Coordinated warranty and burn-in strategies

In product reliability assurance, the warranty and burn-in (W&BI) strategies are usually selected separately, despite the fact that both depend on the early-life failure behavior of the product. This paper treats W&BI strategies together in order to examine the possible benefits of coordinated strategies for product performance management. As these strategies are meaningful only for decreasing hazard-rate systems, a Weibull life distribution is assumed for each system component. A net-profit model that includes an increase in product price as a function of warranty duration is constructed. The model shows how a coordinated W&BI strategy can be selected. The model is quite general and its extension to other cases is explained. A central point that is treated thoroughly is the renewal analysis necessary to determine replacement costs during burn-in and during the warranty period. As part of the analysis, a useful approximation is defined, and efficient optimization routines are identified. An example illustrates the use of analytical methods. The analysis and discussion of the example show that there are advantages in coordinating the selection of W&BI strategies     

Optimal repair-cost limit for a consumer following expiry of a warranty

Previously, repair-cost limits have been determined only for the producer; or the consumer has been assumed always to replace the product on failure outside the warranty period without the possibility of a minimal repair. This paper discusses the optimal repair-cost limit to the warranty literature. The objective is to find an algorithm to obtain the optimal repair-cost limit for the consumer which minimizes his long-run expected cost rate.     

Maintenance strategies for PCM circuit switching

During all the system design phase of an SPC switching system, a considerable effort is devoted to maintenance, both from a hardware and software point of view. The maintenance phases include fault detection, fault analysis (e.g., identification of the faulty security block within the switching system), fault isolation, fault reporting, fault localization, fault clearance, and restoration to service with the eventual requalification and reinitialization of the repaired security block. The paper mainly discusses fault detection and fault analysis strategies with specific reference to PCM digital switching systems. Different means leading to fault detection are presented with reference to central control, network access devices (scanners, drivers, markers), and digital switching network (duplicated or not duplicated). These means include automatic on-line tests (monitoring and routining), on-demand on-line tests, and alarm handling. Fault analysis can be accomplished by means of a deductive or a statistical method. As the latter seems more attractive, three basic methods of statistical fault analysis are presented. They use, respectively, two counters (operation and fault counter) per security block; one fault counter per security block; one "historical" fault stack, in which all the identities of security blocks involved in faulty operations are stored. The above fault analysis strategies are compared mainly in terms of core memory occupancy, processor time, and software complexity.     

Timer expiration time of selective repeat protocol

Timer expiration times shorter than round-trip time are shown to possibly yield superior efficiency of selective repeat protocols, especially in the case of higher delay-bandwidth products and higher bit error rates. Both three-layer and two-layer communication system models are considered. A new timeout management strategy is proposed to be used in a two-layer system allowing a safe decrease of timer expiration time without the risk of inter-layer congestion. Simulation results confirm expectations, and the proposed strategy is compared with previously known multiple-copy transmission methods.     

Discounted warranty cost of minimally repaired series systems

Many factors should be considered in modeling DWC (discounted warranty cost) of repairable systems or products including system structure, components' failure processes, methods of discounting as well as the warranty policy itself. In this paper, we present DWC models for repairable series systems. In particular, a free repair warranty policy and a pro-rata warranty policy are studied. The impact of repair actions on components' failure times is assumed to be minimal, hence NHPPs are used to describe the failure processes. Two types of discounting methods are considered in this paper: a continuous discount function and a discrete discount function. Expressions for both the expected value and variance of DWC are derived. The applications of our findings can be seen in warranty design, warranty reserve determination and risk analysis. Our approach incorporates the information of system structure, the value of time and the impact of repair actions, which are of great importance to warranty cost prediction and evaluation, but have not been sufficiently studied in the literature of warranty analysis.     

An examination of correlation effects among warranty claims

This paper models & examines the impact of correlation in a failure arrival process which generates a warranty claim with each occurring failure. We show that even slight positive correlation in the warranty claims arrival process can significantly impact the expected number of claims observed, and the length of the transient period. We are not suggesting that renewal processes are necessarily inappropriate or incorrect as models for the arriving warranty claims process. Rather, we emphasize the importance of considering correlation in the claims arrival process, and suggest that more research is needed to explore mathematical models which explicitly consider correlation in the warranty analysis framework.     

The following the perturbed leader algorithm and its application for constructing game strategies

A modification of Hannan’s Following the Perturbed Leaded (FPL) algorithm for the case of unlimited gains and losses is considered. Estimates of the prediction error are obtained in terms of the volume v _t and game fluctuation fluc(t) = Δv _t /v _t , where Δv _t = v _t –v _t–1. We prove the asymptotic consistency on the average of this variant of the algorithm for fluc(t) = o(t). Applications of this algorithm for constructing game strategies are considered. Game strategies employing the difference between the “micro” and “macro” volatility of the discrete time series (prices of the financial instrument) are determined for obtaining arbitrage. Mixing these expert strategies is performed on the basis of the variant of Hannan’s algorithm developed in this work.     

Cost analysis of two-attribute warranty policies based on theproduct usage rate

In the so-called two-attribute warranty policy, two types of warranty criteria, such as the age and mileage of an automobile, are employed simultaneously to determine the eligibility of a warranty claim. The authors propose in the paper several decision models that estimate the expected total cost incurred under various types of two-attribute warranty policies. They also perform a sensitivity analysis to study the effects of several model parameters, such as the discount rate, the product usage rate, and the warranty terms, on the total warranty cost     

有限资源条件下新装备维修保障最优策略研究

针对售后服务期内厂家所提供的新装备等产品的预防维修保证策略进行研究.首先建立了资源有限条件下的产品维修成本模型,分析了最优策略的结构及特性,并根据这些特性来确定有效的算法,寻求最优维修次数及维修时机,使得总平均保证成本达到最低限度.最后,针对威布尔寿命分布来推导最优策略.     

The inspiration and expiration DFT spectra for the detection of airways obstruction in human beings

Spectral analysis of inspiration and expiration of the respired volume enables one to not only compare the state of the pulmonary system during the two phases of breathing but also enables one to compare the spectra of normal subjects with those of patients with respiratory ailments. Statistical analysis of the DFT amplitude spectrum of inspired and expired volume of the deep and rapid (DR) breathing maneuver clearly indicates that it is significantly larger in normals (free from AWO) than in patients with airways obstruction (AWO).A multivariate discriminant approach is used to develop a linear discriminant classifier rule. The rule shows that essentially two parameters, viz. the normalized fundamental DFT coefficient of inspired and expired volume of the DR breathing maneuver, contain most of the discriminating information and a linear discriminant function based on the two variates gives a good classification between normals and abnormals.     

浅谈医疗设备的维修与保养

医疗科技在不断地发展,近几年我国医学方面的成就也是可圈可点,重点开展了心脑血管疾病、肿瘤、糖尿病、口腔疾病等的预防控制,医疗工作人员更是遵守职业操守,在自己的岗位上默默奉献着,推动我国医疗技术的发展。紧跟新兴医疗技术的发展,先进的医疗设备也必不可少,从某种程度上讲,其重要性甚至超过了医疗技术本身,就像是枪里的子弹,弓上的箭一样,没有过硬的医疗设备,医疗科技再怎么发展也是纸上谈兵。关于医疗设备,维修和保养极为重要,文章就这两个问题展开详细地阐述。     

Tool assisted H.323 dial‐plan design following formally defined strategies

This paper considers H.323 v4 VoIP networks consisting of gateways and gatekeepers, addressing the task of terminating calls to multiple ISDN networks. Our goal is the maximal utilization of the gatekeeper's centralized routing mechanism for call termination to ISDN networks based on load balancing and resource availability indication (RAI), thus minimizing the need for usage of unwanted (second attempt) overflow mechanisms. We elaborate on the drawbacks of overflow mechanisms and give an overview on different solutions offered in practice by vendors. The discussion justifies the emphasis on load balancing, thus we present an algorithm and tool assisted approach for the systematic assignment of PRIs from ISDN networks to gateways. We follow strictly defined design criteria that lead to an optimized network dial‐plan. We thus offer a stand alone, off‐line solution without the need of any extra add‐ons or upgrades. This is intended to replace the purely intuitive approach followed by today's planners. Our scope is the design rather than the runtime environment; the latter continues to feature the simplicity of a single global RAI per gateway. We consider desirable and non‐desirable link distribution topologies between gateways and ISDN networks based on operational and economic evaluation criteria. These measure the number of ‘wasted’ gateway ports or ‘inappropriately’ allocated network interfaces. Our approach is illustrated through a worked out example showing key features of the proposed algorithm and revealing characteristic cases met in the ISDN interface allocation. Finally, we show how the presented methodology, which presently addresses a H.323 design issue, can provide performance benefits in the VoIP technologies of the immediate future. Copyright © 2005 John Wiley & Sons, Ltd.     

基于状态检修模式下变电检修技术的运用探讨

随着科技的发展,很多领域都可以运用科学技术的优势,实现行业发展的创新,其中,电力行业与科技的融合,是在电网运检技术中加入信息技术,对电网运行情况进行实时监测,以此保障电网的稳定可靠运行,但新技术应用时,依然会遇到不同的问题.故本文是以检修模式为切入点,分析变电检修技术的运用.     

显微镜的维护保养

(一)必须熟练掌握并严格执行使用规程。(二)取送显微镜时一定要一手握住弯臂,另一手托住底座。显微镜不能倾斜,以免目镜从镜筒上端滑出。取送显微镜时要轻拿轻放。     

仪器仪表的计量维护探讨

仪器仪表是测量技术的关键和基础,现代仪器仪表在当今社会具有极为重要的作用,现代仪器仪表的计量与维护发展水平,是国家科技水平和综合国力的重要体现。文章对电子仪器仪表的计量与维护做了相关探讨。     

浅谈江森动力监控系统的维护

介绍了美国江森动力监控系统－－Metasys的一般结构，并结合其网络设备的功能，探讨了在通信企业中对江森动力监控系统维护的注意事项及故障检修的一些方法。     

计算机局域网的维护

介绍了计算机局域网的基本知识，具体分析了计算机局域网的硬件设备和网络协议的使用环境，详细介绍了交换机与集线器之间的不同之处、组建计算机局域网时如何正确选用网络协议。在总结个人工作经验的基础上，详细介绍了网络维护时常见的几个软件工具的使用方法。     

电子设备的维修技术

电子设备在长期的使用过程中,常常会发生故障,使电路无法正常工作,需要维修。通过电子设备的维修实践,证实了“理论是必不可少的基础,实践是提高技术的途径”,并总结出了维修电子设备的八字方针。     

蓄电池组的维护与更换

本文介绍了蓄电池组的维护与更换的措施和事例。