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长春治疗宫颈管粘膜炎多少钱长春妇科大夫在线Don: Time now for another episode of A Moment of Sciences ;Did You Know...; So, Yael, did you know that there have been about twenty-three mass extinctions since life began on earth?唐:现在进入科学时刻另一段情节:“你知道...”那么,雅艾尔,你知道吗,地球上自有生命以来发生过23起物种大灭绝事件?Yael: I know thereve been a few extinctions, Don, but not that many!雅艾尔:我知道几次物种大灭绝,但不知道次数如此多!Don: Yep. Many were of prehistoric bacteria and other single-celled microorganisms. But in the past 540 million years or so there have been about five mass extinctions, mainly of marine plants and animals but also of land organisms.唐:是啊。许多都是史前的细菌或其它单细胞微生物。但是在5.4亿年前已发生过5次大灭绝,主要包括海生植物和动物,当然也有陆生生物。Yael: Well, I know that the dinosaurs disappeared about 65 million years ago, possibly due to a large meteor that crashed into earth and blotted out the sun. But what caused all those other extinctions?雅艾尔:好吧,我知道恐龙大约在六千五百万年前消失,可能是由于一颗大流星撞击地球,遮住阳光引起的。但是什么导致其他物种灭绝的呢?Don: Thats been a mystery for a long time. But now some scientists think that most mass extinctions have been driven by the rise and fall of sea level. That may sound strange, but consider that millions of years ago a shallow sea covered the entire middle section of North America. That sea grew and shrank back several times. Each time it drained it caused entire species of sea plants and creatures to die off. The last time it drained was around 65 million years ago—when the dinosaurs disappeared.唐:长期以来那一直是个谜。但如今一些科学家们认为大多数的灭绝是由于海平面的上升和下降引起的。这也许听起来很奇怪,但考虑到百万年前有一片浅海覆盖在整个北美洲中部就不足为奇了。那片海历经几次扩张和消失,每一次干涸就会导致这个海洋的生物灭绝。最后一次干涸发生在6500万年前恐龙消失的时候。Yael: OK, I understand how a sea vanishing would kill off marine life. But did the seas disappearance also have something to do with the dinosaurs going extinct?雅艾尔:好吧,我明白了海洋的消失会引起海洋生物消失。但海洋的消失与恐龙的灭绝也有联系吗?Don: Maybe. When a sea disappears it has a big effect on climate. All that water provides heat and moisture. And when a sea drains, the climate becomes drier and colder. So the change in climate may have combined with the meteor impact to kill off the dinosaurs. 唐:也许。海洋消失会对气候产生深远的影响。海水能提供热量和湿度。当海水干枯时,气候就会变得更加干燥和寒冷。因此气候变化再加上流星撞击地球足以将恐龙推向毁灭。原文译文属!201305/240934长春哪里做流产手术好 Science and technology科学技术Pilotless aircraft无人机Giving drones a thumbs up向无人机打手势How to integrate the control of piloted and pilotless aircraft如何让指挥有人机的方法适用于无人机DECK officers on American aircraft carriers use hand gestures to guide planes around their vessels.在美国的航空母舰上,甲板指挥员会用手势指挥母舰附近的飞机。These signals are fast, efficient and perfect for a noisy environment.这种信号快速、高效,而且十分适用于嘈杂的环境。Unfortunately, they work only with people.但遗憾的是,只有人才能读懂这些手势。They are utterly lost on robotic drones—and even if a drone is under the control of a remote pilot deep in the bowels of the ship,在无人机上,这一套完全失效;而即便有飞行员在船舱深处远程操控这架飞机,that pilot often has difficulty ing them.他往往也很难识别那些手势。Since drones are becoming more and more important in modern warfare, this is a nuisance.这是个麻烦,因为无人机在现代战争里变得越来越重要了。Life would be easier for all if drones were smart enough to respond directly to a deck officers gesticulations.若无人机的智能达到了足以直接响应甲板指挥员手势的程度,那一切都会好很多。Making them that smart is the goal of Yale Song, a computer scientist at the Massachusetts Institute of Technology.让无人机具备这样的智能是麻省理工学院计算机科学家Yale Song的目标。He is not there yet but,这个目标虽尚未达成,as he reports in ACM Transactions on Interactive Intelligent Systems,不过正如他在《美国计算机学会交互式智能系统学报》所报告的,he and his colleagues David Demirdjian and Randall Davis have developed a promising prototype.他和他的同事David Demirdjian和Randall Davis已开发了一个很有前景的原型系统。To try teaching drones the language of hand signals Mr Song and his colleagues made a series of s in which various deck officers performed to camera a set of 24 commonly used gestures.为了让无人机读懂手语,Yale Song和他的同事制作了一系列视频,视频记录了多位甲板指挥员对着摄象机摆出的24个常用手势。They then fed these s into an algorithm of their own devising that was designed to analyse the position and movement of a human body, and told the algorithm what each gesture represented.然后他们用一个自己设计的算法来处理这些视频,并让算法知道每个手势的意义。The idea was that the algorithm would learn the association and, having seen the same gesture performed by different people,他们的设想是,该算法会记住每个手势所对应的意义,而在对不同人摆出的相同手势进行处理后能够概括出手势本身的意义,would be able to generalise what was going on and thus recognise gestures performed by strangers.从而识别任何人摆出的手势。Unfortunately, it did not quite work out like that.很遗憾,实际与预想的不太一样。In much the same way that spoken language is actually a continuous stream of sound,其实指挥飞行员所用的手语和人说的话差不多。so the language of gestures to pilots is also continuous, with one flowing seamlessly into the next.后者实际上是一串连续的声音,而手语同样也是连续的,因为两个动作之间是连贯的。And the algorithm could not cope with that.但该算法无法处理这种连续的信息。To overcome this difficulty Mr Song imposed gaps by chopping the s up into three-second blocks.为了解决这个问题,Yale Song以3秒为一段将视频截开,在各段之间插入时间间隔。That allowed the computer time for reflection.这样就给计算机留出了响应时间。Its accuracy was also increased by interpreting each block in light of those immediately before and after it,同时识别的准确率也有所提高。因为这样计算机就能根据前一段及后一段的视频来理解当前这一段,to see if the result was a coherent message of the sort a deck officer might actually wish to impart.看看结果是不是那种甲板指挥员可能真的想摆出的有特定意义的手势。The result is a system that gets it right three-quarters of the time.他们最终做出了一个正确率为75%的系统。Obviously that is not enough:显然,那样是不够的:you would not entrust the fate of a multi-million-dollar drone to such a system.你不会将一架价值数百万美元的无人机交给这样的系统。But it is a good start.但这是个好的开始。If Mr Song can push the accuracy up to that displayed by a human pilot, then the task of controlling activity on deck should become a lot easier.若Yale Song能将无人机识别手势的正确率提高至与真人飞行员相当,那么在甲板指挥无人机会容易得多。 /201307/247186长春阴道镜的价格

做无痛人流长春那家好吉大三院住院部电话 Books and arts文艺A history of guerrilla warfare游击战的历史How the weak vanquish the strong以弱胜强之道Fighting an insurgency requires patience, restraint and a good public-relations strategy平定叛乱需要耐心,克制和良好的战略公关Invisible Armies: An Epic History of Guerrilla Warfare from Ancient Times to the Present.《看不见的军队》:一部述说古今游击战的史诗。By Max Boot. Liveright; 750 pages; .作者:Max Boot. Liveright;750页,定价35美元。To be published in Britain in February by W.W. Norton; 25.W.W. Norton将于2月份在英国出版;定价25英镑。Buy from Amazon.com, Amazon.co.uk可以在英国亚马逊网上书城购买。LIKE the poor, guerrilla armies have, it seems, always been with us.游击队就像穷人一样,似乎一直都伴随在我们左右。From the nomadic rebels who brought down the Roman empire to the internet-savvy, plane-exploding jihadists who triggered Americas ill-conceived global war on terror, irregular forces are a constant factor in the history of warfare.游牧叛乱武装打垮了罗马帝国;互联网专家,爆炸飞机的圣战分子使美国开启了思谋不周的全球反恐战争,非正规部队是战争历史中的一个永恒元素。And fighting them has become tougher than ever.现在对付游击武装比以往更棘手。Plenty of literature gives advice on how to beat such maddening foes.很多文献给都教你如何击败这些令人发狂的敌人。Max Boot, a neoconservative American military historian, has done something different.属于新保守派的美国军事历史学家Max Boot做了一些不同的工作,Invisible Armies is a narrative history of guerrilla warfare and terrorism, ranging from what he describes as its origins, in bringing down the Akkadian empire in Mesopotamia in the 22nd century , to the present day.《看不见的军队》叙述了从古至今的游击战和恐怖行动。他认为这种战争起源于公元前22世纪,美索不达米亚的阿卡德帝国就是被游击战摧毁的。The author moves quite quickly over the first 4,000 years or so and only really gets going in the 18th century, with its revolutionary wars of independence.作者很快讲完了前4000年的历史,从18世纪的独立革命战争切入,这大概是真正游击战的发端。Among the many liberal insurgencies he considers are the American revolution; the struggle against Napoleon in the Iberian peninsula; Greeces war for independence against the Ottomans; the wars of unification in Italy and various uprisings against colonial powers, such as the slave revolt against the French that led to the foundation of the Republic of Haiti.在很多自由起义中,他思考了美国革命,伊比利亚半岛反对拿破仑的斗争,希腊人反抗奥斯曼人独立战争,意大利统一之战以及各种反抗殖民势力的起义,如反抗法国的奴隶起义引发了海地共和国的成立。In the 20th century Mr Boot examines the impact of irregular forces in the two world wars; the contribution to insurgent theory of Mao Zedongs seminal work On Guerrilla Warfare, gleaned from his experiences in the Chinese civil war; the very different French and British responses to rebellions against their fading empires; the radical chic revolutionaries of the 1960s and the rise of radical Islamism.Boot先生仔细观察了非正规部队对20世纪两次世界大战的影响;毛泽东那部给起义理论做出贡献的有开创性的著作《论游击战》,这是他从中国内战中收获的经验,不同于逐渐衰落的英法帝国处理叛乱事件;上世纪60年代激进派时髦的革命和极端伊斯兰分子的叛乱。If this sounds a bit like a list, it is because of the way the book is organised. Mr Boot picks a theme, for example, The End of Empire, and then hoovers up into that section all the conflicts that can be made to fit that description.上面的内容有点像开列清单,因为这是本书的组织方式,Boot先生选择一个主题,例如帝国的终结,然后把所有符合主题的斗争收录到这个部分。Each one gets a few pages of lively narrative and a brief analysis of why one side prevailed over the other.每个主题都占据几页篇幅,叙述的很生动,并且简要地分析了一方为何能战胜另一方。The formula works rather well. Even when the author is rattling through fairly familiar territory, such as the failures of the French against the Vietminh, he usually finds something fresh or pithy to say.这种方式的效果很好。即使述说大家熟悉的事情,作者也能讲出点新鲜东西和独到见解。Take, for example, Vo Nguyen Giap, the brilliant Communist general who succeeded in expelling first the French and then the Americans from Vietnam.例如杰出的共产党将领武元甲成功地把法国人和美国人先后赶出越南。Giap closely followed the teachings of Mao in planning a three-stage struggle,first localised guerrilla war, then war of movement and finally general uprising,which he waged with a three-tier force of village militias, full-time guerrillas and a regular army.武元甲密切遵循毛泽东的教导,制定了一个包含三个阶段的斗争—先是局部的游击战,接着实施运动战,最后发动大起义 —他投入了三种力量:民兵、专职游击队和正规军。But where Mao was always cautious to avoid confrontations with more powerful forces, Giaps tendency to roll the dice on premature offensives in 1951, 1968 and again in 1972 could have proved fatal each time had it not been for the psychological and political frailties of the other side.毛泽东总是谨慎地避免和更强大的力量发生对抗,但是武元甲愿意为过早攻击孤注一掷。1951年,1968年和接下来的1972年他都用了这种方法,要不是对方存在着心理上和政策上的弱点,这三次作战就不会造成致命的影响。In guerrilla warfare, what matters most is the ability to shape the story, not the facts on the ground.在游击战中,最重要的是推动战争向前发展的能力,而非战场上的实际情况。This is how guerrillas are able to win wars even as they lose battles.这就是游击队即使战斗失利的情况下仍然能够赢得战争。Because insurgencies pit the weak against the strong, most still end up failing.因为这些起义以弱势抗强敌,大部分还是以失败告终。Between 1775 and 1945 only about a quarter achieved most or all of their aims.Boot先生说,从1775年至1945年,只有四分之一的起义完成了自己的大部分或全部目标。But since 1945 that number has risen to 40%, according to Mr Boot.但是自1945年以来,成功率增长到了40%。Part of the reason for the improving success rate is the rising importance of public opinion.成功率的提高部分原因是公众舆论的重要性日益突出。Since 1945 the sp of democracy, education, mass media and the concept of international law have all conspired,自1945年以来,民主、教育、大众媒体和国际公法的概念得到推广,to sap the will of states engaged in protracted counter-insurgencies.这都削弱了应对长期叛乱的国家意志。In the battle over the narrative, insurgents have many more weapons at their disposal than before.战斗过程中,可供叛乱分子使用的武器比以前多得多。Mr Boot does not conclude that counter-insurgency in the 21st century is a losing game.Boot先生没有推断在21世纪镇压叛乱是徒劳之举。But to prevail requires an understanding of the games rules.然而获胜之前要理解游戏的规则。He is a powerful advocate for the so-called population-centric approach pioneered by the British during the 12-year post-war Malayan Emergency, which lasted until 1960, and rediscovered by American generals,such as David Petraeus and Stanley McChrystal in Iraq and Afghanistan,only after things there had gone disastrously wrong.他极力鼓吹所谓以民众为中心的方法,这是战后英国在应对马来亚12年危机时倡导的理论,美军将领如分别在伊拉克和阿富汗的局势,严重恶化之后对此做出重新发现。The first principle is to abandon conventional military tactics.第一原则是放弃常规战术。Clear and hold beats search and destroy.清除和控制胜过搜寻和破坏。To defeat an insurgency you must provide enough security for ordinary people to live their lives.要平息叛乱,必须给普通民众的生活提供充足的安全保障。The second is that legitimacy is vital for both sides: corrupt or excessively violent governments will always struggle,第二合法性对双方来说都是重要的:腐败或过于暴力的政府一直会引发斗争,but so too will guerrillas who terrorise their own people.但是游击队也会威胁本国人民。The third is staying power.第三是耐力。Firepower is no substitute for patience and boots on the ground.在战场上火力不能取代忍耐力和士气。The people you need on your side must believe that you are in it for the long haul.必须要让你争取的民众相信你会长期和他们在一起。The fourth is that most counter-insurgency campaigns abroad are lost at home.第四大部分在海外开展的镇压叛乱的战斗都输在国内。Liberal democracies have short attention spans, low tolerance for casualties and other calls on their cash.自由主义的民主国家对于需要花钱的重大伤亡事故和其他征召不大关注,容忍度也不高。Unless voters believe that an intervention is necessary for their own security they will quickly withdraw support for it.除非选民认为有必要采取干涉措施才能保障自身的安全,否则他们会很快放弃对这种行动的持。All of which explains why things are not going well in Afghanistan.以上情况都可以解释为什么阿富汗的事情进展不顺。The population-centric approach—and the troop surge needed to realise it came late in the day and with a foolishly rigid deadline.实行以民众为中心的方法和增加部队都来的太晚,而且愚蠢地附带着严格的时限。The Afghan government has some popular legitimacy, but not enough in the places where the insurgency is resilient.阿富汗政府在一定程度上拥有广泛的合法性,但是在叛乱行动回弹的地方该政府的合法性还是不足。Nor has it been possible for American forces to deny the Taliban their sanctuary in Pakistan: insurgencies with outside support are much harder to beat.美国人不可能容忍塔利班在巴基斯坦避难:得到外部持的叛乱更加难以平息。Voters in America and Europe are not prepared to spend any more blood or money on what most presume is a lost cause.美国和欧洲的选民还不想在大部分人看来要注定失败的行动上流更多的血,花更多的钱。Few think that what happens in Afghanistan will affect their own safety.几乎没有人意识到发生在阿富汗的事情会影响到自己的安全。Counter-insurgency may be out of fashion again, but it remains necessary to know how to do it.镇压叛乱可能又过时了。但是我们还需要如何应对叛乱。Mr Boot offers a timely reminder to politicians and generals of the hard-earned lessons of history.Boot先生及时地向军政要人提醒了这个得来不易的历史教训。 /201403/282539长春医大一院专家预约

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