Permanent magnets that are levitated and rotating over a bulk high-temperature superconductor (HTS) form the basis of many superconducting bearing designs. Experiments have shown that the rotational-loss coefficient of friction'' for thrust bearings of this type can be as low as 8 [times] 10[sup [minus]6]. While the loss mechanisms of such bearings are not well understood, the azimuthal homogeneity of the rotating permanent magnet is believed to play an important role in determining the loss. One possible loss mechanism is magnetic hysteresis in the HTS, where the energy loss E per cycle is derived from the critical state model and given by E = K ([Delta]B[sup 3]/J[sub c]) where K is a geometric coefficient, [Delta]B is the variation in magnetic field at the surface of the HTS experienced during a rotation of the levitated magnet, and J[sub c] is the critical current density of the HTS. It is clear that a small decrease in [Delta]B (i.e., decreasing the azimuthal inhomogeneity of the rotating magnetic field) could have profound effects on decreasing E and the rotational coefficient of friction. The role of [Delta]B is also expected to be significant in reducing losses from eddy currents and other mechanisms. Low rotational losses …

Permanent magnets that are levitated and rotating over a bulk high-temperature superconductor (HTS) form the basis of many superconducting bearing designs. Experiments have shown that the rotational-loss``coefficient of friction`` for thrust bearings of this type can be as low as 8 {times} 10{sup {minus}6}. While the loss mechanisms of such bearings are not well understood, the azimuthal homogeneity of the rotating permanent magnet is believed to play an important role in determining the loss. One possible loss mechanism is magnetic hysteresis in the HTS, where the energy loss E per cycle is derived from the critical state model and given by E = K ({Delta}B{sup 3}/J{sub c}) where K is a geometric coefficient, {Delta}B is the variation in magnetic field at the surface of the HTS experienced during a rotation of the levitated magnet, and J{sub c} is the critical current density of the HTS. It is clear that a small decrease in {Delta}B (i.e., decreasing the azimuthal inhomogeneity of the rotating magnetic field) could have profound effects on decreasing E and the rotational coefficient of friction. The role of {Delta}B is also expected to be significant in reducing losses from eddy currents and other mechanisms. Low rotational losses in …

Quantum Monte Carlo calculations of ground and low-lying excited states for nuclei with A {le} 8 are made using a realistic Hamiltonian that fits NN scattering data. Results for more than 40 different (J{pi}, T) states, plus isobaric analogs, are obtained and the known excitation spectra are reproduced reasonably well. Various density and momentum distributions and electromagnetic form factors and moments have also been computed. These are the first microscopic calculations that directly produce nuclear shell structure from realistic NN interactions.

We introduce a novel type of spectrometer that provides a {micro}eV bandpass together with a tunability over a few meV. The technique relies on nuclear resonant scattering (Moessbauer effect) of synchrotrons radiation at the 14.4-keV resonance of {sup 57}Fe. Energy tuning is achieved by the Doppler effect in high speed rotary motion. The resonantly scattered monochromatic radiation is extracted by a polarization filtering technique or by spatial separation due to the ''nuclear lighthouse effect''.

External dosimetry needs at the four Martin Marietta Energy Systems facilities are served by Energy Systems Centralized External Dosimetry System (CEDS). The CEDS is a four plant program with four dosimeter distribution centers and two dosimeter processing centers. Each plant has its own distribution center, while processing centers are located at ORNL and the Y-12 Plant. The program has been granted accreditation by the Department of Energy Laboratory Accreditation Program (DOELAP). The CEDS is a TLD based system which is responsible for whole-body beta-gamma, neutron, and extremity monitoring. Beta-gamma monitoring is performed using the Harshaw/Solon Technologies model 8805 dosimeter. Effective October 1, 1992 the standard silver mylar has been replaced with an Avery mylar foil blackened on the underside with ink. This was done in an effort to reduce the number of light induced suspect readings. At this time we have little operational experience with the new blackened mylars-The CEDS neutron dosimeter is the Harshaw model 8806B. This card/holder configuration contains two TLD-600/TLD-700 chip pairs; one pair is located beneath a cadmium filter and one pair is located beneath a plastic filter. In routine personnel monitoring the CEDS neutron dosimeter is always paired with a CEDS beta-gamma dosimeter.The CEDS extremity …

The MACHO Project is a microlensing survey that monitors the brightnesses of -60 million stars in the Large Magellanic Cloud (LMC), Small Magellanic Cloud, and Galactic bulge. The database presently contains more photometric measurements than previously recorded in the history of astronomy. We describe the calibration of the MACHO two-color photometry and transformation to the standard Kron-Cousins V and R system. This allows for proper comparison with all other observations on the Kron-Cousins standard system. The highest precision calibrations are for -9 million stars in the LMC bar. For these stars, independent photometric measurements in field-overlap regions indicate standard deviations {sigma}{sub V} = {sigma}{sub R} = 0.020 mag. Calibrated MACHO photometry data are compared with published photometric sequences and with new Hubble Space Telescope observations. We additionally describe the first application of these calibrated data: the construction of the �efficiency� color-magnitude diagram which will be used to calculate our experimental sensitivity for detecting microlensing in the LMC.

Split numerical methods have been commonly used in computational physics for many years due to their speed, simplicity, and the accessibility of shock capturing methods in one-dimension. For a variety of reasons, it has been challenging to determine just how accurate operator split methods are, especially in the presence of curved wave features. One of these difficulties has been the lack of multidimensional shock capturing methods. Another is the difficulty of mathematical analysis of dis-continuous flow phenomena. Also, computational studies have been limited due to a lack of multidimensional model problems with analytic solutions that probe the nonlinear features of the flow equations. However, a new genuinely unsplit numerical method has been invented. With the advent of the Space-Time Conservation Element/Solution Element (CE/SE) method, it has become possible to attain high accuracy in multidimensional flows, even in the presence of curved shocks. Examples presented here provide some new evidence of the errors committed in the use of operator split techniques, even those employing �unsplit� corrections. In these problems, the CE/SE method is able to maintain the original cylindrical symmetry of the problem and track the main features of the flow, while the operator split methods fail to maintain symmetry and …

The world`s population, energy demand, and rate of carbon emissions are increasing, but the rates of increase are uncertain. Even modest growth rates present significant challenges to existing and developing technologies for reducing carbon and greenhouse gas emissions while meeting growing energy demands. Nuclear power is currently the most developed alternative to fossil fuel combustion and is one of the options for meeting these challenges. However, there remain significant technical, economic and institutional barriers inhibiting growth of nuclear capacity in the U.S. and slowing implementation worldwide. In the near-term, the major barriers to nuclear power, especially in the U.S., appear to be economic and institutional, with the risks such as safety, waste management and proliferation having reasonably acceptable limits considering the current installed capacity. Future growth of nuclear power, however, may well hinge on continuous evolutionary and perhaps revolutionary reduction of these risks such that the overall risk of nuclear power, aggregated over the entire installed capacity, remains at or below today`s risks.

Thin coatings of Cr-Si-O are assessed for use as a resistor. The submicron thick films are sputter deposited using a (l-x)Ar-(x)O{sub 2} working gas. Several compacts of metal and oxide powders are commercially prepared for use as the sputter targets. The deposition process yields film compositions which range from 2 to 30 at.% Cr and 20 to 45 at.% Si as measured using Rutherford backscattering. A broad range of resistivities from 10{sup 1} to 10{sup 14}{Omega} cm are found as measured through the film thickness between metal pads deposited onto the Cr-Si-O surface. The film structure and morphology are characterized using transmission electron microscopy from which the resistance behavior can be correlated to the distribution of metallic particles. Thermal aging reveals the metastability of the Cr- Si-O film morphology and resistance behavior.

Extending the concept of parton densities onto nonforward matrix elements <p{prime}{vert_bar}O(0,z){vert_bar}p> of quark and gluon light-cone operators, one can use two types of nonperturbative functions: double distributions (DDs) f(x,{alpha};t), F(x,y;t) and skewed (off & nonforward) parton distributions (SPDs) H(x,{xi};t), F{sub {zeta}}(X,t). The authors treat DDs as primary objects producing SPDs after integration. They emphasize the role of DDs in understanding interplay between (x) and {zeta} ({xi}) dependences of SPDs. In particular, the use of DDs is crucial to secure the polynomiality condition: Nth moments of SPDs are Nth degree polynomials in the relevant skewedness parameter {zeta} or {xi}. They propose simple ansaetze for DDs having correct spectral and symmetry properties and derive model expressions for SPDs satisfying all known constraints. Finally, they argue that for small skewedness, one can obtain SPDs from the usual parton densities by averaging the latter with an appropriate weight over the region [X{minus}{zeta},X] (or [ x {minus} {xi}, x + {xi}]).

Sediments in many parts of the New York and New Jersey estuary system are contaminated with toxic organic and inorganic compounds by different sources. Because of the potential environmental consequences, detailed information on the spatial distribution of sediment contaminants is essential in order to carry out routine shipping channel dredging in an environmentally responsible way, and to remediate hot spots cost-effectively and safely. Scientific visualization and scatter data modeling techniques have been successfully applied in analyzing the sparse sampling data of sediment contaminants in New York and New Jersey estuaries, the underlying spatial characteristics of which are otherwise difficult to comprehend. Continuous realizations of contaminant concentrations in the region were obtained by using a spectral domain-decomposition scattered data model and IBM Data Explorer which is a software package for scientific data visualization.

Sediments in many parts of the New York and New Jersey estuary system are contaminated with toxic organic and inorganic compounds by different sources. Because of the potential environmental consequences, detailed information on the spatial distribution of sediment contaminants is essential in order to carry out routine shipping channel dredging in an environmentally responsible way, and to remediate hot spots cost-effectively and safely. Scientific visualization and scatter data modeling techniques have been successfully applied in analyzing the sparse sampling data of sediment contaminants in New York and New Jersey estuaries, the underlying spatial characteristics of which are otherwise difficult to comprehend. Continuous realizations of contaminant concentrations in the region were obtained by using a spectral domain-decomposition scattered data model and IBM Data Explorer which is a software package for scientific data visualization.

For many commercial and military applications, the successive Vacuum Induction Melting of uranium metal in graphite crucibles results in a product which is out of specification in carbon. The current recovery method involves dissolution of the metal in acid and chemical purification. This is both expensive and generates mixed waste. A study was undertaken at Lawrence Livermore National Laboratory to investigate the feasibility of reducing the carbon content of uranium metal using electron beam techniques. Results will be presented on the rate and extent of carbon removal as a function of various operating parameters.

The new NHMFL 60T quasi-continuous magnet produces a flat-top field for a period of 100 ms at 60 Tesla, and for longer time at lower fields, e.g. 0.5 s at 45 Tesla. We have developed for the first time the capability to measure heat capacity at very high magnetic fields in the NHMFL 60T quasi-continuous magnet at LANL, using a probe built out of various plastic materials. The field plateau allows us to utilize a heat-pulse method to obtain heat capacity data. Proof-of-principle heat capacity experiments were performed on a variety of correlated electron systems. Both magnet performance characteristics and physical properties of various materials studied hold out a promise of wide application of this new tool.

A calculation of the total cross section for top quark production in hadron-hadron collisions is presented based on an all-orders perturbative resummation of initial-state gluon radiative contributions to the basic quantum chromodynamics subprocesses. For p{anti p} collisions at center-of-mass energy {radical}s = 1.8 TeV and a top mass of 175 GeV, the authors obtain {sigma}(t{anti t}) = 5.52 {sub {minus}0.45}{sup +0.07} pb. Cross sections are provided as a function of top mass at CERN LHC energies.

The kinetics which drive cascade formation and subsequent collapse into point-defect clusters is investigated by analyzing the microstructure produced in situ by low fluence 100 keV Kr ion irradiations of fcc-Cu over a wide temperature range (18-873 K). The yield of collapsed point-defect clusters is demonstrated unequivocally to be temperature dependent, remaining approximately constant up to lattice temperatures of 573 K and then abruptly decreasing with increasing temperature. This drop in yield is not caused by defect loss during or following ion irradiation. This temperature dependence can be explained by a thermal spike effect. These in-situ yield measurements are compared to previous ex-situ yield measurements in fcc-Ni and bcc-Mo.

We report here on the results of experiments concerning particular bonding processes potentially useful for ultimate miniaturization of microfluidic systems. Direct anodic bonding of continuous thin pyrex glass of 250 {mu}m thickness to silicon substrates gives multiple, large voids in the glass. Etchback of thick glass of 1200 {mu}m thickness bonded to silicon substrates gives thin continuous glass layers of 189 {mu}m thickness without voids over areas of 5 cm {times} 12 cm. Glass was also successfully bonded to glass by thermal bonding at 800{degrees}C over a 5 cm {times} 7 cm area. Anticipated applications include microfabricated DNA sequencing, flow injection analysis, and liquid and gas chromatography microinstruments.

Crystalline nanoprecipitates of Xe have been produced by ion implantation into mazed bicrystalline Al at 300 K, in which the matrix grain boundaries are mainly 90 deg tilt boundaries. Within Al grains, Xe nanocrystals are fee, isotactic with the Al and cuboctohedral in shape with {l_brace}111{r_brace} and {l_brace}100{r_brace} facets. With an off-axial imaging technique, the nanocrystals were structure imaged against a relatively featureless matrix background. In contrast to metal precipitates in Al, such as Pb, Xe precipitates straddling a matrix grain boundary are bicrystals as small as approximately 2 nm in diameter. Larger Xe precipitates tend to avoid boundaries which are inclined away from asymmetrical orientation and which thus have a significant twist component. Under the 1 MeV electron irradiation employed for HREM observation, small Xe nanocrystals near a grain boundary may migrate to the boundary and coalesce with other Xe precipitates. The structural observations are rationalized on a simple geometrical interpretation.

Metallic uranium alloys are candidate materials for use as the fuel phase in very-high-density LEU dispersion fuels. These ductile alloys cannot be converted to powder form by the processes routinely used for oxides or intermetallics. Three methods of powder production from uranium alloys have been investigated within the US-RERTR program. These processes are grinding, cryogenic milling, and hydride-dehydride. In addition, a gas atomization process was investigated using gold as a surrogate for uranium. Grinding was found to be inefficient and introduced impurities into the fuel. Cryogenic milling of machine chips in a steel vial was found to have similar shortcomings. The hydride-dehydride process has historically been used to produce very fine powder that may not be suitable for fuel fabrication. Uranium is made to form its hydride by heating in a hydrogen atmosphere. Subsequent heating under vacuum drives off hydrogen gas and returns the hydride to a metallic state. The volume change on hydride formation results in a fine powder upon dehydriding. The effects of alloying elements, partial hydriding, and subsequent milling treatments on particle size distribution are being explored. Inert gas atomization is used on an industrial scale to produce metal powder. Current designs are not suitable for use …

Sandia National Laboratories has initiated the development of an airborne system for W laser remote sensing measurements. System applications include the detection of effluents associated with the proliferation of weapons of mass destruction and the detection of biological weapon aerosols. This paper discusses the status of the conceptual design development and plans for both the airborne payload (pointing and tracking, laser transmitter, and telescope receiver) and the Altus unmanned aerospace vehicle platform. Hardware design constraints necessary to maintain system weight, power, and volume limitations of the flight platform are identified.

The authors study the importance of the partonic phase produced in relativistic heavy ion collision by comparing the parton cascade model and the hadronic cascade model. Hadron yield, baryon stopping and transverse momentum distribution are calculated with JAM and discussions are given comparing with VNI. Both of these models give good description of experimental data. They also discuss the strangeness production mechanism and the directed transverse flow.

A method for determining the presence of partonic scattering through two-particle correlations is developed and applied to models which have jets and mini-jets in them. We only consider the correlation of mid-rapidity particles because they will be easily measured in large numbers at RHIC. The level of two-particle correlations will be a direct measure of how dense a system is made in Au-Au collisions at RHIC. The STAR TPC will be ideal for making these measurements in the first year of running.

We are undertaking a series of shock compression experiments on polycrystalline and oriented single crystal Ta to investigate the fundamental mechanisms controlling dislocation behavior in Ta and other bcc metals at high strain rate. We compare experimental results to those calculated using an explicit 1-D computer code using the Steinberg-Guinan-Lund rate dependent model (Steinberg and Lund [1989]) to describe the strength properties of Ta in these calculation