4,738 research outputs found

    Non-supersymmetric Microstates of the MSW System

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    We present an analysis parallel to that of Giusto, Ross, and Saxena (arXiv:0708.3845) and construct a discrete family of non-supersymmetric microstate geometries of the Maldacena-Strominger-Witten system. The supergravity configuration in which we look for the smooth microstates is constructed using SO(4,4) dualities applied to an appropriate seed solution. The SO(4,4) approach offers certain technical advantages. Our microstate solutions are smooth in five dimensions, as opposed to all previously known non-supersymmetric microstates with AdS3 cores, which are smooth only in six dimensions. The decoupled geometries for our microstates are related to global AdS3 x S2 by spectral flows.Comment: 38 pages, including appendices and references; v2 refs + one paragraph adde

    Piloted simulator study of allowable time delays in large-airplane response

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    A piloted simulation was performed to determine the permissible time delay and phase shift in the flight control system of a specific large transport-type airplane. The study was conducted with a six degree of freedom ground-based simulator and a math model similar to an advanced wide-body jet transport. Time delays in discrete and lagged form were incorporated into the longitudinal, lateral, and directional control systems of the airplane. Three experienced pilots flew simulated approaches and landings with random localizer and glide slope offsets during instrument tracking as their principal evaluation task. Results of the present study suggest a level 1 (satisfactory) handling qualities limit for the effective time delay of 0.15 sec in both the pitch and roll axes, as opposed to a 0.10-sec limit of the present specification (MIL-F-8785C) for both axes. Also, the present results suggest a level 2 (acceptable but unsatisfactory) handling qualities limit for an effective time delay of 0.82 sec and 0.57 sec for the pitch and roll axes, respectively, as opposed to 0.20 sec of the present specifications for both axes. In the area of phase shift between cockpit input and control surface deflection,the results of this study, flown in turbulent air, suggest less severe phase shift limitations for the approach and landing task-approximately 50 deg. in pitch and 40 deg. in roll - as opposed to 15 deg. of the present specifications for both axes

    Presentations & Paper

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    Strong Metal-Support Interactions: An Extra Layer of Complexity

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    Strong interactions between oxide supports and catalytic metal particles can lead to inhibitive oxide layers forming over the active metal catalyst. Now, adsorbate-induced metal–support interactions have been shown to lead to a porous overlayer in the Rh/TiO2 system that tunes catalyst activity, improving its selectivity for the partial reduction of CO2

    The Impact of Capital Intensive Farming in Thailand: A Computable General Equilibrium Approach

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    The aim of this study is to explore whether efforts to encourage producers to use agricultural machinery and equipment will significantly improve agricultural productivity, income distribution amongst social groups, as well as macroeconomic performance in Thailand. A 2000 Social Accounting Matrix (SAM) of Thailand was constructed as a data set, and then a 20 production-sector Computable General Equilibrium (CGE) model was developed for the Thai economy. The CGE model is employed to simulate the impact of capital-intensive farming on the Thai economy under two different scenarios: technological change and free trade. Four simulations were conducted. Simulation 1 increased the share parameter of capital in the agricultural sector by 5%. Simulation 2 shows a 5% increase in agricultural capital stock. A removal in import tariffs for agricultural machinery sector forms the basis for Simulation 3. The last simulation (Simulation 4) is the combination of the above three simulations. The results for each simulation are divided into four effects: input, output, income and macroeconomic effects. The results of the first two simulations produced opposite outcomes in terms of the four effects. Simulation 2 accelerated the capital intensification of all agricultural sectors, whereas Simulation 1 led to more capital intensity in some agricultural sectors. The effects of the input reallocation had a simultaneous impact on output in every sector. Simulation 1 led to a fall of almost all outputs in the agricultural sectors, whereas there was an increase in agricultural output in Simulation 2. In terms of domestic income effects, as a result of the decline of the average price of factors in Simulation 1, there was a decrease in factor incomes belonging to households and enterprises. Consequently, government revenue decreased by 0.7%. In contrast, Simulation 2 resulted in an increase in all incomes above. Finally, regarding macroeconomic variables, Simulation 1 had a negative impact on private consumption, government consumption, investment, imports and exports, resulting in Gross Domestic Product (GDP) decreasing by 0.8%. On the other hand, Simulation 2 had a positive impact on those same variables, affecting a 0.4% rise of GDP. The effects of Simulation 3 were very small in everything compared with the first two simulations. The effect of Simulation 4 was mostly dominated by Simulations 1 and 2; the negative results of Simulation 1 were compensated by the positive effects of Simulation 2.Capital intensive farming, CGE, general equilibrium, SAM, Thailand, Agricultural and Food Policy, Crop Production/Industries, Environmental Economics and Policy, Farm Management, Productivity Analysis,

    Low-Temperature Activation Conditions for PAMAM Dendrimer Templated Pt Nanoparticles

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    Surface immobilized polyamidoamine (PAMAM) dendrimer templated Pt nanoparticles were employed as precursors to heterogeneous catalysts. CO oxidation catalysis and in situ infrared spectroscopy were used to evaluate conditions for dendrimer removal. Infrared spectroscopy showed thatPAMAMdendrimer amide bonds begin decomposing at temperatures as low as 75 °C. Although the amide stretches are completely removed after 3 h of oxidation at 300 °C, 16 h were required to reach maximum catalytic activity. Further treatment under oxidizing or reducing atmospheres did not cause substantial changes in activity. Infrared spectroscopy of the activated materials indicated that organic residues, probably surface carboxylates, are formed during oxidation. These surface species passivate the Pt NPs, and their removal was required to fully activate the catalyst. Substantially less forcing activation conditions were possible by employing a CO/O2/He oxidation treatment. At appropriate temperatures, CO acts as a protecting group for the Pt surface, helping to prevent fouling of the nanoparticle by organic residues. CO oxidation catalysis and infrared spectroscopy of adsorbed CO indicated that the low temperature activation treatment yielded supported nanoparticles that were substantially similar to those prepared with more forcing conditions

    All <em>P<sub>3</sub></em>-equipackable graphs

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