Publications

We consider bounding the cardinality of an arbitrary triangulation with smallest angle {alpha}. We show that if the local feature size (i.e. distance between disjoint vertices or edges) of the triangulation is within a constant factor of the local feature size of the input, then N < O(1/{alpha})M, where N is the cardinality of the triangulation and M is the cardinality of any other triangulation with smallest angle at least {alpha}. Previous results had an O(1/{alpha}{sup 1/{alpha}}) dependence. Our O(1/{alpha}) dependence is tight for input with a large length to height ratio, in which triangles may be oriented along the long dimension.

Considerable research has been performed on Robotic Visual Servoing (RVS) over the past decade. Using real-time visual feedback, researchers have demonstrated that robotic systems can pick up moving parts, insert bolts, apply sealant, and guide vehicles. With the rapid improvements being made in computing and image processing hardware, one would expect that every robot manufacturer would have a RVS option by the end of the 1990s. So why aren`t the Fanucs, ABBs, Adepts, and Motomans of the world investing heavily in RVS? I would suggest four seasons: cost, complexity, reliability, and lack of demand. Solutions to the first three are approaching the point where RVS could be commercially available; however, the lack of demand is keeping RVS from becoming a reality in the near future. A new set of applications is needed to focus near term RVS development. These must be applications which currently do not have solutions. Once developed and working in one application area, the technology is more likely to quickly spread to other areas. DOE has several applications that are looking for technological solutions, such as agile weapons production, weapons disassembly, decontamination and dismantlement of nuclear facilities, and hazardous waste remediation. This paper will examine a few of these areas and suggest directions for application-driven visual servoing research.

The history and present status of the NCSL intrinsic/Derived Standards Committee is presented, including a review of the current published Recommended Intrinsic/Derived Standard Practices (RISPs) and the four Working Groups that are in the process of developing new RISPs. One of the documents under development is a Reference Catalogue that documents important information associated with over forty intrinsic/derived standards. The generic information on each standard in the Catalogue, as well as its Table of contents, are presented.

Traditionally, electrical connections- between layers of a printed wiring board are formed by mechanically drilling holes through all layers and then plating the resulting structure to provide electrical connections between the layers. The mechanical drilling process is very capital- and labor-intensive and is often a bottleneck in board production. The goal of this program was the development of laser drilling as an alternative to mechanical drilling. Cost advantages and the ability to produce smaller holes were both of interest. Although it had initially been intended to develop all processes at Sandia, suitable emerging processes and materials were identified in industry during the course of the work. Because of these industry efforts, it was decided to terminate the LDRD efforts after the first year of work and to pursue collaborative development efforts with industrial partners. A laser drilling facility is currently being developed at Sandia to pursue this work further.

Large quantities of solid wastes such as rags, kimwipes, swabs, coveralls, gloves, etc., contaminated with oils, greases and hazardous solvents are generated by industry and the government. If the hazardous components (offs, greases and solvents) could be segregated from the much larger bulk of non-hazardous material, then these solid materials could potentially be handled as sanitary waste, at a significant cost savings. AlliedSignal KCP, a typical DOE manufacturing site, spent several hundred thousand dollars in CY92 for disposal of contaminated solid wastes. Similarly, Naval Air Station North Island, San Diego, also spent several hundred thousand dollars in CY91 for disposal of rags. Under the Department of Energy (DOE)/United States Air Force (USAF) Memorandum of Understanding, the objective of this joint AlliedSignal KCP/Sandia National Laboratories project is to demonstrate the feasibility of using supercritical carbon dioxide (SC-CO{sub 2}) to segregate hazardous oils, greases, and organic solvents from non-hazardous solid waste such as rags, wipes, swabs, coveralls, gloves, etc. Supercritical carbon dioxide possesses many of the characteristics desired in an ``environmentally acceptable`` solvent system. It is nontoxic, inexpensive, and recyclable. Carbon dioxide possesses a moderate critical temperature (31{degrees}C) and pressure (1071 psi). At 37{degrees}C and pressures greater than 2000 psi, the density is greater than 0.8 g/cc. Contaminants dissolved in the supercritical CO{sub 2} solvent are separated out by expansion of the fluid to a subcritical pressure where CO{sub 2} is a gas and the dissolved materials precipitate out (usually as a liquid or solid). The gaseous CO{sub 2} can then be recompressed and recycled.

Corporate networks are frequently protected by {open_quotes}firewalls{close_quotes} or gateway systems that control access to/from other networks, e.g., the Internet, in order to reduce the network`s vulnerability to hackers and other unauthorized access. Firewalls typically limit access to particular network nodes and application protocols, and they often perform special authentication and authorization functions. One of the difficult issues associated with network firewalls is determining which applications should be permitted through the firewall. For example, many networks permit the exchange of electronic mail with the outside but do not permit file access to be initiated by outside users, as this might allow outside users to access sensitive data or to surreptitiously modify data or programs (e.g., to intall Trojan Horse software). However, if access through firewalls is severely restricted, legitimate network users may find it difficult or impossible to collaborate with outside users and to share data. Some of the most serious issues regarding firewalls involve setting policies for firewalls with the goal of achieving an acceptable balance between the need for greater functionality and the associated risks. Two common firewall implementation techniques, screening routers and application gateways, are discussed below, followed by some common policies implemented by network firewalls.

Today`s highly competitive global economy is being driven by increasingly rapid technological development. This paper explores the problems of math and science illiteracy in the United States and the potential impact on our economic survival in this environment during the next century. Established educational methods that reward task performance, emphasize passive lecture, and fail to demonstrate relevance to real life are partly to blame. Social norms, stereotypes, and race and gender bias also have an impact. To address this crisis, we need to question the philosophy of an educational system that values task over concept. Many schools have already initiated programs at all grade levels to make math and science learning more relevant, stimulating, and fun. Teaching methods that integrate math and science learning with teamwork, social context, and other academic subjects promote the development of higher-order thinking skills and help students see math and science as necessary skills.

In particle methods, each particle represents a finite region over which there is a distribution of the field quantity of interest. The field value at any point is calculated by summing the distribution functions for all the particles. This summation procedure does not require the use of any connectivities to generate continuous fields. Various AVS modules and networks have been developed that enable us to visualize the results from particle methods. This will be demonstrated by visualizing a numerical simulation of a rising, chaotic bubble. In this fluid dynamics simulation, each particle represents a region with a specified vorticity distribution.

The paper discusses two aspects of Sandia`s Wind Energy Program. The first section of the paper presents a case study of fatigue in wind turbines. This case study was prepared for the American Society of Testing Material`s (ASTM) Standard Technical Publication (STP) on fatigue education. Using the LIFE2 code, the student is lead through the process of cumulative damage summation for wind turbines and typical data are used to demonstrate the range of life estimates that will result from typical parameter variations. The second section summarizes the results from a workshop held by Sandia and the National Renewable Energy Laboratory (NREL) to discuss fatigue life prediction methodologies. This section summarizes the workshop discussions on the use of statistical modeling to deduce the shape and magnitude of the low-probability-of-occurrence, high-stress tail of the load distribution on a wind turbine during normal operation.

The Mixed Waste Landfill Integrated Demonstration (MWLID) focuses on ``in-situ`` characterization, monitoring, remediation, and containment of landfills in arid environments that contain hazardous and mixed waste. The MWLID mission is to assess, demonstrate, and transfer technologies and systems that lead to faster, better, cheaper, and safer cleanup. Most important, the demonstrated technologies will be evaluated against the baseline of conventional technologies and systems. The comparison will include the cost, efficiency, risk, and feasibility of using these innovative technologies at other sites.

Two 75-kW{sub t} alkali-metal pool-boiler solar receivers have been successfully tested at Sandia National Laboratories` National Solar Thermal Test Facility. The first one, Sandia`s `` second-generation pool-boiler receiver,`` was designed to address commercialization issues identified during post-test assessment of Sandia`s first-generation pool-boiler receiver. It was constructed from Haynes alloy 230 and contained the alkali-metal alloy NaK-78. The absorber`s wetted side had a brazed-on powder-metal coating to stabilize boiling. This receiver was evaluated for boiling stability, hot- and warm-restart behavior, and thermal efficiency. Boiling was stable under all conditions. All of the hot restarts were successful. Mild transient hot spots observed during some hot restarts were eliminated by the addition of 1/3 torr of xenon to the vapor space. All of the warm restarts were also successful. The heat-transfer crisis that damaged the first receiver did not recur. Thermal efficiency was 92.3% at 750{degrees}C with 69.6 kW{sub t} solar input. The second receiver tested, Sandia`s ``advanced-concepts receiver,`` was a replica of the first-generation receiver except that the cavities, which were electric-discharge-machined in the absorber for boiling stability, were eliminated. This step was motivated by bench-scale test results that showed that boiling stability improved with increased heated-surface area, tilt of the heated surface from vertical, and added xenon. The bench-scale results suggested that stable boiling might be possible without heated-surface modification in a 75-kW{sub t} receiver. Boiling in the advanced-concepts receiver with 1/3 torr of xenon added has been stable under all conditions, confirming the bench-scale tests.

The Sandia Laser Tracker (LT) systems illuminate a cooperative target with a diverged Argon-ion laser beam and track the resulting bright target using a servo-controlled turning mirror. Raw data is digitally recorded in real time and analyzed later when more time is available. The recorded data consists of azimuth and elevation of the tracking mirror, tracking error signals, and range to the target. If the target is tracked perfectly, the error signals will always be zero. The data reduction for this simplified, zero-error condition can be accomplished with very few lines of code. To date, all data reduction for LTI has been done using this zero-error assumption. The more general data reduction problem using the tracking error signals is a much more involved calculation and is referred to as ``using the error foldback routine.`` Detailed theory and vector analysis behind the data reduction and error decoupling algorithms used in the LT systems are described. Errors and corrections to the original document uncovered in over ten years of use are also noted and corrected.

This report describes the layout and operation of the recently upgraded Sandia Lightning Early Warning Network, which was upgraded from an analog-based to a digital-based telemetry system.

Layered crystalline titanates (CT) [Anthony and Dosch, US Patent 5 177 045 (1993)] are pillared with tetraethyl orthosilicate, 3-aminopropyltrimethoxysilane, and aluminum acetylacetonate to prepare porous and high surface area supports for sulfided NiMo catalyst. Tetra-ethyl orthosilicate or aluminum acetylacetonate intercalated CT are prepared by stepwise intercalation. First, the basal distance is increased by n-alkylammonium ions prior to intercalation with inorganic compounds. However, an aqueous solution of 3-aminopropyltrimethoxysilane could directly pillar CT without first swelling the titanate with n-alkylamine. The catalytic activities for hydrogenation of pyrene of sulfided NiMo supported silica or alumina pillared CT were higher than those of commercial catalysts (Shell324 and Amocat1C). The silicon and aluminum contents of the pillared CT, used as supports, have a considerable effect on the catalytic activities and physical properties of the supports.

The use of laser ignited explosive components has been recognized as a safety enhancement over existing electrical explosive devices (EEDs). Sandia has been pursuing the development of optical ordnance for many years with recent emphasis on developing optical deflagration-to-detonation (DDT) detonators and pyrotechnic actuators. These low energy optical ordnance devices can be ignited with either a semiconductor diode laser, laser diode arrays or a solid state rod laser. By using a semiconductor laser diode, the safety improvement can be made without sacrificing performance since the input energy required for the laser diode and the explosive output are similar to existing electrical systems. The use of higher powered laser diode arrays or rod lasers may have advantages in fast DDT applications or lossy optical environments such as long fiber applications and applications with numerous optical connectors. Recent results from our continued study of optical ignition of explosive and pyrotechnic materials are presented. These areas of investigation can be separated into three different margin categories: (1) the margin relative to intended inputs ( i.e. powder performance as a function of laser input variation), (2) the margin relative to anticipated environments (i.e. powder performance as a function of thermal environment variation), and (3) the margin relative to unintended environments (i.e. responses to abnormal environments or safety).

Rapid evolution in the structure of military forces worldwide is resulting in the retirement of numerous weapon systems. Many of these systems include rocket motors containing highly energetic propellants based on hazardous nitrocellulose/nitroglycerin (NC/NG) mixtures. Even as the surplus quantities of such material increases, however, current disposal methods -- principally open burning and open detonation (OB/OD) -- are coming under close scrutiny from environmental regulators. Environmentally conscious alternatives to disposal of propellant and explosives are thus receiving renewed interest. Recycle and reuse alternatives to OB/OD appear particularly attractive because some of the energetic materials in the inventories of surplus weapon systems represent potentially valuable resources to the commercial explosives and chemical industries. The ability to reclaim such resources is therefore likely to be a key requirement of any successful technology of the future in rocket motor demilitarization. This document consists of view graphs from the poster session.

Cookoff modeling of confined energetic materials involves the coupling of thermal, chemical and mechanical effects. In the past, modeling has focussed on the prediction of thermal runaway with little regard to the effects of mechanical behavior of the energetic material. To address the mechanical response of the energetic material, a constitutive submodel has been developed which can be incorporated into thermal-chemical-mechanical analysis. This work presents development of this submodel and its incorporation into a fully coupled one-dimensional, thermal-chemical-mechanical computer code to simulate thermal initiation of energetic materials. Model predictions include temperature, chemical species, stress, strain, solid/gas pressure, solid/gas density, yield function, and gas volume fraction. Sample results from a scaled aluminum tube filled with RDX exposed to a constant temperature bath at 500 K will be displayed. The micromechanical submodel is based on bubble mechanics which describes nucleation, decomposition, and elastic/plastic mechanical behavior. This constitutive material description requires input of temperatures and reacted fraction of the energetic material as provided by the reactive heat flow code, XCHEM, and the mechanical response is predicted using a quasistatic mechanics code, SANTOS. A parametric sensitivity analysis indicates that a small degree of decomposition causes significant pressurization of the energetic material, which implies that cookoff modeling must consider the strong interaction between thermal-chemistry and mechanics. This document consists of view graphs from the poster session.

The chemical processes involved in the decomposition of energetic materials have been investigated theoretically using quantum chemical methods to determine the thermochemistry and reaction pathways. The Bond-Additivity-Corrected Moller-Plesset 4th order perturbation theory method (BAC-MP4) has been used to determine heats of formation and free energies of reaction intermediates of decomposition. In addition, the BAC-MP4 method has been used to determine action pathways involving these intermediates. A theoretical method for calculating solvation energies has been developed to treat the non-idealities of high pressure and the condensed phase. The resulting chemical processes involving decomposition and ignition are presented for nitrate compounds, nitramines, and nitromethane.

In this presentation, we present modeling of DDT in porous energetic materials and experimental studies of a time-resolved, shock compression of highly porous inert and reactive materials. This combined theoretical and experimental studies explore the nature of the microscale processes of consolidation, deformation and reaction which are key features of the shock response of porous or damaged energetic materials. The theoretical modeling is based on the theory of mixtures in which multiphase mixtures are treated in complete nonequilibrium allowing for internal boundary effects associated mass/momentum and energy exchange between phases, relative flow, rate-dependent compaction behavior, multistage chemistry and interphase boundary effects. Numerous studies of low-velocity impacts using a high resolution adaptive finite element method are presented which replicate experimental observations. The incorporation of this model into multi-material hydrocode analysis will be discussed to address the effects of confinement and its influence on accelerated combustion behavior. The experimental studies will focus on the use of PVDF piezoelectric polymer stress-rate gauge to precisely measure the input and propagating shock stress response of porous materials. In addition to single constituent porous materials, such as granular HMX, we have resolved shock waves in porous composite intermetallic powders that confirm a dispersive wave nature which is highly morphologically and material dependent. This document consists of viewgraphs from the poster session.

``High consequence`` operations are systems, structures, and/or strategies for which it is crucial to provide assured protection against some potential catastrophe or catastrophes. The word ``catastrophe`` implies a significant loss of a resource (e.g., money, lives, health, environment, national security, etc.). The implementation of operations that are to be as catastrophe-free as possible must incorporate a very high level of protection. Unfortunately, real world limitations on available resources, mainly money and time, preclude absolute protection. For this reason, conventional ``risk analysis`` focuses on ``cost-effective`` protection, demonstrating through analysis that the benefits of any protective measures chosen outweigh their cost. This is a ``crisp`` one-parameter (usually monetary) comparison. A major problem with this approach, especially for high consequence operations, is that it may not be possible to accurately determine quantitative ``costs,`` and furthermore, the costs may not be accurately quantifiable. Similarly, it may not be possible to accurately determine or to quantify the benefits of protection in high consequence operations. These weaknesses are addressed in this paper by introducing multiple parameters instead of a single monetary measure both for costs of implementing protective measures and their benefits. In addition, a fuzzy-algebra comparison based on fuzzy number theory is introduced as a tool in providing cost/benefit tradeoff depiction, with the incorporation of measures of the uncertainty that necessarily exists in the input information. The result allows a more informative comparison to be made through use of fuzzy results, especially at the extreme bounds of the uncertainty.

In early October of 1993, an oil shipment of about 1 million barrels was made from the Bayou Choctaw Strategic Petroleum Reserve storage facility to St. James Terminal. During the shipment, oil temperatures and soil temperatures along the pipeline were recorded. The field data were used to make estimations of soil thermal properties, thermal conductivity and specific heat. These data were also used to validate and calibrate a heat transfer code, OILPIP, which has been used to calculate pipeline cooling of oil during a drawdown.

VISAR (Velocity Interferometer System for Any Reflector) is a system that uses the Doppler effect and is widely used for measuring the velocity of projectiles, detonations, flying plates, shock pressures (particle velocity) and other high speed/high acceleration motion. Other methods of measurement such as accelerometers and pressure gauges have disadvantages in that they are sensitive to radiation, electromagnetic pulses, and their mass can drastically alter the velocity of the projectile. VISAR uses single frequency-single mode laser fight focused onto a target of interest. Reflected fight from the target is collected and sent through a modified, unequal leg Michelson interferometer. In the interferometer the light is split into two components which travel through the legs of the interferometer cavity and are then recombined. When the light recombines, an interference pattern is created which can range from dark (destructive interference) to bright (constructive interference). When the target moves, the reflected laser light experiences a frequency shift (increase) with respect to the frequency from the target in a static condition. Since the Doppler shifted light is split and routed through an unequal leg interferometer cavity, there is a time lag of the light containing the Doppler information at the recombination point in the interferometer. The effect of the time lag is to create a sinusoidally changing interference pattern (commonly called fringes). Since the interferometer time delay, laser wavelength, and the speed of light are known, an accurate measurement of target velocity/acceleration may be measured by analyzing both the number of tinges and the speed of tinge generation (system accuracy is 3--4%).

The combustion behavior of energetic materials (e.g., solid propellants) has long been of interest in the fields of propulsion and pyrotechnics. In many such applications, it is becoming increasingly clear that two-phase flow effects play an important role, especially since, during combustion, most homogeneous solid propellants develop thin multi-phase layers at their surfaces in which finite-rate exothermic reactions occur. In addition, there is a growing interest in the behavior of porous energetic solids, since even initially dense materials can develop significant void fractions if, at any time, they are exposed to abnormal thermal environments. The deflagration characteristics of such ``damaged`` materials may then differ significantly from those of the pristine material due, at least in part, to gas flow in the solid/gas preheat region. The presence of gas in the porous solid in turn results in a more pronounced two-phase effect in the multi-phase surface layer, such as in the liquid melt region of nitramine propellants, which thus tend to exhibit extensive bubbling in an exothermic foam layer. The present analysis is largely applicable to this latter class of propellants.

To develop robust models for predicting the response of munitions under abnormal conditions associated with cookoff, it is necessary to be able to accurately characterize the following: the time to ignition, the location of the ignition point within the munition, and the combustive behavior of the damaged energetic material after ignition. For, the response of the munition, as controlled by these parameters, will determine whether its response will be characterized by a relatively mild deflagration or whether it will be characterized by a more damaging detonation. Several of the underlying properties of the energetic materials used in munitions that must be understood in order to accurately characterize these parameters are the chemical and physical changes that occur in these energetic materials as they are heated. The chemical changes involve overcoming the forces that tend to stabilize these materials, such as binding within the crystal lattice or intermolecular hydrogen bonding, and their transformation to less stable forms, such as mixtures of gases with high energy content. The physical changes typically involve phase changes of the material. One significant phase change is the slow transformation of the energetic materials from the solid reactant to gas phase products. This transformation can lead initially to the formation of high pressure gas bubbles within the solid particles and ultimately to changes in the porosity and gas permeability of the energetic material formulation. The presence of these reactive gases within high pressure bubbles can lead to increased hot spot formation of the material if it is compressed. The increased porosity can lead to significant increases in the burn rates of these materials at high pressures.

This paper discusses a thermochemical model for calculating equations of state (EOS) for the detonation products of explosives. This model, which was first presented at the Eighth Detonation Symposium, is available in the PANDA code and is referred to here as ``the Panda model``. The basic features of the PANDA model are as follows. (1) Statistical-mechanical theories are used to construct EOS tables for each of the chemical species that are to be allowed in the detonation products. (2) The ideal mixing model is used to compute the thermodynamic functions for a mixture of these species, and the composition of the system is determined from assumption of chemical equilibrium. (3) For hydrocode calculations, the detonation product EOS are used in tabular form, together with a reactive burn model that allows description of shock-induced initiation and growth or failure as well as ideal detonation wave propagation. This model has been implemented in the three-dimensional Eulerian code, CTH.