2,227 research outputs found
Design and evaluation of fluidized bed heat recovery for diesel engine systems
The potential of utilizing fluidized bed heat exchangers in place of conventional counter-flow heat exchangers for heat recovery from adiabatic diesel engine exhaust gas streams was studied. Fluidized bed heat recovery systems were evaluated in three different heavy duty transport applications: (1) heavy duty diesel truck; (2) diesel locomotives; and (3) diesel marine pushboat. The three applications are characterized by differences in overall power output and annual utilization. For each application, the exhaust gas source is a turbocharged-adiabatic diesel core. Representative subposed exhaust gas heat utilization power cycles were selected for conceptual design efforts including design layouts and performance estimates for the fluidized bed heat recovery heat exchangers. The selected power cycles were: organic rankine with RC-1 working fluid, turbocompound power turbine with steam injection, and stirling engine. Fuel economy improvement predictions are used in conjunction with capital cost estimates and fuel price data to determine payback times for the various cases
Electron transport through an interacting region: The case of a nonorthogonal basis set
The formula derived by Meir and Wingreen [Phys. Rev. Lett. {\bf 68}, 2512
(1992)] for the electron current through a confined, central region containing
interactions is generalized to the case of a nonorthogonal basis set. As in the
original work, the present derivation is based on the nonequilibrium Keldysh
formalism. By replacing the basis functions of the central region by the
corresponding elements of the dual basis, the lead- and central
region-subspaces become mutually orthogonal. The current formula is then
derived in the new basis, using a generalized version of second quantization
and Green's function theory to handle the nonorthogonality within each of the
regions. Finally, the appropriate nonorthogonal form of the perturbation series
for the Green's function is established for the case of electron-electron and
electron-phonon interactions in the central region.Comment: Added references. 8 pages, 1 figur
APENet: LQCD clusters a la APE
Developed by the APE group, APENet is a new high speed, low latency,
3-dimensional interconnect architecture optimized for PC clusters running
LQCD-like numerical applications. The hardware implementation is based on a
single PCI-X 133MHz network interface card hosting six indipendent
bi-directional channels with a peak bandwidth of 676 MB/s each direction. We
discuss preliminary benchmark results showing exciting performances similar or
better than those found in high-end commercial network systems.Comment: Lattice2004(machines), 3 pages, 4 figure
AdS Strings with Torsion: Non-complex Heterotic Compactifications
Combining the effects of fluxes and gaugino condensation in heterotic
supergravity, we use a ten-dimensional approach to find a new class of
four-dimensional supersymmetric AdS compactifications on almost-Hermitian
manifolds of SU(3) structure. Computation of the torsion allows a
classification of the internal geometry, which for a particular combination of
fluxes and condensate, is nearly Kahler. We argue that all moduli are fixed,
and we show that the Kahler potential and superpotential proposed in the
literature yield the correct AdS radius. In the nearly Kahler case, we are able
to solve the H Bianchi using a nonstandard embedding. Finally, we point out
subtleties in deriving the effective superpotential and understanding the
heterotic supergravity in the presence of a gaugino condensate.Comment: 42 pages; v2. added refs, revised discussion of Bianchi for N
Enamel demineralization and remineralization under plaque fluid-like conditions – a QLF study
The present study investigated de- and remineralization in enamel lesions under plaque fluid (PF)-like conditions using quantitative light-induced fluorescence (QLF). Preformed lesions were exposed to partially saturated lactic acid solutions, varying in pH and fluoride concentration ([F]) based on a 5 × 3 factorial study design (0/0.1/0.5/1.5/4 ppm F; pH 4.9/5.2/5.5). Average fluorescence loss (ΔF) was monitored for 11 days. Subsequently, lesions were demineralized in a partially saturated acetic acid solution for two 24-hour periods. Data were analyzed using repeated measures analysis of covariance. Lesions exposed to PF at 4 ppm F and pH 5.5 showed not only the most remineralization (ΔΔF = 28.2 ± 14.0%) for all groups after 11 days, but also the most demineralization (ΔΔF = –19.3 ± 13.5%) after subsequent acetic acid exposure. Increased [F] resulted in more remineralization, regardless of pH. Higher pH values resulted in more remineralization. No remineralization was observed in lesions exposed to F-free solutions, regardless of pH. Remineralization was noticeable under the following conditions: pH 4.9 – [F] = 4 ppm, pH 5.2 – [F] ≧ 1.5 ppm, and pH 5.5 – [F] ≧ 0.5 ppm. Overall, [F] had a stronger effect on remineralization than pH. Subsequent demineralization showed that little protection was offered by PF-like solutions, and further demineralization compared with baseline was observed on lesions not remineralized initially. [F] had a stronger effect on net mineral change than pH. The present study has shown that QLF is a valuable tool in studying lesion de- and remineralization under PF-like conditions, where [F] was shown to be more important than pH
Method of Development and Use of Catalyst-Functionalized Catalytic Particles to Increase the Mass Transfer Rate of Solvents Used in Acid Gas Cleanup
The present invention relates to methods for improving carbon capture using entrained catalytic-particles within an amine solvent. The particles are functionalized and appended with a CO2 hydration catalyst to enhance the kinetics of CO2 hydration and improve overall mass transfer of CO2 from an acid gas
Calculation of Nucleon Electromagnetic Form Factors
The fomalism is developed to express nucleon matrix elements of the
electromagnetic current in terms of form factors consistent with the
translational, rotational, and parity symmetries of a cubic lattice. We
calculate the number of these form factors and show how appropriate linear
combinations approach the continuum limit.Comment: Lattice 2002 (hadronic matrix elements) 3 page
Influence of thermal diffusion on the laser ablation of thin polymer films
The laser ablation of a photosensitive triazene polymer was investigated with a ns XeCl excimer laser over a broad range of thicknesses (10-400nm). We found that the ablation threshold fluence increased dramatically with decreasing film thickness for films thinner than 50nm. Ablation on substrates with different thermal properties (sapphire, fused silica, PMMA) was investigated as well, and a clear influence of the substrate material was obtained. A mathematical model combining thermal diffusion and absorption effects was used to explain the experimental data. The model is in good agreement with the experimental data and shows that heat diffusion into the substrate plays a crucial role for the ablation process of very thin film
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