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Model Accounts (model + account)
Selected AbstractsAn experimental study on the transformer coil leakage currentEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 3 2006Mohamed A. A. Wahab This paper is concerned with the transformer coil dc leakage current under different conditions. These conditions include in-air, and in-oil leakage, currents with or without artificial coil deposits. In-oil leakage, currents are investigated when the coil is immersed in new or used transformer oil at different temperatures. The results showed that the leakage current increases with the increase in the applied voltage and oil temperatures. The rate of increase in leakage current with temperature depends on the transformer oil and coil conditions. The in-oil leakage currents are higher than those obtained in air. The leakage currents measured in used oil are higher than those resulted in new oil. Copper deposits cause higher values of leakage current than iron deposits for the same medium, applied voltage and temperature. Deposits increase the leakage current for different coil surrounding media. A linear model for the leakage current as a function of the applied voltage under different conditions has been found and its validity has been justified by statistical consideration. The parameters of this model account for various experimental conditions. Copyright © 2006 John Wiley & Sons, Ltd. [source] Pontine respiratory-modulated activity before and after vagotomy in decerebrate catsTHE JOURNAL OF PHYSIOLOGY, Issue 17 2008Thomas E. Dick The dorsolateral (DL) pons modulates the respiratory pattern. With the prevention of lung inflation during central inspiratory phase (no-inflation (no-I or delayed-I) tests), DL pontine neuronal activity increased the strength and consistency of its respiratory modulation, properties measured statistically by the ,2 value. This increase could result from enhanced respiratory-modulated drive arising from the medulla normally gated by vagal activity. We hypothesized that DL pontine activity during delayed-I tests would be comparable to that following vagotomy. Ensemble recordings of neuronal activity were obtained before and after vagotomy and during delayed-I tests in decerebrate, paralysed and ventilated cats. In general, changes in activity pattern during the delayed-I tests were similar to those after vagotomy, with the exception of firing-rate differences at the inspiratory,expiratory phase transition. Even activity that was respiratory-modulated with the vagi intact became more modulated while withholding lung inflation and following vagotomy. Furthermore, we recorded activity that was excited by lung inflation as well as changes that persisted past the stimulus cycle. Computer simulations of a recurrent inhibitory neural network model account not only for enhanced respiratory modulation with vagotomy but also the varied activities observed with the vagi intact. We conclude that (a) DL pontine neurones receive both vagal-dependent excitatory inputs and central respiratory drive; (b) even though changes in pontine activity are transient, they can persist after no-I tests whether or not changes in the respiratory pattern occur in the subsequent cycles; and (c) models of respiratory control should depict a recurrent inhibitory circuitry, which can act to maintain the stability and provide plasticity to the respiratory pattern. [source] Analysis of scale dependence of quantitative precipitation forecast verification: A case-study over the Mackenzie river basinTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 620 2006Olivier Bousquet Abstract Six-hour rainfall accumulations derived from radar observations collected during a 3-day summertime precipitation event over central Alberta (Canada) are used to assess the performance of a regional Canadian numerical weather prediction system for quantitative precipitation forecast verification. We show that radar data provide a simple and efficient way to significantly reduce model phase errors associated with misplacement of predicted precipitation patterns. Using wavelet analysis, we determine that the limiting spatial scale of predictability of the model is about six times its grid resolution for 6 h accumulated fields. The use of longer accumulation periods is shown to smooth out forecast errors that may have resulted from slight phase or time shift errors but does not change the limiting scale of predictability. The scale decomposition of the mean-square forecast error also reveals that scales which cannot be accurately reproduced by the model account for about 20% of the total error. Using classical continuous and categorical scores, we show that significantly better model performance can be achieved by smoothing out wavelengths that cannot be predicted. Copyright © 2006 Royal Meteorological Society [source] A Quantitative Theory of Unsecured Consumer Credit with Risk of DefaultECONOMETRICA, Issue 6 2007Satyajit Chatterjee We study, theoretically and quantitatively, the general equilibrium of an economy in which households smooth consumption by means of both a riskless asset and unsecured loans with the option to default. The default option resembles a bankruptcy filing under Chapter 7 of the U.S. Bankruptcy Code. Competitive financial intermediaries offer a menu of loan sizes and interest rates wherein each loan makes zero profits. We prove the existence of a steady-state equilibrium and characterize the circumstances under which a household defaults on its loans. We show that our model accounts for the main statistics regarding bankruptcy and unsecured credit while matching key macroeconomic aggregates, and the earnings and wealth distributions. We use this model to address the implications of a recent policy change that introduces a form of "means testing" for households contemplating a Chapter 7 bankruptcy filing. We find that this policy change yields large welfare gains. [source] Robustness of inference on measured covariates to misspecification of genetic random effects in family studiesGENETIC EPIDEMIOLOGY, Issue 1 2003Ruth M.Pfeiffer Abstract Family studies to identify disease-related genes frequently collect only families with multiple cases. It is often desirable to determine if risk factors that are known to influence disease risk in the general population also play a role in the study families. If so, these factors should be incorporated into the genetic analysis to control for confounding. Pfeiffer et al. [2001 Biometrika 88: 933,948] proposed a variance components or random effects model to account for common familial effects and for different genetic correlations among family members. After adjusting for ascertainment, they found maximum likelihood estimates of the measured exposure effects. Although it is appealing that this model accounts for genetic correlations as well as for the ascertainment of families, in order to perform an analysis one needs to specify the distribution of random genetic effects. The current work investigates the robustness of the proposed model with respect to various misspecifications of genetic random effects in simulations. When the true underlying genetic mechanism is polygenic with a small dominant component, or Mendelian with low allele frequency and penetrance, the effects of misspecification on the estimation of fixed effects in the model are negligible. The model is applied to data from a family study on nasopharyngeal carcinoma in Taiwan. Genet Epidemiol 24:14,23, 2003. © 2003 Wiley-Liss, Inc. [source] Modelling the behaviour of an embankment on soft clay with different constitutive modelsINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 10 2006M. Karstunen Abstract The paper investigates the effect of constitutive models on the predicted response of a simplified benchmark problem, an embankment on soft soil. The soft soil is assumed to have the properties of POKO clay from Finland and five different constitutive models are used to model the deposit. Two of the models are isotropic models, i.e. the Modified Cam Clay model and the Soft-Soil model. The other models are recently proposed constitutive models that account for plastic anisotropy. The S-CLAY1 and S-CLAY1S models are embedded in a standard elasto-plastic framework and account for anisotropy via a rotational hardening law. In addition, the S-CLAY1S model accounts for bonding and destructuration. In contrast, the Multilaminate Model for Clay (MMC) accounts for plastic anisotropy by utilizing so-called multilaminate framework. The results of numerical simulations show that accounting for anisotropy results in notable differences in the predicted settlements and horizontal movements compared to the predictions using the isotropic models. There are also significant differences in the K0 predictions by the different constitutive models and this has a significant impact on the results. Copyright © 2006 John Wiley & Sons, Ltd. [source] A time-dependent multiphysics, multiphase modeling framework for carbon nanotube synthesis using chemical vapor depositionAICHE JOURNAL, Issue 12 2009Mahmoud Reza Hosseini Abstract A time-dependent multiphysics, multiphase model is proposed and fully developed here to describe carbon nanotubes (CNTs) fabrication using chemical vapor deposition (CVD). The fully integrated model accounts for chemical reaction as well as fluid, heat, and mass transport phenomena. The feed components for the CVD process are methane (CH4), as the primary carbon source, and hydrogen (H2). Numerous simulations are performed for a wide range of fabrication temperatures (973.15,1273.15 K) as well as different CH4 (500,1000 sccm) and H2 (250,750 sccm) flow rates. The effect of temperature, total flow rate, and feed mixture ratio on CNTs growth rate as well as the effect of amorphous carbon formation on the final product are calculated and compared with experimental results. The outcomes from this study provide a fundamental understanding and basis for the design of an efficient CNT fabrication process that is capable of producing a high yield of CNTs, with a minimum amount of amorphous carbon. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] External Constraints on Monetary Policy and the Financial AcceleratorJOURNAL OF MONEY, CREDIT AND BANKING, Issue 2-3 2007MARK GERTLER financial crises; exchange rate policy We develop a small open economy macroeconomic model where financial conditions influence aggregate behavior. Our goal is to explore the connection between the exchange rate regime and financial distress. We first show that a calibrated version of the model captures well the behavior of the Korean economy during its financial crisis period of 1997,98. In particular, the model accounts for the sharp increase in lending rates and the large drop in output, employment, investment, and measured productivity. The financial market frictions play an important role, further, explaining roughly half the decline in overall economic activity. We then perform some counterfactual exercises to illustrate how the fixed exchange rate regime likely exacerbated the crisis by tying the hands of monetary policy. [source] RAFT polymerization kinetics: How long are the cross-terminating oligomers?JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 14 2009Dominik Konkolewicz Abstract We extend a new model for the kinetics of reversible addition-fragmentation chain transfer (RAFT) polymerization. The essence of this model is that the termination of the radical intermediate formed by the RAFT process occurs only with very short oligomeric radicals. In this work, we consider cross-termination of oligomers up to two monomers and an initiator fragment. This model accounts for the absence of three-armed stars in the molecular weight distribution, which are predicted by other cross-termination models, since the short third arm makes a negligible difference to the polymer's molecular weight. The model is tested against experiments on styrene mediated by cyano-isopropyl dithiobenzoate, and ESR experiments of the intermediate radical concentration. By comparing our model to experiments, we may determine the significance of cross-termination in RAFT kinetics. Our model suggests that to agree with the known data on RAFT kinetics, the majority of cross-terminating chains are dimeric or shorter. If longer chains are considered in cross-termination reactions, then significant discrepancies with the experiments (distinguishable star polymers in the molecular weight distribution) and quantum calculations will result. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3455,3466, 2009 [source] Manifestation of emerging specialties in journal literature: A growth model of papers, references, exemplars, bibliographic coupling, cocitation, and clustering coefficient distributionJOURNAL OF THE AMERICAN SOCIETY FOR INFORMATION SCIENCE AND TECHNOLOGY, Issue 12 2005Steven A. Morris A model is presented of the manifestation of the birth and development of a scientific specialty in a collection of journal papers. The proposed model, Cumulative Advantage by Paper with Exemplars (CAPE) is an adaptation of Price's cumulative advantage model (D. Price, 1976). Two modifications are made: (a) references are cited in groups by paper, and (b) the model accounts for the generation of highly cited exemplar references immediately after the birth of the specialty. This simple growth process mimics many characteristic features of real collections of papers, including the structure of the paper-to-reference matrix, the reference-per-paper distribution, the paper-per-reference distribution, the bibliographic coupling distribution, the cocitation distribution, the bibliographic coupling clustering coefficient distribution, and the temporal distribution of exemplar references. The model yields a great deal of insight into the process that produces the connectedness and clustering of a collection of articles and references. Two examples are presented and successfully modeled: a collection of 131 articles on MEMS RF (microelectromechnical systems radio frequency) switches, and a collection of 901 articles on the subject of complex networks. [source] DETERMINATION OF MANATEE POPULATION TRENDS ALONG THE ATLANTIC COAST OF FLORIDA USING A BAYESIAN APPROACH WITH TEMPERATURE-ADJUSTED AERIAL SURVEY DATAMARINE MAMMAL SCIENCE, Issue 3 2004Bruce A. Craig Abstract In many animal population survey studies, the construction of a stochastic model provides an effective way to capture underlying biological characteristics that contribute to the overall variation in the data. In this paper we develop a stochastic model to assess the population trend and abundance of the Florida manatee, Trichechus manatus latirostris, along the Atlantic coast of the state, using aerial survey data collected at winter aggregation sites between 1982 and 2001. This model accounts for the method by which the manatees were counted, their movements between surveys, and the behavior of the total population over time. The data suggest an overall increase in the population from 1982 to 1989 of around 5%,7%, a reduction in growth or a leveling off (0%,4% annual growth) from 1990 to 1993, and then an increase again of around 3%,6% since 1994. In winter 2001,2002 (the most recent survey season for which analyses were done), we estimated the adult manatee population along the east coast of Florida to be 1,607 individuals (range = 1,353,1,972; 95% credible interval). Our estimate of manatee abundance corresponds well with maximum counts (approximately 1,600 manatees) produced during synoptic aerial surveys under optimal conditions. Our calculations of trends correspond well with mark and recapture analyses of trends in survival of adult manatees along the east coast through the early 1990s. Our population trend estimates since that time are more optimistic than those generated by mark-recapture models. [source] Marketing Channels and Retail Store Density in East Asia,ASIAN ECONOMIC JOURNAL, Issue 4 2005Kenji Matsui L81; M31 By measuring retail store density with regard to population, several studies have indicated that marketing channels in Asia are different from those in the USA and European countries. The present paper investigates to what extent a model similar to Flath and Nariu (1996) can empirically predict retail densities in Japan and China. The results suggest that the secular decline in the number of retail stores in Japan primarily results from the proliferation of car ownership and the expansion in the average size of a dwelling. We also demonstrate that the model accounts for the large variations in China's retail density. [source] | ||||||||||||||||