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Simulation and analysis of the I-V characteristics of a Schottky diode containing barrier inhomogeneities

SEMICONDUCTOR SCIENCE AND TECHNOLOGY 1997年第7期12卷 899-906页

作者： Chand, S Kumar, J INDIAN INST TECHNOL MAT SCI PROGRAMMEKANPUR 208016UTTAR PRADESHINDIA

The current-voltage (I-V) characteristics of Schottky diodes containing barrier inhomogeneities have been simulated using thermionic emission-diffusion (TED) theory and assuming a Gaussian distribution of barrier heights. The system is considered to have a number of non-interacting parallel diodes with each corresponding to a different barrier height within the distribution limit. The mean and the standard deviation of the Gaussian distribution are taken either as constant or having linear bias dependences. The simulated I-V data are then analysed to study the effects of the distribution parameters and their bias coefficients on the barrier height and the ideality factor over a temperature range of 50-300 K. It is shown that the mere existence of a distribution causes a decrease in the zero-bias barrier height and, in turn, leads to nonlinearity in the activation energy plots. Also, the decrease is greater for high values of standard deviation. Further, the abnormal increase of ideality factor with decrease in temperature occurs due to the bias dependence of the standard deviation of the distribution. Finally, it is demonstrated that the decrease in temperature and increase in standard deviation cause similar effects and both lead to a decrease in barrier height and an increase in ideality factor. Also, the role of the series resistance in adversely influencing the linearity of the log(I)-V characteristics of a Schottky diode containing barrier inhomogeneities is discussed.

关键词： barriers Schottky diodes height IDEALITY FACTOR barrier Inhomogeneities Standard deviation BARRIER HEIGHT Series Resistance Gaussian distribution distributed parameter Simulation Analysis

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Downscaling and projection of winter extreme daily precipitation over North America

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JOURNAL OF CLIMATE 2008年第5期21卷 923-937页

作者： Wang, Jiafeng Zhang, Xuebin Environm Canada Div Climate Res Toronto ON M3H 5T4 Canada

Large-scale atmospheric variables have been statistically downscaled to derive winter (December March) maximum daily precipitation at stations over North America using the generalized extreme value distribution (GEV). Here, the leading principal components of the sea level pressure field and local specific humidity are covariates of the distribution parameters. The GEV parameters are estimated using data from 1949 to 1999 and the r-largest method. This statistical downscaling procedure is found to yield skill over the southern and northern West Coast, central United States, and areas of western and eastern Canada when tested with independent data. The projected changes in covariates or predictors are obtained from transient climate change simulations conducted with the Canadian Centre for Climate Modelling and Analysis (CCCma) Coupled General Circulation Model, version 3.1 (CGCM3.1) forced by the Intergovernmental Panel on Climate Change (IPCC) A2 forcing scenario. They are then used to derive the GEV distribution parameters for the period 2050-99. The projected frequency of the current 20-yr return maximum daily precipitation for that period suggests that extreme precipitation risk will increase heavily over the south and central United States but decrease over the Canadian prairies. The difference between the statistical downscaling results and those estimated using GCM simulation is also discussed.

关键词： atmosphere climatic change grasslands humidity prairies precipitation simulation models winter Canada North America USA atmosphere Canada prairies Grassland Intergovernmental panel on climate change moistening Midwestern United States Winter United States Specific humidity North America Simulation models climate change distributed parameter

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Simulation of Significant Wave Height by Neural Networks and Its Application to Extreme Wave Analysis

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JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY 2009年第4期26卷 778-792页

作者： Aminzadeh-Gohari, A. Bahai, H. Bazargan, H. Shahid Bahonar Univ Kerman Coll Engn Kerman 76169133 Iran Univ Calif Berkeley Dept EECS Berkeley CA 94720 USA Brunel Univ Sch Design & Engn Uxbridge UB8 3PH Middx England

The derivation of the long-term statistical distribution of significant wave heights (H(s)s) is discussed in this paper. The distribution parameters are estimated using artificial neural networks (ANNs) trained with the help of a simulated annealing algorithm and operated in an autoregressive mode. The ANNs were utilized in estimating the parameters of a conditional probability distribution related to a desired H-s given its preceding H(s)s, approximated by a proposed distribution called the hepta-parameter spline. The performance function during training was based on the likelihood function of the statistical method of maximum likelihood estimation (MLE). Given the observed dataset, the most probable weights and biases of the neural networks were determined in such a way that the performance function was optimized. The distribution could be used in the simulation and forecasting of H(s)s. This paper also presents an extreme wave analysis using the simulated H(s)s. The extreme analysis conducted in this study using the maxima method offers an alternative approach, avoiding the unrealistic hypothesis that annual H(s)s are identically distributed, as is conventionally assumed when using the Fisher-Tippet theorem.

关键词： Wave analysis Likelihood Functions simulating Neural network maximum likelihood estimation Wave Height simulated annealing algorithm distributed parameter Significant wave height conditional probability distribution Statistical methods

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Modeling of dynamic data-driven approach for the distributed steel rolling heating furnace temperature field

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NEURAL COMPUTING & APPLICATIONS 2022年第11期34卷 8959-8975页

作者： Bao, Qingfeng Zhang, Sen Guo, Jin Xu, Zhengguang Zhang, Zhenquan Univ Sci & Technol Beijing Sch Automat & Elect Engn Xueyuan Rd Beijing 100083 Peoples R China Univ Sci & Technol Beijing Key Lab Knowledge Automat Ind Proc Minist Educ Xueyuan Rd Beijing 100083 Peoples R China HBIS Grp Chengsteel Co HBIS Chengde 067001 Hebei Peoples R China

The dynamic modeling of the steel rolling heating furnace temperature field (SRHFTF) plays a very important role in the process control of the metallurgical industry. It can control and regulate the temperature of the SRHFTF accurately, save energy consumption and reduce industrial carbon emissions. The SRHFTF is a complex system with nonlinear, strong coupling, and multi-variable, it was difficult to build the mechanism model. Meanwhile, the existing data-driven modeling methodology has a gap which describes the dynamical model structure of SRHFTF. Therefore, this paper studies the neural network dynamic data-driven modeling methodology for the RHFTF. Firstly, the multi-input single-output of the SRHFTF neural network model matrices structure is constructed to improve the model fitting effect. Secondly, an improved neural network back-propagation algorithm is proposed, which has higher accuracy and lower computational cost than static data-driven models. Finally, the effectiveness of the artificial neural network dynamic data-driven model and the INNBP algorithm have been verified by the case of the SRHFTF. The simulation results show that the performance of the dynamic neural network model meets the design requirements.

关键词： Data-driven modeling Model structure Model dynamic distributed parameter Improved neural network back-propagation (INNBP) Steel rolling heating furnace temperature field (SRHFTF)

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An electromechanical finite element model for piezoelectric energy harvester plates

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JOURNAL OF SOUND AND VIBRATION 2009年第1-2期327卷 9-25页

作者： De Marqui Junior, Carlos Erturk, Alper Inman, Daniel J. Univ Sao Paulo Engn Sch Sao Carlos Dept Aeronaut Engn BR-05508 Sao Paulo Brazil Virginia Tech Dept Engn Sci & Mech Ctr Intelligent Mat Syst & Struct Blacksburg VA 24061 USA Virginia Tech Dept Mech Engn Ctr Intelligent Mat Syst & Struct Blacksburg VA 24061 USA

Vibration-based energy harvesting has been investigated by several researchers over the last decade. The goal in this research field is to power small electronic components by converting the waste vibration energy available in their environment into electrical energy. Recent literature shows that piezoelectric transduction has received the most attention for vibration-to-electricity conversion. In practice, cantilevered beams and plates with piezoceramic layers are employed as piezoelectric energy harvesters. The existing piezoelectric energy harvester models are beam-type lumped parameter, approximate distributed parameter and analytical distributed parameter solutions. However, aspect ratios of piezoelectric energy harvesters in several cases are plate-like and predicting the power output to general (symmetric and asymmetric) excitations requires a plate-type formulation which has not been covered in the energy harvesting literature. In this paper. an electromechanically coupled finite element (FE) plate model is presented for predicting the electrical power output of piezoelectric energy harvester plates. Generalized Hamilton's principle for electroelastic bodies is reviewed and the FE model is derived based on the Kirchhoff plate assumptions as typical piezoelectric energy harvesters are thin structures. Presence of conductive electrodes is taken into account in the FE model. The predictions of the FE model are verified against the analytical solution for a unimorph cantilever and then against the experimental and analytical results of a bimorph cantilever with a tip mass reported in the literature. Finally, an optimization problem is solved where the aluminum wing spar of an unmanned air vehicle (UAV) is modified to obtain a generator spar by embedding piezoceramics for the maximum electrical power without exceeding a prescribed mass addition limit. (C) 2009 Elsevier Ltd. All rights reserved.

关键词： Electric power ASPECT RATIO Power output Unmanned Aerial Vehicle harvesters GTF2E1 gene energy harvesting Iron Energy sources distributed parameter

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Modeling nitrogen removal in a constructed wetland treatment system

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WATER SCIENCE AND TECHNOLOGY 2009年第2期60卷 301-309页

作者： Sonavane, P. G. Munavalli, G. R. Walchand Coll Engn Dept Civil Engn Sangli Maharashtra India

A constructed wetland treatment system (CWTS) has been adopted for removal of nitrogen from wastewater. The design methodologies developed for CWTS in previous studies were based on thumb rules, and first order/Monod type kinetics models. The use of kinetic models is system/environment specific. There is scope to assess the potential of other reaction kinetic models for their usefulness and applicability. In the present study, lumped and distributed parameter models incorporated with various reactions kinetic were developed. The various processes were incorporated in distributed parameter model for nitrogen transformations. Laboratory/pilot-scale field experiments were carried out and used for verification and application of models developed. The reaction rate parameters were estimated using non-linear least square analysis. The results showed that the conditions within CWTS can be simulated by plug flow. The plant uptake rate was found to be higher than denitrification for nitrate removal. Nitrification and plant uptake are equally dominant for the removal of ammonia nitrogen. The relative contributions by various processes for nitrogen removal can be established using the distributed parameter model. The developed simulation model can be used as a CWTS planning and design tool for the effective control and treatment of nitrogen induced pollution.

关键词： constructed wetlands distributed parameter lumped parameter nitrogen reaction kinetics treatment

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A generalized method to improve the location accuracy of the single-ended sampled data and lumped parameter model based fault locators

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INTERNATIONAL JOURNAL OF ELECTRICAL POWER & ENERGY SYSTEMS 2009年第5期31卷 201-205页

作者： Lin, Xiangning Weng, Hanli Wang, Bin Three Gorges Univ Coll Elect Engn & Informat Technol Yichang 443002 Hubei Province Peoples R China HUST Dept Elect Engn Wuhan 430074 Peoples R China

The necessity for very high accuracy in fault location is generally becoming more and more important. In this paper, a new generalized algorithm which can improve the accuracy of all fault location algorithms based on the lumped parameter model and single-ended data is presented. The measured distance resulting from the lumped parameter model can be converted to the positive sequence measured impedance matching with the model. Then, the relation between real distance and positive sequence measured impedance of fault circuit based on Bergeron model can be derived according to the analysis of solid grounded faults. Then the improved algorithm resulting from the relation of real distance and measured distance can be obtained. Theoretically, the proposed algorithm is independent of shunt distributed capacitance of transmission lines. Besides, the algorithm is based on power-frequency voltages and currents, and hence high sampling rate is unnecessary. Therefore, it can be implemented in the existing protection devices easily. This paper presents the theory of the technique and the results of ATP simulation tests to demonstrate its performance. (C) 2009 Elsevier Ltd. All rights reserved.

关键词： Single-ended fault location distributed parameter Lumped parameter ATP simulation tests

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In situ small-angle X-ray scattering observations of Pt/NaY catalysts during processing: Sintering of Pt

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JOURNAL OF APPLIED CRYSTALLOGRAPHY 1996年第0期29卷 526-530页

作者： Brumberger, H Goodisman, J Ramaya, R Ciccariello, S UNIV PADUA DIPARTIMENTO FIS GALILEO GALILEII-35131 PADUAITALY

Small-angle X-ray scattering observations on Pt/NaY catalysts, made in situ during calcination and reduction stages of processing, demonstrate the usefulness of this technique in following morphological changes. Observations show that the same platinum species (Pt-0 under the preparation conditions used) is present in the early stages of calcination, carried out at relatively high heating rates, as after reduction, and that the ultimate dispersity of the metal is already reached within 0.5 h of the start of calcination. Increasing aggregation of metal particles occurs at calcination temperatures higher than 573 K, leading to average particle sizes too large to fit the supercages of the zeolite framework. With the assumption that the metal is a Maxwellian distribution of spheres, values of the distribution parameters giving the best fit to the scattering for each catalyst sample are found;from these parameters, average particle radii are calculated.

关键词： Platinum Zeolites Dispersion Particles Zeolites metal particles platinum distributed parameter Small angle X ray scattering Metals Calcination Dispersion

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Dynamics of inhomogeneous populations and global demography models

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JOURNAL OF BIOLOGICAL SYSTEMS 2005年第1期13卷 83-104页

作者： Karev, GP MSD Inc Vienna VA 22180 USA

The dynamic theory of inhomogeneous populations developed during the last decade predicts several essential new dynamic regimes applicable even to the well-known, simple population models. We show that, in an inhomogeneous population with a distributed reproduction coefficient, the entire initial distribution of the coefficient should be used to investigate real population dynamics. In the general case, neither the average rate of growth nor the variance or any finite number of moments of the initial distribution is sufficient to predict the overall population growth. We developed methods for solving the heterogeneous models and explored the dynamics of the total population size together with the reproduction coefficient distribution. We show that, typically, there exists a phase of "hyper-exponential" growth that precedes the well-known exponential phase of population growth in a free regime. The developed formalism is applied to models of global demography and the problem of "population explosion" predicted by the known hyperbolic formula of world population growth. We prove here that the hyperbolic formula presents an exact solution to the Malthus model with an exponentially distributed reproduction coefficient and that "population explosion" is a corollary of certain implicit unrealistic assumptions. Alternative models of world population growth are derived;they show a notable phenomenon, a transition from protracted hyperbolical growth (the phase of "hyper-exponential" development) to the brief transitional phase of exponential growth and, subsequently, to stabilization. The model solutions are consistent with real data and produce relatively accurate forecasts.

关键词： inhomogeneous model distributed parameter population explosion

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Boundary controllability for the Korteweg-de Vries-Burgers equation on a finite domain

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INDIAN JOURNAL OF PURE & APPLIED MATHEMATICS 2024年 1-14页

作者： Li, Jie NingboTech Univ Sch Comp & Data Engn Ningbo 315100 Peoples R China

In this paper, we consider the controllability of the Korteweg-de Vries-Burgers equation on a finite domain. Because the third-order of the Korteweg-de Vries-Burgers equation, there needs three boundary conditions to secure the well-posedness of the system. We show that if we only use the right Neumann boundary condition, then the linear system is exactly contrallable if and only if the length of the spatial domain does not belong to a set of critical values. By contrast, if we also use the right Dirichlet boundary condition besides the right Neumann boundary condition, the linear system is exactly controllable without the limit of the length of the domain. Moreover, we also show that the nonlinear system is local exactly controllable via the method of contraction mapping principle.

关键词： distributed parameter Korteweg-de Vries-Burgers Boundary controllability Hilbert uniqueness method

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