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2019年10月17日 09:23:02|来源:国际在线|编辑:时空爱问
Science and Technolgy科技Metal fatigue in old aircraft老旧飞机的金属疲劳Flying rivets飞行侦查兵A new technique that listens for cracks in ageing aircraft一项侦听老化飞机断裂的新技术WHEN they were built, no one thought they would fly for so long.建造飞机的时候,没人认为它们会飞行这么久。But fitted with new engines and avionics, aircraft can be kept going for a very long time.但是装有新式引擎和航空电子设备的飞机能持续飞行很长一段时间。The average age of the worlds airliners is more than ten years, with some passenger jets 25 years old or more.全世界飞机的平均机龄超过10年,有些客机的机龄超过了25年。Military planes are more geriatric: the Sikorsky Black Hawk helicopter entered service 31 years ago and the Lockheed C-5 Galaxy 40 years back.军用飞机更是超龄:西科斯基公司的黑鹰直升机31年前开始役,洛克希德公司的C-5(运输机)早用到40年了。Both are still going strong.这两款飞机还都强劲地飞行着。Some Boeing KC-135 aerial-refuelling planes, which are based on the venerable 707, have been flying for over 50 years.波音707原型机上发展起来的波音KC-135空中加油机有些已经飞行50多年了。Engineers reckon they could still be in the air when they are 80.工程师们测算80机龄时它们仍然能飞上蓝天。One thing that does ground old aircraft is the impending failure of their aluminium structure from metal fatigue.让老旧飞机搁浅的一件事就是飞机铝构造因为金属疲劳产生的故障隐患。This begins in parts that are subjected to repeated strains, such as where the wings join the fuselage.这种故障始于承受反复拉紧的部位,象机翼与机身的连接处。Constant flexing of the structure concentrates stress, which leads to microscopic cracks.这些构造部位的频繁伸缩使应力集中,导致微裂纹的产生。These cracks become more numerous and eventually large enough for the structure to fail.这些微裂纹越来越多,最后多到足以使这些部位的构造断裂。Aircraft engineers know a lot about how these cracks progress and keep an eye on them in routine overhauls.飞机工程师们对这些裂纹如何发展以及在例行检修中如何注意这些裂纹所知甚详。Nevertheless, they can be difficult and costly to find.不过发现这些裂纹可能很难且费用高昂。Apart from careful visual inspection, techniques like X-rays and ultrasonic probes are also used.除了仔细地目视检查外,也使用象X射线和超声探头这样的技术。Now a British company has come up with a low-cost way of monitoring cracks in aircraft, even while they are airborne.目前一家英国公司提出了一种成本低廉的监测飞机裂纹方法,即使飞机在飞行中(也可进行监测)。The trick that Ultra Electronics uses is to listen for them with a system called Asis.超级电子公司采用的诀窍是侦听带有自动语音识别系统(Asis)的飞机。It does this by fitting small piezoelectric acoustic sensors to parts of the structure to detect the particular frequency of noise caused by a crack in aircraft-grade aluminium.把小型压电声传感器安装到这种构造部位上,检测由航空级铝材裂纹所致的特定频率的噪音,靠这样就能监测飞机裂纹。When first set up, Asis is calibrated to the acoustic signature of the aircraft.安装之初,Asis就按飞机的声波标记图进行了校准。The system can point engineers to where cracks are occurring because the sensors also record the precise moment it is ;heard;.这个系统能向工程师指明哪里正在出现裂纹,因为传感器也记录裂纹噪音被;听到;的精确时刻。As the sound ripples through the structure it arrives at different sensors at different times, which can be used to work out the location and severity of the crack.因为声音呈波形在飞机构造中传播,它在不同的时间到达不同的传感器,这点能用来算出裂纹的位置和严重程度。Once on the ground, a touch-screen device a bit like an iPad is plugged into the system and shows where any cracks are on a three-dimensional image of the aircraft.一经在地面上把有点象iPad的触摸屏设备用插头插入系统中,它就会在飞机的三维图像上显示所有裂纹。Asis will be tried out later this year by Americas Defence Advanced Research Projects Agency.Asis将由美国国防高级研究计划局在今年晚些时候进行试验。A basic set-up to monitor the boom on a small helicopter (a particularly stress-prone part) starts at around ,000, says Rob McDonald, Ultra Electronics marketing director.超级电子公司的营销总监罗伯?麦克唐纳说,监测小型直升机(特别是易受压力的部位)嗡嗡声的基本设备起价大约6.5万美元。As to the future, he expects the company will explore how Asis might also monitor carbon-composite materials, which are being used increasingly in new aircraft.至于未来,他期待公司会探究怎么让Asis也能监测碳复合材料,碳复合材料在新式飞机中的应用渐增。Less is known about the long-term structural integrity of carbon fibre, but it is not prone to corrosion and is extremely tough, so with a bit of care and attention it might allow aircraft to fly even longer.虽然对碳纤维的长期结构完整性所知甚少,但是它不易腐蚀且极为坚硬,因此稍加关注它就可能让飞机飞行得更久。 /201210/206218Science and technology科学技术Bioremediation生物降解Bottom feeders清道夫平菇A novel way of dealing with an unpleasant problem解决烦人难题的新颖方法For your delight and delectation愿你欢愉DESPITE their name, disposable nappies are notoriously difficult to dispose of.一次性尿布,虽然它名字的英文含义为可随意处理的,然而对它的处理却是一个老大难问题。Studies of landfills suggest they may take centuries to rot away.垃圾填埋区的研究显示它们可能要花上几个世纪才会完全腐烂。But Alethia Vázquez-Morillas of the Autonomous Metropolitan University in Mexico City thinks she has found a method of speeding the process up.但墨西哥城自治都市大学的阿莱蒂娅·巴斯克斯·莫莱拉丝认为她已经找到加速此过程的方法。As she and her colleagues describe in Waste Management, cultivating the right type of mushroom on soiled nappies can break down 90% of the material they are made of within two months.正如她与其同事在《废物处理》一文中所描述,以尿布为基壤,培植恰当种类的菇类,能在两个月内将其分解90%。Within four, they are degraded completely.四个月后,它们将被完全降解。What is more, she says, despite their unsavoury diet the fungi in question, Pleurotus ostreatus, are safe to eat.她表示,尽管所讨论的糙皮侧耳口味不佳,但食用安全。To prove the point she has, indeed, eaten them.为了明这一点,她确确实实曾亲口品尝过。The culinary use of oyster mushrooms was one reason why she picked them for the experiment.平菇的食用价值正是她选择其进行实验的原因之一。The species is frequently used in stir-fries and is often added to soups.该食材经常用于煎炸以及常常被添加至汤中。The other reason was that Pleurotus ostreatus is widely used in what is known as mycoremediation—the deployment of fungi to clean up waste.而另一个原因是平菇被广泛用于所谓的茵核降解—即是使用真菌去清理垃圾。It is, for example, aly grown on agricultural materials such as wheat and barley straw,比方说,它已经在处理诸如小麦和大麦秸秆等农业废料以及在类似咖啡渣和特基拉and industrial waste like coffee grounds and the leftovers from making tequila.酒废渣等工业废料上得到逐步推广。Dr Vázquez-Morillas and her colleagues were trying to extend the oyster mushroom’s own culinary range.巴斯克斯·莫莱拉丝士与其同事正试图拓展平菇原有的烹饪范围。The reason nappies are difficult to break down has nothing to do with their use.尿布难于降解跟它有没有被使用过毫无关系。Even a clean nappy would hang around for a long time in a dump.即便是干净的尿布也会在垃圾场长期留存。The main ingredient of a nappy is cellulose, an annoyingly persistent material.尿布的主要组成部分是纤维素,它是一种烦人的顽固性物质。Pleurotus, however, grows on dead or dying trees in the wild and is thus well provided with enzymes that break cellulose down.然而在野外生长在已死或将死树木上的平菇,将恰如其分地分泌出能分解纤维素的酶。And, since Mexicans alone throw away 5 billion nappies every year, there is plenty of material from this source for them to get their mycelia into.而且,既然仅墨西哥每年就有50亿张尿布被丢弃,那么必定有大量此类原料正等着它们的菌丝去分解。The idea that the result might be sold and eaten may be controversial but it is not absurd.销售并食用尿布平菇的想法或许具有争议性,但却并不荒唐。The nappies the researchers used were contaminated only with urine, not faeces.研究人员使用的尿布仅有尿渍,并没有粪便。A healthy person’s urine is sterile and Dr Vázquez-Morillas also treated the nappies with steam, to make sure.健康人类的尿液是无菌的,而巴斯克斯·莫莱拉丝士也对尿布进行了蒸汽高温消毒以确保安全。Such treatment would kill the nasty bugs in faeces, too, though,这样的处理也将杀死粪便中的肮脏虫子,如果有的话,so mushrooms grown on treated nappies should, in theory, be safe to eat.因此生长处理过的尿布上的平菇在理论上应该是可以安全食用。In practice, overcoming the yuck factor might be an insuperable barrier to marketing nappy-grown fungi,实际上,对于销售长在尿布上的平菇而言,克这种主观上令人反感的因素或许是一道不可逾越的障碍,and the cost of the steam treatment could make the exercise futile.而且蒸汽高温消毒的花销可能是不切实际的。Mycoremediation of this sort does not, however, depend for its success on selling the results.然而,此类茵核降解的成功之处并不依赖于销售其产物。Merely getting rid of what would otherwise hang around indefinitely is worthwhile.仅仅是摆脱那些难处理的废物就物有所值了,不然的话那些垃圾可就要无限期地困扰我们了。And of the fungi themselves, Dr Vázquez-Morillas observes,而且对于这些菌类本身,巴斯克斯·莫莱拉丝士道,they are cleaner than most of the vegetables you can find in the market, at least in Mexico.至少在墨西哥,它们要比你在市场上能找得到的大多数蔬菜干净得多。 点击此处下载本期经济学人讲解PDF与音频字幕 /201304/233852

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