Quasi-Periodic Replacement Policy for a Two-Unit Production System

Maintenance optimization of periodic replacement for mono-unit production system is a widely discussed topic.In practice,the replacement for a parallel production system with multi-unit served by one repairman is universal.The replacement action is often implemented in a maintenance window at random,although the replacement period appears as a quasi-periodic event.To optimize these maintenance policies,this study analyzes a bivariate quasi-periodic replacement policy (T,W) for a two-unit parallel production system with a maintenance window and one repairman.One unit of the system is replaced when either a failure occurs or a replacement plan comes in the maintenance window,whichever comes first.If one of the two units is in the replacement,the other may continue operating or waiting until the replacement is completed.An optimal replacement window [T*,T* + W*] can be obtained by jointly considering the system's long-running cost rate and the availability using the genetic algorithm.This study also introduces three examples of the production system with different types of units to illustrate the proposed policy.

Efficient cache replacement framework based on access hotness for spacecraft processors

A notable portion of cachelines in real-world workloads exhibits inner non-uniform access behaviors.However,modern cache management rarely considers this fine-grained feature,which impacts the effective cache capacity of contemporary high-performance spacecraft processors.To harness these non-uniform access behaviors,an efficient cache replacement framework featuring an auxiliary cache specifically designed to retain evicted hot data was proposed.This framework reconstructs the cache replacement policy,facilitating data migration between the main cache and the auxiliary cache.Unlike traditional cacheline-granularity policies,the approach excels at identifying and evicting infrequently used data,thereby optimizing cache utilization.The evaluation shows impressive performance improvement,especially on workloads with irregular access patterns.Benefiting from fine granularity,the proposal achieves superior storage efficiency compared with commonly used cache management schemes,providing a potential optimization opportunity for modern resource-constrained processors,such as spacecraft processors.Furthermore,the framework complements existing modern cache replacement policies and can be seamlessly integrated with minimal modifications,enhancing their overall efficacy.

Optimal quasi-periodic maintenance policies for two-unit series system

To investigate the effects of various random factors on the preventive maintenance （PM） decision-making of one type of two-unit series system, an optimal quasi-periodic PM policy is introduced. Assume that PM is perfect for unit 1 and only mechanical service for unit 2 in the model. PM activity is randomly performed according to a dynamic PM plan distributed in each implementation period. A replacement is determined based on the competing results of unplanned and planned replacements. The unplanned replacement is trigged by a catastrophic failure of unit 2, and the planned replacement is executed when the PM number reaches the threshold N. Through modeling and analysis, a solution algorithm for an optimal implementation period and the PM number is given, and optimal process and parametric sensitivity are provided by a numerical example. Results show that the implementation period should be decreased as soon as possible under the condition of meeting the needs of practice, which can increase mean operating time and decrease the long-run cost rate.

A Cache Replacement Policy Based on Multi-Factors for Named Data Networking

Named Data Networking(NDN)is one of the most excellent future Internet architectures and every router in NDN has the capacity of caching contents passing by.It greatly reduces network traffic and improves the speed of content distribution and retrieval.In order to make full use of the limited caching space in routers,it is an urgent challenge to make an efficient cache replacement policy.However,the existing cache replacement policies only consider very few factors that affect the cache performance.In this paper,we present a cache replacement policy based on multi-factors for NDN(CRPM),in which the content with the least cache value is evicted from the caching space.CRPM fully analyzes multi-factors that affect the caching performance,puts forward the corresponding calculation methods,and utilize the multi-factors to measure the cache value of contents.Furthermore,a new cache value function is constructed,which makes the content with high value be stored in the router as long as possible,so as to ensure the efficient use of cache resources.The simulation results show that CPRM can effectively improve cache hit ratio,enhance cache resource utilization,reduce energy consumption and decrease hit distance of content acquisition.

Optimal Water Pipe Replacement Policy

Water scarcity is the major problem confronting both urban and rural dwellers in Enugu State. This scarcity emanated from indiscriminate pipe failure, lack of adequate maintenance, uncertainty on the time of repair or replacement of pipes etc. There is no systematic approach to determining replacement or repair time of the pipes. Hence, the rule of thumb is used in making such a vital decision. The population is increasing, houses are built but the network is not expanded and the existing ones that were installed for no less than two to three decades ago are not maintained. These compounded the problem of scarcity of water in the state. Replacement or repair of water pipes when they are seen spilling water cannot solve this lingering problem. The solution can be achieved by developing an adequate predictive model for water pipe replacement. Hence, this research is aimed at providing a solution to this problem of water scarcity by suggesting a policy that will be used for better planning. The interests in this paper were to obtain a water pipe failure model, the intensity function λ(t) [failure rate], the reliability R(t) and the optimal time of replacement and they were achieved. It was observed that the failure rate of the pipes increases with time while their reliability deteriorates with time. Hence, the Optimal replacement policy is that each pipe should be replaced after 4th break when the reliability = 0.0011.

DIPP—An LLC Replacement Policy for On-chip Dynamic Heterogeneous Multi-core Architecture

As the big data era is coming, it brings new challenges to the massive data processing. A combination of GPU and CPU on chip is the trend to release the pressure of large scale computing. We found that there are different memory access characteristics between GPU and CPU. The most important one is that the programs of GPU include a large number of threads, which lead to higher access frequency in cache than the CPU programs. Although the LRU policy favors the programs with high memory access frequency, the programs of GPU can’t get the corresponding performance boost even more cache resources are provided. So LRU policy is not suitable for heterogeneous multi-core processor. Based on the different characteristics of GPU and CPU programs on memory access, this paper proposes an LLC dynamic replacement policy--DIPP (Dynamic Insertion / Promotion Policy) for heterogeneous multi-core processors.The core idea of the replacement policy is to reduce the miss rate of the program and enhance the overall system performance by limiting the cache resources that GPU can acquire and reducing the thread interferences between programs. Experiments compare the DIPP replacement policy with LRU and we conduct a classified discussion according to the program results of GPU. Friendly programs enhance 23.29% on the average performance (using arithmetic mean).Large working sets programs can improve 13.95%, compute-intensive programs enhance 9.66% and stream class programs improve 3.8%.

Sensitivity Analysis of the Replacement Problem

The replacement problem can be modeled as a finite, irreducible, homogeneous Markov Chain. In our proposal, we modeled the problem using a Markov decision process and then, the instance is optimized using linear programming. Our goal is to analyze the sensitivity and robustness of the optimal solution across the perturbation of the optimal basis ?obtained from the simplex algorithm. The perturbation ?can be approximated by a given matrix H?such that . Some algebraic relations between the optimal solution and the perturbed instance are obtained and discussed.

论“书同文”政策对“屦/履”历时更替的影响——基于出土资料与传世文献的综合考察

战国“履”的字形和{屦}的用字存在文字异形问题,受“书同文”政策的影响,这一问题在秦王政时期得到了解决。考察先秦至西汉早期出土资料与传世文献可知,同样是受“书同文”政策的影响,至迟在秦朝{履}最终替换{屦}而成为表示“鞋”义的常用词。这表明“书同文”政策确实对汉语用词的变化产生过重要的影响。

债务置换、系统性金融风险与宏观政策搭配

我国推出债务置换政策致力于化解地方政府债务风险问题,但关于该政策能否有效化解风险以及其作用机制如何,目前尚无定论。本文通过构建动态随机一般均衡模型(DSGE)探索如何防范与化解债务置换政策对系统性金融风险的负面影响。理论分析发现,债务置换政策尽管能够缓解地方政府的短期违约风险,但是可能会带来系统性金融风险上升的副作用。其副作用来源于两种渠道:流动性渠道和违约转移渠道,债务置换设计中应该充分关注这两种渠道的副作用。本文还发现,搭配货币政策或宏观审慎政策可以缓解债务置换副作用,相比之下宏观审慎政策更加有效。因此,为更好地保障债务置换政策的成功,本文建议实施“债务置换+宏观审慎”的政策组合。

A Prefetch-Adaptive Intelligent Cache Replacement Policy Based on Machine Learning

Hardware prefetching and replacement policies are two techniques to improve the performance of the memory subsystem.While prefetching hides memory latency and improves performance,interactions take place with the cache replacement policies,thereby introducing performance variability in the application.To improve the accuracy of reuse of cache blocks in the presence of hardware prefetching,we propose Prefetch-Adaptive Intelligent Cache Replacement Policy(PAIC).PAIC is designed with separate predictors for prefetch and demand requests,and uses machine learning to optimize reuse prediction in the presence of prefetching.By distinguishing reuse predictions for prefetch and demand requests,PAIC can better combine the performance benefits from prefetching and replacement policies.We evaluate PAIC on a set of 27 memory-intensive programs from the SPEC 2006 and SPEC 2017.Under single-core configuration,PAIC improves performance over Least Recently Used(LRU)replacement policy by 37.22%,compared with improvements of 32.93%for Signature-based Hit Predictor(SHiP),34.56%for Hawkeye,and 34.43%for Glider.Under the four-core configuration,PAIC improves performance over LRU by 20.99%,versus 13.23%for SHiP,17.89%for Hawkeye and 15.50%for Glider.

修理工单重休假定期检修可修系统的更换策略

针对修理工单重休假定期检修退化可修系统,提出了一种维修更换策略及模型。假定修理工单重休假且休假时间小于定期检修的时间间隔,且假定系统检修“修复如旧”和故障维修“修复非新”,系统在检修期间停止工作,检修不影响系统寿命;假设系统依概率在工作状态、定期检修状态和故障维修状态时达到系统的有效年龄T,以系统的有效年龄T为维修更换策略,分别以系统经长期运行单位时间内的平均停机时间最小和期望效益最大为目标,利用几何过程和更新过程理论建立了系统平均停机时间和期望效益的数学模型,求出其解析表达式,通过计算机利用数值法或分析法求出最优维修更换策略T*。该维修更换策略及模型对于工程实践具有一定的指导意义和参考价值。

The Regional Climate Effects of Replacing Farmland and Re-greening the Desertification Lands with Forest or Grass in West China

The West Development Policy being implemented in China causes significant land use and land cover (LULC) changes in West China, of which the two most important types of LULC change are replacing farmland and re-greening the desertification land with forest or grass. This paper modifies the prevailing regional climate model (RCM) by updating its lower boundary conditions with the up-to-date satellite database of the Global Land Cover Characteristics Database (GLCCD) created by the United States Geological Survey and the University of Nebraska-Lincoln. The modified RCM is used to simulate the possible regional climate changes due to the LULC variations. The preliminary results can be summarized as that the two main types of LULC variation, replacing farmland and greening the desertification lands with forest or grass in west China, will affect the regional climate mostly in northwest and north China, where the surface temperature will decrease and the precipitation will increase. The regional climate adjustments in South, Southwest China and on the Tibet Plateau are uncertain.

A generalized geometric process based repairable system model with bivariate policy

The maintenance model of simple repairable system is studied.We assume that there are two types of failure,namely type Ⅰ failure(repairable failure)and type Ⅱ failure(irrepairable failure).As long as the type Ⅰ failure occurs,the system will be repaired immediately,which is failure repair(FR).Between the(n-1)th and the nth FR,the system is supposed to be preventively repaired(PR)as the consecutive working time of the system reaches λ^(n-1) T,where λ and T are specified values.Further,we assume that the system will go on working when the repair is finished and will be replaced at the occurrence of the Nth type Ⅰ failure or the occurrence of the first type Ⅱ failure,whichever occurs first.In practice,the system will degrade with the increasing number of repairs.That is,the consecutive working time of the system forms a decreasing generalized geometric process(GGP)whereas the successive repair time forms an increasing GGP.A simple bivariate policy(T,N)repairable model is introduced based on GGP.The alternative searching method is used to minimize the cost rate function C(N,T),and the optimal(T,N)^(*) is obtained.Finally,numerical cases are applied to demonstrate the reasonability of this model.

国家药品集中带量采购政策下抗肿瘤药品使用特征分析

目的:探究国家药品集中带量采购政策下抗肿瘤药品的使用特征,为进一步规范可替代品种使用监测、优化药品集采政策提供建议。方法:利用2019年—2020年国家药品供应保障综合管理信息平台的药品采购数据,采用描述性统计方法分析政策实施前后抗肿瘤药品采购金额、用药频度(DDDs)与日均费用(DDDc)的变化情况。结果:政策实施后抗肿瘤集采品种的采购金额与DDDc分别下降了31.87%和51.55%,DDDs上升了40.61%;可替代品种的采购金额与DDDs分别上升了49.20%与41.62%,DDDc变化不明显。从注册评价类型来看,政策实施后集采品种中的仿制药DDDs增幅高于原研药,药品费用下降明显;可替代品种中原研药的采购金额与DDDs的增长率高于仿制药。从可替代程度来看,可替代品种的采购金额、DDDs与DDDc增幅在政策实施后均高于基本可替代品种。结论:国家药品集采政策对抗肿瘤集采品种的降价省费效应显著,使用中选产品逐渐成为患者的一致选择;集采品种对可替代品种的替代效应并不明显,应采用信息化手段开展高替代程度品种的使用限额与用量监测,加快过评仿制药对高价原研药的替代使用。

The Ordering and Replacement Policy for the System with Two Types of Failures

In this paper,the optimal maintenance policy is investigated for a system with stochastic lead time and two types of failures. The system has two types of failures, one type is repairable, when the repairable failure occurs, the system will be repaired by repairman, and the system after repair is not“as good as new". The other type of failure is unrepairable, and when the unrepairable failure occurs the system must be replaced by a new and identical one. The spare system for replacement is available only by order, and the lead time for delivering the spare system is stochastic. The successive survival times of the system form a stochastically decreasing geometric process, the consecutive repair times after failures of the system form a renewal process. By using the renewal process theory and geometric process theory, the explicit expression of the long-run average cost per unit time under ordering policy (N-1) is derived, and the corresponding optimal can be found analytically. Finally, the numerical analyses are given.

OPTIMUM ORDERING POLICY FOR PREVENTIVE AGE REPLACEMENT

Most of the spare ordering policies treated up to now have assumed that preventive and corrective replacement costs are equal, which implies in essential that there is no significant need for preventive replacement. This paper presents an ordering policy for preventive age replacement with minimal repair. Introducing the replacement, repair, inventory holding and shortage costs, the expected cost rate is derived. A procedure to determine jointly the ordering time for a spare and the preventive replacement time for the operating unit so as to minimize the expected cost rate is proposed. To explain the ordering policy and the optimization procedure, a numerical example is also included.

Optimal Age Replacement Policy with Replacement Occurrence While the Warranty is in Effect

This study considers an age replacement policy(ARP) for a repairable product with an increasing failure rate with and without a product warranty. As for the warranty policy to consider in association with such an age replacement policy, we adapt a renewable minimal repair-replacement warrant(MRRW) policy with 2D factors of failure time of the product and its corresponding repair time. The expected cost rate during the life cycle of the product is utilized as a criterion to find the optimal policies for both with and without the product warranty. We determine the optimal replacement age that minimizes the objective function which evaluates the expected cost rate during the product cycle and investigate the impact of several factors on the optimal replacement age. The main objective of this study lies on the generalization of the classical age replacement policy to the situation where a renewable warranty depending on 2D factors is in effect. We present some interesting observations regarding the effect of relevant factors based on numerical analysis.

北京市自建设施供水管理现状、问题及对策建议

以北京市自建设施供水为例,分析了当前存在的问题,从完善管理体制机制、出台配套法规政策、加强日常管理、推动所属自备水源井置换等方面提出解决对策建议。

代理缓存一致性策略和替换策略的研究

针对代理缓存的一致性策略和替换策略还没有很好地结合起来,从而影响了代理缓存系统的整体性能的现状,分别探讨了基于Internet的代理缓存一致性策略和替换策略的处理流程、性能评价指标和研究现状,进而给出将这两种策略结合起来的一致性—替换算法的处理流程,并提出陈旧命中比是其主要性能评价指标,能很好地衡量代理缓存的各种算法的优劣和代理缓存系统的整体性能。

缓存技术在移动数据库中的应用研究

缓存技术是提高数据访问性能的经典技术,已经在计算技术的很多方面得到了成功的应用。在移动计算环境中,由于设备和网络资源的限制,缓存将发挥更加重要的作用。研究了移动数据库中的客户端缓存管理技术,重点讨论了缓存管理的缓存粒度、缓存一致性策略和缓存替换策略3个关键问题。