Official 02 Set 3

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Manila Hemp

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What aspect of Manila hemp fibers does the professor mainly discuss in the lecture
  • A. Similarities between cotton fibers and manila hemp fibers

  • B. Various types of manila hemp fibers

  • C. The economic importance of Manila hemp fibers

  • D. A use of Manila hemp fibers

显示答案 正确答案: D
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    NARRATOR:Listen to part of a lecture from a Botany class.

    FEMALE PROFESSOR:Hi, everyone. Good to see you all today. Actually, I expected the population to be a lot lower today.It typically runs between 50 and 60 percent on the day the research paper is due.Um, I was hoping to have your exams back today, but, uh, the situation was that I went away for the weekend, and I was supposed to get in yesterday at five, and I expected to fully complete all the exams by midnight or so, which is the time that I usually go to bed, but my flight was delayed, and I ended up not getting in until one o’clock in the morning.Anyway, I'll do my best to have them finished by the next time we meet.

    OK. In the last class, we started talking about useful plant fibers. In particular, we talked about cotton fibers, which we said were very useful, not only in the textile industry, but also in the chemical industry, and in the production of many products, such as plastics, paper, explosives, and so on.Today we'll continue talking about useful fibers, and we'll begin with a fiber that's commonly known as "Manila hemp".

    Now, for some strange reason, many people believe that Manila hemp is a hemp plant. But Manila hemp is not really hemp. It's actually a member of the banana family - it even bears little banana-shaped fruits.The "Manila" part of the name makes sense, because Manila hemp is produced chiefly in the Philippine Islands and, of course, the capital city of the Philippines is Manila.

    Now, as fibers go, Manila hemp fibers are very long. They can easily be several feet in length and they're also very strong, very flexible.They have one more characteristic that's very important, and that is that they are exceptionally resistant to salt water.And this combination of characteristics - long, strong, flexible, resistant to salt water - makes Manila hemp a great material for ropes, especially for ropes that are gonna be used on ocean-going ships.In fact, by the early 1940's, even though steel cables were available, most ships in the United States Navy were not moored with steel cables; they were moored with Manila hemp ropes.

    Now, why was that? Well, the main reason was that steel cables degrade very, very quickly in contact with salt water. If you've ever been to San Francisco, you know that the Golden Gate Bridge is red. And it's red because of the zinc paint that goes on those stainless steel cables.That, if they start at one end of the bridge and they work to the other end, by the time they finish, it's already time to go back and start painting the beginning of the bridge again, because the bridge was built with steel cables, and steel cables can't take the salt air unless they're treated repeatedly with a zinc-based paint.

    On the other hand, plant products like Manila hemp, you can drag through the ocean for weeks on end. If you wanna tie your anchor to it and drop it right into the ocean, that's no problem, because plant fibers can stand up for months, even years, in direct contact with salt water.OK. So how do you take plant fibers that individually you could break with your hands and turn them into a rope that's strong enough to moor a ship that weighs thousands of tons? Well, what you do is you extract these long fibers from the Manila hemp plant, and then you take several of these fibers, and you group them into a bundle,because by grouping the fibers you greatly increase their breaking strength - that bundle of fibers is much stronger than any of the individual fibers that compose it.And then you take that bundle of fibers and you twist it a little bit, because by twisting it, you increase its breaking strength even more. And then you take several of these little bundles, and you group and twist them into bigger bundles, which you then group and twist into even bigger bundles, and so on, until eventually, you end up with a very, very strong rope.

  • 旁白:听一段来自植物学课堂的讲座。

    教授:大家好。很高兴见到大家。之前,我还以为今天来听课的人会比上次少很多。一般说来,研究论文上交截止日期那天,来上课人数的流失率会在50%到60%。嗯,我原来有望今天带来你们的考试结果,但是,嗯,情况是这样的,我上周末不在,原本打算昨天5点到,赶在我通常去睡了的午夜前完成全部批改,但是我的航班延误了,直到凌晨1 点钟才到。不管怎么说,我会尽力在下节课前完成。

    在上一节课,我们开始探讨有用的植物纤维。特别是,我们讨论了一些棉纤维,我们说过它们很有用,不仅在纺织业来说,在化工业也是如此,甚至在很多成品的生产方面,比如塑料、纸、炸药等等,也很有用。今天我们继续讨论有用的纤维,我们将从大家熟知的“马尼拉麻”开始。

    如今,因为某种奇怪的原因,很多人认为马尼拉麻是一种麻类植物。但是马尼拉麻并不是麻类植物。它实际上是香蕉科里的一种——它甚至有着形状跟香蕉类似的果实。这名字中的“马尼拉”倒是说得过去,因为马尼拉麻主要产于菲律宾群岛,当然,菲律宾的首都是马尼拉。

    现在,随着人们对纤维的经营开发,马尼拉麻纤维变得很长。它们很容易达到几英尺长,同时很牢固,柔韧性也很好。它们还有一个重要的特征--对咸水有极强的抵抗性。正是这些长、坚韧、牢固、抗盐水特性的组合让马尼拉麻成为绝好的绳索,特别是用在远洋船只上。事实上,在20 世纪40 年代初期,尽管能买到钢丝绳,美国海军绝大多数的船停泊时用的仍不是钢丝绳;这些船用的是马尼拉麻绳。

    为什么会这样呢?主要的原因是钢丝绳接触咸水后很容易腐蚀。如果你去过旧金山的话,你会发现金门大桥是红色的。红的原因是因为锌颜料在钢索上起作用。如果工人们从一头安装钢索到另外一头,到他们完工的时候,就该回来重新油漆一遍了,因为金门大桥是由钢丝建成的,同时钢丝在咸性的空气中容易腐蚀,除非反复给钢丝涂上锌颜料。

    但是,像马尼拉麻这样的植物产品,你可以拖着它们穿过海洋好几个礼拜。如果你想绑上锚,然后将锚扔到海里,一点问题都没有,因为植物纤维能坚持好几个月,甚至好几年,直接与咸水接触。那么你是怎么将只手可以拉断的植物纤维做成强韧到可以泊上万吨船的绳子的?你需要做的是从马尼拉麻里抽出这些长纤维,然后从中拿出几缕,揉成一根,因为通过这样揉搓,极大地加强了这些纤维的抗断强度——这一根的强度比起其中的任何一缕纤维都要强得多。之后,再拿揉搓好的那根纤维捻一下,这样能让其抗断强度得到更大的提升。再后来,你将揉搓好的这些纤维揉搓和编织成更大的绳子,如法炮制,直至做出很大的缆绳。

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    音频1
    解析

    题型分析:主旨题

    原文定位

    Today we’ll continue talking about useful fibers, and we’ll begin with a fiber that’s commonly known as “Manila hemp.

    选项分析

    在讲述了飞机晚点和上次课内容之后,教授说了今天的主题,之后的文章确实也在说Manila Hemp的作用,因此答案选D。A选项,cotton fibers是上次课内容。B选项,various types未提到。C选项,economic importance是上次课的内容。

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