Publications

Acoustic emissions and conventional strain measurements were used to follow the evolution of the damage surface and the plastic potential in a limestone under conditions of triaxial compressions. Confining pressures were chosen such that macroscopically, the limestone exhibited both brittle and ductile behavior. The parameters thus derived are useful for modeling the deformation of a pressure-dependent material and for computing when localization would occur. 10 refs., 8 figs.

The Gaseous Electronics Conference (GEC) RF Reference Cell was developed to enhance studies of radiofrequency (rf) discharge systems analogous to those used to fabricate microelectronic devices. The Reference Cell concept includes both a standard discharge-chamber design and a set of diagnostic tools that can be used to verify that different Cells behave similarly. Voltage and current measurements in Reference Cells in the United States show that, with proper care, plasmas that behave in a similar manner can be generated in different Cells. The versatility of the Reference Cell is illustrated by results on the use of planar laser-induced fluorescence imaging to obtain two-dimensional spatial profiles of SO{sub 2} in an SF{sub 6}/O{sub 2} rf discharge. 4 refs., 5 figs.

We have used the highly sensitive technique of Photothermal Deflection Spectroscopy (PDS) to measure changes in the infrared absorption spectra of MEHPPV, P3HT and Polydiacetylene-4BCMU induced by pumping these polymers with light above the {pi}--{pi}* transition energy. In contrast to previous chopped light transmission measurements of these effects, the PDS technique can directly measure the buildup or decay of the absorption coefficient, {alpha}, on the time scale of second to days. In the case of MEHPPV we observe that the time scale of seconds to days. In the case of MEHPPV we observe that above-gap light causes the appearance of a broad infrared peak in {alpha}, which continues to grow-in hours after the pump light is first applied. For this polymer the general shape of the absorption spectra in the unpumped state mimics the photo-induced changes, suggesting that remnant photo-induced states determine the maximum transparency observed under normal experimental conditions. For P3HT and to a lesser extent, MEHPPV, we also observe irreversible photo-induced absorption components which we tentatively identify with photo-induced oxidation of the polymer matrix. 10 refs., 8 figs.

Present practice in most computer codes intended for the solution of dynamic mechanics problems is to use the classical infinitesimal plasticity relations together with the Jaumann stress rate to account for finite rotations. Use of the Jaumann stress rate is known to lead to oscillating stress-strain response in simple shear at large deformations for elastic and some plastic relations, and is limited to isotropic material descriptions. Formulations of finite deformation plasticity based on the Lagrangian reference configuration and an unrotated configuration have been proposed which, in principle, should overcome these limitations. The latter has been implemented in a finite element computer code. In this paper, it is shown how a Lagrangian description based on the reference configuration may be implemented in computer codes, and how it may be translated into a corresponding Eulerian description based on the current configuration and a description based on the unrotated configuration for comparison with currently used descriptions. 11 refs.

This paper presents information on measures taken by Sandia National Laboratories to prepare for environmental, safety, and health compliance assessments conducted by Tiger Teams'' at Department of Energy facilities.

Woven Kevlar fabrics exhibit a number of beneficial mechanical properties which include strength, flexibility, and relatively low density. The desire to engineer or design Kevlar fabrics for specific applications has stimulated interest in the development of theoretical models which relate their effective mechanical properties to specific aspects of the fabric morphology and microstructure. In this work the author provides a theoretical investigation of the large deformation elastic response of a plane woven Kevlar fabric and compares these theoretical results with experimental data obtained from uniaxially loaded Kevlar fabrics. The theoretical analysis assumes the woven fabric to be a regular network of orthogonal interlaced yarns and the individual yarns are modeled as extensible elastica, thus coupling stretching and bending effects at the outset. This comparison of experiment with theory indicates that the deformation of woven fabric can be quite accurately predicted by modeling the individual yarns as extensible elastica. 2 refs., 1 fig.

The Modular Integrated Video System (MIVS) Image Processing System (MIPS) was developed to assist the International Atomic Energy Agency (IAEA) Inspectorate in the safeguards review of MIVS surveillance data. MIPS is designed to review MIVS surveillance data automatically; firstly detecting significantly changed images and secondly identifying if the changed images show IAEA defined objects of safeguards interest. To achieve this, MIPS uses both digital image processing and neural network techniques. A change detector uses image processing techniques to identify significantly changed images. The MIPS neural network classifier detects images which may show an important object(s). The neural network is trained , i.e., given example images showing the objects that it must recognize, for each different facility. The MIPS change detection algorithms reduce the original MIVS data by eliminating images without significant activity. The MIPS neural network algorithms further reduce this data by eliminating images which may not show a safeguards significant object. The images analyzed by both the change detector and the neural network are available for inspector review. The MIPS algorithms are implemented in commercially available hardware. A high-level menu-driven system interface allows inspectors to train the neural network and to operate both the change detection and neural network classification. An evaluation program was conducted jointly by Sandia National Laboratories (SNL) and the IAEA to determine the systems capabilities on a variety of MIVS data. The MIPS processing techniques and the user interface were evaluated by IAEA inspectors. Performance tests were also completed on a variety of MIVS data. This paper provides a description of the Class II MIPS and the evaluation program and reports on the results of this joint evaluation. 7 refs., 4 figs., 3 tabs.

Gas conductivities of narrow natural fractures in sandstone and chalk were measured under varying stress and pore pressure conditions and showed a decrease in conductivity with increasing net stress. Natural fractures in mudstones exhibited continuously decreasing conductivity upon application of stress, so that correlatable conductivity data could not be obtained. Effective-stress-law behavior for the sandstone and chalk fractures were examined, giving α values in the range of 0.8-1.06, where α is the parameter in the effective-stress law, σ - αP. The value of α for the fracture in chalk was nearly constant, but the values for the fracture in sandstone tended to decrease with increasing stress. Transition Reynold's numbers and turbulence factors for flow through the chalk and sandstone fractures were determined, yielding turbulence factors ranging from 6.0-20×106 ft-1 (2.0-6.6×10-5 cm-1) for differently stressed fractures. The entire flow behavior of these natural fractures, including conductivity, effective-stress law, and turbulence, is controlled by stress and pore pressure. As a result, pressure depletion during production will significantly change the productivity of a reservoir with similar natural fractures.

Betavoltaic power sources operate by converting the nuclear decay energy of beta-emitting radioisotopes into electricity. Since they are not chemically driven, they could operate at temperatures which would either be to hot or too cold for typical chemical batteries. Further, for long lived isotopes, they offer the possibility of multi-decade active lifetimes. Two approaches are being investigated: direct and indirect conversion. Direct conversion cells consist of semiconductor diodes similar to photovoltaic cells. Beta particle directly bombard these cells, generating electron-hole pairs in the semiconductor which are converted to useful power. Many using low power flux beta emitters, wide bandgap semiconductors are required to achieve useful conversion efficiencies. The combination of tritium, as the beta emitter, and gallium phosphide (GaP), as the semiconductor converter, was evaluated. Indirect conversion betacells first convert the beta energy to light with a phosphor, and then to electricity with photovoltaic cells. An indirect conversion power source using a tritium radioluminescent (RL) light is being investigated. Our analysis indicates that this approach has the potential for significant volume and cost savings over the direct conversion method. 7 refs., 11 figs.

Over the past three years, several experiments have been conducted at the Brookhaven National Laboratory Radiation Effects Facility. These experiments have been investigations of proton induced radiation effects in individual electronic components, circuits, operational subsystems and full systems. Our investigations using 170--200 MeV protons have included total dose effects up to 12 Mrad, dose rate effects of the ionizing radiation in the 10{sup 5} to 10{sup 8} rad/s range, the displacement damage effects of the protons up to 10{sup 15} p/cm{sup 2}, and the proton induced thermal shift and thermal-rate effects. The target thickness of many test devices was an appreciable fraction of the range of 200 MeV protons. In our proton beam testing experiments at BNL, dosimetry placed downstream of the target consistently yielded higher dose in rad and in particle fluence than in dosimetry placed upstream of the target. We designed and performed an experiment to study this dose enhancement. The objective of the experiment was to determine the effect of sample thickness on our three methods of dosimetry. The data from the PIN diodes and tantalum calorimeters were consistent and followed the expected DE/DX curve. They show a dose enhancement effect. The proton beam interacts and loses energy as it travels through thick targets. The exiting lower energy beam deposits more energy into the dosimetry because the stopping power increases with decreasing proton energy.

In this paper we review three proposed mechanisms for GaAs ALE and review or present data support or contradiction of these mechanisms. Surface chemistry results clearly demonstrated that TMGa irreversibly chemisorbs on the Ga-rich GaAs(100) surface. The reactive sticking coefficient (RSC) of TMGa on the adsorbate-free Ga-rich GaAs(100) surface was measured to be {approximately}0.5, conclusively demonstrating that the selective adsorption'' mechanism of ALE is not valid. We describe kinetic evidence for methyl radical desorption in support of the adsorbate inhibition'' mechanism. The methyl radical desorption rates determined by temperature programmed desorption (TPD) demonstrate that desorption is at least a factor of {approximately}10 faster from the As-rich c(2 {times} 8)/(2 {times} 4) surface than from the Ga-rich surface. It is disparity in CH{sub 3} desorption rates between the As-rich and Ga-rich surfaces that is largely responsible for GaAs ALE behavior. A gallium alkyl radical (e.g. MMGa) is also observed during TPD and molecular beam experiments, in partial support of the flux balance'' mechanism. Stoichiometry issues of ALE are also discussed. We have discovered that arsine exposures typical of atmospheric pressure and reduced pressure ALE lead to As coverages {ge} 1 ML, which provides the likely solution to the stoichiometry question regarding the arsine cycle. 32 refs., 6 figs.

A procedure was developed to use solder technology in the assembly of a single-crystal quartz accelerometer. 87.5Au-12.5Ge (wt.%) solder films 0.5 {times} 10{sup {minus}6}, 1.0 {times} 10{sup {minus}6}, and 2.0 {times} 10{sup {minus}}6 m thick were formed by the electron beam deposition of individual layers of Au and Ge with thicknesses so that the bulk film composition equals the eutectic composition. Interdiffusion of the Au and Ge formed the solder; thermal-physical measurements showed the multilayer films to behave similarly to bulk 87.5Au-12.5Be solder in process thermal cycles. The 2.0 {times} 10{sup {minus}6}m thick quartz/Au-Ge/quartz bonds had an adhesive tensile strength of 17 {plus minus} 2 MPa. The strength increased to 29 {plus minus} 3 MPa and 27 {plus minus} 12 MPa after thermal shock and thermal cycle exposures respectively. The 1.0 {times} 10{sup {minus}6} m thick bonds exhibited strengths of 16 {plus minus} 3 MPa, 16 MPa and 15 {plus minus} 8 MPa in the as-fabricated, post-thermal shock, and post-thermal cycled samples, respectively. The 0.5 {times} 10{sup {minus}6} m joints produced a large degree of scatter in the strength values. Accelerometers assembled with the 2.0 {times} 10{sup {minus}6} m thick joints demonstrated a significant improvement in temperature performance as opposed to units fabricated with a polyimide adhesive. 8 refs., 12 figs., 8 tabs.

This paper is about the spatial resolution of x-ray microanalysis in thin foils. The theory of the scattering of an electron beam with a thin foil is discussed.

Upon becoming Secretary of the Department of Energy (DOE), Admiral Watkins first pledged to Congress that he would clean-up'' the nuclear weapons production complexes and then initiated many changes in the way DOE facilities are operated. He generated new orders regarding environments, safety, and health and created investigation units called Tiger Teams'' to check on how well his orders were being followed. During the spin-up of this massive undertaking, DOE decided to include all its facilities and not just the ones involved in nuclear production. This resulted in research and development labs, such as Lawrence Livermore, Los Alamos, and Sandia National Laboratories being subjected to more stringent regulations. This paper addresses the action Sandia National Laboratories has taken during the past year, particularly in regard to its pulsed-power accelerators, to come into compliance with the new DOE orders. 2 tabs.

The measurement and understanding of the fracture toughness of ductile cast irons, DCI, are critical to the analysis of nuclear transportation casks made from these alloys. Cask containment must be assured for all loading events from normal handling to accidents during which high loads can be delivered at elevated rates. Cask walls are commonly in the range of 20 to 50 cm thick (or greater) in order to provide requisite nuclear shielding, and this requires that associated mechanical constraint effects must be considered. At elevated temperatures (i.e., in the vicinity of ambient) DCI behaves in an elastic-plastic manner, even for large section sizes (B>20 cm) and moderately high loading rates. However, as the temperature is lowered or the loading rate is increased, ferritic DCI alloys exhibit a relatively sharp transition to linear elastic behavior, with a significant decrease in the fracture toughness. The fracture toughness of a DCI alloy has been measured using linear elastic and elastic-plastic experimental techniques. Measurements have been made as a function of temperature, loading rate and section size. The loading rates span the range which a cask could experience during normal transport and handling, as well as accident events. 15 refs., 7 figs., 4 tabs.

Sandia National Laboratories and the University of New Mexico's Anderson School of Management are developing a program which enables M.B.A. students to assist in commercializing Sandia developed technologies. Thus far, students have prepared detailed business plans (which include market analyses, design and development sections, and pro forma financials) for a wide range of technologies. Potential applications include waste management, cancer treatment, oil and gas transportation, coating of plastics, manufacturing and assembly, and parts inspections. By having graduate students conduct the research necessary to identify positive net-present-value projects, Sandia is able to interest private sector firms in its technologies.

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Several countries propose to permanently dispose of spent reactor fuel as waste in geologic repositories. There is no basis for terminating safeguards on spent fuel, since it does not meet the criteria specified for termination, and conceivably it might be subsequently recovered and used for prohibited purposes. The paper proposed safeguards measures for spent fuel undergoing preparation, emplacement, recoverable storage, and after site closure which are consistent with other IAEA safeguards but which differ in detail, commensurate with the lesser risk of diversion relative to materials in other parts of the fuel cycle. The proposed measures rely on item accountability of discrete units, by means of containment and surveillance. The concept is consistent with the guidelines contained in Part I of the Safeguards Document, INFCIRC/153, but not entirely with Part II, which is based on verified material balances. After final site closure safeguards are limited to infrequent site observations, which would be sufficient to detect any attempts to recover the material. The paper points out the magnitude of effort required for recovery and the difficulty of concealing if from casual observation. 4 refs.

This report is an overview of advanced nonvolatile memory technologies. The memory technologies discussed are: floating gate nonvolatile memory technologies; SNOS nonvolatile technology; ferroelectric technology; and thin film magnetic memories.

This paper addresses the issue of collision avoidance in unknown or partially modeled environments using a capacitive sensor. An eight channel capacitance-based sensor system which can detect obstacles up to 400 mm (16 inches) away has been developed. This sensor can detect both conductive and non-conductive obstacles of arbitrary color and shape. The sensor hardware is reliable and inexpensive, and it may be fabricated using flexible printed circuit boards to provide whole-arm and joint protection for any robot or manipulator. Simple collision avoidance control algorithms have been implemented on a two-link robot arm. The sensor and control system enable the robot arm to avoid a conductive post and a concrete block. 13 refs., 9 figs.

This paper presents two algorithms that construct a set of initial (x, y, {theta}) configurations from which a given action will reliably accomplish a planar manipulation task. The first algorithm applies energy arguments to construct a conservative set of successful initial configurations, while the second algorithm performs numerical integration to construct a set that is much less conservative. The algorithms may be applied to a variety of tasks, including pushing, placing-by-dropping, and force-controlled assembly tasks. Both algorithms consider the task geometry and mechanics, and allow uncertainty in every task parameter except for the object shapes. Experimental results are presented which demonstrate the validity of the algorithms' output for two example manipulation tasks. 16 refs., 8 figs.

Sandia National Laboratories developed an Authenticated Secure Container System (ASCS) for the International Atomic Energy Agency (IAEA). Agency standard weights and safeguards samples can be stored in the ASCS to provide continuity of knowledge. The ASCS consists of an optically clear cover, a base containing the Authenticated Item Monitoring System (AIMS) transmitter, and the AIMS receiver unit for data collection. The ASCS will provide the Inspector with information concerning the status of the system, during a surveillance period, such as state of health, tampering attempts, and movement of the container system. The secure container is located inside a Glove Box with the receiver located remotely from the Glove Box. AIMS technology uses rf transmission from the secure container to the receiver to provide a record of state of health and tampering. The data is stored in the receiver for analysis by the Inspector during a future inspection visit. 2 refs.

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Short communication.

The advent of optical storage has made the digital storage of documents a viable option from both a practical and legal perspective. However, the availability of Optical Disk Storage raises questions regarding the destruction of the stored records and standards of longevity, and the admissibility in court of records produced from optical storage has not been tested. This paper will attempt to address these issues. 6 refs.

Circumvention applications require a memory that retains data through radiation (total dose and transient) and loss of power. Various memory technologies have been reviewed and none, as yet, can meet these requirements. However, if complementary metal oxide silicon (CMOS) and silicon nitride oxide silicon (SNOS) memories are combined in a shadow RAM (random access memory) configuration, the requirements can be fulfilled. © 1991 IEEE

The use of carbon materials in catalytic system has been traditionally associated with their properties as supports. There are, however, some literature data describing their use as catalysts. Our results show that no simple relationship exists between the catalytic activity of some carbon materials for selective cleavage of carbon-carbon bonds adjacent to condensed polyaromatic rings an the elemental composition or surface area of these materials. The activity is dependent, however, upon the precursor used to generate the carbon material. Moreover, for a given precursor the activity is determined by the method of conversion to the carbon material. It remains to be established what elements of structure are responsible for the observed activity in carbon materials that are catalytically active. 12 refs., 7 tabs., 1 fig.

The strain rate in steady shock waves is proportional to the fourth power of shock amplitude for a wide variety of materials over a broad range of strain rates. A model based on this observation gives good agreement not only with steady-wave profiles but also with data on non-steady waves in aluminum. In apparent contrast, data on vanadium and uranium at low strain rates indicates a departure from the fourth power law if the wave profiles are assumed to be steady. However, when predicted profiles are produced by allowing the waves to propagate and evolve over the actual experimental sample thickness, the fourth power model gives excellent agreement with the wave profile data even though the wave profiles in the calculations have not yet reached steady state. The implication is that the experimental data do not represent steady waves, and the model is predicting the correct evolution of non-steady waves in vanadium and uranium. 7 refs., 2 figs.

The National Competitiveness Technology Transfer Act of 1989 has opened up the vast resources of our nation's national laboratories to the electronics industry. The electronics industry stands to gain advanced technology development, increased competitiveness, resource-sharing, and technology protection from this act. Sandia National Laboratories can help our nation's companies and universities in developing and applying advanced, commercially valuable technologies and in solving technological problems. These technological areas are discussed. A clear, non-bureaucratic process of tapping the microelectronics expertise and resources of Sandia National Laboratories is presented.

Highly reactive coal pyrites and unstable museum specimens are easily distinguished from the stable pyrites by the growth of white crystals that cover samples exposed to room atmosphere for short periods of time. Continued exposure to the atmosphere will eventually cause the specimens to fall apart. The term rotten pyrite has been applied to museum specimens that fall apart in this way. SEM studies show that reactive (rotten) pyrites contain between 100 and 10,000 times more dislocations than stable pyrites. Shock-loading of a stable pyrite to 7.5 GPa and 17 GPa increased its reactivity by a factor of two, probably caused by an increase in the number of imperfections. However, shock-loading at 22 GPa decreased the reactivity of pyrite because the imperfections produced at the higher pressure were removed during annealing the sample received at the higher temperature. Although there was a factor of six difference between the most and least reactive shocked MCB (commercial pyrite) samples, shock-loading did not increase the reactivity of the MCB pyrite to that of the Queensland coal pyrite. The results in hand show that while shock-loading produces sufficient imperfections to increase the reactivity of pyrites, there is insufficient data to show that imperfections are the main reason why some coal pyrites are highly reactive. 9 refs., 1 fig., 1 tab.

To implement the Qualified Manufacturers List (QML) approach to hardness assurance in a practical and cost-effective manner, one must identify technology parameters that affect radiation hardness and bring them under statistical process control. To aid this effort, we have developed a wafer-level test system to map test-structure and IC response across a wafer. This system permits current-voltage and charge-pumping measurements on transistors, and high-frequency capacitance-voltage measurements on capacitors. For frequencies up to 50 MHz, the system provides a complete menu of functional and parametric IC tests. Wafer maps and histograms of test-structure and IC response are presented for a 1.2-µm radiation-hardened CMOS technology to illustrate the capabilities of the wafer-level test system. Statistical and “deterministic” approaches to correlate test structure and IC response are discussed for this technology. © 1991 IEEE

Transmitting digital voice via packetized mobile communications systems that employ relatively short packet lengths and narrow bandwidths often necessitates very low bit rate coding of the voice data. Sandia National Laboratories is currently developing an efficient voice coding system operating at 800 bits per second (bps). The coding scheme is a modified version of the 2400 bps NSA LPC-10e standard. The most significant modification to the LPC-10e scheme is the vector quantization of the line spectrum frequencies associated with the synthesis filters. An outline of a hardware implementation for the 800 bps coder is presented. The speech quality of the coder is generally good, although speaker recognition is not possible. Further research is being conducted to reduce the memory requirements and complexity of the vector quantizer, and to increase the quality of the reconstructed speech. 4 refs., 2 figs., 3 tabs.

BA85 is a routine for the quantitative reduction of x-ray data collected from oxide samples in an electron microprobe. BA85 is based on the correction procedures developed by Bence and Albee and is coded in Flextran for use with the TASK8 microprobe operating system. Features include stoichiometry and statistical calculations, the use of a 90 - oxide A-factor matrix which contains all of the common valence states for such elements as Fe and Cr, the ability to analyze up to 45 oxides, and the ability to create and use mineral codes which permit associating up to 15 oxides with three letter mnemonic codes. Entering a mineral code results in the analysis of the oxides associated with it and the performance of one of 21 endmember calculations. 13 refs., 2 figs., 3 tabs.

This paper seeks to improve the synergism between computational aerodynamics and wind tunnel experimentation. In this paper, experimental and computational results are presented for a hypersonic vehicle configuration at Mach 8. Comparisons are made between experimental and computational results in order to improve the accuracy of both approaches. The basic vehicle configuration is a spherically blunted cone with a slice parallel with the axis of the vehicle. The half-angle of the cone is 10 deg. and the ratio of spherical nose radius to base radius in 10%. Onto the slice portion of the vehicle can be attached flaps with three different deflection angles; 10, 20, and 30 deg. All of the experimental results were obtained in the Sandia Mach 8 long duration, blow-down, hypersonic wind tunnel. Flow visualization results include surface oil flow, spark schlieren, and liquid crystal photographs and video. The liquid crystals were used as an aid in verifying that a laminar boundary layer existed over the entire body. An extensive uncertainty analysis was conducted to estimate quantitatively the accuracy of the measurement. Computational aerodynamic force and moment predictions are compared with the wind tunnel data. The Sandia Parabolized Navier-Stokes code is used to generate solutions for the sliced vehicle (no flap) and partial solutions for the flapped vehicle. For the geometry with the flap, an axially separated flow occurs and a time iterative Navier-Stokes code is used to provide comparisons with the data. This paper presents a portion of the results given in earlier works and also discusses new experimental results with this configuration.

Plotting and summary routines available for the TASK8 microprobe operating system are able to accept both spectral and quantitative data. All of the routines are able to be run as subroutines from within the TASK8 program or as stand alone programs. Additionally, the spectral plotting routine can be run from within a modified version of SQ. The quantitative routines currently in use with TASK8. Quantitative output can be sent by the summary program to a serial port that is connected to a VAX or PC in addition to printing it. The plotting codes have been written so that either a Tracor Northern TN2000 or a TN5xxx analyzer may be used with either a Hewlett Packard HP7221 series or a HP7470/HP7550 series plotter. The plotting routine for spectra incorporates a user definable usual was'' option to simplify most input procedures. The quantitative plotting routine offers numerous options including scale expansion, smoothing, auto-labeling, special symbols, and multiple pens. 5 refs., 5 figs.

A computational scheme is presented to solve the unsteady Navier-Stokes equations over a blunt body at high altitude, high Mach number atmospheric reentry flow conditions. This continuum approach is directed to low Reynolds/low density hypersonic flows by accounting for non-zero bulk viscosity effects in near frozen flow conditions. A significant difference from previous studies is the inclusion of the capability to model non-zero bulk viscosity effects. The grid definition for these low Reynolds number, viscous dominated flow fields is especially important in terms of numerical stability and accurate heat transfer solutions. 11 refs., 15 figs.

Difficulties in the accurate heat transfer computation of high speed, blunt body flows have been encountered by numerous researchers. The primary reason for these difficulties has been shown to be the grid dependency of the wall flux quantities. Obviously, the accuracy of the computed heat fluxes will, to a certain extent, depend on the particular numerical scheme employed. This article will be limited to the investigation of the flux vector splitting technique. An attempt has been made to develop procedures which will provide guidelines for selecting appropriate grid systems and, in particular, the grid line distribution near the surface for accurate heat transfer computations. The results have clearly shown the dependency of the heat flux quantities on the grid system. In addition, it is shown that changes in flow Mach number and/or Reynolds number may require further refinement of the grid system. 11 refs., 8 figs.

This paper describes a new technique for the detection of x-rays in electron column instruments used in microanalysis. In electron column instruments, the point source of x-rays is produced by the interaction of a focused electron beam with the sample. Neither of the conventional methods, wavelength dispersive (WDS) nor energy dispersive (EDS) based spectrometry, is optimized for low Z element quantitative analysis. In WDS applications, where the analyte elements are Be through P, chemical effects complicate the x-ray measurement process. Peak positions and shapes are altered, sometimes very strongly, by the electron configurations of the analyte atoms and neighboring atoms. In these cases, the ideal spectrometer would profile the peak and some small amount of continuum on either side of the peak such that an accurate peak area could be calculated. Present WDS spectrometers are serial in nature and cannot directly measure peak areas, often causing errors in the determination of light element concentrations. Bastin and co-workers have developed an elegant method to provide accurate area determinations, using the serial spectrometer, by a three point procedure. The parallel wavelength dispersive spectrometer (PWDS) we propose here is ideally suited for those applications.

A new facility is being constructed for the Primary Standards Laboratory at Sandia National Laboratories in Albuquerque, New Mexico. Salient features of the final design, described briefly in this paper, follow the conceptual design of 1984 to a fairly high degree. Because the facility is in process of construction, this paper is a progress report. 6 refs., 2 figs., 1 tab.

Curved and planar inversion domain boundaries (IDB) in aluminum nitride (AIN) form in sintered AIN ceramics containing oxygen, and oxygen is known to segregate to them. A number of interface models shown in Table 1, have been suggested based upon crystallographic constraints, chemical information and observed high resolution electron microscope (HREM) images. Until recently, problems with simulation of HREM images from AIN have made accurate determination of the structure of the IDB interface difficult. The aim of the present study was to use quantitative analytical electron microscopy (AEM) to determine the oxygen concentration at the IDBs, and then to compare the experimental results with calculated oxygen concentrations for each of the IDB models using a Monte Carlo electron trajectory simulation program. A match, if any, between the experimental and calculated oxygen concentrations would indicate the model which best described the IDB structure. The best match was obtained for Youngman's defect model. 14 refs., 5 figs., 3 tabs.

Plessite in iron meteorites is a two phase structure with an fcc precipitate phase in a bcc matrix. After Fe-Ni martensite forms during slow cooling, the martensite decomposition occurs at different temperatures. The morphology of the precipitates and the Ni content of both precipitate and matrix vary with the local average Ni composition of the plessite. In this study, the plessite structure of two octahedrites, Carlton and Grant, was characterized using the analytical electron microscope (AEM). The composition of the taenite precipitates in various regions of plessite which have 9 to 13 wt% and 15 to 20 wt% Ni composition were measured using an x-ray energy dispersive spectrometer (EDS) in the AEM. To understand the phase transformation processes which occurred during the plessite formation, an experimental set of Fe-Ni binary and Fe-Ni-P ternary alloys were made and analyzed also using the AEM. The alloys, which have 15 to 30 wt% Ni (0.2-0.3 wt% P for ternary alloys), were first homogenized at 1,200{degree}C and quenched to liquid nitrogen temperature to form martensite. They were then isothermally heat treated for 60 to 400 days in the temperature range from 450{degree}C to 300{degree}C. Two phase structures, which are similar to those of plessite, were formed in these alloys. The Fe-Ni phase equilibria measured in the decomposed martensite alloys can be used to explain the difference in Ni composition between precipitates in the high Ni and low Ni plessite regions. 3 refs., 2 figs.

Researchers around the world have demonstrated the effectiveness of titanium dioxide-based photocatalysis for decontaminating water containing hazardous organics and heavy metals. A great advantage of this process is that the organic is completely destroyed, leaving behind only water, carbon dioxide and dilute mineral acids. Also, the process has potential for doing two decontamination jobs at once: oxidizing organics while reducing toxic metals. As part of a program sponsored by the DOE, Sandia National Laboratories is carrying out large-scale tests to study the solar destruction of organics at realistic processing rates in addition to laboratory work aimed at determining the applicability of solar detoxification to the removal of heavy metals. In this paper, we present up-to-date results from Sandia's effort. The large-scale tests illustrate the effectiveness of solar detoxification for a variety of organics and compare measured reaction rates against published values of the rate constants for attack by aqueous hydroxyl radicals. This comparison highlights the importance of hydroxyl radical chemistry in solar detoxification processes. It is concluded that solar detoxification is only feasible for easily destroyed compounds like TCE, and PCE. The chlorinated methanes and ethanes are much more difficult to destroy and require very large solar collectors. In the second part of the paper, laboratory data are presented for a variety of different metals, including Ag, Cd, Cu, Hg, Ni, and Pt. The concentration of dissolved oxygen is one of the variables in the study. It is shown that the presence of dissolved metals can have a profound effect on organic oxidation rate, and that oxygen is not necessarily required for oxidation to occur. It is concluded that solar detoxification would be useful for removing mercury and silver but not for copper, nickel nor cadmium. 38 refs., 7 figs., 2 tabs.

Titanium dioxide (TiO{sub 2}) is a photocatalyst for solar detoxification of water containing organic contaminants such as solvents, PCB's, dioxins, pesticides, and dyes. Unfortunately, the ultraviolet (UV) energy used by TiO{sub 2} ({lambda}<400 nm) only comprises about 4% of the solar spectrum. One way of enhancing the efficiency of solar detoxification technologies is to utilize a larger portion of the solar spectrum to initiate the Tio{sub 2}- catalyzed detoxification chemistry. Metalloporphyrins strongly absorb visible and near infrared radiation. By utilization of a process called photosensitization, adsorption of these dyes onto TiO{sub 2} can enable a much broader portion of the solar spectrum to be used. Photosensitization relies upon the ability of the dye molecule to absorb more of the solar energy than bare TiO{sub 2} and to interact electronically with the TiO{sub 2} surface in such a way as to initiate TiO{sub 2}-based redox photochemistry using the dye-absorbed energy. 16 refs., 7 figs.

This document contains planned actions to correct the deficiencies identified in the Pre-Tiger Team Self-Assessment (PTTSA), January 1991, of Sandia National Laboratories (SNL -- Albuquerque, New Mexico; Tonopah, Nevada; and Kauai, Hawaii). The Self-Assessment was conducted by a Self-Assessment Working Group consisting of 19 department managers, with support from Environment, Safety, and Health (ES H) professionals, from October through December 1990. Findings from other past audits, dating back to 1985, were reviewed and compared with the PTTSA findings to determine if additional findings, key findings, or root causes were warranted. The resulting ES H Action Plan and individual planned actions were prepared by the ES H Action Plan Project Group with assistance from the Program owners/authors during February and March 1991. The plan was reviewed by SNL Management in April 1991. This document serves as a planning instrument for the Laboratories to aid in the scoping and sizing of activities related to ES H compliance for the coming five years. It will be modified as required to ensure a workload/funding balance and to address the findings resulting from the Tiger Team assessment at SNL, Albuquerque. The process of producing this document has served well to prepare SNL, Albuquerque, for the coming task of producing the required post-Tiger Team action plan document. 8 tabs.

The degree of oxidation of drops of aluminum metal was investigated parametrically for a range of melt diameters, relative melt-water velocities, melt temperatures, water temperatures, and ambient pressures using a combined film boiling-metal oxidation model. The model predictions of degree of oxidation were then compared to small-scale experiments involving molten drops of aluminum metal. The conclusions were, first, that for the range of melt temperatures and diameters considered, if an oxide layer forms and blankets the molten aluminum, then no significant oxidation occurs, in agreement with the results of experiments performed under quiescent, steady-state conditions. Second, comparing model results to data from single drop fragmentation experiments indicates that under the transient conditions occurring during rapid fragmentation, the oxide layer is disturbed and oxidation rates are limited primarily by the amount of steam available at the melt surface. Third, for a range of parameters, the heat gain in the melt drop from the oxidation reaction can exceed the heat loss to the surroundings, resulting in thermal runaway and ignition of the melt. This effect is observed experimentally as a threshold temperature effect, predicted to be about 1100 K for the initial single drop study, and between 1500 K and 1600 K for the single drop experiments. 7 refs., 2 tabs.

We present a method to conservatively estimate MOS hardness in space that shares the same technical basis as MIL-STD 883C, Test Method 1019.4, but permits greater latitude in part selection for low-dose space systems. Cobalt-60 irradiation at 50–300 rad(Si)/s followed by 25°C anneal is shown to provide an effective test of oxide-charge related failures at low dose rates that is considerably less conservative than Method 1019.4. For MOS devices with gate oxides thinner than 100 nm, we show that an elevated temperature “rebound test” generally is not required for systems with total dose requirements less than 5 krad(Si). For thicker gate oxides and/or higher-dose system requirements, rebound testing per Method 1019.4 generally is required to ensure that devices do not fail in space due to interface-trap effects. © 1991 IEEE

It is shown that preirradiation channel-mobility and 1/f-noise measurements can reveal a great deal about postirradiation interface- and oxide-trap charge buildup in MOS transistors. A model is developed to explain the observed correlations. 10 refs., 4 figs.

The effectiveness of hardening the SA3300 against SEU using design and design-plus-resistor approaches is presented. The full performance and SEU tolerance requirements are met using R{sub fb} {le} 160 k{Omega}. Lumped-parameter circuit simulations are used to analyze results. 10 refs., 5 figs.

Changes in brine and gas permeability of rock salt as a result of nearby excavation (mine-by) have been measured from the underground workings of the WIPP facility. Prior to the mine-by, the formation responds as a porous medium with a very low brine permeability, a significant pore (brine) pressure and no measurable gas permeability. The mine-by excavation creates a dilated, partially saturated zone in the immediate vicinity of the excavation with an increased permeability to brine and a measurable permeability to gas. The changes in hydrologic properties are discussed in the context of pore structure changes.

The chemical synthesis of advanced ceramic and glass materials by the sol-gel process has become an area of increasing activity in the field of material science. The sol-gel process provides a means to prepare homogeneous, high purity materials with tailored chemical and physical properties. This paper surveyed the nuclear magnetic resonance (NMR) studies of silicon-based sol-gel kinetics. A review of the various models which have been used to analyze the chemical kinetics of various sol-gel systems was presented. The utility of NMR spectroscopy was demonstrated in investigating the influence that various reaction conditions have on the reaction pathways by which sol-gel derived materials are synthesized. By observing in a direct fashion the chemical pathway of the sol-gel, it is often possible to relate the final properties of the material to the formulation and reaction conditions of the sol-gel. The study of reaction kinetics by NMR is expected to play an increasingly important role in understanding sol-gel processing and material properties. 15 refs. (DP)