英語(yǔ)美文精選
英語(yǔ)美文精選
經(jīng)典美文是中華民族文化的精粹,凝聚著前人的智慧、蘊(yùn)含著豐富的情感、營(yíng)造著優(yōu)美的意境。小編精心收集了初中英語(yǔ)美文，供大家欣賞學(xué)習(xí)!
初中英語(yǔ)美文篇1
Nitinol
Nitinol is one of the most extraordinary metals to be discovered this century: A simple alloy ofnickel and titanium, nitinol has some perplexing properties. A metal with a memory, it can bemade to remember any shape into which it is fashioned, returning to that shape whenever it isheated.
For example, a piece of nitinol wire bent to form a circle that is then heated and quenched willremember this shape. It may then be bent or crumpled, but on reheating, will violentlyuntwist, reforming its original shape. This remarkable ability is called Shape Memory Effect(SME); other alloys, such as brasses, are known to possess it to a limited extent. No one fullyunderstands SME,and nitinol remains particularly perplexing, for, whenever it performs thispeculiar feat, it appears to be breaking the laws of thermodynamics by springing back intoshape with greater force than was used to deform it in the first place.
But not only is nitinol capable of remembering, it also has the ability to "learn". If the heating-cooling-crumpling-reheating process is carried out sufficiently often, and the metal is alwayscrumpled in exactly the same way, the nitinol will not only remember its original shape, butgradually it learns to remember its crumpled form as well, and will begin to return to the samecrumpled shape every time it is cooled. Eventually, the metal will crumple and uncrumple, totallyunaided, in response to changes in temperature and without any sign of metal fatigue.
Engineers have produced prototype engines that are driven by the force of nitinol springingfrom one shape to another as it alternately encounters hot and cold water. The energy fromthese remarkable engines is, however, not entirely free: heat energy is required to producethe temperature differences needed to run the engine. But the optimum temperatures atwhich the metal reacts can be controlled by altering the proportions of nickel to titanium; somealloys will even perform at room temperature. The necessary temperature range betweenthe warm and the cold can be as little as twelve degrees centigrade.
鎳鈦合金
鎳鈦諾是這個(gè)世紀(jì)所發(fā)現(xiàn)的最不尋常的金屬之一，作為鎳和鈦的簡(jiǎn)單的一種合金，鎳鈦諾具有一些令人驚嘆的特征。 這是一種有記憶力的金屬，人們可以使它記住它被塑成的任何形狀，并在加熱后恢復(fù)這一形狀。 比如，一節(jié)鎳鈦諾線圈在加熱冷卻后會(huì)記住圓圈這形狀。 隨后它可能被彎折成其它形狀，但一旦再次加熱，就會(huì)迅速地自動(dòng)恢復(fù)成最初的圓圈狀。 這種不尋常的能力被稱(chēng)為形狀記憶效果(SME)。 其它一些合金如黃銅在一定程度上也具有這種特性。 目前人們對(duì) SME 這一特性尚缺乏透徹的認(rèn)識(shí)，而鎳鈦諾尤其使人驚奇，因?yàn)槊慨?dāng)它展現(xiàn)這一驚人的功能時(shí)，似乎都違背了熱力學(xué)原理。 因?yàn)樗诨謴?fù)原有形狀時(shí)所釋放的力比人們使它變形所施加的力大得多。 鎳鈦諾不僅有記憶力，還能"學(xué)習(xí)"。如果加熱-冷卻-彎曲-再加熱這一過(guò)程重復(fù)一定次數(shù)，且每次冷卻后它都被絲毫不差地彎成同一形狀，它不僅可以記住最初的形狀，還能逐漸記住它被彎成的形狀，并開(kāi)始在每次冷卻時(shí)恢復(fù)這一形狀。
最終，它會(huì)自動(dòng)地隨溫度變化而彎曲和恢復(fù)這些形狀，并且沒(méi)有任何疲勞跡象。 工程師們已制造出一些發(fā)動(dòng)機(jī)樣機(jī)，利用鎳鈦合金在交替遇熱水和冷水時(shí)迅速改變形狀所產(chǎn)生的力做推動(dòng)力。 然而這些神奇的發(fā)動(dòng)機(jī)工作時(shí)并非完全不耗能，因?yàn)楸仨氂袩崮軄?lái)制造溫差才能使機(jī)器運(yùn)轉(zhuǎn)。 但人們可以通過(guò)改變合金中鎳鈦的比例來(lái)控制使它反應(yīng)的最佳溫度。 有的鎳鈦合金甚至能在室溫下做出反應(yīng)，冷暖之間的最小溫差只有 12℃。
初中英語(yǔ)美文篇2
Museums
From Boston to Los Angeles, from New York City to Chicago to Dallas, museums are eitherplanning, building, or wrapping up wholesale expansion programs. These programs alreadyhave radically altered facades and floor plans or are expected to do so in the not-too-distantfuture.
In New York City alone, six major institutions have spread up and out into the air space andneighborhoods around them or are preparing to do so.
The reasons for this confluence of activity are complex,but one factor is a considerationeverywhere -- space. With collections expanding, with the needs and functions of museumschanging, empty space has become a very precious commodity.
Probably nowhere in the country is this more true than at the Philadelphia Museum of Art, whichhas needed additional space for decades and which received its last significant facelift ten yearsago. Because of the space crunch, the Art Museum has become increasingly cautious inconsidering acquisitions and donations of art, in some cases passing up opportunities tostrengthen its collections.
Deaccessing --or selling off -- works of art has taken on new importance because of themuseum's space problems. And increasingly, curators have been forced to juggle gallery space,rotating one masterpiece into public view while another is sent to storage.
Despite the clear need for additional gallery and storage space, however, "the museum hasno plan, no plan to break out of its envelope in the next fifteen years," according toPhiladelphia Museum of Art's president.
博物館
從波士頓到洛杉機(jī)，從紐約到芝加哥、到達(dá)拉斯，所有的博物館或者正在籌劃、建造或者正在完成大規(guī)模的擴(kuò)建計(jì)劃。 這些計(jì)劃或者已經(jīng)根本性地改變了博物館門(mén)面與展廳的設(shè)計(jì)，或者預(yù)期在不久的將來(lái)會(huì)這樣做。 單單在紐約市，六個(gè)主要機(jī)構(gòu)或者已經(jīng)向空中和周?chē)鷶U(kuò)展，或者正準(zhǔn)備這樣做。大家一致行動(dòng)的原因是復(fù)雜多樣的，但其中的一個(gè)因素是普遍 考慮的空間問(wèn)題。 隨著收藏品的增多，也隨著博物館的需要和功能的變化，空間已經(jīng)變成了一項(xiàng)非常珍貴的商品。在我國(guó)，也許沒(méi)有任何其他地方比費(fèi)城藝術(shù)博物館更符合這個(gè)事實(shí)。
這個(gè)博物館幾十年來(lái)一直需要額外的空間，十年前進(jìn)行了最后一次重大的翻新。 由于空間緊缺，該藝術(shù)博物館在考慮購(gòu)買(mǎi)與受贈(zèng)藝術(shù)品已越來(lái)越謹(jǐn)慎，有時(shí)甚至放棄增強(qiáng)藝術(shù)收藏的機(jī)會(huì)。由于博物館的空間問(wèn)題，將藝術(shù)品脫手或者說(shuō)賣(mài)掉已經(jīng)有了新的重要意義。 博物館館長(zhǎng)們被迫巧妙輪換利用陳列館的空間，輪流著把一些藝術(shù)杰作向公眾展出，而把另一些送入存儲(chǔ)室中。雖然對(duì)額外的陳列室和存儲(chǔ)室空間需要很明顯，但據(jù)費(fèi)城藝術(shù)博物館經(jīng)理講： "博物館還沒(méi)有在未來(lái)十五年打破這個(gè)束縛的計(jì)劃。"
初中英語(yǔ)美文篇3
Muscles and Human
Body It is in the joints of the human body that movements of the bones take place.Themovement itself is caused by the pull of sheets and cords of very tough tissue called muscle.Muscle tissue has the special ability to shorten itself so that the bone on which it pulls has tomove. When muscle tissue shortens, it also bunches up. Muscle tissue covers the body insheets and bands that lie between the skin and the skeleton.
The bones are the framework of the body, but the muscles fill out the body shape. Mostmuscles extend from one bone to another. When the muscle between the bones shortens, onebone has to move. The point where the muscle is fastened to the unmoving bone is called theorigin of the muscle, whereas the point where the muscle is not fastened to the bone that is tobe moved is called the insertion. Sometimes the muscle is not attached directly to the bone butto a tough, nonstretchable cord, or tendon, that is attached to the bone. Muscles do not push;they can only pull. To bend the arm at the elbow, the muscle at the front of the upper armhas to shorten and bunch up. To unbend the arm other muscles in the back of the arm haveto shorten.
These two sets of muscles - the front and the back - are said to act in opposition to eachother. When one set is working, the other set is usually relaxed. But there are times whenboth of them work. Sometimes muscles are called upon to do more than simply pull in onedirection. They may have to perform a turning motion. To be able to do this, the muscle mustbe attached to the bone at an angle. By pulling, the muscle can cause the bone to pivot. A fewmuscles have special functions. The diaphragm, for example, forces the lungs to take in air. Thispart of breathing is not primarily a bone moving operation.
肌肉和人體
骨骼運(yùn)動(dòng)發(fā)生在人體的關(guān)節(jié)部位。這種運(yùn)動(dòng)是由稱(chēng)為肌肉的片狀或條狀的強(qiáng)韌組織拖動(dòng)而引起的。 肌肉組織有一種特殊的收縮能力，可以帶動(dòng)與之相連的骨骼。 肌肉在收縮的同時(shí)，也會(huì)聚成團(tuán)。肌肉以條狀或片狀形式布滿全身，存在于皮膚與骨架之間。 骨骼是身體的支架，而肌肉則構(gòu)成了人的體形。 大多數(shù)肌肉接兩塊骨頭，但當(dāng)肌肉收縮時(shí)只有一塊骨頭運(yùn)動(dòng)。 肌肉與不動(dòng)骨相連的一端叫肌起端，與動(dòng)骨相連的一端叫附著端。 有些肌肉不與骨骼直接相連，而是連著附在骨骼上的不能收縮的帶狀組織或腱上。 肌肉不能推動(dòng)而只能拉動(dòng)骨骼。 要從肘部彎曲手臂，就要收縮上臂正面的肌肉。 要伸直手臂，背面的肌肉就得收縮。 這兩組肌肉，正面的和背面的，稱(chēng)為相反運(yùn)動(dòng)肌肉。 當(dāng)一組工作時(shí)，另一組就休息。 但有時(shí)它們也一起工作。 有時(shí)我們要求肌肉不僅僅做簡(jiǎn)單的單向拖動(dòng)。 它們需要轉(zhuǎn)動(dòng)。 但只有當(dāng)肌肉與骨骼形成一定角度時(shí)，它們才能轉(zhuǎn)動(dòng)，從而拖動(dòng)骨骼繞某個(gè)軸旋轉(zhuǎn)。 有幾塊肌肉的作用較特殊，例如隔膜肌。 它帶動(dòng)肺部吸入空氣。 呼吸基本上不是骨骼運(yùn)動(dòng)帶動(dòng)的。
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