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1.
浅析气相色谱技术诊断变压器故障的应用 总被引：1，自引：0，他引：1
王力 《科技成果管理与研究》2011,(2):68-70
气相色谱技术能够对运行中的变压器进行实时监测,尽早发现变压器内部故障,因为变压器内部故障时变压器和发热气,中大部气中,通中气的及,变压器故障故障的及部。 相似文献
2.
W.V. Lyon 《Journal of The Franklin Institute》1948,246(2):159-164
The equation developed here is fundamental for an understanding of the behavior of inhomogeneous insulation, especially when the insulating material is of considerable extent in the form of continuous flat sheets, or cables, or discontinuous form as in pole-line construction. The “unit” may then be measured in terms of area in the case of sheets, and in terms of length in the case of cables. It is of basic importance in insulation research, testing, and operation. It furnishes the logical basis for the establishing of safety factors. 相似文献
3.
Reinhold Rüdenberg 《Journal of The Franklin Institute》1942,234(1):39-61
The sudden development of short-circuit currents, and of recovery voltages at interruption of currents, depends on the effects of stator and rotor leakages as well as of saturation in the generating synchronous machines.The non-linear problem of the interaction of these features with the performance of the main windings and auxiliary damper circuits is solved analytically.This leads to a simple graphical representation which is numerically determined by the well-known magnetic and electric characteristics of machine and network and by two time constants of very different magnitudes which are derived from the ordinary data of the machines. Hence the variation with time, of short-circuit currents and of recovery voltages, can easily and rigorously be computed for every given example.The deviations of actual damper circuits from the ideal form and the effects of eddy currents in solid steel parts of the rotor are discussed so far that numerical results can be derived readily.A new transient test for synchronous machines is suggested by which rotor and stator leakage voltages can be measured separately, avoiding the uncertainties of the usual steady state leakage tests. 相似文献
4.
Manipulating and discriminating biological cells of interest using microfluidic and micro total analysis system (μTAS) devices have potential applications in clinical diagnosis and medicine. Cellular focusing in microfluidic devices is a prerequisite for medical applications, such as cell sorting, cell counting, or flow cytometry. In the present study, an insulator-based dielectrophoretic microdevice is designed for the simultaneous filtration and focusing of biological cells. The cells are introduced into the microchannel and hydrodynamically pre-confined by funnel-shaped insulating structures close to the inlet. There are ten sets of X-patterned insulating structures in the microfluidic channel. The main function of the first five sets of insulating structures is to guide the cells by negative dielectrophoretic responses (viable HeLa cells) into the center region of the microchannel. The positive dielectrophoretic cells (dead HeLa cells) are attracted to regions with a high electric-field gradient generated at the edges of the insulating structures. The remaining five sets of insulating structures are mainly used to focus negative dielectrophoretic cells that have escaped from the upstream region. Experiments employing a mixture of dead and viable HeLa cells are conducted to demonstrate the effectiveness of the proposed design. The results indicate that the performance of both filtration and focusing improves with the increasing strength of the applied electric field and a decreasing inlet sample flow rate, which agrees with the trend predicted by the numerical simulations. The filtration efficiency, which is quantitatively investigated, is up to 88% at an applied voltage of 50 V peak-to-peak (1 kHz) and a sample flow rate of 0.5 μl/min. The proposed device can focus viable cells into a single file using a voltage of 35 V peak-to-peak (1 kHz) at a sample flow rate of 1.0 μl/min. 相似文献
5.
This paper introduces an alternative method artificial neural networks (ANN) used to obtain numerical solutions of mathematical models of dynamic systems, represented by ordinary differential equations (ODEs) and partial differential equations (PDEs). The proposed trial solution of differential equations (DEs) consists of two parts: The initial and boundary conditions (BCs) should be satisfied by the first part. However, the second part is not affected from initial and BCs, but it only tries to satisfy DE. This part involves a feedforward ANN containing adjustable parameters (weight and bias). The proposed solution satisfying boundary and initial condition uses a feedforward ANN with one hidden layer varying the neuron number in the hidden layer according to complexity of the considered problem. The ANN having appropriate architecture has been trained with backpropagation algorithm using an adaptive learning rate to satisfy DE. Moreover, we have, first, developed the general formula for the numerical solutions of nth-order initial-value problems by using ANN.For numerical applications, the ODEs that are the mathematical models of linear and non-linear mass-damper-spring systems and the second- and fourth-order PDEs that are the mathematical models of the control of longitudinal vibrations of rods and lateral vibrations of beams have been considered. Finally, the responses of the controlled and non-controlled systems have been obtained. The obtained results have been graphically presented and some conclusion remarks are given. 相似文献
6.
This paper investigates convergence of iterative learning control for linear delay systems with deterministic and random impulses by virtute of the representation of solutions involving a concept of delayed exponential matrix. We address linear delay systems with deterministic impulses by designing a standard P-type learning law via rigorous mathematical analysis. Next, we extend to consider the tracking problem for delay systems with random impulses under randomly varying length circumstances by designing two modified learning laws. We present sufficient conditions for both deterministic and random impulse cases to guarantee the zero-error convergence of tracking error in the sense of Lebesgue-p norm and the expectation of Lebesgue-p norm of stochastic variable, respectively. Finally, numerical examples are given to verify the theoretical results. 相似文献
7.
高压绝缘套管是气体绝缘金属封闭开关设备(GIS)高电压与地电位绝缘的重要元件,其均匀的电场分布与合理的结构,是GIS安全运行的保证。文章针对126 kV GIS高压绝缘套管结构设计与电场分布问题,在电磁场理论基础上,通过建立高压绝缘套管的轴对称电场数学模型,并对套管场域电场进行数值模拟及可视化处理,确定了126 kV GIS高压绝缘套管绝缘设计结构,为产品开发提供数值实验基础。经型式试验验证,产品各项性能指标满足技术规范要求,绝缘试验合格并具有较大的裕度,套管具有良好的技术经济指标。 相似文献
8.
Particle focusing in microfluidic devices is a necessary step in medical applications, such as detection, sorting, counting, and flow cytometry. This study proposes a microdevice that combines insulator-based and metal-electrode dielectrophoresis for the three-dimensional focusing of biological cells. Four insulating structures, which form an X pattern, are employed to confine the electric field in a conducting solution, thereby creating localized field minima in the microchannel. These electrodes, 56-μm-wide at the top and bottom surfaces, are connected to one electric pole of the power source. The electrodes connected to the opposite pole, which are at the sides of the microchannel, have one of three patterns: planar, dual-planar, or three-dimensional. Therefore, low-electric-field regions at the center of the microchannel are generated to restrain the viable HeLa cells with negative dielectrophoretic response. The array of insulating structures aforementioned is used to enhance the performance of confinement. According to numerical simulations, three-dimensional electrodes exhibit the best focusing performance, followed by dual-planar and planar electrodes. Experimental results reveal that increasing the strength of the applied electric field or decreasing the inlet flow rate significantly enhances focusing performance. The smallest width of focusing is 17 μm for an applied voltage and an inlet flow rate of 35 V and 0.5 μl/min, respectively. The effect of the inlet flow rate on focusing is insignificant for an applied voltage of 35 V. The proposed design retains the advantages of insulator-based dielectrophoresis with a relatively low required voltage. Additionally, complicated flow controls are unnecessary for the three-dimensional focusing of cells. 相似文献
9.
本文用数值求解基本控制微分方程组的方法研究了微重力条件下腔体内部固体可燃物表面火焰传播的三维非稳态过程。建立的理论模型考虑了气相有限速率化学反应，以及固相的传热和热解过程，阐明了微重力场中固体表面火蔓延过程可燃表面热解的“表面燃料喷射”效应的重要作用，并建立了相应的数学处理方法。数值模拟的结果反映了微重力大小对竖板火蔓延过程形成重要影响的特点，结果基本合理。 相似文献
10.
Frederick E. Pernot 《Journal of The Franklin Institute》1920,190(3):323-371
This paper contains the results of experiments performed by members of the Signal Corps Research Laboratory, Bureau of Standards, in an attempt to develop a method or methods of signal transmission over submarine cables which would permit of a more effective use of existing cable systems.In the method proposed and developed, signals are transmitted by means of alternating currents simultaneously with the normal battery of direct-current operation of the cable. Currents of several different frequencies may be used, reserving a given frequency for each message, and by tuning or equivalent methods at the receiving end these messages may be separated, so that the simultaneous transmission of a number of messages is redered possible.Accurate determination of the fundamental physical properties of a particular cable for different frequencies has been accompalished, and the results are given herewith. From these physical properties accurate calculations for any length of cable can be made, so that the design of proper apparatus becomes purely a laboratory problem.Actual trial of the proposed alternating-current method was made covering distances up to approximately 700 kilometres, with results which were in all cases completely satisfactory, indicating that the method is an entirely feasible one, and one which will render cables of this length, and undoubtedly of several times this length, much more useful. 相似文献
11.
E.W. Kamen 《Journal of The Franklin Institute》1976,301(6):559-571
An algebraic treatment of operational differential equations with time-varying coefficients is presented in terms of skew rings of differential polynomials defined over a Noetherian ring. Included in this framework are delay differential equations with time- varying coefficients. The operator equations are characterized by transfer matrices which are utilized to construct realizations given by first-order vector differential equations with operator coefficients. It is shown that the realization of matrix equations can be reduced to the realization of scalar equations. Finally, a simple procedure is derived for realizing scalar equations. 相似文献
12.
Robust identification of the linear parameter varying (LPV) finite impulse response (FIR) model with time-varying time delays is considered in this paper. A robust observation model based on Laplace distribution is established to deal with the output data contaminated with the outliers, which are commonly existed in modern industries. A Markov chain model is utilized to model the correlation between the time delays as they do not simply change randomly in reality. A transition probability matrix and an initial probability distribution vector are used to govern the switching mechanism of the time delays. Since it is difficult to optimize the complex log likelihood function directly, the derivations of the proposed algorithm are performed under the framework of Expectation-Maximization (EM) algorithm. A numerical example and a chemical process are utilized to verify the effectiveness of the proposed approach. 相似文献
13.
《Journal of The Franklin Institute》2023,360(11):7085-7104
Mean square exponential input-to-state stability (MSEISS) is considered for stochastic Markovian reaction-diffusion systems (SMRDSs) with impulsive perturbations. Both the boundary input and distributed input are considered in SMRDSs. With the Lyapunov–Krasovskii functional method, impulse theory and inequality techniques, a sufficient condition is established to achieve the MSEISS for SMRDSs with completely known transition rate matrix. Moreover, combined with the obtained sufficient conditions, the effects of the impulse and diffusion terms on MSEISS are demonstrated by examples. Then, the case is studied that the transition rate matrix is partially unknown and sufficient conditions are presented to ensure the MSEISS in light of the introduced free constants. Finally, two numerical examples are given to illustrate the validity of our theoretical results. 相似文献
14.
We conduct a numerical investigation and analytical analysis of the effect of slippage on the thermocapillary migration of a small liquid droplet on a horizontal solid surface. The finite element method is employed to solve the Navier-Stokes equations coupled with the energy equation. The effect of the slip behavior on the droplet migration is determined by using the Navier slip condition at the solid-liquid boundary. The results indicate that the dynamic contact angles and the contact angle hysteresis of the droplet are strictly correlated to the slip coefficient. The enhancement of the slip length leads to an increase in the droplet migration velocity due to the enhancement of the net momentum of thermocapillary convection vortices inside the droplet. A larger contact angle leads to an increase in the migration velocity which in turn enlarges the rate of the droplet migration velocity to the slip length. There is good agreement between the analytical and the numerical results when the dynamic contact angle utilizes in the analytical approach obtained from the results of the numerical computation, and the static contact angle is smaller than 50°. 相似文献
15.
信号与系统课程是电子信息类专业的核心基础课程,在各种经典教材中都采用冲激响应匹配法求解微分方程零时刻的跳变值。本文分析了冲激响应匹配法求解跳变问题存在的问题,提出了一种应用laplace变换求解跳变问题的新方法,简述了此种方法的原理和求解过程。多年的教学经验表明这种方法更简单,更易让学生掌握。 相似文献
16.
国际油价与原油进口的相关关系问题历来备受关注。基于线性模型的传统研究显示,中国原油进口的价格弹性远远低于其他国家的估计范围,而已有的研究很难完全解释这一问题。考虑到经典线性模型很可能掩盖了两者真正的关联机制,本文将从非对称效应的角度解释这一“低弹性之谜”。首先利用非线性检验确认了传统向量自回归模型中的非线性成分,然后建立平滑转换向量自回归模型（LSTVAR）刻画国际油价与原油进口的动态关联机制。广义脉冲响应函数（GIRF）显示,油价冲击对原油进口的影响存在两个维度的非对称效应。首先是正负油价冲击效应的非对称性,特别是在“经济低速发展阶段”表现得尤为显著,油价下跌对原油进口的影响要比油价上涨时的影响更强;其次是不同发展阶段的效应非对称性,无论对于何种冲击,在“经济低速发展阶段”,原油进口对油价变化的反应程度都要比“经济高速发展阶段”的反应程度更加剧烈。本文在两个层次上揭示了油价冲击的非对称效应,进而较为成功地解开了原油进口的“低弹性之谜”,这对于政府在不同经济环境下差异化定向制定相应的原油进口策略和宏观调控政策具有重要启示意义。 相似文献
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18.
基于时国际油价和欧佩克产量的结构性突变检验,本文分三时期建立了国际油价与欧佩克产量的误差修正模型,采用脉冲响应函数和方差分解方法对比不同时期欧佩克产量对国际油价的影响力.结果表明,Ⅲ期国际油价对欧佩克产量冲击的反应期较Ⅱ期提前,国际油价预测均方误差中欧佩克产量贡献率与Ⅰ期接近.表明欧佩克产量对国际油价的短期影响力在逐渐恢复. 相似文献
19.
In this paper, the approximation problem of T–S fuzzy linear singular system for a class of nonlinear singular system with derivative of input is considered and the nonlinear singular system has impulses. Consider a numerical example and a two-wheel drive robot, the T–S fuzzy singular systems are calculated for original system with derivative of input. According to solvability and steps of solving of the two examples, the results are extended to more generally nonlinear singular system with derivative of input. The theorem and algorithm that are given if input-state system is bounded impulse-free item and separable impulse item, it can be approximated by T–S fuzzy singular system with arbitrary accuracy. Finally, a numerical simulation is carried out to show the consistency with theoretical analysis and illustrate the effectiveness of approximation. 相似文献
20.
F.M. Clark 《Journal of The Franklin Institute》1933,215(1):39-67
The characteristics of gas solution in mineral oil are discussed. Data covering the changing gas solubility with temperature and pressure are given.The dielectric strength of oil is shown to be dependent on the kind and amount of its dissolved gas. The dielectric strength-gas content of oil bears a close relation to the recognized dielectric behavior of air itself.It is suggested that the usual dielectric strength of oil measures only the ease of oil “gassing” which may be dependent in part- at least, on dissolved impurities. 相似文献