bluuebunny/crossref_metadata_2025_split huggingface dataset:
Scattering of electromagnetic plane waves by an inclined parallel strip grating
Authors: Shimoda Michinari , Itakura Tokuya 
Published: July 2007

AbstractThe two‐dimensional scattering problem of electromagnetic wave by an inclined parallel strip grating with a periodic structure is analyzed by means of the formulation using the mutual field. A formulation is presented for the analysis of multiple scattering by a strip system with a periodic structure by means of the representation of the scattered field by one strip. The Wiener‐Hopf equations to be satisfied by each scattered field and the representation of scattered waves based on the solution to these equations are obtained. Since the width of the strip in the grating is finite, it is difficult to carry out rigorously the decomposition in the solution of the Wiener‐Hopf equations.The sampling theorem is used for expansion of the unknown function corresponding to the surface current on the strip into a series so that the Wiener‐Hopf equations are reduced to a set of simultaneous equations. In this procedure, the numerical analysis can be carried out independently of the Wood anomaly frequencies and the resonant frequencies between the strips.For evaluation of convergence and errors in the results, the relative error with respect to the extrapolated value and the square error for satisfaction of the boundary condition are computed numerically. The numerical results for the power transmission coefficient by the present method are compared with those by other methods.
Nonradiative dielectric waveguide circuit components using beam‐lead diodes
Authors: Kuroki Futoshi , Yoneyama Tsukasa 
Published: July 2007

AbstractThe nonradiative dielectric waveguide (NRD guide) which has low loss and no radiation at the bends and discontinuities is suitable for millimeter‐wave integrated circuits. In this paper, the NRD guide circuit components using beam‐lead diodes are studied in the 35‐GHz range.The diode mount proposed in this paper consists of a patch antenna and an RF choke etched together on a thin Teflon substrate. A beam‐lead diode is mounted on this structure and the substrate is inserted transversely in the dielectric waveguide. Since this mount has a compact and rigid structure and can be fabricated only by etching, no fabrication difficulty is expected at higher frequencies.A simple matching technique, which uses a thin high‐permittivity sheet and an air gap provided in the dielectric strip, is developed. The performance of a Schottky‐barrier diode detector, a balanced mixer, and a PIN diode pulse modulator were found to be quite excellent.
Gas‐sensor characteristics of SnO2 film
Authors: Matsubara Chihiro , Furukawa Kimihiko , Taketoshi Osamu , Konishi Ryōsuke , Sasakura Hiroshi 
Published: July 2007

AbstractA recent study of the gas sensor device has been aimed at the improvement of gas selectivity and gas distinction. In the present study, to distinguish the kind of gas, three kinds of SnO2 thin films with different resistivities were deposited on glass substrates by vacuum evaporation to evaluate the changes of resistivity and work function due to hydrogen and oxygen in a vacuum system. As a result, it was found that oxygen acts differently in vacuum than in atmosphere.From the results of these experiments by XPS and XRD, a model of oxygen and hydrogen adsorption was proposed. In hydrogen adsorption, the model of carrier release is adequate and in oxygen adsorption, the model of mobility increase is adequate.
Yasuura method for solving two‐dimensional scattering problems. (I) theory
Authors: Okuno Yoichi , Ikuno Hiroyoshi 
Published: July 2007

AbstractWe describe the theory and algorithm of the Yasuura methods (a conventional mode‐matching method, the mode‐matching method with a smoothing procedure, the mode‐matching method with a singular‐smoothed procedure) for solving the problems of scattering by perfectly conducting cylindrical obstacles. Both the E‐wave and the H‐wave are considered. Two types of scatterers with either smooth or edged contour are treated. After formulating the problem, we explain the methods of solution with the proof of convergence. All the methods are reduced to a canonical form of the least‐squares problem. Some remarks on actual numerical computations are also included.
Precise calculation of space‐potential with the boundary of electron gun‐type
Authors: Kajiyama Yoshino 
Published: July 2007

AbstractThe space potential for a given boundary condition is obtained, in general, by digital simulation. In the case of an electron‐gun‐type boundary with sharp edges, confirmation of the numerical accuracy is not straightforward as singular electric field points are contained. In this paper, an accurate computation algorithm is proposed for such cases based on the Green's function method.When the computed values were compared with those by the simulation method, it was found that the present method can arrive at a high‐precision solution in a shorter period of time. In general, the analytical solution of a three‐dimensional boundary value problem containing sharp edges contain function series terms with poor convergence. Hence, the conventional acceleration method is not very effective.This paper obtains a convergence criterion suitable for the nature of the analytical solution and a significant reduction in computational time. From the nature of the basic computation equation, accuracy can be improved easily by an appropriate discretization of the numerical integral. The present method is effective for high‐precision computation of the weak electric field near the cathode. In the aberration analysis of a cathode lens, this method can be used as an effective comparison when the accuracy of the solution by the simulation is confirmed.
Noise characteristics of Er3+‐doped fiber amplifiers pumped by laser diodes
Authors: Yamada Makoto , Shimizu Makoto , Horiguchi Masaharu , Okayasu Masanobu , Sugita Etsuji 
Published: July 2007

AbstractThe noise characteristics of the Er3+‐doped optical fiber amplifier pumped by laser diodes (LD) at 0.98 μm and 1.48 μm are theoretically and experimentally studied. The noise figures of the optical fiber amplifiers pumped by a 0.98–μm band LD and a 1.48–μm band LD estimated from the beat noise between the signal noise and the spontaneous emission were 3.2 and 4.1 dB. It was found that the beat noise between spontaneous emissions and the shot noise of the spontaneous emission were smaller in the 0.98 μm‐band LD than in the 1.48–μm band LD. From these results, it was found that the optical fiber amplifier pumped by the 0.98–μm band LD has lower noise characteristics than those of the amplifier pumped by the 1.48 μm band LD.Further, the signal gain dependence, fiber length dependence and signal wavelength dependence of each noise component were studied. When the signal gain is kept constant, each noise component is not dependent on the fiber length and can be reduced monotonically by increasing the signal gain. When the wavelength deviates from the signal wavelength giving the maximum signal gain, the beat noise between the spontaneous emissions and the shot noise of the spontaneous emission increase.
New approach of adaptive automatic load shedding
Authors: Terzija V. V. , Koglin H.‐J. 
Published: July 2007

AbstractIn the paper a new approach of adaptive automatic load shedding, a procedure for protecting electric power systems from dynamic instability and frequency collapse is presented. It is consisted of two main stages. In the first stage the frequency and the rate of its change are estimated by nonrecursive Newton type algorithm and least error squares method. In the second stage the magnitude of disturbance, i.e. the difference between the generated and the consumed active power is estimated by applying the simplest form of generator swing equation. Results of multimachine test system computer simulations are presented.
Evaluation of the adaptive behaviour of an artificial neural network controller for a hybrid power compensator
Authors: Van Schoor G. , van Wyk J. D. , Shaw I. S. 
Published: July 2007

AbstractAn artificial neural network (ANN) is used to optimally control a hybrid power compensator (HPC) consisting of a static VAR compensator (SVC) and a dynamic compensator (DC) during the compensation of nonlinear loads. The HPC must be controlled to meet minimum requirements in terms of power factor and harmonic distortion, while at the same time minimising its total cost. The ability of the ANN to adapt its output when subjected to a dynamic power system environment to achieve the above, is evaluated. The power system dynamics in this paper constitute line impedance changes and changes in the load conditions of other consumers coupled to the same network. A state space model of the power distribution network together with the HPC forms the basis of evaluation of the mentioned controller. The results obtained reveal that the ANN can meaningfully adapt its output to optimise the HPC performance.
New approach to standing phase angle reduction for power system restoration
Authors: Ketabi A. , Ranjbar A. M. , Feuillet R. 
Published: July 2007

AbstractDuring power system restoration, it is necessary to check the phase angle between two buses before closing circuit breakers to connect a line between them. These angles may occur across a tie line between two systems or between two connected subsystems within a system. In case of large Standing Phase Angle (SPA) difference the synchro‐check relay does not allow closing of the breaker for this line. Therefore, this excessive SPA has to be reduced before attempting to connect the line. In this paper a new and fast method for reducing SPA is presented. For this purpose, the standing phase angle difference between two specific buses is represented in terms of sensitivity factors associated with the change in active power generations and consumption at the buses. Then, the proposed method reschedule generation of selected units or shed load of selected buses to reduce excessive SPA difference between two buses based on sensitivity factors.
The dynamic voltage/current characteristics of vacuum arcs after breakdown at currents in the lower kHz‐range
Authors: Hardt N. , Heimbach M. , Böhme H. , Gentsch D. 
Published: July 2007

AbstractA test set‐up is presented which is able to measure the arc voltage of vacuum interrupters after breakdown with currents in the lower kHz‐range. Arc voltage measurements from this set‐up are presented. The obtained dynamic voltage/current characteristics are discussed and compared to the known voltage current characteristic of a power frequency arc in vacuum. A simple vacuum arc model is presented describing the voltage current characteristic. The model is applied to assess the energy dissipation in the arc.
Effects of toroidal HVDC ground electrode on earth‐return circuits
Authors: Machczyński W. 
Published: July 2007

AbstractThis paper presents a method of evaluation of currents and potentials, excited by conductive effects of high‐voltage direct‐current (HVDC) transmission system, along two parallel earth‐return circuits such as pipelines and cables buried in the vicinity of a toroidal ground electrode. It is assumed that the system considered is linear and that the earth is an isotropic, homogeneous medium of finite conductivity. Conductive coupling between earth‐return circuits is taken into account, whereas the reaction of the conductors' currents on the electrode current is disregarded. The transmission line model of the conductor with earth‐return, a segmental linear approximation of the curve of the primary earth potential distribution along the conductor and the concept of superposition have been used in the method. It should be pointed out, that the method does not require the time consuming numerical integration. The technical applications of the method are illustrated by examples.
A methodology for optimal planning of capacitor installments in deregulated distribution networks
Authors: Rajakovic N. , Drca R. , Arsenijevic N. 
Published: July 2007

AbstractIn this paper methodology for optimal planning of capacitor installments in deregulated distribution networks is presented. The improvements are performed by using heuristics in practical consideration, reducing the number of combinations in a special division search technique. Deregulation aspects are carefully included in modeling of annual costs. It appears that importance of energy costs versus costs of the yearly peak power increases in a deregulated environment.
Core loss estimation in three‐phase transformer using vector hysteresis model and classical loss model incorporated in 2D magnetodynamics
Authors: Deblecker O. , Lobry J. , Broche C. 
Published: July 2007

AbstractThis paper deals with the computation of the magnetic field and core loss in a three‐phase three‐limb transformer at no‐load. The computational algorithm consists of the vector hysteresis model incorporated in 2D magneto‐dynamics via the differential reluctivity tensor. The hysteretic nonlinearity is handled by a simple iteration scheme. The eddy‐current losses in the laminated steel core are accounted for by considering an additional conductivity matrix in the FE equations. The magnetisation‐dependant vector Preisach model with an analytical expression for the distribution function is adopted for describing the hysteretic constitutive law in the rolling and transverse directions of the laminations. The parameters and mean field term are fitted on the basis of a set of BH‐symmetric (quasistatic) loops. Numerical results are presented that confirm the effectiveness of the proposed method for the no‐load simulation of the transformer in the transient and the steady‐states.
An efficient methodology for security assessment of power systems based on distributed optimal power flow
Authors: Hur D. , Park J.‐K. , Kim B. H. 
Published: July 2007

AbstractThis paper presents an algorithm for the parallel solution of the security constrained optimal power flow (SCOPF) problem in a decentralized framework, consisting of regions, using a price‐based mechanism that models each region as an economic unit. We first solve the distributed optimal power flow (OPF) problem to determine the maximum secure simultaneous transfer capability of each tie‐line between adjacent regions by taking only the security constraints imposed on the tie‐lines into account. In this paper, the line outage distribution factors (LODF) calculated at the current state are used to formulate the appended constraints. Once the secure transfer capability of each tie‐line is determined, the intra‐regional SCOPF is performed using the conventional linear programming (LP) approach. A description on the inclusion of security constraints with distributed OPF algorithm will be given, followed by the case study for Korea Electric Power System.
Novel modelling of residual operating time of transformer oil
Authors: Wahab M. A. A. , Hamada M. M. , Zeitoun A. G. , Ismail G. 
Published: July 2007

AbstractThis paper presents techniques developed to accurately model the characteristics of transformer oil for the purpose of predicting the effect of aging on these characteristics. Aging causes some of the transformer oil characteristics to violate the internationally specified limits. The purpose of this simulation is to develop alternative techniques to predict the operating time after which these characteristics would violate the limits. The results obtained from monitoring of twenty in‐service power transformers for long period of operating time up to ten years have been implemented in developing the proposed models. The physical, chemical and electrical characteristics have been determined periodically by internationally specified testing methods. The patterns of violation sequence of the standard limits, against operating time, by different transformer oil characteristics have been revealed and the most common pattern has been determined. The definition of residual operating time (trot) of the different transformer oil characteristics has been introduced. The choice of transformer oil breakdown voltage trot to represent that of the transformer oil characteristics has been justified. Modelling of trot as a function of transformer oil breakdown voltage, total acidity and water content by multiple‐linear regression has been proposed and verified. Also, polynomial regression model of trot as a function only of transformer oil breakdown voltage has been given. The accuracy and applicability of these models and the different modelling techniques have been discussed and proved.
The application of NN technique to automatic generation control for the power system with three areas including smes units
Authors: Demirören A. , Zeynelgil H. L. , Sengör N. S. 
Published: July 2007

AbstractThe study includes an application of layered neural network controller to study automatic generation control (AGC) problem of the power system, which contains superconducting magnetic energy storage (SMES) units. The effectiveness of SMES unit over frequency oscillations improvement against load perturbations in power system is well known. In addition, the proposed control scheme provides the steady state error of frequency and inadvertent interchange of tie‐lines to be maintained in steady state values. The power system considered has three areas two of which including steam turbines while the other containing a hydro turbine, and all of them contain SMES units, in addition. In the power system each area with a steam turbine contains the non‐linearity due to reheat effect of the steam turbine and all of the areas contain upper and lower constraints for generation rate. Only one neural network (NN) controller, which controls all the inputs of each area in the power system, is considered. In the NN controller, back propagation‐through‐time algorithm is used as neural network learning rule. The performance of the power system is simulated by using conventional integral controller and NN controller for the cases with or without SMES units in all areas, separately. By comparing the results for both cases, it can be seen that the performance of NN controller is better than conventional controllers.
“Northern adventure”: A personnel selection game
Authors: Stolovitch Harold D. , Keeps Erica J. , Okros Alan C. 
Published: July 2007

AbstractBetter selection of personnel can reduce training costs and attrition rates by matching candidates more effectively with jobs. But what can trainers do to improve their selection of personnel? One answer is illustrated in an adventure game designed to help measure problem sensitivity in potential candidates for the Canadian Navy's Maritime Surface and Subsurface officer program. This article examines problem sensitivity as an important criterion for officer candidates and the resulting development and testing of the adventure game to measure this attribute. The authors provide ways to adapt this procedure and the test instrument for use with other groups in other situations.
Human resource development already embraces total quality management—or does it?
Authors: Swanson Barbara L. 
Published: July 2007

AbstractHRD professionals who understand total quality management (TQM) have two major challenges: to enlighten management regarding what customer focus and leadership mean and to refuse to assume responsibility that is not theirs. The premise that managers own the human development process in their organizations still requires acceptance and clarification from both parties. Following that, a customer‐supplier partnership between managers and HRD that is based on trust and an understanding of what is needed from each is crucial. The partnership must be clearly defined, engaged in, and then continually evaluated to ascertain its contribution to human resource development for meeting the organization's goals of financial security and growth through continuous improvement.
On estimating the effects of peak demand pricing
Authors: Veall Michael R. 
Published: July 2007

AbstractExtreme value distributions are seldom used in economics, despite what seems to be a natural application to peak demand pricing. This paper estimates the effect of an individual peak demand charge which is a component of the standard industrial electricity rate structure. The extreme value distribution is used in forming the likelihood function of individual peak demand which is then estimated on a sample of five Ontario cement firms from 1970–1977. Goodness‐of‐fit tests tend to support the use of the extreme value distribution.
A parametric test of the negativity of the substitution matrix
Authors: Kodde David A. , Palm Franz C. 
Published: July 2007

AbstractThe negativity of the substitution matrix implies that its latent roots are non‐positive. When inequality restrictions are tested, standard test statistics such as a likelihood ratio or a Wald test are not X2‐distributed in large samples. We propose a Wald test for testing the negativity of the substitution matrix. The asymptotic distribution of the statistic is a mixture of X2‐distributions. The Wald test provides an exact critical value for a given significance level. The problems involved in computing the exact critical value can be avoided by using the upper and lower bound critical values derived by Kodde and Palm (1986). Finally the methods are applied to the empirical results obtained by Barten and Geyskens (1975).
A double‐hurdle model of cigarette consumption
Authors: Jones Andrew M. 
Published: July 2007

AbstractThis paper shows the importance of the double‐hurdle approach for modelling individuals' cigarette consumption, using data from the UK General Household Survey, and argues that participation and consumption should be treated as separate individual choices. The likelihood function for the full double‐hurdle is derived, and it is shown how restrictions on the stochastic specification of the model and auxillary information, which identifies ex‐smokers, allow it to be decomposed. The empirical results highlight the value of the sample separation information and the need to model starting and quitting as separate decisions.
Structural time series analysis and modelling package: A review
Authors: Diebold Francis X. 
Published: July 2007

AbstractThis package performs specialized tasks related to specification, estimation, prediction and diagnostic checking in the context of a particular class of unobserved‐components models. It is menu‐driven and easy to use. Although the present (first) release suffers from a number of limitations, omissions and bugs, it is nevertheless a useful tool in the hands of a knowledgeable user.
Statistical properties of data stretching
Authors: Greenberg E. , Pollard W. A. , Alpert W. T. 
Published: July 2007

AbstractThis research examines the properties of an estimation procedure frequently used because observations on some variables are available only at higher levels of aggregation than others. When this occurs, data are often stretched by repeating observations on variables at higher levels of aggregation. We show that this procedure results in biased estimators of coefficients and error variances. Under some circumstances the estimation based on stretched data has a smaller covariance matrix than that based on aggregated data. Comparisons of mean squared errors depend on unknown coefficients.
From a var model to a structural model, with an application to the wage–price spiral
Authors: Monfort A. , Rabemananjara R. 
Published: July 2007

AbstractIn this paper a VAR model is considered as a general framework in which a structural model can be tested. We carefully describe the hypotheses defining a structural model; this leads us to discuss various notions such as: predeterminedness, non‐causality, exogeneity, contemporaneous identification, overall identification, weak and strong structural forms. Then we propose a test procedure, based on the asymptotic least‐squares method, which allows successive testing of each aspect of a structural model. This procedure is applied to the wage–price spiral.