如如天才2 如如天才2
关注数: 1 粉丝数: 65 发帖数: 12,687 关注贴吧数: 2
Une recherche iter...ative Dans la filière de la fusion thermonucléaire contrôlée par confinement magnétique, le projet phare se nomme iter. Il s'inscrit dans un ensemble de recherches à long terme. Entretien avec Pascale Hennequin Le réacteur expérimental thermonucléaire international ou iter (International Thermonuclear Experimental Reactor) est la principale installation expérimentale d'un projet international mené par l'Union européenne, la Russie, le Japon, les États-Unis, la Chine, la Corée et l'Inde. En construction à Cadarache, dans les Bouches-du-Rhône, ce réacteur coûtera dix milliards d'euros, 20 ans de fonctionnement compris. Pour la Science : Quels sont les objectifs d'iter, après plus de 50 ans de recherches sur la fusion par confinement magnétique ? Pascale Hennequin : Il y a eu des dizaines de grandes expériences de recherche sur la fusion par confinement magnétique, mais surtout trois grandes étapes : l'invention du confinement magnétique toroïdal, c'est-à-dire du stellarator puis du tokamak, dans les décennies 1950-1960 ; dans les années 1980, quelques grands tokamaks ont été construits, notamment en 1983 le réacteur européen jet à Oxford, le plus grand et le plus performant tokamak ; et maintenant, le projet iter à Cadarache. À ce stade, la plupart des recherches portent sur le confinement des quelques grammes de plasma de deutérium-tritium à la température nécessaire pour allumer la fusion. Lors d'une expérience phare du jet, le plasma a fourni une puissance de plus de 15 mégawatts durant environ une seconde pour une puissance injectée de l'ordre de 20 mégawatts. Cela correspond aux objectifs visés à l'époque
150光年外行星发现超级风暴时速近万公里 天文学家已经在另一个太阳系观测到一颗行星上发生的强大“超级风暴”。他们发现,这颗行星上的风速超过每小时6200英里 (9977.93公里/时),它围绕一颗距离地球大约有150光年的像太阳的恒星运行。      “热木星”行星HD209458b的艺术概念 图,天文学家在它上面发现一个超级风暴。      这颗编号为HD209458b的行星,其质量大约是木星的60%,位于飞马座附近。它与主恒星的距离,只是地球和太阳之间距离的二十分之一,其表面温度大约是1000摄氏度。但是由于这颗行星始终只有一面朝向主恒星,因此它可能是一面的温度很高,另一面的温度较低。      美国波士顿麻省理工学院的科学家西蒙·阿布希特博士说:“在地球上,较大的温差显然会引起强风,据我们的最新观测资料显示,HD209458b 上的情况也不例外。”每隔3.5天这颗行星会运行到主恒星前方一次,并在长达3小时的时间里持续阻断恒星发出的一小部分光。      地球上的天文学家通过“凌星”事件,可以对光图像进行分析,寻找与这颗行星大气有关的信息。他们利用智利欧洲南方天文台甚大望远镜上的超低温红 外光栅光谱仪(CRIRES)获得了这些观测结果。该研究不仅发现了HD209458b行星的大气里存在有毒气体一氧化碳的迹象,而且还显示了它的运动速 度是多么快。      科学家通过测量这颗恒星的运行速度,还能计算出它的质量。天文学家表示,HD209458b和我们太阳系里的木星及土星一样,含碳量丰富。主要 研究人员、荷兰莱登天文台的伊格纳斯·斯内勒说:“未来天文学家也许能通过这种观测形式,研究类地行星的大气,查明宇宙的其他地方是否也存在生命。”该研 究成果发表在《自然》杂志上
Why Your Kids Need Recess They might be better off putting down their books and heading outside. There is a paradox when it comes to improving education in America: The system is failing to prepare many kids for success, but we have so much invested in the system that starting over isn't practical, let alone in a time frame that works for today's kids. We need to put a premium on simple, practical changes that have a big impact on teaching and learning within our existing schools. And one of the single best opportunities to do just that happens to be where we would least expect it: on the playground during recess. Most elementary school principals will tell you that recess is the toughest time of the school day. It's when the vast majority of disciplinary problems happen, and too often problems from the playground spill over into the classroom, creating distractions for students and teachers. Americans by and large tend to be pretty nostalgic about recess, but a lot has changed since we were kids. When I was growing up in Washington, D.C., I had the chance to play outside, unsupervised, every day after school, during weekends and all summer long. The older kids taught the younger kids a host of rules--from how to pick teams to how to quickly end disputes--and as the younger kids became the older kids, we passed on this culture of play to the generation behind us. But kids don't get to play outside and be unsupervised the way we used to. And so when kids come to school, they don't bring those skills with them. The conflict and chaos that have replaced the recess we remember can be demoralizing for kids and educators.
A Lover's Complaint FROM off a hill whose concave womb reworded A plaintful story from a sistering vale, My spirits to attend this double voice accorded, And down I laid to list the sad-tuned tale; Ere long espied a fickle maid full pale, Tearing of papers, breaking rings a-twain, Storming her world with sorrow's wind and rain. Upon her head a platted hive of straw, Which fortified her visage from the sun, Whereon the thought might think sometime it saw The carcass of beauty spent and done: Time had not scythed all that youth begun, Nor youth all quit; but, spite of heaven's fell rage, Some beauty peep'd through lattice of sear'd age. Oft did she heave her napkin to her eyne, Which on it had conceited characters, Laundering the silken figures in the brine That season'd woe had pelleted in tears, And often reading what contents it bears; As often shrieking undistinguish'd woe, In clamours of all size, both high and low. Sometimes her levell'd eyes their carriage ride, As they did battery to the spheres intend; Sometime diverted their poor balls are tied To the orbed earth; sometimes they do extend Their view right on; anon their gazes lend To every place at once, and, nowhere fix'd, The mind and sight distractedly commix'd. Her hair, nor loose nor tied in formal plat, Proclaim'd in her a careless hand of pride For some, untuck'd, descended her sheaved hat, Hanging her pale and pined cheek beside; Some in her threaden fillet still did bide, And true to bondage would not break from thence, Though slackly braided in loose negligence. A thousand favours from a maund she drew Of amber, crystal, and of beaded jet, Which one by one she in a river threw, Upon whose weeping margent she was set; Like usury, applying wet to wet, Or monarch's hands that let not bounty fall Where want cries some, but where excess begs all. Of folded schedules had she many a one, Which she perused, sigh'd, tore, and gave the flood; Crack'd many a ring of posied gold and bone Bidding them find their sepulchres in mud; Found yet moe letters sadly penn'd in blood, With sleided silk feat and affectedly Enswathed, and seal'd to curious secrecy. These often bathed she in her fluxive eyes, And often kiss'd, and often 'gan to tear: Cried 'O false blood, thou register of lies, What unapproved witness dost thou bear! Ink would have seem'd more black and damned here!' This said, in top of rage the lines she rents, Big discontent so breaking their contents. A reverend man that grazed his cattle nigh-- Sometime a blusterer, that the ruffle knew Of court, of city, and had let go by The swiftest hours, observed as they flew-- Towards this afflicted fancy fastly drew, And, privileged by age, desires to know In brief the grounds and motives of her woe. So slides he down upon his grained bat, And comely-distant sits he by her side; When he again desires her, being sat,
1 下一页