本病是一慢性呼吸传染病。主要症状为咳 嗽和气喘,病变特征是肺的尖叶、心叶、中间 回本章叶、膈叶前缘呈“肉样”式虾肉样变。 很多国家报道了本病。长期以来该病被认为 回本节是最常发生和经济意义重大的猪病之一饲料 利用率降低20-25%,增重减少2.5-16%

一、植物与环境 1、有关环境的概 （1)环境: （2)生态因子:光照、温度、水分、土壤、大气因子。 （3)生境: （4)生存条件:

1 For the circuit given in Fig. 18-14, the R C2, fc are given find the switched capacitor equivalent

characteristic is assumed to be as shown in Fig. 17-15b 1 Sketch the characteristic of each of the following circuits shown in Fig. 17-31. the diode characteristic is shown in Fig. 17-3le 2 Sketch the transfer characteristic of each of the following circuits shown in Fig. 17-32 the transfer characteristic being vo/v

1 Find the matrix equation in the circuit of Fig. 16-12 by nodal analysis method. Assume that each branch admittance of the circuit is 1S

1 Find F(s) if f(t) = (a)(t-3);(b)4t u(t-3); (c)4 cos to(t-3). 2 Obtain partial-fraction expansions for each of the following rational functions, and find the corresponding time functions:

1 The physical construction of three pairs of coupled coils is shown in Fig. 10-16. Show two different possible locations for the two dots on each pair of coils. 2 For the circuit illustrated in Fig. 10-17 (a) find I and VB; (b) repeat if a 62 resistor is connected between the terminals at the right

I If f(t)=100 for 04.(a) Calculate v at t=T/4.(b) Find the average power delivered by this waveform to a 5Q2 resistor 3 Let v(t)=3-3 cos(100 t-40)+4 sin(200 T t-10)+2.5 cos 300 tt V Find: (a)the average value Var;(b)the rms value V;(c)the period T; (d)v(18ms)

A cosine voltage is zero and increasing at t=-1 6ms; the next zero crossing occurs at t 4.65ms. (a)Calculate T, f, and @.(b) If v(0)=20V, find v(t).(c)By what angle does v(t) I(t)=5cos(t-110°)A? 2 For the sinusoidal waveform shown in

1 If the voltage across a 5F capacitor is 2te -V, find the current and the power 2 In 5s, the voltage across a 40mF capacitor changes from 160v to 220V. Calculating the average current through the capacitor