基于WIA-PA安全标准的网络密钥管理机制设计分析

WIA-PA安全标准隶属于过程自动化领域,是由我国工业无线联盟制定的基于IEEE802.15.4标准的无线网络系统,属于WIA的子标准,主要用于工业过程中无线短程网的控制、测量以及监视。基于WIA-PA安全标准网络密钥管理机制设计的内容主要包括基于WIA-PA安全标准的密钥基本管理设计、基于WIA-PA安全标准的入网安全性设计、基于WIA-PA安全标准的数据流安全传输设计、基于WIA-PA安全标准的系统实用性研究设计、基于WIA-PA安全标准的系统性能研究设计。     

建立军工保密管理长效机制的几点思考

在分析新时期军工企业保密工作面临的新形势的基础上,提出保密管理工作中存在的问题,并从提升管理人员自身素质、建立保密管理体系、加强定密工作、建立保密管理平台和建立商业秘密保护管理机制等方面提出改进建议,以期以点带面,从而建立军工保密管理的长效机制,不断提高保密管理工作的科学化水平。     

Spectrocolorimetric and microscopic techniques for the evaluation of plasticized PVC cleaning: a case study applicable to three-dimensional objects at museums

For the validation of a cleaning method in conservation, the examination of the object's surface after the cleaning and the quantification of the cleaning efficiency are significant steps. In this study, several cleaning solutions were tested on a plasticized poly(vinyl chloride) object whose surface was characterized before and after cleaning by optical microscopy and noncontact profilometry. In addition, different methods to quantify the cleaning efficiency based on spectrocolorimetric and microscopic techniques were provided. The results showed that noncontact profilometry supported by optical microscopy and spectrocolorimetry was very useful for the characterization of the plasticized poly(vinyl chloride) surface before and after the cleaning and also for the determination of the cleaners' efficiency.     

On a novel press system with six links for precision deep drawing

The objective of this paper is to propose a novel press system with six links for precision deep drawing, and verify its feasibility. First, the system is presented and its advantages are discussed. Then, the kinematic analysis of the system is obtained by examining the geometry of the design. Moreover, kinematic dimensions of the variable coupling are found by using optimization method. Furthermore, the proposed approach is illustrated by a design example, its solid model for the proposed design is established, and then kinematic simulation is performed by ADAMS software. Finally, a prototype and an experimental setup are established, and the experiment is conducted. The results show that the proposed new mechanism is feasible and of reasonable accuracy. In addition, it has the advantages of easy manufacture, lower cost, higher precision, and easy adjustability.     

Development of a robot assisted carotid blood flow measurement system

The ultrasound diagnosis of the carotid artery is one of the most common non-invasive methods to detect early stage heart and cerebrovascular diseases. However, the precision and repetitiveness of the probe positioning depend exclusively on the operator's skills and dexterity. For this purpose, we propose the development of a robot assisted system to enhance the accuracy and repetitiveness of the probe positioning to measure the wave intensity (WI) index. In this paper, the Waseda-Tokyo Women's Medical-Aloka Blood Flow Measurement Robot System No. 2 Refined (WTA-2R) is presented. The WTA-2R consists of a conventional ultrasound diagnosis system, a 6-DOFs parallel link slave manipulator, a 6-DOFs serial link passive arm, and a master device. Experiments were carried out to verify its effectiveness in terms of accuracy and required time to perform the task. From the experimental results, the positioning accuracy and reduction of required time were confirmed.     

A constant-force bistable mechanism for force regulation and overload protection

A novel constant-force bistable mechanism (CFBM) allowing constant contact force and overload protection is developed. When a device equipped with a CFBM is loaded by an unknown force exceeding a critical force of the CFBM, the CFBM can snap to its other stable equilibrium state to safeguard the device. The bistability of the mechanism originates from combined compression and bending of the beam structures. Finite element analyses are used to characterize the constant-force behavior and bistability of the mechanism under static loading. A design formulation is proposed to find the CFBM shape for a specified displacement range with constant output force of the mechanism. Prototypes of the CFBM are fabricated and tested. The characteristics of the CFBM predicted by theory are verified by experiments. Using the CFBM, sophisticated sensors and control system for force regulation of machining systems can be eliminated.     

基于无线传感网的轻量级数字签名系统设计

为了确保传感器网络中传输数据的可靠性,本文设计了一个基于对称密码体制的数字签名系统。系统使用对称密码机制来提高效率,采用硬件加密设备保证共享密钥池的安全,通过使用特定的密钥生成算法解决对称密钥的分发问题。实验结果表明,系统能耗低、效率高,具有很强的实用性。     

一种强制访问控制机制的审计方法

目前的安全操作系统模型有很多,以SELinux安全模型,AppArmor安全模型等为大家所熟知,基于这些强制访问控制模型的审计机制也更有不同。本文提供了一种基于轻量级DTE安全模型的审计机制,该机制中的审计信息采用固定大小格式,这样方便对其进行操作。该审计机制有效的监控了系统中主体对客体的所有访问,包括作法用户的操作和合法用户的误操作等。在系统自带的审计机制中,审计信息是系统中所有的审计记录的集合,数量相当庞大,不利于进行分析。本文提出审计开关,对审计记录中的数据进行分类处理,大大提高了检索和查找的速度。     

里底水电站坝址右岸倾倒变形岩体成因机制和变形程度

以里底水电站坝址右岸岩体结构特征为基础,分析了岩体倾倒变形的成因机制.通过对右岸勘探平硐揭露岩层产状的详细量测,结合硐壁物探测试成果,建立了倾倒强烈程度的分级体系,对右岸倾倒岩体进行了划分,为边坡稳定性评价确定了控制边界.     

冻融循环作用下盐渍土病害机理及改良技术综述

盐渍土在冻融循环作用下,主要表现出盐胀和冻胀特性,对土体结构造成破坏,土体发生变形,从而降低土体强度,给工程建设造成危害。为改良盐渍土、防治盐渍土病害,从盐渍土病害产生的机理出发,介绍了结晶压力是导致土体结构发生破坏、土体发生变形的本质因素,证实了结晶压力的大小与孔隙大小有关。水盐迁移会加剧盐胀和冻胀的发生。在冻融循环作用下,水分和盐分向土体表层发生运移。盐渍土的盐－胀特性受土体的干密度、含水量、含盐量、荷载和温度的影响,不同因素的影响程度不同,干密度的影响较含水量小。干密度越大、含水量和含盐量越高、降温速率越慢,盐－冻胀越强烈。荷载对盐－冻胀有抑制作用。通过对盐渍土病害机理的研究,结合盐渍土盐－冻胀的影响因素,从土质改良、加固土体、阻断水盐通道和温度控制四个方面阐述了冻融作用下盐渍土的改良方法,可供盐渍土地区的工程建设参考。目前关于结晶压力的研究主要是定性方面的,水盐迁移的研究以室内试验为主。未来对盐渍土病害机理的研究将主要集中在结晶压力的定量研究和水盐迁移的现场试验等方面。