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lewis
Last activity 2024-7-27

"Satellite Communication simulation(main title)" Undergraduate projects, Do you have any good Ideas?

I have picked the title but don't know which direction to take it. Looking for any and all inspiration. I took the project as it sounded interesting when reading into it, but I'm a satellite novice, and my degree is in electronics.

Off Topic

Muhammad
Last activity 2024-8-26

What do you like most about MATLAB?

"What are your favorite features or functionalities in MATLAB, and how have they positively impacted your projects or research? Any tips or tricks to share?

DH
Last activity 2024-9-23，6:07

Can someone tell me what's wrong with this code? This is a problem from Cody. For example, when n=3, the output should be the matrix [1 2 2 3 3 3]

function ans = your_fcn_name(n)
n;
j=sum(1:n);
a=zeros(1,j);
 for i=1:n
   a(1,((sum(1:(i-1))+1)):(sum(1:(i-1))+i))=i.*ones(1,i);     
 end
 disp

Athanasios Paraskevopoulos
Last activity 2024-7-23

Gabriel's Horn

Gabriel's horn is a shape with the paradoxical property that it has infinite surface area, but a finite volume.

Gabriel’s horn is formed by taking the graph of

with the domain

and rotating it in three dimensions about the

axis.

There is a standard formula for calculating the volume of this shape, for a general function

.Wwe will just state that the volume of the

solid between a and b is:

The surface area of the solid is given by:

One other thing we need to consider is that we are trying to find the value of these integrals between 1 and ∞. An integral with a limit of infinity is called an improper integral and we can't evaluate it simply by plugging the value infinity into the normal equation for a definite integral. Instead, we must first calculate the definite integral up to some finite limit b and then calculate the limit of the result as b tends to ∞:

Volume

We can calculate the horn's volume using the volume integral above, so

The total volume of this infinitely long trumpet isπ.

Surface Area

To determine the surface area, we first need the function’s derivative:

Now plug it into the surface area formula and we have:

This is an improper integral and it's hard to evaluate, but since in our interval

So, we have :

Now,we evaluate this last integral

So the surface are is infinite.

% Define the function for Gabriel's Horn

gabriels_horn = @(x) 1 ./ x;

% Create a range of x values

x = linspace(1, 40, 4000); % Increase the number of points for better accuracy

y = gabriels_horn(x);

% Create the meshgrid

theta = linspace(0, 2 * pi, 6000); % Increase theta points for a smoother surface

[X, T] = meshgrid(x, theta);

Y = gabriels_horn(X) .* cos(T);

Z = gabriels_horn(X) .* sin(T);

% Plot the surface of Gabriel's Horn

figure('Position', [200, 100, 1200, 900]);

surf(X, Y, Z, 'EdgeColor', 'none', 'FaceAlpha', 0.9);

hold on;

% Plot the central axis

plot3(x, zeros(size(x)), zeros(size(x)), 'r', 'LineWidth', 2);

% Set labels

xlabel('x');

ylabel('y');

zlabel('z');

% Adjust colormap and axis properties

colormap('gray');

shading interp; % Smooth shading

% Adjust the view

view(3);

axis tight;

grid on;

% Add formulas as text annotations

dim1 = [0.4 0.7 0.3 0.2];

annotation('textbox',dim1,'String',{'$$V = \pi \int_{1}^{a} \left( \frac{1}{x} \right)^2 dx = \pi \left( 1 - \frac{1}{a} \right)$$', ...

'', ... % Add an empty line for larger gap

'$$\lim_{a \to \infty} V = \lim_{a \to \infty} \pi \left( 1 - \frac{1}{a} \right) = \pi$$'}, ...

'Interpreter','latex','FontSize',12, 'EdgeColor','none', 'FitBoxToText', 'on');

dim2 = [0.4 0.5 0.3 0.2];

annotation('textbox',dim2,'String',{'$$A = 2\pi \int_{1}^{a} \frac{1}{x} \sqrt{1 + \left( -\frac{1}{x^2} \right)^2} dx > 2\pi \int_{1}^{a} \frac{dx}{x} = 2\pi \ln(a)$$', ...

'', ... % Add an empty line for larger gap

'$$\lim_{a \to \infty} A \geq \lim_{a \to \infty} 2\pi \ln(a) = \infty$$'}, ...

'Interpreter','latex','FontSize',12, 'EdgeColor','none', 'FitBoxToText', 'on');

% Add Gabriel's Horn label

dim3 = [0.3 0.9 0.3 0.1];

annotation('textbox',dim3,'String','Gabriel''s Horn', ...

'Interpreter','latex','FontSize',14, 'EdgeColor','none', 'HorizontalAlignment', 'center');

hold off

daspect([3.5 1 1]) % daspect([x y z])

view(-27, 15)

lightangle(-50,0)

lighting('gouraud')

The properties of this figure were first studied by Italian physicist and mathematician Evangelista Torricelli in the 17th century.

Acknowledgment

I would like to express my sincere gratitude to all those who have supported and inspired me throughout this project.

First and foremost, I would like to thank the mathematician and my esteemed colleague, Stavros Tsalapatis, for inspiring me with the fascinating subject of Gabriel's Horn.

I am also deeply thankful to Mr. @Star Strider for his invaluable assistance in completing the final code.

References:

https://www.youtube.com/watch?v=z_-jSmfqlHY&t=14s

binbin
Last activity 2024-7-23

The moment the PMOS switch is turned on, the inrush current is too large and the PMOS burns out…

When it comes to MOS tube burnout, it is usually because it is not working in the SOA workspace, and there is also a case where the MOS tube is overcurrent.

For example, the maximum allowable current of the PMOS transistor in this circuit is 50A, and the maximum current reaches 80+ at the moment when the MOS transistor is turned on, then the current is very large.

At this time, the PMOS is over-specified, and we can see on the SOA curve that it is not working in the SOA range, which will cause the PMOS to be damaged.

So what if you choose a higher current PMOS? Of course you can, but the cost will be higher.

We can choose to adjust the peripheral resistance or capacitor to make the PMOS turn on more slowly, so that the current can be lowered.

For example, when adjusting R1, R2, and the jumper capacitance between gs, when Cgs is adjusted to 1uF, The Ids are only 40A max, which is fine in terms of current, and meets the 80% derating.

(50 amps * 0.8 = 40 amps).

Next, let’s look at the power, from the SOA curve, the opening time of the MOS tube is about 1ms, and the maximum power at this time is 280W.

The normal thermal resistance of the chip is 50°C/W, and the maximum junction temperature can be 302°F.

Assuming the ambient temperature is 77°F, then the instantaneous power that 1ms can withstand is about 357W.

The actual power of PMOS here is 280W, which does not exceed the limit, which means that it works normally in the SOA area.

Therefore, when the current impact of the MOS transistor is large at the moment of turning, the Cgs capacitance can be adjusted appropriately to make the PMOS Working in the SOA area, you can avoid the problem of MOS corruption.

Marisa
Last activity 2024-8-26

Can't click Roll the Dice!

I am trying to earn my Intro to MATLAB badge in Cody, but I cannot click the Roll the Dice! problem. It simply is not letting me click it, therefore I cannot earn my badge. Does anyone know who I should contact or what to do?

Muhammad
Last activity 2024-7-27

Need help to get started with matlab

Hello everyone, i hope you all are in good health. i need to ask you about the help about where i should start to get indulge in matlab. I am an electrical engineer but having experience of construction field. I am new here. Please do help me. I shall be waiting forward to hear from you. I shall be grateful to you. Need recommendations and suggestions from experienced members. Thank you.

James Blanchard
Last activity 2024-7-2

document on solving ODEs and PDEs

I recently wrote up a document which addresses the solution of ordinary and partial differential equations in Matlab (with some Python examples thrown in for those who are interested). For ODEs, both initial and boundary value problems are addressed. For PDEs, it addresses parabolic and elliptic equations. The emphasis is on finite difference approaches and built-in functions are discussed when available. Theory is kept to a minimum. I also provide a discussion of strategies for checking the results, because I think many students are too quick to trust their solutions. For anyone interested, the document can be found at https://blanchard.neep.wisc.edu/SolvingDifferentialEquationsWithMatlab.pdf

Sylvester
Last activity 2024-6-26

Geometry-Based Stochastic Channel Modeling

Kindly link me to the Channel Modeling Group.

I read and compreheneded a paper on channel modeling "An Adaptive Geometry-Based Stochastic Model for Non-Isotropic MIMO Mobile-to-Mobile Channels" except the graphical results obtained from the MATLAB codes. I have tried to replicate the same graphs but to no avail from my codes. And I am really interested in the topic, i have even written to the authors of the paper but as usual, there is no reply from them. Kindly assist if possible.

wireless channel modeling

Saleem
Last activity 2024-6-27

Where to find coding and algorithms problems with solutions?

Hi, I'm looking for sites where I can find coding & algorithms problems and their solutions. I'm doing this workshop in college and I'll need some problems to go over with the students and explain how Matlab works by solving the problems with them and then reviewing and going over different solution options. Does anyone know a website like that? I've tried looking in the Matlab Cody By Mathworks, but didn't exactly find what I'm looking for. Thanks in advance.

Image Analyst
Last activity 2024-9-30，6:59

Ask Me Anything about image analysis or the Mathworks community

Hello, everyone! I’m Mark Hayworth, but you might know me better in the community as Image Analyst. I've been using MATLAB since 2006 (18 years). My background spans a rich career as a former senior scientist and inventor at The Procter & Gamble Company (HQ in Cincinnati). I hold both master’s & Ph.D. degrees in optical sciences from the College of Optical Sciences at the University of Arizona, specializing in imaging, image processing, and image analysis. I have 40+ years of military, academic, and industrial experience with image analysis programming and algorithm development. I have experience designing custom light booths and other imaging systems. I also work with color and monochrome imaging, video analysis, thermal, ultraviolet, hyperspectral, CT, MRI, radiography, profilometry, microscopy, NIR, and Raman spectroscopy, etc. on a huge variety of subjects.

I'm thrilled to participate in MATLAB Central's Ask Me Anything (AMA) session, a fantastic platform for knowledge sharing and community engagement. Following Adam Danz’s insightful AMA on staff contributors in the Answers forum, I’d like to discuss topics in the area of image analysis and processing. I invite you to ask me anything related to this field, whether you're seeking recommendations on tools, looking for tips and tricks, my background, or career development advice. Additionally, I'm more than willing to share insights from my experiences in the MATLAB Answers community, File Exchange, and my role as a member of the Community Advisory Board. If you have questions related to your specific images or your custom MATLAB code though, I'll invite you to ask those in the Answers forum. It's a more appropriate forum for those kinds of questions, plus you can get the benefit of other experts offering their solutions in addition to me.

For the coming weeks, I'll be here to engage with your questions and help shed light on any topics you're curious about.

105

Proving one function is greater than other? by Fatima Majeed

David
Last activity 2024-6-17

Week of June 17th - Must-See MATLAB Central Posts

Hello, everyone!

Over the past few weeks, our community has been buzzing with activity, showcasing the incredible depth of knowledge, creativity, and innovation that makes this forum such a vibrant place. Today, we're excited to highlight some of the noteworthy contributions that have sparked discussions, offered insights, and shared knowledge across various topics. Let's dive in!

Interesting Questions

Fatima Majeed brings us a thought-provoking mathematical challenge, delving into inequalities and the realms beyond (e^e). If you're up for a mathematical journey, this question is a must-see!

How to split/segment csv file into multiple sections? by lil brain

lil brain tackles a practical problem many of us have faced: efficiently segmenting a CSV file based on specific criteria. This post is not only a query but a learning opportunity for anyone dealing with similar data manipulation challenges.

Popular Discussions

Trick: Easy Digit Manipulation by goc3

Discover a simple yet effective trick for digit manipulation from goc3. This tip is especially handy for those frequenting Cody challenges or anyone interested in enhancing their number handling skills in MATLAB.

Run Code in Discussions Area! by Chen Lin

Chen Lin shares an exciting update about the 'Run Code' feature in the Discussions area, highlighting how our community can now directly execute and share code snippets within discussions. This feature marks a significant enhancement in how we interact and solve problems together.

From the Blogs

A Deep Dive into EEG Analysis for Predicting Neurological Outcomes By Tanya Kuruvilla

Connell D`Souza, alongside Team Swarthbeat, explores the cutting-edge application of EEG analysis in predicting neurological outcomes post-cardiac arrest. This blog post offers an in-depth look into the challenges and methodologies of modern medical data analysis.

Crafting the Robots of Tomorrow: The Power of Robot Simulation with MATLAB and Simulink by YJ Lim

Mihir Acharya discusses the pivotal role of MATLAB and Simulink in the future of robotics simulation. Through an engaging conversation with industry analyst George Chowdhury, this post sheds light on overcoming simulation challenges and the exciting possibilities that lie ahead.

We encourage everyone to explore these contributions further and engage with the authors and the community. Your participation is what fuels this community's continual growth and innovation.

Here's to many more discussions, discoveries, and breakthroughs together!

must-see

https://blogs.mathworks.com/community/2015/02/26/lets-code-make-a-cody-video/

Ned Gulley
Last activity 2024-6-13

Make a video: "How I Solved It"

Twitch built an entire business around letting you watch over someone's shoulder while they play video games. I feel like we should be able to make at least a few videos where we get to watch over someone's shoulder while they solve Cody problems. I would pay good money for a front-row seat to watch some of my favorite solvers at work. Like, I want to know, did Alfonso Nieto-Castonon just sit down and bang out some of those answers, or did he have to think about it for a while? What was he thinking about while he solved it? What resources was he drawing on? There's nothing like watching a master craftsman at work.

I can imagine a whole category of Cody videos called "How I Solved It". I tried making one of these myself a while back, but as far as I could tell, nobody else made one.

Here's the direct link to the video: https://www.youtube.com/watch?v=hoSmO1XklAQ

I hereby challenge you to make a "How I Solved It" video and post it here. If you make one, I'll make another one.

Chen Lin
Last activity 2024-6-14

Run Code in Discussions Area!

We're thrilled to share an exciting update with our community: the 'Run Code' feature is now available in the Discussions area!

Simply insert your code into the editor and press the green triangle button to run it. Your code will execute using the latest MATLAB R24a version, and it supports most common toolboxes. Moreover, this innovative feature allows for the running of attached files, further enhancing its utility and flexibility.

The ‘run code’ feature was first introduced in MATLAB Answers. Encouraged by the positive feedback and at the request of our community members, we are now expanding the availability of this feature to more areas within our community.

As always, your feedback is crucial to us, so please don't hesitate to share your thoughts and experiences by leaving a comment.

Ned Gulley
Last activity 2024-6-25

What's your opinion of the Ans Hack?

The Ans Hack is a dubious way to shave a few points off your solution score. Instead of a standard answer like this

function y = times_two(x)
  y = 2*x;
end

you would do this

function ans = times_two(x)
  2*x;
end

The ans variable is automatically created when there is no left-hand side to an evaluated expression. But it makes for an ugly function. I don't think anyone actually defends it as a good practice. The question I would ask is: is it so offensive that it should be specifically disallowed by the rules? Or is it just one of many little hacks that you see in Cody, inelegant but tolerable in the context of the surrounding game?

Incidentally, I wrote about the Ans Hack long ago on the Community Blog. Dealing with user-unfriendly code is also one of the reasons we created the Head-to-Head voting feature. Some techniques are good for your score, and some are good for your code readability. You get to decide with you care about.

Athanasios Paraskevopoulos
Last activity 2024-6-9

Discovering an Excellent Resource on Ordinary Differential Equations

While searching the internet for some books on ordinary differential equations, I came across a link that I believe is very useful for all math students and not only. If you are interested in ODEs, it's worth taking the time to study it.

A First Look at Ordinary Differential Equations by Timothy S. Judson is an excellent resource for anyone looking to understand ODEs better. Here's a brief overview of the main topics covered:

Introduction to ODEs: Basic concepts, definitions, and initial differential equations.
Methods of Solution:

Separable equations
First-order linear equations
Exact equations
Transcendental functions

Applications of ODEs: Practical examples and applications in various scientific fields.
Systems of ODEs: Analysis and solutions of systems of differential equations.
Series and Numerical Methods: Use of series and numerical methods for solving ODEs.

This book provides a clear and comprehensive introduction to ODEs, making it suitable for students and new researchers in mathematics. If you're interested, you can explore the book in more detail here: A First Look at Ordinary Differential Equations.

Athanasios Paraskevopoulos
Last activity 2024-6-6

Numerical Simulation of the Discrete Klein-Gordon Equation: A Study on Damped, Driven Nonlinear Wave Systems with Spatially Extended Initial Conditions

The study of the dynamics of the discrete Klein - Gordon equation (DKG) with friction is given by the equation :

In the above equation, W describes the potential function:

to which every coupled unit

adheres. In Eq. (1), the variable $

$ is the unknown displacement of the oscillator occupying the n-th position of the lattice, and

is the discretization parameter. We denote by h the distance between the oscillators of the lattice. The chain (DKG) contains linear damping with a damping coefficient

, while

is the coefficient of the nonlinear cubic term.

For the DKG chain (1), we will consider the problem of initial-boundary values, with initial conditions

and Dirichlet boundary conditions at the boundary points

and

, that is,

Therefore, when necessary, we will use the short notation

for the one-dimensional discrete Laplacian

Now we want to investigate numerically the dynamics of the system (1)-(2)-(3). Our first aim is to conduct a numerical study of the property of Dynamic Stability of the system, which directly depends on the existence and linear stability of the branches of equilibrium points.

For the discussion of numerical results, it is also important to emphasize the role of the parameter

. By changing the time variable

, we rewrite Eq. (1) in the form

. We consider spatially extended initial conditions of the form:

where

is the distance of the grid and

is the amplitude of the initial condition

We also assume zero initial velocity:

the following graphs for

and

% Parameters
L = 200;  % Length of the system
K = 99;  % Number of spatial points
j = 2;  % Mode number
omega_d = 1;  % Characteristic frequency
beta = 1;  % Nonlinearity parameter
delta = 0.05;  % Damping coefficient
% Spatial grid
h = L / (K + 1);
n = linspace(-L/2, L/2, K+2);  % Spatial points
N = length(n);
omegaDScaled = h * omega_d;
deltaScaled = h * delta;
% Time parameters
dt = 1; % Time step
tmax = 3000; % Maximum time
tspan = 0:dt:tmax; % Time vector
% Values of amplitude 'a' to iterate over
a_values = [2, 1.95, 1.9, 1.85, 1.82];  % Modify this array as needed
% Differential equation solver function
function dYdt = odefun(~, Y, N, h, omegaDScaled, deltaScaled, beta)
    U = Y(1:N);
    Udot = Y(N+1:end);
    Uddot = zeros(size(U));
    % Laplacian (discrete second derivative)
    for k = 2:N-1
        Uddot(k) = (U(k+1) - 2 * U(k) + U(k-1)) ;
    end
    % System of equations
    dUdt = Udot;
    dUdotdt = Uddot - deltaScaled * Udot + omegaDScaled^2 * (U - beta * U.^3);
    % Pack derivatives
    dYdt = [dUdt; dUdotdt];
end
% Create a figure for subplots
figure;
% Initial plot
a_init = 2;  % Example initial amplitude for the initial condition plot
U0_init = a_init *  sin((j * pi * h * n) / L); % Initial displacement
U0_init(1) = 0; % Boundary condition at n = 0
U0_init(end) = 0; % Boundary condition at n = K+1
subplot(3, 2, 1);
plot(n, U0_init, 'r.-', 'LineWidth', 1.5, 'MarkerSize', 10); % Line and marker plot
xlabel('$x_n$', 'Interpreter', 'latex');
ylabel('$U_n$', 'Interpreter', 'latex');
title('$t=0$', 'Interpreter', 'latex');
set(gca, 'FontSize', 12, 'FontName', 'Times');
 xlim([-L/2 L/2]);
ylim([-3 3]);
grid on;
% Loop through each value of 'a' and generate the plot
for i = 1:length(a_values)
    a = a_values(i);
    % Initial conditions
    U0 = a * sin((j * pi * h * n) / L); % Initial displacement
    U0(1) = 0; % Boundary condition at n = 0
    U0(end) = 0; % Boundary condition at n = K+1
    Udot0 = zeros(size(U0)); % Initial velocity
    % Pack initial conditions
    Y0 = [U0, Udot0];
    % Solve ODE
    opts = odeset('RelTol', 1e-5, 'AbsTol', 1e-6);
    [t, Y] = ode45(@(t, Y) odefun(t, Y, N, h, omegaDScaled, deltaScaled, beta), tspan, Y0, opts);
    % Extract solutions
    U = Y(:, 1:N);
    Udot = Y(:, N+1:end);
    % Plot final displacement profile
    subplot(3, 2, i+1);
    plot(n, U(end,:), 'b.-', 'LineWidth', 1.5, 'MarkerSize', 10); % Line and marker plot
    xlabel('$x_n$', 'Interpreter', 'latex');
    ylabel('$U_n$', 'Interpreter', 'latex');
    title(['$t=3000$, $a=', num2str(a), '$'], 'Interpreter', 'latex');
    set(gca, 'FontSize', 12, 'FontName', 'Times');
      xlim([-L/2 L/2]);
ylim([-2 2]);
    grid on;
end
% Adjust layout
set(gcf, 'Position', [100, 100, 1200, 900]); % Adjust figure size as needed

Dynamics for the initial condition ,

, for

, for different amplitude values. By reducing the amplitude values, we observe the convergence to equilibrium points of different branches from

and the appearance of values

for which the solution converges to a non-linear equilibrium point

Parameters:

Detection of a stability threshold

: For

, the initial condition ,

, converges to a non-linear equilibrium point

Characteristics for

, with corresponding norm

where the dynamics appear in the first image of the third row, we observe convergence to a non-linear equilibrium point of branch

This has the same norm and the same energy as the previous case but the final state has a completely different profile. This result suggests secondary bifurcations have occurred in branch

By further reducing the amplitude, distinct values of

are discerned: 1.9, 1.85, 1.81 for which the initial condition

with norms

respectively, converges to a non-linear equilibrium point of branch

This equilibrium point has norm

and energy

. The behavior of this equilibrium is illustrated in the third row and in the first image of the third row of Figure 1, and also in the first image of the third row of Figure 2. For all the values between the aforementioned a, the initial condition

converges to geometrically different non-linear states of branch

as shown in the second image of the first row and the first image of the second row of Figure 2, for amplitudes

and

respectively.

Refference:

Dynamics of nonlinear lattices: asymptotic behavior and study of the existence and stability of tracked oscillations-Vetas Konstantinos (2018)