Tailoring the carrier mobility of semiconducting nanowires by remote dielectrics

The dielectric environment of thin semiconductor nanowires can affect the charge transport properties inside the wire. In this work, it is shown that Coulomb impurity scattering inside thin nanowires can be damped strongly by coating the wire with a high-k dielectric. This will lead to an increase in the mobility of free charges inside the wire.Comment: 4 pages, 3 figure

Warm Asymmetric Nuclear Matter and Proto-Neutron Star

Asymmetric nuclear matter equation of state at finite temperature is studied in SU(2) chiral sigma model using mean field approximation. The effect of temperature on effective mass, entropy, and binding energy is discussed. Treating the system as one with two conserved charges the liquid-gas phase transition is investigated. We have also discussed the effect of proton fraction on critical temperature with and without $\rho$-meson contribution. We have extended our work to study the structure of proto-neutron star with neutron free charge-neutral matter in beta-equilibrium. We found that the mass and radius of the star decreases as it cools from the entropy per baryon S = 2 to S = 0 and the maximum temperature of the core of the star is about 62 MeV for S = 2.Comment: 25 pages, 16 figure

On modeling of the Ae3 temperature of steel

Ae3 temperature of steel is required for many purposes for mechanical processing, thermal treatment and design of steels. However, the models available in the literature are not adequate. An attempt has been made to develop a relation for satisfactory prediction of the Ae3 temper- ature of steel. Ae3 temperature was expressed as a funct-ion of concentration of seven components of steels. The terms upto fourth order in concentration were retained. Total number of terms in the expression was 260. From a careful search of the literature 173 steels for which accurate values of the Ae3 temperature were known were selected. Step wise multiple regression analysis was used to isolate the terms which made significant contribution to the Ae3 temperature. Only nineteen of the 260 terms were found to be significant. These terms predicted the Ae3 temperature with an accuracy which is much more than that offered by the other models. Although other invest-igators have tried to modify the model in various ways, the improvements have not been much. In all these treat-ments the exponents of the concentration parameters have been integral. It is possible to optimize allowing expo- nents as fractions with the help of genetic algorithm. However this technique also does not improve the over all quality of predictions appreciably

Determination of the lowest energy structure of Ag8_8 from first-principles calculations

The ground-state electronic and structural properties, and the electronic excitations of the lowest energy isomers of the Ag$_8$ cluster are calculated using density functional theory (DFT) and time-dependent DFT (TDDFT) in real time and real space scheme, respectively. The optical spectra provided by TDDFT predict that the D$_{2d}$ dodecahedron isomer is the structural minimum of Ag$_8$ cluster. Indeed, it is borne out by the experimental findings.Comment: 4 pages, 2 figures. Accepted in Physical Review A as a brief repor

Control System Implementation and Follow-up within the Cooling and Ventilation Contracts for the LHC

The control system implementation for the cooling and ventilation facilities connected to the LHC Project relies on the technical and human resources that are organised within large-size industrial contracts. Beside the technical aspects, the follow-up of the implementation activities in the framework of such contracts also involves a managerial effort in order to achieve a flexible and coherent control system. The purpose is to assure precise and reliable regulation together with accurate local and remote supervision in conformity with the operational requirements. These objectives can only be reached by a systematic approach that keeps the co-ordination between the in-house and external cross-disciplinary teams as well as the fulfilment of the validation procedures and the contractual formalities. The case that here illustrates this approach is the control system implementation for the heating, ventilation and air conditioning of the LHC surface buildings, which shall extend up to 2004

Friction force on slow charges moving over supported graphene

We provide a theoretical model that describes the dielectric coupling of a 2D layer of graphene, represented by a polarization function in the Random Phase Approximation, and a semi-infinite 3D substrate, represented by a surface response function in a non-local formulation. We concentrate on the role of the dynamic response of the substrate for low-frequency excitations of the combined graphene-substrate system, which give rise to the stopping force on slowly moving charges above graphene. A comparison of the dielectric loss function with experimental HREELS data for graphene on a SiC substrate is used to estimate the damping rate in graphene and to reveal the importance of phonon excitations in an insulating substrate. A signature of the hybridization between graphene's pi plasmon and the substrate's phonon is found in the stopping force. A friction coefficient that is calculated for slow charges moving above graphene on a metallic substrate shows an interplay between the low-energy single-particle excitations in both systems.Comment: 13 pages, 5 figures, submitted to Nanotechnology for a special issue related to the NGC 2009 conference (http://asdn.net/ngc2009/index.shtml

Hydrodynamics of Gas-Liquid-Solid Fluidized and Semi-Fluidized Beds

Two-phase and three-phase fluidized beds have been applied successfully to many industrial processes such as in the H-oil process for hydrogenation and hydrodesulfurization of residual oil, the H-coal process for coal liquefaction, Fischer-Tropsch process, and the bio-oxidation process for wastewater treatment. A semi-fluidized bed has the advantages of both the packed and the fluidized beds as it can partly over come the disadvantages of a fluidized bed, namely back-mixing of solids, attrition of particles and erosion of surfaces, and those of a packed bed, such as non-uniformity in bed temperatures, segregation of solids and channeling. Semi-fluidized beds have been applied successfully to many industrial processes (physical, chemical and biochemical)such as in the filtration, adsorption, catalytic reactions, heavy metal removal and recovery, coal pyrolysis, bio-oxidation, ethanol fermentation, granule tablet manufacturing etc

On the structural and energetic properties of the hydrogen absorber Li2Mg(NH)2

The authors have performed density functional theory based calculations of several possible conformations for the crystal structure of Li2Mg(NH)2 and they confirm the α phase, resolved from both x-ray and neutron diffraction data, as the ground-state configuration. It is also found that although the N–H bond is stronger in Li2Mg(NH)2 than in Li2NH, hydrogen release from Li2Mg(NH)2/LiH mixture displays more favorable thermodynamics than that from the Li2NH∕LiH mixture. The insights gained from this seemingly counterintuitive result should prove helpful in the search for promising hydrogen storage materials