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1.
计算机模拟技术在航空发动机设计中的应用 总被引:4,自引:0,他引:4
通过对过去30多年来航空燃气涡轮发动机性能计算机模拟技术研究的回顾,总结了发动机性能模拟技术的研究方法,分析了发动机模拟技术的现状,提出了发动机计算机模拟技术的三个层次概念,并对目前国内现有技术进行了总结,提出以发动机仿真为目标的发动机性能仿真应是未来发展的方向;还以基于第二层次数学模型的某计算机模拟软件为手段,通过对某型涡扇发动机设计参数的分析和发动机使用过程中各种影响因素的预测分析等.阐述了基于计算机模拟技术的航空燃气涡轮发动机设计技术,分析了计算机模拟技术在发动机设计中的应用。 相似文献
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A general systematic procedure is described for computing the Fourier transform and the ambiguity function of waveforms that are piecewise polynomial. The procedure can be implemented by hand or programmed for execution by a digital computer. The main advantage of the technique is that integration is replaced by a finite summation. Examples include the computation of characteristic function, moments, and the ambiguity function of an amplitude modulated linear FM signal. 相似文献
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Bershad N.J. Merryman P. Sklansky J. 《IEEE transactions on aerospace and electronic systems》1974,(2):245-254
The theory of ?continuous learning? is applied here to the design of nonlinear sampled-data trackers. This theory provides a continuous-motion approximation of the discrete or sampled motion of the actual tracker. The theory prodicts the transient-response performance of the tracker as well as the mean-square errors caused by noise and statistical fluctuations in the signal. Numerical examples of first-order and second-order trackers designed by this technique are presented. These examples illustrate the adaptive behavior predicted by the technique. In one of these examples the trade-off between transient-response performance and the suppression of noise-induced tracking errors is demonstrated. 相似文献
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The problem treated here is the analysis of a class of nonlinear sampled-data systems with a Gaussian input signal. The nonlinear element is a symmetrical limiter (memoryless device) that feeds the linear element. Preceding the limiter is a sampler and zero-order hold unit for data reconstruction. The analysis is predicated on finding an equivalent gain for the nonlinear element such that the mean-square error is a minimum. The nonlinearity is thus replaced by a linear component and the system is then analyzed by conventional techniques. It is also shown that for appropriate sampling rates the sampled-data system is equivalent to a continuous system due to the action of the sampler-hold combination. All calculations pertaining to the limiter input signal require the use of a transfer function that is interior to the feedback loop. However, in developing this transfer function, the overall system is considered so that the system output may be evaluated after the value of equivalent gain has been found. 相似文献
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A sampled-data delay-lock loop (SDDLL) which tracks the arrival time of a biphase modulated, pulsed-envelope RF signal is described. A pseudo-noise (PN) code generator is used as the modulation source as in conventional delay-lock loop tracking devices. Time base shifting of the loop's local clock is performed by digital means. The technique permits the use of a stable-frequency clock to maintain accurate timing between timing correction instants. An expression is derived for the standard deviation of the timing error due to additive Gaussian noise at the SDDLL input. Experimental results are then given which include the effects of control-system quantization error on timing jitter. Assuming that the errors due to input noise and quantized timing corrections are independent and additive, the theoretical and experimental results agree to within approximately one decibel. 相似文献
7.
This work investigates the performance of an all-digital, total-power radiometer (TPR), consisting of RF, mixer, and IF stages followed by an analog-to-digital converter (ADC). Square-law detection and smoothing is performed in a digital computer. A figure of merit, the degradation factor, is defined which compares the digital TPR with an ideal analog TPR. Exact results are obtained which include the effects of saturation, finite step size, and finite sampling rate of the ADC. A good approximation is developed which compares favorably with the exact results under certain conditions. The use of a general digital filter for smoothing is considered. A new parameter, the ?equivalent summation number?, is shown to be analogous to the equivalent integration time of an analog TPR. 相似文献
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试验室环境试验试验项目剪裁专家系统 总被引:2,自引:0,他引:2
说明了某型军用飞机机载设备试验室环境试验试验项目剪裁专家系统的基本情况, 定义了试验室环境试验试验项目剪裁专家系统, 同时利用关系型数据库语言VF6. 0编写了环境试验剪裁专家系统软件,说明了建立的过程及方法, 介绍了剪裁专家系统软件的部分功能及使用方法。为说明专家系统应用的实际过程, 文章最后结合某型飞机机载设备环境试验工作的具体情况, 利用本文介绍的专家系统对某型号任务计算机进行了试验室环境试验试验项目剪裁分析。 相似文献
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Power electronic circuits which contain nonlinear inductances are described by a set of nonlinear state equations. The author presents a sampled-data model for the circuit from which a set of linear state equations can be formulated. In the sampled-data model, the nonlinear inductor is modeled by an ideal sampler, a variable gain, and a clamp. The state variables for the circuit are updated during the simulation using a three-step procedure. One step involves the solution of the linear state equations using a technique such as the state transition matrix approach. Two additional steps are employed to account for the effects of the ideal sampler, variable gain, and clamp.<> 相似文献
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结构惯性参数动态测试与识别 总被引:4,自引:0,他引:4
提出了一种结构惯性参数测试、识别方法。采用试验模态分析技术,将被测结构柔性悬挂,对结构激振,测量激振力和响应,经信号处理、参数识别,最后可得到结构的质量、质心坐标、主惯性矩、惯性主轴等全部惯性参数。某直梁的计算机仿真计算及实际测试结果表明本文提出的理论方法是正确的、有效的。 相似文献
13.
Howard D.D. Sherman S.M. Thomson D.N. Campbell J.J. 《IEEE transactions on aerospace and electronic systems》1974,(6):779-787
The complex indicated angle technique, applicable to monopulse radars, is being investigated as a means of overcoming the serious degradation of elevation measurement caused by multipath when the target is within a beamwidth or so of the horizon. This technique makes use of the quadrature-phase component of the normalized difference signal, as well as the in-phase component. Results of analysis and computer simulation have been published previously. This paper reports results of a test program using a slightly modified AN/FPS-16 monopulse tracking radar and a simulated target. The results to date indicate a potential for high accuracy, though there are limitations as to the applications for which the technique appears feasible. A computer program has been developed to perform the elevation estimate and to resolve ambiguities. 相似文献
14.
在多层架构的分布式软件系统中,如何在层间交换数据,采用何种粒度的对象交换数据,是系统构建时经常遇到的问题。作为J2EE核心设计模式之一的数据传输对象模式的提出,就是为了解决该问题的。通过对数据传输对象模式的研究和分析,针对在架构基于Internet的、分布式的企业级应用中所遇到的问题,吸取了多数据传输对象模式的优点,结合工厂模式和策略模式,利用接口来抽象,提出了一种改进的数据传输对象模式的实现方案,并且应用到了实际软件项目中,从实践中证明了该解决方案是满足可插入性的设计原则的。 相似文献
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This paper describes the design of a digital cross correlator and its application in determining the impulse response in linear systems. The output of the cross correlator, which correlates the input and the output of a linear system excited by noise, is the same as the response of the linear system to a pulse which is identical to the noise autocorrelation. The impulse response error is defined as the normalized mean-square deviation of the actual from the true impulse response. A digital computer simulation confirms that the conventional technique yields the same impulse error as the correlation technique, when the width of the input rectangular pulse is equivalent to the width of the noise autocorrelation function. The operation and design of the digital correlator are discussed. An advantage of the specially designed digital correlator over a general-purpose digital computer is to operate in real time without problems of software and storage. The presented experimental and digitally computed results show that the digital correlator can accurately determine the impulse response, even in presence of perturbations. Only the correlation technique allows measurement of system impulse response without disturbing normal operation. Suggestions are made to simplify the design and improve the speed (bandwidth capability). 相似文献
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DMP-90型力学量综合校准装置 总被引:1,自引:0,他引:1
本装置针对一些小型企业和研究所其计量器具有多品种小批量的特点而开发研制出的综合性力学量校准装置,具有很强的适用性。本文着重介绍其原理及应用。 相似文献
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三维翼跨音速守恒型全位势流高效差分算法的应用 总被引:1,自引:0,他引:1
本文对跨音速守恒型全位势流,用Holst的高效有限差分算法,研制出分析三维翼跨音速流的实用程序。与Holst的TWING程序不同,本文用快速保角转绘生成二维正交O型贴体坐标网格,并以此为基础构造三维贴体坐标网格,因而节省网格生成的机时。本文不仅将方法用到有中等后掠的厚翼,还提供大后掠大根梢比薄翼的计算经验。对根梢比很大,前后缘后掠角相差非常大的机翼,指出本算法的困难,并分析了困难原因。 相似文献
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An analysis of false alarm effects on tracking filter performance in multitarget track-while-scan radars, using variable correlation gates, is presented. The false alarms considered originate from noise, clutter, and crossing targets. The dimensions of the correlation gates are determined by filter prediction and measurement error variances. Track association is implanted either by means of a distance weighted average of the observations or by the nearest neighbor rule. State estimation is performed by means of a second-order discrete Kalman filter, taking into consideration random target maneuvers. Measurements are made in polar coordinates, while target dynamics are estimated in Cartesian coordinates, resulting in coupled linear filter equations. the effect of false alarms on the observation noise covariance matrix, and hence on state estimation errors, is analyzed. A computer simulation example, implementing radar target tracking with a variable correlation gate in the presence of false alarms, is discussed 相似文献
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计算机辅助设计技术是计算机应用的重要发展,是计算机科学的一个重要组成部分。电路分析的专用语言是模拟电路的计算机辅助设计或辅助分析技术(简称为CACD和CACA)的基础。 电路分析语言ECAL是利用FORTRAN语言对语句进行解释执行的一种比较简单,而使用又比较方便的电路分析专用语言,它能对电路进行直流分析、交流分析和暂态分析,而且直流分析的结果可以直接作为交流或暂态分析的初始条件而转入交流或暂态分析。 ECAL语言用接近电路工程人员习惯的输入语句来描述电路,允许使用的元件除常规线性的如电阻、电容、电感、电流源、电压源等以外,还允许使用二极管、晶体三极管和非线性电阻等非线性元件,因此它可以对线性或非线性电路和系统进行分析。 ECAL语言用简单的输出语句来控制分析结果数据的输出形式,它可以是表格、也可以是图形以适应不同的需要。因此它对于工程技术人员来说是一种很有用的分析工具。 相似文献