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小指甲123

新虫 (小有名气)

[求助] 求解方程组 已有3人参与

本人想求解一个八元方程组,MATLAB还不太会用,写的程序如下,可是求出的结果看不懂,求好心人指教啊,新手无金币,还请包涵
g12=9271.1;g21=495.9;T=303.15;R=8.314;
syms x11 x21 x12 x22 r11 r21 r12 r22
alfa=0.2;
R=8.314;
tao12=g12./R./T;
tao21=g21./R./T;
G12=exp(-alfa*tao12);
G21=exp(-alfa*tao12);
>> [x11 x21 x12 x22 r11 r21 r12 r22]=solve(r11-exp(x22.^2.*(tao12.*(G12./(x12+x22.*G12)).^2+tao21.*G21./(x22+x12.*G21).^2)),r12-exp(x22.^2.*(tao12.*(G12./(x12+x22.*G12)).^2+tao21.*G21./(x22+x12.*G21).^2)),r21-exp(x11.^2.*(tao21.*(G21./(x21+x11.*G21)).^2+tao12.*G12./(x11+x21.*G12).^2)),r22-exp(x12.^2.*(tao12.*(G12./(x22+x12.*G12)).^2+tao21.*G21./(x12+x22.*G21).^2)),r11*x11-r12*x12,r21*x21-r22*x22,x11+x21-1,x12+x22-1)
八个方程已检查N遍,应该是没有问题的,跪求指导,好捉急
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小指甲123

新虫 (小有名气)

不好意思不好意思G21=exp(-alfa*tao21);我输错了,但是我改正后,并去除点计算,依旧得不到结果 请指教
2楼2014-10-10 16:30:14
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dingd

铁杆木虫 (职业作家)

【答案】应助回帖

★ ★ ★
感谢参与,应助指数 +1
小指甲123: 金币+3 2014-10-13 19:55:19
不一定有解析解(solve),可以试试数值解(fsolve)
3楼2014-10-10 17:10:48
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zhchh008

金虫 (正式写手)

【答案】应助回帖

感谢参与,应助指数 +1
g12=9271.1;g21=495.9;T=303.15;R=8.314;
syms x11 x21 x12 x22 r11 r21 r12 r22
alfa=0.2;
R=8.314;
tao12=g12./R./T;
tao21=g21./R./T;
G12=exp(-alfa*tao12);
G21=exp(-alfa*tao12);
[x11 x21 x12 x22 r11 r21 r12 r22]=solve(r11-exp(x22.^2.*(tao12.*(G12./(x12+x22.*G12)).^2+tao21.*G21./(x22+x12.*G21).^2)),r12-exp(x22.^2.*(tao12.*(G12./(x12+x22.*G12)).^2+tao21.*G21./(x22+x12.*G21).^2)),r21-exp(x11.^2.*(tao21.*(G21./(x21+x11.*G21)).^2+tao12.*G12./(x11+x21.*G12).^2)),r22-exp(x12.^2.*(tao12.*(G12./(x22+x12.*G12)).^2+tao21.*G21./(x12+x22.*G21).^2)),r11*x11-r12*x12,r21*x21-r22*x22,x11+x21-1,x12+x22-1);
A=[x11 x21 x12 x22 r11 r21 r12 r22];

A =

[ 1.0, 1.0, 7.0948863464639782514303197424122, 43.498233938038027684388468928734, 1.0, 1.0, 0, 0]
4楼2014-10-10 17:15:42
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kabaisun

专家顾问 (正式写手)

【答案】应助回帖

★ ★ ★
感谢参与,应助指数 +1
小指甲123: 金币+3 2014-10-13 19:56:55
调整了你的代码如下,
g12=92711;g21=4959;T=30315;R=8314;
syms x11 x21 x12 x22 r11 r21 r12 r22;
alfa=02;
R=8314;
tao12=g12/R/T;
tao21=g21/R/T;
G12=exp(-alfa*tao12);
G21=exp(-alfa*tao12);


[x11,x21,x12,x22,r11,r21,r12,r22]=solve(r11-exp(x22^2*(tao12*(G12/(x12+x22*G12))^2+...
    tao21*G21/(x22+x12*G21)^2)),r12-exp(x22^2*(tao12*(G12/(x12+x22*G12))^2+tao21*G21/(x22+x12*G21)^2)),r21-exp(x11^2*(tao21*(G21/...
    (x21+x11*G21))^2+tao12*G12/(x11+x21*G12)^2)),r22-exp(x12^2*(tao12*(G12/(x22+x12*G12))^2+...
    tao21*G21/(x12+x22*G21)^2)),r11*x11-r12*x12,r21*x21-r22*x22,x11+x21-1,x12+x22-1,x11,x21,x12,x22,r11,r21,r12,r22)

得到答案:
x11 =

1.0


x21 =

0


x12 =

1.0


x22 =

0


r11 =

1.0


r21 =

1.0003873240019056602666268435283


r12 =

1.0


r22 =

1.0003875801502729735528926509988
严实诚勇
5楼2014-10-10 17:26:54
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zhchh008

金虫 (正式写手)

【答案】应助回帖

clear;
clc;
x0=[9.42432037654593e-05,0.999905767707224,9.42937118586778e-05,0.999905766727689,47.7567973044437,0.999999997930520,47.7567972904117,0.999999979060034];
options = optimoptions('fsolve','Display','iter','MaxFunEvals',50000,'TolX',1e-20);
[x,fval,exitflag,output,jacobian]=fsolve(@myfun,x0,options);

function F=myfun(x)
g12=9271.1;g21=495.9;T=303.15;R=8.314;
alfa=0.2;
R=8.314;
tao12=g12./R./T;
tao21=g21./R./T;
G12=exp(-alfa*tao12);
G21=exp(-alfa*tao21);
F=[x(5)-exp(x(4).^2.*(tao12.*(G12./(x(3)+x(4).*G12)).^2+tao21.*G21./(x(4)+x(3).*G21).^2));
    x(7)-exp(x(4).^2.*(tao12.*(G12./(x(3)+x(4).*G12)).^2+tao21.*G21./(x(4)+x(3).*G21).^2));
    x(6)-exp(x(1).^2.*(tao21.*(G21./(x(2)+x(1).*G21)).^2+tao12.*G12./(x(1)+x(2).*G12).^2));
    x(8)-exp(x(3).^2.*(tao12.*(G12./(x(4)+x(3).*G12)).^2+tao21.*G21./(x(3)+x(4).*G21).^2));
    x(5)*x(1)-x(7)*x(3);
    x(6)*x(2)-x(8)*x(4);
    x(1)+x(2)-1;
    x(3)+x(4)-1];
X=3.66844792052684e-06        0.999996331559379        3.66855860668108e-06        0.999996331558969        47.8248544308314        0.999999999999023        47.8248544308243        0.999999999989381
6楼2014-10-10 18:01:52
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zhchh008

金虫 (正式写手)

引用回帖:
6楼: Originally posted by zhchh008 at 2014-10-10 18:01:52
clear;
clc;
x0=;
options = optimoptions('fsolve','Display','iter','MaxFunEvals',50000,'TolX',1e-20);
=fsolve(@myfun,x0,options);

function F=myfun(x)
g12=9271.1;g21=495.9;T=303.15;R=8.314;
al ...

Equation solved, inaccuracy possible.

The vector of function values is near zero, as measured by the default value
of the function tolerance. However, the last step was ineffective.
7楼2014-10-10 18:02:36
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zhchh008

金虫 (正式写手)

【答案】应助回帖

引用回帖:
4楼: Originally posted by zhchh008 at 2014-10-10 17:15:42
g12=9271.1;g21=495.9;T=303.15;R=8.314;
syms x11 x21 x12 x22 r11 r21 r12 r22
alfa=0.2;
R=8.314;
tao12=g12./R./T;
tao21=g21./R./T;
G12=exp(-alfa*tao12);
G21=exp(-alfa*tao12);
=solve(r11-exp(x22 ...

g12=9271.1;g21=495.9;T=303.15;R=8.314;
syms x11 x21 x12 x22 r11 r21 r12 r22
alfa=0.2;
R=8.314;
tao12=g12./R./T;
tao21=g21./R./T;
G12=exp(-alfa*tao12);
G21=exp(-alfa*tao21);
[x11 x21 x12 x22 r11 r21 r12 r22]=solve(r11-exp(x22.^2.*(tao12.*(G12./(x12+x22.*G12)).^2+tao21.*G21./(x22+x12.*G21).^2)),r12-exp(x22.^2.*(tao12.*(G12./(x12+x22.*G12)).^2+tao21.*G21./(x22+x12.*G21).^2)),r21-exp(x11.^2.*(tao21.*(G21./(x21+x11.*G21)).^2+tao12.*G12./(x11+x21.*G12).^2)),r22-exp(x12.^2.*(tao12.*(G12./(x22+x12.*G12)).^2+tao21.*G21./(x12+x22.*G21).^2)),r11*x11-r12*x12,r21*x21-r22*x22,x11+x21-1,x12+x22-1);
A=[x11 x21 x12 x22 r11 r21 r12 r22];
vpa(A,4)

[ 1.0, 1.0, 7.0949, 47.828, 1.0, 1.0, 0, 0]
8楼2014-10-10 18:11:21
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dingd

铁杆木虫 (职业作家)

【答案】应助回帖

★ ★ ★
小指甲123: 金币+3, ★有帮助 2014-10-13 19:57:18
似乎多解:

1:
r11: 1.0792834745087
x22: 0.241692882646934
x12: 0.758307117353066
r12: 1.0792834745087
r21: 4.21004443723871
x11: 0.758307117353066
x21: 0.241692882646934
r22: 4.21004443723871

2:
r11: 47.8276117781295
x22: 0.999999999706249
x12: 2.93751265462444E-10
r12: 47.8276117781295
r21: 1
x11: 2.93751265481594E-10
x21: 0.999999999706249
r22: 1

3:
r11: 0.999999999999093
x22: -7.89502076435928E-13
x12: 1.0000000000017
r12: 1.00000000000091
r21: 7.09488634654321
x11: 1.00000000000442
x21: -5.32197232964814E-12
r22: 47.8276119995367
9楼2014-10-10 21:16:31
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