已知传输距离D(km)和频率f(MHz)的条件下,自由空间衰耗Ls(dB)的计算公式?
参考答案:
Ls(dB.=32.4+20lgD(Km)+20lgf(MHz)
All the children like Mr Brown very much because he often makes them ________.[ ]
A. laughed
B. laugh
C, laughing
D. to laugh
患儿,女,6岁,夏季发病,因高热1天,惊厥1次住院。查体:嗜睡,面色苍白,四肢发凉,BP70/40mmHg,心率126次/分,心音低钝,颈无抵抗,巴氏征(-)。最可能的诊断是()
A.热性惊厥
B.流行性脑脊髓膜炎
C.中毒型细菌性痢疾
D.结核性脑膜炎
E.急性风湿热