Unavailability analysis of periodically tested standby components

General recursive models are developed for the unavailability and the mission-failure probability of standby equipment subject to periodic testing. The analytic approach allows general distributions for the failure times, test durations, and repair times. It accounts for start-up failures, standby failures, and failures during mission, as well as several categories of human error. Explicit expressions are derived for the unavailabilities and approximate optimal test-intervals for constant standby failure rate     

平面有效散（反）射区的计算公式

三本著名著作给出的平面有效散（反）射区（椭圆）的位置与尺寸的计算公式都有不正确之处，本文推导出它们的正确计算公式 。     

Sensitivity analysis of a coherent system

For the purpose of improving the reliability of a system, several methods can be adopted such as “improvement method”, “redundance method” and “standby method”, which are discussed later. An example is given to show that it is probably better to give a redundance to the component which has lower probability importance than to another which has higher probability importance. So, the new concepts of redundancy sensitivity and standby sensitivity are proposed and the simple relation between these and probability importance is revealed. Moreover, some new results are also presented in this paper.     

A closed-loop coherent PN acquisition system with a pre-loopestimator

We propose a closed-loop system with a pre-loop code phase estimator (PLE) for acquisition of the pseudonoise (PN) signal in direct-sequence spread-spectrum systems. It consists of two major parts: a PLE and a closed-loop acquisition subsystem. The system uses an auxiliary signal, as opposed to the PN signal itself, to correlate with the incoming signal. The PLE uses the correlation result to obtain an estimate of the incoming code phase. Then, starting with this initial estimate, the closed-loop subsystem will acquire the code phase of the incoming PN signal. With coherent carrier demodulation, mean and variance of the acquisition time of the proposed scheme are obtained and compared to those of the conventional serial-search acquisition receiver and the closed-loop system without the pre-loop estimator. Results show that, with proper choices of parameters, the proposed system acquires the PN phase significantly faster than the other two systems     

(Almost) periodic moving average system identification using higherorder cyclic-statistics

This article addresses the problem of (almost) periodic moving average (APMA) system identification. Two new normal equations relating the coefficients of an APMA system and the time-varying higher order cumulants of the measurements are established, from which two new linear algebraic algorithms are presented for system parameter estimation. In addition, a new singular value decomposition (SVD) based algorithm is proposed for determining the system order. Simulation examples are given to demonstrate the performance of these new approaches     

SU(1,1)相干态场与四能级原子相互作用系统中的场熵演化特性

利用双模SU(1,1)相干态场与四能级原子相互作用系统的态函数导出了场熵的计算公式,研究了初始光场参量和原子与光场间的耦合系数对场熵演化的影响.数值计算表明:随着初始场q和ζ参量的增加,场熵的均值逐渐增加,振荡频率增大,场熵演化的周期性随ζ的增加渐趋明显,但振荡幅度却明显减小.同时,随耦合系数的增大,场熵演化曲线的均值变化不明显,而其振荡频率急剧增大,振荡幅度也有所减小且趋于稳定,场熵敏感于原子与光场耦合系数.     

A definition of average time delay for a linear system

A definition is formulated for average time delay in a linear system having a nonlinear phase characteristic. The concept is based upon the determination of the time delay which minimizes the mean-square error between input and output signals.     

MTBF of a complex binary coherent system

It is noted that there has yet been no detailed study of the relationships between the MTBF (mean time between failures) of a system and the sequences of component failures, except for the case of a series system where every component failure causes a system failure. The author defines MTBF anew and derives relationships between the properties of the MTBF of a binary coherent system and the properties of the sequences of component failures, assuming that the lifetime distributions of the components are either new-better-than-used (NBU) exponential or increasing failure rate (IFR). Lower bounds of MTBF that can be used to predict the MTBF and to decide whether the system would satisfy the MTBF requirement are derived     

Clarke components for a system of busbars with pronounced proximity effect

The equations governing multiple straight transmission lines are applied to a configuration of three lines in the same plane. By a transformation with a matrix T, corresponding to the Clarke components, the propagation coefficients and modes can easily be found. A numerical example is given of three busbars showing pronounced proximity effect. The example is calculated by analogue simulation on a capacitor-resistor network.     

Phase-noise-free coherent optical communication system utilizingdifferential polarization shift keying (DPolSK)

An optical communication system utilizing differential polarization modulation, which is free from phase noise, is discussed. The system proved to be immune to essentially all phase jitter. Separate square operations for the x and y channels, followed by multiplication of the two-channel outputs, effectively removed phase jitter. The delay-and-multiply circuit was directly incorporated in the paths of the frequency shifter and the coupler to the local oscillator laser, minimizing the optical power loss     

A phase-control approach for a large-element coherent microwavepower uplink system

Signal combining efficiencies of 98% have been achieved on low-Earth orbiting (LEO) debris with phase-locking of time-overlapped radar pulses from a two-element phased-array consisting of two 34-m beam waveguide steerable paraboloid antennas separated by 204 m. The uplink arraying at 7.19 GHz has been achieved for tracks from about 10° elevation at signal rise to 4° elevation at signal set under varying weather conditions (e.g., hail failing on one antenna). The typical root mean square (RMS) phase error for two coherent 100-μs 50-Hz 5-kW peak pulses reflected from LEO debris with signal-to-noise ratio (SNR) >23 dB is less than 4°. The phase-control system design, methods of calibration, and details of the design control table of phasing error contributors are presented and discussed. Based upon the measured performance, we predict that transmitting antennas for the Deep Space Network (DSN) could be coherently arrayed for up to hours at a time given static phase error calibrations on exo-atmospheric debris. Applications for this technique include low-cost implementation of high-power microwave transmitters for deep-space communication and radars for exploration of other planets and as part of a defense against comets and asteroids     

A method for reducing the channel spacing in a coherent opticalheterodyne system

A method of channel allocation for the reduction of the channel spacings in a heterodyne optical transmission system is proposed and analyzed for the specific case of frequency shift keying (FSK). This technique makes it possible to reduce the average optical interchannel spacing by an amount approximately equal to the intermediate frequency. This can increase the number of channels that can be accommodated within the generally limited continuous tuning range of commercial lasers employed as local oscillators by as much as 100% without the need for auxiliary equipment     

Formulae for determining heterodyne system spurious frequencies that coincide with desired output frequency

In this paper, formulae to determine the lowest order and other higher order spurious frequencies that coincide with desired output signal frequencies of mixers have been derived. The proposed formulae give general expressions that are suitable for any order of heterodyne mixing. The formulae have been verified using a suitable example and compared with the simulation results obtained through the radio frequency simulation software of Advanced Design System. The formulae directly reveal the order of the troublesome spurious frequencies that the designers would encounter in heterodyne systems. In comparison with these direct formulae, the results of existing spurious analysis software are based on the maximum order of simulation carried out. Based on these simulations, the coinciding spurious components have to be manually sorted out. Proposed formulae are quick tools used by the microwave system and circuit designers for choosing and finalizing heterodyne frequencies in their designs without the need for any simulations.     

An example of a hybrid system: coherent optical system with Costasloop in receiver-system for transmission in baseband

The possibility of hybrid system construction is considered in this paper. The coherent optical system is the constituent part of this system. The first part of the system is constructed in passband (optical cable is transmission medium), and the second part of the system is constructed in baseband. The heterodyne optical receiver is used as optical receiver. Estimation is not done just after demodulation, but it is done at the end of the section in baseband. Taking into account shot noise of photodetectors, laser phase noise (transmitter laser and local laser) and noise which is generated during transmission by means of the section in baseband, we determine the performances of the proposed system     

Optimal inspection and replacement of a coherent system

In this paper the problem of optimal inspection and replacement of a coherent system with components having exponential life-time distributions is studied. It is assumed that the states of the components are known at system failures and through checking. The problem is formulated in a semi-Markovian decision process framework.     

A reliability model of a system with dependent components

A model of a multi-component system with dependent components in the time stationary case is presented. A procedure fits the parameters of the model with respect to given data such as the correlation coefficients. The system reliability of the fitted model is evaluated     

新型机器人视觉系统准直相干光束的获取

论述了一种新型的机器人视觉系统所用激光准直光束的获取方法,分析了半导体激光束的像散椭圆高斯光束特性,设计了光束准直系统的光学结构,利用光斑法对准直度进行了检验。实验证明利用这种方法获取的直光束符合该视觉系统的要求。     

Minimal-cost system reliability with discrete-choice sets for components

We focus on systems whose components come from discrete choice sets. In a choice set, the alternatives have increasing cost with increasing reliability. The objective is to ensure minimal cost for achieving a specified reliability for the systems under consideration. Earlier work restricted itself to series-parallel/parallel-series (S/P) systems and provided formulations and algorithms. However, these are not amenable for dealing with more general systems. In this paper, we develop alternative formulations and algorithms based on a dynamic programming approach, and these are generalized for S/P-reducible systems. The algorithms we obtain are pseudo-polynomial and possess fully polynomial approximation schemes. Moreover, the formulations & algorithms are amenable for further generalizations to k-out-of-n : G and k-out-of-n : G-reducible systems, though we cannot claim pseudo-polynomiality in these cases. The results of this paper are useful for developing reliable systems at minimum cost. As such, the formulation & algorithms are of vital interest for systems & reliability professionals & researchers.     

Two-channel coherent optical FDM transmission system with a new frequency stabilisation scheme

A two-channel 140 Mbit/s coherent optical FDM transmission system with a new frequency stabilisation scheme has been developed. In this scheme, low frequency modulation is applied to transmitter laser diodes to lock them at the resonances of a Fabry-Perot interferometer, and a high speed IF AFC circuit is used to eliminate the system performance degradation due to this low frequency modulation. The measured BER is 10/sup -9/ for a received signal power of -41 dBm and no crosstalk between channels is observed with a channel spacing of 4.0 GHz.<>