实际的OFDM系统通常会使用虚拟子载波，以此来避免发送信号受到发送端成形低通滤波器的影响。

In practical OFDM systems, virtual subcarriers are usually used to avoid the transmitted data being distorted by the low-pass filter on the transmitter side.

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管件在内高压成形后的厚度变化趋势是从两端向中间逐渐变薄，且呈现不同的厚度带。

After tube hydroforming, the thickness of tube became thin gradually from both ends to the middle and different thickness bands appeared.

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至少一种预成形线圈用来将该基底织物的第一端连接至第二端。

At least one preformed coil is used to attach the first end of the base fabric to the second end.

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