Science topics: PsychophysicsMotion
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Motion - Science topic

Physical motion, i.e., a change in position of a body or subject as a result of an external force. It is distinguished from MOVEMENT, a process resulting from biological activity.
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I have thought and written that a fourth time dimension is required to enable motion in space, else object motion in three dimensions would create an overlapping smeared mess. But would it? Given matter-wave awareness from particles to de Broglie waves of objects, may we not acknowledge that the wave content of an object could become the object displaced in three dimensions? It would have moved without overlapping and smearing. Or would non-linear wave interactions during the event force us back to the original idea of four actual dimensions with a separate object at each now? What is time in either process?
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“…There is a structure in meaning space that contains time and another structure for dimension. The axes by which we access such structures are language, but language is often inadequate. Wittgenstein pointed out in his Blue and Brown books that common language is not specific enough for philosophy: so, also, science….”
- that is indeed relates to that mainstream philosophy, and so really doesn’t answer rationally scientifically enough to any really philosophical problem – while really mainstream philosophy is a huge set of different and often opposite doctrines, schools, etc., which fiercely struggle with each other, attempting to prove each other that just this doctrine , etc., is true, while other are false,
- and this battle continues at least a couple of thousands of years, while last hundred of years the mainstream doctrines, etc., and philosophers , including “Great Thinkers”, are innumerous.
However what Wittgenstein points, i.e. that this strange and really unscientific situation in this philosophy exists because some “inadequate language”, is, of course rather strange claim – any language is composed from words, which are some notions, i.e. defame some concrete objects/events/processes in Matter and living beings societies, and any language is adequate to the reality completely depending on – what knowledge humans, including philosophers, have about objects/events/processes.
If a knowledge is adequate to the objective reality, then it is applicable be written using any language, if knowledge is transcendent, it is transcendent being written using any language.
That’s all, there cannot be principally any other criteria of “specificity” of any language for any society, including of scientific languages.
Really the existent - and indeed strange - specificity of language for mainstream philosophy is determined by two factors:
- first one is in that philosophy, as it was established ~ 2500 years ago has its subjects for study just fundamental phenomena – and so the philosophical language contains corresponding fundamental notions, first of all “Matter”, “Consciousness”, “Space”, “Time”, unlike to other “ordinary” sciences that study concrete observable and measurable objects/events/processes in Matter, tec.,
- and, what follows from the first, since in mainstream philosophy all really fundamental phenomena/notions till now remain be completely transcendent/uncertain/irrational, so in the mainstream principally any really scientific language isn’t possible;
- whereas, if such language would exist, this language would be understandable not only for philosophers, but for any people, who is able to think logically, objectively, and rationally.
Real solutions of just philosophical problems – and really now of ordinary sciences, which are developed up to the level when the philosophical problems have became, though Meta-scientific, nonetheless already concrete scientific problems,
- can be, and in a number of cases are, solved/clarified only in framework of the 2007 Shevchenko-Tokarevsky’s “The Information as Absolute” conception, recent version of the basic paper see
- where all traditional philosophical phenomena/notions above are really rigorously scientifically defined; and, besides, a number of other really fundamental phenomena/notions, which practically aren’t specific mainstream philosophical subjects for study now, first of all “Information” and “Energy” are scientifically defined as well,
- while all definitions, since aren’t transcendent uncertain assertions, are well understandable on any language for any science.
Note also, that all fundamental phenomena/notions can be scientifically defined only if are defined together, first of all at any definition it is necessary to have the definition of “Consciousness”, since just concrete consciousnesses study the world and define what they study, so say that
“…..But the structures do form in our minds and the formation of such structures is performed by qualities of mind-as-a-whole after which our consciousness is informed: aHa! …. I would like satisfying structures for "time" and "dimension" to form in my mind. Can you help?……”
- really cannot be answering till it isn’t clarified what is “mind” , and for what non-transcendent, not only instinctive reason and by what non-transcendent and non-instinctive way in some “mind” some “structures” appears?
The answers, including what really are "time" and "dimension" , which exist absolutely fundamentally objectively including when no any “minds” exist, and what is “mind” as well, see on at least first dozen of pages in the link above. In concrete application to Matter , including why Matter’s utmost universal spacetime is the fundamentally absolute, fundamentally flat, and fundamentally “Cartesian”, [5]4D spacetime with metrics (cτ,X,Y,Z,ct), see .
Cheers
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In other threads it was suggested that kinetic energy and potential energy compete for curvature. Kinetic energy was said to bend space backward compared to gravity. LaGrange function is well accepted as a factor in determining how celestial bodies move. Action S is calcu;ated for all the possible movements and the smallest S identifies the motion. In GR the calculations predict gravity opposing light and slowing light when approaching.
Questions of gravitational red shift arise which seems to say gravity attracts light.
Dicke supported a competing theory which predicts light losing energy as it departs from a star.
If Dicke is correct then GR is in doubt.
In LaGrange Function Why Is Potential Energy Subtracted From Kinetic Energy?
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There’s no discontinuity in the Lagrangian for the free relativistic particle, when taking the non-relativistic limit.
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Perception is not the ultimate guide for knowledge but as Gallileo captured the actual and empirical, not necessarily the real, similar concerns arise.
In general, the repercussions of Reduction arise because what is actual, i.e final instantiation of underlining process, is not all the story. Further omissions come from the empirical approach since sense means are not always valid projectors of the actual.
Gallilean approach has yielded a framework that empowered our comprehension & ability to define/describe phenomena in the realm of the actual& empirical. His treatise should not be considered more than this i.e descrining the nature of the real and its dynamics.
The reduction of change to motion has been noted but little has been argued about its shortfalls in epistemic practice. This reduction is part of the reduction of the real to the actual since it omits any need to refer to the real to make its claims functional. It also removes philosophical or anthropocentric notions of growth and ultimate ends which is good in one sense but in a pure "reductionist shortfalls" point of view is still a problem dimain restriction.
The description of motion with mathematics is another point neglected. Motion can be described qualitatively or conceptual but such a framework has not been devised.
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Thanks for your thoughts and wishes
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Recent work (Smolin, 2021) tries to overthrow Gallilean reduction of change to motion and representation of motion solely mathematically.
Summary of philosophical approaches to physics projects
**reductionism.. Helps make sense in a physical world overloaded with information. 2 motion, 3 dynamics Laws that everything else dubordinates to-akin an ecpert with main files, mental folfers and subfolders in his head that contains all info about it - so Gallileo has a strong point here in his "error" of reducung motion to math representation etc
**realism-axiological, epistemological, etc
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Ok thanks very much Mr Guynn. You touched a lot of related topics which have social, civil and pedagogical aspectswhich render a separate discussion to be outlibed properly.
However my question aimed mostly at a different issue, that is,
the reconstruction of some physics branches without the aim of reductionism epistemology which was introduced by Gallileo. That is to develop principles and tools of predictions or realist description without reducung the systems to be described.
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Simulations based on Newtonian gravitational theory predict the perihelion advance or precession of Mercury’s orbit to be approximately 532 arc seconds per century [see reference 3 below]. However, the observed value is closer to 575 arc seconds per century [1][2]. Most sources attribute this discrepancy to space-time curvature as described by Einstein’s theory of General Relativity. However, I cannot find any papers documenting a General Relativity based Solar System n-body simulation prediction of Mercury’s precession for comparison.
[1] CLEMENCE, G. M. 1947 The Relativity Effect in Planetary Motions
[2] Ryan S. Park et al 2017 AJ 153 121 Precession of Mercury’s Perihelion from Ranging to the MESSENGER Spacecraft
[3] Souren P. Pogossian 2021 Comparative study of Mercury's perihelion advance
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The Real Story Behind Mercury’s perihelion advance:
[Long after Newton’s law of universal gravitation was generally accepted as the basis of the planetary motion in the solar system, the French astronomer Le Verrier in 1859 announced (based on many years of careful observations and calculations) that the perihelion of the planet Mercury evidently undergoes precession, at a slightly faster rate than can presumably be accounted for by Newtonian mechanics, given the known distribution of the planets and the other objects in the solar system. Since Newton’s laws allows only a unitary and centrally directed force, an explanation for Le Verrier’s finding was arbitrarily attributed to a perturbation caused by the secondary effect of the gravitational forces from other planets; but did not explain why the precession rate varied with different planets, especially the high precession rate of Mercury. The perihelion precession of Mercury is 5,600 arcseconds (1.5556°) per century relative to the Earth. Newtonian mechanics, presumably taking into account all the effects from the other planets, predicts (without strong basis, since it is a very complex many-body problem)a precession of 5,557 arcseconds (1.5436°) per century, but the rest 43 arcseconds (a mere0.076%!) remained un-explained.
In 1898 a German school teacher named Paul Gerber [13] wrote a paper in which he proposed a velocity-dependent propagation of gravity that predicted non-Newtonian 43 arcseconds advance of orbital perihelia per revolution given by the expression k(pi)M/(Lc^2); where c is the posited speed of propagation of gravity, M is the sun's mass, L is the semi-latus-rectum of the orbit, and k is a constant depending on the precise form of the assumed potential. Although there are controversies about this formulation, Gerber showed successfully that a value of the constant k = 6 gave the correct additional 43 arcseconds of Mercury’s perihelion advance.
Albert Einstein in his 1915 - 1916 publications [14,15] claimed to have given a precise account of the discrepancy of precession of Mercury, and deduced Garber’s above relation based on his newly proposed theory of general relativity (GR). The understanding that Einstein’s GR based on impeccable mathematics and a totally different and novel perspective of space and time gave an exact account of the expression given by Garber for the non-Newtonian precession of Mercury; became an instant cause of celebration by Einstein himself. This purported achievement by Einstein is considered [16] a poetic marvel in modern physics and the strongest “proof” of GR! Einstein retroactively admitted (after questions were raised) that Gerber obtained the correct expression for Mercury’s perihelion advance before him. But Einstein dismissed any possibility that someone could explain the additional 43 arcseconds precession of Mercury or that Gerber’s expression for it could be obtained, without using his theory of general relativity.
According to Einstein [17], “Mr. Gehrcke wants to make us believe that the Perihelion shift of mercury can be explained without the theory of relativity. So there are two possibilities. Either you invent special interplanetary masses. [...] Or you rely on a work by Gerber, who already gave the right formula for the Perihelion shift of mercury before me. The experts (?) are not only in agreement that Gerber’s derivation is wrong through and through, but the formula cannot be obtained as a consequence of the main assumption made by Gerber. Mr. Gerber’s work is therefore completely useless, an unsuccessful and erroneous theoretical attempt. I maintain that the theory of general relativity has provided the first real explanation of the perihelion motion of Mercury. I have not mentioned the work by Gerber originally, because I did not know it when I wrote my work on the perihelion motion of Mercury; even if I had been aware of it, I would not have had any reason to mention it".
Einstein’s claim of Mercury’s perihelion advance was contested by so-called “100 authors against Einstein” led by Philipp Lenard, Gehrcke, Silverstein, Reuterdahl et all, who opposed Einstein’s theories accusing him of many things, such as incorrect formulation, plagiarism etc.,and questioned his priority. Ironically, W.W. Engelhardt in his recent publication [18] uses similar reasoning like Einstein and raised the controversial issue that Gerber’s expression cannot be derived from Einstein’s GR. Engelhardt claimed that instead of GR Einstein used a modified Newtonian theory to derive Gerber’s expression and not from his theory of general relativity; hence contest the justification of the claim by Einstein of the proof of his theory of relativity. Engelhardt using purported Einstein’s modified Newtonian mechanics derived an expression for the Gerber’s equation, which is one-third of Gerber’s formula.]
This is a copy of a section, extracted from an article, For the references please see the following article:
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Why isn't the velocity of light given by the speed of the observer plus the speed of the light (addition of velocities)?
Why does the light ray slow down and compensate or speed up and compensate for your motion, so that it is always travels at the speed of light? notwithstanding your motion?
In short, what is the mechanism that means the velocity of light always remains the same, irrespective of the motion of the torch issuing the light ray?
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Thank you very much for your kind invitation to answer this question. My gratitude.
The principle of light speed invariance is obtained by solving Maxwell's equations simultaneously, and is confirmed by Michelson Morey experiment.
And Special Relativity Theory take the principle of light speed invariance as one of its basic postulates and deduced many valuable conclusions.
In my humble opinion inside this article:
A DISCUSSION ABOUT THE NATURE OF TIME
https://doi.org/10.5281/zenodo.7079721 Light propagation in medium, such as water, crystal, vacuum, etc, but not in the void(Vacuum is not void, vacuum are filled with gravitational fields and gravitational fields are physical existence. Thus vacuum is full but not empty).
Therefore, the speed of light depends on the medium, but irrespective of the motion of the torch issuing the light ray.(if light travels in water, it is multiple medium, water plus gravitational field, so it might be more complicated?)
inside this article, I wrote, light does travel in ether,
"ether should be gravitational fields. This is logical because it is known to all that vacuum gravitational fields, in which light can travel, can interact with electromagnetic wave and can bend light, as transparent crystal, in which light can also travel, can also interact with electromagnetic wave. That’s why, when we measure light speed on the surface of the earth, the light speeds are the same in every direction, because light travels at the same speed in the same gravitational fields"
Just for your kind reference.
BR
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Examples in physics are Kinematics (2 categories, all motion experience), Standard model (3 generations, all Particle experiences)
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Are the categories in the study potentially problematic to the study question and study design in any way? How will the new theory be validated? The goal stated above is to consider the reduction of these categories to a theory. This sounds like a top-down approach that would be difficult to methodologically validate. Since the research question is stated to be epistemological as well as experiential in nature, then we may be solving a phenomenological problem with qualitative research. We could consider testing hypotheses. The goal then would be to validate a method that distinguishes justified belief from opinion. Hence, we could maybe look at a workable study design that can do this. How about incorporating thematic analysis? First, investigate what other researchers have done, i.e. where they have utilized sampling for thematic analysis. Then, do the groundwork by working from the bottom up. Design your data collection so that it is comprehensive and interdisciplinary. A working hypothesis will likely emerge from the data that you have categorized and coded. Therefore, instead of reducing categorical data to form a theory, the researcher can find the emergent patterns of meaning via the analysis of the surveillance data that he has collected. The study design comes into play. In other words, design the surveillance to allow for the gathering of data that adequately informs the research question. Rework your hypothesis and rework your surveillance methods as needed. Cycle back as many times as you need to modify and refine the working hypothesis. Now you can work from the ground up and develop a minimum working hypothesis that can be tested through statistical analyses, e.g. an independent-samples t-test using SPSS. Initially, the intended approach seemed to go from top down, via reduction, using categories (presumed to be independent variables) that the researcher did not formulate and code himself. However, a researcher could alternatively investigate a novel solution that comes at the problem from another direction, possibly going from bottom-up instead of top-down. This alternative is grounded in reality and can also be validated. In this way the researcher could possibly develop a novel theory of knowledge (an original epistemological theory) since the expressed intention is to work with experiential data. Otherwise, the researcher might be basing a theory on opinion, which is not useful in regard to an epistemological aim. Going from bottom up to develop a minimum working hypothesis (instead of going from top down to develop a reductionist theory) seems like a possible approach. To answer this question better, we really need to know what the dependent variable is, and we need to categorize the independent variables so that they align with the study aim instead of potentially confounding it. Of course whenever we generalize statistics to parameters we must consider the probabilities of type I and type II errors. So, if possible, increase the sample size, increase the alpha-level of statistical significance, and thereby increase the statistical power of the testing. At least, at the outset of the study, we should be clear on what the research question is, for knowing this will be helpful in informing the study design. There are multiple considerations, as suggested in the following studies:
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Offhand: a free electron, of course, interacts with atoms, but interactions of this kind are chaotically differently directed and mutually compensate in a macroscopic sample. On the scale of nanotechnology, the situation may be different.
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I want to calculate the range of motion of the lumbar model in all 6 directions (Flexion, Extension, Lateral Bending Right and left, Torsion Right and Left) so that I can verify how many degrees my model rotates in one direction. My model contains cortical and cancellous parts of L3 and L4, two facet joints on each vertebra, spring as a ligament, one annulus fibrosis, Five rings of fiber, one nucleus pulpous, and a plate on top of L3 (to apply pressure as a load). My model is working properly in all directions but I don't know how to calculate the ROM. If you can help me I would be very grateful.
Thanks in advance
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hello Utpal Dhar
To calculate the ROM you have to use moment load by dividing the upper (top) surface into four quadrants.
after that, you have to add a remote point on that particular quadrat (or particular location) and measure the flexible rotation.
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Dear all,
I have been trying to use ArtRepair and I have some questions regarding the preprocessing I am doing, and I would be very grateful if you could answer some of them. The preprocessing I am doing is as follows:
1. “art_slice”: Normally the threshold has to be modified until it is inferior to 5%.
- IS IT OKAY IF THE THRESHOLDS ARE DIFFERENT FOR DIFFERENT PARTICIPANTS?
- WHAT TO DO IF THE MASK CREATED IS NOT ACCURATE (THERE SEEMS TO BE DATA OUTSIDE THE HEAD)?
2. Slice timing
3. Realign & reslice
(4). art_despike IF “visual inspection of the ArtGlobal figure uncovers greater than +/-1 % drift in the mean global signal across the entire time series”.
- IS THERE A WAY TO CALCULATE THE PERCENTAGE OF THE SIGNAL DRIFT IN ORDER TO CHECK IF IT’S GREATER THAN +/-1 %? (For example by calculating the % of decrease between the maximum and the minimum value OR the first and the last image?
5. Coregistration
6. Segmentation
7. Normalization
8. Smoothing
(9). art_global: apply if art_despike was not applied.
When using art_global, users are asked “always repairs 1st scan of each?”. IF I ALREADY DELETED THE TWO FIRST DUMMY SCANS, SHOULD I REPLY “YES” OR “NO”?
- IF THERE IS TOO MUCH MOTION, IS IT OKAY TO SKIP “art_motionregress” AND USE THE “.rp” FILE FROM THE REALIGMENT STEP AS MOTION REGRESSORS?
- WHEN USING MOTION REGRESSORS, IS IT BETTER TO LEAVE THE SCAN-TO-SCAN MOVEMENT THRESHOLD AT 0.5 mm/TR?
- IS IT A PROBLEM IF ART_DESPIKE IS PERFORMED FOR SOME PARTICIPANTS AND ART_GLOBAL FOR OTHERS?
Finally, I would like to know if you believe the preprocessing I described is correct or not.
I would be extremely grateful if any of you could answer to these questions, it would be very helpful!
Best,
Ariadna
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Hi Ariadna,
I recently met similar questions and found this post. I was wondering if your questions have been solved.
Thank you!
Best,
Yidian
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Hi all,
I am trying to determine the relative motion between two surfaces in contact. Although I know how to calculate the relative motion, I don't know how to extract the paired nodes (closest nodes) of surfaces in ABAQUS when my geometry of study is undeformed.
For relative motion I will be using the following formula:
If there are contact surfaces named A and B, where there are i-th number of nodes:
X - Relative motion: square root( ( (X Deformed Node1B - X Deformed Node 1A) - (X Undeformed Node1B - X Undeformed Node 1A) )^2 )
Y - Relative motion: square root( ( (Y Deformed Node1B - Y Deformed Node 1A) - (Y Undeformed Node1B - Y Undeformed Node 1A) )^2 )
Z - Relative motion: square root( ( (Z Deformed Node1B - Z Deformed Node 1A) - (Z Undeformed Node1B - Z Undeformed Node 1A) )^2 )
Total relative motion: square root ( (X - Relative motion)^2 + (Y- Relative motion)^2 + (Z - Relative motion)^2 )
Please let me know if I can make my question more understandable or if there's more information required to make it clearer.
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Hi Jose Gaxiola,
I want to determine the relative motion of nodes of two surfaces that are in surface-to-surface contact. I use the probe value to determine near nodes. Is there any reference for this formula that you present?
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The Chandler wobble or Chandler variation of latitude is a small deviation in the Earth's axis of rotation relative to the solid earth, which was discovered by and named after American astronomer Seth Carlo Chandler in 1891. It amounts to change of about 9 metres (30 ft) in the point at which the axis intersects the Earth's surface and has a period of 433 days. This wobble, which is an astronomical nutation, combines with another wobble with a period of one year, so that the total polar motion varies with a period of about 7 years.
Is this wobble sustained by an internal or external mechanism?
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This is pure mechanics. Any rotating body that is not a sphere has such a free nutation. It is not caused by external forces but simply by the form of the body. However, there are variations in the Chandler wobble due to changes in the atmosphere and the oceans. See, e.g., this paper:
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Dear all,
I am using dynamic mesh to simulate bluff body motion, but I do not understand about that method.
What does ''cell height' mean in layering method of dynamic mesh?
is it minimum cell height of the mesh?
regards
Barata
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it is the cell width perpendicular to flow direction. Hope it will help!
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As a result of bottom uplift during an earthquake, an ordinary trochoidal surface (transverse) wave occurs. There are no other opinions. The first slide shows the generally accepted wave generation mechanism. The second slide shows a diagram of the motion of particles in a surface wave. Everyone thinks so. In 2006 in Vienna, at the Intergovernmental Oceanographic Commission's Tsunami (EGU2006), I asked everyone why a tsunami begins with an outflow of water from the coast. My question was of no interest. The third slide shows that the water will first move away from the shore. The fourth slide shows that in the open ocean there is a hole first and then a mountain. Maybe this is not a trochoidal wave, but a Rayleigh wave? The scheme of the Rayleigh wave is shown on the fifth slide. If this is so, then the tsunami formation mechanism (first slide) is wrong?
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Dear Laszlo Attila Horvath.
Your remark is too concise and categorical for a scientist. There is such wisdom: "never say never".
You gave links to the articles "Gravity is a paradym shift in reasoning" and "The real cause of gravity can be proven by facts" which do not consider the physics of the Rayleigh wave and cannot be used as an argument. I can advise you and other participants in the discussion to familiarize yourself with the information on the possibility of the distribution of Rayleigh waves propagating at the boundary of the solid and liquid phases, that is, in the ocean. Simplified quote: “If at the boundary of the solid and liquid phases the speed of sound in the liquid is less than the speed in the solid phase, and this is true for almost all real media (and for the ocean), then a Rayleigh-type wave is generated at the interface. This wave continuously transfers vibrational energy from bottom to top into the liquid phase, forming a wave in it.
Source: Surface acoustic waves - Physical Encyclopedia (femto.com.ua).
It is also well known that seismic Rayleigh waves have much in common with sea surface waves, as well as tsunamis. For example, seismic Rayleigh waves, like tsunamis, begin with depression, and after half the period of the wave, a crest occurs.
Sincerely, Natalia Kucherenko.
Уважаемый Ласло Аттила Хорват.
Ваше замечание слишком лаконично и категорично для ученого. Есть такая мудрость: «никогда не говори никогда».
Вы дали ссылки на статьи "Гравитация парадигмный сдвиг в рассуждениях" и "Настоящая причина гравитации может быть доказана фактами", которые не рассматривают физику волны Рэлея и не могут быть использованы в качестве аргумента. Могу посоветовать Вам и другим участникам дискуссии ознакомиться с информацией о возможности распространения волн Рэлея на границе твердой и жидкой фаз, то есть в океане. Упрощенная цитата: «Если на границе твердой и жидкой фаз скорость звука в жидкости меньше скорости в твердой фазе, а это верно почти для всех реальных сред (и для океан), то волна релеевского типа генерируется на границе раздела фаз. Эта волна непрерывно передает колебательную энергию снизу вверх в жидкую фазу, образуя в ней волну».
Источник: Поверхностные акустические волны - Физическая энциклопедия (femto.com.ua).
Общеизвестно также, что сейсмические волны Рэлея имеют много общего с морскими поверхностными волнами, а также цунами. Например, сейсмические волны Рэлея, как и цунами, начинаются с впадины, а через половину периода волны наступает гребень.
С уважением, Наталия Кучеренко.
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First question: First, is this possible? Then (if any) how much has this been done judging from the title (especially from Poincare's first principles: Les Methodes Nouvelles de la Mechanic Celeste [1892])?
First point: Cornelis de Jager (distinguished solar scientist/winner of the Hale, Janssens (sic?) RAS Gold Medal and the Russian and German astronomical societies' awards etc. - not his full list or honors or science awards) did a paper: "Do Planetary Motions Drive Solar Variability?" with Versteegh, J.M, Solar Physics (2005) 229:175-179. His abstract: "We examine the occasionally forwarded hypothesis that solar activity originates by planetary Newtonian attraction on the Sun. We do this by comparing three accelerations working on solar matter at the tachocline level: Those due to planetary tidal forces, to the motion of the Sun around the planetary system’s centre of gravity, and the observed accelerations at that level. We find that the latter are by a factor of about 1000 larger than the former two and therefore cannot be caused by planetary attractions. We conclude that the cause of the dynamo is purely solar."
Second point (ventured) to Second question: There is a dearth, judging by Kees's answer (and I hazard error here) of analyses of statistical probabilities of "chaotic, unpredictable" effects planets could place upon the sun that Poincare's updated mathematical view of the celestial clockwork (of Newton) might deliver upon de Jager's "three accelerations."
If all of this is silly, please say so.
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Thank you, gentlemen.
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1. If one of the twin brothers rides on a rocket, makes a U-turn while moving at sub-light speed, and returns to meet again, the time progress of the one who moved by rocket will be delayed.
2. If the twin brothers ride on a rocket in the opposite direction, move at sub-light speed, make a U-turn at the same time, proceed in the opposite direction and meet again, the progress of both times will be the same.
Is it a contradiction of special relativity that asymmetric motion 1 and symmetric motion 2 are not the same?
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Is it a contradiction of Euclidean geometry that the length of one side of a triangle is less than the length of the other two sides?
The twin "paradox" is just an analogue of the triangle inequality.
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I am using a Shimadzu AGS-J tensile/ flex testing machine without an extensometer.
The values for tensile strength, flexural strength, % elongation at yield, and % elongation at break are similar to those measured by another lab on the same series of samples. However, the modulus of elasticity (slope of stress/strain) in the initial linear portion of the stress-strain curve is much lower than in the other lab. The load cell and machine motion are checked several times and are within specs. The modulus is measured as a slope between 0.025% and 0.25% strain.
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Hello Serge,
Thanks for your response.
It will be nice to have an extensometer, but I do not have one or can get one for the model I have. You are right; since the strength values match well with the other lab and the load cell is highly accurate at the lower and higher ends, the error must be related to displacement measurement (% strain) or dimensions (thickness and span).
I find 17 to 23% lower modulus values for unfilled PP (168 Kpsi vs. 200 Kpsi) and Nylon 66 (360 psi vs. 403 psi).
I also plotted displacement (mm) vs. time, which is consistent. i.e., no non-linearity and slope match to input test speed. If there was a slip anywhere, I should see some change in the slope. Also, I pre-load samples to make sure there is no slip. I am also using the same tension-compression load cell for both tensile and flexural tests, and the tensile and flex modulus are not the same but close.
What do you mean by machine displacement? Please explain. How can I check if that is the reason for lower values?
Thanks,
Amit
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In dynamic analyses, the size of the element mesh is based on the shortest wave length of interest which is defined from the dominant frequency of the input motion. It should also depend on the vibration frequencies of the analysed system. Furthermore, the wave length should be calculated with the degraded (secant) shear wave velocity: how is the latter estimated?
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Maybe you can find the shear wave velocity by running a small analysis on a simple single material with a very fine mesh. You may be able to keep the reduced problem small enough that you can do lots of runs with different mesh to see if the shear wave velocity has converged.
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See the corresponding blog at https://restframe.blogspot.com
The detection of the existence of the Cosmic Microwave Background Radiation (CMBR) from everywhere around in the universe has puzzled theorists. Not least because of the discovery of a Doppler effect in the data that can only be interpreted as direct related to the velocity and the direction of the motion of the solar system. But if it is correct we have to accept that there exist a rest frame in the universe. Actually we can determine the existence of absolute space and that is not in line with the “belief” of most of the theorists.
There is another method to verify the results: counting the numbers and measuring the brightness of galaxies from everywhere around. The first results – using visible light – were not convincing. But a couple of days ago The Astrophysical Journal Letters published a paper from Jeremy Darling with results that were obtained with the help of radio waves: “The Universe is Brighter in the Direction of Our Motion: Galaxy Counts and Fluxes are Consistent with the CMB Dipole” (https://iopscience.iop.org/article/10.3847/2041-8213/ac6f08).
In other words, it is real. We can determine the existence of "absolute space". Moreover, we know from set theory (mathematics) that absolute space and phenomenological reality must share the same underlying properties otherwise we cannot detect the existence of absolute space. The consequence is that absolute space has a structure too, because phenomenological reality shows structure.
None of the grand theories in physics is founded on the structure of absolute space. Therefore we are facing a serious problem in respect to the foundations of theoretical physics (the conceptual framework of physics).
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As we know, Einstein stated that aether is no longer absolute and used geodesic, it depends on the presence of matter and changes.Empty space has nothing physical and the basis of mechanics is not compatible with it For a system that floats freely in space, its relative position, relative velocity, and rotation are considered And physically it can be considered a feature in itself that is not related to the system The theory of relativity solved this problem by creating a neutral electrical behavior. The point of mass is governed by the law of geodesy, according to which the effects of inertia and gravity are no longer considered separately.In doing so, it attached characteristics to the aether which vary from point to point, determining the metric and the dynamic behaviour of material points, and determined, in their turn, by physical factors, namely the distribution of mass/energy. Thus the aether of general relativity differs from those of classical mechanics and special relativity in that it is not ‘absolute’ but determined, in its locally variable characteristics, by ponderable matter.
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Science Journals (gsjournal.net)
In order to avoid a demand for perfect symmetry in gravitating bodies Newton's law should be applied to small elements in the gravitating body and then integrated. After doing that we see that uniting his law to Fatio's model is possible. Fatio's law implies an ether wind in radial direction to the gravitating body. Therefore, the ether can be falling (perhaps with the same speed as the escape velocity). By doing this assumption we can explain the Pioneer anomaly and the Big Bang as illusions due to ether motions and not motions of bodies.
This explained in the attachment.
Regards from ___ John-Erik
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I said: a small amount is missing. Described.
John-Erik
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Hello,
I've successfully simulated the closure of a flapper non-return valve as illustrated.
The inlet velocity increases gradually with a specific acceleration.
The following UDF is used to specify the motion of the flapper:
#include "udf.h"
DEFINE_SDOF_PROPERTIES(flappers_motion, sdof_prop, dt, time, dtime)
{
Six_DOF_Object *sdof_obj = NULL;
sdof_prop[SDOF_MASS] = 2.73e-3; /* flapper's submerged weight */
sdof_prop[SDOF_IXX] = 2161.86e-9; /* around the hinge */
sdof_prop[SDOF_IYY] = 367.96e-9;
sdof_prop[SDOF_IZZ] = 2471.27e-9;
real m= sdof_prop[SDOF_MASS];
real L= 0.024479 ;
sdof_prop[SDOF_LOAD_M_X] = 0 ;
sdof_prop[SDOF_LOAD_M_Y] = 0.0;
sdof_prop[SDOF_LOAD_M_Z] = 0.0;
real th_deg = theta * 180 * 7 / 22 ; /* valve opening angle, in degree */
sdof_obj = Get_SDOF_Object(DT_PU_NAME(dt));
if (NULLP(sdof_obj))
{
/* Allocate_SDOF_Object must be called with the same name as the udf */
sdof_obj = Allocate_SDOF_Object(DT_PU_NAME(dt));
SDOFO_1DOF_R_P(sdof_obj) = TRUE; /*1DOF rotation*/
SDOFO_DIR(sdof_obj)[0] = 1.0;
SDOFO_DIR(sdof_obj)[1] = 0.0;
SDOFO_DIR(sdof_obj)[2] = 0.0;
SDOFO_CENTER_ROT(sdof_obj)[0] = 0.0;
SDOFO_CENTER_ROT(sdof_obj)[1] = 0.0;
SDOFO_CENTER_ROT(sdof_obj)[2] = 0.0;
SDOFO_CONS_P(sdof_obj) = TRUE; /* constrained motion */
if (SDOFO_CONS_P(sdof_obj))
{
SDOFO_LOC(sdof_obj) = 0.0;
SDOFO_MIN(sdof_obj) = -0.0349 ; /* min allowable angle */
SDOFO_MAX(sdof_obj) = 1.0471 ; /* max allowable angle */
SDOFO_INIT(sdof_obj) = SDOFO_LOC(sdof_obj);
SDOFO_LOC_N(sdof_obj) = SDOFO_LOC(sdof_obj);
}
}
}
But now I want to simulate the closure of the flapper, taking into account the friction at the flapper's hinge.
I tried to just assign the friction value to "sdof_prop[SDOF_LOAD_M_X]" ,but the flapper started to move backwards (opening) until the flow increases, which is not correct.
So I want to get the value of the hydrodynamic torque of the flapper, and compare it to the friction with some kind of "if statement" that may look like this:
real static_friction= 50;
real kinetic_friction=40;
real hydraulic_torque =??? ;
If (hydraulic_torque<static_friction)
{
sdof_prop[SDOF_LOAD_M_X]=0
}
else
{
sdof_prop[SDOF_LOAD_M_X]=-1*kinetic_friction;
}
BUT THE PROBLEM IS :
I don't know the udf code that can get the actual value of the hydraulic_torque on the flapper to compare it to the friction value.
Your help is highly appreciated.
Thanks a lot in advance.
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Ok, I've found how,
In case of someone else has the same issue,
Use the macro :
Compute_force_and_moment
Within the 6dof code
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I am looking for the dataset where the users along with the vehicles are in motion. If the data set contains any social information that would help me alot.
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You are most welcome.
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Hello!
I’m looking for native speakers of English who live in an English-speaking country and who don’t speak any Romance language (Spanish, Portuguese, Italian, French…).
My PhD research is in the field of language and cognition. More specifically, I’m looking into how speakers of different languages lexicalize motion events.
I’ve designed a video description task with 15 short video clips. The platform is mobile-friendly, and this survey will take no longer than 15 minutes of your time. And it’s pretty straightforward: the participants answer a few questions about themselves and then watch and describe what they see in the clips.
If meet the requirements and would like to take part, just follow the link below. https://survey.phonic.ai/624d5e0a269545d4b2d0e359
Thank you a lot for your help! Renan Ferreira Universidade Federal de Pelotas (Brazil)
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Thank you. And thanks for adding that English should be the only mother tongue.
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My laboratory had purchased a set of IMU sensors (perception neuron 3) to capture the motion while performing certain motions. The software can output csv and bvh files. Is it possible to transform the 3 dimensional data to relative joint angle?
For example, to calculate the angle between hip and upper thigh, and thigh and lower leg while performing sitting down motion?
thank you in advance!
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measure :)
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We are looking for tracking (6Dof) a rigid object over a large area (60mx60m) at atleast 50Hz update rate which could guarantee atleast 1mm resolution. We are considering Vicon, Qualisys, Motion Analysis, Simi, Coda motion MoCap systems. Which one of these suits best? Are there any other options?
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Manivannan Muniyandi Passive optical motion capture is the most precise, versatile, and widely used sort of motion capture, and it is a key technology for Vicon.
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I am interested in solving the dimensionless equations for a bubble motion in COMSOL Multiphysics. But do not how to enter the dimensionless equations for density, viscosity, Reynolds number, Weber number, and Froud number as given in the attached papers. Can anyone please help in this problem. I shall be very thankful.
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Dear Thamasha, I understand what you mean, but I am confused. As in Sussan paper, we non-dimensionalized the density, viscosity, and the conservations all. Now to characterize the viscosity we used Reynolds number, for surface tension, Weber number, and gravity by Froude number. I can understand these all. But tell me that viscosity is non-dimensionalized separatly and it should be determined from the Reynolds number. How can I use them simultaneously to define viscosity. Also how for density. I do not how to define the viscosity and density of two fluids. Please can you make a simple mph model to show this. I shall be very thankful.@ Thamasha Samarasinghe.
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In the superionic phase of a material like Cu2X and Ag2X where Ag+ or Cu+ are in motion in addition to the majority carriers of the material, electrons/holes.
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Saurabh Singh Thank you sir.
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I am simulating heaving and pitching motion of an airfoil using
1-translational motion of the outer domain of mesh
2- rotational motion of the inner circular domain of the airfoil wrt the outer transalting domain
My question is :
Which directions I am getting my forces , I get Fx and Fy. but do the axis rotate with the sliding mesh rotation or the fx and fy are always in the horizontal and vertical direction .
The mesh shape is shown for further demonstration.
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I suggest you visit https://aeroptimal.com/mesh (you must create an account to use this module), where you can create a full structured airfoil mesh - https://youtu.be/4Opu0zk7gFk . You can export .su2 .msh .foam .vtk
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Jerk is defined as the rate of change in acceleration. But I would like to know some practical applications of Jerk inorder to have better understanding. I kindly request to suggest me some examples.
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The application of jerk in physics have many instances and one of the example I can shot is simple that the jerk is nothing but it is all about the rate at which any objects acceleration changes with the time or with respect to time.
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Dear all,
I have been confused about the use of restraints in the molecular simulation. As far as I understand, the restraints are added in energy minimization so that only the solvent will optimize and it will orient correctly around our protein. The equilibration is considered the relaxation towards equilibrium of the system, but as the large motion of the protein before sampling is unwanted, the restraints are added again.
Yet, I by chance heard from a senior research that for dt=1fs nvt equilibration, we should not add constraints. (only added for 2fs)
I wonder whether 'constraint' here means 'restraint' or not. If it's restraint, then why should we removed it in case of shorter time steps?
Or maybe I have mistaken the definition/ purpose of the processes?
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In MD simulations, atoms of the macromolecules and of the surrounding solvent undergo a relaxation that usually lasts for tens or hundreds of picoseconds before the system reaches a stationary state. This stage of the MD simulation is called equilibration stage.
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Hi everyone,
I am currently trying to create a contour plot(ABAQUS) of relative micromotions between two surfaces in contact. I have already developed a method for calculation of relative motions. However, I haven't been able to assign my obtained values to the nodes of the geometries that I am evaluating.
Until now, I have read that some people use subroutines to track paired nodes between two surfaces in contact and then they assign the obtained values in a form of a contour plot. Alternatively, developing a MATLAB code and creating a sort of scatter plot with the relative micromotions has also been discussed on some research works.
Nevertheless, I am trying to find a more friendly alternative that doesn't involve a developed code or the use of subroutines.
Creating a field variable from field output is not an option because the first task is to pair closest nodes between surfaces in contact, which is not possible using the operators available here.
If I need to explain myself better, I can provide more details. I will really appreciate any help on this matter.
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Suppose that there is a file of nodal relative motions composed of lines with format X, Y, Z, value. I suggest:
1. Create nodeset from nodes of contact surface.
2. In Initial step create temperature predefined field with type Mapped field using created nodeset.
3. Import XYZ Point data from the mentioned file.
4. Request nodal temperature output.
5. Visualize initial nodal temperatures.
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Dear Honorable Colleagues,
I would like to initiate a discussion concerning the approach presenting active galaxies as stars at extra galactic scale. So, Quasar, Radio galaxy, Blasar and other AGN represent the same type of active galaxies seen at different ages and not from different view angles.
Adopting this idea, we can assume that: the quasar is similar to a T-Tauri star, the Blazar is similar to a neutron star, and the radiogalaxy is similar to an adult age star. If we take the complete chain of star evolution, we can also say that Hot, dust-obscured galaxy (hot DOG) is similar to a protostar, and HFLS3 galaxy is similar to a red giant.
If we take for example the radiogalaxy M87 (NGC 4486) considered as a star of adult age seen on extragalactic scale and we compare it to the Sun which is an adult star seen on the intragalactic scale, we note several common points between these two structures. these common points provide explanations for several phenomena. we cite as example.
1 / The random movement of stars in the nucleus of a radiogalaxy. This phenomenon can be considered as a nuclear reactions at extragalactic scale wich provids energy for the radiogalaxy. This phenomenon is similar to the random motion of the hydrogen protons in the core of adult age star wich is the source of the nuclear reactions.
2/ The supermassive black holes of active galaxies can be considered as stellar spots reproduced at a larger scale (extragalactic scale).
3/The presence of rings, loops and radio lobes in radiogalaxies, explain that the radio galaxies undergo eruptions and prominences at an extragalactic scale, similar to those that occur at intragalactic scale in adulthood stars .
4/ The fact that radio-galaxies are considered as a stars on the extragalactic scale, explains their presence in the center of subgroups of galaxies just like stars which are at the center of their planetary systems.
Other phenomena linked to other types of active galaxies (Quasar, Blazar...) find explanations in this approach.
For more detials, you can consult the link below, of the article titled " New model of unification of active galaxies and the different steps of their formation"
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Hello dear honorable colleague Larissa Borissova.
Thank you very much for your explanations.
I would like to ask you , to kindly give me your opinion on the attached article, if possible
Your opinion is very important for me.
Cordial greetings
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I want to do a dynamic analysis of the disc brake. The disc is rotating and brake pads are pushed onto it through variable pressure.
By revolving disc using Reference point, and using Dynamic implicit, Disc was exploding.
By using Predefined motion to give angular velocity to the disc; the disc is not revolving.
I am attaching the input file and screenshot of the model? Please help me in this regard.
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Set nlgeom=yes.
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Has anyone (in the community of rover path planning and rover motion estimation) used commercial wheeled mobile robots in their research?
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SAF formet is required in MATLAB code for source parameters.
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I am sorry. I don't have it.
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I am an undergraduate student learning the basics of cell culture. I am able to successfully passage Caco-2 cells in T25 and T75 flasks grown in DMEMF12 10% FBS media with no issues. But, when I plate cells in a 12 well plate, I notice cells form a clump in the middle, mostly cells in suspension. In the edges cells are in an even monolayer (see attached picture).
How do I get to plate cells to form an even monolayer?
I seed 0.1 x 10^6 cells per well in 2 mL media. I predilute cells to the final concentration in a 50cc falcon prior to plating.
So far, I have tried decreasing pipette speed, seeding in a dropwise manner to avoid vortex effect, moving the plate in a clockwise or cross motion after seed, and tried plates from two different manufacturers. Are there any other suggestions on how to form an even monolayer?
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Philip Burchell , in regards to how the vibration affects cell density, it is basic wave interference patterns. I've had problems in the past with an incubator that wasn't properly isolated from environmental vibrations (was tight against a counter that conducted vibrations from somewhere in the building) that would create distinct rings of low and high cellular density in 10 and 15 cm plates.
I don't think that is what Hannah Smid is seeing in her flasks, but definitely something to keep in mind when doing cell culture.
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Because I'm working on a different scenario, I'd like to make adjustments and assign different modules while working on a project. I'd like to know where the module may be found.  Please assist me. Thanks.
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Hadi Jabbar Alagealy has the answer.
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Plate tectonics is a theory that states that plates on the Earth's surface move as rigid bodies. GPS is a system that is working independently on the theoretical motions of these theoretical plates, which means that the motions of plates must be visible when studied by passive GPS receivers (if you don't think so, tell us). Some studies work with the so called plate-fixed (net rotation) reference frames, such as e.g. NAD83, that use GPS data, but state that the frame is plate-fixed - no plate motion is visible. My question is: Is it possible that one creates a plate-fixed frame for GPS? If you think so, please, describe the process. I repeat that GPS does not care about the reason why the passive receiver changed its position - so how can you fix your data to a theoretical motion of a plate?
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I concur with Jan
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If I disregard the distinction between passive and active gravitational mass, then we generally associate two types of masses with an object, namely, inertial mass (mI) that appears in F=mIa and gravitational mass (mG) that appears in F=GmGM/r2 for the same object. While this is the theoretical explanation, these equations are meaningless writing unless we provide physical interpretations to those through experiments. Then comes the question that how we measure mI and mG of the same object whose motion is getting studied so as to verify the above equations. Therefore, the question arises whether the unit, in terms of which mI and mG will be expressed, itself is an inertial mass unit or a gravitational mass unit.
I shall be glad if anyone can explain this.
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Also, mass is both a property of a physical body and a measure of its resistance to acceleration (rate of change of velocity with respect to time) when a net force is applied. An object's mass also determines the strength of its gravitational attraction to other bodies. The SI base unit of mass is the kilogram (kg). See the link: https://en.m.wikipedia.org/wiki/Mass
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S-Curve Profile Without Motion Controller , used simple PLC to Create S Curve Motion Profile.
We all know Triangle and trapezoidal motion profile .it is simple formula. But when we talk about S Curve Motion profile then so much calculation come into Picture.
1. Why is needed
In triangular and Trapezoidal Motion profile starting Acceleration is high, jerk is present
And due to jerk material can not handle properly. So many industries require jerk free Motion
2. How to create S curve profile
If we have motion controller, used polynomial CAM. using this we can create motion profile as per our requirement.
3. so my question is can we create S Curve Motion Profile using Simple PLC?
I am also doing R&D on this. and also I got some success but it is not enough .so if anybody doing research on same i would like to know about it. That would be a big help.
i am ready to share my research with you.
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I was performing a cfd analysis of laminar straight pipe flow in Ansys. simply, 1 m length pipe, inlet velocity is 1 m/s and outlet pressure is atmospheric . I found that at the fully developed region, the velocity at nearly 0.5 m from inlet , of course parabolic profile But the center line velocity is nearly 1.9 m/s . So I wanna know why ? why 1 m/s velocity get accelerated to 1.9m/s without any force. Of course fluid velocity also depends on position we call it convective acceleration and fluid get accelerated when area decreases But in straight pipe or two parallel layer , why acceleration happen ?
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to me is very clear. Right before at the exit is no friction force due to the wall of the pipe. The fluid sences that even before its exit. Imagine a bullet with constant force behind it moving in tube. Now imagine a friction less section of the tube before it exits. Will it not the bullet move faster for this interval?
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Sound boom happens when the speed of of a flying object exceeds that of the sound traveling in air. It's not easy to generate such a linear speed. However, this can be relatively easily generated by rotational motion. In other words, if we rotate an object, let's say a disk, fast enough, the speed of disk at the edge can easily be supersonic.
So here are my questions: Has anyone tried similar experiments? What happens when the speed at the edge of the disk exceeds that of sound?
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Thank you Robert. Your reply is very informative. So "the relative speed of earth with respect to ether" is not even a valid question, because the earth drags ether with it. In other words, the Michelson-Morley experiments could be pointless. I cannot help but thinking the rippling effect of this conclusion -- taking off this cornerstone of modern physics.
I guess you are probably right about sound boom effect of a spinning object, but I'm still optimistic about options that make this happen. You might wonder why I'm looking into this. I vaguely feel that this might provides a mechanism to generate lifting forces for flying disks.
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Hey,
i am working with FLUENT at the moment, to simulate a left ventricular contraction.
Normaly i would use different meshes of the LV at different times of a real contraction but unfortenatly i cant do this right now.
Here is my question, does anyone know how to set up something like a contraction. My basic idea is to just take the wall of the LV and move every point to the middle(or a specific point) of the LV at the same speed going reverse after time. Is this even possible to move the wall to a defined point?
I searched for different UDF's but couldnt find a answer for my problem.
I think i have to use the define_cg_motion macro or just a grid_motion macro to solve my problem.
Maybe anyone can help me with that problem.
If not, does someone own a list of possible commands for UDF's under c? I never used UDF's or worked with c so i dont know much about possible commands or tricks to set up the motion!
With best regarts
Calvin
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What is the equation of the LV motion? Do you have the speed or coordinates of the LV wall over time? The CG_MOTION is used for rigid body motion, which means all nodes of the LV wall move with the same velocity, so I think you should use GRID_MOTION.
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there are several methods for estimation of structural dynamic to predict the behaviour of the structure in motion. i am looking for a valid technique to analyze the movement of a bridge with single degree of freedom. i think most of the impact of the movement will be observed from the first mode shape of the structure when it subjected to any movement. i new in this research and want to explore this topic. if anyone can provide me some material regarding this topic i will be thankfull
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I would recommend to watch the differences emerging between ideal modelling and dynamic (dialectical modelling). Ideal modelling is abstract, theoretical, only having main decisive elements, while dynamic (dialectical) modelling shows the motion of the structures with all the elements in time and space, and is a "real life" model. On observing the differences occurring between ideal and dynamic (dialectical) models You can notice and define the motions.
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I've simulated a pitching motion in Ansys Fluent with UDF, a CG_MOTION mocro.The domain is supposed to oscillate but it rotates,judging by animation. The motion is not a pitching one.
DEFINE_CG_MOTION(airfoil, dt, vel, omega, time, dtime)
{
Thread *t;
face_t f;
real NV_VEC(A);
real dv;
/* reset velocities */
NV_S(vel, = , 0.0);
NV_S(omega, = , 0.0);
if (!Data_Valid_P())
return;
/* get the thread pointer for which this motion is defined */
t = DT_THREAD(dt);
/* compute change in velocity, i.e., dv = F * dt / mass
velocity update using explicit Euler formula */
dv = 1.89+0.75 * sin( 0.37 * dtime);
v_prev += dv;
Message("time = %f, x_vel = %f, force = %f\n", time, v_prev);
/* set x-component of velocity */
vel[2] = v_prev;
}
what would be the problem?
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Hi
Just one suggestion, be always sure where exactly you define the sources before compile.
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Very interested in the therapeutic benefits of the rocking motion, such as rocking chairs, rocking a baby, self induced rocking motion, and how the vestibular system or the proprioceptive system is affected.
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Hi Stacy,
There are some works connecting rocking motion, vestibular stimulation and sleep.
One is: Kompotis et al., 2019, Current Biology 29, 392–401
Rocking Promotes Sleep in Mice through Rhythmic
Stimulation of the Vestibular System
Regards,
Enrique
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Assuming that no motion in the normal direction, how would you propose a system of hardware and interconnection as well as the control strategy that will drive the system?
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Sounds analogous to an inverted pendulum. Here is one way to construct something with closely similar dynamics. Take a knee (90° angle) connector for sewage pipe, cut it nicely and mount it on a toy car such that the knee is pointing straight upwards. Place a small ball (i.e. from a roll-on bottle) on top of the knee and try to keep it there stably by moving the toy car back, forth, and sideways (hard to do manually without automated feedback control loop). I guess many feedback control schemes would keep the ball at the top of this curve subject to micromotion.
Aside: If the knee was facing down, mounted on a motor, and the ball is placed inside the 90° curve while the motor is rotated at some angular frequency, the resulting dynamics would resemble Mathieu equations whose stability analysis could be checked from Floquet theory. Incidentally, these are the same dynamics exhibited by a single ion trapped in a linear Paul trap.
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Hello,
I am trying to scale up a shaking table test, and I am wondering what is the factors that should be considered to have a similitude model to the prototype. How can I scale the input motion, shear wave velocity, ...etc.
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Hi Fouad,
I remember to try this in my M.Sc. so here is a tip: there are scale factors suggested by Iai 1989 for 1 g soil-structure-fluid models in 1g gravitational field. These factors have been updated as well. There are scales for length, density, the porosity of the soil, stress, and... Here I have a sample paper for you to have a look:
Best of luck,
Ali
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The position,proper motion and parallax of a star (ra0,dec0,pmra,pmdec,parallax) are required.This information allows that we can now find the position at some other time(t) :
ra=ra0+pmra*(t-t0)+parallax*P(t),
P(t)=[x(t)*sin(ra0)-y(t)*cos(ra0)]/cos(dec0),
Here,t0 is the reference epoch and [x(t),y(t),z(t)] are the Cartesian barycentric Solar system coordinates in au of the earth on the ICRF at time t.
But I find the units of 'ra0' are deg, the units of 'pmra*(t-t0)' are mas,and the units of parallax*P(t) are mas*AU. 'mas' and 'mas*AU' cannot be added.
What should I do?
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Do you actually want the 3-dimensional position in space? Because (1) if you don't, you only need the proper motions, and (2) parallaxes are, in general, so poorly known (even for GAIA data they're among the least accurate numbers) that any change in parallax is far smaller than the original uncertainty in the distance (The reason being that the motions of stars are many orders of magnitude smaller than the speed of light, so any change in their distance in light-years is negligible in time periods small compared to thousands of years. As an example, most stars in our neighborhood had motions of 100 km/sec or less relative to the Sun. Since that's 3 thousand times less than the speed of light, it would take such stars 3 millennia to change their distances by 1 light-year. For an extremely close star, like Proxima Centauri, there might be a measurable change in a century; but for anything more than 100 light-years away, even 3 millennia might be too short a time to get any measurable change -- though in 3000 years, improved technology might change that statement!).
Therefore, presuming you just want to change the position in some earlier coordinates to current coordinates, calculate the number of years involved by subtracting the date of the original position (for most catalogs, the positions are calculated for the equinox involved, so a B1950 or J2000 coordinate would represent the position in 1950 in 1950 coordinates, or the position in 2000 in 2000 coordinates) from the date you want (e.g., right now, it's about 2021.515 (keep in mind that 2021.000 is midnight on Dec 30/31 of 2020, since Dec 31 = Jan 00)). Look up the proper motion in milliarcseconds per year (I usually use SIMBAD, but GAIA is more accurate for stars in its database), multiply that by the number of years involved (21.515 for J2000 coordinates, 71.515 for B1950 coordinates), divide the resulting proper motion in declination by a thousand to get arcseconds (the position is usually given in degrees, arcminutes, and arcseconds), and the resulting proper motion in right ascension by 15 thousand to get seconds of time (since right ascension is measured in hours, minutes and seconds of time), and add or subtract to/from the original positions as needed (keep in mind that if the sign of the declination is the same as the sign of the proper motion, then you add the numbers, but if the signs are opposite, you subtract the proper motion from the declination, and use the sign of the declination).
This gives you the "current" position of the star, but in B1950 or J2000 coordinates. To alter that, use a precession calculator (I like the one on the NED site, at https://ned.ipac.caltech.edu/forms/calculator.html ). Enter the epoch of the original catalog, and its equinox, the "current" right ascension and declination as just calculated, insert the equinox you want (in this example, 2021.515), then hit Calculate. One thing I like about the NED calculator is that, although the original coordinates are probably going to be Equatorial, and the proper motions certainly will be, you can choose your output as Equatorial, Ecliptic, Galactic, or Supergalactic coordinates.
I will note that as someone interested in historical astronomy, in which "old" positions are given for the epoch of observation (e.g., if William Herschel observed an object on Dec 31, 1783, then his original position was for that equinox; though his sister Caroline did update all the coordinates to the equinox of 1800 later on), there are cases where the epoch and equinox may not be "standardized"; but other than for such "historical" cases, any catalog you refer to should, as stated above, give positions for the same epoch as the equinox involved.
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Hello,
Is anyone already worked with MR image data set??? If so, Is there any model to remove the motion artifacts in the MR image data set if contains??? What should we do if we have an MR image with motion artifacts??? Please give me your suggestions if it is possible to remove artifacts once the scan is produced.
Thanks in advance,
Dhanunjaya, Mitta
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Interesting
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Hi dear friends,
I want to simulation a whirl rotational motion and axial distance together in Ansys Fluent or Ansys CFX . For this work, Should I work on dynamic mesh and write UDF? or Is there other way?
In fact, I want to simulate a rotational spherical body in fluid. This body rotates and has a whirl rotational motion and axial displacement together. FSI(Fluid Structure Interaction) simulation can use in this work?
Thank, I am grateful that guide me.
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Hi,
the first question (not answered by the text of your question) is, whether the motion of this rotational spherical body is caused and only determined by the action of fluid forces or whether this body motion is prescribed in some way.
If the motion is prescribed or can be described by formula, than the approach could be:
1) no FSI simulation needed
2) for purely the rotational motion it would be sufficient to assign the calculated surface velocity as a boundary condition to the walls of the rotational spherical body.
3) For the additional axial displacement, the body real needs to be displaced with regard to the originally generated mesh and this could be accomplished by mesh morphing (in CFX) or the so-called "moving-deforming mesh" algorithm in Fluent.
In contrary, if the rotational spherical body can freely move in the fluid under the influence of acting hydrodynamic forces, then a description of the body motion is not possible by simple formula. In this case not a FSI, but a 6DOF (6-degree-of-freedom) simulation would be required. The body itself is not deformable, I assume. So its motion can be described as the motion of a rigid body under the influence of the acting hydrodynamical force and moment on its center of mass. Combining 6DOF with moving-deforming mesh would then do the trick.
Only if the body could deform its shape under the influence of acting hydrodynamical forces, then a FSI would be required.
With best regards,
Dr. Th. Frank.
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There is a method to deblur images via Wiener filter:
I would like to deblur image from the video made by smartphone.
I need to estimate parameters for Wiener filter (Len, Theta, noise level).
How to do it?
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I have found some of the existing solutions so far:
1) Blind Deblurring with a Coupled Adaptive Sparse Prior:
2) Deblurring with no PSF information
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I have a linear actuator of 1kN load capacity, 50mm linear travel, and M35X1mm thread at outer body. The spindle has M10 internal threads which is not through (closed end). I am having leakage from inside the actuator. Is it a way that I can transfer the linear motion with 1 micron precision?
Picture attached for current connections
Thank you in advance
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@mohammad abdoli,
Thank you for your kind information.
I managed to solve this with the steel bellows of reduced thickness.
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  • regarding the Skew-Symmetric property between the mass matrix and the Coriolis matrix, does it always hold the Skew-Symmetric property for any kind of robot dynamics model or it is for a specific robot motion condition??
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Hi, I want to simulate the motion of a Spherical ball in an oil channel with COMSOL.this spherical ball must move the path in the oil with 5 (m/s) alongside the channel, and the water temperature changes In the radial direction.
I want to see the effect of spherical ball motion on the temperature in the pipe. and I can't fix the ball and give a velocity inlet in the channel entrance. I searched a lot but did not find anything similar.
Please guide me on which interfaces I should use. I really need your help ASAP or give me a Related tutorial file.
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The problem is this: there is model of robot, created in Simscape. And knee of this robot is made of "pin-slot-joint", which allows one transnational and one rotational degree of freedom. In transnational motion, it is imposed the stiffness and damping factor, which gives influence also to rotational torque. My aim is to write optimization or control algorithm in such a way that this algorithm should provide such stiffness(in linear direction), which will reduce the rotational torque. By the way, rotational reference motion of knee is provided in advance(as input), and appropriate torque is computed inside of the joint by inverse dynamics. But to create such algorithm, I have no deep information about block dynamics, because block is provided by simscape, and the source code and other information is hidden. By having signals of input stiffness, input motion, and output torque, I need to optimize the torque.  I will be truly grateful if you suggest me something. (I tried to obtain equation, by using my knowledge in mechanics, but there are lots of details are needed such as the mass of the joint actuator, it's radius, the length of the spring and etc. AND I HAVE NO THIS INFORMATION.) If you suggest me something, I will be truly grateful.
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very interesting
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Hello everybody,
I am simulating the motion of sand in a narrow pipe. I tried to create the animation, and I keep the autosave of animation for particular time step in the fluent. The problem now after writing a file in the animation playback screen, it was difficult to visualize the motion of the particle, due to the high length to diameter ratio of the pipe (L=1m, D=0.003m). I wonder if there is any procedure to visualize the motion of particle in the saved animation file.
Other problem I faced in MPM, after I have created the periodicity in fluent, use the TUI command: define>b-c>m-z>m-p….., I am not abling to add the MPM model, using define>mod>add, because TUI still defined with Boundary condition. It is possible to switch off from periodic BC to add MPM model.
Thanks, in advance!
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Many thanks for your replay, actually in the MPM panel I could display injection, it is looking very fine, and I could visualize the location and motion of particle during running the simulation, the problem is how to rely on Fluent Post-Processing the dedicated MPM display functions, could you please suggest me a way how to save animation in MPM for postprocessing?
Best regards!
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I am trying to make a panoramic image but my input images have motion and lens focus blur, if I apply some deblurring technique before images stitching, will this improve my final panorama quality.
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It depends on what kind of deblurring techniques you use. Conventional deblurring techniques are hard to recover the information that is lost. There are some deep learning-based deblurring techniques that can certainly improve your image quality.
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I think we were all surprised at the first time we got to know quantum mechanics that the squared modulus of the wave function is the probability density of the existence of the particle?
The role of the complex numbers here is strange, but the question here is:
Is there an idea that is deeper and easier to understand, so that entering the squared modulus of the complex number becomes a mathematical result from this idea only in order to facilitate the calculations?
Do you share with me my astonishment and my question?
God willing, I think we can find something deeper and even simple, actually I put this reason in my paper:
In summary:
The main idea of this paper is that the continuous trajectory of the particle can not exist, so the motion is a sequence of appearances and disappearances events in space and time, so the particle does always jump to move from one position to another.
So when the particle is in position p1 at time t1, where would it be in time t2?
In classical mechanics, the trajectory exists so the least action principle state that:
The path taken by the particle between times t1 and t2 is the one for which the action is stationary.
So what is the situation in quantum mechanics?
fortunately, we have a principle that is very close to the classical principle, but in this case, we didn't have any path, we have potential new positions, so in general, the particle has some preferred destinations based on a new quantum action principle named "alike action principle" that ensures the existence of physical harmony within our universe, like for example preventing the particle from easily reaching forbidden locations (guarded by fields of great forces).
Therefore, in general, this new constraint in motion could be valid at multiple positions at the same time, so in general, we have multiple acceptable positions at time t2.
Thus the probability of existence came up in our description of the movement in the quantum world.
We suppose that we have a preferred value of action that we call h (Plank constant), the new action principle called the "alike action principle" states:
"The preferred appearance destination position took by the particle at time t is the one for which all the remainders due to S/h (for all imaginary paths which lead to this destination) are stationary".
In other words, it is as having the same (or close to each other) remainder after dividing them by h.
For example, if we have two actions (for two paths) to one destination position, the natural function that verifies this principle is:
sin2((π/h)(S1 − S2)).
So after some steps of the calculation, we derive the relation between the probability density of the existence and the squared modulus of the wave function by deriving the path integral formulation of quantum mechanics, for more details please see the paper.
Thanks.
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mr Khoder
Better to read the Feynman lectures first. Hasn't been beaten by anyone since its publication over 50 years ago. The bible for physicists
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I'm using a slow motion video recorded using an iPhone 7+ to track something but would like to avoid recording a chronometer to know the time the process is taking. I need to measure about 10 seconds with an uncertainty of at most 0.1 s... Is this possible by just counting 2400 frames of my homemade video?
Thanks in advance
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if you can start a stopwatch and include that in the frame of the slomo video you can get a pretty decent approximation of the time.
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Hi everyone,
I am trying to solve a direct dynamic of equation of motion of Stewart platform using ODE45 in MATLAB. Even though I solved the inverse one simply, I had a problem with direct dynamic solution using ODE45 since the Inertia matrix and the Coriolis-Centrifugal terms are functions of states. Which means, inertia matrix and Coriolis-Centrifugal terms will be changed in each step of integrations and they are not specific matrices in all steps.
Also, I am using this article for my project:
AOI: 10.1109/ICCAE.2010.5451249
I would be very happy if someone could help regarding this matter.
Thank you,
Shahin
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Good Evening Mr Shahin Sharafi
I am not much aware of Stewart Platform but definitely, I worked with ODE45 optimization tool. I can share my experience here if it's convenient for you.
ODE45 is an inbuilt matlab function to solve nonstiff differential equations to optimize a system where the inputs and outputs are continuous. As an example, we can say a continuous flow reactor is such a system.
For such a system, we can obtain a system of differential equations, and then we can create a custom function containing those equations as a steady model. After that, if we call the "ode45" function, that will show us the steady-state or the simulated values over time as a set of vectors.
Now, how to use it. That's really simple:
function myFunc = ssmodel(t, X)
Fa=1.5;
Fb=0.5;
Fd=2;
Ta=300;
Tb=Ta;
H=10.^6;
c=5000;
h=500;
k=0.2*(1-exp(1-(X(3)/173)));
myFunc = [Fa+Fb-Fd;...
(1 - X(2)) / X(1) * Fa - X(2) / X(1) * Fb - X(2) * k;
(Ta - X(3)) / X(1) * Fa + (Tb - X(3)) / X(1) * Fb + H / (c * X(1)) - h / c * X(2) * k];
end
As you see in myFunc() there are three right-hand sides of the equations.
T0=300;
Ca0=1;
W0=500;
These are the initial conditions and
[t,X] = ode45(@ssmodel, [0 1000], [W0;Ca0;T0]);
That is the function call by ode45. [t, X] contains the W, Ca and T values after simulation [0, 1000] is the simulation time limit. And that's it. Now to plot them you can use : plot(t,X(:,1));
The first vector set which contains W value will be plotted over [0, 1000] seconds timestamp and so on.
I think that information will help you, if not you can write me back, I can try to help you with some advanced information. Good Luck!
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Working on an experimental setup where participants are asked to move around a small space. As a part of the overall measurement strategy, would like to take GSR measurements to determine potential stress when the distance between participants' bodies changes.
Looking for academic paper recommendations or any links to setups (outside of the FitBit world) that have successfully dealt with this measurement problem.
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Empatica is very expensive for studies that require multipe users
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Sir Isaac Newton's gravitational theory is often viewed as belonging to the philosophical view of the cosmos of the solar system as being mechanical and mechanistic. Newton discovered that the large bodies which orbit about the Sun follow their respective trajectories in accordance with three laws of motion. What accounts for the fact that the planets have been observed to quicken or to retard their motion?
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The explanation is given by Kepler laws:
”Kepler's three laws describe how planetary bodies orbit about the Sun. They describe how (1) planets move in elliptical orbits with the Sun as a focus, (2) a planet covers the same area of space in the same amount of time no matter where it is in its orbit, and (3) a planet’s orbital period is proportional to the size of its orbit (its semi-major axis)”.
discovered
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I have a Define_CG_Motion udf written in c where do I add it to my Ansys fluent project and does it need to be compiled before that?
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Usually a UDF does not need to be pre-compiled.
If the UDF is properly hooked-up in the setup of your case and if the required C-compiler is available in the system and properly setup, then ANSYS Fluent will compile the UDF automatically when the CAS is read into Fluent or if the Fluent simulation is run in batch mode.
Regards,
Dr. Th. Frank.
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