Performance-related reliability measures for a repairable two-unit gracefully degrading system

The system analysed is a two-unit gracefully degrading system with repair. After each repair, the unit is tested to see if the repair meets certain predefined specifications. If it does, the unit is put to operation, otherwise it goes to post-repair. The failure-time and testing-time distributions are exponential whereas all other distributions are arbitrary. The technique of embedded SMP is employed to obtain several system performance parameters, namely, MTFF (mean time to first failure), availability, computational availability, expected number of visits to a certain state etc.     

The nonhomogeneous Poisson process — A model for the reliability of complex repairable systems

Generally the reliability of complex repairable systems is characterized by time dependent rate of occurence of failures. The corresponding mathematical model is the nonhomogeneous Poisson process. This paper comprises mathematical properties of the nonhomogeneous Poisson process, some frequently used types of failure intensity functions, and some results and aspects of statistical inference. The given models are applicable to the reliability of complex repairable systems, software systems, and to the reliability growth problemacy.     

A new method to compute reliability of repairable m-out-of-n systems by arbitrary distributions

In this paper it is presented a new method to compute reliability characteristics of repairable m-out-of-n systems by arbitrary distributed time to failure and time to repair. The method allows to consider the systems with large number of units and does not take much computational times.     

An optimal replacement policy for a three-state repairable system with a monotone process model

In this paper, a deteriorating simple repairable system with three states, including two failure states and one working state, is studied. Assume that the system after repair cannot be "as good as new", and the deterioration of the system is stochastic. Under these assumptions, we use a replacement policy N based on the failure number of the system. Then our aim is to determine an optimal replacement policy N/sup */ such that the average cost rate (i.e., the long-run average cost per unit time) is minimized. An explicit expression of the average cost rate is derived. Then, an optimal replacement policy is determined analytically or numerically. Furthermore, we can find that a repair model for the three-state repairable system in this paper forms a general monotone process model. Finally, we put forward a numerical example, and carry through some discussions and sensitivity analysis of the model in this paper.     

A birth and death model for computing the reliability of a transmission network

This paper considers the finding of an optimal complete repair strategy for a 3 state system with Markovian deterioration. The approach followed here is based upon optimizing a function of both a reliability index for the system, which is chosen here as the expected systems lifetime, and the cost of achieving this reliability index.     

Electromigration reliability evaluation for a three-level metallization process

The electromigration behaviour of triple level Al-1%Si-0.5%Cu thin films is presented as used in a metallization process necessary for high-density CMOS (HDCMOS) ASIC technology. A prediction time-to-failure (TTF_x) formula has been fit and the 0.01% cumulative-failure-function F(t) vs. time has been calculated. Reliability improvement was achieved by using test vehicles baked for t=1400 hrs at T=200°C.Maximum current density design rules are derived as a function of the sigma value for each metal level.     

Autocorrelation function of the quantisation-error process for a sinusoid

This letter investigates the variation in the correlation function of a quantisation-error process with the width of quantisation for a sinusoidal-input process. This process does not comply with the quantisation theorem of Widrow, and, in consequence, the orthogonal expansion procedure of Barrett and Lampard is the adopted analysis technique. The results clearly establish that, for this input, the quantisation-error spectrum is white for practical purposes, even when the quantisation is very coarse.     

Characterization of the calcification process modeled in rat embryonic calvarial culture

An organ culture system to model the physiological calcification process was designed using rat embryonic calvaria as a device for analyzing its mechanism. Standardized calvarial explants were dissected from rat embryos aged 18 and 20 days (E18 and E20) and cultured for 1, 3 and 5 days. The calcium content of the cultured explants was quantified by atomic absorption spectrophotometry. Equivalent explants were fixed, embedded in paraffin, sectioned and stained with von Kossa stain combined with hematoxylin-eosin or processed for energy-dispersive X-ray spectroscopy to determine the concentrations of calcium, phosphorus and carbon in the tissue. The total calcium content increased significantly in E18 and E20 cultured calvaria (E18cc and E20cc) over 5 days of culture. All cultured calvaria were von Kossa-positive, whereas the staining was intensified, and sound osteoblasts and osteocytes were observed in the bone matrix only in E18cc during the 5-day culture period. Concentrations of calcium and carbon increased significantly in E18cc over 5 days, whereas E20 showed little increase. Physiological calcification proceeded in E18cc, but not in E20cc. These results indicate that the organ culture system using E18 calvaria is useful for modeling the physiological calcification process in vitro.     

一种高可靠性SMD型片式NTCR的工艺设计

为进一步提高SMD型片式NTCR性能的可靠性和增加其对机械应力的抵抗力,采用高聚物代替玻璃釉进行瓷体的外包封和柔性材料处理元件端头,对片式NTCR的结构和工艺路线作了改良设计。对所制0603规格元件进行了可靠性试验。结果显示:产品的稳态湿热和耐湿性能提高了25%,引出端镀层连接强度提高了100%。     

Bayes prediction for the number of failures of a repairable system

After observing a repairable system for some time, one may wish to predict the number of failures of the system in some fixed future interval. Such a prediction depends on the: (1) assumed model for the failure process; and (2) length of the interval. The authors use a Bayes approach to obtain point and interval predictions for the number of failures in a future interval. Two situations are discussed: (1) the power law process (PLP) governs failure times during the period of observation, but in the future interval the homogeneous Poisson Process (HPP) governs the failure times; and (2) the failure process is the PLP. A rationale and an example of each situation is presented. They discuss the use of informative and noninformative priors for the parameters of the failure process. The Bayes approach can incorporate both sources of uncertainty: (1) the number of failures in the future interval is random, so even if the parameters of the failure process are known, the number of failures that would occur in a future interval would still not predict with certainty; and (2) the parameters of the failure process are not known and must be estimated from the observed data     

Estimation of system reliability for uncooled optical transmittersusing system reliability function

This paper investigates the system reliability for 155 Mb/s optical transmitters by deriving a system reliability function from reliability data of each component for transmitters, laser diode, photodiode, optical assembly, and driver IC. The reliability data for each component reliability function have been obtained from accelerated aging test. The reliability parameters such as failure rate, mean time-to-failure (MTTF), standard deviation are obtained from a probability plotting method. From the system reliability function, the MTTF of the optical transmitter at 65°C was estimated to be 47000 h with 95% confidence. In this estimation, we introduced modified lifetime of laser diodes and reliability function of optical assembly     

Reliability analysis of a repairable system in a changing environment subject to a general alternating renewal process

This paper considers a repairable system in a changing environment subject to a general alternating renewal process. Using Markov renewal theory we obtain the system availability, failure frequency and reliability function.     

Development of a reliability strategy for new IC component family and process

Development of a credible reliability strategy for the new IC component family and process advancing some aspects of the technology state-of-the-art presents the reliability management with a challenging task, because the new material quality levels and combinations, the new requirements on dimensional tolerances, new impacts of process variations, etc., will result in new, difficult to predict failure mechanisms. However, the managerial need to have a reliability strategy early in the development or planning stages is justified by the risk and cost levels involved.One possible approach to avoid the undefined technological aspects of the problem and still propose an acceptable strategy, an approach developed for the Hewlett-Packard Desktop Computer Division technology operation, is based on the combination of an empirical reliability model with reliability cost models. The behavior of model parameters in time and their values, reflecting different design for reliability and manufacturing screening scenarios, can be estimated with reasonable accuracy which, in turn, allows studies leading to optimum strategy. And, of course, reliability strategy minimizing total cost of reliability and optimizing the cost allocation among R & D, manufacturing and warranty is usually acceptable to all parties involved.This paper describes the logic and the mathematical structure of the models and their application to the development of HP's NMOS process and chip family, with examples of actual parameters used and optimization studies performed. The study results, stated in failure rate, number of expected redesign cycles and screening strategy, are then compared with the actual reliability observed in the field use of manufactured components. This favorable comparison justifies the proposed approach to reliability strategy development, demonstrates the usefulness of the underlaying models and shows a successful example of managing towards maximum productivity of resources dedicated to reliability.     

Calculating the failure frequency of a repairable system

Failure frequency is an important parameter of a repairable system. Combining the techniques of cut set, tie set and exclusive manipulation, a general formula has been derived in this paper. It can give the exact result at any point of time for systems whose component failure and repair times are arbitrarily distributed.     

Function process and reliability analysis of a two-dependent-unit system

In this paper, a two-dependent-unit system is discussed. We assume that the life distribution of the two units is a two-dimensional exponential distribution, and the repair distributions are general distributions, respectively, and the failure unit cannot be repaired “as good as new”. By using a function process, some reliability indices are derived.     

A reliability simulation approach for use in the design process

A simulation model for use in the engineering design process is reported. The simulation model facilities reliability modeling by design engineers and reliability analysts early in the design process. The model applies to preliminary feasibility and design tradeoff studies. The authors describe the model, focus on applications to mission reliability analysis, and give a case study for the voice-communication system of the F-16 fighter aircraft     

Reliability modeling algorithms for a class of large repairable systems

The reliability performance of some multistate large repairable systems cannot be described by a dichotomy of success and failure but by probability and frequency distribution of several levels of performance, algorithms for reliability modeling of such systems consisting of several units, each contributing a finite amount to the total system capacity. The first algorithm describes system model building by the sequential addition of units and the second one can be used for taking off particular units from the system model. The algorithms are fast and can be easily implemented in a computer program.     

Bayes estimation of the extreme-value reliability function

The authors obtain Bayes estimates of the reliability function of the extreme value distribution by using two Bayes approximation procedures: Lindley (1980), and Tierney and Kadane (1986). These estimates were compared to maximum-likelihood estimates (MLE) based on a Monte Carlo simulation study. Jeffreys invariant prior was used in the comparison for both Bayes procedures. The MLE are superior to either of the Bayes estimates, except for small values of t. The simpler Lindley Bayes procedure gives estimates with smaller root-mean-square error than estimates obtained by the Tierney and Kadane procedure except for large values of t. From a practical standpoint, the ML method is easiest to use and more accurate for the extreme value distribution than the two Bayes approximation procedures. Both Bayes procedures seem to perform equally. However, the Lindley method is easier to use with little loss of accuracy     

关于机械制造工艺可靠性的研究

由于机械制造业这是我国第二重要性产业，机械制造业应该存在各个方面积极配合，这项工作复杂而且存在系统性，我国机械制造对比发达国家起步比较晚，面临着比较落后的技术，与国际制造业发展水平比较难跟上。混乱管理机制与短期机械研制时间，这也就导致我国长期存在比较多水平发展的机械制造水平与特别缓慢的发展速度。针对这样的情况，通过研究分析我国机械制造业与强化机械制造工艺可靠性研究存在十分重要的意义。     

Non-parametric distribution of the reliability function for some basic system configurations

In this study, non-parametric distributions of the reliability functions of some basic system configurations which are useful for making inferences about the reliability characteristics of the system are given.