CEST and MEST: Tools for the simulation of radio frequency electric discharges in waveguides

This is the author’s version of a work that was accepted for publication in Simulation Modelling Practice and Theory. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Simulation Modelling Practice and Theory, 16, 9, (2008) http://dx.doi.org/10.1016/j.simpat.2008.08.002In this paper we present two software tools for the simulation of electron multiplication processes in radio frequency (RF) waveguides. The electric discharges are caused by the multiplication of a small initial number of electrons. These are accelerated by the RF field and produce new electrons either by collisions with the walls of the waveguide (ripping new electrons from them), or by ionization of the neutral atoms of a gas inside the device. MEST allows simulating the Multipactor effect, a discharge produced in vacuum and generated by the collision of the electrons with the walls. CEST simulates the discharge when in addition a neutral gas is present in the waveguide, at pressures lower than ground levels (often denominated Corona discharge). The main characteristic of both tools is that they implement individual-based, microscopic models, where every electron is individually represented and tracked. In the case of MEST, the simulation is discrete-event, as the trajectory of each electron can be computed analytically. In CEST we use a hybrid simulation approach. The trajectory of each electron is governed by the Langevin stochastic differential equations that take into account a deterministic RF electric force and the random interaction with the neutral atom background. In addition, wall and ionizing collisions are modelled as discrete events. The tools allow performing batches of simulations with different wall coating materials and gases, and have produced results in good agreement with experimental and theoretical data. The different output forms generated at run-time have proven to be very useful in order to analyze the different discharge processes. The tools are valuable for the selection of the most promising coating materials for the construction of the waveguide, as well as for the identification of safe operating parameters.Work sponsored by the ESA, TRP activity program 17025/03/NL/EC: Surface Treatment and Coating

Investment climate and firm’s economic performance: econometric methodology and application to Turkey's investment climate survey

Government policies and behavior exert a strong influence on the investment climate through their impact on costs, risks and barriers to competition. Key factors affecting the investment climate through their impact on costs are: corruption, taxes, the regulatory burden and extent of red tape in general, factor markets (labor, intermediate materials and capital), the quality of infrastructure, technological and innovation support, and the availability and cost of finance. While the investment climate surveys are quite useful in identifying major issues and bottlenecks as perceived by firms, the data collected is also meant to provide the basic information for an econometric assessment of the impact or contribution of the investment climate (IC) variables on productivity. We believe that improving the investment climate (IC) is a key policy instrument to promote economic growth and to mitigate the institutional, legal, economic and social factors that are constraining the convergence of per capita income and labor productivity of Turkey relative to more developed countries. For that, we need to identify the main investment climate variables that affect economic performance measures like total factor productivity, employment, wages, exports and foreign direct investment and this is the main goal of this paper. In turn, that quantified impact is used in the advocacy for, and design of, investment-climate reforms

Investment climate assessment based on demean Olley and Pakes decompositions: methodology and application to Turkey's investment climate survey

Most empirical studies show strong detrimental evidence that regulatory, and administrative, barriers to entry have on productivity and on firm growth. In this paper we evaluate and measure the total factor productivity (TFP) impacts of having; low quality physical infrastructures (electricity, telecommunications, transport, customs, etc.) and bad social infrastructures (rules of law, informality, corruption, etc.). We suggest evaluating the impact on average productivity (TFP) and on the allocative efficiency of production among firms based on several versions of the Olley and Pakes (O&P) decompositions. We evaluate the advantages and disadvantages of each the O&P decomposition in terms of their IC explanatory power. Once we have measured those IC impacts, we compare them with other sources of empirical information obtained from firm’s perceptions on main bottlenecks for firm growth and from doing business reports of the World Bank (2007). For the econometric analysis, we use firm level data bases from Turkey’s manufacturing sector based on Investment Climate surveys (ICs) done by the World Bank. These ICs are done in many other developing countries and therefore we propose to make crosscountry comparisons based on a new demean concept of TFP that also reduces the heterogeneity if using several robust productivity measures within each country

Independence and matching numbers of some token graphs

Let $G$ be a graph of order $n$ and let $k\in\{1,\ldots,n-1\}$. The $k$-token graph $F_k(G)$ of $G$, is the graph whose vertices are the $k$-subsets of $V(G)$, where two vertices are adjacent in $F_k(G)$ whenever their symmetric difference is an edge of $G$. We study the independence and matching numbers of $F_k(G)$. We present a tight lower bound for the matching number of $F_k(G)$ for the case in which $G$ has either a perfect matching or an almost perfect matching. Also, we estimate the independence number for bipartite $k$-token graphs, and determine the exact value for some graphs.Comment: 16 pages, 4 figures. Third version is a major revision. Some proofs were corrected or simplified. New references adde

Investment climate and firm’s economic performance: econometric methodology and application to Turkey's investment climate survey

Government policies and behavior exert a strong influence on the investment climate through their impact on costs, risks and barriers to competition. Key factors affecting the investment climate through their impact on costs are: corruption, taxes, the regulatory burden and extent of red tape in general, factor markets (labor, intermediate materials and capital), the quality of infrastructure, technological and innovation support, and the availability and cost of finance. While the investment climate surveys are quite useful in identifying major issues and bottlenecks as perceived by firms, the data collected is also meant to provide the basic information for an econometric assessment of the impact or contribution of the investment climate (IC) variables on productivity. We believe that improving the investment climate (IC) is a key policy instrument to promote economic growth and to mitigate the institutional, legal, economic and social factors that are constraining the convergence of per capita income and labor productivity of Turkey relative to more developed countries. For that, we need to identify the main investment climate variables that affect economic performance measures like total factor productivity, employment, wages, exports and foreign direct investment and this is the main goal of this paper. In turn, that quantified impact is used in the advocacy for, and design of, investment-climate reforms.Investment climate, firm level determinants of TFP, Employment, Wages, Exports and FDI, Mean contributions of investment climate

Applying feature reduction analysis to a PPRLM-multiple Gaussian language identification system

This paper presents the application of a feature selection technique such as LDA to a language identification (LID) system. The baseline system consists of a PPRLM module followed by a multiple-Gaussian classifier. This classifier makes use of acoustic scores and duration features of each input utterance. We applied a dimension reduction of the feature space in order to achieve a faster and easier-trainable system. We imputed missing values of our vectors before projecting them on the new space. Our experiments show a very low performance reduction due to the dimension reduction approach. Using a single dimension projection the error rates we have obtained are about 8.73% taking into account the 22 most significant features

Investment climate assessment based on demean Olley and Pakes decompositions: methodology and application to Turkey's investment climate survey

Most empirical studies show strong detrimental evidence that regulatory, and administrative, barriers to entry have on productivity and on firm growth. In this paper we evaluate and measure the total factor productivity (TFP) impacts of having; low quality physical infrastructures (electricity, telecommunications, transport, customs, etc.) and bad social infrastructures (rules of law, informality, corruption, etc.). We suggest evaluating the impact on average productivity (TFP) and on the allocative efficiency of production among firms based on several versions of the Olley and Pakes (O&P) decompositions. We evaluate the advantages and disadvantages of each the O&P decomposition in terms of their IC explanatory power. Once we have measured those IC impacts, we compare them with other sources of empirical information obtained from firm’s perceptions on main bottlenecks for firm growth and from doing business reports of the World Bank (2007). For the econometric analysis, we use firm level data bases from Turkey’s manufacturing sector based on Investment Climate surveys (ICs) done by the World Bank. These ICs are done in many other developing countries and therefore we propose to make crosscountry comparisons based on a new demean concept of TFP that also reduces the heterogeneity if using several robust productivity measures within each country.Total factor productivity, Investment climate, Firm level determinants of allocative efficiency, Robust productivity impacts, Cross country comparisons of demean TFP

A Decision Support System for Investment Evaluation in Information Systems / Information Technology in Public Administration Organisations

Mestrado em Gestão de Sistemas de Informaçãoinfo:eu-repo/semantics/publishedVersio