Random dispersion effects of conductive particles on anisotropic conductive film’s (ACF’s) bonding yield

Microsystem Technologies - In this study, the authors try to analyze the failure probability of Anisotropic Conductive Film (ACF) packages using V-shaped curve method considering the random effects...     

Numerical prediction of elastic properties for carbon nanotubes reinforced composites using a multi-scale method

The main aim of this research was to investigate longitudinal elastic and effective modulus of composites reinforced with zigzag and armchair single-walled (CNT) and multi-walled carbon nanotubes (MWCNT) with different volume fractions and aspect ratios via finite element simulation. A three-phased volume element was adopted for the modeling of nanocomposite behavior and nonlinear spring elements were used to model interphase part joints and the effective force between nanotubes and resin were determined based on Lennard-Jones potential. After the evaluation and validation of the model, elastic modulus and Poisson’s ratio of composites reinforced with zigzag and armchair CNTs with different volume fractions and aspect ratios were extracted. It was found that by increasing volume fraction and aspect ratio, elastic modulus of representative volume element of composite was increased and its Poisson’s ratio was decreased. At similar aspect ratio and volume fraction, the elastic modulus of composites reinforced with armchair CNTs and Poisson’s ratio of those reinforced with zigzag CNTs were higher. Also, results showed that elastic modulus of composite was independent from elastic modulus of interphase.

     

Performance vs. cost of redundant arrays of inexpensive disks

Data redundancy has been widely used to increase data availability in critical applications and several methods have been proposed to organize redundant data across a disk array. Data redundancy consists of either total data replication or the spreading of the data across the disk array along with parity information which can be used to recover missing data in the event of disk failure. In this paper we present an extended comparative analysis, carried out by using discrete event simulation models, between two disk array architectures: the Redundant Arrays of Inexpensive Disks (RAID) level 1 architecture, based on data replication; and the RAID level 5 architecture, based on the use of parity information. The comparison takes both performance and cost aspects into account. We study the performance of these architectures simulating two application environments characterized by different sizes of the data accessed by I/O operations. In addition, several scheduling policies for I/O requests are considered and the impact of non-uniform access to data on performance is investigated.     

Parametric fuzzy study for effects analysis of age on PWR containment cooling system

This paper presents an alternative parametric fuzzy study to subside aging impact analysis on the performance and availability of safety industrial systems. To this sense, a fuzzy fault tree computational system analysis, named of FuzzyFTA, was adopted. FuzzyFTA is a computing system that uses fault tree and fuzzy logic to determine fault event fuzzy importance and associated fuzzy uncertainty measures. The main goal of this approach makes possible, elapsed many years of plant operation, the gray determination of the system critical components and top event occurrence probability. A typical four loops pressurized water reactor (PWR) containment cooling system (CCS) was selected to examine the feasibility of the computational system approach in a real case study. Thus, a commonly found containment spray system and a fan cooler system were modeled. Failure rates, obtained from the operation of a PWR along 20 years, were accounted in the model. The bathtub curve characteristics presents in these failure rates permit the determination of the time-dependent effects of aging degradation more important to the general uncertainty of system. Thus, the system unavailability, considering the component failure rates increase by aging, can be calculated.     

V型微通道热沉的 流体流动与传热问题研究

V型微通道热沉具有体积小、流速小、散热效率高等优点,是将多个DL线阵组装为面阵并实现高性能冷却封装的良好解决方案.本文采用计算流体力学软件Fluent建立了V型微通道的数值模型,研究了其中的流体流动与传热问题.仿真结果表明,设计的V型微通道可满足激光二极管线阵的散热要求.仿真分析结果与V型微通道热沉样品的模拟热源加载实验测试数据对比,吻合较好,证明了数值仿真的有效性.     

Subset simulation method including fitness-based seed selection for reliability analysis

Probability estimation of rare events is a challenging task in the reliability theory. Subset simulation (SS) is a robust simulation technique that transforms a rare event into a sequence of multiple intermediate failure events with large probabilities and efficiently approximates the mentioned probability. Proper handling of a reliability problem by this method requires employing a suitable sampling approach to transmit samples toward the failure set. Markov Chain Monte Carlo (MCMC) is a suitable sampling approach that solves the SS transition phase using the failed sample of each simulation level as the seed of next samples. This paper is aimed to study the seed selection effect on the SS accuracy through several seed selection approaches inspired by the genetic algorithm and particle filter and using the main PDF of the variables to assign a mass function probability to each subset sample in the failure domain. Roulette wheel (I, II), tournament and proportional probability techniques are then employed to choose the weighed samples as seeds to be placed in the MCMC to transmit the samples. To examine the capability of each approach, reliabilities of some engineering problems were investigated and results showed that the proposed approaches could find proper failure sets better than the original SS method, especially in problems with several failure domains.

     

Numerical analyses of peel demolding for UV embossing of high aspect ratio micro-patterning

Ultraviolet (UV) embossing, involving molding against micro-structured molds, is a quick and efficient method to mass produce high aspect ratio micro-features. A crucial challenge to the repeatability and large-scale application of this technique is successful demolding, which escalates in difficulty with increasing aspect ratio, due to increased polymer-mold mechanical interlocking. Some of the key factors affecting UV embossing include the crosslinked polymer shrinkage and material properties, interfacial strength between polymer to mold and the demolding method. This paper presents a new method to simulate the demolding of UV cured polymer from a nickel mold. Hyperelastic material model and rate-independent cohesive zone modeling were employed in the numerical simulation; linear elastic polymer response, although relatively easy to apply, was not adequate. Progressive shrinkage was implemented, leading to delamination of the polymer-mold interface. The subsequent peeling of the cured polymer from the mold was modeled with increasing prescribed displacement. The optimal shrinkage degree was found to increase from 0.92 to 1.9% with increasing mold aspect ratio (aspect ratio is defined as height to width ratio) from 5 to 10.     

移动副速度对空气轴承影响的CFD仿真分析

研究空气轴承优化控制问题,针对高速移动副空气轴承对空气轴承气膜特性会影响定位精度特点,空气轴承采用非结构化网格实现了多节流器气膜的耦合,设计的密度可控的非均匀网格划分方案克服了最大最小尺寸比偏大给实际带来的困难。根据FLUENT用三维双精度耦合隐式标准k-ε粘性湍流两方程模型,仿真得到了不同移动副速度时,阵列多节流器耦合后的质量流量、气膜压强分布和速度分布,为辨识高速移动副时多节流器耦合的气膜数学模型提供了详实数据。当增大移动副速度时,耗气量减小但气膜承载力增加,为高速移动副空气轴承的优化设计提供了依据。     

磁盘阵列多级恢复系统的设计与实现

随着磁盘容量的不断增大,磁盘读写出错的概率也相应增加。为缩短磁盘阵列在磁盘出错后所需的恢复时间、降低磁盘阵列重构的频度,提出一种磁盘阵列的多级恢复系统MARS。该系统根据磁盘的不同健康状态调用盘内坏扇区映射MARS-1,盘间数据迁移MARS-2和磁盘重构MARS3恢复磁盘阵列。实验结果表明,多级恢复系统能有效减少磁盘阵列恢复的时间,降低磁盘阵列的重构次数,减少对系统I/O性能的影响。     

Tracking and disturbance rejection of MIMO nonlinear systems with PI controller

We study tracking and disturbance rejection of a class of MIMO nonlinear systems with linear proportional plus integral (PI) compensator. Roughly speaking, we show that if the given nonlinear plant is exponentially stable and has a strictly increasing dc steady-state I/O map, then a simple PI compensator can be used to yield a stable unity-feedback closed-loop system which asymptotically tracks reference inputs that tend to constant vectors and asymptotically rejects disturbances that tend to constant vectors.     

Prediction and Abnormality Assertion on Emu Brake Pad Based on Multivariate Integrated Random Walk

To better solve the issue with abnormal failure of electric motor unit (EMU) brake pad resulted from various random factors in the ever-changing operating environment, in this paper, a new evaluation method of performance prediction and abnormity decision is proposed based on the Multivariate integrated random walk (MIRW) model. In this method, the state space model of the EMU brake pad performance degradation is firstly established. And then based on the observed data, the brake pad performance degradation trend is extracted by the fixed interval forward - backward smoothing algorithm. Based on it, the future degradation state can be predicted by Kalman predictor. Based on the obtained state estimation values, abnormal failure tolerance range (AFTR) can be determined applying Grubbs criterion to judge whether the brake pad is being in abnormal state before reaching the final failure or not as a new sample appears. In addition, the cumulative failure probability of the brake pad is estimated in the degradation process. Finally, the thickness data of a certain type of EMU brake pad is applied to predict the future degradation state and determine the abnormal condition, and the result shows that the proposed method is more efficient and accurate.     

基于BDD的关联故障树定量分析法研究

利用二元决策图(BDD)中的B—割集和节点概率,提出了基于BDD的关联故障树定量分析新算法。推导了故障树顶事件发生概率和绝对失效强度算法公式,将故障树顶事件发生概率和绝对失效强度计算结合起来,避免了复杂的最小割集和不交化求解过程,显著地减少了布尔代数运算量,给出了算法递归步骤。大量的实例分析验证了此算法的工程实用性。     

Arc length-based aspect ratio selection

The aspect ratio of a plot has a dramatic impact on our ability to perceive trends and patterns in the data. Previous approaches for automatically selecting the aspect ratio have been based on adjusting the orientations or angles of the line segments in the plot. In contrast, we recommend a simple, effective method for selecting the aspect ratio: minimize the arc length of the data curve while keeping the area of the plot constant. The approach is parameterization invariant, robust to a wide range of inputs, preserves visual symmetries in the data, and is a compromise between previously proposed techniques. Further, we demonstrate that it can be effectively used to select the aspect ratio of contour plots. We believe arc length should become the default aspect ratio selection method.     

High-resolution models of motion of macromolecules in cell membranes

The path of a macromolecule on a cell membrane is modeled by a sum of independent identically distributed random variables. Random variables with simple discrete distribution functions capture some important aspects of the jump or hop diffusion reported from single particle tracking experiments that measure the motion of single molecules on a cell membrane. The detail provided by the distribution function for the random variables is critical for accurate simulations of the motion and interactions of macromolecules on the cell membrane. Additionally, the probability distribution for the random variables is easily estimated from single-particle tracking data. The diffusion constant is given by the second moment of the probability distribution, which agrees with the diffusion constant estimated from the mean-square displacement, and thus represents far less information than the distribution function.     

An electrostatic discharge model for thin‐film transistor fabrication

Electrostatic discharge (ESD) is a significant cause of yield loss in thin‐film transistor (TFT) array manufacturing. TFT arrays are at increased risk relative to other electronic components because the TFTs are unprotected; the array has a large inherent capacitance, and TFT processing includes many chucking and conveyance steps that result in triboelectric charge generation. To reduce or eliminate ESD‐caused fallout, an understanding must be gained of an ESD event's fundamental physics, including the mechanism of charge generation, ESD event physics, and TFT failure modes. An equivalent circuit model has been developed to address the physics of how ESD events occur. The ESD event scenarios modeled with this circuit are as follows: (1) the substrate glass is lifted from the chuck, resulting in a non‐uniform static charge; (2) this charge induces a voltage on the A‐side components; (3) the substrate is lifted, causing a voltage increases; (4) the uneven charge generated results in voltage gradients between TFTs, resulting in an ESD event. This model combines the effects of TFT substrate lifting and charge generation, with a simplified equivalent circuit representing the TFT array. The behavior of this circuit was simulated with a spice model (Electronics Research Laboratory of the University of California, Berkeley, CA, USA.) to characterize the ESD pulse.     

条件事件代数研究综述

综述了条件事件代数理论的原理、主要性质和应用．条件事件代数是一门新兴的解决不确定性、概率性和模糊性推理问题的学科,是在确保规则概率与条件概率相容的前提下,把布尔代数上的逻辑运算推广到条件事件(规则)集合中得到的代数系统,目的是为智能系统中的条件推理建立一个数学基础．该文也对比条件事件代数更一般的逻辑系统——关联事件代数理论进行了介绍．     

Detectability in stochastic discrete event systems

A discrete event system possesses the property of detectability if it allows an observer to perfectly estimate the current state of the system after a finite number of observed symbols, i.e., detectability captures the ability of an observer to eventually perfectly estimate the system state. In this paper we analyze detectability in stochastic discrete event systems (SDES) that can be modeled as probabilistic finite automata. More specifically, we define the notion of A-detectability, which characterizes our ability to estimate the current state of a given SDES with increasing certainty as we observe more output symbols. The notion of A-detectability is differentiated from previous notions for detectability in SDES because it takes into account the probability of problematic observation sequences (that do not allow us to perfectly deduce the system state), whereas previous notions for detectability in SDES considered each observation sequence that can be generated by the underlying system. We discuss observer-based techniques that can be used to verify A-detectability, and provide associated necessary and sufficient conditions. We also prove that A-detectability is a PSPACE-hard problem.     

基于RAID50的存储系统高速缓存设计

设计了一种多个控制卡分条的RAID50模型和主机虚拟卷地址到所属高级别阵列、低级别阵列分条的二级地址映射模式，以提高I/O访问的并发性。定义多个连续I/O块为扩展块并等同于Cache页大小，且作为RAID50传输粒度，进一步改善内存与存储设备之间的传输效率。设计了基于Cache描述符控制块的哈希链式查找算法和基于Cache页访问频率计数的二次机会置换算法，实现了一种主机数据接收与RAID50存储设备预读并发进行的策略。结果表明，该设计有效地提高了存储系统的I/O性能。     

数据依赖约束下的任务调度资源选择算法

大数据环境下的计算任务往往具有一定数据依赖性关系(如MapReduce),现有的分布式存储系统任务资源选择策略选择离请求者最近的数据块响应服务,忽略了对数据块所在服务器CPU、磁盘I/O与网络等资源负载状态的考虑。在分析研究系统集群结构、文件分块、数据块存储机制的基础上,定义了集群节点矩阵、CPU负载矩阵、磁盘I/O负载矩阵、网络负载矩阵、文件分块矩阵、数据块存储矩阵与数据块存储节点状态矩阵,为任务与数据之间的依赖性构建了基础数据模型,提出了一种数据依赖约束下的最优资源选择算法(ORS2DC)。任务调度节点负责维护基础数据,MapReduce任务与数据块读取任务由于依赖资源不同而采取不同的选择策略。实验结果表明：所提算法能够为任务选择质量更高的资源,提高任务完成质量的同时减轻了NameNode负担,减小了单点故障发生的概率。