Probabilistic analysis on mesh network fault tolerance

Mesh networks are among the most important interconnection network topologies for large multicomputer systems. Mesh networks perform poorly in tolerating faults in the view of worst-case analysis. On the other hand, such worst cases occur very rarely in realistic situations. In this paper, we study the fault tolerance of 2-D and 3-D mesh networks under a more realistic model in which each network node has an independent failure probability. We first observe that if the node failure probability is fixed, then the connectivity probability of these mesh networks can be arbitrarily small when the network size is sufficiently large. Thus, it is practically important for multicomputer system manufacture to determine the upper bound for node failure probability when the probability of network connectivity and the network size are given. We develop a novel technique to formally derive lower bounds on the connectivity probability for 2-D and 3-D mesh networks. Our study shows that these mesh networks of practical size can tolerate a large number of faulty nodes thus are reliable enough for multicomputer systems. For example, it is formally proved that as long as the node failure probability is bounded by 0.5%$0.5\%$, a 3-D mesh network of up to a million nodes remains connected with a probability larger than 99%$99\%$.     

XAD-4微孔介质半挥发性PAHs吸附机制特征的研究

以"吸附相"机制探讨温度效应(30,50,70 ℃)影响XAD-4七种半挥发性PAHs(AcPy,AcP,Flu,PA,Ant,Fl,Pyr)吸附滞留特征.实验结果显示,随温度30 ℃升至70 ℃,XAD-4微孔介质七种PAHs单位吸附滞留体积(Vg)由31.8～58.5m3降至19.5～24.6 m3;高温环境(70 ℃)PAHs微孔介质吸附可能已由低温环境(30 ℃)孔径吸附转变为表面吸附.此外,讨论了七种气相PAHs化合物单位吸附滞留体积(Vg)与其过冷液蒸汽压(PL)相关性,结果显示两者呈负相关,PAHs已经不是气态型吸附式而是以纳米液态气胶进行微孔吸附行为.本研究结果显现微孔介质比表面积不是PAHs吸附效能唯一关键因子,温度效应与介质孔径效应都可能影响PAHs微孔吸附效能与介质吸附型式(表面吸附vs.孔径吸附).     

Preliminary study on some properties of Co-Cr dental alloy formed by selective laser melting technique

The surface condition, some properties and ion releasing behavior of cobalt-chromium (Co-Cr) dental alloy formed by selective laser melting (SLM) technique were investigated. Before porcelain fused firing, the surface condition of the Co-Cr alloy was observed using a scanning electron microscope (SEM), and then the density and hardness were examined. After porcelain fused firing, the interface of porcelain and alloy was observed, and then the metal-ion release of the samples was tested. SLM technique provides Co-Cr alloy higher hardness than casting method. After degassing-oxidation procedure and porcelain fused firing, the interface of the alloy and porcelain showed excellent combination. Co ion was more than Cr ion released from SLM Co-Cr alloy, the amounts of Co and Cr ions were safe according to ISO security criterion. Considering the properties before and after porcelain fused sintering process, SLM technique is suitable for dental Co-Cr alloy restoration.     

Uniform parallel-machine scheduling to minimize makespan with position-based learning curves

Scheduling with learning effects has become a popular topic in the past decade; however, most of the research focuses on single-machine problems. In many situations, there are machines in parallel and the skills of workers might be different due to their individual experience. In this paper, we study a uniform parallel machine problem in which the objective is to jointly find an optimal assignment of operators to machines and an optimal schedule to minimize the makespan. Two heuristic algorithms are proposed and computational experiments are conducted to evaluate their performance.     

Least eccentric ellipses for geometric Hermite interpolation

We present a rational Bézier solution to the geometric Hermite interpolation problem. Given two points and respective unit tangent vectors, we provide an interpolant that can reproduce a circle if possible. When the tangents permit an ellipse, we produce one that deviates least from a circle. We cast the problem as a theorem and provide its proof, and a method for determining the weights of the control points of a rational curve. Our approach targets ellipses, but we also present a cubic interpolant that can find curves with inflection points and space curves when an ellipse cannot satisfy the tangent constraints.     

Laplace变换求解成层土中污染物一维扩散问题

成层土中污染物的迁移规律较为复杂,将其简化为一维扩散模型.运用Laplace变换和Laplace数值逆变换方法进行了求解,编制了计算程序.计算结果可以退化到单层土的情况,结论与经典的理论解完全一致.通过与现有用数值软件计算结果的对比,检验了解答的正确性;采用的计算方法对一室内试验结果进行了模拟,计算结果和实测数据较为吻合,证明所提方法的可靠性.求解方法可用于求解更为复杂的边界条件下的污染物迁移问题.     

TiAl基合金的片层取向控制技术

定向凝固技术是一种获得具有单一取向凝固组织材料的重要技术,尤其是对于控制高温结构材料TiAl基合金的片层取向,该技术尤为重要。介绍目前广泛应用的控制片层取向方法,并分析各种TiAl基合金片层取向控制技术的应用方法、使用条件、优点和缺点,为今后TiAl基合金的研究和新的加工技术指明方向。     

汶川地震中高原大桥落梁破坏分析

结合实际震后现象对高原大桥的落梁破坏进行模拟分析,对震后落梁现象提出了一个新的解释,即认为地震过程中高原侧桥台后土体先发生破坏,在失去土体的支撑作用下桥台背墙在与邻梁的碰撞中被撞碎并被顶入土体中,从而引起墩台处的墩(台)梁位移增大,并最终导致落梁破坏的发生。     

一种改进的暗原色单幅图像去雾方法

暗原色先验方法可以较好地处理单幅图像去雾,但对理图像中的灰白区域处理效果不好。通过分析暗原色先验原理,得出了暗通道图像和雾的透射分布率以及雾的浓度系数的关系,提出了一种结合峰值信噪比和暗原色优先法则的去雾方法。由实验结果分析,该方法能够更清晰的表现去雾后图像的细节,并且一定程度上克服了原方法在处理图像中灰白区域效果不佳的弱点。     

基于Google SketchUp的虚拟校园三维建模

虚拟现实技术是一门新兴技术,应用领域广泛.文中以吉林建筑工程学院净月校区行政楼建筑外观造型为例,探讨了基于Google SketchUp的三维校园模型的建立,并通过透视效果图进行实际场景的模拟再现.