What is Model: Definition and 1000 Discussions

A model is an informative representation of an object, person or system. The term originally denoted the plans of a building in late 16th-century English, and derived via French and Italian ultimately from Latin modulus, a measure.
Representational models can be broadly divided into the concrete (e.g. physical form) and the abstract (e.g. behavioural patterns, especially as expressed in mathematical form). Of particular importance in the modern context, conceptual models are central to philosophy of science, as almost every scientific theory effectively embeds some kind of model of the physical or human sphere.
In commerce, a model might instead reference a specific version or configuration of a product offering, rather than functioning as a representation of something else.
In taxonomic settings (e.g. biology, architecture, art) a model is sometimes a particular instance of a set of related entities (species, built structures, artistic compositions) chosen as a convenient reference point around which to build discourse; such a model is almost always chosen to typify some central tendency of the group, exemplify the group's defining characteristic, or reify the group's historical lineage.
Kinds of models include:

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  1. B

    Improving Performance of HP.115 Simulator Model: Challenges and Solutions

    Hi everyone, In my project work, I have to "rebuild" the Handley Page HP.115 aircraft, using the simulator in my university. It is a Merlin MP521 and I am using the Excalibur II model editor. The aircraft was used to test the slender delta wing planform at low speeds as part of the Concorde...
  2. K

    Turning a model car with no steering.

    Hi Guys, If I were to build a model car, with each wheel having it's own servo, then how can I make it turn in one direction. Say if I want to turn left, if I cut power to the front left and reduce the speed of the rare wheels will the front left wheel act as a pivot? Or should I cut power of...
  3. P

    Markov model and its differential equation

    Hi guys, I have problem in constructing the corresponding differential equation for a markov model: Given a markov model as shown S1→(a1)→S2→(a2)→S3 S1←(b1)←S2←(b2)←S3 where S1 to S3 are three different states of the system and ai and bi are the forwards and backwards rate constant for...
  4. C

    Can a Spinning Annular Wing Model Plane Fly?

    So, I'm in college studying Aerospace Engineering and I'm going to enter a contest of airplane models. Summing it up, I would like to know if anyone can give any insight on if it is possible (at a reasonable price) to make a Spinning Annular Wing Model Plane (i don't really know if the name is...
  5. S

    Spontaneous symmetry breaking in the standard model

    In the standard model, the Lagrangian contains scalar and spinor and vector fields. But when we consider spontaneous symmetry breaking, we only account for the terms contain only scalar fields, " the scalar potential", in the Lagrangian. And if the scalar fields have vacuum expectation value...
  6. Spinnor

    Adjust parameters of Standard Model so only photons, e-, e+ remain?

    Could you have a hypothetical universe with only photons, electrons, and positrons by adjusting the parameters of the Standard Model to eliminate all the "other" stuff? If so is String Theory flexible enough to model a hypothetical universe with only photons, electrons, positrons, and...
  7. R

    Raising and Lowering Operators in the Lipkin Model

    Homework Statement I am trying to calculate the expectation value of an operator in the Lipkin model of nuclear physics. The background isn't important because my problem in really just a math problem. Homework Equations The anticommutation relation \begin{align*} a_{p\sigma}...
  8. D

    Lumped tire model : bristle deflection

    Hi, And thank you for your time! :) I've been studying and coding for more than a month on a physics engine for car driving simulation. Right now, I'm trying to change the whole tire model currently based on Pacejka for a more advanced one. After quite a lot of reading on the topic, I decided...
  9. T

    Inverter propagation delay using the RC delay model

    Hi~ Actually I am fine with calculating the delay but I haven't got the concept clearly enough. Both nmos and pmos have their equivalent RC models. I understand how the RC model of nmos works when its on or off but I don't get how the pmos turns out this way. When its off, the upper part...
  10. I

    Lead Screw model in Creo and calculations

    Hi I'm trying to make a lead screw in Creo which would be used to move a 400lb load linearly along the ground. This would be turned manually using a lever as shown in the pic (not the complete model). I have used a lead screw with a major diameter of 1 1/4 and determined the torque to move...
  11. adoion

    Exploring Niels Bohr's Atomic Model

    hi, ive got a really simple question. niels bohr proposed a model of the atom in witch the electron cannot fall into any energy state but must fall be in certain discreet values and this helps explain why the electron doesn't clumb with the nucleus almost instantly. not the atom needed to...
  12. F

    Does the Drude model predict the emission of em waves?

    The Drude model of electrical conduction has the charge carriers being accelerated by an electric field and then interacting with the lattice ions. The cycle is then repeated. An unbound charged particle if accelerated emits electromagnetic waves. Does that mean that a prediction of the Drude...
  13. K

    Magnetic dipole-dipole interaction model

    Hello, I'd like to calculate magnetic dipole-dipole interaction energy. Actually, I've tried to find models for the calculation, but most of them are just a simple point dipole-dipole interaction model. I can't utilize this simple point dipole-dipole interaction model directly because...
  14. F

    Model to draw an absolute straight line

    I am looking for information to assist me in designing a model or program to draw a straight line bisecting the universe. Ok maybe just the Milky Way galaxy. I would like to view this line from various points 1. as viewed from a point on Earth (possibly one of the poles) 2. as viewed from a...
  15. maajdl

    Ising model, same interaction with all spins

    Hello, I just read a question about the Ising model, and this reminds me of an old interrogation I had long ago. It is simply that: The Ising model deals with spins interacting only with close neighbors. I would be interested in a model where all spins interact with each other in exactly the...
  16. A

    Ising Model for Spins: External Magnetic Field Effect

    I think most of you are familiar with this model (sum runs over nearest neighbours): H = -J ∑S_iz * S_jz It demonstrates one of the succeses of meanfield theory as one can succesfully introduce: S_iz = <S_iz> + S_iz - <S_iz> = <S_iz> + δS_iz Such that: S_iz*S_jz ≈ 2S_iz<S_jz> +...
  17. R

    Choosing the Right AC Adaptor: A Guide to Model Names, Compatibility, and Cost

    I want to replace an adaptor for some appliance. The part that is sold in an official website of the product is expensive. So I'm looking for compatible models. Is it usually OK to only consider matching Output Voltage and current? S018QU2400050 is written on the apator. I think 24 stands...
  18. P

    About Markowitz Model in Financial Math

    https://www.dropbox.com/s/4gwmoo00hn523fk/hi.jpg I've been working on it for several days...the dual problem is way easier but the professor asked us the do the primal one
  19. F

    Regression Analysis - Constructing a Model ((Need ))

    Hello, I am trying to construct a general function/method based on two sets of minimum/maximum data point constraints, which can take on new values in different situations. The only known data for this general function is the starting point (y-axis intercept) and the x-range. The rate of...
  20. T

    How to Model Drude Materials using FDTD

    Hello all, I have been learning to use FDTD to model light interaction with various materials. I've successfully managed to model light interaction with semiconductors/insulators. However, I've been having trouble understanding how to incorporate metals into this model. The code becomes...
  21. PsychonautQQ

    Einstein Model vs Debye model.

    In the Einstein model, atoms are treated as independent oscillators. The Debye model on the other hand, treats atoms as coupled oscillators vibrating collectively. However, the collective modes are regarded here as independent. What is the meaning of this independence and how does it contrast...
  22. V

    How to make a fair model for competition please?

    Hi, English is not my native language. I manage first time a competition on social media, where: 1. people bring a photo and gather like on it. The top 3 likes will go to final, 2. in the final, they play with a small robot as a vacuum cleaner to clean an area of 1mX1.5m which has 1 pin in...
  23. Absentee

    Sommerfeld model and fine spectral lines

    Hey guys! First time posting on this site. Been reading for quite a while and really loving it! :thumbs:! I'm a chemistry student and reading my book in general chemistry I couldn't understand two things about Sommersfeld's atomic model. I believe i understand the whole concept but what...
  24. E

    Estimate the error variance of Autoregressive model

    Hi everyone, hopefully someone can help For an vector AR(1) model of the form y(t)=Ay(t-1) + et How does one estimate the variance of the white noise input. I was under the impression that one can simply use the residual of the model fit and estimate the variance from this, when I do a...
  25. Z

    Electron energy levels in Bohr model

    Homework Statement At the bottom of this linked-to screen below is an equation for E = - ... = - .... = - 13.6 Z^2 / n^2 eV https://en.wikipedia.org/wiki/Bohr_model#Electron_energy_levelsHomework Equations I'm using the following values for the formula Z=1 n=1 K sub e = 8.987 x 10^9...
  26. V

    Database of theories beyond the standard model?

    I am a programmer and physics fan. A speaker (Lawrence Krauss?) at https://origins.asu.edu/events/great-debate-parallel-realities-probing-fundamental-physics (not on youtube yet) said physics theories beyond the standard model are an under-determined problem. There are 7,000 theories that fit...
  27. julcab12

    Competing model on Firewall Paradox

    http://arxiv.org/abs/1401.4097 Fuzzball "The fuzzball construction resolves the black hole information paradox by making spacetime end just before the horizon is reached. But if there is no traditional horizon, then do we lose the elegant relations of black hole thermodynamics? Using an...
  28. MarkFL

    MHB Mathematical Modeling Problem for 500-gal Aquarium Impurities

    Here is the question: I have posted a link there to this thread so the OP can view my work.
  29. S

    Pressure regulator model: how to study its stability

    Hi all, I need a model of a pneumatic pressure regulator. The model should be as simplest as possible and use an optimization solver to identify the regulator parameters in order to fit the performance I find in the datasheet of a commercial pressure regulator. I have already done a model...
  30. C

    Places to study Physics Beyond The Standard Model.

    I am a MSc student and I am looking for a place to do my PhD in Physics Beyond the Standard Model (Theoretical side). Any suggestions for a place to apply?. I know that there are the traditional elite places like MIT, Standford, Berkeley and so on but I am looking for other suggestions given...
  31. M

    Kronig-Penny Model: Exploring Electron Behavior in Solids

    Hi everybody, I have participated in a course about solid state physics and have been introduced with Kronig-Penny model. Now in this model, so far I understood we solve the nature of wave function of an electron inside an array of potential barrier. It very nicely explains the concept of...
  32. B

    Veracity of Simple Molecular Model

    Hello Everyone, I understand that sometimes in physics we make a model of some physical system purely for theoretical convenience, as it allows us to calculate certain properties of the system very easily; although, sometimes these models aren't actually what is going on, but it doesn't matter...
  33. V

    Effects of Load on Diode Circuit with Exponential Model

    Homework Statement The circuit in the diagram utilizes three identical diodes having I_S = 10−16 A. Find the value of the current I required to obtain an output voltage V_o = 2.4 V. If a current of 1 mA is drawn away from the output terminal by a load, what is the change in output...
  34. G

    Bohr model and quantum model

    Please excuse for my less knowledge in the subject.But I have genuine inquisitiveness. My Question is: If we assume electrons traveling in the orbit around nucleus like planets by inverse square law then electron must always be in the plannar path i,e. never coming out of plane of motion.Then...
  35. M

    An Expanding Wavefront Model ?

    We all know that photons are the particle representation of an EM 2-D wavefront and as the front expands the space between photons increases. We also know that particles of matter can exhibit wave properties. So in an analogous fashion to light, I'm thinking that each of the fundamental...
  36. S

    How to model transient conditions?

    Hello, I am graduate student in NE within the US. I am working on a grant that examines a small (10-100 microns) ceramic film region on the outside of the cladding region. I have assessed the neutronic impact, as well as a thermal impact (heat transfer coefficients, etc.) of the additional...
  37. S

    Eddington-LeMaitre model (expanding universe,cosmological constant)

    I'm trying to solve Friedmann equations for ##k=1 ## & ##p=0## (matter). These are equations: $$3(\dot{R}^2 +1)/R^2 -λ =8πGε$$ $$(2R\ddot{R}+\dot{R}^2 +1)/R^2 -λ=0$$ If we use ##(\dot{R}^2 +1) /R^2## and put it in the second equation: ##\ddot{R}+ω^2/6=0## & ##ω^2=8πGε-2λ## If ##ω^2=0##, then...
  38. tomwilliam2

    Variation of Hubble constant in model universe

    Homework Statement For a problem I'm doing, I am considering a universe in which k=0, and I'm told that I can consider most of the expansion to have happened during a phase when only one of the density parameters was dominant (I know which one, as well), but I don't know the scale factor or...
  39. C

    Drude model electron interaction

    In every source I've checked so far, we make the assumption that we can neglect electron-electron interaction in this model but they always fail to give any reason to answer why this is plausible. Does anyone know how physicists convinced themselves of this at the time and even now (other than...
  40. D

    Transformer model in power system

    Hello I am interesting in transformers lately, and I noticed that most commonly used method for representing transformers in power systems is by symmetrical components. Now, I am wondering - is there any way that we can represent and calculate transformer in phase system, totally without...
  41. M

    Is this a good forecasting model?

    Hi, Please see the attached Excel file. I have a sample of 70 data pairs. The correlation between X and Y is -0.68. The OLS regression coefficient is statistically significant as shown in the file. However, with a R^2 of 0.40, I am not sure if my model would be good enough to forecast Y...
  42. J

    Mathematical Model needed for new product.

    Hi All, Have the following given and would like some help with the 3 questions below. Any help will be greatly appreciated :) City 1 TOTAL POPULATION CITY 1 100,000 Avg Age of Population 27.8 Median Age (Male) 20.5 Median Age (Female) 27.8 % Male Population 46.43% % Female Population 53.57%...
  43. L

    SEMF Liquid Drop Model Homework: Struggling with (ii)

    Homework Statement See attachment. Only struggling with (ii). Homework Equations The Attempt at a Solution So ultimately after doing everything, calculating B(ε)-B(0) & assuming z>>1 and z2/A > 47 I find that B(ε)-B(0) > 0.048ε2A2/3 I don't really see how this tells me if the nuclei will...
  44. B

    Is an AR(2) Model Stationary Under These Conditions?

    Homework Statement Consider the AR(2) model (1 - x1*B - x2*B^2)Xt = εt. Show that Xt is a stationary process if and only if the following inequalities are satisfied: x1+ x2 < 1 x2-x1< 1 |x2| < 1 The Attempt at a Solution 1 - x1*B - x2*B^2 = 0 |B| > 1 so then use quadratic formula...
  45. Q

    Symmetry Groups of the Standard Model: SU(3) x SU(2) x U(1)

    I have a question regarding symmetry groups. I've often heard that the Standard Model is a SU(3) x SU(2) x U(1) theory. From what I understand these groups contain the symmetries under which the Lagrangian function is invariant. If so, what does every one of the 3 groups above contain (what...
  46. P

    Testing regression model with F-test

    Hey guys. I have some trouble understanding how the F-test is used for testing the viability of a regression model. Before I delve into the background/question, just wanted to post a link that discusses the topic briefly: http://www.stat.yale.edu/Courses/1997-98/101/anovareg.htm So, coming...
  47. G

    Applicability of Ising model on real materials

    Hi I chose a Monte Carlo simulation of the 2D Ising model as my Computational Physics course project. Unfortunately, I ran intro problems when formulating the exact problem since my professor probably wants me to simulate a real life material and extract magnetization curve M(T,H) out of it...
  48. E

    Model for spread of contagious disease.

    Hello guys, I am quite unsure in how to start the modeling for population. If I define y as the number of infected persons and y' as the rate of spread is it correct? I see the number of contacts between infected and non infected persons to be equal to the number of infected persons. Otherwise I...
  49. N

    How are dark matter, general relativity, and standard model related?

    In other words, can dark matter be reconciled with GR without drastically changing the idea that force is due to space-time curvature? and in the case of the standard model is there any thoughts of how the force of dark matter is transmitted via the exchange of a particle? It seems that this...
  50. C

    Mathematical Model for Convection Current

    I have a difficult problem on my research exploration for math. I am modeling the convection currents of boiling water in a pot, which is heated by an electric stove. There is a constant supply of energy at 8000 watts (the average for a stove) that heats the pot from the bottom of the pot...
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