向自然学习如何让无人机着陆 | 复杂文摘翻译
目录
17. 向自然学习如何让无人机着陆（Learning from nature how to land aerial robots）
18. 肠道微生物内部合作的演化（The evolution of cooperation within the gut microbiota）
19. 具有一个对称轴的四体中心构型 （Central configurations of four bodies with an axis of symmetry）
20. 进化中的稳式非平衡：大小基本固定的种群在进化中的无穷动力学 （Evolutionarily stable disequilibrium: endless dynamics of evolution in a stationary population）
21. 复杂性实验室 （Complexity Labs）
（更多文摘请点击阅读原文。）
17. 向自然学习如何让无人机着陆（Learning from nature how to land aerialrobots）
May 19, 9:27 PM Fromscience.sciencemag.org
by Mirko Kovac
(Translated by 阿勺，edited by 唐璐)
One of the main challenges for aerial robots is thehigh-energy consumption of powered flight, which limits flight times totypically only tens of minutes for systems below 2 kg in weight (1). Thislimitation greatly reduces their utility for sensing and inspection tasks,where longer hovering times would be beneficial. Perching onto structures cansave energy and maintain a high, stable observation or resting position, but itrequires a coordination of flight dynamics and some means of attaching to thestructure. Birds and insects have mastered the ability to perch successfullyand have inspired perching robots at various sizes. On page 978 of this issue,Graule et al. (2) describe a perching robotic insect that represents thesmallest flying robot platform that can autonomously attach to surfaces. At amass of only 100 mg, it combines advanced flight control with adaptivemechanical dampers and electro-adhesion to perch on a variety of natural andartificial structures.
译文：
无人机主要挑战之一是持续飞行时的高能耗，因续航能力不足，无人机飞行时间有限，在承重≦2Kg的条件下，最多飞行几十分钟，极大地减弱感应和拍摄任务的功用，如能长时间悬停对解决这一问题是有帮助的。如果无人机可以附着在物体上，就能节省电量，以及保持高效、稳定的拍摄或测试的机位，但该技术要求飞行动力学和附着物体的方法相结合。鸟类和昆虫类已成功掌握了附着在物体上的能力，并激发人们创造出不同尺寸的仿生无人机，Graule等人描述了一种代表最小无人机平台的栖息机器昆虫，可自主地附着在物体表面，在体重仅有100mg的条件下，它将自适应机械阻尼器和静电吸附与先进的飞行控制结合到一起，实现了对各种自然和人工物体的附着。
原文链接：
http://dx.doi.org/10.1126/science.aaf6605
18. 肠道微生物内部合作的演化（The evolution of cooperation within the gut microbiota）
May 13, 4:17 PM Fromwww.nature.com
by Seth Rakoff-Nahoum, Kevin R. Foster & Laurie E.Comstock
(Translated by 秦德盛)
Little is known about cooperative behaviour among the gut microbiota; here, limited cooperation is demonstrated for Bacteroides the taiotaomicron, but Bacteroides ovatusis found to extracellularly digest a polysaccharide not for its own use, but to cooperatively feed other species such as Bacteroides vulgatus from which it receives return benefits.
译文：
人们对肠道微生物之间的合作行为所知甚少。本文中多型拟杆菌（Bacteroides thetaiotaomicron）有限的合作行为被证实，研究人员们发现卵型拟杆菌（Bacteroides ovatus）消化胞外多糖不是为了自己使用，而是为了给其他种群——例如普通拟杆菌（Bacteroides vulgatus）——提供食物，并从这些种群那里获取回报。
原文链接：
http://dx.doi.org/10.1038/nature17626
19. 具有一个对称轴的四体中心构型（Central configurations offour bodies with an axis of symmetry）
May 18, 4:14 PM Fromlink.springer.com
by Bálint Érdi, Zalán Czirják
(Translatedby -阎赫，editedby 傅渥成)
A complete solution is given for a symmetriccase of the problem of the planar central configurations of four bodies, whentwo bodies are on an axis of symmetry, and the other two bodies have equalmasses and are situated symmetrically with respect to the axis of symmetry. Thepositions of the bodies on the axis of symmetry are described by anglecoordinates with respect to the outside bodies. The solution is such, thatgiving the angle coordinates, the masses for which the given configuration is acentral configuration, can be computed from simple analytical expressions ofthe angles. The central configurations can be described as one-parameterfamilies, and these are discussed in detail in one convex and two concavecases. The derived formulae represent exact analytical solutions of thefour-body problem.
译文：
当两个质点在一个对称轴上，而其它两个质点具有相等的质量、并相对于对称轴对称分布时，就会赋予四体的平面中心构型问题的在对称情况下的一个完全解。位于对称轴上的质点用其相对于外侧质点的夹角为坐标进行描述。本问题的解是这样的：给定角坐标，在假定中心构型的情况下，质量的解可以通过角度的简单解析表达式进行计算。中心构型可以描述为单参数族，且其性质可以被详细地讨论，它可能表现为一种凸的情况和两种凹的情况。推导的公式代表四体问题的精确解析解。
原文链接：
http://link.springer.com/article/10.1007%2Fs10569-016-9672-5
20.
进化中的稳式非平衡：大小基本固定的种群在进化中的无穷动力学（Evolutionarily stable disequilibrium: endless dynamics of evolution in astationary population）
May 19, 9:19 PM Fromrspb.royalsocietypublishing.org
by Nobuto Takeuchi, Kunihiko Kaneko, Paulien Hogeweg
(Translated by 孟庆业，edited by 傅渥成)
Evolution is often conceived as changes in theproperties of a population over generations. Does this notion exhaust thepossible dynamics of evolution? Life is hierarchically organized, and evolutioncan operate at multiple levels with conflicting tendencies. Using a minimalmodel of such conflicting multilevel evolution, we demonstrate the possibilityof a novel mode of evolution that challenges the above notion: individualsceaselessly modify their genetically inherited phenotype and fitness alongtheir lines of descent, without involving apparent changes in the properties ofthe population. The model assumes a population of primitive cells (protocells,for short), each containing a population of replicating catalytic molecules.Protocells are selected towards maximizing the catalytic activity of internalmolecules, whereas molecules tend to evolve towards minimizing it in order tomaximize their relative fitness within a protocell. These conflictingevolutionary tendencies at different levels and genetic drift drive thelineages of protocells to oscillate endlessly between high and lowintracellular catalytic activity, i.e. high and low fitness, along their linesof descent. This oscillation, however, occurs independently in differentlineages, so that the population as a whole appears stationary. Therefore,ongoing evolution can be hidden behind an apparently stationary populationowing to conflicting multilevel evolution.
译文：
通常认为进化是种群在一代代繁衍中所产生的性质改变。这种观念涵盖了所有可能的进化动力学了吗？生命是层次化地组织起来的，而且进化有可能在相互之间存在冲突性倾向的多个层次上发挥其影响。我们用一个最简单的层次间有冲突的多层次进化模型，展示了可能存在一种新的不同于上述观念的的进化模式。在通常的进化观念中，个体会在一代代繁衍中不停的改变它们由基因遗传的表现型和适应度，但并不会使种群的性质产生明显变化。这个模型基于一群原始细胞（简写为 protocells），每个原始细胞都包含了很多具有催化能力的可复制分子。原始细胞因自然选择趋向于使内部分子的催化活性最强，而内部分子为了最大化在原始细胞内的相对适应度，趋向于使自己的催化活性最差。这种在不同层次上有所冲突的进化趋势和遗传漂变会使原始细胞后代中的内部分子所具有的催化活性（亦即适应度）在一代代中高高低低来回震荡。然而，这种震荡在不同后代中都会发生，以至于种群大小基本保持不变。因此，表面上大小保持不变的种群会因为相互冲突的多层次进化模式而不断进化。
原文链接：
http://rspb.royalsocietypublishing.org/content/283/1830/20153109#sec-2
21. 复杂性实验室（Complexity Labs）
May 12, 9:28 PM Fromcomplexitylabs.io
by Complexity Labs
(Translated by -庞博,edited by 唐璐)
Complexity Labs is an online resource dedicated to thearea of complex systems providing a wide variety of users with information,research, learning and media content relating to this exciting new area. Ourmission statement is to assist in the development of a coherent, robust andaccessible framework for modelling, designing and managing complex systems.
译文：
复杂性实验室（Complexity Labs：http://complexitylabs.io/)是一个关于复杂系统的在线资源，它为多个领域的用户提供了有关这个令人兴奋的新领域的讯息、研究进展、学习材料等内容。该网站的使命是为复杂系统的建模、设计及管理开发出一个一致、稳健且易于使用的框架。
原文链接：
http://complexitylabs.io
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