An indirect method for determining cross sections for reactions proceeding through a compound nucleus is presented. The appropriate theoretical framework for applications of this method is reviewed and theoretical and experimental challenges that need to be addressed in applications of the method are outlined. Two approximations are considered and their advantages and limitations are discussed.

We present evidence that the simplest particle-physics scalar-field models of dynamical dark energy can be separated into distinct behaviors based on the acceleration or deceleration of the field as it evolves down its potential towards a zero minimum. We show that these models occupy narrow regions in the phase-plane of w and w', the dark energy equation-of-state and its time-derivative in units of the Hubble time. Restricting an energy scale of the dark energy microphysics limits how closely a scalar field can resemble a cosmological constant. These results, indicating a desired measurement resolution of order \sigma(w')\approx (1+w), define firm targets for observational tests of the physics of dark energy.

This paper presents a numerical technique for analyzing the containment vessel subjected to the combined loading of closure-bolt torque and internal pressure. The detailed stress distributions in the O-rings generated by both the torque load and the internal pressure can be evaluated by using this method. Consequently, the sealing performance of the O-rings can be determined. The material of the O-rings can be represented by any available constitutive equation for hyperelastic material. In the numerical calculation of this paper, the form of the Mooney-Rivlin strain energy potential is used. The technique treats both the preloading process of bolt tightening and the application of internal pressure as slow dynamic loads. Consequently, the problem can be evaluated using explicit numerical integration scheme.

Work performed under NEER sponsorship at UIUC included two primary activities, small-angle x-ray scattering measurements and molecular dynamics simulations.

This project worked to improve the efficiency of the steel casting industry by reducing the variability that occurs because of process and product variation. The project focused on the post shakeout operations since roughly half of the production costs are in this area. These improvements will reduce the amount of variability, making it easier to manage the operation and improve the competitiveness. The reduction in variability will also reduce the need for many rework operations, which will result in a direct reduction of energy usage, particularly by the reduction of repeated heat treatment operations. Further energy savings will be realized from the reduction of scrap and reduced handling. Field studies were conducted at ten steel foundries that represented the U.S. steel casting industry, for a total of over 100 weeks of production observation. These studies quantified the amount of variability, and looked toward determining the source. A focus of the data collected was the grinding operations since this is a major effort in the cleaning room, and it represents the overall casting quality. The grinding was divided into two categories, expected and unexpected. Expected grinding is that in which the location of the effort is known prior to making the …

Summary Chemical processes occurring at night in the lowest part of the urban atmosphere, the so called nocturnal boundary layer (NBL), can influence the composition of the atmosphere during the night as well as the following day. They may impact the budgets of some of the most important pollutants, such as ozone and nitrogen oxides, as well as influence size and composition of particular matter. Few studies have thus far concentrated on the nocturnal chemistry of the urban NBL, most likely due to the strong influence of vertical transport and mixing, which requires the measurement of trace gas profiles instead of simple point observations. Motivated by our lack of observations and understanding of nocturnal chemistry, the focus of this project was the study of the vertical distribution of trace gases and the altitude dependence of nocturnal chemistry under polluted conditions through field observations and modeling studies. The analysis of three field experiments (TEXAQS, Houston, 2000; Phoenix Sunrise Ozone Experiment, 2001; NAPOX, Boston, 2002), two of which were performed in this project, showed that ozone concentrations typically increase with height in the lowest 150m, while NO2 typically decreases. NO3, the dominant nocturnal radical species, showed much higher concentrations in the upper …

Recent gyrokinetic simulations of electron temperature gradient (ETG) turbulence with flux-tube continuum codes vs. the global particle-in-cell (PIC) code GTC yielded different results despite similar plasma parameters. Differences between the simulations results were attributed to insufficient phase-space resolution and novel physics associated with toroidicity and/or global simulations. We have reproduced the results of the global PIC code using the flux-tube PIC code PG3EQ, thereby eliminating global effects as the cause of the discrepancy. We show that the late-time decay of ETG turbulence and the steady-state heat transport observed in these PIC simulations results from discrete particle noise. Discrete particle noise is a numerical artifact, so both these PG3EQ simulations and the previous GTC simulations have nothing to say about steady-state ETG turbulence and the associated anomalous heat transport. In the course of this work we develop three diagnostics which can help to determine if a particular PIC simulation has become dominated by discrete particle noise.

DC745 is a commercially available silicone elastomer consisting of dimethyl, methylphenyl, and vinyl-methyl siloxane monomers crosslinked with a peroxide vinyl specific curing agent. It is generally considered to age gracefully and to be resistant to chemical and thermally harsh environments. However, little data exists on the radiation resistance of this commonly used silicone elastomer. We report static {sup 1}H NMR studies of residual dipolar couplings in DC745 solid elastomers subject to exposure to ionizing gamma radiation. {sup 1}H spin-echo NMR data shows that with increasing dose, the segmental dynamics decrease is consistent with radiatively induced crosslinking. {sup 1}H multiple quantum NMR was used to assess changes in the network structure and observed the presence of a bimodal distribution of residual dipolar couplings, <{Omega}{sub d}>, that were dose dependent. The domain with the lower <{Omega}{sub d}> has been assigned to the polymer network while the domain with the higher <{Omega}{sub d}> has been assigned to polymer chains interacting with the inorganic filler surfaces. In samples exposed to radiation, the residual dipolar couplings in both reservoirs were observed to increase and the populations were observed to be dose dependent. The NMR results are compared to Differential Scanning Calorimetry (DSC) and a two-step …

This paper presents a quasi-static technique to evaluate the structural deformation of the four stacked B-25 boxes subjected to the static loads of overlaying soil and to determine the effect of corrosion on the deformation. Although the boxes are subjected to a static load, the structural responses of the boxes vary with time. The analytical results indeed show that the deflection, buckling and post buckling of the components of the stacked boxes occur in sequence rather than simultaneously. Therefore, it is more appropriate to treat the problems considered as quasistatic rather than static; namely, the structural response of the stacked boxes are dynamic but with very long duration. Furthermore, the finite-element model has complex contact and slide conditions between the interfaces of the adjoining components, and thus its numerical solution is more tractable by using explicit time integration schemes. The analysis covers the three corrosion scenarios following various time lengths of initial burial under an interim soil cover. The results qualitatively agree with expected differences in deformation for different degrees of corrosion subsidence potential reduction that can be achieved.

We have developed and streamlined the experimental systems: (a) Laser-induced solution deposition (LISD) photosynthesis, ball-milling, and chemical synthesis of Fe, Co, and Cu nanoparticle catalysts; (b) Sol-gel method for mesoporous {gamma}-Al{sub 2}O{sub 3}, SiO{sub 2}, hybrid alumina/silica granular supports; (c) Three sol-gel/oil-drop catalyst preparation methods to incorporate metal nanoparticles into mesoporous 1 mm granular supports; (d) Low-cost GC-TCD system with hydrogen as carrier gas for the determination of wide spectrum of alkanes produced during the F-T reactions; and (e) Gas-flow reactor and microchannel reactor for fast screening of catalysts. The LISD method could produce Co, Cu, and Fe (5 nm) nanoparticles, but in milligram quantities. We could produce nanoparticles in gram quantities using high-energy ball milling and chemical synthesis methods. Ball milling gave wide particle size distribution compared to the chemical synthesis method that gave almost uniform size ({approx}5 nm) particles. Metal nanoparticles Cu, Co, Fe, Cu/Co, Cu/Fe and Co/Fe were loaded (2-12 wt%) uniformly into {gamma}-Al{sub 2}O{sub 3}, SiO{sub 2}, or alumina/silica hybrid supports by combined sol-gel/oil-drop methods followed by calcination and hydrogenation steps, prior to syngas FT reaction studies. The properties of metal loaded {gamma}-Al{sub 2}O{sub 3} granules were compared for the two precursors: aluminum tri-sec-butoxide (ALTSB) and …