Vanadium-base alloys are being considered as candidates for the first wall in advanced V-Li blanket concepts in fusion reactor systems. However, a primary deterrent to the use of these alloys at elevated temperatures is their relatively high affinity for interstitial impurities, i.e., O, N, H, and C. The authors conducted a systematic study to determine the effects of time, temperature, and oxygen partial pressure (pO{sub 2}) in the exposure environment on O uptake, scaling kinetics, and scale microstructure in V-(4--5) wt.% Cr-(4--5) wt.% Ti alloys. Oxidation experiments were conducted on the alloys at pO{sub 2} in the range of 5 x 10{sup {minus}6}-760 torr (6.6 x 10{sup {minus}4}-1 x 10{sup 5} Pa) at several temperatures in the range of 350--700 C. Models that describe the oxidation kinetics, oxide type and thickness, alloy grain size, and depth of O diffusion in the substrate of the two alloys were determined and compared. Weight change data were correlated with time by a parabolic relationship. The parabolic rate constant was calculated for various exposure conditions and the temperature dependence of the constant was described by an Arrhenius relationship. The results showed that the activation energy for the oxidation process is fairly constant at pO{sub …

A systematic study is underway at Argonne National Laboratory to evaluate the mechanical properties of several V-Cr-Ti alloys after exposure to environments containing hydrogen at various partial pressures. The goal is to correlate the chemistry of the exposure environment with hydrogen uptake by the samples and with the resulting influence on microstructures and tensile properties of the alloys. Other variables examined are specimen cooling rate and synergistic effects, if any, of oxygen and hydrogen on tensile behavior of the alloys. Experiments were conducted to evaluate the effect of pH{sub 2} in the range of 3 x 10{sup {minus}6} and 1 torr on tensile properties of two V-Cr-Ti alloys. Up to pH{sub 2} of 0.05 torr, negligible effect of H was observed on either maximum engineering stress or uniform and total elongation. However, uniform and total elongation decreased substantially when the alloys were exposed at 500 C to 1.0 torr of H{sub 2} pressure. Preliminary data from sequential exposures of the materials to low-pO{sub 2} and several low-pH{sub 2} environments did not reveal adverse effects on the maximum engineering stress or on uniform and total elongation when the alloy contained {approx} 2,000 wppm O and 16 wppm H. Furthermore, tests in …

This paper will describe an algorithm for detecting and classifying seismic and acoustic signals for unattended ground sensors. The algorithm must be computationally efficient and continuously process a data stream in order to establish whether or not a desired signal has changed state (turned-on or off). The paper will focus on describing a Fourier based technique that compares the running power spectral density estimate of the data to a predetermined signature in order to determine if the desired signal has changed state. How to establish the signature and the detection thresholds will be discussed as well as the theoretical statistics of the algorithm for the Gaussian noise case with results from simulated data. Actual seismic data results will also be discussed along with techniques used to reduce false alarms due to the inherent nonstationary noise environments found with actual data.

A computational analysis of the combined effects of feed oil injection parameters in a commercial-scale fluidized catalytic cracking riser reactor was performed using a three-phase, multiple species kinetic cracking computer code. The analysis showed that the injection operating parameters (droplet diameter and injection velocity) had strong impacts on the gasoline yields of the FCC unit. A spray injection Reynolds number combining the two parameters was defined. A correlation between the spray injection Reynolds number and the gasoline product yields for various feed injection conditions was developed. A range of spray injection Reynolds number for the maximum gasoline yield was identified.

This paper characterizes the homotopy properties and the global topology of the space of positions of vehicles which are constrained to travel without intersecting on a network of paths. The space is determined by the number of vehicles and the network. Paths in the space correspond to simultaneous non-intersecting motions of all vehicles. The authors therefore focus on computing the homotopy type of the space, and show how to do so in the general case. Understanding the homotopy type of the space is the central issue in controlling the vehicles, as it gives a complete description of the distinct ways that vehicles may move safely on the network. The authors exhibit graphs, products of graphs, and amalgamations of products of graphs that are homotopy equivalent to the full configuration space, and are far simpler than might be expected. The results indicate how a control system for such a network of vehicles (such as a fleet of automatically guided vehicles guided by wires buried in a factory floor) may be implemented.

The Multivariate State Estimation Technique (MSET) has been developed at Argonne National Laboratory (ANL) and applied for real time surveillance applications for the purposes of signal validation, sensor operability validation, equipment health monitoring, incipient component fault annunciation, and process anomaly identification. Although MSET was originally developed for applications in the commercial nuclear industry, it has recently been spun off for applications in fields such as aerospace, manufacturing, transportation, robotics, and ship propulsion. Notwithstanding these types of successful applications of MSET in industry, it is necessary for safety-critical and mission-critical applications of MSET to have reliability analysis methods, including a propagation-of-uncertainty tool, which is needed to support safety evaluations in a variety of industries, and technical-specification-change requests in the case of the nuclear industry. For these and related applications, a general purpose uncertainty analysis tool for MSET has been developed that uses Monte Carlo simulation with Latin Hypercube Sampling. For any new application of MSET, the uncertainty analysis tool developed here may be used to investigate quantitative propagation-of-uncertainty behavior for all sensors under surveillance. In addition to supporting safety analysis of surveillance systems that are based on MSET, the tool developed here can be employed in parametric studies to support system …

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It is convenient to consider 2 broad categories of climate-related modeling studies for which it is necessary to specify some kind of lower boundary conditions. The first of these categories is the use of general circulation or weather forecasting models, perhaps modified to carry out climate simulations. In these models, one normally has to specify something about the albedo of the surface to get the radiation balance right, the surface roughness to get the momentum exchange right, and the surface moisture availability to get the surface heat and water vapor fluxes right. Correctly specifying the surface moisture availability can be a major problem and may involve a sophisticated land surface parameterization scheme to take into account plant and soil characteristics. It is reasonable to expect that misrepresenting the water vapor flux by 10--20% on average over continental scales could lead to significant errors in simulated precipitation, temperatures, and circulation patterns. The Atmospheric Radiation Measurement (ARM) Program is focused, however, on clouds and radiation; and it has chosen Cloud and Radiation Testbeds (CART) as the principal tool with which to carry out its work. In this context, what the authors are concerned about for the lower boundary conditions is somewhat different. …

In a previous study of tangent site chains near a surface, the inhomogeneous density profiles were found through Density Functional theory. In the current study, the surface tensions of these systems are found from the results of the previous study through a thermodynamic integration. The calculated surface tensions are then compared to those found directly through computer simulation. Both the surface tension and surface excess for polymeric systems are shown to qualitatively differ from those of atomic systems, although certain similarities are seen at high densities.

The Solvay process utilizes two alkalis in sequential order to convert CO{sub 2} to sodium carbonate for commercial use. The ability to transform CO{sub 2} into sodium carbonate cost-effectively would be a breakthrough in CO{sub 2} sequestration by providing benign long-term storage of CO{sub 2}. However, the Solvay process was not designed for CO{sub 2} sequestration and is not practical for use in the sequestration of CO{sub 2} from fossil fuel power plants. This paper investigates methods to modify the process in order to make it effective for the control of power plant CO{sub 2} emissions. The new modified process, called the Dual Alkali Approach, attempts to replace either or both bases, ammonia and lime, in the Solvay process with other compounds to make CO{sub 2} capture and separation efficient. Ammonia was replaced with different amines in aqueous solutions of salts and it was found that bicarbonate precipitation did occur. A method to regenerate the amine in the second step has not been implemented. However, the second step in Solvay Process has been implemented without using lime, namely, ammonia has been regenerated from an ammonium chloride solution using activated carbon. The HCl adsorbed in the activated carbon was removed by …

Measurements at the central facility of the Southern Great Plains (SGP) Cloud and Radiation Testbed (CART) are intended to verify, improve, and develop parameterizations in radiative flux models that are subsequently used in General Circulation Models (GCMs). The reliability of this approach depends upon the representativeness of the local measurements at the central facility for the site as a whole or on how these measurements can be interpreted so as to accurately represent increasingly large scales. The variation of surface energy budget terms over the SGP CART site is extremely large. Surface layer measurements of the sensible heat flux (H) often vary by a factor of 2 or more at the CART site (Coulter et al. 1996). The Planetary Boundary Layer (PBL) effectively integrates the local inputs across large scales; because the mixed layer height (h) is principally driven by H, it can, in principal, be used for estimates of surface heat flux over scales on the order of tens of kilometers. By combining measurements of h from radiosondes or radar wind profiles with a one-dimensional model of mixed layer height, they are investigating the ability of diagnosing large-scale heat fluxes. The authors have developed a procedure using the model …

Mercury stabilization and solidification is a significant challenge for conventional stabilization technologies. This is because of the stringent regulatory limits on leaching of its stabilized products. In a conventional cement stabilization process, Hg is converted at high pH to its hydroxide, which is not a very insoluble compound; hence the preferred route for Hg sulfidation to convert it into insoluble cinnabar (HgS). Unfortunately, efficient formation of this compound is pH-dependent. At a high pH, one obtains a more soluble Hg sulfate, in a very low pH range, insufficient immobilization occurs because of the escape of hydrogen sulfide, while efficient formation of HgS occurs only in a moderately acidic region. Thus, the pH range of 4 to 8 is where stabilization with Chemically Bonded Phosphate Ceramics (CBPC) is carried out. This paper discusses the authors experience on bench-scale stabilization of various US Department of Energy (DOE) waste streams containing Hg in the CBPC process. This process was developed to treat DOE's mixed waste streams. It is a room-temperature-setting process based on an acid-base reaction between magnesium oxide and monopotassium phosphate solution that forms a dense ceramic within hours. For Hg stabilization, addition of a small amount (< 1 wt.%) of Na{sub …

A lattice-Monte Carlo approach was developed to simulate ferroelectric domain behavior. The model utilizes a Hamiltonian for the total energy that includes electrostatic terms (involving dipole-dipole interactions, local polarization gradients, and applied electric field), and elastic strain energy. The contributions of these energy components to the domain structure and to the overall applied field response of the system were examined. In general, the model exhibited domain structure characteristics consistent with those observed in a tetragonally distorted ferroelectric. Good qualitative agreement between the appearance of simulated electrical hysteresis loops and those characteristic of real ferroelectric materials was found.

Since the 1997 Atmospheric Radiation Measurement (ARM) Science Team Meeting, the North Slope of Alaska and Adjacent Arctic Ocean (NSA/AAO) Cloud and Radiation Testbed (CART) site has come into being. Much has happened even since the 1998 Science Team Meeting at which this paper was presented. To maximize its usefulness, this paper has been updated to include developments through July 1998.

Interfaces play an important role in determining the effect of electric fields on the mechanism of the formation spinel by solid-state reaction. The reaction occurs by the movement of phase boundaries but the rate of this movement can be affected by grain boundaries in the reactants or in the reaction product. Only by understanding these relationships will it be possible to engineer their behavior. As a particular example of such a study, MgIn{sub 2}O{sub 4} can be formed by the reaction between single-crystal MgO substrate and a thin film of In{sub 2}O{sub 3} with or without an applied electric field. High-resolution backscattered electron (BSE) imaging and electron backscattered diffraction (EBSD) in a scanning electron microscope (SEM) has been used to obtain complementary chemical and crystallographic information.

There has been an increasing amount of interest in silsesquioxanes and polysilsesquioxanes. They have been used as models for silica surfaces and have been shown to have great potential for several industrial applications. Typical synthesis of polysilsesquioxanes involves the hydrolysis of organotricholorosilanes and/or organotrialkoxysilanes in the presence of acid or base catalysts, usually in the presence of organic solvents.

The in vitro volubility of airborne uranium dusts collected at a former uranium processing facility now undergoing safe shutdown, decontamination and dismantling was evaluated by immersing air filters from high volume samplers in simulated lung fluid and measuring the {sup 238}U in sequential dissolution fractions using specific radiochemical analysis for uranium. X rays and photons from the decay of uranium and thorium remaining on the filter after each dissolution period were also directly measured using a planar germanium detector as a means for rapidly evaluating the volubility of the uranium bearing dusts. Results of these analyses demonstrate that two -distinct types of uranium bearing dusts were collected on the filters depending upon the location of the air samplers. The first material exhibited a dissolution half-time much less than one day and was most likely UO{sub 3}. The dissolution rate of the second material, which was most likely U{sub 3}O{sub 8}, exhibited two components. Approximately one-third of this material dissolved with a halftime much less than one day. The remaining two-thirds of the material dissolved with half times between 230 {+-} 16 d and 1350 {+-} 202 d. The dissolution rates for uranium determined by radiochemical analysis and by gamma spectrometry …

Disilaoxacyclopentanes have proven to be excellent precursors to sol-gel type materials. These materials have shown promise as precursors for encapsulation and microelectronics applications. The polymers are highly crosslinked and are structurally similar to traditional sol-gels, but unlike typical sol-gels they are prepared without the use of solvents and water, they have low VOC's and show little shrinkage during processing.

Models are presented of sodium tellurite glasses in the composition range (Na{sub 2}0){sub x}-(TeO{sub 2}){sub 1{minus}x}. 0.1 < x < 0.3. The models combine self-consistently data from three different and complementary sources: sodium-23 nuclear magnetic resonance (NMR), neutron diffraction, and x-ray diffraction. The models were generated using the Reverse Monte Carlo algorithm, modified to include NMR data in addition to diffraction data. The presence in the models of all five tellurite polyhedra consistent with the Te{sup +4} oxidation state were found to be necessary to achieve agreement with the data. The distribution of polyhedra among these types varied from a predominance of highly bridged species at low sodium content, to polyhedra with one or zero bridging oxygen at high sodium content. The models indicate that the sodium cations themselves form sodium oxide clusters particularly at the x = 0.2 composition.

The U.S. Department of Energy's Rebuild America is partnering with public and private housing organizations throughout the nation to make building improvements and provide solutions to housing needs while saving energy and reducing utility costs. This paper describes the partnership development, technical assistance, and other types of support Rebuild America offers that excites housing organizations to form Rebuild America partnerships. Successful partnerships are highlighted that demonstrate the wide-range of projects Rebuild America partners are performing, with a detailed description of four notable case studies.

Refrigerator energy use is a dominant component of total energy use for many low-income households. Poorly operating or inefficient refrigerators can place an unnecessary financial burden on those households or the public agencies that pay their electricity bills, such as housing authorities. This paper presents an analytic tool that is low cost and easy to use. The procedure can be implemented with minimal staff training. The tool enables housing providers or weatherization agencies to identify poorly operating or high use refrigerators and target them for replacement or repair. The use of the procedure is illustrated, and its value for participants in a bulk refrigerator purchase and replacement program is discussed.

The authors report on Shubnikov-de Haas (SdH) and de Haas-van Alphen (dHvA) results for the highly two-dimensional (2D) organic superconductors {kappa}-(ET){sub 2}I{sub 3} ({Tc} = 3.5 K) and {beta}{double_prime}-(ET){sub 2}SF{sub 5}CH{sub 2}CF{sub 2}SO{sub 3} ({Tc} = 4.4 K). The SdH oscillations of both materials show an apparent deviation from the well-understood 2D dHvA signal at low temperatures and high magnetic fields. For {kappa}-(ET){sub 2}I{sub 3}, the mechanism leading to this behavior still needs to be clarified. For {beta}{double_prime}-(ET){sub 2}SF{sub 5}CH{sub 2}CF{sub 2}SO{sub 3}, an anomalous steady background part of the magnetoresistance seems to account for the observed discrepancies.

Non-conservation of CP symmetry can manifest itself in non-lepton ichyperon decays as a difference in the decay parameter between the strange-baryon decay and its charge conjugate. By comparing the decay distribution in the {Lambda} helicity frame for the decay sequence {Xi}{sup -} {yields} {Lambda}{pi}{sup -}, {Lambda} {yields} p{pi}{sup -} with that of {bar {Xi}}{sup +} decay, E756 at Fermilab did not observe any CP-odd effect at the 10{sup -2} level. The status of a follow-up experiment, HyperCP (FNAL E871), to search for CP violation in charged {Xi}-{Lambda} decay with a sensitivity of 10{sup -4} is also presented.