A panel research experiment (PRE) was designed, built, and tested as a scaled-down model of a direct absorption receiver (DAR). The PRE is a 3-MWt DAR experiment that will allow flow testing with molten nitrate salt and provide a test bed for DAR testing with actual solar heating. In a solar central receiver system DAR, the heat absorbing fluid (a blackened molten nitrate salt) flows in a thin film down a vertical panel (rather than through tubes as in conventional receiver designs) and absorbs the concentrated solar flux directly. The ability of the flowing salt film to absorb the incident solar flux depends on the panel design, hydraulic and thermal fluid flow characteristics, and fluid blackener properties. Testing of the PRE is being conducted to demonstrate the engineering feasibility of the DAR concept. The DAR concept is being investigated because it offers numerous potential performance and economic advantages for production of electricity when compared to other solar receiver designs. The PRE utilized a 1-m wide by 6-m long absorber panel. The salt flow tests are being used to investigate component performance, panel deformations, and fluid stability. Salt flow testing has demonstrated that all the DAR components work as designed and that there are fluid stability issues that need to be addressed. Future solar testing will include steady-state and transient experiments, thermal loss measurements, responses to severe flux and temperature gradients and determination of peak flux capability, and optimized operation. In this paper, we describe the design, construction, and some preliminary flow test results of the Panel Research Experiment.
An obvious group of applications for HTS materials is microwave and millimeter wave circuitry. Besides low loss, the unique features of these materials, such as flux flow, can be exploited. We have been concentrating on the Tl-Ca-Ba-Cu-O family of materials. The film growth techniques, lithographic processing methods and the characteristics of several devices we have developed will be presented. These devices include a flux flow-based transistor with demonstrated operation at over 35 GHz, real gain in a 50 ω system and potentially useful non-linearities and impedance levels. A number of passive microwave components are under investigation to form a more complete HTS microwave technology group.
Proceedings of the Intersociety Energy Conversion Engineering Conference
Arnold Jr., Charles
The lifetimes of zinc/bromine flow batteries may be limited by the durability of components which are fabricated from thermoplastic materials and exposed to bromine-containing electrolytes. Examples of such components are flowframes and carbon-filled plastic electrodes. In early versions of the zinc/bromine battery, flowframes and electrodes were made from copolymers of propylene and ethylene. In later versions of the zinc/bromine battery, these materials were replaced by poly(vinyl chloride) (PVC) and polyethyle (flowframes) and polyethylene as the plastic component in electrodes. We found that carbon-plastic electrodes made from polypropylene rich copolymers were swelled and chemically attacked by the bromine-containing electrolytes. As a result, warpage occurred and the battery failed. On the basis of accelerated aging studies we estimated the lifetimes of the electrode and its polypropylene based component to be 96 and 10 months, respectively. The enhanced stability of the electrode was attributed to the presence of carbon which is known to be an antioxidant for thermoxidation. In accelerated exposure tests, bromine-containing electrolytes were also found to attack and leach out the additives used in PVC flowframes. PVC itself was only slightly degraded by the electrolyte. A commercial fluorocarbon, TefzelR, which contains no additives, was determined to be stable in bromine-containing electrolytes and is recommended as a replacement for PVC. Currently, aging studies on carbonfilled polyethylene electrodes are in progress.
The state-of-the-art of parabolic dish solar concentrators is the faceted, glass-metal dish. The mass-production costs of glass-metal dishes may be high because they do not incorporate the innovations of design and materials developed over the last eight years. Therefore, Sandia National Laboratories has undertaken to develop two stretched-membrane parabolic dish concentrators for the Department of Energy's Solar Thermal Program. These solar concentrators are being designed for integration with an advanced solar receiver and a Stirling engine/generator in a 25-kWe power production unit. The first dish, which builds on the successful design of the stretched-membrane heliostats, is to be a low-risk, near-term commercial solar concentrator. This solar concentrator comprises twelve large, 3.6-meter diameter, stretched-membrane facets that are formed into parabolic shapes either with a large vacuum or by preforming the thin membranes plastically. The focal length-to-diameter ratios (f/D) for the facets are about 3.0, relatively large for a dish but much lower than heliostats where they typically range from 50 to 100. Two contractors are currently fabricating facets for this dish, and a third contractor is designing the facet support structure and pedestal for the dish. The second stretched-membrane concentrator is a single-element monolithic dish with an f/D of 0.6. The dish is shaped into a parabola by plastically yielding the membrane using a combination of uniform and nonuniform loading. Initial measurements of the of the dish indicate that it has a slope error of 3.6 milliradian (one standard deviation) relative to a perfect parabola. In this paper, the designs of the two stretched-membrane dishes are analyzed using the computer code CIRCE to model the optical performance of the concentrators and a thermal model, which includes conduction, convection, and radiation heat transfer, to calculate the thermal losses from the cavity solar receivers. The solar collector efficiency, defined as the product of the optical efficiency of the collector and the thermal efficiency of the receiver, is optimized for comparing the performance of several solar concentrator configurations. Ten facet arrangements for the faceted stretched-membrane dish and the single-element stretched-membrane dish are modeled and their performances compared with that of a state-of-the art glass-metal dish. Last, the initial designs of these two stretched-membrane dishes are described along with the results of preliminary performance measurements on their respective optical elements.
A three-dimensional finite element structural analysis of the Intermediate Scale Borehole Test at the WIPP has been performed. The analysis provides insight into how a relatively new excavation in a creeping medium responds when introduced into an existing pillar which has been undergoing stress redistribution for 5.7 years. The stress field of the volume of material in the immediate vicinity of the borehole changes significantly when the hole is drilled. Closure of the hole is predicted to be larger in the vertical direction than in the horizontal direction, leading to an ovaling of the hole. The relatively high stresses near the hole persist even at the end of the simulation, 2 years after the hole is drilled.
As part of the Yucca Mountain Project, our research program to develop and validate conceptual models for flow and transport through unsaturated fractured rock integrates fundamental physical experimentation with conceptual model formulation and mathematical modeling. Our research is directed toward developing and validating macroscopic, continuum-based models and supporting effective property models because of their widespread utility within the context of this project. Success relative to the development and validation of effective property models is predicted on a firm understanding of the basic physics governing flow through fractured media, specifically in the areas of unsaturated flow and transport in a single fracture and fracture-matrix interaction.
Construction of well-posed scenarios for the range of conditions possible at any proposed repository site is a critical first step to assessing total system performance. Event tree construction is the method that is being used to develop potential failure scenarios for the proposed nuclear waste repository at Yucca Mountain. An event tree begins with an initial event or condition. Subsequent events are listed in a sequence, leading eventually to release of radionuclides to the accessible environment. Ensuring the validity of the scenarios requires iteration between problems constructed using scenarios contained in the event tree sequence, experimental results, and numerical analyses. Details not adequately captured within the tree initially may become more apparent as a result of analyses. To illustrate this process, we discuss the iterations used to develop numerical analyses for PACE-90 using basaltic igneous activity and human-intrusion event trees.
Three series of measurements were performed on oriented cores of several Yucca Mountain tuffs to determine the importance of mechanical anisotropy in the intact rock. Outcrop and drillhole samples were tested for acoustic velocities, linear compressibilities, and strengths in different orientations. The present data sets are preliminary, but suggest the tuffs are transversely anisotropic for these mechanical properties. The planar fabric that produces the anisotropy is believed to be predominantly the result of the preferred orientation of shards and pumice fragments. The potential of significant anisotropy has direct relevance to the formulation of constitutive formulation and the analyses of an underground opening within Yucca Mountain.
Yucca Mountain, located in southwestern Nevada, is the site for a proposed high-level nuclear waste repository. The hydrologic units at Yucca Mountain appear to have quite different material characteristics. Additionally, measurements show that the material properties within each hydrologic unit vary significantly. Rock core samples taken from this site indicate that the volcanic tuff is highly fractured and nonhomogeneous. Modeling studies were conducted to determine the effects of material heterogeneities on the flow of water through rock. Multiple numerical calculations were made using random variations in spatial distributions of material properties. The results of these material variations on flow resistance, mechanical dispersion, and channeling were determined. Computed results were compared with a linear analytical model. Good agreement was obtained in the majority of the flow cases investigated.
Under the sponsorship of the US Nuclear Regulatory Commission (NRC), Sandia National Laboratories (SNL) is developing a performance assessment methodology for the analysis of long-term disposal and isolation of high-level nuclear wastes (HLW) in alternative geologic media. As part of this exercise, SNL created a conceptualization of ground-water flow and radionuclide transport in the far field of a hypothetical HLW repository site located in unsaturated, fractured tuff formations. This study provides a foundation for the development of conceptual mathematical, and numerical models to be used in this performance assessment methodology. This conceptualization is site specific in terms of geometry, the regional ground-water flow system, stratigraphy, and structure in that these are based on information from Yucca Mountain located on the Nevada Test Site. However, in terms of processes in unsaturated, fractured, porous media, the model is generic. This report also provides a review and evaluation of previously proposed conceptual models of unsaturated and saturated flow and solute transport. This report provides a qualitative description of a hypothetical HLW repository site in fractured tuff. However, evaluation of the current knowledge of flow and transport at Yucca Mountain does not yield a single conceptual model. Instead, multiple conceptual models are possible given the existing information.
Sandia National Laboratories, as a participant in the Yucca Mountain Project, administered by the Nevada Operations Office of the US Department of Energy, is in the process of evaluating a proposed site for geologic disposal of high-level nuclear wastes in the volcanic tuffs at Yucca Mountain, Nevada. In a repository, loads will be imposed on the rock mass as a result of excavation of the openings and heating of the rock by the nuclear waste. In an attempt to gain a better understanding of the thermal, mechanical, and thermomechanical response of fractured tuff, a series of experiments have been performed, and measurements have been taken in the welded and nonwelded tuffs at the G-Tunnel underground test facility at Rainier Mesa, Nevada. Comparisons between measured and calculated data of the G-Tunnel High-Pressure Flatjack Development Experiment are presented in this investigation. Calculated results were obtained from two dimensional finite element analysis using a recently developed compliant-joint rock-mass model. The purpose of this work was to assess the predictive capability of the model based on limited material property data for the G-Tunnel welded tuff. The results of this evaluation are discussed.
A new facility is being constructed for the Primary Standards Laboratory (PSL) at Sandia National Laboratories in Albuquerque, New Mexico. Features of the final design are at the state of the art and were developed over a number of years of study and design effort. Based on experience and evaluation of anticipated needs, a philosophy was established for the design and followed through the effort. A temperature control limit of {plus minus}0.01{degrees}C is required for some of the dimensional measuring spaces; isolation from vibration and electromagnetic interference (EMI) are required for all measurement spaces. The requirements for the facility and the principal design features are presented. 4 refs.
Two devices or tools are described which can be used to evaluate the ability of chip passivation or postbond coatings to protect a Si device from moisture penetration and resultant Al corrosion. The first device is a test chip with a number of Al triple track and other corrosion measurement structures. The authors present HAST data to illustrate the use of this chip in measuring failure rates and determining failure modes. The second device is a rugged, moisture sensitive, porous Si capacitor, which is compatible with high temperature passivation and postbond IC processing. Data are presented showing the stability of the device relative to that of an anodized Al moisture sensor and showing the variation of capacitance with moisture. Data are also presented showing that the capacitor can respond to a point source of water located over the porous region but remotely from the top electrode.
While the backscattered field as a function of angular incidence of a plane wave for dihedral corner reflectors having right, acute, and obtuse angles has been studied extensively, it has generally been stated that the RCS of a 90{degree} dihedral corner reflector oriented for maximum backscattered return to a radar is given by the expression {sigma} = 8{pi}a{sup 2}b{sup 2}/{lambda}{sup 2}. The intent of this paper is to present experimental results which demonstrate that not only does the RCS of a dihedral corner reflector oriented for maximum backscattered return differ significantly from this value, but that high range resolution measurements of the dihedral can serve to identify the dominant contributors to the backscattered field. Further, inclusion of these backscattered components in an analytical calculation will allow an accurate calibration model to be generated. 6 refs., 8 figs.
Computer-aided molecular design (CAMD) has been used to define the structural conformations and intramolecular interactions of bituminous coal models. Molecular dynamics studies have produced representative minimum energy conformations for several published molecular models. These studies show the importance of van der Waals (vdW) and hydrogen-bonding interactions as cohesive forces responsible for the three-dimensional (folded) structures of the coal methods. Calculations on pairs of small ring compounds representative of those found in coal clusters demonstrate that aromatics exhibit stronger vdW interactions compared with saturated ring compounds. Correlations of the vdW interactions compared with saturated ring compounds. Correlations of vdW interactions with boiling points also show differences between aromatics and saturated rings. 23 refs., 2 figs., 1 tab.
Large computational physics codes are increasing in complexity as customers demand improved physics packages and more flexible algorithms and problem specifications. It is not uncommon for a code to exceed one hundred thousand lines of FORTRAN, and some codes are much larger. This poses a considerable challenge for program management. The Computational Physics Research and Development Division at Sandia National Laboratories is aggressively pursuing C++ as the language of choice for new coding efforts. We feel that we cannot meet the stringent customer requirements and delivery schedules we now face with either FORTRAN77 or Fortran-90. 8 refs., 3 tabs.
Cleaning, plating, and painting are chemically intensive processes that involve toxic and potentially carcinogenic materials that pose a significant threat to the environment. EPA/OSHA, the Clean Air Act, and the Montreal Protocol are forcing development of environmentally sound materials and processes. A review is given of the materials and processes that are under investigation that will minimize the environmental impact of these operations. 7 refs.
The Recirculating Linear Accelerator (RLA) is returning to operation with a new relativistic electron beam (REB) injector and a modified accelerating cavity. Upon completion of our pulsed-power test program, we will capture the injected beam on an Ion Focussed Regime (IFR) guiding channel in either a spiral or a closed racetrack drift tube. The relativistic beam will recirculate for four passes through two accelerating cavities, in phase with the ringing cavity voltage, and increase to 8--12 MeV before being extracted. We designed the METGLAS ribbon-wound core, inductively isolated, four-stage injector to produce beam parameters of 4 MeV. 10--20 kA, and 40--55 ns FWHM. The three-line radial cavity is being modified to improve the 1-MV accelerating pulse shape while an advanced cavity design study is in progress. This is a continuation of the Sandia National Laboratory program to develop compact, high-voltage gradient, linear induction accelerators. The RLA concept is based on guiding an injected REB with an IFR channel. This channel is formed from a plasma created with a low energy electron beam inside a beam line containing about 2 {times} 10{sup {minus}4} Torr of argon. The REB is injected onto the IFR channel and is transported down the beamline through a water dielectric accelerating cavity based on the ET-2 design. If the round-tip path of the beam matches the period of the cavity, the REB can be further accelerated by the ringing waveform on every subsequent pass. We have installed the new REB injector because we need a higher amplitude, longer duration., flat-topped pulse shape with a colder beam than that produced by the previous injector. We made extensive use of computer simulations in the form of network solver and electrostatic field stress analysis codes to aid in the design and modifications for the new RLA. The pulsed-power performance of the RLA injector and cavity and the associated driving hardware are discussed.
A major center with emphasis on validation of nondestructive inspection techniques for aging aircraft, the Aging Aircraft NDI Development and Demonstration Center (AANC), has been funded by the FAA at Sandia National Laboratories. The Center has been assigned specific tasks in developing techniques for the nondestructive inspection of static engine parts, assessing inspection reliability (POD experiments), developing test beds for nondestructive inspection validation, maintaining a FAA library of characterized aircraft structural test specimens, and leasing a hangar to house a high flight cycle transport aircraft for use as a full scale test bed. 3 refs.
This paper describes procedure used to produce a test-validated finite element model of a three-stage solid propellant booster system. A series of system-level modal tests were performed for several inert and live propellant configurations. Test-analysis models (TAMs) were used to provide pretest support of the live propellant system tests. Confidence in the model was established by a test-analysis correlation procedure. Optimization techniques were used to determine appropriate model updates. 11 refs., 8 figs., 3 tabs.
Soldering is often referred to as a mature technology whose fundamentals were established long ago. Yet a multitude of soldering problems persist, not the least of which are related to the wetting and spreading of solder. The Buff-Goodrich approach to thermodynamics of capillarity is utilized in a review of basic wetting principles. These thermodynamics allow a very compact formulation of capillary phenomena which is used to calculate various meniscus shapes and wetting forces. These shapes and forces lend themselves to experimental techniques, such as the sessile drop and the Wilhelmy plate, for measuring useful surface and interfacial energies. The familiar equations of Young, Wilhelmy, and Neumann are all derived with this approach. The force-energy duality of surface energy is discussed and the force method is developed and used to derive the Herring relations for anisotropic surfaces. The importance of contact angle hysteresis which results from surface roughness and chemical inhomogeneity is presented and Young's equation is modified to reflect these ever present effects. Finally, an analysis of wetting with simultaneous metallurigical reaction is given and used to discuss solder wetting phenomena. 60 refs., 13 figs.
Titanium dioxide (TiO{sub 2}) is a known photocatalyst for solar detoxification of water containing organic contaminants including PCB's and dioxins. Unfortunately, the UV light used by the photocatalyst only comprises about 4% of the strong spectrum. Metalloporphyrins strongly absorb in the visible and near infrared region. Using visible light, we have investigated Ni(II) uroporphyrin (NiUroP), Sn(IV)Cl{sub 2} uroporphyrin (SnUroP) and Sn(IV)Cl{sub 2} tetrakis(p-carboxyphenyl) porphyrin (SnTCPP) as possible enhancers of destruction of a model organic compound, salicylic acid (SA), by means of photosensitization of colloidal TiO{sub 2} particles. All three porphyrins are found to adsorb reversibly onto the colloidal TiO{sub 2} upon variation of pH. Adsorption of porphyrins results in the increased colloidal stability of fine TiO{sub 2} particles in the pH range 5--8. While NiUroP on TiO{sub 2} does not show any enhancement of photodestruction, the adsorption of SnUroP increases the destruction rate compared to that of the bare TiO{sub 2} surface. The effect of ambient oxygen on the observed photolability of the Sn porphyrins and enhancement of photodestruction of SA was also investigated. SnTCPP does not photodecompose upon illumination either in the presence or absence of TiO{sub 2}, but neither does it bind to the photocatalyst at pH 6. At pH 4.5 it adsorbs onto TiO{sub 2} but it also photodecompose at this pH. We are attempting to stabilize the adsorbed porphyrins by adding suitable peripheral substituents onto the porphyrin macrocycle. 27 refs., 6 figs.
The frequency response of the Faraday rotation in fiber current sensors is computed and measured for sensor coils of noncircular cross section and with displaced coil and conductor axes. Resonances are observed at higher frequencies with magnitudes approaching that of the low frequency response. Narrowband current sensors at frequencies above 100 MHz are reported. 7 refs., 4 figs.
We have designed and tested a system for applying a ramped vertical magnetic field for turning the electron beam in the IFR Recirculating Linear Accelerator. The field is highly uniform over two Gaussian beam radii, and can be adjusted for a large radial gradient for increased energy bandwidth. The system includes shielding of the current-carrying rods to protect the pulser from REB induced fields and to reduce the effect of REB images on the beam transport to negligible levels. The system has been tested on the IBEX accelerator with > 95% peak current transport and > 90% charge transport through a 90{degree} turn. 2 refs., 6 figs.
The cleaning efficiency of five alternative solvents for chlorofluorocarbons (CFCs) and chlorohydrocarbons (CHCs) used in the manufacture of certain electronic components was studied. These solvents were evaluated in the first phase of a two-phase program to remove various manufacturing contaminants such as oils, greases, mold release, and body oils. Results have shown that EXXATE 1000 and EC-7 were able to effectively remove these contaminants from copper board substrates. 4 refs., 5 figs., 1 tab.
Eight Gulf Coast salt domes have emerged as candidate sites for possible expansion of the Strategic Petroleum Reserve (SPR) to one billion barrels. Two existing SPR sites, Big Hill, TX, and Weeks Island, LA, are among the eight that are being considered. To achieve the billion barrel capacity, some 25 new leached caverns would be constructed, and would probably be established in two separate sites in Louisiana and Texas because of distribution requirements. Geotechnical factors involved in siting studies have centered first and foremost on cavern integrity and environmental acceptability, once logistical suitability is realized. Other factors have involved subsidence and flooding potential, loss of coastal marshlands, seismicity, brine injection well utility, and co-use by multiple operators. 5 refs., 11 figs., 2 tabs.
Hertel, E.S.; Chhabildas, L.C.; Yarrington, L.; Hill, S.A.
A series of numerical simulations has been performed using the multi-dimensional hydrodynamics code CTH to computationally determine a ballistic limit for a Whipple bumper shield. The ballistic limit is generally characterized as a critical diameter such that particle diameters greater than the ballistic limit will generate debris clouds that will penetrate the rear wall and particle diameters less than the ballistic limit will not. The particular shield design used for these analyses is defined as a 1.27 mm bumper, a 102 mm void space, and a 3.18 mm rear wall. Since debris shape is expected to be a contributing factor in the impact phenomena, two different shapes are considered for the numerical simulations. The particle shapes considered were flat plates of constant 1 mm thickness and varying diameters and spheres of varying diameters. The critical diameter (ballistic limit) was determined over the velocity range 4 km/s to 15 km/s for both geometries. 13 refs., 2 figs.
In response to a request from the US Government, Sandia National Laboratories has developed an instrumentation system to monitor the conditions along an underwater, rotating drive shaft. It was desired to study the structural integrity and signal acquisition capabilities of the Shaft Instrumentation System (SIS) in an environment which closely simulates the actual deployment conditions. In this manner, the SIS response to ill-defined conditions, such as flow field turbulence or temperature fluctuations, could be determined. An Underwater Spin Facility was developed in order to verify the operation of the instrumentation and telemetric data acquisition system in a combined environment of external pressure, transient axial loads and centrifugal force. The main components of the Underwater Spin Facility are a large, five foot diameter pressure vessel, a dynamically sealed shaft, a drive train assembly and a shaker table interface which is used to apply the axial loads. This paper presents a detailed description of the design of the Underwater Spin Facility. It also discusses the SIS certification test program in order to demonstrate the successful performance of the Underwater Spin Facility. 8 refs., 10 figs.
The Magma Energy Program is a speculative endeavor regarding practical utility of electrical power production from the thermal energy which reside in magma. The systematic investigation has identified an number of research areas which have application to the utilization of magma energy and to the field of geothermal energy. Eight topics were identified which involve thermal processes and which are areas for the application of the techniques of numerical simulation. These areas are: (1) two-phase flow of the working fluid in the wellbore, (2) thermodynamic cycles for the production of electrical power, (3) optimization of the entire system, (4) solidification and fracturing of the magma caused by the energy extraction process, (5) heat transfer and fluid flow within an open, direct-contact, heat-exchanger, (6) thermal convection in the overlying geothermal region, (7) thermal convection within the magma body, and (8) induced natural convection near the thermal energy extraction device. Modeling issues have been identified which will require systematic investigation in order to develop the most appropriate strategies for numerical simulation. It appears that numerical simulations will be of ever increasing importance to the study of geothermal processes as the size and complexity of the systems of interest increase. It is anticipated that, in the future, greater emphasis will be placed on the numerical simulation of large-scale, three-dimensional, transient, mixed convection in viscous flows and porous media. Increased computational capabilities, e.g.; massively parallel computers, will allow for the detailed study of specific processes in fractured media, non-Darcy effects in porous media, and non-Newtonian effects. 23 refs., 13 figs., 1 tab.
Sensitivity studies have been conducted for the gas release from the Waste Isolation Pilot Plant (WIPP) using the TOUGH2 computer code with performance measures of peak repository pressure and gas migration distance at 1000 years. The effect of formation permeabilities including impermeable halite, two-phase characteristic curves including different models and residual saturations, and other variations was studied to determine their impact on the performance of the WIPP repository. 15 refs., 7 figs., 2 tabs.
The standard operating mode produces bremsstrahlung with an endpoint energy of about 18 MeV. This paper describes a new mode with a 8.5 MeV endpoint energy and the same standard mode pulse characteristics achieved by operating only half of the accelerator at full charge with the advantage of minimal setup time. An extension of the new half-voltage mode is to use the other half of the accelerator for delivering a second pulse at a later time with the same technique. The double pulse mode is ideal for beam generation which requires a long interpulse time in the millisecond regime. The beam characteristics of the two half-voltage pulses are nearly identical with the nominal radiation pulse full width at half maximum of 21 ns and 10--90 risetime of 11 ns recorded by the same Compton diode radiation monitors on instruments triggered 30 ms apart.
A series of shock-loading experiments on a nitrocellulose-based (NC-based) gun propellant was conducted using a light-gas gun. The intent of this work was to characterize the shock sensitivity of the gun propellant. The initial objectives were to obtained Hugoniot data and to investigate the pressure threshold at which a reaction initiates. For the Hugoniot/reaction threshold experiments, 1/4-length grains of propellant were mounted on the front of projectiles and were impacted onto either polymethylmethacrylate (PMMA), fused silica or sapphire targets at velocities as high as 1.4 mm/{mu}s, the upper limit of the gun. The particle velocity data obtained from the VISAR (Velocity Interferometer System for Any Reflector) records for the propellant fit a Hugoniot curve found in the Russian literature for a double-base, NC-nitroglycerine propellant. The density initial bulk sound velocity, and empirical parameter S values for the gun propellant were 1.63 g/cm{sup 3}, 1.70 mm/{mu}s and 1.85, respectively. VISAR data were also used to obtained the ignition threshold pressures of the gun propellant. Reactions were observed at impact pressures of 2.6 GPa and above. 5 refs., 6 figs., 1 tab.
We report on the use of a deposition/etch approach to the loss of selectivity problem, using high activity fluorine chemistries in the etch step. Proof-of-concept experiments were initially performed in a hot wall system, the excellent results obtained lead us to prove out the concept in a commercially available cold wall Genus reactor. We observed that WF{sub 6} is ineffective as an etchant of W. The technique has been able to produce perfectly selective depositions 1 micron thick in both hot wall, and cold wall, systems. Sheet resistivity values and film morphology are good. 9 refs., 4 figs., 1 tab.
This paper's main result is an O(({radical}{bar m}lgm)(n lg n) + mlg n)-time algorithm for computing the kth smallest entry in each row of an m {times} n totally monotone array. (A two-dimensional A = a(i,j) is totally monotone if for all i{sub 1} < i{sub 2} and j{sub 1} < j{sup 2}, < a(i{sub 1},j{sub 2}) implies a(i{sub 2},j{sub 1})). For large values of k (in particular, for k=(n/2)), this algorithm is significantly faster than the O(k(m+n))-time algorithm for the same problem due to Kravets and Park. An immediate consequence of this result is an O(n{sup 3/2} lg{sup 2}n)-time algorithm for computing the kth nearest neighbor of each vertex of a convex n-gon. In addition to the main result, we also give an O(n lg m)-time algorithm for computing an approximate median in each row of an m {times} n totally monotone array; this approximate median is an entry whose rank in its row lies between (n/4) and (3n/4) {minus} 1. 20 refs., 3 figs.
This paper presents a practical algorithm for partitioning a program into sequential threads. A thread is a sequence of instructions, possibly including branches, which can be scheduled as an indivisible unit on a von Neumann-like processor. The partitioning algorithm is designed for a non-strict (but not lazy) language with non-strict data structures and side-effects. The primary target of the proposed compilation strategy is large-scale parallel systems which rely on multithreading at the processor level to tolerate long communication latencies. As such, the algorithm incorporates a mechanism to balance the desire to maximize thread length with the desire to expose useful high-level parallelism. Although this paper focuses on non-strict semantics in conjunction with a parallel multithreaded architecture, the partitioning analysis is equally well suited (with appropriate simplifications) to a non-strict language on a sequential machine or a strict language on a parallel multithreaded machine. Our analysis is accomplished without compromising non-strict semantics and without creating dependencies which sacrifice useful high-level parallelism. It can also exploit known dependency information. The analysis starts with a traditional dataflow graph and partitions it into a set of interrelated threads. 16 refs., 9 figs.
The Silver Bullet Skunk Works, and experimental product realization team at AT T Consumer Products, designed and shipped a new telephone answering system to market in eight months, approximately one year faster than previous AT T products of similar complexity. This paper outlines the Design for X'' (DFX) philosophies and the team structure that enabled the group to accelerate the Product Realization Process. The Answering System 1300, developed in record time, was a successful product that met its schedule and cost objectives, and sold out its entire high-volume manufacturing run. Lessons learned from the Skunk Works experience have since been applied to other development activities in AT T Consumer Products. 3 figs.
Increasingly stringent air emission standards in various states has dictated the elimination of engineering finishes which are derived from high volatile organic compound (VOC) paint chemistries. In July 1989, Allied-Signal, Inc., Kansas City Division, Kansas City, Missouri, voluntarily closed its paint facility, due to non-compliance with local air emission standards. The following details the materials selection and evaluations which led to current processing using low VOC paints, which permitted the Allied Signal, Inc., paint facility to achieve compliance and resume operations. 1 tab.
We have developed a model which utilizes a probabilistic failure criterion to describe intergranular stress corrosion cracking (IGSCC). A two-dimensional array of elements representing a section of a pipe wall is analyzed, with each element in the array representing a segment of grain boundary. The failure criterion is applied repetitively to each element of the array that is exposed to the interior of the pipe (i.e. the corrosive fluid) until that element dissolves, thereby exposing the next element. A number of environmental, mechanical, and materials factors have been incorporated into the model, including: (1) the macroscopic applied stress profile, (2) the stress history, (3) the extent and grain-to- grain distribution of carbide sensitization levels, which can be applied to a subset of elements comprising a grain boundary, and (4) a data set containing IGSCC crack growth rates as function of applied stress intensity and sensitization level averaged over a large population of grains. The latter information was obtained from the literature for AISI 304 stainless steel under light water nuclear reactor primary coolant environmental conditions. The resulting crack growth simulations are presented and discussed. 14 refs., 10 figs.
Edge finishing and deburring of parts is a tedious operation that should be automated. This paper describes the use of direct-drive XY table in the automated edge finishing of machined parts. The table is faster and more accurate than an articulated robot, thus where planar motion in a small work area is sufficient it is preferable. Hybrid force/position control is used to guide the table (with mounted workpiece) past the tool and maintain the contact force at the desired level. A six-axis force sensor on the tool spindle is used to measure contact force. We identified a dynamic model for the table from experimental measurements and used this model to design a force/position controller for the table. An example application of the table in the deburring of an actual jet engine turbine hub is presented. 5 refs., 12 figs.
This paper justifies the need for and describes studies of brine chemistry under way for German and American high- and intermediate-level radioactive waste repositories in domal and bedded salt formation. In particular, it discusses the origin and composition of fluids that could enter these repositories and some sampling, modeling, and statistical techniques used to characterize them. 24 refs., 4 figs., 5 tabs.
Historically, characterization of fluid flow and transport of soluble elements in the unsaturated, or vadose, zone has been limited. Until recently, most of the interest in transport of water-soluble pollutants has been focused on aquifer contamination, i.e. saturated conditions. Vadose zone investigations are hampered by a lack of appropriate technology for the necessary measurements; little work has been done to relate laboratory measurements to field-scale effects; and development and validation of computational models has been limited, in part through lack of data. We describe here results of a small-scale field experiment in which existing technology is used to quantify fluid movement following controlled infiltration. 6 refs., 2 figs.
Sandia National Laboratories has considerable experience with video systems used for alarm assessment. Until recently the camera of choice for lighted security applications was the monochrome vacuum tube video camera. However, with recent advancements in the solid state imager technology, the integration of tube cameras in security systems may soon become obsolete. The sensitivity and resolution of solid state imagers is approaching that of vacuum tube imagers. In addition, solid state cameras have a relatively long lifetime and require little maintenance. Initial equipment costs are similar. Due to the increased performance of solid state imagers, Sandia has established an ongoing program to evaluate these cameras. The evaluations are performed mainly to verify manufacturers' specifications for resolution, sensitivity, and signal to noise ratio, which are the critical camera parameters that should be considered when designing video systems. This report defines these parameters, describes the test procedures, and provides test results. 1 figs., 2 tabs.
Zeolite-based tritium lamps are a possible alternative to traditional tritium gas tube light sources. Rare earth luminescing centers may be ion-exchanged into zeolite matrices. Close proximity of tritium atoms to the rare earths can be provided by highly tritiated water sorbed within the pore structure of the zeolite aluminosilicate matrix. Zeolites are optically clear and radiation stable. Light outputs from tritium-loaded zeolites are shown here to exceed 2{mu}W/cm{sup 2}, with good stability. Procedures for obtaining light sources are presented and results are discussed. The possible use of these luminescent materials as process monitors for zeolite absorption columns in tritium service is also discussed. 13 refs., 3 figs.
To provide a method for addressing the uncertainty associated with conceptual models developed for performance assessment of waste management sites, probabilistic networks have been applied to the conceptual model development process. The application of probabilistic networks provides a graphical representation of the reasoning process that goes into developing conceptual models. Probability tables associated with decision points in the process provide a quantification of the uncertainty that is associated with the resulting conceptual models. To support the development of this probabilistic network, a formal process is being designed and implemented to elicit expert information about the conceptual model development process. This paper discusses the approach to designing this expert judgment elicitation process. 10 refs.
The short-transverse (S-T) stress corrosion cracking (SCC) behavior of Al-Li-CU alloy 2090 was studied using a static load SCC test technique. Time to failure was measured as a function of applied potential in several different environments. Rapid SCC failures (< 10 hours) were observed only when the following criteria were satisfied: E{sub br, T1} < E{sub applied} < E{sub br, matrix} where potentials refer to the breakaway potentials of the subgrain boundary T{sub 1} (Al{sub 2}CuLi) phase and the {alpha}-Al matrix phase. E{sub br} values were measured using potentiodynamic polarization of bulk materials intended to simulate the individual phases found in the subgrain boundary region. Results strongly suggest an anodic dissolution based SCC mechanism for this alloy where selective dissolution of T{sub 1} on the subgrain boundary is a critical step. The unusual pre-exposure embrittlement phenomenon demonstrated by Al- Li alloys is also shown to be consistent with these simple SCC criteria. 21 refs., 9 figs., 6 tabs.
One of the possible consequences of disruptions is the generation of runaway electrons which can impact plasma facing components and cause damage due to high local energy deposition. This problem becomes more serious as the machine size and plasma current increases. Since large size and high currents are characteristics of proposed future machines, control of runaway generation is an important design consideration. A lumped circuit model for disruption runaway electron generation indicates that control circuitry on strongly influence runaway behavior. A comparison of disruption data from several shots on JET and D3-D with model results, demonstrate the effects of plasma motion on runaway number density and energy. 6 refs., 12 figs.
Benchmarking a network file server introduces some unique considerations over traditional benchmarking scenarios. Since the user is executing on a client system interconnected to the file server, the client and network must be provided for during benchmarking. During a recent procurement action, Sandia National Laboratories was challenged to develop a benchmark suite that would accurately test the network requirements. This paper describes the benchmark design and summarizes the experience gained from the benchmark executions. 8 refs., 2 figs.
The electromagnetic field in a mode-stirred chamber is a random process. Samples of this random process are random variables. Different realizations of this random variable can be obtained by changing the paddle-wheel angle, changing the frequency, or changing the location at which the sample is taken. Correlation widths can be defined for each of these three variables. For examples, the spatial correlation width is the distance a point sensor must be moved to realize an uncorrelated value of the field (paddle-wheel angle and frequency held constant). Likewise, the paddle-wheel correlation width is the angle through which the paddle wheel must turn to yield an uncorrelated value (location and frequency held constant). The frequency correlation width is the frequency change required to yield an uncorrelated value (location and paddle-wheel angle held constant). These values were determined experimentally for the sandia mode-stirred chamber by sampling the field at equal increments (for each variable) and calculating an autocorrelation function. The autocorrelation function is a random process (because it is calculated from a random process) and must be averaged to determine it width. The correlation widths were found to be less than 0.1{degree} for paddle-wheel angle, 50 kHz for frequency, and half a wavelength for spatial location. 4 refs., 3 figs., 2 tabs.