Many parallel applications require periodic redistribution of workloads and associated data. In a distributed memory computer, this redistribution can be difficult if limited memory is available for receiving messages. The authors propose a model for optimizing the exchange of messages under such circumstances which they call the minimum phase remapping problem. They first show that the problem is NP-Complete, and then analyze several methodologies for addressing it. First, they show how the problem can be phrased as an instance of multi-commodity flow. Next, they study a continuous approximation to the problem. They show that this continuous approximation has a solution which requires at most two more phases than the optimal discrete solution, but the question of how to consistently obtain a good discrete solution from the continuous problem remains open. Finally, they devise a simple and practical approximation algorithm for the problem with a bound of 1.5 times the optimal number of phases.

Effective use of a parallel computer requires that a calculation be carefully divided among the processors. This load balancing problem appears in many guises and has been a fervent area of research for the past decade or more. Although great progress has been made, and useful software tools developed, a number of challenges remain. It is the conviction of the author that these challenges will be easier to address if programmers first come to terms with some significant shortcomings in their current perspectives. This paper tries to identify several areas in which the prevailing point of view is either mistaken or insufficient. The goal is to motivate new ideas and directions for this important field.

The macroscopic warm-fluid model developed by Lund and Davidson [Phys.Plasmas 5, 3028 (1998)] is used in the smooth-focusing approximation to investigate detailed stability properties of an intense charged particle beam with pressure anisotropy, assuming small-amplitude electrostatic pertubations about a waterbag equilibrium.

The performance of a 1 cm{sup 2} thermophotovoltaic (TPV) module was recently measured in a photonic cavity test system. A conversion efficiency of 11.7% was measured at a radiator temperature of 1076 C and a module temperature of 29.9 C. This experiment achieved the highest direct measurement of efficiency for an integrated TPV system. Efficiency was calculated from the ratio of the peak (load matched) electrical power output and the heat absorption rate. Measurements of these two parameters were made simultaneously to assure the validity of the measured efficiency value. This test was conducted in a photonic cavity which mimicked a typical flat-plate TPV system. The radiator was a large, flat graphite surface. The module was affixed to the top of a copper pedestal for heat absorption measurements. The heat absorption rate was proportional to the axial temperature gradient in the pedestal under steady-state conditions. The test was run in a vacuum to eliminate conductive and convective heat transfer mechanisms. The photonic cavity provides the optimal test environment for TPV efficiency measurements because it incorporates all important physical phenomena found in an integrated TPV system: high radiator emissivity and blackbody spectral shape, photon recycling, Lambertian distribution of incident radiation and …

Preliminary Monte Carlo simulations have demonstrated that passive Nuclear Materials Identification System (NMIS) measurements can be used to determine the mass of Pu in AT400-R containers with measurement times as short as a few minutes. The sensitivity of the proposed detectors to gamma rays should enhance this measurement method because the gamma rays from fission, induced or spontaneous, escape this container more easily than neutrons. In these calculations, the container contained two Pu spheres with mass varying between 0.5 and 2 Kg with {approximately}6 wt% {sup 240 }Pu.

The concept of a muon storage ring based Neutrino Source (Neutrino Factory) has sparked considerable interest in the High Energy Physics community. Besides providing a first phase of a muon collider facility, it would generate more intense and well collimated neutrino beams than currently available. The BNL-AGS or some other proton driver would provide an intense proton beam that hits a target, produces pions that decay into muons. The muons must be cooled, accelerated and injected into a storage ring with a long straight section where they decay. The decays occurring in the straight sections of the ring would generate neutrino beams that could be directed to detectors located thousands of kilometers away, allowing studies of neutrino oscillations with precisions not currently accessible. For example, with the neutrino source at BNL, detectors at Soudan, Minnesota (1,715 km), and Gran Sasso, Italy (6,527 km) become very interesting possibilities. The feasibility of constructing and operating such a muon-storage-ring based Neutrino-Factory, including geotechnical questions related to building non-planar storage rings (e.g. at 8{degree} angle for BNL-Soudan, and 3{degree} angle for BNL-Gran Sasso) along with the design of the muon capture, cooling, acceleration, and storage ring for such a facility is being explored by …

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We have performed x-ray spectroscopic experiments in homogeneous gas bag plasmas where we independently measure the temperature with Thomson scattering. We find that collisional radiative (kinetics) modeling of the intensities of the He-{beta} line and its dielectronic capture satellites is generally in agreement with the measured spectra. On the other hand, for the particular case of satellites arising from inner-shell electron collisional excitation, we find discrepancies of up to a factor of two between experiment and kinetics models. We have ruled out possible effects on the line emission due to plasma gradients, radiative transport, and suprathermal electron excitation leaving errors in the atomic physics modeling to be the most likely explanation. The determination that there are problems with the collisionally populated states is important for the interpretation of inertial confinement fusion capsule implosions where electron densities and temperature have been measured using the spectral line shape of the He-{beta} transition of Ar XVII. The analysis of the implosion data has required Stark broadening calculations coupled to a kinetics model to calculate the detailed line intensities and widths. Despite remaining discrepancies, the good agreement between the experimental dielectronic capture satellites and the HULLAC calculations suggests that HULLAC is a more appropriate …

This work points out that the costates are actually discontinuous functions of time for optimal control problems with Coloumb friction. In particular these discontinuities occur at the time points where the velocity of the system changes sign. To the authors knowledge, this has not been noted before. This phenomenon is demonstrated on a minimum-time problem with Coloumb friction and the consistency of discontinuous costates and switching functions with respect to the input switches is shown.

Thin resist films (< 1500 {angstrom}) based on DUV chemical approaches have been demonstrated for use in EUV lithography. Resists with good sensitivity (5--6 mJ/cm{sup 2}) were observed but imaging mechanisms, in particular as they affect sensitivity, are poorly understood. To clarify mechanisms leading to photosensitivity, acid-generation efficiency at both EUV and DUV wavelengths was measured for the most promising EUV resist compositions as well as initial radiation damage experiments. In previous work, polymer composition was found to be more important in determining the relative dose to print of resists to EUV and DUV radiation than was PAG composition. Here, acid generating efficiency for several polymers upon exposure to EUV and DW are compared to gain insight into the role of the polymer and PAG in converting the incident EUV photon energy into resist images. It is shown that acid generation efficiencies at EUV do not track efficiencies measured on identical films with DUV exposures, and is attributable to polymer and polymer/PAG interactions. No particular structural feature of the polymer could be correlated to the acid generation results. Radiation damage studies showed that polymers that create acid in different yields at EUV do not show differences in radiation damage, as …

This paper presents a new approach to a gesture-tracking system using real-time range on-demand. The system represents a gesture-controlled interface for interactive visual exploration of large data sets. The paper describes a method performing range processing only when necessary and where necessary. Range data is processed only for non-static regions of interest. This is accomplished by a set of filters on the color, motion, and range data. The speedup achieved is between 41% and 54%. The algorithm also includes a robust skin-color segmentation insensitive to illumination changes. Selective range processing results in dynamic regional range images (DRRIs). This development is also placed in a broader context of a biological visual system emulation, specifically redundancies and attention mechanisms.

One of the most significant challenges for technology characterization and future analysis is to keep instrumentation and techniques in step with the development of technology itself. Not only are dimensions shrinking and new materials being employed, but the rate of change is increasing. According to the 1999 International Technology Roadmap for Semiconductors (ITRS) the number and difficulty of the technical challenges continue to increase as technology moves forward. It could be argued that technology cannot be developed without appropriate analytical technique, nevertheless while much effort is being directed at materials and processes, only a small proportion is being directed at analysis. Whereas previous versions of the Semiconductor Industry Association roadmap contained a small number of implicit references to characterization and analysis, the 1999 ITRS contains many explicit references. It is clear that characterization is now woven through the roadmap, and technology developers in all areas appreciate the fact that new instrumentation and techniques will be required to sustain the rate of development the semiconductor industry has seen in recent years. Late in 1999, a subcommittee of the Sematech Product Analysis Forum reviewed the ITRS and identified a top-ten list of challenges which the failure analysis community will face as present …

Urban infrastructure impacts the surface and atmospheric properties, such as wind, temperature, turbulence and radiation budgets. The well-recognized urban heat island phenomenon, characterized by the temperature contrast between the city and the surrounding rural area, is one such impact. Many field experiments have been conducted to study the urban heat island effect, which is typically most intense under clear sky and weak ambient wind conditions at night. In some cases, a cool island may even exist during the day. To consider these urban effects in a numerical model with horizontal grid resolution on the order of kilometers, some sort of parameterization is required to account for the sub-grid building impacts on these effects. To this end, Brown and Williams (1998) have developed an urban parameterization by extending Yamada's (1982) forest canopy scheme to include drag, turbulent production, anthropogenic and rooftop heating effects, and radiation balance in a mesoscale model. In this study, we further modify this urban parameterization by adding the rooftop surface energy equation to eliminate a simplifying assumption that the rooftop is at the same temperature as the air. The objective of this work is to assess the impact of individual process of this modified urban canopy parameterization …

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Plasma facing components in TFTR contain an important record of plasma wall interactions in reactor grade DT plasmas. Tiles, flakes, wall coupons and dust samples have been retrieved from the TFTR vessel for analysis. Selected samples have been baked to release tritium and assay the tritium content. The in-vessel tritium inventory is estimated to be 0.5 g and is consistent with the in-vessel tritium inventory derived from the difference between tritium fueling and tritium exhaust. Relatively high concentrations of tritium were found at the top and bottom of the bumper limiter, as predicted by earlier BBQ modeling. The distribution of tritium on the limiter and vessel wall showed complex patterns of co-deposition.

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The Nuclear Materials Identification System (NMIS) developed by the Instrumentation and Controls Division of the Oak Ridge National Laboratory and the Oak Ridge Y-12 Plant has been used at the Oak Ridge Y-12 plant to perform enhanced receipts confirmation measurements providing mass estimates on low mass HEU metal pieces in shipping containers. For this application, NMIS was used in its active mode with a small Cf source on one side of the shipping container and detectors on the other side. Second order correlation measurements with calibration standards were utilized to obtain the mass of HEU. This was the first use of NMIS for receipts at the Y-12 Plant. This was a cost-effective method for measuring the mass of receipts with as many as 64 items measured in one day. This paper describes the reasons for using the NMIS for this application. The measurement technique and evaluation of the measurement data for this application are also described.

The Multi-Canister Overpacks (MCOs) will contain spent nuclear fuel (SNF) removed from the K East and West Basins. The SNF will be placed in fuel storage baskets that will be stacked inside the MCOs. Approximately 400 MCOS and 2170 baskets will fabricated for this purpose. These MCOs, loaded with SNF, will be placed in interim storage in the Canister Storage Building (CSB) located in the 200 Area of the Hanford Site.

The drainage of water from the emplacement drift is essential for the performance of the EBS. The unsaturated flow properties of the surrounding rock matrix and fractures determine how well the water will be naturally drained. To enhance natural drainage, it may be necessary to introduce engineered drainage features (e.g. drilled holes in the drifts), that will ensure communication of the flow into the fracture system. The purpose of the Water Drainage Model is to quantify and evaluate the capability of the drift to remove water naturally, using the selected conceptual repository design as a basis (CRWMS M&O, 1999d). The analysis will provide input to the Water Distribution and Removal Model of the EBS. The model is intended to be used to provide postclosure analysis of temperatures and drainage from the EBS. It has been determined that drainage from the EBS is a factor important to the postclosure safety case.

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The Z machine at Sandia National Laboratories (SNL) is the most powerful multi-module synchronized pulsed-power accelerator in the world. Rapid development of z-pinch loads on Z has led to outstanding progress in the last few years, resulting in radiative powers of up to 280 TW in 4 ns and a total radiated x-ray energy of 1.8 MJ. The present goal is to demonstrate single-shot, high-yield fusion capsules. Pulsed power is a robust and inexpensive technology, which should be well suited for Inertial Fusion Energy, but a rep-rated capability is needed. Recent developments have led to a viable conceptual approach for a rep-rated z-pinch power plant for IFE. This concept exploits the advantages of going to high yield (a few GJ) at low rep-rate ({approximately} 0.1 Hz), and using a Recyclable Transmission Line (RTL) to provide the necessary standoff between the fusion target and the power plant chamber. In this approach, a portion of the transmission line near the capsule is replaced after each shot. The RTL should be constructed of materials that can easily be separated from the liquid coolant stream and refabricated for a subsequent shots. One possibility is that most of the RTL is formed by casting FLiBe, …

Newsletter of the Texas Department of Health discussing the news, activities, and events of the organization and other information related to health in Texas.

For the past several years, the Alternating Gradient Synchrotron (AGS) at Brookhaven National Laboratory (USA) has provided ions of iron, silicon and gold, at energies from 600 MeV/nucleon to 10 GeV/nucleon, for the US National Aeronautics and Space Administration (NASA) radiobiology research program. NASA has recently funded the construction of a new dedicated ion facility, the Booster Applications Facility (BAF). The Booster synchrotron will supply ion beams ranging from protons to gold, in an energy range from 40--3,000 MeV/nucleon with maximum beam intensities of 10{sup 10} to 10{sup 11} ions per pulse. The BAF Project is described and the future AGS and BAF operation plans are presented.

Both the developed and developing nations of the world would like to move toward a position of sustainable development while paying attention to the restoration of natural resources, improving the environment, and improving the quality of life. The impacts of geothermal development projects are generally positive. It is important, however, that the environmental issues associated with development be addressed in a systematic fashion. Drafted early in the project planning stage, a well-prepared Environmental Impact Assessment (EIA) can significantly add to the quality of the overall project. An EIA customarily ends with the decision to proceed with the project. The environmental analysis process could be more effective if regular monitoring, detailed in the EIA, continues during project implementation. Geothermal development EIAs should be analytic rather than encyclopedic, emphasizing the impacts most closely associated with energy sector development. Air quality, water resources and quality, geologic factors, and socioeconomic issues will invariably be the most important factors. The purpose of an EIA should not be to generate paperwork, but to enable superb response. The EIA should be intended to help public officials make decisions that are based on an understanding of environmental consequences and take proper actions. The EIA process has been defined …