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Daniel Niu


Last seen: 11 months ago |  Active since 2022

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why the two split-step fourier methods using fft and ifft is equivalent ?
clear close all N = 512; % Number of Fourier modes dt = .005; % Size of time step tfinal = 2; % Final time M = round(tfinal...

11 months ago | 1 answer | 0

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Question


when do I need use fftshift?
Bx = 10; A = sqrt(log(2))/(2*pi*Bx); fs = 500; %sampling frequency dt = 1/fs; %time step T=1; %total time window t = -...

11 months ago | 1 answer | 0

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Question


how to get the correct plot of function sin(N+1)*pi*x^2/sin(pi*x)^2 with different N
% Define the value of N format long N = 1000; % Define a range of x values %x = linspace(-0.01*pi,0.01*pi, 1000); % You ca...

1 year ago | 3 answers | 0

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Question


How to use disp in matlab?
disp('Solutions for f''(x) = 0:'); Dear friend, I have some trouble with disp. why in the above code, the result is Solutions f...

1 year ago | 1 answer | 0

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Question


why the wavefunction is wrong by solving the Schrodinger equation numerically.?
clear % Constants in atomic units V0 = 0.37; a0 = 8; hbar = 1; % Reduced Planck's constant m = 1;...

1 year ago | 0 answers | 0

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why the simulation period is wrong about schrodinger equation in a harmonic potential
clear; % Clear workspace variables N = 1024; x = linspace(-64, 64, N); dx = x(2) - x(1); psi = gaussian_wavepacket(x, -32...

1 year ago | 1 answer | 0

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answer

Question


How do you control the end of streamline?
Dear friends, I am plot electric field line between two circle. I want the electric line end at the outer circle. I can not fi...

1 year ago | 1 answer | 0

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Question


How to plot frequency spectrum of a piecewise function in matlab?
Dear friends, I want to plot the frequency spectrum of this function: f(t)=1/2*(1+cos(pi*t)) when -1<t<1 otherwise,f(t)=0 I ...

2 years ago | 4 answers | 0

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answers

Answered
how to smooth or filter the signal like this?
@Star Strider Dear Strider, I see an answer from you by Email. But I can not see the answer here. Would you mind post your an...

2 years ago | 0

Question


how to smooth or filter the signal like this?
How to smooth the signal like this？ I want to do fourier transform of the data attached. I only need the sharp peak in the dat...

2 years ago | 4 answers | 0

4

answers

Question


how to do sensitivity analysis of three variables using MATLAB
Dear friends, How to do sensitivity analysis for this formula? There are three variables A, B and C. Your help would be highly...

2 years ago | 1 answer | 0

1

answer

Question


how to find the noise frequency in ECG signal?
I perform the fft, but I still don't know which frequency is the noise except 1200 Hz. I also want to flter the noise using FIR ...

2 years ago | 0 answers | 0

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answers

Question


how to plot 3D figure like this?
Dear friends, How to plot 3D figure like this considering square wave =sin(x)+1/3sin(3x)+1/5sin(5x)+... Your help would be hig...

2 years ago | 1 answer | 0

1

answer

Question


how to solve a set of differential equation systems like this?
Dear friend, How to solve a ordinary differential equation systems like above using MATLAB? a=b=c=1 Your help would b...

2 years ago | 2 answers | 0

2

answers

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how to solve ODE with variable coefficients?
Dear friend, How to solve ODE with variable coefficients like this? where the speed s_r and s_f depend on the distance they ...

2 years ago | 1 answer | 0

1

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Question


how filter the noise frequency of an audio file with notch filter
Dear friend, I want to filter the 464 Hz noise in an audio file. but using the filtfilt functio I get the NaN. what is my pro...

2 years ago | 1 answer | 0

1

answer

Question


Maximize Linear Programming using linprog Problem is unbounded?
Dear friends, what is my mistake about the problem? Your help would be highly appreciated! clc,clear; objectiveFunction = ...

2 years ago | 2 answers | 0

2

answers

Question


how to interpolate outside the domain of x?
Dear friends, I am doing some interpolation about GDP increase rate,please see the attached excel file. The result seems beyond...

2 years ago | 2 answers | 0

2

answers

Question


how to do coordinate transformation around a fixed axis using robotics toolbox or spatial math toolbox?
Dear friends, If the initial frame {s} rotate around a screw axis S which is defined by rotaion unit axis omega=(0.7,0.0,0.7) ,...

2 years ago | 1 answer | 0

1

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how to do half-wave rectification for an array?
Dear friends, how to do half-wave rectification for an array? that is, how to replace all the negative value of an array with z...

2 years ago | 1 answer | 0

1

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Question


how to generate random number in a rectangle like this?
the inscribed rectangle has length 4 and width 2. The shadow part can appear randomly. How to achieve that using MATLAB? Your...

2 years ago | 1 answer | 0

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Question


how to find the smallest taxicab number or Ramanujan number like 1729 larger than N?
I write a .m file to find the a b c d of a taxicab number. The program run well when the num=1729 or some other taxicab number. ...

2 years ago | 1 answer | 0

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Question


how to check whether a vector in a subspace or not?
I want to know how to check a vector in b can be expressed by the basis of a subspace. Or whether the vector in b in the subspac...

2 years ago | 1 answer | 0

1

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Question


how to plot a periodic function fro negative to positive?
Dear friend, How to plot a periodic function for example 2*x from negative to positive? I know a method to plot periodic funct...

2 years ago | 2 answers | 0

2

answers

Question


How to multiply two cell array
Dear friend, How to achieve the goal of multiply two cell array using MATLAB like this? A={1,2,3},B={'a','b','c'} to achieve ...

2 years ago | 1 answer | 0

1

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Question


how to plot the exponential fourier series in matlab?
I expand a periodic function exp(-t) with T=3. then sum the series to compare with the original function. However, I think the ...

2 years ago | 1 answer | 0

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Question


what is the problem of my code doing inverse Poisson cumulative distribution?
Dear friends, I write a code doing inverse Poisson cumulative distribution. However, the code get same results compared to icdf...

2 years ago | 1 answer | 0

1

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Question


what is my problem using split operator methods on gaussian wave packet time evolution in free space
dt = 0.005; % Size of time step tfinal = 2; % Final time M = round(tfinal/dt); % Total number of time steps N = 512; % Numb...

2 years ago | 1 answer | 0

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