换能器阵元的不同排列组合决定其指向性，波束形成是多波束测量的关键技术。文中 通过数学计算总结了不同换能器阵进行波束形成的工作原理，并介绍了利用二维DFT进行频 域波束形成的一般方法。最后结合现役多波束测深系统，简单解释说明不同系统所采用的波束 形成技术。-Transducer using an array of different permutations and combinations to determine its directivity, beam formation is

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In distribution systems, the load has been a sudden increase or decreases and it is like as nonlinear loads so the load draw non-sinusoidal currents the AC mains and causes the load harmonics and reactive power, and excessive neutral currents