异构P2P网络的分布式查询协议

从P2P网络节点的异构性出发,考虑了节点物理位置,提出了一种分层的混合路由查询协议。该协议利用时间戳在局部实现了节点逻辑位置和物理位置的统一,并引入超级节点解决了节点负载失衡和性能瓶颈的问题。在仿真平台P2PSim上的性能测试表明,该协议在大规模P2P网络中优于Kademlia、Chord、Tapestry。     

OFDM系统二维变换域信道估计算法

着重分析OFDM系统的二维变换域(2-D transform-domain)的导频辅助信道估计。在变换域中对导频位置的信道频率响应(CFR)矩阵采用右下补零和中间补零两种方式进行插值,以获得整个信道的频率响应。考虑到上述两种方法带来的插值误差,提出了根据时间、频率方向的导频数目采用不同的补零数量和补零方式。采用Simulink构建基带仿真系统,仿真改进前后的系统误比特率(BER)并和其他二维插值方式进行比较。结果表明,该改进方法显著地提高了基于变换域信道估计的准确性,降低了系统的误比特率。     

对等网络泛洪DDoS攻击的防御机制

研究Gnutella协议的P2P网络中DDoS攻击,提出一种分布式的基于节点标识识别和节点流量实时检测过滤的自适应性DDoS攻击防御机制。通过在节点本地构建的信任和信誉机制对恶意节点主动阻断及对消息包的DDoS攻击特征的实时检测策略,实现对DDoS攻击的防范。仿真实验结果表明,该机制能有效地隔断网络中75%恶意消息数,节点能阻断80%的恶意消息数的转发,提高了网络抵御DDoS攻击的效能。     

竖直矩形通道降膜吸收器热质性能的试验研究

试验研究了溴化锂水溶液沿竖直矩形通道降膜吸收过程的传热传质情况。结果表明,溴化锂水溶液降膜流量、吸收压力、溶液进口浓度及进口温度对总传热系数、平均降膜吸收率的影响比较大。     

I~2C总线与PC机接口设计

介绍一种简单、成本低的 I2 C总线与 PC机的接口卡 ,普通微机便可以与 I2 C系列的外接设备数据传输 ,构成一个工业自动化生产过程的监控系统     

3-二茂铁基-2-丁烯酸钠对失血性血虚小鼠的补血作用

合成了 3-二茂铁基 - 2 -丁烯酸钠 ,并对其补血活性进行了测试 ,表明 3 -二茂铁基 - 2 -丁烯酸钠具有良好的补血作用 在给药剂量分别为 5mg/kg、1 0mg/kg时 ,以 5mg/kg剂量给药时补血效果更佳     

A note on the queue with a random set-up time under a restricted admissibility policy with a Bernoulli vacation schedule

This paper deals with the queue size distribution of an M^x/G/1 queue with a random set-up time and with a Bernoulli vacation schedule under a restricted admissibility policy. This generalizes the model studied by Madan and Choudhury [Sankhyá 66 (2004) 175–193].     

Output-Flexibilität in der Dienstleistungsproduktion

Zusammenfassung  Den Ausgangspunkt der überlegungen bildet die Interpretation von Dienstleistungen als Probleml?sungen, die eine M?glichkeit zur formalen Analyse der Output-Flexibilit?t er?ffnet. Im vorliegenden Beitrag werden in einer eigenschaftsorientierten Betrachtung zun?chst die Komponenten der Output-Flexibilit?t identifiziert, um dann darauf aufbauend ein Kalkül zur Gestaltung der Output-Flexibilit?t von Dienstleistungsunternehmungen abzuleiten.

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Summary  Output flexibility enables the service provider to cope with both uncertainties in demand and the external production factor. This paper aims at formulating a calculus for the design of output flexibility based on production theory. The interpretation of services as specific problem solutions serves as a basis for a feature-oriented modelling of service production.

Die Autoren danken zwei anonymen Gutachtern für wertvolle Verbesserungsvorschl?ge.     

Improved algorithms for largest cardinality 2-interval pattern problem

The 2-INTERVAL PATTERN problem is to find the largest constrained pattern in a set of 2-intervals. The constrained pattern is a subset of the given 2-intervals such that any pair of them are R-comparable, where model . The problem stems from the study of general representation of RNA secondary structures. In this paper, we give three improved algorithms for different models. Firstly, an O(n{log} n +L) algorithm is proposed for the case , where is the total length of all 2-intervals (density d is the maximum number of 2-intervals over any point). This improves previous O(n ²log n) algorithm. Secondly, we use dynamic programming techniques to obtain an O(nlog n + dn) algorithm for the case R = { <, ⊏ }, which improves previous O(n ²) result. Finally, we present another algorithm for the case with disjoint support(interval ground set), which improves previous O(n ²□n) upper bound. A preliminary version of this article appears in Proceedings of the 16th Annual International Symposium on Algorithms and Computation, Springer LNCS, Vol. 3827, pp. 412–421, Hainan, China, December 19–21, 2005.