Development of a simulator to calculate an optimal slab heating pattern for reheat furnaces

To improve energy consumption and to meet quality requirements for the slab heating process of reheat furnaces in hot strip mills, a new optimal slab heat pattern calculation simulator has been developed. The simulator consists of the following functions; (1) two-dimensional (slab thickness direction and slab length direction) slab temperature calculation function, which is capable of calculating skidmarks along the length of a slab, (2) furnace heat balance calculation function, (3) optimizing calculation function of slab heat pattern using a linear programming method. The simulator developed has been installed into a furnace computer control system for an actual plant. This paper describes the functions of the simulator and simulation results using the simulator. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 120 (3): 42–53, 1997     

FDTD method for the scattered-field equation to calculate the radar cross-section of a three-dimensional target

A discrete finite-difference time-domain (FDTD) method based on Maxwell’s equations is proposed to solve the scattered-field equation for dispersive media. The equations for the scattered field in a plasma medium are first derived, then used to calculate the radar cross-section (RCS) of three-dimensional targets, viz. a plasma sphere and a rectangular plate. When using such an FDTD method to compute the far-field scattering characteristics of a target, the near- to far-field transformation technique is generally required, which involves artificial setting a connection boundary between the total and scattered field in the computational space in order to calculate the latter and thereby the RCS of the target. This connection boundary must be set separately and appropriate computational grids added. However, by discretizing the Maxwell’s equations describing the scattered field, the resulting field in the computational space is already the scattered field and can be used directly to calculate the far-field properties of the target. In this way, the additional processing for the edge of the scattered field and computational space is avoided. Numerical calculations herein show that this FDTD approach for the scattered field is universal to some extent, being suitable for not only homogeneous but also dispersive media.     

开关线性复合式并网回馈功率变换器的研究

论文提出了开关线性复合式并网回馈功率变换器的技术方案，详细地分析了其技术构成、工作原理和控制方案，讨论了基于开关线性复合技术的功率缓冲器的电气特性和用于并网回馈的强大优势，并分析了兼顾功率缓冲器高效优波原则进行设计的Γ型LC低通滤波器的设计和参数计算，通过实验验证了理论分析的结论。     

Training locked-in patients: a challenge for the use of brain-computer interfaces

Training severely paralyzed patients to use a brain-computer interface (BCI) for communication poses a number of issues and problems. Over the past six years, we have trained 11 patients to self-regulate their slow cortical brain potentials and to use this skill to move a cursor on a computer screen. This paper describes our experiences with this patient group including the problems of accepting and rejecting patients, communicating and interacting with patients, how training may be affected by social, familial, and institutional circumstances, and the importance of motivation and available reinforcers.     

How to calculate the optimal diameter of a pole tip and winding parameters for DC valve electric magnets with round pole tips

Numerical expressions for determining the pole tip diameter that will secure the highest electromagnetic moment are obtained. How different factors influence the optimal diameter of the pole tip is estimated. A formula for calculating the pole tip optimal diameter in a wide range of variation by considering the mode of magnet operation and power supply, permissible overheating, winding relative height, and armature angular position is given. A procedure for determining the winding parameters at the stage of electromagnet design is specified.     

The use of electron-beam technology to produce bimetallic contacts for electrical plants

The process of producing compounds of VM-80 tungsten–copper alloy with BrX1Tsr chrome–zircon bronze using the methods of electron-beam brazing, surfacing, and welding is considered as applied to creating billets for producing bimetallic electrical contacts. The structures of the bimetallic contact and the main processes of electron-beam brazing, surfacing and welding of the specified materials are studied; the microstructure and mechanical properties of joints produced by the methods of electron-beam brazing and surfacing are investigated; and practical recommendations are given for the performance of further thermal treatment so as to improve the mechanical properties of obtained compounds. The results of this work may be of interest for specialists in the area of electrical-equipment design.     

The use of EEG modifications due to motor imagery for brain-computer interfaces

The opening of a communication channel between brain and computer [brain-computer interface (BCI)] is possible by using changes in electroencephalogram (EEG) power spectra related to the imagination of movements. In this paper, we present results obtained by recording EEG during an upper limb motor imagery task in a total of 18 subjects by using low-resolution surface Laplacian, different linear and quadratic classifiers, as well as a variable number of scalp electrodes, from 2 to 26. The results (variable correct classification rate of mental imagery between 75% and 95%) suggest that it is possible to recognize quite reliably ongoing mental movement imagery for BCI applications.     

The use of a spreadsheet for sinusoidal steady-state transmissionline and optics problems

It is shown how a spreadsheet on a personal computer can be used for sinusoidal steady-state transmission line and optics problems. It gives students the experience of programming the equations rather than relying on special-purpose software written by someone else. At the same time, the students do not need to expend too much effort on coding in a standard computer language, and the numerical effort is accomplished by the computer rather than a hand-held calculator     

The reliability of a segmentation methodology for assessing intramuscular adipose tissue and other soft-tissue compartments of lower leg MRI images

Objective

Determine the reliability of a magnetic resonance (MR) image segmentation protocol for quantifying intramuscular adipose tissue (IntraMAT), subcutaneous adipose tissue, total muscle and intermuscular adipose tissue (InterMAT) of the lower leg.

Materials and methods

Ten axial lower leg MRI slices were obtained from 21 postmenopausal women using a 1 Tesla peripheral MRI system. Images were analyzed using sliceOmatic? software. The average cross-sectional areas of the tissues were computed for the ten slices. Intra-rater and inter-rater reliability were determined and expressed as the standard error of measurement (SEM) (absolute reliability) and intraclass coefficient (ICC) (relative reliability).

Results

Intra-rater and inter-rater reliability for IntraMAT were 0.991 (95 % confidence interval [CI] 0.978–0.996, p < 0.05) and 0.983 (95 % CI 0.958–9.993, p < 0.05), respectively. For the other soft tissue compartments, the ICCs were all >0.90 (p < 0.05). The absolute intra-rater and inter-rater reliability (expressed as SEM) for segmenting IntraMAT were 22.19 mm² (95 % CI 16.97–32.04) and 78.89 mm² (95 % CI 60.36–113.92), respectively.

Conclusion

This is a reliable segmentation protocol for quantifying IntraMAT and other soft-tissue compartments of the lower leg. A standard operating procedure manual is provided to assist users, and SEM values can be used to estimate sample size and determine confidence in repeated measurements in future research.

     

The application of the BAGIRA code for a computational analysis of accident conditions involving a small leak from the reactor coolant circuit on the PSB-VVER test facility

We present the results from a verification of the BAGIRA thermal and hydrodynamic code on the basis of the 3% Leak of Coolant from the Cold Pipeline experiment carried out on the PSB-VVER integral test facility.     

The use of a topological list for calculating the parameters of electric-power systems on the basis of the node-voltage method

The software implementation of the node-voltage equations for calculating the parameters of electric-power systems on the basis of the topological list is considered. Of the well-known modifications of the node-voltage method, it is proposed to use the equations for node voltages in the form of a current balance when specifying a constant-conductivity load. To eliminate the harmonic components during calculations, the equation for each element of the electric-power system is represented in the Park–Gorev axes. When forming the matrices of the nodal conductivities and specifying currents, a topological list that is based on the principle of piecemeal contributions is used. The key advantages of the method that is based on the topological list are that it is unnecessary to observe the order of numbering rows and that this method is highly algorithmic, thus providing the minimization of the computational efforts in compiling equations on a computer. The essence of the piecemeal-contribution principle lies in the successive formation of matrix coefficients, as row-by-row processing of the topological list is performed. An algorithm for the formation of equations according to the node-voltage method using the topological list in the form of a block diagram is presented. Calculation using the node-voltage method on the basis of the topological list is an independent task, as well as representing a component of more complex types of calculations, such as optimization of the normal modes, stability analysis, reliability assessment, etc. The interrelations between individual components of the process of solving the problem of calculating stationary and quasi-stationary operating modes of the electric-power system with respect to input and output information are shown. The formation of the equations of the structural elements in stationary and quasi-stationary modes of the electric-power system of a factory is based on the linearization of the initial node-voltage equations.     

The general equations of 3-phase transformers with a symmetrical and linear magnetic circuit for use in network calculations

Contents In this paper general differential equations are derived for the 3-phase transformer with the help of the symmetrical component transformation. With respect to their phase shifting properties the 3-phase transformers can be divided into two basic groups, depending on whether or not the phase displacement is an even multiple of /6. This holds for both the steady state and for the transients. Only the appearance of a zero sequence component system may introduced differences. The derivation of the equations gives a clear insight into the internal behaviour of the transformer. The applicability of the general equations is demonstrated in an example.

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Die allgemeinen Gleichungen für dreiphasige Transformatoren mit symmetrischem und linearem magnetischen Kreis für Netzberechnungen

Übersicht In diesem Aufsatz wird mit Hilfe der Transformation symmetrischer Komponenten ein allgemeines Gleichungssystem für dreiphasige Transformatoren entwickelt. Bezüglich der Phasendrehung lassen sich alle dreiphasigen Transformatoren in nur zwei Gruppen einteilen, wobei innerhalb einer Gruppe die Transformatoren ein-und dasselbe stationäre und dynamische Verhalten haben. Lediglich ein Nullsystem kann innerhalb einer Gruppe Unterschiede einbringen. Bei Entwicklung der Gleichungen erhält man eine gute Einsicht in das innere Verhalten der unterschiedlichen Transformatoren. Anhand eines Beispiels wird die Anwendungsfähigkeit des allgemeinen Gleichungssystems erläutert.

     

A minimal set of electrodes for motor imagery BCI to control an assistive device in chronic stroke subjects: a multi-session study

The brain-computer interface (BCI) system has been developed to assist people with motor disability. To make the system more user-friendly, it is a challenge to reduce the electrode preparation time and have a good reliability. This study aims to find a minimal set of electrodes for an individual stroke subject for motor imagery to control an assistive device using functional electrical stimulation for 20 sessions with accuracy higher than 90%. The characteristics of this minimal electrode set were evaluated with two popular algorithms: Fisher's criterion and support-vector machine recursive feature elimination (SVM-RFE). The number of calibration sessions for channel selection required for robust control of these 20 sessions was also investigated. Five chronic stroke patients were recruited for the study. Our results suggested that the number of calibration sessions for channel selection did not have a significant effect on the classification accuracy. A performance index devised in this study showed that one training day with 12 electrodes using the SVM-RFE method achieved the best balance between the number of electrodes and accuracy in the 20-session data. Generally, 8-36 channels were required to maintain accuracy higher than 90% in 20 BCI training sessions for chronic stroke patients.     

The use of supercritical parameters of a coolant—A promising path to development of nuclear power plant water-cooled reactors in the 21st century

A modern concept of the development of water-cooled reactors of nuclear power plants (NPPs) is considered. Data on the design of NPPs with supercritical-parameters coolant and the results of experimental studies are presented.     

耦合电容器高频电容与极间介质关系的研究

对不同极间介质的耦合电容器的高频电容进行理论分析、计算和实验研究后指出,在结构、固有电感类同的条件下,耦合电容器高频电容随极间介质中非极性介质的比例增加而上升,５００ｋＨｚ时可超过额定值的１５０％。同时极间介质为膜纸复合的耦合电容器在ＧＢ／Ｔ４７０５—９２推荐的工作温度范围内高频电容不会低于额定值的８０％。     

The use of positron emission tomography and [18F]fluorodeoxyglucose for functional imaging of muscular activity during exercise with a stride assistance system.

The aim of this study was to investigate the use of [18F]fluorodeoxyglucose and positron emission tomography (FDG PET) for quantitative evaluation of glucose metabolism in skeletal muscle during walking. Ten young males underwent FDG PET twice during walks, which were done with or without an automated stride assistance system (SAS). Walk ratios were significantly increased by the SAS in seven subjects. Regional glucose metabolism in muscles between the crista iliaca and the planta was clearly visualized in all ten subjects. Glucose utilization increased significantly in the tibialis posterior and medial gastrocnemius muscles of the seven subjects in whom walk ratios were increased by the SAS. FDG PET is useful for analysis of muscle activity during exercise and rehabilitation.     

Fuzzy-control of a hand orthosis for restoring tip pinch, lateralpinch, and cylindrical prehensions to patients with elbow flexion intact

This study examines, through simulation, the use of fuzzy logic as a feasible control scheme for a hand orthosis that can restore fingertip pinch, lateral pinch, and cylindrical grasps to individuals suffering from C5-C7 spinal cord injuries. A simplified hand orthosis model, consisting of four fingers and a thumb, was derived for the purpose of planning appropriate grasp trajectories and for validating the fuzzy logic control architecture. For comparison a PID controller was also designed. Fuzzy logic is advantageous for this system since it eliminates solving coupled nonlinear equations of motion. For the various grips, the fuzzy controller produced better performance than the PID controller     

The role of energy conservation technologies in selecting a rational scheme for supplying heat to large towns

We present the results from a comprehensive analysis of power engineering of a town, using Moscow as an example; statistical initial data; and results obtained from surveys and calculations, as well as preliminary conclusions on how efficiently energy resources are produced, transported, distributed, and used by end consumers.     

数字化变电站集中式保护应对边界信息缺失新方法研究

数字化变电站集中式保护装置统一处理全站实时信息,有利于改善保护的性能。然而由于网络通信、电子互感器发生故障等原因可能造成集中式保护装置采集的实时信息缺失,使得集中式保护无法迅速、有选择性的切除故障,影响保护系统的可靠性。提出一种数字化变电站集中式保护应对边界信息缺失新方法,当故障发生时,如果出现一条线路电流采样值信息缺失,在假设母线没有发生故障前提下利用基尔霍夫电流定律合成信息缺失线路的电流,然后通过常规三段式线路保护判据切除故障。如果在信息缺失线路保护第一段检测到故障发生,则在无延时跳开该线路断路器之后