Future challenges facing the nonproliferation community will undoubtedly change the normal way of doing business'' in international safeguards. New technology will emerge in support of compliance concepts such as transparency and openness, regional security assurance, bilateral cooperation, and special. or non-routine inspections. Technologies address in remote unattended monitoring, integrated on-site monitoring, environmental monitoring, satellite and aerial over-flight systems, equipment for special inspectios, and sharable data information fusion and management, are just a few examples of potential technologics for new nonproliferation monitoring regimes.
Evolution of the microstructure of Al-2wt.%Cu thin films is examined with respect to how the presence of copper can influence electromigration behavior. After an anneal that simulates a thin film sintering step, the microstructure of the Al-Cu films consisted of 1 [mu]m aluminum grains with [theta]-phase A1[sub 2]Cu precipitates at grain boundaries and triple points. The grain size and precipitation distribution did not change with subsequent heat treatments. Upon cooling to room temperature the heat treatment of the films near the Al/Al+[theta] solvus temperature results in depletion of copper at the aluminum grain boundaries. Heat treatments lower in the two phase region (200 to 300C) result in enrichment of copper at the aluminum grain boundaries. Here, it is proposed that electromigration behavior of aluminum is improved by adding copper because the copper enrichment in the form of A1[sub 2]Cu phase may hinder aluminum diffusion along the grain boundaries.
C++ is commonly described as an object-oriented programming language because of its strong support for classes with multiple inheritance and polymorphism. However, for a growing community of numerical programmers, an equally important feature of C++ is its support of operator overloading on abstract data types. The authors choose to call the resulting style of programming object-oriented numerics. They believe that much of object-oriented numerics is orthogonal to conventional object-oriented programming. As a case study, they discuss two strong shock physics codes written in C++ that they're currently developing. These codes use both polymorphic classes (typical of traditional object-oriented programming) and abstract data types with overloaded operators (typical of object-oriented numerics). They believe that C++ translators can generate efficient code for many numerical objects. However, for the important case of smart arrays (which are used to represent matrices and the fields found in partial differential equations) fundamental difficulties remain. The authors discuss the two most important of these, namely, the aliasing ambiguity and the proliferation of temporaries, and present some possible solutions.
The solution of Grand Challenge Problems will require computations which are too large to fit in the memories of even the largest machines. Inevitably new designs of I/O systems will be necessary to support them. Through our implementations of an out-of-core LU factorization we have learned several important lessons about what I/O systems should be like. In particular we believe that the I/O system must provide the programmer with the ability to explicitly manage storage. One method of doing so is to have a partitioned secondary storage in which each processor owns a logical disk. Along with operating system enhancements which allow overheads such as buffer copying to be avoided, this sort of I/O system meets the needs of high performance computing.
An eXplosive CHEMical kinetics code, XCHEM was developed to solve the reactive diffusion equations associated with thermal ignition of energetic material. This method-of-lines code uses stiff numerical methods and adaptive meshing. Solution accuracy is maintained between multilayered materials consisting of blends of reactive components and/or inert materials. Phase change and variable properties are included in one-dimensional slab, cylindrical and spherical geometries. Temperature-dependent thermal properties was incorporated and modification of thermal conductivities to include decomposition effects are estimated using solid/gas volume fractions determined by species fractions. Gas transport properties are also included. Time varying temperature, heat flux, convective and thermal radiation boundary conditions, and layer to layer contact resistances are also implemented. The global kinetic mechanism developed at Lawrence Livermore National Laboratory (LLNL) by McGuire and Tarver used to fit One-Dimensional Time to eXplosion (ODTX) data for the conventional energetic materials (HMX, RDX, TNT, and TATB) are presented as sample calculations representative of multistep chemistry. Calculated and measured ignition times for explosive mixtures of Comp B (RDX/TNT), Octol, (HMX/TNT), PBX 9404 (HMX/NC), and RX-26-AF (HMX/TATB) are compared. Geometry and size effects are accurately modeled, and calculations are compared to experiments with time varying boundary conditions. Finally, XCHEM calculations of initiation of an AN/oil/water emulsion, resistively heated, are compared to measurements.
Diamond films were deposited on tungsten substrates by a filament-assisted chemical vapor deposition process as a function of seven different processing parameters. The effect of variations in measured film characteristics such as growth rate, texture, diamond-to-nondiamond carbon Raman band intensity ratio and strain on the adhesion between the diamond film/tungsten substrate pairs as measured by a tensile pull method were investigated. The measured adhesion values do not correlate with any of the measured film characteristics mentioned above. The problem arises because of the non-reproducibility of the adhesion test results, due to the non-uniformity of film thickness, surface preparation and structural homogeneity across the full area of the substrate.
Strained-layer semiconductors have revolutionized modern heterostructure devices by exploiting the modification of semiconductor band structure associated with the coherent strain of lattice-mismatched heteroepitaxy. The modified band structure improves transport of holes in heterostructures and enhances the operation of semiconductor lasers. Strained-layer epitaxy also can create materials whose band gaps match wavelengths (e.g. 1.06 μm and 1.32 μm) not attainable in ternary epitaxial systems lattice matched to binary substrates. Other benefits arise from metallurgical effects of modulated strain fields on dislocations. Lattice mismatched epitaxial layers that exceed the limits of equilibrium thermodynamics will degrade under sufficient thermal processing by converting the as-grown coherent epitaxy into a network of strain-relieving dislocations. After presenting the effects of strain on band structure, we describe the stability criterion for rapid-thermal processing of strained-layer structures and the effects of exceeding the thermodynamic limits. Finally, device results are reviewed for structures that benefit from high temperature processing of strained-layer superlattices.
The porosity of sol-gel thin films may be tailored for specific applications through control of the size and structure of inorganic polymers within the coating sol, the extent of polymer reaction and interpenetration during film formation, and the magnitude of the capillary pressure exerted during the final stage of drying. By maximizing the capillary pressure and avoiding excessive condensation, dense insulating films may be prepared as passivation layers on silicon substrates. Such films can exhibit excellent dielectric integrity, viz., low interface trap densities and insulating properties approaching those of thermally grown SiO[sub 2]. Alternatively, through exploitation of the scaling relationship of mass and density of fractal objects, silica films can be prepared that show a variation in porosity (7--29 %) and refractive index (1.42--1.31) desired for applications in sensors, membranes, and photonics.
At Sandia National Laboratories, the Engineering Sciences Center has made a commitment to integrate AVS into our computing environment as the primary tool for scientific visualization. AVS will be used on an everyday basis by a broad spectrum of users ranging from the occasional computer user to AVS module developers. Additionally, AVS will be used to visualize structured grid, unstructured grid, gridless, 1D, 2D, 3D, steady-state, transient, computational, and experimental data. The following is one user's perspective on how AVS meets this task. Several examples of how AVS is currently being utilized will be given along with some future directions.
Sandia National Laboratories and the Allied Signal-Kansas City Plant (AS-KCP) are engaged in a program called the Integrated Manufacturing and Design Initiative, or IMDI. The focus of IMDI is to develop and implement concurrent engineering processes for the realization of weapon components.'' An explicit part of each of the activities within IMDI is an increased concern for environmental impacts associated with design, and a desire to minimize those impacts through the implementation of Environmentally Conscious Manufacturing, or ECM. These same concerns and desires are shared within the Department of Energy's Manufacturing Complex, and are gaining strong support throughout US industrial sectors as well. Therefore, the development and application of an environmental life cycle analysis framework, the thrust of this specific effort, is most consistent not only with the overall objectives of IMDI, but with those of DOE and private industry.
When an object is subjected to the flow of combustion gas at a different temperature, the thermal responses of the object and the surrounding gas become coupled. The ability to model this interaction is of primary interest in the design of components which must withstand fire environments. One approach has been to decouple the problem and treat the incident flux on the surface of the object as being emitted from a blackbody at an approximate gas temperature. By neglecting the presence of the participating media, this technique overpredicts the heat fluxes initially acting on the object surface. The main goal of this work is to quantify the differences inherent in treating the combustion media as a blackbody as opposed to a gray gas. This objective is accomplished by solving the coupled participating media radiation and conduction heat transfer problem. A transient conduction analysis of a vertical flat plate was performed using a gray gas model to provide a radiation boundary condition. A 1-D finite difference algorithm was used to solve the conduction problem at locations along the plate. The results are presented in terms of nondimensional parameters and include both average and local heat fluxes as a function of time. Early in the transient, a reduction in net heat fluxes of up to 65% was observed for the gray gas results as compared to the blackbody cases. This reduction in the initial net heat flux results in lower surface temperatures for the gray gas case. Due to the initially reduced surface temperatures, the gray gas net heat flux exceeds the net blackbody heat flux with increasing time. For radiation Biot numbers greater than 5, or values of the radiation parameter less than 10-2, the differences inherent in treating the media as a gray gas are negligible and the blackbody assumption is valid. Overall, the results clearly indicate the importance of participating media treatment in the modeling of the thermal response of objects in fires and large combustion systems.
This paper gives an estimate of the cost to produce electricity from hot-dry rock (HDR). Employment of the energy in HDR for the production of electricity requires drilling multiple wells from the surface to the hot rock, connecting the wells through hydraulic fracturing, and then circulating water through the fracture system to extract heat from the rock. The basic HDR system modeled in this paper consists of an injection well, two production wells, the fracture system (or HDR reservoir), and a binary power plant. Water is pumped into the reservoir through the injection well where it is heated and then recovered through the production wells. Upon recovery, the hot water is pumped through a heat exchanger transferring heat to the binary, or working, fluid in the power plant. The power plant is a net 5.1-MW[sub e] binary plant employing dry cooling. Make-up water is supplied by a local well. In this paper, the cost of producing electricity with the basic system is estimated as the sum of the costs of the individual parts. The effects on cost of variations to certain assumptions, as well as the sensitivity of costs to different aspects of the basic system, are also investigated.
We describe an algorithm for the static load balancing of scientific computations that generalizes and improves upon spectral bisection. Through a novel use of multiple eigenvectors, our new spectral algorithm can divide a computation into 4 or 8 pieces at once. This leads to balanced partitions that have lower communication overhead and are less expensive to compute than those of spectral bisection. In addition, our approach automatically works to minimize message contention on a hypercube or mesh architecture.
This paper describes a collaborative effort between Sandia National Laboratories and the Rocketdyne Division of Rockwell International Corporation to develop an automated braze paste dispensing system for rocket engine nozzle manufacturing. The motivation for automating this manufacturing process is to reduce the amount of labor and excess material required. A critical requirement for this system is the automatic location of key nozzle features using non-contact sensors. Sandia has demonstrated that the low-cost Multi-Axis Seam Tracking (MAST) capacitive sensor can be used to accurately locate the nozzle surface and tube gaps.
We report our progress on the physical optics modelling of Sandia/AT T SXPL experiments. The code is benchmarked and the 10X Schwarzchild system is being studied.
A parallel processor that is optimized for real-time linear control has been developed. This modular system consists of A/D modules, D/A modules, and floating-point processor modules. The scalable processor uses up to 1,000 Motorola DSP96002 floating-point processors for a peak computational rate of 60 GFLOPS. Sampling rates up to 625 kHz are supported by this analog-in to analog-out controller. The high processing rate and parallel architecture make this processor suitable for computing state-space equations and other multiply/accumulate-intensive digital filters. Processor features include 14-bit conversion devices, low input-to-output latency, 240 Mbyte/s synchronous backplane bus, low-skew clock distribution circuit, VME connection to host computer, parallelizing code generator, and look-up-tables for actuator linearization. This processor was designed primarily for experiments in structural control. The A/D modules sample sensors mounted on the structure and the floating-point processor modules compute the outputs using the programmed control equations. The outputs are sent through the D/A module to the power amps used to drive the structure's actuators. The host computer is a Sun workstation. An OpenWindows-based control panel is provided to facilitate data transfer to and from the processor, as well as to control the operating mode of the processor. A diagnostic mode is provided to allow stimulation of the structure and acquisition of the structural response via sensor inputs.
A high speed readout imaging system utilizing a commercial flash X-ray machine and miniature X-ray detectors has been developed. This system was designed to operate in the environment near a nuclear detonation where film or camera imaging cannot be used. The temporal resolution of the system is set by the 20 nanosecond FWHM of the X-ray pulse. The spatial resolution of the system was determined by the size and close packing of the PIN diodes used as the X-ray detectors. In the array used here, the PIN diodes have an active area of 2mm in diameter and were placed 3.8mm center to center. Computer-generated images using algorithms developed for this system are presented and compared with an image captured on film in the laboratory.
This paper discusses a nonideal solution model of the metallic phases of reactor core debris. The metal phase model is based on the Kohler equation for a 37 component system. The binary subsystems are assumed to have subregular interactions. The model is parameterized by comparison to available data and by estimating subregular interactions using the methods developed by Miedama et al. The model is shown to predict phase separation in the metallic phase of core debris. The model also predicts reduced chemical activities of zirconium and tellurium in the metal phase. A model of the oxide phase of core debris is described briefly. The model treats the oxide phase as an associated solution. The chemical activities of solution components are determined by the existence and interactions of species formed from the components.
Pool-boiler reflux receivers have been considered as an alternative to heat pipes for the input of concentrated solar energy to Stirling-cycle engines in dish-Stirling electric generation systems. Fool boilers offer simplicity in desip and fabrication. Pool-boiler solar receiver operation has been demonstrated for short periods of time. However, in order to generate cost-effective electricity, the receiver must operate without significant maintenance for the entire system life. At least one theory explaining incipient-boiling behavior of alkali metals indicates that favorable start-up behavior should deteriorate over time. Many factors affect the stability and startup behavior of the boiling system. Therefore, it is necessary to simulate the full-scale design in every detail as much as possible, including flux levels materials, and operating cycles. On-sun testing is impractical due to the limited test time available. No boiling system has been demonstrated with the current porous boiling enhancement surface and materials for a significant period of time. A test vessel was constructed with a Friction Coatings Inc. porous boiling enhancement surface. The vessel is heated with a quartz lamp array providing about 92 W/Cm[sup 2] peak incident thermal flux. The vessel is charged with NaK-78, which is liquid at room temperature. This allows the elimination of costly electric preheating, both on this test and on full-scale receivers. The vessel is fabricated from Haynes 230 alloy, selected for its high temperature strength and oxidation resistance. The vessel operates at 750[degrees]C around the clock, with a 1/2-hour shutdown cycle to ambient every 8 hours. Temperature data is continually collected. The test design and initial (first 2500 hours and 300 start-ups) test data are presented here. The test is designed to operate for 10,000 hours, and will be complete in the spring of 1994.
Sandia National Laboratories has the qualification evaluation responsibility for the design of certain components intended for use in nuclear weapons. Specific techniques in assurance and assessment have been developed to provide the quality evidence that the software has been properly qualified for use. Qualification Evaluation is a process for assessing the suitability of either a process used to develop or manufacture the product, or the product itself. The qualification process uses a team approach to evaluating a product or process, chaired by a Quality Assurance professional, with other members representing the design organization, the systems organization, and the production agency. Suitable for use implies that adequate and appropriate definition and documentation has been produced and formally released, adequate verification and validation activities have taken place to ensure proper operation, and the software product meets all requirements, explicitly or otherwise.
Upon achieving ignition and gain, the Laboratory Microfusion Facility (LMF) will be a major tool for Inertial Confinement Fusion (ICF) research and defense applications. Our concept for delivering [approximately]10 MJ with a peak on-target light ion power of [approximately]700 TW involves a multi-modular approach using an extension of the compact inductively isolated cavity and Magnetically Insulated Transmission Line (MITL) Voltage Adder technology that is presently being used in several large accelerators at Sandia/New Mexico. The LMF driver design consists of twelve 8-TW and twelve 38-TW accelerating modules, each with a triaxial MITL/Adder that delivers power to a two stage ion extraction diode. The desired energy, power pulse shape, and deposition uniformity on an ICF target can be achieved by controlling the energy and firing sequence of the A'' and B'' accelerator modules, plus optimizing the beam transport and focusing. The multi-modular configuration reduces risk by not scaling significantly beyond existing machines and offers the flexibility of staged construction. It permits modular driver testing at the full operating level required by the LMF.
Parallel computers are becoming more powerful and more complex in response to the demand for computing power by scientists and engineers. Inevitably, new and more complex I/O systems will be developed for these systems. In particular we believe that the I/O system must provide the programmer with the ability to explicitly manage storage (despite the trend toward complex parallel file systems and caching schemes). One method of doing so is to have a partitioned secondary storage in which each processor owns a logical disk. Along with operating system enhancements which allow overheads such as buffer copying to be avoided and libraries to support optimal remapping of data, this sort of I/O system meets the needs of high performance computing.
The design-basis, defense-related, transuranic waste to be emplaced in the Waste Isolation Pilot Plant may, if sufficient H2O, nutrients, and viable microorganisms are present, generate significant quantities of gas in the repository after filling and sealing. We summarize recent results of laboratory studies of anoxic corrosion and microbial activity, the most potentially significant processes. We also discuss possible implications for the repository gas budget.