Optimizing lead time and resource utilization for service enterprises

Lead time is generally defined as the period of time for which customers have to wait before receiving completed products or services from enterprises. In the key public utility markets, such as telecommunications market, that are tightly regulated by government watchdogs, service enterprises are obliged to provide equivalent services to all their customers. In the context of service lead time, this means that “standard lead times” should be universally applied to all customers. Existing industrial practice in deriving “standard lead time” is manual and erroneous. Regardless of the variances of demand and resource across geographical areas and across time horizon, service enterprises are generally confined to single fixed “standard lead times”. Ill-derived “standard lead times” lead to wrong promises made to customers, which not only forces service engineers to work overtime to deal with overflowing jobs but also incur huge compensation costs due to delayed or failed customer services. In this paper, we set out to tackle the “standard lead time” problem. In particular, we devised an automated approach to testing the existence of legal optimal allocation schemes based on actual customer demand, enterprise resource and assumed standard lead time. We first modelled this as a combinatorial optimisation problem; we then experimented a heuristic local search method, namely “single day shift”, inspired by previous work on virtual telescope scheduling; further on, we improved the first method by introducing a new heuristics, namely “multiple day spread”, which achieved a speed of search for optimal solutions, 1.29 times faster than the first method. A case study on comparisons between existing default “standard lead time” and the calculated one using our approach for a telecommunication service provider was conducted to demonstrate the necessity and effectiveness of this approach. Finally, we compared our approach with related work. We concluded that our approach is more suitable for the problem of optimizing lead time and resource utilisation, and the results from our work are widely applicable to various industry sectors that concern equivalent customer services, balanced work load and optimal lead times.     

The relationship between work productivity and acute responses at different levels of production standard times

Work productivity is typically associated with production standard times. Harder production standards generally result in higher work productivity. However, the tasks become more repetitive in harder production standard time and workers may be exposed to higher rates of acute responses which will lead to higher risks of contracting work-related musculoskeletal disorders (WMSDs). Hence, this paper seeks to investigate the relationship between work productivity and acute responses at different levels of production standard times. Twenty industrial workers performed repetitive tasks at three different levels of production standard time (PS), corresponding to “normal (PSN)”, “hard (PSH)” and “very hard (PSVH)”. The work productivity and muscle activity were recorded along these experimental tasks. The work productivity target was not attainable for hard and very hard production standard times. This can be attributed to the manifestations of acute responses (muscle activity, muscle fatigue, and perceived muscle fatigue), which increases as the production standard time becomes harder. There is a strong correlation between muscle activity, perceived muscle fatigue and work productivity at different levels of production standard time. The relationship among these variables is found to be significantly linear (R = 0.784, p < 0.01). The findings of this study are indeed beneficial to assess the existing work productivity of workers and serves as a reference for future work productivity planning in order to minimize the risk of contracting WMSDs.     

Efficient method of adaptive sign detection for 4×4 determinants using a standard arithmetic processing unit

We propose an efficient and exact method for the adaptive sign detection of 4×4 determinants using a standard arithmetic unit. The entities of determinants are variable length integers (integers of arbitrary bit length). The integers are expressed in 16-bit data units, and the sign detection is reduced to the computation of 4×4 determinants of 16-bit integers. To accelerate the computation, the calculation is performed by using a standard arithmetic unit. We have implemented our method and confirmed that it significantly improves the computation time of 4×4 determinants. The method can be applicable to many geometric algorithms that need the exact sign evaluation of 4×4 determinants, especially to construct robust geometric algorithms.     

Superposition properties and performance bounds of stochastictimed-event graphs

This paper addresses the performance evaluation of stochastic timed-event graphs. The transition firing times are random variables with general distribution. We first consider a stochastic timed-event graph in which the firing times are generated by time superposition (or addition) of two sets of random variable sequences. Properties of this system are established. Chiefly, we prove that the average cycle time is subadditive, i.e., it is smaller than the sum of the average cycle times of the two stochastic timed-event graphs in which the firing times are generated by one of the two sets of random variable sequences, respectively. Based on these superposition properties, we derive various upper bounds of the average cycle time of a general stochastic timed-event graph. In particular, we obtain upper bounds which converge to the exact average cycle time as the standard deviations of the firing times decrease. Finally, we derive performance bounds for stochastic timed-event graphs with bounded firing times     

Reaction times to neon,LED, and fast incandescent brake lamps

Standard incandescent brake lamps have a relatively slow rise time. It takes approximately a quarter of a second for them to reach 90% of asymptotic light output, causing potential delays in responses by following drivers. The present study evaluated reaction times to brake signals from standard incandescent brake lamps and from three alternative brake lamps with substantially faster rise times: neon, LED, and fast incandescent. The study, performed in a laboratory, simulated a daytime driving condition. The subject's task was to respond as quickly as possible to the onset of either of two brake lamps in the visual periphery, while engaged in a central tracking task. Brake signals were presented at two levels of luminous intensity. The results showed that reaction times to the alternative brake lamps were faster than to the standard incandescent lamp, with the advantage averaging 166?ms for the LED and neon lamps, and 135?ms for the fast incandescent lamp. A reduction of the signals' luminous intensity from 42 cd to 5 cd increased the reaction time by 84?ms.     

椭圆曲线上高效可完全模拟的不经意传输协议

不经意传输协议是安全多方计算的一个关键技术,是当前网络与信息安全研究的热点。基于双线性对及椭圆曲线上的困难问题,分别设计了半诚实模型下和标准恶意模型下的安全高效N选1不经意传输协议。,在半诚实模型下设计了一个椭圆曲线上的不经意传输协议,该协议只需2轮交互,接收方需要2次双线性对运算和1次椭圆曲线倍点运算,发送方需要n次椭圆曲线倍点运算和n次模幂运算,协议的安全可规约到椭圆曲线上的离散对数问题;构建了基于椭圆曲线上双线性对的零知识证明方案,并设计了一个恶意模型下的不经意传输协议,该协议只需3轮交互,接收者需要3次双线性对运算和3次椭圆曲线倍点运算,发送者需要n+1次椭圆曲线倍点运算和n+1次模幂运算,协议能在标准恶意模型下抵抗参与者的恶意攻击行为。实验结果得到在半诚实模型下协议平均运行时间需要0.787 9 s,在标准恶意模型下协议平均运行时间需要1.205 6 s,进一步论证协议的速度。     

H.264快速模式确定方法

H.264/AVC是最新的视频编码标准,与以前的视频标准相比编码效率最多提高了50%。与此同时,H.264编码器的计算复杂度也比H.263提高了约3倍。这对于资源受限的应用系统来说是个巨大的挑战。分析发现,H.264编码器中宏块的模式确定占了编码时间的90%左右。论文提出了一种简单而有效的快速模式确定方法,模拟试验的结果表明,该方法在编码性能几乎没有降低的情况下,总体编码时间比传统方法减少了50%以上。     

Matrix analytical model of an ATM output buffer with self-similar traffic

Renewal processes with asymptotically hyperbolic interarrival time distributions are shown to exhibit self-similar behavior. An output buffer of an ATM switch is modeled as a discrete time queue with a single server, deterministic service times and self-similar renewal process input. A matrix geometric solution is found for the stationary distribution of states. For the case of hyperbolically distributed interarrival times, the mean and standard deviation of queue length are plotted for various values of the queue utilization and the self-similarity parameter of the arrival process. The self-similarity is found to have a significant impact on the performance of the queue.     

分布式GIS软件体系结构

分布式GIS将成为互联网时代人类生存所依赖的一种基础设施,目前GIS软件的开发大都采用一体化的形式。作者认为应当将GIS软件体系结构从整体上作为标准来研究,并提出分布式GIS软件体系结构五层模型,探讨了各层的组织与功能,将GIS软件体系结构作为整体标准来研究,有利于GIS有产业化和社会化,加速GIS成为互联网时代人类社会的基础设施。     

基于标准差和亮暗分布排序的分形图像编码

针对分形图像编码花费时间较长的问题,提出一种基于标准差和亮暗分布排序的快速分形图像编码算法.在全体码本中预先排除标准差较小的定义域块,以减少码本数量,仅对亮暗分布与值域块相似或相反的定义域块进行匹配搜索,从而完成编码.仿真结果表明,该算法较局部方差算法和正负跳变算法的编码速度分别提高了10倍和5倍,重构图像的峰值信噪比也有所提升.     

Parallel implementation of backpropagation neural networks on aheterogeneous array of transputers

This paper analyzes parallel implementation of the backpropagation training algorithm on a heterogeneous transputer network (i.e., transputers of different speed and memory) connected in a pipelined ring topology. Training-set parallelism is employed as the parallelizing paradigm for the backpropagation algorithm. It is shown through analysis that finding the optimal allocation of the training patterns amongst the processors to minimize the time for a training epoch is a mixed integer programming problem. Using mixed integer programming optimal pattern allocations for heterogeneous processor networks having a mixture of T805-20 (20 MHz) and T805-25 (25 MHz) transputers are theoretically found for two benchmark problems. The time for an epoch corresponding to the optimal pattern allocations is then obtained experimentally for the benchmark problems from the T805-20, TS805-25 heterogeneous networks. A Monte Carlo simulation study is carried out to statistically verify the optimality of the epoch time obtained from the mixed integer programming based allocations. In this study pattern allocations are randomly generated and the corresponding time for an epoch is experimentally obtained from the heterogeneous network. The mean and standard deviation for the epoch times from the random allocations are then compared with the optimal epoch time. The results show the optimal epoch time to be always lower than the mean epoch times by more than three standard deviations (3sigma) for all the sample sizes used in the study thus giving validity to the theoretical analysis.     

开放量子行走的击中时分析

作为量子搜索算法研究的一个基本工具,量子行走是一个重要研究课题。同时,击中时是衡量量子行走到达某一目标顶点速度的标准,对量子算法研究具有广泛的应用。在开放量子环境下,给出开放量子行走的四种击中时定义：单次击中时、并行击中时、平均击中时和极限击中时。区分四种击中时,说明前两种用于刻画开放量子行走局部到达目标顶点,而后两种从全局和极限角度分析目标顶点到达情况。针对同质开放量子行走、异质开放量子行走和嵌套开放量子行走,分别给出四种击中时具体计算。     

Probabilistic temporal reasoning and its application to fossil power plant operation

Many real-world applications, such as industrial diagnosis, require an adequate representation and inference mechanism that combines uncertainty and time. In this work, we propose a novel approach for representing dynamic domains under uncertainty based on a probabilistic framework, called temporal nodes Bayesian networks (TNBN). The TNBN model is an extension of a standard Bayesian network, in which each temporal node represents an event or state change of a variable and the arcs represent causal–temporal relationships between nodes. A temporal node has associated a probability distribution for its time of occurrence, where time is discretized in a finite number of temporal intervals; allowing a different number of intervals for each node and a different duration for the intervals within a node (multiple granularity). The main difference with previous probabilistic temporal models is that the representation is based on state changes at different times instead of state values at different times. Given this model, we can reason about the probability of occurrence of certain events, for diagnosis or prediction, using standard probability propagation techniques developed for Bayesian networks. The proposed approach is applied to fossil power plant diagnosis through two detailed case studies: power load increment and control level system failure. The results show that the proposed formalism could help to improve power plant availability through early diagnosis of events and disturbances.     

Robust commit time decisions and bounds for measuring demand-side quality costs

In this paper, we discuss a single machine processing multi-product situation. The upper and lower bounds of demand-side costs and optimal commit delivery time range with only the mean and standard deviation of the processing time distribution are obtained. We propose two robust commit delivery times, one using the mid-point of the optimal solution range and the other using the min-max regret criterion. The expected value of distribution information, which measures the maximum amount a decision-maker is willing to pay for the true knowledge of the distribution, is used to evaluate the performance of the delivery times. An extension to the situation where information of orders in a queue is available is also discussed. Numerical examples show that both decision rules are promising, and they have potential for practical applications.     

面向三维特征描述子的自适应二进制简化方法

在三维（3D）局部特征描述子研究中,准确度、匹配时间以及内存消耗存在此消彼长的问题。针对上述问题,基于统计理论中的标准差原理提出一种面向3D特征描述子的自适应二进制简化方法。首先,通过改变简化模型中二值化单元长度和标准差个数来生成不同的二进制特征描述子;然后,将它们应用到当前被广泛使用的基于签名的方向直方图（SHOT）描述子中,并通过实验确定最优的二值化单元长度和标准差个数的组合;最后,将最优组合下的简化描述子命名为SD-SHOT。实验结果表明,与未进行简化的SHOT描述子相比,SD-SHOT在关键点匹配时间上减少为原来的1/15,内存占有率降低为原来的1/32;与现有主流简化方法如B-SHOT等相比,SD-SHOT的性能达到了综合最优水平。此外,在由五种不同类别的物体构成的实际机器人分拣场景中验证了所提方法的有效性。     

Some features of two fieldbuses of the IEC 61158 standard

The IEC 61158 is on the way to become an international fieldbus standard after a long period of contrasts and misunderstandings. The final standard document results from the joining of eight among the most diffused fieldbus protocols.This paper takes into consideration one of the most popular fieldbus of the final standard document, Profibus, and examines the differences with the original IEC 61158 Technical Specification (which is also included in the standard). The analysis concerns the data link layer of the two fieldbuses: Profibus is based on a token passing technique, while the IEC fieldbus realises a mixed access combining token passing with a centralised scheduling procedure managed by a special node named Link Active Scheduler (LAS). Two parameters of the data link layers have been in particular considered: the cycle time and the medium access efficiency. In particular, the evaluation of the cycle times has been carried out using analytical models which are valid under the hypothesis that the token holding times of the stations are sufficiently long to satisfy all the service requests coming from the users, that is a typical situation of a network not overloaded. Considerations have also been made to investigate the behaviours of the cycle times when the network traffic increases.     

Optimization of the material flow in a manufacturing plant by use of artificial bee colony algorithm

To survive in today’s competitive global market, companies must perform strategic changes in order to increase productivity, eliminating wasted materials, time, and effort. This study will examine how to optimize the time and effort required to supply raw material to different production lines in a manufacturing plant in Juarez, Mexico by minimizing the distance an operator must travel to distribute material from a warehouse to a set of different production lines with corresponding demand. The core focus of this study is similar to that of the Vehicle Routing Problem in that it is treated as a combinatorial optimization problem. The artificial bee colony algorithm is applied in order to find the optimal distribution of material with the aim of establishing a standard time for this duty by examining how this is applied in a local manufacturing plant. Results show that using this approach may be convenient to set standard times in the selected company.     

Method for HDR-like imaging using industrial digital cameras

Dynamic range of the scene can be significantly wider than the dynamic range of an image because of limitations of A/D conversion. In such a situation, numerous details of the scene cannot be adequately shown on the image. Standard industrial digital cameras are equipped with an auto-exposure function that automatically sets both the aperture value and cameras exposure time. When measuring a scene with atypical distribution of light and dark elements, the indicated auto-exposure time may not be optimal. The aim of work was to improve, with minimal cost, the performance of standard industrial digital cameras. We propose a low complexity method for creating HDR-like image using three images captured with different exposure times. The proposed method consists of three algorithms: (1) algorithm for estimating whether the auto-exposure time is optimal, (2) algorithm which determines exposure times for two additional images (one with shorter and another with longer than auto-exposure time), and (3) algorithm for HDR-like imaging based on fusion of three previously obtained images. Method is implemented on FPGA inserted into standard industrial digital camera. Results show that the proposed approach produces high quality HDR-like scene-mapped 8-bit images with minimal computational cost. All improvements may be noticed through the performance evaluation.

     

Expected Response Times for Closed-Loop Multivehicle AMHS

We present an analytical approach for estimating the expected time for an automated material handling system (AMHS) to respond to move requests at loading stations in a vehicle-based, unidirectional, closed-loop AMHS. The expected response times are important for estimating the expected work-in-process (WIP) levels at the loading stations for design purposes, and for evaluating the performance of the AMHS as delayed response can impact the production cycle times. The expected response time approximation is validated by comparing the analytical model to the simulation results using a SEMATECH 300 mm hypothetical fab data set. Note to Practitioners - This paper describes an analytic method for estimating the average time for the AMHS to respond to lots ready for movement in a 300 mm wafer fab. The analysis is based on a large-scale model, requires standard solvers, and provides a very fast and reasonably accurate alternative to high-fidelity simulation. It is intended to support the early stage of fab design/redesign, allowing engineers to examine many different options before committing to the time and expense of simulation.     

Incorporating Waiting Time in Competitive Location Models

In this paper we propose a metaheuristic to solve a new version of the Maximum Capture Problem. In the original MCP, market capture is obtained by lower traveling distances or lower traveling time, in this new version not only the traveling time but also the waiting time will affect the market share. This problem is hard to solve using standard optimization techniques. Metaheuristics are shown to offer accurate results within acceptable computing times.