Respected Sir,
I m doing my Master's Thesis on the topic microwave induced Thermo acoustical emission. I would like to know how do I start the simulation. Actually I am new to k-wave and i would like to know how to simulate equations using k-wave. It would be very helpful.
Please help.
Thank u
Dear Patil,
The acoustic modelling of microwave-induced thermoacoustics is the same as photoacoustics (except you may need to take into account the length of your excitation pulse). A good place to start is to run some of the examples in the toolbox, and to read the manual, which is on the documentation page.
If you have any specific k-Wave related questions, please post them here and we'll endeavour to answer them.
Best wishes,
Ben
Prof. Ben,
Thank you for your quick response. I read the post on the forum that discussed about thermo-acoustic signal and its simulation. It was of great help. But i would like to know if there's any problem with this code(i have tried it but m not sure its correct or not). Also I am not sure how to decide the sensors not picking up the source signal(I mean the sensor should pick up thermo-acoustic rather than the microwave itself)...
clear all;
% create the computational grid
Nx = 128; % number of grid points in the x (row) direction
Ny = 128; % number of grid points in the y (column) direction
dx = 50e-3/Nx; % grid point spacing in the x direction [m]
dy = dx; % grid point spacing in the y direction [m]
kgrid = makeGrid(Nx, dx, Ny, dy);
% define the properties of the propagation medium
medium.sound_speed = 1540; % [m/s]
medium.alpha_coeff = 0.003660; % [dB/(MHz^y cm)]
medium.alpha_power = 1.5 ;
% create the time array
[kgrid.t_array dt] = makeTime(kgrid, medium.sound_speed);
% define a single source point
source.p_mask = zeros(Nx, Ny);
source.p_mask(end - Nx/4, Ny/2) = 1;
% define a time varying sinusoidal source
source_freq = 2.45e9; % [Hz]
source_mag = 0.25; % [Pa]
gruneisen = 0.11;
pulsewidth = 1e-6;
t_offset = 5e-6;
gaussian = exp(-((kgrid.t_array-t_offset)/pulsewidth).^2)/(pulsewidth*sqrt(pi));
source.p = source_mag*gruneisen*gaussian;
% filter the source to remove high frequencies not supported by the grid
source.p = filterTimeSeries(kgrid, medium, source.p);
% define a single sensor point
sensor.mask = zeros(Nx, Ny);
sensor.mask(Nx/4, Ny/2) = 1;
% define the acoustic parameters to record
sensor.record = {'p', 'p_final'};
% % run the simulation
sensor_data = kspaceFirstOrder2D(kgrid, medium, source, sensor);
% plot the final wave-field
figure;
imagesc(kgrid.y_vec*1e3, kgrid.x_vec*1e3, sensor_data.p_final + source.p_mask + sensor.mask, [-1 1]);
colormap(getColorMap);
ylabel('x-position [mm]');
xlabel('y-position [mm]');
axis image;
% plot the simulated sensor data
figure;
[t_sc, scale, prefix] = scaleSI(max(kgrid.t_array(:)));
subplot(2, 1, 1), plot(kgrid.t_array*scale, source.p, 'k-');
xlabel(['Time [' prefix 's]']);
ylabel('Signal Amplitude');
axis tight;
title('Input Pressure Signal');
subplot(2, 1, 2), plot(kgrid.t_array*scale, sensor_data.p, 'r-');
xlabel(['Time [' prefix 's]']);
ylabel('Signal Amplitude');
axis tight;
title('Sensor Pressure Signal');thank you in advance
Hi Patil,
k-Wave is a versatile tool for modelling in photoacoustics and thermoacoustics, but there is some learning required to get the most out of it. There are many examples in the k-Wave toolbox relevant to forward simulation and image reconstruction in thermoacoustics. You can find these examples in the MATLAB help browser by selecting “k-Wave Toolbox” from the contents page. In versions of MATLAB prior to 2012b, the help browser is opened by clicking on the blue question mark icon on the menu bar. In MATLAB 2012b (and later), the documentation is accessed by selecting “Help” from the ribbon bar, and then clicking on “Supplemental Software”. There is also a lot of information in the k-Wave manual that you may find helpful.
If you have any specific questions related to your simulations, e.g., error messages you don't understand, or a specific scenario you're having trouble implementing, please let us know.
Kind regards,
Brad.
Respected Sir,
I would like to somethings about k wave. Since I am doing thermo-acoustic emission can i have more than three properties for the propagation medium ?? (except sound speed, Alpha coeff and alpha power). I would also like to add some more parameters like Heat capacity at const. Pressure or realtive permitivity and permeability.
Secondly I did not find the examples on thermo acoustics. All the examples are based on the reconstruction.
I would also like to know that how do i define the microwave energy as the source(Just by defining the frequency and magnitude)
Thank you in advance
Hi Patil,
The k-Wave Toolbox currently only includes acoustic models, and thus can only be used to model the acoustic part of photoacoustics and thermoacoustics, i.e., after the absorbed light or electromagnetic energy has been converted in acoustic pressure. If you want to model the propagation of EM waves, you'll have to use another package I'm afraid.
Regarding the forward and inverse acoustic problems for thermoacoustics, these are the same as in photoacoustics. However, in the thermoacoustic case, you may need to consider the length of the EM pulse. In this case, you could take a look a the Time Varying Source Problems examples.
Sorry for the confusion,
Brad.
Hi Prof Brad,
I will definitely look for the Time Varying Source problems.....
And i did not understand about the different package. Do u mean to say that only k-wave would not be possible to solve ?? or anything else ??
Please clarify....
I will try out the Time Varying Source and come back to you for sure..
Thank u
Abhishek
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