We extend a multi-level preconditioned solution method for a linear discontinuous discretization of the P{sub 1} equations in two-dimensional Cartesian geometry to three-dimensional, unstructured tetrahedral meshes. A diffusion synthetic acceleration (DSA) method based on these P{sub 1} equations is applied to linear discontinuous S{sub N} transport source iterations on tetrahedral meshes. It is a fully consistent method because the P{sub 1} equations and the transport equation are both discretized with a linear discontinuous finite element basis. Fourier analyses and computational results show the DSA scheme is stable and very effective. We compare the fully consistent scheme to other 'partially consistent' DSA methods.

This report describes an integral experiment of tritium production in water by neutrons from the LANSCE/WNR spallation neutron source. Neutron energies covered the range from 1 MeV to about 300 MeV. The neutron fluence was determined with a 238U fission chamber. After irradiation, the water samples were analyzed for tritium. The results are compared with calculations and agreement is found to within a factor of 2.

Idaho National Engineering and Environmental Laboratory (INEEL) has developed an automated computer program, Data Review Expert System (DRXS), for reviewing nondestructive assay (NDA) data. DRXS significantly reduces the data review time needed to meet characterization requirements for the Waste Isolation Pilot Plant (WIPP). Los Alamos National Laboratory (LANL) is in the process of developing a computer program, Software System Logic for Intelligent Certification (SSLIC), to automate other tasks associa ted with characterization of Transuranic Waste (TRU) samples. LANL has incorporated a version of DRXS specific to LANL's isotopic data into SSLIC. This version of SSLIC was audited by the National Transuranic Program on October, 24, 2001. This paper will present the results of the audit, and discuss future plans for SSLIC including the integration on the INEELLANL developed Rule Editor.

A cryogenic test rig was designed and fabricated to measure the heat leak from room temperature to 2 K from the Accelerator Production of Tritium (APT) 700 MHz, 210 kW continuous wave (CW) co-axial power coupler (PC). The outer conductor of the PC is stainless steel with 15 {micro}m copper film on the inside. The copper inner conductor operates at room temperature and contributes considerable infra-red radiation heat load to 2 K. Two thermal intercept heat exchangers cooled by supercritical helium are incorporated into the outer conductor to reduce the heat conducted to the lowest temperatures. A brief description of the experimental apparatus is presented. A comparison of the experimental measurements and the predictions of a detailed thermal model is given. There is also a discussion of anomalous behavior observed in the thermal intercepts, and fluctuations in the helium coolant properties.

The efficient implementation of collective communication patterns in a parallel machine is a challenging design effort, that requires the solution of many problems. In this paper we present an in-depth description of how the Quadrics network supports both hardware- and software-based collectives. We describe the main features of the two building blocks of this network, a network interface that can perform zero-copy user-level communication and a wormhole switch. We also focus our attention on the routing and $ow control algorithms, deadlock avoidance and on how the processing nodes are integrated in a global, virtual shared memory. Experimental results conducted on 64-node AlphaServer cluster indicate that the time to complete the hardware-based barrier synchronization on the whole network is as low as 6 ps, with veiy good scalability. Good latency and scalability are also achieved with the software-based synchronization, which takes about 15 ps. With the broadcast, similar performance is achieved by the hardware- and software-based implementations, which can deliver messages of up to 256 b,ytes in 13 ps and can get a sustained bandwidth of 288 Mbyteshec on all the nodes, with wressages larger than 64KB. The hardware-based barrier is almost insensitive to the network congestion, with 93% of the …

A major concern for the DARHT second axis (2 kA, 18.6 MeV, 2000 ns) is that ions or ionized neutrals released from solid surfaces (e.g., apertures, septum, dumps, and targets) by beam impact can be accelerated and trapped by the beam potential. This positive charge will be electrically attracted to the beam and could disrupt it. Possible release mechanisms include electron induced desorption of neutrals or ions, thermal desorption due to target heating and melting or vaporization of the solid target. To study this, experiments were performed on the DARHT first axis. Here, the beam, focused to a range of diameters, is transmitted through thin foils made of various materials. The time-dependent beam radial profile is measured downstream of the target. For low current density (depending on the material used), the downstream-beam profile is time invariant as expected. At higher current density, the downstream-beam radius changes during the pulse followed by transverse instability. Data, particle-in-cell simulations, and comparisons are presented.

Surfactants are macromolecules with unique properties. They commonly contain a polar head group with a nonpolar hydrocarbon chain. These properties allow surfactants to solubilize greases and other nonpolar molecules. One particular way that this is accomplished is through the formation of micelles. Micelles are formed at the critical micelle concentration (cmc), which varies depending upon the nature of the surfactant and also the media in which the surfactant resides. These micelles can take a variety of shapes, but are generally characterized by surrounding the grease with the nonpolar hydrocarbon chains, exposing only the polarized head groups to the media, usually water. This property of easy solubilization has made surfactants a very attractive industrial agent, They are used most conventionally as industrial cleaning agents and detergents. However, they also have lesser-known applications in conjunction with polymers and other macromolecular mixtures, often creating a system with novel properties, such as increased solubilization and smoother mixture consistency. A recently developed field has investigated the self-assembly of polymers and polyelectrolytes onto thin film surfaces. There are many reasons for studying this process, such as for second harmonic generation purposes and bioassays. In this study, the interaction between the anionic polyelectrolyte poly[1-[4-(3-carboxy-4-hydroxyphenylazo)benzenesulfonamido]-1,2-ethanediyl, sodium salt] (PAZO) …

Los Alamos National Laboratory (LANL) is located in Los Alamos, New Mexico and is operated by the University of California (UC) for the U.S. Department of Energy (DOE). The primary mission of Los Alainos National Laboratory is to support the nuclear weapons program for the Department of Energy. There are over 10,000 personnel at Los Alamos employed by DOE, UC and various subcontractors. The Strategic Computing Complex (SCC) supports the weapons program by computer simulation of weapon detonations, taking the place of underground testing banned by international treaty. The SCC is a 300,000 square foot, three story facility that will hold approximately 300 personnel that perform the simulations required to certify the U.S. weapons stockpile. The SCC is basically a support system for up to two large computers, weapons designers, physicists, and computer scientists. The heart of the facility is a 43,500 square foot computer room that is designed to hold computers that did not yet exist.

The authors have investigated the DC and AC magnetic properties of a bulk glassy Fe{sub 65.5}Cr{sub 4}Mo{sub 4}Ga{sub 4}P{sub 12}B{sub 5.5}C{sub 5} alloy. In the annealed state the alloy has coercivity H{sub C} and maximum DC permeability {mu}{sub m} of approximately 0.4 A/m (5 mOe) and 2.8 x 10{sup 5}, comparable to those found in annealed zero-magnetostriction Co-based alloys. The low H{sub C} found in the bulk glassy alloy is attributed to the low ratio of surface-roughness to sample thickness, and low residual internal-stress. The total power loss in the annealed bulk glass is about one order of magnitude lower than that of rapidly quenched Fe-based glassy ribbons. This is attributed to a low anomalous eddy-current loss.

The use of piezoelectric materials in conjunction with passive inductance-resistance-capacitance (RLC) circuits to dampen specific vibration modes is explored. The piezoelectric materials convert mechanical energy to electrical energy, which is then dissipated in the RLC circuit through joule heating. An impulse is applied to a simple cantilevered beam and by varying the inductance and resistance values, the natural oscillation frequency fcir the RLC circuit is tuned to dampen the first mode of vibration.

Magnetotransport properties of pure Mg metal and MgB{sub 2} samples with varying amounts of unreacted Mg are systematically studied in magnetic fields up to 18 T. With increasing quantity of Mg, the inhomogeneous MgB{sub 2} samples show greatly decreased residual resistivity, enhanced residual resistance ratio (RRR) and enhanced magnetoresistance (MR), gradually approaching the transport behaviors of pure Mg metal. We use the generalized effective medium theory to show that the large RRR and MR of the inhomogeneous MgB{sub 2} samples can be quantitatively explained by a two-phase model in which the two phases are MgB{sub 2} and pure Mg.

Systematics have been created for neutron spectra from the 7Li(p,n) reaction at 0 degrees in the 50-200 MeV proton energy region. The available experimental data in the continuum part of the spectra show satisfactory overall agreement with a representation based on the phase-space distribution corresponding to the three-body breakup process 7Li(p,n 3He){alpha}, with empirical correction factors, which depend regularly on incident energy. Validation of the systematics included folding of the predicted neutron spectra with standard 238U neutron fission cross section. Modeled in this way distributions of neutron-induced fission events agree reasonably with experimental data. KEYWORDS: quasi-monoenergetic neutron beam, monitoring, nuclear data library, MCNPX code.

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The potential of Computational Fluid Dynamics as a tool for design and analysis of the Circulating Fluidized Bed Reactor is considered. The ruminations are largely philosophical in nature, and are based mainly on experience. An assessment of where CFD may, or may not, be a helpful tool for developing the needed understanding, is furnished. To motivate this assessment, a clarification of what composes a CFD analysis is provided. Status of CFD usage in CFBR problems is summarized briefly. Some successes and failures of CFD in CFBR analysis are also discussed; this suggests a practical way to proceed toward the goal of adding CFD as a useful tool, to be used in combination with well-defined experiments, for CFBR needs. The conclusion is that there remains substantial hope that CFD could be very useful in this application. In order to make the hope a reality, nontrivial, and achievable, advances in multiphase flow theory must be made.

One of the reasons for building our gas-driven two-stage gun at Los Alamos was to be able to do shock initiation experiments on high explosives that were too insensitive to initiate with the single-stage gun. In past ARA meetings we have discussed the operation of the gun and the magnetic gauge measurement method. During the past couple of years we have done a number of magnetic gauge experiments on both liquid and solid high explosives. Shock initiation of high explosives depends on the nature of the material - whether it is homogeneous (liquid) or heterogeneous (pressed solid). In the solid explosives, mostly heterogeneous behavior has been measured. In the liquid explosive isopropyl nitrate, classic homogeneous initiation has been measured including the formation of a superdetonation in the shocked liquid. Experiments in both materials are discussed including the particle (mass) velocity profiles at a number of Lagrangian positions in the flow, progress of the shock front as measured by shock tracker gauges, and the position when the reactive wave reaches a detonation condition. The two-stage gun, in conjunction with the multiple magnetic gauging method, has proven very useful for generating new information in initiation experiments. Information from these experiments is of …

Fuel cells are devices that electrochemically convert fuel, usually hydrogen gas, to directly produce electricity. Fuel cells were initially developed for use in the space program to provide electricity and drinking water for astronauts. Fuel cells are under development for use in the automobile industry to power cars and buses with the advantage of lower emissions and higher efficiency than internal combustion engines. Fuel cells also have great potential to be used in portable consumer products like cellular phones and laptop computers, as well as military applications. In fact, any products that use batteries can be powered by fuel cells. In this project, we examine fuel cell system trade-offs between fuel cell type and energy storage/hydrogen production for portable power generation. The types of fuel cells being examined include stored hydrogen PEM (polymer electrolyte), direct methanol fuel cells (DMFC) and indirect methanol fuel cells, where methanol is reformed producing hydrogen. These fuel cells systems can operate at or near ambient conditions, which make them potentially optimal for use in manned personal power applications. The expected power production for these systems is in the range of milliwatts to 500 watts of electrical power for either personal or soldier field use. The …

I discuss several examples of critical phenomena in O(N) models where topological excitations play an important role at criticality. I focus particular attention on the O(2) model in 3D, where recent measurements of the vortex string length distribution in equilibrium suggest the existence of a quantitative picture of the critical behavior in terms of defects. The compatibility of this perspective with renormalization group predictions is examined.

Inventory planning and scheduling at the Los Alamos National Laboratory nuclear facility (TA-55) has become increasingly demanding given the limited supply of nuclear materials available for weapons production. This limitation comes from the shutdown of nuclear production reactors as well as the declaration of materials excess to national security within the DOE complex. The materials that have been declared excess to national security cannot be used in support of nuclear weapons activities and must be appropriately dispositioned. The matrices of the excess materials and the materials in the weapons; stream are often similar, if not identical, and must be processed and/or packaged utilizing the same personnel and facility resources. In order to segregate these materials and continue weapons production and dispositioning operations concurrently, careful tracking at the item level is required. Scheduling and campaigning of these materials must also be carefully monitored in order to meet both nuclear weapons production schedules as well as dispositioning milestones. All planning activities must consider the impact of processing operations on severely constrained resources including the special nuclear materials storage vault, the nondestructive assay laboratory, and the waste management and shipping operations. This paper details the methodologies and the use of simulation and other …

The effect of MnS inclusion orientation on damage evolution and fracture toughness in HYlOO steel is investigated in the context of anisotropic damage modeling at the continuum level. Experimental notched-bar data sets are analyzed and modeled using finite element calculations with constitutive behavior that assumes isotropic elastoplastic behavior in conjunction with anisotropic damage.

We continue the study initiated in [Ro01] on Stackelberg Scheduling Strategies. We are given a set of n independent parallel machines or equivalently a set of n parallel edges on which certain flow has to be sent. Each edge e is endowed with a latency function l{sub e}({center_dot}). The setting is that of a non-cooperative game: players choose edges so as minimize their individual latencies. Additionally, there is a single player who control as fraction ?? of the total flow. The goal is to find a strategy for the leader (i.e. an assignment of flow to indivual links) such that the selfish users react so as to minimize the total latency of the system. Building on the recent results in [Ro01, RT00], we show the following: 1. We devise a fully polynomial approximate scheme for the problem of finding the cheapest Stackelberg Strategy: given a performance requirement, our algorithm runs in time polynomial in n and {var_epsilon} and produces a Stackelberg strategy s, whose associated cost is within a 1 + {var_epsilon} factor of the optimum stackelberg strategy s*. The result is extended to obtain a polynomial-approximation scheme when instances are restricted to layered directed graphs in which each layer …

This Recommendation/International Standard uses a transformation of tile components. In this Annex and all of its sub clauses, the flow charts and tables are normative only in the sense that they are defining an output that alternative implementations shall duplicate.

We present recent results of laboratory and field experiments designed to validate and quantify the phenomenon of seismically enhanced oil production in marginal reservoirs. Controlled laboratory experiments were performed where mechanical stress oscillations at 100 Hz or less were applied to sandstone cores while flowing oil and/or brine at constant flow rates. Steady-state flow and simulated flooding experiments indicated that stress stimulation causes significant changes in the ability of one fluid to displace the other and on the preference that the rock has for trapping one fluid over the other. For Berea sandstone, which is highly water wet, stress stimulation caused oil production to be impeded during water floods and caused the bulk fluid pressure drop across the core to increase during steady-state simultaneous flow of oil and brine. A possible explanation of these observations is that stimulation caused the core to become more oil wet. Field stimulation tests on producing reservoirs at Lost Hills, California were performed using a downhole fluid pressure pulsation device. Stimulation was applied in one well for 50 days total during July - November 2000. Two groups of producing wells were monitored for changes in oil cut and oil production during the test. A control …

It has long been known that there are fundamental differences between homogeneous and heterogeneous high explosives. The shock initiation behavior of these materials was first described in the literature by Campbell et al, in 1961. Chaiken was also involved in describing this process for liquid nitromethane. Since then, there have been a number of studies which have added considerable incite into the shock initiation/detonation behavior of these materials. We only give a few references here (Refs. 4 - 11) and these should be considered representative; e.g. they do not represent an exhaustive list of references available. Many of these studies were done on homogeneous explosives, most often nitromethane (NM) and include particle velocity gauge measurements, optical temperature measurements, VISAR measurements, as well as streak camera measurements of interfaces. In some cases NM was heterogenized by gelling and adding silica particles. Homogeneous materials are typically liquids or single crystals in which there are a minimal number of physical imperfections (e.g. bubbles or voids) that can cause perturbations in the input shock and the flow behind it. Homogeneous materials viewed with macroscopic probes characteristic of detonation physics experiments appear uniform. Heterogeneous explosives are generally all other types; these are usually pressed, cast, …

We have recently completed a novel whole-head MEG system based on the Superconducting Imaging-Surface (SIS) concept originally proposed by van Hulsteyn, et al.[l]. The SIS concept is generally described as a source near a superconducting surface. The source field induces Meissner currents in the superconductor equivalent to a source image 'behind' the surface. A sensor (SQUIDS in our system) placed on the source-side of the SIS will measure the superposed fields from the real and image sources. A second consequence of the Meissner effect is to shield the SQUIDS sensors near the SIS from external or background fields. The shape of the SIS used in our MEG system is a hemisphere with two cut-outs at the nominal ear-locations. A brim is added around the entire periphery with a smooth 0.5 cm radius transition between brim and hemisphere. Benefits of the SIS concept over existing systems include significantly enhanced signal-to-noise as a consequence of the SIS shielding and inherently generating pseudo-first order gradient fields at the sensors. One of the most significant challenges in realizing this system has been to accurately describe how the SIS system impacts the forward physics of any source model. Two approaches have been examined. The first …