Publications

Microstructural-level residual stresses arise in ceramics due to thermal expansion anisotropy. The magnitude of these stresses can be very high and may cause spontaneous microcracking during the processing of these materials. The orientation data obtained by backscattered electron diffraction and grain boundary energies obtained by AFM were used in conjunction with an object oriented finite element analysis package (OOF) to predict the magnitude of residual stresses in alumina. Crack initiation and propagation were also simulated based on the Griffith fracture criterion.

Incomplete convergence in numerical simulation such as computational physics simulations and/or Monte Carlo simulations can enter into the calculation of the objective function in an optimization problem, producing noise, bias, and topo- graphical inaccuracy in the objective function. These affect accuracy and convergence rate in the optimization problem. This paper is concerned with global searching of a diverse parameter space, graduating to accelerated local convergence to a (hopefully) global optimum, in a framework that acknowledges convergence uncertainty and manages model resolu- tion to efficiently reduce uncertainty in the final optimum. In its own right, the global-to-local optimization engine employed here (devised for noise tolerance) performs better than other classical and contemporary optimization approaches tried individually and in combination on the "industrial" test problem to be presented.

This is a period of ever-tightening defense budgets and continuing pressure on the public sector to be more commercial-like, Property policies, practices, and regulations are increasingly being challenged and changed. In these times, we must be leaders in understanding and defining the value of our profession from a commercial standpoint so that we can provide the right services to our customers and explain and defend the value of those services. To do so, we must step outside current property management practices, regulations, and oversight. We must learn to think and speak in the language of those who fund us--a financial language of risk, cost, and benefit. Regardless of regulation and oversight, our bosses are demanding that we demonstrate (financially) the benefits of current practice, or else. This article is intended to be the beginning of an effort to understand and define our profession in terms of risk, cost, and benefit so that we can meet these new challenges. The first step in this effort must be defining and measuring risk, cost, and benefit. Our costs, although sometimes difficult to capture, are easy to understand: they are almost exclusively the effort, both within and without the property management organization, involved in managing property. Unfortunately, property risks and benefits are not so simple or so well understood. Generally, risks and benefits are identified and measured through physical inventory results: potential and actual shortages. This paper will explore the weaknesses in the current understanding and use of shortage information as the yardstick for property management risks and performance. It will define a new framework for understanding the purpose and value of property management. And finally, it will set a course for a new method of measuring and valuing physical inventoty shortages. This new method will yield accurate and useful measures of property management risk and benefit. Once risk and benefit are accurately understood and measured, it will be possible to evaluate, adjust, and explain property management practices and regulations from a commercial, financial perspective; it will be possible for us to be the leaders in redefining the purpose and value of the property management profession for today's environment.

Interest in the critical dynamics of superfluid ⁴ He in microgravity conditions has motivated the development of new high resolution thermometry technol- ogy for use in space experiments near 2K. The current material commonly used as the temperature sensing element for high resolution thermometers (HRTs) is copper ammonium bromide [Cu(NH₄)₂Br₄2H₂0) or "CAB", which undergoes a ferromagnetic phase transition at 1.8K1. HRTs made from CAB have demonstrated low drift (< 10fK/s) and a temperature resolu- tion of O.lnK. Unfortunately, paramagnetic salts such as CAB are difficult to prepare and handle, corrosive to most metals, and become dehydrated if kept, under vacuum conditions at room temperature. We have developed a magnetic thermometer using dilute magnetic alloys of Mn or Fe dissolved in a pure Pd matrix. These metallic thermometers are easy to fabricate, chemically inert, and mechanically robust. Unlike salts, they may be directly soldered to the stage to be measured. Also, the Curie temperature can be varied by changing the concentration of Fe or Mn, making them available for use in a wide temperature range. Susceptibility measurements, as well as preliminary noise and drifl measurements, show them, to have sub-nK resolution, with a drift of less than 10^-13 K/s.

Abstract not provided.

Commercial telemedicine systems are increasingly functional, incorporating video-conferencing capabilities, diagnostic peripherals, medication reminders, and patient education services. However, these systems (1) rarely utilize information architectures which allow them to be easily integrated with existing health information networks and (2) do not always protect patient confidentiality with adequate security mechanisms. Using object-oriented methods and software wrappers, we illustrate the transformation of an existing stand-alone telemedicine system into `plug-and-play' components that function in a distributed medical information environment. We show, through the use of open standards and published component interfaces, that commercial telemedicine offerings which were once incompatible with electronic patient record systems can now share relevant data with clinical information repositories while at the same time hiding the proprietary implementations of the respective systems. Additionally, we illustrate how leading-edge technology can secure this distributed telemedicine environment, maintaining patient confidentiality and the integrity of the associated electronic medical data. Information surety technology also encourages the development of telemedicine systems that have both read and write access to electronic medical records containing patient-identifiable information. The win-win approach to telemedicine information system development preserves investments in legacy software and hardware while promoting security and interoperability in a distributed environment.

The Sandia ACRR (a Hazard Category 2 Nuclear Reactor Facility) was defueled in June 1997 to modify the reactor core and control system to produce medical radioisotopes for the Department of Energy (DOE) Isotope Production Program. The DOE determined that an Operational Readiness Review (ORR) was required to confirm readiness to begin operations within the revised safety basis. This paper addresses the ORR Process, lessons learned from the Sandia and DOE ORRS of the ACRR, and the use of the ORR to confirm authorization basis implementation.

The Sandia National Laboratories/New Mexico (SNL/NM) Environmental Restoration Project is halfway through excavating the Classified Waste Landfill in Technical Area II, a disposal area for weapon components for approximately 40 years. While the planning phase of any project is important, it is only a means of getting to the field implementation phase where reality quickly sinks in. Documents outlining the general processes are developed, heavy equipment, supply needs, requisite skills, and staffing levels are anticipated, and contingencies for waste management are put in place. However, the nature of landfill excavation dictates that even the most detailed plans will probably change. This project is proving that trying to account for undefined variables and predicting the total cost of landfill remediation is very difficult if the contents are not well known. In landfill excavation, contingency cannot be minimized. During development of the waste management plan, it was recognized that even the best forecasting could not formulate the perfect cradle-to-grave processes because waste streams are rarely definable before excavation begins. Typically, as excavation progresses and waste streams are generated, new characterization information allows further definition of disposal options which, in turn, modify the generation/management process. A general plan combined with close involvement of waste management personnel to resolve characterization and packaging questions during generation has worked very well. And, as expected, each new pit excavated creates new waste management challenges. The material excavated consists primarily of classified weapon assemblies and related components, so disposition must include demilitarization and sanitization. The demilitarization task at the start of the project was provided by an SNL/NM group that has since lost their funding and operational capability. This project is having to take on the task of disassembly, destruction, and recycling of classified components, along with the associated costs and infrastmcture. Very stringent radiological controls were imposed on site operations during the planning phase. Radiological controls that are not justified significantly impact the efficiency and cost of operations. If the initial approach is too conservative, there should be well-defined provisions for scaling down the protective measures to reflect the actual risks. Once the effectiveness of early detection, monitoring, and surveys is proven, radiological controls and postings should be re-evaluated to verify that they are appropriate. High levels of heavy metals dust were not anticipated during the planning phase but were suspected, then confirmed, during material handling. Respiratory protection and monitoring were upgraded accordingly and the costs added to the baseline. In contrast to radiological constraints, industrial hygiene guidelines were worked into the process with a minimum of adverse impact. While a lot of unforeseen expenses occur, some expected costs can be reduced. During the planning phase, the anticipated need to adequately characterize a variety of radionuclides in soil led to using Large Area Gamma Spectroscopy (LAGS) to survey all the soil excavated. About a quarter of the way through the project, it was obvious that very little radioactive material was present in the excavated soils. Since all the soil is processed through a screen plant, producing a fairly homogeneous mix, a more common method of sampling soil piles was implemented to replace the LAGS unit, increase productivity, and reduce costs. In summary, the most important lesson is to expect and be ready to change. Excavating a landfill requires the flexibility to quickly adjust processes to handle the unknown variables, and close attention to detail so all the different facets of the project are kept under control.

Thermally stimulated current and capacitance voltage methods are used to investigate the thermal stability of trapped electrons associated with radiation-induced trapped positive charge in metaloxide-semiconductor capacitors. The density of deeply trapped electrons in radiation-hardened 45 nm oxides exceeds that of shallow electrons by a factor of ∼3 after radiation exposure, and by up to a factor of 10 or more during biased annealing. Shallow electron traps anneal faster than deep traps, and exhibit response that is qualitatively consistent with existing models of compensated E′γ centers in SiO2. Deeper traps may be part of a different dipole complex, and/or have shifted energy levels that inhibit charge exchange with the Si. © 1999 American Institute of Physics.

Thermite mixtures, intermetallic reactants, and metal fuels have long been used in pyrotechnic applications. Advantages of these systems typically include high energy density, high combustion temperature, and a wide range of gas production. They generally exhibit high temperature stability and possess insensitive ignition properties. For the specific applications of humanitarian demining and disposal of unexploded ordnance, these pyrotechnic formulations offer additional benefits. The combination of high thermal input with low brisance can be used to neutralize the energetic materials in mines and other ordnance without the "explosive" high-blast-pressure events that can cause extensive collateral damage to personnel, facilities, and the environment. In this paper, we review the applications, benefits, and characteristics of thermite mixtures, intermetallic reactants, and metal fuels. Calculated values for reactant density, heat of reaction (per unit mass and per unit volume), and reaction temperature (without and with consideration of phase changes and the variation of specific heat values) are tabulated. These data are ranked in several ways, according to density, heat of reaction, reaction temperature, and gas production.

The effects on electrochemical performance of the nitrogen content of disordered carbons derived from polymethacryonitrile (PMAN)-divinylbenzene (DVB) copolymers were examined in galvanostatic cycling tests between 2 V and 0.01 V vs. Li/Li+ in lM LiPF₆/ethylene carbonate (EC)-dimethyl carbonate (DMC). The first-cycle reversible capacities and coulombic efficiencies increased with increase in the level of nitrogen for samples prepared at 700°C. However, the degree of fade also increased. Similar tests were performed on materials that were additionally heated at 1,000° and 1,300°C for five hours. Loss of nitrogen, oxygen, and hydrogen occurred under these conditions, with none remaining at the highest temperature in all cases but one. The pyrolysis temperature dominated the electrochemical performance for these samples, with lower reversible and irreversible capacities for the first intercalation cycle as the pyrolysis temperature was increased. Fade was reduced and coulombic efficiencies also improved with increase in temperate. The large irreversible capacities and high fade of these materials makes them unsuitable for use in Li-ion cells.

Cooperative monitoring holds the promise of utilizing many technologies from conflicts of the past to implement agreements of peace in the future. Important approaches to accomplish this are to develop the framework for assessing monitoring opportunities and to provide education and training on the technologies and experience available for sharing with others. The Cooperative Monitoring Center (CMC) at Sandia National Laboratories is working closely with agencies throughout the federal government, academics at home and abroad, and regional organizations to provide the technical tools needed to assess, design, analyze, and implement these cooperative agreements. In doing so, the goals of building regional confidence and increasing trust and communication can be furthered.

Several techniques to predict pad failure during tungsten CMP were investigated for a specific consumable set. These techniques include blanket polish rate measurements and metrics derived from two endpoint detection schemes. Blanket polish rate decreased significantly near pad failure. Metrics from the thermal endpoint technique included change in peak temperature, change in the time to reach peak temperature, and the change in the slope of the temperature trace just prior to peak temperature all as a function of pad life. Average carrier motor current before endpoint was also investigated. Changes in these metrics were observed however these changes, excluding time to peak process temperature, were either not consistent between pads or too noisy to be reliable predictors of pad failure.

This paper details the analysis of vibration monitoring for end-point control in oxide CMP processes. Two piezoelectric accelerometers were integrated onto the backside of a stainless steel polishing head of an IPEC 472 polisher. One sensor was placed perpendicular to the carrier plate (vertical) and the other parallel to the plate (horizontal). Wafers patterned with metal and coated with oxide material were polished at different speeds and pressures. Our results show that it is possible to sense a change in the vibration signal over time during planarization of oxide material on patterned wafers. The horizontal accelerometer showed more sensitivity to change in vibration amplitude compared to the vertical accelerometer for a given polish condition. At low carrier and platen rotation rates, the change in vibration signal over time at fixed frequencies decreased approximately ½ - 1 order of magnitude (over the 2 to 10 psi polish pressure ranges). At high rotation speeds, the vibration signal remained essentially constant indicating that other factors dominated the vibration signaL These results show that while it is possible to sense changes in acceleration during polishing, more robust hardware and signal processing algorithms are required to ensure its use over a wide range of process conditions.

Abstract not provided.

Casing deformation in wells is a common problem in many geothermal fields. Casing remediation is necessary to keep wells in production and occasionally, to even enter the well for an approved plug and abandonment procedure. The costly alternative to casing remediation is to incur the expense of drilling a new well to maintain production or drilling a well to intersect a badly damaged well below the deformation for abandonment purposes. The U.S. Department of Energy and the Geothermal Drilling Organization sponsor research and development work at Sandia National Laboratories in an effort to reduce these remediation expenditures. Sandia, in cooperation with Halliburton Energy Services, has developed a low cost, commercially available, bridge-plug-type packer for use in geothermal well environments. This report documents the development and testing of this tool for use in casing remediation work.

Silicon micromachine designs include engines that consist of orthog- onally oriented linear comb drive actuators mechanically connected to a rotating gear. These gears are as small as 50 {micro}m in diameter and can be driven at rotation rates exceeding 300,000 rpm. Generally, these en- gines will run with non-uniform rotation rates if the drive signals are not properly designed and maintained over a range of system parameters. We present a method for producing constant rotation rates in a micro-engine driven by an orthogonal linkage system. We show that provided the val- ues of certain masses, springs, damping factors, and lever arms are in the right proportions, the system behaves as though it were symmetrical. We will refer to systems built in this way as being quasi-symmetrical. We show that if a system is built quasi-symmetrically , then it is possible to achieve constant rotation rates even if one does not know the form of the friction function, or the value of the friction. We analyze this case in some detail.

In this paper we present an approach that facilitates the validation of high consequence system requirements. This approach consists of automatically generating a graphical representation from an informal document. Our choice of a graphical notation is statecharts. We proceed in two steps: we first extract a hierarchical decomposition tree from a textual description, then we draw a graph that models the statechart in a hierarchical fashion. The resulting drawing is an effective requirements assessment tool that allows the end user to easily pinpoint inconsistencies and incompleteness.

We investigate the apparent charge transfer between adatoms in the GeXPb[l.XjGe(lll) interface both experimentally and theoretically. Scanning tunneling microscopy and surface core level measurements suggest significant charge transfer from the Ge adatoms to the Pb adatoms. However, first-principles calculations unambiguously find that the total electronic displacement is negligibly small, and that the results of published experiments can be explained as a result of bond rearrangement.

Friction force microscopy measurements of a polydiacetylene monolayer film reveal a 300% friction anisotropy that is correlated with the film structure. The film consists of a monolayer of the red form of N-(2-ethanol)- 10,12 pentacosadiynamide, prepared on a Langmuir trough and deposited on a mica substrate. As confirmed by atomic force microscopy and fluorescence microscopy, the monolayer consists of domains of linearly oriented conjugated backbones with pendant hydrocarbon side chains above and below the backbones. Maximum friction occurs when the sliding direction is perpendicular to the backbone. We propose that the backbones impose anisotropic packing of the hydrocarbon side chains which leads to the observed friction anisotropy. Friction anisotropy is therefore a sensitive, optically-independent indicator of polymer backbone direction and monolayer structural properties.

Abstract not provided.

We have synthesized the Z and E isomers of 1,4-bis(triethoxysilyl)-2- butene and polymerized them under acid and base catalyzed sol-gel conditions. As expected the E system formed crosslinked, insoluble gels. The Z isomer, by nature of its geometry, formed high molecular weight, soluble polymeric products under acidic conditions. We were able to prepare and isolate both the cyclic disilsesquioxane monomer, and its dimer. Comparison of their spectral characterization with that of the soluble polymers suggests that the cyclics are present within the polymers. lle synthesis of a dimer likely present at some early stage of the polymerization suggests that we may be able to control the reaction and form rigid polymers with controllable tacticity. In addition, most of the gels were found to be non-porous indicating that the gels were, in fact, more compliant than ethenylene-bridged polysilsesquioxanes leading to collapse of pores during drying.

The detection of mines, both during and after hostilities, is a growing international problem. It limits military operations during wartime and unrecovered mines create tragic consequences for civilians. From a purely humanitarian standpoint an estimated 100 million or more unrecovered mines are located in over 60 countries worldwide. This paper presents an overview of some of the technologies currently being investigated by Sandia National Laboratories for the detection and monitoring of minefields in land and water environments. The three technical areas described in this paper are: 1) the development of new mathematical techniques for combining or fusing the data from multiple sources for enhanced decision-making; 2) an environmental fate and transport (EF&T) analysis approach that is central to improving trace chemical sensing technique; and 3) the investigation of an underwater range imaging device to aid in locating and characterizing mines and other obstacles in coastal waters.

In the scanning electron microscope (SEM), using electron backscattered diffraction (EBSD), it is possible to measure the spacing of the layers in the reciprocal lattice. These values are of great use in confirming the identification of phases. The technique derives the layer spacing from the HOLZ rings which appear in patterns from many materials. The method adapts results from convergent-beam electron diffraction (CBED) in the transmission electron microscope (TEM). For many materials the measured layer spacing compares well with the calculated layer spacing. A noted exception is for higher atomic number materials. In these cases an extrapolation procedure is described that requires layer spacing measurements at a range of accelerating voltages. This procedure is shown to improves the accuracy of the technique significantly. The application of layer spacing measurements in EBSD is shown to be of use for the analysis of two polytypes of SiC.

Our vision of the future of information systems is one that includes engineered collectives of software agents which are situated in an environment over years and which increasingly improve the performance of the overall system of which they are a part. At a minimum, the movement of agent and multi-agent technology into National Security applications, including their use in information assurance, is apparent today. The use of deliberative, autonomous agents in high-consequence/high-security applications will require a commensurate level of protection and confidence in the predictability of system-level behavior. At Sandia National Laboratories, we have defined and are addressing a research agenda that integrates the surety (safety, security, and reliability) into agent-based systems at a deep level. Surety is addressed at multiple levels: The integrity of individual agents must be protected by addressing potential failure modes and vulnerabilities to malevolent threats. Providing for the surety of the collective requires attention to communications surety issues and mechanisms for identifying and working with trusted collaborators. At the highest level, using agent-based collectives within a large-scale distributed system requires the development of principled design methods to deliver the desired emergent performance or surety characteristics. This position paper will outline the research directions underway at Sandia, will discuss relevant work being performed elsewhere, and will report progress to date toward assurance in agent-based systems.

The solution-mediated syntheses and single crystal structures of (CH₃NH₃)₃·Zn₄0(AsO₄)₃ and (CH₃NH₃)₃·Zn₄O(P0₄)₃ are reported. These compounds are built up from vertex-sharing three-dimensional Zn0₄ + AsO₄/P0₄ tetrahedral frameworks encapsulating methylammonium cations in three-dimensional channel systems. These phases are closely related to the zeolite- like M₃Zn₄O(XO₄)₃·nH₂O family of phases. Crystal data for (CH₃NH₃)₃·Zn₄0(AsO₄)₃, M, = 790.47, monoclinic, space group P2₁ (No. 4), a = 7.814 (3)Å, b = 15.498 (6)Å, c = 7.815 (3) Å, {beta} = 92.91 (2)0, V = 945.1 (9) ų, Z = 2, R(F) = 3.01%, R_W(F) = 3.98% (2301 reflections, 236 parameters). Crystal data for (CH₃NH₃)₃·Zn₄0(P0₄)₃: M, = 658.63, monoclinic, space group P2₁ (No. 4), a = 7.6569 (5) Å, b = 15.241 (1)Å, c= 7.6589 (5) Å, {beta} = 92.740 (1)0, V= 892.7 (5) ų, Z = 2, R(F)= 8.07%, R_W(F)= 9.60% (2694 reflections, 106 parameters).

Zeolite W has been synthesized using organometallic silicon and aluminum precursors in two hydrothermal systems: organocation containing and organocation-free. The reaction using the organocation yielded a fully crystalline, relatively uniform crystal size product, with no organic molecules occluded in the pores. In contrast, the product obtained from an identical reaction, except for the absence of the organocation, contained amorphous as well as crystalline material and the crystalline phase showed a large diversity of both crystal size and morphology. The use of organometallic precursors, either with or without an organocation, allows for the crystallization of the MER framework at much lower 0H/Si02 and (K+ Na - Al)/Si ratios than is typical of inorganic systems. The reaction products were characterized by XRD, SEM, EDS, and thermal analyses.

The solution-mediated syntheses and single crystal structures of (N₂C₆H₁₄)·Zn(HPO₄)₂·H₂O (I), H₃N(CH₂)₃NH₃·Zn₂(HPO₄)₃ (II), and (N₂C₆H₁₄)·Zn₃(HPO₄)₄ (III) are described. These phases contain vertex-sharing Zn0₄ and HP0₄ tetrahedra, accompanied by doubly- protonated organic cations. Despite their formal chemical relationship, as members of the series of t·Zn_n(HP0₄)_n+1 (t= template, n = 1-3), these phases adopt fimdamentally different crystal structures, as one-dimensional, two-dimensional, and three-dimensional Zn0₄/HP0₄ networks, for I, II, and III respectively. Similarities and differences to some other zinc phosphates are briefly discussed. Crystal data: (N₂C₆H₁₄)·Zn(HP0₄)₂·H₂0, M_r = 389.54, monoclinic, space group P2₁/n (No. 14), a = 9.864 (4) Å, b = 8.679 (4) Å, c = 15.780 (3) Å, β = 106.86 (2)°, V= 1294.2 (8) ų, Z = 4, R(F) = 4.58%, R_W(F) = 5.28% [1055 reflections with I >3σ(I)]. H₃N(CH₂)₃NH₃·Zn₂(HP0₄)₃, M_r = 494.84, monoclinic, space group P2₁/c (No. 14), a= 8.593 (2)Å, b= 9.602 (2)Å, c= 17.001 (3)Å, β= 93.571 (8)°, V = 1400.0 (5) ų, Z = 4, R(F) = 4.09%, R_W(F) = 4.81% [2794 reflections with I > 3σ (I)]. (N₂C₆H₁₄)·Zn₃(HP0₄)₄, M_r= 694.25, monoclinic, space group P2₁/n (No. 14), a = 9.535 (2) Å, b = 23.246 (4)Å, c= 9.587 (2)Å, β= 117.74 (2)°, V= 1880.8 (8) ų, Z = 4, R(F) = 3.23%, R_W(F) = 3.89% [4255 reflections with 1> 3σ(I)].

Due to the vast diversity of chemical media in which metal separations are executed, a wide range of ion separation materials are employed. This results in an ongoing effort to discover new phases with novel ion exchange properties. We present here the synthesis of a novel class of thermally and chemically stable microporous, niobate-based materials. Ion exchange studies show these new phases are highly selective for Sr²⁺ and other bivalent metals.

Silica nanoparticles exhibiting hexagonal, cubic, and vesicular mesostructures have been prepared using aerosol assisted, self-assembled process. This process begins with homogennous aerosol droplets containing silica source, water, ethanol, and surfactant, in which surfactant concentration is far below the critical micelle concentration (cmc). Solvent evaporation enriches silica and surfactant inducing interfacial self-assembly confined to a spherical aerosol droplet and results in formation of completely solid, ordered spherical particles with stable hexagonal, cubic, or vesicular mesostructures.

Understanding of single and multi-phase flow and transport in fractures can be greatly enhanced through experimentation in transparent systems (analogs or replicas) where light transmission techniques yield quantitative measurements of aperture, solute concentration, and phase saturation fields. Here we quanti@ aperture field measurement error and demonstrate the influence of this error on the results of flow and transport simulations (hypothesized experimental results) through saturated and partially saturated fractures. find that precision and accuracy can be balanced to greatly improve the technique and We present a measurement protocol to obtain a minimum error field. Simulation results show an increased sensitivity to error as we move from flow to transport and from saturated to partially saturated conditions. Significant sensitivity under partially saturated conditions results in differences in channeling and multiple-peaked breakthrough curves. These results emphasize the critical importance of defining and minimizing error for studies of flow and transpoti in single fractures.

An investigation of the synthesis of novel dodecaarylporphyrins using the Suzuki coupling reaction of arylboronic acids with octabromotetraarylporphyrins is reported. Studies of the dynamic properties of these new porphyrins using variable temperature (VT) ¹H NMR spectroscopy and molecular mechanics provide interesting insights into their dynamic properties, including the first determination of {beta} aryl rotation in a porphyrin system.

The time evolution of the amplitude of periodic nanoscale ripple patterns formed on Ar+ sputtered Si(OOl ) surfaces was examined using a recently developed in situ spectroscopic technique. At sufficiently long times, we find that the amplitude does not continue to grow exponentially as predicted by the standard Bradley-Harper sputter rippling model. In accounting for this discrepancy, we rule out effects related to the concentration of mobile species, high surface curvature, surface energy anisotropy, and ion-surface interactions. We observe that for all wavelengths the amplitude ceases to grow when the width of the topmost terrace of the ripples is reduced to approximately 25 nm. This observation suggests that a short circuit relaxation mechanism limits amplitude . growth. A strategy for influencing the ultimate ripple amplitude is discussed.

Optimal selection of array sensors for a chemical sensing application is a nontrivial task. It is commonly believed that "more is better" when choosing the number of sensors required to achieve good chemical selectivity. However, cost and system complexity issues point towards the choice of small arrays. A quantitative array optimization is carried out to explore the selectivity of arrays of partially-selective chemical sensors as a function of array size. It is shown that modest numbers (dozens) of target analytes are completely distinguished with a range of arrays sizes. However, the array selectivity and the robustness against sensor sensitivity variability are significantly degraded if the array size is increased above a certain number of sensors, so that relatively small arrays provide the best performance. The results also suggest that data analyses for very large arrays of partially-selective sensors will be optimized by separately anal yzing small sensor subsets.

Controlled impact experiments have been performed to determine the spall strength of four different concrete compositions. The four concrete compositions are identified as, `SAC-5, CSPC', ("3/4") large, and ("3/8") small, Aggregate. They differ primarily in aggregate size but with average densities varying by less than five percent. Wave profiles from sixteen experiments, with shock amplitudes of 0.07 to 0.55 GPa, concentrate primarily within the elastic regime. Free-surface particle velocity measurements indicate consistent pullback signals in the release profiles, denoting average span strength of approximately 40 MPa. It is the purpose of this paper to present spall measurements under uniaxial strain loading. Notwithstanding considerable wave structure that is a unique characteristic to the heterogeneous nature of the scaled concrete, the spall amplitudes appear reproducible and consistent over the pressure range reported in this study.

This paper summarizes the current status of the treatment of human reliability in fire risk analyses for nuclear power plants and identifies areas that need to be addressed. A new approach is suggested to improve the modeling.

Many hazardous material handling needs exist in remote unstructured environments. Currently these operations are accomplished using personnel in direct contact with the hazards. A safe and cost effective alternative to this approach is the use of intelligent robotic systems for safe handling, packaging, transport, and even excavation of hazardous materials. The Intelligent Systems and Robotics Center of Sandia National Laboratories has developed and deployed robotic technologies for use in hazardous environments, three of which have been deployed in DOE production facilities for handling of special nuclear materials. Other systems are currently under development for packaging special nuclear materials. This paper presents an overview of the research activities, including five delivered systems, at %ndia National Laboratories on the use of robotics in hazardous environments.

Thermal instabilities were identified in SONY-type lithium-ion cells and correlated with interactions of cell constituents and reaction products. Three temperature regions of interaction were identified and associated with the state of charge (degree of Li intercalation) of the cell. Anodes were shown to undergo exothermic reactions as low as 100°C involving the solid electrolyte interface (SEI) layer and the LiPF₆ salt in the electrolyte (EC: PC: DEC/LiPF₆). These reactions could account for the thermal runaway observed in these cells beginning at 100°C. Exothermic reactions were also observed in the 200°C-300°C region between the intercalated lithium anodes, the LiPF₆ salt and the PVDF. These reactions were followed by a high- temperature reaction region, 300°C-400°C, also involving the PVDF binder and the intercalated lithium anodes. The solvent was not directly involved in these reactions but served as a moderator and transport medhun. Cathode exotherrnic reactions with the PVDF binder were observed above 200oC and increased with the state of charge (decreasing Li content). This offers an explanation for the observed lower thermal runaway temperatures for charged cells.

This paper reports progress on implementing a new capability of adaptive mesh refinement into the Eulerian multimaterial shock- physics code CTH. The adaptivity is block-based with refinement and unrefinement occurring in an isotropic 2:1 manner. The code is designed to run on serial, multiprocessor and massive parallel platforms. An approximate factor of three in memory and performance improvements over comparable resolution non-adaptive calculations has-been demonstrated for a number of problems.

The nucleation of GaN thin films on GaAs is investigated for growth at 620 "C. An rf plasma cell is used to generate chemically active nitrogen from N₂. An arsenic flux is used in the first eight monolayer of nitride growth to enhance nucleation of the cubic phase. Subsequent growth does not require an As flux to preserve the cubic phase. The nucleation of smooth interfaces and GaN films with low stacking fault densities is dependent upon relative concentrations of active nitrogen species in the plasma and on the nitrogen to gallium flux ratio.

A management system approach for evaluating environment, safety, health, and quality is in use at Sandia National Laboratories (SNL). Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under contract DE-AC04-94AL85000. As a multi-program national laboratory, SNL has many diverse operations including research, engineering development and applications, production, and central services supporting all activities and operations. Basic research examples include fusion power generation, nuclear reactor experiments, and investigation of combustion processes. Engineering development examples are design, testing, and prototype developments of micro-mechanical systems for safe'~arding computer systems, air bags for automobiles, satellite systems, design of transportation systems for nuclear materials, and systems for use in medical applications such as diagnostics and surgery. Production operations include manufacture of instrumented detection devices, radioisotopes, and replacement parts for previously produced engineered systems. Support services include facilities engineering, construction, and site management, site security, packaging and transportation of hazardous materials wastes, ES&H functional programs to establish requirements and guidance to comply with federal, state, local, and contractual requirements and work safety. In this diverse environment, unlike more traditional single function business units, an integrated consistent management system is not typical. Instead, each type of diverse activity has its own management system designed and distributed around the operations, personnel, customers, and facilities (e.g., hazards involved, security, regulatory requirements, and locations). Laboratory managers are not likely to have experience in the more traditional hierarchical or command and control structures and thus do not share oversight expectations found in centralized management systems. The resulting corporate management system gives the appearance of an assembly of multiple, nearly independent operating units. The executive management system maintains these separate units, encouraging autonomy and creativity by establishing a minimum of requirements and procedures. In any organization, senior management has a responsibility to ensure that all operating units are meeting requirements. Part of this responsibility is fulfilled by conducting oversight or assurance activities, to determine the effectiveness of established systems in meeting requirements and performance expectations. Internal independent assessment is one of these assurance activities. Independent appraisals are combined with external audits and appraisals, self-assessments, peer reviews, project reviews, and other internal and external audits (e.g., financial, contractual) for a more complete assurance view. At SNL, internal independent appraisals are performed by the Audit Center, which reports directly to the Executive Vice President. ES&H independent appraisals are the responsibility of the ES&H and Quality Assessments Department, with a staff complement of eight. With our organization's charter to perform internal, independent appraisals, we set out to develop an approach and associated tools, which would be useful in the overall SNL environment and within our resource limitations.

Solid Polymer Electrolytes (SPE) are widely used in batteries and fuel cells because of the high ionic conductivity that can be achieved at room temperature. The ions are usually Li or protons, although other ions can be shown to conduct in these polymer films. There has been very little work on using these films as chemical sensors. We have found that thin films of polymers like polyethyleneoxide (PEO) are very sensitive to low concentrations of volatile organic compounds (VOCS) like common solvents. We will present impedance spectroscopy of PEO films in the frequency range 0.01 Hz to 1 MHz for different concentrations of VOCS. We find that the measurement frequency is important for distinguishing ionic conductivity from the double layer capacitance and parasitic capacitances.

A procedure has been developed to represent the loading on a penetrator and its motion during oblique penetration into geologic media. The penetrator is modeled with the explicit dynamics, finite element computer program PRONTO 3D and the coupled pressure on the penetrator is given in a new loading option based on a separate cavity expansion (CE) solution that accounts for the pressure-reduction from a nearby target free surface. The free-surface influ- ence distance is selected in a predictive manner by considering the pressure to expand a spherical cavity in a finite radius sphere of the target material. The CE/PRONTO 3D procedure allows a detailed description of the penetrator for predicting shock environments or structural failure dur- ing the entire penetration event and is sufficiently rapid to be used in design optimization. It has been evaluated by comparing its results with data from two field tests of a full-scale penetrator into frozen soil at an impact angles of 49.6 and 52.5 degrees from the horizontal. The measured penetrator rotations were 24 and 22 degrees, respectively. In the simulation, the rotation was21 degrees and predominately resulted from the pressure reduction of the free surface. Good agree- ment was also found for the penetration depth and axial and lateral acceleration at two locations in the penetrator.

Chemical Equilibrium calculations are presented that are relevant to the purification of molten silicon by gas-blowing. The equilibrium distributions of silicon, boron, phosphorus carbon and iron among the solid, liquid and gas phases are reported for a variety of added chemicals, temperatures and total pressures. The identities of the dominant chemical species for each element in each phase are also provided for these conditions. The added gases examined are O(2), air, water, wet air, HCl, Cl(2), Cl(2)/O(2), SiCl(4), NH(3), NH(4)OH, and NH(4)Cl. These calculations suggest possible purification schemes, although kinetic or transport limitations may prove to be significant

Results from a Fire Test with a three-by-three stack of standard 6 m long International Standards Organization shipping containers containing combustible fuels and empty radioactive materials packages are reported and discussed. The stack is intended to simulate fire conditions that could occur during on-deck stowage on container cargo ships. The fire is initated by locating the container stack adjacent to a 9.8 x 6 m pool fire. Temperatures of both cargoes (empty and simulated radioactive materials packages) and containers are recorded and reported. Observations on the duration, intensity and spread of the fire are discussed. Based on the results, models for simulation of fire exposure of radioactive materials packages in such fires are suggested.

As a way to bootstrap the DISCOM(2) Distance Computing Program the SP2 Pilot Project was launched in March 1998. The Pilot was directed towards creating an environment to allow Sandia users to run their applications on the Accelerated Strategic Computing Initiative's (ASCI) Blue Pacific computation platform, the unclassified IBM SP2 platform at Lawrence Livermore National Laboratory (LLNL). The DISCOM(2) Pilot leverages the ASCI PSE (Problem solving Environment) efforts in networking and services to baseline the performance of the current system. Efforts in the following areas of the pilot are documented: applications, services, networking, visualization, and the system model. It details not only the running of two Sandia codes CTH and COYOTE on the Blue Pacific platform, but also the buildong of the Sandia National Laboratories (SNL) proxy environment of the RS6000 platforms to support the Sandia users.

Eigenanalysis is a critical component of structural dynamics which is essential for determinating the vibrational response of systems. This effort addresses the development of numerical algorithms associated with scalable eigensolver techniques suitable for use on massively parallel, distributed memory computers that are capable of solving large scale structural dynamics problems. An iterative Lanczos method was determined to be the best choice for the application. Scalability of the eigenproblem depends on scalability of the underlying linear solver. A multi-level solver (FETI) was selected as most promising for this component. Issues relating to heterogeneous materials, mechanisms and multipoint constraints have been examined, and the linear solver algorithm has been developed to incorporate features that result in a scalable, robust algorithm for practical structural dynamics applications. The resulting tools have been demonstrated on large problems representative of a weapon's system.

Thermal instabilities were identified in SONY-type lithium-ion cells and correlated with interactions of cell constituents and reaction products. Three temperature regions of interaction were identified and associated with the state of charge (degree of Li intercalation) of the cell. Anodes were shown to undergo exothermic reactions as low as 100 degree C involving the solid electrolyte interface (SEI) layer and the LiPF(6) salt in the electrolyte (EC-PC:DEC/IM LiPF(6)). These reactions could account for the thermal runaway observed in these cells beginning at 100 degree C. Exothermic reactions were also observed in the 200 degree C to 300 degree C region between the intercalated lithium anodes, the LiPF(6) salt, and the PVDF. These reactions were followed by a high-temperature reaction region, 300 degree C to 400 degree C, also involving the PVDF binder and the intercalated lithium anodes. The solvent was not directly involved in these reactions but served as a moderator and transport medium. Cathode exothermic reactions with the PVDF binder were observed above 200 degree C and increased with the state of charge (decreasing Li content). The stability of the PVDF binder as a function of electrochemical cycling was studied using FTIR. The infrared spectra from the extracts of both electrodes indicate that PVDF is chemically modified by exposure to the lithium cell electrolyte (as well as electrochemical cycling) in conjunction with NMP extraction. Preconditioning of PVDF to dehydrohalogenation, which may be occurring by reaction with LiPf(6), makes the PVDF susceptible to attack by a range of nucleophiles.

The steady state and transient thermal behavior of an electromigration test structure was analyzed. The test structure was a Sandia SHIELD (Self-stressing HIgh fregquency rELiability Device) electromigration test device manufactured by an outside vendor. This device has a high frequency oscillator circuit, a buffer circuit to isolate and drive the metal line to the tested (DUT), the DUT to be electromigrated itself, a metal resistance thermometry monitor, and a heater elment to temperature accelerate the electromigration effect.

A furnace has been built for the purpose of producing anisotropic porous metals through solid-gas eutectic solidification. This process allows control of continuously formed anisotropic pores in metals and was discovered at the State Metallurgical Academic' University in Dnepropetrovsk Ukraine. The process incorporates hydrogen gas within the metal as it solidifies from the molten state. Metals which do not form hydrides, including iron, nickel, aluminum, copper and others can be formed in this manner. The furnace is housed within a ~.64 meter³ (30 ft³) ASME code stamped cylindrical stainless steel vacuum/pressure vessel. The vessel is a water chilled vertical cylinder with removable covers at the top and bottom. It can be evacuated to 20 mTorr or pressurized to 5.5 MPa (800 psi). A charge of 2700 cc (167 in³) of molten metal can be melted in a crucible in the upper portion within a watercooled 30 cm (12 in.) ID induction coil. A 175 kW Inductotherm power source energizes the coil. Vertical actuation of a ceramic stopper rod allows the molten metal to be tapped into a solidification mold beneath the melting crucible. The cylindrical mold rests on a water cooled copper base inducing directional solidification from the bottom. Mixtures of hydrogen and argon gases are introduced during the process. The system is remotely controlled and located in a structure with frangible walls specially designed for possible ambient pressure excursions as a result of equipment failure. This paper includes a general description of the furnace and operating procedure and a detailed description of the control, monitoring and interlock systems.