搜索结果

论文/程序题目	作者	下载	主要内容介绍	Hits
Intermittent search strategies when losing time becomes efficient	O. B磂nichou,M. Coppey		In this letter, we show that intermittent search strategies, alternating active search phases and non-reactive displacement phases, are universal for a wide class of problems involving search time optimization. More precisely, we address the general question of determining in which cases a searcher should, or should not, interrupt his search activity by 搇osing攖ime in non-reactive phases of mere displacement, and which durations of each phase optimize the search time. Using a representative analytical model, we show that intermittent strategies do optimize the search time as soon as the target is 揹ifficult?to detect, and we explicitly give the optimal search strategies, which depend on the memory skills of the searcher.	511
Intermittent search strategies when losing time becomes efficient	O. B磂nichou,M. Coppey		In this letter, we show that intermittent search strategies, alternating active search phases and non-reactive displacement phases, are universal for a wide class of problems involving search time optimization. More precisely, we address the general question of determining in which cases a searcher should, or should not, interrupt his search activity by 搇osing攖ime in non-reactive phases of mere displacement, and which durations of each phase optimize the search time. Using a representative analytical model, we show that intermittent strategies do optimize the search time as soon as the target is 揹ifficult?to detect, and we explicitly give the optimal search strategies, which depend on the memory skills of the searcher.	511
Two dimesional intermittent search process:an alternative to Levy flight strategies	O. Bénichou,C. Loverdo		Lévy flights are known to be optimal search strategies in the particular case of revisitable targets. In the relevant situation of nonrevisitable targets, we propose an alternative model of two-dimensional 2D search processes, which explicitly relies on the widely observed intermittent behavior of foraging animals. We show analytically that intermittent strategies can minimize the search time, and therefore do constitute real optimal strategies. We study two representative modes of target detection and determine which features of the search time are robust and do not depend on the specific characteristics of detection mechanisms. In particular, both modes lead to a global minimum of the search time as a function of the typical times spent in each state, for the same optimal duration of the ballistic phase. This last quantity could be a universal feature of 2D intermittent search strategies.	434
Search research	Michael F. Shlesinger		How does one best search for non-replenishable targets at unknown positions? An optimized search strategy could be applied to situations as diverse as animal foraging and time-sensitive rescue missions.	418
Scaling laws of marine predator search behaviour	David W. Sims,Emily J. Southall		Many free-ranging predators have to make foraging decisions with little, if any, knowledge of present resource distribution and availability The optimal search strategy they should use to maximize encounter rates with prey in heterogeneous natural environments remains a largely unresolved issue in ecology1–3. Le´vy walks4 are specialized random walks giving rise to fractal movement trajectories that may represent an optimal solution for searching complex landscapes5. However, the adaptive significance of this putative strategy in response to natural prey distributions remains untested6,7. Here we analyse over a million movement displacements recorded from animal-attached electronic tags to show that diverse marine predators—sharks, bony fishes, sea turtles and penguins—exhibit Le´vy-walk-like behaviour close to a theoretical optimum2. Prey density distributions also display Le´vy-like fractal patterns, suggesting response movements by predators to prey distributions. Simulations show that predators have higher encounter rates when adopting Le´vy-type foraging in natural-like prey fields compared with purely random landscapes. This is consistent with the hypothesis that observed search patterns are adapted to observed statistical patterns of the landscape. This may explain why Le´vy-like behaviour seems to be widespread among diverse organisms3, from microbes8 to humans9, as a ‘rule’that evolved in response to patchy resource distributions.	603
The scaling laws of human travel	D. Brockmann,L. Hufnagel		The dynamic spatial redistribution of individuals is a key driving force of various spatiotemporal phenomena on geographical scales. It can synchronize populations of interacting species, stabilize them, and diversify gene pools1–3. Human travel, for example, is responsible for the geographical spread of human infectious disease4–9. In the light of increasing international trade, intensified human mobility and the imminent threat of an influenza A epidemic10, the knowledge of dynamical and statistical properties of human travel is of fundamental importance. Despite its crucial role, a quantitative assessment of these properties on geographical scales remains elusive, and the assumption that humans disperse diffusively still prevails in models. Here we report on a solid and quantitative assessment of human travelling statistics by analysing the circulation of bank notes in the United States. Using a comprehensive data set of over a million individual displacements, we find that dispersal is anomalous in two ways. First, the distribution of travelling distances decays as a power law, indicating that trajectories of bank notes are reminiscent of scalefree random walks known as Le´vy flights. Second, the probability of remaining in a small, spatially confined region for a time T is dominated by algebraically long tails that attenuate the superdiffusive spread.We show that human travelling behaviour can be described mathematically on many spatiotemporal scales by a two-parameter continuous-time random walk model to a surprising accuracy, and conclude that human travel on geographical scales is an ambivalent and effectively superdiffusive process.	623
中间过程临界现象——分数阶算子理论、方法、进展及其在现代力学中的应用	徐明瑜,谭文长		从物理学特别是力学的观点出发，简要介绍了用以描述物理和力学中的中间过程核临界现象的分数阶算子（尤指分数阶微积分和分数阶微分方程）理论、方法的最新进展以及在现代力学各个领域中的应用，其中也包括了作者今年来在这一领域所作的工作。最后，对这一学科的发展进行了展望和评价	729
牛顿法解方程之混沌情况1.38	黄为		本版本最新更新：1.可以用鼠标右键自由拖动；2.可以用鼠标左键自由选择区域观看，双击还原区域；3.修改程序作图方式BUG，也加快了程序运行速度；4.其他一些小的改进。牛顿法解复方程专题：对复方程f(z)=0 , f(z)为复多项式函数，设函数g(z)= z - f(z) / f'(z) ,其中 f'(z) 为函数f(z) 的导函数。则函 g(Z) 就是复多项式方程求解的牛顿迭代公式。对于选定的起始点， g(z) 迭代大多都会收敛于多项式f(z) = 0 的某个根，但也可能存在许多点，使 g(z) 迭代根本就收敛，甚至可能出现混沌的状态。	1885
电脑中的花园---Lindermayer系统展示	keats		Lindermayer系统（简称L系统）是一种分形图形生成的方法，其主要原理是设定基本简单的绘图规则，然后让计算机根据这些规则进行反复跌代，就可以生成各种各样的图形来。用L系统可以非常逼真的模拟植物的生长过程。	1982
java版本随机函数跌代系统	keats		运用随机函数跌代系统原理绘制出精彩的分形图像。程序自带图形库，并且，用户可以自定义仿射变幻的规则，还可以对整个图形进行平移、缩放等操作。	1361
电子书：分形艺术	刘华杰		本书以优美的笔调简明介绍了分形概念，从科学与艺术相结合的角度尝试分析了分形图形艺术的意义、前景。更为重要的是，作者详细讲述了制作精美分形图形的技巧，并给出大量源程序。作者的用意就是推广普及分形艺术，使更多的读者在最短的时间里掌握必要的技巧，能够亲手制作出更多更美的图形。本书配有大量黑白、彩色分形图片，体现了科学与艺术的完美结合，是读书人理想的收藏品。与本书配套还同时发行光盘(价格另计)：收有本书HTML版面、方正*.S2版面及纯文本文件；大量彩色分形图片；有用的分形图形计算程序；特别地,还包括著名软件Fractint 19.5及其全部源代码!	4781
FractMus	Diaz Jerez		一个非常cool的分形音乐生成软件，功能非常强大。用分形的算法生成美妙的MIDI音乐！计算机作曲成为可能。	1491
Fractal Explorer（分形探索者）	kiev,ukraine		这是一个绘制各种分形图形的软件，可以自己定义生成的规则。	1574
分形软件:HSS的分形风暴	hss		动态生成非常漂亮的分形图像！	1592
分形软件:HSS的牛顿法解方程之混沌情况	hss		牛顿法解复方程专题：对复方程f(z)=0 , f(z)为复多项式函数，设函数g(z)= z - f(z) / f'(z) ,其中 f'(z) 为函数f(z) 的导函数。则函 g(Z) 就是复多项式方程求解的牛顿迭代公式。对于选定的起始点， g(z) 迭代大多都会收敛于多项式f(z) = 0 的某个根，但也可能存在许多点，使 g(z) 迭代根本就收敛，甚至可能出现混沌的状态。	1133
分形软件:HSS的L系统	hss		L系统：L系统这个名字的字母L，是指美国的生物学家 Aristid Lindenmayer 。他于1968年提出了研究植物形态与生长的描述方法，开始时只着重于植物的拓扑结构，即植物组件(主干、旁支等)之间的相邻关系，后来把几何解释加进描述过程，形成了后来被人称呼的L系统。将L系统引入图形学，形成一类自然景物模拟的有效方法。	1261
分形软件:HSS的Julia集和Manderbrolt集绘制工具	hss		绘制出复杂的Julia集和Manderbrolt集，这两个集合都是由简单的复数跌代公式产生的，但是演化出来的结构缺是十分复杂的。	1507
分形软件:HSS的IFS系统	hss		IFS系统：迭代函数系统简记IFS(Iterated Function System)。它的最早论述是由Hutchinson(1981)给出的。IFS的基本思想认定对象的全貌与局部，在一定仿射变换的意义下，具有自相似结构。	1060
分形软件:Hss的函数跌代系统	hss		利用这个软件可以绘制出美妙的分形图，其中算法使用了分形中的函数跌代系统原理。	1129

第1页/ 共1页