syms y(x) R1 = 1.2e-3; R2 = 9.2e-3; Cin = 1.1e6; Cwall = 1.86e8; PN = 8; qout = 0; eqn = diff(y,x,2)+(1/R1/Cin+1/Cwall/Cin+1/R2/Cwall)*diff(y,x,1)+1/R1/R2/Cin/Cwall*y==(R1+R2)/R2/Cwall*x+qout/Cwall/R2; a=diff(y); cond = [y(0)==0, subs(a,x,0)==0]; ySol(x) = dsolve(eqn, cond);排版一下

syms y(x)
R1 = 1.2e-3;
R2 = 9.2e-3;
Cin = 1.1e6;
Cwall = 1.86e8;
PN = 8;
qout = 0;
eqn = diff(y,x,2)+(1/R1/Cin+1/Cwall/Cin+1/R2/Cwall)*diff(y,x,1)+1/R1/R2/Cin/Cwall*y==(R1+R2)/R2/Cwall*x+qout/Cwall/R2;
a = diff(y);
cond = [y(0)==0, subs(a,x,0)==0];
ySol(x) = dsolve(eqn, cond);

相关问题

给出matlab程序，其中R1 = 1.2e-3; R2 = 9.2e-3; Cin = 1.1e6/60; Cwall = 1.86e8/60; PN = 8000; qin = 20; qout = 0; u1 = diff(u); v1 = diff(v);

根据题目给出的参数和变量，可以编写如下的Matlab程序：

% 定义常数
R1 = 1.2e-3;
R2 = 9.2e-3;
Cin = 1.1e6/60;
Cwall = 1.86e8/60;
PN = 8000;
qin = 20;
qout = 0;

% 定义常微分方程
syms u v
eq1 = Cin*u == PN - (u - v)/R1;
eq2 = Cwall*v == (u - v)/R1 - (v - qout)/R2;

% 求解稳态解
u_steadystate = solve(eq1, u);
v_steadystate = solve(eq2, v);

% 输出稳态解
fprintf('u_steadystate = %f\n', double(u_steadystate));
fprintf('v_steadystate = %f\n', double(v_steadystate));

% 求解u和v对时间的导数
u1 = diff(u);
v1 = diff(v);

% 定义时间t和初值条件
tspan = [0 100];
y0 = [u_steadystate, v_steadystate];

% 定义ODE函数
odefun = @(t, y) [Cin*(PN - (y(1) - y(2))/R1) - qin; ...
                  Cwall*((y(1) - y(2))/R1 - (y(2) - qout)/R2)];

% 求解ODE方程
[t, y] = ode45(odefun, tspan, y0);

% 绘制u和v随时间变化的图像
figure;
plot(t, y(:, 1), 'r-', t, y(:, 2), 'b--', 'LineWidth', 2);
xlabel('Time (s)');
ylabel('Value');
legend('u', 'v');
title('u and v vs. Time');

该程序首先求解常微分方程的稳态解，然后定义ODE函数，使用ode45函数求解ODE方程，最后绘制u和v随时间变化的图像。

有没有问题：syms y(x) R1=1.2e-3; R2=9.2e-3; Cin=1.1e6; Cwall=1.86e8; PN=8; qout=0; eqn = diff(y,x,2)+(1/R1/Cin+1/Cwall/Cin+1/R2/Cwall)*diff(y,x,1)+1/R1/R2/Cin/Cwall*y==(R1+R2)/R2/Cwall*x+qout/Cwall/R2; ySol(x) =dsolve(eqn,'y(0)=0,Dy(0)=0','x');

这个代码是存在问题的。

首先，在微分方程中缺少一个初始条件，无法确定特定的解。因此，需要添加一个初始条件来求解特定的解。

其次，y(0)和Dy(0)是已知条件，应该使用这两个条件来定义初始条件，而不是将其作为字符串传递给dsolve函数。

最后，dsolve函数的第二个参数应该是一个向量，包含所有的初始条件，而不是单独传递初始条件。

综上所述，修正后的代码如下：

syms y(x)
R1 = 1.2e-3;  
R2 = 9.2e-3;  
Cin = 1.1e6;  
Cwall = 1.86e8;  
PN = 8;  
qout = 0;  
eqn = diff(y,x,2)+(1/R1/Cin+1/Cwall/Cin+1/R2/Cwall)*diff(y,x,1)+1/R1/R2/Cin/Cwall*y==(R1+R2)/R2/Cwall*x+qout/Cwall/R2; 
cond = [y(0)==0, diff(y)(0)==0]; % 定义初始条件向量
ySol(x) = dsolve(eqn, cond); % 求解微分方程及初始条件

这里将y(0)和Dy(0)定义为初始条件向量cond，并将其传递给dsolve函数。注意，diff(y)(0)应该修改为diff(y)(0)==0，因为Dy(0)=0是初始条件之一。