Computer graphics simulation of a CNC lathe

A software system for simulation of the machining operations of a computerized numerically-controlled lathe is described. The microcomputer-based, BASIC software reads part program instructions from a sequential file, analyzes each instruction for errors and provides printed output describing the machine commands called for by the instruction as well as graphic output for tool motions. In an educational environment, the system can be used as a substitute for the more expensive machine tool or as a diagnostic and preview tool prior to actual machining.     

基于无干扰理论的虚拟机可信启动研究

云计算作为一种新型高价值计算系统,目前被广泛应用于各行业领域;等保2.0中也提出了对其应用主动免疫可信计算技术进行动态可信验证的要求.云计算模式下,虚拟机作为用户使用云服务的直接载体,其可信启动是虚拟机运行环境可信的基础.但由于虚拟机以进程的形式运行在物理节点上,其启动过程呈现出高动态性,且多虚拟机域间存在非预期干扰等特点;而现有的虚拟机可信启动方案存在虚拟机启动过程的动态防护性不足、缺乏多虚拟域间非预期干扰性排除等问题.针对上述问题,提出一种基于无干扰理论的虚拟机可信启动研究方案.首先,基于无干扰理论,提出了虚拟机进程的运行时可信定理;进一步地,给出了虚拟机可信启动的定义并证明了虚拟机可信启动判定定理.其次,依据虚拟机可信启动判定定理,基于系统调用设计监测控制逻辑,对虚拟机启动过程进行主动动态度量与主动控制.实验结果表明所提方案能够有效排除复杂云环境下多虚拟机间非预期干扰,保证虚拟机启动过程的动态可信性,且性能开销较小.     

Building Automated Trust Negotiation architecture in virtual computing environment

Automated Trust Negotiation (ATN) is an important method to establish trust relationship between two strangers by exchanging their access control policies and credentials. Unfortunately, ATN is not widely adopted because of the complexity and multiformity of negotiation policies, especially in virtual computing environment, where the situation becomes worse than in traditional computing environment, due to the fact that a host with multiple virtual machines needs to be deployed with multiple negotiation policies. Moreover, all of these policies for each virtual machine must be upgraded and checked. To ease the burden on the administrator when deploying ATN access control policies and credentials in virtual computing environment, we propose an automated trusted negotiation architecture called virtual automated trust negotiation (VATN) to centralize ATN policies and credentials for multiple virtual machines in a physical node into a privileged virtual machine. VATN puts policy compliance checker and credential verification control in each virtual machine to improve the execution efficiency of trust negotiation. We implement VATN in Xen virtualization platform. Finally, we discuss the correctness of policy consistency checking and make performance analysis of VATN implemented in Xen.     

面向嵌入式系统的优化编译器生成器设计

构造嵌入式系统是一个硬件软件的协同设计问题 .嵌入式软件的有效开发需要相应编译器的支持 .由于嵌入式系统存储空间有限 ,所以编译器生成的机器代码必须非常紧凑 .我们可以使用编译器的生成器来提高编译器的开发效率 .本文给出了一种编译器生成器的设计原理 ,利用该编译器生成器可以迅速生成面向某种指令系统和机器特征 ,并且能够对输出代码进行自动紧凑的编译器     

一个RISC流水结构机器QHRC上的编译时指令调度器

RISC体系结构常采用流水结构来提高机器的执行速度.然而,指令互锁现象的频繁出现严重影响了机器的执行效率.本文给出了一个流水结构机器上的基于机器描述表格化及参量化的指令调度算法。并利用该指令调度器作为工具,对多种解决指令互锁方案效果进行分析.最后,给出了一种兼顾硬件可行性与软件有效性的解决指令互锁的高性能方案。该算法的复杂度为O(n~2)。     

基于Alpha处理器的系统级仿真实现

以Alpha处理器作为实现平台,将系统仿真软件QEMU移植到Alpha上,使基于x86结构的Linux操作系统可以运行在系统虚拟机中,实现Alpha处理器与x86程序的兼容。对该虚拟机进行性能测试,通过统计代码膨胀率,找出制约虚拟机性能的指令类型,为虚拟机性能优化工作提供参考数据。     

An architectural framework for supporting heterogeneousinstruction-set architectures

An architectural framework that allows software applications and operating system code written for a given instruction set to migrate to different, higher performance architectures is described. The framework provides a hardware mechanism that enhances application performance while keeping the same program behavior from a user perspective. The framework is designed to accommodate program exceptions, self-modifying code, tracing, and debugging. Examples are given for IBM System/390 operating-system code and AIX utilities, showing the performance potential of the scheme using a very long instruction word (VLIW) machine as the high-performance target architecture     

Design and implementation of the secure compiler and virtual machine for developing secure IoT services

Recent years have seen the development of computing environments for IoT (Internet of Things) services, which exchange large amounts of information using various heterogeneous devices that are always connected to networks. Since the data communication and services occur on a variety of devices, which not only include traditional computing environments and mobile devices such as smartphones, but also household appliances, embedded devices, and sensor nodes, the security requirements are becoming increasingly important at this point in time. Already, in the case of mobile applications, security has emerged as a new issue, as the dissemination and use of mobile applications have been rapidly expanding. This software, including IoT services and mobile applications, is continuously exposed to malicious attacks by hackers, because it exchanges data in the open Internet environment. The security weaknesses of this software are the direct cause of software breaches causing serious economic loss. In recent years, the awareness that developing secure software is intrinsically the most effective way to eliminate the software vulnerability, rather than strengthening the security system of the external environment, has increased. Therefore, methodology based on the use of secure coding rules and checking tools is attracting attention to prevent software breaches in the coding stage to eliminate the above vulnerabilities. This paper proposes a compiler and a virtual machine with secure software concepts for developing secure and trustworthy services for IoT environments. By using a compiler and virtual machine, we approach the problem in two stages: a prevention stage, in which the secure compiler removes the security weaknesses from the source code during the application development phase, and a monitoring stage, in which the secure virtual machine monitors abnormal behavior such as buffer overflow attacks or untrusted input data handling while applications are running.     

基于威布尔分布的云计算能耗优化模型研究

针对云计算环境中复杂的虚拟机正常运行状态,提出将虚拟机运行看成由硬软件串联的可修复系统,用威布尔分布描述虚拟机硬软件正常运行的方法来建模缓解云计算高能耗问题。运用半马尔科夫过程刻画虚拟机运行过程、Laplace-Stielties变换简化数值计算、Bayesian定理去除限制条件,构建处理器利用率与能耗、性能的关系模型。再结合可修复系统寿命分布理论,调整虚拟机正常运行的威布尔分布函数,得到不同形状参数下处理器运行能耗以及给定任务完成时间,最终分析形状参数、处理器利用率与能耗-性能隐含关系并给出有效降低处理器运行能耗的合理化建议。数值分析表明：增大形状参数比提高利用率更显著降低处理器运行能耗;优化虚拟机配置使得形状参数变大,可以明显降低处理器运行能耗,同时避免云系统性能过度损耗。     

基于增强型虚拟机的软件保护技术

针对目前日益严峻的软件保护问题,对现有基于虚拟机的软件保护技术进行分析与研究,对虚拟机保护技术进行了改进,设计了一种增强型虚拟机软件保护技术。采用了虚拟花指令序列与虚拟指令模糊变换技术,并对虚拟机的虚拟指令系统做了改进,从而提高了虚拟机执行的复杂程度与迷惑程度,具有高强度的反逆向、防篡改、防破解的特点。实验分析表明,增强型虚拟机保护技术明显优于普通型虚拟机保护技术。     

一种用于Java虚拟机的类型化低级语言

为了能够减小运算系统的需信任计算基础、描述较小粒度的安全策略，目前的研究倾向于从程序设计语言和编译器入手来提高软件的安全性．基于以上研究背景设计了一种类型化的低级语言TLL,TLL是一种为Java虚拟机即时编译器设计的类型安全中间语言，以构造一个具有更小需信任计算基础的Java虚拟机系统为目的．TLL的类型系统基于多态的类型化λ演算，它具有丰富的表现力且能够编码各种高级语言的抽象．基于TLL的一个虚拟机原型系统已经实现，它可以作为实现一个高安全且面向多种源语言的运行时系统的起点．     

一种针对Xen超级调用的入侵防护方法

云计算技术已飞速发展并被广泛应用,虚拟化作为云计算的重要支撑,提高了平台对资源的利用效率与管理能力。作为一款开源虚拟化软件,Xen独特的设计思想与优良的虚拟化性能使其被许多云服务商采用,然而Xen虚拟机监视器同样面临着许多安全问题。Xen为虚拟机提供的特权接口可能被虚拟机恶意代码利用,攻击者可以借此攻击Xen或者运行其上的虚拟机。文章针对Xen向虚拟机提供的超级调用接口面临被恶意虚拟机内核代码利用的问题,提出了一种基于执行路径的分析方法,用以追溯发起该超级调用的虚拟机执行路径,与一个最初的路径训练集进行对比,可以避免超级调用被恶意虚拟机内核代码利用。该方法通过追溯虚拟机内核堆栈信息,结合指令分析与虚拟机内核符号表信息,实现了虚拟化平台下对虚拟机执行路径的动态追踪与重构。在Xen下进行实验,通过创建新的虚拟机并让其单独运行来获得训练集,训练集中包含所有发起该超级调用的虚拟机路径信息。在随后虚拟机运行过程中针对该超级调用动态构造出对应的虚拟机执行路径,将其与训练集对比,避免非正常执行路径的超级调用发生。     

一种可编程链路测试系统的设计与实现

针对目前卫星地面站链路测试系统测试流程固化的问题,采用了虚拟机的思想,设计了一个执行测试指令的指令机,基于该指令机,实现了一种可编程的链路测试系统;该系统为不同的链路测试建立了一个统一的测试框架,简化了软件系统的结构;同时,该系统定义了自己的测试脚本格式,极大地增强了测试系统的可编程性和可扩展性;实际应用中编写了14种链路测试脚本,形成通用测试库,基于该库顺利完成了该站的链路指标测试工作,系统运行稳定,测试数据准确可靠;通过修改脚本,可以方便地设计新的测试流程,大大提高了测试的可扩充性和测试效率,具有一定的实用性和推广价值。     

面向BW104x软流水框架

现代高性能数字信号处理器大多数采用超长指令字体系结构,通过在同一时钟周期发射多条指令以便获得更高的运算性能来发掘目标机器指令级别并行性.介绍了BW104x目标体系特征,BWDSP104X是一款针对高性能计算领域设计的处理器,采用16发射、单指令流,多数据流架构.为了充分利用多簇及簇内硬件资源,基于open64编译基础设施提出了后端软流水优化,其中包括循环选择,资源依赖数据依赖计算,采用经典的模调度方法进行软流水调度,为解决不同迭代变量冲突引入模变量拓展模块.实验结果证明流水后性能相对流水前有了很好的提升.     

A framework for computation-memory algorithmic optimization for signal processing

The heterogeneity of today's computing environment means computation-intensive signal processing algorithms must be optimized for performance in a machine dependent fashion. In this paper, we present a dynamic memory model and associated optimization framework that finds a machine-dependent, near-optimal implementation of an algorithm by exploiting the computation-memory tradeoff. By optimal, we mean an implementation that has the fastest running time given the specification of the machine memory hierarchy. We discuss two instantiations of the framework: fast IP address lookup, and fast nonuniform scalar quantizer and unstructured vector quantizer encoding. Experiments show that both instantiations outperform techniques that ignore this computation-memory tradeoff.     

DJM: a global distributed virtual machine on the Internet

In this paper, we present the design and implementation of a novel model of distributed computing on the Internet and Intranet environment. Our model is called the Distributed Java Machine (DJM). It is a global distributed virtual machine used to realize the concept of ‘network is the computer’. DJM explores coarse-grained parallelism by using the under-utilized workstations on the network, combining the elements of object-oriented technology, distributed computing, World-Wide Web and Java programming. It can run on machines with heterogeneous hardware and software platforms without relinking or recompilation. DJM has two unique features. First, using an original applet helper mechanism, DJM allows machines without any DJM software and of different levels of ‘trust’ to work together. Secondly, DJM has implemented concurrency enhancement mechanisms (one-way message, future and redirected future) to increase the efficiency of method invocation. The prototype of DJM has been implemented and tested under both the Intranet and the Internet environments. Using the workstations from our teaching laboratories, which are already running under normal loading, experimental results show that we can achieve a speedup of about 5–8 times by 14 workstations in a Local Area Network (LAN) environment, and about 4.5 times speedup for eight workstations in a Wide Area Network (WAN) environment. © 1998 John Wiley & Sons, Ltd.     

Robust comprehension of natural language instructions by a domestic service robot

We present a method through which domestic service robots can comprehend natural language instructions. For each action type, a variety of natural language expressions can be used, for example, the instruction, ‘Go to the kitchen’ can also be expressed as ‘Move to the kitchen.’ We are of the view that natural language instructions are intuitive and, therefore, constitute one of the most user-friendly robot instruction methods. In this paper, we propose a method that enables robots to comprehend instructions spoken by a human user in his/her natural language. The proposed method combines action-type classification, which is based on a support vector machine, and slot extraction, which is based on conditional random fields, both of which are required in order for a robot to execute an action. Further, by considering the co-occurrence relationship between the action type and the slots along with the speech recognition score, the proposed method can avoid degradation of the robot’s comprehension accuracy in noisy environments, where inaccurate speech recognition can be problematic. We conducted experiments using a Japanese instruction data-set collected using a questionnaire-based survey. Experimental results show that the robot’s comprehension accuracy is higher in a noisy environment using our method than when using a baseline method with only a 1-best speech recognition result.     

普适计算环境下的虚拟机技术研究

普适计算环境中资源和服务利用率较低,传统应用程序在该环境下无法兼容。为此,提出一种适用于普适计算环境的虚拟机技术。使用设备请求代理屏蔽复杂的普适计算网络环境,对上层应用提供统一硬件平台,支持多个普适计算应用同时运行。实验结果表明,该虚拟化技术能兼容传统应用,提高普适计算资源和服务的利用率。