In many micro-scale fluid dynamics problems, molecular-level processes can control the interfacial energy and viscoelastic properties at a liquid-solid interface. This leads to a flow behavior that is very different from those similar fluid dynamics problems at the macro-scale. Presently, continuum modeling fails to capture this flow behavior. Molecular dynamics simulations have been applied to investigate these complex fluid-wall interactions at the nano-scale. Results show that the influence of the wall crystal lattice orientation on the fluid-wall interactions can be very important. To address those problems involving interactions of multiple length scales, a coupled atomistic-continuum model has been developed and applied to analyze flow in channels with atomically smooth walls. The present coupling strategy uses the molecular dynamics technique to probe the non-equilibrium flow near the channel walls and applies constraints to the fluid particle motion, which is coupled to the continuum flow modeling in the interior region. We have applied this new methodology to investigate Couette flow in micro-channels.
Improvements have been made at TRIUMF to permit higher proton intensities of up to 1010 cm-2s-1 over the energy range 20-500 MeV. This improved capability enables the study of displacement damage effects that require higher fluence irradiations. In addition, a high energy neutron irradiation capability has been developed for terrestrial cosmic ray soft error rate (SER) characterization of integrated circuits. The neutron beam characteristics of this facility are similar to those currently available at the Los Alamos National Laboratory WNR test facility. SER data measured on several SRAMs using the TRIUMF neutron beam are in good agreement with the results obtained on the same devices using the WNR facility. The TRIUMF neutron beam also contains thermal neutrons that can be easily removed by a sheet of cadmium. The ability to choose whether thermal neurons are present is a useful attribute not possible at the WNR.
This document provides the Technical Safety Requirements (TSR) for the Sandia National Laboratories Gamma Irradiation Facility (GIF). The TSR is a compilation of requirements that define the conditions, the safe boundaries, and the administrative controls necessary to ensure the safe operation of a nuclear facility and to reduce the potential risk to the public and facility workers from uncontrolled releases of radioactive or other hazardous materials. These requirements constitute an agreement between DOE and Sandia National Laboratories management regarding the safe operation of the Gamma Irradiation Facility.
Our research plan is two-fold: first, we have extended our biological model of bottom-up visual attention with several recently characterized cortical interactions that are known to be responsible for human performance in certain visual tasks, and second, we have used an eyetracking system for collecting human eye movement data, from which we can calibrate the new additions to the model. We acquired an infrared video eyetracking system, which we are using to record observers' eye position with high temporal (120Hz) and spatial ({+-} 0.25 deg visual angle) accuracy. We collected eye movement scan paths from observers as they view computer-generated fractals, rural and urban outdoor scenes, and overhead satellite imagery. We found that, with very high statistical significance (10 to 12 z-scores), the saliency model accurately predicts locations that human observers will find interesting. We adopted our model of short-range interactions among overlapping spatial orientation channels to better predict bottom-up stimulus-driven attention in humans. This enhanced model is even more accurate in its predictions of human observers' eye movements. We are currently incorporating biologically plausible long-range interactions among orientation channels, which will aid in the detection of elongated contours such as rivers, roads, airstrips, and other man-made structures.
Previous work on sample design has been focused on constructing designs for samples taken at point locations. Significantly less work has been done on sample design for data collected along transects. A review of approaches to point and transect sampling design shows that transects can be considered as a sequential set of point samples. Any two sampling designs can be compared through using each one to predict the value of the quantity being measured on a fixed reference grid. The quality of a design is quantified in two ways: computing either the sum or the product of the eigenvalues of the variance matrix of the prediction error. An important aspect of this analysis is that the reduction of the mean prediction error variance (MPEV) can be calculated for any proposed sample design, including one with straight and/or meandering transects, prior to taking those samples. This reduction in variance can be used as a ''stopping rule'' to determine when enough transect sampling has been completed on the site. Two approaches for the optimization of the transect locations are presented. The first minimizes the sum of the eigenvalues of the predictive error, and the second minimizes the product of these eigenvalues. Simulated annealing is used to identify transect locations that meet either of these objectives. This algorithm is applied to a hypothetical site to determine the optimal locations of two iterations of meandering transects given a previously existing straight transect. The MPEV calculation is also used on both a hypothetical site and on data collected at the Isleta Pueblo to evaluate its potential as a stopping rule. Results show that three or four rounds of systematic sampling with straight parallel transects covering 30 percent or less of the site, can reduce the initial MPEV by as much as 90 percent. The amount of reduction in MPEV can be used as a stopping rule, but the relationship between MPEV and the results of excavation versus no-further-action decisions is site specific and cannot be calculated prior to the sampling. It may be advantageous to use the reduction in MPEV as a stopping rule for systematic sampling across the site that can then be followed by focused sampling in areas identified has having UXO during the systematic sampling. The techniques presented here provide answers to the questions of ''Where to sample?'' and ''When to stop?'' and are capable of running in near real time to support iterative site characterization campaigns.
Solidification is an important aspect of welding, brazing, soldering, LENS fabrication, and casting. The current trend toward utilizing large-scale process simulations and materials response models for simulation-based engineering is driving the development of new modeling techniques. However, the effective utilization of these models is, in many cases, limited by a lack of fundamental understanding of the physical processes and interactions involved. In addition, experimental validation of model predictions is required. We have developed new and expanded experimental techniques, particularly those needed for in-situ measurement of the morphological and kinetic features of the solidification process. The new high-speed, high-resolution video techniques and data extraction methods developed in this work have been used to identify several unexpected features of the solidification process, including the observation that the solidification front is often far more dynamic than previously thought. In order to demonstrate the utility of the video techniques, correlations have been made between the in-situ observations and the final solidification microstructure. Experimental methods for determination of the solidification velocity in highly dynamic pulsed laser welds have been developed, implemented, and used to validate and refine laser welding models. Using post solidification metallographic techniques, we have discovered a previously unreported orientation relationship between ferrite and austenite in the Fe-Cr-Ni alloy system, and have characterized the conditions under which this new relationship develops. Taken together, the work has expanded both our understanding of, and our ability to characterize, solidification phenomena in complex alloy systems and processes.
This report summarizes a variety of the most useful and commonly applied methods for obtaining Dempster-Shafer structures, and their mathematical kin probability boxes, from empirical information or theoretical knowledge. The report includes a review of the aggregation methods for handling agreement and conflict when multiple such objects are obtained from different sources.
The microcombustor described in this report was developed primarily for thermal management in microsystems and as a platform for micro-scale flame ionization detectors (microFID). The microcombustor consists of a thin-film heater/thermal sensor patterned on a thin insulating membrane that is suspended from its edges over a silicon frame. This micromachined design has very low heat capacity and thermal conductivity and is an ideal platform for heating catalytic materials placed on its surface. Catalysts play an important role in this design since they provide a convenient surface-based method for flame ignition and stabilization. The free-standing platform used in the microcombustor mitigates large heat losses arising from large surface-to-volume ratios typical of the microdomain, and, together with the insulating platform, permit combustion on the microscale. Surface oxidation, flame ignition and flame stabilization have been demonstrated with this design for hydrogen and hydrocarbon fuels premixed with air. Unoptimized heat densities of 38 mW/mm{sup 2} have been achieved for the purpose of heating microsystems. Importantly, the microcombustor design expands the limits of flammability (Low as compared with conventional diffusion flames); an unoptimized LoF of 1-32% for natural gas in air was demonstrated with the microcombustor, whereas conventionally 4-16% observed. The LoF for hydrogen, methane, propane and ethane are likewise expanded. This feature will permit the use of this technology in many portable applications were reduced temperatures, lean fuel/air mixes or low gas flows are required. By coupling miniature electrodes and an electrometer circuit with the microcombustor, the first ever demonstration of a microFID utilizing premixed fuel and a catalytically-stabilized flame has been performed; the detection of -1-3% of ethane in hydrogen/air is shown. This report describes work done to develop the microcombustor for microsystem heating and flame ionization detection and includes a description of modeling and simulation performed to understand the basic operation of this device. Ancillary research on the use of the microcombustor in calorimetric gas sensing is also described where appropriate.
The purpose of microstructural control is to optimize materials properties. To that end, they have developed sophisticated and successful computational models of both microstructural evolution and mechanical response. However, coupling these models to quantitatively predict the properties of a given microstructure poses a challenge. This problem arises because most continuum response models, such as finite element, finite volume, or material point methods, do not incorporate a real length scale. Thus, two self-similar polycrystals have identical mechanical properties regardless of grain size, in conflict with theory and observations. In this project, they took a tiered risk approach to incorporate microstructure and its resultant length scales in mechanical response simulations. Techniques considered include low-risk, low-benefit methods, as well as higher-payoff, higher-risk methods. Methods studied include a constitutive response model with a local length-scale parameter, a power-law hardening rate gradient near grain boundaries, a local Voce hardening law, and strain-gradient polycrystal plasticity. These techniques were validated on a variety of systems for which theoretical analyses and/or experimental data exist. The results may be used to generate improved constitutive models that explicitly depend upon microstructure and to provide insight into microstructural deformation and failure processes. Furthermore, because mechanical state drives microstructural evolution, a strain-enhanced grain growth model was coupled with the mechanical response simulations. The coupled model predicts both properties as a function of microstructure and microstructural development as a function of processing conditions.
A laser safety and hazard analysis was performed for the ARES laser system based on the 2000 version of the American National Standards Institute's (ANSI) Standard Z136.1,for Safe Use of Lasers and the 2000 version of the ANSI Standard Z136.6, for Safe Use of Lasers Outdoors. The ARES laser system is a Van/Truck based mobile platform, which is used to perform laser interaction experiments and tests at various national test sites.
A laser safety and hazard analysis was performed for the AURA laser system based on the 2000 version of the American National Standards Institute's (ANSI) Standard Z136.1, for ''Safe Use of Lasers'' and the 2000 version of the ANSI Standard Z136.6, for ''Safe Use of Lasers Outdoors''. The trailer based AURA laser system is a mobile platform, which is used to perform laser interaction experiments and tests at various national test sites. The trailer (B70) based AURA laser system is generally operated on the United State Air Force Starfire Optical Range (SOR) at Kirtland Air Force Base (KAFB), New Mexico. The laser is used to perform laser interaction testing inside the laser trailer as well as outside the trailer at target sites located at various distances from the exit telescope. In order to protect personnel, who work inside the Nominal Hazard Zone (NHZ), from hazardous laser emission exposures it was necessary to determine the Maximum Permissible Exposure (MPE) for each laser wavelength (wavelength bands) and calculate the appropriate minimum Optical Density (OD{sub min}) of the laser safety eyewear used by authorized personnel and the Nominal Ocular Hazard Distance (NOHD) to protect unauthorized personnel who may have violated the boundaries of the control area and enter into the laser's NHZ.
Circuit simulation tools (e.g., SPICE) have become invaluable in the development and design of electronic circuits. Similarly, device-scale simulation tools (e.g., DaVinci) are commonly used in the design of individual semiconductor components. Some problems, such as single-event upset (SEU), require the fidelity of a mesh-based device simulator but are only meaningful when dynamically coupled with an external circuit. For such problems a mixed-level simulator is desirable, but the two types of simulation generally have different (sometimes conflicting) numerical requirements. To address these considerations, we have investigated variations of the two-level Newton algorithm, which preserves tight coupling between the circuit and the partial differential equations (PDE) device, while optimizing the numerics for both.
The effects of photocurrents in nuclear weapons induced by proximal nuclear detonations are well known and remain a serious hostile environment threat for the US stockpile. This report describes the final results of an LDRD study of the physical phenomena underlying prompt photocurrents in microelectronic devices and circuits. The goals of this project were to obtain an improved understanding of these phenomena, and to incorporate improved models of photocurrent effects into simulation codes to assist designers in meeting hostile radiation requirements with minimum build and test cycles. We have also developed a new capability on the ion microbeam accelerator in Sandia's Ion Beam Materials Research Laboratory (the Transient Radiation Microscope, or TRM) to supply ionizing radiation in selected micro-regions of a device. The dose rates achieved in this new facility approach those possible with conventional large-scale dose-rate sources at Sandia such as HERMES III and Saturn. It is now possible to test the physics and models in device physics simulators such as Davinci in ways not previously possible. We found that the physical models in Davinci are well suited to calculating prompt photocurrents in microelectronic devices, and that the TRM can reproduce results from conventional large-scale dose-rate sources in devices where the charge-collection depth is less than the range of the ions used in the TRM.
We are currently exploring and developing a new statistical mechanics approach to designing self organizing and self assembling systems that is unique to SNL. The primary application target for this ongoing research is the development of new kinds of nanoscale components and hardware systems. However, a surprising out of the box connection to software development is emerging from this effort. With some amount of modification, the collective behavior physics ideas for enabling simple hardware components to self organize may also provide design methods for a new class of software modules. Large numbers of these relatively small software components, if designed correctly, would be able to self assemble into a variety of much larger and more complex software systems. This self organization process would be steered to yield desired sets of system properties. If successful, this would provide a radical (disruptive technology) path to developing complex, high reliability software unlike any known today. The special work needed to evaluate this high risk, high payoff opportunity does not fit well into existing SNL funding categories, as it is well outside of the mainstreams of both conventional software development practices and the nanoscience research area that spawned it. We proposed a small LDRD effort aimed at appropriately generalizing these collective behavior physics concepts and testing their feasibility for achieving the self organization of large software systems. Our favorable results motivate an expanded effort to fully develop self-organizing software as a new technology.
This document was prepared to support the Department of Energy's compliance with Sections 106 and 110 of the National Historic Preservation Act. It provides an overview of the historic context in which Sandia National Laboratories/California was created and developed. Establishing such a context allows for a reasonable and reasoned historical assessment of Sandia National Laboratories/California properties. The Cold War arms race provides the primary historical context for the SNL/CA built environment.
We present a technique for determining non-linear resistances, capacitances, and inductances from ring down data in a non-linear RLC circuit. Although the governing differential equations are non-linear, we are able to solve this problem using linear least squares without doing any sort of non-linear iteration.
Military test and training ranges operate with live fire engagements to provide realism important to the maintenance of key tactical skills. Ordnance detonations during these operations typically produce minute residues of parent explosive chemical compounds. Occasional low order detonations also disperse solid phase energetic material onto the surface soil. These detonation remnants are implicated in chemical contamination impacts to groundwater on a limited set of ranges where environmental characterization projects have occurred. Key questions arise regarding how these residues and the environmental conditions (e.g. weather and geostratigraphy) contribute to groundwater pollution impacts. This report documents interim results of experimental work evaluating mass transfer processes from solid phase energetics to soil pore water. The experimental work is used as a basis to formulate a mass transfer numerical model, which has been incorporated into the porous media simulation code T2TNT. Experimental work to date with Composition B explosive has shown that column tests typically produce effluents near the temperature dependent solubility limits for RDX and TNT. The influence of water flow rate, temperature, porous media saturation and mass loading is documented. The mass transfer model formulation uses a mass transfer coefficient and surface area function and shows good agreement with the experimental data. Continued experimental work is necessary to evaluate solid phase particle size and 2-dimensional effects, and actual low order detonation debris. Simulation model improvements will continue leading to a capability to complete screening assessments of the impacts of military range operations on groundwater quality.
The GEO-SEQ Project is investigating methods for geological sequestration of CO{sub 2}. This project, which is directed by LBNL and includes a number of other industrial, university, and National Laboratory partners, is evaluating computer simulation models including TOUGH2. One of the problems to be considered is Enhanced Coal Bed Methane (ECBM) recovery. In this scenario, CO2 is pumped into methane-rich coal beds. Due to adsorption processes, the CO2 is sorbed onto the coal, which displaces the previously sorbed methane (CH4). The released methane can then be recovered, at least partially offsetting the cost of CO2 sequestration. Modifications have been made to the EOS7R equation of state in TOUGH2 to include the extended Langmuir isotherm for sorbing gases, including the change in porosity associated with the sorbed gas mass. Comparison to hand calculations for pure gas and binary mixtures shows very good agreement. Application to a CO{sub 2} well injection problem given by Law et al. (2002) shows good agreement considering the differences in the equations of state.
Rapid detection and identification of bacteria and other pathogens is important for many civilian and military applications. The taxonomic significance, or the ability to differentiate one microorganism from another, using fatty acid content and distribution is well known. For analysis fatty acids are usually converted to fatty acid methyl esters (FAMEs). Bench-top methods are commercially available and recent publications have demonstrated that FAMEs can be obtained from whole bacterial cells in an in situ single-step pyrolysis/methylation analysis. This report documents the progress made during a three year Laboratory Directed Research and Development (LDRD) program funded to investigate the use of microfabricated components (developed for other sensing applications) for the rapid identification of bioorganisms based upon pyrolysis and FAME analysis. Components investigated include a micropyrolyzer, a microGC, and a surface acoustic wave (SAW) array detector. Results demonstrate that the micropyrolyzer can pyrolyze whole cell bacteria samples using only milliwatts of power to produce FAMEs from bacterial samples. The microGC is shown to separate FAMEs of biological interest, and the SAW array is shown to detect volatile FAMEs. Results for each component and their capabilities and limitations are presented and discussed. This project has produced the first published work showing successful pyrolysis/methylation of fatty acids and related analytes using a microfabricated pyrolysis device.
The Defense Advanced Research Projects Agency (DARPA) has recognized that biological and chemical toxins are a real and growing threat to troops, civilians, and the ecosystem. The Explosives Components Facility at Sandia National Laboratories (SNL) has been working with the University of Montana, the Southwest Research Institute, and other agencies to evaluate the feasibility of directing honeybees to specific targets, and for environmental sampling of biological and chemical ''agents of harm''. Recent work has focused on finding and locating buried landmines and unexploded ordnance (UXO). Tests have demonstrated that honeybees can be trained to efficiently and accurately locate explosive signatures in the environment. However, it is difficult to visually track the bees and determine precisely where the targets are located. Video equipment is not practical due to its limited resolution and range. In addition, it is often unsafe to install such equipment in a field. A technology is needed to provide investigators with the standoff capability to track bees and accurately map the location of the suspected targets. This report documents Light Detection and Ranging (LIDAR) tests that were performed by SNL. These tests have shown that a LIDAR system can be used to track honeybees. The LIDAR system can provide both the range and coordinates of the target so that the location of buried munitions can be accurately mapped for subsequent removal.
This paper presents a description of the SIERRA Framework Version 3 parallel transfer operators. The high-level design including object interrelationships, as well as requirements for their use, is discussed. Transfer operators are used for moving field data from one computational mesh to another. The need for this service spans many different applications. The most common application is to enable loose coupling of multiple physics modules, such as for the coupling of a quasi-statics analysis with a thermal analysis. The SIERRA transfer operators support the transfer of nodal and element fields between meshes of different, arbitrary parallel decompositions. Also supplied are ''copy'' transfer operators for efficient transfer of fields between identical meshes. A ''copy'' transfer operator is also implemented for constraint objects. Each of these transfer operators is described. Also, two different parallel algorithms are presented for handling the geometric misalignment between different parallel-distributed meshes.
In a Synthetic Aperture Radar (SAR) system, the purpose of the receiver is to process incoming radar signals in order to obtain target information and ultimately construct an image of the target area. Incoming raw signals are usually in the microwave frequency range and are typically processed with analog circuitry, requiring hardware designed specifically for the desired signal processing operations. A more flexible approach is to process the signals in the digital domain. Recent advances in analog-to-digital converter (ADC) and Field Programmable Gate Array (FPGA) technology allow direct digital processing of wideband intermediate frequency (IF) signals. Modern ADCs can achieve sampling rates in excess of 1GS/s, and modern FPGAs can contain millions of logic gates operating at frequencies over 100 MHz. The combination of these technologies is necessary to implement a digital radar receiver capable of performing high speed, sophisticated and scalable DSP designs that are not possible with analog systems. Additionally, FPGA technology allows designs to be modified as the design parameters change without the need for redesigning circuit boards, potentially saving both time and money. For typical radars receivers, there is a need for operation at multiple ranges, which requires filters with multiple decimation rates, i.e., multiple bandwidths. In previous radar receivers, variable decimation was implemented by switching between SAW filters to achieve an acceptable filter configuration. While this method works, it is rather ''brute force'' because it duplicates a large amount of hardware and requires a new filter to be added for each IF bandwidth. By implementing the filter digitally in FPGAs, a larger number of decimation values (and consequently a larger number of bandwidths) can be implemented with no need for extra components. High performance, wide bandwidth radar systems also place high demands on the DSP throughput of a given digital receiver. In such applications, the maximum clock frequency of a given FPGA is not adequate to support the required data throughput. This problem can be overcome by employing a parallel implementation of the pane filter. The parallel pane filter uses a polyphase parallelization technique to achieve an aggregate data rate which is twice that of the FPGA clock frequency. This is achieved at the expense of roughly doubling the FPGA resource usage.
The Nuclear Regulatory Commission (NRC) approves new package designs for shipping fissile quantities of UF{sub 6}. Currently there are three packages approved by the NRC for domestic shipments of fissile quantities of UF{sub 6}: NCI-21PF-1; UX-30; and ESP30X. For approval by the NRC, packages must be subjected to a sequence of physical tests to simulate transportation accident conditions as described in 10 CFR Part 71. The primary objective of this project was to relate the conditions experienced by these packages in the tests described in 10 CFR Part 71 to conditions potentially encountered in actual accidents and to estimate the probabilities of such accidents. Comparison of the effects of actual accident conditions to 10 CFR Part 71 tests was achieved by means of computer modeling of structural effects on the packages due to impacts with actual surfaces, and thermal effects resulting from test and other fire scenarios. In addition, the likelihood of encountering bodies of water or sufficient rainfall to cause complete or partial immersion during transport over representative truck routes was assessed. Modeled effects, and their associated probabilities, were combined with existing event-tree data, plus accident rates and other characteristics gathered from representative routes, to derive generalized probabilities of encountering accident conditions comparable to the 10 CFR Part 71 conditions. This analysis suggests that the regulatory conditions are unlikely to be exceeded in real accidents, i.e. the likelihood of UF{sub 6} being dispersed as a result of accident impact or fire is small. Moreover, given that an accident has occurred, exposure to water by fire-fighting, heavy rain or submersion in a body of water is even less probable by factors ranging from 0.5 to 8E-6.