Antenatal fetal risk assessment by blood-flow velocity waveforms

The purpose of this article is to study a system for antepartum fetal evaluation. The task is to investigate the Doppler ultrasound measurements of the umbilical artery and the cerebral artery to relate the health status of a fetus by using discriminant functions of pattern recognition. The authors then analyze the individual effects of various blood-flow velocity waveforms using principal component analysis.     

An evaluation method of voltage sag using a risk assessment model in power distribution systems

In this paper we explore a new method for evaluating the impact of voltage sags in the power distribution systems. The proposed method incorporates the generalization of the evaluation method as well as the effects of voltage sags on customers. To generalize the evaluation method, historical reliability data will be used. We take into account the impact of voltage sags on customers using a representative power acceptability curve and a fuzzy model. The final result of the evaluation model yields on a yearly basis the magnitude of customers’ risk caused by voltage sags. The evaluation methodology is divided into the analytic and probabilistic method. The time sequential Monte Carlo simulation is used as probabilistic method. The proposed method is tested using the modified Roy Billinton Test System (RBTS) form and the reliability data of Korea Electric Power Corporation (KEPCO) system. Through the case study, we verify that the proposed method evaluate the actual impact of voltage sags and can be effectively applied to the real system using the historical reliability data as the conventional reliability indices in power distribution systems.     

Voltage balancing of islanded microgrids using a time-domain technique

In this paper, voltage balancing and frequency control of converter-fed, islanded microgrids, using a novel time-domain technique which has not been applied for such applications is discussed in detail. In particular, the connection of single-phase loads to the islanded microgrid causes voltage unbalance and this is eliminated by supplying the negative-sequence component of the voltage from the converter. The negative sequence components of the voltage and current are extracted using the aforementioned time-domain technique. The simulations are carried out in RSCAD™ and experimental results are provided to validate the concept.     

A pumping technique using electrohydrodynamic flow inside a gel

We demonstrated a new type of electrohydrodynamic (EHD) pump that had a pair of electrodes placed inside a gel (poly(vinyl alcohol) swollen by dimethyl sulfoxide). The fluid (decahydronaphthalene) was in contact with the gel surface. During a voltage application to the electrodes, the EHD flow of dimethyl sulfoxide inside the gel caused the flow of the fluid outside the gel. An advantage of this pumping technique is that one can dissolve some chemicals in the fluid without the fear of their electrochemical decomposition because the electrodes inside the gel are not in contact with the fluid.     

Annual risk assessment for overload security

This paper presents an approach to assess the cumulative risk associated with overload security for the purposes of mid-term power system planning. The work is motivated by a need to refine bulk power system reliability assessment to meet the needs of the restructured industry. There are two main contributions to the work. First, the assessment is performed over a year-long trajectory of hourly operating conditions, resulting in reliability assessment of all expected conditions and not just a limited number of snapshots. Secondly, the assessment is quantified by a risk index comprised of summed products of probability and consequence. This index is a good indicator of the actual reliability level, it is decomposable, and it can be effectively integrated into economic decision making paradigms. The work is illustrated using the 1996 IEEE Reliability Test System     

Situation assessment of glaucoma using a hybrid fuzzy neuralnetwork

Describes a differential diagnostic-decision support system to aid in early detection in primary-care environments. In general, the authors are able to give correct differential diagnostic support under primary-care conditions without any further financial investments. In some cases, it is difficult to differentiate between “glaucomatous” and “pathological” situation classes. There is an unclear transition between these two situations. Initial tests of a combination crisp/fuzzy output refined the authors' results, and these are now under investigation. More data are needed for the “normal” class. An evaluation of the complete monitoring system will be started, including all components and sampling of more data sets. For consecutive patient cases, time-dependent characteristic changes in the visual fields could be detected. Further developmental work will be done in this area, parallel to the growth of the database     

AC-HVDC solution and security assessment using a diakoptical method

The paper describes a direct solution of an HVDC link within an AC loadflow solution and a direct security analysis using diakoptical techniques. The direct solution is faster than the more conventional boundary iterative method and therefore is more economical when used for regular calculation such as security assessment and transient stability analysis. It can easily be incorporated in existing AC loadflow algorithms.     

Small perturbation performance of a synchronous machine using d-decomposition technique

The D-decomposition method of analysis is used to determine the small perturbation response of a synchronous machine. Computed results are presented in the form of stability contour diagrams showing the boundaries of absolute stability or with arbitrary degrees of damping in terms of the parameters of a conventional proportional voltage regulator. The influence of the damping factor on system response is illustrated with time—domain characteristics.     

Examining fetal heart-rate variability using matching pursuits

A new approach to time-frequency analysis of fetal heart rate (FHR) variability is the matching pursuit (MP) method. MP analysis is proposed as away to capture complex energy structures ranging from burst-type to continuous activity in the time-frequency plane that other methods such as power-spectrum analysis and wavelet transforms may not detect. This article summarizes previous FHR analysis techniques, presents the MP algorithm, and shows the advantages of the MP method over other methods of FHR analysis     

Analyzing fetal breathing rates using matching pursuits

Spontaneous breathing movements in the fetus tend to occur intermittently, and do not become continuous until after birth. In both the primate and the ovine species, breathing movements have been observed to have a high degree of variability in instantaneous breathing rates. In this study, ewes were surgically instrumented for chronic intrauterine recording of fetal diaphragmatic EMG. The matching pursuit (MP) method was used to examine the effects of morphine on fetal breathing rates in both time and frequency domains. The matching pursuit method was chosen since the classical Fourier transform may not represent signals which have stationary characteristics and wavelet transform may not represent signals whose Fourier transforms have a narrow frequency support. The authors' results show that the MP method was superior to both short time Fourier and wavelet transforms in identifying multiple periodicities in a highly nonstationary signal such as fetal breathing     

Ethical risk assessment: valuing public perceptions

Engineers are confronted with an array of moral issues and dilemmas as the complexity modern technology results in equally complex efforts to assess the accompanying environmental and safety risks. The author examines the connections between engineering ethics, risk communication, and the engineering culture. First moral issues in risk assessment are reviewed and the ethical responsibilities of engineers with respect to risk assessment and risk communication are discussed. The conventional model of risk communication, which holds that only experts possess relevant risk information, is then critiqued, and the findings of social scientists and humanists with respect to the dual importance of expert and public risk information are reviewed. Following a discussion of the prevailing engineering culture, particularly as it relates to the problems involved in risk communication, some suggestions are made for transforming the engineering culture in a manner conducive to more meaningful discussion of risk     

基于LCC的变电站改造风险评估模型研究

变电站改造评估应以变电站改造风险评估为依据,结合LCC经济性评价,从全寿命资产管理的角度进行综合分析.通过建立变电站风险评估模型,分析设备风险和系统风险,并对风险成本采用LCC方法进行量化分析,多方案对比、论证及选择和优化,最终决策改造方案.     

Design of single-sided linear induction motors using a nonlinear optimization technique

Both low-speed wheel-on-rail and the medium-speed Maglev transport system with single-sided linear induction motor (SLIM) propulsion have been in practical application. This paper presents the method of optimizing the design parameters of SLIMs using the nonlinear optimization method. The optimization problem is formulated by the use of the design formulas taking into account the end effect, skin effect and airgap leakage, and the transformation method and the simplex method are applied to solve the problem. Seven parameters, such as the number of poles, the pole pitch and the stack height, are chosen as the independent variables. The output kW/input kVA, the maximum flux density in the core teeth, the temperature increase, the primary length, the stack height and the maximum thrust are selected as the constraint functions. The performance characteristics are estimated using space harmonic analysis as well as the approximate equations. The method is applied to the SLIM design for urban transit, and the maximum speed is about 70 km/h. As the transformation methods, the interior point transformation and the exterior point transformation are compared from the viewpoints of accuracy and CPU time. The design is analyzed under several objective functions, the primary weight, the input kVA and the cost of secondary materials.     

Control of permanent magnet motor drives using a new positionestimation technique

Permanent magnet motor drives require absolute position information so that winding currents can be modulated in synchronism with the rotor. The eradication of such sensors has been the subject of many publications. This paper describes the principles and implementation of a new algorithm for combined flux-linkage and position estimation in permanent magnet motors. The algorithm uses the machine's flux-linkage versus current versus position characteristic and is thus able to take account of machine nonlinearities. The position estimator utilizes the characteristic in a generalized nonintrusive estimation scheme, which is effective over the whole range of operating conditions. The paper shows implementation of the estimator as embedded code in a digital signal processor-based drive system. Experimental results demonstrate the performance of the algorithm under steady-state and transient conditions, when the drive is operating closed loop sensorless, i.e., with the rotor position being provided by the position estimator     

Root loci design using Dickson's technique

Traditional techniques for determining the root loci were developed by Evans. Given the characteristic equation {1+G(s)H(s)=0}, Evans root locus method requires the magnitude of G(s)H(s) to be equal to minus one and is well established for determining the pole locations as the system gains are changed. In this paper, nontraditional techniques for developing the root loci of control systems are introduced. Illustrations are developed by using a method for plotting the root loci that involves setting the real and the imaginary portions of the characteristic equation equal to zero. Setting the real and imaginary parts of the characteristic equation equal to zero arises from work in the theory of equations by Dickson. Application of this technique allows adjustment of the gain, to establish the system requirements, and introduces collateral equations subject to unique geometric interpretation     

Reliability and price risk assessment of a restructured power system with hybrid market structure

In a restructured power system with hybrid market structure, generation companies and customers trade electricity and reserve either through a centralized power pool or by bilateral contracts based on their price and reliability offers and requirements. This results in difficulty in price and reliability management of such power systems. This paper presents techniques to evaluate both reliabilities and prices for the pool and bilateral customers in a hybrid power market. In these techniques, reliability and price models for the power pool and bilateral suppliers have been developed using reliability network equivalents to easily include various agreements among market participants. Customer responses to prices are modeled using customer damage functions. The reliability and price problems with and without considering agreements are formulated using improved optimal power flow techniques based on these models. The correlation between reliabilities and prices has been considered in the techniques. The modified IEEE Reliability Test System has been analyzed to illustrate the proposed techniques.     

Rigorous field analysis of a spherical shield by using the multipole technique

Contents The vector spherical multipole analysis is applied to determine the shielding effectiveness and the scattering cross sections of a homogeneous spherical shell with arbitrary thickness and material parameters. This canonical EMC-problem is formulated as a classical three-domain-problem and then solved rigorously with respect to the continuity-conditions of the tangential field components. Numerical results are presented especially for a shell material with low conductivity. In case of a well conducting thin shell an asymptotic evaluation of the multipole solution leads exactly to the results obtained byKaden, but in addition the amplitude of the shielding effectiveness at the resonance frequencies can be predicted.

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Sphärische Multipolanalyse des elektromagnetischen Feldes eines Kugelschirms

Übersicht Die vektorielle sphärische Multipolanalyse wird herangezogen zur Berechnung der Schirmdämpfung und der Streuquerschnitte eines homogenen Kugelschirms endlicher Dicke mit beliebigen Materialparametern. Dieses kanonische EMV-Problem wird als klassisches Drei-Raum-Problem formuliert und unter Verwendung der Stetigkeitsbedingungen für die tangentialen Feldkomponenten streng gelöst. Numerische Auswertungen werden präsentiert speziell für den Fall eines Schirms mit niedriger Leitfähigkeit. Eine asymptotische Auswertung der strengen Theorie für den Fall einer sehr dünnen Kugelschale mit hoher Leitfähigkeit führt exakt zu der Lösung vonKaden. Zusätzlich kann jedoch auch die Amplitude der Schirmdämpfung in den Resonanzpunkten angegeben werden.

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This work was supported in part by the Deutsche Forschungsgemeinschaft (DFG).     

Estimation of charge distribution on a bulky solid dielectric using regularization technique

We have been studying a multi‐point charge measurement method using an electrostatic probe. In this technique, charge densities x must be estimated from the probe outputs b by an inverse calculation based on an equation A x = b . The matrix A is obtained by applying a numerical field calculation technique. When the matrix A is in ill‐condition, the solution often makes no sense, including extremely large errors. Therefore, we apply the regularized least squares method (RLS) with a penalty term to perform the inverse calculation stably for the ill‐conditioned matrix. The penalty term imposes some constraints on the solutions. In this paper, first, we have analyzed the accuracy of the charge distribution estimated by the inverse calculation. Although the perturbation bound of the solution errors has already been proposed for the least squares method, it has not yet been given for the RLS. We have derived the equations that express the perturbation bound of the solution errors in applying the RLS to evaluate the estimation accuracy. Second, we have applied the above equations to an experimental result for a cylindrical dielectric solid, and estimated the charge distribution represented by 10,140 unknowns. We have utilized an iteration technique and the symmetric configuration of the measured arrangement so as to reduce the amount of operations and memory capacity required for the inverse calculation. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 163(2): 1–13, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20412     

High voltage AC resistive current measurements using a computerbased digital watts technique

A computer-based technique is described which can accurately determine high-voltage AC resistive currents by obtaining the watts loss of the test specimen and dividing by the true r.m.s. (t.r.m.s.) value of the applied voltage Therefore, the normal concern for guarding against stray capacitive currents and for the exact repetition of test setup geometry on successive testing are not required for accurate measurements of AC resistive current. The watts loss calculation is based on the general formula for average watts so that the resistive current can be measured accurately with some harmonics of the fundamental present in both the test current and the supply voltage. A digital oscilloscope is used to acquire the test voltage and current so that special-purpose amplifiers are not required. The overall system accuracy is verified to less than ±1.21% of full-scale current. A microprocessor was used to compute the following parameters: average power, t.r.m.s. voltage, t.r.m.s. resistive current, t.r.m.s. capacitive current, total t.r.m.s. current, and the magnitude of calculated measurement error. The waveforms displayed are volt-ampere, voltage, and total current. An EHV aerial lift boom, a 115 kV station post insulator, and a metal-oxide surge arrester are evaluated using this technique to illustrate the measurement advantages