PTE考生目前最大的问题之一就是练习题缺乏。除了有限的基本官方书（PLUS，Testbuilder, OG）之外

Lithium ion batteries power everything these days from smartphones to electric cars.

They’ve been a great advance in portable power storage.

On the downside, their spread also makes a big contribution to electronic waste dumps often found in developing countries.

But IBM scientists in India may have come up with a way to decrease the numbers of discarded batteries while also bringing electricity to underserved parts of the world.

They developed an experimental power supply, called the UrJar, consisting of reusable lithium ion cells salvaged from three-year-old laptop battery packs.

For a study of the technology, the researchers enlisted street vendors who had no access to grid electricity.

Most users reported good results.

Several of them used the UrJar to keep an LED light going for up to six hours daily.

For one participant, the power supply meant keeping the business open two hours later than usual.

IBM presented its findings the first week of December at the Symposium on Computing for Development in San Jose, California.

The UrJar isn’t ready for the market quite yet.

But it shows that one person’s trash could literally light up someone’s life halfway around the world.

Lithium ion batteries：锂电池

underserved：[ʌndə’sɜ:vd]  服务不周到的

salvaged：[ˈsælvɪdʒ]   回收利用

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