We have created a logic-based, Turing-complete language for stochastic modeling. Since the inference scheme for this language is based on a variant of Pearl's loopy belief propagation algorithm, we call it Loopy Logic. Traditional Bayesian networks have limited expressive power, basically constrained to finite domains as in the propositional calculus. Our language contains variables that can capture general classes of situations, events and relationships. A first-order language is also able to reason about potentially infinite classes and situations using constructs such as hidden Markov models(HMMs). Our language uses an Expectation-Maximization (EM) type learning of parameters. This has a natural fit with the Loopy Belief Propagation used for inference since both can be viewed as iterative message passing algorithms. We present the syntax and theoretical foundations for our Loopy Logic language. We then demonstrate three examples of stochastic modeling and diagnosis that explore the representational power of the language. A mechanical fault detection example displays how Loopy Logic can model time-series processes using an HMM variant. A digital circuit example exhibits the probabilistic modeling capabilities, and finally, a parameter fitting example demonstrates the power for learning unknown stochastic values.
The C6 project 'Encapsulation Processes' has been designed to obtain experimental measurements for discovery of phenomena critical to improving these processes, as well as data required in the verification and validation plan (Rao et al. 2001) for model validation of flow in progressively complex geometries. We have observed and recorded the flow of clear, Newtonian liquids and opaque, rheologically complex suspensions in two mold geometries. The first geometry is a simple wineglass geometry in a cylinder and is reported here in Part 1. The results in a more realistic encapsulation geometry are reported in Part 2.
Diagnostic tracer layers of Al and/or Mg have been embedded in Dynamic Hohlraum targets which are imploded on Sandia National Laboratories Z generator by surrounding them with nested arrays of tungsten wires. The K-shell lines of these elements are observed, usually in absorption, in both time-resolved and time-integrated spectra. The radiation physics of line formation in this environment is well understood and captured with a detailed model. A {chi}{sup 2} fit to the measured line intensities is used in conjunction with the model to determine the hohlraums intrinsic properties. Among other features, our analyses find no evidence of intrinsic top-bottom asymmetry in the Dynamic Hohlraums.
Dipicolinic acid (DPA, 2,6-pyridinedicarboxylic acid) is a substance uniquely present in bacterial spores such as that from anthrax (B. anthracis). It is known that DPA can be detected by the long-lived fluorescence of its terbium chelate; the best limit of detection (LOD) reported thus far using a large benchtop gated fluorescence instrument using a pulsed Xe lamp is 2 nM. We use a novel AlGaN light-emitting diode (LED) fabricated on a sapphire substrate that has peak emission at 291 nm. Although the overlap of the emission band of this LED with the absorption band of Tb-DPA ({lambda}{sub max} doublet: 273, 279 nm) is not ideal, we demonstrate that a compact detector based on this LED and an off-the-shelf gated photodetection module can provide an LOD of 0.4 nM, thus providing a basis for convenient early warning detectors.
X-ray spectra and images from Al (with 5% of Mg and some with 5% of NaF dopants) and Cu (pure and with 4% of Ni) wire arrays and X-pinches were accumulated in experiments on the 1 MA pulsed power generator at UNR. In particular, axially and radially resolved K-shell X-ray spectra of Al, Mg, and Na and L-shell X-ray spectra of Cu and Ni were recorded by a KAP crystal (in a spectral region from 6 to 15 Aring) through different slits from 50 mum to 3 mm. In addition, spatially integrated harder X-ray spectra were monitored by a LiF crystal. Non-LTE kinetic models of Al, Mg, and Na, and of Cu and Ni provided spatially resolved electron temperatures and densities for experiments with Al and Cu loads, respectively. Advantages of using alloys and dopants with small concentrations for spectroscopic plasma diagnostics will be presented. Dependence of the plasma's spatial structures, temperatures, and densities from wire material and load configurations, sizes, and masses will be discussed .
The purpose of this report is to provide school administrators with the ability to determine their security system requirements, so they can make informed decisions when working with vendors and others to improve their security posture. This is accomplished by (1) explaining a systems-based approach to defining the objectives and needs of the system, and (2), providing information on the ability of common components (sensors, cameras, metal detectors, etc) to achieve those objectives, in an effectively integrated system.
This document describes the specimen and transportation containers currently available for use with hazardous and infectious materials. A detailed comparison of advantages, disadvantages, and costs of the different technologies is included. Short- and long-term recommendations are also provided.3 DraftDraftDraftExecutive SummaryThe Federal Bureau of Investigation's Hazardous Materials Response Unit currently has hazardous material transport containers for shipping 1-quart paint cans and small amounts of contaminated forensic evidence, but the containers may not be able to maintain their integrity under accident conditions or for some types of hazardous materials. This report provides guidance and recommendations on the availability of packages for the safe and secure transport of evidence consisting of or contaminated with hazardous chemicals or infectious materials. Only non-bulk containers were considered because these are appropriate for transport on small aircraft. This report will addresses packaging and transportation concerns for Hazardous Classes 3, 4, 5, 6, 8, and 9 materials. If the evidence is known or suspected of belonging to one of these Hazardous Classes, it must be packaged in accordance with the provisions of 49 CFR Part 173. The anthrax scare of several years ago, and less well publicized incidents involving unknown and uncharacterized substances, has required that suspicious substances be sent to appropriate analytical laboratories for analysis and characterization. Transportation of potentially hazardous or infectious material to an appropriate analytical laboratory requires transport containers that maintain both the biological and chemical integrity of the substance in question. As a rule, only relatively small quantities will be available for analysis. Appropriate transportation packaging is needed that will maintain the integrity of the substance, will not allow biological alteration, will not react chemically with the substance being shipped, and will otherwise maintain it as nearly as possible in its original condition.The recommendations provided are short-term solutions to the problems of shipping evidence, and have considered only currently commercially available containers. These containers may not be appropriate for all cases. Design, testing, and certification of new transportation containers would be necessary to provide a container appropriate for all cases.Table 1 provides a summary of the recommendations for each class of hazardous material.Table 1: Summary of RecommendationsContainerCost1-quart paint can with ArmlockTM seal ringLabelMaster(r)%242.90 eachHazard Class 3, 4, 5, 8, or 9 Small ContainersTC Hazardous Material Transport ContainerCurrently in Use4 DraftDraftDraftTable 1: Summary of Recommendations (continued)ContainerCost55-gallon open or closed-head steel drumsAll-Pak, Inc.%2458.28 - %2473.62 eachHazard Class 3, 4, 5, 8, or 9 Large Containers95-gallon poly overpack LabelMaster(r)%24194.50 each1-liter glass container with plastic coatingLabelMaster(r)%243.35 - %243.70 eachHazard Class 6 Division 6.1 Poisonous by Inhalation (PIH) Small ContainersTC Hazardous Material Transport ContainerCurrently in Use20 to 55-gallon PIH overpacksLabelMaster(r)%24142.50 - %24170.50 eachHazard Class 6 Division 6.1 Poisonous by Inhalation (PIH) Large Containers65 to 95-gallon poly overpacksLabelMaster(r)%24163.30 - %24194.50 each1-liter transparent containerCurrently in UseHazard Class 6 Division 6.2 Infectious Material Small ContainersInfectious Substance ShipperSource Packaging of NE, Inc.%24336.00 eachNone Commercially AvailableN/AHazard Class 6 Division 6.2 Infectious Material Large ContainersNone Commercially Available N/A5
Experimental results are presented for stress evolution, in vacuum and electrolyte, for the first monolayer of Cu on Au(111). In electrolyte the monolayer is pseudomorphic and the stress-thickness change is -0.60 N/m, while conventional epitaxy theory predicts a value of +7.76 N/m. In vacuum, the monolayer is incoherent with the underlying gold. Using a combination of first-principles based calculations and molecular dynamic simulations we analyzed these results and demonstrate that in electrolyte, overlayer coherency is maintained owing to anion adsorption.
We apply density functional theory (DFT) and the DFT+U technique to study the adsorption of transition metal porphine molecules on atomistically flat Au(111) surfaces. DFT calculations using the Perdew?Burke?Ernzerhof exchange correlation functional correctly predict the palladium porphine (PdP) low-spin ground state. PdP is found to adsorb preferentially on gold in a flat geometry, not in an edgewise geometry, in qualitative agreement with experiments on substituted porphyrins. It exhibits no covalent bonding to Au(111), and the binding energy is a small fraction of an electronvolt. The DFT+U technique, parametrized to B3LYP-predicted spin state ordering of the Mn d-electrons, is found to be crucial for reproducing the correct magnetic moment and geometry of the isolated manganese porphine (MnP) molecule. Adsorption of Mn(II)P on Au(111) substantially alters the Mn ion spin state. Its interaction with the gold substrate is stronger and more site-specific than that of PdP. The binding can be partially reversed by applying an electric potential, which leads to significant changes in the electronic and magnetic properties of adsorbed MnP and 0.1 {angstrom} changes in the Mn-nitrogen distances within the porphine macrocycle. We conjecture that this DFT+U approach may be a useful general method for modeling first-row transition metal ion complexes in a condensed-matter setting.
We developed a pyrometer that operates near the high-temperature bandgap of GaN, thus solving the transparency problem once a {approx} 1 {micro}m thick GaN epilayer has been established. The system collects radiation in the near-UV (380-415 nm) and has an effective detection wavelength of {approx}405 nm. By simultaneously measuring reflectance we also correct for emissivity changes when films of differing optical properties (e.g. AlGaN) are deposited on the GaN template. We recently modified the pyrometer hardware and software to enable measurements in a multiwafer Veeco D-125 OMVPE system. A method of synchronizing and indexing the detection system with the wafer platen was developed; so signals only from the desired wafer(s) could be measured, while rejecting thermal emission signals from the platen. Despite losses in optical throughput and duty cycle we are able to maintain adequate performance from 700 to 1100 C.
We present the solution of a 1D radial MHD model of the plasma ablated from multi-MA wire array implosions extending a recently obtained steady state solution [J.P. Chittenden, et al. Phys. Plasmas 11, 1118 (2004)] to a driving current that is exponential in time. We obtain a solution for the flow in almost analytical form by reducing the partial differential equations to a set of ordinary differential equations with a single parameter. We compute the mass weighted density width, and find the regime in which it agrees to a few percent with that of a simpler approximation to the ablated plasma flow, for which the driving current is linear in time, and the flow velocity constant. Assuming that the density width at the end of the ablation period is proportional to width of the plasma sheath at stagnation, we obtain a scaling relationship for peak X-ray power. We compare this relationship to experimental peak X-ray powers for tungsten wire arrays on the Z pulsed power generator of Sandia National Laboratories, and to previously proposed scaling hypotheses. We also use this scaling to project peak X-ray powers on ZR, a higher peak current modification of Z, presently under design.
Summary from only given. The capabilities of the Z accelerator will be significantly enhanced by the Z Refurbishment (ZR) project [McDaniel DH, 2002]. The performance of a single ZR module is currently being characterized in the pre-production engineering evaluation test bed, Z20 [Lehr, JM, 2003]. Z20 is thoroughly diagnosed so that electrical performance of the module can be established. Circuit models of Z20 have been developed and validated in both Screamer [1985] and Bertha [1989] circuit codes. For the purposes of predicting ZR performance, a full ZR circuit model has also been developed in Bertha. The full ZR model (using operating parameters demonstrated on Z20) indicates that the required 26 MA, 100 ns implosion time, output load current pulse will be achieved on ZR. In this paper, the electrical characterization of Z20 and development of the single module circuit models will be discussed in detail. The full ZR model will also be discussed and the results of several system studies conducted to predict ZR performance will be presented.
The stress evolution during electrodeposition of NiMn from a sulfamate-based bath was investigated as a function of Mn concentration and current density. The NiMn stress evolution with film thickness exhibited an initial high transitional stress region followed by a region of steady-state stress with a magnitude that depended on deposition rate, similar to the previously reported stress evolution in electrodeposited Ni [S. J. Hearne and J. A. Floro, J. Appl. Phys. 97, 014901-1 (2005)]. The incorporation of increasing amounts of Mn resulted in a linear increase in the steady-state stress at constant current density. However, no significant changes in the texture or grain size were observed, which indicates that an atomistic process is driving the changes in steady-state stress. Additionally, microstrain measured by ex situ x-ray diffraction increased with increasing Mn content, which was likely the result of localized lattice distortions associated with substitutional incorporation of Mn and/or increased twin density.
The summary of this report is: (1) The Kernal Density Estimator (KDE) model using log data provides the most conservative estimates; (2) The Empirical Tolerance Limit (ETL) model provides the least conservative estimates; (3) The results for the Karhunen-Loeve (K-L) and Normal Tolerance Limit (NTL) models lie in between the extremes; (4) The NTL results ended up being as credible as any of the other methods. This may be related to the fact that the data appeared to fit a lognormal distribution for higher values of {beta}; (5) The discrepancy between these methods appears to widen for higher values of {beta} and {gamma}; (6) The reasons for the extreme difference in the KDE results depending on whether one uses the raw data or the log of the data is not clear at this time; and (7) Which model will best suit our needs is not clear at this time.
The chemical and structural changes within thin films of (3-glycidoxypropyl)trimethoxysilane (GPS) after exposure for various periods of time to air saturated with either D 2O or H 2O at 80°C were studied. The X-ray and neutron reflectivity (XR and NR), combined wuth attenuated total reflection infrared (ATR-IR) spectroscopy were used. The chemical degradation mechanism was identified by IR as hydrolysis of siloxane bonds. GPS films were prepared by dip-coating, which resulted in a greater and more variable thickness than for the spin-coated samples, for ATR-IR. The little changes in the reflectivity data was observed for films conditioned with D 2O at 80°C for one month.
Identifying the areas to be protected is an important part of the development of measures for physical protection against sabotage at complex nuclear facilities. In June 1999, the International Atomic Energy Agency published INFCIRC/225/Rev.4, 'The Physical Protection of Nuclear Material and Nuclear Facilities.' This guidance recommends that 'Safety specialists, in close cooperation with physical protection specialists, should evaluate the consequences of malevolent acts, considered in the context of the State's design basis threat, to identify nuclear material, or the minimum complement of equipment, systems or devices to be protected against sabotage.' This report presents a structured, transparent approach for identifying the areas that contain this minimum complement of equipment, systems, and devices to be protected against sabotage that is applicable to complex nuclear facilities. The method builds upon safety analyses to develop sabotage fault trees that reflect sabotage scenarios that could cause unacceptable radiological consequences. The sabotage actions represented in the fault trees are linked to the areas from which they can be accomplished. The fault tree is then transformed (by negation) into its dual, the protection location tree, which reflects the sabotage actions that must be prevented in order to prevent unacceptable radiological consequences. The minimum path sets of this fault tree dual yield, through the area linkage, sets of areas, each of which contains nuclear material, or a minimum complement of equipment, systems or devices that, if protected, will prevent sabotage. This method also provides guidance for the selection of the minimum path set that permits optimization of the trade-offs among physical protection effectiveness, safety impact, cost and operational impact.
This report is the latest in a continuing series that highlights the recent technical accomplishments associated with the work being performed within the Materials and Process Sciences Center. Our research and development activities primarily address the materials-engineering needs of Sandia's Nuclear-Weapons (NW) program. In addition, we have significant efforts that support programs managed by the other laboratory business units. Our wide range of activities occurs within six thematic areas: Materials Aging and Reliability, Scientifically Engineered Materials, Materials Processing, Materials Characterization, Materials for Microsystems, and Materials Modeling and Simulation. We believe these highlights collectively demonstrate the importance that a strong materials-science base has on the ultimate success of the NW program and the overall DOE technology portfolio.
This Final Report on the Monitoring Phase of the former Weeks Island Strategic Petroleum Reserve crude oil storage facility details the results of five years of monitoring of various surface accessible quantities at the decommissioned facility. The Weeks Island mine was authorized by the State of Louisiana as a Strategic Petroleum Reserve oil storage facility from 1979 until decommissioning of the facility in 1999. Discovery of a sinkhole over the facility in 1992 with freshwater inflow to the facility threatened the integrity of the oil storage and led to the decision to remove the oil, fill the chambers with brine, and decommission the facility. Thereafter, a monitoring phase, by agreement between the Department of Energy and the State, addressed facility stability and environmental concerns. Monitoring of the surface ground water and the brine of the underground chambers from the East Fill Hole produced no evidence of hydrocarbon contamination, which suggests that any unrecovered oil remaining in the underground chambers has been contained. Ever diminishing progression of the initial major sinkhole, and a subsequent minor sinkhole, with time was verification of the response of sinkholes to filling of the facility with brine. Brine filling of the facility ostensively eliminates any further growth or new formation from freshwater inflow. Continued monitoring of sinkhole response, together with continued surface surveillance for environmental problems, confirmed the intended results of brine pressurization. Surface subsidence measurements over the mine continued throughout the monitoring phase. And finally, the outward flow of brine was monitored as a measure of the creep closure of the mine chambers. Results of each of these monitoring activities are presented, with their correlation toward assuring the stability and environmental security of the decommissioned facility. The results suggest that the decommissioning was successful and no contamination of the surface environment by crude oil has been found.
Goal of this study was to develop and characterize novel polymeric materials as pseudostationary phases in electrokinetic chromatography. Fundamental studies have characterized the chromatographic selectivity of the materials as a function of chemical structure and molecular conformation. The selectivities of the polymers has been studied extensively, resulting in a large body of fundamental knowledge regarding the performance and selectivity of polymeric pseudostationary phases. Two polymers have also been used for amino acid and peptide separations, and with laser induced fluorescence detection. The polymers performed well for the separation of derivatized amino acids, and provided some significant differences in selectivity relative to a commonly used micellar pseudostationary phase. The polymers did not perform well for peptide separations. The polymers were compatible with laser induced fluorescence detection, indicating that they should also be compatible with chip-based separations.
The recent interests in developing multiscale model-based simulation procedures have brought about the challenging tasks of bridging different spatial and temporal scales within a unified framework. However, the research focus has been on the scale effect in the spatial domain with the loading rate being assumed to be quasi-static. Although material properties are rate-dependent in nature, little has been done in understanding combined loading rate and specimen size effects on the material properties at different scales. In addition, the length and time scales that can be probed by the molecular level simulations are still fairly limited due to the limitation of computational capability. Based on the experimental and computational capabilities available, therefore, an attempt is made in this report to formulate a hyper-surface in both spatial and temporal domains to predict combined size and rate effects on the mechanical properties of engineering materials. To demonstrate the features of the proposed hyper-surface, tungsten specimens of various sizes under various loading rates are considered with a focus on the uniaxial loading path. The mechanical responses of tungsten specimens under other loading paths are also explored to better understand the size effect. It appears from the preliminary results that the proposed procedure might provide an effective means to bridge different spatial and temporal scales in a unified multiscale modeling framework, and facilitate the application of nanoscale research results to engineering practice.
Power sources capable of supplying tens of watts are needed for a wide variety of applications including portable electronics, sensors, micro aerial vehicles, and mini-robotics systems. The utility of these devices is often limited by the energy and power density capabilities of batteries. A small combustion engine using liquid hydrocarbon fuel could potentially increase both power and energy density by an order of magnitude or more. This report describes initial development work on a meso-scale external combustion engine based on the Stirling cycle. Although other engine designs perform better at macro-scales, we believe the Stirling engine cycle is better suited to small-scale applications. The ideal Stirling cycle requires efficient heat transfer. Consequently, unlike other thermodynamic cycles, the high heat transfer rates that are inherent with miniature devices are an advantage for the Stirling cycle. Furthermore, since the Stirling engine uses external combustion, the combustor and engine can be scaled and optimized semi-independently. Continuous combustion minimizes issues with flame initiation and propagation. It also allows consideration of a variety of techniques to promote combustion that would be difficult in a miniature internal combustion engine. The project included design and fabrication of both the engine and the combustor. Two engine designs were developed. The first used a cylindrical piston design fabricated with conventional machining processes. The second design, based on the Wankel rotor geometry, was fabricated by through-mold electroforming of nickel in SU8 and LIGA micromolds. These technologies provided the requisite precision and tight tolerances needed for efficient micro-engine operation. Electroformed nickel is ideal for micro-engine applications because of its high strength and ductility. A rotary geometry was chosen because its planar geometry was more compatible with the fabrication process. SU8 lithography provided rapid prototypes to verify the design. A final high precision engine was created via LIGA. The micro-combustor was based on an excess enthalpy concept. Development of a micro-combustor included both modeling and experiments. We developed a suite of simulation tools both in support of the design of the prototype combustors, and to investigate more fundamental aspects of combustion at small scales. Issues of heat management and integration with the micro-scale Stirling engine were pursued using CFD simulations. We found that by choice of the operating conditions and channel dimensions energy conversion occurs by catalysis-dominated or catalysis-then-homogeneous phase combustion. The purpose of the experimental effort in micro-combustion was to study the feasibility and explore the design parameters of excess enthalpy combustors. The efforts were guided by the necessity for a practical device that could be implemented in a miniature power generator, or as a stand-alone device used for heat generation. Several devices were fabricated and successfully tested using methane as the fuel.
We have synthesized defect-free aluminosilicate and silicalite zeolite thin films supported on commercially available alpha and gamma alumina disk substrates. We have also built a permeation unit that can test both pure and mixed gases from room temperature to 250 C. Results indicate fluxes on the order of 10{sup -6} to 10{sup -7} mole/(m{sup 2}Pa sec) and excellent separation values for H{sub 2} or CO{sub 2}. For the Al/Si membrane: H{sub 2}/N{sub 2} {ge} 61, H{sub 2}/CO{sub 2} {ge} 80, H{sub 2}/CH{sub 4} = 7, CH{sub 4}/CO{sub 2} {ge} 11; for the TPA/Si membrane: H{sub 2}/N{sub 2} {ge} 61, H{sub 2}/CO{sub 2} {ge} 80, H{sub 2}/CH{sub 4} = 7, CH{sub 4}/CO{sub 2} {ge} 11. Our data show that we can use the adsorption ability plus the effective pore diameter of the zeolite to 'tune' the selectivity of the membrane. Another avenue of research is into bulk novel molecular sieve materials, with the goal of 'tuning' pore sizes to molecular sieving needs. A novel crystalline 12-ring microporous gallophosphate material is described.
This paper is about making reversible logic a reality for supercomputing. Reversible logic offers a way to exceed certain basic limits on the performance of computers, yet a powerful case will have to be made to justify its substantial development expense. This paper explores the limits of current, irreversible logic for supercomputers, thus forming a threshold above which reversible logic is the only solution. Problems above this threshold are discussed, with the science and mitigation of global warming being discussed in detail. To further develop the idea of using reversible logic in supercomputing, a design for a 1 Zettaflops supercomputer as required for addressing global climate warming is presented. However, to create such a design requires deviations from the mainstream of both the software for climate simulation and research directions of reversible logic. These deviations provide direction on how to make reversible logic practical.
Binding of porphyrin to murine ferrochelatase, the terminal enzyme of the heme biosynthetic pathway, is investigated by employing a set of variants harboring mutations in a putative porphyrin-binding loop. Using resonance Raman (RR) spectroscopy, the structural properties of the ferrochelatase-bound porphyrins are examined, especially with respect to the porphyrin deformation occurring in the environment of the active site. This deformation is thought to be a key step in the enzymatic insertion of ferrous iron into the porphyrin ring to make heme. Our previous RR spectroscopic studies of binding of porphyrin to murine ferrochelatase led us to propose that the wild-type enzyme induces porphyrin distortion even in the absence of the metal ion substrate. Here, we broaden this view by presenting evidence that the degree of a specific nonplanar porphyrin deformation contributes to the catalytic efficiency of ferrochelatase and its variants. The results also suggest that the conserved Trp256 (murine ferrochelatase numbering) is partially responsible for the observed porphyrin deformation. Binding of porphyrin to the ferrochelatase variants causes a decrease in the intensity of RR out-of-plane vibrational mode {gamma}{sub 15}, a saddling-like mode that is strong in the wild-type enzyme. In particular, the variant with a catalytic efficiency 1 order of magnitude lower than that of the wild-type enzyme is estimated to produce less than 30% of the wild-type saddling deformation. These results suggest that specific conserved loop residues (especially Trp256) are directly involved in the saddling of the porphyrin substrate.
In contrast to traditional terascale simulations that have known, fixed data inputs, dynamic data-driven (DDD) applications are characterized by unknown data and informed by dynamic observations. DDD simulations give rise to inverse problems of determining unknown data from sparse observations. The main difficulty is that the optimality system is a boundary value problem in 4D space-time, even though the forward simulation is an initial value problem. We construct special-purpose parallel multigrid algorithms that exploit the spectral structure of the inverse operator. Experiments on problems of localizing airborne contaminant release from sparse observations in a regional atmospheric transport model demonstrate that 17-million-parameter inversion can be effected at a cost of just 18 forward simulations with high parallel efficiency. On 1024 Alphaserver EV68 processors, the turnaround time is just 29 minutes. Moreover, inverse problems with 135 million parameters - corresponding to 139 billion total space-time unknowns - are solved in less than 5 hours on the same number of processors. These results suggest that ultra-high resolution data-driven inversion can be carried out sufficiently rapidly for simulation-based 'real-time' hazard assessment.
Accurate and efficient turbulence simulation in complex geometries is a formidable chal-lenge. Traditional methods are often limited by low accuracy and/or restrictions to simplegeometries. We explore the merger of Discontinuous Galerkin (DG) spatial discretizationswith Variational Multi-Scale (VMS) modeling, termed Local VMS (LVMS), to overcomethese limitations. DG spatial discretizations support arbitrarily high-order accuracy on un-structured grids amenable for complex geometries. Furthermore, high-order, hierarchicalrepresentation within DG provides a natural framework fora prioriscale separation crucialfor VMS implementation. We show that the combined benefits of DG and VMS within theLVMS method leads to promising new approach to LES for use in complex geometries.The efficacy of LVMS for turbulence simulation is assessed by application to fully-developed turbulent channelflow. First, a detailed spatial resolution study is undertakento record the effects of the DG discretization on turbulence statistics. Here, the localhp[?]refinement capabilites of DG are exploited to obtain reliable low-order statistics effi-ciently. Likewise, resolution guidelines for simulating wall-bounded turbulence using DGare established. We also explore the influence of enforcing Dirichlet boundary conditionsindirectly through numericalfluxes in DG which allows the solution to jump (slip) at thechannel walls. These jumps are effective in simulating the influence of the wall commen-surate with the local resolution and this feature of DG is effective in mitigating near-wallresolution requirements. In particular, we show that by locally modifying the numericalviscousflux used at the wall, we are able to regulate the near-wall slip through a penaltythat leads to improved shear-stress predictions. This work, demonstrates the potential ofthe numerical viscousflux to act as a numerically consistent wall-model and this successwarrents future research.As in any high-order numerical method some mechanism is required to control aliasingeffects due to nonlinear interactions and to ensure nonlinear stability of the method. Inthis context, we evaluate the merits of two approaches to de-aliasing -- spectralfilteringand polynomial dealiasing. While both approaches are successful, polynomial-dealiasingis found to be better suited for use in large-eddy simulation. Finally, results using LVMSare reported and show good agreement with reference direct numerical simulation therebydemonstrating the effectiveness of LVMS for wall-bounded turbulence. This success pavesthe way for future applications of LVMS to more complex turbulentflows.3
Flow-generated noise, especially rotorcraft noise has been a serious concern for bothcommercial and military applications. A particular important noise source for rotor-craft is Blade-Vortex-Interaction (BVI)noise, a high amplitude, impulsive sound thatoften dominates other rotorcraft noise sources. Usually BVI noise is caused by theunsteady flow changes around various rotor blades due to interactions with vorticespreviously shed by the blades. A promising approach for reducing the BVI noise isto use on-blade controls, such as suction/blowing, micro-flaps/jets, and smart struc-tures. Because the design and implementation of such experiments to evaluate suchsystems are very expensive, efficient computational tools coupled with optimal con-trol systems are required to explore the relevant physics and evaluate the feasibilityof using various micro-fluidic devices before committing to hardware.In this thesis the research is to formulate and implement efficient computationaltools for the development and study of optimal control and design strategies for com-plex flow and acoustic systems with emphasis on rotorcraft applications, especiallyBVI noise control problem. The main purpose of aeroacoustic computations is todetermine the sound intensity and directivity far away from the noise source. How-ever, the computational cost of using a high-fidelity flow-physics model across thefull domain is usually prohibitive and itmight also be less accurate because of thenumerical diffusion and other problems. Taking advantage of the multi-physics andmulti-scale structure of this aeroacoustic problem, we develop a multi-model, multi-domain (near-field/far-field) method based on a discontinuous Galerkin discretiza-tion. In this approach the coupling of multi-domains and multi-models is achievedby weakly enforcing continuity of normal fluxes across a coupling surface. For ourinterested aeroacoustics control problem, the adjoint equations that determine thesensitivity of the cost functional to changes in control are also solved with same ap-proach by weakly enforcing continuity ofnormal fluxes across a coupling surface.Such formulations have been validated extensively for several aeroacoustics state andcontrol problems.A multi-model based optimal control framework has been constructed and ap-plied to our interested BVI noise control problem. This model problem consists ofthe interaction of a compressible vortex with Bell AH-1 rotor blade with wall-normal3 velocity used as control on the rotor blade surface. The computational domain isdecomposed into the near-field and far-field. The near-field is obtained by numericalsolution of the Navier-Stokes equations while far away from the noise source, wherethe effect of nonlinearities is negligible, the linearized Euler equations are used tomodel the acoustic wave propagation. The BVI wave packet is targeted by definingan objective function that measures the square amplitude of pressure fluctuations inan observation region, at a time interval encompassing the dominant leading edgecompressibility waves. Our control results show that a 12dB reduction in the ob-servation region is obtained. Interestingly, the control mechanism focuses on theobservation region and only minimize the sound level in that region at the expense ofother regions. The vortex strength and trajectory get barely changed. However, theoptimal control does alter the interaction of the vortical and potential fields, whichis the source of BVI noise. While this results in a slight increase in drag, there is asignificant reduction in the temporal gradient of lift leading to a reduction in BVIsound levels.4
Catamount is designed to be a low overhead operating system for a parallel computing environment. Functionality is limited to the minimum set needed to run a scientific computation. The design choices and implementations will be presented. A massively parallel processor (MPP), high performance computing (HPC) system is particularly sensitive to operating system overhead. Traditional, multi-purpose, operating systems are designed to support a wide range of usage models and requirements. To support the range of needs, a large number of system processes are provided and are often interdependent on each other. The overhead of these processes leads to an unpredictable amount of processor time available to a parallel application. Except in the case of the most embarrassingly parallel of applications, an MPP application must share interim results with its peers before it can make further progress. These synchronization events are made at specific points in the application code. If one processor takes longer to reach that point than all the other processors, everyone must wait. The overall finish time is increased. Sandia National Laboratories began addressing this problem more than a decade ago with an architecture based on node specialization. Sets of nodes in an MPP are designated to perform specific tasks, each running an operating system best suited to the specialized function. Sandia chose to not use a multi-purpose operating system for the computational nodes and instead began developing its first light weight operating system, SUNMOS, which ran on the compute nodes on the Intel Paragon system. Based on its viability, the architecture evolved into the PUMA operating system. Intel ported PUMA to the ASCI Red TFLOPS system, thus creating the Cougar operating system. Most recently, Cougar has been ported to Cray's XT3 system and renamed to Catamount. As the references indicate, there are a number of descriptions of the predecessor operating systems. While the majority of those discussions still apply to Catamount, this paper takes a fresh look at the architecture as it is currently implemented.
We address the problem of partitioning and dynamic load balancing on clusters with heterogeneous hardware resources. We propose DRUM, a model that encapsulates hardware resources and their interconnection topology. DRUM provides monitoring facilities for dynamic evaluation of communication, memory, and processing capabilities. Heterogeneity is quantified by merging the information from the monitors to produce a scalar number called 'power.' This power allows DRUM to be used easily by existing load-balancing procedures such as those in the Zoltan Toolkit while placing minimal burden on application programmers. We demonstrate the use of DRUM to guide load balancing in the adaptive solution of a Laplace equation on a heterogeneous cluster. We observed a significant reduction in execution time compared to traditional methods.
Many problems from engineering and the sciences require the solution of sequences of linear systems where the matrix and right-hand side change from one system to the next, and the linear systems are not available simultaneously. We review a class of Krylov subspace methods for sequences of linear systems, which can significantly reduce the cost of solving the next system in the sequence by 'recycling' subspace information from previous systems. These methods have been successfully applied to sequences of linear systems arising from several different application areas. We analyze a particular method, GCRO-DR, that recycles approximate invariant subspaces, and establish residual bounds that suggest a convergence rate similar to one obtained by removing select eigenvector components from the initial residual. We review implications of this analysis, which suggests problem classes where we expect this technique to be particularly effective. From this analysis and related numerical experiments we also demonstrate that recycling the invariant subspace corresponding to the eigenvalues of smallest absolute magnitude is often not the best choice, especially for nonsymmetric problems, and that GCRO-DR will, in practice, select better subspaces. These results suggest possibilities for improvement in the subspace selection process.
The present ITSE journal special issue on 'Learning About Social Interaction through Gaming' is the result of an invitation to the attendees of a one-day workshop on 'Social Learning Through Gaming' co-organized by the guest editors and held at the Human Factors in Computing Systems (CHI) conference on April 26, 2004 in Vienna, Austria. CHI is one of the premiere conferences on human-computer interaction. CHI 2004 attracted hundreds of delegates from all over the world. The CHI workshop program results from a competitive selection process. The Social Learning through Gaming workshop was filled to capacity and attended by approximately 25 participants from Europe and North America who submitted position papers that were refereed and selected for participation based on the relevancy and innovativeness of the research. The participants came together to share research on play, learning, games, interactive technologies, and what playing and designing games can teach us about social behaviors. The present special issue focuses on learning about social aspects through gaming: learning to socialize through games and learning games through social behavior.
The presence of mechanical joints--typified by the lap joint--in otherwise linear structures has been accommodated in structural dynamics via ad hoc methods for a century. The methods range from tuning linear models to approximate non-linear behavior in restricted load ranges to various methods which introduce joint dissipation in a post-processing stage. Other methods, employing constitutive models for the joints are being developed and their routine use is on the horizon.
We have measured the temperature dependence of mechanical dissipation in tetrahedral amorphous carbon flexural and torsional resonators over the temperature range from 300 to 1023 K. The mechanical dissipation was found to be controlled by defects within the material, and the magnitude and temperature dependence of the dissipation were found to depend on whether flexural or torsional vibrational modes were excited. The defects that were active under flexural stresses have a relatively flat concentration from 0.4 to 0.7 eV with an ever increasing defect concentration up to 1.9 eV. Under shear stresses (torsion), the defect activation energies increase immediately beginning at 0.4 eV, with increasing defect concentration at higher energies.
Solid solutions of lead-based perovskites are the backbone materials of the piezoelectric components for transducer, actuator, and resonator applications. These components, typically small in size, are fabricated from large sintered ceramic slugs using grinding and lapping processes. These operations increase manufacturing costs and produce a large hazardous waste stream, especially when component size decreases. To reduce costs and hazardous wastes associated with the production of these components, an injection molding technique is being investigated to replace the machining processes. The first step in the new technique is to compound an organic carrier with a ceramic powder. The organic carrier is a thermoplastic based system composed of a main carrier, a binder, and a surfactant. Understanding the rheology of the compounded material is necessary to minimize the creation of defects such as voids or cavities during the injection-molding process. An experiment was performed to model the effects of changes in the composition and processing of the material on the rheological behavior. Factors studied included: the surfactant of the organic carrier system, the solid loading of the compounded material, and compounding time. The effects of these factors on the viscosity of the material were investigated.
We report the experimental realization of a new type of optical parametric oscillator in which oscillation is achieved by polarization rotation in a linear retarder, followed by nonlinear polarization mixing. The mixing is performed by a type II degenerate parametric downconversion in a periodically poled KTP crystal pumped by a 1064 nm pulsed Nd:YAG pump. A single, linearly polarized beam, precisely at the degenerate wavelength is generated. The output spectrum has a narrow linewidth (below the instrumentation bandwidth of 1 nm) and is highly stable with respect to variations in the crystal temperature.
Concepts from Complexity Science are valuable and allow a simulation approach for critical infrastructures that is flexible and has wide ranging applications.
A large-scale field demonstration comparing final landfill cover designs was constructed and monitored at Sandia National Laboratories in Albuquerque, New Mexico. Two conventional designs (a RCRA Subtitle 'D' Soil Cover and a RCRA Subtitle 'C' Compacted Clay Cover) were constructed side-by-side with four alternative cover test plots designed for arid environments. The demonstration was intended to evaluate the various cover designs based on their respective water balance performance, ease and reliability of construction, and cost. A portion of this project involves the characterization of vegetation establishment and growth on the landfill covers. The various prototype landfill covers were expected to have varying flux rates (Dwyer et al 2000). The landfill covers were further expected to influence vegetation establishment and growth, which may impact site erosion potential and long-term site integrity. Objectives of this phase were to quantify the types of plants occupying each site, the percentage of ground covered by these plants, the density (number of plants per unit area) of plants, and the plant biomass production. The results of this vegetation analysis are presented in this report.3 DRAFT07/06/14AcknowledgementsWe would like to thank all technical and support staff from Sandia and the USDA Forest Service's Rocky Mountain Station not included in the authors' list of this document for their valuable contributions to this research. We would also like to acknowledge the Department of Energy's Subsurface Contaminants Focus Area for funding this work.4
This Work Plan identifies and outlines interim measures to address nitrate contamination in groundwater at the Burn Site, Sandia National Laboratories/New Mexico. The New Mexico Environment Department has required implementation of interim measures for nitrate-contaminated groundwater at the Burn Site. The purpose of interim measures is to prevent human or environmental exposure to nitrate-contaminated groundwater originating from the Burn Site. This Work Plan details a summary of current information about the Burn Site, interim measures activities for stabilization, and project management responsibilities to accomplish this purpose.
We show that the orientation of pentacene molecules is controlled by the electronic structure of the surface on which they are deposited. We suggest that the near-Fermi level density of states above the surface controls the interaction of the substrate with the pentacene {pi} orbitals. A reduction of this density as compared to noble metals, realized in semimetallic Bi(001) and Si(111)(5 x 2)Au surfaces, results in pentacene standing up. Interestingly, pentacene grown on Bi(001) is highly ordered, yielding the first vertically oriented epitaxial pentacene thin films observed to date.
This report documents activities related to the ASCI AD Resistance Weld Process Modeling Project AD2003-15. Activities up to and including FY2004 are discussed. This was the third year for this multi year project, the objective of which is to position the SIERRA computational tools for the solution of resistance welding problems. The process of interest is a three-way coupled problem involving current flow, temperature buildup and large plastic deformation. The DSW application is the reclamation stem weld used in the manufacture of high pressure gas bottles. This is the first year the CALAGIO suite of codes (eCALORE, CALORE, and ADAGIO) was used to successfully solve a three-way coupled problem in SIERRA. This report discusses the application of CALAGIO to the tapered bar acceptance problem and a similar but independent tapered bar simulation of a companion C6 experiment. New additions to the EMMI constitutive model and issues related to CALAGIO performance are also discussed.
Classical density functional theory (DFT) is applied to study properties of fully detailed, realistic models of poly(dimethylsiloxane) liquids near silica surfaces and compared to results from molecular dynamics simulations. In solving the DFT equations, the direct correlation functions are obtained from the polymer reference interaction site model (PRISM) theory for the repulsive parts of the interatomic interactions, and the attractions are treated via the random-phase approximation (RPA). Good agreement between density profiles calculated from DFT and from the simulations is obtained with empirical scaling of the direct correlation functions. Separate scaling factors are required for the PRISM and RPA parts of the direct correlation functions. Theoretical predictions of stress profiles, normal pressure, and surface tensions are also in reasonable agreement with simulation results.
In the crystal structure of the title compound, C{sub 4}H{sub 4}N{sub 2}O{sub 3}, the packing is dominated by intermolecular carbonyl-carbonyl interactions and N-H...O hydrogen bonds.
The solution of the governing steady transport equations for momentum, heat and mass transfer in fluids undergoing non-equilibrium chemical reactions can be extremely challenging. The difficulties arise from both the complexity of the nonlinear solution behavior as well as the nonlinear, coupled, non-symmetric nature of the system of algebraic equations that results from spatial discretization of the PDEs. In this paper, we briefly review progress on developing a stabilized finite element (FE) capability for numerical solution of these challenging problems. The discussion considers the stabilized FE formulation for the low Mach number Navier-Stokes equations with heat and mass transport with non-equilibrium chemical reactions, and the solution methods necessary for detailed analysis of these complex systems. The solution algorithms include robust nonlinear and linear solution schemes, parameter continuation methods, and linear stability analysis techniques. Our discussion considers computational efficiency, scalability, and some implementation issues of the solution methods. Computational results are presented for a CFD benchmark problem as well as for a number of large-scale, 2D and 3D, engineering transport/reaction applications.
Highly ordered gold nanocrystal (NC)/silica films are synthesized by self-assembly of water-soluble gold NC micelles and silica using a sol-gel spin coating technique. The optical properties are analyzed using ellipsometry and ultraviolet-visible spectroscopy. Transmission and absorption spectra were measured for wavelengths ranging from 200 to 2000 nm. The absorption spectra show a strong surface plasmon absorption band at {approx}520 nm for all samples. Charge transport behavior of the films was examined using metal-oxide-semiconductor (MOS) and metal-insulator-metal (MIM) structures. MOS capacitor samples exhibit charge storage with discharge behavior dominated by electron transport within the gold NC arrays. Low temperature current-voltage measurements on MIM devices reveal electrical conduction with a thermal activation energy of {approx}90 meV. For temperatures less than 100 K, the I-V characteristics of the NC film exhibits a strong coulomb blockade effect, with a threshold voltage of {approx}0.5 V measured at 78 K.
A new approach is proposed for the a posteriori error estimation of both global spatial and parameter error in parameterized nonlinear reaction-diffusion problems. The technique is based on linear equations relating the linearized spatial and parameter error to the weak residual. Computable local element error indicators are derived for local contributions to the global spatial and parameter error, along with corresponding global error indicators. The effectiveness of the error indicators is demonstrated using model problems for the case of regular points and simple turning points. In addition, a new turning point predictor and adaptive algorithm for accurately computing turning points are introduced.
The intense magnetic field produced by the 20 MA Z accelerator is used as an impulsive pressure source to accelerate metal flyer plates to high velocity for the purpose of performing plate impact, shock wave experiments. This capability has been significantly enhanced by the recently developed pulse shaping capability of Z, which enables tailoring the rise time to peak current for a specific material and drive pressure to avoid shock formation within the flyer plate during acceleration. Consequently, full advantage can be taken of the available current to achieve the maximum possible magnetic drive pressure. In this way, peak magnetic drive pressures up to 490 GPa have been produced, which shocklessly accelerated 850 {micro}m aluminum (6061-T6) flyer plates to peak velocities of 34 km/s. We discuss magnetohydrodynamic (MHD) simulations that are used to optimize the magnetic pressure for a given flyer load and to determine the shape of the current rise time that precludes shock formation within the flyer during acceleration to peak velocity. In addition, we present results pertaining to plate impact, shock wave experiments in which the aluminum flyer plates were magnetically accelerated across a vacuum gap and impacted z-cut, {alpha}-quartz targets. Accurate measurements of resulting quartz shock velocities are presented and analyzed through high-fidelity MHD simulations enhanced using optimization techniques. Results show that a fraction of the flyer remains at solid density at impact, that the fraction of material at solid density decreases with increasing magnetic pressure, and that the observed abrupt decrease in the quartz shock velocity is well correlated with the melt transition in the aluminum flyer.