Vol. 9, No. 1 (1953)
1953-01-05
1953, 9 (1): 15-35.
doi: 10.7498/aps.9.15
Abstract +
本工作依据微分磁化率的观测,以研究铁、镍、和几种铁钴合金在室温和高温下的趋近饱和现象。由实验结果得知,在数百到6000奥斯特的磁场下微分磁化率和磁场强度的关系可用下式表出:((?I)/(?H))T=A/H2+(2B)/H3+ C/H1/2+D,式中I表磁化强度,H表磁场强度,T表温度。在室温附近,式中末两项比前两项小得多,所以末两项的总值可以约略用一常数来代替;但在高温下就不然了。如果将一曾经驯炼的试品逐步加以冷作则系数A和B最初跟冷作程度作跳跃式的增加;但对于经过剧烈冷作的试品上式就不适用。在驯炼状态下,A和B跟温度的上升而减小;到消失时温度还相当低于居里点。因本实验中所得数据的准确度不够所以不能依据它们来确定D的值;但如果将D略去而计算系数C的值,则可以确定到九成。C的数量级和它跟温度变化的情形大致是和Holstein和Primakoff的理论相符的系数B和磁晶各向异性系数K1的平方成正比;但用B的实验值和B的理论式比较而算得的K1则和从单晶体观测所得的K1只有数量级的符合。
1953, 9 (1): 45-56.
doi: 10.7498/aps.9.45
Abstract +
A method based upon simple diffraction theory is described for the calculation of modified paraboloid reflectors to produce from a point source a shaped beam of arbitrary shape in one plane and uniformly narrow in the perpendicular planes. A specific application of the shaped beam antennas is in connection with radar antennas designed for height finding. In this case the antenna must have a sharp elevation beam for obtaining precise elevation information and a rapid elevation scan. The beam must be relatively broad in azimuth in order that the target will be held in the beam long enough to obtain height information. If a fixed minimum of illumination is to be achieved at a given linear distance on both sides of the center line of the azimuth beam, the amplitude pattern must have the so-called “double cosecant” or “beavertail' shape.
