SDN中基于KMOBPSO的高可靠性控制器部署算法

针对SDN中控制器系统的单节点故障问题,兼顾系统成本和系统时延,应用N+1冗余备份模型来提高SDN控制器部署的可靠性,并将其抽象为多目标优化问题.同时,提出了一种融合K-means聚类算法和遗传算子的多目标二进制粒子群算法——KMOBPSO算法,以求解SDN控制器高可靠性部署问题的解.仿真结果表明,所提算法具有求解精度高、分布均匀、沿Pareto前沿面覆盖广的特点,能够显著提高SDN中控制器部署的可靠性.     

贴片设备的选择

随着电子工业的飞速发展,贴片设备已被广泛应用于大规模电子组装生产上。文章就贴片机选型时应注意的几个关键技术问题作简单介绍,希望对企业选择贴装设备有一定的帮助。     

Geometric quadrisection in linear time, with application to VLSI placement

We consider the following problem: given a set of points in the plane, each with a weight, and capacities of the four quadrants, assign each point to one of the quadrants such that the total weight of points assigned to a quadrant does not exceed its capacity, and the total distance is minimized.

This problem is most important in placement of VLSI circuits and is likely to have other applications. It is NP-hard, but the fractional relaxation always has an optimal solution which is “almost” integral. Hence for large instances, it suffices to solve the fractional relaxation. The main result of this paper is a linear-time algorithm for this relaxation. It is based on a structure theorem describing optimal solutions by so-called “American maps” and makes sophisticated use of binary search techniques and weighted median computations.

This algorithm is a main subroutine of a VLSI placement tool that is used for the design of many of the most complex chips.     

LED生产过程中的质量控制

对LED封装过程可能出现的问题逐一指出，并提出解决的办法，着重介绍封装位置对LED发光亮度的影响。以期引起LED封装管理人员及工作人员的注意。     

Preprocessing of rotamers for protein design calculations

We have developed a process that significantly reduces the number of rotamers in computational protein design calculations. This process, which we call Vegas, results in dramatic computational performance increases when used with algorithms based on the dead-end elimination (DEE) theorem. Vegas estimates the energy of each rotamer at each position by fixing each rotamer in turn and utilizing various search algorithms to optimize the remaining positions. Algorithms used for this context specific optimization can include Monte Carlo, self-consistent mean field, and the evaluation of an expression that generates a lower bound energy for the fixed rotamer. Rotamers with energies above a user-defined cutoff value are eliminated. We found that using Vegas to preprocess rotamers significantly reduced the calculation time of subsequent DEE-based algorithms while retaining the global minimum energy conformation. For a full boundary design of a 51 amino acid fragment of engrailed homeodomain, the total calculation time was reduced by 12-fold.     

Exact rotamer optimization for protein design

Computational methods play a central role in the rational design of novel proteins. The present work describes a new hybrid exact rotamer optimization (HERO) method that builds on previous dead-end elimination algorithms to yield dramatic performance enhancements. Measured on experimentally validated physical models, these improvements make it possible to perform previously intractable designs of entire protein core, surface, or boundary regions. Computational demonstrations include a full core design of the variable domains of the light and heavy chains of catalytic antibody 48G7 FAB with 74 residues and 10(128) conformations, a full core/boundary design of the beta1 domain of protein G with 25 residues and 10(53) conformations, and a full surface design of the beta1 domain of protein G with 27 residues and 10(60) conformations. In addition, a full sequence design of the beta1 domain of protein G is used to demonstrate the strong dependence of algorithm performance on the exact form of the potential function and the fidelity of the rotamer library. These results emphasize that search algorithm performance for protein design can only be meaningfully evaluated on physical models that have been subjected to experimental scrutiny. The new algorithm greatly facilitates ongoing efforts to engineer increasingly complex protein features.     

A probabilistic framework for next best view estimation in a cluttered environment

In this article, we present an information gain-based variant of the next best view problem for occluded environment. Our proposed method utilizes a belief model of the unobserved space to estimate the expected information gain of each possible viewpoint. More precise, this belief model allows a more precise estimation of the visibility of occluded space and with that a more accurate prediction of the potential information gain of new viewing positions. We present experimental evaluation on a robotic platform for active data acquisition, however due to the generality of our approach it also applies to a wide variety of 3D reconstruction problems. With the evaluation done in simulation and on a real robotic platform, exploring and acquiring data from different environments we demonstrate the generality and usefulness of our approach for next best view estimation and autonomous data acquisition.     

基于分片的云虚拟机安全保护技术

在典型的IaaS云中,用户使用云服务需要通过虚拟机实现。最近有研究表明,在大多数常用的加密协议(如SSL/TLS等)中,至关重要的加密密钥,可能被攻击者通过跨虚拟机的旁路攻击截获。针对这种攻击方式,提出了一种云虚拟机密钥保护系统,通过将加密密钥随机分割为多个分片,并将每个分片存储于不同的虚拟机中,能有效保护云中的加密密钥,抵御各类跨虚拟机的旁路攻击。此外,云虚拟机密钥保护系统会周期性地对加密密钥进行重新分割,即便攻击者能够截获局部的加密密钥,也无法进行还原。将云虚拟机密钥保护系统作为一种对应用软件透明的扩展库,运行在亚马逊EC2云的web服务器,取得了较好的成果。     

从用户角度看芯片贴装头技术

现代制造商一直特别看重在变动过程中迅速重新配置平台型贴装机的灵活性,以便能够对变动后的产品实现最优的贴装能力.现在,平台型贴装设备上提供的新一代贴装头技术扩展了这些系统的能力,可以提供高速芯片贴装功能,实现能够在不需重新配置,不会影响精度、良品率或产能的情况下,贴装常用的各种元件.它能使未来几代装配商将从更加灵活、自适应和精确的贴装头中受益,他们将提高利用率,大大降低变动时间,明显减少支持高速度、低成本、快速交货周期制造环境所需的反应时间.     

圆片级封装的凸点制作技术

圆片级封装是一种先进的电子封装技术,近年来,圆片级封装技术的发展速度很快,主要应用于系统级芯片、光电器件和MEMS等.凸点制作是圆片级封装工艺的关键工序,目前凸点制作工艺方法有多种,重点介绍常用的电镀法、植球法和蒸发沉积法凸点工艺,分别介绍这三种凸点制作技术的工艺流程、关键技术.