超碰免费人人操|国产视频二区久久艹人人操|欧美激情第一页在线|久热最新无码中文视频|91精品国际成人|亚洲成人精品在线视频青青草|久草免费高清完整在线观看|你懂的AV在线日本黄网页|国产黄色AV日韩女同网|欧美成人色区导航片av

и  ôk

r(sh)g2022-10-12 20:21:46 иԇ ҪͶ

и  ôk

и ϤӢZôk?

и  ôk

ڽиԇETSƳµ ͿZIJмӢĴԼmĿ횳J(rn)ڄ_ʼ֪@(g)׃(dng)СҲXñ^@ġETS@ꌦ(du)иԇĸ׃󲿷ֶһЩ΢{(dio)ͬr(sh)Ҳ(hu)o³ֵm(yng)r(sh)g ߸׃s]κֱӾ_ʼУƺЩǺСм(x)һETSĕr(sh)һֱDZ^(yn)֔(jn)?sh)?du)}}Ҳ@Ȼ˵ԒСJ(rn)˽o迼m(yng)r(sh)gи мʹ(ni)F(xin)(yng)ԓҲ(hu)̫ߣ(hu)(du)ҵijɿ(j)̫Ӱ

ETSҪ{(dio)?

(du)ETS@ĸ׃PXÿԳ@߀ǏČ(sh)֣иԇ@ô(jng)v˺Î״δ׃ԭҪ߀ϣ܉ͨ^иԇ˽ⱱУ@ČW(xu)g(sh)ĭh(hun)һ(g)Էdz(qing)ćĴW(xu)HHĽ߀Ӣģ޵Լ(g)ҵĽԼv˸õ׌W(xu)ǰm(yng)У@h(hun)ȥ܉ٵ_չW(xu)(x)@ӵĸ׃ҲͲ

Α(yng)(du)и еİ?

(du)Α(yng)(du)@һ׃䌍(sh)@(g)}ܺ(jin)?yn)鱾|(zh)ρf߀ǶӢZԲeҲ(hu)؄e(du)ڿԇxF(xin)߀^h(yun)ͬW(xu)䌍(sh)B(yng)(du)ӢʽdȤȿһЩӢһЩӢʽLie to me֮ȸһӢʽ֮̎ͨ^ һЩo(j)ƬDŽeIJԼӢʽ ˮƽ;ԇühͲҪ̫r(sh)g@ETSṩsample ͸ ҪעӢʽӢZһЩ~ϸʽһą^(q)eҲHҪעҲҪע~Rϵļ(x)΢e

ڰĴmb@ɂ(g)ҸӢǧzf|“(lin)ϵ@ɷNҲӢʽ^ӽһЩl(f)ϵą^(q)eֻҪھW(wng)һҎ(gu)ȻעͿˣ̫^ړ(dn)

и (x)(du)ı

Look at our topographical map and you'll see that the middle third of the North American continent from the Rocky Mountains almost to the Mississippi River is pretty flat.

ۂ'ΈD㌢ꑵg֮һɽ}ൽȺஔ(dng)?sh)ƽ?/p>

This is the Great Plains.

@Ǵƽԭ

This kind of area is sometimes called a prairie, sometimes a steppe. That's s-t-e-p-p-e.

@N^(q)Еr(sh)QԭЕr(sh)(Q)ɲԭs-t-e-p-p-e

The defining features are level terrain, dry climate, and an absence of trees.

͵ˮƽĵ؄(sh)Ě߀Иľȱ

The Great Plains are actually the former bed of a shallow inland sea.

ƽԭŒ(sh)ǰ\(ni)ꑺĺ

Over millions of years, sediment left by glaciers, water, and wind smoothed out the dry sea bed.

(sh)fԁµijeˮL(fng)ѸĺŪƽˡ

As I said, the Great Plaints are bordered on the west by the Rocky Mountains.

f^ǘƽԭͬɽ}

And it's really the Rockies that are responsible for the formation of the grasslands.

ɽ}γɲԭԭ

The mountains are so high that they block the heavy moist air traveling eastward from the Pacific Ocean.

ɽ}֮סˁ̫ƽ|M(jn)ıشij՚

Lighter, drier air passes over the mountains.

pһЩһЩĿ՚Խ^ɽ}

Until people intervened with irrigation and farms, only grass could grow on the dry, windy plain.

˂ùȺr(nng)(chng)A(y)֮ǰֻвLڸL(fng)ƽԭ

In fact, we can divide the Great Plains into three zones.

Œ(sh)҂ܰѴƽԭֳ(g)^(q)

In the west, where it's driest and windiest, the grass is very short.

棬ﲢL(fng)Ǻܰ

In the eastern zone, there's more rain and grass grows as high as 360 centimeters.

ږ|؅^(q)иˮL_(d)360

In the middle third, there's a mix of grass species that grow to an intermediate height.

gĵ(g)(zone)һ(g)Lg߶ȵIJݵNĻw

и (x)(du)ı

Scientists are always on the lookout for alternative sources of energy.

ƌW(xu)ҿڌԴ

Today we're going to discuss one that's so plentiful they say it could supply more energy than all the coal and oil in the world.

҂̽ӑһN˳f܉ṩеú̿ʯ͸

It's found in something called gas hydrate and, believe it or not, that's a kind of ice.

l(f)F(xin)ijNwˮ(Ė||)Ų㣬һN

That's right. But the water in this ice was way down below the Earth's surface when it was frozen, so it was under a lot of pressure.

ǵģ@Nˮڮ(dng)Y(ji)r(sh)(hu)º(ĵط)(hu)ںܴĉ֮(ԉܴ)

And trapped inside the crystals of ice are individual molecules of methane --- that's what's in natural gas.

ڱľwеdž΂(g)ļӡ@Ȼ

All this makes gas hydrate pretty strange stuff.

@Щ(r)ʹÚwˮ(ɞ)ԎĖ|

If you touch a match to a piece of this ice, it'll burst into flame.

һ|@ӵһKһȼ

And when geologists bring a chunk of it up to the surface to study at normal air pressure and temperature, gas hydrate begins to hiss and bubble, and in less than half an hour, the ice melts and the methane inside escapes into the air.

(dng)?sh)|(zh)W(xu)ҰһK@N()ρоr(sh)≺͜ض£wˮ_ʼ˻˻ðڲ낀(g)Сr(sh)(ĕr(sh)g)ڻļ՚

Now, as you might guess, this can make gas hydrate kind of hard for miners to handle.

F(xin)ڣゃܲµ@ʹwˮ(du)ڵVfc(din)y̎

And then there's the problem of where it's located in frozen arctic regions or in ocean waters off the Atlantic coast, and up to a mile down.

Ȼ̎λõĆ}ڱıO؅^(q)x_󺣰_(d)һӢĺˮ

Environmentalists warn that mining it could even be disastrous.

h(hun)Ҿf_Ǟ(zi)yԵ

Offshore drilling could allow seawater to seep down into the huge icy deposits and release tons of methane up into the atmosphere.

x@̽ܕ(hu)ȻˮBıeጷşo(sh)ļρM(jn)՚

And methane, our listeners may recall, is a greenhouse gas that could really worsen the problem of global warming.

飬ۂ (yng)ԓһNҚwĿʹȫ׃ůĆ}Ӑ

So, gas hydrate may offer some interesting possibilities.

ˣwˮṩһЩP(gun)עİl(f)չ

But, with all these drawbacks, I'm not going to hold my breath waiting for it to fuel my furnace.

Sе@Щȱc(din)Ҳ(hu)סҵĺȴȼҵĠt

и  ôkP(gun)£

˼ ļ08-20

Pc(din)˼ гҊĿ09-29

 ˼ 10-03

2016и ָ(do)֮и c(din)11-02

ô˷˼  Ć}08-16

и (jng)زľx08-11

и ԇ11-11

и 08-23

и ָ08-17

и (jng)ԇ12-18