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81.
非结构化P2P中搜索算法的性能分析 总被引:1,自引:0,他引:1
欧阳柏成 《计算机工程与科学》2009,31(6)
资源搜索是P2P应用所面临的最核心问题之一,相关的非结构化P2P系统主要采用了查询消息泛洪和信息索引机制.本文分析了非结构化P2P中几种典型的搜索算法,阐述了其搜索原理和搜索性能 .与其他研究不同,本文通过大量的模拟实验来验证搜索算法的性能;在不同网络规模中,通过对每一种搜索算法的查询成功率、搜索产生消息数和成功查询所用平均跳数进行比较分析,给出了相关结论. 相似文献
82.
研制了基于氯霉素抗体包被Fe3O4/Au金磁纳米微粒(GMP)和三乙撑四胺铜(II)(CuL)共固定修饰平面热解石墨电极的安培免疫传感器(PRG|CuL / anti CAP-GMP),用于测定鱼肉中CAP含量.该免疫传感器是利用外加磁场,将anti CAP-GMP吸引到CuL修饰的PRG电极(PRG|CuL)表面制备而成.CuL对H2O2还原具有良好的电催化能力,当该传感器在含CAP样品液中温育后,CAP与电极表面的anti CAP的免疫结合物导致CuL对H2O2的催化还原电流(I)降低,电流下降值(△I)和CAP浓度成正比,可用于CAP定量测定.在25℃的pH=6.5磷酸盐缓冲液(PBS)中温育30 min,该传感器对CAP的检测线性范围为0.6~110 ng/mL,检出下限为0.092 ng/mL(3σ法).应用于鱼肉中CAP检测并与传统的液相色谱法(HPLC)比较,结果一致,其添加回收率在97%~104%之间.该免疫传感器集分离、富集为一体,电极表面可更新,检测灵敏快速,对于水产品中痕量氯霉素分析提供了一种新颖的方法. 相似文献
83.
Quanqing Xu Hengtao Shen Zaiben Chen Bin Cui Xiaofang Zhou Yafei Dai 《Frontiers of Computer Science in China》2009,3(3):381-395
The concept of Peer-to-Peer (P2P) has been introduced into mobile networks, which has led to the emergence of mobile P2P networks,
and originated potential applications in many fields. However,mobile P2P networks are subject to the limitations of transmission
range, and highly dynamic and unpredictable network topology, giving rise to many new challenges for efficient information
retrieval. In this paper, we propose an automatic and economical hybrid information retrieval approach based on cooperative
cache. In this method, the region covered by a mobile P2P network is partitioned into subregions, each of which is identified
by a unique ID and known to all peers. All the subregions then constitute a mobile Kademlia (MKad) network. The proposed hybrid
retrieval approach aims to utilize the floodingbased and Distributed Hash Table (DHT)-based schemes in MKad for indexing and
searching according to the designed utility functions. To further facilitate information retrieval, we present an effective
cache update method by considering all relevant factors. At the same time, the combination of two different methods for cache
update is also introduced. One of them is pull based on time stamp including two different pulls: an on-demand pull and a
periodical pull, and the other is a push strategy using update records. Furthermore, we provide detailed mathematical analysis
on the cache hit ratio of our approach. Simulation experiments in NS-2 showed that the proposed approach is more accurate
and efficient than the existing methods. 相似文献
84.
伴随着互联网的发展,电子商务逐渐进入我们的经济生活中。作为网络经济的产物,电子商务企业与传统企业在竞争优势上存在巨大差异。面对着日益激烈的竞争,电子商务企业如何保持核心竞争力优势对企业的生存尤为重要。本文聚焦于C2C领域,并以淘宝网为例,尝试从企业核心竞争力的角度诠释电子商务企业与传统企业竞争优势的差异和竞争力培养的着力点。 相似文献
85.
86.
Words that appear as constrained subsequences in a text-string are considered as possible indicators of the host string structure, hence also as a possible means of sequence comparison and classification. The constraint consists of imposing a bound on the number ω of positions in the text that may intervene between any two consecutive characters of a subsequence. A subset of such ω-sequences is then characterized that consists, in intuitive terms, of sequences that could not be enriched with more characters without losing some occurrence in the text. A compact spatial representation is then proposed for these representative sequences, within which a number of parameters can be defined and measured. In the final part of the paper, such parameters are empirically analyzed on a small collection of text-strings endowed with various degrees of structure. 相似文献
87.
88.
Liz de Rome Elizabeth A. Taylor Rodney J. Croft Julie Brown Michael Fitzharris 《Ergonomics》2016,59(4):504-513
Motorcycle protective clothing can be uncomfortably hot during summer, and this experiment was designed to evaluate the physiological significance of that burden. Twelve males participated in four, 90-min trials (cycling 30 W) across three environments (25, 30, 35 °C [all 40% relative humidity]). Clothing was modified between full and minimal injury protection. Both ensembles were tested at 25 °C, with only the more protective ensemble investigated at 30 and 35 °C. At 35 °C, auditory canal temperature rose at 0.02 °C min?1 (SD 0.005), deviating from all other trials (p < 0.05). The thresholds for moderate (>38.5 °C) and profound hyperthermia (>40.0 °C) were predicted to occur within 105 min (SD 20.6) and 180 min (SD 33.0), respectively. Profound hyperthermia might eventuate in ~10 h at 30 °C, but should not occur at 25 °C. These outcomes demonstrate a need to enhance the heat dissipation capabilities of motorcycle clothing designed for summer use in hot climates, but without compromising impact protection.
Practitioner’s Summary:
Motorcycle protective clothing can be uncomfortably hot during summer. This experiment was designed to evaluate the physiological significance of this burden across climatic states. In the heat, moderate (>38.5 °C) and profound hyperthermia (>40.0 °C) were predicted to occur within 105 and 180 min, respectively. 相似文献
89.
针对常规平面成像技术表现形式单一,容易视觉疲劳等问题,提出一种新型的基于FPGA/ARM异构双核控制的磁性介质显示系统,实现磁性介质的立体动态成像;本系统通过在Altera DE1-SoC的Linux平台上构建Lighttpd轻量级Web服务器和设计开发功能程序、底层驱动程序、自定义IP核和Verilog逻辑译码程序来实现该显示系统的软硬件开发;本系统具有网络设备跨平台控制能力、磁流体精确控制能力以及多种样式的汉字和图案显示能力;大量实验表明该系统能够通过控制磁流体完美的表现出立体书法、绘画图案,且系统运行稳定可靠。 相似文献
90.
秦玉龙 《单片机与嵌入式系统应用》2017,17(6)
介绍了基于Avalon总线的WM8731音频编解码控制器IP核的设计,包括音频数据访问接口模块和Avalon-MM接口模块等,并利用SOPC技术将其封装成可重用的IP核.自定义IP核的使用,有效降低了该芯片的开发难度,同时也使系统易于扩展和升级,具有较高的灵活性.在Quartus Ⅱ和ModelSim下使用VHDL语言完成了控制器的设计、仿真以及Nios Ⅱ系统的构建,并通过SignalTap Ⅱ逻辑分析仪进行了硬件测试.仿真和测试结果表明,该控制器满足WM8731各项时序要求. 相似文献