Finite element meshes are used to approximate the solution to some differential equation when no exact solution exists. A finite element mesh consists of many small (but finite, not infinitesimal or differential) regions of space that partition the problem domain, {Omega}. Each region, or element, or cell has an associated polynomial map, {Phi}, that converts the coordinates of any point, x = ( x y z ), in the element into another value, f(x), that is an approximate solution to the differential equation, as in Figure 1(a). This representation works quite well for axis-aligned regions of space, but when there are curved boundaries on the problem domain, {Omega}, it becomes algorithmically much more difficult to define {Phi} in terms of x. Rather, we define an archetypal element in a new coordinate space, r = ( r s t ), which has a simple, axis-aligned boundary (see Figure 1(b)) and place two maps onto our archetypal element:
In Phase I of this project, reported in SAND97-1922, Sandia National Laboratories applied a systems approach to identifying innovative biomedical technologies with the potential to reduce U.S. health care delivery costs while maintaining care quality. The effort provided roadmaps for the development and integration of technology to meet perceived care delivery requirements and an economic analysis model for development of care pathway costs for two conditions: coronary artery disease (CAD) and benign prostatic hypertrophy (BPH). Phases II and III of this project, which are presented in this report, were directed at detailing the parameters of telemedicine that influence care delivery costs and quality. These results were used to identify and field test the communication, interoperability, and security capabilities needed for cost-effective, secure, and reliable health care via telemedicine.
Bulk and surface energies are calculated for endmembers of the isostructural rhombohedral carbonate mineral family, including Ca, Cd, Co, Fe, Mg, Mn, Ni, and Zn compositions. The calculations for the bulk agree with the densities, bond distances, bond angles, and lattice enthalpies reported in the literature. The calculated energies also correlate with measured dissolution rates: the lattice energies show a log-linear relationship to the macroscopic dissolution rates at circumneutral pH. Moreover, the energies of ion pairs translated along surface steps are calculated and found to predict experimentally observed microscopic step retreat velocities. Finally, pit formation excess energies decrease with increasing pit size, which is consistent with the nonlinear dissolution kinetics hypothesized for the initial stages of pit formation.
This paper develops a general framework for applying algebraic multigrid techniques to constrained systems of linear algebraic equations that arise in applications with discretized PDEs. We discuss constraint coarsening strategies for constructing multigrid coarse grid spaces and several classes of multigrid smoothers for these systems. The potential of these methods is investigated with their application to contact problems in solid mechanics. Published in 2004 by John Wiley &Sons, Ltd.
The effects of side wall movement on granular packings were investigated. The studies showed that the resultant structure of the pack did not depend strongly on the magnitude of the wall movement, as long as the packing was moved for an equivalent distance. The main effect of wall movement was to drive the particle-wall and particle-particle contacts to the Coulomb criterion. This forced the packing in the high wall velocity case to obey the Janssen form, which took the Coulomb criterion as one of its main assumptions.
The conversion of nitrogen in char (char-N) to NO was studied both experimentally and computationally. In the experiments, pulverized coal char was produced from a U.S. high-volatile bituminous coal and burned in a dilute suspension at 1170 K, 1370 K and 1570 K, at an excess oxygen concentration of 8% (dry), with different levels of background NO. In some experiments, hydrogen bromide (HBr) was added to the vitiated air as a tool to alter the concentration of gas-phase radicals. During char combustion, low NO concentration and high temperature promoted the conversion of char-N to NO. HBr addition altered NO production in a way that depended on temperature. At 1170 K the presence of HBr increased NO production by 80%, whereas the addition of HBr decreased NO production at higher temperatures by 20%. To explain these results, three mechanistic descriptions of char-N evolution during combustion were evaluated with computational models that simulated (a) homogeneous chemistry in a plug-flow reactor with entrained particle combustion, and (b) homogeneous chemistry in the boundary layer surrounding a reacting particle. The observed effect of HBr on NO production could only be captured by a chemical mechanism that considered significant release of HCN from the char particle. Release of HCN also explained changes in NO production with temperature and NO concentration. Thus, the combination of experiments and simulations suggests that HCN evolution from the char during pulverized coal combustion plays an essential role in net NO production. Keywords: Coal; Char; Nitric oxide; Halogen.
AlGaN/GaN test structures were fabricated with an etched constriction. A nitrogen plasma treatment was used to remove the disordered layer, including natural oxides on the AlGaN surface, before the growth of the silicon nitride passivation film on several of the test structures. A pulsed voltage input, with a 200 ns pulse width, and a four-point measurement were used in a 50 {Omega} environment to determine the room temperature velocity-field characteristic of the structures. The samples performed similarly over low fields, giving a low-field mobility of 545 cm{sup 2} V{sup -1} s{sup -1}. The surface treated sample performed slightly better at higher fields than the untreated sample. The highest velocity measured was 1.25 x 10{sup 7} cm s{sup -1} at a field of 26 kV cm{sup -1}.
We demonstrate the presence of a resonant interaction between a pair of coupled quantum wires, which are realized in the ultra-high mobility two-dimensional electron gas of a GaAs/AlGaAs quantum well. Measuring the conductance of one wire, as the width of the other is varied, we observe a resonant peak in its conductance that is correlated with the point at which the swept wire pinches off. We discuss this behavior in terms of recent theoretical predictions concerning local spin-moment formation in quantum wires.
This report describes a new algorithm for the joint estimation of carrier phase, symbol timing and data in a Turbo coded phase shift keyed (PSK) digital communications system. Jointly estimating phase, timing and data can give processing gains of several dB over conventional processing, which consists of joint estimation of carrier phase and symbol timing followed by estimation of the Turbo-coded data. The new joint estimator allows delay and phase locked loops (DLL/PLL) to work at lower bit energies where Turbo codes are most useful. Performance results of software simulations and of a field test are given, as are details of a field programmable gate array (FPGA) implementation that is currently in design.
Containment of chemical wastes in near-surface and repository environments is accomplished by designing engineered barriers to fluid flow. Containment barrier technologies such as clay liners, soil/bentonite slurry walls, soil/plastic walls, artificially grouted sediments and soils, and colloidal gelling materials are intended to stop fluid transport and prevent plume migration. However, despite their effectiveness in the short-term, all of these barriers exhibit geochemical or geomechanical instability over the long-term resulting in degradation of the barrier and its ability to contain waste. No technologically practical or economically affordable technologies or methods exist at present for accomplishing total remediation, contaminant removal, or destruction-degradation in situ. A new type of containment barrier with a potentially broad range of environmental stability and longevity could result in significant cost-savings. This report documents a research program designed to establish the viability of a proposed new type of containment barrier derived from in situ precipitation of clays in the pore space of contaminated soils or sediments. The concept builds upon technologies that exist for colloidal or gel stabilization. Clays have the advantages of being geologically compatible with the near-surface environment and naturally sorptive for a range of contaminants, and further, the precipitation of clays could result in reduced permeability and hydraulic conductivity, and increased mechanical stability through cementation of soil particles. While limited success was achieved under certain controlled laboratory conditions, the results did not warrant continuation to the field stage for multiple reasons, and the research program was thus concluded with Phase 2.
Thermionic energy conversion in a miniature format shows potential as a viable, high efficiency, micro to macro-scale power source. A microminiature thermionic converter (MTC) with inter-electrode spacings on the order of microns has been prototyped and evaluated at Sandia. The remaining enabling technology is the development of low work function materials and processes that can be integrated into these converters to increase power production at modest temperatures (800 - 1300 K). The electrode materials are not well understood and the electrode thermionic properties are highly sensitive to manufacturing processes. Advanced theoretical, modeling, and fabrication capabilities are required to achieve optimum performance for MTC diodes. This report describes the modeling and fabrication efforts performed to develop micro dispenser cathodes for use in the MTC.
Li-ion cells are being developed for high-power applications in hybrid electric vehicles currently being designed for the FreedomCAR (Freedom Cooperative Automotive Research) program. These cells offer superior performance in terms of power and energy density over current cell chemistries. Cells using this chemistry are the basis of battery systems for both gasoline and fuel cell based hybrids. However, the safety of these cells needs to be understood and improved for eventual widespread commercial application in hybrid electric vehicles. The thermal behavior of commercial and prototype cells has been measured under varying conditions of cell composition, age and state-of-charge (SOC). The thermal runaway behavior of full cells has been measured along with the thermal properties of the cell components. We have also measured gas generation and gas composition over the temperature range corresponding to the thermal runaway regime. These studies have allowed characterization of cell thermal abuse tolerance and an understanding of the mechanisms that result in cell thermal runaway.
The Mixed Waste Landfill occupies 2.6 acres in the north-central portion of Technical Area 3 at Sandia National Laboratories, Albuquerque, New Mexico. The landfill accepted low-level radioactive and mixed waste from March 1959 to December 1988. This report represents the Corrective Measures Study that has been conducted for the Mixed Waste Landfill. The purpose of the study was to identify, develop, and evaluate corrective measures alternatives and recommend the corrective measure(s) to be taken at the site. Based upon detailed evaluation and risk assessment using guidance provided by the U.S. Environmental Protection Agency and the New Mexico Environment Department, the U.S. Department of Energy and Sandia National Laboratories recommend that a vegetative soil cover be deployed as the preferred corrective measure for the Mixed Waste Landfill. The cover would be of sufficient thickness to store precipitation, minimize infiltration and deep percolation, support a healthy vegetative community, and perform with minimal maintenance by emulating the natural analogue ecosystem. There would be no intrusive remedial activities at the site and therefore no potential for exposure to the waste. This alternative poses minimal risk to site workers implementing institutional controls associated with long-term environmental monitoring as well as routine maintenance and surveillance of the site.
A model of malicious attacks against an infrastructure system is developed that uses a network representation of the system structure together with a Hidden Markov Model of an attack at a node of that system and a Markov Decision Process model of attacker strategy across the system as a whole. We use information systems as an illustration, but the analytic structure developed can also apply to attacks against physical facilities or other systems that provide services to customers. This structure provides an explicit mechanism to evaluate expected losses from malicious attacks, and to evaluate changes in those losses that would result from system hardening. Thus, we provide a basis for evaluating the benefits of system hardening. The model also allows investigation of the potential for the purchase of an insurance contract to cover the potential losses when safeguards are breached and the system fails.
The work reported in this document involves a development effort to provide combat commanders and systems engineers with a capability to explore and optimize system concepts that include operational concepts as part of the design effort. An infrastructure and analytic framework has been designed and partially developed that meets a gap in systems engineering design for combat related complex systems. The system consists of three major components: The first component consists of a design environment that permits the combat commander to perform 'what-if' types of analyses in which parts of a course of action (COA) can be automated by generic system constructs. The second component consists of suites of optimization tools designed to integrate into the analytical architecture to explore the massive design space of an integrated design and operational space. These optimization tools have been selected for their utility in requirements development and operational concept development. The third component involves the design of a modeling paradigm for the complex system that takes advantage of functional definitions and the coupled state space representations, generic measures of effectiveness and performance, and a number of modeling constructs to maximize the efficiency of computer simulations. The system architecture has been developed to allow for a future extension in which the operational concept development aspects can be performed in a co-evolutionary process to ensure the most robust designs may be gleaned from the design space(s).
Program transformation is a restricted form of software construction that can be amenable to formal verification. When successful, the nature of the evidence provided by such a verification is considered strong and can constitute a major component of an argument that a high-consequence or safety-critical system meets its dependability requirements. This article explores the application of novel higher-order strategic programming techniques to the development of a portion of a class loader for a restricted implementation of the Java Virtual Machine (JVM). The implementation is called the SSP and is intended for use in high-consequence safety-critical embedded systems. Verification of the strategic program using ACL2 is also discussed.
In many strategic systems, the choice combinator provides a powerful mechanism for controlling the application of rules and strategies to terms. The ability of the choice combinator to exercise control over rewriting is based on the premise that the success and failure of strategy application can be observed. In this paper we present a higher-order strategic framework with the ability to dynamically construct strategies containing the choice combinator. To this framework, a combinator called hide is introduced that prevents the successful application of a strategy from being observed by the choice combinator. We then explore the impact of this new combinator on a real-world problem involving a restricted implementation of the Java Virtual Machine.
This report assembles models for the response of a wire interacting with a conducting ground to an electromagnetic pulse excitation. The cases of an infinite wire above the ground as well as resting on the ground and buried beneath the ground are treated. The focus is on the characteristics and propagation of the transmission line mode. Approximations are used to simplify the description and formulas are obtained for the current. The semi-infinite case, where the short circuit current can be nearly twice that of the infinite line, is also examined.
Network-centric systems that depend on mobile wireless ad hoc networks for their information exchange require detailed analysis to support their development. In many cases, this critical analysis is best provided with high-fidelity system simulations that include the effects of network architectures and protocols. In this research, we developed a high-fidelity system simulation capability using an HLA federation. The HLA federation, consisting of the Umbra system simulator and OPNET Modeler network simulator, provides a means for the system simulator to both affect, and be affected by, events in the network simulator. Advances are also made in increasing the fidelity of the wireless communication channel and reducing simulation run-time with a dead reckoning capability. A simulation experiment is included to demonstrate the developed modeling and simulation capability.
We have researched several new focused ion beam (FIB) micro-fabrication techniques that offer control of feature shape and the ability to accurately define features onto nonplanar substrates. These FIB-based processes are considered useful for prototyping, reverse engineering, and small-lot manufacturing. Ion beam-based techniques have been developed for defining features in miniature, nonplanar substrates. We demonstrate helices in cylindrical substrates having diameters from 100 {micro}m to 3 mm. Ion beam lathe processes sputter-define 10-{micro}m wide features in cylindrical substrates and tubes. For larger substrates, we combine focused ion beam milling with ultra-precision lathe turning techniques to accurately define 25-100 {micro}m features over many meters of path length. In several cases, we combine the feature defining capability of focused ion beam bombardment with additive techniques such as evaporation, sputter deposition and electroplating in order to build geometrically-complex, functionally-simple devices. Damascene methods that fabricate bound, metal microcoils have been developed for cylindrical substrates. Effects of focused ion milling on surface morphology are also highlighted in a study of ion-milled diamond.
A survey has been carried out to quantify the performance and life of over 700,000 valve-regulated lead-acid (VRLA) cells, which have been or are being used in stationary applications across the United States. The findings derived from this study have not identified any fundamental flaws of VRLA battery technology. There is evidence that some cell designs are more successful in float duty than others. A significant number of the VRLA cells covered by the survey were found to have provided satisfactory performance.
Though the Global Positioning System has revolutionized navigation in the modern age, it is limited in its capability for some applications because an unobstructed line of sight to a minimum of four satellites is required. One way of augmenting the system in small areas is by employing pseudolites to broadcast additional signals that can be used to improve the user's position solution. At the Navigation Systems Testing Laboratory (NSTL) at NASA's Johnson Space Center in Houston, TX, research has been underway on the use of pseudolites to perform precision relative navigation. Based on the findings of previous research done at the NSTL, the method used to process the pseudolite measurements is an extended Kalman filter of the double differenced carrier phase measurements. By employing simulations of the system, as well as processing previously collected data in a real time manner, sub-meter tracking of a moving receiver with carrier phase measurements in the extended Kalman filter appears to be possible.
The ASCI supercomputing program is broadly defined as running physics simulations on progressively more powerful digital computers. What happens if we extrapolate the computer technology to its end? We have developed a model for key ASCI computations running on a hypothetical computer whose technology is parameterized in ways that account for advancing technology. This model includes technology information such as Moore's Law for transistor scaling and developments in cooling technology. The model also includes limits imposed by laws of physics, such as thermodynamic limits on power dissipation, limits on cooling, and the limitation of signal propagation velocity to the speed of light. We apply this model and show that ASCI computations will advance smoothly for another 10-20 years to an 'end game' defined by thermodynamic limits and the speed of light. Performance levels at the end game will vary greatly by specific problem, but will be in the Exaflops to Zetaflops range for currently anticipated problems. We have also found an architecture that would be within a constant factor of giving optimal performance at the end game. This architecture is an evolutionary derivative of the mesh-connected microprocessor (such as ASCI Red Storm or IBM Blue Gene/L). We provide designs for the necessary enhancement to microprocessor functionality and the power-efficiency of both the processor and memory system. The technology we develop in the foregoing provides a 'perfect' computer model with which we can rate the quality of realizable computer designs, both in this writing and as a way of designing future computers. This report focuses on classical computers based on irreversible digital logic, and more specifically on algorithms that simulate space computing, irreversible logic, analog computers, and other ways to address stockpile stewardship that are outside the scope of this report.
This report summarizes research advances pursued with award funding issued by the DOE to Drexel University through the Presidential Early Career Award (PECASE) program. Professor Rich Cairncross was the recipient of this award in 1997. With it he pursued two related research topics under Sandia's guidance that address the outstanding issue of fluid-structural interactions of liquids with deformable solid materials, focusing mainly on the ubiquitous dynamic wetting problem. The project focus in the first four years was aimed at deriving a predictive numerical modeling approach for the motion of the dynamic contact line on a deformable substrate. A formulation of physical model equations was derived in the context of the Galerkin finite element method in an arbitrary Lagrangian/Eulerian (ALE) frame of reference. The formulation was successfully integrated in Sandia's Goma finite element code and tested on several technologically important thin-film coating problems. The model equations, the finite-element implementation, and results from several applications are given in this report. In the last year of the five-year project the same physical concepts were extended towards the problem of capillary imbibition in deformable porous media. A synopsis of this preliminary modeling and experimental effort is also discussed.
Science historian James Burke is well known for his stories about how technological innovations are intertwined and embedded in the culture of the time, for example, how the steam engine led to safety matches, imitation diamonds, and the landing on the moon.1 A lesson commonly drawn from his stories is that the path of science and technology (S&T) is nonlinear and unpredictable. Viewed another way, the lesson is that the solution to one problem can lead to solutions to other problems that are not obviously linked in advance, i.e., there is a ripple effect. The motto for Sandia's approach to research and development (R&D) is 'Science with the mission in mind.' In our view, our missions contain the problems that inspire our R&D, and the resulting solutions almost always have multiple benefits. As discussed below, Sandia's Laboratory Directed Research and Development (LDRD) Program is structured to bring problems relevant to our missions to the attention of researchers. LDRD projects are then selected on the basis of their programmatic merit as well as their technical merit. Considerable effort is made to communicate between investment areas to create the ripple effect. In recent years, attention to the ripple effect and to the performance of the LDRD Program, in general, has increased. Inside Sandia, as it is the sole source of discretionary research funding, LDRD funding is recognized as being the most precious of research dollars. Hence, there is great interest in maximizing its impact, especially through the ripple effect. Outside Sandia, there is increased scrutiny of the program's performance to be sure that it is not a 'sandbox' in which researchers play without relevance to national security needs. Let us therefore address the performance of the LDRD Program in fiscal year 2003 and then show how it is designed to maximize impact.
The ASCI Grid Services (initially called Distributed Resource Management) project was started under DisCom{sup 2} when distant and distributed computing was identified as a technology critical to the success of the ASCI Program. The goals of the Grid Services project has and continues to be to provide easy, consistent access to all the ASCI hardware and software resources across the nuclear weapons complex using computational grid technologies, increase the usability of ASCI hardware and software resources by providing interfaces for resource monitoring, job submission, job monitoring, and job control, and enable the effective use of high-end computing capability through complex-wide resource scheduling and brokering. In order to increase acceptance of the new technology, the goal included providing these services in both the unclassified as well as the classified user's environment. This paper summarizes the many accomplishments and lessons learned over approximately five years of the ASCI Grid Services Project. It also provides suggestions on how to renew/restart the effort for grid services capability when the situation is right for that need.
To establish mechanical material properties of cellular concrete mixes, a series of quasi-static, compression and tension tests have been completed. This report summarizes the test methods, set-up, relevant observations, and results from the constitutive experimental efforts. Results from the uniaxial and triaxial compression tests established failure criteria for the cellular concrete in terms of stress invariants I{sub 1} and J{sub 2}. {radical}J{sub 2} (MPa) = 297.2 - 278.7 exp{sup -0.000455 I}{sub 1}{sup (MPa)} for the 90-pcf concrete {radical}J{sub 2} (MPa) = 211.4 - 204.2 exp {sup -0.000628 I}{sub 1}{sup (MPa)} for the 60-pcf concrete
For many decades, engineers and scientists have studied the effects of high power microwaves (HPM) on electronics. These studies usually focus on means of delivering energy to upset electronic equipment and ways to protect equipment from HPM. The motivation for these studies is to develop the knowledge necessary either to cause disruption or to protect electronics from disruption. Since electronic circuits must absorb sufficient energy to fail and the source used to deliver this energy is far away from the electronic circuit, the source must emit a large quantity of energy. In free space, for example, as the distance between the source and the target increases, the source energy must increase by the square of distance. The HPM community has dedicated substantial resources to the development of higher energy sources as a result. Recently, members of the HPM community suggested a new disruption mechanism that could potentially cause system disruptions at much lower energy levels. The new mechanism, based on nonlinear dynamics, requires an expanded theory of circuit operation. This report summarizes an investigation of electronic circuit nonlinear behavior as it applies to inductor-resistor-diode circuits (known as the Linsay circuit) and phased-locked-loops. With the improvement in computing power and the need to model circuit behavior with greater precision, the nonlinear effects of circuit has become very important. In addition, every integrated circuit has as part of its design a protective circuit. These protective circuits use some variation of semiconductor junctions that can interact with parasitic components, present in every real system. Hence, the protective circuit can behave as a Linsay circuit. Although the nonlinear behavior is understandable, it is difficult to model accurately. Many researchers have used classical diode models successfully to show nonlinear effects within predicted regions of operation. However, these models do not accurately predict measured results. This study shows that models based on SPICE, although they exhibit chaotic behavior, do not properly reproduce circuit behavior without modifying diode parameters. This report describes the models and considerations used to model circuit behavior in the nonlinear range of operation. Further, it describes how a modified SPICE diode model improves the simulation results. We also studied the nonlinear behavior of a phased-locked-loop. Phased-locked loops are fundamental building block to many major systems (aileron, seeker heads, etc). We showed that an injected RF signal could drive the phased-locked-loop into chaos. During these chaotic episodes, the frequency of the phased-locked-loop takes excursion outside its normal range of operation. In addition to these excursions, the phased-locked-loop and the system it is controlling requires some time to get back into normal operation. The phased-locked-loop only needs to be upset enough long enough to keep it off balance.
A variety of multivariate calibration algorithms for quantitative spectral analyses were investigated and compared, and new algorithms were developed in the course of this Laboratory Directed Research and Development project. We were able to demonstrate the ability of the hybrid classical least squares/partial least squares (CLSIPLS) calibration algorithms to maintain calibrations in the presence of spectrometer drift and to transfer calibrations between spectrometers from the same or different manufacturers. These methods were found to be as good or better in prediction ability as the commonly used partial least squares (PLS) method. We also present the theory for an entirely new class of algorithms labeled augmented classical least squares (ACLS) methods. New factor selection methods are developed and described for the ACLS algorithms. These factor selection methods are demonstrated using near-infrared spectra collected from a system of dilute aqueous solutions. The ACLS algorithm is also shown to provide improved ease of use and better prediction ability than PLS when transferring calibrations between near-infrared calibrations from the same manufacturer. Finally, simulations incorporating either ideal or realistic errors in the spectra were used to compare the prediction abilities of the new ACLS algorithm with that of PLS. We found that in the presence of realistic errors with non-uniform spectral error variance across spectral channels or with spectral errors correlated between frequency channels, ACLS methods generally out-performed the more commonly used PLS method. These results demonstrate the need for realistic error structure in simulations when the prediction abilities of various algorithms are compared. The combination of equal or superior prediction ability and the ease of use of the ACLS algorithms make the new ACLS methods the preferred algorithms to use for multivariate spectral calibrations.
The goal of this Laboratory Directed Research & Development (LDRD) effort was to design, synthesize, and evaluate organic-inorganic nanocomposite membranes for solubility-based separations, such as the removal of higher hydrocarbons from air streams, using experiment and theory. We synthesized membranes by depositing alkylchlorosilanes on the nanoporous surfaces of alumina substrates, using techniques from the self-assembled monolayer literature to control the microstructure. We measured the permeability of these membranes to different gas species, in order to evaluate their performance in solubility-based separations. Membrane design goals were met by manipulating the pore size, alkyl group size, and alkyl surface density. We employed molecular dynamics simulation to gain further understanding of the relationship between membrane microstructure and separation performance.
The Maximum Permissible Exposure (MPE) is central to laser hazard analysis and is in general a function of the radiant wavelength. The selection of a laser for a particular application may allow for flexibility in the selection of the radiant wavelength. This flexibility would allow the selection of a particular laser based on the MPE and the hazards associated with that radiant wavelength. The Calculations of the MPEs for various laser wavelength ranges are presented. Techniques for determining eye safe viewing distances for both aided and unaided viewing and the determination of flight hazard distances are presented as well.
A key factor in our ability to produce and predict the stability of metal-based macro- to nano-scale structures and devices is a fundamental understanding of the localized nature of corrosion. Corrosion processes where physical dimensions become critical in the degradation process include localized corrosion initiation in passivated metals, microgalvanic interactions in metal alloys, and localized corrosion in structurally complex materials like nanocrystalline metal films under atmospheric and inundated conditions. This project focuses on two areas of corrosion science where a fundamental understanding of processes occurring at critical dimensions is not currently available. Sandia will study the critical length scales necessary for passive film breakdown in the inundated aluminum (Al) system and the chemical processes and transport in ultra-thin water films relevant to the atmospheric corrosion of nanocrystalline tungsten (W) films. Techniques are required that provide spatial information without significantly perturbing or masking the underlying relationships. Al passive film breakdown is governed by the relationship between area of the film sampled and its defect structure. We will combine low current measurements with microelectrodes to study the size scale required to observe a single initiation event and record electrochemical breakdown events. The resulting quantitative measure of stability will be correlated with metal grain size, secondary phase size and distribution to understand which metal properties control stability at the macro- and nano-scale. Mechanisms of atmospheric corrosion on W are dependent on the physical dimensions and continuity of adsorbed water layers as well as the chemical reactions that take place in this layer. We will combine electrochemical and scanning probe microscopic techniques to monitor the chemistry and resulting material transport in these thin surface layers. A description of the length scales responsible for driving the corrosion of the nanocrystalline metal films will be developed. The techniques developed and information derived from this work will be used to understand and predict degradation processes in microelectronic and microsystem devices critical to Sandia's mission.
Chemical disinfection and inactivation of viruses is largely understudied, but is very important especially in the case of highly infectious viruses. The purpose of this LDRD was to determine the efficacy of the Sandia National Laboratories developed decontamination formulations against Bovine Coronavirus (BCV) as a surrogate for the coronavirus that causes Severe Acute Respiratory Syndrome (SARS) in humans. The outbreak of SARS in late 2002 resulted from a highly infectious virus that was able to survive and remain infectious for extended periods. For this study, preliminary testing with Escherichia coli MS-2 (MS-2) and Escherichia coli T4 (T4) bacteriophages was conducted to develop virucidal methodology for verifying the inactivation after treatment with the test formulations following AOAC germicidal methodologies. After the determination of various experimental parameters (i.e. exposure, concentration) of the formulations, final testing was conducted on BCV. All experiments were conducted with various organic challenges (horse serum, bovine feces, compost) for results that more accurately represent field use condition. The MS-2 and T4 were slightly more resistant than BCV and required a 2 minute exposure while BCV was completely inactivated after a 1 minute exposure. These results were also consistent for the testing conducted in the presence of the various organic challenges indicating that the test formulations are highly effective for real world application.
Microelectromechanical systems (MEMS) comprise a new class of devices that include various forms of sensors and actuators. Recent studies have shown that microscale cantilever structures are able to detect a wide range of chemicals, biomolecules or even single bacterial cells. In this approach, cantilever deflection replaces optical fluorescence detection thereby eliminating complex chemical tagging steps that are difficult to achieve with chip-based architectures. A key challenge to utilizing this new detection scheme is the incorporation of functionalized MEMS structures within complex microfluidic channel architectures. The ability to accomplish this integration is currently limited by the processing approaches used to seal lids on pre-etched microfluidic channels. This report describes Sandia's first construction of MEMS instrumented microfluidic chips, which were fabricated by combining our leading capabilities in MEMS processing with our low-temperature photolithographic method for fabricating microfluidic channels. We have explored in-situ cantilevers and other similar passive MEMS devices as a new approach to directly sense fluid transport, and have successfully monitored local flow rates and viscosities within microfluidic channels. Actuated MEMS structures have also been incorporated into microfluidic channels, and the electrical requirements for actuation in liquids have been quantified with an elegant theory. Electrostatic actuation in water has been accomplished, and a novel technique for monitoring local electrical conductivities has been invented.
The lead probe neutron detector was originally designed by Spencer and Jacobs in 1965. The detector is based on lead activation due to the following neutron scattering reactions: {sup 207}Pb(n, n'){sup 207m}Pb and {sup 208}Pb(n, 2n){sup 207m}Pb. Delayed gammas from the metastable state of {sup 207m}Pb are counted using a plastic scintillator. The half-life of {sup 207m}Pb is 0.8 seconds. In the work reported here, MCNP was used to optimize the efficiency of the lead probe by suitably modifying the original geometry. A prototype detector was then built and tested. A 'layer cake' design was investigated in which thin (< 5 mm) layers of lead were sandwiched between thicker ({approx} 1 - 2 cm) layers of scintillator. An optimized 'layer cake' design had Figures of Merit (derived from the code) which were a factor of 3 greater than the original lead probe for DD neutrons, and a factor of 4 greater for DT neutrons, while containing 30% less lead. A smaller scale, 'proof of principle' prototype was built by Bechtel/Nevada to verify the code results. Its response to DD neutrons was measured using the DD dense plasma focus at Texas A&M and it conformed to the predicted performance. A voltage and discriminator sweep was performed to determine optimum sensitivity settings. It was determined that a calibration operating point could be obtained using a {sup 133}Ba 'bolt' as is the case with the original lead probe.
This report summarizes the analytical and experimental efforts for the Laboratory Directed Research and Development (LDRD) project entitled 'Obstacle Detection for Autonomous Navigation'. The principal goal of this project was to develop a mathematical framework for obstacle detection. The framework provides a basis for solutions to many complex obstacle detection problems critical to successful autonomous navigation. Another goal of this project was to characterize sensing requirements in terms of physical characteristics of obstacles, vehicles, and terrain. For example, a specific vehicle traveling at a specific velocity over a specific terrain requires a sensor with a certain range of detection, resolution, field-of-view, and sufficient sensitivity to specific obstacle characteristics. In some cases, combinations of sensors were required to distinguish between different hazardous obstacles and benign terrain. In our framework, the problem was posed as a multidimensional, multiple-hypothesis, pattern recognition problem. Features were extracted from selected sensors that allow hazardous obstacles to be distinguished from benign terrain and other types of obstacles. Another unique thrust of this project was to characterize different terrain classes with respect to both positive (e.g., rocks, trees, fences) and negative (e.g., holes, ditches, drop-offs) obstacles. The density of various hazards per square kilometer was statistically quantified for different terrain categories (e.g., high desert, ponderosa forest, and prairie). This quantification reflects the scale, or size, and mobility of different types of vehicles. The tradeoffs between obstacle detection, position location, path planning, and vehicle mobility capabilities were also to be characterized.
This report addresses the development of automated video-screening technology to assist security forces in protecting our homeland against terrorist threats. A threat of specific interest to this project is the covert placement and subsequent remote detonation of bombs (e.g., briefcase bombs) inside crowded public facilities. Different from existing video motion detection systems, the video-screening technology described in this report is capable of detecting changes in the static background of an otherwise, dynamic environment - environments where motion and human activities are persistent. Our goal was to quickly detect changes in the background - even under conditions when the background is visible to the camera less than 5% of the time. Instead of subtracting the background to detect movement or changes in a scene, we subtracted the dynamic scene variations to produce an estimate of the static background. Subsequent comparisons of static background estimates are used to detect changes in the background. Detected changes can be used to alert security forces of the presence and location of potential threats. The results of this research are summarized in two MS Power-point presentations included with this report.
A significant barrier to the deployment of distributed energy resources (DER) onto the power grid is uncertainty on the part of utility engineers regarding impacts of DER on their distribution systems. Because of the many possible combinations of DER and local power system characteristics, these impacts can most effectively be studied by computer simulation. The goal of this LDRD project was to develop and experimentally validate models of transient and steady state source behavior for incorporation into utility distribution analysis tools. Development of these models had not been prioritized either by the distributed-generation industry or by the inverter industry. A functioning model of a selected inverter-based DER was developed in collaboration with both the manufacturer and industrial power systems analysts. The model was written in the PSCAD simulation language, a variant of the ElectroMagnetic Transients Program (EMTP), a code that is widely used and accepted by utilities. A stakeholder team was formed and a methodology was established to address the problem. A list of detailed DER/utility interaction concerns was developed and prioritized. The list indicated that the scope of the problem significantly exceeded resources available for this LDRD project. As this work progresses under separate funding, the model will be refined and experimentally validated. It will then be incorporated in utility distribution analysis tools and used to study a variety of DER issues. The key next step will be design of the validation experiments.
Drainage of water from the region between an advancing probe tip and a flat sample is reconsidered under the assumption that the tip and sample surfaces are both coated by a thin water "interphase" (of width approximately a few nanometers) whose viscosity is much higher than that of the bulk liquid. A formula derived by solving the Navier-Stokes equations allows one to extract an interphase viscosity of ∼59 kPa·s (or ∼6.6 × 10 7 times the viscosity of bulk water at 25°C) from interfacial force microscope measurements with both tip and sample functionalized hydrophilic by OH-terminated tri(ethylene glycol) undecylthiol, self-assambled monolayers.
Coherent cross-track synthetic aperture radar (SAR) stereo is shown to produce high-resolution three-dimensional maps of the earth surface. This mode utilizes image pairs with common synthetic apertures but different squint angles allowing automated stereo correspondence and disparity estimation using complex correlation calculations. This paper presents two Ku-hand, coherent cross-track stereo collects over rolling and rugged terrain. The first collect generates a digital elevation map (DEM) with 1-m posts over rolling terrain using complex SAR imagery with spatial resolution of 0.125 m and a stereo convergence angle of 13.8°. The second collect produces multiple DEMs with 3-m posts over rugged terrain utilizing complex SAR imagery with spatial resolutions better than 0.5 m and stereo convergence angles greater than 40°. The resulting DEMS are compared to ground-truth DEMs and relative height root-mean-square (RMS), linear error 90-percent confidence (LE90), and maximum height error are reported.
We introduce a filter-based evolutionary algorithm (FEA) for constrained optimization. The filter used by an FEA explicitly imposes the concept of dominance on a partially ordered solution set. We show that the algorithm is provably robust for both linear and nonlinear problems and constraints. FEAs use a finite pattern of mutation offsets, and our analysis is closely related to recent convergence results for pattern search methods. We discuss how properties of this pattern impact the ability of an FEA to converge to a constrained local optimum.
The geologic model implicit in the original site characterization report for the Bayou Choctaw Strategic Petroleum Reserve Site near Baton Rouge, Louisiana, has been converted to a numerical, computer-based three-dimensional model. The original site characterization model was successfully converted with minimal modifications and use of new information. The geometries of the salt diapir, selected adjacent sedimentary horizons, and a number of faults have been modeled. Models of a partial set of the several storage caverns that have been solution-mined within the salt mass are also included. Collectively, the converted model appears to be a relatively realistic representation of the geology of the Bayou Choctaw site as known from existing data. A small number of geometric inconsistencies and other problems inherent in 2-D vs. 3-D modeling have been noted. Most of the major inconsistencies involve faults inferred from drill hole data only. Modem computer software allows visualization of the resulting site model and its component submodels with a degree of detail and flexibility that was not possible with conventional, two-dimensional and paper-based geologic maps and cross sections. The enhanced visualizations may be of particular value in conveying geologic concepts involved in the Bayou Choctaw Strategic Petroleum Reserve site to a lay audience. A Microsoft WindowsTM PC-based viewer and user-manipulable model files illustrating selected features of the converted model are included in this report.
These Technical Safety Requirements (TSRs) identify the operational conditions, boundaries, and administrative controls for the safe operation of the Auxiliary Hot Cell Facility (AHCF) at Sandia National Laboratories, in compliance with 10 CFR 830, 'Nuclear Safety Management.' The bases for the TSRs are established in the AHCF Documented Safety Analysis (DSA), which was issued in compliance with 10 CFR 830, Subpart B, 'Safety Basis Requirements.' The AHCF Limiting Conditions of Operation (LCOs) apply only to the ventilation system, the high efficiency particulate air (HEPA) filters, and the inventory. Surveillance Requirements (SRs) apply to the ventilation system, HEPA filters, and associated monitoring equipment; to certain passive design features; and to the inventory. No Safety Limits are necessary, because the AHCF is a Hazard Category 3 nuclear facility.