关键词：瓯海环球教育寒假班,雅思. 环球教育 瓯海环球教育寒假班,雅思.
瓯海环球教育寒假班,雅思.温州雅思培训，温州出国语言培训，雅思辅导班、雅思备考，温州环球雅思经典格言： 见面少叙寒暄话，多把艺术谈几声。。
温州环球雅思培训课程：
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雅思基础（保
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雅思精品（6分）班
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6.5分高分班(选修外教口语)
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雅思mini精英班
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雅思“6分无限时”班
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高中生雅思“6段式”
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6.5分高分(选修词汇或语法)
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“4+1”式预备a套餐班
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“4+1”式预备b套餐班
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雅思狂人写作系列课程
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海外求生口语班
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雅思全真语法课
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雅思外教口语集训课程
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“四大名教”精讲点题班
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r1（高分级） r2(强化级)课程
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雅思语法提高班
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瓯海环球教育寒假班,雅思.
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r3(预备级+强化级)课程
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雅思全真词汇班
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雅思强化（6分）班
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温州雅思培训，温州出国语言培训，雅思辅导班、雅思备考，温州环球雅思经典格言：问候不一定要稳重其事，但一定要真挚感人。瓯海环球教育寒假班,雅思.。
瓯海环球教育寒假班,雅思. 雅思模拟试题在雅思备考过程中所起的作用不可小觑，通过模拟练习题，我们可以很直接地了解到自己的备考状况，从而可以更有针对性地进行之后的复习。希望以下内容能够对大家的雅思备考有所帮助!
Sun's fickle heart may leave us cold
□ 25 January 2007
□ From New Scientist Print Edition.
□ Stuart Clark
1.There's a dimmer switch inside the sun that causes its brightness to rise and fall on timescales of around 100,000 years - exactly the same period as between ice ages on Earth. So says a physicist who has created a computer model of our star's core.
2.Robert Ehrlich of George Mason University in Fairfax, Virginia, modelled the effect of temperature fluctuations in the sun's interior. According to the standard view, the temperature of the sun's core is held constant by the opposing pressures of gravity and nuclear fusion. However, Ehrlich believed that slight variations should be possible.
3.He took as his starting point the work of Attila Grandpierre of the Konkoly Observatory of the Hungarian Academy of Sciences. In 2005, Grandpierre and a collaborator, Gábor ágoston, calculated that magnetic fields in the sun's core could produce small instabilities in the solar plasma. These instabilities would induce localised oscillations in temperature.
4.Ehrlich's model shows that whilst most of these oscillations cancel each other out, some reinforce one another and become long-lived temperature variations. The favoured frequencies allow the sun's core temperature to oscillate around its average temperature of 13.6 million kelvin in cycles lasting either 100,000 or 41,000 years. Ehrlich says that random interactions within the sun's magnetic field could flip the fluctuations from one cycle length to the other.
5.These two timescales are instantly recognisable to anyone familiar with Earth's ice ages: for the past million years, ice ages have occurred roughly every 100,000 years. Before that, they occurred roughly every 41,000 years.
6.Most scientists believe that the ice ages are the result of subtle changes in Earth's orbit, known as the Milankovitch cycles. One such cycle describes the way Earth's orbit gradually changes shape from a circle to a slight ellipse and back again roughly every 100,000 years. The theory says this alters the amount of solar radiation that Earth receives, triggering the ice ages. However, a persistent problem with this theory has been its inability to explain why the ice ages changed frequency a million years ago.
7."In Milankovitch, there is certainly no good idea why the frequency should change from one to another," says Neil Edwards, a climatologist at the Open University in Milton Keynes, UK. Nor is the transition problem the only one the Milankovitch theory faces. Ehrlich and other critics claim that the temperature variations caused by Milankovitch cycles are simply not big enough to drive ice ages.
8.However, Edwards believes the small changes in solar heating produced by Milankovitch cycles are then amplified by feedback mechanisms on Earth. For example, if sea ice begins to form because of a slight cooling, carbon dioxide that would otherwise have found its way into the atmosphere as part of the carbon cycle is locked into the ice. That weakens the greenhouse effect and Earth grows even colder.
9.According to Edwards, there is no lack of such mechanisms. "If you add their effects together, there is more than enough feedback to make Milankovitch work," he says. "The problem now is identifying which mechanisms are at work." This is why scientists like Edwards are not yet ready to give up on the current theory. "Milankovitch cycles give us ice ages roughly when we observe them to happen. We can calculate where we are in the cycle and compare it with observation," he says. "I can't see any way of testing [Ehrlich's] idea to see where we are in the temperature oscillation."瓯海环球教育寒假班,雅思.温州雅思培训，温州出国语言培训，雅思辅导班、雅思备考，温州环球雅思经典格言：世界因为有我而更美好。。
雅思考试备考课程 25年培训经验，温州雅思培训，温州出国语言培训，雅思辅导班、雅思备考，温州环球雅思经典格言：不羡慕别人的成就，只专注当下的努力！惟有努力奋斗，才能成就梦想。瓯海环球教育寒假班,雅思.。
