Efficient Algorithms for Cache-Throughput Analysis in Cellular-D2D 5G Networks

In this paper, we propose a two-tiered segment-based Device-to-Device (S-D2D) caching approach to decrease the startup and playback delay experienced by Video-on-Demand (VoD) users in a cellular network. In the S-D2D caching approach cache space of each mobile device is divided into two cache-blocks. The first cache-block reserve for caching and delivering the beginning portion of the most popular video files and the second cache-block caches the latter portion of the requested video files ‘fully or partially’ depending on the users’ video watching behaviour and popularity of videos. In this approach before caching, video is divided and grouped in a sequence of fixed-sized fragments called segments. To control the admission to both cache-blocks and improve the system throughput, we further propose and evaluate three cache admission control algorithms. We also propose a video segment access protocol to elaborate on how to cache and share the video segments in a segmentation based D2D caching architecture. We formulate an optimisation problem and find the optimal cache probability and beginning-segment size that maximise the cache-throughput probability of beginning-segments. To solve the non-convex cache-throughout maximisation problem, we derive an iterative algorithm, where the optimal solution is derived in each step. We used extensive simulations to evaluate the performance of our proposed S-D2D caching system.     

Efficient Routing Protection Algorithm in Large-Scale Networks

With an increasing urgent demand for fast recovery routing mechanisms in large-scale networks, minimizing network disruption caused by network failure has become critical. However, a large number of relevant studies have shown that network failures occur on the Internet inevitably and frequently. The current routing protocols deployed on the Internet adopt the reconvergence mechanism to cope with network failures. During the reconvergence process, the packets may be lost because of inconsistent routing information, which reduces the network’s availability greatly and affects the Internet service provider’s (ISP’s) service quality and reputation seriously. Therefore, improving network availability has become an urgent problem. As such, the Internet Engineering Task Force suggests the use of downstream path criterion (DC) to address all single-link failure scenarios. However, existing methods for implementing DC schemes are time consuming, require a large amount of router CPU resources, and may deteriorate router capability. Thus, the computation overhead introduced by existing DC schemes is significant, especially in large-scale networks. Therefore, this study proposes an efficient intra-domain routing protection algorithm (ERPA) in large-scale networks. Theoretical analysis indicates that the time complexity of ERPA is less than that of constructing a shortest path tree. Experimental results show that ERPA can reduce the computation overhead significantly compared with the existing algorithms while offering the same network availability as DC.     

Forecasting service parts demand for a discontinued product

Stochastic demand forecasting methods for service parts of a discontinued product are proposed. The identified four major factors are the number of product sales, the discard rate of the product, the failure rate of the service part, and the replacement probability of the failed part. During a given period, typically a year, the number of failed service parts is estimated using the first three factors, and then the demand for those service parts is obtained with the use of the last factor. A stochastic model is derived to estimate the demand in a certain prediction interval, and the closed-form solutions in the case of a constant failure rate are provided. An approximate model is proposed to render actual computation possible when the part failure time is not distributed exponentially. Numerical data from the automotive industry are used to validate the model.     

A method of estimating railway axle stress spectra

All British railway axles require regular non-destructive testing to ensure that no dangerous cracks are present. The required periodicity for such testing can be calculated using probabilistic fracture mechanics, which outputs the probability of service failure as a function of inspection interval. A major input to this process is the stress histogram experienced by the axle. Such histograms have been measured for a typical British railway vehicle over two years, and the findings have been used to develop a methodology to predict axle stresses that can in principle be applied to any vehicle and route.     

基于地域文化的高速公路服务区品牌化构建研究

目的针对高速公路服务区转型发展的迫切需求,以地域文化为突破口对其品牌建设路径进行分析与探讨。方法通过分析高速公路服务区品牌现状及问题,以及地域文化对于服务区品牌塑造的价值意义,归纳出将地域文化与服务区品牌进行创新结合的方法。结果针对高速公路服务区品牌定位、品牌形象与品牌体验等提出了基于地域文化的高速公路服务区品牌化构建路径。结论针对现阶段高速公路服务区品牌定位不明、同质化严重、资源利用不足等症结,高速公路服务区应当依托在地文化基因整合地区资源,以文化沟通产业进行价值重构与品牌定位,以用户感知需求构建功能化视觉体系,以文化体验提升服务业态,使服务区成为具有识别性与持续动力的交通商业体。     

平行钢索的锈蚀时变失效概率分析

在综合锈蚀开始时间的概率模型和锈蚀面积扩展的概率模型的基础上,建立了平行拉索锈蚀时变失效概率模型。根据不同检测周期钢丝锈蚀概率树形结构的特点,提出了锈蚀概率计算的分枝约界方法,有效地解决了计算量指数级增长的问题。模型参数分析和拉索失效概率算例表明：在模型参数统计评估正确性的前提下,该模型能够预测在役拉索任何检修周期的钢丝锈蚀的数目及其概率,能够计算任意时刻钢丝锈蚀的总量,进而分析拉索的时变失效概率。该模型的提出是对拉索锈蚀失效问题的一种探索研究,对拉索检测评估研究具有一定的参考价值。     

交通量持续增长下既有拱桥车载效应极值概率

桥梁结构在服役期间受到环境侵蚀和均值增大的相关荷载作用,承载力降低,安全状况不容乐观。为了准确评估服役桥梁在剩余使用寿命内的安全性能,需要考虑结构抗力劣化的非平稳特性以及荷载的时间相关性。该文基于时变可靠度理论,采用Gamma分布描述结构抗力的非平稳劣化过程,并用二维联合分布函数表示相邻荷载的相关性,基于贝叶斯原理,提出了计算公式,并采用蒙特卡洛模拟 (MCS) 对计算结果进行了验证。对四川省某钢筋混凝土简支梁桥的时变可靠度分析结果表明：在单次条件概率分子的二重积分结果大于0.7时,公式计算结果与MCS结果接近,证明了其正确性;Gamma劣化过程的尺度参数越大,荷载的时间相关性越弱,结构失效概率越大;当作用于结构的车辆荷载年均增长率超过2%时,桥梁在30年内失效的概率较大,需要对结构进行定期监测、养护和维修。

     

Cross-layer design for block subchannel allocation and admission control in the IEEE 802.16 OFDMA networks

The flexibility of orthogonal frequency-division multiple access (OFDMA) technology necessitates a compromise between spectrum efficiency and quality of service (QoS) in IEEE 802.16 broadband wireless networks. This article proposes a complete solution with the nice feature of adaptive modulation and a coding scheme to provide both delay and loss rate guarantees for real-time services. The proposed method first determines the subframe boundary according to the current downlink and uplink backlogs. To comply with the IEEE 802.16 standard, the proposed method then groups contiguous subchannels and allocates them to proper connections based on the current loss rate and available modulation and coding schemes for each connection. By modeling the aggregated required subchannels as a Gaussian distribution, this study develops a simple admission control algorithm by checking if there are enough resources for a new connection. Simulation results show that the proposed solution can provide QoS guarantee with high spectrum efficiency.     

定位服务设计

目的梳理服务设计的学科缘起及相关研究成果,从商业语境和设计原则两个维度界定不同的服务设计理念。方法通过比较管理、经济和设计不同领域对服务作为管理手段、商品、设计对象的不同解读,理清服务设计的不同研究视角;通过回顾国内外服务设计的研究成果,分析服务设计研究和实践的困惑与瓶颈;结合案例,分析服务的不同商业定位和解读不同的服务设计原则,定位不同的服务设计理念。结论当服务以产品的附加价值出现,并基于效率原则进行设计时,服务设计往往是针对相对稳定目标的服务加工;基于同样的原则,但以服务作为核心主体时,服务设计的主要内容常常是服务流程的再造;当服务设计的目标是创造意义,即便以产品附加价值出现,服务也将为产品增加功能属性之外的新的内容,重塑产品意义;当以意义创造为目的,全面创新服务体系时,服务设计是理念、商业模式和范式的转变。     

Estimation of shear strain in the region of a restraint for a layered plate

Results are given for an anaytical estimate of shear strain in the region of a restraint for a regular long layered plate under the action of a uniformly distributed dynamic load. An approximate dependence for the maximum values of shear in the support on loading duration, material properties, thickness and number of plate layers is obtained using Laplace transforms. It is shown that with an increase in the number of plate layers there is a reduction in the probability of shear failure in the support.Translated from Problemy Prochnosti, No. 3, pp. 106–110, March, 1990.     

套筒灌浆连接受力失效机理与有限元仿真验证EI北大核心CSCD

针对套筒灌浆连接的传力机理尚未完全明确,从理论上分析了受拉时接头的荷载传递路径与方式,提出了基于拟合系数、组合系数、整体系数的套筒灌浆连接受拉承载力计算方法与失效模式识别依据。进一步通过收集国内外试验数据的拟合分析,明确了单调递增受拉、反复拉压作用下拟合系数的取值分别为0.203、0.158。结合高温后套筒灌浆连接反复拉压作用下试验数据的分析结果,建议组合系数、整体系数均取1.2(400℃高温作用后,后者取1.0)。最后,开展高温后套筒灌浆连接反复拉压作用有限元仿真,明确了套筒灌浆连接失效模式转变、承载力明显下降的临界温度分别为400℃、800℃。此外,还发现新建的套筒灌浆连接承载力计算方法的结果与模拟值最大偏差不超过8.2%,表明二者均能较好地反映高温后套筒灌浆连接承载力演变规律,为套筒灌浆连接设计方法的形成提供了理论依据。     

Decision analysis for deteriorating structures

Measures that improve durability of a structure usually increase its initial cost. Thus, in order to make a decision about a cost-effective solution the life-cycle cost of a structure including cost of structural failure needs to be considered. Due to uncertainties associated with structural properties, loads and environmental conditions the cost of structural failure is a random variable. The paper derives probability distributions of the cost of failure of a single structure and a group of identical structures when single or multiple failures are possible during the service life of a structure. The probability distributions are based on cumulative probabilities of failure of a single structure over its service life. It is assumed that failures occur at discrete points in time, the cost of failure set at the time of decision making remains constant for a particular design solution and the discount rate is a deterministic parameter not changing with time. The probability distributions can be employed to evaluate the expected life-cycle cost or the expected utility, which is then used in decision making. An example, which considers the selection of durability specifications for a reinforced concrete structure built on the coast, illustrates the use of the derived probability distributions.     

基于演化博弈的应急物资生产能力储备策略

研究政府和企业共同储备应急物资生产能力的合作问题,就3种不同条件（无任何措施、惩罚、惩罚和补贴并行）政府和协议企业之间在应急物资生产能力的共同储备进行演化博弈分析。分析表明：在一定条件下,企业储备的收益和成本,政府定期或不定期检查的成本、政府奖惩力度等是影响双方合作的关键因素。通过算例对所得结论进行验证,最后给出应急物资生产能力储备的策略建议。     

Structural Health Monitoring of Railroad Wheels Using Wheel Impact Load Detectors

This paper proposes two quantitative criteria for removing railroad wheels from service, based on real-time structural health monitoring trends that are developed using data collected from trains while in service. The data is collected using wheel impact load detectors (WILDs). These impact load trends are able to distinguish wheels with a high probability of failure from high-impact wheels with a low probability of failure. The trends indicate the critical wheels that actually need to be removed, while at the same time allowing wheels that aren’t critical to remain in service. As a result, the safety of the railroad will be much improved by being able to identify and remove wheels that have high likelihood of causing catastrophic failures.     

Research of rail traction shafts and axles fractures towards impact of service conditions and fatigue damage accumulation

Traction shafts and axles of railway vehicles are designed to be safe and reliable in normal service conditions. Accidental and unpredictable conditions including bad exploitation (rail tracks, maintenance and extreme long service life) make the probability of shaft and axle fracture realistic. This article contains the experience and analysis of the traction shafts and axles fractures and fracture processes. Research also shows service conditions with results presented in the form of service stress spectrums. Besides normal service conditions, the results also include unpredictable phenomenon such as natural torsion vibrations of the shaft and wheels caused by stick–slip processes at the moment of the set in motion of a full-loaded train or at the moment of braking. These vibrations create an extremely high level of torque which is the main cause of cracks initialization. The next part of the article contains the results of the traction shafts and axles endurance research. The results of testing are transformed using the results of calculation by the FE method and by statistical estimation of the failure probability distribution. The main part refers to the interaction (impact) of service stress probability and failure (endurance) probability, which leads to the traction shaft (axle) reliability definition. Using the established model, locomotive traction shaft reliability is calculated and analyzed. The final part of the article contains suggestions for the traction shafts (axles) failure prevention.     

Probabilistic risk analysis and risk-based priority scale for the tiles of the space shuttle

The thermal protection system of the space shuttle is one of its most critical subsystems because it protects the orbiter from heavy heat loads at reentry into the atmosphere. To optimize NASA's allocation of risk management resources, a probabilistic risk analysis model is developed for the black tiles, and a risk-criticality index is computed for each tile based on its contribution to the overall probability of loss of vehicle and crew (LOV/C). This assessment is based on the susceptibility of the tiles (i.e. their probabilities of debonding), and on the vulnerability of the orbiter to specific tile losses given the criticality of the subsystems under the aluminum skin in various locations. The two main initiating events are linked to the debonding of a tile, caused either by debris hits or by a weak bond because of poor tile installation. The PRA model relies on a partition of the orbiter's surface according to four parameters: the probability of debris hits, the probability of secondary tile loss once a first tile has debonded, the probability of burnthrough given a failure patch of specified size, and the probability of LOV given a hole in the orbiter's aluminum skin. The results show that the contribution of the tiles to the overall probability of LOV is about 10%. They also include a map of the orbiter's surface showing the relative risk-criticality of tiles at various locations. It was found that 85% of the risk can be attributed to 15% of the tiles, thus allowing the management to allocate more effort and resources to the maintenance of the most risk-critical tiles.     

Failure Analysis of Stacker-cum-Reclaimer in Ore Handling Plant

A catastrophic failure of a Stacker-cum-Reclaimer led to loss of several days of service in one ore handling plant in India. The failure was severe enough to initiate an investigation into the possible causes of failure and estimation of the residual life for other units of Stacker-cum-Reclaimer of the same design and age, working in the plant. The failure analysis included a visual inspection of the failed structure, metallographic studies, static stress and stability analysis under normal operating conditions, stress analysis for a possible impact load on the structure, experimental stress analysis, and fatigue life cycle analysis. The results obtained indicate that the failure could be caused by an impact load arising out of some operational conditions resulting from the conditions of the rail track on which the machine travels. The material properties, the physical conditions of the material, and a fatigue analysis indicate that the existing system can work for several more decades, provided some checkpoints are planned and instituted to monitor the health of the structure at regular intervals.     

Plumbing Hardware Failure Analyses

The hardware used for plumbing assemblies play an important role in modern home, business, and industrial systems. Engineered plumbing hardware made from metals allow for an extensive network of plumbing assemblies accommodating complex designs which facilitate product and installation effectiveness, in addition to maintaining cost efficiency. Examples of plumbing hardware include fittings, valves, drains, fixtures, pipes, and so on. These materials are often subjected to a range of environments dependent on local water chemistry as well as varying service environments and installation techniques. Given the vast number of components in use failures do occur, often as a result of extreme service conditions or inappropriate installation techniques. Understanding the failure mechanisms associated with plumbing hardware and their assemblies is an important step in material and design optimization for future development. In view of that, this paper provides a range of plumbing component failure case studies for potable and non-potable water systems.     

An exponentially weighted moving average control chart for Bernoulli data

We consider a production process in which units are produced in a sequential manner. The units can, for example, be man‐ ufactured items or services, provided to clients.Each unit produced can be a failure with probability p or a success (non‐failure) with probability (1?p). A novel exponentially weighted moving average (EWMA) control chart intended for surveillance of the probability of failure, p, is described. The chart is based on counting the number of non‐failures produced between failures in combina‐ tion with a variance‐stabilizing transformation. The distribution function of the transformation is given and its limit for small values of p is derived. Control of high yield processes is discussed and the chart is shown to perform very well in comparison with both the most common alternative EWMA chart and the CUSUM chart. The construction and the use of the proposed EWMA chart are described and a practical example is given. It is demonstrated how the method communicates the current failure probability in a direct and interpretable way, which makes it well suited for surveillance of a great variety of activities in industry or in the service sector such as in hospitals, for example. Copyright © 2009 John Wiley & Sons, Ltd.     

Flexibility in manufacturing enterprises

A manufacturing enterprise is a collection of interrelated, flexible, optimized business processes delivering value to the customers through high quality products and services, faster than competition. This view of an enterprise enables one to consider the entire business system including the suppliers, product development, manufacturing, logistics, distribution, and retailing and to smoothen out the interfaces between them. Performance measures and performance measurement are important for monitoring, control and management. We identify and discuss eight performance measures for generic business processes. These include lead time, customer service, dependability, quality, flexibility, cost, capacity, and asset utilization. In this paper, we concentrate on flexibility of business processes with special emphasis on the supply chain and order-to-delivery processes. We attempt to provide clear definitions and measures of various types of flexibilities as well as discuss the relationship between product structure and supply chain flexibility. The relationship between uncertainties, flexibility, technology, and product structure is clearly brought out in this paper.