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高中三年级英语

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    A professor of environmental health and his students began studying the idea of rooftop gardening for cities. “I think vertical farming is an idea that can work in a big way,” said Despommier.
    Why would we want to build skyscrapers filled with vegetables when we’ve been farming on the ground for 10,000 years? Because as the world’s population grows—from 7 billion now to as much as 9 billion by 2050—we could run out of productive soil and water. Most of the population growth will occur in cities that can’t easily feed themselves. And the fact is that modern agriculture as well as everything associated with it – chemical fertilizers and transportation full of carbon—is a significant contributor to climate change, and suddenly vertical farming doesn’t seem so magic in the sky.
    “Vertical farming could allow food to be grown locally and sustainably,” says Glen Kertz, CEO of Valcent. The result saves space — vital in urban areas — and allows farmers to irrigate and fertilize with far less waste.
    At Valcent’s El Paso lab, crops grow in rows on conveyor belts. Moving them gives the plants the precise amount of light and nutrients needed, letting them grow 15 times as much vegetable as on a normal farm with 5% of the water that traditional agriculture does.
    Despommier plans to build a 30-story, city-block-size vertical farm that would have transparent walls to maximize sunlight and would produce enough food for 50, 000 people. But it would cost hundreds of millions to build a full-scale skyscraper farm. That’s the main drawback: construction and energy costs would probably make vertically raised food more costly than traditional crops.

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序数词

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  • 序数词

序数词的概念:

表示顺序的数称为序数词。如:first, second, third, fourth。


序数词的构成与用法

1、序数词的构成:
①一般来说,是由相应的基数词加词尾th构成。
   例:four+th→fourth
           six+th→sixth
           seven+th→seventh
           ten+th→tenth
②下面这些基数词在变为序数词时,有特殊的变化。
例:one→first
        two→second
        three→third
        five→fifth
        eight→eighth
        nine→ninth
        twelve→twelfth
③十位整数序数词的构成方法是将基数词的词y变成i,然后再加eth。
例:twenty→twentieth
        thirty→thirtieth
        forty→fortieth
        ninety→ninetieth
④两位或两位以上的基数词变成序数词时,仅将个位数变成序数词。
例:twenty-one→twenty-first
        thirty-five→thirty-fifth
        a hundred and fifty-three→a hundred and fifty-third

2、序数词的用法:
①序数词在使用时,一般加上定冠词。
例:the first book
        the second floor
        the third day
        the fourth week.
②序数词在多数情况下都用作定语,有的也可以作表语、主语和宾语。
例:The may1st is Labour Day. 五月一日是劳动节。
        My room is on the second floor. 我的房间在二楼。
        The first is larger than the secon.(主语)第一个比第二个大。
        Read the book from the first.(宾语)从开头读这本书。
        You'll be the sixth to write.(表语)你将是第六个写的。
③序数词的前面可以加上不定冠词,用来表示“再一”,“又一”的意思。
例:You may have a third try. 你可以第三次尝试。


序数词知识体系:

 


约数的表达方法

用tens/dozens/scores/hundreds/thousands/millions of 表示“几十、几百、上千、成千上万”等。
如:The boy bought dozens of pencils.            
        Thousands of people died in the earthquake.
注意: (A):dozen, score, hundred, thousand, million等表示确切数量时,不用复数。
如:five dozen (of) eggs   五打鸡蛋
        hree hundred people  三百个人

分数词的构成和用法:

1)分数词构成法:
分数词(FractionalNumerals)由基数词和序数词构成,基数词代表分子,序数词代表分母。除了分子为1的情况下,序数词都要用复数形式:
如:1/4:one-fourth
        5/9:five-ninths
        2/3:two-thirds
       17/5:three and two-fifths
       7/12:seven-twelfths
       379/8:forty-seven and three-eighths
此外还有下面表示法:
如:1/2:a(one) half
        1/4:a(one) quarter
        3/4:three-quarters
        9/4:two and a quarter
        3/2:one and half
        31/4:seven and three quarters