六、其他雅思成绩单寄送注意事项
如考生的成绩单由于投寄失败被退回英国文化教育协会，考生会在2个工作日内收到电子邮件通知，提醒考生登录报名网站个人主页申请退回成绩单重新寄送 。考生申请退回成绩单重新寄送时，需要提供准确的寄送地址、邮编及联系电话，并支付EMS快递费用(北京：14元，国内其他城市：22元) 。
退回成绩单重新寄送申请一旦确认付费，将无法更改或取消 。考生可以提前在NEEA账户中预存快递费用，也可直接使用NEEA帐户余额支付 。余额不足时，需要先进行帐户充值，再确认支付 。考生申请提交成功后，退回成绩单将在3个工作日内由英国文化教育协会重新寄出，新的EMS单号会更新在报名网站个人主页，考生同时会收到电子邮件通知 。
雅思阅读全真练习系列：Sun's fickle heart may leave us cold
Sun's fickle heart may leave us cold
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.
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