基于SS序列集成电路布线技术

集成电路(IC)是在半导体基片上形成的完整的电子线路。当前芯片里的电路与系统日趋复杂,超大规模集成电路(VLSI)设计技术水平也在逐渐提高。VLSI设计中一般采用分级设计的方法。布图设计过程是整个VLSI分级设计中非常关键的步骤之一。基于Single-Sequence的集成电路布图就是在SS编解码的应用下对芯片中各单元的摆放进行优化从而达到芯片面积利用率最大化。本文重点介绍了在SS序列生成版图后各单元间连线的设计以及如何根据水平/垂直约束图提取版图中各单元的坐标。并根据要连模块的位置关系对其连线经过的模块进行有条件加线宽的处理。     

基于SS序列集成电路布线技术

集成电路（IC）是在半导体基片上形成的完整的电子线路。当前芯片里的电路与系统日趋复杂,超大规模集成电路（VLSI）设计技术水平也在逐渐提高。VLSI设计中一般采用分级设计的方法。布图设计过程是整个VLSI分级设计中非常关键的步骤之一。基于Single-Sequence的集成电路布图就是在SS编解码的应用下对芯片中各单元的摆放进行优化从而达到芯片面积利用率最大化。本文重点介绍了在SS序列生成版图后各单元间连线的设计以及如何根据水平／垂直约束图提取版图中各单元的坐标。并根据要连模块的位置关系对其连线经过的模块进行有条件加线宽的处理。     

一种考虑电压岛边界约束的多电压布图算法

多电压设计(multiple supply voltage,MSV)是降低SoC功耗的有效方法之一.为便于电压岛供电引脚的放置,提出了一种考虑电压岛边界约束的多电压布图算法.首先,基于切分树表示的布图解特点,提出一种边界检查算法快速确定所有模块的边界信息.其次,以优化功耗为目标采用改进动态规划方法进行多电压分配并构建电压岛.最后,以模拟退火算法作为搜索引擎对芯片的面积、线长和功耗进行协同优化.为减少SA迭代次数,采用了一个两阶段的降温策略.对GSRC电路的实验结果表明,该算法可获得满足边界约束的多电压布图,且和不考虑边界约束时相比,仅在功耗上平均增加5.2％.     

用于验证工艺开发包的测试芯片自动生成流程

在工艺开发包的验证过程中,需要手动地在版图编辑器中对参数化单元进行实例化和摆放绕线,由此产生大量测试芯片。为此,提出一种用于验证工艺开发包的测试芯片自动生成流程,采用软件接口产生Skill脚本和工艺开发包交互,以获取工艺开发包的信息、发送命令对工艺开发包进行操作的方法,能自动地对参数化单元予以实例化,自动地摆放绕线,并实现测试芯片版图的布局规划。用该软件接口针对某代工厂的40 nm半导体工艺开发包开发一套测试芯片,产生一条测试芯片的平均时间为5.2 s左右,结果证明该方法是有效的,能缩短工艺开发包的验证时间。     

片上TCAM的研究和应用

为了提高片上TCAM的摆放密度和降低功耗,基于IBM 32 nm工艺库提供的TCAM的特性和优先编码器硬核,设计出同时满足多个查找宽度的外围控制电路。相比于之前的设计和实现,该设计可以减少TCAM的块数和相关寄存器的数量,减少片上TCAM的摆放面积,降低芯片的整体功耗。该设计已经成功应用于公司第4代路由交换ASIC芯片上。     

基于Single—Sequence布图规划线长约束问题的研究

布图规划是VLSI设计中非常重要的步骤。Single—Sequenc是一种非常有用的表示布图的编码方法。在实际的布图规划中,由于线长对芯片性能有较大的影响,因此为了使芯片的整体性能达到最优,考虑线长因素,使线长尽可能短。该论文提出了在用模拟退火算法寻求最优布图的同时,通过对算法加以改进,考虑线长约束条件,有效地解决了布图规划的线长约束问题。     

确定区域详细布线算法

提出了一种确定区域的详细布线算法,它能对不同设计模式进行布线。该算法能适用于任意多层布线情况,并且支持不同布线层具有的不同工艺参数,在构造布线树时,考虑芯片当前的走线拥挤度,使布线比较平均,并加快了算法运行速度、改善了布线质量,在连接两点线网时,构造基于二维迷宫布线结果的分层图,提出了一种对分层图的启发式染色算示来进行布线层分配,大大提高算法布线速度,采用拆线重布的方法来处理布线失败的线网。     

利用公共子序列求解固定边框布图问题

提出一种新的固定边框的布图算法．该算法采用SP表示方法,以公共子序列为基础,在随机搜索过程中限定布图宽度的变化,从而使减小芯片面积的目标与固定边框的目标在一定程度上取得一致．与现有的固定边框布图算法相比,文中算法在边框更紧凑、宽长比更大的条件下具有更高的成功率和更短的运行时间．此外,文中算法在布图初始阶段就可以对固定边框的合理性进行评估,避免了因给定的边框不合理而带来的时间上的浪费．     

上界可控的门矩阵布图算法

文中介绍了上界可控的门矩阵布图算法(简称为GMLCUB).由于引进了虚界差这一新思想,使门矩阵布图由局部优化转变为准全局优化,并由此得到了理想的结果.     

硅基TPMS集成传感器研究

本文介绍了一种应用于轮胎压力监测系统(TPMS)的传感器芯片的设计与制作.该传感器芯片集成了压阻式压力传感器和单电阻结构的温度传感器,根据量程需要,硅杯膜的厚度与面积比比较大,所以高应力区向膜外扩展,通过改变桥臂电阻的摆放位置和形状,提高了传感器的灵敏度,并且通过采取高浓度注入电阻拐角区域,得到了较好的零点输出.     

Holarchy formation and optimization in holonic manufacturing systems with contract net

Holonic manufacturing systems (HMS) is based on the notion of holon, an autonomous, cooperative and intelligent entity to provide a econfigurable, flexible and decentralized manufacturing environment to respond to changing needs and opportunities. A set of holons that cooperate to achieve a goal forms a holarchy. How to design a mechanism to form a holarchy to achieve a goal while minimizing the overall cost is a challenge. The objectives of this paper are to propose models and develop collaborative algorithms to guide the holons to form a holarchy to coherently move toward the desired goal state ultimately. We adopt contract net protocol (CNP) to model mutual selection of holons in forming a holarchy. We formulate a holarchy optimization problem to minimize the cost subject to the feasibility constraints. To analyze the feasibility of a holarchy, a Petri net (PN) model is proposed. As classical PN models do not take into account the cost involved in firing transitions, we augment the PN model with cost functions in the problem formulation. Due to the distributed architecture of HMS, the internal structure of each potential holarchy that acts as bidder in CNP is not available to the manager. A key issue is to determine the feasibility of a holarchy without constructing the whole PN model of the given hierarchy. We study the feasible conditions for a holarchy and propose a collaborative algorithm to analyze the feasibility and award contracts to holons without constructing the whole model of a holarchy.     

Voices that cannot be heard: Can shyness explain how we communicate on Facebook versus face-to-face?

Social networking sites have gained popularity among all populations, especially young adults. Personality traits were found to be predictive of how individuals use social media. Therefore, this study sought to examine the association between shyness and self-disclosure to a Facebook friend as well as self-disclosure to a face-to-face friend. Two studies were conducted. The first study tested how shyness and social loneliness are related to self-disclosure to a Facebook friend to whom an individual talks most often. The second, follow-up study tested how shyness is related to self-disclosure to a Facebook friend to whom a person speaks to only though Facebook, and also to a face-to-face friend to whom the participants talk only face-to-face and never through Facebook. Participants were college students from a large research university in the United States. Study 1 found a negative association between shyness and self-disclosure to a Facebook friend. Study 2 found a negative association between shyness and self-disclosure to a face-to-face friend. The theoretical implications and limitations are discussed.     

Design of phononic materials/structures for surface wave devices using topology optimization

We develop a topology optimization approach to design two- and three-dimensional phononic (elastic) materials, focusing primarily on surface wave filters and waveguides. These utilize propagation modes that transmit elastic waves where the energy is contained near a free surface of a material. The design of surface wave devices is particularly attractive given recent advances in nano- and micromanufacturing processes, such as thin-film deposition, etching, and lithography, which make it possible to precisely place thin film materials on a substrate with submicron feature resolution. We apply our topology optimization approach to a series of three problems where the layout of two materials (silicon and aluminum) is sought to achieve a prescribed objective: (1) a grating to filter bulk waves of a prescribed frequency in two and three dimensions, (2) a surface wave device that uses a patterned thin film to filter waves of a single or range of frequencies, and (3) a fully three-dimensional structure to guide a wave generated by a harmonic input on a free surface to a specified output port on the surface. From the first to the third example, the resulting topologies increase in sophistication. The results demonstrate the power and promise of our computational framework to design sophisticated surface wave devices.     

A distributed learning model for Freshwater Ecology practical classes

Abstract This paper describes a case study where a distributed learning model was used to enhance the traditional teaching of a freshwater ecology practical class by providing students with a student-centred constructivist environment. Prior to the practical session, a website was created and students were encouraged to think about the morphological adaptations of stream organisms. They were then divided into groups and taken to a real stream to collect specimens and bring them back to the laboratory for further examination and discussion. After the practical, each student group was required to produce a web page concerning the adaptations of the stream organisms to answer a set of online tutorial questions, and to participate in web-based discussion. Feedback by questionnaire showed that the great majority of students enjoyed working with the website and found the content very useful. More than half of the students preferred this type of web-assisted, student-centred practical to conventional practicals, while about a third showed no special preference between the two approaches.     

Learning criterion and inductive behaviour

Inductive behaviours may be classified according to their aim. We intend to show that there are at least two kinds of inductive behaviours. Most of the publications seem to take into consideration only one of these: to copy as exactly as possible the behaviour of a probability process. After a brief discussion to explain the necessity of a learning criterion and a recall about one criterion, representative of most of them, we shall define a new criterion, and show why it is better fitted to learn the laws of a deterministic process from a set of observations.This criterion has been used to implement a program which builds an acceptor of natural language sentences in a CAI environment using a tutorial strategy, and then for a question answering device. As attractive as the results are, their improvement requires a semantic model. We give the basic principles of a model which we currently develop, and whose main feature is approximation.     

Semantic constraint specification and verification of ebXML business process specifications

Electronic Business using eXtensible Markup Language (ebXML) Business Process Specification Schema (BPSS) supports the specification of the set of elements required to configure a runtime system in order to execute a set of ebXML business transactions. The BPSS is available in two stand-alone representations; a UML version and an XML version. Due to the limitations of UML notations and XML syntax, however, the current ebXML BPSS specification is insufficient to formally specify semantic constraints of modeling elements. In this study, we propose a classification scheme for BPSS semantic constraints, and describe how to represent those semantic constraints formally using Object Constraint Language. As a way to verify a particular Business Process Specification (BPS) with formal semantic constraint modeling, we suggest a rule-based approach to represent the formal semantic constraints, and describe a detail mechanism to apply the rule-based specified constraints to the BPS in a prototype implementation.     

USBWall: A novel security mechanism to protect against maliciously reprogrammed USB devices

Universal Serial Bus (USB) is a popular choice of interfacing computer systems with peripherals. With the increasing support of modern operating systems, it is now truly plug-and-play for most USB devices. However, this great convenience comes with a risk that can allow a device to perform arbitrary actions at any time while it is connected. Researchers have confirmed that a simple USB device such as a mass storage device can be disguised to have an additional functionality such as a keyboard. An unauthorized keyboard attachment can compromise the security of the host by allowing arbitrary keystrokes to enter the host. This undetectable threat differs from traditional virus that spreads via USB devices due to the location where it is stored and the way it behaves. We propose a novel way to protect the host via a software/hardware solution we named a USBWall. USBWall uses BeagleBone Black (BBB), a low-cost open-source computer, to act as a middleware to enumerate the devices on behalf of the host. We developed a program to assist the user to identify the risk of a device. We present a simulated USB device with malicious firmware to the USBWall. Based on the results, we confirm that using the USBWall to enumerate USB devices on behalf of the host eliminates risks to the hosts.     

Hybrid job offer recommender system in a social network

Recommender systems (RSs) play a very important role in web navigation, ensuring that the users easily find the information they are looking for. Today's social networks contain a large amount of information and it is necessary that they employ a mechanism that will guide users to the information they are interested in. However, to be able to recommend content according to user preferences, it is necessary to analyse their profiles and determine their preferences. The present work proposes a job offer RS for a career‐oriented social network. The recommendation system is a hybrid, it consists of a case‐based reasoning (CBR) system and an argumentation framework, based on a multi‐agent system (MAS) architecture. The CBR system uses a series of metrics and similar cases to decide whether a job offer is likely to be recommended to a user. Besides, the argumentation framework extends the system with an argumentation CBR, through which old and similar cases can be obtained from the CBR system. Finally, a discussion process is established amongst the agents who debate using their experience from past cases to take a final decision.     

Using the Manhattan distance for computing the multiobjective Markov chains problem

This paper presents a novel method for computing the multi-objective problem in the case of a metric state space using the Manhattan distance. The problem is restricted to a class of ergodic controllable finite Markov chains. This optimization approach is developed for converging to an optimal solution that corresponds to a strong Pareto optimal point in the Pareto front. The method consists of a two-step iterated procedure: (a) the first step consists on an approximation to a strong Pareto optimal point and, (b) the second step is a refinement of the previous approximation. We formulate the problem adding the Tikhonov's regularization method to ensure the convergence of the cost-functions to a unique strong point into the Pareto front. We prove that there exists an optimal solution that is a strong Pareto optimal solution and it is the closest solution to the utopian point of the Pareto front. The proposed solution is validated theoretically and by a numerical example considering the vehicle routing planning problem.