With the promising new results of fast z-pinch technology developed at Sandia National Laboratories, we are investigating using z-pinch driven high-yield Inertial Confinement Fusion (ICF) as a fusion power plant energy source. These investigations have led to a novel fusion system concept based on an attempt to separate many of the difficult fusion engineering issues and a strict reliance on existing technology, or a reasonable extrapolation of existing technology, wherever possible. In this paper, we describe the main components of such a system with a focus on the fusion chamber dynamics. The concept works with all of the electrically-coupled ICF proposed fusion designs. It is proposed that a z-pinch driven ICF power system can be feasibly operated at high yields (1 to 30 GJ) with a relatively low pulse rate (0.01-0.1 Hz). To deliver the required current from the rep-rated pulse power driver to the z-pinch diode, a Recyclable Transmission Line (RTL) and the integrated target hardware are fabricated, vacuum pumped, and aligned prior to loading for each power pulse. In this z-pinch driven system, no laser or ion beams propagate in the chamber such that the portion of the chamber outside the RTL does not need to be under vacuum. Additionally, by utilizing a graded-density solid lithium or fluorine/lithium/beryllium eutectic (FLiBe) blanket between the source and the first-wall the system can breed its own fuel absorb a large majority of the fusion energy released from each capsule and shield the first-wall from a damaging neutron flux. This neutron shielding significantly reduces the neutron energy fluence at the first-wall such that radiation damage should be minimal and will not limit the first-wall lifetime. Assuming a 4 m radius, 8 m tall cylindrical chamber design with an 80 cm thick spherical FLiBe blanket, our calculations suggest that a 20 cm thick 6061-T6 Al chamber wall will reach the equivalent uranium ore radioactivity level within 100 years after a 30 year plant operation. The implication of this low radioactivity is that a z-pinch driven power plant may not require deep geologic waste storage.
This paper presents models and measurements of antenna input impedance in resonant cavities at high frequencies.The behavior of input impedance is useful in determining the transmission and reception characteristics of an antenna (as well as the transmission characteristics of certain apertures). Results are presented for both the case where the cavity is undermoded (modes with separate and discrete spectra) as well as the over moded case (modes with overlapping spectra). A modal series is constructed and analyzed to determine the impedance statistical distribution. Both electrically small as well as electrically longer resonant and wall mounted antennas are analyzed. Measurements in a large mode stirred chamber cavity are compared with calculations. Finally a method based on power arguments is given, yielding simple formulas for the impedance distribution.
We investigate a well-motivated mesh untangling objective function whose optimization automatically produces non-inverted elements when possible. Examples show the procedure is highly effective on simplicial meshes and on non-simplicial (e.g., hexahedral) meshes constructed via mapping or sweeping algorithms. The current whisker-weaving (WW) algorithm in CUBIT usually produces hexahedral meshes that are unsuitable for analyses due to inverted elements. The majority of these meshes cannot be untangled using the new objective function. The most likely source of the difficulty is poor mesh topology.
In this paper, an acetone planar laser-induced fluorescence (PLIF) technique for nonintrusive, temperature imaging is demonstrated in gas-phase (Pr = 0.72) turbulent Rayleigh-Benard convection at Rayleigh number, Ra = 1.3 x 10{sup 5}. The PLIF technique provides quantitative, spatially correlated temperature data without the flow intrusion or time lag associated with physical probes and without the significant path averaging that plagues most optical heat-transfer diagnostic tools, such as the Mach-Zehnder interferometer, thus making PLIF an attractive choice for quantitative thermal imaging in easily perturbed, complex three-dimensional flow fields. The instantaneous (20-ns integration time) thermal images presented have a spatial resolution of 176 x 176 x 500 {micro}m and a single-pulse temperature measurement precision of {+-}5.5 K, or 5.4 % of the total temperature difference. These images represent a 2-D slice through a complex, 3-D flow allowing for the thermal structure of the turbulence to be quantified. Statistics such as the horizontally averaged temperature profile, rms temperature fluctuation, two-point spatial correlations, and conditionally averaged plume structures are computed from an ensemble of 100 temperature images. The profiles of the mean temperature and rms temperature fluctuation are in good agreement with previously published data, and the results obtained from the two-point spatial correlations and conditionally averaged temperature fields show the importance of large-scale coherent structures in this turbulent flow.
Very fine-grained Ni and Cu films were formed using pulsed laser deposition onto fused silica substrates. The grain sizes in the films were characterized by electron microscopy, and the mechanical properties were determined by ultra-low load indentation, with finite-element modeling used to evaluate the properties of the layers separately from those of the substrate. Some Ni films were also examined after annealing to 350 and 450 °C to enlarge the grain sizes. These preliminary results show that the observed hardnesses are consistent with a simple extension of the Hall-Petch relationship to grain sizes as small as 11 nm for Ni and 32 nm for Cu.
We present the application of a new knowledge visualization tool, VxInsight, to the mapping and analysis of patent databases. Patent data are mined and placed in a database, relationships between the patents are identified, primarily using the citation and classification structures, then the patents are clustered using a proprietary force-directed placement algorithm. Related patents cluster together to produce a 3-D landscape view of the tens of thousands of patents. The user can navigate the landscape by zooming into or out of regions of interest. Querying the underlying database places a colored marker on each patent matching the query. Automatically generated labels, showing landscape content, update continually upon zooming. Optionally, citation links between patents may be shown on the landscape. The combination of these features enables powerful analyses of patent databases.
We use atom-tracking scanning tunneling microscopy to study the diffusion of Pd in the Pd/Cu(001) surface alloy. By following the motion of individual Pd atoms incorporated in the surface, we show that Pd diffuses by a vacancy-exchange, mechanism. We measure an effective activation energy for the diffusion of incorporated Pd atoms of 0.88 eV, which is consistent with an ab initio calculated barrier of 0.94 eV.
Between 1965 and 1979 there were five documented and one or more inferred attempts to stimulate the production from hydrocarbon reservoirs by detonating nuclear devices in reservoir strata. Of the five documented tests, three were carried out by the US in low-permeability, natural-gas bearing, sandstone-shale formations, and two were done in the USSR within oil-bearing carbonates. The objectives of the US stimulation efforts were to increase porosity and permeability in a reservoir around a specific well by creating a chimney of rock rubble with fractures extending beyond it, and to connect superimposed reservoir layers. In the USSR, the intent was to extensively fracture an existing reservoir in the more general vicinity of producing wells, again increasing overall permeability and porosity. In both countries, the ultimate goals were to increase production rates and ultimate recovery from the reservoirs. Subsurface explosive devices ranging from 2.3 to about 100 kilotons were used at depths ranging from 1208 m (3963 ft) to 2568 m (8427 ft). Post-shot problems were encountered, including smaller-than-calculated fracture zones, formation damage, radioactivity of the product, and dilution of the BTU value of tie natural gas with inflammable gases created by the explosion. Reports also suggest that production-enhancement factors from these tests fell short of expectations. Ultimately, the enhanced-production benefits of the tests were insufficient to support continuation of the pro-grams within increasingly adversarial political, economic, and social climates, and attempts to stimulate hydrocarbon reservoirs with nuclear devices have been terminated in both countries.
Shock excitations are normally random process realizations, and most of our efforts to represent them either directly or indirectly reflect this fact. The most common indirect representation of shock sources is the shock response spectrum. It seeks to establish the damage-causing potential of random shocks in terms of responses excited in linear, single-degree-of-freedom systems. This paper shows that shock sources can be represented directly by developing the probabilistic and statistical structure that underlies the random shock source. Confidence bounds on process statistics and probabilities of specific excitation levels can be established from the model. Some numerical examples are presented.
Ion Beam Induced Luminescence (IBIL) and Ion Beam Induced Charge Collection (IBICC) have been applied in the study of the luminescence emission efficiency and investigation of the homogeneity of the luminescence emission in phosphors. The IBIL imaging was performed by using sharply focused ion beams or broad/partially-focused ion beams. The luminescence emission homogeneity in samples was examined to reveal possible distributed crystal-defects that may lead to the inhomogeneity of the luminescence emission in samples.The purpose of the study is to search for suitable luminescent thin films that have high homogeneity of luminescence emission, large IBIL efficiency under heavy ion excitation, and can be placed as a thin layer on the top of microelectronic devices to be analyzed with Ion Photon Emission Microscopy (IPEM). The emission yield was found to be low for organic materials, due to saturation of the light output dependence on the energy deposition of heavy ions. The emission yield of a typical Bicron plastic scintillator is about 70 photons/ion/micron. Inorganic materials may have higher IBIL yield under high-energy and heavy-ion excitation, but the challenging problem is the inhomogeneity of the IBIL emission. The IBIL image techniques are applied in the investigation of the homogeneity of a GaN epitaxial thin film, a zircon single crystal and a thin layer coated by Thiogallate(EuII) ceramic.
This paper investigates the questions of what statistical information about a memory request sequence is useful to have in making page replacement decisions: Our starting point is the Markov Request Model for page request sequences. Although the utility of modeling page request sequences by the Markov model has been recently put into doubt, we find that two previously suggested algorithms (Maximum Hitting Time and Dominating Distribution) which are based on the Markov model work well on the trace data used in this study. Interestingly, both of these algorithms perform equally well despite the fact that the theoretical results for these two algorithms differ dramatically. We then develop succinct characteristics of memory access patterns in an attempt to approximate the simpler of the two algorithms. Finally, we investigate how to collect these characteristics in an online manner in order to have a purely online algorithm.
The Xyce{trademark} Parallel Electronic Simulator has been written to support the simulation needs of the Sandia National Laboratories electrical designers. As such, the development has focused on providing the capability to solve extremely large circuit problems by supporting large-scale parallel computing platforms (up to thousands of processors). In addition, they are providing improved performance for numerical kernels using state-of-the-art algorithms, support for modeling circuit phenomena at a variety of abstraction levels and using object-oriented and modern coding-practices that ensure the code will be maintainable and extensible far into the future. The code is a parallel code in the most general sense of the phrase--a message passing parallel implementation--which allows it to run efficiently on the widest possible number of computing platforms. These include serial, shared-memory and distributed-memory parallel as well as heterogeneous platforms. Furthermore, careful attention has been paid to the specific nature of circuit-simulation problems to ensure that optimal parallel efficiency is achieved even as the number of processors grows.
New standards for ac current and voltage measurements, thin-film multifunction thermal converters (MJTCS), have been fabricated using thin-film and micro-electro-mechanical systems (MEMS) technology. Improved sensitivity and accuracy over single-junction thermoelements and targeted performance will allow new measurement approaches in traditionally troublesome areas such as the low frequency and high current regimes. A review is presented of new microfabrication techniques and packaging methods that have resulted from a collaborative effort at Sandia National Laboratories and the National Institute of Standards and Technology (MHZ).
We investigated the late-time (asymptotic) behavior of tracer test breakthrough curves (BTCs) with rate-limited mass transfer (e.g., in dual-porosity or multiporosity systems) and found that the late-time concentration c is given by the simple expression c = tad{c0g - [m0(∂g/∂t)]}, for t ≫ tad and tα ≫ tad, where tad is the advection time, c0 is the initial concentration in the medium, m0 is the zeroth moment of the injection pulse, and tα is the mean residence time in the immobile domain (i.e., the characteristic mass transfer time). The function g is proportional to the residence time distribution in the immobile domain; we tabulate g for many geometries, including several distributed (multirate) models of mass transfer. Using this expression, we examine the behavior of late-time concentration for a number of mass transfer models. One key result is that if rate-limited mass transfer causes the BTC to behave as a power law at late time (i.e., c ̃ t-k), then the underlying density function of rate coefficients must also be a power law with the form αk-3 as α → 0. This is true for both density functions of first-order and diffusion rate coefficients. BTCs with k < 3 persisting to the end of the experiment indicate a mean residence time longer than the experiment, and possibly an infinite residence time, and also suggest an effective rate coefficient that is either undefined or changes as a function of observation time. We apply our analysis to breakthrough curves from single-well injection-withdrawal tests at the Waste Isolation Pilot Plant, New Mexico. We investigated the late-time (asymptotic) behavior of tracer test breakthrough curves (BTCs) with rate-limited mass transfer (e.g., in dual-porosity or multiporosity systems) and found that the late-time concentration c is given by the simple expression c = tad{c0g - [m0(∂g/∂t)]}, for t ≫ tad and tα ≫ t ad, where tad is the advection time, c0 is the initial concentration in the medium, m0 is the zeroth moment of the injection pulse, and tα is the mean residence time in the immobile domain (i.e., the characteristic mass transfer time). The function g is proportional to the residence time distribution in the immobile domain; we tabulate g for many geometries, including several distributed (multirate) models of mass transfer. Using this expression, we examine the behavior of late-time concentration for a number of mass transfer models. One key result is that if rate-limited mass transfer causes the BTC to behave as a power law at late time (i.e., c t-k), then the underlying density function of rate coefficients must also be a power law with the form αk-3 as α → 0. This is true for both density functions of first-order and diffusion rate coefficients. BTCs with k < 3 persisting to the end of the experiment indicate a mean residence time longer than the experiment, and possibly an infinite residence time, and also suggest an effective rate coefficient that is either undefined or changes as a function of observation time. We apply our analysis to breakthrough curves from single-well injection-withdrawal tests at the Waste Isolation Pilot Plant, New Mexico.
Interferometric synthetic aperture radar (IFSAR) extends the two-dimensional imaging capability of traditional synthetic aperture radar to three-dimensions by using an aperture in the elevation plane to estimate the 3-D structure of the target. The operation of this additional aperture can be viewed from a null-steering point of view rather than the traditional phase determination point of view. Knowing that IFSAR can be viewed from the null-steering perspective allows us to take advantage of the mathematical foundation developed for null-steering arrays. In addition, in some problems of interest in IFSAR the null-steering perspective provides better intuition and suggests alternative solutions. One example is the problem of estimating building height where layover is present.
Low residual stress silicon oxynitride thin films are investigated for use as a replacement for silicon dioxide (SiO2) as sacrificial layer in surface micromachined microelectrical-mechanical systems (MEMS). It is observed that the level of residual stress in oxynitrides is a function of the nitrogen content in the film. MEMS film stacks are prepared using both SiO2 and oxynitride sacrificial layers. Wafer bow measurements indicate that wafers processed with oxynitride release layers are significantly flatter. Polycrystalline Si (poly-Si) cantilevers fabricated under the same conditions are observed to be flatter when processed with oxynitride rather than SiO2 sacrificial layers. These results are attributed to the lower post-processing residual stress of oxynitride compared to SiO2.
Two major problems associated with Si-based MEMS (MicroElectroMechanical Systems) devices are stiction and wear. Surface modifications are needed to reduce both adhesion and friction in micromechanical structures to solve these problems. In this paper, we will present a CVD (Chemical Vapor Deposition) process that selectively coats MEMS devices with tungsten and significantly enhances device durability. Tungsten CVD is used in the integrated-circuit industry, which makes this approach manufacturable. This selective deposition process results in a very conformal coating and can potentially address both stiction and wear problems confronting MEMS processing. The selective deposition of tungsten is accomplished through the silicon reduction of WF6. The self-limiting nature of this selective. We deposition process ensures the consistency necessary for process control. The tungsten is deposited after the removal of the sacrificial oxides to minimize stress and process integration problems. Tungsten coating adheres well and is hard and conducting, requirements for device performance. Furthermore, since the deposited tungsten infiltrates under adhered silicon parts and the volume of W deposited is less than the amount of Si consumed, it appears to be possible to release stuck parts that are contacted over small areas such as dimples. The wear resistance of selectively coated W parts has been shown to be significantly improved on microengine test structures.
A new type of surface micromachined ratcheting actuation system has been developed at the Microelectronics Development Laboratory at Sandia National Laboratories. The actuator uses a torsional electrostatic comb drive that is coupled to an external ring gear through a ratcheting scheme. The actuator can be operated with a single square wave, has minimal rubbing surfaces, maximizes comb finger density, and can be used for open-loop position control. The prototypes function as intended with a minimum demonstrated operating voltage of 18V. The equations of motion are developed for the torsional electrostatic comb drive. The resonant frequency, voltage vs. displacement and force delivery characteristics are predicted and compared with the fabricated device's performance.
An increasing number of applications are requiring fiber transmission of high-intensity laser pulses. Our particular interests have led us to examine carefully the fiber transmission of Q-switched pulses from multimode Nd:YAG lasers at their fundamental wavelength. The maximum pulse energy that can be transmitted through a particular fiber is limited by the onset of laser-induced breakdown and damage mechanisms. Laser breakdown at the fiber entrance face is often the first limiting process to be encountered, but other mechanisms can result in catastrophic damage at either fiber face, within the initial `entry' segment of the fiber, and at other internal sites along the fiber path. In the course of our studies we have examined a number of factors that govern the relative importance of different mechanisms, including laser characteristics, the design and alignment of injection optics, fiber end-face preparation, and fiber routing. The present study emphasizes the important criteria for injection optics in high-intensity fiber transmission, and illustrates the opportunities that now exist for innovative designs of optics to meet these criteria. Our consideration of diffractive optics to achieve desired injection criteria began in 1993, and we have evaluated a progression of designs since that time. In the present study, two recent designs for injection optics are compared by testing a sufficient number of fibers with each design to establish statistics for the onset of laser-induced breakdown and damage. In this testing we attempted to hold constant other factors that can influence damage statistics. Both designs performed well, although one was less successful in meeting all injection criteria and consequently showed a susceptibility to a particular damage process.
A transient, multidimensional model has been developed to simulate proton exchange membrane fuel cells. The model accounts simultaneously for electrochemical kinetics, current distribution, hydrodynamics, and multicomponent transport. A single set of conservation equations valid for flow channels, gas-diffusion electrodes, catalyst layers, and the membrane region are developed and numerically solved using a finite-volume-based computational fluid dynamics technique. The numerical model is validated against published experimental data with good agreement. Subsequently, the model is applied to explore hydrogen dilution effects in the anode feed. The predicted polarization curves under hydrogen dilution conditions are in qualitative agreement with recent experiments reported in the literature. The detailed two-dimensional electrochemical and flow/transport simulations further reveal that in the presence of hydrogen dilution in the fuel stream, hydrogen is depleted at the reaction surface, resulting in substantial anode mass transport polarization and hence a lower current density that is limited by hydrogen transport from the fuel stream to the reaction site. Finally, a transient simulation of the cell current density response to a step change in cell voltage is reported.
Correctly identifying the possible alteration products and accurately predicting their occurrence in a repository-relevant environment are the key for source-term calculations in a repository performance assessment. Uraninite in uranium deposits has long been used as a natural analog to spent fuel in a repository because of their chemical and structural similarity. In this paper, a SEM/AEM investigation has been conducted on a partially alterated uraninite sample from a uranium ore deposit of Shinkolobwe of Congo. The mineral formation sequences were identified: uraninite→uranyl hydrates→uranyl silicates→Ca-uranyl silicates or uraninite→uranyl silicates→Ca-uranyl silicates. Reaction-path calculations were conducted for the oxidative dissolution of spent fuel in a representative Yucca Mountain groundwater. The predicted sequence is in general consistent with the SEM observations. The calculations also show that uranium carbonate minerals are unlikely to become major solubility-controlling mineral phases in a Yucca Mountain environment. Some discrepancies between model predictions and field observations are observed. Those discrepancies may result from poorly constrained thermodynamic data for uranyl silicate minerals.
Crystalline phases of pyrochlore (e.g., CaPuTi2O7, CaUTi2O7) have been proposed as a durable ceramic waste form for disposal of high level radioactive wastes including surplus weapons-usable plutonium. In this paper, we use a linear free energy relationship to predict the Gibbs free energies of formation of pyrochlore phases (CaMTi2O7). The Pu-pyrochlore phase is predicted to be stable with respect to PuO2, CaTiO3, and TiO2 at room temperatures. Pu-pyrochlore is expected to be stable in a geologic repository where silica and carbonate components are absent or limited. We suggest that a repository in a salt formation be an ideal environment for disposal of high level, pyrochlore-based ceramic wastes. In such environment, adding CaO as a backfill will make pyrochlore minerals thermodynamically stable and therefore effectively prevents actinide release from these mineral phases.
Interfaces play an important role in determining the effect of electric fields on the mechanism of the formation of spinel by solid-state reaction. The reaction occurs by the movement of phase boundaries but the rate of this movement can be affected by grain boundaries in the reactants or in the reaction product. Only by understanding these relationships will it be possible to engineer their behavior. As a particular example of such a study, MgIn2O4 can be formed by the reaction between single-crystal MgO substrate and a thin film of In2O3 with or without an applied electric field. High-resolution backscattered electron (BSE) imaging and electron backscattered diffraction (EBSD) in a scanning electron microscope (SEM) has been used to obtain complementary chemical and crystallographic information.
A new class of semiconductor lasers that can potentially produce much more short pulse energy is presented. This new laser is not limited in volume or aspect ratio by the depth of a p-n junction and are created from current filaments in semi-insulating GaAs. A current filament semiconductor lasers (CFSL) that have produced 75 nJ of 890 nm radiation in 1.5 ns were tested. A filaments as long as 3.4 cm and several hundred microns in diameter in high gain GaAs photoconductive switches were observed. Their smallest dimension can be more than 100 times the carrier diffusion length in GaAs. The spectral narrowing, lasing thresholds, beam divergence, temporal narrowing and energies which imply lasing for several configurations of CFSL are reported.
Failure analysis (FA) tools have been applied to analyze tungsten coated polysilicon microengines. These devices were stressed under accelerated conditions at ambient temperatures and pressure. Preliminary results illustrating the failure modes of microengines operated under variable humidity and ultra-high drive frequency will also be shown. Analysis of tungsten coated microengines revealed the absence of wear debris in microengines operated under ambient conditions. Plan view imaging of these microengines using scanning electron microscopy (SEM) revealed no accumulation of wear debris on the surface of the gears or ground plane on microengines operated under standard laboratory conditions. Friction bearing surfaces were exposed and analyzed using the focused ion beam (FIB). These cross sections revealed no accumulation of debris along friction bearing surfaces. By using transmission electron microscopy (TEM) in conjunction with electron energy loss spectroscopy (EELS), we were able to identify the thickness, elemental analysis, and crystallographic properties of tungsten coated MEMS devices. Atomic force microscopy was also utilized to analyze the surface roughness of friction bearing surfaces.
One method of providing the mode selectivity necessary to insure single mode operation in a large diameter VCSEL is to independently control the size of the gain region and that of the optical mode. Numerical simulations quantity this approach by predicting lateral mode discrimination for different sized gain apertures. Calculations are experimentally confirmed by the fabrication and testing of 850 nm VCSELs employing hybrid ion implantation/selective oxidation that produce a single-mode output of more than 5 mW.
In this paper we concern ourselves with modified versions of the traditional brachistochrone and tautochrone problems. In the modified version of each problem the constant gravity model is replaced with an attractive inverse square law, consequently we name these the 1/r2 brachistochrone and 1/r2 tautochrone problems. With regard to the 1/r2 brachistochrone problem, we show that the shape of the minimizing curve is formally constructed from an infinite series of elliptic integrals, and we use a numerical optimal control technique to generate the trajectories. The 1/r2 tautochrone problem is solved using fractional calculus techniques and we show that the solution satisfies Lagrange's rule for tautochronous curves.
Electrostatic discharge (ESD) and electrical overstress (EOS) damage of Micro-Electro-Mechanical Systems (MEMS) has been identified as a new failure mode. This failure mode has not been previously recognized or addressed primarily due to the mechanical nature and functionality of these systems, as well as the physical failure signature that resembles stiction. Because many MEMS devices function by electrostatic actuation, the possibility of these devices not only being susceptible to ESD or EOS damage but also having a high probability of suffering catastrophic failure due to ESD or EOS is very real. Results from previous experiments have shown stationary comb fingers adhered to the ground plane on MEMS devices tested in shock, vibration, and benign environments. Using Sandia polysilicon microengines, we have conducted tests to establish and explain the ESD/EOS failure mechanism of MEMS devices. These devices were electronically and optically inspected prior to and after ESD and EOS testing. This paper will address the issues surrounding MEMS susceptibility to ESD and EOS damage as well as describe the experimental method and results found from ESD and EOS testing. The tests were conducted using conventional IC failure analysis and reliability assessment characterization tools. In this paper we will also present a thermal model to accurately depict the heat exchange between an electrostatic comb finger and the ground plane during an ESD event.
Thermally-Induced Voltage Alteration (TIVA) is a relatively new technique for locating electrical defects in integrated circuits [1,2]. This paper describes a novel application of TIVA, to locate design anomalies. A newly designed integrated circuit with high and inconsistent Quiescent Power Supply Current (IDDQ) was initially diagnosed with limited success using various failsite isolation techniques. The TIVA technique was successful in accurately locating design anomalies. Results from TIVA identified a spurious ring oscillator in the design. Design modifications carried out using a focussed ion beam (FIB), verified the accuracy of the results from TIVA. This study clearly extends the use of TIVA beyond that of locating electrical defects and anomalies into the realm of design debugging.
LM111 voltage comparators exhibit a wide range of total-dose-induced degradation. Simulations show this variability may be a natural consequence of the low base doping of the substrate PNP (SPNP) input transistors. Low base doping increases the SPNPs collector to base breakdown voltage, current gain, and densities. The build-up of oxide trapped charge (N OT) and interface traps (N IT) is shown to be a function of pre-irradiation bakes. Experimental data indicate that, despite its structural similarities to the LM111, irradiated input transistors of the LM124 operational amplifier do not exhibit the same sensitivity to variations in pre-irradiation thermal cycles. Further disparities in LM111 and LM124 responses may result from a difference in the oxide defect build-up in the two part types. Variations in processing, packaging, and circuit effects are suggested as potential explanations.
A record high fundamental-mode power of 5.1 mW was achieved from coupled-resonator vertical-cavity lasers (CRVCLs). In conventional VCSELs, the extent to which the gain volume may be increased is limited by the onset of multi-mode operation. Results indicate that this limitation is circumvented in a coupled-resonator device allowing high power fundamental-mode operation.
Critical infrastructures are central to our national defense and our economic well being, but many are taken for granted. Presidential Decision Directive (PDD) 63 highlights the importance of eight of our critical infrastructures and outlines a plan for action. Greatly enhanced physical security systems will be required to protect these national assets from new and emerging threats. Sandia National Laboratories has been the lead laboratory for the Department of Energy (DOE) in developing and deploying physical security systems for the past twenty-five years. Many of the tools, processes, and systems employed in the protection of high-consequence facilities can be adapted to the civilian infrastructure.
Over the past several years, extensive databases have been developed for the S-N behavior of various mate&& used in wind turbine blades, primarily fiberglass composites. These data are typically presented both in their "raw" form and curve fit to define their average properties. For design, confidence limits must be placed on these descriptions. In particular, most designs call for the "95195" design values; namely, with a 95 percent level of confidence, thedesiguerisassuredthat95percentofthematerial will 'meet or exceed the design value. For such material properties as the ultimate streng& the procedures for estimating its value at a particular confidence level is wellffiedifthemeasured values follow a normal or a log-normal distribution. Namely, based upon the number of sample points and their standard deviation, a commonly-found table may be used to determine the survival percentagea t a particular confidencel evel with respect to its mean value. The same is true for fatigue data at a constaut stress level (the number of cycles to failure N at stress level SI). However, when the stress level is allowed to vary, as with a typical S-N fatigue curve, the proceduresf or determmingc onfidencel imits are not as well delked. This paper outlines techn.iques for determimng confklence limits of fatigue data Different approachesto estimating the 95195l evel are compared. Data from the MSUIDOE and the FACT fatigue databam are used to illustrate typical results.
A MEMS test structure capable of measuring friction between polysilicon surfaces under a variety of test conditions has been refined from previous designs. The device is applied here to measuring friction coefficients of polysilicon surfaces under different environmental, loading, and surface conditions. Two methods for qualitatively comparing friction coefficients (μ) using the device are presented. Samples that have been coated with a self-assembled monolayer of the lubricating film perfluorinated-decyltrichlorosilane (PFTS) have a coefficient of friction that is approximately one-half that of samples dried using super-critical CO2 (SCCO2) drying. Qualitative results indicate that μ is independent of normal pressure. Wear is shown to increase μ for both supercritically dried samples and PFTS coated samples, though the mechanisms appear to be different. Super critically dried surfaces appear to degrade continuously with increased wear cycles, while PFTS coated samples reach a steady state friction value after about 105 cycles.
In 1993, the Government Performance and Results Act (GPRA, PL 103-62) was enacted. GPRA, which applies to all federal programs, has three components: strategic plans, annual performance plans, and metrics to show how well annual plans are being followed. As part of meeting the GRPA requirement in FY2000, a 14-member external peer review panel (the Garwin Committee) was convened on May 17-19, 2000 to review Sandia National Laboratories' Pulsed Power Programs as a component of the Performance Appraisal Process negotiated with the Department of Energy (DOE). The scope of the review included activities in inertial confinement fission (ICF), weapon physics, development of radiation sources for weapons effects simulation, x-ray radiography, basic research in high energy density physics (HEDP), and pulsed power technology research and development. In his charge to the committee, Jeffrey Quintenz, Director of Pulsed Power Sciences (1600) asked that the review be based on four criteria (1) quality of science, technology, and engineering, (2) programmatic performance, management, and planning, (3) relevance to national needs and agency missions, and (4) performance in the operation and construction of major research facilities. In addition, specific programmatic questions were posed by the director and by the DOE-Defense Programs (DP). The accompanying report, produced as a SAND document, is the report of the committee's findings.
This paper identifies active research topics concerning human machine interfaces for intelligent machine systems. The paper was compiled by performing a series of literature searches and organizing the information according to the author's interest in better directing his own Human Machine Interface (HMI) research. Introductory literature from outside the HMI communities is also referenced to provide context.
This report summarizes the results of work conducted by the Semiconductor Manufacturing Technologies Program at Sandia National Laboratories (Sandia) during 1999. This work was performed by one working group: the Semiconductor Equipment Technology Center (SETEC). The group's projects included Numerical/Experimental Characterization of the Growth of Single-Crystal Calcium Fluoride (CaF{sub 2}); The Use of High-Resolution Transmission Electron Microscopy (HRTEM) Imaging for Certifying Critical-Dimension Reference Materials Fabricated with Silicon Micromachining; Assembly Test Chip for Flip Chip on Board; Plasma Mechanism Validation: Modeling and Experimentation; and Model-Based Reduction of Contamination in Gate-Quality Nitride Reactor. During 1999, all projects focused on meeting customer needs in a timely manner and ensuring that projects were aligned with the goals of the National Technology Roadmap for Semiconductors sponsored by the Semiconductor Industry Association and with Sandia's defense mission. This report also provides a short history of the Sandia/SEMATECH relationship and a brief on all projects completed during the seven years of the program.
This report describes the features of Aspen-EE (Electricity Enhancement), a new model for simulating the interdependent effects of market decisions and disruptions in the electric power system on other critical infrastructures in the US economy. Aspen-EE extends and modifies the capabilities of Aspen, an agent-based model previously developed by Sandia National Laboratories. Aspen-EE was tested on a series of scenarios in which the rules governing electric power trades were changed. Analysis of the scenario results indicates that the power generation company agents will adjust the quantity of power bid into each market as a function of the market rules. Results indicate that when two power markets are faced with identical economic circumstances, the traditionally higher-priced market sees its market clearing price decline, while the traditionally lower-priced market sees a relative increase in market clearing price. These results indicate that Aspen-EE is predicting power market trends that are consistent with expected economic behavior.
This report discusses an automatic target recognition (ATR) algorithm for synthetic aperture radar (SAR) imagery that is based on coherent change detection techniques. The algorithm relies on templates created from training data to identify targets. Objects are identified or rejected as targets by comparing their SAR signatures with templates using the same complex correlation scheme developed for coherent change detection. Preliminary results are presented in addition to future recommendations.
Current approaches to reliability are not adequate to keep pace with the need for faster, better and cheaper products and systems. This is especially true in high consequence of failure applications. The original proposal for the LDRD was to look at this challenge and see if there was a new paradigm that could make reliability predictions, along with a quantitative estimate of the risk in that prediction, in a way that was faster, better and cheaper. Such an approach would be based on the underlying science models that are the backbone of reliability predictions. The new paradigm would be implemented in two software tools: the Virtual Reliability Realization System (VRRS) and the Reliability Expert System (REX). The three-year LDRD was funded at a reduced level for the first year ($120K vs. $250K) and not renewed. Because of the reduced funding, we concentrated on the initial development of the expertise system. We developed an interactive semiconductor calculation tool needed for reliability analyses. We also were able to generate a basic functional system using Microsoft Siteserver Commerce Edition and Microsoft Sequel Server. The base system has the capability to store Office documents from multiple authors, and has the ability to track and charge for usage. The full outline of the knowledge model has been incorporated as well as examples of various types of content.
>This report describes the innovative modeling approach developed as a result of a 3-year Laboratory Directed Research and Development project. The overall goal of this project was to provide an effective suite of solvers for advanced production planning at facilities in the nuclear weapons complex (NWC). We focused our development activities on problems related to operations at the DOE's Pantex Plant. These types of scheduling problems appear in many contexts other than Pantex--both within the NWC (e.g., Neutron Generators) and in other commercial manufacturing settings. We successfully developed an innovative and effective solution strategy for these types of problems. We have tested this approach on actual data from Pantex, and from Org. 14000 (Neutron Generator production). This report focuses on the mathematical representation of the modeling approach and presents three representative studies using Pantex data. Results associated with the Neutron Generator facility will be published in a subsequent SAND report. The approach to task-based scheduling described here represents a significant addition to the literature for large-scale, realistic scheduling problems in a variety of production settings.
This report describes the design of PICO, a C++ framework for implementing general parallel branch-and-bound algorithms. The PICO framework provides a mechanism for the efficient implementation of a wide range of branch-and-bound methods on an equally wide range of parallel computing platforms. We first discuss the basic architecture of PICO, including the application class hierarchy and the package's serial and parallel layers. We next describe the design of the serial layer, and its central notion of manipulating subproblem states. Then, we discuss the design of the parallel layer, which includes flexible processor clustering and communication rates, various load balancing mechanisms, and a non-preemptive task scheduler running on each processor. We describe the application of the package to a branch-and-bound method for mixed integer programming, along with computational results on the ASCI Red massively parallel computer. Finally we describe the application of the branch-and-bound mixed-integer programming code to a resource constrained project scheduling problem for Pantex.
The Air Force's Electronic Systems Center has funded Sandia National Laboratories to develop an Automatic Target Recognition (ATR) System for the Air Force's Joint STARS platform using Mercury Computer systems hardware. This report provides general theory on the internal operations of the Real-Time ATR system and provides some basic techniques that can be used to reconfigure the system and monitor its runtime operation. In addition, general information on how to interface an image formation processor and a human machine interface to the ATR is provided. This report is not meant to be a tutorial on the ATR algorithms.
A pointing control system is developed and tested for a flying gimbaled telescope. The two-axis pointing system is capable of sub-microradian pointing stability and high accuracy in the presence of large host vehicle jitter. The telescope also has high agility--it is capable of a 50-degree retarget (in both axes simultaneously) in less than 2 seconds. To achieve the design specifications, high-accuracy, high-resolution, two-speed resolvers were used, resulting in gimbal-angle measurements stable to 1.5 microradians. In addition, on-axis inertial angle displacement sensors were mounted on the telescope to provide host-vehicle jitter cancellation. The inertial angle sensors are accurate to about 100 nanoradians, but do not measure low frequency displacements below 2 Hz. The gimbal command signal includes host-vehicle attitude information, which is band-limited. This provides jitter data below 20 Hz, but includes a variable latency between 15 and 25 milliseconds. One of the most challenging aspects of this design was to combine the inertial-angle-sensor data with the less perfect information in the command signal to achieve maximum jitter reduction. The optimum blending of these two signals, along with the feedback compensation were designed using Quantitative Feedback Theory.
The purpose of this research was to develop a science-based understanding of the early-time behavior of electric surface arcing in air at atmospheric pressure. As a first step towards accomplishing this, we used a kinetic approach to model an electron swarm as it evolved in a neutral gas under the influence of an applied electric field. A computer code was written in which pseudo-particles, each representing some number of electrons, were accelerated by an electric field. The electric field due to the charged particles was calculated efficiently using a tree algorithm. Collision of the electrons with the background gas led to the creation of new particles through the processes of ionization and photoionization. These processes were accounted for using measured cross-section data and Monte Carlo methods. A dielectric half-space was modeled by imaging the charges in its surface. Secondary electron emission from the surface, resulting in surface charging, was also calculated. Simulation results show the characteristics of a streamer in three dimensions. A numerical instability was encountered before the streamer matured to form branching.
Prediction of the evolution of microstructures in weapons systems is critical to meeting the objectives of stockpile stewardship in accordance with the Nuclear Weapons Test Ban Treaty. For example, accurate simulation of microstructural evolution in solder joints, cermets, PZT power generators, etc. is necessary for predicting the performance, aging, and reliability both of individual components and of entire weapons systems. A recently developed but promising approach called the ''Phase-Field Model'' (PFM) has the potential of allowing the accurate quantitative prediction of microstructural evolution, with all the spatial and thermodynamic complexity of a real microstructure. Simulating with the PFM requires solving a set of coupled nonlinear differential equations, one for each material variable (e.g., grain orientation, phase, composition, stresses, anisotropy, etc.). While the PFM is versatile and is able to incorporate the necessary complexity for modeling real material systems, it is very computationally intensive, and it has been a difficult and major challenge to formulate an efficient algorithmic implementation of the approach. We found that second order in space algorithm is more stable and leads to more accurate results. However, the computational requirements still remain high, so we have developed a single field algorithm to reduce the computations by 2 orders of magnitude. We have created a 3-D parallel version of the basic phase-field (PF model) and benchmarked it performance. Preliminary results indicate that we will be able to run very large problems effectively with the new parallel code. Microstructural evolution in a diffusion couple was simulated using PFM to simultaneously simulate grain growth, diffusion and phase transformation. Solute drag in a variable composition material, a process no other model can simulate, was successfully simulated using the phase-field model. The phase field model was used to study the evolution of fractal high curvature structures to show that these structures have very different morphological and kinetic behaviors than those of equi-axed structures.
Roll-isolated inertial measurement units are developed at Sandia for use in the instrumentation, guidance, and control of rapidly spinning vehicles. Roll-isolation is accomplished by supporting the inertial instrument cluster (gyros and accelerometers) on a single gimbal, the axis of which is parallel to the vehicle's spin axis. A rotary motor on the gimbal is driven by a servo loop to null the roll gyro output, thus inertially stabilizing the gimbal and instrument cluster while the vehicle spins around it. Roll-isolation prevents saturation of the roll gyro by the high vehicle spin rate, and vastly reduces measurement errors arising from gyro scale factor and alignment uncertainties. Nine versions of Sandia-developed roll-isolated inertial measurement units have been flown on a total of 27 flight tests since 1972.
In order to provide real-time data for validation of three dimensional numerical simulations of heterogeneous materials subjected to impact loading, an optically recording velocity interferometer system (ORVIS) has been adapted to a line-imaging instrument capable of generating precise mesoscopic scale measurements of spatially resolved velocity variations during dynamic deformation. Combining independently variable target magnification and interferometer fringe spacing, this instrument can probe a velocity field along line segments up to 15 mm in length. In high magnification operation, spatial resolution better than 10 {micro}m can be achieved. For events appropriate to short recording times, streak camera recording can provide temporal resolution better than 0.2 ns. A robust method for extracting spatially resolved velocity-time profiles from streak camera image data has been developed and incorporated into a computer program that utilizes a standard VISAR analysis platform. The use of line-imaging ORVIS to obtain measurements of the mesoscopic scale dynamic response of shocked samples has been demonstrated on several different classes of heterogeneous materials. Studies have focused on pressed, granular sugar as a simulant material for the widely used explosive HMX. For low-density (65% theoretical maximum density) pressings of sugar, material response has been investigated as a function of both impact velocity and changes in particle size distribution. The experimental results provide a consistent picture of the dispersive nature of the wave transmitted through these samples and reveal both transverse and longitudinal wave structures on mesoscopic scales. This observed behavior is consistent with the highly structured mesoscopic response predicted by 3-D simulations. Preliminary line-imaging ORVIS measurements on HMX as well as other heterogeneous materials such as foam and glass-reinforced polyester are also discussed.
VxInsight provides a visual mechanism for browsing, exploring and retrieving information from a database. The graphical display conveys information about the relationship between objects in several ways and on multiple scales. In this way, individual objects are always observed within a larger context. For example, consider a database consisting of a set of scientific papers. Imagine that the papers have been organized in a two dimensional geometry so that related papers are located close to each other. Now construct a landscape where the altitude reflects the local density of papers. Papers on physics will form a mountain range, and a different range will stand over the biological papers. In between will be research reports from biophysics and other bridging disciplines. Now, imagine exploring these mountains. If we zoom in closer, the physics mountains will resolve into a set of sub-disciplines. Eventually, by zooming in far enough, the individual papers become visible. By pointing and clicking you can learn more about papers of interest or retrieve their full text. Although physical proximity conveys a great deal of information about the relationship between documents, you can also see which papers reference which others, by drawing lines between the citing and cited papers. For even more information, you can choose to highlight papers by a particular researcher or a particular institution, or show the accumulation of papers through time, watching some disciplines explode and other stagnate. VxInsight is a general purpose tool, which enables this kind of interaction with wide variety of relational data: documents, patents, web pages, and financial transactions are just a few examples. The tool allows users to interactively browse, explore and retrieve information from the database in an intuitive way.
Data mining involves the discovery and fusion of features from large databases to establish minimal probability of error (MPE) decision and estimation models. Our approach combines a weighted nearest neighbor (WNN) decision model for classification and estimation with genetic algorithms (GA) for feature discovery and model optimization. The WNN model is used to provide a mathematical framework for adaptively discovering and fusing features into near-MPE decision algorithms. The GA is used to discover weighted features and select decision points for the WNN decision model to achieve near-MPE decisions. The performance of the WNN fusion model is demonstrated on the first of two very different problems to demonstrate its robust and practical application to a wide variety of data-mining problems. The first problem involves the isolation of factors that cause hepatitis C virus (HCV) and requires the evaluation of large databases to establish the critical features that can detect with minimal error whether a person is at risk of having HCV. This requires discovering and extracting relevant information (features) from a questionnaire database and combining (fusing) them to achieve a minimal error decision rule. The primary objective of the research is to develop a practical basis for fusing information from questionnaires administered at hospitals to identify and verify features important to isolate risk factors for HCV. The basic problem involves creating a feature database from the questionnaire information, discovering features that provide sufficient information to reliably identify when a person is at risk under conditions with uncertainties caused by recording errors and evasive tactics of people answering the questionnaire. The results of this study demonstrate the WNN fusion algorithm ability to perform in supervised learning environments. The second phase of the research project is directed at the unsupervised learning environment. In this environment the feature data is presented without any classification. Clustering algorithms are developed to partition the feature data into clusters based upon similarity measure models. After the feature data is clustered and classified the supervised WNN fusion algorithms are used to classify the data based upon the minimal probability of error decision rule.
This report provides a summary of the LDRD project titled: An Electromagnetic Imaging System for Environmental Site Reconnaissance. The major initial challenge of this LDRD was to develop a ground penetrating radar (GPR) whose peak and average radiated power surpassed that of any other in existence. Goals were set to use such a system to detect the following: (1) disrupted soil layers where there is potential for buried waste, (2) buried objects such as 55-gallon drums at depths up to 3 m, and (3) detecting contaminated soil. Initial modeling of the problem suggested that for soil conditions similar to Puerto Rican clay loam, moisture content 10 percent (conductivity = 0.01 mhos at 350 MHz), a buried 55-gallon drum could be detected in a straightforward manner by an UWB GPR system at a depth of 3 meters. From the simulations, the highest attenuation ({minus}50 dB) was the result of scattering from a 3-m deep vertically orientated drum. A system loss of {minus}100 dB is a typical limit for all kinds of radar systems (either direct time-domain or swept frequency). The modeling work also determined that the waveshape of the pulse scattered off the buried drum would be relatively insensitive to drum orientation, and thus easier to detect with the GPR system.
Hydrogen atom-hydrogen atom scattering is a prototype for many of the fundamental principles of atomic collisions. In this work we present the formalism and the predictions of a time-dependent self-consistent-field description of the H + H system for scattering in the intermediate energy regime of 1-100 keV. Because of the unrestricted nature of the numerical orbital description, this method includes the effects of an unlimited basis set within each orbital. Electron exchange and a limited amount of electron correlation are included as well. We solve numerically coupled three-dimensional Schrodinger equations for the two-electron orbitals in singlet and triplet symmetries. Excitation and ionization cross sections are computed and compared with other theory and experiment. The results capture many features of the problem but illustrate a need for more quantitative experimental information concerning the H + H system in this energy range.
The cookoff of energetic materials involves the combined effects of several physical and chemical processes. These processes include heat transfer, chemical decomposition, and mechanical response. The interaction and coupling between these processes influence both the time-to-event and the violence of reaction. The prediction of the behavior of explosives during cookoff, particularly with respect to reaction violence, is a challenging task. To this end, a joint DoD/DOE program has been initiated to develop models for cookoff, and to perform experiments to validate those models. In this paper, a series of cookoff analyses are presented and compared with data from a number of experiments for the aluminized, RDX-based, Navy explosive PBXN-109. The traditional thermal-chemical analysis is used to calculate time-to-event and characterize the heat transfer and boundary conditions. A reaction mechanism based on Tarver and McGuire's work on RDX{sup 2} was adjusted to match the spherical one-dimensional time-to-explosion data. The predicted time-to-event using this reaction mechanism compares favorably with the validation tests. Coupled thermal-chemical-mechanical analysis is used to calculate the mechanical response of the confinement and the energetic material state prior to ignition. The predicted state of the material includes the temperature, stress-field, porosity, and extent of reaction. There is little experimental data for comparison to these calculations. The hoop strain in the confining steel tube gives an estimation of the radial stress in the explosive. The inferred pressure from the measured hoop strain and calculated radial stress agree qualitatively. However, validation of the mechanical response model and the chemical reaction mechanism requires more data. A post-ignition burn dynamics model was applied to calculate the confinement dynamics. The burn dynamics calculations suffer from a lack of characterization of the confinement for the flaw-dominated failure mode experienced in the tests. High-pressure burning rates are needed for more detailed post-ignition studies. Sub-models for chemistry, mechanical response and burn dynamics need to be validated against data from less complex experiments. The sub-models can then be used in integrated analysis for comparison with experimental data taken during integrated tests.
Since the discovery of surfactant-templated silica by Mobil scientists in 1992, mesostructured silica has been synthesized in various forms including thin films, powders, particles, and fibers. In general, mesostructured silica has potential applications, such as in separation, catalysis, sensors, and fluidic microsystems. In respect to these potential applications, mesostructured silica in the form of thin films is perhaps one of the most promising candidates. The preparation of mesostructured silica films through preferential solvent evaporation-induced self-assembly (EISA) has recently received much attention in the laboratories. However, no amphiphile/silica films with reverse mesophases have ever been made through this EISA procedure. Furthermore, templates employed to date have been either surfactants or poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) triblock copolymers, such as pluronic P-123, both of which are water-soluble and alcohol-soluble. Due to their relatively low molecular weight, the templated silica films with mesoscopic order have been limited to relatively small characteristic length scales. In the present communication, the authors report a novel synthetic method to prepare mesostructured amphiphilic/silica films with regular and reverse mesophases of large characteristic length scales. This method involves evaporation-induced self-assembly (EISA) of amphiphilic polystyrene-block-poly(ethylene oxide) (PS-b-PEO) diblock copolymers. In the present study, the PS-b-PEO diblocks are denoted as, for example, PS(215)-b-PEO(100), showing that this particular sample contains 215 S repeat units and 100 EO repeat units. This PS(215)-b-PEO(100) diblock possesses high molecular weight and does not directly mix with water or alcohol. To the authors knowledge, no studies have reported the use of water-insoluble and alcohol-insoluble amphiphilic diblocks as structure-directing agents in the synthesis of mesostructured silica films through EISA. It is believed that the present system is the first to yield amphiphile/silica films with regular and reverse mesophases, as well as curved multi-bilayer mesostructures, through EISA. The ready formation of the diblock/silica films with multi-bilayer vesicular mesostructures is discussed.
Heat pipes are often proposed as cooling system components for small fission reactors. SAFE-300 and STAR-C are two reactor concepts that use heat pipes as an integral part of the cooling system. Heat pipes have been used in reactors to cool components within radiation tests (Deverall, 1973); however, no reactor has been built or tested that uses heat pipes solely as the primary cooling system. Heat pipe cooled reactors will likely require the development of a test reactor to determine the main differences in operational behavior from forced cooled reactors. The purpose of this paper is to describe the results of a systems code capable of modeling the coupling between the reactor kinetics and heat pipe controlled heat transport. Heat transport in heat pipe reactors is complex and highly system dependent. Nevertheless, in general terms it relies on heat flowing from the fuel pins through the heat pipe, to the heat exchanger, and then ultimately into the power conversion system and heat sink. A system model is described that is capable of modeling coupled reactor kinetics phenomena, heat transfer dynamics within the fuel pins, and the transient behavior of heat pipes (including the melting of the working fluid). The paper focuses primarily on the coupling effects caused by reactor feedback and compares the observations with forced cooled reactors. A number of reactor startup transients have been modeled, and issues such as power peaking, and power-to-flow mismatches, and loading transients were examined, including the possibility of heat flow from the heat exchanger back into the reactor. This system model is envisioned as a tool to be used for screening various heat pipe cooled reactor concepts, for designing and developing test facility requirements, for use in safety evaluations, and for developing test criteria for in-pile and out-of-pile test facilities.
An integrated approach, combining the continuum theory of sintering and Potts model based mesostructure evolution analysis, is used to solve the problem of bi-layered structure sintering. Two types of bi-layered structures are considered: layers of the same material with different initial porosity, and layers of two different materials. The effective sintering stress for the bi-layer powder sintering is derived, both at the meso- and the macroscopic levels. Macroscopic shape distortions and spatial distributions of porosity are determined as functions of the dimensionless specific time of sintering. The effect of the thickness of the layers on shrinkage, warpage, and pore-grain structure is studied. Ceramic ZnO powders are employed as a model experimental system to assess the model predictions.
This paper presents an analysis technique used to generate the structural response at locations not measured during the ejection of a captive-carried store. The ejection shock event is complicated by the fact that forces may be imparted to the store at eight distinct locations. The technique derives forcing functions by combining the initial field test data for a limited number of measurement locations with Frequency Response Functions (FRFs) measured using a traditional modal-type impact (tap) test at the same locations. The derived forcing functions were then used with tap test FRFs measured at additional locations of interest to produce the desired response data.
Operating in a potentially hostile city is every soldier's nightmare. The staggering complexity of the urban environment means that deadly threats--or non-combatants-may lurk behind every corner, doorway, or window. Urban operations present an almost unparalleled challenge to the modern professional military. The complexity of urban operations is further amplified by the diversity of missions that the military will be called upon to conduct in urban terrain. Peace-making and peace-keeping missions, urban raids to seize airports or WMD sites or to rescue hostages, and extended urban combat operations all present different sorts of challenges for planners and troops on the ground. Technology almost never serves as a magic bullet, and past predictions of technological miracles pile high on the ash heap of history. At the same time, it is a vital element of planning in the modern age to consider and, if possible, take advantage of emerging technologies. We believe that technologies can assist military operations in urbanized terrain (MOUT) in three primary areas, which are discussed.
This paper summarizes an evaluation of a treatment loop designed to upgrade the quality of spent rinse waters discharged from 10 wet benches located in the fab at Sandia's Microelectronics Development Laboratory (MDL). The goal of the treatment loop is to make these waters, presently being discharged to the fab's acid waste neutralization (AWN) station, suitable for recycling as feed water back into the fab's ultrapure water (UPW) plant. The MDL typically operates 2 shifts per day, 5 days per week. Without any treatment, the properties of the spent rinse waters now being collected have been shown to be compatible with recycling about 30% (50/168) of the time (weekends primarily, when the fab is idling) which corresponds to about 12% of the present water discharged from the fab to the AWN. The primary goal of adding a treatment loop is to increase the percentage of recyclable water from these 10 wet benches to near 100%, increasing the percentage of total recyclable water to near 40% of the total present fab discharge to the AWN. A second goal is to demonstrate compatibility with recycling this treated spent rinse water to the present R/O product water tank, reducing both the present volume of R/O reject water and the present load on the R/O. The approach taken to demonstrate achieving these goals is to compare all the common metrics of water quality for the treated spent rinse waters with those of the present R/O product water. Showing that the treated rinse water is equal or superior in quality to the water presently stored in the R/O tank by every metric all the time is assumed to be sufficient argument for proceeding with plans to incorporate recycling of these spent rinse waters back into MDL's R/O tank.
The use of plasma spray to deposit thin metal-sulfide cathode films is described in this paper. Conventional electroactive stack components in thermal batteries are constructed from pressed-powder parts that are difficult to fabricate in large diameters in thicknesses <0.010. Plasma-sprayed electrodes do not steer from this difficulty, allowing greater energy densities and specific energies to be realized. Various co-spraying agents have been found suitable for improving the mechanical as well as electrochemical properties of plasma-sprayed cathodes for thermal batteries. These electrodes generally show equal or improved performance over conventional pressed-powder electrodes. A number of areas for future growth and development of plasma-spray technology is discussed.