起始套中特殊反射的作用

MULTAN法推引相角是以起始套反射开始逐轮进行迭代、扩大。由于起始套中的特殊反射包括确定原点的一般反射取值有限,所以一旦由它们组合的新反射的相角值有较大偏差时,就无法利用MULTAN的多解值特性从自身来缩小它,而只能依靠正切式中的其它项给以弥补。然而,当这种情况发生在相角推引的最初几步时,由于此时往往仅有很少几项参与运算,加之它们的|E|值较大,权也高,势必会左右全过程的成败。处置这类失败的可行办法应该是从分析收敛图入手,改换那些可疑的反射。本文在一个MULTAN-80失败的例子上进行了7项试验,其结果充分证实了这一切。 关键词：

THE ROLE OF SPECIAL REFLEXIONS IN A SET OF STARTING PHASES

Phase development in the MULTAN procedure is based on the permutation of the starting phase set. When a new phase of a gereral reflection is derived from the combination of two special reflections of the starting set, it may result in large error. If this occurs in the early stage of the phase development, the error is difficult to be eliminated afterwards. The wrong phase should then strongly affect the process of the phase development and leads sometimes to the failure of the structure determination. One way of dealing with this problem is to check the convergence mapping carefully and change some of the reflections in the starting set. Tests have been made on modifying a starting set that led to the MULTAN failure. It turns out that just a slight but proper modification of the starting set can greatly improve the process of phase development and leads to the correct solution of the structure.