A study of frequency prediction for power systems

A frequency predictor is identified from simulated measurements of power and frequency on a power system. An on-line Ieast-squares algorithm is used along with a new system structure test for model order identification. A comparison of this system structure test with other model order identification tests is also included. The performance of the resultant predictor is then determined as a function of both the prediction interval and the sampling rate and measurement noise levels on the power and frequency measurements used for the predictor. The results indicate an increase in prediction error with the length of the prediction interval because the predictor loses its principal dependence of "P-f" (power-frequency) dynamics in the power system and depends more strongly on the random load fluctuations over the prediction interval. The modeling error was shown to be unaffected by sampling rate and by measurement noise levels below that of the present power-frequency recorder [2], but was affected by measurement noise levels above the values on the present recorder. This accuracy of the model for small prediction intervals justifies the future use of frequency measurements in power system identification and justifies the use of least-squares algorithms using these measurements. The results on sampling rate and measurement noise imply that the present recorder [2] is an "optimal" design and that the RTDAS [5] will be an even better tool for use in power system model identification.     

罐式集装箱流固耦合冲击响应谱分析计算

为模拟罐式集装箱的铁路冲击试验过程,用流固耦合模型进行响应谱分析计算,并采用虚拟质量法处理罐内液体.试验表明该方法比瞬态计算方法更实用,并且符合国际标准要求.该方法准确高效,可增加试验成功的可能性,减少产品研发设计成本.     

Fractional order [proportional derivative] controller for a class of fractional order systems

Recently, fractional order systems (FOS) have attracted more and more attention in various fields. But the control design techniques available for the FOS suffer from the lack of direct systematic approaches. In this paper, we focus on a given type of simple model of FOS. A fractional order [proportional derivative] (FO-[PD]) controller is proposed for this class of FOS, and a practical and systematic tuning procedure has been developed for the proposed FO-[PD] controller synthesis. The fairness issue in comparing with other controllers such as the traditional integer order PID (IO-PID) controller and the fractional order proportional derivative (FO-PD) controller has been addressed under the same number of design parameters and the same specifications. Fair comparisons of the three controllers (i.e., IO-PID, FO-PD and FO-[PD]) via the simulation tests illustrate that, the IO-PID controller designed may not always be stabilizing to achieve flat-phase specification while both FO-PD and FO-[PD] controllers designed are always stabilizing. Furthermore, the proposed FO-[PD] controller outperforms FO-PD controller for the class of fractional order systems.     

An easily testable optimal-time VLSI-multiplier

Summary We consider the design of a tree-multiplier, which is a modified version of a Wallace tree-multiplier [16] made suitable for VLSI design by Luk and Vuillemin [12]. It is shown that 4 log(n) + 3 test patterns suffice to exhaustively test the multiplier with respect to the cellular fault model (which includes tests for all single stuck at faults). Some slight modifications of the multiplier prove, that these tests can be applied without increasing the number of input ports substantially.     

Routh table test for stability of commensurate fractional degree polynomials and their commensurate fractional order systems

A Routh table test for stability of commensurate fractional degree polynomials and their commensurate fractional order systems is presented via an auxiliary integer degree polynomial. The presented Routh test is a classical Routh table test on the auxiliary integer degree polynomial derived from and for the commensurate fractional degree polynomial. The theoretical proof of this proposed approach is provided by utilizing Argument principle and Cauchy index. Illustrative examples show efficiency of the presented approach for stability test of commensurate fractional degree polynomials and commensurate fractional order systems. So far, only one Routh-type test approach [1] is available for the commensurate fractional degree polynomials in the literature. Thus, this classical Routh-type test approach and the one in [1] both can be applied to stability analysis and design for the fractional order systems, while the one presented in this paper is easy for peoples, who are familiar with the classical Routh table test, to use.     

The sizes and powers of some stochastic dominance tests: A Monte Carlo study for correlated and heteroskedastic distributions

Testing for stochastic dominance among distributions is an important issue in the study of asset management, income inequality, and market efficiency. This paper conducts Monte Carlo simulations to examine the sizes and powers of several commonly used stochastic dominance tests when the underlying distributions are correlated or heteroskedastic. Our Monte Carlo study shows that the test developed by Davidson and Duclos [R. Davidson, J.Y. Duclos, Statistical inference for stochastic dominance and for the measurement of poverty and inequality, Econometrica 68 (6) (2000) 1435–1464] has better size and power performances than two alternative tests developed by Kaur et al. [A. Kaur, B.L.S.P. Rao, H. Singh, Testing for second order stochastic dominance of two distributions, Econ. Theory 10 (1994) 849–866] and Anderson [G. Anderson, Nonparametric tests of stochastic dominance in income distributions, Econometrica 64 (1996) 1183–1193]. In addition, we find that when the underlying distributions are heteroskedastic, both the size and power of the test developed by Davidson and Duclos [R. Davidson, J.Y. Duclos, Statistical inference for stochastic dominance and for the measurement of poverty and inequality, Econometrica 68 (6) (2000) 1435–1464] are superior to those of the two alternative tests.     

Statistical analysis of proficiency testing results under elliptical distributions

The use of inter-laboratory test comparisons to determine the performance of individual laboratories for specific tests (or for calibration) [ISO/IEC Guide 43-1, 1997. Proficiency testing by interlaboratory comparisons — Part I: Development and operation of proficiency testing schemes] is called Proficiency Testing (PT). In this paper we propose the use of the generalized likelihood ratio test to compare the performance of the group of laboratories for specific tests relative to the assigned value and illustrate the procedure considering an actual data from the PT program in the area of volume. The proposed test extends the test criteria in use allowing to test for the consistency of the group of laboratories. Moreover, the class of elliptical distributions are considered for the obtained measurements.     

Comparison of exact parametric tests for high-dimensional data

Several proposals for exact or at least conservative parametric multivariate tests in the general linear model are considered that are applicable also for high-dimensional data, where the dimension of the observations may exceed the sample size. The common feature is the inclusion of principal component transformations into the test. Whereas a test proposal by Srivastava and von Rosen [Srivastava, M.S., von Rosen, D., 2004. MANOVA with singular variance matrix. Acta et Commentationes Universitatis Tartuensis de Mathematica 8, 253-269] originally assumes that the multivariate data have a known reduced rank which is used in the construction of the test, several versions of so-called PC tests by Läuter and colleagues accept a reduction of variance and utilize it for a “stabilization” of the test in terms of power. The different tests are compared with respect to their philosophy as well as in their performance in two real data examples and in simulation studies. It is shown that the test of Srivastava and von Rosen is a conservative test, even when a rank is assumed that is smaller than the true one. It is, however, less conservative than the conservative version of the PC test derived for the construction of a convenient confidence region for the investigated effects. The exact PC tests turns out to have the largest power.     

直流他励电机拖动性能实验的同一电路实现

直流电机拖动性能包括电机的起动、制动、正反转、调速和机械特性,以往实验需要每个部分单独连接一个电路图。基于其知识结构间的内在联系,通过整体上的步骤安排,在同一个电路中实现直流他励电机拖动性能的实验。     

Simulation study of the tests of uniform association based on the power-divergence

In this paper, a simulation study is presented to analyze the behavior of the family of test statistics proposed by Conde and Salicrú [J. Conde, M. Salicrú, Uniform association in contingency tables associated to Csiszár divergence, Statistics and Probability Letters, 37 (1998) 149-154] using the ?-divergence measures, that include as special case the power-divergence [N. Cressie, T.R.C. Read, Multinomial goodness-of-fit tests, Journal of the Royal Statistic Society, Series B, 46 (1984) 440-464] for the analysis of uniform association between two classification processes, based on the local odd ratios. For the above test statistics the significance level and its power are evaluated for different sample sizes when we consider a 3 × 2 contingency table.     

Testing the random walk hypothesis through robust estimation of correlation

This paper uses Monte Carlo simulations to examine the properties of the conventional Pearson and some of the most well-known robust to outliers estimators of correlation in the presence of general heteroskedasticity. We show that the tests of a random walk based on the Pearson autocorrelation coefficient, including the Lo and MacKinlay [1988. Stock market prices do not follow random walks: evidence from a simple specification test. Rev. Financial Studies 1, 41-66] robust form of the variance-ratio test, can be unreliable in the presence of some forms of conditional heteroskedasticity. As an alternative to the Pearson autocorrelation coefficient, we propose the median coefficient of autocorrelation. Our simulation results show that, in contrast to the Pearson autocorrelation coefficient, the median coefficient of autocorrelation is robust to conditional heteroskedasticity. When applied to exchange rate returns, the variance-ratio test based on the median autocorrelation coefficient provides stronger evidence against the random walk hypothesis compared with the Lo and MacKinlay [1988. Stock market prices do not follow random walks: evidence from a simple specification test. Rev. Financial Studies 1, 41-66] robust variance-ratio test.     

Dealing with structural constraints in self-optimizing control engineering

This paper deals with new design methods for self-optimizing control structures, i.e., the selection of controlled variables which guarantee almost optimal operation. Two types of structural solutions are considered. The first type has been previously addressed by other authors [1], [2], [3], [4] and refers to structures where all controlled variables are linear combinations of the same process variable set. In the practically more relevant second type, each controlled variable consists of a linear combination of an individual process variable set. Design methods for both types are developed. They are compared with respect to optimality and computational performance by means of repeated random tests. For further illustration, the newly developed methods are applied to a previously considered practical example from the academic field [5], [3].     

An analysis of EDF schedulability on a multiprocessor

A new schedulability test is derived for preemptive deadline scheduling of periodic or sporadic real-time tasks on a single-queue m-server system. The new test allows the task deadline to be more or less than the task period, and is based on a new analysis concept, called a /spl mu/-busy interval. This generalizes a result of Goossens et al. [2003] that a system of periodic tasks with maximum individual task utilization u/sub max/ is EDF-schedulable on m processors if the total utilization does not exceed m(1 /sup max/)+u/sub max/. The new test allows the analysis of hybrid EDF-US [x] scheduling, and the conclusion that EDF-US[1/2] is optimal, with a guaranteed worst-case schedulable utilization of (m +1)/2.     

功耗限制下RTL数据通路非扫描BIST方法的延时分析

可测性设计（DFT）方法广泛应用于数字电路测试中．通过添加测试硬件,用来降低测试的复杂性。但添加测试硬件后,往往会引起电路的延时变大,从而降低电路的性能,甚至引起延时故障。针对寄存器传输级（RTL）数据通路,文献[1]提出了两种功耗限制下非扫描内建自测试（BIST）方法。跟以前的方法相比较,这两个方法取得较短的测试应用时间和较低的测试硬件开销。本文对这两个方法对电路延时的影响进行分析。实验结果表明,在保持同样的测试应用时间和测试硬件开销的前提下,电路的延时有稍微增加。     

Approximation of powers of some tests in one-way MANOVA type multivariate generalized linear model

The test of an equality of expected values of response vectors in one-way MANOVA type multivariate generalized linear models can be based on deviance or score statistic. This paper aims at approximation of the power of these tests under local alternatives. As indicated by presented simulation study, these approximations perform well over a wide range of models and sample sizes. Approximation of the power of these tests based on a noncentral χ² distribution derived by Fahrmeir [Fahrmeir, L., 1987. Asymptotic testing theory for generalized linear models. Statistics 18 (1), 65-76] is considered for comparison in the simulation study. The approximation derived in this paper performs better for small sample sizes. The simulation study also provides comparison of the considered tests.     

Development of a test suite for the verification of implementations of the IPsec v2 security protocol

The paper is devoted to the design of a test suite for testing the conformance of implementations of Internet nodes to the specifications of the new security protocol IPsec v2 [1–7]. The test suite is generated using the automated testing technology UniTESK [8] and the package CTesK [9], which implements this technology. The work was performed in the Institute for System Programming of the Russian Academy of Sciences within the project “Verification of security functions for the new generation protocol IPsec v2.” Requirements for the implementations of IPsec v2 were systemized, and formal specifications and a prototype of the test suite for the verification of implementations of IPsec v2, including implementations of the automatic generation of security associations of IKEv2, were developed. A method used to formalize the requirements for IPsec v2, a procedure for generating the test suite, and testing results for some available implementations are described. The results show that the verification method proposed in this paper effectively automates the testing of such complex protocols as security protocols.     

矩形乘法器的另一结构设计

文章给出了矩形乘法器的另一个结构设计,该设计在计算速度上优于文献[1]的方案而劣于文献[2]的方案,在流水线分级方面则比文献[2]的方案有灵活性。这一实现把大整数乘的数据相关之时间代价降为1个二选一选通器加上3位加法器所需的时间,即把乘法器流水线的节拍时间值降到了该值,从而大大提高了用流水线实现大整数乘的效率。在某些应用中,用矩形乘法器来实现平行四边形乘法器的功能,则可大大降低规模。     

一种保留进位阵列乘法器的分析

复杂的VLSI电路的分析,对设计验证、故障诊断与测试都至关重要.对于一个用某种连结性语言描述的几千个门以上的电路,除了用CAD工具去处理之外,人们对它无法理解,没有直观的印象.电路图很难画,画出来也很难读懂.因此,与自顶向下的设计相反,研究自下而上的分析方法很有必要.本文介绍一种电路的结构分析方法.基于此方法,我们分析出国际通用的ISCAS十个电路实例中的C6288是一种保留进位阵列乘法器.因而对C6288的功能、结构都搞得一清二楚.     

A note on inversion of linear systems

An explicit relation showing the equivalence of tests of existence of inverses of a linear dynamical system as constructed by Silverman [1] and Sain and Massey [2] is given.