Influence of age and body size on alarm responses in a freshwater snail Pomacea canaliculata

A hypothesis that size selection of prey by predators elicits size-specific responses from prey was examined. Freshwater snails, Pomacea canaliculata, ages 1, 3, 7, 15, 30, or 60 days, were given an extract of 3-day-old snails, and 3-day-old snails were given extracts of snails of the other ages or eggs. Snails 15 days or younger crawled out of the water in response to the 3-day-old snail extract, but older ones did not. The 3-day-old snails responded to the extracts of snails of all examined ages, but not to the extract of eggs. Snails of four size classes, 3-days-old, small (shell lengths 8–12 mm), medium (13–20 mm), and large (>28 mm) were given extracts of snails of each of these four classes. The 3-day-old snails crawled out of the water in response to the extract of 3-day-old snails, but showed a lower or no response to other extracts. Larger snails buried themselves in the soil in response to the extract of snails of similar sizes. These responses are discussed in the context of the evolution of the snail's avoidance behavior in response to the size-dependent prey choice by the predator.     

Neural Network Applications in Petroleum Exploration Based on Statistical Space Mapping

1 IntroductionThe seismic prospecting method has beenwidely used in petroleum exploration field. And dueto the complexity of the stratum structure, how to usethe mass seismic data to get the precise forecastresult is actracting more and more attention. However,lithology differentiation criterion could not be set upthrough seismic data only because of the lack oflithology information in seismic data. In the past,petroleum exploration experts demarcated thelithology of the seismic data through t…     

An automatic differentiation platform: Odyssée

Numerous automatic differentiation strategies can be imagined to produce all kind of derivative programs under a wide range of complexity constraints, but there is no way to prototype and evaluate them on real size applications with reasonable effort. Since the development of an automatic differentiation platform is prohibitively expensive, using an existing platform to share investments between the different research teams is a good solution. Odyssée is an open automatic differentiation tool that enables the development of program analysis as well as program transformation for automatic differentiation. It has been used to differentiate large size industrial programs (300 000 lines of Fortran 77) and to prototype diverse new automatic differentiation algorithms. Its source is now freely available, a cooperative research project can therefore be based on it without financial or contractual constraint.     

昆明地区粉、砂土液化判别存在问题的讨论

就昆明地区饱和粉土、粉砂的液化判别存在的实际问题，结合实际工程，分别采用标准灌入法和静力触探法进行判别、比较，针对判别结果存在的问题提出相应的完善措施和改进建议．     

Proportional loss rate differentiation in a FIFO queue

The relative differentiated service model is one of several models proposed for service differentiation in networks [IEEE Network Sept/Oct (1999) 26]. In this model, an assurance is given that ‘higher classes will be better, or at least no worse than lower classes.’ This paper describes a relative loss rate differentiation scheme based on RED. The scheme is used for differentially dropping packets in a FIFO queue during times of congestion. The main idea is, if packet losses are unavoidable in the FIFO queuing system, then they should be distributed among the different service classes in the queue in inverse proportion to the service price or weight assigned to each class. The simulation studies using TCP traffic show that the scheme is very effective in ensuring relative loss rate differentiation between service classes.     

Scalable service differentiation using purely end-to-end mechanisms: features and limitations

We investigate schemes for achieving service differentiation via weighted end-to-end congestion control mechanisms within the framework of the additive-increase-multiplicative-decrease (AIMD) principle, and study their performance as instantiations of the TCP protocol.Our first approach considers a class of weighted AIMD algorithms. This approach does not scale well in practice because it leads to excessive loss for flows with large weights, thereby causing early timeouts and a reduction in throughput.Our second approach considers a class of loss adaptive weighted AIMD algorithms. This approach scales by an order of magnitude compared to the previous approach, but is more susceptible to short-term unfairness and is sensitive to the accuracy of loss estimates.We conclude that adapting the congestion control parameters to the loss characteristics is critical to scalable service differentiation; on the other hand, estimating loss characteristics using purely end-to-end mechanisms is an inherently difficult problem.     

IEEE 802.11无线局域网的区分服务机制研究

文中探讨了在IEEE 802．II无线局域网中提供区分服务的有关问题，分析了有线网络中提供区分服务的QoS机制不适用于无线网络的原因，介绍了IEEE 802．II媒体访问控制层上的一种基于初始竞争窗口CWmin的按节点区分的优先级机制，并在此基础上给出了基于流的区分方法。仿真实验表明，基于节点的优先级区分机制对UDP流已经可以达到比较理想的效果，而对于TCP流效果并不明显，但基于流的区分服务机制能够对TCP流进行很好的区分。     

严格反馈随机非线性系统的自适应逆最优控制

讨论了自适应逆最优控制问题可解定理，基于Ito微分规则和Backstepping方法，给出了具有标准Wiener噪声扰动和未知定常参数的严格反馈随机非线性系统的全局依概率渐近稳定和自适应逆最优控制策略的设计方法，该方法可同时获得控制律和自适应律。仿真结果表明了控制算法的有效性。     

大干扰稳定中低频振荡模式的作用研究

该文在向量场正则形理论的指引下，提出了数值求解向量场非线形正则变换系数的算法，实现了非线性向量场的正则变换，得到了电力系统状态方程的2阶解析解和鉴别大干扰下主导低频振荡模式的方法。在此基础上，通过研究低频振荡模式与其它模式以及状态变量间的非线性相关作用，把低频振荡模式与系统大干扰稳定联系在一起。从另一个侧面揭示了以往大干扰稳定分析中所无法涉及的新现象，得到了一些新的观点和新的见解。     

一种适用于流媒体传输的无线TCP友好速率控制机制

综合无线错误丢包以及拥塞丢包事件的统计特征,基于丢包区分,本文提出一种适用于流媒体传输的无线TCP友好速率控制(Wireless TCP-Friendly Rate Control,WTFRC)方程并建立实用的速率控制机制.该机制包括服务器或者代理发送端和用户接收端两部分,分别负责往返传输时间(Round-Trip Time,RTT)估计、发送速率估计调整和丢包区分、丢包率(Pack-et Loss Ratio,PLR)统计、接收速率估计.仿真结果验证了该机制能够获得较高的吞吐量和较平缓的发送速率,并具备较好的TCP友好特征.