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枣阳市妇幼保健中医院治疗慢性肠炎多少钱Sit on a swing, let someone push you, and away you go.坐上秋千,身后一人使劲一推,你便飞了出去,翱翔半空。But what happens if the person who pushed you walks away, and you want to swing faster and higher.但要是再身后推你的人走开了,而你仍想秋千荡得更高更快,那该如何?If youve ever been in the second grade, you know the solution to that.这个问题,只要你上了二年级,就知道该怎么做。Just startpumping your legs-stretching them forward then drawing them up underneath you-and youcan make yourself swing higher.首先用以摇晃双腿,再向前伸展开来,最后将腿滑向身体之下,秋千就能荡得更高。Have you ever wondered why this is?但你是否想过这是什么原理?Swings work by converting potential energy into kinetic energy, then kinetic energy back intopotential energy, over and over again.秋千的工作原理是将势能转化为动能,然后又将动能再转化为势能,一遍遍的重复这个过程。The kinetic energy is the fast part of swinging; its the speed you have as you rush back and forth.动能是秋千快的一部分能量,表现为来回运动时的速度。Potential energy is the high part of swinging.势能存在于秋千荡的的高度之中。The higher you go on the swing, the more potential energy you have.秋千荡得越高,所获得的势能也就越大。Even though youre not moving at the very top of each swing, you can think of your height asyour potential for speed.即使在秋千的顶点你并没有运动,但你仍然可以将你的高度认为是潜在的速度。A physicist would say that your kinetic energy-that is, your speed-is“stored” as potential energy at the top of each swing.物理学家会告诉你,动能,也就是速度,储存在每次摆动顶端的势能里。More height is more speed, just waiting to happen.这就意味着,荡得越高,速度也就越快。You can increase the energy of your swing in two separate ways.以下两种方式都可以增加摇摆的能量。If someone pushes you, that increases your kinetic energy.要是有人在身后推你,那将增加动能。By pumping your legs, you can increase your potential energy.摇晃双腿的方式,增加的是势能。By raising your legs at the top ofeach swing, you can raise the overall center of mass of your body, effectively raising the height ofyour swing.当双腿达到每次摇摆的顶部,身体重心也提高,这就有效的提升了秋千高度。Pump after pump, the energy you burn in your legs increases your swings potential energy.不断的摇晃,双腿产生的能量将增加势能。That extra height will add up, giving you a wilder swing ride.由此,秋千会荡得更高,更精。 201407/311127襄阳妇保医院收费贵吗 Last time, we talked about “motional induction,” aphenomenon by which the ocean generates a magnetic field.上次,我们提到过动生电磁感应:海洋产生磁场的一种现象。It works like this: earth has its own magnetic field.地球有自己的磁场,The oceanhas plenty of charged atoms in it, in the form of dissolved salt.海洋有无数溶解盐形式的带电原子,These atoms are in motion because the ocean flows.随着海洋运动而运动。Charged atoms moving through a magnetic field will induce an electric current.在磁场中运动的带电原子会引起电流,And an electriccurrent will, in turn, create another magnetic field.而电流反过来又回形成另一个磁场。The ocean should generate its own magneticfield.这样海洋应该就形成了自己的磁场。You said should. How could we know this “motional induction” is happening?你说“应该”,我们怎么知道这种动生电磁感应确有其事?Direct evidence came in 2003 from scientists working at the University of Washington and aresearch institute in Potsdam, Germany.直到2003年,华盛顿大学和德国波兹坦的某研究学院。These researchers used a magnetometer on board anorbiting satellite.研究人员将磁力计放在轨道卫星上,实海洋的磁场真是存在。First, they figured out what the magnetic field of the planet should be.最初,磁力计上的数据让科学家以为是地球磁场作用的。After subtracting thisfigure, they found there was still some leftover magnetic field.而后,他们发现除去这个因素后,仍然有磁场存在。Next, the team made a computer model of what kind of magnetic field the ocean shouldgenerate through motional induction.研究人员又电脑模拟在动生电磁感应让海洋产生哪种磁场,Sure enough, their prediction matched the excessmagnetic field measured by the satellite.当然,科学家的推论和卫星上测出的“另一个”磁场吻合。The satellite also found that magneticintensity over the oceans peaked every twelve and a halfhours, but not over the land. Can you guess why?卫星还发现,海洋磁场每隔12个半小时就会出现高峰,但是地球磁场不受影响。你能猜到原因吗?Every twelve hours…Oh, I get it— tides!每隔12个半小时?我知道了!是潮汐。Exactly right!完全正确!The tides rise and fall every twelve and half hours, just as that extra magneticenergy swells and diminishes.潮汐每隔12个半小时潮起潮落,正好和“另一个”磁场高低峰吻合。This is very strong evidence that motional induction is real… andthe ocean has its own magnetism.这正是磁场感应存在的真凭实据,海洋确实有自己独特的磁力。201405/302437谷城妇幼保健院中医院割包皮怎么样

襄阳市中医院治疗子宫内膜炎多少钱Books and Arts; Book Review; Economic history;Centuries of trial and error;How economists rescued mankind from squalor and deprivation;文艺;书评;经济学史;数百年的反复试验;经济学家们如何救人类于悲惨贫穷;Grand Pursuit: The Story of Economic Genius. By Sylvia Nasar.《宏伟事业——经济学天才的故事》西尔维亚·娜萨著。In an essay in his popular magazine, Household Words, Charles Dickens issued a challenge to economists to humanise their discipline. “Political economy is a mere skeleton unless it has a little human covering and filling out,” he wrote in the inaugural issue in 1854. “A little human bloom upon it, and a little human warmth in it.”查尔斯·狄更斯曾经办了一本颇受欢迎的杂志,叫《家常话》,1854年,在创刊号上,他给经济学家提出了一项挑战,即要让经济学更人性化,他说,“没有一点人性为其蔽体、充实其血肉,政治经济学就是一具骷髅。要有一点人性才能让它开花,让它有温度。”This is a challenge to which economics and economists have mostly failed to rise. In her new book Sylvia Nasar, a former economics correspondent at the New York Times and now at Columbia University, has at least gone part of the way to satisfying Dickenss wishes. “Grand Pursuit” is a history of economics which is full of flesh, bloom and warmth. The author demonstrates that there is far more to economics than Thomas Carlyles “dismal science”. And she does so with all the style and panache that you would expect from the author of the 1998 bestseller, “A Beautiful Mind”, about John Forbes Nash, the tortured genius behind game theory.遗憾的是,大多时候,经济学以及经济学家并没有完成人性这点要求。但是,在这书里,狄更斯的愿望,至少已有部分得到满足。本书作者西尔维亚·娜萨,曾是《纽约时报》的经济专栏记者,如今就职于哥伦比亚大学,这本书记叙的经济学史有血有肉,有花有果,有热情有温度,作者可算明了经济学不是托马斯·卡莱尔所讲的“沉闷的科学”。娜萨还写过一本书《美丽心灵》,那是1998年的畅销书,讲述受精神分裂症折磨的弈论天才约翰·福布斯·纳什的故事。对于《美丽心灵》的作者,其文风和辞藻在《宏伟事业》中得到延续,不失读者所望。It turns out that economists—or at least the handful of geniuses that Ms Nasar discusses—are a peculiarly interesting bunch. John Maynard Keynes was an exotic mixture of Bloomsbury intellectual and civil-servant mandarin with a touch of Puck thrown in. Joseph Schumpeter was an obsessive scholar who spent his spare moments riding thoroughbreds, collecting mistresses and, on the odd occasion, taking part in orgies. Irving Fisher, the Yale economist who declared, in October 1929, that stocks had reached “what looks like a permanently high plateau”, was a health nut and prohibitionist. Joan Robinson, whom Schumpeter dubbed “one of our best men”, wore Mao suits and pronounced that North Korea was bound to outperform the South.原来经济学家都是特别有趣的一群人,至少娜萨女士在书里写的那些天才们都特别有趣。约翰·梅纳德·凯恩斯是英国伦敦布鲁姆斯伯里区知识分子和政界要人的结合,还有点英国民间传说中迫克精灵的味道,是个奇怪的混合体。约瑟夫·熊彼得醉心学问,闲暇时爱骑好马,爱搜猎情人,偶尔参与狂欢。而耶鲁大学经济学家欧文·费希尔是一位十分注重健康生活的人,奉行禁酒,他在1929年十月判断股市到达“永久性的高点”。熊彼得封之为“我们最好的男人之一”的琼·罗宾逊夫人,喜欢穿中山装,断言朝鲜必定会胜过韩国。Ms Nasars story is made all the more appealing by the fact that she does almost nothing to conceal her prejudices. She has little time for Karl Marx, a man who was so convinced of his rightness, and so buried in his books in the British Library, that he failed to observe the world around him. He did not bother to visit a single British factory. He refused to exchange a word with the intellectual titans of the time, including Charles Darwin and George Eliot, both of whom lived just a few miles from his front door. He ignored overwhelming statistical evidence that the working classs share of the nations wealth was increasing. By contrast, Alfred Marshall was everything that Marx was not: the embodiment of all that was best in Victorian high- mindedness. Marshall was alive to what was going on around him. He frequently visited factories and firms, and travelled around the worlds new “empire of energy”, the ed States. He threw his weight behind popular education and incremental reform.娜萨女士从不费心遮掩自己的偏见,这让她的故事更有可读性。书中关于卡尔·马克思的篇幅甚短。马克思对自己的公正颇有信心,但他总在大英国书馆埋头读书,没有时间去好好观察身边的世界,他连一家英国工厂都没去参观过,也拒绝和当时思想大家交流。查尔斯·达尔文和乔治·艾略特离他住地几英里外,他们却从未讲过话。势不可挡的统计数据,足以表明工人阶级占有国家财富的份额在增长,他对此视而不见。阿尔弗雷德·马歇尔与马克思截然相反,他是维多利亚时期优秀品质的化身,关心身边世界,经常访问工厂企业,环游世界新的“活力帝国”——美国。他全心全力持大众教育和逐渐改革。In lesser hands Ms Nasars story might have degenerated into a series of pen portraits: tittle-tattle for the middlebrow. But she unifies her account with a series of big questions. How, for example, did humanity escape from the grinding poverty that has been its lot through most of human history? Why was a static society replaced by a dynamic one? And how best to cope with the booms and busts that have been capitalisms peculiar contribution to human life?如果娜萨女士文笔稍差一些,这些故事就要成了一堆钢笔肖像速写,成了关于一帮知识界平庸人物的杂淡。但是她用一些大问题对叙述加以统一,比如,人类是如何从占据其历史大部分时间的凄惨贫穷中逃离出来的?比如,为何动态社会取代了静态社会?又比如,资本主义给人类生活带来它特有的贡献——经济繁荣与衰退的循环往复,对此什么才是最好的处理方式?In Marxs view the capitalist system, for all its ability to unleash productive power, was haunted by a contradiction: the drive to increase profits would immiserate the poor and lead to crises of overproduction. But Marshall demonstrated that capitalism advances not by immiserating the poor, but by boosting productivity. Factory owners make relentless small improvements that allow them to produce both higher wages and lower prices, thereby sping the gains of material progress throughout society. Schumpeter further expanded the idea of productivity increases. The economy doesnt simply get bigger and bigger. It goes through a constant process of discombobulation as entrepreneurs invent new products and processes. Marx got it upside down: capitalisms recurrent crises actually make it stronger.在马克思看来,资本主义系统,虽然能解放生产力,却有着不可调和的矛盾,即对高额利润的追逐将让劳苦大众的生活更为悲惨,并导致生产过剩,出现经济危机。但是根据马歇尔的论,资本主义的发展并非依靠加大对穷人的剥削,而是靠着提高生产力。工厂主永不停止地进行微小的改进,因此在提高工资的同时能降低产品价格,从而使物质的进步惠及整个社会。熊彼得进一步充实了生产力发展的观点,经济的发展并非简单地变得越来越大,随着企业家发明新产品新工作程序,它经常经历混乱。马克思没有认识到周期性的经济危机事实上发展了资本主义。Economics was a practical as well as an analytical science. From the left, Beatrice Potter Webb argued that mass destitution could be cured by “the household state”. Fisher showed that good management of the money supply could contribute to stability. Keynes insisted that crises could be prevented if the government could act as the spender of last resort, just as the central bank was lender of last resort.经济学是一门分析科学,也是一门实践科学。比阿特丽斯·波特·韦伯认为“每个家庭自为国家”能够解决大众贫穷的问题,费希尔让我们知道,对货帀供应进行良好管理有助于保持经济稳定。凯恩斯坚持认为,如果政府能在最后时刻出手消费,中央能在最后时刻提供贷款,便能阻止经济危机的发生。“Grand Pursuit” peters out at the end. It is easy to see why Ms Nasar thought Amartya Sen might be the right terminus for her train. He is an economic genius who has devoted his life to thinking about the elimination of the most dramatic form of want: famine. But it is, nevertheless, odd to end a history of economics without discussing the financial crisis of 2007-08 and the furious arguments it has engendered within the economics profession. Surely the likes of Paul Krugman and Lawrence Summers should have had at least a walk-on role at the close of the story. But that is a blemish in what is generally a wonderful book. “Grand Pursuit” deserves a place not only in every economists study but also on every serious ers bedside table.《宏伟事业》逐渐进入尾声,娜萨女士选择阿马蒂亚·森作为本书最后一位经济学家,原因可以理解,阿马蒂亚·森是一位经济学天才,毕生研究怎样消除饥荒。但是,作为一本写经济学历史的书,没有论及2007-08年的经济危机以及由此产生的激烈论争就结束了,这不合常理。像保罗·克鲁格曼,劳伦斯·萨默斯这些人,本该在本书最后章节有所提及,。不过,这本书总体来说很精,《宏伟事业》不仅值得每一位经济学家研读,也可作为严肃书籍读者的床头书。 /201306/242929 If youve ever driven in LA, you know that people dont cooperate terribly well.如果你在洛杉矶开过车,你就会知道那里路上人们配合得不是很好,Traffic jams, folks cutting folks off,people shouting at you out their windows . . .its a real headache.致使交通阻塞,水泄不通,人们透过车窗口大嚷大叫,真是让人头痛!Wed all do a lot better–at least, wed all movethrough congestion a lot faster–if we were ants.如果我们能效仿蚂蚁,那么,至少拥堵的交通移动地可以更快些!Why ants, you ask?你可能会问:为什么是蚂蚁呢?Thats what Ian Couzin of Princeton University wanted to know.普林斯顿大学的Ian Couzin也曾经疑惑过。You mayhave seen films of huge numbers of South American Army Ants zooming across the grass onraids and coming back with all sorts of goodies to eat.你可能曾看过电影里成群结队的南美洲军蚁 “行军”穿过草丛,而后满载而归。So why dont they crash into each otherand suffer ant-gridlock the way humans do?那么,为什么他们不会撞上对方,像人类一样,交通阻塞呢?One answer: Couzin found is that army ants follow asimple procedure:Couzin 发现有个原因能解释:军蚁行进的方式很简单,everybody coming home has the right-of-way.所有蚂蚁回家都有“优先权”。Even a simple rule like that: if you going out, same-phrase side; if you coming home, dont same-phrase side; works terrifically.很简单的守则:出门就走同向边;回家就走逆向边,屡试不爽。It results in a stream of home-going ants passing unobstructedthrough the center of a crowd of out-going ants.这样一来,回家的一群蚂蚁会畅通无阻地穿过成群结队的出门蚂蚁群。Among other things, this means raiding partiescan go any direction from the anthill, because nobody has to remember some complicated ruleabout turning left or turning right.这样,蚁冢中的蚂蚁群可以自由行进,因为无须忌讳向左或向右的复杂规则。Also, the guys bringing home the goodies will always beprotected on both sides by out-going ants. Simple!两侧要出门的蚂蚁也会保护背着东西回家的蚂蚁群。再简单不过了!So, would this work in LA?那么,洛杉矶能借鉴吗?Probably not. Thousands of human beings just cant be made to followa behavioral rule like that.也许不行,成千上万的人是不可能遵守蚂蚁群的规则的。Somebody would try to get a little bit ahead, then somebody else wouldsee that and get angry, and pretty soon, youre back to LA traffic.有些人想方设法在更前面,其他人看到了就会生气,不一会儿,又会回到洛杉矶交通的状态。For better or worse, people justdont think like ants.不管怎样,人们是无法像蚂蚁般思考的。 201408/318061襄阳人民医院无痛人流怎么样襄阳中医男科医院可以做输软管吻合术吗




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