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How does the wave propagate (ultrasound) through the solids?
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Maha Ch
How does the wave propagate (ultrasound) through the solids?
Hi,
I will begin by the lastest question and explain how it works.
Most of the pulser are square wave because it is easier to achieve technically. The pulse duration has to be low compared to the working period of the transducer and so it can be assumed that you excite your transducer with a Diras impulse. Doing that you have the impulse response of the transducer as an output (it is the signal used for time arrival determination for exemple).
As said by Michael Foegelle, the most important thing to see is the fourier transform of the excitation.. So if the duration of the excitation is not negligible, the transducer response is not exactly the same with a square signal than with a sine signal. Typically, the square signal will contain several harmonics.
The frequency response of your system can change according to your medium if you are in contact with due to the mechanical load which change the boundary conditions of your transducers.
The velocity can also change according to frequency (in reality it is always the case in my knowledge).
I will begin by the lastest question and explain how it works.
Most of the pulser are square wave because it is easier to achieve technically. The pulse duration has to be low compared to the working period of the transducer and so it can be assumed that you excite your transducer with a Diras impulse. Doing that you have the impulse response of the transducer as an output (it is the signal used for time arrival determination for exemple).
As said by Michael Foegelle, the most important thing to see is the fourier transform of the excitation.. So if the duration of the excitation is not negligible, the transducer response is not exactly the same with a square signal than with a sine signal. Typically, the square signal will contain several harmonics.
The frequency response of your system can change according to your medium if you are in contact with due to the mechanical load which change the boundary conditions of your transducers.
The velocity can also change according to frequency (in reality it is always the case in my knowledge).
I will begin by the lastest question and explain how it works.
Most of the pulser are square wave because it is easier to achieve technically. The pulse duration has to be low compared to the working period of the transducer and so it can be assumed that you excite your transducer with a Diras impulse. Doing that you have the impulse response of the transducer as an output (it is the signal used for time arrival determination for exemple).
As said by Michael Foegelle, the most important thing to see is the fourier transform of the excitation.. So if the duration of the excitation is not negligible, the transducer response is not exactly the same with a square signal than with a sine signal. Typically, the square signal will contain several harmonics.
The frequency response of your system can change according to your medium if you are in contact with due to the mechanical load which change the boundary conditions of your transducers.
The velocity can also change according to frequency (in reality it is always the case in my knowledge).
I will begin by the lastest question and explain how it works.
Most of the pulser are square wave because it is easier to achieve technically. The pulse duration has to be low compared to the working period of the transducer and so it can be assumed that you excite your transducer with a Diras impulse. Doing that you have the impulse response of the transducer as an output (it is the signal used for time arrival determination for exemple).
As said by Michael Foegelle, the most important thing to see is the fourier transform of the excitation.. So if the duration of the excitation is not negligible, the transducer response is not exactly the same with a square signal than with a sine signal. Typically, the square signal will contain several harmonics.
The frequency response of your system can change according to your medium if you are in contact with due to the mechanical load which change the boundary conditions of your transducers.
The velocity can also change according to frequency (in reality it is always the case in my knowledge).
Ultrasound waves propagates in solid by either longitudinal waves or transverse waves. The first type is called also the compression waves in which the molecules of the materials are displaced in the direction of the propagation making alternate compression and expansive of the material. In the transverse wave the molecules of the materials moves in a plane perpendicular to the propagation direction. And so it is a sheer wave which depends only on the sheer coefficient of the material. If the speed of the wave is equal to the speed of the energy which means that the phase velocity is equal to the group velocity, then the speed will not depend on the frequency otherwise it will depend on and in this case the material will be dispersive meaning the the velocity changes with the frequency of the wave. The wave equation can be written in the form: x(t) = A sin(wt - 2 pi x/lambda), where w is the frequency of the wave, lambda the wavelength and A is the amplitude of the displacement of the molecules from their rest position. So the elementary wave is sinusoidal wave. When we can hear it it will be a single tone like the sound emitted by a vibrating fork. I will speak in the next post about the different excitation waveforms. Best wishes
Ultrasound waves propagates in solid by either longitudinal waves or transverse waves. The first type is called also the compression waves in which the molecules of the materials are displaced in the direction of the propagation making alternate compression and expansive of the material. In the transverse wave the molecules of the materials moves in a plane perpendicular to the propagation direction. And so it is a sheer wave which depends only on the sheer coefficient of the material. If the speed of the wave is equal to the speed of the energy which means that the phase velocity is equal to the group velocity, then the speed will not depend on the frequency otherwise it will depend on and in this case the material will be dispersive meaning the the velocity changes with the frequency of the wave. The wave equation can be written in the form: x(t) = A sin(wt - 2 pi x/lambda), where w is the frequency of the wave, lambda the wavelength and A is the amplitude of the displacement of the molecules from their rest position. So the elementary wave is sinusoidal wave. When we can hear it it will be a single tone like the sound emitted by a vibrating fork. I will speak in the next post about the different excitation waveforms. Best wishes
Ok, so there are a number of disparate questions here as you've laid it out. So first off, sound propagating through a solid (unlike through air) can be either a compression wave (like air) or a transverse wave (like flicking a rope) or some combination thereof. A surface acoustic wave is actually a superposition of both with atoms moving elliptically with different rotation orientations depending on their proximity to the surface.
Now, from the context of your other statements, I'm not sure that's what you're really asking. It sounds like you're talking about dispersion, which can certainly happen. However, I think what you're referring to as far as the impulse corresponds to the envelope of the impulse, not the actual frequency dependence. Going back to the work we did in magnetacoustics, the traditional way of exciting a bulk wave was to hit a transducer with a Gaussian shaped pulse of the resonant frequency of the transducer. That could also have been a rectangular pulse, but the frequency content would still be primarily the resonant frequency (e.g. 30 MHz). Note that that is far different from hitting the crystal with a single voltage pulse, rectangular or Gaussian, that would induce all sorts of frequencies based on the Fourier content of the pulse. However, the transducer probably would basically ignore most of that frequency content anyway.
At any rate, you would need to look at the Fourier content of the impulse you use to determine what spectral content actually hits the transducer. Even the square pulse of a single frequency has higher order content due to the ends. The Gaussian envelope helps reduce that.
Interestingly, talking about Fourier transforms, we eventually replaced all the complicated analog pulse forming hardware with a vector network analyzer that could take a narrow band frequency sweep and then transform that to the time domain to obtain the impulse response of the output. That allowed gating out the RF coupling from the much slower propagation through the crystal to get the acoustic component.
Ok, so there are a number of disparate questions here as you've laid it out. So first off, sound propagating through a solid (unlike through air) can be either a compression wave (like air) or a transverse wave (like flicking a rope) or some combination thereof. A surface acoustic wave is actually a superposition of both with atoms moving elliptically with different rotation orientations depending on their proximity to the surface.
Now, from the context of your other statements, I'm not sure that's what you're really asking. It sounds like you're talking about dispersion, which can certainly happen. However, I think what you're referring to as far as the impulse corresponds to the envelope of the impulse, not the actual frequency dependence. Going back to the work we did in magnetacoustics, the traditional way of exciting a bulk wave was to hit a transducer with a Gaussian shaped pulse of the resonant frequency of the transducer. That could also have been a rectangular pulse, but the frequency content would still be primarily the resonant frequency (e.g. 30 MHz). Note that that is far different from hitting the crystal with a single voltage pulse, rectangular or Gaussian, that would induce all sorts of frequencies based on the Fourier content of the pulse. However, the transducer probably would basically ignore most of that frequency content anyway.
At any rate, you would need to look at the Fourier content of the impulse you use to determine what spectral content actually hits the transducer. Even the square pulse of a single frequency has higher order content due to the ends. The Gaussian envelope helps reduce that.
Interestingly, talking about Fourier transforms, we eventually replaced all the complicated analog pulse forming hardware with a vector network analyzer that could take a narrow band frequency sweep and then transform that to the time domain to obtain the impulse response of the output. That allowed gating out the RF coupling from the much slower propagation through the crystal to get the acoustic component.
Sir, 1- Is it possible to tune the onset temperature(Ts) of a conventional superconductor(BCS superconductor) by sending an ultrasonic wave in it? 2- Similarly the materials having a spin phonon or spin lattice coupling(Like any type 2 multiferroic ), is it possible to tune the magnetic property or dielectric property of this kind of material by sending an ultrasonic wave of certain magnitude in this materials?
Sir, 1- Is it possible to tune the onset temperature(Ts) of a conventional superconductor(BCS superconductor) by sending an ultrasonic wave in it? 2- Similarly the materials having a spin phonon or spin lattice coupling(Like any type 2 multiferroic ), is it possible to tune the magnetic property or dielectric property of this kind of material by sending an ultrasonic wave of certain magnitude in this materials?
Let us talk about the normal beam to the soft tissue. Every soft tissue has an impedance. When we go from one soft tissue to another Z changes. Part of the beam will be transmitted and part will reflected. Using this model we can use transmission line equations.
Let us talk about the normal beam to the soft tissue. Every soft tissue has an impedance. When we go from one soft tissue to another Z changes. Part of the beam will be transmitted and part will reflected. Using this model we can use transmission line equations.
Ok, so there are a number of disparate questions here as you've laid it out. So first off, sound propagating through a solid (unlike through air) can be either a compression wave (like air) or a transverse wave (like flicking a rope) or some combination thereof. A surface acoustic wave is actually a superposition of both with atoms moving elliptically with different rotation orientations depending on their proximity to the surface.
Now, from the context of your other statements, I'm not sure that's what you're really asking. It sounds like you're talking about dispersion, which can certainly happen. However, I think what you're referring to as far as the impulse corresponds to the envelope of the impulse, not the actual frequency dependence. Going back to the work we did in magnetacoustics, the traditional way of exciting a bulk wave was to hit a transducer with a Gaussian shaped pulse of the resonant frequency of the transducer. That could also have been a rectangular pulse, but the frequency content would still be primarily the resonant frequency (e.g. 30 MHz). Note that that is far different from hitting the crystal with a single voltage pulse, rectangular or Gaussian, that would induce all sorts of frequencies based on the Fourier content of the pulse. However, the transducer probably would basically ignore most of that frequency content anyway.
At any rate, you would need to look at the Fourier content of the impulse you use to determine what spectral content actually hits the transducer. Even the square pulse of a single frequency has higher order content due to the ends. The Gaussian envelope helps reduce that.
Interestingly, talking about Fourier transforms, we eventually replaced all the complicated analog pulse forming hardware with a vector network analyzer that could take a narrow band frequency sweep and then transform that to the time domain to obtain the impulse response of the output. That allowed gating out the RF coupling from the much slower propagation through the crystal to get the acoustic component.
Ok, so there are a number of disparate questions here as you've laid it out. So first off, sound propagating through a solid (unlike through air) can be either a compression wave (like air) or a transverse wave (like flicking a rope) or some combination thereof. A surface acoustic wave is actually a superposition of both with atoms moving elliptically with different rotation orientations depending on their proximity to the surface.
Now, from the context of your other statements, I'm not sure that's what you're really asking. It sounds like you're talking about dispersion, which can certainly happen. However, I think what you're referring to as far as the impulse corresponds to the envelope of the impulse, not the actual frequency dependence. Going back to the work we did in magnetacoustics, the traditional way of exciting a bulk wave was to hit a transducer with a Gaussian shaped pulse of the resonant frequency of the transducer. That could also have been a rectangular pulse, but the frequency content would still be primarily the resonant frequency (e.g. 30 MHz). Note that that is far different from hitting the crystal with a single voltage pulse, rectangular or Gaussian, that would induce all sorts of frequencies based on the Fourier content of the pulse. However, the transducer probably would basically ignore most of that frequency content anyway.
At any rate, you would need to look at the Fourier content of the impulse you use to determine what spectral content actually hits the transducer. Even the square pulse of a single frequency has higher order content due to the ends. The Gaussian envelope helps reduce that.
Interestingly, talking about Fourier transforms, we eventually replaced all the complicated analog pulse forming hardware with a vector network analyzer that could take a narrow band frequency sweep and then transform that to the time domain to obtain the impulse response of the output. That allowed gating out the RF coupling from the much slower propagation through the crystal to get the acoustic component.
Interesting questions Biswajit, although you might want to start your own thread on this.
I'm rusty on this since it's been a long time since my graduate research days when I was working in this area, but if I had to take a guess on 1, I'd say possibly, but probably only in the down direction. As I recall, BCS superconductors operate on electron/phonon interactions, but I'm not sure if a coherent phonon (your acoustic wave) could be made to enhance superconductivity, or would just be seen as a source of heat, thereby artificially raising the temperature. In the strictest sense, of course, the onset temperature wouldn't have changed then, since the localized temperature (i.e. the actual vibration of the lattice) would be higher than the ambient.
On 2, that's an interesting thought, but it seems to me that since the distortion of the lattice would be very localized and temporary (not to mention, generally very small on any scale that was likely to affect bulk magnetic or dielectric properties) that the net effect would likely be zero. On a related note, it would seem that a good place to start to look for this sort of effect (if it hasn't already been done) would be to test a sample under varied static pressure. If it's possible to alter those properties by squeezing the sample to force the atoms closer together, then an acoustic wave that distorts the lattice might introduce some of the same effect. Again, it seems like you'd need a pretty significant distortion to impact the bulk properties of the material, but who knows? Maybe since the coupling is localized, it only matters what's happening at the interaction site. It still feels like the average effect would be zero.
On the other hand, if you had a 1D superconductor and could make the ultrasonic phonon coherent with that interaction, then maybe. Of course since 1D superconductors theoretically don't exist, then you have to ask what you might be able to do to a 2D superconductor. The interesting thing is that you now have several degrees of freedom to evaluate using both compression and transverse waves either normal to or parallel to the plane of superconductivity. There could be some interesting effects there. I know that when I was completing my graduate work on the magnetoacoustic effect (an old method for calipering the Fermi surface on pure metal crystals), a professor in the neighboring lab was interested in trying out the technique on the then new high Tc superconductors he was working on, but I don't know that anything ever came of it. Last time I visited, our monster variable electromagnet was still there, but I don't believe it'd been touched since I left.
Oh well, enough rambling on a topic that I'm far from expert on these days. Just applying a bit of analytical thinking to the ideas you've raised. Time to get back to my day job!
Interesting questions Biswajit, although you might want to start your own thread on this.
I'm rusty on this since it's been a long time since my graduate research days when I was working in this area, but if I had to take a guess on 1, I'd say possibly, but probably only in the down direction. As I recall, BCS superconductors operate on electron/phonon interactions, but I'm not sure if a coherent phonon (your acoustic wave) could be made to enhance superconductivity, or would just be seen as a source of heat, thereby artificially raising the temperature. In the strictest sense, of course, the onset temperature wouldn't have changed then, since the localized temperature (i.e. the actual vibration of the lattice) would be higher than the ambient.
On 2, that's an interesting thought, but it seems to me that since the distortion of the lattice would be very localized and temporary (not to mention, generally very small on any scale that was likely to affect bulk magnetic or dielectric properties) that the net effect would likely be zero. On a related note, it would seem that a good place to start to look for this sort of effect (if it hasn't already been done) would be to test a sample under varied static pressure. If it's possible to alter those properties by squeezing the sample to force the atoms closer together, then an acoustic wave that distorts the lattice might introduce some of the same effect. Again, it seems like you'd need a pretty significant distortion to impact the bulk properties of the material, but who knows? Maybe since the coupling is localized, it only matters what's happening at the interaction site. It still feels like the average effect would be zero.
On the other hand, if you had a 1D superconductor and could make the ultrasonic phonon coherent with that interaction, then maybe. Of course since 1D superconductors theoretically don't exist, then you have to ask what you might be able to do to a 2D superconductor. The interesting thing is that you now have several degrees of freedom to evaluate using both compression and transverse waves either normal to or parallel to the plane of superconductivity. There could be some interesting effects there. I know that when I was completing my graduate work on the magnetoacoustic effect (an old method for calipering the Fermi surface on pure metal crystals), a professor in the neighboring lab was interested in trying out the technique on the then new high Tc superconductors he was working on, but I don't know that anything ever came of it. Last time I visited, our monster variable electromagnet was still there, but I don't believe it'd been touched since I left.
Oh well, enough rambling on a topic that I'm far from expert on these days. Just applying a bit of analytical thinking to the ideas you've raised. Time to get back to my day job!
Hi,
I will begin by the lastest question and explain how it works.
Most of the pulser are square wave because it is easier to achieve technically. The pulse duration has to be low compared to the working period of the transducer and so it can be assumed that you excite your transducer with a Diras impulse. Doing that you have the impulse response of the transducer as an output (it is the signal used for time arrival determination for exemple).
As said by Michael Foegelle, the most important thing to see is the fourier transform of the excitation.. So if the duration of the excitation is not negligible, the transducer response is not exactly the same with a square signal than with a sine signal. Typically, the square signal will contain several harmonics.
The frequency response of your system can change according to your medium if you are in contact with due to the mechanical load which change the boundary conditions of your transducers.
The velocity can also change according to frequency (in reality it is always the case in my knowledge).
Hope it helps,
Bustillo julien
Hi,
I will begin by the lastest question and explain how it works.
Most of the pulser are square wave because it is easier to achieve technically. The pulse duration has to be low compared to the working period of the transducer and so it can be assumed that you excite your transducer with a Diras impulse. Doing that you have the impulse response of the transducer as an output (it is the signal used for time arrival determination for exemple).
As said by Michael Foegelle, the most important thing to see is the fourier transform of the excitation.. So if the duration of the excitation is not negligible, the transducer response is not exactly the same with a square signal than with a sine signal. Typically, the square signal will contain several harmonics.
The frequency response of your system can change according to your medium if you are in contact with due to the mechanical load which change the boundary conditions of your transducers.
The velocity can also change according to frequency (in reality it is always the case in my knowledge).
Hope it helps,
Bustillo julien
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VOTE
Hi,
I will begin by the lastest question and explain how it works.
Most of the pulser are square wave because it is easier to achieve technically. The pulse duration has to be low compared to the working period of the transducer and so it can be assumed that you excite your transducer with a Diras impulse. Doing that you have the impulse response of the transducer as an output (it is the signal used for time arrival determination for exemple).
As said by Michael Foegelle, the most important thing to see is the fourier transform of the excitation.. So if the duration of the excitation is not negligible, the transducer response is not exactly the same with a square signal than with a sine signal. Typically, the square signal will contain several harmonics.
The frequency response of your system can change according to your medium if you are in contact with due to the mechanical load which change the boundary conditions of your transducers.
The velocity can also change according to frequency (in reality it is always the case in my knowledge).
Hope it helps,
Bustillo julien
Hi,
I will begin by the lastest question and explain how it works.
Most of the pulser are square wave because it is easier to achieve technically. The pulse duration has to be low compared to the working period of the transducer and so it can be assumed that you excite your transducer with a Diras impulse. Doing that you have the impulse response of the transducer as an output (it is the signal used for time arrival determination for exemple).
As said by Michael Foegelle, the most important thing to see is the fourier transform of the excitation.. So if the duration of the excitation is not negligible, the transducer response is not exactly the same with a square signal than with a sine signal. Typically, the square signal will contain several harmonics.
The frequency response of your system can change according to your medium if you are in contact with due to the mechanical load which change the boundary conditions of your transducers.
The velocity can also change according to frequency (in reality it is always the case in my knowledge).
Hope it helps,
Bustillo julien
More
VOTE
Ultrasound waves propagates in solid by either longitudinal waves or transverse waves. The first type is called also the compression waves in which the molecules of the materials are displaced in the direction of the propagation making alternate compression and expansive of the material. In the transverse wave the molecules of the materials moves in a plane perpendicular to the propagation direction. And so it is a sheer wave which depends only on the sheer coefficient of the material.
If the speed of the wave is equal to the speed of the energy which means that the phase velocity is equal to the group velocity, then the speed will not depend on the frequency otherwise it will depend on and in this case the material will be dispersive meaning the the velocity changes with the frequency of the wave.
The wave equation can be written in the form:
x(t) = A sin(wt - 2 pi x/lambda),
where w is the frequency of the wave, lambda the wavelength and A is the amplitude of the displacement of the molecules from their rest position.
So the elementary wave is sinusoidal wave.
When we can hear it it will be a single tone like the sound emitted by a vibrating fork.
I will speak in the next post about the different excitation waveforms.
Best wishes
Ultrasound waves propagates in solid by either longitudinal waves or transverse waves. The first type is called also the compression waves in which the molecules of the materials are displaced in the direction of the propagation making alternate compression and expansive of the material. In the transverse wave the molecules of the materials moves in a plane perpendicular to the propagation direction. And so it is a sheer wave which depends only on the sheer coefficient of the material.
If the speed of the wave is equal to the speed of the energy which means that the phase velocity is equal to the group velocity, then the speed will not depend on the frequency otherwise it will depend on and in this case the material will be dispersive meaning the the velocity changes with the frequency of the wave.
The wave equation can be written in the form:
x(t) = A sin(wt - 2 pi x/lambda),
where w is the frequency of the wave, lambda the wavelength and A is the amplitude of the displacement of the molecules from their rest position.
So the elementary wave is sinusoidal wave.
When we can hear it it will be a single tone like the sound emitted by a vibrating fork.
I will speak in the next post about the different excitation waveforms.
Best wishes
More
VOTE
Ok, so there are a number of disparate questions here as you've laid it out. So first off, sound propagating through a solid (unlike through air) can be either a compression wave (like air) or a transverse wave (like flicking a rope) or some combination thereof. A surface acoustic wave is actually a superposition of both with atoms moving elliptically with different rotation orientations depending on their proximity to the surface.
Now, from the context of your other statements, I'm not sure that's what you're really asking. It sounds like you're talking about dispersion, which can certainly happen. However, I think what you're referring to as far as the impulse corresponds to the envelope of the impulse, not the actual frequency dependence. Going back to the work we did in magnetacoustics, the traditional way of exciting a bulk wave was to hit a transducer with a Gaussian shaped pulse of the resonant frequency of the transducer. That could also have been a rectangular pulse, but the frequency content would still be primarily the resonant frequency (e.g. 30 MHz). Note that that is far different from hitting the crystal with a single voltage pulse, rectangular or Gaussian, that would induce all sorts of frequencies based on the Fourier content of the pulse. However, the transducer probably would basically ignore most of that frequency content anyway.
At any rate, you would need to look at the Fourier content of the impulse you use to determine what spectral content actually hits the transducer. Even the square pulse of a single frequency has higher order content due to the ends. The Gaussian envelope helps reduce that.
Interestingly, talking about Fourier transforms, we eventually replaced all the complicated analog pulse forming hardware with a vector network analyzer that could take a narrow band frequency sweep and then transform that to the time domain to obtain the impulse response of the output. That allowed gating out the RF coupling from the much slower propagation through the crystal to get the acoustic component.
Ok, so there are a number of disparate questions here as you've laid it out. So first off, sound propagating through a solid (unlike through air) can be either a compression wave (like air) or a transverse wave (like flicking a rope) or some combination thereof. A surface acoustic wave is actually a superposition of both with atoms moving elliptically with different rotation orientations depending on their proximity to the surface.
Now, from the context of your other statements, I'm not sure that's what you're really asking. It sounds like you're talking about dispersion, which can certainly happen. However, I think what you're referring to as far as the impulse corresponds to the envelope of the impulse, not the actual frequency dependence. Going back to the work we did in magnetacoustics, the traditional way of exciting a bulk wave was to hit a transducer with a Gaussian shaped pulse of the resonant frequency of the transducer. That could also have been a rectangular pulse, but the frequency content would still be primarily the resonant frequency (e.g. 30 MHz). Note that that is far different from hitting the crystal with a single voltage pulse, rectangular or Gaussian, that would induce all sorts of frequencies based on the Fourier content of the pulse. However, the transducer probably would basically ignore most of that frequency content anyway.
At any rate, you would need to look at the Fourier content of the impulse you use to determine what spectral content actually hits the transducer. Even the square pulse of a single frequency has higher order content due to the ends. The Gaussian envelope helps reduce that.
Interestingly, talking about Fourier transforms, we eventually replaced all the complicated analog pulse forming hardware with a vector network analyzer that could take a narrow band frequency sweep and then transform that to the time domain to obtain the impulse response of the output. That allowed gating out the RF coupling from the much slower propagation through the crystal to get the acoustic component.
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Thank you!
Thank you!
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Michael Foegelle
Thank you Michael Foegelle sir, i will think further and discuss again
Michael Foegelle
Thank you Michael Foegelle sir, i will think further and discuss again
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Sir,
1- Is it possible to tune the onset temperature(Ts) of a conventional superconductor(BCS superconductor) by sending an ultrasonic wave in it?
2- Similarly the materials having a spin phonon or spin lattice coupling(Like any type 2 multiferroic ), is it possible to tune the magnetic property or dielectric property of this kind of material by sending an ultrasonic wave of certain magnitude in this materials?
Sir,
1- Is it possible to tune the onset temperature(Ts) of a conventional superconductor(BCS superconductor) by sending an ultrasonic wave in it?
2- Similarly the materials having a spin phonon or spin lattice coupling(Like any type 2 multiferroic ), is it possible to tune the magnetic property or dielectric property of this kind of material by sending an ultrasonic wave of certain magnitude in this materials?
More
VOTE
Vasily Baynak there are a complete information here Thesis Diseño De Un Prototipo Para La Medición De Espesores Usando ...
Vasily Baynak there are a complete information here Thesis Diseño De Un Prototipo Para La Medición De Espesores Usando ...
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Let us talk about the normal beam to the soft tissue.
Every soft tissue has an impedance.
When we go from one soft tissue to another Z changes.
Part of the beam will be transmitted and part will reflected.
Using this model we can use transmission line equations.
Let us talk about the normal beam to the soft tissue.
Every soft tissue has an impedance.
When we go from one soft tissue to another Z changes.
Part of the beam will be transmitted and part will reflected.
Using this model we can use transmission line equations.
More
VOTE
Ok, so there are a number of disparate questions here as you've laid it out. So first off, sound propagating through a solid (unlike through air) can be either a compression wave (like air) or a transverse wave (like flicking a rope) or some combination thereof. A surface acoustic wave is actually a superposition of both with atoms moving elliptically with different rotation orientations depending on their proximity to the surface.
Now, from the context of your other statements, I'm not sure that's what you're really asking. It sounds like you're talking about dispersion, which can certainly happen. However, I think what you're referring to as far as the impulse corresponds to the envelope of the impulse, not the actual frequency dependence. Going back to the work we did in magnetacoustics, the traditional way of exciting a bulk wave was to hit a transducer with a Gaussian shaped pulse of the resonant frequency of the transducer. That could also have been a rectangular pulse, but the frequency content would still be primarily the resonant frequency (e.g. 30 MHz). Note that that is far different from hitting the crystal with a single voltage pulse, rectangular or Gaussian, that would induce all sorts of frequencies based on the Fourier content of the pulse. However, the transducer probably would basically ignore most of that frequency content anyway.
At any rate, you would need to look at the Fourier content of the impulse you use to determine what spectral content actually hits the transducer. Even the square pulse of a single frequency has higher order content due to the ends. The Gaussian envelope helps reduce that.
Interestingly, talking about Fourier transforms, we eventually replaced all the complicated analog pulse forming hardware with a vector network analyzer that could take a narrow band frequency sweep and then transform that to the time domain to obtain the impulse response of the output. That allowed gating out the RF coupling from the much slower propagation through the crystal to get the acoustic component.
Ok, so there are a number of disparate questions here as you've laid it out. So first off, sound propagating through a solid (unlike through air) can be either a compression wave (like air) or a transverse wave (like flicking a rope) or some combination thereof. A surface acoustic wave is actually a superposition of both with atoms moving elliptically with different rotation orientations depending on their proximity to the surface.
Now, from the context of your other statements, I'm not sure that's what you're really asking. It sounds like you're talking about dispersion, which can certainly happen. However, I think what you're referring to as far as the impulse corresponds to the envelope of the impulse, not the actual frequency dependence. Going back to the work we did in magnetacoustics, the traditional way of exciting a bulk wave was to hit a transducer with a Gaussian shaped pulse of the resonant frequency of the transducer. That could also have been a rectangular pulse, but the frequency content would still be primarily the resonant frequency (e.g. 30 MHz). Note that that is far different from hitting the crystal with a single voltage pulse, rectangular or Gaussian, that would induce all sorts of frequencies based on the Fourier content of the pulse. However, the transducer probably would basically ignore most of that frequency content anyway.
At any rate, you would need to look at the Fourier content of the impulse you use to determine what spectral content actually hits the transducer. Even the square pulse of a single frequency has higher order content due to the ends. The Gaussian envelope helps reduce that.
Interestingly, talking about Fourier transforms, we eventually replaced all the complicated analog pulse forming hardware with a vector network analyzer that could take a narrow band frequency sweep and then transform that to the time domain to obtain the impulse response of the output. That allowed gating out the RF coupling from the much slower propagation through the crystal to get the acoustic component.
More
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Interesting questions Biswajit, although you might want to start your own thread on this.
I'm rusty on this since it's been a long time since my graduate research days when I was working in this area, but if I had to take a guess on 1, I'd say possibly, but probably only in the down direction. As I recall, BCS superconductors operate on electron/phonon interactions, but I'm not sure if a coherent phonon (your acoustic wave) could be made to enhance superconductivity, or would just be seen as a source of heat, thereby artificially raising the temperature. In the strictest sense, of course, the onset temperature wouldn't have changed then, since the localized temperature (i.e. the actual vibration of the lattice) would be higher than the ambient.
On 2, that's an interesting thought, but it seems to me that since the distortion of the lattice would be very localized and temporary (not to mention, generally very small on any scale that was likely to affect bulk magnetic or dielectric properties) that the net effect would likely be zero. On a related note, it would seem that a good place to start to look for this sort of effect (if it hasn't already been done) would be to test a sample under varied static pressure. If it's possible to alter those properties by squeezing the sample to force the atoms closer together, then an acoustic wave that distorts the lattice might introduce some of the same effect. Again, it seems like you'd need a pretty significant distortion to impact the bulk properties of the material, but who knows? Maybe since the coupling is localized, it only matters what's happening at the interaction site. It still feels like the average effect would be zero.
On the other hand, if you had a 1D superconductor and could make the ultrasonic phonon coherent with that interaction, then maybe. Of course since 1D superconductors theoretically don't exist, then you have to ask what you might be able to do to a 2D superconductor. The interesting thing is that you now have several degrees of freedom to evaluate using both compression and transverse waves either normal to or parallel to the plane of superconductivity. There could be some interesting effects there. I know that when I was completing my graduate work on the magnetoacoustic effect (an old method for calipering the Fermi surface on pure metal crystals), a professor in the neighboring lab was interested in trying out the technique on the then new high Tc superconductors he was working on, but I don't know that anything ever came of it. Last time I visited, our monster variable electromagnet was still there, but I don't believe it'd been touched since I left.
Oh well, enough rambling on a topic that I'm far from expert on these days. Just applying a bit of analytical thinking to the ideas you've raised. Time to get back to my day job!
Thanks,
Michael
Interesting questions Biswajit, although you might want to start your own thread on this.
I'm rusty on this since it's been a long time since my graduate research days when I was working in this area, but if I had to take a guess on 1, I'd say possibly, but probably only in the down direction. As I recall, BCS superconductors operate on electron/phonon interactions, but I'm not sure if a coherent phonon (your acoustic wave) could be made to enhance superconductivity, or would just be seen as a source of heat, thereby artificially raising the temperature. In the strictest sense, of course, the onset temperature wouldn't have changed then, since the localized temperature (i.e. the actual vibration of the lattice) would be higher than the ambient.
On 2, that's an interesting thought, but it seems to me that since the distortion of the lattice would be very localized and temporary (not to mention, generally very small on any scale that was likely to affect bulk magnetic or dielectric properties) that the net effect would likely be zero. On a related note, it would seem that a good place to start to look for this sort of effect (if it hasn't already been done) would be to test a sample under varied static pressure. If it's possible to alter those properties by squeezing the sample to force the atoms closer together, then an acoustic wave that distorts the lattice might introduce some of the same effect. Again, it seems like you'd need a pretty significant distortion to impact the bulk properties of the material, but who knows? Maybe since the coupling is localized, it only matters what's happening at the interaction site. It still feels like the average effect would be zero.
On the other hand, if you had a 1D superconductor and could make the ultrasonic phonon coherent with that interaction, then maybe. Of course since 1D superconductors theoretically don't exist, then you have to ask what you might be able to do to a 2D superconductor. The interesting thing is that you now have several degrees of freedom to evaluate using both compression and transverse waves either normal to or parallel to the plane of superconductivity. There could be some interesting effects there. I know that when I was completing my graduate work on the magnetoacoustic effect (an old method for calipering the Fermi surface on pure metal crystals), a professor in the neighboring lab was interested in trying out the technique on the then new high Tc superconductors he was working on, but I don't know that anything ever came of it. Last time I visited, our monster variable electromagnet was still there, but I don't believe it'd been touched since I left.
Oh well, enough rambling on a topic that I'm far from expert on these days. Just applying a bit of analytical thinking to the ideas you've raised. Time to get back to my day job!
Thanks,
Michael
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