Author Archives: nirmaljoshi

Learn and tell others.

Code aster tutorial for load varying with time and depth

Here I post two tutorial in code aster/ salome meca as follows:
1. Applying varying load
In this tutorial, simple vertical element is considered in which a vertically varying load is applied by defining a function.

2. Analysis of dam for varying water level
This is a typical analysis of dam where water level is assumed to fluctuate with time. Since two variables changes i.e. time and water depth, we need to make an external file to read the pressure (load). This tutorial will show how to do it.

Google script to extract email information

This code helps to get summary of email such as subject, received date etc. Code is for the unread emails; remove lines with if condition check to read all emails.
Make a new google sheet> tools>script editor and copy and paste it. You will require to authorize the use of code while executing it.

function retriveUnreadMessages() {
// imports subject, from (email), received date of all unread email in inbox of gmail account
// the data is then written in the google spreadsheet
//reference:https://developers.google.com/apps-script/reference/spreadsheet/spreadsheet#appendRow(Object)
//

//-----------google sheet part
var ss=SpreadsheetApp.getActiveSheet();
var date1=new Date().toISOString().slice(0, 10);
ss.appendRow(["***** new execution = ",date1,"*****"]);// append a new information line where the new execution is done because data is appended at the end

//-----------------------------------------gmail part-----
// Log the subject lines of your Inbox
var threads = GmailApp.getInboxThreads();
// number of message to retrive
var n= threads.length;
for (var i = 0; i < n; i++) {

// check if there is unread messages in a thread
if(threads[i].isUnread)
{

var subject1=threads[i].getFirstMessageSubject(); // subjet of thread
var email1=threads[i].getMessages(); // messages inside the thread
// check if the individual message is unread
for (var j = 0; j < email1.length; j++) {
if(email1[j].isUnread)
{
var message_sender=email1[j].getFrom();
var message_sendDateTime=email1[j].getDate();
}
ss.appendRow([i,j,subject1,message_sender,message_sendDateTime]); //write data to spreadsheet.. it is appended to new row

}
}
}
}

Fractals in matlab/octave

Codes in matlab/octave for generating some popular fractals:

Mandelbrot

mandelbrot

function mandelbrotmain()
clear variables; clc;

maxit=200;
x=[-2,1];
y=[-1 1];

xpix=601;
ypix=401;

x=linspace(x(1),x(2),xpix);
y=linspace(y(1),y(2),ypix);
[xG, yG]=meshgrid(x,y);

c=mb(maxit,xG,yG);

figure
imagesc(x,y,c);
colormap([1 1 1;0 0 0]);
axis on;
grind on;

endfunction

function count=mb(maxItr,xG,yG)
c=xG+1i*yG;
count=ones(size(c));
z=c;

for n=1:maxItr
z=z.*z+c;
inside=abs(z)<=2;
count=count+inside;
endfor
endfunction

 

Sierpinski triangle
sierpinski

clc;
clear variables;
close windows;

clf

N=500;
x=zeros(1,N);y=x;r=x;
for a=2:N
c=randi([0 2]);
r(a)=c;
switch c
case 0
x(a)=0.5*x(a-1);
y(a)=0.5*y(a-1);
case 1
x(a)=0.5*x(a-1)+.25;
y(a)=0.5*y(a-1)+sqrt(3)/4;
case 2
x(a)=0.5*x(a-1)+.5;
y(a)=0.5*y(a-1);
end
end
plot(x,y,’o’)
title(‘Sierpinski’s triangle’)
legend(sprintf(‘N=%d Iterations’,N))

 

Fractal tree
fractaltrree

function treemain
tic
clear all;
depth = 7;
figure 1;
hold on;

drawTree2(0, 0, 90, depth);
toc;
endfunction

function drawTree2(x1, y1, angle, depth)
deg_to_rad = pi / 180.0;
rot=30; #degrees :: rotation from second iteration
branchLength=100*depth;
if (depth != 0)
x2 = x1 + cos(angle * deg_to_rad) * branchLength;
y2 = y1 + sin(angle * deg_to_rad) * branchLength ;
line([x1, x2], [y1, y2],’LineWidth’,depth);
drawTree2(x2, y2, angle – rot, depth – 1);
drawTree2(x2, y2, angle + rot, depth – 1);

endif
endfunction

 

A note on fractal (from HH Hardey):
There are upper and lower limits to describe natural objects by fractals. A figure may look like a fern leaf, but continued generation of the “leaf on larger and larger scales produces only a larger and larger fern leaf. A fern “plant” will never be produced. Similarly, there is a smallest scale to which a fractal description applies. As the overall fern leaf pattern is repeated on smaller and smaller scales, eventually the scale of a single fern plant cell will be reached. A single cell does not look like the overall shape.

Using Math Kernal Library (MKL) in visual studio with Fortran

First install MKL from intel website

To use intel MKL library inside visual studio do the followings:
1. Right click the project>Properties
2. In Property page>Fortran>Libraries set (a) Runtime library : Multithreaded and (b) Use Intel MKL: Sequential
mklsetting

Once this setting is done, you can compile the file in DEBUG mode. Repeat the same process (1-2) for RELEASE mode too once more.(Note exe of DEBUG mode is far slower than exe of RELEASE mode. The settings to set are listed below.

To do the same thing MANUALLY (which gives more insight to the code) do the following in each DEBUG and RELEASE mode.
1. Property page>Fortran>General>Additional Include Directories: C:\Program Files (x86)\IntelSWTools\compilers_and_libraries_2019.4.245\windows\mkl\include
2. Property page>Fortran>Preprocessor>Preprocess source file: Yes
3. Property page>Linker>General>Additional Library Directories:C:\Program Files (x86)\IntelSWTools\compilers_and_libraries_2019.4.245\windows\mkl\lib\ia32_win
4. Property page>Linker>Input>Additional Dependencies: mkl_intel_c.lib mkl_intel_thread.lib mkl_core.lib libiomp5md.lib

The manual setting is described in the video as well:

For method to install Fortran in visual studio see this post.

Specific gravity of soil particles

Consider the following figure.
specific gravity
W1= weight of empty vessel
W2= Weight of vessel + weight of sample
W3=Weight of vessel + weight of sample+Water
W4=Weight of vessel + Water

Here,
Weight of solid = W2-W1

Similarly, from last two figures
W3-W4=Weight of solid- Weight of water
or, W3-W4= W2-W1 -Weight of water
or, Weight of water=(W2-W1)-(W3-W4)(= weight of equal volume of water as that of solid)

Now,
specific-gravity=\frac{weight of solid}{weight of equal volume of water}
i.e. \rho_s=\frac{(W2-W1)}{(W2-W1)-(W3-W4)}