# Physics

5
Which techniques are used for three-dimensional imaging outside the visible light?

Since conventional optics does not always work in the range outside the visible light (UV, IR) , it is very interesting how 3D imaging can be applied in this range.

Can somebody give relevant references?

Hi Vladimir. There is no information structure 'blur' in the phenomenon of vision. No motion blur, no depth of field. There are no pictures in vision. No picture frames and no frames per second. As there are no pictures to call up then there is no binocular fusion going on. We have developed a new form of illusionary space based on perceptual structure not the fundamentals of optics. This is termed Vision-Space instead of picture space. Its spatial saliency is not on the 1,2,3D curve. It's experiential spatial saliency or ExpD! Presentation list attached and articles are on my page.

14
Can you recommend other approaches to describe light propagation except ray propagation approach and wave field propagation?

I want to know, if I have additional options to represent light propagation. Mainly to describe imaging process. Relevant references are welcome. Thank you in advance!

This may or may not be of interest. We have developed a new form of illusionary space called Vision-Space. The space that occurs to us within the phenomenon of vision. This includes a field potential that's set out radially when we either make a fixation or centre it on ourselves. The point being that it has nothing to do with the fundamentals of optics. The irritating thing for physics is that this field structure is generating proximity cues that relate to the real distances between objects and surfaces in the environment. So the field structure is provisioning an implicit form of spatial awareness even on a monocular basis (this is quite wrongly referred to a 'peripheral vision'). Nothing to do with 'depth' perception through occlusion or perspective cues. Vision is actually entirely non-photographically rendered. I attach a list of presentations.  Why is this of interest here? Because this field structure appears to derived from information in noise. We appear to be unfolding a data potential from noise that's emanating from the environment. A form of decoherence at the retina with the pays element being preserved and streamed? A function for rods at photopic levels working with ipRGC on something other than light intensity? Environmental signal in radiance? There are articles on my page. "Having the courage of your perceptions" attempts to cover the physics angle.

6
Is there any software to analyze ftir results?

I have got ftir transmission curve but can not analyze it, can anyone suggest the best way to analyze it with either software or  manual methods related to analysis of ftir curve. The manual analysis should include formulas or tables to justify the results through physics

Libraries always help you for known compound. But if  you synthesize new compound then you should refer to the reference / text books

10
Which important points should be considered in plotting a bifurcation diagram?

When we want to plot a bifurcation diagram for a flow or map, we should consider some important points. Some of them have been mentioned in [1]. For example we should be careful about coexisting attractors, transient behaviors, proper quality of the diagram (resolution, marker size,…), and dealing with more than one bifurcation parameters.
I want to know if there are additional important points that some may encounter during obtaining a bifurcation diagram.
[1] J. C. Sprott, “A proposed standard for the publication of new chaotic systems” Int. J. Bifurcation Chaos, 21, 2391 (2011).

While plotting bifurcation diagram, one should know the range of the parameter to be varied as well as the initial conditions. Stability of fixed points at different parameter values provide necessary knowledge in this regard

18
Do you think that scientific research is more or less efficient now than in 1900's?
In the first half of 1900's (1900-1950) most of modern physics theories and discoveries were achieved (quantum physics, atomic physics, nuclear physics, high energy physics, astrophysics, solid state physics, solid state electronics, microelectroics, integration...) with much less means, equipments and funding than now.

In the second half of 1900's (1950-2000), most of the discoveries were more or less an improvement or a limited innovation with respect to what was already found before 1950. At the same time the funding being put in research are increasing drastically.

Do you agree that there is a decreasing efficiency of scientific research worldwide which started at the end of the 1900's and is more evident in 2000' years?

Following the previous posts I can comment from my experience as Director of scientific organizations, and Director of Research in an industrial international company. Managing research is difficult because it requires to conciliate two, often, contradictory goals : leave as much freedom as possible to the people with sufficient ressources, and get results that can be useful for you or others (the management of patents is a business). One key factor to achieve that is the organization of research around structuring topics, meaning that there is a continuity between projects, and the results which have been obtained by one team can be used by others. This is not only a matter of documentation, publishing papers, but also of concepts that are clearly understood by everybody, of models that can be easily adjusted, or in industry of models which can forecast the results, saving time and money.

I think that even in fundamental research it is important to supply this framework in which all the workers can do their job. However there is the risk that this framework stifles innovation, and the risk is specially high when the framework is ill designed. There are hundreds of interpretations of quantum physics, and a lot of time is wasted just to try to understand what it means...

22
How do we create virtual electrical elements in electronics? Are they really "elements" or circuits?

To build electronic circuits, first of all we need the natural electrical elements resistors, capacitors and inductors. However, in many cases we are not satisfied with the performance of these passive components and try to improve them in an artificial way. For this purpose, in electronics we have been inventing a variety of clever and sophisticated techniques to create artificial (synthetic, virtual) elements. The question is, "How do we make virtual elements?"

Like magicians, in electronics we convert the imperfect passive elements into perfect active "elements" (by applying the virtual ground configuration)... or we transform some element (a capacitor) into its dual (an inductor) by swapping the voltage across and the current through it (gyrators)... or we transmute the passive circuits into their opposite mirror doubles (negative impedance)... or we even create completely new electrical elements (memristors)... Thus, for some reasons, we frequently replace the natural electrical elements by their circuit equivalents - a gyrator, multiplier, memristor, negative resistor (capacitor, inductor...)

It is important to note that all these virtual "elements" (electronic circuits) emulate only particular properties (usually, the time behavior) of the genuine elements... they are not real, they are just an illusion...

Genuine elements. The general property of passive electrical elements is taking (consuming) energy from the input source; resistors dissipate this energy while capacitors and inductors store (accumulate, "steal") it. But how do they do it?

Let's assume the considered passive element is connected in series to the exciting voltage source. What does it do in this case? It subtracts a portion of voltage from the whole input voltage: the resistor "creates" an opposing voltage drop across itself while the capacitor and inductor "create" an opposing voltage (a kind of emf). Resistors do this by throwing out (dissipating) energy while capacitors and inductors do it by taking energy from the excitation source, accumulating it into itself and setting it against the input source. In the first case there is a voltage drop while in the second case there is a voltage (emf).

So, we can emulate these passive elements by replacing them with some other elements producing the same opposing voltage (having an opposite to the input voltage polarity when travelling along the loop). Then, we can modify or even create mirror active (negative) "copies" of these passive elements by replacing them with sources producing the same but now "helping" voltage (having the same as the input voltage polarity when travelling along the loop). This is the main idea of the substitution and inverse substitution theorem perfectly considered by Prof. Lutz von Wangenheim in his work:

* Emulating by (varying) voltage. First, we may replace the original elements by varying voltage sources and this is the most natural way of making emulated capacitors and inductors (as they behave as varying through time voltage sources). Op-amp gyrator, multiplying, memcapacitive and meminductive circuits do it in this way. In these circuits, the op-amp output voltage represents the voltage across the according capacitor or inductor.

In the case of the true negative resistor, the ordinary ohmic resistor is replaced again with a voltage source (exactly as in the case of gyrators and multipliers) but it has the same polarity as the input voltage source so that it adds an additional  voltage to the input voltage. For example, the negative impedance converter with voltage inversion (VNIC) is a dynamic voltage source emulating a negative resistor by adding a voltage that is equal to the voltage drop across a real ohmic resistor.

It is interesting that we can change the properties of the ordinary constant voltage source by  properly varying its voltage (as in the attached picture below).
The emulation by including an additional voltage source is the basis of the Miller theorem (see https://en.wikipedia.org/wiki/Miller_theorem#Applications).

* Emulating by (varying) resistance. But a memristor can do the same by replacing the voltage by an equivalent voltage drop across a dynamic time-dependent resistor. Transistor gyrator and multiplying circuits do it in a similar way.

It is interesting that we can change the properties of the ordinary ohmic resistor by properly varying its resistance. A good example of this technique is the creation of the negative differential resistor:

So, to emulate passive elements (to create virtual elements), we may replace the elements behaving as resistors with (properly varying) resistors, and elements behaving as sources - with (properly varying) sources. But it seems we can do it by swapping these correspondences - replacing the elements behaving as sources with resistors, and elements behaving as resistors with sources... Am I right? Please, discuss.

------------------------

I was inspired to ask this question mainly by the numerous discussions between me and Prof. Lutz von Wangenheim mostly in the questions below...

https://www.researchgate.net/post/Are_electrical_sources_elements_with_static_negative_impedance_If_so_is_there_any_benefit_from_this_concept

https://www.researchgate.net/post/Does_the_op-amp_in_all_the_inverting_circuits_with_negative_feedback_behave_as_a_negative_impedance_element_negative_resistor_capacitor_etc

https://www.researchgate.net/post/Does_the_amplifier_in_negative_feedback_systems_possess_negative_impedance?

...and especially, by his idea about the inverse substitution theorem (IST) proposed by him in the question below:

https://www.researchgate.net/post/Can_we_formulate_Kirchhoffs_laws_for_resistances_KRL_and_conductances_KGL_based_on_KVL_and_KCL/2

Quote: "In basic theory, people talks about the quadripole. But a practitioner will never ask himself if a transistor is a quadripole or not.."

Perhaps he will not ask himself, but he should be aware that he actually is using a quadripole (at latest during applying of feedback).

99+
What is the biggest scientific coincidence that you know?
For me the two more important are:

1. The phase transition liquid-solid for the water is that the solid state is less dense.
2. The dielectric screening in metals is such that the Coulomb interaction among the electrons falls at a distance of the Bohr radius.

The first one has many important applications as the one of allowing the live in rivers during winter or so on. On the other hand, there are also very interesting electric and thermodynamic phase transitions for this material

The second, thanks to have a so local electric interaction it allows to have almost free electrons at quite high electronic density in matter and therefore to apply theories so useful as the bands in solids. Over all in metals

Dear Robin,

I have only reading the abstract of the paper, could I have the rest of the paper? Thank you

3
1. How to make a battery set-up using activated carbon/iron oxide composite powder?

This composite has good capacitance behavior due to it's high surface area. Hence, your suggestion is valuable for me to use these composite in a battery's application.

Dear Rashid & Dear Ceyhun,

Yes, Lithium ion batteries only.

46
Is it possible to neutralize all the positive resistances in a circuit by an equivalent negative resistance?

I have asked this question with two purposes - first, at the request of Barrie Gilbert to terminate the irrelevant discussions in the question below...

https://www.researchgate.net/post/whats_the_real_behavior_of_rc_circuits

... and second, to answer the question of Erik Lindberg asked at the end of this discussion.

In the discussed arrangement (an RC circuit with various leakages), there are three resistances in parallel - R, Rc and Rv, and the equivalent resistance is Re = R||Rc||Rv. My idea is to connect a variable (N-shaped) negative resistor in parallel to Re and begin adjusting its resistance RN. Depending on its value, it will "eat" some part of Re and it will dissapear (become infinite):

1. RN = Rv (Rv is neutralized) or RN = Rc (Rc is neutralized)

2. RN = Rc||Rv (both Rc and Rv are neutralized)

3. RN = Rc||Rv||R (all the positive resistances are neutralized)

In case 2 (a load canceller), I thought we should obtain a perfect exponential shape... and this should solve the leakage problem. The next my idea was that if we continue decreasing this "destroying" negative resistance beyond this point of exact leakage neutralization, it will begin "eating" a part of the positive resistance of the "useful" resistor R... and finally (case 3), it will destroy all the resistance R. This means that the resistor R as though already has an infinite resistance... and behaves as an ideal current source... Actually, this is the idea of the Howland current source and its special case here - Deboo integrator. But while in the classic Deboo integrator the negative resistor (INIC) neutralizes only the positive resistance R, here it neutralizes all the resistances in parallel (the useful R and harmful leakages).

So, my question now is, "What happens if we try to neutralize all the positive resistances by an equivalent negative resistance (case 3)?"

My doubt is that, as a result of this 100% neutralization, this circuit will become unstable, and if the negative resistance begins dominating over the equivalent positive resistance, the effective resistance (the result of the neutralization) would become fully negative. And here, I suppose, the voltage across the capacitor will begin self-increasing in an avalanche like manner... From other side, the reactance of the capacitor C still remains... and it is a kind of a positive "resistance" (impedance)... and it turns out the circuit should remain stable...

The same problem exists in the Wien bridge oscillator... and it is solved there by applying a non-linear negative feedback in the INIC... Maybe it is possible to keep the circuit stable in a similar way?

we are talking for a current mirror with increased output resistance where the regulated cascode is  much better than a simple cascode and the output swing is the same

2
What are the anomalies of water?
Water has density, diffusion, specific heat, compressibility unusual behaviors. Why?

Take a look at these books,

Ben Mustapha, Zied, et al. "Automatic classification of water-leaving radiance anomalies from global SeaWiFS imagery: Application to the detection of phytoplankton groups in open ocean waters." Remote Sensing of Environment 146 (2014): 97-112.

Sun, Chang Q. "Structure order, local potentials, and physical anomalies of water ice." arXiv preprint arXiv:1402.3880 (2014).

10
What is the physical significance of bessel's function in acoustics ?

why is it used in acoustical formulation ?

Physical meaning? Then Bessel function is the base function (or eigen function) to represent your solution in the radial direction for the physical problem.

11
What is the shape of this induced field induced by temporal current variation in a in a coil?

My question is prompted by Problem P. 4263 (May 2010) of the webpage www.komal.hu, which contains physics problems from Hungary (in English).

OK; if that is the case, I consider the question answered. Thanks to you all.

7
Which 3D dissipative chaotic flow has the highest Kaplan–Yorke dimension?

Most of the continuous chaotic systems (chaotic flows) like Lorenz, Rössler, Sprott systems (cases B-S) have a Kaplan–Yorke dimension slightly greater than 2:
1. Is there any 3D dissipative chaotic flow with a Kaplan-Yorke dimension near 3?
2. Which 3D dissipative chaotic flow has the highest Kaplan-Yorke dimension?
Regards,

In a dissipative chaotic flow of 3D system, the highest value of KY dimension is depends on the system. Generaly, KY dimension is changed continuously between 2 to 3 in a 3D ode system.

99+
Why do you think that it is particularly physics the science which seems to show more proclivity to get surrounded by crackpots?
Before answering this post, make yourself sure you are not a quack, else you shall be deleted. Please check:
John Baez crackpot guide http://math.ucr.edu/home/baez/crackpot.html
Siegel's Are you a quack? http://insti.physics.sunysb.edu/~siegel/quack.html

Oh bologna!

18
What are the measures used in different countries to stimulate publication activity?
The main problem of Post-Soviet science is connected with its weak "visibility" that leads to its weak global competitiveness. Very weak growth rates of publication activities of the Post-Soviet countries are noted. In these countries, publication activities of scientists in the journals that are included into the Web of Science and SCOPUS databases are by no means stimulated.
On the SCIMAGO platform, by means of the operator «Compare», I generated graphics on dynamics of publications by Russian and Ukrainian scientists in comparison with the total publication activity in Iran and Turkey (graph).
It is well known that Iran and Turkey implemented stimulating measures aimed at supporting the publication activities of their scientists many years ago. About ten years ago in Turkey a reward of $100 to$300 US dollars was offered for one SCI- publication, depending on the impact factor of the journal. In Iran for one such publication, a reward ranging from 300 to 500 Euros is currently offered by the State University. Besides, they have government grants for the support of such publication activities (up to 20,000 Euros for approximately ten publications). This explains the reason why in 2012 Iran bypasses Russia in total publication activities (graph).
I’m interested in the examples of stimulating measures that are being granted by different countries in the form of publication micro-grants. Generalization of these measures would allow to adapt them for the conditions of Post Soviet countries, where in many fields of knowledge their is absence of publication practice of results of researches in internationally recognized journals.

Instiutional-level cash bonus schemes for publishing in approved journals appear to be far more common than is often realised.

The practice is not confined to the Third World, but documented for individual institutions in European countries such as Austria, Denmark, France,  Italy, Netherlands, and Norway. It is also found in elsewhere, in countries as diverse as the United States, Australia, South Korea, Egypt, Israel and the Philippines.  I have been attempting to assemble information about such institutional policies for a year or two, but it is extremely difficult to get a coherent picture.

I suspect that it will be almost impossible to demonstrate the effectiveness of institutional schemes as they rarely occur in a vacuum.  The same factor applies to national-level schemes. They seem effective enough (within narrow parameters), but correlation does not prove causation.  Countriesoften bring in such reward programs as part of a wider policy package. When such schemes are cut, the context may be a general reduction in funding for higher education.

7
Is there any condition for the wave packets of different particles to interact?

Do the wave packets of different particles interact at all? If yes, What are the different conditions for such interaction and what is the mathematical treatment for them?

It is evident that the question you have raised is far from being trivial.

As I stressed is not well posed, as you can see from the answer you are receiving. From the QM point of view as soon as you define two particles and you add a label to them boson or fermions you define an interaction, implicit in the symmetrization or anti-symmetrization of the initial wave function describing the  evolution of the quantum system. Again the problem is that when you provide the time evolution of a such a system you define a single system not interacting with itself.

The best

Pino

2
Can anyone help with a common cation heterostructures e.g. AB/AC?
In the hybrid microstructures with constituents i.e. AB/AC with a common cation "A". Can anybody help me that how does this common cation "A" would benefit the formation of heterojunction? How would it be useful than the case where there is neither any common anion or common cation?

typically, when we think over making a heterostructure with two mataerials, we need consider lattice and thermal match, and chemical compatibility of these two materials. If there is a common element between two materials, the chemical compatibility could be better. At least the chance of chemical diffusion is reduced.

20
Latent heat
Why does latent heat does not increase temperature?

Thanks parag for still following the question stream. This was the original question. Kindly share your views.

4
Are Fermat and Wilson behind Pythagoras in Nature?

Does any one have a view on the possiblity that Fermat's and Wilson's Theorem might be the background cause of Pythagoras all around us?

Indeed, I have a similar feeling, but I can not, of course, prove it. I think a similar idea underlies (for Pytaghor) the undelivered "simple and amazing" proof of the Great theorem of Fermat. As far as we studied, the Pythagoreans believed that the basis of nature are the numbers even wrote poems about it. Today we witness the coloring with millions of colors obtained by numbers. Greetings: Anna Tomova.

2
Can anyone provide the physical and mechanical properties of Mg6Sn3Ca?

I have been searching in all search engines to find the phy and mech properties of the above material for exact figures. Kindly provide me that information.

Thank you sir for your bit information. Some how i got a clue in understanding their behaviour. But for my research work i was needed the exact values of Mechanical and physical properties of that TX63.

Anyway thank you once again Sir. Can you provide me your email id or contact number sir for better communication about the materials properties.

6
Can we have a heat equation with a negative heat source term? If yes what will be the physical interpretation of negative heat source?

The equation I am considering is given by

\dfrac{\partial T}{\partial t}=\nabla cdot ( \nabla \lambda T))+ (\nabla \cdot v T)+H,  T is  the  temperature,  and  H is  the heat generation rate( source term).  My question is whether H can be negative?

1
What is the basic physical explanation of the acceptor-bound-exciton peak in PL for ZnMgO?

I have got references claiming acceptor peak at 3.33 eV [J.C. Fan, C.Y. Zhu, B. Yang, S. Fung, C.D. Beling, G. Brauer, W. Anwand, D. Grambole, K.S. Wong, Y.C. Zhong, Z. Xie, C.C. Ling, J. Vac. Sci. Technol., A 29, 03A103-4 (2011)]for ZnMgO. However,there are also several references claiming this peak at 3.33 eV due to donor-bound exciton peak.

Kindly provide me some basic physics behind it.

10
Is it possible to electrically insulate an aluminum block by fabrication?

Their is an aluminum block that is internally hollow. It has to be electrically insulated but thermally active.

Is it to possible to electrically insulate it by depositing a layer of Aluminum Nitride or Silicon carbide or magnesium oxide.

If yes, what should be the fabrication process and what should be the thickness of deposition.

Any information or experience with regards to the subject is welcomed.

@ R.Brian Peters

Thank you

2
What are the limitations when using the method of Williamson Hall for research into the size and strain in nanowires GaN?
Can I apply this method in general for such objects?

I'm also using W_H analysis for my samples. I found one journal based on W-H analysis on GaN nanowires

Title: Macro- and micro-strain in GaN nanowires on Si(111)

14
What are the steps to make a good review of scientific papers?
What are the steps to make a good review of scientific papers? Who can advise me? Can we use a software for review of a paper? If so, is there a free software?

I forgot something very important: the using of design of experiments (DOE) and the application of estadistics to analize the results too.

1
In what fields of study can we utilize factorization in polynomial rings?
I am searching for recent studies on other fields of study, like biology, chemistry, engineering, physics, nanotechnology, etc, on which we can find connections among factorization domains in algebra, divisio algorithm, etc.
10
Which is more elastic steel or rubber and why?
I know that steel has large elasticity but don't know why.

Steel , #support @krishna Garg sir answer

6
Is the scientific method natural to humans, or does it require a special effort? What about other animals?
Take the average person you meet - how do they make decisions? What about evolution - has the scientific method ever had any influence on genetic mutation, or has any other aspect of evolution had any influence on living beings?

Edward -

The "What about other animals?" caught my attention, and reading through the other answers first, I think that Aliza came closest to what I was thinking. You do see the basics of experimentation by other animals. A lot if it had to be accidental at first, like a large bird dropping a clam on a rock to open it, or just having fun, like a parrot or similar bird I saw had taught itself to use a peanut shell as a bucket from which it drank. But other primates use tools, and some examples of basic elements of scientific methodology have to be found in large numbers in other animals.

Perhaps the disappointment we feel is that humans have learned something about 'perfecting' the scientific method, yet often seem to avoid it. However, I think that many use it more than they realize. Someone who didn't want to take high school algebra may claim for the rest of their lives that they "never used it," without being fully conscious of the many thousands of subtle uses of logic they made that may have been inspired by abilities they honed in that experience with algebra. However, you could say this is more related to the Ancient Greek Philosophy of logic, which fell short of full science or they would possible have gone beyond the 'four elements.' But it is something and it gave modern science a start.

However, it is true that there is a great deal of interference with science in modern society. I heard or read that in North Carolina, the legislature decided that climate change was not to be considered in official documents, due to its inconvenience, so in effect it was outlawed. At one point the US Bureau of the Census, trying to avoid undercounting minorities, was criticized by Congress, at least one member going so far as to say that "sampling" was some kind of magic, not to be trusted. As a statistician, I was very embarrassed for the US. I've seen office politics that I had to struggle with and often lose against while trying to take the most clearly correct actions. The foolishness, irrationality, and too often selfish and hateful nature of humans can sometimes drown rational and socially progressive views, which you would think would contradict the evolutionary progress that was part of the inquiry Edward made. But perhaps we are just overreacting when we see it that way. Perhaps when we see irrational behavior (or otherwise disappointing behavior that I realize I mixed in here) we weigh that too heavily, and do not give enough credit to the scientific nature that is present in humans and other animals. It isn't perfect, but it's there.

Jim