First uptime and downtime joint distribution of a duplication system with random switching time

This paper deals with a 2-unit cold standby redundant system with random switching time and imperfect switchover. In model I we study the system without preventive maintenance (PM), but in model II we study the same system with PM. For the two models we find: (1) the joint distribution of the first uptime and downtime of the system; (2) the sojourn time distribution of the system down as a marginal distribution of the joint distribution; (3) the mean downtime.     

First uptime and disappointment time joint distribution of an intermittently used system

This paper derives the explicit expression for joint distribution of first uptime and disappointment time of an intermittently used 2-unit cold-standby redundant system. In particular we deduce the first disappointment time distributions as marginal distributions of the joint ones. At the end some special cases are derived.     

用于机载激光测深系统的时间间隔测量模块

机载海洋激光测深系统不仅要求精确测量激光从海表的入射点到海底目标点之间的距离,还要精确测定飞机到海表入射点之间的距离,为水深数据的海浪校正而确定平均海平面以及波高。为此设计和研制了一高精度时间间隔测量器,该单元基于专用时间数字转换芯片开发,采用延迟线插入法技术,双通道工作,具有高时间分辨率(最高可达250ps)和高测量重复率的特性。给出硬件和软件设计方法以及单元的测试结果。     

Distribution of time to non-availability of a reliability system

The author derives in this paper the distribution of the time to non-availability of a system which under-goes the following states, viz. (i) operative (ii) failed, and (iii) repair. Special cases are discussed and tables are provided at the end.     

Improvement of mini-fab uptime by using multitask and multifunctional tools

Multitask and multifunctional tools can process alternative operations, for example, LPCVD depositions of both Poly Si and SiN films with good repeatability and few particulates. Using those tools, we can reduce the total number of tools and the number of "only-one" tools which exist for a type of tool in the fab. We have also evaluated mini-fab availabilities using both a full calculation method and an approximate calculation method. The results show that tool reduction is more effective in obtaining good fab availability and uptime. The reduction of "only-one" tools is very important to improving mini-fab availability. The approximate calculation is simple for estimating the fab availability and offers the possibility to extend mega-fab estimations. It is also possible to use in the case that there are variations of MTTR, MTBF, and excess tool numbers.     

基于FPGA的时间间隔测量模块设计

介绍一种基于FPGA技术的时间间隔测量方法,通过分析FPGA的主要技术优势及其在工业控制领域中所处的重要地位,给出设计时问间隔测量模块所选用的FPGA器件并进行硬件设计,以及所选用的软件并进行软件设计.描述时间间隔测量模块的软件及硬件设计方法,给出设计过程的硬件原理图及软件流程图,并对设计的各功能模块进行功能时序仿真.     

The number of working periods of a repairable Markov system duringa finite time interval

In reliability analysis, continuous parameter homogeneous irreducible finite Markov processes are used to model repairable systems with time-independent transition rates between individual states. The state space is then partitioned into the set of up states and the set of down states. The number of completed repair events during a finite time interval is an important (undiscounted) cost measure for such a system; it can be expressed in terms of the number of working periods during the same time interval. This paper derives a closed-form expression for the PMF of this latter quantity. The tool used is a recent result on the joint distribution of sojourn times in finite Markov processes. The MatLab implementation of the Markov model of a 2-unit parallel power transmission system is used to demonstrate the utility of the formula. The quantity examined is the number of completed repairs during a finite time interval. The method is viable in this case whereas the more usual randomization technique is not     

Optimization of pulse radiation from dipole arrays for maximum energy in a specified time interval

The optimum solution for maximized radiated energy in a specified time interval from anN-element dipole array at a specified farfield position is presented. The solution is obtained in terms of time-domain dipole terminal voltages which are constrained in bandwidth and total input energy, with the currents on the dipoles satisfying Pocklington's integral equation. The orthogonality of characteristic terminal modes is used in the derivation of the optimum solution, and the far-zone field is expanded as a finite sum of characteristic modal fields with unknown mode coefficients. The optimum mode coefficients are found in terms of prolate spheroidal wave functions. An additional constraint can be used to find the optimum solution with a reduced sidelobe level. The effects of signal bandwidth and time interval specification on the peak field intensity and energy density in the direction of optimization are shown and limiting cases are found to agree with previous results.     

On minimum step response rise time of linear low-pass systems under the constraint of a given noise bandwidth

If the step-response rise time of a linear low-pass system is to be a minimum under the constraint of a given noise bandwidth, the systems parameters should be so tuned that the step response is strictly free from overshoot. This conclusion is also true when the system bandwidth is defined as its 3-dB bandwidth.     

Distribution of standard frequency and time signals

This paper reviews the present methods of distributing standard frequency and time signals (SFTS), which include the use of high-frequency, low-frequency, and very-low-frequency radio signals, portable clocks, satellites, and RF cables and lines. The range of accuracies attained with most of these systems is included along with an indication of the sources of error. Information is also included on the accuracy of signals generated by frequency dividers and multipliers. Details regarding the techniques, the propagation media, and the equipment used in the distribution systems described are not included. Also, the generation of the signals is not discussed.     

A BiCMOS time interval digitizer based on fully-differential,current-steering circuits

A time interval digitizer cell with a 0-16 ns input range and a nominal LSB width of 1.0 ns has been integrated in a 2-μm BiCMOS technology, The circuit exhibits both integral and differential nonlinearity below 0.15 LSB and a timing error of 0.32 ns RMS. Logic gate propagation delays are used as time measurement units, and the nominal value of the delays is set by an on-chip phase-locked loop (PLL). Fully-differential, current-steering circuits with low voltage swings are used to implement the time interval digitizer so as to generate minimal switching noise. The cell is to be used in the monolithic, multi-channel realization of a high-sensitivity, mixed-signal data acquisition front-end. By virtue of the time digitization architecture used, the average power dissipation of the cell is only 19.8 mW, despite the use of circuits that dissipate static power, and the layout area is a compact 448 μm×634 μm     

脉冲激光测距中高精度时间间隔系统设计

时间间隔测量系统采用基于时间数字转换芯片TDC-GP22实现了高精度脉冲激光测距。采用高性能STM32单片机作为主控器,SPLLL90_3半导体激光二极管,AD500-9作为接收的光电探测器。测量结果通过SPI通信接口传送给单片机,经单片机处理后的数据传给LCD12864显示器。测试结果表明,该测量方法精度可达65 ps,系统结构简单、可行性高。     

False alarm and correct detection probabilities over a time interval for restricted classes of failure detection algorithms

The statistical analysis of failure detection decisions in terms of the instantaneous probabilities of false alarm and correct detection for a specified failure magnitude at each check-time have previously been performed for several different failure detection techniques that utilize a Kalman filter. By performing a discrete-time specialization of a result of Gallager and Helstrom on a tightened upper bound for continuous-time level-crossing probabilities, upper bounds on the probabilities of false alarm and correct detection over a time interval have been obtained for the specific technique of CR2 tailnre detection (to allow an accounting for the effect of time correlations of the filter estimates). When these upper bounds are optimized to be as tight as possible to the desired probabilities, the resulting optimization problem for discrete-time is a collection of quadratic programming (QP) problems, which may easily be solved exactly without recourse to approximate solutions as were resorted to in the continuous-time formulation. This technique for evaluating tightened upper bounds on the false alarm and correct detection probabilities may be of general interest, since it can be applied to any failure detection technique or signal detection technique that can relate an exceeding of the deterministic decision threshold by the test statistic directly to a deterministic level being exceeded by a scalar Gaussian random process.     

时间间隔测量系统用于激光测距及其误差浅析

文中从影响激光测距精度的因素分析入手,提出了最具影响力的因素,阐述了提高测距精度的途径和方法,简要介绍了时间间隔测量（T.I.M）系统及其关键技术之一－－模拟扩展器的工作原理,从理论和实例两方面分析了引进该技术对提高测距精度的实际效果,分析了其中的利弊和应注意的问题。     

质心干扰中机载红外弹、箔条弹投放间隔时间的讨论

叙述了质心干扰中箔条弹、红外弹发射间隔时间不当的危害 ,通过公式推导给出了计算发射间隔时间的方法及步骤。     

Incentivize maximum continuous time interval coverage under budget constraint in mobile crowd sensing

Mobile crowd sensing has become an effective approach to meet the demand in large scale sensing applications. In mobile crowd sensing applications, incentive mechanisms are necessary to compensate the resource consumptions and manual efforts of smartphone users. In this paper, we focus on exploring budget feasible frameworks for a novel and practical mobile crowd sensing scenario, where the platform expects to maximize the continuous time interval coverage under budget constraint. We present the system model and formulate the budget feasible maximum continuous time duration problem for this scenario. We design two budget feasible frameworks: BFF-STI and BFF-BTI, and integrate MST as the truthful mechanism to maximize the social efficiency. Then we extend the budget feasible frameworks to the general case, in which each user can bid multiple time intervals simultaneously. We show the proposed budget feasible frameworks are computationally efficient, individually rational, truthful and budget feasible. Through extensive simulations, we demonstrate that our budget feasible frameworks are efficient with different parameter settings. The simulation results also show that BFF-STI has superiority in large scale mobile crowd sensing applications, while BFF-STI is more suitable for long-term sensing applications.     

Sequential interval estimation procedures for the mean exponential survival time and reliability function

The problems of confidence interval estimation are considered (a) for estimating the mean of a one-parameter exponential distribution and (b) for estimating the reliability function associated with the one-parameter exponential distribution. For the estimation problem (a), the confidence interval of ‘preassigned width and coverage probability’ is considered. For the estimation problem (b), the confidence interval of ‘fixed-ratio width and preassigned coverage probability’ is proposed. The failure of the fixed sample size procedures to deal with these estimation problems is established and sequential procedures are proposed to deal with them. The proposed sequential procedures are proved to be ‘asymptotically efficient and consistent’ in the Chow-Robbins [Chow and Robbins, Ann. Math. Statist. 36,457–462 (1965)] sense. Asymptotic distributions of the stopping times are derived and second-order approximations are obtained for the average sample numbers associated with them.     

Fitting a bandlimited signal to given points

One of the fundamental problems in communications is the transmission of a signal through a bandlimited channel. It should, therefore, be of great interest to find a general method of transmitting an arbitrarily close approximation to any finite signal through a channel which is arbitrarily bandlimited. The present paper develops such a method and evaluates the cost in time and energy to accomplish this feat. The problem of fitting an arbitrarily bandlimited signal to a finite number of arbitrary points is solved, and the minimum energy signal, fitting the points and having a spectrum confined to the given pass band, is found. The behavior of this signal, with shrinking bandwidth, is investigated.     

Short codes with a given covering radius

The covering radius r of a code is the maximum distance from any vector in the space containing the code to the nearest codeword. The authors introduce a new function l(m,r), called the length function, which equals the smallest length of a binary code of codimension m and covering radius r. They investigate basic properties of the length function. Projective geometries over larger fields are used to construct families of codes which improve significantly the upper bound for l(m,2) obtained by amalgamation of Hamming codes. General methods are developed for ruling out the existence of codes of covering radius 2 with a given codimension and length resulting in lower bounds for l(m,2). A table is presented which gives the best results now known for l(m,r) with m⩽12 and r⩽12     

Synthesis of a slot radiator with a given radiation pattern

Synthesis of a slot cylindrical radiator with a given radiation pattern is studied. For a Gaussian pattern, the phenomenon of superdirectivity is analyzed and the parameters of the radiator providing for the optimal spread in the orders of the amplitudes of the currents on slots are estimated.