The determination of diameter and length of tube well filter is always a problem not being completely solved for a long time in tube well engineering from theoretical and practical point of view.

长期以来，管井过滤器直径和长度确定一直是管井工程未完全解决的理论和实践课题，迄今，有关规定不同，存在学术见解分歧，也存在诸多值得讨论的问题。

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And actually, a question that might come up, I just explained, the sodium channel, you might say, well, how do potassium channels work then, because I can understand how you can filter something big out, but how do you filter out something small.

实际上，可能大家会问一个问题，我刚解释过，钠离子通道，你可以说，好吧，那么钾离子通道该如何起作用呢，因为我可以理解你是如何把大东西过滤掉的，但是你如何把小东西过滤掉呢？

麻省理工公开课 - 化学原理课程节选

In case you don't have your smartphone app handy, the taps are equipped with LED lights to show the water's filter status as well -- blue means clean, yellow means not so much and red means you should probably get a new filter, pronto.

ENGADGET

It attaches to well tubes like a regular filter or is placed in a trench to intercept the contaminated groundwater from a landfill.

CNN: Filter cleans arsenic-tainted water

The TV Wonder 650 is based on the Theater 650 chip, including a "motion-adaptive 3D comb filter" as well as noise reduction, and touts the ability to work in Vista systems, even though it's still questionable whether the rest of your system will.

ENGADGET: ATI releases TV Wonder 650 OTA HDTV tuner card