2楼: Originally posted by dingd at 2015-07-22 11:13:35
用数值解试试：fsolve

4楼: Originally posted by dingd at 2015-07-22 12:56:03
左右括号都不匹配吧，看Matlab的fsolve帮助

clear all;clc
format long

x0=10;

Sk=69,Ac=35.19,Nc=1.3,qb=2.15e5,Ag=15350,qf=2.13e5,l3=30,As=825,Ns=1.3,a=1.38e-3,b=2.0e-5,T=540,t=4000,qbt=1.75e5,
Dm=349,p=2.1,n2=1.78,l0=450,abt=1.405e-5,OT=510,A11=-5.345e-9,Ab=16054,n1=1.608,m2=1.02,A2=5.83e-9,qft=1.71e5,Di=300,l1=60,
l2=40,aft=1.455e-5,tf=68,Dk=1.679,qpt=1.0e5;

[x fval]=fsolve(@(Sg)     (Sk/Ac)^(1/Nc)+qb*Ag*Sk+2*qf*Ag*Sk*l3-((Sg/As)^(1/Ns)+Dk*(a+b*T)*log(t)+qbt*(Ag*Sg+pi*Dm^2*p/4)+(A11*Ab^(-n1)*(Ag*Sg+pi*Dm^2*p/4)^n1*t^m2+A2*Ab^(-n2)*(Ag*Sg+pi*Dm^2*p/4)^n2*t)*l0+abt*OT*l0+2*qft*(pi*Di^2*p*l1/4+pi*(Dm^2-Di^2)*p*l2/4+Ag*Sg*l3)+2*qpt*p-2*aft*tf*OT),x0);
x=x
fval=fval

6楼: Originally posted by 月只蓝 at 2015-07-23 12:45:56
clear all;clc
format long

x0=10;

Sk=69,Ac=35.19,Nc=1.3,qb=2.15e5,Ag=15350,qf=2.13e5,l3=30,As=825,Ns=1.3,a=1.38e-3,b=2.0e-5,T=540,t=4000,qbt=1.75e5,
Dm=349,p=2.1,n2=1.78,l0=450,abt=1.405e- ...

6楼: Originally posted by 月只蓝 at 2015-07-23 12:45:56
clear all;clc
format long

x0=10;

Sk=69,Ac=35.19,Nc=1.3,qb=2.15e5,Ag=15350,qf=2.13e5,l3=30,As=825,Ns=1.3,a=1.38e-3,b=2.0e-5,T=540,t=4000,qbt=1.75e5,
Dm=349,p=2.1,n2=1.78,l0=450,abt=1.405e- ...