数学建模社区-数学中国

标题: [求助]高手帮我解决一下这个问题? [打印本页]

作者: hongwei1983 时间: 2007-12-30 11:46
标题: [求助]高手帮我解决一下这个问题?

s0=pi*(12.85/2)^2;
s1=s0;
s2=pi*(54.2/2)^2;
s3=316;
s4=s2;
s5=pi*(11.1/2)^2;
u1=10;
u2=s1*u1/s2;
u3=s2*u2/s3;
u4=s3*u3/s4;
u5=s4*u4/s5;
l1=32;
l3=20.5;
l6=13.5;
l7=187;
l8=l7;
c=340;
M1=u1/c;
m1=s1/s0;
M2=u1/c;
m2=s2/s0;
a2=s2/s1;
M3=u2/c;
m3=s2/s0;
M4=u3/c;
m4=s3/s0;
a4=s3/s2;
M5=u3/c;
m5=s3/s0;
a5=s4/s3;
M6=u4/c;
m6=s4/s0;
M7=u5/c;
m7=s5/s0;
a7=m7/m6;
m77=m6-m7;
M8=u5/c;
m8=s5/s0;
m=s5/s0;
for f=50:5:60
k=2*pi*f/c;
T1=[cos((k*l1)/(1-M1^2)) j*sin((k*l1)/(1-M1^2))/m1;j*m1*sin((k*l1)/(1-M1^2)) cos((k*l1)/(1-M1^2))]
T2=[1 -2*M2*(1-1/a2)/(m2*a2);0 1]
T3=[cos((k*l3)/(1-M3^2)) j*sin((k*l3)/(1-M3^2))/m3;j*m3*sin((k*l3)/(1-M3^2)) cos((k*l3)/(1-M3^2))]
T4=[1 (1-a4^2)*M4/m4;0 1]
T5=[1 -2*M5*(1-1/a5)/(m5*a5);0 1]
T6=[cos((k*l6)/(1-M6^2)) j*sin((k*l6)/(1-M6^2))/m6;j*m6*sin((k*l6)/(1-M6^2)) cos((k*l6)/(1-M6^2))]
T7=[1-j*m77*(a7^2)*M7*tan(k*l7)/m7 (1-a7^2)*M7/m7;j*m77*tan(k*l7) 1+j*m77*M7*tan(k*l7)/m7]
T8=[cos((k*l8)/(1-M8^2)) j*sin((k*l8)/(1-M8^2))/m8;j*m8*sin((k*l8)/(1-M8^2)) cos((k*l8)/(1-M8^2))]
T=T1*T2*T3*T4*T5*T6*T7*T8
A=T(1,1)
B=T(1,2)
C=T(2,1)
D=T(2,2)
L=10*log10((abs(A+m*B+C+m*D)).^2/(4*m^2))
end

我想出(f,L)的图形显示该怎么做?

作者: liwenhui 时间: 2008-3-2 10:00

如果第40行的for语句的步长是5的话（就是你的程序里这句：for f=50:5:60），那么画出的结果是一段折线。我觉得这样的折线没有意义，你自己可以看看，修改后的程序如下：

s0=pi*(12.85/2)^2;
s1=s0;
s2=pi*(54.2/2)^2;
s3=316;
s4=s2;
s5=pi*(11.1/2)^2;
u1=10;
u2=s1*u1/s2;
u3=s2*u2/s3;
u4=s3*u3/s4;
u5=s4*u4/s5;
l1=32;
l3=20.5;
l6=13.5;
l7=187;
l8=l7;
c=340;
M1=u1/c;
m1=s1/s0;
M2=u1/c;
m2=s2/s0;
a2=s2/s1;
M3=u2/c;
m3=s2/s0;
M4=u3/c;
m4=s3/s0;
a4=s3/s2;
M5=u3/c;
m5=s3/s0;
a5=s4/s3;
M6=u4/c;
m6=s4/s0;
M7=u5/c;
m7=s5/s0;
a7=m7/m6;
m77=m6-m7;
M8=u5/c;
m8=s5/s0;
m=s5/s0;
kj=[];
kz1=1;
for f=50:5:60
k=2*pi*f/c;
T1=[cos((k*l1)/(1-M1^2)) j*sin((k*l1)/(1-M1^2))/m1;j*m1*sin((k*l1)/(1-M1^2)) cos((k*l1)/(1-M1^2))];
T2=[1 -2*M2*(1-1/a2)/(m2*a2);0 1];
T3=[cos((k*l3)/(1-M3^2)) j*sin((k*l3)/(1-M3^2))/m3;j*m3*sin((k*l3)/(1-M3^2)) cos((k*l3)/(1-M3^2))];
T4=[1 (1-a4^2)*M4/m4;0 1];
T5=[1 -2*M5*(1-1/a5)/(m5*a5);0 1];
T6=[cos((k*l6)/(1-M6^2)) j*sin((k*l6)/(1-M6^2))/m6;j*m6*sin((k*l6)/(1-M6^2)) cos((k*l6)/(1-M6^2))];
T7=[1-j*m77*(a7^2)*M7*tan(k*l7)/m7 (1-a7^2)*M7/m7;j*m77*tan(k*l7) 1+j*m77*M7*tan(k*l7)/m7];
T8=[cos((k*l8)/(1-M8^2)) j*sin((k*l8)/(1-M8^2))/m8;j*m8*sin((k*l8)/(1-M8^2)) cos((k*l8)/(1-M8^2))];
T=T1*T2*T3*T4*T5*T6*T7*T8;
A=T(1,1);
B=T(1,2);
C=T(2,1);
D=T(2,2);
L=10*log10((abs(A+m*B+C+m*D)).^2/(4*m^2));
kj(1,kz1)=L;
kz1=kz1+1;
end
f2=50:5:60;
cc=kj;
plot(f2,cc)