Publications

Hydrolysis and condensation of organically bridged bis-triethoxysilanes, (EtO){sub 3}Si-R-Si(OEt){sub 3}, results in the formation of three dimensional organic/inorganic hybrid networks (Equation 1). Properties of these materials, including porosity, are dependent on the nature of the bridging group, R. Flexible groups (akylene-spacers longer than five carbons in length) polymerize under acidic conditions to give non-porous materials. Rigid groups (such as arylene-, alkynylene-, or alkenylene) form non-porous, microporous, and macroporous gels. In many cases the pore size distributions are quite narrow. One of the motivations for preparing hybrid organic-inorganic materials is to extend the range of properties available with sol-gel systems by incorporating organic groups into the inorganic network. For example, organically modified silica gels arc either prepared by co-polymerizing an organoalkoxysilane with a silica precursor or surface silylating the inorganic gel. This can serve to increase hydrophobicity or to introduce some reactive organic functionality. However, the type and orientation of these organic functionalities is difficult to control. Furthermore, many organoalkoxysilanes can act to inhibitor even prevent gelation, limiting the final density of organic functionalities. We have devised a new route for preparing highly functionalized pores in hybrid materials using bridging groups that are thermally converted into the desired functionalities after the gel has been obtained. In this paper, we present the preparation and characterization of bridged polysilsesquioxanes with Diels-Alder adducts as the bridging groups from the sol-gel polymerization of monomers 2 and 4. The bridging groups are constructed such that the retro Diela-Alder reaction releases the dienes and leaves the dienophiles as integral parts of the network polymers. In the rigid architecture of a xerogel, this loss of organic functionality should liberate sufficient space to modify the overall porosity. Furthermore, the new porosity will be functionalized with the dienophilic olefin bridging group. We also demonstrate that by changing the type of Diels-Alder adduct used as the bridging group, we can change the temperature at which the retro-Diels-Alder reaction will occur.

This paper describes the model and method used to obtain the periodically estimated uncertainties for measurement of the scattering parameters S{sub 11} and S{sub 22} on a Vector Network Analyzer (VNA). A thru-reflect-line (TRL) method is employed as a second tier calibration to obtain uncertainty estimates using an NIST-calibrated standard. An example of tabulated listings of these uncertainty estimates is presented and the uncertainties obtained for a VNA with 7 mm, 3.5 mm, and type N coaxial interfaces used in the laboratory over several years are summarized.

The study of ecology is taking on increasing global importance as the value of well-functioning ecosystems to human well-being becomes better understood. However, the use of technological systems for the study of ecology lags behind the use of technologies in the study of other disciplines important to human well-being, such as medicine, chemistry and physics. The authors outline four different kinds of large-scale data needs required by land managers for the development of sustainable land use strategies, and which can be obtained with current or future technological systems. They then outline a hypothetical resource management scenario in which data on all those needs are collected using remote and in situ technologies, transmitted to a central location, analyzed, and then disseminated for regional use in maintaining sustainable grazing systems. They conclude by highlighting various data-collection systems and data-sharing networks already in operation.

Laser induced fluorescence has been used to measure the spatial distribution of the two lowest energy argon excited states, 1s{sub 5} and 1s{sub 4}, in inductively driven plasmas containing argon, chlorine and boron trichloride. The behavior of the two energy levels with plasma conditions was significantly different, probably because the 1s{sub 5} level is metastable and the 1s{sub 4} level is radiatively coupled to the ground state but is radiation trapped. The argon data is compared with a global model to identify the relative importance of processes such as electron collisional mixing and radiation trapping. The trends in the data suggest that both processes play a major role in determining the excited state density. At lower rfpower and pressure, excited state spatial distributions in pure argon were peaked in the center of the discharge, with an approximately Gaussian profile. However, for the highest rfpowers and pressures investigated, the spatial distributions tended to flatten in the center of the discharge while the density at the edge of the discharge was unaffected. The spatially resolved excited state density measurements were combined with previous line integrated measurements in the same discharge geometry to derive spatially resolved, absolute densities of the 1s{sub 5} and 1s{sub 4} argon excited states and gas temperature spatial distributions. Fluorescence lifetime was a strong fi.mction of the rf power, pressure, argon fraction and spatial location. Increasing the power or pressure resulted in a factor of two decrease in the fluorescence lifetime while adding Cl{sub 2} or BCl{sub 3} increased the fluorescence lifetime. Excited state quenching rates are derived from the data. When Cl{sub 2} or BCl{sub 3} was added to the plasma, the maximum argon metastable density depended on the gas and ratio. When chlorine was added to the argon plasma, the spatial density profiles were independent of chlorine fraction. While it is energetically possible for argon excited states to dissociate some of the molecular species present in this discharge, it does not appear to be a significant source of dissociation. The major source of interaction between the argon and the molecular species BCl{sub 3} and Cl{sub 2} appears to be through modification of the electron density.

Electron and negative ion densities have been measured in inductively coupled discharges containing C{sub 2}F{sub 6} and CHF{sub 3}. Line integrated electron density was determined using a microwave interferometer, negative ion densities were inferred using laser photodetachment spectroscopy, and electron temperature was determined using a Langmuir probe. For the range of induction powers, pressures and bias power investigated, the electron density peaked at 9 x 10{sup 12} cm{sup -2} (line-integrated) or approximately 9 x 10{sup 11} cm{sup -3}. The negative ion density peaked at approximately 1.3 x 10{sup 11} cm{sup -3}. A maximum in the negative ion density as a function of induction coil power was observed. The maximum is attributed to a power dependent change in the density of one or more of the potential negative ion precursor species since the electron temperature did not depend strongly on power. The variation of photodetachment with laser wavelength indicated that the dominant negative ion was F{sup -}. Measurement of the decay of the negative ion density in the afterglow of a pulse modulated discharge was used to determine the ion-ion recombination rate for CF{sub 4}, C{sub 2}F{sub 6} and CHF{sub 3} discharges.

The load mitigation and energy capture characteristics of twist-coupled HAWT blades that are mounted on a variable speed rotor are investigated in this paper. These blades are designed to twist toward feather as they bend with pretwist set to achieve a desirable twist distribution at rated power. For this investigation, the ADAMS-WT software has been modified to include blade models with bending-twist coupling. Using twist-coupled and uncoupled models, the ADAMS software is exercised for steady wind environments to generate C{sub p} curves at a number of operating speeds to compare the efficiencies of the two models. The ADAMS software is also used to generate the response of a twist-coupled variable speed rotor to a spectrum of stochastic wind time series. This spectrum contains time series with two mean wind speeds at two turbulence levels. Power control is achieved by imposing a reactive torque on the low speed shaft proportional to the RPM squared with the coefficient specified so that the rotor operates at peak efficiency in the linear aerodynamic range, and by limiting the maximum RPM to take advantage of the stall controlled nature of the rotor. Fatigue calculations are done for the generated load histories using a range of material exponents that represent materials from welded steel to aluminum to composites, and results are compared with the damage computed for the rotor without twist-coupling. Results indicate that significant reductions in damage are achieved across the spectrum of applied wind loading without any degradation in power production.

The behavior of H in p-GaN(Mg) at temperatures >400 C is modeled by using energies and vibrational frequencies from density-functional theory to parameterize transport and reaction equations. Predictions agree semiquantitatively with experiment for the solubility, uptake, and release of the H when account is taken of a surface barrier. Hydrogen is introduced into GaN during growth by metal-organic chemical vapor deposition (MOCVD) and subsequent device processing. This impurity affects electrical properties substantially, notably in p-type GaN doped with Mg where it reduces the effective acceptor concentration. Application of density-functional theory to the zincblende and wurtzite forms of GaN has indicated that dissociated H in interstitial solution assumes positive, neutral, and negative charge states. The neutral species is found to be less stable than one or the other of the charged states for all Fermi energies. Hydrogen is predicted to form a bound neutral complex with Mg, and a local vibrational mode ascribed to this complex has been observed. The authors are developing a unified mathematical description of the diffusion, reactions, uptake, and release of H in GaN at the elevated temperatures of growth and processing. Their treatment is based on zero-temperature energies from density functional theory. One objective is to assess the consistency of theory with experiment at a more quantitative level than previously. A further goal is prediction of H behavior pertinent to device processing. Herein is discussed aspects relating to p-type GaN(Mg).

We present a microscopic theory of the excitonic Stokes and anti-Stokes energy transfer mechanisms between two widely separated unequal quantum wells with a large energy mismatch ({Delta}) at low temperatures (T). Exciton transfer through dipolar coupling, photon-exchange coupling and over-barrier ionization of the excitons through exciton-exciton Auger processes are examined. The energy transfer rate is calculated as a function of T and the center-to-center distance d between the two wells. The rates depend sensitively on T for plane-wave excitons. For located excitons, the rates depend on T only through the T-dependence of the localization radius.

This paper discusses the application of multiple characterization methods to radioactive wastes generated by the Sandia National Laboratories/New Mexico (SNL/NM) Environmental Restoration (ER) Project during the excavation of buried materials at the Classified Waste Landfill (CWLF) and the Radioactive Waste Landfill (RWL). These waste streams include nuclear weapon components and other refuse that are surface contaminated or contain sealed radioactive sources with unknown radioactivity content. Characterization of radioactive constituents in RWL and CWLF waste has been problematic, due primarily to the lack of documented characterization data prior to burial. A second difficulty derives from the limited information that ER project personnel have about weapons component design and testing that was conducted in the early days of the Cold War. To reduce the uncertainties and achieve the best possible waste characterization, the ER Project has applied both project-specific and industry-standard characterization methods that, in combination, serve to define the types and quantities of radionuclide constituents in the waste. The resulting characterization data have been used to develop waste profiles for meeting disposal site waste acceptance criteria.

The presence of damage in the form of microcracks can increase the permeability of salt. In this paper, an analytical formulation of the permeability of damaged rock salt is presented for both initially intact and porous conditions. The analysis shows that permeability is related to the connected (i.e., gas accessible) volumetric strain and porosity according to two different power-laws, which may be summed to give the overall behavior of a porous salt with damage. This relationship was incorporated into a constitutive model, known as the Multimechanism Deformation Coupled Fracture (MDCF) model, which has been formulated to describe the inelastic flow behavior of rock salt due to coupled creep, damage, and healing. The extended model was used to calculate the permeability of rock salt from the Waste Isolation Pilot Plant (WIPP) site under conditions where damage evolved with stress over a time period. Permeability changes resulting from both damage development under deviatoric stresses and damage healing under hydrostatic pressures were considered. The calculated results were compared against experimental data from the literature, which indicated that permeability in damaged intact WIPP salt depends on the magnitude of the gas accessible volumetric strain and not on the total volumetric strain. Consequently, the permeability of WIPP salt is significantly affected by the kinetics of crack closure, but shows little dependence on the kinetics of crack removal by sintering.

This work combines focused ion beam sputtering and ultra-precision machining for microfabrication of metal alloys and polymers. Specifically, micro-end mills are made by Ga ion beam sputtering of a cylindrical tool shank. Using an ion energy of 20 keV, the focused beam defines the tool cutting edges that have submicrometer radii of curvature. We demonstrate 25 μm diameter micromilling tools having 2, 4 and 5 cutting edges. These tools fabricate fine channels, 26-28 microns wide, in 6061 aluminum, brass, and polymethyl methacrylate. Micro-tools are structurally robust and operate for more than 5 hours without fracture.

Hydrogen was ion-implanted into wurtzite-phase GaN, and its transport, bound states, and microstructural effects during annealing up to 980°C were investigated by nuclear-reaction profiling, ion-channeling analysis, transmission electron microscopy, and infrared (IR) vibrational spectroscopy. At implanted concentrations vl at.%, faceted H2 bubbles formed, enabling identification of energetically preferred surfaces, examination of passivating N-H states on these surfaces, and determination of the diffusivity-solubility product of the H. Additionally, the formation and evolution of point and extended defects arising from implantation and bubble formation were characterized. At implanted H concentrations AÜ.1 at.%, bubble formation was not observed, and ion-channeling analysis indicated a defect-related H site located within the [0001] channel. © 1999 Materials Research Society.

We present advances in the application of laser scanning confocal microscopy (LSCM) to image, reconstruct, and characterize statistically the microgeometry of porous geologic and engineering materials. We discuss technical and practical aspects of this imaging technique, including both its advantages and limitations. Confocal imaging can be used to optically section a material, with sub-micron resolution possible in the lateral and axial planes. The resultant volumetric image data, consisting of fluorescence intensities for typically ~50 million voxels in XYZ space, can be used to reconstruct the three-dimensional structure of the two-phase medium. We present several examples of this application, including studying pore geometry in sandstone, characterizing brittle failure processes in low-porosity rock deformed under triaxial loading conditions in the laboratory, and analyzing the microstructure of porous ceramic insulations. We then describe approaches to extract statistical microgeometric descriptions from volumetric image data, and present results derived from confocal volumetric data sets. Finally, we develop the use of confocal image data to automatically generate a three-dimensional mesh for numerical pore-scale flow simulations.

Inertial MEMS sensors such as accelerometers and angular rotation sensing devices continue to improve in performance as advances in design and processing are made. Present state-of-the-art accelerometers have achieved performance levels in the laboratory that are consistent with requirements for successful application in tactical weapon navigation systems. However, sensor performance parameters that are of interest to the designer of inertial navigation systems are frequently not adequately addressed by the MEMS manufacturer. This paper addresses the testing and characterization of a MEMS accelerometer from an inertial navigation perspective. The paper discusses test objectives, data reduction techniques and presents results from the test of a three-axis MEMS accelerometer conducted at Sandia National Laboratories during 1997. The test was structured to achieve visibility and characterization of the accelerometer bias and scale factor stability over time and temperature. Sandia is a multi-program laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under contract DE-AC04-94AL85000.

The solidification behavior and resultant solidification cracking susceptibility of autogenous gas tungsten arc fusion welds in Alloy HR-160 was investigated by Varestraint testing, differential thermal analysis and various microstructural characterization techniques. The alloy exhibited a liquidus temperature of 1387 °C and initiated solidification by a primary L→γ reaction in which Ni, Si and Ti segregated to the interdendritic liquid and cosegregated to the γ dendrite cores. Chromium exhibited no preference for segregation to the solid or liquid phase during solidification. Solidification terminated at ≈1162 °C by a eutectic-type L→[γ+ (Ni,Co)16(Ti,Cr)6Si7] reaction. The (Ni,Co)16(Ti,Cr)6Si7] phase is found to be analogous to the G phase that forms in the Ni-Ti-Si and Co-Ti-Si ternary systems, and similarities are found between the solidification behavior of this commercial multicomponent alloy and the simple Ni-Si and Ni-Ti binary systems. Reasonable agreement is obtained between the calculated and measured volume percent of the [γ+(Ni,Co)16(Ti,Cr)6Si7] eutectic-type constituent with the Scheil equation using experimentally determined k values for Si and Ti from electron microprobe data. The alloy exhibited a very high susceptibility to solidification cracking in the Varestraint test. This is attributed to a large solidification temperature range of 225 °C and the presence of 2-5 vol-% solute-rich interdendritic liquid that preferentially wets the grain boundaries and interdendritic regions.

Wet oxidation of high-Al-content AlGaAs semiconductor layers in vertical cavity surface emitting lasers (VCSELs) has produced devices with record low threshold currents and voltages and with wall-plug efficiencies greater than 50%. Wet oxidation of buried AlGaAs layers has been employed to reduce the problems associated with substrate current leakage in GaAs-oninsulator (GOI) MESFETs. Wet oxidation has also been considered as a route to the long-sought goal of a III-V MIS technology. To continue improving device designs for even higher performance and to establish a truly manufacturable technology based on wet oxidation, the effect of oxidation of a given layer on the properties of the entire device structure must be understood. The oxidation of a given layer can strongly affect the electrical and chemical properties of adjacent layers. Many of these effects are derived from the production of large amounts of elemental As during the oxidation reaction, the resultant generation of point defects, and the diffusion of these defects into adjacent regions. This can modify the chemical and electrical properties of these regions in ways that can impact device design, fabrication, and performance. Current understanding of the problem is discussed here ©1999 Materials Research Society.

The diffuse behavior of penetrants in simple polymer melts was investigated by molecular dynamics simulation. For the case where the polymer melt consisted of pearl-necklace chains, the diffusive behavior of the loose pearl penetrants was seen to be qualitatively different than would be expected in realistic models of polymer melts. In particular, there was little or no "non-Fickian" region; the variation of the diffusion coefficient with the penetrant diameter was what one would expect for diffusion through small molecular liquids; and, finally, the long time tail of the velocity autocorrelation displayed a "-3/2" power law form, also as in the small molecular liquid case. When the chains' backbone motion was further constrained by the introduction of a bond angle potential, the qualitative nature of the penetrant diffusion became more "polymer-like." A non-Fickian region developed; the diffusion coefficient varied more rapidly with penetrant diameter; and the velocity autocorrelation function developed a "-5/2" power law tail. © 1999 American Institute of Physics.

Three-dimensional photonic lattices are engineered 'materials' which are the photonic analogues of semiconductors. These structures were first proposed and demonstrated in the mid-to-late 1980's. However, due to fabrication difficulties, lattices active in the infrared are only just emerging. Wide ranges of structures and fabrication approaches have been investigated. The most promising approach for many potential applications is a diamond-like structure fabricated using silicon microprocessing techniques. This approach has enabled the fabrication of 3-D silicon photonic lattices active in the infrared. The structures display band gaps centered from 12μ down to 1.55μ.

Failure analysis (FA) tools have been applied to analyze failing polysilicon microengines. These devices were stressed to failure under accelerated conditions in both oxidizing and non-oxidizing environments. The dominant failure mechanism of these microengines was identified as wear of rubbing surfaces. This often results in either seized microengines or microengines with broken pin joints. Analysis of these failed polysilicon devices found that wear debris was produced in both oxidizing and non-oxidizing environments. By varying the relative percent humidity (%RH), we observed an increase in the amount of wear debris with decreasing humidity. Plan view imaging using scanning electron microscopy revealed build-up of wear debris on the surface of microengines. Focused ion beam (FIB) cross sections revealed the location and build-up of wear debris within the microengine. Seized regions were also observed in the pin joint area using FIB processing. By using transmission electron microscopy in conjunction with energy dispersive x-ray spectroscopy (EDX) and electron energy loss spectroscopy (EELS), we were able to identify wear debris produced in low (1.8% RH), medium and high (39% RH) humidities.

We have been studying the use of spectral imagery to locate targets in spectrally interfering backgrounds. In making performance estimates for various sensors it has become evident that some calculations are unreliable because of overfitting. Hence, we began a thorough study of the problem of overfitting in multivariate classification. In this paper we present some model based results describing the problem. From the model we know the ideal covariance matrix, the ideal discriminant vector, and the ideal classification performance. We then investigate how experimental conditions such as noise, number of bands, and number of samples cause discrepancies from the ideal results. We also suggest ways to discover and alleviate overfitting.

We discuss an electrostatics problem whose solution must lie in the set script capital L sign of all real n-by-n symmetric matrices with all row sums equal to zero. With respect to the Frobenius norm, we provide an algorithm that finds the member of script capital L sign which is closest to any given n-by-n matrix, and determines the distance between the two. This algorithm makes it practical to find the distances to script capital L sign of finite element approximate solutions of the electrostatics problem, and to reject those which are not sufficiently close. © 1999 Elsevier Science Inc. All rights reserved.

In this paper a hybrid, finite element - boundary element method which can be used to solve for particle advection-diffusion in infinite domains with variable advective fields is presented. In previous work either boundary element, finite element, or difference methods have been used to solve for particle motion in advective-diffusive domains. These methods have a number of limitations. Due to the complexity of computing spatially dependent Green's functions, the boundary element method is limited to domains containing only constant advective fields, and due to their inherent formulation, finite element and finite difference methods are limited to only domains of finite spatial extent. Thus, finite element and finite difference methods are limited to finite space problems for which the boundary element method is not, and the boundary element method is limited to constant advection field problems for which finite element and finite difference methods are not. In this paper it is proposed to split a domain into two subdomains, and for each of these sub domains, apply the appropriate solution method; thereby, producing a method for the total infinite space, variable advective field domain.

The strength and modulus of amorphous diamond, a new material for surface micromachined MEMS and sensors, was tested in uniaxial tension by pulling laterally with a flat tipped diamond in a nanoindenter. Several sample designs were attempted. Of those, only the single layer specimen with a 1 by 2 {micro}m gage cross section and a fixed end rigidly attached to the substrate was successful. Tensile load was calculated by resolving the measured lateral and normal forces into the applied tensile force and frictional losses. Displacement was corrected for machine compliance using the differential stiffness method. Post-mortem examination of the samples was performed to document the failure mode. The load-displacement data from those samples that failed in the gage section was converted to stress-strain curves using carefully measured gage cross section dimensions. Mean fracture strength was found to be 8.5 {+-} 1.4 GPa and the modulus was 831 {+-} 94 GPa. Tensile results are compared to hardness and modulus measurements made using a nanoindenter.

The behavior of MEMS devices is limited by the strength of critical features such as thin ligaments, oxide cuts joining layers, pin joints and hinges. Devices fabricated at Sandia's Microelectronic Development Laboratory have been successfully tested to investigate these features. A series of measurements were performed on samples with gage lengths of 15 to 1000 microns, using conventional and tungsten coated samples as well as samples that include the critical features of standard components in the test section. Specimens have a freely moving pin joint on one end that anchors the sample to the silicon die to allow rotation to reduce effects of bending. Each sample is loaded in uniaxial tension by pulling laterally with a flat tipped diamond in a computer-controlled Nanoindenter. Load is calculated by resolving the measured lateral and normal forces into the applied tensile force and frictional losses. The specimen cross section and gage length dimensions were verified by measuring against a standard in the SEM. Multiple tests can be programmed at one time and performed without operator assistance allowing the collection of significant populations of data.

Sandia National Laboratories is developing polyurethane foam as a chemical grout for lost circulation zones. In past work polyurethane foam was tried with limited success in laboratory tests and GDO sponsored field tests. Goals were that the foam expanded significantly and harden to a drillable firmness quickly. Since that earlier work there have been improvements in polyurethane chemistry and the causes of the failures of previous tests have been identified. Recent success in applying pure solution grouts (proper classification of polyurethane - Naudts) in boreholes encourages reevaluating its use to control lost circulation. These successes include conformance control in the oil patch (e.g. Ng) and dam remediation projects. In civil engineering, polyurethane is becoming the material of choice for sealing boreholes with large voids and high inflows, conditions associated with the worst lost circulation problems. Demonstration of a delivery mechanism is yet to be done in a geothermal borehole.

Abstract not provided.

A design of experiments (DoE) was performed at Ceramtec to improve the yield of a cermet part known as the feedthru insulator. The factors chosen to be varied in this DoE were syringe orifice size, fill condition, solvent, and surfactant. These factors were chosen because of their anticipated effect on the cermet slurry and its consequences to the feedthru insulator in succeeding fabrication operations. Response variables to the DoE were chosen to be indirect indicators of production yield for the feedthru insulator. The solvent amount used to mix the cermet slurry had the greatest overall effect on the response variables. Based upon this DoE, there is the potential to improve the yield not only for the feedthru insulator but for other cermet parts as well. This report thoroughly documents the DoE and contains additional information regarding the feedthru insulator.

For a wide variety of scientific and engineering problems the desired solution corresponds to an optimal set of objective function parameters, where the objective function measures a solution's quality. The main goal of the LDRD ''Global Optimization for Engineering Science Problems'' was the development of new robust and efficient optimization algorithms that can be used to find globally optimal solutions to complex optimization problems. This SAND report summarizes the technical accomplishments of this LDRD, discusses lessons learned and describes open research issues.

This report presents a specification for the Portals 3.0 message passing interface. Portals 3.0 is intended to allow scalable, high-performance network communication between nodes of a parallel computing system. Specifically, it is designed to support a parallel computing platform composed of clusters of commodity workstations connected by a commodity system area network fabric. In addition, Portals 3.0 is well suited to massively parallel processing and embedded systems. Portals 3.0 represents an adoption of the data movement layer developed for massively parallel processing platforms, such as the 4500-node Intel TeraFLOPS machine.

An algorithm is developed to control a pulsed {Delta}V thruster on a small satellite to allow it to fly in formation with a host satellite undergoing time dependent atmospheric drag deceleration. The algorithm uses four short thrusts per orbit to correct for differences in the average radii of the satellites due to differences in drag and one thrust to symmetrize the orbits. The radial difference between the orbits is the only input to the algorithm. The algorithm automatically stabilizes the orbits after ejection and includes provisions to allow azimuthal positional changes by modifying the drag compensation pulses. The algorithm gives radial and azimuthal deadbands of 50 cm and 3 m for a radial measurement accuracy of {+-} 5 cm and {+-} 60% period variation in the drag coefficient of the host. Approaches to further reduce the deadbands are described. The methodology of establishing a stable orbit after ejection is illustrated in an appendix. The results show the optimum ejection angle to minimize stabilization thrust is upward at 86{sup o} from the orbital velocity. At this angle the stabilization velocity that must be supplied by the thruster is half the ejection velocity. An ejection velocity of 0.02 m/sat 86{sup o} gives an azimuthal separation after ejection and orbit stabilization of 187 m. A description of liquid based gas thrusters suitable for the satellite control is included in an appendix.

This report is a summary of the work completed for an LDRD project. The objective of the project was to develop a solid freeform fabrication technique for ceramics and composites from fine particle slurries. The work was successful and resulted in the demonstration of a manufacturing technique called robocasting. Some ceramic components may pow be fabricated without the use of molds or tooling by dispensing colloidal suspensions through an orifice and stacking two-dimensional layers into three-dimensional shapes. Any conceivable two-dimensional pattern may be ''written'' layer by layer into a three-dimensional shape. Development of the robocasting technique required the materials expertise for fabrication and theological control of very highly concentrated fine particle slurries, and development of robotics for process control and optimization. Several ceramic materials have been manufactured and characterized. Development of techniques for robocasting multiple materials simultaneously have also been developed to build parts with unique structures or graded compositions.

The U.S. Department of Energy (DOE) has been cooperating with the Republic of Kazakhstanin Combined Threat Reduction (CTR) activities at the BN350 reactor located at the Mangyshlak Atomic Energy Complex (MAEC) in the city of Aktau, Kazakhstan since 1994. DOE contract personnel have been stationed at this facility for the last two years and DOE representatives regularly visit this location to oversee the continuing cooperative activities. Continued future cooperation is planned. A Russian news report in September 1999 indicated that 75 metric tons of organic peroxides stored at the Plastics Plant near Aktau were in danger of exploding and killing or injuring nearby residents. To ensure the health and safety of the personnel at the BN350 site, the DOE conducted a study to investigate the potential danger to the BN350 site posed by these materials at the Plastics Plant. The study conclusion was that while the organic peroxides do have hazards associated with them, the BN350 site is a safe distance from the Plastics Plant. Further, because the Plastics Plant and MAEC have cooperative fire-fighting agreements,and the Plastics Plant had exhausted its reserve of fire-fighting foam, there was the possibility of the Plastics Plant depleting the store of fire-fighting foam at the BN350 site. Subsequently, the DOE decided to purchase fire-fighting foam for the Plastics Plant to ensure the availability of free-fighting foam at the BN350 site.

Analysis programs have been having to deal with more and more complex objects as the capability to model fine detail increases. This can make them unacceptably slow. This project attempts to find heuristics for removing features from models in an automatic fashion in order to reduce polygon count. The approach is not one of theoretical completeness but rather one of trying to achieve useful results with scattered practical ideas. By removing a few simple things such as screw holes, slots, chambers, and fillets, large gains can be realized. Results varied but a reduction in the number of polygons by a factor of 10 is not unusual.

Abstract not provided.

Currently the most common method to determine the contents of a package suspected of containing an explosive device is to use transmission radiography. This technique requires that an x-ray source and film be placed on opposite sides of the package. This poses a problem if the package is placed so that only one side is accessible, such as against a wall. There is also a threat to personnel and property since explosive devices may be booby trapped. The authors have developed a method to x-ray a package using backscattered x-rays based on similar work for landmine detection. This procedure eliminates the use of film behind the target. All of the detection is done from the same side as the source. Backscatter experiments at Sandia National Laboratories have been conducted on mock bombs in packages. They are able to readily identify the bomb components. The images that are obtained in this procedure are done in real time and the image is displayed on a computer screen. Preliminary experiments have also imaged objects within or behind a wall. They are currently using a scanning x-ray source and scintillating plastic detectors. It can take several hours to image a briefcase size object. This time could be reduced if better x-ray detection methods could be used. They have looked at using pinhole photography and CCD cameras to reduce this time.

This report summarizes general guidelines for the development of Verification and Validation (V and V) plans for ASCI code projects at Sandia National Laboratories. The main content categories recommended by these guidelines for explicit treatment in Sandia V and V plans are (1) stockpile drivers influencing the code development project (2) the key phenomena to be modeled by the individual code; (3) software verification strategy and test plan; and (4) code validation strategy and test plans. The authors of this document anticipate that the needed content of the V and V plans for the Sandia ASCI codes will evolve as time passes. These needs will be reflected by future versions of this document.

This paper describes formulations of the Evaluation Planning Module that have been developed since its inception. This module is one of the core algorithms in the Pantex Process Model, a computerized model to support production planning in a complex manufacturing system at the Pantex Plant, a US Department of Energy facility. Pantex is responsible for three major DOE programs -- nuclear weapons disposal, stockpile evaluation, and stockpile maintenance -- using shared facilities, technicians, and equipment. The model reflects the interactions of scheduling constraints, material flow constraints, and the availability of required technicians and facilities.

The Auxiliary Hot Cell Facility (AHCF) at Sandia National Laboratories, New Mexico (SNL/NM) will be a Hazard Category 3 nuclear facility used to characterize, treat, and repackage radioactive and mixed material and waste for reuse, recycling, or ultimate disposal. A significant upgrade to a previous facility, the Temporary Hot Cell, will be implemented to perform this mission. The following major features will be added: a permanent shield wall; eight floor silos; new roof portals in the hot-cell roof; an upgraded ventilation system; and upgraded hot-cell jib crane; and video cameras to record operations and facilitate remote-handled operations. No safety-class systems, structures, and components will be present in the AHCF. There will be five safety-significant SSCs: hot cell structure, permanent shield wall, shield plugs, ventilation system, and HEPA filters. The type and quantity of radionuclides that could be located in the AHCF are defined primarily by SNL/NM's legacy materials, which include radioactive, transuranic, and mixed waste. The risk to the public or the environment presented by the AHCF is minor due to the inventory limitations of the Hazard Category 3 classification. Potential doses at the exclusion boundary are well below the evaluation guidelines of 25 rem. Potential for worker exposure is limited by the passive design features incorporated in the AHCF and by SNL's radiation protection program. There is no potential for exposure of the public to chemical hazards above the Emergency Response Protection Guidelines Level 2.

The importance of turbulent fluctuations in temperature and species concentration in thermal radiation transport modeling for combustion applications is well accepted by the radiation transport and combustion communities. A number of experimental and theoretical studies over the last twenty years have shown that fluctuations in the temperature and species concentrations may increase the effective emittance of a turbulent flame by as much as 50% to 300% over the value that would be expected from the mean temperatures and concentrations. With the possibility of such a large effect on the principal mode of heat transfer from a fire, it is extremely important for fire modeling efforts that turbulence radiation interaction be well characterized and possible modeling approaches understood. Toward this end, this report seeks to accomplish three goals. First, the principal turbulence radiation interaction closure terms are defined. Second, an order of magnitude analysis is performed to understand the relative importance of the various closure terms. Finally, the state of the art in turbulence radiation interaction closure modeling is reviewed. Hydrocarbon pool fire applications are of particular interest in this report and this is the perspective from which this review proceeds. Experimental and theoretical analysis suggests that, for this type of heavily sooting flame, the turbulent radiation interaction effect is dominated by the nonlinear dependence of the Planck function on the temperature. Additional effects due to the correlation between turbulent fluctuations in the absorptivity and temperature may be small relative to the Planck function effect for heavily sooting flames. This observation is drawn from a number of experimental and theoretical discussions. Nevertheless, additional analysis and data is needed to validate this observation for heavily sooting buoyancy dominated plumes.

Abstract not provided.

Designing and developing the 1.7 to 2.1-MJ Power Conditioning System (PCS), that will power the flashlamps of the main and power amplifiers for the National Ignition Facility (NIF) lasers, is one of several responsibilities assumed by Sandia National Labs (SNL) in support of the NIF Project. Maxwell Physics International has been a partner in this process. The NIF is currently being constructed at Lawrence Livermore National Labs (LLNL). The test facility that has evolved over the last three years to satisfy the project requirements is called FANTM, for the First Article NIF Test Module. It was built at SNL and operated for about 17,000 shots to demonstrate component performance expectations over the lifetime of NIF. A few modules similar to the one shown in Fig. 1 will be used initially in the amplifier test phase of the project. The final full NIF system will require at least 192 of them in four capacitor bays. This paper briefly summarizes the final design of the FANTM facility and compares its performance with the predictions of circuit simulations for both normal operation and fault-mode response. Applying both the measured and modeled power pulse waveforms as input to a physics-based, semi-empirical amplifier gain code indicates that the 20-capacitor PCS can satisfy the NIF requirement for an average gain coefficient of 5.00 %/cm and can exceed 5.20 %/cm with 24 capacitors.

Embedded resistor circuits have been generated with the use of a Micropen system Ag conductor paste (DuPont 6142D), a new experimental resistor ink from DuPont (E84005-140), and Low Temperature Co-fired Ceramic (LTCC) green tape (DuPont A951). Sample circuits were processed under varying peak temperature ranges (835 C-875 C) and peak soak times (10 min-720 min). Resistors were characterized by SEM, TEM, EDS, and high-temperature XRD. Results indicate that devitrification of resistor glass phase to Celcian, Hexacelcian, and a Zinc-silicate phase occurred in the firing ranges used (835-875 C) but kinetics of divitrification vary substantially over this temperature range. The resistor material appears structurally and chemically compatible with the LTCC. RuO{sub 2} grains do not significantly react with the devitrifying matrix material during processing. RuO{sub 2} grains coarsen significantly with extended time and temperature and the electrical properties appear to be strongly affected by the change in RuO{sub 2} grain size.

Design Tools use a Web-based Java interface to guide a product designer through the design-to-analysis cycle for a specific, well-constrained design problem. When these Design Tools are mapped onto a Web-based distributed architecture for high-performance computing, the result is a family of Distributed Design Tools (DDTs). The software components that enable this mapping consist of a Task Sequencer, a generic Script Execution Service, and the storage of both data and metadata in an active, object-oriented database called the Product Database Operator (PDO). The benefits of DDTs include improved security, reliability, scalability (in both problem size and computing hardware), robustness, and reusability. In addition, access to the PDO unlocks its wide range of services for distributed components, such as lookup and launch capability, persistent shared memory for communication between cooperating services, state management, event notification, and archival of design-to-analysis session data.

The addition of up to approximately 16 mole% Cs{sub 2}O to vitreous P{sub 2}O{sub 5} reduces the glass transition temperature (T{sub g}) by 150 K, whereas further additions up to 50 mole% produce little additional change in T{sub g}. {sup 31}P magic angle spinning nuclear magnetic resonance spectra indicate that the phosphate network is progressively dipolymerized over the entire range of compositions. The property trend is explained by a transition in the Cs{sup +} coordination environment, from isolated Cs-polyhedra below {approximately}16 mole% Cs{sub 2}O to a corner-sharing Cs-polyhedral sub-structure in the glasses with greater Cs{sub 2}O contents. This modifier transition does not occur in Al-phosphate glasses. {sup 27}Al MAS NMR spectra indicate that the average Al coordination number decreases with increasing Al{sub 2}O{sub 3} content to avoid the formation of Al-O-Al bonds in these binary phosphate glasses.

The Sandia National Laboratories/New Mexico (SNL/NM)Environmental Restoration Project is currently excavating the Classified Waste Landfill in Technical Area II, a disposal area for weapon components for approximately 40 years until it closed in 1987. Many different types of classified parts were disposed in unlined trenches and pits throughout the course of the landfill's history. A percentage of the parts contain explosives and/or radioactive components or contamination. The excavation has progressed backward chronologically from the last trenches filled through to the earlier pits. Excavation commenced in March 1998, and approximately 75 percent of the site (as defined by geophysical anomalies) has been completed as of November 1999. The material excavated consists primarily of classified weapon assemblies and related components, so disposition must include demilitarization and sanitization. This has resulted in substantial waste minimization and cost avoidance for the project as upwards of 90 percent of the classified materials are being demilitarized and recycled. The project is using field screening and lab analysis in conjunction with preliminary and in-process risk assessments to characterize soil and make waste determinations in a timely a fashion as possible. Challenges in waste management have prompted the adoption of innovative solutions. The hand-picked crew (both management and field staff) and the ability to quickly adapt to changing conditions has ensured the success of the project. The current schedule is to complete excavation in July 2000, with follow-on verification sampling, demilitarization, and waste management activities following.

Hydrogen atom-hydrogen atom scattering is a prototype for many of the fundamental principles of atomic collisions. In this paper we present an approximation to the H + H system for scattering in the intermediate energy regime of 1-100 keV. The approximation ignores electron exchange and two-electron excitation by assuming that one of the atoms is frozen in the 1s state. We allow for the evolution of the active electron by numerically solving the 3D Schrodinger equation. This approximation is by nature most appropriate for higher-energy collisions. The results capture many features of the problem and are in harmony with recent theoretical studies. Excitation and ionization cross sections are computed and compared with other theory and experiment. New insight into the mechanism of excitation and ionization is inferred from the solutions.

AR coating design for multi-junction solar cells can be more challenging than in the single junction case. Reasons for this are discussed. Analytical expressions used to optimize AR coatings for single junction solar cells are extended for use in monolithic, series interconnected multi-junction solar cell AR coating design. The result is an analytical expression which relates the solar cell performance (through J{sub SC}) directly to the AR coating design through the device reflectance. It is also illustrated how AR coating design can be used to provide an additional degree of freedom for current matching multi-junction devices.

We report on a new method to make nanostructures, in this case selenium nanowires, in aqueous solution at room temperature. We used the protein cytochrome c{sub 3} to reduce selenate (SeO{sub 4}{sup 2{minus}}) to selenium (Se{sup 0}). Cytochrome c{sub 3} is known for its ability to catalyze reduction of metals including U{sup VI} {yields} U{sup IV}, Cr{sup VI} {yields} Cr{sup III}, Mo{sup VI} {yields} Mo{sup IV}, Cu{sup II} {yields} Cu{sup 0}, Pb{sup II} {yields} Pb{sup 0}, Hg{sup II} {yields} Hg{sup 0}. Nanoparticles of Se{sup 0} precipitated from an aqueous solution at room temperature, followed by spontaneous self-assembling into nanowires. Cytochrome c{sub 3} was extracted from the sulfate-reducing bacteria Desulfovibrio vulgaris (strain Holdenborough) and isolated by the procedure of DerVartanian and Legall.

Ceramics represent a unique class of materials that are distinguished from common metals and plastics by their: (1) high hardness, stiffness, and good wear properties (i.e., abrasion resistance); (2) ability to withstand high temperatures (i.e., refractoriness); (3) chemical durability; and (4) electrical properties that allow them to be electrical insulators, semiconductors, or ionic conductors. Ceramics can be broken down into two general categories, traditional and advanced ceramics. Traditional ceramics include common household products such as clay pots, tiles, pipe, and bricks, porcelain china, sinks, and electrical insulators, and thermally insulating refractory bricks for ovens and fireplaces. Advanced ceramics, also referred to as ''high-tech'' ceramics, include products such as spark plug bodies, piston rings, catalyst supports, and water pump seals for automobiles, thermally insulating tiles for the space shuttle, sodium vapor lamp tubes in streetlights, and the capacitors, resistors, transducers, and varistors in the solid-state electronics we use daily. The major differences between traditional and advanced ceramics are in the processing tolerances and cost. Traditional ceramics are manufactured with inexpensive raw materials, are relatively tolerant of minor process deviations, and are relatively inexpensive. Advanced ceramics are typically made with more refined raw materials and processing to optimize a given property or combination of properties (e.g., mechanical, electrical, dielectric, optical, thermal, physical, and/or magnetic) for a given application. Advanced ceramics generally have improved performance and reliability over traditional ceramics, but are typically more expensive. Additionally, advanced ceramics are typically more sensitive to the chemical and physical defects present in the starting raw materials, or those that are introduced during manufacturing.

A technique has been developed to selectively induce metastable pitting while preventing the transition to stable pit growth. The current-limited imposed-potential (CLIP) technique limits available cathodic current to an initiated site using a resistor in series with the working electrode to form a voltage divider. Potentiodynamic CLIP testing yields a distribution of breakdown potentials from a single experiment. Potentiostatic CLIP testing yields induction time data, which can be used as input to a calculation of germination rate. Initial data indicate that a one-to-one correlation exists between electrochemical transients and observed pitting sites. The CLIP technique provides a consistent means of gathering quantitative potential and current transients associated with localized oxide breakdown.

The Chemical Waste Landfill (CWL) at Sandia National Laboratories/New Mexico (SNL/NM) is a 1.9-acre disposal site that was used for the disposal of chemical wastes generated by many of SNL/NM research laboratories from 1962 until 1985. These laboratories were primarily involved in the design, research and development of non-nuclear components of nuclear weapons and the waste generated by these labs included small quantities of a wide assortment of chemical products. A Resource Conservation and Recovery Act (RCRA) Closure Plan for the Chemical Waste Landfill was approved by the New Mexico Environment Department (NMED) in 1992. Subsequent site characterization activities identified the presence of significant amounts of chromium in the soil as far as 80 feet below ground surface (fbgs) and the delineation of a solvent plume in the vadose zone that extends to groundwater approximately 500 fbgs. Trichloroethylene (TCE) was detected in some groundwater samples at concentrations slightly above the drinking water limit of 5 parts per billion. In 1997 an active vapor extraction system reduced the size of the TCE vapor plume and for the last six quarterly sampling events groundwater samples have not detected TCE above the drinking water standard. A source term removal, being conducted as a Voluntary Corrective Measure (VCM), began in September 1998 and is expected to take up to two years. Four distinct disposal areas were identified from historical data and the contents of disposal pits and trenches in these areas, in addition to much of the highly contaminated soil surrounding the disposal cells, are currently being excavated. Buried waste and debris are expected to extend to a depth of 12 to 15 fbgs. Excavation will focus on the removal of buried debris and contaminated soil in a sequential, area by area manner and will proceed to whatever depth is required in order to remove all pit contents. Up to 50,000 cubic yards of soil and debris will be removed and managed during the excavation of the CWL. As part of the excavation process, soil is being separated from the buried debris using a 2-inch mechanical screen. After separation from the soil, debris items are further-segregated by matrix into the following categories: wood, scrap metal, concrete/aggregates, resins, compatible debris, intact chemical containers, radioactive and mixed waste, and high hazard items. One of the greatest sources of hazards throughout the excavation process is the removal of numerous intact chemical containers with unknown contents. A large portion of the excavated soil is contaminated with metals and/or solvents, Polychlorinated biphenyls (PCBs) are also known to be present. Most of the contaminated soils being excavated will be taken to the nearby Corrective Action Management Unit (CAMU) for treatment and management while a majority of the containers will be taken to the Hazardous Waste Management Facility or the Radioactive and Mixed Waste Management Facility for proper treatment and/or disposal at permitted offsite facilities.

A cryogenic, {beta}-layered NIF ignition capsule with a beryllium ablator that employs a BeO dopant (2% O) for opacity control is described. The design has an optimized yield of 12 MJ and uses a ''reduced drive'' hohlraum temperature pulse shape that peaks at {approx}250 eV. Shock timing sensitivity calculations have been performed for this capsule design. Individual uncertainties of (1) {approx}200 ps in the timing of the ''footpulse; (2) {approx}5% in the x-ray flux of the foot pulse and first step; (3) {approx}10% in the ablator EOS; or (4) {approx} 5 {micro}m in the DT ice layer thickness each have a significant impact on thermonuclear yield. Combined uncertainties have greater impact than isolated, individual issues. For example, a combination of uncertainties of: 200 ps in the foot + 2 eV in the foot + 5 pm in the DT thickness results in a calculation that produces only {approx}1% of the original design yield. A second, more speculative, capsule concept utilizing a liquid DT ablator is also discussed. This design produces a 5 MJ yield in a 250 eV peak drive calculation.

Pulsed power is a robust and inexpensive technology for obtaining high powers. Considerable progress has been made on developing light ion beams as a means of transporting this power to inertial fusion capsules. However, further progress is hampered by the lack of an adequate ion source. Alternatively, z-pinches can efficiently convert pulsed power into thermal radiation, which can be used to drive an inertial fusion capsule. However, a z-pinch driven fusion explosion will destroy a portion of the transmission line that delivers the electrical power to the z-pinch. They investigate several options for providing standoff for z-pinch driven fusion. Recyclable Transmission Lines (RTLs) appear to be the most promising approach.

This paper reports on significant advances in electrothermal bent beam actuators. Designs for long throw linear and rotary actuators are described. Silicon p++ devices showed 20--30 {mu}m displacements with 150 {micro}N loads at actuation levels of 6--8 V, and 250--300 mW. An electroplated version provided 15 {mu}m displacements at 0.8 V and 450 mW. Inchworm type devices are reported that had linear displacements of 100 {micro}m with 200 {micro}N loads. Refinements in the modeling to account for non-linear thermal expansion coefficients and buckling are also reported.

Controlled impact methodology has been used on a powdergun to obtain dynamic behavior properties of Tributyl Phosphate (TBP). A novel test methodology is used to provide extremely accurate equation of state data of the liquid. A thin aluminum plate used for confining the liquid also serves as a diagnostic to provide reshock states and subsequent release adiabats from the reshocked state. Polar polymer, polyvinylidene fluoride (PVDF) gauges and velocity interferometer system for any reflector (VISAR) provided redundant and precise data of temporal resolution to five nanoseconds and shock velocity measurements of better than 1%. The design and test methodologies are presented in this paper.

We report a novel sol-gel dip-coating process to form dual-layer microporous silica membranes with improved membrane performance and reproducibility. First, we deposit a surfactant-templated silica (STS) intermediate layer on top of a commercial {gamma}-alumina support both to improve its ''surface finish'' and to prevent a subsequently deposited microporous overlayer from penetrating into the support. Second, membranes are processed under clean room conditions to avoid dust contamination and, third, membranes are vacuum-calcined to promote further pore shrinkage and impart surface hydrophobicity. The resulting asymmetric membrane exhibits a gradual change in pore diameter from 50{angstrom} ({gamma}-alumina support layer) to 10-12{angstrom} (STS intermediate layer), and then to 3-4{angstrom} (30nm thick, ultramicroporous silica top-layer). Compared to a single-layer process using only the microporous overlayer, the dual-layer process improves both flux and selectivity. For the industrially important problem of natural gas purification, the combined CO{sub 2} flux [(3{approx} 0.5) x 10{sup {minus}4} cm{sup 3}(STP)/(s{center_dot}cm{sup 2}{center_dot}cm-Hg)] and CO{sub 2}/CH{sub 4} separation factors [200{approx}600] are superior to all previously reported values for separation of a 50/50 (v/v) CO{sub 2}/CH{sub 4} gas mixture. In addition, the membrane selectively separated hydrogen from a simulated reformate from partial oxidation of methanol as evidenced by a high concentration of hydrogen recovery.

{sup 13}C-enriched polyethylene was subjected to {gamma}-irradiation in the presence of air at 25 and 80 C for total doses ranging from 71 to 355 kGy. Significant quantities of hydroperoxides were detected in the 25 C irradiated sample by {sup 13}C magic angle spinning NMR spectroscopy. This method of detection was performed on the solid polymer and required no chemical derivatization or addition of solvent. The chemical stability and subsequent products of the hydroperoxide species were studied by annealing the irradiated samples in air at temperatures ranging from 22 to 110 C. A time-temperature superposition analysis provided an activation energy of 108 kJ/mol for the hydroperoxide decomposition process. The primary products of hydroperoxide decomposition were ketones and secondary alcohols with lesser amounts of acids and esters. EPR measurements suggest that the reactive hydroperoxide species reside in the amorphous phase of polyethylene, consistent with degradation occurring in the amorphous phase.

Structure within thin epoxy films is investigated by neutron reflectivity (NR) as a function of resin/cross-linker composition and cure temperature. Variation in the cross-link density normal to the substrate surface is examined by swelling the films with the good solvent d-nitrobenzene (d-NB). The principal observation is a large excess of d-NB near the air surface. This is not a wetting layer, but rather indicates a lower cross-link density in the near-surface region. This effect is due to preferential segregation of the cross-linker to the air surface, driven by the lower surface tension of the cross-linker relative to the epoxide oligomers. The magnitude of the effect is a function of composition and cure temperature. Exclusion of d-NB from the region immediately adjacent to the substrate surface is also observed, possibly indicating a tightly bound layer of epoxy. Regarding swelling in the bulk of the films, the behavior is nonsymmetric with departure from the stoichiometric ratio. The films deficient in curing agent show greater equilibrium swelling and faster swelling kinetics than the films with an excess of curing agent.

Waveguiding by total internal reflection is demonstrated within AlxGa1-xAs semiconductor heterostructures which have been fully oxidized in water vapor at ∼490°C. Refractive index, mode propagation constant, propagation loss (≤ 3 cm-1) at λ0 = 1.3 and 1.55 μm, secondary ion mass spectrometry depth profile, and Fourier transform infrared transmission spectra measurements are presented to characterize a multimode single-heterostructure oxide waveguide. An index contrast of Δn = 0.06 is observed between oxidized x = 0.4 and x = 0.8 AlxGa1-xAs oxide layers. Absorption loss at 1.55 μm is observed due to OH groups. Near-field images are presented showing waveguiding in a single-mode oxide double heterostructure. © 1999 American Institute of Physics.

The concept of building extremely small satellites which, either independently or as a collective, can perform missions which are comparable to their much larger cousins, has fascinated scientists and engineers for several years now. In addition to the now commonplace microelectronic integrated circuits, the more recent advent of technologies such as photonic integrated circuits (PIC's) and micro-electromechanical systems (MEMS) have placed such a goal within their grasp. Key to the acceptance of this technology will be the ability to manufacture these very small satellites in quantity without sacrificing their performance or versatility. In support of its nuclear treaty verification, proliferation monitoring and other remote sensing missions, Sandia National laboratories has had a 35-year history of providing highly capable systems, densely packaged for unintrusive piggyback missions on government satellites. As monitoring requirements have become more challenging and remote sensing technologies become more sophisticated, packaging greater capability into these systems has become a requirement. Likewise, dwindling budgets are pushing satellite programs toward smaller and smaller platforms, reinforcing the need for smaller, cheaper satellite systems. In the next step of its miniaturization plan, Sandia has begun development of technologies for a highly integrated miniature satellite. The focus of this development is to achieve nanosat or smaller dimensions while maintaining significant capability utilizing semiconductor wafer-level integration and, at the same time promoting affordability through modular generic construction.

A technique has been developed for producing calibrated metal hydride films for use in the measurement of high-energy (5--15 MeV) particle reaction cross sections for hydrogen and helium isotopes on hydrogen isotopes. Absolute concentrations of various hydrogen isotopes in the film is expected to be determined to better than {+-}2% leading to the capacity of accurately measuring various reaction cross sections. Hydrogen isotope concentrations from near 100% to 5% can be made accurately and reproducibly. This is accomplished with the use of high accuracy pressure measurements coupled with high accuracy mass spectrometric measurements of each constituent partial pressure of the gas mixture during loading of the metal occluder films. Various techniques are used to verify the amount of metal present as well as the amount of hydrogen isotopes; high energy ion scattering analysis, PV measurements before, during and after loading, and thermal desorption/mass spectrometry measurements. The most appropriate metal to use for the occluder film appears to be titanium but other occluder metals are also being considered. Calibrated gas ratio samples, previously prepared, are used for the loading gas. Deviations from this calibrated gas ratio are measured using mass spectrometry during and after the loading process thereby determining the loading of the various hydrogen isotopes. These techniques are discussed and pertinent issues presented.

Many aerospace structures must survive severe high frequency, hypersonic, random vibration during their flights. The random vibrations are generated by the turbulent boundary layer developed along the exterior of the structures during flight. These environments have not been simulated very well in the past using a fixed-based, single exciter input with an upper frequency range of 2 kHz. This study investigates the possibility of using acoustic ardor independently controlled multiple exciters to more accurately simulate hypersonic flight vibration. The test configuration, equipment, and methodology are described. Comparisons with actual flight measurements and previous single exciter simulations are also presented.

The optical gain spectra for compressive-strained and lattice-matched GaInNAs/GaAs quantum wells are computed using a microscopic laser theory. From these spectra, the peak gain and carrier radiative decay rate as functions of carrier density are determined. These dependences allow the study of lasing threshold current density for different GaInNAs/GaAs laser structures. © 1999 American Institute of Physics.

This study examines adhesion between silane-coated micromachined surfaces that are exposed to humid conditions. Our quantitative values for interfacial adhesion energies are determined from an in-situ optical measurement of deformations in partly-adhered cantilever beams. We coated micromachined cantilevers with either ODTS (C{sub 18}H{sub 37}SiCl{sub 3}) or FDTS (C{sub 8}F{sub 17}C{sub 2}H{sub 4}SiCl{sub 3}) with the objective of creating hydrophobic surfaces whose adhesion would be independent of humidity. In both cases, the adhesion energy is significantly lower than for uncoated, hydrophilic surfaces. For relative humidities (RH) less than 95% (ODTS) and 80% (FDTS) the adhesion energy was extremely low and constant. In fact, ODTS-coated beams exposed to saturated humidity conditions and long (48 hour) exposures showed only a factor of two increase in adhesion energy. Surprisingly, FDTS coated beams, which initially have a higher contact angle (115{degree}) with water than do ODTS coated beams (112{degree}), proved to be much more sensitive to humidity. The FDTS coated surfaces showed a factor of one hundred increase in adhesion energy after a seven hour exposure to 90% RH. Atomic force microscopy revealed agglomerated coating material after exposed to high RH, suggesting a redistribution of the monolayer film. This agglomeration was more prominent for FDTS than ODTS. These findings suggest a new mechanism for uptake of moisture under high humidity conditions. At high humidities, the silane coatings can reconfigure from a surface to a bulk phase leaving behind locally hydrophilic sites which increase the average measured adhesion energy. In order for the adhesion increase to be observed, a significant fraction of the monolayer must be converted from the surface to the bulk phase.

The connection is made between the normal-coordinate structural decomposition (NSD) and the vibronic molecular states and spectra of porphyrins. NSD is a procedure that provides a description of the distortion of a porphyrin from a D{sub 4h} symmetric reference structure in terms of equivalent displacements along the normal coordinates. Expressions for the optical absorption spectra with vibrational structure are developed with these NSD-determined deformations as parameters, and the expressions are applied to the UV-visible absorption spectra porphyrins.

We show that for general input sets linear feedback shift registers (LFSRS) do not provide compression comparable to current, standard algorithms, at least not on the current, standard input files. Rather, LFSRS provide performance on a par with simple, run-length encoding schemes. We exercised three different ways of using LFSRS on the Canterbury, Canterbury Oarge set, the Calgory Corpora, and on three, large graphics files of our own.

Wind-energy researchers at Sandia National Laboratories have developed a new, light-weight, modular data acquisition system capable of acquiring long-term, continuous, multi-channel time-series data from operating wind-turbines. New hardware features have been added to this system to make it more flexible and permit programming via telemetry. User-friendly Windows-based software has been developed for programming the hardware and acquiring, storing, analyzing, and archiving the data. This paper briefly reviews the major components of the system, summarizes the recent hardware enhancements and operating experiences, and discusses the features and capabilities of the software programs that have been developed.

Typical laboratory testing of Polycrystalline Diamond Compact (PDC) bits is performed on relatively rigid setups. Even in hard rock, PDC bits exhibit reasonable life using such testing schemes. Unfortunately, field experience indicates otherwise. In this paper, the authors show that introducing compliance in testing setups provides better simulation of actual field conditions. Using such a scheme, they show that chatter can be severe even in softer rock, such as sandstone, and very destructive to the cutters in hard rock, such as sierra white granite.

Al{sub 2}Cu thin films ({approximately}382 nm) are fabricated by melting and resolidifying Al/Cu bilayers in the presence of a {approximately}3 nm Al{sub 2}O{sub 3} passivating layer. X-ray Photoelectron Spectroscopy (XPS) measures a 1.0 eV shift of the Cu2p{sub 3/2} peak and a 1.6 eV shift of the valence band relative to metallic Cu upon Al{sub 2}Cu formation. Scanning Electron Microscopy (SEM) and Electron Back-Scattered Diffraction (EBSD) show that the Al{sub 2}Cu film is composed of 30--70 {mu}m wide and 10--25 mm long cellular grains with (110) orientation. The atomic composition of the film as estimated by Energy Dispersive Spectroscopy (EDS) is 67{+-}2% Al and 33{+-}2% Cu. XPS scans of Al{sub 2}O{sub 3}/Al{sub 2}Cu taken before and after air exposure indicate that the upper Al{sub 2}Cu layers undergo further oxidation to Al{sub 2}O{sub 3} even in the presence of {approximately}5 nm Al{sub 2}O{sub 3}. The majority of Cu produced from oxidation is believed to migrate below the Al{sub 2}O{sub 3} layers, based upon the lack of evidence for metallic Cu in the XPS scans. In contrast to Al/Cu passivated with Al{sub 2}O{sub 3}, melting/resolidifying the Al/Cu bilayer without Al{sub 2}O{sub 3} results in phase-segregated dendritic film growth.

On rare occasions, the coining of a new term brings new ideas to a field by virtue of a shift in viewpoint. A recent example is complexity, which collected together, from a core of deep results in mathematics and hydrodynamics, a clan of fields whose kinship had been revealed by the new term itself. More often such appellations merely follow fashionable trends. So it took courage on the part of the founders of SUPERMAT to promote their vision. Marcel Ausloos (Universite de Liege, Belgium) and Gilbert Vacquier (Universite de Marseille, France) have shown us a way to resonate as a new chord in materials science. As the first conference on supermaterials, SUPERMAT and its companion SMART 99 have begun to reveal new branches of research from the established pathways explored in superconductivity. At the conclusion of SUPERMAT in Giens, France, the participants were as energized by the exciting science that had been covered during the week as they were impressed by the French food, wine, scenery and hospitality. If the definition of a supermaterial is not obvious now-after the conference-it was certainly not obvious before it. Nevertheless, the conferees were drawn inexorably together by the conference theme. Perhaps it is not appropriate to try to understand this self organization, which surely is even more complex than the self organization of electrons in a high temperature superconductor, the theory for which still eludes us after 13 years! A clue to the working definition of a supermaterial can be derived empirically from the topics that were discussed at SUPERMAT and SMART 99. In addition to superconductors, they heard about magnetic effects of many kinds, including giant and even colossal ones that presumably trump super ones, organic conductors, photoconductors, and even four-hundred-year-old Japanese ceramics. Topics discussed were synthesis, processing, characterization and theory, and applications.

Typical Laboratory testing of Polycrystalline Diamond Compact (PDC) bits is performed on relatively rigid setups. Even in hard rock, PDC bits exhibit reasonable life using such testing schemes. Unfortunately, field experience indicates otherwise. In this paper, they show that introducing compliance in testing setups, provides better simulation of actual field conditions. Using such a scheme, they show that chatter can be severe even in softer rock, such as sandstone, and very destructive to the cutters in hard rock, such as sierra white granite.

Peak x-ray powers as high as 280 {+-} 40 TW have been generated from the implosion of tungsten wire arrays on the Z Accelerator at Sandia National Laboratories. The high x-ray powers radiated by these z-pinches provide an attractive new driver option for high yield inertial confinement fusion (ICF). The high x-ray powers appear to be a result of using a large number of wires in the array which decreases the perturbation seed to the magnetic Rayleigh-Taylor (MRT) instability and diminishes other 3-D effects. Simulations to confirm this hypothesis require a 3-D MHD code capability, and associated databases, to follow the evolution of the wires from cold solid through melt, vaporization, ionization, and finally to dense imploded plasma. Strong coupling plays a role in this process, the importance of which depends on the wire material and the current time history of the pulsed power driver. Strong coupling regimes are involved in the plasmas in the convolute and transmission line of the powerflow system. Strong coupling can also play a role in the physics of the z-pinch-driven high yield ICF target. Finally, strong coupling can occur in certain z-pinch-driven application experiments.

This work combines focused ion beam sputtering and ultra-precision machining as a first step in fabricating microstructure in metals and alloys. Specifically, {approx}25{micro}m diameter micro-end mills are made from cobalt M42 high-speed steel and C2 micrograin tungsten carbide tool blanks by ion beam sputtering. A 20 keV focused gallium beam defines tool cutting edges having radii of curvature < 0.1{micro}m. Micro-end mills having 2, 4 and 5 cutting edges successfully machine small trenches in 6061-T4 aluminum, brass, 4340 steel and polymethyl methacrylate. Machined trench widths are approximately equal to the tool diameters and surface roughnesses (rms) are {approx}150 nm or less. Microtools are robust and operate for more than 6 hours without fracture. Results from ultra-precision machining aluminum at feed rates as high as 50 mm/minute are included.

This paper presents techniques for fabricating microscopic, nonplanar features in a variety of materials. Micro-grooving and micro-threading tools having cutting dimensions of 10-30{micro}m are made by focused ion beam sputtering and used in ultra-precision machining. Tool fabrication involves directing a 20 keV gallium beam at polished cylindrical punches made of cobalt M42 high-speed steel or C2 tungsten carbide. This creates cutting edges having radii of curvature less than 0.4 {micro}m, and rake features similar to conventional lathe tools. Clearance for minimizing frictional drag of a tool results from the sputter yield dependence on ion herd target incidence angle. Numerically controlled, ultra-precision machining with micro-grooving tools results in a close matching between tool width and feature size. Microtools controllably machine 13 {micro}m wide, 4 {micro}m deep, helical grooves in polymethyl methacrylate and 6061-T6 Al cylindrical substrates. Micro-grooving tools also fabricate sinusoidal waveform features in polished metal substrates.

Recent success on the Saturn and Z accelerators at Sandia National Laboratories have demonstrated the ability to scale z-pinch parameters to increasingly larger current pulsed power facilities. Next generation machines will require even larger currents (>20 MA), placing further demands on pulsed power technology. To this end, experiments have been carried out on Saturn operating in a long pulse mode, investigating the potential of lower voltages and longer implosion times while still maintaining pinch fidelity. High wire number, 25 mm diameter tungsten arrays were imploded with implosion times ranging from 130 to 240 ns. The results were comparable to those observed in the Saturn short pulse mode, with risetimes on the order of 4.5 to 6.5 ns. Experimental data will be presented, along with two dimensional radiation magnetohydrodynamic simulations used to explain and reproduce the experiment.

Motivated by the problem of determining stress distributions in granular materials, we study the effect of finite transport correlation times on the propagation of nonlinear wavefronts in reaction diffusion systems. We obtain new results such as the possibility of spatial oscillations in the wavefront shape for certain values of the system parameters and high enough wavefront speeds. We also generalize earlier known results concerning the minimum wavefront speed and shape-speed relationships stemming from the finiteness of the correlation times. Analytic investigations are made possible by a piece-wise linear representation of the nonlinearity.

On Nov. 1, 1999, Sandia National Laboratories celebrates its 50th birthday. Although Sandia has its roots in the World War II-era Manhattan Project, Sandia began operating as a separate nuclear weapons engineering laboratory under the management of AT&T on Nov. 1, 1949. Today the lab employs more than 7,000 people at its two sites in Albuquerque and Livermore, California, and has research and development missions in national security, energy and environmental technologies, and U.S. economic competitiveness. Lockheed Martin Corporation operates Sandia for the US. Department of Energy.

The authors have demonstrated a functional Pnp heterojunction bipolar transistor (HBT) using InGaAsN. The metalorganic vapor phase epitaxy (MOCVD) grown Al{sub 0.3}Ga{sub 0.7}As/In{sub 0.03}Ga{sub 0.97}As{sub 0.99}N{sub 0.01} HBT takes advantage of the narrower bandgap energy (E{sub g} = 1.25eV) of In{sub 0.03}Ga{sub 0.97}As{sub 0.99}N{sub 0.01}, which is lattice matched to GaAs. Compared with the Al{sub 0.3}Ga{sub 0.7}As/GaAs material system, the Al{sub 0.3}Ga{sub 0.7}As/In{sub 0.03}Ga{sub 0.97}As{sub 0.99}N{sub 0.01} material system has a larger conduction band offset, while the valence band offset remains comparable. This characteristic band alignment is very suitable for Pnp HBT applications. The device's peak current gain is 23 and it has a turn on voltage of 0.77V, which is 0.25V lower than in a comparable Pnp Al{sub 0.3}Ga{sub 0.7}As/GaAs HBT.

Plasma-induced etch damage can degrade the electrical and optical performance of III-V nitride electronic and photonic devices. We have investigated the etch-induced damage of an Inductively Coupled Plasma (ICP) etch system on the electrical performance of mesa-isolated GaN pn-junction diodes. GaN p-i-n mesa diodes were formed by Cl{sub 2}/BCl{sub 3}/Ar ICP etching under different plasma conditions. The reverse leakage current in the mesa diodes showed a strong relationship to chamber pressure, ion energy, and plasma flux. Plasma induced damage was minimized at moderate flux conditions ({le} 500 W), pressures {ge}2 mTorr, and at ion energies below approximately -275 V.

Numerous sites in the United States and around the world are contaminated with depleted uranium (DU) in various forms. A prevalent form is fragmented DU originating from various scientific tests involving high explosives and DU during weapon-development programs, at firing practice ranges, or in war theaters where DU was used in armor-piercing projectiles. The contamination at these sites is typically very heterogeneous, with discrete, visually identifiable DU fragments mixed with native soil. The bulk-averaged DU activity is quite low, whereas DU fragments, which are distinct from the soil matrix, have much higher specific activity. DU is best known as a dark metal that is nearly twice as dense as lead, but DU in the environment readily weathers (oxidizes) to a distinctive bright yellow color that is quite visible. While the specific activity (amount of radioactivity per mass of soil) of DU is relatively low and presents only a minor radiological hazard, the fact that DU is radioactive and visually identifiable makes it desirable to remove the DU ''contamination'' from the environment. The typical approach to conducting this DU remediation is to use radiation-detection instruments to identify the contaminant and then to separate it from the adjacent soil, packaging it for disposal as radioactive waste. This process can be performed manually or by specialized, automated equipment. Alternatively, a more cost-effective approach might be simple mechanical or gravimetric separation of the DU fragments from the host soil matrix. At SNL/NM, both the automated and simple mechanical approaches have recently been employed. This paper discusses the pros/cons of the two approaches.

This paper discusses the development and application of process knowledge (PK) to the characterization of radioactive wastes generated during the excavation of buried materials at the Sandia National Laboratories/New Mexico (SNL/NM) Classified Waste Landfill (CWLF). The CWLF, located in SNL/NM Technical Area II, is a 1.5-acre site that received nuclear weapon components and related materials from about 1950 through 1987. These materials were used in the development and testing of nuclear weapon designs. The CWLF is being remediated by the SNL/NM Environmental Restoration (ER) Project pursuant to regulations of the New Mexico Environment Department. A goal of the CWLF project is to maximize the amount of excavated materials that can be demilitarized and recycled. However, some of these materials are radioactively contaminated and, if they cannot be decontaminated, are destined to require disposal as radioactive waste. Five major radioactive waste streams have been designated on the CWLF project, including: unclassified soft radioactive waste--consists of soft, compatible trash such as paper, plastic, and plywood; unclassified solid radioactive waste--includes scrap metal, other unclassified hardware items, and soil; unclassified mixed waste--contains the same materials as unclassified soft or solid radioactive waste, but also contains one or more Resource Conservation and Recovery Act (RCRA) constituents; classified radioactive waste--consists of classified artifacts, usually weapons components, that contain only radioactive contaminants; and classified mixed waste--comprises radioactive classified material that also contains RCRA constituents. These waste streams contain a variety of radionuclides that exist both as surface contamination and as sealed sources. To characterize these wastes, the CWLF project's waste management team is relying on data obtained from direct measurement of radionuclide activity content to the maximum extent possible and, in cases where direct measurement is not technically feasible, from accumulated PK of the excavated materials.

Since the mid-1980's, there have been a number of commercially available parallel computers with hundreds or thousands of processors. These machines have provided a new capability to the scientific community, and they been used successfully by scientists and engineers although with varying degrees of success. One of the reasons for the limited success is the difficulty, or perceived difficulty, in developing code for these machines. In this paper we discuss many of the issues and challenges in developing scalable hardware, system software and algorithms for machines comprising hundreds or thousands of processors.

The history of high consequence accidents is rich with events wherein the actions, or inaction, of humans was critical to the sequence of events preceding the accident. Moreover, it has been reported that human error may contribute to 80% of accidents, if not more (dougherty and Fragola, 1988). Within the safety community, this reality is widely recognized and there is a substantially greater awareness of the human contribution to system safety today than has ever existed in the past. Despite these facts, and some measurable reduction in accident rates, when accidents do occur, there is a common lament. No matter how hard we try, we continue to have accidents. Accompanying this lament, there is often bewilderment expressed in statements such as, ''There's no explanation for why he/she did what they did''. It is believed that these statements are a symptom of inadequacies in how they think about humans and their role within technological systems. In particular, while there has never been a greater awareness of human factors, conceptual models of human involvement in engineered systems are often incomplete and in some cases, inaccurate.

We estimate the total in-vessel deuterium retention in Alcator C-Mod from a run campaign of about 1090 plasmas. The estimate is based on measurements of deuterium retained on 22 molybdenum tiles from the inner wall and divertor. The areal density of deuterium on the tiles was measured by nuclear reaction analysis. From these data, the in-vessel deuterium inventory is estimated to be about 0.1 gram, assuming the deuterium coverage is toroidally symmetric. Most of the retained deuterium is on the walls of the main plasma chamber, only about 2.5% of the deuterium is in the divertor. The D coverage is consistent with a layer saturated by implantation with ions and charge-exchange neutrals from the plasma. This contrasts with tokamaks with carbon plasma-facing components (PFC's) where long-term retention of tritium and deuterium is large and mainly in the divertor due to codeposition with carbon eroded by the plasma. The low deuterium retention in the C-Mod divertor is mainly due to the absence of carbon PFC's in C-Mod and the low erosion rate of Mo.

This paper reviews the technology options for a fission-based electric propulsion system for interstellar precursor missions. To achieve a total {Delta}V of more than 100 km/s in less than a decade of thrusting with an electric propulsion system of 10,000s Isp requires a specific mass for the power system of less than 35 kg/kWe. Three possible configurations are described: (1) a UZrH-fueled,NaK-cooled reactor with a steam Rankine conversion system,(2) a UN-fueled gas-cooled reactor with a recuperated Brayton conversion system, and (3) a UN-fueled heat pipe-cooled reactor with a recuperated Brayton conversion system. All three of these systems have the potential to meet the specific mass requirements for interstellar precursor missions in the near term. Advanced versions of a fission-based electric propulsion system might travel as much as several light years in 200 years.

Kuiper Belt Objects (KBOs) are a recently-discovered set of solar system bodies which lie at about the orbit of Pluto (40 AU) out to about 100 astronomical units (AU). There are estimated to be about 100,000 KBOS with a diameter greater than 100 km. KBOS are postulated to be composed of the pristine material which formed our solar system and may even have organic materials in them. A detailed study of KBO size, orbit distribution, structure, and surface composition could shed light on the origins of the solar system and perhaps even on the origin of life in our solar system. A rendezvous mission including a lander would be needed to perform chemical analysis of the surface and sub-surface composition of KBOS. These requirements set the size of the science probe at around a ton. Mission analyses show that a fission-powered system with an electric thruster could rendezvous at 40 AU in about 13.0 years with a total {Delta}V of 46 krnk. It would deliver a 1000-kg science payload while providing ample onboard power for relaying data back to earth. The launch mass of the entire system (power, thrusters, propellant, navigation, communication, structure, science payload, etc.) would be 7984 kg if it were placed into an earth-escape trajectory (C=O). Alternatively, the system could be placed into a 700-km earth orbit with more propellant,yielding a total mass in LEO of 8618 kg, and then spiral out of earth orbit to arrive at the KBO in 14.3 years. To achieve this performance, a fission power system with 100 kW of electrical power and a total mass (reactor, shield, conversion, and radiator) of about 2350 kg. Three possible configurations are proposed: (1) a UZrH-fueled, NaK-cooled reactor with a steam Rankine conversion system, (2) a UN-fueled gas-cooled reactor with a recuperated Brayton conversion system, and (3) a UN-fueled heatpipe-cooled reactor with a recuperated Brayton conversion system. (Boiling and condensation in the Rankine system is a technical risk at present.) All three of these systems have the potential to meet the weight requirement for the trip and to be built in the near term.

The paper describes a methodology for designing a web site for human factor engineers that is applicable for designing a web site for a group of people. Many web pages on the World Wide Web are not organized in a format that allows a user to efficiently find information. Often the information and hypertext links on web pages are not organized into intuitive groups. Intuition implies that a person is able to use their knowledge of a paradigm to solve a problem. Intuitive groups are categories that allow web page users to find information by using their intuition or mental models of categories. In order to improve the human factors engineers efficiency for finding information on the World Wide Web, research was performed to develop a web site that serves as a tool for finding information effectively. The paper describes a methodology for designing a web site for a group of people who perform similar task in an organization.

We report spurious-free dynamic-range measurements of 850-nm vertical-cavity surface-emitting lasers in short multimode links for radio frequency communication. For a 27-m fiber link, the dynamic range at optimal bias was greater than 95 dB·Hz2/3 for modulation frequencies between 1 and 5.5 GHz, which exceeds the requirements for antenna remoting in microcellular networks. In a free-space link, we have measured the highest dynamic range in an 850-nm vertical-cavity surface-emitting laser of 113 dB·Hz2/3 at 900 MHz. We have also investigated the effects of modal noise and differential mode delay on the dynamic range for longer lengths of fiber.

Over the last decade, multi-axis machine tools and robots based on parallel kinematic mechanisms (PKMs) have been developed and marketed worldwide. Positional accuracy in these machines is controlled by accurate knowledge of the kinematic parameters which consists of the joint center locations and distances between joint pairs. Since these machines tend to be rather large in size, the kinematic parameters (joint center locations, and initial strut lengths) are difficult to determine when these machines are in their fully assembled state. Work recently completed by the University of Florida and Sandia National Laboratories has yielded a method for determining all of the kinematic parameters of an assembled parallel kinematic device. This paper contains a brief synopsis of the calibration method created, an error budget, an uncertainty analysis for the recovered kinematic parameters and the propagation of these uncertainties to the tool tip.

Defects in silicon-on-insulator (SOI) buried oxides are normally considered deleterious to device operation. Similarly, exposing devices to hydrogen at elevated temperatures often can lead to radiation-induced charge buildup. However, in this work, we take advantage of as-processed defects in SOI buried oxides and moderate temperature hydrogen anneals to generate mobile protons in the buried oxide to form the basis of a ''protonic'' nonvolatile memory. Capacitors and fully-processed transistors were fabricated. SOI buried oxides are exposed to hydrogen at moderate temperatures using a variety of anneal conditions to optimize the density of mobile protons. A fast ramp cool down anneal was found to yield the maximum number of mobile protons. Unfortunately, we were unable to obtain uniform mobile proton concentrations across a wafer. Capacitors were irradiated to investigate the potential use of protonic memories for space and weapon applications. Irradiating under a negative top-gate bias or with no applied bias was observed to cause little degradation in the number of mobile protons. However, irradiating to a total dose of 100 krad(SiO{sub 2}) under a positive top-gate bias caused approximately a 100% reduction in the number of mobile protons. Cycling capacitors up to 10{sup 4} cycles had little effect on the switching characteristics. No change in the retention characteristics were observed for times up to 3 x 10{sup 4} s for capacitors stored unbiased at 200 C. These results show the proof-of-concept for a protonic nonvolatile memory. Two memory architectures are proposed for a protonic non-destructive, nonvolatile memory.

Salinas provides a massively parallel implementation of structural dynamics finite element analysis, required for high fidelity, validated models used in modal, vibration, static and shock analysis of weapons systems. This document provides a users guide to the input for Salinas. Details of input specifications for the different solution types, output options, element types and parameters are included. The appendices contain detailed examples, and instructions for running the software on parallel platforms.

The desire to provide a measure of computer network availability at Sandia National Laboratories has existed for along time. Several attempts were made to build this measure by accurately recording network failures, identifying the type of network element involved, the root cause of the problem, and the time to repair the fault. Recognizing the limitations of available methods, it became obvious that another approach of determining network availability had to be defined. The chosen concept involved the periodic sampling of network services and applications from various network locations. A measure of ''network'' availability was then calculated based on the ratio of polling success to failure. The effort required to gather the information and produce a useful metric is not prohibitive and the information gained has verified long held feelings regarding network performance with real data.

This document describes the implementation of periodic boundary conditions in the ALEGRA finite element code. ALEGRA is an arbitrary Lagrangian-Eulerian multi-physics code with both explicit and implicit numerical algorithms. The periodic boundary implementation requires a consistent set of boundary input sets which are used to describe virtual periodic regions. The implementation is noninvasive to the majority of the ALEGRA coding and is based on the distributed memory parallel framework in ALEGRA. The technique involves extending the ghost element concept for interprocessor boundary communications in ALEGRA to additionally support on- and off-processor periodic boundary communications. The user interface, algorithmic details and sample computations are given.

The end of the Cold War finds the international community no longer divided into two opposing blocks. The concerns that the community now faces are becoming more fluid, less focused, and, in many ways, much less predictable. Issues of religion, ethnicity, and nationalism; the possible proliferation of Weapons of Mass Destruction; and the diffusion of technology and information processing throughout the world community have greatly changed the international security landscape in the last decade. Although our challenges appear formidable, the United Nations, State Parties, nongovernmental organizations, and the arms control community are moving to address and lessen these concerns through both formal and informal efforts. Many of the multilateral agreements (e.g., NPT, BWC, CWC, CTBT, MTCR), as well as the bilateral efforts that are taking place between Washington and Moscow employ confidence-building and transparency measures. These measures along with on-site inspection and other verification procedures lessen suspicion and distrust and reduce uncertainty, thus enhancing stability, confidence, and cooperation.

In October 1996, an interdisciplinary team began a three-year LDRD project to study the plasma processes of reactive ion etching and plasma-enhanced chemical vapor deposition on large-area silicon devices. The goal was to develop numerical models that could be used in a variety of applications for surface cleaning, selective etching, and thin-film deposition. Silicon solar cells were chosen as the experimental vehicle for this project because an innovative device design was identified that would benefit from immediate performance improvement using a combination of plasma etching and deposition processes. This report presents a summary of the technical accomplishments and conclusions of the team.

The System of Labs Direct Fabrication Technology program was intended to foster cooperation and development in a cooperative effort between Sandia National Labs, Idaho National Energy and Environment Lab and Oak Ridge National Lab. The goal of this program was to bring together LENS (Laser Engineered Net Shaping) from Sandia, INEEL's spray forming process and the alloy development expertise of ORNL. This program investigated the feasibility of combining the LENS and spray forming processes to exploit the best features of both approaches. Further, since both processes were thought to result in a rapidly solidified structure, the alloy design expertise of ORNL offered the opportunity for alloy design or processing options which could more fully utilize the unique capabilities of the processes.

In an attempt to automatically produce high-quality all-hex meshes, we investigated a mesh improvement strategy: given an initial poor-quality all-hex mesh, we iteratively changed the element connectivity, adding and deleting elements and nodes, and optimized the node positions. We found a set of hex reconnection primitives. We improved the optimization algorithms so they can untangle a negative-Jacobian mesh, even considering Jacobians on the boundary, and subsequently optimize the condition number of elements in an untangled mesh. However, even after applying both the primitives and optimization we were unable to produce high-quality meshes in certain regions. Our experiences suggest that many boundary configurations of quadrilaterals admit no hexahedral mesh with positive Jacobians, although we have no proof of this.

Predicting the behavior of ion channel proteins is important for understanding biological effects of drugs and toxins. These problems involve steady state transport of ions through very small (1-2 atoms wide) pores. FY99 LDRD funding was used to begin investigations of ion channel proteins using a molecular theory approach. Much of our efforts involved establishing the soundness of the approach by direct comparison with grand canonical molecular dynamics simulations of simple model systems. In addition, several dimensional ion channel models have been implemented to demonstrate the viability of the approach, The seed funding provided by this LDRD grant resulted in 50K of DOWOBER funds for FY99, an invitation to submit a full length 0(500K) proposal for consideration to DOWOBER, and start a larger LDRD effort in computational biophysics beginning in FY00.

Estimation of the potential radiological risks associated with highway transport of radioactive materials (RAM) requires input data describing population densities adjacent to all portions of the route to be traveled. Previously, aggregated risks for entire multi-state routes were adequately estimated from population data with low geographic resolution. Current demands for geographically-specific risk estimates require similar increases in resolution of population density adjacent to route segments. With the advent of commercial geographic information systems (GISs) and databases describing highways, U.S. Census Blocks, and other information that is geographically distributed, it became feasible to determine and tabulate population characteristics along transportation routes with 1-kilometer resolution. This report describes an automated method of collecting population data adjacent to route segments (for calculation of incident-free doses) based on a commercial GIS. It also describes a statistical method of resolving remaining resolution issues, and an adaptation of the automation method to collection of data on population under a hypothetical plume of contamination resulting from a potential transportation accident.

Polarimetry is the method of recording the state of polarization of light. Imaging polarimetry extends this method to recording the spatially resolved state of polarization within a scene. Imaging-polarimetry data have the potential to improve the detection of manmade objects in natural backgrounds. We have constructed a midwave infrared complete imaging polarimeter consisting of a fixed wire-grid polarizer and rotating form-birefringent retarder. The retardance and the orientation angles of the retarder were optimized to minimize the sensitivity of the instrument to noise in the measurements. The optimal retardance was found to be 132{degree} rather than the typical 90{degree}. The complete imaging polarimeter utilized a liquid-nitrogen cooled PtSi camera. The fixed wire-grid polarizer was located at the cold stop inside the camera dewar. The complete imaging polarimeter was operated in the 4.42-5 {micro}m spectral range. A series of imaging experiments was performed using as targets a surface of water, an automobile, and an aircraft. Further analysis of the polarization measurements revealed that in all three cases the magnitude of circular polarization was comparable to the noise in the calculated Stokes-vector components.