The study of gain properties in group-III nitride quantum wells is complicated by several factors. In view of this, an approach is presented that involves a first-principles bandstructure calculation, the results of which are incorporated into a microscopic laser theory. The band structure calculation applies a density-functional method. This method provides a single analytical model for computing the group-II nitride material properties, thus ensuring consistency in the values for the different bandstructure parameters, and circumventing the discrepancies present in the literature due to different experimental conditions, or different computational methods. With a complete set of the relevant material parameters, it is possible to study the effects of strain and quantum confinement.
Monochromatic imaging was used to investigate the excited-state density distributions of Fe and Fe+ in the inter-electrode gap region of a 3,100 A dc metal vapor arc burning between molten iron surfaces in a vacuum arc furnace. Multiple images were acquired at four wavelengths. The images were corrected and Abel inverted to yield the absolute radial intensity distributions for Fe and Fe+ in the inter-electrode gap region. The results show a structured, axisymmetric plasma consisting of a high density 'core' of Fe+ emitters centered between the electrode surfaces situated against a relatively broad, flat excited-state Fe distribution.
The Smart Gun Technology Project has a goal to eliminate the capability of an unauthorized user from firing a law enforcement officer`s firearm by implementing {open_quote}smart{close_quote} technologies. Smart technologies are those that can in some manner identify an officer. This report will identify, describe, and grade various technologies as compared to the requirements that were obtained from officers. This report does not make a final recommendation for a smart gun technology, nor does it give the complete design of a smart gun system.
Numerical studies have been made of an infiltration experiment at Fran Ridge using the TOUGH2 code to aid in the selection of computational models for performance assessment. The exercise investigates the capabilities of TOUGH2 to model transient flows through highly fractured tuff and provides a possible means of calibration. Two distinctly different conceptual models were used in the TOUGH2 code, the dual permeability model and the equivalent continuum model. The infiltration test modeled involved the infiltration of dyed ponded water for 36 minutes. The 205 gallon filtration of water observed in the experiment was subsequently modeled using measured Fran Ridge fracture frequencies, and a specified fracture aperture of 285 {mu}m. The dual permeability formulation predicted considerable infiltration along the fracture network, which was in agreement with the experimental observations. As expected, minimal fracture penetration of the infiltrating water was calculated using the equivalent continuum model, thus demonstrating that this model is not appropriate for modeling the highly transient experiment. It is therefore recommended that the dual permeability model be given priority when computing high-flux infiltration for use in performance assessment studies.
6th Symposium on Multidisciplinary Analysis and Optimization
Campbell, J.E.; Painton, L.A.
This paper examines a novel optimization technique called genetic algorithms and its application to the optimization of reliability allocation strategies. Reliability allocation should occur in the initial stages of design, when the objective is to determine an optimal breakdown or allocation of reliability to certain components or subassemblies in order to meet system objectives. The reliability allocation optimization is applied to the design of a cluster tool, a highly complex piece of equipment used in semiconductor manufacturing. The problem formulation is presented, including decision variables, performance measures and constraints, and genetic algorithm parameters. Piecewise “effort curves” specifying the amount of effort required to achieve a certain level of reliability for each component or subassembly are defined. The genetic algorithm evolves or picks those combinations of “effort” or reliability levels for each component which optimize the objective of maximizing Mean Time Between Failures while staying within a budget. The results show that the genetic algorithm is very efficient at finding a set of robust solutions. A time history of the optimization is presented, along with histograms of the solution space fitness, MTBF, and cost for comparative purposes.
Conference Proceedings from the International Symposium for Testing and Failure Analysis
Liang, A.Y.
We present the results of recent failure analysis of an advanced, 0.5 um, fully planarized, triple metallization CMOS technology. A variety of failure analysis (FA) tools and techniques were used to localize and identify defects generated by wafer processing. These include light (photon) emission microscopy (LE), fluorescent microthermal imaging (FMI), focused ion beam cross sectioning, SEM/voltage contrast imaging, resistive contrast imaging (RCI), and e-beam testing using an IDS-5000 with an HP 82000. The defects identified included inter- and intra-metal shorts, gate oxide shorts due to plasma processing damage, and high contact resistance due to the contact etch and deposition process. Root causes of these defects were determined and corrective action was taken to improve yield and reliability.
Polysilicon surface micromachining is a technology for manufacturing Micro-Electro-Mechanical Systems (MEMS) which has, as its basis, the manufacturing methods and tool sets used to manufacture the integrated electronic circuit. This paper describes a three-level mechanical-polysiiicon surface-micromachining technology and includes a discussion of the advantages of this level of process complexity along with issues which affect device fabrication and performance. Historically, the primary obstacles to multi-level polysilicon fabrication were related to the severe wafer topography generated by the repetition of film depositions and etching. The introduction of Chemical Mechanical Polishing (CMP) to surface micromachining has largely removed these issues and opened significant avenues for device complexity. Several examples of three-level devices with the benefits of CMP are presented. Of primary hindrance to the widespread use of polysilicon surface micromachining, and in particular microactuation mechanisms, are issues related to the device surfaces. The closing discussion examines the potential of several latter and postfabrication processes to circumvent or to directly alleviate the surface problems.
We apply a number of complementary characterization techniques including electron paramagnetic resonance, optical absorption, and photoluminescence spectroscopies to characterize a wide range of different ZnO phosphor powders. We generally observe a good correlation between the 510-nm green emission intensity and the density of paramagnetic isolated oxygen vacancies. In addition, both quantities are found to peak at a free-carrier concentration ne, of about 1.4×1018 cm-3. We also find that the green emission intensity can be strongly influenced by free-carrier depletion at the particle surface, especially for small particles and/or low doping. Our data suggest that the green PL in ZnO phosphors is due to the recombination of electrons in singly occupied oxygen vacancies with photoexcited holes in the valence band.
Silicon solar cell efficiencies of 17.1%, 16.4%, 14.8%, and 14.9% have been achieved on FZ, Cz, multicrystalline (mc-Si), and dendritic web (DW) silicon, respectively, using simplified, cost-effective rapid thermal processing (RTP). These represent the highest reported efficiencies for solar cells processed with simultaneous front and back diffusion with no conventional high-temperature furnace steps. Appropriate diffusion temperature coupled with the added in-situ anneal resulted in suitable minority-carrier lifetime and diffusion profiles for high-efficiency cells. The cooling rate associated with the in-situ anneal can improve the lifetime and lower the reverse saturation current density (Jo), however, this effect is material and base resistivity specific. PECVD antireflection (AR) coatings provided low reflectance and efficient front surface and bulk defect passivation. Conventional cells fabricated on FZ silicon by furnace diffusions and oxidations gave an efficiency of 18.8% due to greater short wavelength response and lower Jo.
With the eventual phase-out of chlorofluorocarbons and hydrochlorofluorocarbons, and restrictive regulations concerning the use of other volatile organic compounds as cleaning solvents, it is essential to seek new, environmentally acceptable cleaning processes. We are investigating supercritical carbon dioxide (CO2) as an alternative solvent for precision cleaning of machined metal parts in governmental and industrial cleaning processes. The compatibility of metals in supercritical-fluid cleaning media with respect to corrosion must be addressed. In this work, a screening study of the corrosive effects of supercritical CO2 and several supercritical cosolvents on selected metals was conducted. Sample coupons of stainless steel (grades 304LSS, 316SS), aluminum (grades 2024, 6061, 7075), carbon steel (1018), and copper (CDA 101) were statically exposed to pure supercritical CO2, water-saturated supercritical CO2, 10 wt % methanol/CO2 cosolvent, and 4 wt % tetrahydrofurfuryl alcohol (THFA)/CO2 at 24,138 kPa (3500 psig) and 323 K (50 °C) for 24 h. Gravimetric analysis and magnified visual inspection of the coupons were performed before and after the exposure tests. Surface analyses including electron microprobe analysis (EMPA), X-ray photoelectron spectroscopy (XPS), and Auger electron spectroscopy (AES) were done where visual and gravimetric changes were indicative of corrosive attack. The metal alloys were found to be compatible with the supercritical test media barring a few exceptions. Corrosive attack was observed on 1018 carbon steel in the water-saturated CO2 environment, and also on 2024 aluminum and CDA 101 copper, both in the 10 wt % methanol-CO2 cosolvent. The results of all compatibility testing are reported, and hypotheses are formed in an attempt to explain possible corrosion mechanisms.
A survey of existing data has been completed in order to examine the hazards to people exposed on the ground and to in-flight aircraft by debris produced during high-altitude, rocket-boosted flight tests. These data were then analyzed to quantify the particle sizes and energy levels below which the fragments no longer pose a hazard. The survey results are presented here and recommendations made regarding the minimum energy levels and minimum particle size that need be considered in a flight safety analysis.
Crystal lattices are infinite periodic graphs that occur naturally in a variety of geometries and which are of fundamental importance in polymer science. Discrete models of protein folding use crystal lattices to define the space of protein conformations. Because various crystal lattices provide discretizations of the same physical phenomenon, it is reasonable to expect that there will exist "invariants" across lattices that define fundamental properties of the protein folding process; an invariant defines a property that transcends particular lattice formulations. This paper identifies two classes of invariants, defined in terms of sublattices that are related to the design of algorithms for the structure prediction problem. The first class of invariants is used to define a master approximation algorithm for which provable performance guarantees exist. This algorithm can be applied to generalizations of the hydrophobic-hydrophilic model that have lattices other than the cubic lattice, including most of the crystal lattices commonly used in protein folding lattice models. The second class of invariants applies to a related lattice model. Using these invariants, we show that for this model the structure prediction problem is intractable across a variety of threedimensional lattices. It turns out that these two classes of invariants are respectively sublattices of the two-and three-dimensional square lattice. As the square lattices are the standard lattices used in empirical protein folding studies, our results provide a rigorous confirmation of the ability of these lattices to provide insight into biological phenomenon. Our results are the first in the literature that identify algorithmic paradigms for the protein structure prediction problem that transcend particular lattice formulations.
This is a brochure about the Solar Thermal Design Assistance Center of Sandia National Laboratories: technical assistance, testing, technology development, education, and customer services
This small booklet tells the profile, mission, operations, services, and data base of Sandia National Laboratories Photovoltaic Design Assistance Center
Reactor power supplies offer many attractive characteristics for lunar surface applications. The Topaz II reactor resulted from an extensive development program in the former Soviet Union. Flight quality reactor units remain from this program and are currently under evaluation in the United States. This paper examines the potential for applying the Topaz II, originally developed to provide spacecraft power, as a lunar surface power supply.
In accordance with the Nuclear Regulatory Commission regulation regarding groundwater travel times at geologic repositories, various models of unsaturated flow in fractured tuff have been developed and implemented to assess groundwater travel times at the potential repository at Yucca Mountain, Nevada. Kaplan used one-dimensional models to describe the uncertainty and sensitivity of travel times to various processes at Yucca Mountain. Robey and Arnold et al. used a two-dimensional equivalent continuum model (ECM) with inter- and intra-unit heterogeneity in an attempt to assess fast-flow paths through the unsaturated, fractured tuff at Yucca Mountain (GWTT-94). However, significant flow through the fractures in previous models was not simulated due to the characteristics of the ECM, which requires the matrix to be nearly saturated before flow through the fractures is initiated. In the current study (GWTT-95), four two-dimensional cross-sections at Yucca Mountain are simulated using both the ECM and dual-permeability (DK) models. The properties of both the fracture and matrix domains are geostatistically simulated, yielding completely heterogeneous continua. Then, simulations of flow through the four cross-sections are performed using spatially nonuniform infiltration boundary conditions. Steady-state groundwater travel times from the potential repository to the water table are calculated.
The next total-system performance-assessment (TSPA) analyses are designed to aid DOE in performing an ``investment analysis`` for Yucca Mountain. This TSPA must try to bound the uncertainties for several issues that will contribute to the decision whether the US should proceed with the development of a nuclear-waste repository at Yucca Mountain. Because site-characterization experiments and data collection will continue for the foreseeable future, the next TSPA (called TSPA-IA) will again only be able to use partially developed models and partial data sets. In contrast to previous analyses however, TSPA-IA must address more specific questions to be of assistance to the investment-analysis deliberations.
Unsaturated flow has been modeled through four cross-sections at Yucca Mountain, Nevada, for the purpose of determining groundwater particle travel times from the potential repository to the water table. This work will be combined with the results of flow modeling in the saturated zone for the purpose of evaluating the suitability of the potential repository under the criteria of 10CFR960. One criterion states, in part, that the groundwater travel time (GWTT) from the repository to the accessible environment must exceed 1,000 years along the fastest path of likely and significant radionuclide travel. Sensitivity analyses have been conducted for one geostatistical realization of one cross-section for the purpose of (1) evaluating the importance of hydrological parameters having some uncertainty and (2) examining conceptual models of flow by altering the numerical implementation of the conceptual model (dual permeability (DK) and the equivalent continuum model (ECM). Results of comparisons of the ECM and DK model are also presented in Ho et al.
The performance of waste packages containing high-level nuclear wastes at underground repositories such as the potential repository at Yucca Mountain, Nevada, depends, in part, on the thermodynamic environment immediately surrounding the buried waste packages. For example, degradation of the waste packages can be caused by corrosive and microbial processes, which are influenced by both the relative humidity and temperature within the emplacement drifts. In this paper, the effects of conduction, convection, and radiation are investigated for a heat-generating waste package in an empty-drift. Simulations explicitly modeling radiation from the waste package to the drift wall are compared simulations using only conduction. Temperatures, relative humidities, and vapor mass fractions are compared at various locations within the drift. In addition, the effects of convection on relative humidity and moisture distribution within the drift are presented.
The Radiological Environment Modeling System (REMS) quantifies dose to humans in radiation environments using the IGRIP (Interactive Graphical Robot Instruction Program) and Deneb/ERGO (Ergonomics) simulation software products. These commercially available products are augmented with custom C code to provide the radiation exposure information to and collect the radiation dose information from the workcell simulations. The emphasis of this paper is on the IGRIP and Deneb/ERGO parts of REMS, since that represents the extension to existing capabilities developed by the authors. Through the use of any radiation transport code or measured data, a radiation exposure input database may be formulated. User-specified IGRIP simulations utilize these database files to compute and accumulate dose to human devices (Deneb`s ERGO human) during simulated operations around radiation sources. Timing, distances, shielding, and human activity may be modeled accurately in the simulations. The accumulated dose is recorded in output files, and the user is able to process and view this output. REMS was developed because the proposed reduction in the yearly radiation exposure limit will preclude or require changes in many of the manual operations currently being utilized in the Weapons Complex. This is particularly relevant in the area of dismantlement activities at the Pantex Plant in Amarillo, TX. Therefore, a capability was needed to be able to quantify the dose associated with certain manual processes so that the benefits of automation could be identified and understood.
A technique called the Natural Excitation Technique or has been developed to response extract response parameters from large operational structure when subjected to random and unmeasured forces such as wind, road noise, aerodynamics, or waves. Six applications of NExT to ambient excitation testing and NExT analysis are surveyed in this paper with a minimum of technical detail. In the first application, NExT was applied to a controlled-yaw Horizontal-Axis Wind Turbine (HAWT). By controlling the yaw degree of freedom an important class of rotating coordinate system effects are reduced. A new shape extraction procedure was applied to this data set with good results. The second application was to a free-yaw HAWT. The complexity of the response has prompted further analytical studies and the development of a specialized visualization package. The third application of NExT was to a parked three-bladed Vertical-Axis Wind Turbine (VAWT) in which traditional modal testing could not excite all modes of interest. The shape extraction process used cross-correlation functions directly in a time-domain shape-fitting routine. The fourth application was to ground transportation systems. Ongoing work to improve driver and passenger comfort in tractor-trailer vehicles and to refine automobile body and tire models will use NExT. NExT has been used to process ambient vibration data for Finite Element Model correlation and is being used to study Structural Health Monitoring with ambient excitation. Shape fitting was performed using amplitude and phase information taken directly from the cross-spectra. The final application is to an offshore structure. This work is on-going, however initial studies have found a high-modal density, high noise content, and sparse data set.
Future advances in the application of photonic interconnects will involve the insertion of parallel-channel links into Multi-Chip Modules (MCMS) and board-level parallel connections. Such applications will drive photonic link components into more compact forms that consume far less power than traditional telecommunication data links. These will make use of new device-level technologies such as vertical cavity surface-emitting lasers and special low-power parallel photoreceiver circuits. Depending on the application, these device technologies will often be monolithically integrated to reduce the amount of board or module real estate required by the photonics. Highly parallel MCM and board-level applications will also require simplified drive circuitry, lower cost, and higher reliability than has been demonstrated in photonic and optoelectronic technologies. An example is found in two-dimensional point-to-point array interconnects for MCM stacking. These interconnects are based on high-efficiency Vertical Cavity Surface Emitting Lasers (VCSELs), Heterojunction Bipolar Transistor (HBT) photoreceivers, integrated micro-optics, and MCM-compatible packaging techniques. Individual channels have been demonstrated at 100 Mb/s, operating with a direct 3.3V CMOS electronic interface while using 45 mW of electrical power. These results demonstrate how optoelectronic device technologies can be optimized for low-power parallel link applications.
Most routing problems depend on several important variables: transport distance, population exposure, accident rate, mandated roads (e.g., HM-164 regulations), and proximity to emergency response resources are typical. These variables may need to be minimized or maximized, and often are weighted. `Objectives` to be satisfied by the analysis are thus created. The resulting problems can be approached by combining spatial analysis techniques from geographic information systems (GIS) with multiobjective analysis techniques from the field of operations research (OR); we call this hybrid multiobjective spatial analysis` (MOSA). MOSA can be used to discover, display, and compare a range of solutions that satisfy a set of objectives to varying degrees. For instance, a suite of solutions may include: one solution that provides short transport distances, but at a cost of high exposure; another solution that provides low exposure, but long distances; and a range of solutions between these two extremes.
Three and four-layer backpropagation artificial neural networks have been used to predict the power output of a liquid metal reflux solar receiver. The networks were trained using on-sun test data recorded at Sandia National Laboratories in Albuquerque, New Mexico. The preliminary results presented in this paper are a comparison of how different size networks train on this particular data. The results give encouragement that it will be possible to predict output power of a liquid metal receiver under a variety of operating conditions using artificial neural networks.
We have conducted a real time, two-dimensional light scattering study of the nonlinear dynamics of field-induced structures in an electrorheological fluid subjected to oscillatory shear. We have developed a kinetic chain model of the observed dynamics by considering the response of a fragmenting/aggregating particle chain to the prevailing hydrodynamic and electrostatic forces. This structural theory is then used to describe the nonlinear rheology of ER fluids.
This paper describes recent work to make high quality quartz gauge (temporal and spatial) shock wave measurements in a pulsed ion beam environment. Intense ion beam radiation, nominally 1 MeV protons, was deposited into material samples instrumented with shunted quartz gauges adjacent to the ion deposition zone. Fluence levels were chosen to excite three fundamentally different material response modes (1) strong vapor, (2) combined vapor and melt phase and (3) thermoelastic material response. A unique quartz gauge design was utilized that employed printed circuit board (PCB) technology to facilitate electrical shielding, ruggedness, and fabrication @e meeting the essential one dimensional requirements of the characterized Sandia shunted quartz gauge. Shock loading and unloading experiments were conducted to evaluate the piezoelectric response of the coupled quartz gauge/PCB transducer. High fidelity shock wave profiles were recorded at the three ion fluence levels providing dynamic material response data for vapor, melt and solid material phases.
Terminal propagation is a method developed in the circuit placement community for adding constraints to graph partitioning problems. This paper adapts and expands this idea, and applies it to the problem of partitioning data structures among the processors of a parallel computer. We show how the constraints in terminal propagation can be used to encourage partitions in which messages are communicated only between architecturally near processors. We then show how these constraints can be handled in two important partitioning algorithms, spectral bisection and multilevel-KL. We compare the quality of partitions generated by these algorithms to each other and to Partitions generated by more familiar techniques.
The viscous response of electrorheological fluids is usually manipulated through the use of DC or uniaxial AC electric fields. The result is that fibrillated structures parallel to the field form in a quiescent fluid; the distortion of such structures in a flow determines the enhanced viscous response, at least at low and moderate flow rates. We have conducted preliminary studies of electrorheological response in a different field configurations rotating electric field. With respect to the uniaxial AC case. there are two new developments in this type of field. The structures formed are disk-like, in the plane of the rotating field. Furthermore, the structures rotate either with or against the field, depending on the dielectric or conductivity contrast with the surrounding fluid.
This document presents details of the verification process of the RADTRAN computer code which was established for the calculation of risk estimates for radioactive materials transportation by highway, rail, air, and waterborne modes.
Because of the complexity, volume of data and calculations required, one preferred analytical tool to perform transportation risk assessments is the RADTRAN computer code. RADTRAN combines user-determined material, packaging, transportation, demographic and meteorological factors, with health physics data to calculate expected radiological consequences and accident risk from transporting radioactive materials by all commercial modes including truck, rail, ship, air and barge. The computer code consists of two major modules for each transport mode: the incident-free module, in which doses from normal transport are calculated; and the accident module, in which dose consequences and probabilities are evaluated to generate risk estimates. The purpose of this presentation is to describe the development of a standardized procedure to perform transportation radiological risk assessments employing conventional spreadsheet programs to automate generation of RADTRAN input files and post-processing analysis of the resulting output.
This document presents details of the environmental activities that occurred during 1994 at Sandia National Laboratories. Topics include: Background about Sandia; radiation facts; sources of radiation; environmental monitoring; discussion of radiation detectors; radioactive waste management; environmental restoration; and quality assurance.
The mission of the American Textile (AMTEX{trademark}) Partnership is to engage the unique technical resources of the Department of Energy National Laboratories to work with the US Integrated Textile Complex (US ITC) and research universities to develop and deploy technologies that will increase the competitiveness of the US ITC. The objectives of the Demand Activated Manufacturing Architecture (DAMA) project of AMTEX are: (1) to determine strategic business structure changes for the US ITC; (2) to establish a textile industry electronic marketplace, (3) to provide methods for US ITC education ad implementation of an electronic marketplace. The Enterprise Modeling and Simulation Task of DAMA is focusing on the first DAMA goal as described in another paper of this conference. The Cooperative Business Management (CBM) Task of DAMA is developing computer-based tools that will render system-wide information accessible for improved decision making. Three CBM strategies and the associated computer tools being developed to support their implementation are described in this paper. This effort is addressing the second DAMA goal to establish a textile industry electronic marketplace in concert with the Connectivity and Infrastructure Task of DAMA. As the CBM tools mature, they will be commercialized through the DAMA Education, Outreach and Commercialization Task of DAMA to achieve the third and final DAMA goal.
The Aging Aircraft NDI Validation Center (AANC) was established by the Federal Aviation Administration Technical Center (FAATC) at Sandia National Laboratories in August of 1991. The goal of the AANC is to provide independent validation of technologies intended to enhance the structural inspection of aging commuter and transport aircraft. The deliverables from the AANC`s validation activities are assessments of the reliability of existing and emerging inspection technologies as well as analyses of the cost benefits to be derived from their implementation. This paper describes the methodology developed by the AANC to assess the performance of NDI techniques. In particular, an experiment being developed to evaluate corrosion detection devices will be presented. The experiment uses engineered test specimens, as well as complete aircraft test beds to provide metrics for NDI validation.
Sandia`s Institutional Plan is by necessity a large document. As their missions have grown and diversified over the past decades, the variety of technical and site activities has increased. The programs and activities described here cover an enormous breadth of scientific and technological effort--from the creation of new materials to the development of a Sandia-wide electronic communications system. Today, there are three major themes that greatly influence this work. First, every federally funded institution is being challenged to find ways to become more cost effective, as the US seeks to reduce the deficit and achieve a balanced federal spending plan. Sandia is evaluating its business and operational processes to reduce the overall costs. Second, in response to the Galvin Task Force`s report ``Alternative Futures for the Department of Energy National Laboratories``, Sandia and the Department of Energy are working jointly to reduce the burden of administrative and compliance activities in order to devote more of the total effort to their principal research and development missions. Third, they are reevaluating the match between their missions and the programs they will emphasize in the future. They must demonstrate that Sandia`s roles--in national security, energy security, environmental integrity, and national scientific and technology agenda support--fit their special capabilities and skills and thus ensure their place in these missions for the longer planning horizon. The following areas are covered here: Sandia`s mission; laboratory directives; programmatic activities; technology partnerships and commercialization; Sandia`s resources; and protecting resources and the community.
A new approach to product development is described that integrates various unit operations into a unified ``knowledge-base``. This knowledge-base is easily accessible to all members of the design team due to the advent of high performance and networking capabilities of today`s desktop computers. This permits rapid optimization of the product`s material, shape, and manufacturing processes that satisfy the customer`s performance requirements while maximizing economic return for the manufacturer.
The Department of Energy (DOE) has been developing a planning process for mixed low-level waste (MLLW) disposal in conjunction with the affected states for over two years and has screened the potential disposal sites from 49 to 15. A radiological performance evaluation was conducted on these fifteen sites to further identify their strengths and weaknesses for disposal of MLLW. Technical analyses are on-going. The disposal evaluation process has sufficiently satisfied the affected states` concerns to the point that disposal has not been a major issue in the consent order process for site treatment plans. Additionally, a large amount of technical and institutional information on several DOE sites has been summarized. The relative technical capabilities of the remaining fifteen sites have been demonstrated, and the benefits of waste form and disposal facility performance have been quantified. However, the final disposal configuration has not yet been determined. Additionally, the MLLW disposal planning efforts will need to integrate more closely with the low-level waste disposal activities before a final MLLW disposal configuration can be determined. Recent Environmental Protection Agency efforts related to the definition of hazardous wastes may also affect the process.
The growth of polycrystalline and amorphous aluminum-oxygen alloy films using electron-beam evaporation of Al in the presence of an O{sub 2} electron-cyclotron-resonance (ECR) plasma was investigated for film compositions varying from 40% Al (Al{sub 2}O{sub 3}) to near 100% Al (AlO{sub x}). Processing parameters such as deposition temperature and ion energy were varied to study their effects on surface texture and film microstructure. The Al-rich films (AlO{sub x}) contain polycrystalline fcc Al grains with finely dispersed second-phase particles of {gamma}-Al{sub 2}O{sub 3} (1-2 nm in size). The surface roughness of these films was measured by atomic force microscopy and found to increase with sample bias and deposition temperature. Stoichiometric Al{sub 2}O{sub 3} films grown at 100{degrees}C and 400{degrees}C without an applied bias were amorphous, while an applied bias of -140 V formed a nanocrystalline {gamma}-Al{sub 2}O{sub 3} film at 400{degrees}C. The surface roughness of the Al{sub 2}O{sub 3} increased with temperature while ion irradiation produced a smoother surface.
Sandia National Laboratories` (SNL) Technical Library is now responsible for providing citation verification management support for all references cited in technical reports issued by the Nuclear Waste Management (NWM) Program. This paper dancing how this process is managed for the Yucca Mountain Site Characterization (YWP), Waste Isolation Pilot Plant (WIPP), Idaho National Engineering Laboratory (INEL), and Greater Confinement Disposal (GCD) projects. Since technical reports are the main product of these projects, emphasis is placed on meeting the constantly evolving needs of these customers in a timely and cost-effective manner.
Various applications are currently motivating interest in the transmission of very high laser intensities through optical fibers. As intensities within a fiber are increased, however, laser breakdown or laser-induced fiber damage will eventually occur and interrupt fiber transmission. For a number of years we have been studying these effects during the transmission of Q-switched, Nd/YAG laser pulses through step-index, multimode, fused-silica fiber. We have found that fiber transmission is often limited by a plasma-forming breakdown occurring at the fiber entrance face. This breakdown results in subtle surface modifications that can leave the surface more resistant to further breakdown or damage events. Catastrophic fiber damage can also occur as a result of a number of different mechanisms, with damage appearing at fiber end faces, within the initial ``entry`` segment of the fiber path, and at other internal sites due to effects related to the particular fiber routing. An overview of these past observations is presented, and issues requiring further study are identified.
A long standing problem in low-temperature plasma discharge physics is to understand in detail the mutual interaction of real exposed surfaces (electrodes) with the reactive plasma environment. In particular, one wishes to discern the influence of these surfaces on the plasma parameters given their contributions from secondary electrons and ions. This paper briefly reviews the known surface interaction processes as well as currently available diagnostics to study the interface between plasmas and surfaces. Next comes a discussion describing the application of plasma-modulated electroreflectance to this research and some potential experimental techniques.
Low-energy deposition of Al(O) alloys from an electron cyclotron resonance (ECR) plasma offers a scaleable method for the synthesis of thick, high-strength Al layers. This work compares alloy layers formed by an ECR-0{sub 2} plasma in conjunction with Al evaporation to 0-implanted Al (ion energies 25-200 keV); and it examines the effects of volume fraction of A1{sub 2}0{sub 3} phase and deposition temperature on the yield stress of the material. TEM showed the Al(O) alloys contain a dense dispersion of small {gamma}-Al{sub 2}0{sub 3} precipitates ({approximately}l nm) in a fine-grain (10-100 nm) fcc Al matrix when deposited at a temperature of {approximately}100C, similar to the microstructure for gigapascal-strength 0-implanted Al. Nanoindentation gave hardnesses for ECR films from 1.1 to 3.2 GPa, and finite-element modeling gave yield stresses up to 1.3 {plus_minus} 0.2 GPa with an elastic modulus of 66 GPa {plus_minus} 6 GPa (similar to pure bulk Al). The yield stress of a polycrystalline pure Al layer was only 0.19 {plus_minus} 0.02 GPa, which was increased to 0.87 {plus_minus} 0.15 GPa by implantation with 5 at. % 0.
Several effects of seismic activity on the release of radionuclides from a potential repository at Yucca Mountain are quantified. Future seismic events are predicted using data from the seismic hazard analysis conducted for the Exploratory Studies Facility (ESF). Phenomenological models are developed, including rockfall (thermal-mechanical and seismic) in unbackfilled emplacement drifts, container damage caused by fault displacement within the repository, and flow-path chance caused by changes in strain. Using the composite-porosity flow model (relatively large-scale, regular percolation), seismic events show little effect on total-system releases; using the weeps flow model (episodic pulses of flow in locally saturated fractures), container damage and flow-path changes cause over an order of magnitude increase in releases. In separate calculations using, more realistic representations of faulting, water-table rise caused by seismically induced changes in strain are seen to be higher than previously estimated by others, but not sufficient to reach a potential repository.
Development of a vapor generator for consistently producing accurate amounts of vapor from low vapor pressure explosive materials is a pressing need within the explosives detection community. Of particular importance for reproducibility and widespread acceptance of results is the correlation of such a vapor generator to a National Institute of Standards and Technology (NIST) mass standard. This paper describes an explosives vapor generator recently developed at Varian in which a solid explosive sample in a precision bore glass tube is put in an oven at constant temperature, and vapor diff-using from the top of the tube is entrained in a carrier gas flow. The rate of vapor output is thus dependent on both the equilibrium vapor pressure of the solid at oven temperature and the rate of diffusion up the length of the tube. Correlation to a NIST mass standard is achieved by periodic weighing of the sample tube on a microbalance. We report results obtained with the explosives TNT and RDX. Results for TNT show that the mass output rate is constant over hundreds of hours of continuous use, with outputs of {approximately} 10--2000 pg/sec for oven temperatures in the range of 60--120{degrees}C. Both the mass loss experiments and calibration with an ion mobility spectrometer (IMS) give a TNT mass output value of 85 pg/sec at 79{degrees}C, and this result is supported by transport theory calculations. Mass loss curves for RDX are also linear with time, and show the expected exponential increase of mass output with oven temperature.
This paper presents an implemented algorithm that automatically designs fixtures and assembly pallets to hold three-dimensional parts. The designed fixtures rigidly constrain and locate the part, obey task constraints, are robust to part shape variations, are easy to load, and are economical to produce. The algorithm is guaranteed to find the global optimum solution that satisfies these and other pragmatic conditions. We present the results of the algorithm applied to several practical manufacturing problems. For these complex problems the algorithm typically returns initial high-quality fixture designs in less than two minutes, and identifies th global optimum design in just over an hour.
Multichip modules (MCMs) containing power components need a substrate with excellent heat spreading capability both to avoid hot spots and to move dissipated heat toward the system heat sinks. Polycrystalline diamond is an excellent MCM heat spreading substrate but remains several orders of magnitude too expensive and somewhat more difficult to process than conventional mother-board materials. Today`s power MCMs concentrate on moderately priced silicon wafers and aluminum nitride ceramic with their improved thermal conductivity and good thermal expansion match to power semiconductor components, in comparison to traditional alumina and printed wiring board materials. However, even silicon and AlN substrates are challenged by designers` thermal needs. We report on the fabrication of micro-heat pipes embedded in silicon MCM substrates (5{times}5 cm) by the use of micromachined capillary wick structures and hermetic micro-cavities. This passive microstructure results in more than a 5 times improvement in heat spreading capability of the silicon MCM substrate over a large range of power densities and operating temperatures as compared with silicon alone. Thus diamond-like cooling is possible at silicon prices.
This paper describes a study in which HTML style guides were characterized, compared to established HCI style guides, and evaluated against findings from HCI reviews of web paces and applications. Findings showed little consistency among the 21 HTML style guides assessed, with 75% of recommendations appearing in only one style guide. While there was some overlap, only 20% of HTML relevant recommendations from established style guides were found in HTML style guides. HTML style guides emphasized common look and feel, information display, and navigation issues with little mention of many issues prominent in established style guides such as help, message boxes and data entry. This difference is reinforced by other results showing that HTML style guides addressed concerns of web information content pages with much greater success than web-based applications. It is concluded that while the WWW represents a unique HCI environment, development of HTML style guides has been less rigorous, with issues associated with web-based applications largely ignored.
Piezoelectric actuators provide high frequency, force, and stiffness capabilities along with reasonable Stroke limits, all of which can be used to increase performance levels in precision manufacturing systems. This paper describes two examples of embedding piezoelectric actuators in structural components for vibration control. One example involves suppressing the self excited chatter phenomenon in the metal cutting process of a milling machine and the other involves damping vibrations induced by rigid body stepping of a photolithography platen. Finite element modeling and analyses are essential for locating and sizing the actuators and permit further simulation studies of the response of the dynamic system. Experimental results are given for embedding piezoelectric actuators in a cantilevered bar configuration, which was used as a surrogate machine tool structure. These results are incorporated into a previously developed milling process simulation and the effect of the control on the cutting process stability diagram is quantified. Experimental results are also given for embedding three piezoelectric actuators in a surrogate photolithography platen to suppress vibrations. These results demonstrate the potential benefit that can be realized by applying advances from the field of adaptive structures to problems in precision manufacturing.
Electron cyclotron resonance (ECR) etching of GaN in Cl{sub 2}/H{sub 2}/Ar, C1{sub 2}/SF{sub 6}/Ar, BCl{sub 3}/H{sub 2}/Ar and BCl{sub 3}/SF{sub 6}/Ar plasmas is reported as a function of percent H{sub 2} and SF{sub 6}. GaN etch rates were found to be 2 to 3 times greater in Cl{sub 2}/H{sub 2}/Ar discharges than in BCl{sub 3}/H{sub 2}/Ar discharges independent of the H{sub 2} concentration. In both discharges, the etch rates decreased as the H{sub 2} concentration increased above 10%. When SF{sub 6} was substituted for H{sub 2}, the GaN etch rates in BCl{sub 3}-based plasmas were greater than those for the Cl{sub 2}-based discharges as the SF{sub 6} concentration increased. GaN etch rates were greater in Cl{sub 2}/H{sub 2}/Ar discharges as compared to Cl{sub 2}SF{sub 6}/Ar discharges whereas the opposite trend was observed for BCl{sub 3}-based discharges. Variations in surface morphology and near-surface stoichiometry due to plasma chemistries were also investigated using atomic force microscopy and Auger spectroscopy, respectively.
A ``debris-less`` laser-plasma source (LPS) of extreme-UV radiation has been developed by Kubiak, et al. This is a huge step forward for the extreme-UV lithography program (EUVL) because it will extend the life of the collecting mirrors that face the source. This source has a 300-{mu}m diameter (D source) which is larger than the earlier, {approximately}75-{mu}m diameter plasma balls created on metal targets. The larger source size requires that the Etendu of the system must also be larger if the source radiation is to be used efficiently. A family of 4-mirror, scanning, ring-field lithography cameras has been designed that can be efficiently coupled to a ``debris-less`` LPS. The most promising design has a 0.085-numerical aperture (NA{sub camera}) for printing {approx} 100-nm features. At the image plane it has 13 nm of distortion and a 98% Strehl ratio across its 7-mm wide ring-field ({Delta}r).
VICTORIA-92 is a mechanistic computer code for analyzing fission product behavior within the reactor coolant system (RCS) during a severe reactor accident. It provides detailed predictions of the release of radionuclides and nonradioactive materials from the core and transport of these materials within the RCS. The modeling accounts for the chemical and aerosol processes that affect radionuclide behavior. Coupling of detailed chemistry and aerosol packages is a unique feature of VICTORIA; it allows exploration of phenomena involving deposition, revaporization, and re-entrainment that cannot be resolved with other codes. The purpose of this work is to determine the attenuation of fission products in the RCS and on the secondary side of the steam generator in an accident initiated by a steam generator tube rupture (SGTR). As a class, bypass sequences have been identified in NUREG-1150 as being risk dominant for the Surry and Sequoyah pressurized water reactor (PWR) plants.
When assembling a product, humans, robots, and other automation employ a variety of tools to manipulate, attach, and test parts and subassemblies. This paper proposes a framework lo represent and reason about geometric accessibility constraints for a wide variety of assembly tools. Central to the framework is a use volume encoding a minimum space that must be free in an assembly state to apply a given tool, and placement constraints on where that volume must be placed relative to the parts on which the tool acts. Determining whether a tool can be applied in a given assembly state is an instance of the FINDPLACE problem. In addition, we present more efficient methods lo integrate the framework into assembly planning. For tools that are applied either before or after their target parts are mated, one method preprocesses a single tool application for all possible states of assembly of a product. For tools applied after their target parts are mated, a complementary method guarantees polynomial-time assembly planning. We describe experiments with an initial implementation of the framework and a library of seven tools.
In a virtual environment with multiple participants, it is necessary that the user`s actions be replicated by synthetic human forms. Whole body digitizers would be the most realistic solution for capturing the individual participant`s human form, however the best of the digitizers available are not interactive and are therefore not suitable for real-time interaction. Usually, a limited number of sensors are used as constraints on the synthetic human form. Inverse kinematics algorithms are applied to satisfy these sensor constraints. These algorithms result in slower interaction because of their iterative nature, especially when there are a large number of participants. To support real-time interaction in a virtual environment, there is a need to generate closed for solutions and fast searching algorithms. In this paper, a new closed form solution for the arms (and legs) is developed using two magnetic sensors. In developing this solution, we use the biomechanical relationship between the lower arm and the upper arm to provide an analytical, non-iterative solution, We have also outlined a solution for the whole human body by using up to ten magnetic sensors to break the human skeleton into smaller kinematic chains. In developing our algorithms, we use the knowledge of natural body postures to generate faster solutions for real-time interaction.
The underlying report for this paper evaluates options for using depleted uranium as shielding materials for transport systems for disposal of vitrified high-level waste (VHLW). In addition, economic analyses are presented to compare costs associated with these options to costs, associated with existing and proposed storage, transport, and diposal capabilities. A more detailed evaluation is provided elsewhere. (Yoshimura et al. 1995.)
This paper discusses the core damage frequency (CDF) insights gained by analyzing the results of the Individual Plant Examinations (IPES) for two groups of plants: boiling water reactor (BWR) 3/4 plants with Reactor Core Isolation Cooling systems, and Westinghouse 4-loop plants. Wide variability was observed for the plant CDFs and for the CDFs of the contributing accident classes. On average, transients-with loss of injection, station blackout sequences, and transients with loss of decay heat removal are important contributors for the BWR 3/4 plants, while transients, station blackout sequences, and loss-of-coolant accidents are important for the Westinghouse 4-loop plants. The key factors that contribute to the variability in the results are discussed. The results are often driven by plant-specific design and operational characteristics, but differences in modeling approaches are also important for some accident classes.
Local public opposition to federal bureaucratic decisions has resulted in public agencies rethinking the role of stakeholders in decision making. Efforts to include stakeholders directly in the decision-making process are on the increase. Unfortunately, many attempts to involve members of the public in decisions involving complex technical issues have failed. A key problem has been defining a meaningful role for the public in the process of arriving at a technical decision. This paper describes a successful effort by Sandia National Laboratories (SNL) in New Mexico to involve stakeholders in an important technical decision associated with its Environmental Restoration (ER) Project. The decision was where to locate a Corrective Action Management Unit (CAMU), a facility intended to consolidate and store wastes generated from the cleanup of hazardous waste sites. A formal priority setting process known as the Laboratory Integration Prioritization System (LIPS) was adapted to provide an approach for involving the public. Although rarely applied to stakeholder participation, the LIPS process proved surprisingly effective. It produced a consensus over a selected site and enhanced public trust and understanding of Project activities.
System Certification is a regulatory concept which is intended to expand the scope of radioactive material transport regulations by allowing alternative means for proving compliance with the requisite standards of safety set out in transport regulations. In practice it may allow more stringent requirements in one aspect of the regulations to be substituted for less stringent application in other areas so long as the safety standard provided by regulation is preserved. The concept is widely perceived as the imposition of operational controls in exchange for relaxation of packaging standards, but that is only one possibility in the spectrum of potential actions under a System Certification provision in IAEA or national regulations.
Sandia has made considerable progress in the past year on the MELCOR code for integrated severe nuclear reactor accident analysis. Actinities for the past year are presented.
The design and analysis of a high brightness electron beam experiment under construction at Sandia National Laboratory is presented. The beam energy is 12 MeV, the current 35-40 kA, the rms radius 0.5 mm, and the pulse duration FWHM 40 ns. The accelerator is SABRE a pulsed inductive voltage adder, and the electron source is a magnetically immersed foilless diode. This experiment has as its goal to stretch the technology to the edge and produce the highest possible electron current in a submillimeter radius beam.
The quality assurance requirements that apply to the effort to achieve safe transportation, storage, and disposal of high-level nuclear waste specify that ``design control`` be applied to design activities. That effort also involves extensive scientific investigation activities to, among other things, develop information that may be used in engineering design activities. Individuals who are charged with the implementation of such quality assurance requirements have come to a variety of conclusions about whether there is any firm linkage between design control and the conduct of scientific investigations. This paper contends that there is a reasonable and necessary linkage between ``design control`` and scientific activities, though not a connection that has traditionally been made and not one addressed in the QA standards for radioactive waste management programs.
The III-V nitride-containing semiconductors InN, GaN, and AIN and their ternary alloys are the focus of extensive research for application to visible light emitters and as the basis for high temperature electronics. Recent advances in ion implantation doping of GaN and studies of the effect of rapid thermal annealing up to 1100{degrees}C are making new device structures possible. Both p- and n-type implantation doping of GaN has been achieved using Mg co-implanted with P for p-type and Si-implantation for n-type. Electrical activation was achieved by rapid thermal anneals in excess of 1000{degrees}C. Atomic force microscopy studies of the surface of GaN after a series of anneals from 750 to 1100{degrees}C shows that the surface morphology gets smoother following anneals in Ar or N{sub 2}. The photoluminescence of the annealed samples also shows enhanced bandedge emission for both annealing ambients. For the deep level emission near 2.2 eV, the sample annealed in N{sub 2} shows slightly reduced emission while the sample annealed in Ar shows increased emission. These annealing results suggest a combination of defect interactions occur during the high temperature processing.
Inclusion of renewable energy sources in national and international energy strategies is a key component of a viable global energy future. The global energy balance is going to shift radically in the near future brought about by significant increases in population in China and India, and increases in the energy intensity of developing countries. To better understand the consequences of such global shifts in energy requirements and to develop appropriate energy strategies to respond to these shifts, we need to look at the factors driving choices among supply options by geopolitical consumers and the impact these factors can have on the future energy mix.
High-speed optoelectronic modulators are becoming increasingly important in microwave applications. These devices are necessarily electrically large and hence require velocity matching of the microwave signal to the light. A design methodology for velocity matched electrodes on doped semiconductor devices will be presented. As an example of a successful device design, experimental results on a >10 bandwidth high-efficiency (>15{degrees}/V/mm) Mach Zehnder interferometer will be presented.
Articles in this issue include ``Molten salt corrosion testing,`` ``Pulsed ion beams for thermal surface treatment: Improved corrosion, wear, and hardness properties at low cost,`` ``Unmasking hidden armaments: Superconducting gravity sensor could find underground weapons, bunkers,`` ``Charbroiled burgers, heterocyclic amines, and cancer: Molecular modeling identifies dangerous mutagens,`` ``Revolutionary airbag offers increased safety options,`` ``EcoSys{sup TM}: an expert system for `Green Design` ``, ``Sandia, salt, and oil: Labs` diagnostics and analysis help maintain vital US oil reserve,`` and ``Automated fixture design speeds development for prototypes and production``.
Drilling is ubiquitous in oil, gas, geothermal, minerals, water well, and mining industries. Drilling and well completion account for 25% to 50% of the cost of producing power from geothermal energy. Reduced drilling costs will reduce the cost of electricity produced from geothermal resources. Undoubtedly, there are concepts for advanced drilling systems that have yet to be studied. However, the breadth and depth of previous efforts in this area almost guarantee that any new efforts will at least initially build on an idea or a variation of an idea that has already been investigated. Therefore, a review of previous efforts, coupled with a characterization of viable advanced drilling systems and the current state of technology as it applies to those systems, provide the basis for this study.
In order to understand and evaluate materials for use in Li ion rechargeable battery electrodes, we have modeled the crystal structures of various Mn oxide and Li Mn oxide compounds. We have modeled the MnO{sub 2} polymorphs and several spinels with intermediate compositions based on the amount of Li inserted into the tetrahedral site. 3-D representations of the structures provide a basis for identifying site occupancies, coordinations, Mn valence, order-disorder, and potentially new dopants for enhanced cathode behavior. XRD simulations of the crystal structures provide good agreement with observed patterns for synthesized samples. Ionic modeling of these materials consists of an energy minimization approach using Coulombic, repulsive, and van der Waals interactions. Modeling using electronic polarizabilities (shell model) allows a systematic analysis of changes in lattice energy, cell volume, and the relative stability of doped structures using ions such as Al, Ti, Ni, and Co.
Several novel polysilanes synthesized by the free-radical hydrosilation of oligomeric polyphenylsilane or poly(p-tert- butylphenylsilane) were examined for lithographic behavior. This recently developed route into substituted polysilanes has allowed for the rational design of a variety of polysilanes with a typical chemical properties such as alcohol and aqueous base solubility. Many of the polysilane resists made could be developed in aqueous sodium carbonate and bicarbonate solutions. These materials represent environmentally friendly polysilane resists in both their synthesis and processing.
Results from a chamber study to characterize emissions from combustion of selected pure energetic materials are presented in this paper. The study was carried out as a part of a comprehensive air pathways risk assessment for a propellant and explosive manufacturing facility that engages in open burning methods for manufacturing waste disposal. Materials selected for emissions characterization in this study included both aluminized and non-aluminized composite propellant, a double base propellant and a plastic bonded explosive. Combustion tests in a specialized chamber revealed very low emissions for gaseous products of incomplete combustion such as carbon monoxide and nitrogen oxides. Analysis of gaseous and aerosol emission products for a pre-selected target analyte list that included both volatile and semi-volatile organics revealed either low or non-detectable emissions for the four energetic types tested. Hydrogen chloride was detected as a major emission product from propellants containing ammonium perchlorate. Results from this work reveal that about one-half of the chlorine in the original material is released as hydrogen chloride. Based on earlier work, the balance of the chlorine emissions is expected to be in the form of chlorine gas.
Analysis of processes used for the production of single crystal turbine components reveals significant shortcomings. Inadequate consideration has been made of the fact the system is cooling dominated and that the amount of cooling tends to increase as the emissive cooling area expands during the process. Experimental evidence suggests that during processing, this increased cooling causes the solidification interface to move away from the baffle and become curved. The motion of the interface results in a decrease in the solidification gradient. The combination of these actions can result in variations in PDAS (primary dendrite arm spacing), grain misalignment and the production of defects. It is shown that despite this tendency, microstructural stabilization may be achieved through the use of the heat of fusion as an internal process heat source.
We present calculations of the specific contact resistance for metals to GaN. The calculations include a correct determination of the Fermi level taking into account the effect of the degenerate doping levels, required in creating tunneling ohmic contacts. Using a recently reported improved WKB approximation suitable in representing the depletion width at the metal-semiconductor interface, and a two band k-p model for the effective masses, specific contact resistance was determined as a function of doping concentration. The specific contact resistance was calculated using the best data available for barrier heights, effective masses and dielectric coefficients for GaN. Because the barrier height at the metal-semiconductor interface has a very large effect on the contact resistance and the available data is sketchy or uncertain, the effect of varying the barrier height on the calculated specific contact resistance was investigated. Further, since the III-V nitrides are being considered for high temperature device applications, the specific contact resistance was also determined as a function of temperature.
Lost circulation is a persistent problem in geothermal drilling and often accounts for a significant fraction of the cost of drilling a typical geothermal well. The US Department of Energy sponsors work at Sandia National Laboratories to develop technology for reducing lost circulation costs. This paper describes a downhole tool that has been developed at Sandia for improving the effectiveness and reducing the cost of cementing operations used to treat lost circulation zones. This tool, known as the drillable straddle packer, is a low-cost, disposable assembly used for isolating a loss zone and directing the flow of cement into the zone. This paper describes the tool concept, hardware design, deployment procedure, laboratory testing, and technical issues addressed during the development process.
Variation of model size as determined by grid density is studied for both model refinement and damage detection. In model refinement 3 it is found that a large model with a fine grid is preferable in order to achieve a reasonable correlation between the experimental response and the finite element model. A smaller model falls victim to the inaccuracies of the finite element method. As the grid become increasing finer, the FE method approaches an accurate representation. In damage detection the FE method is only a starting point. The model is refined with a matrix method which doesn`t retain the FE approximation, therefore a smaller model that captures most of the dynamics of the structure can be used and is preferable.
This paper presents a high bandwidth fiber-optic communication system intended for post accident recovery of weapons. The system provides bi-directional multichannel, and multi-media communications. Two smaller systems that were developed as direct spin-offs of the larger system are also briefly discussed.
To model the shock-induced behavior of porous or damaged energetic materials, a nonequilibrium mixture theory has been developed and incorporated into the shock physics code, CTH. Foundation for this multiphase model is based on a continuum mixture formulation given by Baer and Nunziato. In this nonequilibrium approach, multiple thermodynamic and mechanics fields are resolved including the effects of material relative motion, rate-dependent compaction, drag and heat transfer interphase effects and multiple-step combustion. Benchmark calculations are presented which simulate low-velocity piston impact on a propellant porous bed and experimentally-measured wave features are well replicated with this model. This mixture model introduces micromechanical models for the initiation and growth of reactive multicomponent flow which are key features to describe shock initiation and self-accelerated deflagration-to-detonation combustion behavior. To complement one-dimensional simulation, two dimensional numerical simulations are presented which indicate wave curvature effects due to the loss of wall confinement.
This contribution presents some lessons learned in the development of cooperation and knowledge transfer across the numerous interfaces involved in managing a corporate research laboratory.
This contribution addresses requirements for ATM signaling channel authentication. Signaling channel authentication is an ATM security service that binds an ATM signaling message to its source. By creating this binding, the message recipient, and even a third party, can confidently verify that the message originated from its claimed source. This provides a useful mechanism to mitigate a number of threats. For example, a denial of service attack which attempts to tear-down an active connection by surreptitiously injecting RELEASE or DROP PARTY messages could be easily thwarted when authenticity assurances are in place for the signaling channel. Signaling channel authentication could also be used to provide the required auditing information for accurate billing which is impervious to repudiation. Finally, depending on the signaling channel authentication mechanism, end-to-end integrity of the message (or at least part of it) can be provided. None of these capabilities exist in the current specifications.
Crystal lattices are infinite periodic graphs that occur naturally in a variety of geometries and which are of fundamental importance in polymer science. Discrete models of protein folding use crystal lattices to define the space of protein conformations. Because various crystal lattices provide discretizations of the same physical phenomenon, it is reasonable to expect that there will exist ``invariants`` across lattices that define fundamental properties of protein folding process; an invariant defines a property that transcends particular lattice formulations. This paper identifies two classes of invariants, defined in terms of sublattices that are related to the design of algorithms for the structure prediction problem. The first class of invariants is, used to define a master approximation algorithm for which provable performance guarantees exist. This algorithm can be applied to generalizations of the hydrophobic-hydrophilic model that have lattices other than the cubic lattice, including most of the crystal lattices commonly used in protein folding lattice models. The second class of invariants applies to a related lattice model. Using these invariants, we show that for this model the structure prediction problem is intractable across a variety of three-dimensional lattices. It`` turns out that these two classes of invariants are respectively sublattices of the two- and three-dimensional square lattice. As the square lattices are the standard lattices used in empirical protein folding` studies, our results provide a rigorous confirmation of the ability of these lattices to provide insight into biological phenomenon. Our results are the first in the literature that identify algorithmic paradigms for the protein structure prediction problem which transcend particular lattice formulations.
Approximately 13% by volume of the US Department of Energy (DOE) current backlog of radioactive waste is characterized as high-level waste. Transportation of these wastes requires that the waste package have adequate shielding against gamma radiation. This project investigates the radiation shielding performance of titanium and depleted uranium, which have been proposed for use as gamma shielding materials in DOE transportation packages, by experimentally determining their buildup factors. Buildup factors are important in shield heating and radiation damage calculations. A point-isotropic-source type of buildup factor is the most useful for application in the point-kernal approach utilized in many simple shielding codes. The point-kernal method provides reasonable results for cases in which the shield is made of one solid material and the source can be approximated as one homogeneous material. The point-kernal method has been incorporated into a large number of shielding codes treating three-dimensional geometry using buildup factor data in some form. Buildup factors vary with a number of parameters such as the distance of penetration through the attenuating medium; the geometric configuration of the attenuating medium, source and detector position; the composition of the medium; the detector response function; and the energy and direction of emission of the source photons, ideally taken to be monoenergetic and isotropic.
It is likely that the ongoing process to produce the 1996 version of the IAEA Regulation for the Safe Transport of Radioactive Materials, IAEA Safety Series 6(SS 6) will result in a more stringent package qualification standard for air transport of large quantities of radioactive materials (RAM) than is included in the 1990 version. During the process to define the scope of the new requirements there was extensive discussion of their impact on, and application to, fissile material package qualification criteria. Since fissile materials are shipped in a variety of packaging ranging from exempt to Type B, each packaging of each type must be evaluated for its ability to maintain subcriticality both alone and in arrays and in both damaged and undamaged condition. In the 1990 version of SS 6 "damaged" means the condition of a package after it had undergone the "tests for demonstrating the ability to withstand accident conditions in transport," i.e., Type B qualification tests. These tests conditions are typical of severe accidents in surface modes but are less severe than air mode qualification test environments to be applied to Type C packages. As a result, questions arose about the need for a corresponding change in the 1996 SS 6 to define "damaged" to include the Type C test regime for criticality evaluations of fissile packages in air transport.
Intense, pulsed ion beams were used to melt and rapidly resolidify Types 316F, 316L and sensitized 304 stainless steel surfaces to eliminate the negative effects of microstructural heterogeneity on localized corrosion resistance. Anodic polarization curves determined for 316F and 316L showed that passive current densities were reduced and pitting potentials were increased due to ion beam treatment. Type 304 samples sensitized at 600°C for 100 h showed no evidence of grain boundary attack when surfaces were ion beam treated. Equivalent ion beam treatments were conducted with a 6061-T6 aluminum alloy. Electrochemical impedance experiments conducted with this alloy exposed to an aerated chloride solution showed that the onset of pitting was delayed compared to untreated control samples.
Inorganic polycrystalline hydrotalcite, Li2[Al2(OH)6]2·CO3·3H2O, coatings can be formed on aluminum and aluminum alloys by exposure to alkaline lithium carbonate solutions. This process is conducted using methods similar to traditional chromate conversion coating procedures, but does not use or produce toxic chemicals. The coating provides anodic protection and delays the onset of pitting during anodic polarization. Cathodic reactions are also inhibited which may also contribute to corrosion protection. Recent studies have shown that corrosion resistance can be increased by sealing hydrotalcite coated surfaces to transition metal salt solutions including Ce(NO3)3, KMnO4 and Li2MoO4. Results from these studies are also reported.
The Department of Energy's (DOE) non-nuclear facilities generally require only a qualitative accident analysis to assess facility risks in accordance with DOE Order 5481.1B, Safety Analysis and Review System [DOE, 1986]. Achieving a meaningful qualitative assessment of risk necessarily requires the use of suitable non-numerical assessment criteria. Typically, the methods and criteria for assigning facility specific accident scenarios to the qualitative severity and likelihood classification system in the DOE order requires significant judgement in many applications. Systematic methods for more consistently assigning the total accident scenario frequency and associated consequences are required to substantiate and enhance future risk ranking between various activities at Sandia National Laboratories (SNL). Currently, Sandia National Laboratories' Risk Management and National Environmental Policy Act (NEPA) department has initiated a project to develop improved criteria for performing qualitative risk assessments in accordance with the DOE order requirements. Products of this effort are an improved set of qualitative descriptions that permit: (1) definition of the severity for both technical and programmatic consequences that may result from a variety of accident scenarios and, (2) qualitative representation of the likelihood of occurrence. These sets of descriptions are intended to provide, in a qualitative manner, definitions that can be compared with the DOE criteria for assessing facility risks.
Water determination in semiconductor process gases is desirable in order to extend the life of gas delivery systems and improve wafer yields. We review our work in applying Fourier transform infrared spectroscopy to this problem, where a 10 ppb detection limit has been demonstrated for water in N2, HCl, and HBr. The potential for optical determination of other contaminants in these gases is discussed. Also, alternative optical spectroscopic approaches are briefly described. Finally, we discuss methods for dealing with interference arising from water in the instrument beam path, yet outside the sample cell.
Liquid properties are measured from the changes they induce in the resonant frequency and damping of thickness-shear mode quartz resonators. A smooth-surfaced resonator viscously entrains the contacting fluid and responds to the density-viscosity product. Separation of density and viscosity is accomplished using two devices: one with a smooth surface and one with a corrugated surface that traps fluid. By observing the difference in stored and dissipated energies in the contacting fluid, its non-Newtonian characteristics can also be determined.
American Society of Mechanical Engineers, Pressure Vessels and Piping Division (Publication) PVP
Spray, S.D.; Cooper, J.A.
The use of passive safety concepts to achieve very high levels of assured safety is described. Some background on safety implementations and safety assessment methodology are reviewed, the salient features of passive safety implementations are demonstrated, and some applications for which passive safety is particularly appropriate are suggested. Included are requirements on components and processes, and design principles. Critical agents (humans, stress, equipment, and timing) are some of the pertinent factors considered.
This paper reviews the evolution of polymer electrolytes from the conventional PEO-LiX salt complexes to the more conducting polyphosphazene and copolymers, gelled electrolytes etc. It also reviews the various chemical approaches including modifying PEO to synthesizing complicated polymer architecture. In addition, it discusses the effect of various lithium salts on the conductivity of PEO-based polymers. Charge/discharge and cycle life data of polymer cells containing oxide and chalcogenide cathodes and lithium (Li) anode will be reviewed. Finally, future research directions to improve the electrolyte properties will be presented.
Conference Proceedings - Lasers and Electro-Optics Society Annual Meeting-LEOS
Lear, K.L.
Structure based on aluminum-oxide layers have led to dramatic improvements in VCSELs such as power conversion efficiencies in excess of 50% and threshold currents below 10μA. The low index, insulating aluminum-oxide, formed by selective wet thermal oxidation of AlGaAs, serves as an effective index guide as well as a current injection aperture. This paper presents data on devices with either two aligned apertures above and below the active region or with a single effective aperture above the active region leading to slope efficiencies of up to 1W/A.
Proceedings of SPIE - The International Society for Optical Engineering
Eaton, W.P.; Smith, J.H.
A surface micromachined pressure sensor array has been designed and fabricated. The sensors are based upon deformable, silicon nitride diaphragms with polysilicon piezoresistors. Absolute pressure is detected by virtue of reference pressure cavities underneath the diaphragms. For this type of sensor, design tradeoffs must be made among allowable diaphragm deflection, diaphragm size, and desirable pressure ranges. Several fabrication issues were observed and addressed. Offset voltage, sensitivity, and nonlinearity of 100 μm diameter sensors were measured.
The effect of solvent addition on the phase separation, mechanical properties and thermal stability of silica/siloxane composite materials prepared by in situ reinforcement was examined. The addition of a solvent enhances the miscibility of the reinforcement precursor, a partial hydrolyzate of tetraethoxysilane (TEOS-PH), with the polydimethylsiloxane (PDMS) polymer. As a result, the phase separation at the micron level, termed the large-scale structure, diminished in size. This decrease in particle size resulting from the addition of moderate amounts of solvent was accompanied by an improvement in the mechanical properties. However, solvent addition in the excess of 50 weight percent led to a decrease in mechanical properties even though the large-scale structure continued to diminish in size. Small Angle X-Ray Scattering (SAXS) was used to examine the angstrom level or small-scale structure. This small-scale structure was only affected by the presence of solvent, not the amount. The silica/siloxane composite materials showed the same thermal transition temperatures as the original PDMS material.
The preparation of light emitting diodes employing a new class of materials, 5,10-dihetera-5,10-dihydro-indeno[3,2b]indenes, as hole transport agents is described. These materials have been found to be more resistant to degradation by singlet oxygen than a poly(p-phenylene vinylene) (PPV) derivative.
Extensions of the German LIGA process have brought about fabrication capability suitable for cost effective production of precision engineered components. The process attributes allow fabrication of mechanical components which are not capable of being made via conventional subtractive machining methods. Two process improvements have been responsible for this extended capability which involve the areas of thick photoresist application and planarization via precision lapping. Application of low-stress x-ray photoresist has been achieved using room temperature solvent bonding of a preformed photoresist sheet. Precision diamond lapping and polishing has provided a flexible process for the planarization of a wide variety of electroplated metals in the presence of photoresist. Exposure results from the 2.5 GeV National Synchrotron Light Source storage ring at Brookhaven National Laboratory have shown that structural heights of several millimeter and above are possible. The process capabilities are also well suited for microactuator fabrication. Linear and rotational magnetic microactuators have been constructed which use coil winding technology with LIGA fabricated coil forms. Actuator output forces of 1 milliNewton have been obtained with power dissipation on the order of milliWatts. A rotational microdynamometer system which is capable of measuring torque-speed data is also discussed.
Plasma processes for etching and desmear of electronic components and printed wiring boards (PWB) are difficult to predict and control. Non-uniformity of most plasma processes and sensitivity to environmental changes make it difficult to maintain process stability from day to day. To assure plasma process performance, weight loss coupons or post-plasma destructive testing must be used. The problem with these techniques is that they are not real-time methods and do not allow for immediate diagnosis and process correction. These tests often require scrapping some fraction of a batch to insure the integrity of the rest. Since these tests verify a successful cycle with post-plasma diagnostics, poor test results often determine that a batch is substandard and the resulting parts unusable. These tests are a costly part of the overall fabrication cost. A more efficient method of testing would allow for constant monitoring of plasma conditions and process control. Process anomalies should be detected and corrected before the parts being treated are damaged. Real time monitoring would allow for instantaneous corrections. Multiple site monitoring would allow for process mapping within one system or simultaneous monitoring of multiple systems. Optical emission spectroscopy conducted external to the plasma apparatus would allow for this sort of multifunctional analysis without perturbing the glow discharge. In this paper, optical emission spectroscopy for non-intrusive, in situ process control will be explored along with applications of this technique towards process control, failure analysis and endpoint determination.