基于期望首达时间的形状距离学习算法

由于逐对形状匹配不能很好地反映形状间相似度,因此需要引入后期处理步骤提升检索精度. 为了得到上下文敏感的形状相似度,本文提出了一种基于期望首达时间（Mean first-passage time,MFPT）的形状距离学习方法. 在利用标准形状匹配方法得到距离矩阵的基础上,建立离散时间马尔可夫链对形状流形结构进行分析.将形状样本视作状态,利用不同状态之间完成一次状态转移的平均时间步长,即期望首达时间,表示形状间的距离.期望首达时间能够结合测地距离发掘空间流形结构,并可以通过线性方程进行有效求解.分别对不同数据进行实验分析,本文所提出的方法在相同条件下能够达到更高的形状检索精度.     

含时滞项的双稳系统中平均首次穿越时间的研究

研究了含时滞项的非对称双稳系统中的平均首次穿越时间问题.应用小时滞近似方法,得到了系统的Fokker-Planck方程及稳态概率密度函数,进而得到了系统的平均首次穿越时间的表达式,最后对理论结果做了数值模拟.数值计算结果表明:(1)时滞量的大小对系统的稳态概率密度函数的影响是不一样的,当0<τ<0.175时,系统的稳态概率密度函数曲线仍然为双峰形状;当τ>0.175时,系统的稳态概率密度函数曲线呈现出阱状.(2)在0<τ<0.175时,讨论了系统的乘性和加性噪声强度对系统的平均首次穿越时间的影响,发现平均首次穿越时间T -乘性噪声强度曲线上有最小值出现,而T -加性噪声强度曲线是单调的.     

一种基于广义期望首达时间的形状距离学习算法

形状距离学习是形状匹配框架中引入的后处理步骤, 能够有效改善逐对计算得到的形状间距离.利用期望首达时间分析形状间相似度可能导致距离更新不准确, 针对这一问题提出了一种基于广义期望首达时间 (Generalized mean first-passage time, GMFPT) 的形状距离学习方法.将形状样本集合视作状态空间, 广义期望首达时间表示质点由一个状态转移至指定状态集合所需的平均时间步长, 本文将其视作更新后的形状间距离.通过引入广义期望首达时间, 形状距离学习方法能够有效地分析上下文相关的形状相似度, 显式地挖掘样本空间流形中的最短路径, 并消除冗余上下文形状信息的影响.将所提出的方法应用到不同形状数据集中进行仿真实验, 本文方法比其他方法能够得到更准确的形状检索结果.     

Dynamic behavior of periodic potential system driven by cross-correlated non-Gaussian noise and Gaussian white noise

The dynamic behavior of the periodic potential system driven by the cross-correlated non-Gaussian noise and Gaussian white noise is studied in this article. According to path integral method and unified color noise approximation, the periodic potential system is transformed into a stochastic equivalent Stratonovich stochastic differential equation. Then the Fokker–Planck equation and the expression of the steady-state probability density are derived. The fourth-order Runge–Kutta algorithm is used to calculate the times response of the system. Meanwhile, the probability density function (PDF) of the first-passage time (FPT) is simulated, and the mean first-passage time (MFPT) is obtained by averaging these values. Finally, the influence of noise parameters on MFPT and PDF of FPT is analyzed.     

Seamless handover supported by parallel polling and dynamic multicast group in connected WLAN micro-cells system

WLAN (Wireless Local Area Network) has been seen to be one of the promising access technologies that adapts to 4G cellular network systems in providing very high speed connection with QoS guarantee through the polling function. However, when the handover happens, the contention-based medium access mechanism which is mainly used in WLAN is invoked and introduces unbounded transmission delay due to idle time periods and retransmission because of collision during the handover. If this technique is expanded to use in a microcellular network such as connected WLAN micro-cells, contention-based mechanism, therefore, should not be used to handle the MT’s handover, especially for vehicular users who change access point every few seconds. To overcome these difficulties in handover, we introduce parallel polling scheme in dynamic LMC (Logical Macro Cell) which can reduce delays much and remove packet loss rate. LMC is a virtual single macro cell which is built on a multicast group of adjacent micro-cells. In the same LMC, polling signals are sent from every BS (base station) to give MT (mobile terminal) permission to access one of these BSs. Instead of wasting much time to contend for resources of a new BS during handover, the MT answers the polling as an acknowledgment to connect to that new BS. The polling response is controlled to multicast to all BSs of the same LMC via the core network to synchronize for the next polling cycle. LMC is controlled to dynamically change when the MT comes in a new BS to make polling signals be continuous in a new LMC. Through analytical and simulation results, we show that the parallel polling scheme can achieve no handover latency, no packet loss and maintain mobile users’ throughput stably in the high traffic load condition though it causes overhead on the neighboring cells in both of wired and wireless sections. At speeds of up to70 m/s, the MT can still maintain its stable connection. OMNeT++ simulator with INET project is used to evaluate our proposal.     

An apple image segmentation method based on a color index obtained by a genetic algorithm

Harvesting and spraying robots based on machine vision have become important in modern agricultural engineering. Fast segmentation of fruit images is the main task of robotic picking and spraying in orchards. In this paper, a color index-based segmentation method for apple images was proposed. It can automatically obtain a specific color index according to the image segmentation task. This method was used to obtain color index and segmentation thresholds for segmenting apple images. The mean pixel segment accuracy, mean intersection over union, mean dice similarity coefficient, and mean segment time was 0.90, 0.81, 0.98, and 20 (ms). The result showed that this method could segment apple in orchard images effectively and fastly. It could be used in precise apple planting management. At the same time, this paper provided a systematic method to get a specific color index.

     

Application of the spectral method to estimate the structural reliability of a reactor containment

In this paper structural reliability is studied for the Secondary Containment of a nuclear power plant subjected to ground motions during an earthquake. The occurrence of earthquakes is modeled by a filtered Poisson process and the ground motion by a stationary normal process. Within linear-elastic material behavior the structural response is evaluated in terms of power spectral density. Hereby the interaction between soil and structure is taken into account.It is assumed that the structural failure occurs if the resulting stress exceeds the ultimate shear stress for the first time. The probability of failure for the whole structure is approximated by summing these first-passage probabilities of hot-spots. Finally the structural reliability is estimated.This approach is exemplified to the concrete hull of the reactor Biblis B where the given record is considered as a representative sample of an ergodic stochastic process.     

一种结合硬件特征的并行内存故障检测方案

针对March类内存检测算法越来越复杂、检测时间越来越长,且更适用于对嵌入式内存芯片的检测等问题,提出一种结合硬件特征的并行内存故障检测方案。该方案包括2种并行检测方法:(1)根据DDR2的结构和工作原理设计的芯片级并行,可以并行检测一个DDR2内部的多个内存芯片。(2)根据访存控制器的结构和工作原理设计的访存控制器级并行,可并行检测多个DDR2内存条。对于芯片级并行,访存带宽越大,即并行检测的芯片个数越多,并行效果越好,从1个芯片到并行检测8个芯片,内存的检测时间几乎是呈线性递减的。对于访存控制器级并行,访存控制器数量越多并行效果越好,从1个LMC到2个LMC,内存的检测时间几乎减少了一倍。实验结果表明,2种并行检测方法不仅能够成倍加快检测速度,而且更适用于用户对内存的检测。     

含不同时滞项的双稳系统中平均首次穿越时间的研究

研究了乘性噪声和加性噪声共同作用下含有两种不同时滞项的双稳系统中的平均首次穿越时间．首先通过近似方法得到了平均首次穿越时间的解析式，然后研究了乘性噪声强度、时滞量及噪声关联强度对平均首次穿越时间的影响．当噪声关联强度取正值时，平均首次穿越时间T1（x-→x＋）是乘性噪声强度及两种时滞量的非但调函数，是噪声关联强度的单调递增函数．包含在确定力与振荡力中的时滞量分别影响T1（x-→x＋）的最大值及对应的噪声强度．平均首次穿越时间T2（x＋→x-）是包含在确定力中的时滞量的非单调函数，是乘性噪声强度、另一种时滞量及噪声关联强度的单调递减函数．     

The effect of experience and socio-economic status on web searching performance: a South African perspective

The digital divide can be described in terms of two dimensions: access and usage. Many statistics exist to prove the existence of the gap with regard to access to information and communication technology, and specifically the Internet, in South Africa. In this study, the focus was on users' aptitude in searching for information on the World Wide Web once access had been obtained. It was found that experience of 20 browser sessions is not adequate to ensure that learners from lower socio-economic communities improve in their ability to obtain the correct information during web searches but learners from higher socio-economic communities may, depending on the level of difficulty of the task and the phase of search, benefit from this amount of experience. Web experience has no effect on users' efficiency in terms of the number of mouse clicks made although socio-economic status (SES) is a significant predictor of efficiency for users with no or limited experience. Although low-SES users make fewer clicks en route to an answer as they gain experience, it does not necessarily mean that they perform better in obtaining the correct information.     

Analysis of a multi-server queue with two priority classes and (M, N)-threshold service schedule I: non-preemptive priority

In this paper, we propose an ( M , N )-threshold non-preemptive priority service schedule for a queueing system consisting of two-parallel queues and a multi-server. The arrival process for each queue is Poisson, and the service times are exponentially distributed with different means. We derive the generating functions of the stationary joint queue-length distribution, and then obtain the mean queue length and the mean waiting time for each queue.     

Analysis of transmission delay for a structured-priority packet-switching system

We consider a priority-based packet-switching system with three phases of the packet transmission time. Each packet belongs to one of several priority classes, and the packets of each class arrive at a switch in a Poisson process. The switch transmits queued packets on a priority basis with three phases of preemption mechanism. Namely, the transmission time of each packet consists of a preemptive-repeat part for the header, a preemptive-resume part for the information field, and a nonpreemptive part for the trailer. By an exact analysis of the associated queueing model, we obtain the Laplace-Stieltjes transform of the distribution function for the delay, i.e., the time from arrival to transmission completion, of a packet for each class. We derive a set of equations that calculates the mean response time for each class recursively. Based on this result, we plot the numerical values of the mean response times for several parameter settings. The probability generating function and the mean for the number of packets of each class present in the system at an arbitrary time are also given.     

Response time distribution in a multiprogrammed computer with terminal traffic

The central server model has been used to study a computer with a CPU and disks and operating with a fixed limit on the level of multiprogramming. An approximation of this model is to treat the CPU and disk subsystem as a single state-dependent server. Under some assumptions, such an approximation is known to give good results for the mean response time. This paper is concerned with two issues about this approximation. First, we obtain a complete characterization of the response time distribution. Second, based on this characterization, a numerically feasible method is developed for computing the response time distribution. When applied to several examples involving a CPU and several disks, this method yielded results which compared well with those obtained by a simulation of the central server model.     

Two kinds of optimal controls for probabilistic mix-valued logical dynamic networks

This paper addresses two kinds of optimal control problems of probabilistic mix-valued logical control networks by using the semi-tensor product of matrices, and presents a number of new results on the optimal finite-horizon control and the first-passage model based control problems, respectively. Firstly, the probabilistic mix-valued logical control network is expressed in an algebraic form by the semi-tensor product method, based on which the optimal finite-horizon control problem is studied and a new algorithm for choosing a sequence of control actions is established to minimize a given cost functional over finite steps. Secondly, the first-passage model of probabilistic mix-valued logical networks is given and a new algorithm for designing the optimal control scheme is proposed to maximize the corresponding probability criterion. FinMly, an illustrative example is studied to support our new results/algorithms.     

半导体激光宫颈糜烂治疗仪故障在线监测研究

传统的半导体激光宫颈糜烂治疗仪故障监测方法是基于基极短路法实现在线监测,监测过程中存在平均时延过高的问题。为此,设计半导体激光宫颈糜烂治疗仪故障在线监测方法。分析半导体激光治疗仪常见故障,以此为基础,引用合适的微型传感器,选择LMC662芯片作为前置放大器,设计相应的前置放大电路,利用无线传感网络技术向监测中心发送故障报警信息,实现治疗仪故障在线监测。测试结果表明:传统的监测方法测试的平均时延为46 ms,设计的治疗仪在线监测方法测试的平均时延为24 ms,两者相比,设计的治疗仪在线监测方法平均时延更小,该方法更适合应用在实际项目中。     

Solving a bi-criteria permutation flow-shop problem using shuffled frog-leaping algorithm

Flow shop problems as a typical manufacturing challenge have gained wide attention in academic fields. In this paper, we consider a bi-criteria permutation flow shop scheduling problem, where the weighted mean completion time and the weighted mean tardiness are to be minimized simultaneously. Due to the complexity of the problem, it is very difficult to obtain optimum solution for this kind of problems by means of traditional approaches. Therefore, a new multi-objective shuffled frog-leaping algorithm (MOSFLA) is introduced for the first time to search locally Pareto-optimal frontier for the given problem. To prove the efficiency of the proposed algorithm, various test problems are solved and the reliability of the proposed algorithm, based on some comparison metrics, is compared with three distinguished multi-objective genetic algorithms, i.e. PS-NC GA, NSGA-II, and SPEA-II. The computational results show that the proposed MOSFLA performs better than the above genetic algorithms, especially for the large-sized problems.     

A Provably Correct Translation of the λ-Calculus into a Mathematical Model of C++

We introduce a translation of the simply typed λ-calculus into C++, and give a mathematical proof of the correctness of this translation. For this purpose we develop a suitable fragment of C++ together with a denotational semantics. We introduce a formal translation of the λ-calculus into this fragment, and show that this translation is correct with respect to the denotational semantics. We show as well a completeness result, namely that by translating λ-terms we obtain essentially all C++ terms in this fragment. We introduce a mathematical model for the evaluation of programs of this fragment, and show that the evaluation computes the correct result with respect to this semantics.     

Long-term tool elimination planning for a wafer fab

Wafer manufacturers must make decisions regarding tool elimination due to changes caused by demand, product mixes, and overseas fab capacity expansion. Such a problem is raised by leading semiconductor manufacturers in Taiwan. This paper is aimed at developing a sound mechanism for tool portfolio elimination based on determining which equipment can be pruned. In the proposed mechanism, product mix, wafer output, capital expenditure, tool utilization, protective capacity, and cycle time are taken into the overall evaluation. This paper develops an integer programming model to avoid trial-and-error and to obtain the optimal solution. Compared to the current industry approach, the results show that the proposed mechanism can effectively identify the correct tools for elimination with a large capital savings and little cycle time impact.     

Full-parameter vision navigation based on scene matching for aircrafts

Vision navigation based on scene matching between real-time images and a reference image has many advantages over the commonly used inertial navigation system （INS）, such as no cumulative measurement errors for long-endurance flight. Recent developments in vision navigation are mainly used for partial navigation parameters measurements, such as the position and the relative velocity, which cannot meet the requirements of completely autonomous navigation. We present the concept, principle and method of full-parameter vision navigation （FPVN） based on scene matching. The proposed method can obtain the three-dimensional （3D） position and attitude angles of an aircraft by the scene matching for multiple feature points instead of a single point in existing vision navigations. Thus, FPVN can achieve the geodetic position coordinates and attitude angles of the aircraft and then the velocity vector, attitude angular velocity and acceleration can be derived by the time differentials, which provide a full set of navigation parameters for aircrafts and unmanned aerial vehicles （UAVs）. The method can be combined with the INS and the cumulative errors of the INS can be corrected using the measurements of FPVN rather than satellite navigation systems. The approach provides a completely autonomous and accurate navigation method for long-endurance flight without the help of satellites.     

一种光纤电压传感器的研究

利用BGO(锗酸铋)晶体作传感头的光纤电压传感器,并用偏振光分析法推出了它的数学模型.利用稳频后的He-Ne激光器作为测量光源;采用补偿测量方案消除晶体自然双折射(应力、温度等)引起的误差;讨论了各光学元件粘接方位角误差对测量精度的影响;系统中用间接测量法测量空气的折射率,对测量方程进行实时修正;采用高精度屏蔽电压器和小波分析算法提高系统的信噪比.实验结果表明,其测量电压误差不大于0.92%.