Parallel Load Research Articles

超高圧系統全停電時の復旧操作における需給制御のエキスパートシステム化

Present-day power systems operate with high reliability, and it is rare that a blackout will extend over an entire system swiftly and securely. This paper considers automatic power supply to loads after a complete blackout of a system. First, taking into account characteristics of generators, loads, and initial power sources, a method is proposed of allocating several generators to each load in parallel to the system and supplying power to the load sequentially. Second, to remove the imbalance between supply and demand of power, a method is proposed of adjusting the amount of supply and generation according to a present imbalance and the sum of past ones. Third, to automatically issue orders for start-up, parallel, follow-up, stand-by, and stoppage of generators, several rules for each power station are set and an expert system is made based on them. Finally, the expert system is applied to a model power system, and it is verified that it can restore loads without any trouble for a complete blackout which occur at any time of a day and in any restoration pattern.

ConClass: a framework for real-time distributed knowledge-based processing

We have developed a problem-solving framework, called ConClass, that is capable of classifying continuous real-time problems dynamically and concurrently on a distributed system. ConClass provides an efficient development environment for describing and decomposing a classification problem and synthesizing solutions. In ConClass, decomposed concurrent subproblems specified by the application developer effectively correspond to the actual distributed hardware elements. This scheme is useful for designing and implementing efficient distributed processing, making it easier to anticipate and evaluate system behavior. The ConClass system provides an object replication feature that prevents any particular object from being overloaded. In order to deal with an indeterminate amount of problem data, ConClass dynamically creates object networks that justify hypothesized solutions, and thus achieves a dynamic load distribution. A number of efficient execution mechanisms that manage a variety of asynchronous aspects of distributed processing have been implemented without using schedulers or synchronization schemes that are liable to develop bottlenecks. We have confirmed the efficiency of parallel distributed processing and load balancing of ConClass with an experimental application. >

An examination of load shedding during fatigue fracture

The existence of fatigue markings across the entire fracture surface of certain failed components implies that load shedding had occurred during the course of the fracture process. In order to examine the role of load shedding, a sample containing three parallel load paths with the central path being cracked was tested in fatigue using fixed grips. Loads in the three load paths, measured with strain gauges, were observed to be in good agreement with values predicted by theoretical analysis, based upon compliance calculations. Measured fatigue crack propagation rates also agreed well with those predicted from theoretical calculations.

Application of parallel processing techniques to improving the efficiency of MM2 molecular mechanics calculations

AbstractThe application of parallel processing techniques to molecular mechanics calculations is evaluated. Using the standard molecular mechanics package, MM2, four different parallel versions of the program are implemented in a four‐processor computing environment. A set of 529 test structures is used to compare the efficiency of the parallel versions of MM2 to a standard serial version of the program. Statistics describing execution times and program execution cycles are gathered and analyzed. The effects of parallel processing overhead and computer system load are explored, and the practical utility of parallel processing in molecular mechanics is estimated. The results of these parallelization experiments indicate that for geometry optimizations requiring significant amounts of computing time an improvement in program execution speed approaching 50% is realizable. © 1993 John Wiley & Sons, Inc.

Prediction Method for Local Scour by Warmed Cooling‐Water Jets

This paper describes an investigation on a numerical prediction method to estimate local scour due to the cooling‐water jets discharged from power stations. The method presented simulates the unsteady convection and diffusion of the warmed jets with a two‐equation turbulence model within the calculation area being deformed by the local scour. The profile of the scoured sand bed is predicted by computing the amount of both the bed load and the suspended load in parallel with the simulation of the flow itself. The prediction method was applied to three kinds of experiments: a three‐dimensional warm‐jet experiment above a fixed bed, and two local‐scour experiments carried out under two‐ and three‐dimensional flows. The validity of the numerical prediction method was reasonably confirmed by these comparisons of results.

Three-dimensional finite element stress analysis of the dentate human mandible.

The biomechanical events which accompany functional loading of the human mandible are not fully understood. The techniques normally used to record them are highly invasive. Computer modelling offers a promising alternative approach in this regard, with the additional ability to predict regional stresses and strains in inaccessible locations. In this study, we built two three-dimensional finite element (FE) models of a human mandible reconstructed from tomographs of a dry dentate jaw. The first model was used for a complete mechanical characterization of physical events. It also provided comparative data for the second model, which had an increased vertical corpus depth. In both cases, boundary conditions included rigid restraints at the first right molar and endosteal cortical surfaces of the articular eminences of temporal bones. Groups of parallel multiple vectors simulated individual masticatory muscle loads. The models were solved for displacements, stresses, strains, and forces. The simulated muscle loads in the first model deformed the mandible helically upward and toward its right (working) side. The highest principal stresses occurred at the bite point, anterior aspects of the coronoid processes, symphyseal region, and right and left sides of the mandibular corpus. In general, the observed principal stresses and strains were highest on the periosteal cortical surface and alveolar bone. At the symphyseal region, maximum principal stresses and strains were highest on the lower lingual mandibular aspect, whereas minimum principal stresses and strains were highest on its upper labial side. Subcondylar principal strains and condylar forces were higher on the left (balancing or nonbiting) side than on the right mandibular side, with condylar forces more concentrated on the anteromedial aspect of the working-side condyle and on the central and lateral aspects of the left. When compared with in vivo strain data from macaques during comparable biting events, the predictive strain values from the first model were qualitatively similar. In the second model, the reduced tensile stress on the working-side, and decreased shear stress bilaterally, confirmed that lower stresses occurred on the lower mandibular border with increased jaw depth. Our results suggested that although the mandible behaved in a beam-like manner, its corpus acted more like a combination of open and closed cross sections due to the presence of tooth sockets, at least for the task modelled.(ABSTRACT TRUNCATED AT 400 WORDS)

Prediction of Local Scour Caused by Warmed Cooling-Water Jets

This paper describes an investigation on a numerical prediction method to estimate local scour due to the cooling-water jets discharged from power stations. The method presented simulates the unsteady convection and diffusion processes of the warmed jets with a two-equation turbulence model within the calculation area being deformed by the local scour. The profile of the scoured sand bed is predicted by computing the amount of both the bed load and the suspended load in parallel with the simulation of the flow itself. The prediction method was applied to the experiments and its validity was reasonably confirmed.

High-frequency power transmission and selective distribution among loads by using distributed constant lines

A widely used high-frequency induction heating system usually consists of a high-frequency power source and a load circuit to be heated. Since such a system can heat only one load circuit, heating two or more loads requires that other sytems be devised. Several problems result, including the need for many power sources, switches, and high-frequency power transmission lines. To solve these problems, the authors propose a new system that can selectively supply two induction heating circuits with high-frequency power. This system is composed of a high-frequency voltage-type inverter, a parallel resonant load circuit, and a series resonant load circuit, which are connected in series by distributed constant lines of specific length. Analysis of the operating characteristics of the system confirms that the system can supply the loads with high-frequency power selectively and efficiently, with minimum interference between loads. The authors have compared theoretical simulation waveforms with actual waveforms observed on experimental equipment with output ratings of 1 to 2 MHz and 1 kW. As a result, experimental data agree well with theoretical data. This paper describes an operating principle and operating conditions of the system, and verifies that the theory we discuss is reasonable.

Physical computation

AbstractPhysical computation embraces a variety of physical analogies used to tackle non‐traditional problems. We describe Monte Carlo and deterministic methods, including simulated annealing and neural networks. Applications include economic change in Eastern Europe, the travelling salesman problem, vehicle navigation, track finding, and parallel computer load balancing. We show how different problems are suitable for the different various approaches to optimizatton—there is no universally applicable method.

Characteristics of electric power transmission on high-frequency inverter having distributed constant line at load side

An induction heating system aimed at improving the characteristics of high-frequency power supplied from the high-frequency, inverter to the parallel resonant load circuit is proposed, and its transmission efficiency is studied. In this system, high-frequency power can be supplied by lowering the effect of the inductance component accompanied by wiring between the inverter circuit and the resonant load circuit. Impedance matching between the inverter and the resonant circuit and high-efficiency power transmission from the inverter to the load circuit are possible. If a flexible coaxial cable is used as the distributed constant line, it is easy to cope with the case in which comparative distance exists between the inverter part and the heating part or the case in which the heating part is moved. >

High Frequency Power Transmission and Selective Division among Loads by Using Distributed Constant Line.

At present, a high frequency induction heating system usually consists of a high frequency power source and a heated load circuit. But some systems are necessary to heat up two or more loads.In such a case, there are many problems. For an example, the same number of the power source or switches, changing loads, are required. In addition, many high frequency power transmissionlines should be laid for the plural load circuits.The authers offer a new system, which can be able to supply the high frequency power slectively and effectively to two induction heating circuits, the system is composed of a high frequency voltage type inverter, a parallel resonant load circuit and a series resonant load circuit, and they are connected in series by the distributed constant lines, having the specific length.This paper describes the operating principle of the system and the optimum operating conditions. And also through the analyses of the operating characteristics of the system, the paper explaines the facts that the effective and selective transmissions of the high frequency power to the loads are available and the minimum interference between the loads for the supplied power divisions is accomplished.Finally, the theoretical simulation waveforms are compared with the actual waveforms obtained from the test equipment, having the output ratings of 1 to 2MHz and 1kW, and they correspond with each other. So it is clarified that the theory described in the paper is reasonable.

Synthesis procedure for active integrated radiating elements

This letter demonstrates a technique for the synthesis of a new integrated active radiating element topology. The approach adopted uses a microwave MESFET operating in large signal mode as the active device in an oscillator configuration. The oscillator has as its parallel feedback element and load element a microstrip patch antenna. The synthesis approach developed in this paper uses numerical optimisation to find the optimum terminal voltages for a given MESFET at a specified frequency. A set of explicit equations are presented in terms of these optimum terminal voltages. These allow the active radiating element terminations to be realised analytically. An NE71000 chip is used as the active device in the active radiating element circuit. Construction is on RT Duriod 5880 and the circuit operated at 10.2 GHz with 30mW power delivered to the antenna.

Simulation and control of a 20-kHz spacecraft power system

A detailed computer representation of four Mapham inverters connected in a series-parallel arrangement has been implemented. System performance is illustrated by computer traces for the four Mapham inverters connected to a Litz cable with parallel resistance and DC receiver loads at the receiving end of the transmission cable. Methods of voltage control and load sharing between the inverters are demonstrated. The computer representation is used to design and demonstrate the advantages of a feedforward voltage-control strategy. It is shown that with a computer simulation of this type, the performance and control of spacecraft power systems can be investigated with relative ease and facility. >

Impact of cycloconverter harmonics

Findings from a study on the harmonics generated by a 15 MVA three-phase 13.2 kV 60 Hz to single-phase 24/12 kV 25 Hz static frequency converter (SFC) or cycloconverter are summarized. At light loads, some of the characteristic harmonics (e.g. 10 Hz, 110 Hz) have magnitudes that exceed the fundamental frequency. Since the three-phase components at these frequencies do not necessarily nullify each other, many frequency components, in addition to zero-sequence components, can be measured in the neutral (residual) current. Because of low system impedance at harmonic frequencies, the voltage at the 13.2 kV substation supplying the SFC is not severely affected. A worst-case scenario for the voltage spectrum is presented. The corresponding distortion factor is calculated to be 4.12%. The power factor of an assumed parallel load is calculated using this scenario, and the effect of the SFC harmonics on the power factor is found to be insignificant. However, depending on the system impedances, the shunt capacitors for power factor compensation at the assumed load may be ineffective due to harmonic resonance.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A distributed load‐balancing system and its application to list‐processing oriented data‐flow machine dfm

AbstractThis paper proposes a group load‐balancing system (GLB) for the multiprocessor system which can manage and allocate the load in parallel and in a distributed way. In GLB, the resources are grouped hierarchically and the request for the resource allocated to a group is assigned to the subgroup with the minimum load in that group. Consequently, the group load data are updated at each allocation time, maintaining the accurate value, leading to a high load‐balancing ability. GLB is applied to the data‐flow machine DFM II and the evaluation was made by RT level simulator. The following result was obtained: (1) The performance is improved by 20 to 30 percent compared with the random allocation; (2) the maximum performance is obtained when the processor load is set equal to the number of active state processes; (3) the load balancing can be achieved within the difference of 5 processes on the average.

Design of Matching Circuitry for 100-kHz MOSFET Induction Heating Power Supply

This paper is concerned with the design of matching circuitry for a full-bridge current-fed MOSFET inverter feeding a parallel resonant induction heating load. Circuit operation is explained and analyzed and a means of suppressing ringing between parasitic lead inductance and drain-source capacitance using a filter is described. Guidelines for the selection of filter components are outlined.

Suppression of drain source ringing in 100 kHz MOSFET induction heating power supply

The letter is concerned with a full bridge, current-fed MOSFET inverter feeding a parallel resonant induction heating load. A means of suppressing ringing between parasitic lead inductance and drain source capacitance is described.

Stresses in a coil spring of arbitrary cross section. 3rd report Effects of ends of the spring under parallel compressive loads.

This paper presents the theoretical results of the stresses in a coil spring of arbitrary cross section. The analysis consists of two parts one of which is concerned with the displacements, the angles of rotation, the resultant forces and the resultant moments which occur in a helical spring during the loading. The results in this problem are derived by application of the curved beam theory in which all displacements and all forces in three orthogonal directions of the coil spring are included with consideration of constraints of the edges of the spring. At the second step, the paper presents the expressions for stresses in the spring due to the compression in the direction of the axis of the cylindrical spring when both edges are kept to be parallel during the deformation by use of the author's results given in the preceding paper (1st report). Numerical calculations have been carried out for four cases of a circular cross-section spring, an elliptical cross section spring, a rectangular cross section spring and an oval section spring.

Sensitivity of beam type load cell to off-center loading (3rd report, Shapes for reducing sensitivity)

For a parallel beam load cell, the sensitivity to off-center loading can be reduced by changing the shapes of the beams. Longitudinal load position sensitivity is reduced by thinning the beams at their mid-section, whereby the neutral axis for bending about the transverse axis is changed. The bending and the shearing strains of beams due to transverse load position changes are reduced by making two holes in the beam sections on which a strain gage is mounted, whereby the stiffness of the horizontal bending of the beams increases.

Characteristics of Induction Conveyor Motors in the Generating mode

In a downhill conveyor system, the drive motors become generators feeding real power to the electrical system. A general method using the cascade network concept and a digital computer is proposed to study the conveyor motors' operation in the motoring and generating modes. By use of the proposed method, a long downhill conveyor system with many stages of induction conveyor motor is studied. Various parameters are considered such as different types of feeder, the amount of shunt capacitor, and the amount of local load in parallel with the conveyor motors. Based on the computed results for the various cases, the electrical performance of a typical downhill conveyor system is summarized. From that, some engineering considerations are proposed to facilitate the design of a technically and economically sound downhill conveyor system. In particular, the conclusion may be drawn that the use of a cable feeder has many advantages, i.e., flat voltage profile along the feeder, relatively low line current and conductor loss, and avoidance of shunt capacitors. Furthermore, it is feasible to interconnect two substations when the conveyor motors are in the generating mode. The power (real and reactive) flow from the generators toward the two substations is affected by differences in the magnitude and angle of the voltage at each substation.