differential-equations

来源： https://stackoverflow.com/questions/63629161/time-dependent-schrodinger-equation-on-3d-lattice-in-julia

来源： https://stackoverflow.com/questions/41725646/python-user-input-equation

来源： https://stackoverflow.com/questions/41725646/python-user-input-equation

来源： https://stackoverflow.com/questions/41725646/python-user-input-equation

问题 I wrote the code to solve Lorenz equations using RK-4 method in C++. I have to plot the attractor plot and I have some difficulty in solving the 3 first order coupled differential equation using RK-4 method. Here is my code: /* Solving 3 coupled first order differential equations using RK4 for the Lorentz system dxdt = sig*(y - x) {f} dydt = x*(rho - z) - y {g} dzdt = x*y - bet*z {k} */ #include<iostream> #include<cmath> #include<fstream> #include <iomanip> using namespace std; double sig =

问题 I wrote the code to solve Lorenz equations using RK-4 method in C++. I have to plot the attractor plot and I have some difficulty in solving the 3 first order coupled differential equation using RK-4 method. Here is my code: /* Solving 3 coupled first order differential equations using RK4 for the Lorentz system dxdt = sig*(y - x) {f} dydt = x*(rho - z) - y {g} dzdt = x*y - bet*z {k} */ #include<iostream> #include<cmath> #include<fstream> #include <iomanip> using namespace std; double sig =

问题 I am currently trying to get a two body problem to work, that I can then upgrade to more planets, but it is not working. It is outputting me impossible positions. Does anyone know what is causing that? This is the code I use: day = 60*60*24 # Constants G = 6.67408e-11 dt = 0.1*day au = 1.496e11 t = 0 class CelBody: def __init__(self, id, name, x0, y0, z0, vx0, vy0, vz0, mass, vector, ax0, ay0, az0, totalforcex, totalforcey, totalforcez): self.ax0 = ax0 self.ay0 = ay0 self.az0 = az0 self.ax =

问题 #including the differential equations and parameters def model(x,dydx,p): s=p[0] #first parameter a=p[1] #second parameter dydx[0] = -2*(s+a)*y[0]+2*s*y[1]+s/2*y[2] dydx[1] = +2*(s+a)*y[1]-2*s*y[0]-s/2*y[2] dydx[2] = -(s+a)*y[2] return np.vstack(dydx[0],dydx[1],dydx[2]) # boundary conditions def bc(ya, yb,yc, p): s=p[0] a=p[1] I0=1 return np.array(([ya[0], yb[0],yc[0],a,s])) #x values x = np.array([1, 2, 3, 4, 5, 6, 7, 8, 9]) y = np.zeros((3, x.size)) #p= np.zeros((3, d.size)) #y initial

问题 Hi i've been asked to solve SIR model using fsolve command in MATLAB, and Euler 3 point backward. I'm really confused on how to proceed, please help. This is what i have so far. I created a function for 3BDF scheme but i'm not sure how to proceed with fsolve and solve the system of nonlinear ODEs. The SIR model is shown as and 3BDF scheme is formulated as clc clear all gamma=1/7; beta=1/3; ode1= @(R,S,I) -(beta*I*S)/(S+I+R); ode2= @(R,S,I) (beta*I*S)/(S+I+R)-I*gamma; ode3= @(I) gamma*I; f(t,

问题 I would like to adapt an initial-value-problem (IVP) to a boundary-value-problem (BVP) using scipy.integrate.solve_bvp . A similar question was asked here, but I do not follow everything explained in the answer. The example below regarding the SIR model was taken from this website. Here, the initial condition y0 is taken to be the initial value of S , I , and R at time x0[0] . This system of ODEs is given by the function SIR below, which returns [dS/dt, dI/dt, dR/dt] over the interval from x