Publications

The authors have synthesized and characterized two novel Sr compounds: [Sr({mu}-ONc){sub 2}(HONc){sub 4}]{sub 2} (1, ONc = O{sub 2}CCH{sub 2}CMe{sub 3}), and Sr{sub 5}({mu}{sub 4}-O)({mu}{sub 3}-ONep){sub 4}({mu}-ONep){sub 4}(HONep)(solv){sub 4} [ONep = OCH{sub 2}CMe{sub 3}, solv = tetrahydrofuran (THF), 2a; 1-methyl-imidazole (MeIm), (2b)], that demonstrate increased solubility in comparison to the commercially available Sr precursors. The two metal centers of 1 share 4 unidentate bridging {mu}-ONc ligands and complete their octahedral geometry through the coordination of 4 monodentate terminal HONc ligands. The structure arrangement of the central core of 2a and b are identical, wherein 4 octahedral Sr atoms are arranged in a square geometry around a {mu}{sub 4}-O ligand. An additional 7-coordinated Sr atom sits directly atop the {mu}{sub 4}-O to form a square base pyramidal arrangement of the Sr atoms but the apical Sr-O distance is too long to be considered a bond. In solution, compound 1 is disrupted forming a monomer but 2a and b retain their structures.

Plate impact, shock wave experiments provide a unique method to investigate the time-dependent mechanisms and the kinetics associated with pressure-induced phenomena, such as chemical reactions and phase transformations. The very rapid and well defined loading conditions associated with plate-impact experiments permit real-time examination of the shock-induced changes. Further, the ability to propagate the shock wave along various crystallographic directions provides the means to perform careful analysis of the stress and orientational dependence. Recently, an experimental method has been developed to observe real-time changes in the absorption transmission of materials, with 100 or 200 ps resolution, in single-event, plate impact shock experiments [1-4]. These data can provide useful information regarding the material under investigation. In particular, the dependence of the absorption edge on photon energy can distinguish between direct and indirect electronic transitions, and can provide an estimate of the band-gap energy of the material [5]. Along with ab-initio techniques to calculate the electronic structure of a crystalline system, this electronic information can be used to gain insight regarding the crystal structure. As described in Ref. [1,2,4] the wurtzite-to-rocksalt phase transition in cadmium sulfide (CdS) is well suited to investigation through the use of fast electronic spectroscopy; the wurtzite and rocksalt phases exhibit a direct and indirect band gap with band gap energies of 2.5 and 1.5-1.7 eV, respectively [6-8]. The intent of this work was to use picosecond electronic spectroscopy and ab-initio methods to examine the real-time structural changes that occur in the initial stages of the shock-induced wurtzite-to-rocksalt phase transition in single crystal CdS.

Recently there has been a noted worldwide increase in violent actions including attempted sabotage at nuclear power plants. Several organizations, such as the International Atomic Energy Agency and the US Nuclear Regulatory Commission, have guidelines, recommendations, and formal threat- and risk-assessment processes for the protection of nuclear assets. Other examples are the former Defense Special Weapons Agency, which used a risk-assessment model to evaluate force-protection security requirements for terrorist incidents at DOD military bases. The US DOE uses a graded approach to protect its assets based on risk and vulnerability assessments. The Federal Aviation Administration and Federal Bureau of Investigation conduct joint threat and vulnerability assessments on high-risk US airports. Several private companies under contract to government agencies use formal risk-assessment models and methods to identify security requirements. The purpose of this paper is to survey these methods and present an overview of all potential types of sabotage at nuclear power plants. The paper discusses emerging threats and current methods of choice for sabotage--especially vehicle bombs and chemical attacks. Potential consequences of sabotage acts, including economic and political; not just those that may result in unacceptable radiological exposure to the public, are also discussed. Applicability of risk-assessment methods and mitigation techniques are also presented.

The vulnerability analysis methodology developed for fixed nuclear material sites has proven to be extremely effective in assessing associated transportation issues. The basic methods and techniques used are directly applicable to conducting a transportation vulnerability analysis. The purpose of this paper is to illustrate that the same physical protection elements (detection, delay, and response) are present, although the response force plays a dominant role in preventing the theft or sabotage of material. Transportation systems are continuously exposed to the general public whereas the fixed site location by its very nature restricts general public access.

To date, the Department of Energy's (DOE) Material Protection, Control, and Accountancy (MPC and A) program has assisted in the implementation of operational site-wide MPC and A systems at several nuclear facilities in Russia. Eleven sites from the civilian sector have completed the site-wide installations and two have completed sub-site installations. By the end of 1999, several additional sites will have completed site-wide and sub-site system installations through DOE assistance. the effort at the completed sites has focused primarily on the design, integration, and installation of upgraded MPC and A systems. In most cases, little work has been performed to ensure that the installed systems will be sustained. Because of concerns that the installed systems would not be operated in the future, DOE established a sustainability pilot program involving the 11 sites. The purpose of DOE's MPC and A Sustainability Program is to ensure that MPC and A upgrades installed at sites in Russia are effective and will continue to operate over the long term. The program mission is to work with sites where rapid upgrades have been completed to cultivate enduring and consistent MPC and A practices. The program attempts to assist the Russian sites to develop MPC and A organizations that will operate, maintain, and continue to improve the systems and procedures. Future assistance will strive to understand and incorporate culturally sensitive approaches so that the sites take ownership for all MPC and A matters. This paper describes the efforts of the sustainability program to date.

This work has been performed as part of the search for possible ways to utilize the capabilities of laser and particle beams techniques in shock wave and equation of state physics. The peculiarity of these techniques is that we have to deal with micron-thick targets and not well reproducible incident shock wave parameters, so all measurements should be of a high resolution and be done in one shot. Besides the Hugoniots, the experimental basis for creating the equations of state includes isentropes corresponding to unloading of shock-compressed matter. Experimental isentrope data are most important in the region of vaporization. With guns or explosive facilities, the unloading isentrope is recovered from a series of experiments where the shock wave parameters in plates of standard low-impedance materials placed behind the sample are measured [1,2]. The specific internal energy and specific volume are calculated from the measured p(u) release curve which corresponds to the Riemann integral. This way is not quite suitable for experiments with beam techniques where the incident shock waves are not well reproducible. The thick foil method [3] provides a few experimental points on the isentrope in one shot. When a higher shock impedance foil is placed on the surface of the material studied, the release phase occurs by steps, whose durations correspond to that for the shock wave to go back and forth in the foil. The velocity during the different steps, connected with the knowledge of the Hugoniot of the foil, allows us to determine a few points on the isentropic unloading curve. However, the method becomes insensitive when the low pressure range of vaporization is reached in the course of the unloading. The isentrope in this region can be measured by recording the smooth acceleration of a thin witness plate foil. With the mass of the foil known, measurements of the foil acceleration will give us the vapor pressure.

The Autoridad Regulatoria Nuclear of Argentina (ARN), the International Atomic Energy Agency (IAEA), ABACC, the US Department of Energy, and the US Support Program POTAS, cooperated in the development of a Remote Monitoring System for nuclear nonproliferation efforts. This system was installed at the Embalse Nuclear Power Station last year to evaluate the feasibility of using radiation sensors in monitoring the transfer of spent fuel from the spent fuel pond to dry storage. The key element in this process is to maintain continuity of knowledge throughout the entire transfer process. This project evaluated the fundamental design and implementation of the Remote Monitoring System in its application to regional and international safeguard efficiency. New technology has been developed to enhance the design of the system to include storage capability on board sensor platforms. This evaluation has led to design enhancements that will assure that no data loss will occur during loss of RF transmission of the sensors.

J. P. Wilcoxon and G. A. Samara Crystalline, size-selected Si nanocrystals in the size range 1.8-10 nm grown in inverse micellar cages exhibit highly structured optical absorption and photoluminescence (PL) across the visible range of the spectrum. The most intense PL for the smallest nanocrystals produced This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, make any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. to induce a useful level of visible photoluminescence (PL) from silicon (Si). The approaches understood. Visible PL has been observed from Si nanocrystals, or quantum dots, produced by a variety of techniques including aerosols,2 colloids,3 and ion implantation.4 However, all of The optical absorption spectra of our nanocrystals are much richer in spectral features spectrum of bulk Si where the spectral features reflect the details of the band structure shown in nanocrystals estimated to have a Si core diameter of 1-2 nm. These measured quantum those in the spectrum of bulk Si in Fig. 1 are striking indicating that nanocrystals of this size 8-Room temperature PL results on an HPLC size-selected, purified 2 nm nanocrystals but blue shifted by -0.4 eV due to quantum confinement. Excitation at 245 nm yields the PL shows the PL spectrum for a similar sample excited at 490 nm (2.53 eV) trapped excitons at the surface of Si nanocrystals. The excitons are obtained for dimer bonds 1.8- 10 nm. These nanocrystals retain bulk-like optical absorption and an indirect bandgap Figure 1. The absorption spectrum of d = 2 nm Si nanocrystals compared to that of bulk7 Si. Figure 2. The extinction and PL (excitation at 490 nm) spectra ford= 8-10 nm Si nanocrystals.

Multiple-energy (30-325 keV) O{sup +} implantation into GaN field-effect transistor structures (n {approximately} 10{sup 18} cm{sup {minus}3}, 3000 {angstrom} thick) can produce as-implanted sheet resistances of 4 x 10{sup 12} {Omega}/{open_square}, provided care is taken to ensure compensation of the region up to the projected range of the lowest energy implant. The sheet resistance remains above 10{sup 7} {Omega}/{open_square} to annealing temperatures of {approximately} 650 C and displays an activation energy of 0.29 eV. No diffusion of the implanted oxygen was observed for anneals up to 800 C.

The thermal oxidation of pentacontane (C{sub 50}H{sub 102}), and of the homopolymer polyisoprene, has been investigated using {sup 17}O NMR spectroscopy. By performing the oxidation using {sup 17}O labeled O{sub 2} gas, it is possible to easily identify degradation products, even at relatively low concentrations. It is demonstrated that details of the degradation mechanism can be obtained from analysis of the {sup 17}O NMR spectra as a function of total oxidation. Pentacontane reveals the widest variety of reaction products, and exhibits changes in the relative product distributions with increasing O{sub 2} consumption. At low levels of oxygen incorporation, peroxides are the major oxidation product, while at later stages of degradation these species are replaced by increasing concentrations of ketones, alcohols, carboxylic acids and esters. Analyzing the product distribution can help in identification of the different free-radical decomposition pathways of hydroperoxides, including recombination, proton abstraction and chain scission, as well as secondary reactions. The {sup 17}O NMR spectra of thermally oxidized polyisoprene reveal fewer degradation functionalities, but exhibit an increased complexity in the type of observed degradation species due to structural features such as unsaturation and methyl branching. Alcohols and ethers formed from hydrogen abstraction and free radical termination.

A new forcefield model was developed for modeling phosphate materials that have many important applications in the electronics and biomedical industries. Molecular dynamics simulations of a series of lithium phosphate glass compositions were performed using the new forcefield model. A high concentration of three member rings (P{sub 3}O{sub 3}) was found in the glass of intermediate composition (0.2 Li{sub 2}O {center_dot} 0.8 P{sub 2}O{sub 5}) that corresponds to the minimum in the glass transition temperature curve for the compositional series.

An eddy-current scanning system is being developed to allow the International Atomic Energy Agency (IAEA) to verify the integrity of nuclear material storage containers. Such a system is necessary to detect attempts to remove material from the containers in facilities where continuous surveillance of the containers is not practical. Initial tests have shown that the eddy-current system is also capable of verifying the identity of each container using the electromagnetic signature of its welds. The DOE-3013 containers proposed for use in some US facilities are made of an austenitic stainless steel alloy, which is nonmagnetic in its normal condition. When the material is cold worked by forming or by local stresses experienced in welding, it loses its austenitic grain structure and its magnetic permeability increases. This change in magnetic permeability can be measured using an eddy-current probe specifically designed for this purpose. Initial tests have shown that variations of magnetic permeability and material conductivity in and around welds can be detected, and form a pattern unique to the container. The changes in conductivity that are present around a mechanically inserted plug can also be detected. Further development of the system is currently underway to adapt the system to verifying the integrity and identity of sealable, tamper-indicating enclosures designed to prevent unauthorized access to measurement equipment used to verify international agreements.

Surface texture promotes enhanced light absorption in Si solar cells. The quality of lower cost multicrystalline-silicon (mc-Si) has increased to the point that its cell performance is close to that of single c-Si cells, with the major difference resulting from the inability to texture mc-Si affordably. This has reduced the cost-per-watt advantage of mc-Si. Surface texturing aimed at enhanced absorption in Si has been historically obtained by creating multimicrometer-sized pyramids using anisotropic wet etchants on single-crystalline silicon that take advantage of its single crystalline orientation. Since the surface feature sizes are several times the length of the incident solar wavelengths involved, the optical analysis of the reflected and absorbed light can be understood using geometrical optics. Geometrical textures reduce reflection and improve absorption by double-bounce and oblique light coupling into the semiconductor. However, geometrical texturing suffers from several disadvantages that limit its effectiveness. Some of these are listed below: (a) Wet-chemical anisotropic etching used to form random pyramids on <100> crystal orientation is not effective in the texturing of low-cost multicrystalline wafers, (b) Anti-reflection films deposited on random features to reduce reflection have a resonant structure limiting their effectiveness to a narrow range of angles and wavelengths. Various forms of surface texturing have been applied to mc-Si in research, including laser-structuring, mechanical grinding, porous-Si etching, and photolithographically defined etching. However, these may be too costly to ever be used in large-scale production. A Japanese firm has reported the development of an RIE process using Cl{sub 2} gas, which textures multiple wafers per batch, making it attractive for mass-production [1]. Using this process, they have produced a 17.1% efficient 225-cm{sup 2} mc-Si cell, which is the highest efficiency mc-Si cell of its size ever reported. This proves that RIE texturing does not cause performance-limiting damage to Si cells. In this paper, we will discuss an RIE texturing process that avoids the use of toxic and corrosive Cl{sub 2} gas.

The safe, secure and reliable application of Microelectromechanical Systems (MEMS) devices requires knowledge about the distribution in material and mechanical properties of the small-scale structures. A new testing program at Sandia is quantifying the strength distribution using polysilicon samples that reflect the dimensions of critical MEMS components. The strength of polysilicon fabricated at Sandia's Microelectronic Development Laboratory was successfully measured using samples 2.5 microns thick, 1.7 microns wide with lengths between 15 and 25 microns. These tensile specimens have a freely moving hub on one end that anchors the sample to the silicon die and allows free rotation. Each sample is loaded in uniaxial tension by pulling laterally with a flat tipped diamond in a computer-controlled Nanoindenter. The stress-strain curve is calculated using the specimen cross section and gage length dimensions verified by measuring against a standard in the SEM.

In this paper, we introduce a new approach for altering the properties of bridged polysilsesquioxane xerogels using post-processing mobilization of the polymeric network. The bridging organic group contains latent functionalities that can be liberated thermally, photochemically, or by chemical means after the gel has been processed to a xerogel. These modifications can produce changes in density, volubility, porosity, and or chemical properties of the material. Since every monomer possesses two latent functional groups, the technique allows for the introduction of high levels of functionality in hybrid organic-inorganic materials. Dialkylenecarbonate-bridged polysilsesquioxane gels were prepared by the sol-gel polymerization of bis(triethoxysilylpropyl)carbonate (1) and bis(triethoxysilylisobutyl)-carbonate (2). Thermal treatment of the resulting non-porous xerogels and aerogels at 300-350 C resulted in quantitative decarboxylation of the dialkylenecarbonate bridging groups to give new hydroxyalkyl and olefinic substituted polysilsesquioxane monolithic xerogels and aerogels that can not be directly prepared through direct sol-gel polymerization of organotrialkoxysilanes.

Sandia National Laboratories has demonstrated significant performance gains in crystalline silicon solar cell technology through the use of plasma-processing for the deposition of silicon nitride by Plasma Enhanced Chemical Vapor Deposition (PECVD), plasma-hydrogenation of the nitride layer, and reactive-ion etching of the silicon surface prior to the deposition to decrease the reflectivity of the surface. One of the major problems of implementing plasma processing into a cell production line is the batch configuration and/or low throughput of the systems currently available. This report describes the concept of a new in-line plasma processing system that could meet the industrial requirements for a high-throughput and cost effective solution for mass production of solar cells.

Surface texturing of Si to enhance absorption particularly in the IR spectral region has been extensively investigated. Previous research chiefly examined approaches based on geometrical optics. These surface textures typically consist of pyramids with dimensions much larger than optical wavelengths. We have investigated a physical optics approach that relies on surface texture features comparable to, or smaller than, the optical wavelengths inside the semiconductor material. Light interaction at this are strongly dependent on incident polarization and surface profile. Nanoscale textures can be tuned for either narrow band, or broad band absorptive behavior. Lowest broadband reflection has been observed for triangular profiles with linewidths significantly less than 100 nm. Si nanostructures have been integrated into large ({approximately}42 cm{sup 2}) area solar cells, Internal quantum efficiency measurements in comparison with polished and conventionally textured cells show lower efficiency in the UV-visible (350-680 mu), but significantly higher IR (700-1200 nm) efficiency.

This paper describes preliminary results in the development of an acoustic wave (SAW) microsensor array. The array is based on a novel configuration that allows for three sensors and a phase reference. Two configurations of the integrated array are discussed: a hybrid multichip-module based on a quartz SAW sensor with GaAs microelectronics and a fully monolithic GaAs-based SAW. Preliminary data are also presented for the use of the integrated SAW array in a gas-phase chemical micro system that incorporates microfabricated sample collectors and concentrators along with gas chromatography (GC) columns.

Chemically sensitive polymers coated on delay lines utilizing shear horizontal surface acoustic wave (SH-SAW) sensors are investigated for the detection of organic analytes in liquid environments. The SH-SAW sensor platform was designed and fabricated on 36{degree} rotated Y-cut LiTaO{sub 3}. By depositing a SiO{sub 2} dielectric layer over the entire device prior to applying the polymer film, partial electrical passivation of the interdigital transducers (IDT) is obtained while increasing the mass sensitivity of the device. Changes in the mechanical properties of the chemically sensitive polymer materials were clearly detectable through a frequency shift at least one order of magnitude larger than that of a coated-quartz crystal resonator (QCR) in a similar experiment.

Low energy electron microscopy (LEEM) and scanning tunneling microscopy (STM) have been used to investigate the faceting of W(111) as induced by Pt. The atomically rough W(111) surface, when fully covered with a monolayer film of Pt and annealed to temperatures higher than {approximately}750 K, experiences a significant morphological restructuring: the initially planar surface undergoes a faceting transition and forms three-sided pyramids with {l_brace}211{r_brace} faces. When Pt is dosed onto the heated surface, the transition from planar to faceted structure proceeds through the nucleation and growth of spatially separated faceted regions, as shown by LEEM. STM reveals the atomic structure of the partially faceted surface, with large planar regions, dotted by clusters of pyramids of various sizes.

The rotorcraft industry is constantly evaluating new types of lightweight composite materials that not only enhance the safety and reliability of rotor components, but also improve performance and extend operating life as well. The tests required for these evaluations are typically quite complex requiring massive test fixtures, in many cases, along with multiple actuators for loading test articles at various points simultaneously. This paper discusses the background for development of the facility, as well as hardware and overall system design and implementation. Additional topics that are covered include data acquisition, implementation of nondestructive inspection techniques during the test process, and some results from the initial test series performed in the facility.

The Accident Response Mobile Manipulator System (ARMMS) is a teleoperated emergency response vehicle that deploys two hydraulic manipulators, five cameras, and an array of sensors to the scene of an incident. It is operated from a remote base station that can be situated up to four kilometers away from the site. Recently, a modular telerobot control architecture called SMART (Sandia's Modular Architecture for Robotic and Teleoperation) was applied to ARMMS to improve the precision, safety, and operability of the manipulators on board. Using SMART, a prototype manipulator control system was developed in a couple of days, and an integrated working system was demonstrated within a couple of months. New capabilities such as camera teleoperation, autonomous tool changeout and dual manipulator control have been incorporated. The final system incorporates twenty-two separate modules and implements eight different behavior modes. This paper describes the integration of SMART into the ARMMS system.

This paper presents a practical approach for integrating automatically designed fixtures with automated assembly planning. Product assembly problems vary widely; here the focus is on assemblies that are characterized by a single base part to which a number of smaller parts and subassemblies are attached. This method starts with three-dimension at CAD descriptions of an assembly whose assembly tasks require a fixture to hold the base part. It then combines algorithms that automatically design assembly pallets to hold the base part with algorithms that automatically generate assembly sequences. The designed fixtures rigidly constrain and locate the part, obey task constraints, are robust to part shape variations, are easy to load, and are economical to produce. The algorithm is guaranteed to find the global optimum solution that satisfies these and other pragmatic conditions. The assembly planner consists of four main elements: a user interface, a constraint system, a search engine, and an animation module. The planner expresses all constraints at a sequencing level, specifying orders and conditions on part mating operations in a number of ways. Fast replanning enables an interactive plan-view-constrain-replan cycle that aids in constrain discovery and documentation. The combined algorithms guarantee that the fixture will hold the base part without interfering with any of the assembly operations. This paper presents an overview of the planners, the integration approach, and the results of the integrated algorithms applied to several practical manufacturing problems. For these problems initial high-quality fixture designs and assembly sequences are generated in a matter of minutes with global optimum solutions identified in just over an hour.

Automatic assembly sequencing and visualization tools are valuable in determining the best assembly sequences, but without Human Factors and Figure Models (HFFMs) it is difficult to evaluate or visualize human interaction. In industry, accelerating technological advances and shorter market windows have forced companies to turn to an agile manufacturing paradigm. This trend has promoted computerized automation of product design and manufacturing processes, such as automated assembly planning. However, all automated assembly planning software tools assume that the individual components fly into their assembled configuration and generate what appear to be perfectly valid operations, but in reality some operations cannot physically be carried out by a human. For example, the use of a ratchet may be reasoned feasible for an assembly operation; however, when a hand is placed on the tool the operation is no longer feasible, perhaps because of inaccessibility, insufficient strength or human interference with assembly components. Similarly, human figure modeling algorithms may indicate that assembly operations are not feasible and consequently force design modifications, however, if they had the capability to quickly generate alternative assembly sequences, they might have identified a feasible solution. To solve this problem, HFFMs must be integrated with automated assembly planning which allows engineers to quickly verify that assembly operations are possible and to see ways to make the designs even better. This paper presents a framework for integrating geometry-based assembly planning algorithms with commercially available human figure modeling software packages. Experimental results to selected applications along with lessons learned are presented.

A molecular-level understanding of mineral-water interactions is critical for the evaluation and prediction of the sorption properties of clay minerals that may be used in various chemical and radioactive waste disposal methods. Molecular models of metal sorption incorporate empirical energy force fields, based on molecular orbital calculations and spectroscopic data, that account for Coulombic, van der Waals attractive, and short-range repulsive energies. The summation of the non-bonded energy terms at equally-spaced grid points surrounding a mineral substrate provides a three dimensional potential energy grid. The energy map can be used to determine the optimal sorption sites of metal ions on the exposed surfaces of the mineral. By using this approach, we have evaluated the crystallographic and compositional control of metal sorption on the surfaces of kaolinite and illite. Estimates of the relative sorption energy and most stable sorption sites are derived based on a rigid ion approximation.

Environmental scientists have long appreciated that the distribution coefficient (the ''K{sub d}'' or ''constant K{sub d}'') approach predicts the partitioning of heavy metals between sediment and groundwater inaccurately; nonetheless, transport models applied to problems of environmental protection and groundwater remediation almost invariably employ this technique. To examine the consequences of this practice, we consider transport in one dimension of Pb and other heavy metals through an aquifer containing hydrous ferric oxide, onto which heavy metals sorb strongly. We compare the predictions of models calculated using the K{sub d} approach to those given by surface complexation theory, which is more realistic physically and chemically. The two modeling techniques give qualitatively differing results that lead to divergent cleanup strategies. The results for surface complexation theory show that water flushing is ineffective at displacing significant amounts of Pb from the sorbing surface. The effluent from such treatment contains a ''tail'' of small but significant levels of contamination that persists indefinitely. Subsurface zones of Pb contamination, furthermore, are largely immobile in flowing groundwater. These results stand in sharp contrast to the predictions of models constructed using the k{sub d} approach, yet are consistent with experience in the laboratory and field.

We demonstrate a ''universal solvent sensor'' constructed from a small array of carbon/polymer composite chemiresistors that respond to solvents spanning a wide range of Hildebrand volubility parameters. Conductive carbon particles provide electrical continuity in these composite films. When the polymer matrix absorbs solvent vapors, the composite film swells, the average separation between carbon particles increases, and an increase in film resistance results, as some of the conduction pathways are broken. The adverse effects of contact resistance at high solvent concentrations are reported. Solvent vapors including isooctane, ethanol, dlisopropyhnethylphosphonate (DIMP), and water are correctly identified (''classified'') using three chemiresistors, their composite coatings chosen to span the full range of volubility parameters. With the same three sensors, binary mixtures of solvent vapor and water vapor are correctly classified, following classification, two sensors suffice to determine the concentrations of both vapor components. Polyethylene vinylacetate and polyvinyl alcohol (PVA) are two such polymers that are used to classify binary mixtures of DIMP with water vapor; the PVA/carbon-particle-composite films are sensitive to less than 0.25{degree}A relative humidity. The Sandia-developed VERI (Visual-Empirical Region of Influence) technique is used as a method of pattern recognition to classify the solvents and mixtures and to distinguish them from water vapor. In many cases, the response of a given composite sensing film to a binary mixture deviates significantly from the sum of the responses to the isolated vapor components at the same concentrations. While these nonlinearities pose significant difficulty for (primarily) linear methods such as principal components analysis, VERI handles both linear and nonlinear data with equal ease. In the present study the maximum speciation accuracy is achieved by an array containing three or four sensor elements, with the addition of more sensors resulting in a measurable accuracy decrease.

We have observed discrete random telegraph signals (RTS'S) in the drain voltages of three, observed above 30 K were thermally activated. The switching rate for the only RTS observed below 30 K was thermally activated above 30 K but temperature-independent below 10 K. To our knowledge, this cross-over from thermal activation to tunneling behavior has not been previously observed for RTS's Metal-oxide-semiconductor field-effect transistors (MCEWETS) often exhibit relatively large levels of low-frequency (1/fl noise) [1,2]. Much evidence suggests that this noise is related to the capture all cases, switching rates have been thermally activated, often with different activation energies for capture and/or emission is accompanied by lattice relaxation. Though thermally activated behavior has sufficiently low temperatures [7,9]. While not observed in MOSFETS, cross-over from thermal activation to configurational tunneling has been observed for RTS's in junctions [13]. drain voltage was observed to randomly switch between two discrete levels, designated as Vup and Vdn, similar to RTS's reported by others [2,7'- 11 ]. We have characterized six RTS `S for temperatures above 30 K where thermally activated switching rates are observed. The properties of five of these have been the trap, i.e., the mean time a captured charge carrier spends in the trap before it is emitted. Similarly, we identify the mean time in the low resistance state ( trup in state Vup) as the capture time rc. F@ure 1 shows a typical time trace of the drain-voltage fluctuation &d(t)= Vd(t)+Vd>. This indicate that both the mean capture and emission times become independent of Tat low temperatures and where a= capture or emission, is temperature independent. The solid curve in Figure 3(a) (mean capture time) was obtained using a weighted nonlinear charge carriers are not in thermal equilibrium with the lattice, i.e., that while the lattice is being cooled Instead, we believe that the transition from thermally activated to temperature-independent switching rates is associated with a lattice relaxation mechanism similar to that observed in metal- insulator-metal tunnel junctions [13]. Capture and emission of carriers are mediated by lattice relaxation, which proceeds via a thermally activated process at higher temperatures and a configurational tunneling electron capture rate depended on both lattice and electron temperatures while the emission rate Fkure 2. Arrhenius plot showing the thermally-activated behavior of both the mean capture (triangle) and emission (square) times of the RTS for temperatures above 20 K'.

The Ministry of the Russian Federation for Atomic Energy (MINATOM) and the US Department of Energy (DOE) are engaged in joint, cooperative efforts to reduce the likelihood of nuclear proliferation by enhancing Material Protection, Control and Accounting (MPC&A) systems in both countries. Mayak Production Association (Mayak) is a major Russian nuclear enterprise within the nuclear complex that is operated by lylINATOM. This paper describes the nature, scope, and status of the joint, cooperative efforts to enhance existing MPC&A systems at Mayak. Current cooperative efforts are focused on enhancements to the existing MPC&A systems at two of the plants operated by Mayak that work with proliferation-sensitive nuclear materials.

A distributed temperature sensor (DTS) system, utilizing Raman backscattering to measure temperatures of optical fiber, has recently been installed in production wells at the Beowawe and Dixie Valley, NV, geothermal fields. The system has the potential to reduce the cost and complexity of acquiring temperature logs. However, the optical transmission of the initial fibers installed at Beawawe degraded over several months, resulting in temperature errors. Optical transmission spectra of the failed fibers indicate hydroxide contamination via hydrogen diffusion as a possible failure mechanism. Additional fibers with coatings designed to resist hydrogen diffusion were installed and have maintained their optical transmission over several months in the 340-360 F Beowawe wells. The same fibers installed in a 470 F Dixie Valley well rapidly failed. Possible methods to prevent fiber degradation include encasing the fiber in metallic buffer layer that resists hydrogen diffusion. Additional methods to correct temperature errors include using additional optical sources to measure fiber losses at the operating wavelengths. Although the DTS system is expected to have one degree F accuracy, we have observed an average accuracy of five degrees. The fiber connections appear to be the uncertainty source. Using connectors with greater stability should restore accuracy.

We have developed a new approach (the LQR method) for calculating the reflectivity and transmission spectra of a multilayer optical material with N interfaces, as an alternative to the matrix method. The approach allows the inclusion of the effects of interface roughness by introducing a ''rough'' element between adjacent layers. For this purpose we have developed an empirical model, which describes the effect of interface roughness on an optical beam passing through or being reflected from an interface. An assessment of the interface roughness of a multilayer structure was carried out by fitting the experimental reflectivity spectrum of GaAs/AlGaAs multiple quantum well samples with and without oxidation of the barrier layers. The refractive index and the thickness of the oxidized layers were also obtained from the fit.

SUMMiT (Sandia Ultra-planar Multi-level MEMS Technology) at the Sandia National Laboratories' MDL (Microelectronics Development Laboratory) is a standardized MEMS (Microelectromechanical Systems) technology that allows designers to fabricate concept prototypes. This technology provides four polysilicon layers plus three sacrificial oxide layers (with the third oxide layer being planarized) to enable fabrication of complex mechanical systems-on-a-chip. Quantified reproducibility of the SUMMiT process is important for process engineers as well as designers. Summary statistics for critical MEMS technology parameters such as film thickness, line width, and sheet resistance will be reported for the SUMMiT process. Additionally, data from Van der Pauw test structures will be presented. Data on film thickness, film uniformity and critical dimensions of etched line widths are collected from both process and monitor wafers during manufacturing using film thickness metrology tools and SEM tools. A standardized diagnostic module is included in each SWiT run to obtain post-processing parametric data to monitor run-to-run reproducibility such as Van der Pauw structures for measuring sheet resistance. This characterization of the SUMMiT process enables design for manufacturability in the SUMMiT technology.

The implementation of a backscattered x-ray landmine detection system has been demonstrated in laboratories at both Sandia National Laboratories (SNL) and the University of Florida (UF) The next step was to evaluate the modality by assembling a system for fieldwork and to evaluate the systems performance with real landmines. To assess the system's response to a variety of objects, buried simulated plastic and metal antitank landmines, surface simulated plastic antipersonnel landmines, and surface metal fragments were used as targets for the field test. The location of the test site was an unprepared field at SNL. The tests conducted using real landmines were held at UF using various burial depths. The field tests yielded the same levels of discrimination between soil and landmines that had been detected in laboratory experiments. The tests on the real landmines showed that the simulated landmines were a good approximation. The real landmines also contained internal features that would allow not only the detection of the landmines, but also the identification of them.

This contribution proposes strawman techniques for Security Service Discovery by ATM endsystems in ATM networks. Candidate techniques include ILMI extensions, ANS extensions and new ATM anycast addresses. Another option is a new protocol based on an IETF service discovery protocol, such as Service Location Protocol (SLP). Finally, this contribution provides strawman requirements for Security-Based Routing in ATM networks.

As a result of the Safeguards Arrangement between the US Department of Energy (DOE) and the Australian Safeguards and Non-Proliferation Office (ASNO) concerning international safeguards R and D, ASNO and Sandia National Laboratories (SNL) have agreed to jointly develop a remote monitoring system at the HIFAR reactor, Lucas Heights, Australia. The HIFAR reactor is a high flux research reactor operated by the Australian Nuclear Science and Technology Organization (ANSTO). The objective of the system is to remotely monitor the entire Material Balance Area (MBA) AS-A to include: fresh fuel the reactor core; spent fuel in the cropping/irradiation pond, international pond, dry spent fuel storage facility, and Dounreay flasks; and spent fuel during designated transport. The purpose is to reduce on-site inspection effort at the HIFAR reactor.

Improvements in the last decade in InP materials growth, device processing techniques, characterization, and circuit design have enabled solid-state power performance through 122 GHz. Although originally targeted for low-noise and power performance at mm-wave frequencies (>30 GHz), InP HEMTs could become the preferred device for frequencies as low as 800 MHz. This investment has benefited the microwave frequency regime with higher efficiency and power densities at lower operating voltages. State-of-the-art microwave performance at lower operating voltage provides a path to smaller, lighter-weight systems in the battery operated arena of commercial and defense electronics. This paper describes an InP HEMT technology being investigated for many power and low-noise amplifier applications from UHF to W-band frequencies. Specifically the technology demonstrated 640mW/mm power density, 27 dB gain, and 84% power-added efficiency at L-band with a bias of 3.0 volts. Based on the author's literature search, this is a record efficiency at L-band with an operating voltage of less than 5 volts.

Long-term nuclear material storage will require in-vault data verification, sensor testing, error and alarm response, inventory, and maintenance operations. System concept development efforts for a comprehensive nuclear material management system have identified the use of a small flexible mobile automation platform to perform these surveillance and maintenance operations. In order to have near-term wide-range application in the Complex, a mobile surveillance system must be small, flexible, and adaptable enough to allow retrofit into existing special nuclear material facilities. The objective of the Mobile Surveillance and Monitoring Robot project is to satisfy these needs by development of a human scale mobile robot to monitor the state of health, physical security and safety of items in storage and process; recognize and respond to alarms, threats, and off-normal operating conditions; and perform material handling and maintenance operations. The system will integrate a tool kit of onboard sensors and monitors, maintenance equipment and capability, and SNL developed non-lethal threat response technology with the intelligence to identify threats and develop and implement first response strategies for abnormal signals and alarm conditions. System versatility will be enhanced by incorporating a robot arm, vision and force sensing, robust obstacle avoidance, and appropriate monitoring and sensing equipment.

Two novel Group IV precursors, titanium (IV) neo-pentoxide, [Ti({mu}-ONep)(ONep){sub 3}]{sub 2} (l), and zirconium (IV) neo-pentoxide, [Zr({mu}-ONep)(ONep){sub 3}]{sub 2} (2), were reported to possess relatively high volatility at low temperatures. These compounds were therefore investigated as MOCVD precursors using a lamp-heated cold-wall CVD reactor and direct sublimation without carrier gas. The ONep derivatives proved to be competitive precursors for the production of thin films of the appropriate MO{sub 2} (M = Ti or Zr) materials in comparison to other metallo-organic precursors. Compound 1 was found to sublime at 120 C with a deposition rate of {approximately}0.350 {mu}m/min onto a substrate at 330 C forming the anatase phase with < 1% residual C found in the final film. Compound 2 was found to sublime at 160 C and deposited as crystalline material at 300 C with < 1% residual C found in the final film. A comparison to standard alkoxide and {beta}-diketonates is presented where appropriate.

Conductor inks containing silver and palladium, used in ceramic co-fired circuits, sometimes undergo an anomalously large expansion during heating in the temperature range where interdiffusion occurs. Therefore, the interdiffusion of silver and palladium was studied during heating in both air and argon using both powder and foil samples. Measurements on a powder compact made of a mixture of Ag and Pd (80% Ag) particles indicated that a very rapid expansion occurred between 375 and 400 C when heated in air but only a slight expansion occurred in Ar. A pre-alloyed powder with the same composition did not expand during heating. In situ high temperature x-ray diffraction studies indicated that both powders oxidized during heating in air, with the mixture oxidizing more and that interdiffusion occurred between 300 and 500 C. Microstructural examination indicated that larger particles with internal pores had formed in the mixture heated in air to 375 C due to rearrangement during interdiffusion. A porous region much thicker than the original silver film formed on a palladium foil sample when it was heated in air, whereas in inert atmosphere pores formed only in the silver film, indicating a Kirkendall effect occurs in both cases. Based on these results, it was concluded that the expansion of the Ag-Pd powder mixture was due to interdiffusion in the presence of oxygen, not solely to the oxidation of the Pd.

The analysis precision of any multivariate calibration method will be severely degraded if unmodeled sources of spectral variation are present in the unknown sample spectra. This paper describes a synthetic method for correcting for the errors generated by the presence of unmodeled components or other sources of unmodeled spectral variation. If the spectral shape of the unmodeled component can be obtained and mathematically added to the original calibration spectra, then a new synthetic multivariate calibration model can be generated to accommodate the presence of the unmodeled source of spectral variation. This new method is demonstrated for the presence of unmodeled temperature variations in the unknown sample spectra of dilute aqueous solutions of urea, creatinine, and NaCl. When constant-temperature PLS models are applied to spectra of samples of variable temperature, the standard errors of prediction (SEP) are approximately an order of magnitude higher than that of the original cross-validated SEPs of the constant-temperature partial least squares models. Synthetic models using the classical least squares estimates of temperature from pure water or variable-temperature mixture sample spectra reduce the errors significantly for the variable temperature samples. Spectrometer drift adds additional error to the analyte determinations, but a method is demonstrated that can minimize the effect of drift on prediction errors through the measurement of the spectra of a small subset of samples during both calibration and prediction. In addition, sample temperature can be predicted with high precision with this new synthetic model without the need to recalibrate using actual variable-temperature sample data. The synthetic methods eliminate the need for expensive generation of new calibration samples and collection of their spectra. The methods are quite general and can be applied using any known source of spectral variation and can be used with any multivariate calibration method.

Many studies have investigated the behavior of transition metal dopants in the YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} 123 superconductors. Much of this research has focused on the effects of metal ions such as Co, Fe, Zn, Ni when they are substituted for the copper ions at Cu(1) and Cu(2) sites, commonly referred to as the chain and plane sites, respectively. Trivalent ions such as Co{sup +3} and Fe{sup +3}have been shown to behave similarly in their substitution effects, displaying site preference on the Cu(1) site [3-8]. This site preference has been established with the use of techniques such as neutron diffraction and Moessbauer spectroscopy [4,5]. Thermogravimetry, electron diffraction, and analysis of lattice parameters as a function of dopant also yield results consistent with those of the structural studies with respect to the chain site preference of both Co and Fe [3,4,6-8]. The very fast convergence of a and b lattice parameters to that of the tetragonal structure, occurring at x = 0.3 Co dopant (i.e. YBa{sub 2}Cu{sub 2.7}Co{sub 0.3}O{sub 7{minus}{delta}}) for high-oxygen-content samples, coupled with information derived from diffuse scattering and oxidation behavior of these samples, has been described in detail by several authors in terms of the Co and Fe ions creating ''microchains'' at Cu(1) sites within the 123 compound [4,7-8]. The Cu(1) site dopants decrease T{sub c} at a rate of 2 to 5 K/at. %, varying to some extent with site preference [4,9].

In this paper numerical simulations of Mach 10 air flow over a hollow cylinder flare are presented in comparison with recent experimental results. The numerical study is performed using a Direct Simulation Monte Carlo code and the experimental results were obtained in the ONERA R5Ch wind tunnel. The flow phenomena involved include shock wave boundary layer interaction in hypersonic laminar flow. An analysis of the requirements on the grid resolution, number of particle simulators and run time is performed. Measured and calculated surface properties including pressure and heat transfer are compared.

In this paper, we summarize the rationale for an advanced system called Diagnostics-While-Drilling (DWD) and describe its benefits, preliminary configuration, and essential characteristics. The central concept is a closed data circuit in which downhole sensors collect information and send it to the surface via a high-speed data link, where it is combined with surface measurements and processed through drilling advisory software. The driller then uses this information to adjust the drilling process, sending control signals back downhole with real-time knowledge of their effects on performance. We outline a Program Plan for DOE, university, and industry to cooperate in the development of DWD technology.

The use of unattended monitoring systems for monitoring the status of high value assets and processes has proven to be less costly and less intrusive than the on-site inspections which they are intended to replace. However, these systems present a classic information overload problem to anyone trying to analyze the resulting sensor data. These data are typically so voluminous and contain information at such a low level that the significance of any single reading (e.g., a door open event) is not obvious. Sophisticated, automated techniques are needed to extract expected patterns in the data and isolate and characterize the remaining patterns that are due to undeclared activities. This paper describes a data analysis engine that runs a state machine model of each facility and its sensor suite. It analyzes the raw sensor data, converting and combining the inputs from many sensors into operator domain level information. It compares the resulting activities against a set of activities declared by an inspector or operator, and then presents the differences in a form comprehensible to an inspector. Although the current analysis engine was written with international nuclear material safeguards, nonproliferation, and transparency in mind, since there is no information about any particular facility in the software, there is no reason why it cannot be applied anywhere it is important to verify processes are occurring as expected, to detect intrusion into a secured area, or to detect the diversion of valuable assets.

The authors have successfully synthesized highly crystalline, size-selected indirect band-gap nanocrystals (NC) of Si, Ge and MoS{sub 2} in the size range 2-10 nm in inverse micelles and studied their optical absorption and photoluminescence (PL) properties using liquid chromatography. Room temperature, visible PL from these nanocrystals was demonstrated in the range 700-350 nm (1.8-3.5 eV). their experimental results are interpreted in terms of the corresponding electronic structure of the bulk materials and it is demonstrated that these nanocrystals retain bulk-like electronic character to sizes as small as 2 nm, but the absorbance energies are strongly blue-shifted by quantum confinement. The experimental results on Si-NCs are also compared to earlier work on Si clusters grown by other techniques and to the predictions of various model calculations. Currently, the wide variations in the theoretical predictions of the various models along with considerable uncertainties in experimental size determination for clusters less than 3-4 nm, make it difficult to select the best model.

Many applications produce three-dimensional points that must be further processed to generate a surface. Surface reconstruction algorithms that start with a set of unorganized points are extremely time-consuming. Sometimes, however, points are generated such that there is additional information available to the reconstruction algorithm. We present Spiraling Edge, a specialized algorithm for surface reconstruction that is three orders of magnitude faster than algorithms for the general case. In addition to sample point locations, our algorithm starts with normal information and knowledge of each point's neighbors. Our algorithm produces a localized approximation to the surface by creating a star-shaped triangulation between a point and a subset of its nearest neighbors. This surface patch is extended by locally triangulating each of the points along the edge of the patch. As each edge point is triangulated, it is removed from the edge and new edge points along the patch's edge are inserted in its place. The updated edge spirals out over the surface until the edge encounters a surface boundary and stops growing in that direction, or until the edge reduces to a small hole that is filled by the final triangle.

Visualization systems are complex dynamic software systems. Debugging such systems is difficult using conventional debuggers because the programmer must try to imagine the three-dimensional geometry based on a list of positions and attributes. In addition, the programmer must be able to mentally animate changes in those positions and attributes to grasp dynamic behaviors within the algorithm. In this paper we shall show that representing geometry, attributes, and relationships graphically permits visual pattern recognition skills to be applied to the debugging problem. The particular application is a particle system used for isosurface extraction from volumetric data. Coloring particles based on individual attributes is especially helpful when these colorings are viewed as animations over successive iterations in the program. Although we describe a particular application, the types of tools that we discuss can be applied to a variety of problems.

Sandia National Laboratories and the Russian Federal Nuclear Center-All Russian Research Institute for Experimental Physics (VNIIEF) (also known as Arzamas-16) are collaborating on ways to assure the highest standards of safety, security, and international accountability of fissile material. For these collaborations, sensors and information technologies have been identified as important in reaching these standards in a cost-effective manner. Specifically, Sandia and VNIIEF have established a series of remote monitoring field trials to provide a mechanism for joint research and development on storage monitoring systems. These efforts consist of the ''Container-to-Container'', ''Magazine-to-Magazine'', and ''Facility-to-Facility'' field trials. This paper will describe the evaluation exercise Sandia and VNIIEF conducted on the Magazine-to-Magazine systems. Topics covered will include a description of the evaluation philosophy, how the various sensors and system features were tested, evaluation results, and lessons learned.

The precise pore sizes defined by crystalline zeolite lattices have led to intensive research on zeolite membranes. Unfortunately zeolites have proven to be extremely difficult to prepare in a defect-free thin film form needed for membrane flux and selectivity. We introduce tetrapropylammonium (TPA), a structure-directing agent for zeolite ZSM-5, into a silica sol and exploit the development of high solvation stresses to create templated amorphous silicas with pore apertures comparable in size to those of ZSM-5. Silicon and carbon NMR experiments were performed to evaluate the efficacy of our templating approach. The {sup 29}Si NMR spectrum of the silica matrix was observed by an intermolecular cross-polarization experiment involving the {sup 1}H nuclei of TPA and the {sup 29}Si nuclei in the silica matrix. The efficiency of the cross-polarization interaction was used to investigate the degree to which the matrix formed a tight cage surrounding the template molecule. Bulk xerogels, prepared by gelation and slow drying of the corresponding sols, exhibited only weak interactions between the two sets of nuclei. Thin film xerogels, where drying stresses are greater, exhibited significantly increased interactions. Intramolecular cross-polarization experiments between the {sup 1}H and {sup 13}C nuclei of the template molecule demonstrated that much of the increased efficiency was a result of reduced rotational mobility of the TPA molecule.

The microscopic origin of compact triangular islands on close-packed surfaces is identified using kinetic Monte Carlo simulations with energy barriers obtained from density-functional calculations. In contrast to earlier accounts, corner diffusion anisotropy is found to control the shape of compact islands at intermediate temperatures. We rationalize the correlation between the orientation of dendrites grown at low temperatures and triangular islands grown at higher temperatures, and explain why in some systems dendrites grow fat before turning compact.