Topology-aware peer-to-peer overlay network for Ad-hoc

The mismatch between the structured peer-to-peer (P2P) overlay network, which is based on Hashing, and the actual physical network, leads to query repeatedly passing through some nodes in the actual route when it is applied in Ad-hoc networks. An approach of getting an appropriate node identifier (ID) bearing its local physical information is proposed, in which the traditional theory of getting node ID through Hashing the node's Internet protocol (IP) address is abandoned, and a topology-aware overlay network suiting Ad-hoc networks is constructed. The simulation results show that the overlay network constructed in the proposed method can avoid the route being iteratively accessed. Meanwhile, it can effectively minimize the latency and improve the load balance.     

Overlay mark optimization for thick-film resist overlay metrology

For thick resist implant layers, such as a high voltage P well and a deep N well, systematic and uncorrectable overlay residues brought about by the tapered resist profiles were found. It was found that the tapered profile is closely related to the pattern density. Potential solutions of the manufacturing problem include hardening the film solidness or balancing the exposure density. In this paper, instead of focusing on the process change methodology,we intend to solve the issue of the overlay metrology error from the perspective of the overlay mark design. Based on the comparison of the overlay performances between the proposed overlay mark and the original design, it is shown that the optimized overlay mark target achieves better performance in terms of profiles, dynamic precision,tool induced shift (TIS), and residues. Furthermore, five types of overlay marks with dummy bars are studied, and a recommendation for the overlay marks is given.     

考虑覆盖层地基材料空间变异性的沥青混凝土心墙坝地震响应研究

河床覆盖土层参数不确定性往往显著影响其上覆沥青混凝土心墙坝的地震响应.将空间随机场模拟技术与有限元方法相结合,根据动力等效线性模型参数敏感性分析结果选取动力随机参数,采用正态或对数正态分布函数考虑覆盖层材料参数的空间变异性,采用高斯型自相关函数考虑空间相关性,采用Python进行协方差分解法生成随机参数库,并对ABAQ...     

OMAC: A new access control architecture for overlay multicast communications

Multicast communications concern the transfer of data among multiple users. Multicast communications can be provided at the network layer—an example is IP multicast—or at the application layer, also called overlay multicast. An important issue in multicast communications is to control how different users—senders, receivers, and delivery nodes—access the transmitted data as well as the network resources. Many researchers have proposed solutions addressing access control in IP multicast. However, little attention has been paid to overlay multicast. In this paper, we investigate the access control issues in overlay multicast and present OMAC: a new solution to address these issues. OMAC provides access control for senders, receivers, and delivery nodes in overlay multicast. The proposed architecture, which is based on symmetric key cryptosystem, centralizes the authentication process in one server whereas it distributes the authorization process among the delivery nodes. Moreover, delivery nodes are utilized as a buffer zone between end systems and the authentication server, making it less exposed to malicious end systems. To evaluate our work, we have used simulation to compare the performance of OMAC against previous solutions. Results of the simulation show that OMAC outperforms previous multicast access control schemes. Copyright © 2010 John Wiley & Sons, Ltd.     

旧水泥混凝土桥面改造施工工艺的探讨

结合北京市二环路中的桥区旧水泥混凝土路面的改造,介绍了对旧水泥混凝土路面进行改造处理及加铺时的施工工艺.     

基于侧边抛磨与覆盖材料的光纤光栅温度补偿新方法

提出并演示验证了将负热光系数的聚合物材料覆盖在侧边抛磨光纤光栅的抛磨区实现光纤光栅温度补偿的新方法。实验结果表明,这种新方法的温度补偿效果良好,封装后的光纤光栅处在63～79℃的环境温度时,可使其温度敏感度降低为未补偿时的1/16;当处在58～101℃的环境温度时,其温度敏感度降低为未补偿时的1/4。温度补偿封装后的光纤光栅器件直径只有2mm,长度为20mm。     

容迟网络体系结构及其关键技术研究

当前的Intemet体系结构和其中许多协议无法很好的适用存在高延迟和频繁割裂的网络.当端节点具有严格的能量和存储限制时,这一问题将更加恶化.由于移动性和特殊应用需求,使得像陆地移动网络、军事无线自组织网络、星际网络及无线传感器网络等这样的受限网络缺乏“保持连接”的基础结构.这些受限网络有它们自己的专有协议而不采用TCP/IP协议.为了实现这些网络之间的互联,国际上提出了在端到端连接和节点资源都受限时的一种新型网络体系结构和应用接口,称为延迟容忍网络(简称容迟网络,DIN,Delay-Tolerant Networks).DTN作为网络互联时传输层上的覆盖网可用来满足随意的异步消息可靠转发.本文研究分析了容迟网络的应用背景、体系结构、关键技术和一些开放问题,并给出了未来的发展方向和应用前景.     

Effect of anisotropic characteristics on the mechanical behavior of asphalt concrete overlay

Asphalt concrete (AC) overlays placed over old asphalt pavement have become an alternative to repairing and reinforcing pavements. The strength contributed by the AC overlay is strongly influenced by the anisotropic properties of the pavement material. This study was conducted to analyze the influence of anisotropy, modulus gradient properties, and the condition of the AC overlay and old pavement contact plane on the mechanical behaviors of AC overlays, as well as to quantify the influence of the degree of anisotropy on the mechanical behaviors of AC overlay by a sensitivity analysis (SA). The mechanical behaviors of the AC overlay were numerically obtained using the three-dimensional finite element method with the aid of ABAQUS, a commercial program. Variations in the AC overlay’s modulus as a function of temperature as well as the contact state between the AC overlay and AC layer were considered. The SA is based on standardized regression coefficients method. Comparing the mechanical behavior in terms of surface deflection, stress, and strain of the anisotropy model against those corresponding to the isotropic model under static loads show that the anisotropic properties had greater effects on the mechanical behavior of the AC overlay. In addition, the maximum shear stress in the AC overlay was the most significant output parameter affected by the degree of anisotropy. Therefore, future research concerning the reinforcement and repair of pavements should consider the anisotropic properties of the pavement materials.     

化工学科世界高水平大学的学科结构特征比较

本文以QS世界大学排名化学工程领域前50名大学的SCIE论文数据为基础,利用重复二分法聚类将其划分为5种类型,分析每种类型的学科结构特征,并采用科学层叠图对不同类型中代表性高校的学科分布进行了横向比较。研究结果可为我国高校化学工程学科的“双一流”建设提供对标参考,为高校制定学科发展规划、优化学科结构布局等提供借鉴。     

关于精确平均点度随机网络仿真模型的研究

为提高仿真模型的可信度，提出了一种随机网络生成算法。研究内容包括：随机节点的区域性分布，中心节点、OVERLAY功能节点的选择，实验推演新的概率连通公式，增加点度分类约束策略及随机网络快速连通策略等。在算法基础上建立了具有精确平均点度的随机网络仿真模型。对该随机网络仿真模型的性能做了一定的阐述、模拟和分析，表明该模型是通用性的、可定制的。与现有算法相比，该算法收敛性好，并能线性逼近所模拟的实际网络。