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gina_et_berg
gina_et_berg
最後のアクティビティ: 2019 年 7 月 16 日

can you please help in solving a pde numerically

Hello: your help is greatly appreciated, I am trying to solve the following pde numerically with ode45 (if possible). There are three equations in total. I keep getting an error. know parameters: v, D(j), KL(j), cs(j) The IC and BC are provided in the m.file. pde:

    % code
% Initial, final values of independent variable
tspan = [0 7];
P=1, F2=2, F3=3;
c_initial_1= zeros(N+1,1);
c_initial_2= zeros(N+1,1);
c_initial_3= zeros(N+1,1)
if t == 0
c_initial_2(1,2) = cs(2)
c_initial_3(1,3) = cs(3)
c_initial_1(1,1) = cinj
end
  [t, c, kF2, kF3, kP, n2, m2, n3, m3, q, r] = ode45(@ode, tspan, c_initial_1,c_initial_2, c_initial_3);
function [dcdt] = ode(t, c, k2, k3, kP, n2, m2, n3, m3, q, r)
global N dx dxs
dcdt = zeros(N,N)
for i = 1:N
    for j = P:F3 % j== 1:3 1=persulfate, 2 Fraction 2, and 3 Fraction 3
        if j == 1
            epsilon = 1
        else 
            epsilon = 0
        end 
        dcdt(i, j) = (-v/(2*dx))*(c(i+1,j)-c(i-1,j))+(D(j)/dxs)*(c(i+1,j)...
            -2*c(i,j)-c(i-1,j))+(1-epsilon)*kL(j)*(cs(j)-c(i,j))- ...
            (1-epsilon)*k(j)*(c(i,j)^n(j)*(c(i,1)^m(j))- ...
            epsilon*kP*(c(i,j+epsilon)+c(i,j+2*epsilon))^q *c(i,1)^r
        dcdt(N+2,j) = dcdt(N-1,j)
        dcdt(0,j) = dcdt(2,j)
        if t == 0
            dcdt(1,P) = cinj 
        end
    end
end
end
end

dc(i,j)/dt=-v*(dc(i,j)/dx)+D(j)*d/dx(dc(i,j)/dx)+(1-epsilon)*kL(j)*(cs(j)-c(i,j))+(1-epsilon)*k(j)*c(i,j)^n(j) * c(i,1)^m(j) + epsilon*kp*[c(i,j+epsilon)+c(i,j+2*epsilon)]^r * c(i,1)^q

Jacky Wong
Jacky Wong
最後のアクティビティ: 2019 年 7 月 19 日

Single Phase Transformator Simulation

Good day everyone,

I'm trying to simulate a single phase transformator by using Simulink. I've got the current values: R1 = 3 Ohm R2 = 0.03 Ohm X1 = 6.5 Ohm X2 = 0.07 Ohm Rc = 100k Ohm Xm = 15k Ohm f = 60 Hz Uprim = 2400V Usec = 240V S = 29kVA cos Phi = 0.8

And I've made the current calculations: L1 = X1/2*pi*f = 17,24 mH L2 = X2/2*pi*f = 185.68 uH Lm = Xm/2*pi*f = 39.79 H S = Urms*Irms => Irms = 120.83 A P = Urms*Irms*cos Phi = 23200 W Q = Urms*Irms*sin Phi = 17400 VAr Q>0 so Q = ohms-inductive => QL = 17400, QC = 0

I've made the current circuit and simulated it, but somehow my secondairy output voltage is only at 225Vrms. Can someone explain to me why that's the case? Did do something wrong in my calculations or in my simulation?

Mohammad Tauquir Iqbal
Mohammad Tauquir Iqbal
最後のアクティビティ: 2019 年 7 月 27 日

closed loop in the c2000 platfrom using MAtlab

i am confused about how to run as a closed loop. how to do closed-loop control of phase shift using matlab. i am using c2000 embedded by Matlab.

DINGUI Kacou Franck-Daniel
DINGUI Kacou Franck-Daniel
最後のアクティビティ: 2019 年 6 月 6 日

Traitements automatique de données

Bonjour A tous,

Je vous écris pour solliciter votre aide si possible. Je travaille en ce moment sur un projet qui consiste a un traitement d'image.

J'utilise une camera thermique associée a une logiciel. Avec ce logiciel, j'enregistre une film de 4 secondes. En gros j'ai une vidéo constituée de 100 images.

Une image comprend 90 pixels donc les valeurs de ces pixels sont reparties en sous forme matricielle (10x9). Ce qui fait que pour les 100 images, j'ai 100 matrices.

L’idée c'est d'avoir une image moyenne donc une moyenne des 100 matrices.

Le problème c'est que je fais le traitement avec ce logiciel. Pour la suite des travaux j'utilise matlab.

J'ai donc besoin de créer un programme sous matlab qui me permet de lire le fichier recueilli par ce logiciel de traitement d'image en me refaisant sortir de façon automatique une moyenne de ces 100 matrices.

Je vous joins en copie un exemple de ce fichier.

J'ai donc besoin de piste pour le programmer.

Je vous remercie d'avance.

Bien cordialement,

Yahav Morag
Yahav Morag
最後のアクティビティ: 2019 年 6 月 4 日

implementing arbitrary transfer function in Simscape Electrical

Hi, In my circuit, I have an element for which I don't have its equivalent circuit. What I have is a lookup table of its frequency response (magnitude and phase), which is complicated and cannot be represented by a lumped parameters equivalent circuit, and also some of its elements are frequency-dependent. Even if I do obtain somehow its transfer function Laplace representation (using e.g. "System identification" toolbox, and I want to add it to my circuit simulation (Simscape Electrical) as a block.

Does anyone have an idea how to do it? Thank you!

Eric Cigan
Eric Cigan
最後のアクティビティ: 2019 年 5 月 31 日

Power electronics applications on Xilinx UltraScale+ MPSoC devices

We've been hearing from more and more customers who are interested in using Xilinx's new Zynq UltraScale+ devices in power electronics control applications. The attraction appears to be the dual-core ARM Cortex-R5 processors, which are well suited to hard real time applications. Are you looking at Zynq UltraScale+ MPSoCs as a platform for power electronics control? If so, we'd love to hear from you as we look at support for these devices.

In the meantime, MathWorks offers a reference design example for FOC motor control on Zynq-7000 devices that many customers have used as a basis for developing Simulink models for C and HDL code generation.

Hi guys could u guys please help me explain what is happening on this 3 graphs. I am an electrical student and just to be honest i am not a smart student but I'm willing to learn. Please do help me.Ive got my simulation i managed to generate perfect sin wave but i just couldn't explain on the graphs i simulated.

Tony Lennon
Tony Lennon
最後のアクティビティ: 2019 年 6 月 20 日

Using FPGAs for power electronics control design

With the need for higher sampling frequencies, power electronics control engineers are moving some of their controller implementations to FPGAs or FPGA-based SoCs. Besides the use of wide-band gap semiconductors (GaN and SiC), what other reasons are driving the need for higher controller sampling frequencies? Let us know your thoughts.

If you have not seen this yet, in Release 2018b we added several examples to Simulink Control Design that show how to use this product to tune the gains of field-oriented controllers.

The first two examples make use of Closed-Loop PID Autotuner block . We show how to use this block to tune multiple loops in the motor control system, one loop at a time.

One of the examples shows tuning the controller gains for a PMSM:

Tune Field-Oriented Controllers Using Closed-Loop PID Autotuner Block

The other example shows how to tune four loops for an asynchronous machine (inductance motor):

Tune Field-Oriented Controllers for an Asynchronous Machine Using Closed-Loop PID Autotuner Block

This approach works well when you have initial gains that provide stable response, and you want to fine tune the controller to improve performance.

What do you do when you start with a new design and need to design your controller from scratch? That is what the third example is showing. Here we design all 3 loops (id, iq, speed) for a PMSM by running an AC sweep to compute a frequency response, then identifying a state-space model using System Identification Toolbox, and finally tuning all 3 loops simultaneously to provide desired performance.

Check it out here:

Tune Field-Oriented Controllers Using SYSTUNE

What do you think about these examples?

Share your opinion.

Arkadiy

Dear MATLAB community,
How can I help my close friend who's bad at math and programming learn MATLAB?
He's a final year chemical engineering student who struggles even to plot two functions on the same graph in his computational fluid dynamics class (there was no prereq for matlab skills).
In his first year, I saw him get dragged through the introductory engineering classes which was his first encounter with MATLAB. Students were taught a few rudimentary programming skills and then were expected to make a code for a 'simple' tic-tac-toe game. It took him hours of blank looks and tutoring to even understand the simplest of boolean operators. He was never able to write a working function without the supervision of a friend or tutor. Needless to say, he was permanently scarred by the experience and swore to avoid using it forever.
After 3 years of avoiding MATLAB, he realised how not knowing it hurt him during his final year project. He had to solve a system of pdes to model the performance of a reactor and practically speaking, MATLAB was the most suitable software at hand. He ended up having to get a friend to help him code the equations in while also having to oversimplify his model.
The weird thing is that: most students from his chemical engineering faculty were not expected or encouraged to use MATLAB, almost all of their prior assignments required no use of MATLAB except that infamous first year course, and most of his peers also avoided using MATLAB and resorted to Excel. It is my understanding that Excel cannot match MATLAB's efficiency and clarity when solving calculus problems so it was not uncommon to see extremely long Excel spreadsheets.
Anyway, my friend is, with the help of a friend's past year MATLAB codes, trying to finish up his computational fluid dynamics assignment that's due soon. He finishes university in 2 weeks time.
Even though he knows that not every engineer has to use MATLAB in the workplace, he somehow wishes he was able to learn MATLAB at his glacial pace. I find it such a pity that he was never able to keep up with the pace of learning that was expected which begs the question: are students who are too slow at learning programming better of in a different field of study?
If you've managed to read to the end of this, thank you so much. I just don't know how to help my friend and I'm hoping some of you might be able to suggest how I can help him be better at it. I believe he has potential but needs special help when it comes to MATLAB.
All helpful and constructive suggestions considered,
Thank You All
Axel Nordin Fürdös
Axel Nordin Fürdös
最後のアクティビティ: 2020 年 12 月 26 日

Mathworks and Matlab merchandise

Hi there! This is kind of an unusual question, but here it goes. I am a big time Matlab enthusiast and I met some of your representatives at Formula Student Germany back in August. There was a booth were your product was showcased but most importantly there was Matlab merchandise such as stickers, rub-on-tattoos and pens with the mathworks logo being handed out. This merchandise is increadibly popular with me and my nerdy friends. But sadly I didnt bring much with me from the event. Is it possible to get ahold some of it? Is it for sale? Are you willing to sponsor some geeky engineering students?

I am new in MATLAB programming. I want to learn matlab . I want to know about is any matlab or simulink contest available. Please answer me. Thanks
Jan
Jan
最後のアクティビティ: 2013 年 8 月 9 日

Magic strings and numbers in Matlab

Some of Matlab's toolbox functions are affected by magic strings or magic numbers, which are strings or numbers with a deeper meaning besides the normal value. Both are considered as bad programming patters, because they provoke confusions, when the magic keys appear with the normal meaning by accident. See http://en.wikipedia.org/wiki/Anti-pattern
Example 1:
clear('myVariable')
clear('variables')
While the 1st clears the variable myVariable, the later clears all variables. Here 'variables' has a meta-meaning. The problem appears, when 'variables' is an existing variable:
a = 1;
variables = 2;
clear('variables')
disp(a) % >> 1
Only variables is cleared, which cannot be understood directly when its definition is 1000 lines before.
Example 2:
uicontrol('String', 'default')
This creates a button with the empty string '' instead of the expected 'default', because this is the magic string to invoke the default value get(0, 'DefaultUIControlString'). The same concerns properties of other graphic objects also, e.g. the 'name' property of figure or the string of uimenu. There is a workaround which allows the user to display 'default': Simply use '\default'. Unfortunately this is doubled magic, because in consequence it is impossible to display the string '\default'. Obviously a bad idea.
Example 3:
Graphic handles are doubles (although gobject of the new R2013a seems, like this is subject to changes? [EDITED: Yes, it changed with HG2 in R2014a]). But then a handle can be confused with data:
a = axes; % e.g. 0.0048828125
plot(a, 2, '+')
But you cannot draw the point [0.0048828125, 2] by this way, because the 1st input is considered as handle of the parent. Here all possible values of handles are magic. Collisions are very unlikely, but there is no way to avoid them reliably - as long as handles have the type double.
Question:
Which functions are concerned by magic values? What are the pitfalls and workarounds?
Laila
Laila
最後のアクティビティ: 2024 年 2 月 27 日

How do I can delete my account?

How do I can delete my account?
Matt Fig
Matt Fig
最後のアクティビティ: 2023 年 2 月 23 日

Share your favorite snippet or utility

I am wondering what others use for those little short-cuts or niceties in MATLAB. I have in mind something you wrote or something somebody else wrote or an underused MW function.
Here are my two favorites.
This is a simple script I use. Here is the entire contents of CLC.m (yes, it is capitalized):
clear all,close all,clc
Very simple, but I use it all the time. Here is another one I use so often that I forget not every machine has it (though every machine should, IMO):
whats
Here is an underused MW function that I occasionally employ when working on someone else's machine. The usual response is, "Wait, what did you just do?"
home
What are some of yours?
Adam Kaas
Adam Kaas
最後のアクティビティ: 2012 年 6 月 6 日

Coolest things MATLAB can do

As I'm becoming more and more familiar with MATLAB, I'm starting to fall in love with it. I was wondering what are the coolest things that you all know MATLAB can do? As for me so far, the auto-code generation into another language is the coolest thing.
Walter Roberson
Walter Roberson
最後のアクティビティ: 2021 年 1 月 25 日

What can be programmed "without any built-in functions" ?

It is not uncommon for students to be assigned questions which they are required to complete "without using any built-in functions". There is not a great deal that can be programmed in MATLAB without using any built-in functions, but a little can be done -- but what, exactly is possible?
What a "built-in function" is, exactly, is open to interpretation. In the below, I refer instead to "publicly visible routines". Keywords (see below) are not publicly visible routines (they are "statements" or components of statements.) Any documented operation or call that invokes a MATLAB-supplied .m or .p or mex file or built-in library to do its work is a publicly visible routines. If you can use documented methods override the normal meaning of a statement or expression in practice by supplying alternate code, then the code probably involves publicly visible routines. If the language design is such that you could use documented methods to override the normal meaning of a statement or expression in theory (such as the behavior of adding two double, the code for which is in practice bundled into an internal MATLAB library), then I would still consider that a call to a publicly visible routine.
A MATLAB-supplied routine that is not documented, which is used for internal MATLAB purposes, could perhaps be held not to be a publicly visible routine, but it certainly would still be a "built-in function".
I exclude from the list any routine which there is no direct way to access, and is only used for internal purposes, such as the memory allocation routines.
This is what I have come up with:
  • the names defined as "keywords" do not in themselves involve function calls to publicly visible routines. These keywords currently include 'break', 'case', 'catch', 'classdef', 'continue', 'else', 'elseif', 'end', 'for', 'function', 'global', 'if', 'otherwise', 'parfor', 'persistent', 'return', 'spmd', 'switch', 'try', 'while'. There is no functional form of any of these: for example, one cannot use global(s) to declare the name contained in the variable "s" to be global. (However, you can define an "end" method; https://www.mathworks.com/help/matlab/matlab_oop/object-end-indexing.html )
  • scalar numeric double precision real-valued constants are handled at parse time, including unary plus and unary minus in front of them
  • scalar numeric double precision constants followed immediately by "i" or "j" create a complex-value constant at parse time, including unary plus and unary minus in front of them
  • whether a complete complex constant with real and imaginary part is handled at parse time is unknown
  • literal character vectors and string objects are handled at parse time
  • in sufficiently new versions, int64() and uint64() around an integer constant is handled at parse time. This was a change from previous versions which handled it at run time (after the integer had been converted to double precision...)
  • whether any other casts such as uint16() or logical() are now handled at parse time is unknown
  • assignment of a compete variable (no indexing, no substructure references, etc.) to a plain variable (no indexing, no substructure references, etc.) does not involve any function calls to publicly visible routines (unless I have overlooked a case involving objects)
  • "if" or "while" applied to a scalar logical constant or to a scalar logical variable does not involve any function calls to publicly visible routines. However, it is not known whether there is any method to construct a logical value without calling a MATLAB routine: "true" and "false" are MATLAB routines, not constants, and logical() of a numeric constant might be handled at run time
  • "for" in which the range is named as a scalar constant or scalar variable do not involve any function calls to publicly visible routines; for example, "for K = 5"
  • defining an anonymous function does not involve any function calls to publicly visible routines
I may have overlooked something due to shortage of chocolate in my bloodstream.
The language described above is not Turing complete, and is not "sufficiently powerful" for the purposes of the Church-Rosser Theorem of general-purpose computability. It is also not possible to do any arithmetic in it, as arithmetic must be reducible to the Peano Postulates, and those require at the very least the ability to compare a value for equality with 0, which in MATLAB would require a call to the MATLAB routine "eq".
Paulo Silva
Paulo Silva
最後のアクティビティ: 2022 年 8 月 12 日

Do you think that MATLAB is expensive?

We all know that MATLAB is probably the best software for engineering purposes, I think it's a little expensive unless you have it for free on your school or place you work, please share your opinion about MATLAB cost, including toolboxes, student versions... is it that expensive?
Doug Hull
Doug Hull
最後のアクティビティ: 2015 年 2 月 17 日

How did you learn MATLAB?

I think a lot about how to more effectively teach MATLAB, internally to new hires, but also through my blog.
How did you learn MATLAB, what knowledge of programming did you have coming into learning MATLAB? When did you learn it is important also as the resources available have expanded radically in the last 15 years.
Answers from new users who are just beginning down this path are of particular interest, as those are who we can help the most.
Paulo Silva
Paulo Silva
最後のアクティビティ: 2016 年 10 月 22 日

How long have you been using matlab? tell us your story

Don't be shy, what was your matlab learning curve, how many years or months, what were the difficulties to begin with.
I think that the answers would be most valuable for new users, maybe you can also tell us the tricks that allowed you to master some parts or all matlab.
Now it's your turn...