Vancouver missed out on the top spot because its infrastructure score had fallen due to periodic closures of a key motorway.

温哥华之所以与第一名失之交臂，原因就在于关闭了一个重要的高速公路而导致“基础设施”这项得分下降。

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Moire pattern caused by the cascade of periodic structures of LCD, Fresnel lens, and Lenticular lens, etc. is a key concern in designing a high quality LCD rear projection screen.

莫尔条纹是由LCD、菲涅尔透镜和微结构透镜等周期性结构的层叠引起的，对于设计高质量的LCD背投影屏幕至关重要。

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Perform periodic maintenance and repair on door closure systems, including but not limited to key card systems and electromagnetic systems.

执行定期保养及维修门关闭系统，包括但不限于钥匙卡系统和电磁系统。

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He's mandated police checkpoints on key roads across the country and periodic monitoring by police helicopters as well.

FORBES: Safe Streets Act

Another key was geographical diversification to protect Cemex against the periodic collapse of the Mexican peso.

FORBES: Cement meets the cyberworld