Publications

Bubble-column reactors are used in the chemical processing industry for two-phase and three-phase chemical reactions. Hydrodynamic effects must be considered when attempting to scale these reactors to sizes of industrial interest, and diagnostics are needed to acquire data for the validation of multiphase scaling predictions. This paper discusses the use of differential pressure (DP) and gamma- densitometry tomography (GDT) measurements to ascertain the gas distribution in a two-phase bubble column reactor. Tests were performed on an industrial scale reactor (3-m tall, 0.48-m inside diameter) using a 5-Curie cesium-137 source with a sodium-iodide scintillation detector. GDT results provide information on the time- averaged cross-sectional distribution of gas in the liquid, and DP measurements provide information on the time and volume averaged axial distribution of gas. Close agreement was observed between the two methods of measuring the gas distribution in the bubble column. The results clearly show that, for a fixed volumetric flowrate through the reactor, increasing the system pressure leads to an increase in the gas volume fraction or ``gas holdup`` in the liquid. It is also shown from this work that GDT can provide useful diagnostic information on industrial scale bubble-column reactors.

Numerical simulations of pressure-driven particulate Stokes flows are performed in cylindrical and rectangular conduits using a parallel boundary element code. Spherical particles are randomly placed in the conduits and a pressure drop between the ends of the conduits is imposed by the boundary conditions to induce a Poiseuille-like flow field. The instantaneous velocities of the particles are then calculated, as well as the additional pressure drop necessary to maintain a constant flow rate. Because the results depend on the spatial distribution of the particles, several random configurations of particles are examined for each case. Depending on two different interpretations of the numerical results, the solid phase can be represented as either leading or lagging the fluid phase. Both of the analyses and interpretations are presented.

The transient dynamics finite element computer program, PRONTO-3D, has been used in conjunction with a damage constitutive model to study the influence of detonation timing on rock fragmentation during blasting. The primary motivation of this study is to investigate the effectiveness of precise detonators in improving fragmentation. PRONTO-3D simulations show that a delay time of 0.0 sec between adjacent blastholes results in significantly more fragmentation than a 0.5 ms delay.

A probabilistic risk assessment was completed for a former radioactive waste disposal site. The site, two unlined surface impoundment, was designed as part of the Liquid Waste Disposal System (LWDS) to receive radioactive effluent from nuclear reactors in Technical Area-V (TA-V) at Sandia National Laboratories/New Mexico (SNL/NM). First, a statistical comparison of site sampling results to natural background, using EPA methods, and a spatial distribution analysis were performed. Risk assessment was conducted with SNL/NM`s Probabilistic Risk Evaluation and Characterization Investigation System model. The risk assessment indicated that contamination from several constituents might have been high enough to require remediation. However, further analysis based on expected site closure activities and recent EPA guidance indicated that No Further Action was acceptable.

Room Q is a 109-m-long cylindrical excavation in the Salado Formation at the Waste Isolation Pilot Plant (WIPP) site. Fifteen boreholes were drilled and instrumented around Room Q so that tests could be conducted to determine the effects of room excavation on the hydraulic properties of the surrounding evaporate rocks. Pressure-buildup and pressure-pulse tests were conducted in all of the boreholes before Room Q was mined. The data sets from only eight of the boreholes are adequate for parameter estimation, and five of those are of poor quality. Constant-pressure flow tests and pressure-buildup tests were conducted after Room Q was mined, producing eleven interpretable data sets, including two of poor quality. Pre-mining transmissivities interpreted from the three good-quality data sets ranged from 1 x 10{sup -15} to 5 x 10{sup -14} m{sup 2}/s (permeability-thickness products of 2 x 10{sup -22} to 9 x 10{sup -21} m{sup 3}) for test intervals ranging in length from 0.85 to 1.37 m. Pre-mining average permeabilities, which can be considered representative of undisturbed, far-field conditions, were 6 x 10{sup -20} and 8 x 10{sup -20} m{sup 2} for anhydrite, and 3 x 10{sup -22} m{sup 2} for halite. Post-mining transmissivities interpreted from the good-quality data sets ranged from 1 x 10{sup -16} to 3 x 10{sup -13} m{sup 2}/s (permeability-thickness products of 2 x 10{sup -23} to 5 x 10{sup -20} m{sup 3}). Post-mining average permeabilities for anhydrite ranged from 8 x 10{sup -20} to 1 x 10{sup -19} m{sup 2}. The changes in hydraulic properties and pore pressures that were observed can be attributed to one or a combination of three processes: stress reduction, changes in pore connectivity, and flow towards Room Q. The effects of the three processes cannot be individually quantified with the available data.

Plasma disruptions are a serious concern in tokamak design because of the high impulsive heat loads which can cause strong erosion of divertor materials due to enhanced sputtering, or melting/ablation in the most severe cases. Predictions of net erosion rates and hence component lifetimes are very difficult and are highly dependent on the plasma conditions over the divertor target. It is therefore necessary to characterize the properties of the scrape-off plasma near the divertor target plate under these special conditions. Here, plasma/wall interaction studies are being carried out using the Divertor Materials Exposure System (DiMES) on DIII-D. The objective of the experiment is to determine the kinetic energy and flux of deuterium ions reaching the divertor target during argon-induced radiative disruptions. The experiment utilizes a special slotted ion analyzer mounted over a Si sample to collect the fast charge-exchange (CX) deuterium neutrals emitted within the recycled cold neutral layer (CNL) which serves as a CX target for the incident ions. A theoretical interpretation of the experiment reveals a strong forward pitch-angle dependence in the approaching ion distribution function. The depth distribution of the trapped D in the Si sample was measured using low-energy direct recoil spectroscopy. Comparison with the TRIM code using monoenergetic ions indicated that the best fit to the data was obtained for an ion energy of 100 eV. An estimate of the CNL thickness {integral}nd{ell} indicates that during disruptions the CNL cushion is thick enough to reduce the local ion heat load by {approximately}30% due to CX refluxing.

This paper describes a study in which Web style guides were characterized, compared to traditional human-computer interface (HCI) style guides, and evaluated against findings from HCI reviews of web pages and applications. Findings showed little consistency among the 21 Web style guides assessed, with 75% of recommendations appearing in only one style guide. While there was some overlap, only 20% of Web-relevant recommendations from traditional style guides were found in Web style guides. Web style guides emphasized common look and feel, information display, and navigation issues, with little mention of many issues prominent in traditional style guides such as help, message boxes, and data entry. This difference is reinforced by other results showing that Web style guides address Web information-only pages with much greater success than web-based control enabling features, like buttons and entry fields. It is concluded that while the WWW represents a unique graphical user interface (GUI) environment, development of Web style guides has been less rigorous, with issues associated with web-based control enabling features neglected.

Measurements of the linewidths of submicrometer features made by different metrology techniques have frequently been characterized by differences of up to 90 nm. The purpose of the work reported here is to address the special difficulties that this phenomenon presents to the certification of reference materials for the calibration of linewidth-measurement instruments. Accordingly, a new test structure has been designed, fabricated, and undergone preliminary tests. Its distinguishing characteristics are assured cross-sectional profile geometries with known side-wall slopes, surface planarity, and compositional uniformity when it is formed in mono-crystalline material at selected orientations to the crystal lattice. To allow the extraction of electrical linewidth, the structure is replicated in a silicon film of uniform conductivity which is separated from the silicon substrate by a buried oxide layer. The utilization of a Silicon-On-Insulator (SKI) substrate further allows the selective removal of substrate material from local regions below the reference features, thus facilitating measurements by optical and electron-beam transmission microscopy. The combination of planar feature surfaces having known side-wall slopes is anticipated to eliminate factors which are believed to be responsible for methods divergence in linewidth measurements, a capability which is a prerequisite for reliable certification of the linewidths of features on reference materials.

As part of the preparation process during assembly of thermally activated batteries, the stainless steel piece parts are normally cleaned by vapor degreasing with trichloroethylene. Severe restrictions on the use of chlorinated and fluorinated hydrocarbons in recent years prompted the evaluation of a number of aqueous cleaners as a replacement technology for this application. A total of seven commercial aqueous degreasers was evaluated in this study at several dilution ratios and temperatures. One organic cleaner was also examined under ambient conditions. The effectiveness of the cleaner was determined by the use of x-ray photoelectron spectroscopy (XPS), which is a surface analytical technique that is very sensitive to low levels of surface contaminants. A quartz-crystal microbalance (QCM) that is immersed in the cleaning bath was evaluated as a tool for monitoring the bath cleanliness. The best overall cleaning results were obtained with Micro, Impro-Clean 3800, and Sonicor cleaners.

The extraction of the modal parameters for closely spaced modes in the frequency domain is a common problem. However, it is made more difficult if the damping for the closely spaced modes is high. Data from a structure with more than three percent viscous damping is presented which exhibits this phenomenon. Traditional experimental techniques failed to identify all the modal parameters of three closely spaced modes. Mode shapes from an analytical model are manipulated to produce a modal filter which is used to calculate enhanced frequency response functions from which the modal parameters can be more readily identified. Discussion of the advantages and disadvantages of this technique as compared with traditional frequency response function enhancement techniques will be presented.

Three related conversion coating methods are described that are based on film formation which occurs when aluminum alloys are exposed to alkaline Li salt solutions. Representative examples of the processing methods, resulting coating structure, composition and morphology are presented. The corrosion resistance of these coatings to aerated 0.5 M NaCl solution has been evaluated as a function of total processing time using electrochemical impedance spectroscopy (EIS). This evaluation shows that excellent corrosion resistance can be uniformly achieved using no more than 20 minutes of process time for 6061-T6. Using current methods a minimum of 80 minutes of process time is required to get marginally acceptable corrosion resistance for 2024-T3. Longer processing times are required to achieve uniformly good corrosion resistance.

As a result of Sandia`s radiation hardening testing on a variety of its explosive components, radioactive waste streams were generated and have to be disposed of as radioactive waste. Due to the combined hazards of explosives and radioactivity, Sandia`s Radioactive and Mixed Waste Management organization did not have a mechanism for disposal of these waste streams. This report documents the study done to provide a method for the removal of the explosive hazard from those waste streams. The report includes the design of the equipment used, procedures followed, results from waste stream analog tests and the results from the actual explosive inerting tests on radioactive samples. As a result of the inerting treatment, the waste streams were rendered non-explosive and, thus, manageable through normal radioactive waste disposal channels.

Short communication.

Molten salt used as a heat transfer fluid in central-receiver so ar power plants has a high freezing point (430{degrees}F (221{degrees}C)). It is very likely during the life of the plant that the receiver will accidentally freeze up due to equipment malfunction or operator error. Experiments were conducted to measure the effects of a molten salt receiver freeze-up and recovery event and methods to thaw the receiver. In addition, simulated freeze/thaw experiments were conducted to determine what happens when salt freezes and is thawed in receiver tubes and to quantify the damage caused to candidate receiver tube materials. Fourteen tube samples of various materials, diameters and wall thicknesses were tested to destruction. Results of these tests are presented in this paper.

Chlorine-argon-based reactive-ion-beam etching was used successfully to etch novel InGaAlAs (1.32 {mu}m-wavelength Fabry-Perot resonator transmission) modulators. Resulting etch is very smooth, anisotropic, and has low etch-induced (sidewall) damage. Use of this simple chemistry eliminates difficulties with polymer formation encountered in hydrocarbon-based etches.

Sandia National Laboratories (SNL) is studying the safety of shipping, radioactive materials (RAM) by sea, the SeaRAM project (McConnell, et al. 1995), which is sponsored by the US Department of Energy (DOE). The project is concerned with the potential effects of ship collisions and fires on onboard RAM packages. Existing methodologies are being assessed to determine their adequacy to predict the effect of ship collisions and fires on RAM packages and to estimate whether or not a given accident might lead to a release of radioactivity. The eventual goal is to develop a set of validated methods, which have been checked by comparison with test data and/or detailed finite element analyses, for predicting the consequences of ship collisions and fires. These methods could then be used to provide input for overall risk assessments of RAM sea transport. The emphasis of this paper is on methods for predicting- effects of ship collisions.

This report addresses the testing and evaluation of commercial fiber optic intrusion detection systems in interior applications. The applications include laying optical fiber cable above suspended ceilings to detect removal of ceiling tiles, embedding optical fibers inside a tamper or item monitoring blanket that could be placed over an asset, and installing optical fibers on a door to detect movement or penetration. Detection capability of the fiber optic sensors as well as nuisance and false alarm information were focused on during the evaluation. Fiber optic sensor processing, system components, and system setup are described.

Continued operation of nuclear power plants for periods that extend beyond their original 40-year license period is a desirable option for many U.S. utilities. U.S. Nuclear Regulatory Commission (NRC) approval of operating license renewals is necessary before continued operation becomes a reality. Effective aging management for plant components is important to reliability and safety, regardless of current plant age or extended life expectations. However, the NRC requires that aging evaluations be performed and the effectiveness of aging management programs be demonstrated for components considered within the scope of license renewal before granting approval for operation beyond 40 years. Both the NRC and the utility want assurance that plant components will be highly reliable during both the current license term and throughout the extended operating period. In addition, effective aging management must be demonstrated to support Maintenance Rule (10 CFR 50.65) activities.

This report describes the development of an agent-based microanalytic simulation model of the US economy. The microsimulation model capitalizes on recent technological advances in evolutionary learning and parallel computing. Results are reported for a test problem that was run using the model. The test results demonstrate the model`s ability to predict business-like cycles in an economy where prices and inventories are allowed to vary. Since most economic forecasting models have difficulty predicting any kind of cyclic behavior. These results show the potential of microanalytic simulation models to improve economic policy analysis and to provide new insights into underlying economic principles. Work already has begun on a more detailed model.

The Center for Solder Science and Technology at Sandia National Laboratories has developed a solderability test for evaluating fundamental solder flow over PWB (printed wiring boards) surface finishes. The work supports a cooperative research and development agreement between Sandia, the National Center for Manufacturing Sciences (NCMS), and several industrial partners. An important facet of the effort involved the ``engineering`` of copper surfaces through mechanical and chemical roughening. The roughened topography enhances solder flow, especially over very fine features. In this paper, we describe how etching with different chemical solutions can affect solder flow on a specially designed ball grid array test vehicle (BGATV). The effects of circuit geometry, solution concentration, and etching time are discussed. Surface roughness and solder flow data are presented to support the roughening premise. Noticeable improvements in solder wettability were observed on uniformly etched surfaces having relatively steep peak-to-valley slopes.

Polyxylylenes are thermoplastics used as encapsulants for electronic devices. Five polyxylylenes were prepared by pyrolysis of [2.2]paracyclophanes and characterized by solid state {sup 13}C NMR spectroscopy. The chemical shift data, in combination with interrupted decoupling experiments, allowed assignment of resonances to their carbon sources in the polymers. This confirmed the integrity of the xylylene building block in the polymers and is consistent with linear polymers. No crosslinking could be detected within the NMR sensitivity limits. Residual paracyclophane was detected by {sup 13}C CP MAS NMR spectroscopy in the polyxylylene samples prepared at room temperature; however discrete {sup 13}C resonances due to amorphous and crystalline phases in the polymers were not resolved.

Various metrics are formulated for the uncertainty of calculated neutron activities for dosimetry reactions. The correlations between the uncertainty metrics are examined. The uncertainty data are presented for the dosimetry reactions and can be used to guide the selection of sensors used in spectrum determinations.

We report on ohmic contacts to Si-implanted and un-implanted n-type GaN on sapphire. A ring shaped contact design avoids the need to isolate the contact structures by additional implantation or etching. Metal layers of Al and Ti/Al were investigated. On un-implanted GaN, post metalization annealing was performed in an RTA for 30 seconds in N{sub 2} at 700, 800, and 900 C. A minimum specific contact resistance (r{sub c}) of 1.4{times}10{sup -5} {Omega}{minus}cm{sup 2} was measured for Ti/Al at an annealing temperature of 800 C. Although these values are reasonably low, variations of 95% in specific contact resistance were measured within a 500 {mu}m distance on the wafer. These results are most likely caused by the presence of compensating hydrogen. Specific contact resistance variation was reduced from 95 to 10% by annealing at 900 C prior to metalization. On Si-implanted GaN, un-annealed ohmic contacts were formed with Ti/Al metalization. The implant activation anneal of 1120 C generates nitrogen vacancies that leave the surface heavily n-type, which makes un-annealed ohmic contacts with low contact resistivity possible.

CARLOS-3D is a three-dimensional scattering code which was developed under the sponsorship of the Electromagnetic Code Consortium, and is currently used by over 80 aerospace companies and government agencies. The code has been extensively validated and runs on both serial workstations and parallel super computers such as the Intel Paragon. CARLOS-3D is a three-dimensional surface integral equation scattering code based on a Galerkin method of moments formulation employing Rao- Wilton-Glisson roof-top basis for triangular faceted surfaces. Fully arbitrary 3D geometries composed of multiple conducting and homogeneous bulk dielectric materials can be modeled. This presentation describes some of the extensions to the CARLOS-3D code, and how the operator structure of the code facilitated these improvements. Body of revolution (BOR) and two-dimensional geometries were incorporated by simply including new input routines, and the appropriate Galerkin matrix operator routines. Some additional modifications were required in the combined field integral equation matrix generation routine due to the symmetric nature of the BOR and 2D operators. Quadrilateral patched surfaces with linear roof-top basis functions were also implemented in the same manner. Quadrilateral facets and triangular facets can be used in combination to more efficiently model geometries with both large smooth surfaces and surfaces with fine detail such as gaps and cracks. Since the parallel implementation in CARLOS-3D is at high level, these changes were independent of the computer platform being used. This approach minimizes code maintenance, while providing capabilities with little additional effort. Results are presented showing the performance and accuracy of the code for some large scattering problems. Comparisons between triangular faceted and quadrilateral faceted geometry representations will be shown for some complex scatterers.

Approximately 1.5 billion tons of hazardous materials (hazmat) are transported in the US annually, and most reach their destinations safely. However, there are infrequent transportation accidents in which hazmat is released from its packaging. These accidental releases can potentially affect the health of the exposed population and damage the surrounding environment. Although these events are rare, they cause genuine public concern. Therefore, the US Department of Transportation Research & Special Programs Administration (DOT- RSPA) has sponsored a project to evaluate the protection provided by the current bulk (defined as larger than 118 gallons) packagings used to transport materials that have been classified as Poison Inhalation Hazards (PIH) and recommend performance standards for these PIH packagings. This project was limited to evaluating bulk packagings larger than 2000 gallons. This project involved classifying the PIH into severity categories so that only one set of packaging performance criteria would be needed for each severity category rather than a separate set of performance criteria for each individual PIH. By grouping the PIH into Hazard Zones, Packaging Groups and performance standards for these Hazard Zones can be defined. Each Hazard Zone can correspond to a Packaging Group or, as in 49CFR173 for non-bulk packagings, one Packaging Group may cover more than one Hazard Zone. If the packaging groups are chosen to correspond to the classification categories presented in this report, then the maximum allowable leak rates used to define these categories could be used as the maximum allowable leak rates for the performance oriented packaging standards. The results discussed in this report are intended to provide quantitative guidance for the appropriate authorities to use in making these decisions.

A treatability study has been conducted on liquid low-level and mixed wastes using the stabilization agents Aquaset, Aquaset II, Aquaset II-H, Petroset, Petroset-H, and Petroset and Petroset II. A total of 40 different waste types with activities ranging from 10{sup {minus}14} to 10{sup {minus}4} curies/ml have been stabilized. Reported data for each waste include its chemical and radiological composition and the optimum composition or range of compositions (weight of agent/volume of waste) for each stabilization agent used. All wastes were successfully stabilized with one or more of the stabilization agents and all final waste forms passed the Paint Filter Liquids Test (EPA Method 9095).

A novel approach to mitigating chatter vibrations in machine tools is presented. Encountered in many types of metal removal processes, chatter is a dangerous condition which results from the interaction of the cutting dynamics with the modal characteristics of the machine-workpiece assembly. Tool vibrations are recored on the surface of the workpiece during metal removal, imposing a waviness which alters the chip thickness during subsequent cutting passes. Deviations from the nominal chip thickness effect changes in the cutting force which, under certain conditions, can further excite vibrations. The chatter mitigation strategy presented is based on periodically altering the impedance of the cutting tool assembly. A cyclic electric (or magnetic) field is applied to the spindle quill which contains an electro-rheological (or magneto-rheological) fluid. The variable yield stress in the fluid affects the coupling of the spindle to the machine tool structure, changing the natural frequency of oscillation. Altering the modal characteristics in this fashion disrupts the modulation of current tool vibrations with previous tool vibrations recorded on the workpiece surface. Results from a simulated milling process reveal that significant reductions in vibration amplitude can be achieved through proper selection of fluid and excitation frequency.

An overview of surface micromachining projects at the Microelectronics Development Laboratory of Sandia National Laboratories is presented. Development efforts are underway for a variety of surface micromachined sensors and actuators. A technology that embeds micromechanical devices below the surface of the wafer prior to microelectronics fabrication has also been developed for integrating microelectronics with surface micromachined micromechanical devices.

This paper suggests that inexorable changes in the society are presenting both challenges and a rich selection of technologies for responding to these challenges. The citizen is more demanding of environmental and personal protection, and of information. Simultaneously, the commercial and government information technologies markets are providing new technologies like commercial off-the-shelf (COTS) software, common datasets, ``open`` GIS, recordable CD-ROM, and the World Wide Web. Thus one has the raw ingredients for creating new techniques and tools for spatial analysis, and these tools can support participative study and decision-making. By carrying out a strategy of thorough and demonstrably correct science, design, and development, can move forward into a new generation of participative risk assessment and routing for radioactive and hazardous materials.

This document presents the results of a system analysis and market survey of commercially available alarm communication systems for potential use as an alternate sensor communication system. Only those systems that report alarm/sensor information to a central control panel were considered. The communication systems surveyed include wireless radio frequency (RF) systems, spread spectrum systems, fiber optic systems, twisted pair/copper wire, cellular systems, and other types of communication equipment. All systems are commercially available, and most information was obtained by telephone conversations with the manufacturer, personal interviews at security conferences, and countless reviews of the manufacturers` data sheets. Many systems were identified, but only those that met a minimum set of system requirements were included. Other systems that appeared to be applicable usually did not provide adequate data encryption or could not interface directly to the system. While such features could be incorporated using additional hardware, doing so would make the system more expensive and conflict with the idea of purchasing a single unit that meets the minimum set of requirements. Several systems greatly exceed the scope of this project and utilizing such systems would mean investing in more capacity than is really needed.

The US and other leading nations are at the forefront of a global trend to implement both national and international enterprise networks via information highways. New or upgraded cabling infrastructures are essential to support these activities. Professionals in the telecommunications industry are keenly aware of the challenges presented by such cabling upgrades. Desktop connectivity must be established before quantum leaps in information flow, as suggested by new technologies and global concepts. Some businesses with campus-type facilities have undertaken this formidable challenge. Universities and other higher-level learning institutions, corporate research facilities, independent and government-funded laboratories, financial institutions, medical facilities, and unique suburban housing test sites have risen to this challenge. Sandia National Laboratories is one such organization. This report presents the lessons learned from this project and gives 13 specific recommendations for manufacturers, buyers, and installers.

The effect of ROSA pretreatment on the solderability of environmentally stressed PWB test coupons was investigated. The PWB surface finish was an electroplated, reflowed solder. Test results demonstrated the ability to recover plated-through-hole fill of steam aged samples with solder after ROSA processing. ROSA offers an alternative method for restoring the solderability of aged PWB surfaces.

This report uses the scenarios described in NUREG/CR-6075 and NUREG/CR-6075, Supplement 1, to address the direct containment heating (DCH) issue for all Westinghouse plants with large dry or subatmospheric containments. DCH is considered resolved if the conditional containment failure probability (CCFP) is less than 0.1. Loads versus strength evaluations of the CCFP were performed for each plant using plant-specific information. The DCH issue is considered resolved for a plant if a screening phase results in a CCFP less than 0.01, which is more stringent than the overall success criterion. If the screening phase CCFP for a plant is greater than 0.01, then refined containment loads evaluations must be performed and/or the probability of high pressure at vessel breach must be analyzed. These analyses could be used separately or could be integrated together to recalculate the CCFP for an individual plant to reduce the CCFP to meet the overall success criterion of less than 0.1. The CCFPs for all of the Westinghouse plants with dry containments were less than 0.01 at the screening phase, and thus, the DCH issue is resolved for these plants based on containment loads alone. No additional analyses are required.

In this paper, a review of the Spatial Twist Contiuum and the basic whisker weaving algorithm are given. Progress in the detection and resolution of several types of degeneracies formed by whisker weaving are discussed. These examples include so-called knife doublets, triple doublets, through-cells and through-chords. Knife doublets and triple doublets are resolved by preventing their formation a-priori, which forces whisker weaving to remove the element(s) causing the degeneracy. Through-chords and through-cells are left in the weave and resolved after the weave has been closed. The paper concludes with three examples of geometries ``closed`` by whisker weaving.

The DELSOL computer code was used to model the annual Performance for numerous off-axis alignments of the Lugo heliostats located at the Solar Two site in Dagget, California. Recommended canting times are presented for the Lugo heliostats based upon their location in the field. Predicted annual performance of an off-axis alignment was actually higher than for on-axis alignment in some cases, and approximately equal if the recommended times are used. The annual performances of Solar One heliostats located nearby were also calculated, and illustrated the poorer performance expected of the Lugo heliostats.

A novel technique has been used to test the relative low cycle thermal fatigue resistance of different grades of US and Russian beryllium, which is proposed as plasma facing armor for fusion reactor first wall, limiter, and divertor components. The 30 kW electron beam test system at Sandia National Laboratories was used to sweep the beam spot along one direction at 1 Hz. This produces a localized temperature ``spike`` of 750{degree}C for each pass of the beam. Large thermal stresses in excess of the yield strength are generated due to very high spot heat flux, 250 MW/m{sup 2}. Cyclic plastic strains on the order of 0.6% produced visible cracking on the heated surface in less than 3000 cycles. An in-vacuo fiber optic borescope was used to visually inspect the beryllium surfaces for crack initiation. Grades of US beryllium tested included: S-65C, S- 65H, S-200F, S-200F-H, SR-200, I-400, extruded high purity, HIP`d spherical powder, porous beryllium (94% and 98% dense), Be/30% BeO, Be/60% BeO, and TiBe{sub 12}. Russian grades included: TGP-56, TShGT, DShG-200, and TShG-56. Both the number of cycles to crack initiation, and the depth of crack propagation, were measured. The most fatigue resistant grades were S-65C, DShG-200, TShGT, and TShG-56. Rolled sheet Be (SR-200) showed excellent crack propagation resistance in the plane of rolling, despite early formation of delamination cracks. Only one sample showed no evidence of surface melting, Extruded (T). Metallographic and chemical analyses are provided. Good agreement was found between the measured depth of cracks and a 2-D elastic-plastic finite element stress analysis.

The Sandia National Laboratories Environmental Restoration Project is expected to generate relatively large volumes of hazardous waste as a result of cleanup operations. These volumes will exceed the Laboratories existing waste management capacity. This paper presents four options for managing remediation wastes, including three alternatives for on-site waste management utilizing a corrective action management unit (CAMU). Costs are estimated for each of the four options based on current volumetric estimates of hazardous waste. Cost equations are derived for each of the options with the variables being waste volumes, the major unknowns in the analysis. These equations provide a means to update cost estimates as volume estimates change. This approach may be helpful to others facing similar waste management decisions.

The natural dip of the Salado Formation at the Waste Isolation Pilot Plant (WIPP), although regionally only about 111, has the potential to affect brine inflow and gas-migration distances due to buoyancy forces. Current models, including those in WIPP Performance Assessment calculations, assume a perfectly horizontal repository and stratigraphy. With the addition of buoyancy forces due to the dip, brine and gas flow patterns can be affected. Brine inflow may increase due to countercurrent flow, and gas may preferentially migrate up dip. This scoping study has used analytical and numerical modeling to evaluate the impact of the dip on brine inflow and gas-migration distances at the WIPP in one, two, and three dimensions. Sensitivities to interbed permeabilities, two-phase curves, gas-generation rates, and interbed fracturing were studied.

Sandia National Laboratories is involved in a safety assessment for the shipment of radioactive material by sea. One part of this study is investigation of the consequences of ship-to-ship collisions. This paper describes two sets of finite element analyses performed to assess the structural response of a small freighter and the loading imparted to radioactive material (RAM) packages during several postulated collision scenarios with another ship. The first series of analyses was performed to evaluate the amount of penetration of the freighter hull by a striking ship of various masses and initial velocities. Although these analyses included a representation of a single RAM package, the package was not impacted during the collision so forces on the package could not be computed. Therefore, a second series of analyses incorporating a representation of a row of seven packages was performed to ensure direct package impact by the striking ship. Average forces on a package were evaluated for several initial velocities and masses of the striking ship. In addition to. providing insight to ship and package response during a few postulated ship collisions scenarios, these analyses will be used to benchmark simpler ship collision models used in probabilistic risk assessment analyses.

The scientific issues concerning disposal of radioactive wastes in salt formations have received 40 years of attention since the National Academy of Sciences (NAS) first addressed this issue in the mid-50s. For the last 21 years, Sandia National Laboratories (SNL) have directed site specific studies for the Waste Isolation Pilot Plant (WIPP). This paper will focus primarily on the WIPP scientific studies now in their concluding stages, the major scientific controversies regarding the site, and some of the surprises encountered during the course of these scientific investigations. The WIPP project`s present understanding of the scientific processes involved continues to support the site as a satisfactory, safe location for the disposal of defense-related transuranic waste and one which will be shown to be in compliance with Environmental Protection Agency (EPA) standards. Compliance will be evaluated by incorporating data from these experiments into Performance Assessment (PA) models developed to describe the physical and chemical processes that could occur at the WIPP during the next 10,000 years under a variety of scenarios. The resulting compliance document is scheduled to be presented to the EPA in October 1996 and all relevant information from scientific studies will be included in this application and the supporting analyses. Studies supporting this compliance application conclude the major period of scientific investigation for the WIPP. Further studies will be of a ``confirmatory`` and monitoring nature.

Knowledge of in situ stress and how stress changes with reservoir depletion and pore pressure drawdown is important in a multi-disciplinary approach to reservoir characterization, reservoir management, and improved oil recovery projects. This report summarizes a compilation of in situ stress data from six fields showing the effects of pore pressure and production-induced changes in pore pressure on the minimum horizontal stress. The in situ stress data and corresponding pore pressure data were obtained from field records of the operating companies and published reports. Horizontal stress was determined from closure pressure data of hydraulic fractures and leak-off tests. The stress measurements clearly demonstrate that the total minimum-horizontal stress is dependent on pore pressure. A decrease in pore pressure either by geologic processes or production of a reservoir will result in a decrease in the total minimum-horizontal stress. The magnitude of changes in stress state with net changes in pore pressure is dependent on local field conditions and cannot be accurately predicted by the uniaxial strain model that is commonly used by the petroleum industry.

In the early 1980s, the US Department of Energy (DOE) implemented a program to encourage beneficial uses of nuclear byproduct materials, such as cesium-137 and strontium-90, created during the production of defense materials. Potential uses of the cesium-137 ({sup 137}CS) isotope included sterilizing medical products, maintaining the quality of certain food products, and disinfecting municipal sewage sludge. Strontium-90 ({sup 90}Sr) is a good heat source and has been used in thermoelectric generators and other products that require a constant supply of heat. During that same period, a proposed facility in Albuquerque, New Mexico, was designed to use cesium-137 to sterilize sewage sludge. To support the sewage sludge treatment facility, Sandia National Laboratories was funded by the DOE to develop a Nuclear Regulatory Commission (NRC)-certified Type B shipping container to transport cesium chloride (CsCl) or strontium fluoride (SrF{sub 2}) capsules produced by the Hanford Waste Encapsulation and Storage Facility (WESF) in the State of Washington. The primary purpose of the Beneficial Uses Shipping System (BUSS) cask is to provide shielding and confinement, as well as impact, puncture, and thermal protection for certified, special form contents during transport under normal and hypothetical accident conditions. The BUSS cask was designed to meet dimensional and weight constraints of the WESF and user facilities. Attaining as-low-as-reasonably-achievable (ALARA) radiation exposures in the design and operation of the transport system was a major design goal. Another goal was to obtain regulatory approval of the design by preparing a safety analysis report for packaging (SARP) (Yoshimura et al. 1993).

The Programmatic Environmental Impact Statement for Tritium Supply and Recycling considers several methods for the production of tritium. One of these methods is the Accelerator Production of Tritium. This report summarizes the design characteristics of APT including the accelerator, target/blanket, tritium extraction facility, and the balance of plant. Two spallation targets are considered: (1) a tungsten neutron-source target and (2) a lead neutron-source target. In the tungsten target concept, the neutrons are captured by the circulating He-3, thus producing tritium; in the lead target concept, the tritium is produced by neutron capture by Li-6 in a surrounding lithium-aluminum blanket. This report also provides information to support the PEIS including construction and operational resource needs, waste generation, and potential routine and accidental releases of radioactive material. The focus of the report is on the impacts of a facility that will produce 3/8th of the baseline goal of tritium. However, some information is provided on the impacts of APT facilities that would produce smaller quantities.

Short communication.

The Environmental Restoration Project at Sandia National Laboratories, New Mexico is tasked with assessing and remediating the Mixed Waste Landfill in Technical Area III. The Mixed Waste Landfill is a 2.6 acre, inactive radioactive and mixed waste disposal site. In 1993 and 1994, an extensive passive and active soil gas sampling program was undertaken to identify and quantify volatile organic compounds in the subsurface at the landfill. Passive soil gas surveys identified levels of PCE, TCE, 1,1, 1-TCA, toluene, 1,1,2-trichlorotrifluoroethane, dichloroethyne, and acetone above background. Verification by active soil gas sampling confirmed concentrations of PCE, TCE, 1,1,1-TCA, and 1,1,2-trichloro-1,2,2-trifluoroethane at depths of 10 and 30 feet below ground surface. In addition, dichlorodifluoroethane and trichlorofluoromethane were detected during active soil gas sampling. All of the volatile organic compounds detected during the active soil gas survey were present in the low ppb range.

This paper presents the results of an instantaneous profile test conducted near the Mixed Waste Landfill at Sandia National Laboratories/New Mexico. The purpose of the test was to measure the unsaturated hydraulic properties of soils near the Mixed Waste Landfill, including the relations between hydraulic conductivity, moisture content, and soil water tension. A 4.7 meter by 4.7 meter plot was saturated with water to a depth of 2 meters, and the wetting and drying responses of the vertical profile were observed. These data were analyzed to obtain in situ measurements of the unsaturated hydraulic properties.

We describe methods for measuring dynamical properties for underdense materials (e.g. snow) over a stress range of roughly 0. 1 - 4 GPa. Particular material properties measured by the present methods include Hugoniot states, reshock states and release paths. The underdense materials may pose three primary experimental difficulties. Snow in particular is perishable; it can melt or sublime during storage, preparation and testing. Many of these materials are brittle and crushable; they cannot withstand such treatment as traditional machining or launch in a gun system. Finally, with increasing porosity the calculated Hugoniot density becomes rapidly more sensitive to errors in wave time-of-arrival measurements. A family of 36 impact tests was conducted on snow and six proposed snow simulants at Sandia, yielding reliable Hugoniot states, somewhat less reliable reshock 3 states, and limited release property information. Natural snow of density {approximately}0.5 gm/cm{sup 3}, a lightweight concrete of density {approximately}0.7 gm/cm{sup 3} and a {open_quotes}snow-matching grout{close_quotes} of density {approximately}0.28 gm/cm 3 were the subjects of the majority of the tests. Hydrocode calculations using CTH were performed to elucidate sensitivities to edge effects as well as to assess the applicability of SESAME 2-state models to these materials. Simulations modeling snow as porous water provided good agreement for Hugoniot stresses to 1 GPa; a porous ice model was preferred for higher Hugoniot stresses. On the other hand, simulations of tests on snow, lightweight concrete and the snow-matching grout based on (respectively) porous ice, tuff and polyethylene showed a too-stiff response. Other methods for characterizing these materials are discussed. Based on the Hugoniot properties, the snow-matching grout appears to be a better snow simulant than does the lightweight concrete.

This paper uses two high-cycle fatigue data bases, US blade materials and one for European materials the service lifetime of a wind turbine blade sit WISPER load spectrum for northern European sit 19921 and the WISPER protocol load spectrum farm sites. The US data base, developed by Mandell, et al. (1995), contains over 2200 data points that were obtained using coupon testing procedures. These data are used to construct a Goodman diagram that is suitable for analyzing wind turbine blades. This result is compared to the Goodman diagram derived from the European fatigue data base FACT. The LIFE2 fatigue analysis code for wind turbines is then used to predict the service lifetime of a turbine blade subjected to the two loading histories. The results of this study indicate that the WISPER load spectrum from northern European sites significantly underestimates the WISPER protocol load spectrum from a US wind farm site; i.e., the WISPER load spectrum significantly underestimates the number and magnitude of the loads observed at a US wind farm site. Further, the analyses demonstrate that the European and the US fatigue material data bases are in general agreement for the prediction of tensile failures. However, for compressive failures, the two data bases are significantly different, with the US data base predicting significantly shorter service lifetimes than the European data base.

For many years the standard weak-link, pulse-discharge capacitors for DOE systems have utilized either the dry-wrap-and-fill, buried-foil Mylar capacitor or the Flourinert-filled, extended-foil Mylar capacitor designs. New stringent system requirements demanded a low-inductance, weak-link capacitor with higher energy density than the dry-wrap-and-fill, extended-foil Mylar capacitor. The hoop-shaped requirement, so that vital components could be thermally protected inside the weak-link capacitor, made the Flourinert capacitor design too expensive, complex and impractical. The low-inductance requirement eliminated the standard dry-wrap-and-fill, buried-foil design. This paper discusses evolvement of the close-tap-pair design of a buried-foil capacitor, which resulted in a capacitor that met the volume, shape, inductance, and reliability requirements.

The Prosperity Game conducted for the Laboratory Development Division of National Laboratories on May 24--25, 1995, focused on the individual and organizational autonomy plaguing the Department of Energy (DOE)-Congress-Laboratories` ability to manage the wrenching change of declining budgets. Prosperity Games are an outgrowth and adaptation of move/countermove and seminar War Games. Each Prosperity Game is unique in that both the game format and the player contributions vary from game to game. This particular Prosperity Game was played by volunteers from Sandia National Laboratories, Eastman Kodak, IBM, and AT&T. Since the participants fully control the content of the games, the specific outcomes will be different when the team for each laboratory, Congress, DOE, and the Laboratory Operating Board (now Laboratory Operations Board) is composed of executives from those respective organizations. Nevertheless, the strategies and implementing agreements suggest that the Prosperity Games stimulate cooperative behaviors and may permit the executives of the institutions to safely explore the consequences of a family of DOE concert.

Delta is an object-oriented code architecture based on the finite element method which enables simulation of a wide range of engineering mechanics problems in a parallel processing environment. Written in C{sup ++}, Delta is a natural framework for algorithm development and for research involving coupling of mechanics from different Engineering Science disciplines. To enhance flexibility and encourage code reuse, the architecture provides a clean separation of the major aspects of finite element programming. Spatial discretization, temporal discretization, and the solution of linear and nonlinear systems of equations are each implemented separately, independent from the governing field equations. Other attractive features of the Delta architecture include support for constitutive models with internal variables, reusable ``matrix-free`` equation solvers, and support for region-to-region variations in the governing equations and the active degrees of freedom. A demonstration code built from the Delta architecture has been used in two-dimensional and three-dimensional simulations involving dynamic and quasi-static solid mechanics, transient and steady heat transport, and flow in porous media.

Candidate models and correlations describing entrainment and dispersal of core debris from reactor cavities in direct containment heating (DCH) event, are assessed against a data base of approximately 600 experiments performed previously at Brookhaven National Laboratory and Sandia National Laboratories reactor cavities was studied. Cavity geometries studied are those of the Surry and Zion nuclear power plants and scale factors of 1/42 and 1/10 were studied for both geometries. Other parameters varied in the experiments include gas pressure driving the dispersal, identities of the driving gas and of the simulant fluid, orifice diameter in the pressure vessel, and volume of the gas pressure vessel. Correlations were assessed in terms of their ability to reproduce the observed trends in the fractions dispersed as the experimental parameters were varied. For the fraction of the debris dispersed, the correlations recommended for inclusion in the CONTAIN code are the Tutu-Ginsberg correlations, the integral form of the correlation proposed by Levy and a modified form of the Whalley-Hewitt correlation. For entrainment rates, the recommended correlations are the time-dependent forms of the Levy correlation, a correlation suggested by Tutu, and the modified Whalley-Hewitt correlation.

This paper describes a product realization process developed at Sandia National Laboratories by the A-PRIMED project that integrates many of the key components of ``agile manufacturing`` (Nagel & Dove, 1992) into a complete, step-by-step, design-to-production process. For two separate product realization efforts, each geared to a different set of requirements, A-PRIMED demonstrated product realization of a custom device in less than a month. A-PRIMED used a discriminator (a precision electro mechanical device) as the demonstration device, but the process is readily adaptable to other electro mechanical products. The process begins with a qualified design parameter space (Diegert et al, 1995). From that point, the product realization process encompasses all facets of requirements development, analysis and testing, design, manufacturing, robot assembly and quality assurance, as well as product data management and concurrent engineering. In developing the product realization process, A-PRIMED employed an iterative approach whereby after each build, the process was reviewed and refinements were made on the basis of lessons learned. This paper describes the integration of project functions and product realization technologies to develop a product realization process that on repeated iterations, was proven successful.

We recently described a near-surface imaging scheme that employs disilanes and a bilayer resist scheme which together dramatically improve silicon contrast. A relatively thin 0.25 to 0.1 {mu}m imaging layer of a chemically amplified photo-crosslinking resist (Shipley XP-8844 or XP-9472) is spin coated on top of a thicker (0.25-0.5 {mu}m) layer of hard-baked resist (such as Shipley MP-1807). This bilayer scheme improves silicon contrast and provides additional advantages such as providing a planarizing layer and a processing layer.

The US Department of Energy conducted the 1994 Fernald (Ohio) field characterization demonstration project to evaluate the performance of a group of both industry-standard and proposed alternative technologies in describing the nature and extent of uranium contamination in surficial soils. Detector stability and measurement reproducibility under actual operating conditions encountered in the field is critical to establishing the credibility of the proposed alternative characterization methods. Comparability of measured uranium activities to those reported by conventional, US Environmental Protection Agency (EPA)-certified laboratory methods is also required. The eleven (11) technologies demonstrated included (1) EPA-standard soil sampling and laboratory mass-spectroscopy analyses, and currently-accepted field-screening techniques using (2) sodium-iodide scintillometers, (3) FIDLER low-energy scintillometers, and (4) a field-portable x-ray fluorescence spectrometer. Proposed advanced characterization techniques included (5) alpha-track detectors, (6) a high-energy beta scintillometer, (7) electret ionization chambers, (8) and (9) a high-resolution gamma-ray spectrometer in two different configurations, (10) a field-adapted laser ablation-inductively coupled plasma-atomic emission spectroscopy (ICP-AES) technique, and (11) a long-range alpha detector. Measurement reproducibility and the accuracy of each method were tested by acquiring numerous replicate measurements of total uranium activity at each of two ``standard sites`` located within the main field demonstration area. Meteorological variables including temperature, relative humidity. and 24-hour rainfall quantities were also recorded in conjunction with the standard-sites measurements.

Some dynamic environments are characterized by time histories that are not Gaussian. A more accurate simulation of these environments can be generated if a realization of a non Gaussian time history can be reproduced which has a specified auto spectral density (also called power spectral density) and a specified skewness and kurtosis (not necessarily the skewness and kurtosis of a Gaussian time history). The mean square of the waveform is reproduced if the spectrum is reproduced. Modern waveform reproduction techniques can be used to reproduce the realized waveform on an electrodynamic or electrohydraulic shaker. A method is presented for the generation of realizations of zero mean non Gaussian random time histories with a specified auto spectral density, skewness, and kurtosis. Kurtosis, defined in this paper as E[{chi}{sup 4}]/E{sup 2}[{chi}{sup 2}], greater than 3 can be realized. Realizations of the random process are generated with a generalization of shot noise.

This report introduces and evaluates system analysis tools that were developed, or are under development, for the Robotics Technology Development Program (RTDP). Additionally, it discusses system analysis work completed using these tools aimed at completing a system analysis of the retrieval of waste from underground storage tanks on the Hanford Reservation near Richland, Washington. The tools developed and evaluated include a mixture of commercially available tools adapted to RTDP requirements, and some tools developed in house. The tools that are included in this report include: a Process Diagramming Tool, a Cost Modeling Tool, an Amortization Modeling Tool, a graphical simulation linked to the Cost Modeling Tool, a decision assistance tool, and a system thinking tool. Additionally, the importance of performance testing to the RTDP and the results of such testing executed is discussed. Further, the results of the Tank Waste Retrieval (TWR) System Diagram, the TWR Operations Cost Model, and the TWR Amortization Model are presented, and the implication of the results are discussed. Finally, the RTDP system analysis tools are assessed and some recommendations are made regarding continuing development of the tools and process.

In order to create sub micron vias between metal layers on silicon IC circuits, the tungsten filled via processes have been in a constant state of development over the past 15 years. Processing is complex, expensive, and difficult to reproduce. The introduction of galvanic cells, via undercutting, and exposed plugs are just some of the plagues that have hit several users of the technology. Discussed in this paper is an alternative approach to the complex tungsten filled via interconnect process. The proposed process yields well at sub micron geometries, is easy to perform, and is inexpensive compared to the tungsten filled via process. Contact resistance improves greatly over the standard tungsten process. The test run achieved a mean value of 0.25 ohms per via compared to historic tungsten process that yields 0.4 ohms per via. The distribution was also excellent with sigma recorded at 0.025 ohms per via.

We report the threshold characteristics of small oxide-confined vertical-cavity surface emitting lasers. Abrupt threshold transitions 105 times the spontaneous emission background are obtained at injection currents as low as 470 nanoampere.

Military specified, ceramic packaged and radiation hardened components will disappear before the end of the century. The only long-term sustainable alternative may well be to use plastic packaged Commercial Components. The material in this report comes from the Defense Logistics Agency sponsored Plastic Package Availability Program and from an AT and T field reliability study. It summarizes Case Studies from companies which have been building and fielding highly reliable commercial and DOD military systems using plastic commercial components. Findings are, that when properly selected commercial components are operated within the true limitations of their design and packaging, they are as reliable as today`s Mil Spec components. Further, they offer cost, space and weight savings, shared manufacturing and field test experience with industry, and access to the most modern technology. Also reported are potential problems that may be encountered when using commercial components, their long term storage and use reliability characteristics, recommended design processes and supplier selection practices, commercial best business practices, and a semiconductor manufacturer`s view of the military`s switch to commercial plastic microcircuits.

This paper outlines the use of a Failure Modes and Effects Analysis for the safety assessment of a robotic system being developed at Sandia National Laboratories. The robotic system, The Weigh and Leak Check System, is to replace a manual process at the Department of Energy facility at Pantex by which nuclear material is inspected for weight and leakage. Failure Modes and Effects Analyses were completed for the robotics process to ensure that safety goals for the system had been meet. These analyses showed that the risks to people and the internal and external environment were acceptable.

We have demonstrated a new semiconductor laser device that may be useful in high speed characterization of cell morphology for diagnosis of disease. This laser device has critical advantages over conventional cell fluorescence detection methods since it provides intense, monochromatic, low divergence light signals that are emitted from lasing modes confined by a cell. Further, the device integrates biological structures with semiconductor materials at the wafer level to reduce size and simplify cell preparation. This microcavity semiconductor laser comprises a vertical cavity surface-emitting semiconductor, to provide gain and feedback for light confined by cells, and a dielectric mirror to close the cavity. Transparent cells loaded into the cavity act as dielectric waveguides to define transverse electromagnetic modes. Light emitted from the microcavity can be resolved into narrow spectral modes, high-contrast/coherent light images, or time-dependent pulses that reveal cell morphology and size. We have used this laser device as a cytometer in two basic configurations. First, as a probe of individual cells by spectral analysis of cell modes. Second, as scanning cytometer for rapidly probing large numbers of cells by pulse height spectroscopy.

This report provides an Executive Summary of the various elements of the Materials Sciences Program which is funded by the Division of Materials Sciences, Office of Basic Energy Sciences, U.S. Department of Energy at Sandia National Laboratories, New Mexico.

This report pertains to a Laboratory Directed Research and Development project which was funded for FY94 and FY95. The goal was to develop building blocks for small, cheap sensors that use optical spectroscopy as a means of detecting chemical analytes. Such sensors can have an impact on a wide variety of technologies, such as: industrial process control, environmental monitors, chemical analysis in medicine, and automotive monitors. We describe work in fabricating and demonstrating a waveguide/grating device that can serve as the wavelength dispersive component in a miniature spectrometer. Also, we describe the invention and modeling of a new way to construct an array of optical interference filters using sub-wavelength lithography to tune the index of refraction of a fixed Fabry-Perot cavity. Next we describe progress in more efficiently calculating the fields in grating devices. Finally we present the invention of a new type of near field optical probe, applicable to scanning microscopy or optical data storage, which is based on a circular grating constructed in a waveguide. This result diverges from the original goal of the project but is quite significant in that it promises to increase the data storage capacity of CD-ROMs by 10 times.

This work gives a proof of convergence for a randomized learning algorithm that describes how anoles (lizards found in the Carribean) learn a foraging threshold distance. This model assumes that an anole will pursue a prey if and only if it is within this threshold of the anole`s perch. This learning algorithm was proposed by the biologist Roughgarden and his colleagues. They experimentally confirmed that this algorithm quickly converges to the foraging threshold that is predicted by optimal foraging theory our analysis provides an analytic confirmation that the learning algorithm converses to this optimal foraging threshold with high probability.

Space reactor safety activities and decisions have evolved over the last decade. Important safety decisions have been made in the SP-100, Space Exploration Initiative, NEPSTP, SNTP, and Bimodal Space Reactor programs. In addition, international guidance on space reactor safety has been instituted. Space reactor safety decisions and practices have developed in the areas of inadvertent criticality, reentry, radiological release, orbital operation, programmatic, and policy. In general, the lessons learned point out the importance of carefully reviewing previous safety practices for appropriateness to space nuclear programs in general and to the specific mission under consideration.

We have measured modal damping using strain-gauge data from an operating wind turbine. This new technique for measuring modal damping is easier and less expensive than previously used methods. Auto-correlation and cross-correlation functions of the strain-gauge data have been shown to consist of decaying sinusoids which correspond to the modal frequencies and damping ratios of the wind turbine. We have verified the method by extracting damping values from an analytically generated data set. Actual operating response data from the DOE/Sandia 34-m Test Bed has been used to calculate modal damping ratios as a function of rotor rotation rate. This capability will allow more accurate fatigue life prediction and control. © 1996 by ASME.

Silicon solar cell efficiencies of 17.1%, 16.4%, 14.8%, and 14.9% have been achieved on FZ, Cz, multicrystalline (mc-Si), and dendritic web (DW) silicon, respectively, using simplified, cost-effective rapid thermal processing (RTP). These represent the highest reported efficiencies for solar cells processed with simultaneous front and back diffusion with no conventional high-temperature furnace steps. Appropriate diffusion temperature coupled with the added in-situ anneal resulted in suitable minority-carrier lifetime and diffusion profiles for high-efficiency cells. The cooling rate associated with the in-situ anneal can improve the lifetime and lower the reverse saturation current density (Jo), however, this effect is material and base resistivity specific. PECVD antireflection (AR) coatings provided low reflectance and efficient front surface and bulk defect passivation. Conventional cells fabricated on FZ silicon by furnace diffusions and oxidations gave an efficiency of 18.8% due to greater short wavelength response and lower Jo.

We have developed a new magnetic monocusp ion source for single aperture applications such as neutron generators. Coupling solenoidal magnetic fields on both sides of a monocusp magnetic field has generated over 70% atomic deuterium ions at pressures as low as 0.4 Pa (3 mTorr). This article describes the performance and characteristics of the solenoidal and monocusp ion source. © 1996 American Institute of Physics.

With the eventual phase-out of chlorofluorocarbons and hydrochlorofluorocarbons, and restrictive regulations concerning the use of other volatile organic compounds as cleaning solvents, it is essential to seek new, environmentally acceptable cleaning processes. We are investigating supercritical carbon dioxide (CO2) as an alternative solvent for precision cleaning of machined metal parts in governmental and industrial cleaning processes. The compatibility of metals in supercritical-fluid cleaning media with respect to corrosion must be addressed. In this work, a screening study of the corrosive effects of supercritical CO2 and several supercritical cosolvents on selected metals was conducted. Sample coupons of stainless steel (grades 304LSS, 316SS), aluminum (grades 2024, 6061, 7075), carbon steel (1018), and copper (CDA 101) were statically exposed to pure supercritical CO2, water-saturated supercritical CO2, 10 wt % methanol/CO2 cosolvent, and 4 wt % tetrahydrofurfuryl alcohol (THFA)/CO2 at 24,138 kPa (3500 psig) and 323 K (50 °C) for 24 h. Gravimetric analysis and magnified visual inspection of the coupons were performed before and after the exposure tests. Surface analyses including electron microprobe analysis (EMPA), X-ray photoelectron spectroscopy (XPS), and Auger electron spectroscopy (AES) were done where visual and gravimetric changes were indicative of corrosive attack. The metal alloys were found to be compatible with the supercritical test media barring a few exceptions. Corrosive attack was observed on 1018 carbon steel in the water-saturated CO2 environment, and also on 2024 aluminum and CDA 101 copper, both in the 10 wt % methanol-CO2 cosolvent. The results of all compatibility testing are reported, and hypotheses are formed in an attempt to explain possible corrosion mechanisms.

A survey of existing data has been completed in order to examine the hazards to people exposed on the ground and to in-flight aircraft by debris produced during high-altitude, rocket-boosted flight tests. These data were then analyzed to quantify the particle sizes and energy levels below which the fragments no longer pose a hazard. The survey results are presented here and recommendations made regarding the minimum energy levels and minimum particle size that need be considered in a flight safety analysis.

Metastable SiGe films were grown by MBE on Si (001) substrates and annealed to promote varying degrees of partial relaxation. X-ray diffraction reciprocal-space analysis was then used to monitor the structural evolution of the displacement fields of the dislocation array with increasing misfit density. The diffuse-x-ray-scattering patterns of the dislocated heterolayers were compared with lineal-misfit densities determined by defect etching, leading us to develop a geometric model which provides a framework for understanding the early-stage evolution of the displacement fields of the dislocation array, and which also explicitly links diffuse x-ray intensity to misfit density. At low misfit density, the diffuse intensity arises from two-dimensional displacement fields associated with single-nonoverlapping dislocations. As misfit density increases, the displacement fields of individual dislocations increasingly overlap producing three-dimensional displacements. The evolving diffuse intensity reflects the transition from 2-D to 3-D displacement fields. Finally, it is demonstrated that the diffuse x-ray intensity of the strained epilayer can be used to accurately measure lineal misfit-dislocation densities from 400 to 20,000 lines/cm.

The most commonly used solder for electrical interconnects in electronic packages is the near eutectic 60Sn-40Pb alloy. This alloy has a number of processing advantages (suitable melting point of 183°C and good wetting behavior). However, under conditions of cyclic strain and temperature (thermomechanical fatigue) the microstructure of this alloy undergoes a heterogeneous coarsening and failure process that makes the prediction of solder joint lifetime complex. A finite element simulation methodology to predict solder joint mechanical behavior, that includes microstructural evolution, has been developed. The mechanical constitutive behavior was incorporated into the time dependent internal state variable viscoplastic model through experimental creep tests. The microstructural evolution is incorporated through a series of mathematical relations that describe mass flow in a temperature/strain environment. The model has been found to simulate observed thermomechanical fatigue behavior in solder joints.

The FD-TD method and the Berenger Perfectly Matched Layer (PML) absorbing condition are applied to the modeling of a 32-element patch array. Numerical results for the return loss at the array feed are presented and compared to measured results for the purpose of model validation.

One of the Department of Energy's programs for assuring the safety and security of nuclear weapons, nuclear power plants and hazardous material containers is discussed. A Fire Science and Technology program has been established at Sandia National Laboratories to integrate those technologies needed for creating validated numerical simulations of real fires and the response by real objects exposed to fire. This paper describes Sandia's program for integrating fire science and technology into predictive capabilities which provide engineering solutions to high-consequence fire-related problems. The integration of solid materials and fire issues will be emphasized.

Extensive surface pressure measurements were obtained on a hypersonic vehicle configuration at Mach 8 for the purpose of computational fluid dynamics code validation. Experiments were conducted in the Sandia National Laboratories hypersonic wind tunnel. All measurements were made for laminar flow conditions at a Reynolds number (based on model length) of 1.81 x 106 and perfect gas conditions. The basic vehicle configuration is a spherically blunted, 10° half-angle cone, with a slice parallel to the axis of the vehicle. Flaps of varying angle (10, 20, and 30°) could be attached to the aft portion of the slice. Surface pressure measurements at 96 locations on the body surface were obtained for angles of attack from -10 to +18° and for various roll angles. All three deflected flap angles produced separated flow on the sliced portion of the body in front of the flap. Because of the three-dimensional expansion over the slice, the separated flow on the slice and flap was also highly threedimensional. The results of the present experiment provide extensive surface pressure measurements for the validation of computational fluid dynamics codes for separated flow caused by an embedded shock wave.

An experimental investigation into active control of bending vibrations in thick plate-like structural elements is described. This work is motivated by vibration problems encountered in manufacturing processes that require greater control authority than is available from conventional surface mounted PZT patches or PVDF films. The focus of this experiment is a surrogate photolithography platen in which PZT stacks are mounted in cutouts on the platen top surface. These actuators provide significant vibration control authority by generating moments in the platen through their compressive loads. A Positive Position Feedback control law is used to significantly augment the damping in the first two bending modes. The implications of the experimental results for photolithography machines are discussed.

The Federal Aviation Administration Technical Center (FAATC) has initiated several research projects to assess the structural integrity of the aging commercial aircraft fleet. One area of research involves the understanding of a phenomenon known as “Widespread Fatigue Damage” or WFD, which refers to a type of multiple element cracking that degrades the damage tolerance capability of an aircraft structure. Research on WFD has been performed both experimentally and analytically including finite element modeling of fuselage lap splice joints by the Volpe Center. Fuselage pressurization tests have also been conducted at the FAA's Airworthiness Assurance NDI Validation Center (AANC) to obtain strain gage data from select locations on the FAA/AANC 737 Transport Aircraft Test Bed. One-hundred strain channels were used to monitor five different lap splice bays including the fuselage skin and substructure elements. These test results have been used to evaluate the accuracy of the analytical models and to support general aircraft analysis efforts. This paper documents the strain fields measured during the AANC tests and successfully correlates the results with analytical predictions.

A high-electrooptic-efficiency Mach-Zehnder intensity modulator is demonstrated with a bandwidth exceeding 40 GHZ. The 1 mm-long modulator has a switching voltage comparable to undoped semiconductor designs of much greater length.

We present the design and experimental verification of a Tapered-Rib Adiabatic-Following Fiber Coupler (TRAFFiC). This device is a monolithically integratable structure fabricated in AlGaAs designed to increase the coupling efficiency of conventional optical fibers to tightly confined semiconductor waveguide devices. This approach offers the possibility of significantly reducing fiber butt coupling losses from the typical values of 7 to 10 dB to values of 0.5 to 3 dB. This long-standing packaging problem is one of the major impediments to the widespread acceptance of semiconductor-based optoelectronics. Moreover, the design can be implemented with minimal increase in fabrication complexity since it uses only epitaxial growth, lithography and etching.

A strategy is presented to develop computationally efficient models for a class of structures containing nonlinearities. Those structures are ones for which the predominant nonlinearity is in the interfaces of linear subsystems. In those cases, one hopes to achieve low order models for the linear subsystems coupled with simplistic models for the interfaces. The theme of this paper is that of deducing the properties of the nonlinear interfaces by examining the properties of the full nonlinear structure in light of the known properties of the linear subsystems. Situations where such problems arise include those where the nonlinearity derives from sliding friction or stick-slip friction. Those conditions can seriously compromise system performance if not addressed adequately, occasionally leading to either sloppy control or complete loss of stability. It is the problem of identifying those nonlinear subsystems that is addressed here.

Mode-locked semiconductor lasers have drawn considerable attention as compact, reliable, and relatively inexpensive sources of short optical pulses. Advances in the design of such lasers have resulted in vast improvements in pulsewidth and noise performance, at a very wide range of repetition rates. An attractive application for these lasers would be to serve as alternatives for large benchtop laser systems such as dye lasers and solid-state lasers. However, mode- locked semiconductor lasers have not yet approached the performance of such systems in terms of output power. Different techniques for overcoming the problem of low output power from mode-locked semiconductor lasers are discussed. Flared and arrayed lasers have been used successfully to increase the pulse saturation energy limit by increasing the gain cross section. Further improvements have been achieved by use of the MOPA configuration, which utilizes a flared semiconductor amplifier stage to amplify pulses to energies of 120 pJ and peak powers of nearly 30 W.

The knowledge gained from the observations and simulations of the impact of comet Shoemaker-Levy 9 (SL9) with Jupiter has led us to consider the threat of impact-generated plumes to satellites in low-Earth orbit (LEO). Preliminary simulations suggest that impacts of a size that recur about once per century on Earth generate plumes that rise to nearly 1000 km over an area thousands of km in diameter. Interacting plumes from multiple impacts rise to higher altitudes. Detailed modeling of such plumes is needed to quantify this threat to satellites in LEO. Careful observations of high-energy atmospheric entry events using both satellite and ground-based instruments would provide validation for these computational models. © 1996 American Society of Civil Engineers.

Thermal expansion measurements were conducted as a function of confining pressure on welded specimens of Topopah Spring Member tuff recovered from borehole USW SD-12 at Yucca Mountain, NV, Each specimen was tested at confining pressures between 1 and 30 MPa over a nominal temperature range of 25 to 250 °C. On several specimens, the higher confining pressure thermal cycles were performed first to inhibit thermal effects, such as cracking, that occur at lower confining pressures in other rock types. The coefficient of thermal expansion for welded tuff increases with temperature. At temperatures below 100 °C the mean coefficient of thermal expansion range from 7.7 to 10.8 x 10-6 °C-1. As temperatures approach 250 °C, the thermal expansions increase markedly to values of 14.2 to 20.6 x 10-6 °C-1. The effect of confining pressure on thermal expansion for tuff is small.

This paper discusses ongoing work to develop structural health monitoring techniques for composite aerospace structures such as aircraft control surfaces, fuselage sections or repairs, and reusable launch vehicle fuel tanks. The overall project is divided into four tasks: operational evaluation, diagnostic measurements, information condensation, and damage detection. Five composite plates were constructed to study delaminations, disbonds, and fluid retention issues as the initial step in creating an operational system. These two foot by two foot plates were graphite-epoxy with nomex honeycomb cores. The diagnostic measurements are composed of modal tests with a scanning laser vibrometer at over 500 scan points per plate covering the frequency range up to 2000 Hz. This data has been reduced into experimental dynamic-response matrices using a generic software package developed at the University of Colorado at Boulder. The continuing effort will entail performing a series of damage identification studies to detect, localize, and determine the extent of the damage. This work is providing understanding and algorithm development for a global NDE technique for composite aerospace structures.

During the past two years significant performance advances have been achieved in selectively oxidized vertical-cavity surface emitting lasers (VCSELs), many of which have established overall benchmark records for semiconductor lasers. These oxidized VCSEL structures leverage the high oxidation selectivity of Al(Ga)As and the capability of forming buried oxide layers within the epilayers of the laser. This paper reviews the advances made in device fabrication, structure and performance of selectively oxidized VCSELs.

Sealing fractures in nuclear waste repositories concerns all programs investigating deep burial as a means of disposal. Because the most likely mechanism for contaminant migration is by dissolution and movement through groundwater, sealing programs are seeking low-viscosity sealants that are chemically, min-eralogically, and physically compatible with their host. This paper presents the results of collaborative work directed by Sandia National Laboratories (SNL) and supported by Whitesell Laboratories (WL), operated by Atomic Energy of Canada, Ltd. The work was undertaken in support of the Waste Isolation Pilot Plant (WIPP). This effort addresses the technology associated with long-term isolation of nuclear waste in a natural salt medium. The work presented is part of the WIPP plugging and sealing program, specifically the development and optimization of an ultrafine cementitious grout that can be injected to lower excessive, strain-induced hydraulic conductivity in the fractured rock termed the Distributed Rock Zone (DRZ) surrounding underground excavations. Innovative equipment and procedures employed in the laboratory produced a usable cement-based grout; 90% of the particles are smaller than 10 microns and the average size is 4 microns (Ahrens et al., 1996). The process involved simultaneous wet pulverization and mixing. The grout was used for a successful in situ test underground at the WIPP. Injection of grout sealed microfractures as small as 8 microns and lowered the gas transmissivity of the DRZ by up to three orders of magnitude. Following the WIPP test, additional work produced an improved version of the grout containing particles 90% smaller than 6 microns and averaging 2 microns. This grout can be produced in a dry form ready to mix.

Synthetic Aperture Radar (SAR) has been proven an effective sensor in a wide variety of applications. Many of these uses require transmission and/or processing of the image data in a lossless manner. With the current state of SAR technology, the amount of data contained in a single image may be massive, whether the application requires the entire complex image or magnitude data only. In either case, some type of compression may be required to losslessly transmit this data in a given bandwidth or store it in a reasonable volume. This paper provides the results of applying several lossless compression schemes to SAR imagery.

In this paper, a damage mechanics mcxlel is described for determining progressive damage process of unidirectional graphite/epoxy composite plates containing a central hole subjected to off-axis uniaxial tension. The inelastic behavior of these composite materials is attributed to the irreversible thermcxlynamics processes involving energy dissipation and stiffness variation caused by damage initiation and accumulation. The mechanical response of the composites is investigated by using a nonlinear finite element procedure fotmulated with a set of damage coupled constitutive equations. Separate damage criteria are derived for fiber failure and for matrix or fiber/matrix interaction failure in unidirectional composites. Validation of the damage mcxlel is achieved by comparing the numerical prediction and experimental data obtained from Moire interferometry technique. It has been found that failure of the composite material near the hole region takes the form of an extensive damage zone. The macrocrack initiates at the material point near the hole boundary with high damage value and propagates along the direction of damage zone extension. Preliminary results indicate that the proposed damage mcxlel is an effective methcxl of studying progressive failure behavior of unidirectional composite laminates containing a circular hole and can be readily extended to examine the damage response of composite structures.

We present results using near-infrared (NIR) cameras to study emission. characteristics of common defect classes for integrated circuits (ICs). The cameras are based on a liquid nitrogen cooled HgCdTe imaging array with high quantum efficiency and very low read noise. The array was developed for infrared astronomy and has high quantum efficiency in the wavelength range from 0.8 to 2.5 µn. For comparison, the same set of samples used to characterize the performance of the NIR camera were studied using a non-intensified, liquid-nitrogen-cooled, slow scan CCD camera (with a spectral range from 400-1100 nm). Our results show that the NIR camera images all of the defect classes studied here with much shorter integration times than the cooled CCD, suggesting that photon emission beyond 1 µm is significantly stronger than at shorter wavelengths.

Fluorescent microthermal imaging (FMI) involves coating a sample surface with a thin fluorescent film that, upon exposure to UV light source, emits temperature-dependent fluorescence [1-7]. The principle behind FMI was thoroughly reviewed at the ISTFA in 1994 [8, 9]. In two recent publications [10,11], we identified several factors in film preparation and data processing that dramatically improved the thermal resolution and sensitivity of FMI. These factors include signal averaging, the use of base mixture films, film stabilization and film curing. These findings significantly enhance the capability of FMI as a failure analysis tool. In this paper, we show several examples that use FMI to quickly localize heat-generating defects ("hot spots"). When used with other failure analysis techniques such as focused ion beam (FIB) cross sectioning and scanning electron microscope (SEM) imaging, we demonstrate that FMI is a powerful tool to efficiently identify the root cause of failures in complex ICs. In addition to defect localization, we use a failing IC to determine the sensitivity of FMI (i.e., the lowest power that can be detected) in an ideal situation where the defects are very localized and near the surface.

A new method of signature analysis is presented and explained. This method of signature analysis can be based on either experiential knowledge of failure analysis, observed data, or a combination of both. The method can also be used on low numbers of failures or even single failures. It uses the Dempster-Shafer theory to calculate failure mechanism confidence. The model is developed in the paper and an example is given for its use.

A Monte Carlo procedure for the construction of complementary cumulative distribution functions (CCDFs) for comparison with the U.S. Environmental Protection Agency (EPA) release limits for radioactive waste disposal (40 CFR 191, Subpart B) is described and illustrated with results from a recent performance assessment (PA) for the Waste Isolation Pilot Plant (WIPP). The Monte Carlo procedure produces CCDF estimates similar to those obtained with importance sampling in several recent PAs for the WIPP. The advantages of the Monte Carlo procedure over importance sampling include increased resolution in the calculation of probabilities for complex scenarios involving drilling intrusions and better use of the necessarily limited number of mechanistic calculations that underlie CCDF construction.

Low dielectric constant insulating films, such as SiO2 and fluorine doped SiOx, are an important class of materials in semiconductor manufacturing. Evaluation of a new process to grow low temperature SiOxFy films using an electron cyclotron resonance plasma (ECR) was done. Ion beam analysis techniques were used to characterize the compositions of the insulating films and correlate this with their physical and electrical properties. Since Si, O, F and H are of primary interest in these films, three different techniques were utilized in order to get a more thorough analysis. 2.8 MeV He Rutherford Backscattering Spectrometery (RBS) revealed the Si and O content, but because of the low fluorine concentrations (2-10 at.%) RBS proved difficult for analysis of the F content. Instead, Nuclear Reaction Analysis (NRA), which used 872 keV protons in the 19F(p, αγ)16O reaction, was employed. Finally, 30 MeV Si Elastic Recoil Detection (ERD) was used to obtain the H concentration and supplement the O analysis. The dielectric constant decreased from ε = 4 to ε = 3.55 as the F concentration increased from 0 to 10%.

The fluorescent microthermal imaging technique (FMI) involves coating a sample surface with an inorganic-based thin film that, upon exposure to UV light, emits temperature-dependent fluorescence [1-8]. FMI offers the ability to create thermal maps of integrated circuits with a thermal resolution theoretically limited to 1 m°C and a spatial resolution which is diffraction-limited to 0.3 μm. Even though the fluorescent microthermal imaging (FMI) technique has been around for more than a decade, many factors that can significantly affect the thermal image quality have not been systematically studied and characterized. After a brief review of FMI theory, we will present our recent results demonstrating for the first time three important factors that have a dramatic impact on the thermal quality and sensitivity of FMI. First, the limitations imparted by photon shot noise and improvement in the signal-to-noise ratio realized through signal averaging will be discussed. Second, ultraviolet bleaching, an unavoidable problem with FMI as it currently is performed, will be characterized to identify ways to minimize its effect. Finally, the impact of film dilution on thermal sensitivity will be discussed.

The complexation of neptunium(V), Np(V), with the acetate anion. Ac-, was measured in sodium chloride media to high concentration using an extraction technique. The data were interpreted using the thermodynamic formalism of Pitzer, which is valid to high electrolyte concentrations. A consistent model for the deprotonation constants of acetic acid in NaCl and NaClO4 media was developed. For the concentrations of acetate expected in a waste repository, only the neutral complex NpO2Ac(aq) was important in describing the interactions between the neptunyl ion and acetate. The thermodynamic stability constant β1010 for the reaction NpO2+ + Ac- ↔ NpO2Ac was calculated to be 1.46±0.22. This weak complexing behavior between the neptunyl ion and acetate indicates that acetate will not significantly enhance dissolved Np(V) concentrations in ground waters associated with nuclear waste repositories that may contain acetate.

The paper describes New Ventures, a new initiative at Sandia National Laboratories that encourages the creation of new businesses based on laboratory technology as a timely, efficient means of technology transfer. Sandia's New Ventures program has shown that a dedicated effort can produce significant results. In the three years prior to this program's launch, just two ventures per year on average were created based on laboratory technology. By comparison, the New Ventures program has enabled 20 new ventures in its first nine months of full operation. Our experience has yielded several lessons: • most ventures result from Sandia entrepreneurs, from technologies that are well matched to market needs, and from laboratory projects that are ready for production; • Entrepreneurship issues are tremendously complex, requiring policy changes to reduce risk, manage intellectual property and licensing determinations, plan for potential conflicts of interest, and tailor other strategies; • A new ventures program must advocate these policy changes, assist entrepreneurs, put significant effort into matching outside companies to inside technologies, and identify lab projects ready for manufacture; • Connection to the local business community is vital to good commercialization matches and to the development of Sandia entrepreneurs; • Lab employees are far more interested in pursuing Technology Transfer Leaves of Absence than anticipated.

A new inorganic ion exchange material, called SNL-1, has been prepared at Sandia National Laboratories. Development samples of SNL-1 have been determined to have high selectivity for the adsorption of Sr from highly acidic solutions (1 M HNO3). This paper presents results obtained for the material in batch ion exchange tests conducted at various solution pH values and in the presence of a number of competing cations. Results from a continuous flow column ion exchange experiment are also presented.

Reported is the result of an experimental investigation of fire-induced response of a 96 kg/m3 closed cell rigid polyurethane foam. The specimen is 0.37 m in diameter, and 152 mm thick, placed in a cylindrical test vessel. The fire condition is simulated by heating the bottom of the test vessel to 1283 K using a radiant heat source. Real-time x-ray shows that the degradation process involves the progression of a charring front into the virgin material. The charred region has a regular and graded structure consisting of a packed bubble outer layer and successive layers of thin shells. The layer-to-layer permeability appears to be poor. There are indications that gas vents laterally. The shell-like structure might be the result of lateral venting. Although the foam degradation process is quite complicated, the in-depth temperature responses in the uncharred foam appear to be consistent with steady state ablation. The measured temperature responses are well represented by the exponential distribution for steady state ablation. An estimate of the thermal diffusivity of the foam is obtained from the ablation model. The experiment is part of a more comprehensive program to develop material response models of foams and encapsulants.

For flame spread over solid materials, there has traditionally been a large technology gap between fundamental combustion research and the somewhat simplistic approaches used for practical, real-world applications. Recent advances in computational hardware and computational fluid dynamics (CFD)-based software have led to the development of fire field models. These models, when used in conjunction with material burning models, have the potential to bridge the gap between research and application by implementing physics-based engineering models in a transient, multi-dimensional tool. This paper discusses the coupling that is necessary between fire field models and burning material models for the simulation of solid material fires. Fire field models are capable of providing detailed information about the local fire environment. This information serves as an input to the solid material combustion submodel, which subsequently calculates the impact of the fire environment on the material. The response of the solid material (in terms of thermal response, decomposition, charring, and off-gassing) is then fed back into the field model as a source of mass, momentum and energy. The critical parameters which must be passed between the field model and the material burning model have been identified. Many computational issues must be addressed when developing such an interface. Some examples include the ability to track multiple fuels and species, local ignition criteria, and the need to use local grid refinement over the burning material of interest.