The body-centered tetragonal (BCT) structure in quenched Fe-C steels is usually illustrated to show a linear change in the c and a axes with an increase in carbon content from 0 to 1.4%C. The work of Campbell and Fink, however, shows that this continuous linear relationship is not correct. Rather, it was shown that the body-centered-cubic (BCC) structure is the stable structure from 0 to 0.6 wt%C with the c/a ratio equal to unity. An abrupt change in the c/a ratio to 1.02 occurs at 0.6 wt%C. The BCT structure forms, and the c/a ratio increases with further increase in carbon content. An identical observation is noted in quenched Fe-N steels. This discontinuity is explained by a change in the transformation process. It is proposed that a two-step transformation process occurs in the low carbon region, with the FCC first transforming to HCP and then from HCP to BCC. In the high carbon region, the FCC structure transforms to the BCT structure. The results are explained with the Engel-Brewer theory of valence and crystal structure of the elements. An understanding of the strength of quenched iron-carbon steels plays a key role in the proposed explanation of the c/a anomaly based …

Previous research has identified links between changes in sea surface temperature (SST) and hurricane intensity. We use climate models to study the possible causes of SST changes in Atlantic and Pacific tropical cyclogenesis regions. The observed SST increases in these regions range from 0.32 to 0.67 C over the 20th century. The 22 climate models examined here suggest that century-timescale SST changes of this magnitude cannot be explained solely by unforced variability of the climate system, even under conservative assumptions regarding the magnitude of this variability. Model simulations that include external forcing by combined anthropogenic and natural factors are generally capable of replicating observed SST changes in both tropical cyclogenesis regions.

Eleven types of manganese-containing electrode materialswere subjected to long-term storage at 55oC in 1M LiPF6 ethylenecarbonate/dimethyl carbonate (EC/DMC) solutions. The amount of manganesedissolution observed depended upon the sample surface area, the averageMn oxidation state, the structure, and substitution levels of themanganese oxide. In some cases, structural changes such as solvateformation were exacerbated by the high temperature storage, andcontributed to capacity fading upon cycling even in the absence ofsignificant Mn dissolution. The most stable materials appear to beTi-substituted tunnel structures and mixed metal layered oxides with Mnin the +4 oxidation state.

The Multiple Habitat Sampling Protocol (MHSP) is a bioassessment method designed to assess the ecological health of South Carolina streams on the basis of macroinvertebrate samples collected from natural substrates. The MHSP is computed by averaging the EPT (number of Ephemeroptera, Plecoptera, Trichoptera taxa) and BI (a biotic index that reflects the pollution tolerances of individual taxa) to produce a bioclassification score. The MHSP produced low bioclassification scores that could falsely indicate environmental degradation in some undisturbed, high quality streams in the Sandhills ecoregion. This problem had two causes: (1) the metrics (especially EPT) were significantly related to stream size, which confounded stream size effects with environmental impacts, and (2) the scoring criteria for EPT were too high for some Sandhills streams, likely because of unrecognized heterogeneity among the Sandhills streams from which the criteria were derived. We corrected these problems by developing new scoring criteria from ecologically comparable undisturbed streams and by utilizing residuals from regressions of the metrics on stream width to normalize for stream size. The MHSP and related protocols are effective methods for assessing environmental quality but allowances must be made for the effects of stream size and the potential ecological heterogeneity that naturally exists among …

Solving linear systems arising from systems of partial differential equations, multigrid and multilevel methods have proven optimal complexity and efficiency properties. Due to shortcomings of geometric approaches, algebraic multigrid methods have been developed. One example is the filtering algebraic multigrid method introduced by C. Wagner. This paper proposes a variant of Wagner's method with substantially improved robustness properties. The method is used in an adaptive, self-correcting framework and tested numerically.

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To improve the LSM-YSZ cathode performance of intermediate temperature solid oxide fuel cells (SOFCs), Sm0.6Sr0.4CoO3-sigma (SSC) perovskite nanoparticles are incorporated into the cathodes by a reaction-infiltration process. The SSC particles are {approx}20 to 80nm in diameter, and intimately adhere to the pore walls of the preformed LSM-YSZ cathodes. The SSC particles dramatically enhance single-cell performance with a 97 percent H2+3 percent H2O fuel, between 600 C and 800 C. Consideration of a simplified TPB (triple phase boundary) reaction geometry indicates that the enhancement may be attributed to the high electrocatalytic activity of SSC for electrochemical reduction of oxygen in a region that can be located a small distance away from the strict triple phase boundaries. The implication of this work for developing high-performance electrodes is also discussed.

The properties of ultrahigh carbon steels (UHCS) are strongly influenced by aluminum additions. Hardness studies of quenched UHCS-Al alloys reveal that the temperature for the start of transformation increases with increases in aluminum content. It is shown that this change is a function of the atomic percent of solute and of the valence state when comparisons are made with UHCSs containing silicon and tin as solutes. The thermal expansion of UHCSs with dilute aluminum additions shows no discontinuity in the vicinity of the ferrite-austenite transformation temperature. This is the result of a three phase region of ferrite, carbides and austenite. The slope of the expansion curve is higher in the austenite range than in the ferrite range as a result of the dissolution of carbon in austenite with temperature. Processing to achieve a fine grain size in UHCS-Al alloys was principally by hot and warm working (HWW) followed by isothermal warm working (IWW). The high temperature mechanical properties of a UHCS-10Al-1.5C material show nearly Newtonian-viscous behavior at 900 to 1000 C. Tensile elongations of 1200% without failure were achieved in the 1.5%C material. The high oxidation corrosion resistance of the UHCS-10Al materials is described.

Adaptive mesh refinement (AMR) is a powerful technique thatreduces the resources necessary to solve otherwise in-tractable problemsin computational science. The AMR strategy solves the problem on arelatively coarse grid, and dynamically refines it in regions requiringhigher resolution. However, AMR codes tend to be far more complicatedthan their uniform grid counterparts due to the software infrastructurenecessary to dynamically manage the hierarchical grid framework. Despitethis complexity, it is generally believed that future multi-scaleapplications will increasingly rely on adaptive methods to study problemsat unprecedented scale and resolution. Recently, a new generation ofparallel-vector architectures have become available that promise toachieve extremely high sustained performance for a wide range ofapplications, and are the foundation of many leadership-class computingsystems worldwide. It is therefore imperative to understand the tradeoffsbetween conventional scalar and parallel-vector platforms for solvingAMR-based calculations. In this paper, we examine the HyperCLaw AMRframework to compare and contrast performance on the Cray X1E, IBM Power3and Power5, and SGI Altix. To the best of our knowledge, this is thefirst work that investigates and characterizes the performance of an AMRcalculation on modern parallel-vector systems.

Potential CO{sub 2} reservoirs are often geologically complex and possible leakage pathways such as those created. Reservoir heterogeneity can affect injectivity, storage capacity, and trapping rate. Similarly, discontinuous caprocks and faults can create risk of CO{sub 2} leakage. The characteristics of potential CO{sub 2} reservoirs need to be well understood to increase confidence in injection project success. Reservoir site characterization will likely involve the collection and integration of multiple geological, geophysical, and geochemical data sets. We have developed a computational tool to more realistically render lithologic models using multiple geological and geophysical techniques. Importantly, the approach formally and quantitatively integrates available data and provides a strict measure of probability and uncertainty in the subsurface. The method will characterize solution uncertainties whether they stem from unknown reservoir properties, measurement error, or poor sensitivity of geophysical techniques.

The decay properties of {sup 290}116 and {sup 291}116, and the dependence of their production cross sections on the excitation energies of the compound nucleus, {sup 293}116, have been measured in the {sup 245}Cm({sup 48}Ca,xn){sup 293-x}116 reaction. These isotopes of element 116 are the decay daughters of element 118 isotopes, which are produced via the {sup 249}Cf+{sup 48}Ca reaction. They performed the element 118 experiment at two projectile energies, corresponding to {sup 297}118 compound nucleus excitation energies of E* = 29.2 {+-} 2.5 and 34.4 {+-} 2.3 MeV. During an irradiation with a total beam dose of 4.1 x 10{sup 19} {sup 48}Ca projectiles, three similar decay chains consisting of two or three consecutive {alpha} decays and terminated by a spontaneous fission (SF) with high total kinetic energy of about 230 MeV were observed. The three decay chains originated from the even-even isotope {sup 294}118 (E{sub {alpha}} = 11.65 {+-} 0.06 MeV, T{sub {alpha}} = 0.89{sub -0.31}{sup +1.07} ms) produced in the 3n-evaporation channel of the {sup 249}Cf+{sup 48}Ca reaction with a maximum cross section of 0.5{sub -0.3}{sup +1.6} pb.

One approach for heating a target to ''Warm Dense Matter'' conditions (similar, for example, to the interiors of giant planets or certain stages in inertial confinement fusion targets), is to use intense ion beams as the heating source (see refs.[6] and [7] and references therein for motivation and accelerator concepts). By consideration of ion beam phase-space constraints, both at the injector, and at the final focus, and consideration of simple equations of state and relations for ion stopping, approximate conditions at the target foil may be calculated. Thus, target temperature and pressure may be calculated as a function of ion mass, ion energy, pulse duration, velocity tilt, and other accelerator parameters. We connect some of these basic parameters to help search the extensive parameter space including ion mass, ion energy, total charge in beam pulse, beam emittance, target thickness and density.

Machida found in tracking studies [Shinji Machida, presentation at the FFAG05 Workshop, Kyoto University Research Reactor Institute, Osaka, Japan, 5-9 December 2005] that the time of flight in a linear non-scaling FFAG depended on the transverse amplitude of the particles. I compute a relationship between the transverse amplitude dependence of the time of flight and the variation of tune with energy and explain its physical origin.

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Fixed field alternating gradient accelerators have many features which require careful modeling in simulation. They accept beams over an extremely large momentum range, generally at least a factor of 2. They often use magnets whose lengths are comparable to their apertures. The beam often makes large angles with respect to the magnet axis and pole face normal. In some applications (muons in particular), the beam occupies a substantial fraction of the magnet aperture. The longitudinal dynamics in these machines often differ significantly from what one finds in more conventional machines such as synchrotrons. These characteristics require that simulation codes be careful to avoid inappropriate approximations in describing particle motion in FFAGs. One must properly treat the coordinate system geometry independently from the magnetic fields. One cannot blindly assume that phase space variables are small. One must take magnet end fields properly into account. Finally, one must carefully consider what it means to have a ''matched'' distribution that is injected into these machines.

Crevice corrosion is currently studied using either one of two techniques depending on the data needed. The first method is a multi-crevice former over a metallic sample; this provides information on the severity of crevice corrosion (depth, position, frequency) but delivers little to no electrochemical information [1]. The second method involves the potentiodynamic or potentiostatic study of an uncreviced sample in model crevice solution or under a crevice former in aggressive solution [2]. Crevice corrosion is highly dependent on the position in the crevice. The distance from the crevice mouth will affect the depth of attack, the solution composition and pH, and the ohmic drop and the true potential in the crevice [3-6]. These in turn affect the current density as a function of potential and position. A Multi-Channel Micro-Electrode Analyzer (MMA) has been recently used to demonstrate the interaction between localized corrosion sites (pitting corrosion and intergranular corrosion) [7]. MMA can provide spatial resolution of electrochemical properties in the crevice. By coupling such a tool with scaling laws derived from experimental data (a simple equation linking the depth of crevice corrosion initiation to the crevice gap), it is possible to produce highly instrumented crevices, rescaled to enable spatial resolution …

Crevice corrosion is currently studied using either one of two techniques depending on the data needed. The first method is a multi-crevice former over a metallic sample; this provides information on the severity of crevice corrosion (depth, position, frequency) but delivers little to no electrochemical information [1]. The second method involves the potentiodynamic or potentiostatic study of an uncreviced sample in model crevice solution or under a crevice former in aggressive solution [2]. Crevice corrosion is highly dependent on the position in the crevice. The distance from the crevice mouth will affect the depth of attack, the solution composition and pH, and the ohmic drop and the true potential in the crevice [3-6]. These in turn affect the current density as a function of potential and position. An Multi-Channel Micro-Electrode Analyzer' (MMA) has been recently used to demonstrate the interaction between localized corrosion sites (pitting corrosion and intergranular corrosion) [7]. MMA can provide spatial resolution of electrochemical properties in the crevice. By coupling such a tool with scaling laws derived from experimental data (a simple equation linking the depth of crevice corrosion initiation to the crevice gap), it is possible to produce highly instrumented crevices, rescaled to enable spatial resolution …

In the past decade tens of millions of dollars have beenspent by water resource agencies in California to restore the nativesalmon fishery in the San Joaquin River and its major tributaries. Anexcavated deep water ship channel (DWSC), through which the river runs onits way to the Bay/Delta and Pacific Ocean, experiences episodes of lowdissolved oxygen which acts as a barrier to anadromous fish migration anda threat to the long-term survival of the salmon run. An emergencyresponse management system is under development to forecast theseepisodes of low dissolved oxygen and to deploy measures that will raisedissolved oxygen concentrations to prevent damage to the fisheryresource. The emergency response management system has been designed tointeract with a real-time water quality monitoring network and is servedby a comprehensive data management and forecasting model toolbox. TheBay/Delta and Tributaries (BDAT) Cooperative Data Management System is adistributed, web accessible database that contains terabytes ofinformation on all aspects of the ecology of the Bay/Delta and upperwatersheds. The complexity of the problem dictates data integration froma variety of monitoring programs. A unique data templating system hasbeen constructed to serve the needs of cooperating scientists who wish toshare their data and to simplify and streamline data uploading into themaster database. …

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One of the greatest challenges in evaluating reliability of digital I&C systems is how to obtain better failure rate estimates of digital components. A common practice of the digital component failure rate estimation is attempting to use empirical formulae to capture the impacts of various factors on the failure rates. The applicability of an empirical formula is questionable because it is not based on laws of physics and requires good data, which is scarce in general. In this study, the concept of population variability of the Hierarchical Bayesian Method (HBM) is applied to estimating the failure rate of a digital component using available data. Markov Chain Monte Carlo (MCMC) simulation is used to implement the HBM. Results are analyzed and compared by selecting different distribution types and priors distributions. Inspired by the sensitivity calculations and based on review of analytic derivations, it seems reasonable to suggest avoiding the use of gamma distribution in two-stage Bayesian analysis and HBM analysis.

The E164/E164X plasma wakefield experiment studies beam-plasma interactions at the Stanford Linear Acceleration Center (SLAC). Due to SLAC's recent ability to variably compress bunches longitudinally from 650 {micro}m down to 20 {micro}m, the incoming beam is sufficiently dense to field ionize the neutral lithium (Li) vapor. The field ionization effects are characterized by the beams energy loss through the Li vapor column. Experiment results are presented.

The U. S. Department of Energy, Office of River Protection and the CH2M HILL Hanford Group, Inc. are responsible for the operations, cleanup, and closure activities at the Hanford Tank Farms. There are 177 tanks overall in the tank farms, 149 single-shell tanks (see Figure 1), and 28 double-shell tanks (see Figure 2). The single-shell tanks were constructed 40 to 60 years ago and all have exceeded their design life. The single-shell tanks do not meet Resource Conservation and Recovery Act of 1976 [1] requirements. Accordingly, radioactive waste is being retrieved from the single-shell tanks and transferred to double-shell tanks for storage prior to treatment through vitrification and disposal. Following retrieval of as much waste as is technically possible from the single-shell tanks, the Office of River Protection plans to close the single-shell tanks in accordance with the Hanford Federal Facility Agreement and Consent Order [2] and the Atomic Energy Act of 1954 [3] requirements. The double-shell tanks will remain in operation through much of the cleanup mission until sufficient waste has been treated such that the Office of River Protection can commence closing the double-shell tanks. At the current time, however, the focus is on retrieving waste and closing …

The ILC beam dumps are a key part of the accelerator design. At Snowmass 2005, the current status of the beam dump designs was reviewed, and the options for the overall dump layout considered. This paper describes the available dump options for the baseline and the alternatives and considers issues for the dumps that require resolution.

The Technology Goals for Generation IV nuclear energy systems highlight Proliferation Resistance and Physical Protection (PR&PP) as one of the four goal areas for Generation 1V nuclear technology. Accordingly, an evaluation methodology is being developed by a PR&PP Experts Group. This paper presents a possible approach, which is based on Markov modeling, to the evaluation methodology for Generation IV nuclear energy systems being developed for PR&PP. Using the Markov model, a variety of proliferation scenarios can be constructed and the proliferation resistance measures can be quantified, particularly the probability of detection. To model the system with increased fidelity, the Markov model is further developed to incorporate multiple safeguards approaches in this paper. The approach to the determination of the associated parameters is presented. Evaluations of diversion scenarios for an example sodium fast reactor (ESFR) energy system are used to illustrate the methodology. The Markov model is particularly useful because it can provide the probability density function of the time it takes for the effort to be detected at a specific stage of the proliferation effort.