改扩建工程中桥梁PHC管桩基础的应用

在改建工程中,为了减小桥梁拓宽后原桥和新建部分的不均匀沉降给结构带来的不利影响,桥梁改扩建尽可能采用桩基础。桥梁桩基础是工程施工中的关键环节,其施工质量对拓宽桥梁工程的整体质量有着重要的影响。本文以京港澳高速公路改扩建工程为依托,探讨了PHC预制管桩较传统的钻孔灌注桩的优势,详细介绍公路改扩建工程中桥梁PHC预制管桩的施工要点,对收锤标准进行了分析和验证。最后对桥梁PHC管桩施工注意事项进行了介绍,可为类似改扩建项目中桥梁PHC管桩施工提供经验与借鉴。

短时退火对5754铝合金组织与力学性能的影响

选择1.2mm的5754铝合金冷轧板材在160℃~540℃进行3min保温退火,模拟气垫炉短时退火工艺,通过拉伸性能测试、硬度测试与金相显微组织观察等,研究材料力学及显微组织的演变规律。结果表明,低温热处理时材料发生回复,材料保持与冷轧态一致的纤维状组织,随退火温度升高,强度、硬度开始降低,延伸率有所提升。

面向国产处理器大数据一体机的基因压缩技术研究

大数据一体机作为大数据时代的基础设施,其自主安全可控显得尤为重要。基因数据因其巨大的社会价值、经济价值及军事价值,其安全是国家安全的一部分。因此,存储、分析与处理基因数据是国产处理器大数据一体机的重要应用之一。文中首先介绍了国产处理器大数据一体机和基因序列文件主要格式,然后分为无参考序列基因压缩算法和基于参考序列基因压缩算法综述了FASTA格式基因数据压缩技术及基因压缩并行化技术的发展历程和研究现状,同时在国产处理器大数据一体机上验证了近年来优秀基因压缩算法的性能。研究面向国产处理器大数据一体机的基因压缩技术对解决基因数据安全和基因压缩技术自主可控具有很重要的意义,也为我国基因处理技术的全面国产化提供了参考。

ENERGY EFFICIENT DISTRIBUTED STEGANOGRAPHY FOR SECURE COMMUNICATION IN WIRELESS MULTIMEDIA SENSOR NETWORKS

A secure communication mechanism is necessary in the applications of Wireless Multimedia Sensor Networks (WMSNs), which is more vulnerable to security attacks due to the presence of multimedia data. Additionally, given the limited technological resources (in term of energy, computation, bandwidth, and storage) of sensor nodes, security and privacy policies have to be combined with energy-aware algorithms and distributed processing of multimedia contents in WMSNs. To solve these problems in this paper, an energy efficient distributed steganography scheme, which combines steganography technique with the concept of distributed computing, is proposed for secure communication in WMSNs. The simulation results show that the proposed method can achieve considerable energy efficiency while assuring the communication security simultaneously.

LOCALIZATION ALGORITHM BASED ON MINIMUM CONDITION NUMBER FOR WIRELESS SENSOR NETWORKS

During range-based self-localization of Wireless Sensor Network (WSN) nodes, the number and placement methods of beacon nodes have a great influence on the accuracy of localization. This paper proves a theorem which describes the relationship between the placement of beacon nodes and whether the node can be located in 3D indoor environment. In fact, as the highest locating accuracy can be acquired when the beacon nodes form one or more equilateral triangles in 2D plane, we generalizes this conclusion to 3D space, and proposes a beacon nodes selection algorithm based on the minimum condition number to get the higher locating accuracy, which can minimize the influence of distance measurement error. Simulation results show that the algorithm is effective and feasible.

A NEW APPROACH TO DVC COMBINED WITH ROI EXTRACTION AND RESIDUAL VIDEO CODING FOR MULTIMEDIA SENSOR NETWORKS

The Wyner-Ziv distributed video coding scheme is characterized for its intraframe encoder and interframe decoder which can also approach the efficiency of an interframe encoder-decoder system. In Wyner-Ziv residual coding of video, the residual of a frame with respect to a reference frame is Wyner-Ziv encoded, which can reduces the input entropy and leads to a higher coding efficiency than directly encoding the original frame. In this paper, we propose a new approach of residual coding combined with Region Of Interest (ROI) extraction. Experimental results show that, the proposed scheme achieves better rate-distortion performance compared to conventional Wyner-Ziv coding scheme.

A NEW PRIVACY-PRESERVING EUCLID-DISTANCE PROTOCOL AND ITS APPLICATIONS IN WSNS

Recently, privacy concerns become an increasingly critical issue. Secure multi-party computation plays an important role in privacy-preserving. Secure multi-party computational geometry is a new field of secure multi-party computation. In this paper, we devote to investigating the solutions to some secure geometric problems in a cooperative environment. The problem is collaboratively computing the Euclid-distance between two private vectors without disclosing the private input to each other. A general privacy-preserving Euclid-distance protocol is firstly presented as a building block and is proved to be secure and efficient in the comparison with the previous methods. And we proposed a new protocol for the application in Wireless Sensor Networks (WSNs), based on the novel Euclid-distance protocol and Density-Based Clustering Protocol (DBCP), so that the nodes from two sides can compute cooperatively to divide them into clusters without disclosing their location information to the opposite side.

A HYBRID PETRI-NET MODEL OF GRID WORKFLOW

In order to effectively control the random tasks submitted and executed in grid workflow,a grid workflow model based on hybrid petri-net is presented. This model is composed of random petri-net,colored petri-net and general petri-net. Therein random petri-net declares the relationship between the number of grid users' random tasks and the size of service window and computes the server intensity of grid system. Colored petri-net sets different color for places with grid services and provides the valid interfaces for grid resource allocation and task scheduling. The experiment indicated that the model presented in this letter could compute the valve between the number of users' random tasks and the size of grid service window in grid workflow management system.

THE STRATEGY OF RESOURCE MANAGEMENT BASED ON GRID COMPUTING

This paper analyzes the defaults of traditional method according to the resource management method of grid computing based on virtual organization. It supports the concept to ameliorate the resource management with mobile agent and gives the ameliorated resource management model. Also pointed out is the methodology of ameliorating resource management and the way to realize in reality.

预拉伸变形对6016铝合金显微组织及性能的影响

在气垫炉生产线固溶淬火、预时效处理后,通过拉伸测试、金相测试及表面观察,研究了6016铝合金经过不同拉伸变形后组织及性能的变化。结果表明,在0%~16%拉伸范围内,随着变形量的增加,T4态材料的屈服强度、抗拉强度均逐渐增加,但是幅度逐渐变小;伸长率、n值逐渐下降,r值有缓慢下降趋势,但是不明显。烤漆后屈服强度、抗拉强度均逐渐增加,到16%时有降低的趋势,延伸率逐渐降低。材料的晶粒形貌从等轴状演变为拉长的椭圆状,罗平线的形貌逐渐变得明显。

Topology control based on quantum genetic algorithm in sensor networks

Nowadays,two trends appear in the application of sensor networks in which both multi-service and quality of service(QoS)are supported.In terms of the goal of low energy consumption and high connectivity,the control on topology is crucial.The algorithm of topology control based on quantum genetic algorithm in sensor networks is proposed.An advantage of the quantum genetic algorithm over the conventional genetic algorithm is demonstrated in simulation experiments.The goals of high connectivity and low consumption of energy are reached.

Wavelet analysis method for detection of DDoS attack on the basis of self-similarity

As the traditional methods were not suitable for the detection of small distribute denial of service(DDoS)attack and identification of busy traffic,on the basis of the influence of DDoS attack,one wavelet analysis method was proposed.Wavelet method of coefficient variance analysis was deduced and a software model for the method was designed.In addition,key issues of the choice of wavelet and calculation of Hurst were resolved.The experimental results show that the proposed method has more advantages in accurately identifying busy traffic and detection of small DDoS attack.

A secure model for mobile agent based on encrypted circuit construction

As a new technology,mobile agent(MA)shows a wide application in the field of network technology.However,security has been one of the crucial problems in its application.A new protection model based on a trusted element is presented in this paper.The trusted element,which differs from the traditional trusted hardware such as a smart card or a co-processor,offers a third party service based on an encrypted circuit construction.The procedure of constructing an encrypted circuit is introduced and the method of using the trusted service to protect the MA is also described.An application example is given to show how to use the new model at the end of the paper.