Magnesocene (biscyclopentadienylmagnesium) is a common precursor used for the p-type doping of GaN and other group III nitride materials. Unfortunately, difficulties remain with predictably controlling the incorporation of Mg during metal organic chemical vapor deposition (MOCVD) film growth, which often exhibits poorly understood "memory effects." Although the formation of a reaction product between magnesocene and ammonia has been previously speculated, one has never been experimentally isolated or identified. We have spectroscopically observed and identified, for the first time, the adducts formed between magnesocene and ammonia. Density functional theory (DFT) quantum chemistry calculations have also been performed on the system to determine the structures and energetics of the reaction products. It was found that ammonia can form condensable Lewis acid - base complexes with magnesocene in both 1:1 and 2:1 ratios (i.e., NH 3-MgCp 2 and (NH 3) 2-MgCp 2) via nucleophilic attack of NH 3 at the positively charged Mg center of MgCp 2. Adduct formation is reversible, and the 1:1 and 2:1 products can be converted to one another by controlling the NH 3 partial pressure. The formation and condensation of both adducts at room temperature is the probable parasitic source that leads to many of the observed Mg incorporation difficulties during the p-type doping of group III nitride materials.
The FAA's Airworthiness Assurance NDI Validation Center, in conjunction with the Commercial Aircraft Composite Repair Committee, developed a set of composite reference standards to be used in NDT equipment calibration for accomplishment of damage assessment and post-repair inspection of all commercial aircraft composites. In this program, a series of NDI tests on a matrix of composite aircraft structures and prototype reference standards were completed in order to minimize the number of standards needed to carry out composite inspections on aircraft. Two tasks, related to composite laminates and non-metallic composite honeycomb configurations, were addressed. A suite of 64 honeycomb panels, representing the bounding conditions of honeycomb construction on aircraft, was inspected using a wide array of NDI techniques. An analysis of the resulting data determined the variables that play a key role in setting up NDT equipment. This has resulted in a set of minimum honeycomb NDI reference standards that include these key variables. A sequence of subsequent tests determined that this minimum honeycomb reference standard set is able to fully support inspections over the full range of honeycomb construction scenarios found on commercial aircraft. In the solid composite laminate arena, G11 Phenolic was identified as a good generic solid laminate reference standard material. Testing determined matches in key velocity and acoustic impedance properties, as well as, low attenuation relative to carbon laminates. Furthermore, comparisons of resonance testing response curves from the G11 Phenolic NDI reference standard was very similar to the resonance response curves measured on the existing carbon and fiberglass laminates. NDI data shows that this material should work for both pulse-echo (velocity-based) and resonance (acoustic impedance-based) inspections.
Cross-sections for the elastic recoil of hydrogen isotopes, including tritium, have been measured for 4He2+ ions in the energy range of 9.0-11.6 MeV. These cross-sections have been measured at a scattering angle of 30° in the laboratory frame. Cross-sections were measured by allowing a 4He2+ beam to fall incident on solid targets of ErH2, ErD2 and ErT2, each of 500 nm nominal thickness and known areal densities of H, D, T and Er. The uncertainty in each cross-section is estimated to be ±3.2%. Published by Elsevier B.V.
The effect of the density and in-plane distribution of interfacial interactions on crack initiation in an epoxy-silicon joint was studied in nominally pure shear loading. Well-defined combinations of strong (specific) and weak (nonspecific) interactions were created using self-assembling monolayers. The in-plane distribution of strong and weak interactions was varied by employing two deposition methods: depositing mixtures of molecules with different terminal groups resulting in a nominally random distribution, and depositing methyl-terminated molecules in domains defined lithographically with the remaining area interacting through strong acid-base interactions. The two distributions lead to very different fracture behavior. For the case of the methyl-terminated domains (50 μm on a side) fabricated lithographically, the joint shear strength varies almost linearly with the area fraction of strongly interacting sites. From this we infer that cracks nucleate on or near the interface over nearly the entire range of bonded area fraction and do so at nearly the same value of local stress (load/bonded area). We postulate that the imposed heterogeneity in interfacial interactions results in heterogeneous stress and strain fields within the epoxy in close proximity to the interface. Simply, the bonded areas carry load while the methyl terminated domains carry negligible load. Stress is amplified adjacent to the well-bonded regions (and reduced adjacent to the poorly bonded regions), and this leads to crack initiation by plastic deformation and chain scission within the epoxy near the interface. For the case of mixed monolayers, the dependence is entirely different. At low areal density of strongly interacting sites, the joint shear strength is below the detection limit of our transducer for a significant range of mixed monolayer composition. With increasing density of strongly interacting sites, a sharp increase in joint shear strength occurs at a methyl terminated area fraction of roughly 0.90. We postulate that this coincides with the onset of yielding in the epoxy. For methyl-terminated area fractions less than 0.85, the joint shear strength becomes independent of the interfacial interactions. This indicates that fracture no longer initiates on the interface but away from the interface by a competing mechanism, likely plastic deformation and chain scission within the bulk epoxy. The data demonstrate that the in-plane distribution of interaction sites alone can affect the location of crack nucleation and the far-field stress required.
This report describes the methodology and results of a project to develop a neural network for the prediction of the measured hydraulic conductivity or transmissivity in a series of boreholes at the Tono, Japan study site. Geophysical measurements were used as the input to EL feed-forward neural network. A simple genetic algorithm was used to evolve the architecture and parameters of the neural network in conjunction with an optimal subset of geophysical measurements for the prediction of hydraulic conductivity. The first attempt was focused on the estimation of the class of the hydraulic conductivity, high, medium or low, from the geophysical logs. This estimation was done while using the genetic algorithm to simultaneously determine which geophysical logs were the most important and optimizing the architecture of the neural network. Initial results showed that certain geophysical logs provided more information than others- most notably the 'short-normal', micro-resistivity, porosity and sonic logs provided the most information on hydraulic conductivity. The neural network produced excellent training results with accuracy of 90 percent or greater, but was unable to produce accurate predictions of the hydraulic conductivity class. The second attempt at prediction was done using a new methodology and a modified data set. The new methodology builds on the results of the first attempts at prediction by limiting the choices of geophysical logs to only those that provide significant information. Additionally, this second attempt uses a modified data set and predicts transmissivity instead of hydraulic conductivity. Results of these simulations indicate that the most informative geophysical measurements for the prediction of transmissivity are depth and sonic log. The long normal resistivity and self potential borehole logs are moderately informative. In addition, it was found that porosity and crack counts (clear, open, or hairline) do not inform predictions of hydraulic transmissivity.
A novel layered manganese(II) phosphate, Mn3(PO 4)4·2(H3NCH2CH 2)3N·6(H2O), has been synthesized solvothermally using tris(2-aminoethyl)amine (TREN) as a template. The structure was solved ab initio using X-ray powder diffraction data and confirmed by molecular modeling. The compound was further characterized by SEM, IR spectroscopy, photoluminescence, and elemental and thermal analysis. The compound crystallizes in the trigonal space group P3c1 with a = 8.8706(4) Å, c = 26.158(2) Å, and V = 1782.6(2) Å3. The structure consists of layers of comer sharing Mn(II)O4 and PO 4 tetrahedra forming infinite [Mn3(PO4) 4]6- macroanions with 4.6 net topology, sandwiched by layers of TREN and water molecules. The protonated TREN molecules provide charge balancing for the inorganic sheets; the interlayer stability is accomplished mainly by a network of hydrogen bonds between water molecules and the inorganic macroanions. This hybrid organic/inorganic layered material can be reversibly dehydrated.
ITS is a powerful and user-friendly software package permitting state of the art Monte Carlo solution of linear time-independent couple electron/photon radiation transport problems, with or without the presence of macroscopic electric and magnetic fields of arbitrary spatial dependence. Our goal has been to simultaneously maximize operational simplicity and physical accuracy. Through a set of preprocessor directives, the user selects one of the many ITS codes. The ease with which the makefile system is applied combines with an input scheme based on order-independent descriptive keywords that makes maximum use of defaults and internal error checking to provide experimentalists and theorists alike with a method for the routine but rigorous solution of sophisticated radiation transport problems. Physical rigor is provided by employing accurate cross sections, sampling distributions, and physical models for describing the production and transport of the electron/photon cascade from 1.0 GeV down to 1.0 keV. The availability of source code permits the more sophisticated user to tailor the codes to specific applications and to extend the capabilities of the codes to more complex applications. Version 5.0, the latest version of ITS, contains (1) improvements to the ITS 3.0 continuous-energy codes, (2)multigroup codes with adjoint transport capabilities, and (3) parallel implementations of all ITS codes. Moreover the general user friendliness of the software has been enhanced through increased internal error checking and improved code portability.
As part of the U.S. Department of Energy's Wind Partnerships for Advanced Component Technologies (WindPACT) program, Global Energy Concepts, LLC is performing a Blade System Design Study (BSDS) concerning innovations in materials, processes and structural configurations for application to wind turbine blades in the multi-megawatt range. The BSDS Volume I project report addresses issues and constraints identified to scaling conventional blade designs to the megawatt size range, and evaluated candidate materials, manufacturing and design innovations for overcoming and improving large blade economics. The current report (Volume II), presents additional discussion of materials and manufacturing issues for large blades, including a summary of current trends in commercial blade manufacturing. Specifications are then developed to guide the preliminary design of MW-scale blades. Using preliminary design calculations for a 3.0 MW blade, parametric analyses are performed to quantify the potential benefits in stiffness and decreased gravity loading by replacement of a baseline fiberglass spar with carbon-fiberglass hybrid material. Complete preliminary designs are then presented for 3.0 MW and 5.0 MW blades that incorporate fiberglass-to-carbon transitions at mid-span. Based on analysis of these designs, technical issues are identified and discussed. Finally, recommendations are made for composites testing under Part I1 of the BSDS, and the initial planned test matrix for that program is presented.
Resin transfer molding (RTM) is a closed mold process for making composite materials. It has the potential to produce parts more cost effectively than hand lay-up or other methods. However, fluid flow tends to be unpredictable and parts the size of a wind turbine blade are difficult to engineer without some predictive method for resin flow. There were five goals of this study. The first was to determine permeabilities for three fabrics commonly used for RTM over a useful range of fiber volume fractions. Next, relations to estimate permeabilities in mixed fabric lay-ups were evaluated. Flow in blade substructures was analyzed and compared to predictions. Flow in a full-scale blade was predicted and substructure results were used to validate the accuracy of a full-scale blade prediction.
This study presents results obtained for four hybrid designs of the Northern Power Systems (NPS) 9.2-meter prototype version of the ERS-100 wind turbine rotor blade. The ERS-100 wind turbine rotor blade was designed and developed by TPI composites. The baseline design uses e-glass unidirectional fibers in combination with {+-}45-degree and random mat layers for the skin and spar cap. This project involves developing structural finite element models of the baseline design and carbon hybrid designs with and without twist-bend coupling. All designs were evaluated for a unit load condition and two extreme wind conditions. The unit load condition was used to evaluate the static deflection, twist and twist-coupling parameter. Maximum deflections and strains were determined for the extreme wind conditions. Linear and nonlinear buckling loads were determined for a tip load condition. The results indicate that carbon fibers can be used to produce twist-coupled designs with comparable deflections, strains and buckling loads to the e-glass baseline.
The goal of this project was to identify a viable, non-destructive methodology for the detection of cracks in electrically poled piezoelectric ceramics used in neutron generator power supply units. The following methods were investigated: Impedance Spectroscopy, Scanning Acoustic Microscopy, Lock-in Thermography, Photo-acoustic Microscopy, and Scanned Vicinal Light. In addition to the exploration of these techniques for crack detection, special consideration was given to the feasibility of integrating these approaches to the Automatic Visual Inspection System (AVIS) that was developed for mapping defects such as chips, pits and voids in piezoelectric ceramic components. Scanned Vicinal Light was shown to be the most effective method of automatically detecting and quantifying cracks in ceramic components. This method is also very effective for crack detection in other translucent ceramics.
The National Nuclear Security Administration (NNSA) Office of Nonproliferation Policy sponsored an international biosecurity symposium at Sandia National Laboratories (SNL). The event, entitled 'Securing High Consequence Pathogens and Toxins', took place from February 1 to February 6, 2004 and was hosted by Dr. Reynolds M. Salerno, Principal Member of the Technical Staff and Program Manager of the Biosecurity program at Sandia. Over 60 bioscience and policy experts from 14 countries gathered to discuss biosecurity, a strategy aimed at preventing the theft and sabotage of dangerous pathogens and toxins from bioscience facilities. Presentations delivered during the symposium were interspersed with targeted discussions that elucidated, among other things, the need for subsequent regional workshops on biosecurity, and a desire for additional work toward developing international biosecurity guidelines.
This document describes ROCIT, a neural-inspired object recognition algorithm based on a rank-order coding scheme that uses a light-weight neuron model. ROCIT coarsely simulates a subset of the human ventral visual stream from the retina through the inferior temporal cortex. It was designed to provide an extensible baseline from which to improve the fidelity of the ventral stream model and explore the engineering potential of rank order coding with respect to object recognition. This report describes the baseline algorithm, the model's neural network architecture, the theoretical basis for the approach, and reviews the history of similar implementations. Illustrative results are used to clarify algorithm details. A formal benchmark to the 1998 FERET fafc test shows above average performance, which is encouraging. The report concludes with a brief review of potential algorithmic extensions for obtaining scale and rotational invariance.
Sandia National Laboratories, California (SNL/CA) is a government-owned/contractor-operated laboratory. Sandia Corporation, a Lockheed Martin Company, operates the laboratory for the Department of Energy's (DOE) National Nuclear Security Administration. The DOE Sandia Site Office oversees operations at the site, using Sandia Corporation as a management and operating contractor. This Site Environmental Report for 2003 was prepared in accordance with DOE Order 231.1A. The report provides a summary of environmental monitoring information and compliance activities that occurred at SNL/CA during calendar year 2003. General site and environmental program information is also included.
Obfuscation protects software by making the code more difficult to understand. We review a collection of obfuscation techniques. We then consider what would constitute a theory of obfuscation. Several possibilities that could lead to such a theory are explored.
This document is intended to contain a detailed description of the mathematical formulation of Xyce, a massively parallel SPICE-style circuit simulator developed at Sandia National Laboratories. The target audience of this document are people in the role of 'service provider'. An example of such a person would be a linear solver expert who is spending a small fraction of his time developing solver algorithms for Xyce. Such a person probably is not an expert in circuit simulation, and would benefit from an description of the equations solved by Xyce. In this document, modified nodal analysis (MNA) is described in detail, with a number of examples. Issues that are unique to circuit simulation, such as voltage limiting, are also described in detail.
The objective is a significant advancement in the state-of-the-art of accelerometer design for tactical grade (or better) applications. The design goals are <1 milli-G bias stability across environments and $200 cost. This quantum leap in performance improvement and cost reduction can only be achieved by a radical new approach, not incremental improvements to existing concepts. This novel levitated closed-loop accelerometer is implemented as a hybrid micromachine. The hybrid approach frees the designer from the limitations of any given monolithic process and dramatically expands the available design space. The design can be tailored to the dynamic range, resolution, bandwidth, and environmental requirements of the application while still preserving all of the benefits of monolithic MEMS fabrication - extreme precision, small size, low cost, and low power. An accelerometer was designed and prototype hardware was built, driving the successful development and refinement of several 'never been done before' fabrication processes. Many of these process developments are commercially valuable and are key enablers for the realization of a wide variety of useful micro-devices. While controlled levitation of a proof mass has yet to be realized, the overall design concept remains sound. This was clearly demonstrated by the stable and reliable closed-loop control of a proof mass at the test structure level. Furthermore, the hybrid MEMS implementation is the most promising approach for achieving the ambitious cost and performance targets. It is strongly recommended that Sandia remain committed to the original goal.
This document is the final report for the Compressed Air Energy Storage Monitoring to Support Refrigerated-Mined Rock Cavern Technology (CAES Monitoring to Support RMRCT) (DE-FC26-01NT40868) project to have been conducted by CAES Development Co., along with Sandia National Laboratories. This document provides a final report covering tasks 1.0 and subtasks 2.1, 2.2, and 2.5 of task 2.0 of the Statement of Project Objectives and constitutes the final project deliverable. The proposed work was to have provided physical measurements and analyses of large-scale rock mass response to pressure cycling. The goal was to develop proof-of-concept data for a previously developed and DOE sponsored technology (RMRCT or Refrigerated-Mined Rock Cavern Technology). In the RMRCT concept, a room and pillar mine developed in rock serves as a pressure vessel. That vessel will need to contain pressure of about 1370 psi (and cycle down to 300 psi). The measurements gathered in this study would have provided a means to determine directly rock mass response during cyclic loading on the same scale, under similar pressure conditions. The CAES project has been delayed due to national economic unrest in the energy sector.
This SAND report is the final report on Sandia's Grand Challenge LDRD Project 27328, 'A Revolution in Lighting -- Building the Science and Technology Base for Ultra-Efficient Solid-state Lighting.' This project, which for brevity we refer to as the SSL GCLDRD, is considered one of Sandia's most successful GCLDRDs. As a result, this report reviews not only technical highlights, but also the genesis of the idea for Solid-state Lighting (SSL), the initiation of the SSL GCLDRD, and the goals, scope, success metrics, and evolution of the SSL GCLDRD over the course of its life. One way in which the SSL GCLDRD was different from other GCLDRDs was that it coincided with a larger effort by the SSL community - primarily industrial companies investing in SSL, but also universities, trade organizations, and other Department of Energy (DOE) national laboratories - to support a national initiative in SSL R&D. Sandia was a major player in publicizing the tremendous energy savings potential of SSL, and in helping to develop, unify and support community consensus for such an initiative. Hence, our activities in this area, discussed in Chapter 6, were substantial: white papers; SSL technology workshops and roadmaps; support for the Optoelectronics Industry Development Association (OIDA), DOE and Senator Bingaman's office; extensive public relations and media activities; and a worldwide SSL community website. Many science and technology advances and breakthroughs were also enabled under this GCLDRD, resulting in: 55 publications; 124 presentations; 10 book chapters and reports; 5 U.S. patent applications including 1 already issued; and 14 patent disclosures not yet applied for. Twenty-six invited talks were given, at prestigious venues such as the American Physical Society Meeting, the Materials Research Society Meeting, the AVS International Symposium, and the Electrochemical Society Meeting. This report contains a summary of these science and technology advances and breakthroughs, with Chapters 1-5 devoted to the five technical task areas: 1 Fundamental Materials Physics; 2 111-Nitride Growth Chemistry and Substrate Physics; 3 111-Nitride MOCVD Reactor Design and In-Situ Monitoring; 4 Advanced Light-Emitting Devices; and 5 Phosphors and Encapsulants. Chapter 7 (Appendix A) contains a listing of publications, presentations, and patents. Finally, the SSL GCLDRD resulted in numerous actual and pending follow-on programs for Sandia, including multiple grants from DOE and the Defense Advanced Research Projects Agency (DARPA), and Cooperative Research and Development Agreements (CRADAs) with SSL companies. Many of these follow-on programs arose out of contacts developed through our External Advisory Committee (EAC). In h s and other ways, the EAC played a very important role. Chapter 8 (Appendix B) contains the full (unedited) text of the EAC reviews that were held periodically during the course of the project.
Procedures to predict the reliability of electrical circuits are discussed. Three cases are introduced and discussed. In Case 1, an analyst predicts the probability of any failure in the intended relations between circuit inputs and circuit outputs. In Case 2, an analyst predicts the probability that specified unintended outputs would occur. In Case 3, an analyst considers coupling between circuits. Logic models are given for the three cases, and sources of failure probabilities of components are mentioned. Methods of analysis are given, software tools are mentioned, and recommendations for presentation and review of results are discussed.
This paper describes an 'Annex', or task, that is part of the International Energy Agency's Geothermal Implementing Agreement. Annex 7 is aimed at improving the state of the art in geothermal drilling, and has three subtasks: an international database on drilling cost and performance, a 'best practices' drilling handbook, and collaborative testing among participating countries. Drilling is an essential and expensive part of geothermal exploration, production, and maintenance. High temperature, corrosive fluids, and hard, fractured formations increase the cost of drilling, logging, and completing geothermal wells, compared to oil and gas. Cost reductions are critical because drilling and completing the production and injection well field can account for approximately half the capital cost for a geothermal power project. Geothermal drilling cost reduction can take many forms, e.g., faster drilling rates, increased bit or tool life, less trouble (twist-offs, stuck pipe, etc.), higher per-well production through multilaterals, and others. Annex 7 addresses all aspects of geothermal well construction, including developing a detailed understanding of worldwide geothermal drilling costs, understanding geothermal drilling practices and how they vary across the globe, and development of improved drilling technology. Objectives for Annex 7 include: (1) Quantitatively understand geothermal drilling costs and performance from around the world and identify ways to improve costs, performance, and productivity. (2) Identify and develop new and improved technologies for significantly reducing the cost of geothermal well construction. (3) Inform the international geothermal community about these drilling technologies. (4) Provide a vehicle for international cooperation, collaborative field tests, and data sharing toward the development and demonstration of improved geothermal drilling technology.
The Radiatively Driven Hypersonic Wind Tunnel (RDHWT) program requires an unprecedented 2-3 MeV electron beam energy source at an average beam power of approximately 200MW. This system injects energy downstream of a conventional supersonic air nozzle to minimize plenum temperature requirements for duplicating flight conditions above Mach 8 for long run-times. Direct-current electron accelerator technology is being developed to meet the objectives of a radiatively driven Mach 12 wind tunnel with a free stream dynamic pressure q=2000 psf. Due to the nature of research and industrial applications, there has never been a requirement for a single accelerator module with an output power exceeding approximately 500 kW. Although a 200MW module is a two-order of magnitude extrapolation from demonstrated power levels, the scaling of accelerator components to this level appears feasible. Accelerator system concepts are rapidly maturing and a clear technology development path has been established. Additionally, energy addition experiments have been conducted up to 800 kW into a supersonic airflow. This paper will discuss progress in the development of electron beam accelerator technology as an energy addition source for the RDHWT program and results of electron beam energy addition experiments conducted at Sandia National Laboratories.
The adsorption of myoglobin to Langmuir monolayers of a metal-chelating lipid in crystalline phase was studied using neutron and X-ray reflectivity (NR and XR) and grazing incidence X-ray diffraction (GIXD). In this system, adsorption is due to the interaction between chelated divalent copper or nickel ions and the histidine moieties at the outer surface of the protein. The binding interaction of histidine with the Ni-IDA complex is known to be much weaker than that with Cu-IDA. Adsorption was examined under conditions of constant surface area with an initial pressure of 40 mN/m. After {approx}12 h little further change in reflectivity was detected, although the surface pressure continued to slowly increase. For chelated Cu{sup 2+} ions, the adsorbed layer structure in the final state was examined for bulk myoglobin concentrations of 0.10 and 10 {micro}M. For the case of 10 {micro}M, the final layer thickness was 43 {angstrom}. This corresponds well to the two thicker dimensions of myoglobin in the native state (44 {angstrom} x 44 {angstrom} x 25 {angstrom}) and so is consistent with an end-on orientation for this disk-shaped protein at high packing density. However, the final average volume fraction of amino acid segments in the layer was 0.55, which is substantially greater than the value of 0.44 calculated for a completed monolayer from the crystal structure. This suggests an alternative interpretation based on denaturation. GIXD was used to follow the effect of protein binding on the crystalline packing of the lipids and to check for crystallinity within the layer of adsorbed myoglobin. Despite the strong adsorption of myoglobin, very little change was observed in the structure of the DSIDA film. There was no direct evidence in the XR or GIXD for peptide insertion into the lipid tail region. Also, no evidence for in-plane crystallinity within the adsorbed layer of myoglobin was observed. For 0.1 {micro}M bulk myoglobin concentration, the average segment volume fraction was only 0.13 and the layer thickness was {le}25 {angstrom}. Adsorption of myoglobin to DSIDA-loaded with Ni{sup 2+} was examined at bulk concentrations of 10 and 50 {micro}M. At 10 {micro}M myoglobin, the adsorbed amount was comparable to that obtained for adsorption to Cu{sup 2+}-loaded DSIDA monolayers at 0.1 {micro}M. But interestingly, the adsorbed layer thickness was 38 {angstrom}, substantially greater than that obtained at low coverage with Cu-IDA. This indicates that either there are different preferred orientations for isolated myoglobin molecules adsorbed to Cu-IDA and Ni-IDA monolayer films or else myoglobin denatures to a different extent in the two cases. Either interpretation can be explained by the very different binding energies for individual interactions in the two cases. At 50 {micro}M myoglobin, the thickness and segement volume fraction in the adsorbed layer for Ni-IDA were comparable to the values obtained with Cu-IDA at 10 {micro}M myoglobin.
The ability of future integrated metal-semiconductor micro-systems such as RF MEMS to perform highly complex functions will depend on developing freestanding metal structures that offer improved conductivity and reflectivity over polysilicon structures. For example, metal-based RF MEMS technology could replace the bulky RF system presently used in communications, navigation, and avionics systems. However, stress gradients that induce warpage of active components have prevented the implementation of this technology. Figure 1, is an interference micrograph image of a series of cantilever beams fabricated from electrodeposited Ni. The curvature in the beams was the result of stress gradients intrinsic to the electrodeposition process. To study the sources of the stress in electrodeposition of Ni we have incorporated a wafer curvature based stress sensor, the multibeam optical stress sensor, into an electrodeposition cell. We have determined that there are two regions of stress induced by electrodepositing Ni from a sulfamate-based bath (Fig 2). The stress evolution during the first region, 0-1000{angstrom}, was determined to be dependent only on the substrate material (Au vs. Cu), whereas the stress evolution during the second region, >1000{angstrom}, was highly dependent on the deposition conditions. In this region, the stress varied from +0.5 GPa to -0.5GPa, depending solely on the deposition rate. We examined four likely sources for the compressive intrinsic stress, i.e. reduction in tensile stress, and determined that only the adatom diffusion into grain boundaries model of Sheldon, et al. could account for the observed compressive stress. In the presentation, we shall discuss the compressive stress generation mechanisms considered and the ramifications of these results on fabrication of electrodeposited Ni for MEMS applications.
The critical time step needed for explicit time integration of laminated shell finite element models is presented. Each layer is restricted to be orthotropic when viewed from a properly oriented material coordinate system. Mindlin shell theory is used in determining the laminated response that includes the effects of transverse shear. The effects of the membrane-bending coupling matrix from the laminate material model are included. Such a coupling matrix arises even in the case of non-symmetric lay-ups of differing isotropic layers. Single point integration is assumed to be used in determining a uniform strain response from the element. Using a technique based upon one from the literature, reduced eigenvalue problems are established to determine the remaining non-zero frequencies. It is shown that the eigenvalue problem arising from the inplane normal and shear stresses is decoupled from that arising from the transverse shear stresses. A verification example is presented where the exact and approximate results are compared.
The production and aging of silicone materials remains an important issue in the weapons stockpile due to their utilization in a wide variety of components and systems within the stockpile. Changes in the physical characteristics of silicone materials due to long term desiccation has been identified as one of the major aging effects observed in silicone pad components. Here we report relaxation nuclear magnetic resonance imaging (R-NMRI) spectroscopy characterization of the silica-filled and unfilled polydimethylsiloxane (PDMS) and polydiphenylsiloxane (PDPS) copolymer (M9787) silicone pads within desiccating environments. These studies were directed at providing additional details about the heterogeneity of the desiccation process. Uniform NMR spin-spin relaxation time (T2) images were observed across the pad thickness indicating that the drying process is approximately uniform, and that the desiccation of the M9787 silicone pad is not a H2O diffusion limited process. In a P2O5 desiccation environment, significant reduction of T2 was observed for the silica-filled and unfilled M9787 silicone pad for desiccation up to 225 days. A very small reduction in T2 was observed for the unfilled copolymer between 225 and 487 days. The increase in relative stiffness with desiccation was found to be higher for the unfilled copolymer. These R-NMRI results are correlated to local changes in the modulus of the material
Oxygen plasma treatment of poly(dimethylsiloxane) (PDMS) thin films produced a hydrophilic surface that was biocompatible and resistant to biofouling in microfluidic studies. Thin film coatings of PDMS were previously developed to provide protection for semiconductor-based microoptical devices from rapid degradation by biofluids. However, the hydrophobic surface of native PDMS induced rapid clogging of microfluidic channels with glial cells. To evaluate the various issues of surface hydrophobicity and chemistry on material biocompatibility, we tested both native and oxidized PDMS (ox-PDMS) coatings as well as bare silicon and hydrophobic alkane and hydrophilic oligoethylene glycol silane monolayer coated under both cell culture and microfluidic studies. For the culture studies, the observed trend was that the hydrophilic surfaces supported cell adhesion and growth, whereas the hydrophobic ones were inhibitive. However, for the fluidic studies, a glass-silicon microfluidic device coated with the hydrophilic ox-PDMS had an unperturbed flow rate over 14 min of operation, whereas the uncoated device suffered a loss in rate of 12%, and the native PDMS coating showed a loss of nearly 40%. Possible protein modification of the surfaces from the culture medium also were examined with adsorbed films of albumin, collagen, and fibrinogen to evaluate their effect on cell adhesion.
Shock wave compression of poled Pb{sub 0.99}(Zr{sub 0.95}Ti{sub 0.05}){sub 0.98}Nb{sub 0.02}O{sub 3} (PZT 95/5-2Nb) results in rapid depoling and release of bound charge. In the current study, planar-impact experiments with this material were conducted on a gas-gun facility to determine Hugoniot states, to examine constitutive mechanical properties during shock propagation, and to investigate shock-induced depoling characteristics. A previous article summarized results from the first two of these areas, and this article summarizes the depoling studies. A baseline material, similar to materials used in previous studies, was examined in detail. More limited experiments were conducted with other materials to investigate the effects of different porous microstructures. Experiments were conducted over a wide range of conditions in order to examine the effects of varying shock strength, poling orientation, input wave shape, electric field strength, porous microstructure at a fixed density, and initial density. Depoling currents were recorded in an external circuit under either short-circuit or high-field conditions, and provide a convenient means of examining the kinetics associated with the ferroelectric-to-antiferroelectric phase transition. For sufficiently strong shock waves, the measured short-circuit currents indicate that the phase transition is very rapid and essentially complete. As shock strengths are reduced, short-circuit currents show increasing rise times and decreasing final levels at the end of shock transit. These features indicate that the transition kinetics can be characterized in terms of both a transition rate and a limiting degree of transition achieved in a given shock experiment. The presence of a strong electric field does not appear to have a significant effect on transition kinetics at high shock stresses, but has a strong effect at low stresses. As was found for constitutive mechanical properties, only small effects on measured currents resulted from differences in the porous microstructure of common-density materials, but large effects were observed when initial density was varied. To examine transition kinetics in more detail, short-circuit currents obtained with the baseline material and several approximate methods were used to estimate values for the rate and degree of transition as functions of shock properties. Differences between these currents and currents measured in high-field experiments using the same impact conditions were used to examine field effects on transition kinetics and corresponding dielectric properties.
The physical and welding a metallurgy of gadolinium- (Gd-) enriched Ni-based alloys has been examined using a combination of differential thermal analysis, hot ductility testing. Varestraint testing, and various microstructural characterization techniques. Three different matrix compositions were chosen that were similar to commercial Ni-Cr-Mo base alloys (UNS N06455, N06022, and N06059). A ternary Ni-Cr-Gd alloy was also examined. The Gd level of each alloy was {approx}2 wt-%. All the alloys initiated solidification by formation of primary austenite and terminated solidification by a Liquid {gamma} + Ni{sub 5}Gd eutectic-type reaction at {approx}1270 C. The solidification temperature ranges of the alloys varied from {approx}100 to 130 C (depending on alloy composition). This is a substantial reduction compared to the solidification temperature range to Gd-enriched stainless steels (360 to 400 C) that terminate solidification by a peritectic reaction at {approx}1060 C. The higher-temperature eutectic reaction that occurs in the Ni-based alloys is accompanied by significant improvements in hot ductility and solidification cracking resistance. The results of this research demonstrate that Gd-enriched Ni-based alloys are excellent candidate materials for nuclear criticality control in spent nuclear fuel storage applications that require production and fabrication of large amounts of material through conventional ingot metallurgy and fusion welding techniques.
Atomistic simulations were performed to investigate high temperature wetting phenomena for metals. A sessile drop configuration was modeled for two systems: Ag(l) on Cu and Pb(l) on Cu. The former case is an eutectic binary and the wetting kinetics were greatly enhanced by the presence of aggressive interdiffusion between Ag and Cu. Wetting kinetics were directly dependent upon dissolution kinetics. The dissolution rate was nearly identical for Ag(l) on Cu(100) compared to Cu(111); as such, the spreading rate was very similar on both surfaces. Pb and Cu are bulk immiscible so spreading of Pb(l) on Cu occurred in the absence of significant substrate dissolution. For Pb(l) on Cu(111) a precursor wetting film of atomic thickness emerged from the partially wetting liquid drop and rapidly covered the surface. For Pb(l) on Cu(100), a foot was also observed to emerge from a partially wetting drop; however, spreading kinetics were dramatically slower for Pb(l) on Cu(100) than on Cu(111). For the former, a surface alloying reaction was observed to occur as the liquid wet the surface. The alloying reaction was associated with dramatically decreased wetting kinetics on Cu(100) versus Cu(111), where no alloying was observed. These two cases demonstrate markedly different atomistic mechanisms of wetting where, for Ag(l) on Cu, the dissolution reaction is associated with increased wetting kinetics while, for Pb(l) on Cu, the surface alloying reaction is associated with decreased wetting kinetics.
The force on and the heat flux to the NASA Mars Reconnaissance Orbiter (MRO) during drag passes are analyzed. Aerobraking takes place in the higher/rarefied levels of the Martian atmosphere, where traditional continuum flui d dynamics methods cannot be applied. Therefore, molecular gas dynamics simulations such as the Direct Simulation Monte Carlo Method are used to calculate these flow fields and provide heating and aerodynamic predictions for the vehicles. The heating and aerodynamic predictions calculated for the MRO include the heat transfer coefficient (C{sub h}), calculated for a number of angles of attack and the drag coefficient (C{sub D}) calculated for a number of altitudes and velocities. Bridging relations are sought that are applicable over the range of conditions of interest. A sensitivity analysis of the results to the chemical reaction rates, surface accommodation and temperature is also performed.
This reports tabulates the Test and Evaluation results of the Access Class Switch tests conducted by members of Department 9336. About 15 switches were reviewed for use in the enterprise network as access tier switches as defined in a three tier architecture. The Access Switch Tier has several functions including: aggregate customer desktop ports, preserve and apply QoS tags, provide switched LAN access, provide VLAN assignment, as well as others. The typical switch size is 48 or less user ports. The evaluation team reviewed network switch evaluation reports from the Tolly Group as well as other sources. We then used these reports as a starting point to identify particular switches for evaluation. In general we reviewed the products of dominant equipment manufacturers. Also, based on architectural design requirements, the majority of the switches tested were of relatively small monolithic unit variety.
The effects of ruffling on the axial ligation properties of a series of nickel(II) tetra(alkyl)porphyrins have been investigated with UV-visible absorption spectroscopy, resonance Raman spectroscopy, X-ray crystallography, classical molecular mechanics calculations, and normal-coordinate structural decomposition analysis. For the modestly nonplanar porphyrins, porphyrin ruffling is found to cause a decrease in binding affinity for pyrrolidine and piperidine, mainly caused by a decrease in the binding constant for addition of the first axial ligand; ligand binding is completely inhibited for the more nonplanar porphyrins. The lowered affinity, resulting from the large energies required to expand the core and flatten the porphyrin to accommodate the large high-spin nickel(II) ion, has implications for nickel porphyrin-based molecular devices and the function of heme proteins and methyl-coenzyme M reductase.
{sup 13}CH{sub 4} was injected with a toroidally-symmetric gas system into 22 identical lower-single-null L-mode discharges on DIII-D. The injection level was adjusted so that it did not significantly perturb the core or divertor plasmas, with a duration of {approx}3 s on each shot, for a total of {approx}300 T L of injected particles. The plasma shape remained very constant; the divertor strike points were controlled to {approx}1 cm at the divertor plate. At the beginning of the subsequent machine vent, 29 carbon tiles were removed for nuclear reaction analysis of {sup 13}C content to determine regions of carbon deposition. It was found that only the tiles inboard of the inner strike point had appreciable {sup 13}C above background. Visible spectroscopy measurements of the carbon injection and comparisons with modeling are consistent with carbon transport by means of scrape-off layer flow.
The objective of this research was the development of tools and techniques for the identification of critical nodes within critical infrastructures. These are nodes that, if disrupted through natural events or terrorist action, would cause the most widespread, immediate damage. This research focuses on one particular element of the national infrastructure: the bulk power system. Through the identification of critical elements and the quantification of the consequences of their failure, site-specific vulnerability analyses can be focused at those locations where additional security measures could be effectively implemented. In particular, with appropriate sizing and placement within the grid, distributed generation in the form of regional power parks may reduce or even prevent the impact of widespread network power outages. Even without additional security measures, increased awareness of sensitive power grid locations can provide a basis for more effective national, state and local emergency planning. A number of methods for identifying critical nodes were investigated: small-world (or network theory), polyhedral dynamics, and an artificial intelligence-based search method - particle swarm optimization. PSO was found to be the only viable approach and was applied to a variety of industry accepted test networks to validate the ability of the approach to identify sets of critical nodes. The approach was coded in a software package called Buzzard and integrated with a traditional power flow code. A number of industry accepted test networks were employed to validate the approach. The techniques (and software) are not unique to power grid network, but could be applied to a variety of complex, interacting infrastructures.
Chemical transport through human skin can play a significant role in human exposure to toxic chemicals in the workplace, as well as to chemical/biological warfare agents in the battlefield. The viability of transdermal drug delivery also relies on chemical transport processes through the skin. Models of percutaneous absorption are needed for risk-based exposure assessments and drug-delivery analyses, but previous mechanistic models have been largely deterministic. A probabilistic, transient, three-phase model of percutaneous absorption of chemicals has been developed to assess the relative importance of uncertain parameters and processes that may be important to risk-based assessments. Penetration routes through the skin that were modeled include the following: (1) intercellular diffusion through the multiphase stratum corneum; (2) aqueous-phase diffusion through sweat ducts; and (3) oil-phase diffusion through hair follicles. Uncertainty distributions were developed for the model parameters, and a Monte Carlo analysis was performed to simulate probability distributions of mass fluxes through each of the routes. Sensitivity analyses using stepwise linear regression were also performed to identify model parameters that were most important to the simulated mass fluxes at different times. This probabilistic analysis of percutaneous absorption (PAPA) method has been developed to improve risk-based exposure assessments and transdermal drug-delivery analyses, where parameters and processes can be highly uncertain.
In this article we report on the electrical characteristics of single wall carbon nanotubes (SWCNTs) wrapped with single-stranded deoxyribonucleic acid (ssDNA). We fabricate these devices using a solution-based method whereby SWCNTs are dispersed in aqueous solution using 20-mer ssDNA, and are placed across pairs of Au electrodes using alternating current dielectrophoresis (ACDEP). In addition to current voltage characteristics, we evaluate our devices using scanning electron microscopy and atomic force microscopy. We find that ACDEP with ssDNA based suspensions results in individual SWCNTs bridging metal electrodes, free of carbon debris, while similar devices prepared using the Triton X-100 surfactant yield nanotube bundles, and frequently have carbon debris attached to the nanotubes. Furthermore, the presence of ssDNA around the nanotubes does not appear to appreciably affect the overall electrical characteristics of the devices. In addition to comparing the properties of several devices prepared on nominally clean Au electrodes, we also investigate the effects of self-assembled monolayers of C{sub 14}H{sub 29}-SH alkyl thiol and benzyl mercaptan on the adhesion and electrical transport across the metal/SWCNT/metal devices.
The Sandia National Laboratories Nuclear Weapons Strategic Management Unit (NWSMU) is pursuing performance excellence, by focusing on compliance with the ISO 9001:2000 standard for quality management systems. The NWSMU also intends to achieve ISO Certification and eventually reach levels of performance excellence that are consistent with those of Malcolm Baldrige National Quality Award winners. In that context, this report documents a study undertaken to answer these questions: {sm_bullet} Would achieving ISO 9001:2000 compliance or certification help an organization prepare to achieve Baldrige-level performance excellence? {sm_bullet} Would pursuing Baldrige-based performance excellence help an organization achieve ISO certification? {sm_bullet} What are the areas where the Baldrige and ISO systems are most closely aligned? The study produced answers to those questions, as well as a number of comparisons and contrasts between the ISO standard and the Baldrige criteria.
Laser-induced fluorescence-dip spectroscopy was used to measure two-dimensional (2-D) maps of the electric field present in an argon discharge above a ratio frequency-powered, nonuniform surface. Electric fields were obtained from experimentally measured Stark shifts of the energy of argon Rydberg states. The 2-D maps of the electric fields demonstrated that nonuniformities present on an electrode have long-range effects on the structure of the sheath.
We performed molecular dynamics simulations of chain systems to investigate general relationships between the system mobility and computed scalar quantities. Three quantities were found that had a simple one-to-one relationship with mobility: packing fraction, potential energy density, and the value of the static structure factor at the first peak. The chain center-of-mass mobility as a function of these three quantities could be described equally well by either a Vogel-Fulcher type or a power law equation.
Percolation theory is now standard in the analysis of polycrystalline materials where the grain boundaries can be divided into two distinct classes, namely 'good' boundaries that have favorable properties and 'bad' boundaries that seriously degrade the material performance. Grain-boundary engineering (GBE) strives to improve material behavior by engineering the volume fraction c and arrangement of good grain boundaries. Two key percolative processes in GBE materials are the onset of percolation of a strongly connected aggregate of grains, and the onset of a connected path of weak grain boundaries. Using realistic polycrystalline microstructures, we find that in two dimensions the threshold for strong aggregate percolation c{sub SAP} and the threshold for weak boundary percolation c{sub WBP} are equivalent and have the value c{sub SAP} = c{sub WBP} = 0.38(1), which is slightly higher than the threshold found for regular hexagonal grain structures, c{sub RH} = 2 sin({pi}/18) = 0.347. In three dimensions strong aggregate percolation and weak boundary percolation occur at different locations and we find c{sub SAP} = 0.12(3) and c{sub WBP} = 0.77(3). The critical current in high T{sub c} materials and the cohesive energy in structural systems are related to the critical manifold problem in statistical physics. We develop a theory of critical manifolds in GBE materials, which has three distinct regimes: (1) low concentrations, where random manifold theory applies, (2) critical concentrations where percolative scaling theory applies, and (3) high concentrations, c > c{sub SAP}, where the theory of periodic elastic media applies. Regime (3) is perhaps most important practically and is characterized by a critical length L{sub c}, which is the size of cleavage regions on the critical manifold. In the limit of high contrast {open_square} {yields} 0, we find that in two dimensions L{sub c} {proportional_to} gc/(1-c), while in three dimensions L{sub c} {proportional_to} g exp[b{sub 0}c/(1-c)]/[c(1-c)]{sup 1/2}, where g is the average grain size, {open_square} is the ratio of the bonding energy of the weak boundaries to that of the strong boundaries, and b{sub 0} is a constant which is of order 1. Many of the properties of GBE materials can be related to L{sub c}, which diverges algebraically on approach to c=1 in two dimensions, but diverges exponentially in that limit in three dimensions. We emphasize that GBE percolation processes and critical manifold behavior are very different in two dimensions as compared to three dimensions. For this reason, the use of two dimensional models to understand the behavior of bulk GBE materials can be misleading.
This report documents the calculation of radionuclide content in the pressurized water reactor (PWR) spent fuel samples planned for use in the Spent Fuel Ratio (SPR) Experiments at Sandia National Laboratories, Albuquerque, New Mexico (SNL) to aid in experiment planning. The calculation methods using the ORIGEN2 and ORIGEN-ARP computer codes and the input modeling of the planned PWR spent fuel from the H. B. Robinson and the Surry nuclear power plants are discussed. The safety hazards for the calculated nuclide inventories in the spent fuel samples are characterized by the potential airborne dose and by the portion of the nuclear facility hazard category 2 and 3 thresholds that the experiment samples would present. In addition, the gamma ray photon energy source for the nuclide inventories is tabulated to facilitate subsequent calculation of the direct and shielded dose rates expected from the samples. The relative hazards of the high burnup 72 gigawatt-day per metric ton of uranium (GWd/MTU) spent fuel from H. B. Robinson and the medium burnup 36 GWd/MTU spent fuel from Surry are compared against a parametric calculation of various fuel burnups to assess the potential for higher hazard PWR fuel samples.
Two-dimensional maps of the sheath electric fields formed around a metal-dielectric interface were measured in a radio frequency (rf) argon plasma using laser-induced fluorescence-dip spectroscopy. Experimentally determined Stark shifts of the argon Rydberg 13d[3/2]1 state were used to quantify the electric fields in the sheath as functions of the rf cycle, voltage, and pressure. Both the structure of the sheath fields and the discharge characteristics in the region above the electrode depend on the discharge conditions and the configuration of the surface. Dissimilar materials placed adjacent to each other result in electric fields with a component parallel to the electrode surface.
Rare earth doped yttrium oxide (yttria) and silicate, Y{sub 2}O{sub 3}:Eu and Y{sub 2}SiO{sub 5}:Tb, are the most promising phosphors for advanced devices such as flat panel field-emission-displays. However, their light yield for electron excitation has proven to be lower than that predicted by early models. New experimental data are needed to improve the theoretical understanding of the cathodoluminescence (CL) that will, in turn, lead to materials that are significantly brighter. Beside the existing CL and photo luminescence (PL) measurements, one can provide new information by studying ion-induced luminescence (IL). Ions penetrate substantially deeper than electrons and their light yield should therefore not depend on surface effects. Moreover, the energy density released by ions can be much higher than that of electrons and photons, which results in possible saturation effects, further testing the adequacy of models. We exposed the above yttrium compounds to three ion beams, H (3 MeV), C (20 MeV), Cu (50 MeV), which have substantially different electronic stopping powers. H was selected to provide an excitation close to CL, but without surface effects. The C and Cu allowed an evaluation of saturation effects because of their higher stopping powers. The IL experiments involved measuring the transient light intensity signal radiating from thin phosphor layers following their exposure to {approx}200 ns ion beam pulses. We present the transient yield curves for the two materials and discuss a general model for this behavior.
The plastic behavior of crystalline materials is mainly controlled by the nucleation and motion of lattice dislocations. We report in situ dynamic transmission electron microscope observations of nanocrystalline nickel films with an average grain size of about 10 nanometers, which show that grain boundary-mediated processes have become a prominent deformation mode. Additionally, trapped lattice dislocations are observed in individual grains following deformation. This change in the deformation mode arises from the grain size-dependent competition between the deformation controlled by nucleation and motion of dislocations and the deformation controlled by diffusion-assisted grain boundary processes.
In complex simulation systems where humans interact with computer-generated agents, information display and the interplay of virtual agents have become dominant media and modalities of interface design. This design strategy is reflected in augmented reality (AR), an environment where humans interact with computer-generated agents in real-time. AR systems can generate large amount of information, multiple solutions in less time, and perform far better in time-constrained problem solving. The capabilities of AR have been leveraged to augment cognition in human information processing. In this sort of augmented cognition (AC) work system, while technology has become the main source for information acquisition from the environment, the human sensory and memory capacities have failed to cope with the magnitude and scale of information they encounter. This situation generates opportunity for excessive cognitive workloads, a major factor in degraded human performance. From the human effectiveness point of view, research is needed to develop, model, and validate simulation tools that can measure the effectiveness of an AR technology used to support the amplification of human cognition. These tools will allow us to predict human performance for tasks executed under an AC tool construct. This paper presents an exploration of ergonomics issues relevant to AR and AC systems design. Additionally, proposed research to investigate those ergonomic issues is discussed.
By using a multipole-conformal mapping expansion for the wire currents we examine the accuracy of approximations for the transfer inductance of a one dimensional array of wires (wire grid). A simple uniform fit is constructed by introduction of the decay factor from bipolar coordinates into existing formulas for this inductance.
In theory, it should be possible to infer realistic genetic networks from time series microarray data. In practice, however, network discovery has proved problematic. The three major challenges are: (1) inferring the network; (2) estimating the stability of the inferred network; and (3) making the network visually accessible to the user. Here we describe a method, tested on publicly available time series microarray data, which addresses these concerns. The inference of genetic networks from genome-wide experimental data is an important biological problem which has received much attention. Approaches to this problem have typically included application of clustering algorithms [6]; the use of Boolean networks [12, 1, 10]; the use of Bayesian networks [8, 11]; and the use of continuous models [21, 14, 19]. Overviews of the problem and general approaches to network inference can be found in [4, 3]. Our approach to network inference is similar to earlier methods in that we use both clustering and Boolean network inference. However, we have attempted to extend the process to better serve the end-user, the biologist. In particular, we have incorporated a system to assess the reliability of our network, and we have developed tools which allow interactive visualization of the proposed network.
Laser-extinction diagnostics can provide spatially and temporally resolved measurements of attenuation from combustion-generated soot within the path of the beam. When laser-extinction techniques are utilized in high-pressure combustion environments, however, a number of complications may be encountered that are not present in low-pressure environments. Several of these experimental difficulties were investigated in diesel engine environments, and solutions that facilitated acquisition of reliable laser-extinction data were demonstrated. Beam steering due to refractive index gradients within the combusting gases was observed, and a full-angle beam divergence of over 100 mrad was measured. A spatial-filtering scheme was employed to reduce the collection of forward-scattered light and background combustion luminosity while ensuring full collection of the steered beam. To further reject combustion luminosity, a narrow-bandpass laser-line filter was employed, after diffusing the transmitted light sufficiently to avoid the effects of significant spatial non-uniformities of the filter. As the windows were subjected to thermal and mechanical stresses, dynamic etaloning effects due to the photoelastic properties of synthetic fused silica were observed. Dynamic changes in the polarization of the exit beam were also observed, as stress-induced birefringence in the windows caused dynamic phase retardation of the transmitted beam. Although these photoelastic effects could not be eliminated, they were mitigated by introducing curvature to the wavefronts in the laser-extinction beam and using polarization-insensitive elements in the detection optics. Soot deposits on window surfaces were removed ablatively using a coaxial, high-energy, pulsed Nd:YAG laser beam.
India and Pakistan have created sizeable ballistic missile forces and are continuing to develop and enlarge them. These forces can be both stabilizing (e.g., providing a survivable force for deterrence) and destabilizing (e.g., creating strategic asymmetries). Missile forces will be a factor in bilateral relations for the foreseeable future, so restraint is necessary to curtail their destabilizing effects. Such restraint, however, must develop within an atmosphere of low trust. This report presents a set of political and operational options, both unilateral and bilateral, that decreases tensions, helps rebuild the bilateral relationship, and prepares the ground for future steps in structural arms control. Significant steps, which build on precedents and do not require extensive cooperation, are possible despite strained relations. The approach is made up of three distinct phases: (1) tension reduction measures, (2) confidence building measures, and (3) arms control agreements. The goal of the first phase is to initiate unilateral steps that are substantive and decrease tensions, establish missiles as a security topic for bilateral discussion, and set precedents for limited bilateral cooperation. The second phase would build confidence by expanding current bilateral security agreements, formalizing bilateral understandings, and beginning discussion of monitoring procedures. The third phase could include bilateral agreements limiting some characteristics of national missile forces including the cooperative incorporation of monitoring and verification.
Pb deposition on Cu(111) causes the surface to self-assemble into periodically arranged domains of a Pb-rich phase and a Pb-poor phase. Using low-energy electron microscopy (LEEM) we provide evidence that the observed temperature-dependent periodicity of these self-assembled domain patterns is the result of changing domain-boundary free energy. We determine the free energy of boundaries at different temperatures from a capillary wave analysis of the thermal fluctuations of the boundaries and find that it varies from 22 meV/nm at 600 K to 8 meV/nm at 650 K. Combining this result with previous measurements of the surface stress difference between the two phases we find that the theory of surface-stress-induced domain formation can quantitatively account for the observed periodicities.
A technique for manufacturing wires with imposed modulation in radius with axial wavelengths as short as 1 mm is presented. Extruded aluminum 5056 with 15 {micro}m diameter was masked and chemically etched to reduce the radius by {approx}20% in selected regions. Characterized by scanning electron microscopy, the modulation in radius is a step function with a {approx}10 {micro}m wide conical transition between thick and thin segments, with some pitting in etched regions. Techniques for mounting and aligning these wires in arrays for fast z-pinch experiments will be discussed. Axially mass-modulated wire arrays of this type will allow the study of seeded Rayleigh-Taylor instabilities in z pinches, corona formation, wire initiation with varying current density in the wire core, and correlation of perturbations between adjacent wires. This tool will support magnetohydrodynamics code validation in complex three-dimensional geometries, and perhaps x-ray pulse shaping.
We use low-energy electron microscopy to study the mechanisms of thermal smoothing on Rh(001) surfaces at high temperature. By examining the change of areas of two-dimensional islands as a function of time and temperature, we find that smoothing from 1210 K to 1450 K is limited by the rate of surface diffusion on terraces and not by bulk vacancy diffusion as observed in other systems in the same temperature range. However, the activation energy we measure for island decay is inconsistent with previous measurements and calculations of the activation energy of surface diffusion and the adatom formation energy. This inconsistency combined with an unexpectedly large activation entropy suggests a surface transport mechanism other than simple hopping of adatoms across the surface.
This report documents the efforts and accomplishments of the LIGA electrodeposition modeling project which was headed by the ASCI Materials and Physics Modeling Program. A multi-dimensional framework based on GOMA was developed for modeling time-dependent diffusion and migration of multiple charged species in a dilute electrolyte solution with reduction electro-chemical reactions on moving deposition surfaces. By combining the species mass conservation equations with the electroneutrality constraint, a Poisson equation that explicitly describes the electrolyte potential was derived. The set of coupled, nonlinear equations governing species transport, electric potential, velocity, hydrodynamic pressure, and mesh motion were solved in GOMA, using the finite-element method and a fully-coupled implicit solution scheme via Newton's method. By treating the finite-element mesh as a pseudo solid with an arbitrary Lagrangian-Eulerian formulation and by repeatedly performing re-meshing with CUBIT and re-mapping with MAPVAR, the moving deposition surfaces were tracked explicitly from start of deposition until the trenches were filled with metal, thus enabling the computation of local current densities that potentially influence the microstructure and frictional/mechanical properties of the deposit. The multi-dimensional, multi-species, transient computational framework was demonstrated in case studies of two-dimensional nickel electrodeposition in single and multiple trenches, without and with bath stirring or forced flow. Effects of buoyancy-induced convection on deposition were also investigated. To further illustrate its utility, the framework was employed to simulate deposition in microscreen-based LIGA molds. Lastly, future needs for modeling LIGA electrodeposition are discussed.
One challenge faced by engineers today is replicating an operating environment such as transportation in a test lab. This paper focuses on the process of identifying sine-on-random content in an aircraft transportation environment, although the methodology can be applied to other events. The ultimate goal of this effort was to develop an automated way to identify significant peaks in the PSDs of the operating data, catalog the peaks, and determine whether each peak was sinusoidal or random in nature. This information helps design a test environment that accurately reflects the operating environment. A series of Matlab functions have been developed to achieve this goal with a relatively high degree of accuracy. The software is able to distinguish between sine-on-random and random-on-random peaks in most cases. This paper describes the approach taken for converting the time history segments to the frequency domain, identifying peaks from the resulting PSD, and filtering the time histories to determine the peak amplitude and characteristics. This approach is validated through some contrived data, and then applied to actual test data. Observations and conclusions, including limitations of this process, are also presented.
The experimental and computational investigations of nanosecond electrical explosion of thin Al wire in vacuum are presented. We have demonstrated that increasing the current rate leads to increased energy deposited before voltage collapse. Laser shadowgrams of the overheated Al core exhibit axial stratification with a {approx}100 {micro}m period. The experimental evidence for synchronization of the wire expansion and light emission with voltage collapse is presented. Two-wavelength interferometry shows an expanding Al core in a low-ionized gas condition with increasing ionization toward the periphery. Hydrocarbons are indicated in optical spectra and their influence on breakdown physics is discussed. The radial velocity of low-density plasma reaches a value of {approx}100 km/s. The possibility of an overcritical phase transition due to high pressure is discussed. 1D MHD simulation shows good agreement with experimental data. MHD simulation demonstrates separation of the exploding wire into a high-density cold core and a low-density hot corona as well as fast rejection of the current from the wire core to the corona during voltage collapse. Important features of the dynamics for wire core and corona follow from the MHD simulation and are discussed.
Seeding and autocatalytic reduction of platinum salts in aqueous surfactant solution using ascorbic acid as the reductant leads to remarkable dendritic metal nanostructures. In micellar surfactant solutions, spherical dendritic metal nanostructures are obtained, and the smallest of these nanodendrites resemble assemblies of joined nanoparticles and the nanodendrites are single crystals. With liposomes as the template, dendritic platinum sheets in the form of thin circular disks or solid foam-like nanomaterials can be made. Synthetic control over the morphology of these nanodendrites, nanosheets, and nanostructured foams is realized by using a tin-porphyrin photocatalyst to conveniently and effectively produce a large initial population of catalytic growth centers. The concentration of seed particles determines the ultimate average size and uniformity of these novel two- and three-dimensional platinum nanostructures.
On April 22 and 23, 2004, a diverse group of 14 policymakers, modelers, analysts, and scholars met with some 22 members of the Sandia National Laboratories staff to explores ways in which the relationships between modelers and policymakers in the energy and environment fields (with an emphasis on energy) could be made more productive for both. This report is not a transcription of that workshop, but draws very heavily on its proceedings. It first describes the concept of modeling, the varying ways in which models are used to support policymaking, and the institutional context for those uses. It then proposes that the goal of modelers and policymakers should be a relationship of mutual trust, built on a foundation of communication, supported by the twin pillars of policy relevance and technical credibility. The report suggests 20 guidelines to help modelers improve the relationship, followed by 10 guidelines to help policymakers toward the same goal.
The Vulcan fire-field model is employed to simulate the evolution of pool fires and the distribution of fire suppressants in a engine nacelle simulator. The objective is to identify conditions for which suppression will and will not be successful in order to (1) provide input on experimental design and (2) to test the model's predictive capabilities through comparison with future test results. Pool fires, where the fuel pool is on the bottom of the nacelle, have been selected for these tests because they have been identified as among the most challenging to suppress. Modeling of the production HFC-125 fire suppression system predicts that all pool fires are extinguished. Removing nozzles and reducing the rate of suppressant injection eventually lead to a predicted failure to suppress the fires. The stability of the fires, and therefore the difficulty in extinguishing them, depends on a variety of additional factors as discussed in the text.
We have developed and implemented a method, which given a three-dimensional object can infer from topology the two-dimensional masks needed to produce that object with surface micromachining. The masks produced by this design tool can be generic, process independent masks, or if given process constraints, specific for a target process. This design tool calculates the two-dimensional mask set required to produce a given three-dimensional model by investigating the vertical topology to the model. The 3D model is first separated into bodies that are non-intersecting, made from different materials or only linked through a ground plane. Next, for each body unique vertical cross sections are located and arranged into a tree based on their topological relationship. A branch-wise search of the tree uncovers locations where deposition boundaries must lie and identifies candidate masks creating a generic mask set for the 3D model. Finally, in the last step specific process requirements are considered that may constrain the generic mask set. Constraints can include the thickness or number of deposition layers, specific ordering of masks as required by a process and type of material used in a given layer. Candidate masks are reconciled with the process constraints through a constrained optimization.
This manual describes the use of the Xyce Parallel Electronic Simulator. Xyce has been designed as a SPICE-compatible, high-performance analog circuit simulator capable of simulating electrical circuits at a variety of abstraction levels. Primarily, Xyce has been written to support the simulation needs of the Sandia National Laboratories electrical designers. This development has focused on improving capability the current state-of-the-art in the following areas: {sm_bullet} Capability to solve extremely large circuit problems by supporting large-scale parallel computing platforms (up to thousands of processors). Note that this includes support for most popular parallel and serial computers. {sm_bullet} Improved performance for all numerical kernels (e.g., time integrator, nonlinear and linear solvers) through state-of-the-art algorithms and novel techniques. {sm_bullet} Device models which are specifically tailored to meet Sandia's needs, including many radiation-aware devices. {sm_bullet} A client-server or multi-tiered operating model wherein the numerical kernel can operate independently of the graphical user interface (GUI). {sm_bullet} Object-oriented code design and implementation using modern coding practices that ensure that the Xyce Parallel Electronic Simulator will be maintainable and extensible far into the future. Xyce is a parallel code in the most general sense of the phrase - a message passing of computing platforms. These include serial, shared-memory and distributed-memory parallel implementation - which allows it to run efficiently on the widest possible number parallel as well as heterogeneous platforms. Careful attention has been paid to the specific nature of circuit-simulation problems to ensure that optimal parallel efficiency is achieved as the number of processors grows. One feature required by designers is the ability to add device models, many specific to the needs of Sandia, to the code. To this end, the device package in the Xyce These input formats include standard analytical models, behavioral models look-up Parallel Electronic Simulator is designed to support a variety of device model inputs. tables, and mesh-level PDE device models. Combined with this flexible interface is an architectural design that greatly simplifies the addition of circuit models. One of the most important feature of Xyce is in providing a platform for computational research and development aimed specifically at the needs of the Laboratory. With Xyce, Sandia now has an 'in-house' capability with which both new electrical (e.g., device model development) and algorithmic (e.g., faster time-integration methods) research and development can be performed. Ultimately, these capabilities are migrated to end users.
This document is a reference guide to the Xyce Parallel Electronic Simulator, and is a companion document to the Xyce Users' Guide. The focus of this document is (to the extent possible) exhaustively list device parameters, solver options, parser options, and other usage details of Xyce. This document is not intended to be a tutorial. Users who are new to circuit simulation are better served by the Xyce Users' Guide.
The surface micromachining processes used to manufacture MEMS devices and integrated circuits transpire at such small length scales and are sufficiently complex that a theoretical analysis of them is particularly inviting. Under development at Sandia National Laboratories (SNL) is Chemically Induced Surface Evolution with Level Sets (ChISELS), a level-set based feature-scale modeler of such processes. The theoretical models used, a description of the software and some example results are presented here. The focus to date has been of low-pressure and plasma enhanced chemical vapor deposition (low-pressure chemical vapor deposition, LPCVD and PECVD) processes. Both are employed in SNLs SUMMiT V technology. Examples of step coverage of SiO{sub 2} into a trench by each of the LPCVD and PECVD process are presented.
The thermochemistry of the transition-metal fluorides and chlorides MF{sub n} and MCl{sub n} (M = Cr, Mn, Fe; n = 1, 2) has been characterized by high-level ab initio electronic structure methods. Geometries and harmonic vibrational frequencies were computed at the B3LYP level of theory using triple-{zeta} basis sets including diffuse and polarization functions. Heats of formation were computed from isogyric reaction energies at the CCSD(T) level using high-quality basis sets, including corrections for core-valence correlation and scalar relativistic effects. To investigate the possible linearity of the ground states of CrCl{sub 2} and CrF{sub 2}, we performed geometry optimizations for these species at the CCSD(T) level using large basis sets. In both cases, a bent ({sup 5}B{sub 2}) minimum structure was located, but the bent structure is only slightly below the linear form, which was found to be a transition state. For all of the investigated halides, polynomial fits were carried out for the heat capacity and the standard enthalpy and entropy in the 300-3000 K temperature range.
The modeling of fluid/structure interaction is of growing importance in both energy and environmental applications. Because of the inherent complexity, these problems must be simulated on parallel machines in order to achieve high resolution. The purpose of this research was to investigate techniques for coupling flow and geomechanics in porous media that are suitable for parallel computation. In particular, our main objective was to develop an iterative technique which can be as accurate as a fully coupled model but which allows for robust and efficient coupling of existing complex models (software). A parallel linear elastic module was developed which was coupled to a three phase three-component black oil model in IPARS (Integrated Parallel Accurate Reservoir Simulator). An iterative de-coupling technique was introduced at each time step. The resulting nonlinear iteration involved solving for displacements and flow sequentially. Rock compressibility was used in the flow model to account for the effect of deformation on the pore volume. Convergence was achieved when the mass balance for each component satisfied a given tolerance. This approach was validated by comparison with a fully coupled approach implemented in the British PetroledAmoco ACRES simulator. Another objective of this work was to develop an efficient parallel solver for the elasticity equations. A preconditioned conjugate gradient solver was implemented to solve the algebraic system arising from tensor product linear Galerkin approximations for the displacements. Three preconditioners were developed: LSOR (line successive over-relaxation), block Jacobi, and agglomeration multi-grid. The latter approach involved coarsening the 3D system to 2D and using LSOR as a smoother that is followed by applying geometric multi-grid with SOR (successive over-relaxation) as a smoother. Preliminary tests on a 64-node Beowulf cluster at CSM indicate that the agglomeration multi-grid approach is robust and efficient.
The couple on a ball rotating relative to an otherwise quiescent suspension of comparably-sized, neutrally buoyant spheres is studied both experimentally and numerically. Apparent 'slip' relative to the analytical solution for a sphere spinning in a Newtonian fluid (based upon the viscosity of the suspension) is determined in suspensions with volume fractions c ranging from 0.03 to 0.50. This apparent slip results in a decrease of the measured torque on the spinning ball when the radius of the ball becomes comparable with that of the suspended spheres. Over the range of our data, the slip becomes more pronounced as the concentration c increases. At c = 0.25, three-dimensional boundary-element simulations agree well with the experimental data. Moreover, at c = 0.03, good agreement exists between such calculations and theoretical predictions of rotary slip in dilute suspensions.
An aged polybutadiene-based elastomer was reacted with trifluoroacetic anhydride (TFAA) and subsequently analyzed via 19F NMR spectroscopy. Derivatization between the TFAA and hydroxyl functionalities produced during thermo-oxidative aging was achieved, resulting in the formation of trifluoroester groups on the polymer. Primary and secondary alcohols were confirmed to be the main oxidation products of this material, and the total percent oxidation correlated with data obtained from oxidation rate measurements. The chemical derivatization appears to be highly sensitive and can be used to establish the presence and identity of oxidation products in aged polymeric materials. This methodology represents a novel condition monitoring approach for the detection of chemical changes that are otherwise difficult to analyze.
In the present work the authors describe the adaptation of a standard SEM into a flexible microjoining tool. The system incorporates exceptional control of energy input and its location, environmental cleanliness, part manipulation and especially, part imaging. Beam energetics, modeling of thermal flow in a simple geometry, significant effects of surface energy on molten pools and beam size characterization are treated. Examples of small to micro fusion welds and molten zones produced in a variety of materials (Ni, tool steel, Tophet C, Si) and sizes are given. Future directions are also suggested.
High-resolution, variable temperature PL experiments were performed in the spectral region associated with recombination processes involving the ground and excited states of the neutral donor bound excitons. High-resolution infrared measurements in combination with high-sensitive SIMS unambiguously identified Si and O shallow donors and yield their ground state binding energies. These binding energies are in excellent agreement with values obtained by the analysis of the two-electron-satellite PL spectra considering the participation of ground and excited state donor bound excitons. This work clarifies conflicting aspects existing in donor identification and the binding energies of the impurities and excitons.
Solid-state light sources emitting at wavelengths less than 300 nm would enable technological advances in many areas such as fluorescence-based biological agent detection, non-line-of-sight communications, water purification, and industrial processing including ink drying and epoxy curing. In this paper, we present our recent progress in the development of LEDs with emission between 237 and 297 nm. We will discuss growth and design issues of deep-UV LEDs, including transport in Si-doped AlGaN layers. The LEDs are designed for bottom emission so that improved heat sinking and light extraction can be achieved by flip chipping. To date, we have demonstrated 2.25 mW of output power at 295 nm from 1 mm x 1 mm LEDs operated at 500 mA. Shorter wavelength LEDs emitting at 276 nm have achieved an output power of 1.3 mW at 400 mA. The heterostructure designs that we have employed have suppressed deep level emission to intensities that are up to 330 x lower than the primary quantum well emission.
A stereoscopic particle image velocimetry (PIV) instrument has been constructed for a transonic wind tunnel to study the interaction created by a supersonic axisymmetric jet exhausting from a flat plate into a subsonic compressible crossflow. Data have been acquired in the crossplane of the interaction at a single station in the farfield, in which the bulk particle motion is aligned with the out-of-plane velocity component. The resulting vector fields distinctly show the strength and location of the induced counter-rotating vortex pair as well as the remnant of the horseshoe vortex that wraps around the jet plume as it first exhausts from the nozzle. Data taken for four different values of the jet-to-freestream dynamic pressure ratio reveal the resulting change in vortex strength, size, and position. Vorticity fields were derived from the in-plane velocity data, but limited convergence of the present small data sets prevented any conclusions about the symmetry of the flowfield. Comparison of the present data is made with two-dimensional PIV data previously acquired in the streamwise plane.
Powder phosphors of ZnS:Ag,Cl coated with SiO{sub 2} (22 or 130 nm nanoparticles), SnO{sub 2} or Al{sub 2}O{sub 3} showed different cathodoluminescent (CL) brightness versus time (temporal CL quenching) behavior as compared to noncoated phosphors. At high current density (e.g., 300-800 {micro}A/cm{sup 2}), the CL emission intensity of coated ZnS:Ag,Cl decayed over the first {approx}15 s of electron beam irradiation, which was postulated to result from a large concentration of nonradiative surface centers generated during surface modification of the phosphor, and from localization of generated electrons at the surface due to primary beam-induced internal electric fields. During the first {approx}15 s of excitation, generated electrons are postulated to be redistributed by this induced internal electric fields, resulting in increased nonradiative surface recombination between electrons and holes. The formation of a nonradiative surface layer either from electron-stimulated surface chemical reactions on coated or from heat treatment of noncoated ZnS:Ag,Cl powder phosphors were shown to affect temporal CL quenching.
Femtosecond differential reflectivity spectroscopy (DRS) and four-wave mixing (FWM) experiments were performed simultaneously to study the initial temporal dynamics of the exciton line-shapes in GaN epilayers. Beats between the A-B excitons were found only for positive time delay in both DRS and FWM experiments. The rise time at negative time delay for the DRS was much slower than the FWM signal or differential transmission spectroscopy at the exciton resonance. A numerical solution of a six band semiconductor Bloch equation model including nonlinearities at the Hartree-Fock level shows that this slow rise in the DRS results from excitation induced dephasing, that is, the strong density dependence of the dephasing time which changes with the laser excitation energy.
The diagonal-mass-matrix spectral element method has proven very successful in geophysical applications dominated by wave propagation. For these problems, the ability to run fully explicit time stepping schemes at relatively high order makes the method more competitive then finite element methods which require the inversion of a mass matrix. The method relies on Gauss-Lobatto points to be successful, since the grid points used are required to produce well conditioned polynomial interpolants, and be high quality 'Gauss-like' quadrature points that exactly integrate a space of polynomials of higher dimension than the number of quadrature points. These two requirements have traditionally limited the diagonal-mass-matrix spectral element method to use square or quadrilateral elements, where tensor products of Gauss-Lobatto points can be used. In non-tensor product domains such as the triangle, both optimal interpolation points and Gauss-like quadrature points are difficult to construct and there are few analytic results. To extend the diagonal-mass-matrix spectral element method to (for example) triangular elements, one must find appropriate points numerically. One successful approach has been to perform numerical searches for high quality interpolation points, as measured by the Lebesgue constant (Such as minimum energy electrostatic points and Fekete points). However, these points typically do not have any Gauss-like quadrature properties. In this work, we describe a new numerical method to look for Gauss-like quadrature points in the triangle, based on a previous algorithm for computing Fekete points. Performing a brute force search for such points is extremely difficult. A common strategy to increase the numerical efficiency of these searches is to reduce the number of unknowns by imposing symmetry conditions on the quadrature points. Motivated by spectral element methods, we propose a different way to reduce the number of unknowns: We look for quadrature formula that have the same number of points as the number of basis functions used in the spectral element method's transform algorithm. This is an important requirement if they are to be used in a diagonal-mass-matrix spectral element method. This restriction allows for the construction of cardinal functions (Lagrange interpolating polynomials). The ability to construct cardinal functions leads to a remarkable expression relating the variation in the quadrature weights to the variation in the quadrature points. This relation in turn leads to an analytical expression for the gradient of the quadrature error with respect to the quadrature points. Thus the quadrature weights have been completely removed from the optimization problem, and we can implement an exact steepest descent algorithm for driving the quadrature error to zero. Results from the algorithm will be presented for the triangle and the sphere.
Using in situ wafer-curvature measurements of thin-film stress, we determine the critical thickness for strain relaxation in Al{sub x}Ga{sub 1-x}N/GaN heterostructures with 0.14 {le} x {le} 1. The surface morphology of selected films is examined by atomic force microscopy. Comparison of these measurements with critical-thickness models for brittle fracture and dislocation glide suggests that the onset of strain relaxation occurs by surface fracture for all compositions. Misfit-dislocations follow initial fracture, with slip-system selection occurring under the influence of composition-dependent changes in surface morphology.
We report our development of terahertz (THz) quantum-cascade lasers (QCLs) based on two novel features. First, the depopulation of the lower radiative level is achieved through resonant longitudinal optical (LO-)phonon scattering. This depopulation mechanism is robust at high temperatures and high injection levels. In contrast to infrared QCLs that also use LO-phonon scattering for depopulation, in our THz lasers the selectivity of the depopulation scattering is achieved through a combination of resonant tunneling and LO-phonon scattering, hence the term resonant phonon. This resonant-phonon scheme allows a highly selective depopulation of the lower radiative level with a sub-picosecond lifetime, while maintaining a relatively long upper level lifetime (>5 ps) that is due to upper-to-ground-state scattering. The second feature of our lasers is that mode confinement is achieved by using a novel double-sided metal-metal waveguide, which yields an essentially unity mode confinement factor and therefore a low total cavity loss at THz frequencies. Based on these two unique features, we have achieved some record performance, including, but not limited to, the highest pulsed operating temperature of 137 K, the highest continuous-wave operating temperature of 97 K, and the longest wavelength of 141 {micro}m (corresponding to 2.1 THz) without the assistance of a magnetic field.
Progress in understanding the physics of dynamic-hohlraums is reviewed for a system capable of generating 13 TW of axial radiation for high temperature (>200 eV) radiation-flow experiments and ICF capsule implosions.
This paper explores the possibility of separating and classifying remotely-sensed multispectral data from rocks and minerals onto seven geological rock-type groups. These groups are extracted from the general categories of metamorphic, igneous and sedimentary rocks. The study is performed under ideal conditions for which the data is generated according to laboratory hyperspectral data for the members, which are, in turn, passed through the Multi-spectral Thermal Imager (MTI) filters yielding 15 bands. The main challenge in separability is the small size of the training data sets, which initially did not permit direct application of Bayesian decision theory. To enable Bayseian classification, the original training data is linearly perturbed with the addition minerals, vegetation, soil, water and other valid impurities. As a result, the size of the training data is significantly increased and accurate estimates of the covariance matrices are achieved. In addition, a set of reduced (five) linearly-extracted canonical features that are optimal in providing the most important information about the data is determined. An alternative nonlinear feature-selection method is also employed based on spectral indices comprising a small subset of all possible ratios between bands. By applying three optimization strategies, combinations of two and three ratios are found that provide reliable separability and classification between all seven groups according to the Bhattacharyya distance. To set a benchmark to which the MTI capability in rock classification can be compared, an optimization strategy is performed for the selection of optimal multispectral filters, other than the MTI filters, and an improvement in classification is predicted.
Twinning is ubiquitous in electroplated metals. Here, we identify and discuss unique aspects of twinning found in electrodeposited Ni-Mn alloys. Previous reports concluded that the twin boundaries effectively refine the grain size, which enhances mechanical strength. Quantitative measurements from transmission electron microscopy (TEM) images show that the relative boundary length in the as-plated microstructure primarily comprises twin interfaces. Detailed TEM characterization reveals a range of length scales associated with twinning beginning with colonies ({approx}1000 nm) down to the width of individual twins, which is typically <50 nm. We also consider the connection between the crystallographic texture of the electrodeposit and the orientation of the twin planes with respect to the plating direction. The Ni-Mn alloy deposits in this work possess a 110-fiber texture. While twinning can occur on {l_brace}111{r_brace} planes either perpendicular or oblique to the plating direction in {l_brace}110{r_brace}-oriented grains, plan-view TEM images show that twins form primarily on those planes parallel to the plating direction. Therefore, grains enclosed by twins and multiply twinned particles are produced. Another important consequence of a high twin density is the formation of large numbers of twin-related junctions. We measure an area density of twin junctions that is comparable to the density of dislocations in a heavily cold-worked metal.
The radiographic integrated test stand (RITS-3) is a 5-MV, 160-kA, 70-ns inductive voltage adder accelerator at Sandia National Laboratories used to develop critical understanding of x-ray sources and flash radiographic drivers. On RITS-3 three pulse forming lines (PFLs) are used to drive three inductive voltage adder cavities. Each PFL contains a fast-pulse-charged, self-breakdown annular water switch that is used for initial pulse shaping and timing. Low loss in the switches combined with good synchronization is required for efficient operation of the accelerator. Switch maintenance is closely monitored over time to determine the effects of wear on switch breakdown performance.
An incident location must be translated into an address that responders can find on the ground. In populated areas it's street name and address number. For sparsely populated areas or highways it's typically road name and nearest milepost number. This is paired with road intersection information to help responders approach the incident as quickly and safely as possible. If responders are new to the area, or for cross-country response, more assistance is needed. If dispatchers had mileposts as points on their maps they could provide this assistance as well as vital information to public safety authorities as the incident unfolds. Mileposts are already universally understood and used. The missing rural response piece is to get milepost locations onto dispatch and control center screens.
This paper describes the integration of lookmarks into the ParaView visualization tool. Lookmarks are pointers to views of specific parts of a dataset. They were so named because lookmarks are to a visualization tool and dataset as bookmarks are to a browser and the World Wide Web. A lookmark can be saved and organized among other lookmarks within the context of ParaView. Then at a later time, either in the same ParaView session or in a different one, it can be regenerated, displaying the exact view of the data that had previously been saved. This allows the user to pick up where they left off, to continue to adjust the view or otherwise manipulate the data. Lookmarks facilitate collaboration between users who wish to share views of a dataset. They enable more effective data comparison because they can be applied to other datasets. They also serve as a way of organizing a user's data. Ultimately, a lookmark is a time-saving tool that automates the recreation of a complex view of the data.
Brief disclosures may often be sufficient for the filing of a Technical Advance with Sandia's Intellectual Property Center, but still be inadequate to facilitate an optimum patent application where more detail and explanation are required. Consequently, the crafting of a patent application may require considerably more additional interaction between the application preparer and the inventors. This inefficiency can be considerably mitigated if the inventors address some critical aspects of a patent application when they write a technical report.
At 70 miles per hour, overcoming aerodynamic drag represents about 65% of the total energy expenditure for a typical heavy truck vehicle. The goal of this US Department of Energy supported consortium is to establish a clear understanding of the drag producing flow phenomena. This is being accomplished through joint experiments and computations, leading to the smart design of drag reducing devices. This paper will describe our objective and approach, provide an overview of our efforts and accomplishments, and discuss our future direction.
Sandia National Laboratories has been conducting studies on performance of laboratory and commercial lithium-ion and other types of electrochemical cells using inductive models [1]. The objectives of these investigations are: (1) To develop procedures and techniques to rapidly determine performance degradation rates while these cells undergo life tests; (2) To model cell voltage and capacity in order to simulate cell performance characteristics under variable load and temperature conditions; (3) To model rechargeable battery degradation under charge/discharge cycles and many other conditions. The inductive model and methodology are particularly useful when complicated cell performance behaviors are involved, which are often difficult to be interpreted from simple empirical approaches. We find that the inductive model can be used effectively: (1) To enable efficient predictions of battery life; (2) To characterize system behavior. Inductive models provide convenient tools to characterize system behavior using experimentally or analytically derived data in an efficient and robust framework. The approach does not require detailed phenomenological development. There are certain advantages unique to this approach. Among these advantages is the ability to avoid making measurements of hard to determine physical parameters or having to understand cell processes sufficiently to write mathematical functions describing their behavior. We used artificial neural network for inductive modeling, along with ancillary mathematical tools to improve their accuracy. This paper summarizes efforts to use inductive tools for cell and battery modeling. Examples of numerical results will be presented. One of them is related to high power lithium-ion batteries tested under the U.S. Department of Energy Advanced Technology Development Program for hybrid vehicle applications. Sandia National Laboratories is involved in the development of accelerated life testing and thermal abuse tests to enhance the understanding of power and capacity fade issues and predict life of the battery under a nominal use condition. This paper will use power and capacity fade behaviors of a Ni-oxide-based lithium-ion battery system to illustrate how effective the inductive model can interpret the cell behavior and provide predictions of life. We will discuss the analysis of the fading behavior associated with the cell performance and explain how the model can predict cell performance.
Significantly improving the scalability of large structured adaptive mesh refinement (SAMR) applications is challenging. It requires sophisticated capabilities for using the underlying parallel computer's resources in the most efficient way. This is non-trivial, since the basic conditions for how to allocate the resources change dramatically during run-time due to the dynamics inherent in these applications. This paper presents a first characterization of a hybrid and dynamic partitioner for parallel SAMR applications. Specifically, we investigate parameter settings for trade-offs like communication vs. load balance and speed vs. quality. The key contribution is that the characterization shows that the partitioner is able to respond accurately to stimuli from system and application state, and hence adapt to various SAMR scenarios. This potentially reduces the run-time for large SAMR applications.
Cadmium plating on metal surfaces is commonly used for corrosion protection and to achieve good solderability on the 304L stainless steel shell of the MC4636 lightning arrestor connector (LAC) for the W76-1 system. This study examined the use of zinc as a potential substitute for the cadmium protective surface finish. Tests were performed with an R and RMA flux and test temperatures of 230 C, 245 C, and 260 C. Contact angle, {theta}{sub c}, served as the generalized solderability metric. The wetting rate and wetting time parameters were also collected. The solderability ({theta}{sub c}) of the Erie Plating Cd/Ni coatings was better than that of similar Amphenol coatings. Although the {theta}{sub c} data indicated that both Cd/Ni platings would provide adequate solderability, the wetting rate and wetting time data showed the Amphenol coatings to have better performance. The Zn/Ni coatings exhibited non-wetting under all flux and temperature conditions. Based on the results of these tests, it has been demonstrated that zinc plating is not a viable alternate to cadmium plating for the LAC connectors.
A major research goal of the national spherical torus experiment is establishing long-pulse, high beta, high confinement operation and its physics basis. This research has been enabled by facility capabilities developed during 2001 and 2002, including neutral beam (up to 7 MW) and high harmonic fast wave (HHFW) heating (up to 6 MW), toroidal fields up to 6 kG, plasma currents up to 1.5 MA, flexible shape control, and wall preparation techniques. These capabilities have enabled the generation of plasmas with {beta}{sub T} {triple_bond} <p>/(B{sub T0}{sup 2}/2{mu}{sub 0}) of up to 35%. Normalized beta values often exceed the no-wall limit, and studies suggest that passive wall mode stabilization enables this for H mode plasmas with broad pressure profiles. The viability of long, high bootstrap current fraction operations has been established for ELMing H mode plasmas with toroidal beta values in excess of 15% and sustained for several current relaxation times. Improvements in wall conditioning and fueling are likely contributing to a reduction in H mode power thresholds. Electron thermal conduction is the dominant thermal loss channel in auxiliary heated plasmas examined thus far. HHFW effectively heats electrons, and its acceleration of fast beam ions has been observed. Evidence for HHFW current drive is obtained by comparison of the loop voltage evolution in plasmas with matched density and temperature profiles but varying phases of launched HHFW waves. Studies of emissions from electron Bernstein waves indicate a density scale length dependence of their transmission across the upper hybrid resonance near the plasma edge that is consistent with theoretical predictions. A peak heat flux to the divertor targets of 10 MW m{sup -2} has been measured in the H mode, with large asymmetries being observed in the power deposition between the inner and outer strike points. Non-inductive plasma startup studies have focused on coaxial helicity injection. With this technique, toroidal currents up to 400 kA have been driven, and studies to assess flux closure and coupling to other current drive techniques have begun.
Research on the spherical torus (or spherical tokamak) (ST) is being pursued to explore the scientific benefits of modifying the field line structure from that in more moderate aspect ratio devices, such as the conventional tokamak. The ST experiments are being conducted in various US research facilities including the MA-class National Spherical Torus Experiment (NSTX) at Princeton, and three medium sized ST research facilities: PEGASUS at University of Wisconsin, HIT-II at University of Washington, and CDX-U at Princeton. In the context of the fusion energy development path being formulated in the US, an ST-based Component Test Facility (CTF) and, ultimately a Demo device, are being discussed. For these, it is essential to develop high performance, steady-state operational scenarios. The relevant scientific issues are energy confinement, MHD stability at high beta ({beta}), non-inductive sustainment, Ohmic-solenoid-free start-up, and power and particle handling. In the confinement area, the NSTX experiments have shown that the confinement can be up to 50% better than the ITER-98-pby2 H-mode scaling, consistent with the requirements for an ST-based CTF and Demo. In NSTX, CTF-relevant average toroidal beta values {beta}{sub T} of up to 35% with a near unity central {beta}{sub T} have been obtained. NSTX will be exploring advanced regimes where {beta}{sub T} up to 40% can be sustained through active stabilization of resistive wall modes. To date, the most successful technique for non-inductive sustainment in NSTX is the high beta poloidal regime, where discharges with a high non-inductive fraction ({approx}60% bootstrap current+NBI current drive) were sustained over the resistive skin time. Research on radio-frequency (RF) based heating and current drive utilizing high harmonic fast wave and electron Bernstein wave is also pursued on NSTX, PEGASUS, and CDX-U. For non-inductive start-up, the coaxial helicity injection, developed in HIT/HIT-II, has been adopted on NSTX to test the method up to I{sub p} {approx} 500 kA. In parallel, start-up using a RF current drive and only external poloidal field coils are being developed on NSTX. The area of power and particle handling is expected to be challenging because of the higher power density expected in the ST relative to that in conventional aspect-ratio tokamaks. Due to its promise for power and particle handling, liquid lithium is being studied in CDX-U as a potential plasma-facing surface for a fusion reactor.
Hyphendated LC-MS techniques are quickly becoming the standard tool for protemic analyses. For large homogeneous samples, bulk processing methods and capillary injection and separation techniques are suitable. However, for analysis of small or heterogeneous samples, techniques that can manipulate picoliter samples without dilution are required or samples will be lost or corrupted; further, static nanospray-type flowrates are required to maximize SNR. Microchip-level integration of sample injection with separation and mass spectrometry allow small-volume analytes to be processed on chip and immediately injected without dilution for analysis. An on-chip HPLC was fabricated using in situ polymerization of both fixed and mobile polymer monoliths. Integration of the chip with a nanospray MS emitter enables identification of peptides by the use of tandem MS. The chip is capable of analyzing of very small sample volumes (< 200 pl) in short times (< 3 min).