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# Physics - Science topic

Physics related research discussions
Questions related to Physics
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In my early education I was taught radioactive decay was - in general - not affected by environmental variables. This seems to have been disputed in recent years. I'm curious about the current state of the debate. Are there good reasons to think radioactive decay rates are affected by environmental variables?
Yes
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A small eccentric motor vibrates on a floor supported by a single rod. Changing the voltage applied to motor the rpm frequency changes. Still why the frequency of whole system remains constant even if system is considered steady state response? I conducted an experiment and found the frequency remains constant for whatever voltage I choose for the motor. Shouldn't the forced frequency be equal to the frequency of oscillation of system. I also changed the rod dimensions but the frequency of system changed but remained constant for whatever voltage I used.
The frequency of the system is a constant because it is essentially the square root of stiffness divided by mass with some variation due to boundary conditions. As long as these remain constant, so will the frequency. The rotational frequency is different and, as you have observed, changes with the frequency of the electrical supply.
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Every metal has its own work function. if several metals are used in multilayer structures such as [Co/Ni] multilayer what will be the effect of the work function of the electrode? Can these multilayer structures change the individual workfunction?
Peres, L., A. Bou, C. Cornille, Damien Barakel, and P. Torchio. "Work function measurement of multilayer electrodes using Kelvin probe force microscopy." Journal of Physics D: Applied Physics 50, no. 13 (2017): 13LT01.
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Is is possible to find out if a material can function as a cathode or anode by just looking at cyclic voltammetry.
Hi Lokesh,
Can I ask more about your goals with this project? You can in principle get almost any conductive material to act as either a cathode or an anode based on the potential you apply to that material, so long as you have a counter electrode to facilitate the closure of the circuit. The question is how good of an anode or cathode your material is, and that will largely depend on what reaction you want to occur within that material or at its surface.
To give a concrete example - and sorry here if I am using a different sign convention (these things can be tricky, but I come from a U.S. Chemical Engineering background): if I apply a cathodic (negative/reductive) potential to a platinum electrode in a conductive aqueous solution, I'll drive a net cathodic/reductive reaction (such as hydrogen evolution). If I apply an anodic (positive/oxidative) potential to that same platinum electrode in that same aqueous solution, I'll drive a net anodic/oxidative reaction (such as oxygen evolution). And if I have two platinum electrodes in the system at the same time, then one can act as a counter to the other; one will drive hydrogen evolution, and the other, oxygen evolution. There is nothing different about the electrodes or the solutions they are in, except the fact that I am controlling the relative potentials of the electrodes through the input of energy into a potentiostat (or similar device). Note: this is an electrolytic example, but I'm happy to discuss things from a galvanic cell perspective if that is more useful.
Best wishes,
Kindle
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What is the best way to teach physics? And what methodology could be adopted? Share your opinion or experience so that we can enhance our teaching whether in the classroom or even in the daily life of our social relationships.
To teach only distinguished students by any way even if you are failing Teacher. Such students are independents
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Hi,
I am trying to measure resistivity/conductivity across a diamond shaped conductor with small extrusion so this is an irregular shape conductor. I am trying to find the geometrical effect on the shape of conductor.
Resistance = (Resistivity*Length)/Area (1)
This formula works very well for a uniformed section. e.g. a cube of (L=B=H=10 mm )of Copper
my results verifies my analytical calculation.
if I add a small extrusion(L:2mm B:2mm H:2 mm)to a Copper conductor (L:10mm B:10mm H:2 mm) and apply a small voltage through that extrusion.
analytically the Area of cross section should be the area of extrusion.(2X2= 4mm^2)
But the LS Dyna simulation results doesn't match this time with the analytical value.
I have kept all condition same.
Then I tried by taking the entire area of conductor (not just the extrusion) as the area of cross section of (10X2= 20mm^2)
The two sections have different area of cross section therefore current
injection will be spread outward in the section. In series circuit, current is same throughout
and the Voltage is a scalar potential. We impose a voltage at the inlet. Same as case1. For the
Case 1 our Equivalent Resistance was same as the Circuit Resistance. The Change in Geometry
Resistance is calculated using eqn (1) with 2 conductor in series. We have current injected through A1 which
then enters our model through A2. The A2 theoretically is same as A1. However, the results of
the LS dyna show a big margin of error when A1=A2, whereas the results give a good
approximation when the A2 is taken as Equivalent Area with the width of the section taken as
the entire width of 10 mm instead of 2 mm
Analytical and Simulation difference in value of current, due to difference.
I am stuck at this basic problem, Refer to the image for understanding the 2 cases.
help will be appreciated.
Dear Abin Alex,
It's a very very important question related to engineering and technology.
The basic idea lies in Physics.
We know the measurement procedure of resistivity of any arbitrary shape of two dimensional object by Van der Pow method.
But , for three dimensional object , I am also trying to find a solution of Calculation of the resistance.
I tried to calculate the resistance of a solid sphere between two diagonally opposite points. But it's so lengthy process.
I am not satisfied. For the any two corner point of a cube, I don't find any solution.
Thanks
N Das
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By dynamical systems, I mean systems that can be modeled by ODEs.
For linear ODEs, we can investigate the stability by eigenvalues, and for nonlinear systems as well as linear systems we can use the Lyapunov stability theory.
I want to know is there any other method to investigate the stability of dynamical systems?
An alternative method of demonstrating stability is given by Vasile Mihai POPOV, a great scientist of Romanian origin, who settled in the USA.
The theory of hyperstability (it has been renamed the theory of stability for positive systems) belongs exclusively to him ... (1965).
See Yakubovic-Kalman-Popov theorem, Popov-Belevitch-Hautus criterion, etc.
If the Liapunov (1892) method involves "guessing the optimal construction" of the Liapunov function to obtain a domain close to the maximum stability domain, Popov's stability criterion provides the maximum stability domain for nonlinearity parameters in the system (see Hurwitz , Aizerman hypothesis, etc.).
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What are different coil shapes used in Transcranial Magnetic Stimulation? What are their differences (in induced current)? Do they have different applications?
Hi,
Actually, the influence of inductance value in a coil on TMS is eddy current strength. In addition, the coil design in physical configuration can affect the TMS distribution or depth. The TMS coil with eight shapes is commonly used in clinical application due to better high resolution than the round coil.
You can refer to the article below. Good luck!
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I am just asking the norms in the academic community where many review papers are being also published as book chapters with very little changes. Is it ethical or not.
I don't think that is appropriate and it is against the scientific ethics.
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As you know, a time crystal shows oscillations with a period longer than the driving force. Is it possible to use this feature in molecular machine synthesis? Does this provide any advantages to molecular machines?
Thank you so much for pointing out the article, Dear Cüneyt Altındaş.
I see that it is related to a time symmetry breaking state and that there were two possibilities, classical and quantum time crystals.
I will try to understand the idea of the classical time crystal. The authors point out two simple hamiltonians, with broke spatial and inversion symmetry. They find some lagrangians that would be interesting to compare to the lagrangian of isotropic crystals.
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The very common experiment in optics to demonstrate that light behaves same as the wave is single-slit diffraction.
If we assume that the thickness of the barriers is 0.1 mm, then the length of a slot along the optical axis will be a long route as a green photon will measure it nearly two hundred times larger than its own size.
Now the question is how the photon behaves along with that long route? Does it behave as a particle or wave? If the exit of the slot or a pinhole is causing photon behaves as a wave then why the entrance wouldn't do that? And if we accept that photon behaves like a wave as it enters the single slit or the pinhole, then formally we should apply the Fresnel diffraction equation from the entry of the slot that will lead us to nowhere.
In my opinion, wave-particle duality is leading us solely to some useful approximation but it doesn't talk about reality, as it cannot explain a sort of experiments that unfortunately have been ignored or left behind such as the glory of the shadow, and also the stretching the shadows when they meet each other and so on.
For sure, wave-particle duality is not the end of science and for sure five hundred years later people will not consider the existence as do we do now the same as us that we don't see the things same as our ancestors, so we should be open-minded to be able to open the new horizons.
Natalia S Duxbury > “Particle is a real physical object. But what is the wave made of???? Wave function is a mathematical construction”.
Very well said, could not agree more! Theoretical physics for the last (more than) hundred years and specially since Albert Einstein has been an enormous waste in terms of human, natural and economic resources and most of all at the heavy cost of intellectual advance of humanity.
The truth is that formally trained modern theoretical physicists unwittingly follow a philosophy/epistemology (a branch of knowledge that they routinely disparage!), namely Kantianism that has already been discredited long ago by G.W.F. Hegel, the worthy protégé of Kant himself! Modern theoretical “physicists” - following Einstein, are not concerned with knowing objective reality as it is in-itself (ontology), but only with the subjective data (epistemology) they can gather about it; so in actual sense they are trying to understand the working of their own minds, rather than external reality!
The Kantian premise is that objective reality is a messy, chaotic, unwieldy and unknowable thing-in-itself; because it does not follow the pristine precincts of good old commonsense, causality, formal logic and the notions of rationality that have been developed by philosophers starting from the early Greeks. The only thing man can do (Kant posited) is to use his sense perceptions, experimental data, his thought, imagination, fantasy or whatever subjective data he can gather about the objective reality to get on with life. What man at best can do, is to organize this data through his subjective thought, mental tools, logical schemata, mathematical (geometrical, algebraic, symmetry) structures and representations, logical categories, theories etc. to get as much of an “understanding” of objective reality as possible, to deal with it comfortably! A good theory is the one that can cover as much of this data, as well as future possible ones (predictability). This is what is historically known as scholasticism - an endless debate to justify one's subjective choice from various theories; but there is no way to judge who is right, except the power of individual’s proficiency in debating skills!
After the quantum phenomena, the Kantian view of the world became a "self-evident truth" for natural science, if there was any doubt about it before, at all. Theoretical physics led by Albert Einstein embraced the Kantian view of the world whole heartedly and universally and like Moses led an Exodus of the physicists to the promised land of thought and mathematics - his "Castle in the Air", as we see now. According to the Kantian view, objective reality is like an invisible Cheshire cat, which remains unknown, we only deal with the “smile” of the cat that we can perceive through our sense perceptions and process through our subjective mental tools.
From a materialist dialectical world view (that I subscribe to) the quantum phenomena is the most fundamental aspect of objective reality, which abolishes “spacetime” or any other esoteric “fields". All forces are mediated by the exchange of virtual particles. The virtual particles become real particles if enough energy equivalence of their mass is available. Light at all wavelengths are particles that can propagate as wave. Please see the following articles and other related publications, questions and comments in my RG profile:
Ambartsumian, Arp and the Breeding Galaxies:
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As human population expand, our greed too. Growth in electricity network, causing substantially damage to bird’s population, like mostly collision with electricity line. as per my knowledge, there are two ways to prevent death from electricity, like if it is high or medium power voltage lines, then we made underground line, and if it is low voltage line then we do insulation of line, but it is much expensive and laborious. So, is there any other methods or interdisciplinary approach to avoid death of birds?
Mostly medium to large size birds face obstacle during flight like Crane sp, Bustard, peafowl, Flamingo etc
Rubén Barone thank you for sharing information, i would like to read more about it.
Thank you very much
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Indeed, I have observed that there is some scientific journals that listed in Scopus sources of not good quality from scientific point of view. At the same time some Universities are depending on Scoups in a similar manner to that of Thomson & Routers or Clarivate analytics.
LanguagesEnglishAccessProvidersElsevierCostSubscriptionCoverageDisciplinesLife sciences; social sciences; physical sciences; health sciencesTemporal coverage2004–presentGeospatial coverageWorldwideNo. of records69 millionLinks
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Was Aristotle actually wrong when he stated: "Objects fall at a speed that is proportional to their weight. In other words, if you took a wooden object and a metal object of the same size and dropped them both, the heavier metal object would fall at a proportionally faster speed ". Or is it that he was smart enough to combine all the physical forces and give a sum up image of what would happen?!!
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Currently designing power system for Lunar rover. Solar power and RTG are the planned power sources during sunlit periods however secondary Li-ion batteries will be used to operate in PSR's, these will of course rely on solar power to recharge as the RTG produces only 30We. By calculation the batteries should take around 3-5hrs to recharge however I'm concerned about the power required to do this? Simply, P=IV and so if the 60Ah 28V battery has a 7 amp charge current it would require 196W (7*28). This seems high but I can't seem to justify another method of calculating this??
I also ask for advice on how to distribute the batteries throughout the rover? Fewer large packs with high Ah ratings or smaller packs but more of them?
Dear Shannon,
I agree with colleagues above to calculate the energy demand for charging a battery with 28 volt, and 60 Ah. It is required to set the depth of charge such that to preserve its lifetime. May be 80 percent for lithium ion batteries are acceptable but you have to review it returning to the data sheets of the battery.
So need to charge the battery for .8x 60= 48 Ah.
The charging time depends on the charging current.
One must be aware there is specific nominal charging current for any battery.
Physically the such battery size is composed fro an assembly of battery cells.
For space it is always advisable to divide them into units which can better handled
and also that may allow a total more nominal charging current.
Such that you charge it in smaller time than the sun shine period.
So the period of charging is dictated by time of sunshine, then it remains to select the battery of the group of batteries that will satisfy the nominal charging current.
The Ah=48= Nominal charging current x sun shine hours. For charging form the PV generator you need to put a controller between the Generator and the battery
to grantee the safe operation of the battery.
For the best charging method of the battery please see the paper:
The needed energy will be more than the stored energy because the charging process efficiency is less than one. So one has to divide the stored energy by the efficiency to get the total required energy from the charging electric generator.
As for the thermal variations, as the battery will be in a container with the electronics the whole container will be thermally regulated to reduce the temperature fluctuations to that can be accommodated by the components.
Best wishes
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One day I heard from a Cosmologist professor that we have worlds with several times at the same time( or multi-time )! This subject makes my mind busy these days! I never saw that professor again. Do we have books about this? What is your opinion? What is the difference between a world without the time or a world with multi-time?
First, it is moot to discuss whether UFOs are real or not. UFO means "unidentified flying object". One may doubt whether some of these objects were really observed. But there are enough reports about cases where there undeniably was some observation but no subsequent identification. So, clearly UFOs existed and continue to exist, but their explanation may be mundane in all cases.
Second, the discussions of the different times that are in use in physics somehow miss the point. Of course, each (pointlike) object with a mass has a proper time and another observer may relate this to some global time by a rate different from one. But that does not change the fact that the dynamics of that object is described by a differential equation that can be formulated using a single independent time variable (and three independent spatial variables). So the "dimensionality of time" is always one, so to speak. (Except in the case of a complex time alluded to above, but that is not connected with any physics, apparently.)
So the interesting question is this: are there cases in physics where the dynamics of an object depends on more than a single time? I don't know of any actual theories in physics setting up such a kind of dynamical equations. In science fiction, there is a situation, where multiple times appear. That would happen, if time travel were possible and the past could be changed. The only way to avoid logical contradictions then (causal loops like the grandfather paradox) would be that when you travel in the past, you arrive in a parallel time line. So time would have two coordinates, one corresponding to the ordinary time and the other describing an "orthogonal" shift in "time" by which a parallel universe would differ from ours. So when you travel to the past you land at a point that is shifted in that orthogonal time (or else you shift orthogonally by landing) and the future of that world, which up to the point in ordinary time where you end up with your time machine would have had the same history as your own, would be open. So you could change things, but the changes would pertain not to the world you came from, but to one shifted in the second time direction. Time would be essentially two-dimensional and time travel to the past would force you to shift you away from the one-dimensional line on which you lived.
But as I said, that is science fiction.
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I'm currently designing solar panels for a lunar rover MSc project. Two options of the solar panel are being considered, 1) The solar cells are directly mounted to the rover body however the maximum space available is around 0.66m2, constraining power production but less mass of mounting/structure supports 2) A panel made up of solar cells is mounted slightly away from the body but in the same orientation, this would allow for a bigger size however increased mass for the construction of the panel and the mount structure. I'm asking for opinions on how to trade these methods off and the typical masses to expect, currently the bare solar masses is below 1kg for sizes around 1m2 and under. Thanks!
welcome,
wish you success in designing and constructing you panel.
I think you can use the a hybrid solution. That is to mount the solar cells on the body of the rover and make an extension aluminum plate which is oxidized to mount on it the rest of required solar cell array.
Since there is no rain then you must can construct the encapsulation from sheets of glass covering the solar cells without cementing them to the cells.
The most important thing that you support the cells protecting them from the environment with the minimum weight and highest strength.
I think you you can satisfy the weight budget of the PV array.
I would like to introduce the encapsulation ideas for terrestrial panels but they will be mounted in desert.
You may find some inspiration in them:
and
Best wishes
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These are all very specific questions related to some lab questions I am supposed to fill out. I was able to do the first part, and know the equation for the Lande factor for the second, but I do not know exactly what the terms are going to be. Secondly, the Doppler question is very confusing to me because the reference material I have does not talk about this at all. Would the equation I want to use be the " full width at half maximum" equation I was able to find on Wikipedia here: https://en.wikipedia.org/wiki/Doppler_broadening? This just seems like the only thing I could find which has terms that I could look up and use from the problem. I have attached the questions for more details on these questions. Thank you.
It is possible experimentally by the ESR or EPR seupts
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physic and engineering properties of sub tropic peat because i want to compare with tropical peat
Dear Dr. Faisal,
The following pdf file of a research paper published in Agricultural and Forest Meteorology (Kandel et al., 2018) may be of some use for your reference on temperate peat soil.
With best regards
P.S. Brahmanand
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Dear all,
I am trying to compute the theoretical efficiency of a photovoltaic cell using the method described in the attached paper, which is based on the classical Shockley and Queisser arguments (available here: )
Part of the calculation involves the efficiency factor n_rec = V_oc / Vg where V_oc is the open circuit voltage and Vg the bandgap voltage (Equation 13).
As a far as I understand, from a physical standpoint n_rec should be smaller than 1, since V_oc cannot be superior to Vg. Nevertheless, I do obtain n_rec values higher than 1 (i.e. V_oc > Vg), when I consider for instance a blackbody emitter at 6000K, a PV cell temperature = 300K, 100% radiative recombinations (f_rec = 1) and a bandgap of 1 eV.
Therefore, I am wondering: is there something wrong with my calculation ? or does the model have some limitation that I am not aware of ?
From a mathematical standpoint, I don't see what enforces V_OC < Vg, would someone be able to explain this?
Thanks a lot for your help!
Dear Quentin,
the open circuit voltage is determined by the difference of the quasi-fermi-levels. Therefrom you can differ the following cases:
- In low doped semiconductors and at low excitation levels you have V_oc/Vg < 1 as expected.
- In degenerated material you have V_oc/Vg >1 because the fermi-level lies within the bands.
- At high excitation levels (excess carrier concentration compares with the equilibrium concentration) the quasi Fermi level shifts into the bands due to the fact that the bands are filled with carriers. In this nonequilibrium case you find V_oc/Vg > 1 too.
With Regard
R. Mitdank
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Dear Sirs,
I think many knows the ideas due to Jules Henri Poincaré that the physics laws can be formally rewriten as a space-time curvature or as new geometry solely without forces. It is because the physics laws and geometry laws only together are verified in the experiment. So we can arbitrary choose the one of them.
Do you know any works, researchers who realized this idea. I understand that it is just fantasy as it is not proved in the experiment for all forces excepting gravitation.
Do you know works where three Newtons laws are rewritten as just space-time curvature or 5D space curvature or the like without FORCES. Kaluzi-Klein theory is only about electricity.
Force, mass, and energy are a parallel set of descriptions of the effects of special relativistic Thomas Precession. All matter and space, and their interactions are described with distance in three dimensions, time, and their derivatives.
Newton's first law of motion is , "Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it."
Yet the concept of motion requires at least two objects, and if there are two objects, then there is always an external force, which is gravitation.
So the idea of rewriting Newton's laws without force (or mass or energy) is good, but it should be extended to incorporate the most basic non-linear effects of motion in space time, which are special relativity and Thomas Precession.
See my article describing the recent discovery of the effects of Thomas Precession the particle and galactic scales.
Article Thomas Precession is the Basis for the Structure of Matter and Space
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I am interested in collaborating with any researcher working on modelling corona virus using fractional derivatives. If you are a researcher or you have a related project, please feel free to let me know if you need someone to collaborate with you on this research study. If you know someone else working on this research project, please share my collaboration interest with him.her. I would be very happy to collaborate on this research project with other researchers worldwide.
Thank you very much Dr. Abdelkader Mohamed Elsayed and Dr., Rashid Nasrolahpour ! I greatly appreciate that!
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At the moment, only the lazy one doesn't investigate high-entropy materials. But what is that?
It is always good to return to the original definition and meaning of the terms.
Entropy is often correlated with the disorder but not always. Entropy is the measure of unknown information. How do we understand this? The trick is to understand what is macrostate and what microstate.
* Macrostate is observable value.
* Microstate usually not.
Unknown are microstates as we can not measure them.
Just an example with a dice, where we can observe microstates. Macrostate is the sum of all values of all thrown dice. The trick is that there are existing many microstates giving one macrostate. Not every macrostate has the same number of microstates.
Macro states with the highest number of associated microstates have logically the highest probability to be observed in the system as far as all microstates have the same probability It leads to the original Boltzmann definition of entropy.
When there are microstates with different probabilities, we just group them together and we get the well-known definition of Boltzmann entropy and similar Shannon entropy
H = - sum(p_i * ln(p_i))
They are the same except for the Boltzmann constant.
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Distribution dominates policy. Resources are injected at a point and distribute across communities. Can the distribution be almost instantaneous as in the heat equation? Do the resources morph and distribute, drawing in the wave equation? Where is stability (cf. Laplace equation)? These seem basic questions of public policy. Yet, the big three rarely feature in scholarship on public policy. Why?
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I was thinking of the fact that as far I know as a 2nd-year undergrad student, Economists always state their inference by taking other things constant or Ceteris Paribus. But in real state everything changes, so can we use the law of relativity or the illusion of time concept of physics and apply it to economics? Please do give your opinion. Thank You!
If I may, I suggest you read "More Heat Than Light" (Mirowski). It's a comparative history of economics and physics. And you can explore the "complexity economics" area, too.
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We know that by drawing a magnet close to a closed circular circuit, a current in the circuit is induced. Why? (I don't mean the mathematical description or the law of Faraday's induction, what is the cause of physics? What causes electrons to move?)
Answer : As the magnet approaches the ring, the distribution of the magnetic field around the ring changes. Changing the distribution of the magnetic field around the ring leads to the generation of an electric field (on the ring plate). This electric field can change the distribution of ring electrons. Changing the electrons of the ring can create an induced potential in the ring circuit. The induced potential generated in the circuit circuit generates the induced electric current in the circuit circuit. (You can track the appropriate calculations from Maxwell's equations (especially the third and fourth equations)) Hope you got the answer right.
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In experiments we only deal with hermitian operators and they are called physical observables. But in quantum theory non-hermitian operators also exist. Are we using them only as a mathematical requirement or is there any other reason for their existence?
Non-hermitian means that the operator does not have its self-adjoint:
T \ne T*
Without a self-adjoint, there is a missing symmetry and unitarity in operations in Hilbert or Banach space. The solutions are therefore complex, and the eigenvalues also. Such eigenvalues have therefore no direct physical meaning, unless they are either scaled by some complex number (see Nimrod Moiseyev works), or the operator is made self-adjoint in a bounded domain where it gives real eigenvalues.
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In physics, we have a number of "fundamental" variables: force, mass, velocity, acceleration, time, position, electric field, spin, charge, etc
How do we know that we have in fact got the most compact set of variables? If we were to examine the physics textbooks of an intelligent alien civilization, could it be they have cleverly set up their system of variables so that they don't need (say) "mass"? Maybe mass is accounted by everything else and is hence redundant? Maybe the aliens have factored mass out of their physics and it is not needed?
Bottom line question: how do we know that each of the physical variables we commonly use are fundamental and not, in fact, redundant?
Has anyone tried to formally prove we have a non-redundant compact set?
Is this even something that is possible to prove? Is it an unprovable question to start with? How do we set about trying to prove it?
Respected D Abbott
Very good question but ans is difficult.
I don't tell anything about aliens.
I just want to tell some thing about mass.
So far as I think is that The Principle of extremum action as the basis principle of natrure.
Action is , you know, actually the world length between two events.
More precisely action is proportional to world length between two events.
The proportionality constant is something called "mass" ( with a negative sign) .
So, if we don't want to consider mass as a variable, we will fail to explain the time evolution of systems of different mass and Physics will not be able to explain the natural events.
Though, for Fields , mass is not the proportionality constant of action because for fields like EM field ,there is no mass.
I don't know whether the time evolution of a massive system can be explained without mass or not.
Thanks and Regards
N Das
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In the age of Covid19, is there a basic conflict between science and superstition in the discipline of medical knowledge? Are there some simple, sensible, robust and reasonable ways to distinguish a scientific statement (or fact) from a superstitious statement?
To stay focused, the topic will concentrate on science versus superstition in the scientific discipline of medicine. We will try our very best to stay focused and not stray off track. it is very easy to wander off message and be all over the map. i will try to summarize the key conclusions from time to time.
In the age of the Corona Virus, there are so many statements out there. The statements may not be scientific. But if they are not scientific, are they false? Are they fake? Are they simply statements based on superstition.
What should we do if people believe in statements that are not based on science? Should we be polite and tolerate their beliefs?
As long as people do not harm others, then from society’s point of view, the fact that people hold non-scientific hypotheses is probably benign. However, the trouble starts when the same people act these beliefs, and then cause harm to others. The question arises: what should society do in this case?
Based on the discussion, there are two assumptions and four categories.
Assumption1: Beliefs cannot be justified or unjustified.
Assumption2: hypotheses can be disproven
Scientific hypotheses that are based on justified facts in natural causation. Or scientific hypotheses have not been disproven (I prefer the negative formulation because we may never be able to prove anything but we are unable to disprove it.)
Since science cannot give a definitive answer, there are many competing answers that merit our attention, and we may not be able to select among them.
Non-scientific hypotheses are unjustified facts that may be “proven” in the future with better evidence and facts.
Pseudo-scientific hypotheses: not sure where these fit in?
Superstitions are unjustified beliefs in supernatural causation.
Joseph Tham, thanks for a thought provoking question. I think we should tolerate and respect beliefs and ideas that are not considered scientific. Our intolerance of such beliefs and ideas could be the result of a lack of understanding of the science behind them. We should therefore subject them to rigorous testing using the scientific method. A practical example is the fact that the World Health Organization has not dismissed out of hand the herbal remedy from Madagascar that is claimed to prevent illness from COVID-19. Instead the remedy is going to be tested using established scientific principles. The null hypothesis can then be rejected or accepted. This is how Indigenous Knowledge Systems contribute to scientific advancement.
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One of the consequences of relativistic physics is the rejection of the well-known concepts of space and time in science, and replacing them with the new concept of Minkowski space-time or simply space-time.
In classical mechanics, the three spatial dimensions in Cartesian coordinates are usually denoted by x, y and z. The dimensional symbol of each is L. Time is represented by t with the dimensional symbol of T.
In relativistic physics x, y and z are still intactly used for the three spatial dimensions, but time is replaced by ct. It means its dimension has changed from T to L. Therefore, this new time is yet another spatial dimension. One thus wonders where and what is time in space-time?
Probably, due to this awkwardness, ct is not commonly used by physicists as the notion for time after more than a century since its introduction and despite the fact that it applies to any object at any speed.
The root of this manipulation of time comes directly from Lorentz transformations equations. But what are the consequences of this change?
We are told that an observer in any inertial reference frame is allowed to consider its own frame to be stationary. However, the space-time concept tells us that if the same observer does not move at all in the same frame, he or she still moves at the new so-called time dimension with the speed of light! In fact, every object which is apparently moving at a constant speed through space is actually moving with the speed of light in space-time, divided partially in time and partially in spatial directions. The difference is that going at the speed of light in the time direction is disassociated with momentum energy but going at the fraction of that speed in the other three dimensions accumulates substantial momentum energy, reaching infinity when approaching the speed of light.
Dear Prof. Ziaedin Shafiei
As a conservative physicist & non-expert in relativity, I would like to answer your question in the following way, as it is elaborated in Landau & Lifschitz classical book: the Classical Theory of Fields. They introduced the idea of the light cone many years ago to described events in space-time in a general way. For them: time is an axis, space is another axis & 1/c the inverse speed of light is the slope of the plot. Hereby, my answer is: t is the time.
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Hi,
I'm attempting to create nonlinear metamaterial structures in comsol and I don't know how to measure second harmonic generation.
How do I measure that frequency x goes into structure and generates frequency 2x ?
Thanks for any help.
Does this work?
One fundamental problem I am facing how to see the frequency components (in ewfd physics, frequency-domain study) in COMSOL other than the excited one( mean by the mode at other frequencies).
A very simple experiment if I take one 500nm width by 30 nm height Si waveguide (2d simulation), and excite it with 193.42 THz at port 1 end, now if I want to see the frequency components at 300 or 200 THz it should appear null or no field components. But how to observe it in COMSOL (the modes or the field components can be seen at 193.42 THz since it's the excited one).
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Einstein, based on his argument in section 6 of 1905 paper, claimed:
“If a unit electric point charge is in motion in an electromagnetic field, the force acting upon it is equal to the electric force which is present at the locality of the charge, and which we ascertain by transformation of the field to a system of co-ordinates at rest relatively to the electrical charge.”
Simply, total electromagnetic forces, acting on a moving charge, claimed to be equal calculated in any inertial reference frame; F’ = F.
Using an example, Feynman, in his lectures, failed to prove that electromagnetic forces are equal if calculated in the two inertial frames suggested by Einstein.
His result was F’ = γ F
Why did Feynman fail? Can you find an example to support Einstein’s claim?
Attached file presents and reviews Feynman’s analysis and calculation.
It is an interesting point Prof. Ziaedin Shafiei
Prof. R. Feynman has some issues about some applications of electromagnetism.
For example: According to Prof. Paulo Roberto Silva, in his famous lectures Prof. Feynman didn´t derive the Drude model for the electrical conductivity. We know that he worked a lot on superconductivity, and in the section called: Tensors chap 31. of 2 Volume Feynman Lectures, he briefly talks about the conductivity tensor j=σ E, but he calls it as tensor of inertia in analogy to the moment of inertia & there he stops to elaborate further. No mention to the Drude model.
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All metaphors are false. But, on restricting this discussion to natural sciences, we hope to use a particular metaphor to clarify important areas in physics and often in dispute by researchers -- also in other areas, including those not a natural science.
The metaphor is that, all one can do in natural sciences is to be a "customer service rep" for someone else's product -- nature.
For example, I did not invent it, and works for billions of years, without halting. I am just the front-end of nature's message, the customer service rep. One can always ask questions and consult the manual, the universe, in case of doubts.
Of course, natural scientists are much more. Some view that our task is to find in all the relative data from phenomena (which is all physics is limited to measure), the absolute, the universally valid, the invariant, that is hidden in them, as Max Planck said first.
But the metaphor above can be useful, especially in other areas, including those not a natural science.
Some "disgruntled customers" (DC), familiar to any well-intentioned customer service rep, remain disgruntled, even when explained that it is not a bug, such that the speed of light is constant to all inertial observers in vacuo, it is a feature of the universe. A feature, not a bug.
When a DC understands, the average DC does not say "thank you", it should be a selfless customer service, good for the soul.
There is also a tendency for a DC to all but hide in silence until all his false answers (in nature, which is the arbiter of falsehoods) are diluted. By RG, or hidden in life. Then, he likely goes back and says it is a new feature, the old bug, that he just invented, and is just "spreading around".
Or, a DC can also repeat a fallacious interpretation, say we never measured it otherwise but locally. Natural science can explain that the Earth moves, the Sun moves, across the galaxy, we launch transmitters beyond the Solar system, and we can see and measure electromagnetism, light, billions of years away, across many galaxies. Then, what is a DC to do?
The average DC understands, but there is always the probability that a DC will name another fallacious argument, ad infinitum if life would physically allow, to deny what could be simply explained, it is not a bug, the DC bug -- it is a supposed feature.
It is a good customer service of someone else's product, though, because there is, actually, no DC. The concept of a DC is a mirage, itself a bug.
Everyone counts, DC or not, in the school called life, and even non-cooperation clarifies, inspires selflessness, is cooperation. Everyone cooperates.
Cooperation is a collective effect, producing unexpected efects.
Even those who try their mortal hand and time in life to be contrarian, a DC, just like Humpty-Dumpty, using nursery rhymes as a scholarly principle, trying strategies to get points at RG, get into a cabal to dialogue and create hits in search.
All is a legitimate, defensible, good use of their limited time, in the school of life, even as if, so may seem to them, that there is no future to account for, to earn.
So, a good customer service should handle all cases, sometimes with silence -- The trust that all is fine, there is no disaster in the whole universe, no wars but progress, it is an open-ended universe in harmony with laws we ignore, but feel more and more in the few laws we already know, and find out.
Nature is in no danger by humans. Everything is already solved, we just have to find it.
To help, Nature has many good customer service reps, in what should be done as a selfless customer service, a good task for the soul. And anyone can always ask questions and consult the manual, the universe, in case of doubts.
All: See
Deleted research item The research item mentioned here has been deleted
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The invisible hand was a vivid metaphor for how the market works. No more, no less. It was an attractive metaphor. It was simple and perhaps simplistic. However, people are reading too much into this metaphor, and the misunderstanding has created tremendous confusion.
That's a good question
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My question is Can we attain 50-60 Hz Sound frequency on flowing water through tubes? while in background pump is working or other sounds are there (no noise cancellation).
What happens if we have high crossflow velocity of the water lets say 2 to 3 m/s.
Nice Cotribution Franklin Felber
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Dear Sirs,
Everybody knows plane and spherical wave solutions of Maxwell equations, e.g for decaying plane wave E=E0*exp(-kx)*cos(w(t-x/v)). But seems to me they give the unreal situation that the wave amplitude is nonzero at different points of space at given time moment. Could you advise the experiment or natural phenomenon which produces such a wave in nature?
Maybe we have infinte speed of the EM interaction? Do you know any real solution of Maxwel equations which exists only in one space point at the given time moment? Maybe using delta function? Or maybe there is my mistake?
Nice Dear Joaquin Diaz-alonso
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Is there any matematerial which can reflect right handed circular polarization into Left handed circular polarization or vice versa of the EM waves operating in ultra-wide band?
Any good conductor, e.g. a metal surface, reverses the direction of circular polarization on reflection, for all frequencies for which it is a good conductor.
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What does it actually mean to exist? How is it different from non-existence? How can we be sure if something exists or does not exist? I have made a case that these questions are more fundamental than the usually dubbed first question "Why is there something rather than nothing"? Here is a ready link for which I would appreciate your comments.
Please do feel free to share the link with your colleagues and friends who you think might be interested in this topic.
to have actual being; be:The world exists, whether you like it or not.
to have life or animation; live.
to continue to be or live:Belief in magic still exists.
to have being in a specified place or under certain conditions; be found; occur:Hunger exists in many parts of the world.
to achieve the basic needs of existence, as food and shelter:He's not living, he's merely existing. Dictionary.com
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Hello, fellow researchers, I'm looking for the drivers for a plasma diagnostics instrument. PlasCalc 2000, Originally from Mikropack GmbH , later sold to Ocean Optics, now Ocean Inside. We lost the software disk, contacted Ocean Inside and they told us that the instrument is obsolete and no longer provide software/service. I appreciate your help.
Thanks.
Thank you Dirk Luetzenkirchen-Hecht for your kind suggestion. I will try what I have in an older system.
Regards.
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Dear all. The Normal distribution (or Gaussian) is mostly used in statistics, natural science and engineering. Their importance is linked with the Central Limit Theorem. Is there any ideas how to predict the numbers and parameters of thos Gaussians ? Or any efficient deterministic tool to decompose Gaussian to a finite sum of Gaussian basic functions with parameter estimations ? Thank you in advance.
For Central Limit Theorem, the random variables are not necessarily gaussian but they have to be independent and identically distributed (in classical CLT). They can come from any distribution. Moreover, CLT is an approximation. Do you have a prior knowledge that the resultant gaussian variable is composed using gaussian variables? In that case, using the convolutional properties of normal random variables can give you an idea.
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May I ask a question on thermodynamic? We know that U(V,T) (caloric eq. of state) and S(P,V) (thermodynamic eq of state) can both be derived from thermodynamic potentials (U F G H) and the fundamental relations. However, U(V,T) doesn't hold full thermodynamic info of the system as U(S,V) does, yet S(P,V) also holds full thermodynamic info of the system.
In which step in derivation to get U(T,V) from U(S,V) lost the thermodynamic info? (the derivation is briefly：1.  derive U=TdS+ PdV on V, 2. replace the derivative using Maxwell eq. and 3. finally substitute ideal gas eq or van der waal eq)
Why the similar derivation to get S(P,V) retain full thermodynamic info?
Even if we only have U(T,V), can't we get P using ideal gas eq, then calculate the S by designing  reversible processes from (P0,V0,T0) to (P',V',T')? If we can still get S, why U(T,V) doesn't have full thermodynamic info?
Natural variables for U: S, V, Ni (for simple systems)
Natural variables for S: U, V, Ni (for simple systems)
T is the partial derivative of U with respect to S, maintaining V and Ni constants:
T=(∂U/∂S)V,Ni
If from the fundamental relationship U=U(S,V,N) you replace S by T just by solving for S in T=T(U,S,V,Ni) and substituting in U=U(S,V,N), then, you loose information because you are replacing a variable with a derivative with respect to that variable.
This problem is worked out with the Lengendre transform. If you search on internet, you may find simple examples: how to change y=f(x) to z=g(p), where p is ∂y/∂x=2x, in the two ways, the incorrect one (calculation of p and plain substitution of p by removing x) and the correct one (calculation of p and applying the Legendre transform, z=g(p)=px-f). In fact, because you do not loose information with the Legendre transform, you may go backwards from z to y, which is not possible with the incorrect way.
Therefore, it is a mathematical "trick".
Applying the Legendre transform to U, with respect to T and S, you get a new thermodynamic potential F=U-TS, the Helmholtz energy, whose natural variables are T, V, and Ni. Beware of the minus sign applied to the Legendre transform (i.e., F is not equal to TS-U, but U-TS).
For a system at constant U, V, and Ni, any possible process will maximize S.
For a system at constant S, V, and Ni, any possible process will minimize U, but not F.
For a system at constant T, V, and Ni, any possible process will minimize F, but not U.
The Legendre transform connecting two thermodynamic potentials parallels the Laplace transform connecting the corresponding partition functions.
The Legendre transform is not only employed in Thermodynamics and Statistical Physics, but also in Classical Mechanics and other fields.
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The Riemann zeta function or Euler–Riemann zeta hypothesis is the more challenging and unsolved problem in mathematics. What's the applications in physics and science engineering ? Some research advances to solve it ?
By trying to answer your question I found the following reference with many examples on how the zeta functions (the reference doesn´t call it Riemann z functions) are all related in a natural way to eigenvalues of specific boundary value problems.
In statistical physics Z Riemann function is found in:
1. Deriving the Stefan–Boltzmann law from Planck's law is a very simple application in Black body radiation. (see the reference below, the same chapter, pp 186)
2. Sommerfeld expansion to calculate the thermodynamical properties of normal metals. The entropy, energy & specific heat for a degenerate electron gas. Please, for details of the calculation check: L. Landau and E. Lifshitz, Vol. 6, Statistical Physics, Pergamon 1980, Part I, chapter VI---Solids, #67 pp. 168-171.
3. Bose-Einstein condesante calculations (transition temperature and so on) pp. 180-181 of the same reference. All thermodymical properties of bose gases.
4. Many other applications, see fox example any classical text on math methods for phys.
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Angular shape not spherical
Or
Other than spherical geometry.
All particles are angular. A sphere is a mathematical concept only.
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Movement in musical scores does not have an equation of motion or a calculus of variations.
Is there any other kind of harmonic motion that does not obey Newtonian law?
Of course, frequency is velocity-like but I do not see this in the literature.
I understand that the force field may be uniform so dF = 0, but is it not true there must be a force if movement occurs.
Mechanics. Newton's first axiom says that, in the absence of an external force, a body either is at rest or moves with constant velocity. In fact, this is a statement opposing Aristotle's view that a force is needed to keep a body in motion at any non-zero velocity.
Other than that trivial movment in the absence of a force, one might argue that quantum mechanical zero-point motion is movement without a force.
So there are several places outside music where movement appears without a force. In fact, I doubt the applicability of the same notion of movement as in physics to the "flow of notes". Movement in music is a different concept from that of movement in physics. The same word has different connotations in different fields. I believe, it would be easy to argue that with a similar change of meaning to the word force, you would find that the "flow of notes" does not happen without a force.
There is a tendency of confusing and therefore (often unintentionally) abusing notions having the same name but meaning different things in different contexts. For example, when people speak about energy they gain by meditation, this has nothing to do with an energy that might be describable by a hamiltonian or be subjected to energy conservation.
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Some petroleum and geophysics companies use controlled-source seismology for Mineral Inspection and cavity detection. These methods based on impulsive source controllers such as (dynamite, air gun seismic source, etc.). More efficient techniques use a Seismic vibrator for seismic wave generator such as chirp, sine or square seismic waves.
I wonder if recents detections of Gravitational Waves coming from earth or space using optical interferometry, and how to distinguish between each of them, especially when seismic wave have a same chirp form such as Gravitational Waves?
Example of Seismic Source: http://seismicsource.com/html/index.php
Go to https://gracedb.ligo.org/superevents/public/O3/ You will see lots of candidates, 56 to be exact. Half of them have been rejected. The rejected ones, have shape of gravitational waves but turned out to be noise from other sources, such as cleaning equipment. Many "confirmed" ones were detected only by one detector, such as GW190425 (the only confirmed detection from the 3rd run) or GW170817 ( the only one supposedly with a visual). LIGO mistook different types of noise for grav waves before so nothing can be ruled out.
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Economics struggles with rigour. Development struggles with prejudicial questions. So, why don't we teach our young people social physics? Look at social space as a phenomenon of physics. Deeper economics tried that. But that attempt seems to have ended with Paul Samuelson and his lot. Why? Anyway, it is time for the more complex emerging economies to teach social physics instead of development economics.
Social physics can be incorporated in development economics.
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In the literature, fractal derivatives provide many physical insights and geometrical interpretations, but I am wondering where we can apply this particular derivative appropriately. Please refer me to references or examples because I am very interested to learn more about new derivatives and their applications!! I greatly appreciate all the brilliant efforts in this discussion!!
Thank you very much Dr. P.K. Karmakar !!
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If global warming cannot be resolved by controlling/minimising gas emissions, then extraordinary measures may be the only viable options, one of such ideas is placing a solar shield between the sun and earth at the L1 lagrangian point to obtain a reduction in solar insolation . It may sound crazy, more like science fiction to know that a disk of 2000km in diameter would be necessary to reduce solar radiation reaching earth by 1.7%. I wonder about the sort of stresses that would be experienced by such an enormous body. Also, what sort of materials' properties would be required to withstand the conditions at L1, for example solar radiation, other rays. While it is possible to calculate the disk's orbital velocity around the sun, its angular velocity (around its axis) is difficult to calculate. I would be grateful if those with relevant experience could share their thoughts about how such calculations could be achieved.
The following article is relevant:
This paper presents a novel method of space-based geoengineering which uses the mass of a captured near Earth asteroid to gravitationally anchor a cloud of unprocessed dust in the vicinity of the L1 position to reduce the level of solar insolation at Earth. It has subsequently been shown that a cloud contained within the zero-velocity curve of the largest near Earth asteroid, Ganymed, can lead to an insolation reduction of 6.58% on Earth, which is significantly larger than the 1.7% required to offset a 2 °C increase in mean global temperature. The masses of the next largest near Earth asteroids are found to be too small to achieve the required level of insolation reduction, however, they are significant enough to be used as part of a portfolio of geoengineering schemes.
Cheers
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Hi there
what is the formula of magnetic field force applying on Ferromagnetic material?
can we use the formula of magnetic field applying on magnetic dipoles force to calculate the magnetic field force applying on Ferromagnetic material?
I wasn't sure how to insert Greek characters in RG answers, so my0 stands for the permeability of vacuum = 4 * pi * 10^-7.
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There are many existing publishers that publish high quality books in mathematics, but my question here is: I want some suggestions about publishers who most likely publish books in the field of fractional calculus and fractional differential equations because I am interested in submitting a book proposal for a suggested publisher. Could you please share you information/knowledge about such recommended publishers in this specific field of research in mathematics? I would greatly appreciate your brilliant efforts and time!!
Thank you Dr.
Mila Ilieva
!!
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I need steps for measuring the Fatigue endurance and retention of polarization. I soft. There is no option for these measurement. They have other option like P-E loop, hysteresis, I-V, leakage etc.
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We have a solution with an oxygen concentration of 6.5 ppm. How to Calculate Oxygen Pressure in a Solution Using Oxygen Concentration?
A solution of two ideal gases? in that case the theory for calculating thermodynamical properties in solutions was well elaborated, since molecules do not interact each other in ideas gases and additive properties hold well for the individual components of the mixture.
Please, for a general undestanding of the problem, you could check the book by Acad. L. Landau and E. Lifshitz, Vol. 6, Statistical Physics, Pergamon 1980, Part I, chapter IX---Solutions, #93 Pag. 279.
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I am trying to couple light from Laser with M^2=1, wavelength = 1030nm and beam diameter = 1.3mm. Please suggest a lens for efficient coupling into PCF (say 2um core). As far as I know, I have two options, either to use Aspheric lens or Microscope objective, however, I am not really sure which one would be a best choice. As I understood (Please advice if right or wrong)
For efficient coupling, these points should be considered.
1) N.A of lens should be equal or close to that of fibre (PCF)
2) Lens focus diameter should be equal to core size of the fibre (PCF)
3) Input beam should be parallel to Optical axis (Collimated)
Thanks
Abbas N. regarding your 3 points:
1) There is no need for the lens NA to equal that of the fibre. Usually, coupling will be more efficient if the lens NA exceeds that of the fibre, provided the lens aperture (entrance pupil) is sufficiently large to avoid vignetting the input beam.
2) Coupling is optimised when the beam is focussed to a spot whose field profile matches the field distribution of the fibre mode. Typically, both launch spot and mode profile are approximately Gaussian, and the matching criterion is for the launch spot diameter to equal the mode field diameter.
3) Launching the collimated input beam parallel to the optical axis of the lens which in turn is coincident with the optical axis of the fibre will minimise mode mismatch due to tilt errors and lens aberrations.
More specifically, you specify a beam quality factor M2 = 1, so the beam is close to an ideal Gaussian beam. When focussed by a lens, the radius of the beam waist at 1/e2 intensity, w0, is related to the wavelength, λ, and the divergence half-angle, θ, also at 1/e2 intensity by: θ = M2 λ / π w0
Your collimated input beam width is W=0.65 mm. If the focal length of the lens is f, the radius of the beam at the lens principal plane is W = θ f = f λ / π w0
provided the lens NA > sin θ. https://www.newport.com/n/gaussian-beam-optics
The fibre mode field diameter will be comparable to the fibre core diameter, but need not be identical. The relationship depends on wavelength, and the extent to which the evanescent field extends into the cladding.
If we assume that the beam spot radius is equal to the fibre radius, w0 = a = 1 μm, then we require a lens focal length f = π W w0 / λ = 1.98 mm.
A larger mode field diameter will require a proportionately larger focal length. A 2.8 μm mode field diameter will require a focal length of approximately 2.8 mm. The exact value is not too critical. If the mode field radius is r0, the coupling efficiency (assuming Gaussian profile for both fibre mode and excitation) is:
η = 4 w02 r02 / (w02 + r02)2
A 40% mismatch between launch spot diameter and mode field diameter degrades the theoretical coupling efficiency by only 11% (to 89%).
Regarding the choice between microscope objective and aspheric lens, both are capable of diffraction-limited performance for a monochromatic beam aligned with the optical axis. The microscope objective will be more complex, because it must deliver high resolution imaging over a relatively wide field of view, with illumination comprising a broad range of wavelengths.
The exact focal length of microscope objectives is not always stated. Magnification depends on the distance between objective and eyepiece. Tube lengths of order 160 mm are common, so a crude estimate for high power objectives is focal length f = 160 mm / magnification.
The 60x objective suggested by Suchita Yadav. would have a focal length around 2.7 mm, and would be a reasonable choice, especially if the fibre MFD is larger than 2 μm, but an 80x objective may be better. A 40x objective with 4 mm focal length is probably be too long.
If the microscope objective is optimised for visible wavelengths, there may be some additional losses due to surface reflections at infra-red wavelengths.
Note that a weak supplementary lens can be used to modify the diameter of the beam as it enters the focussing lens, and adjust the spot size for optimum coupling.
Hope this helps.
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Are there any good comprehensive review article on qubits? As in, one that gives a whole summary of all the possible platform and compare their strengths and weaknesses, like trapped ion, superconducting qubits, nuclear spin, quantum dots,etc.
Dear Derek Oh , please take a look at Prof. Daniel Lidar´s page:
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Hello everyone,
I was just wondering what is the conception of an infinite ground plane when it comes to the metamaterials. For example, there are times that you need to use an infinite ground plane and I want to know how it affects the metamaterials' properties at the atomic level or how the electrons interact in the Physics point of view??
Or maybe, what are the interactions between E-fields and H-fields inside the structure??
Any answer would be a huge help...
Tnx
Actually, I'm aware of setting an infinite ground plane in CST, I was just wondering what are the visual ramifications of adding an infinite ground plane to the structure compared to a finite ground plane?!
Regards
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In the theory of relativity the upper bound of velocity is included by using the Lorentz transformation. Therefore the theory of relativity can give no answer to my why question. However, in my preprint I explain why:
In theoretical electrical engineering you learn that the group velocity of electromagnetic waves in wave guides can not exceed c. The reason is the electromagnetic properties of empty space and the group velocity of electromagnetic waves. This is derived without needing the Lorentz transformation.
Dear Colleagues,
This point is treated in electromagnetic wave propagation. The speed is limited by the transfer of energy from the magnetic form to the electric form and vice verse.
It is so that the wave is propagated by when the magnetic field collapses it builds the electric rings in the side space and when the electric rings collapse they build
magnetic rings beside them. This this build and collapse lasts some time then the waves takes time to propagate a specific distance.
Best wishes
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how to spliced different different core size (MFD) fibres ( single mode to graded index multimode). I am trying to splice SMF to GIMF, to fabricate SMF-GIMF-SMF saturable absorber.
Although, I could splice with apparently no power loss (shows 0dB loss). However, splicer shows "Bubble Error", even after several attempts.
note:Please have a look at the photos attached
Thanks
Hi Abbas
I have the same question! I am trying to fabricate SMF-GIMF-SMF structure for sensor application. I tried many times to splice the fibres. I manipulated with different splicer parameters as prefusion time, overlap, arc power and so on, but almost always I got splice with a black vertical line (fig. 1).
Once I got good splice. It happened when I accidentally broke the bad splice and respliced it again. Unfortunately, I could never repeat it.
At fig.2 you can see two spectrums. The blue one corresponds to SMF-GIMF-SMF with both bad splices. The red one corrensponds to SMF-GIMF-SMF that have one good splice. The second spectrum had a much better contrast then the first one. This is due to the fact that the modes in GIMF fibre are more equally coupled to the SMF fiber. Thus, there is a difference between coupling coefficients of modes in GIFM to SMF fibre for the "bad" and "good" splice.
P.S. Abbas, please, let me know if you will find a method, how to splice it without bubbles and black curves!:)
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I am manipulating water vapor data obtained by radiosondeo, according to the manual these are given in units of water vapor mixture ratio (g / kg) but in the article I use this data are used in g / cm **2. I am a beginner in the subject of atmospheric chemistry and do not handle this type of units much.
Radiosondes provide mixing ratios at various pressure levels. These values need to be integrated to obtain the total column value, i.e., total (or integrated) precipitable water in g/cm2. There are a few slightly different integration formulas, which are described in this important report:
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Hi there,
my question concerns a situation in which the law of free fall and the relativity of simultaneity come into play simultaneously.
The general assumptions are as follows:
1. if we let two objects fall at the same time, they will reach the surface at the same time, regardless of their mass (although gravity has a stronger effect on larger masses, inertia is also greater to the same extent).
2. the relativity of simultaneity shows impressively that different observers moving relatively to each other do not have to agree on whether two events really happen at the same time, depending on their reference system.
My question now is, what happens, if we combine both things. A person is standing in a space ship and lets two objects with different masses fall simultaneously through a technical apparatus (atomic clock). In his frame of reference this person has no problem - he sees that both objects arrive at the floor at the same time. But what does an external observer see when the space ship passes? Does he now have the impression that the objects no longer fall onto the surface at the same time, even though the law of free fall implies uniform acceleration? Or must all external observers agree that both objects reach the floor at the same time, because the law of free fall cannot be circumvented? Or is it the case that the external observer could observe that the person in the space ship does not drop the objects at the same time, although the person in the space ship observes that the objects are dropped at the same time?
Simple and straightforward:
If the space separation between the two freely falling objects is very small, then you can regard them as a single extended small object (a string), therefore all observers see the same fall. BUT, if the space separation is finite (noticeable), then what is the simultaneous drop for the spaceship observer, it is not simultaneous for other observers, and so is the free fall! Space separation is the key!
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As the explanation goes, hole is a figment to the absence of electron as it moves to some different energy state as a result of absorption of energy of some kind. That is, I think of holes as voids, which are "said to" have positive charge for the sake of charge neutrality because there once happened to be an electron at that place. But, it doesn't have it's own actual charge like any other physical charged particle (like an electron), right? Then, how can we define an exciton that is based on coulombic forces between an electron (in conduction band) and a hole (valence band), which actually requires presence of two physical charges?
Dear Prof. Saransh Gupta Maybe you find interesting a reading of the following book: Quasiparticles by Prof. M. I. Kaganov, and Academician I. M. Lifzhits.
I was introduced to the topic of quasiparticles many years ago by one of the authors and I find extremely useful to read the book particularly to understand the use of the phenomenological approach of Quasiparticles in Quantum Solid State Theory. Regards.
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Both Matter and Energy is essentially one and the same thing interchangeably but still it differs in this respect that Energy spreads,
Sir Isaac Newton in his book (Principia Mathematica), stated that it is the property of matter to attract and hence gravitational force is the force of attraction.
Can I say in this regard that Energy is responsible for the force of gravity?,
Since Energy following the second law of thermodynamics and moving from higher state to lower state is in motion as it spreads outward and by Newton's laws of Motion:
The movement(referring Newton's first law) is due to a force outwards, possibly due to the second law of thermodynamics,
Then by Newton's third law, there must be a force equal and opposite that contracts.
This might also explain why matter which is in the form of energy does not spread out completely (being interchanged into energy all at once) and hence remains compressed,
Then is it true that Gravitational Force is the opposing force that balances the force of entropy..., Which is but the property of energy.
So can one say that gravitational force is the result of spread of Energy?
Hai Shubham:
The question about inertia would be helpful in getting more understanding of that. Maybe have also considering Newton's laws 3rd, 2nd, & 1st may be more appropriate with physics 3rd law providing the observational aspect that is easy to demonstrate.
Energy & entropy will be coming together with the force definition to moving away from inertia.
Rajan Iyer
ENGINEERINGINC MEDITERRANEAN HELLENIC GLOBAL PLATFORM
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Let us consider two boxes of different energies that are separated by a barrier and box 1 is filled with many electrons. The barrier allows the electrons to tunnel from box 1 to the other side with a 1% probability. In the event that an electron in a given time frame does tunnel through the barrier, does this affect the probability that a different electron teleports through the barrier during the same time frame, or is this probability statistically independent? Therefore in the extreme case, do we know if the probability of ALL electrons tunneling is equal to P(1 electron tunneling)^(Number of electrons). Let us assume that the change in energy due to electrons filling/leaving certain energy levels is negligible.
There are essentially two ways of looking at this issue. One is Juan Weisz's way - totally correctly making use of wave functions and probability densities.
Another way is to look at the physical mechanism whereby quantum tunneling happens. In a nutshell, to tunnel through an energy barrier, a particle must borrow energy from a nearby virtual particle, and relinquish back that energy to the virtual particle within the alloted permissible time frame (as per Heisenberg's relationship linking virtual energy to permissible duration of virtual existence.)
To tunnel, the particle needs not the presence of a suitable virtual particle nearby: by suitable is meant capable of fleetingly lending out the exact right amout of energy needed for the tunneling event to occur. It is, by the way, the exact selfsame mechanism that allows any individual atom of a radioactive element to decay: there is an energy barrier that must be hurdled before decay can occur, and borrowing virtual energy from a suitable nearby virtual particle is what enables overcoming that barrier.)
The amount of energy that must be borrowed depends on the particle or entity (atom, etc.: anything can tunnel) that must tunnel. If the requisite energy is high, then the occurence of matching virtual particles is statistically rarer (which is why some half-lives are long, and some are short.)
If the energy to be borrowed is low, then separate occurences of tunneling remain statistically independent of anything that happens around - as is for instance the case with carbon-8, which needs so very little energy to decay: there are so many low-energy virtual particles popping up all the time within the quantum foam that no interference with the environment occurs.) When however the requisite tunneling or decay energy is high, then suitable matching virtual particles are much rarer (think osmium-186). In that case: an atom of, say, Osmium-186 could conceivably snap up the rare suitable such virtual particle and thus interfere with and prevent another nearby atom from having its chance at decay - until the next nearby suitable virtual particle pops up, and as such statistical independence could not hold.
For any particular particle or atom, the best is to do the calculation. You can extrapolate the statistics of the appearance of suitable-energy virtual particles from the measured values of half times, see e.g. the table at https://en.wikipedia.org/wiki/List_of_radioactive_nuclides_by_half-life
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One remembers, first, that all matter used in anything is constructed of atoms, where atoms are made of particles, where quantum mechanics (QM) physically works.
Any physics, chemistry, engineering, computer science, even mathematics -- where the electrons, light, wave, and number behaviors are determining these fields by Nature -- will obey quantum rules, such as NO "law of the excluded middle" and NO "axiom of choice", and where QM principles play main roles.
One reads, for example, at Stanford U. that: the concepts and techniques of quantum mechanics are essential in many areas of engineering and science such as materials science, nanotechnology, electronic devices, and photonics.
Nominations by participants here (in order of appearance) include:
Superfluidity, superconductivity, HVDC with QM rectification by a thyristor (semiconductor), incandescence, laser, quantum decoherence, entanglement, P-type or N-type semiconductors, transistor radio, and the entire known universe for 13.8 billion years so far.
What is your reasoned opinion? What is your best example of QM having visible effects on microscopic and macroscopic scales?
One thing that comes to mind in regards to your primary question is hydrodynamic quantum analogs. These experiments were done at MIT in July of 2013 published in Physical Review Letters E. Dr. Daniel M. Harris displayed that "a coherent wavelike statistical behavior emerges from the complex underlying dynamics and that the probability distribution is prescribed by the Faraday wave mode of the corral." I hope this helps!
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Saida, If you have a look at a Dieke diagram it'll be apparent to you that the energy states of La are well separated (gs and es) way above its bandgap so no emission line will fall in the visible region. And La doesn't have 4f electrons as the other lanthanide ions do. Also, other emissive lanthanide ions which are often used as emitters, have energy levels that are separated by energies falling in the visible range. However, due to the inner shell configuration of these 4f ions, it's very unlikely that you can directly excite a 4f-4f transition in these- so you'll see little-to-no emission intensity. However, if you have La in the material it can absorb the incident energy and efficiently transfer it to the emitting lanthanide ion in an indirect way. But this energy transfer is strong enough that it populates the emissive states of your lanthanide activator and you'll see the fluorescence occurring from them. That's why you see an increase in luminescence efficiency in the presence of La.
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Lazare Carnot, the father of Sadi Carnot who laid the foundations of thermodynamics with his 1824 monograph on the motive power of heat, authored the 1786 Essai sur les machines en général. Since Sadi Carnot is said to have used some of his father's ideas in his 1824 monograph, for historical reasons (at least) it would be interesting to read the 1824 monograph in view of the 1786 essai. Hence the question: is there an English translation? If so, where?
The 1786 work can be found online at the BnF: Bibliothèque nationale de France.
Scientific papers are useful for their ideas, not the text. In addition, these ideas evolve with time, so it's not useful, for understanding the technical content, to read the earliest papers on the subject. The only reason to read Carnot these days is for the history, not the technical content. Any textbook on thermodynamics will do.
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Hey all
Technical papers or not
Is there one search engine that embraces all the detailed procedures and guidlines for lab scale processes and synthesis methods
Dear Gabris Mahamid, Such a database aggregated and sorted at this stage is being developed. It has not been tested and therefore cannot be seen. The development is of large companies such as: Web of Science, Scopus, Google Scholar and Google Academia, Microsoft Academic, Semantic Scholar and others. There is only a partial finding at this stage of these data companies on specific topics in specific areas. Wishing you success in research. Emil Yankov
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As the "distribution lecturer" from the once cult film "Carnival Night" said: "Is there life on Mars, is there life on Mars - this is unknown to science." 66 years ago, when the Eldar Ryazanov took off his famous tape, any other answer would not give a synod academics. And what does today's science say, and not only about the Red Planet? If you ask the question a bit, are there other residences of life in the Universe?
so it needs a time
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Please explain to me step by step method to calculate the Electron Density of a Low-Temperature Argon DC Glow Discharge Plasma using Optical Emission Spectroscopy.
This laboratory plasma is produced by DC Glow Discharge of
(i) Argon gas
or
(ii) Some other gas mixed with Argon gas
The applied voltage ranges from 300 - 500 volt, whereas the pressure ranges from 0.10 - 0.20 millibar.
I expect my Electron Temperature and Electron Density to be approximate of the order of1 eV and 10^14 - 10^15 per meter cube, respectively.
with your resolution and expected density, it could be borderline. If you are unable to see H-beta, I'd suggest a higher lying line, like H6-H8, see PHYSICAL REVIEW E 75, 016401 (2007)
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While I am looking for academic positions in Canada, they are constantly asking for a research proposal in NSERC format. I never had an experience of making a proposal in that format.
Hence, I am requesting the research community here in to share their proposals. If you want to share with me only, please send it as a message. I will keep it confidential.
Any sample of proposal (awarded/non-awarded) in that format will be great help for me to fasten up and amend my proposal. I am very much grateful if someone can share their sample proposals.