-O-polyethylene oxide urethane (TESP), to evaluate the biocompatibility and surface passivation those coatings provide. These films were exposed to solutions containing serum albumin proteins (4 mg/mL), glial cells in culturing media, and glial cells under fluid flow. While the OTMS surface resisted cell spreading and growth under culture conditions, the same surface induced biofouling in a cell flow experiment with a microfluidic structure. Interestingly, the TESP surface, which was supportive of cell adhesion and proliferation under cell culturing conditions, effectively passivated the microfluidic structure to cell adhesion and biofouling. The results suggest that the cell adhesion process is not only dependent on the chemistry of the surface but also on the time allotted to the cell to probe the surface.

InxGa1-xAs1-yNy quaternary alloys offer the promise of longer wavelength, ≥ 1.3 μm optical transceivers grown on GaAs substrates. To achieve acceptable radiative efficiencies at 1.3 μm, highly-strained InGaAsN quantum wells (x ≈ 0.4, y ≈ 0.005) are being developed as laser active regions. By introducing GaAsP layers into the active region for strain-compensation, gain can be increased using multiple InGaAsN quantum wells. In this work, we report the first strain-compensated, 1.3 μm InGaAsN MQW lasers. Our devices were grown by metal-organic chemical vapor deposition. Lasers with InGaAsN quantum well active regions are proving superior to lasers constructed with competing active region materials. Under pulsed operation, our 1.3 μm InGaAsN lasers displayed negligible blue-shift from the low-injection LED emission, and state-of-the-art characteristic temperature (159 K) was obtained for a 1.3 μm laser.

Recent advances in the development and application of self-assembly templating techniques have opened up the possibility of tailoring membranes for specific separation problems. A new self-assembly processing route to generate inorganic membrane films has made it feasible to finely control both the three-dimensional (3D) porosity and the chemical nature of the adsorbing structures. Chemical sites can be added to a porous membrane either after the inorganic scaffolding has been put in place or, alternatively, chemical sites can be co-assembled in a one-step process. To provide guidance to the optimized use of these 'designer' membranes we have developed a substantial modeling program that focuses on permeation through porous materials. The key issues that need to be modeled concern 1) the equilibrium adsorption behavior in a variety of 3D porous structures, ranging from straight pore channels to fractal structures, 2) the transport (i.e. diffusion) behavior in these structures. Enriching the problem is the presence of reactive groups that may be present on the surface. An important part of the design of actual membranes is to optimize these reactive sites with respect to their strength as characterized by the equilibrium constant, and the positioning of these sites on the adsorbing surface. What makes the technological problem challenging is that the industrial application requires both high flux and high selectivity. What makes the modeling challenging is the smallness of the length scale (molecular) that characterizes the surface reaction and the confinement in the pores. This precludes the use of traditional continuum engineering methods. However, we must also capture the 3D connectivity of the porous structure which is characterized by a larger than molecular length scale. We will discuss how we have used lattice models and both Monte Carlo and 3D density functional theory methods to tackle these modeling challenges.

Frictional energy dissipation in joints is an issue of long-standing interest in the effort to predict damping of built up structures. Even obtaining a qualitative understanding of how energy dissipation depends on applied loads has not yet been accomplished. Goodman[l] postulated that in harmonic loading, the energy dissipation per cycle would go as the cube of the amplitude of loading. Though experiment does support a power-law relationship, the exponent tends to be lower than Goodman predicted. Recent calculations discussed here suggest that the cause of that deviation has to with reshaping of the contact patch over each loading period.

We present and analyze a class of evolutionary algorithms for unconstrained and bound constrained optimization on R(n): evolutionary pattern search algorithms (EPSAs). EPSAs adaptively modify the step size of the mutation operator in response to the success of previous optimization steps. The design of EPSAs is inspired by recent analyses of pattern search methods. We show that EPSAs can be cast as stochastic pattern search methods, and we use this observation to prove that EPSAs have a probabilistic, weak stationary point convergence theory. This convergence theory is distinguished by the fact that the analysis does not approximate the stochastic process of EPSAs, and hence it exactly characterizes their convergence properties.

The ASTM standards provide guidance and instruction on how to field and interpret reactor dosimetry. They provide a roadmap towards understanding the current "state-of-the-art" in reactor dosimetry, as reflected by the technical community. The consensus basis to the ASTM standards assures the user of an unbiased presentation of technical procedures and interpretations of the measurements. Some insight into the types of standards and the way in which they are organized can assist one in using them in an expeditious manner. Two examples are presented to help orient new users to the breadth and interrelationship between the ASTM nuclear metrology standards. One example involves the testing of a new "widget" to verify the radiation hardness. The second example involves quantifying the radiation damage at a pressure vessel critical weld location through surveillance dosimetry and calculation.

This report describes the initial definition of the Verification and Validation (V and V) Plan Peer Review Process at Sandia National Laboratories. V and V peer review at Sandia is intended to assess the ASCI code team V and V planning process and execution. Our peer review definition is designed to assess the V and V planning process in terms of the content specified by the Sandia Guidelines for V and V plans. Therefore, the peer review process and process for improving the Guidelines are necessarily synchronized, and form parts of a larger quality improvement process supporting the ASCI V and V program at Sandia.

Abstract not provided.

Application of the World Wide Web (WWW) for the transfer of sensor data from remote locations to laboratories and offices is a largely ignored application of the WWW. We have investigated several architectures for this application including simple web server/client architectures and variations of this approach. In addition, we have evaluated several commercial approaches and other techniques that have been investigated and are in the literature. Finally, we have provided conclusions based on the results of our study offering suggestions about the advantages and disadvantages of each of the approaches studied.

Abstract not provided.

Abstract not provided.

This primer presents a succinct summary of the evolution of U.S. nuclear deterrence policy from the initial development of nuclear weapons until the present day. This is not a definitive history but an introduction to deterrence policy for those with limited background in this area. The concept of deterrence is discussed in several ways--in a general description of deterrence theory, in an historical review of nuclear policy evolution, in a discussion of the future of deterrence, in historical examples of deterrence successes and failures, and in a review of significant contributors to the study of nuclear policy. The intent is to present an authoritative, unclassified account. To accomplish this, to the extent possible, primary source documents were located and utilized if they were available and declassified. These included unclassified Presidential nuclear policy guidance from the Presidential libraries, official JCS histories and State Department Foreign Relations histories. The writings of noted nuclear strategists and historians were also valuable resources for this primer on U.S. strategic nuclear policy.

A set of vertical extension fractures, striking N-S to NNE-SSW but with local variations, is present in both the outcrop and subsurface in both Mesaverde and Dakota sandstones. Additional sets of conjugate shear fractures have been recognized in outcrops of Dakota strata and may be present in the subsurface. However, the deformation bands prevalent locally in outcrops in parts of the basin as yet have no documented subsurface equivalent. The immature Mesaverde sandstones typically contain relatively long, irregular extension fractures, whereas the quartzitic Dakota sandstones contain short, sub-parallel, closely spaced, extension fractures, and locally conjugate shear planes as well. Outcrops typically display secondary cross fractures which are rare in the subsurface, although oblique fractures associated with local structures such as the Hogback monocline may be present in similar subsurface structures. Spacings of the bed-normal extension fractures are approximately equal to or less than the thicknesses of the beds in which they formed, in both outcrop and subsurface. Fracture intensities increase in association with faults, where there is a gradation from intense fracturing into fault breccia. Bioturbation and minimal cementation locally inhibited fracture development in both formations, and the vertical limits of fracture growth are typically at bedding/lithology contrasts. Fracture mineralizations have been largely dissolved or replaced in outcrops, but local examples of preserved mineralization show that the quartz and calcite common to subsurface fractures were originally present in outcrop fractures. North-south trending compressive stresses created by southward indentation of the San Juan dome area (where Precambrian rocks are exposed at an elevation of 14,000 ft) and northward indentation of the Zuni uplift, controlled Laramide-age fracturing. Contemporaneous right-lateral transpressive wrench motion due to northeastward translation of the basin was both concentrated at the basin margins (Nacimiento uplift and Hogback monocline on east and west edges respectively) and distributed across the strata depth.

Abstract not provided.

This LDRD is aimed to place Sandia at the forefront of GaN-based technologies. Two important themes of this LDRD are: (1) The demonstration of novel GaN-based devices which have not yet been much explored and yet are coherent with Sandia's and DOE's mission objectives. UV optoelectronic and piezoelectric devices are just two examples. (2) To demonstrate front-end monolithic integration of GaN with Si-based microelectronics. Key issues pertinent to the successful completion of this LDRD have been identified to be (1) The growth and defect control of AlGaN and GaN, and (2) strain relief during/after the heteroepitaxy of GaN on Si and the separation/transfer of GaN layers to different wafer templates.

Abstract not provided.

The free volume distribution has been a qualitatively useful concept by which dynamical properties of polymers, such as the penetrant diffusion constant, viscosity, and glass transition temperature, could be correlated with static properties. In an effort to put this on a more quantitative footing, we define the free volume distribution as the probability of finding a spherical cavity of radius R in a polymer liquid. This is identical to the insertion probability in scaled particle theory, and is related to the chemical potential of hard spheres of radius R in a polymer in the Henry's law limit. We used the Polymer Reference Interaction Site Model (PRISM) theory to compute the free volume distribution of semiflexible polymer melts as a function of chain stiffness. Good agreement was found with the corresponding free volume distributions obtained from MD simulations. Surprisingly, the free volume distribution was insensitive to the chain stiffness, even though the single chain structure and the intermolecular pair correlation functions showed a strong dependence on chain stiffness. We also calculated the free volume distributions of polyisobutylene (PIB) and polyethylene (PE) at 298K and at elevated temperatures from PRISM theory. We found that PIB has more of its free volume distributed in smaller size cavities than for PE at the same temperature.

Engineers at Sandia National Laboratories are combining entertainment industry software with traditional data collection techniques to create an interactive visualization tool. By replacing the usual flight simulator joystick with a telemetry data stream, experimental data is combined with existing three-dimensional (3D) engineering models. Users are immersed in their experiment, allowing interaction with and comprehension of complex data sets. Software tools are currently under development for post flight data visualization, and their usefulness and reusability have been demonstrated on numerous spaced-based programs within Sandia. However, data from remote sensors are subject to transmission errors that yield nonphysical behavior in real-time data visualization applications. We propose to investigate the applicability of real-time processing algorithms and estimation theories, such as Kalman filters, that have been successfully applied in other fields. Results will be integrated into existing postflight visualization tools for Proof-of-Concept validation and for potential integration of real-time applications.

Abstract not provided.

Double-diffusive finger convection is a hydrodynamic instability that can occur when two components with different diffusivities are oppositely stratified with respect to the fluid density gradient as a critical condition is exceeded. Laboratory experiments were designed using sodium chloride and sucrose solutions in a Hele-Shaw cell. A high resolution, full field, light transmission technique was used to study the development of the instability. The initial buoyancy ratio (R{sub p}), which is a ratio of fluid density contributions by the two solutes, was varied systematically in the experiments so that the range of parameter space spanned conditions that were nearly stable (R{sub p} = 2.8) to those that were moderately unstable (R{sub p} = 1.4). In systems of low R{sub p}, fingers develop within several minutes, merge with adjacent fingers, form conduits, and stall before newer-generated fingers travel through the conduits and continue the process. Solute fluxes in low R{sub p} systems quickly reach steady state and are on the order of 10{sup {minus}6} m{sup 2} sec{sup {minus}1}. In the higher R{sub p} experiments, fingers are slower to evolve and do not interact as dynamically as in the lower R{sub p} systems. Our experiment with initial R{sub p} = 2.8 exhibited flux on the order of that expected for a similar diffusive system (i.e., 10{sup {minus}7} m{sup 2} sec{sup {minus}1}), although the structures were very different than the pattern of transport expected in a diffusing system. Mass flux decayed as t{sup 1/2} in two experiments each with initial R{sub p} = 2.4 and 2.8.

An experimental investigation was conducted to study double-diffusive finger convection in a Hele-Shaw cell by layering a sucrose solution over a more-dense sodium chloride (NaCl) solution. The solutal Rayleigh numbers were on the order of 60,000, based upon the height of the cell (25 cm), and the buoyancy ratio was 1.2. A full-field light transmission technique was used to measure a dye tracer dissolved in the NaCl solution. They analyze the concentration fields to yield the temporal evolution of length scales associated with the vertical and horizontal finger structure as well as the mass flux. These measures show a rapid progression through two early stages to a mature stage and finally a rundown period where mass flux decays rapidly. The data are useful for the development and evaluation of numerical simulators designed to model diffusion and convection of multiple components in porous media. The results are useful for correct formulation at both the process scale (the scale of the experiment) and effective scale (where the lab-scale processes are averaged-up to produce averaged parameters). A fundamental understanding of the fine-scale dynamics of double-diffusive finger convection is necessary in order to successfully parameterize large-scale systems.

The synthesis, structure and some properties of C{sub 2}H{sub 7}N{sub 4}O {center_dot} ZnPO{sub 4} (guanylurea zinc phosphate) are reported. The cationic template was prepared in situ by partial hydrolysis of the neutral 2-cyanoguanidine starting material. The resulting structure contains a new, unprotonated, zincophosphate layer topology as well as unusual N-H-O template-to-template hydrogen bonds which help to stabilize a ''double sandwich'' of templating cations between the inorganic sheets. Crystal data: C{sub 2}H{sub 7}N{sub 4}O {center_dot} ZnPO{sub 4}, M{sub r} = 229.44, monoclinic, P2{sub 1}/c, a = 13.6453 (9) {angstrom}, b = 5.0716 (3) {angstrom}, c = 10.6005 (7) {angstrom}, {beta} = 95.918 (2){sup 0}, V = 729.7 (1) {angstrom}{sup 3}, R(F) = 0.034, wR(F) = 0.034.

Laboratory experiments utilizing different near-infrared (NIR) sensitive imaging techniques for LADAR range gated imaging at eye-safe wavelengths are presented. An OPO/OPA configuration incorporating a nonlinear crystal for wavelength conversion of 1.56 micron probe or broadcast laser light to 807 nm light by utilizing a second pump laser at 532 nm for gating and gain, was evaluated for sensitivity, resolution, and general image quality. These data are presented with similar test results obtained from an image intensifier based upon a transferred electron (TE) photocathode with high quantum efficiency (QE) in the 1-2 micron range, with a P-20 phosphor output screen. Data presented include range-gated imaging performance in a cloud chamber with varying optical attenuation of laser reflectance images.

Research is presented on infrared (IR) and near infrared (NIR) sensitive sensor technologies for use in a high speed shuttered/intensified digital video camera system for range-gated imaging at ''eye-safe'' wavelengths in the region of 1.5 microns. The study is based upon nonlinear crystals used for second harmonic generation (SHG) in optical parametric oscillators (OPOS) for conversion of NIR and IR laser light to visible range light for detection with generic S-20 photocathodes. The intensifiers are ''stripline'' geometry 18-mm diameter microchannel plate intensifiers (MCPIIS), designed by Los Alamos National Laboratory and manufactured by Philips Photonics. The MCPIIS are designed for fast optical shattering with exposures in the 100-200 ps range, and are coupled to a fast readout CCD camera. Conversion efficiency and resolution for the wavelength conversion process are reported. Experimental set-ups for the wavelength shifting and the optical configurations for producing and transporting laser reflectance images are discussed.

A new way of providing calibration services is evolving which employs the Internet to expand present capabilities and make the calibration process more interactive. Sandia National Laboratories and the National Institute of Standards and Technology are collaborating to set up and demonstrate a remote calibration of multijunction calibrators using this Internet-based technique that is becoming known as e-calibration. This paper describes the measurement philosophy and the Internet resources that can provide real-time audio/video/data exchange, consultation and training, as well as web-accessible test procedures, software and calibration reports. The communication system utilizes commercial hardware and software that should be easy to integrate into most calibration laboratories.

Palmierite (K{sub 2}Pb(SO{sub 4}){sub 2}) has been prepared via a chemical synthesis method. Intensity differences were observed when X-ray powder data from the newly synthesized compound were compared to the published powder diffraction card (PDF) 29-1015 for Palmierite. Investigation of these differences indicated the possibility of preferred orientation and/or chemical inhomogeneity affecting intensities, particularly those of the basal (00{ell}) reflections. Annealing of the Palmierite was found to reduce the effects of preferred orientation. Electron microprobe analysis confirmed K:Pb:S as 2:1:2 for the annealed Palmierite powder. Subsequent least-squares refinement and Rietveld analysis of the annealed powder showed peak intensities very close to that of a calculated Palmierite pattern (based on single crystal data), yet substantially higher than many of the PDF 29-1015 published intensities. Further investigation of peak intensity variation via calculated patterns suggested that the intensity discrepancies between the annealed sample and those found in PDF 29-1015 were potentially due to chemical variation in the K{sub 2}Pb(SO{sub 4}){sub 2} composition. X-ray powder diffraction and crystal data for Palmierite are reported for the annealed sample. Palmierite is Trigonal/Hexagonal with unit cell parameters a = 5.497(1){angstrom}, c = 20.864(2) {angstrom}, space group R-3m (166), and Z = 3.

A semi-analytical solution is developed for one-dimensional steady infiltration in unsaturated fractured rock. The differential form of the mass conservation equation is integrated to yield an analytical expression relating elevation to a function of capillary pressure and relative permeability of the fracture and rock matrix. Constitutive relationships for unsaturated flow in this analysis are taken from van Genuchten [1980] and Mualem [1976], but alternative relations can also be implemented in the integral solution. Expressions are presented for the liquid saturations and pore velocities in the fracture, matrix, and effective continuum materials as a function of capillary pressure and elevation. Results of the analytical solution are applied to examples of infiltration in fractured rock consisting of both homogeneous and composite (layered) domains. The analytical results are also compared to numerical simulations to demonstrate the use of the analytical solution as a benchmarking tool to address computational issues such as grid refinement.

The Database of Environmental Parameters, Organizations, and Tools (DEPOT) has been developed by the Department of Energy (DOE) as a central warehouse for access to data essential for environmental risk assessment analyses. Initial efforts have concentrated on groundwater and vadose zone transport data and bioaccumulation factors. DEPOT seeks to provide a source of referenced data that, wherever possible, includes the level of uncertainty associated with these parameters. Based on the amount of data available for a particular parameter, uncertainty is expressed as a standard deviation or a distribution function. DEPOT also provides DOE site-specific performance assessment data, pathway-specific transport data, and links to environmental regulations, disposal site waste acceptance criteria, other environmental parameter databases, and environmental risk assessment models.

Monitoring of dielectric thin-film production in the microelectronics industry is generally accomplished by depositing a representative film on a monitor wafer and determining the film properties off line. One of the most important dielectric thin films in the manufacture of integrated circuits is borophosphosilicate glass (BPSG). The critical properties of BPSG thin films are the boron content, phosphorus content and film thickness. We have completed an experimental study that demonstrates that infrared emission spectroscopy coupled with multivariate analysis can be used to simultaneous y determine these properties directly from the spectra of product wafers, thus eliminating the need of producing monitor wafers. In addition, infrared emission data can be used to simultaneously determine the film temperature, which is an important film production parameter. The infrared data required to make these determinations can be collected on a time scale that is much faster than the film deposition time, hence infrared emission is an ideal candidate for an in-situ process monitor for dielectric thin-film production.

The elevated temperature creep properties of the 50Au-50Cu wt% and 47Au-50Cu-3Ni braze alloys have been evaluated over the temperature range 250-850 C. At elevated temperatures, i.e., 450-850 C, both alloys were tested in the annealed condition (2 hrs. 750 C/water quenched). The minimum strain rate properties over this temperature range are well fit by the Garofalo sinh equation. At lower temperatures (250 and 350 C), power law equations were found to characterize the data for both alloys. For samples held long periods of time at 375 C (96 hrs.) and slowly cooled to room temperature, an ordering reaction was observed. For the case of the 50Au-50Cu braze alloy, the stress necessary to reach the same, strain rate increased by about 15% above the baseline data. The limited data for ordered 47Au-50Cu-3Ni alloy reflected a,smaller strength increase. However, the sluggishness of this ordering reaction in both alloys does not appear to pose a problem for braze joints cooled at reasonable rates following brazing.

The structural changes in the heme macrocycle and substituents caused by binding of Ca{sup 2+} to the diheme cytochrome c peroxidase from Paracoccuspantotrophus were clarified by resonance Raman spectroscopy of the inactive filly oxidized form of the enzyme. The changes in the macrocycle vibrational modes are consistent with a Ca{sup 2+}-dependent increase in the out-of-plane distortion of the low-potential heme, the proposed peroxidatic heme. Most of the increase in out-of-plane distortion occurs when the high affinity site I is occupied, but a small further increase in distortion occurs when site II is also occupied by Ca{sup 2+}or Mg{sup 2+}. This increase in the heme distortion also explains the red shift in the Soret absorption band that occurs upon Ca{sup 2+} binding. Changes also occur in the low frequency substituent modes of the heme, indicating that a structural change in the covalently attached fingerprint pentapeptide of the LP heme occurs upon CM{sup 2+} binding to site I. These structural changes, possibly enhanced in the semi-reduced form of the enzyme, may lead to loss of the sixth ligand at the peroxidatic heme and activation of the enzyme.

The purpose of the program is to investigate the response of representative scale models of nuclear containment to pressure loading beyond the design basis accident and to compare analytical predictions to measured behavior. This objective is accomplished by conducting static, pneumatic overpressurization tests of scale models at ambient temperature. This research program consists of testing two scale models: a steel containment vessel (SCV) model (tested in 1996) and a prestressed concrete containment vessel (PCCV) model, which is the subject of this paper.