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:

View More On Wikipedia.org
Recent contents Top users
  1. M

    I How to propagate errors through a regression & non-linear model?

    Hi, I was working on a predictive linear regression model and was hoping to obtain some bounds to represent the uncertainty present in the model. Question: I suppose this boils down into two separate components: 1. What is a good measure of uncertainty from a linear regression model? MSE, or...
  2. Astronuc

    Auto/Motor How can cogging torque be reduced in permanent magnet synchronous motors?

    This Tesla Model S Owner Repairs His Own Car, because after the warranty period expires, you're on your own. Greg Furstenwerth was an early adopter of the Tesla Model S, but once the car was out of warranty he had a hard time getting the parts and service he needed. So he took on the repairs...
  3. G

    Load model in TensorFlow gives a different result than the original one

    First of all, I'm using TensorFlow version 2.3.0 The code I'm using is the following: from tensorflow.keras.models import Sequential from tensorflow.keras.layers import Dense, Flatten, Conv2D, MaxPooling2D from tensorflow.keras.callbacks import ModelCheckpoint def get_new_model(): model =...
  4. K

    Thermodynamics: Ideal gas model

    Do particles have air in between them in the ideal gas model? I think the answer is 'no, but I am not quite sure about the explanation. Is it because in an ideal gas model, the volume of the particles is negligible? Thank you.
  5. momoneedsphysicshelp

    Nonconservative Forces Problem with a Model Airplane

    I am sure that the answer will be negative, but I'm not 100% sure on how to solve the problem. My initial answer was -350 J. Please help. Thanks!
  6. T

    What are the limitations of the Explicit Finite Difference Model?

    Homework Statement:: Discuss the limitation of the Explicit Finite Difference Model. Relevant Equations:: no formula Hello there, I have to discuss the limitations of using the Explicit Finite Difference model to calculate a 2D Heat Diffusion through an aluminium place, however, I really...
  7. G

    Using complex numbers to model 3 phase AC

    Assume a transformer as above, with 230V L-N, and I want to work out the L-L voltage. A phasor diagram will show me that the voltages are 120° out of phase. (230∠0°) + (230∠120°) = (230cos0 + j230sin0) + (230cos120 + j230sin120) = 230 + (-115 + j199.2) 115 + j199.2 = 230∠60 What I’m looking...
  8. ChrisVer

    A What is the problem with the particle masses in the Standard Model?

    Hi, Several times I encounter the argument that there is a "problem" with the masses in the Standard Model that we try to "understand". From the one side, you have people who ask why the neutrino masses are so small, and from the other side they ask why the top quark mass is so large. The...
  9. M

    Energy landscape in the two state model (Boltzmann distribution)

    From an excel file I can get the probability of each energy state Εi and I saw at Wikipedia that the probability of each energy is proportional with e^−Εi/KT, from this I find the energy of every micro state. Also from the formula which I found on a paper I can get a curve like the curve...
  10. Z

    Is the concept of "potential" just a mathematical model?

    is the concept of potential just a mathematical model
  11. C

    MHB Write function to model combined rate

    The assignment states: Pipe A takes 20 hours longer to fill swimming pool than pipe B. Together, pipe A and pipe B can fill the swimming pool in 30 hours. The assignment question I am stuck on is to write a function R(x) that models the combined rate of the two pipes in relation to the time it...
  12. P

    Heat Diffusion Equation - Using BCs to model as an orthonormal system

    I've tried to show b) by using the sine Fourier series on ##[0,2a]##, to get ##g_k = \Sigma_{n=0}^{2a} \sqrt\frac{2}{a} Sin(q_k x)## Therefore ##\sqrt\frac{2}{a} = \frac{1}{a} \int_0^{2a} Sin(q_kx)g_k dx## These are equal therefore it is an orthonomal basis. I'm not sure if this is correct so...
  13. M

    Engineering Converting a series connected transfer function to the state space model

    Hi, I have a question about a homework problem: I am not sure why I do not seem to get the same answers when using different methods. Question: Given transfer functions G(s) = \frac{s - 1}{s + 4} and C(s) = \frac{1}{s - 1} , find the state space models for those systems. Then find the...
  14. A

    Finding a good descriptive model of the electric circuit (for 8th graders)

    Since this quesstion popped up in this thread I thought it might be better to create a new thread: https://www.physicsforums.com/threads/a-question-about-an-electrons-movement-in-a-dc-circuit.997736/ The question is the following: What kind of descriptive model could/should one use while first...
  15. omega_minus

    I Best way to quantify how well a model fits data

    Hello, I have recorded time-domain data from an experiment. I am using a finite difference time domain algorithm to simulate the experiment. The model has been tuned to resemble the data fairly well but I'd like to be able to quantify the fit. Most of what I see online seems to be about...
  16. S

    I Wheeler's Pre-geometry model and multiple universes?

    John A Wheeler proposed that the universe emerged from a primordial chaos (some sort of pre-geometry or pre-space) from where all physics emerged in the universe. I thought this could be interesting in the context of multiple universes. Therefore, has any well renowned physicist considered...
  17. Rzbs

    I Semiclassical model of electron dynamics

    Why do we exclude interband transitions in semiclassical model of electton dynamics? I mean why it is an assumption in this model?
  18. Will26040

    Engineering Tuning Rules for Lag Dominated FOPDT (first-order plus deadtime) model

    I am trying to find an alternative tuning rule for use with the transfer function specified. Please could someone help by pointing me in the right direction, thanks. Process transfer function: ## \frac {27e^{-3s}} {30s+1} ## Also, am I right in thinking that this process transfer function is...
  19. S

    I Is there any inflationary model without a fundamental theory?

    Cosmological inflationary models are general models in the sense that they could be applied to a variety of fundamental theories. Most physicists working in inflation assume that there is only one (but yet unknown) fundamental theory which through inflation would produce multiple regions or...
  20. E

    Here is a 3D model I made of the Mir space station

    This is a 3D model I made of the Mir space station.
  21. P

    Bohr's model and a statement in my textbook

    In satellite motion around a planet, if the satellite is in orbit, it experiences only the gravitational force and its energy in orbit is constant (see 'https://openstax.org/books/university-physics-volume-1/pages/13-4-satellite-orbits-and-energy'): It's not radiating energy, is it? Its...
  22. M

    Check Inversion Symmetry: Honeycomb Kitaev Model

  23. NickTheFill

    Modelling the tyre as a spring in a quarter car model

    Hi everyone I've just completed a mechanical engineering degree, and one aspect of the classic 2DoF quarter car model that still bugs me is the representation of the tyre as a linear spring attached to the ground. Does anyone have any experience of modelling the system with the tyre spring...
  24. S

    Assignment on the tight binding model

    Summary:: Due tight-binding model I derived the energy spectrum of the particle, showing that it comprises three energy bands E+(k), E−(k) and E0(k)=0. Now, I have to find the dispersion laws. Why do I have a flat energy band? What is its physical significance?. Also, what happens to the...
  25. Rzbs

    A Wannier function in tight-binding model

    What is the relation between Wannier function and LCAO in tight-binding (TB) model? I know in TB we use LCAO but why we have an alternative approch using Wannier function? For example as said in this lecture note: But I don't understand why we use wannier function? Or in general why we use a...
  26. john baez

    A Octonions and the Standard Model

    I've slowly been writing a thread on octonions and particle physics, just to explain some facts in a self-contained way, with all the proofs. I don't know where this will lead. I'm certainly not presenting a theory of physics, much less advocating one. Mainly it's just fun. Octonions and...
  27. DarkMattrHole

    B Question regarding 'beauty' in the theories that go beyond the standard model

    There has been a lot of talk about the value of beauty in theoretical physics. There seems to be a lot of little things that are beautiful because they make sense, according to what we already know, like the discovery of anti-particles, and recently the Higgs. The standard model was revealed...
  28. J

    I Born rule in classical Ising model: Feynman -> Boltzmann ensemble?

    Quantum mechanics is often said to be equivalent with Feynman path ensemble, which "after Wick rotation" becomes Boltzmann path ensemble, also called euclidean path integrals (popular for numerical calculations), or random walk/diffusion MERW (maximal entropy random walk). But Boltzmann path...
  29. Quantum23

    A What is gravity in the superfluid vacuum model of quantum gravity?

    It has been hypothesized by quantum field theory that the vacuum is not empty due to the energy time uncertainity relationship. Instead it is filled with a sea of virtual particles popping in and out of existence and renormalized to the observed value we see today in experiments like the casimir...
  30. M

    A Solution to an ODE (Leaky Integrate and Fire Neuron Model)

    I'm looking for a general analytical solution to a particular ODE that comes up in neuroscience a lot. My feeling is that such a solution can't be obtained, otherwise someone would have presented it by now, but I don't have a good understanding of why it is so hard to solve. The equations as...
  31. M

    Fully analytical solution for the "Leaky Integrate and Fire" Neuron model

    Does anyone know if it is possible to develop a fully analytical solution for a leaky integrate and fire neuron driven by arbitrary time-varying current? Here's what I have so far (setting as many possible constants to 0 and 1): The equations: ## \dot{V} = - V + I(t) ## and if ##V(t) = 1##...
  32. A

    Create a model for a collision

    My homework consists of trying to create a simple model for a collision. But I have trouble understanding a specific part of the assignment, namely what g-force is. I'm guessing that I'm allowed to make assumptions. But without understanding adequately the definition for g-force, I don't think...
  33. JackFyre

    B Clarification about Bohr's atomic model

    Hey guys! Not a brain scratcher as such, just a clarification. When we talk about Bohr's postulates for his atomic model, would the Bohr-Bury scheme be involved in it? like in his postulates?
  34. M

    Soliton model of the action potential

    Has anyone else come across the soliton model of the action potential? https://en.wikipedia.org/wiki/Soliton_model_in_neuroscience It seems extremely non-mainstream, especially given that it presented as an alternative to the Hodgkin-Huxley model, which is undoubtedly the most successful...
  35. Sunny Singh

    Relaxation time and average electron velocity in Drude model

    If τ is the relaxation time, τ means, on average the time between two collisions for an electron moving under a constant electric field inside a metal. Now according to the assumptions of drude model, the electron acquires an additional velocity of \frac{-eEt}{m}where t is the time elapsed since...
  36. S

    I Bootstrap model and different laws?

    Physicist Geoffrey Chew proposed the concept of bootstrap (related to S-matrix theory) where he denied that fundamental laws of nature existed at all, as it is indicated in a writing in his memory written by one of his collaborators ([https://www.fritjofcapra.net/in-memoriam-geoffrey-chew/])...
  37. J

    I How to choose a random walk to best model diffusion?

    To choose random walk on a graph, it seems natural to to assume that the walker jumps using each possible edge with the same probability (1/degree) - such GRW (generic random walk) maximizes entropy locally (for each step). Discretizing continuous space and taking infinitesimal limit we get...
  38. sbrothy

    B Beyond the Standard Model Explanations of GW190521

    Title says it all. Maybe it belongs more in Astrophysics but given the title... "Beyond the Standard Model Explanations of GW190521" - - - - https://arxiv.org/abs/2009.01213 If this is for real I'm surprised it's gotten so little attention..? EDIT PS: (for my own convenience mostly) ...
  39. somasimple

    Where are these connections "anatomically" located in the HH model?

    Hi, Here is a basic picture of the famous electric circuit of the HH model. Can someone please tell me the anatomical locations of the connections marked in red in the cell? Thanks.
  40. AndreasC

    I What are the most important phenomena that the Standard Model can't explain?

    I guess the crux of the question is, where are we more likely to encounter new physics? The standard model already explains almost every experimental result, but not EVERY result. But what are some of the most important results that are either incompatible with the standard model or just...
  41. Danny Boy

    A Quantum Ising model correlation function query

    In this paper, on quantum Ising model dynamics, they consider the Hamiltonian $$\mathcal{H} = \sum_{j < k} J_{jk} \hat{\sigma}_{j}^{z}\hat{\sigma}_{k}^{z}$$ and the correlation function $$\mathcal{G} = \langle \mathcal{T}_C(\hat{\sigma}^{a_n}_{j_n}(t_n^*)\cdot\cdot\cdot...
  42. M

    Fluids: Kistler contact angle model

    Hi PF! I keep seeing Kistler's contact angle model wrote like this $$ \theta_d = f(Ca+f^{-1}(\theta_e)) : f = \arccos\left( 1-2\tanh\left( 5.15 \left( \frac{x}{1+1.31x^{0.99}} \right)^{0.706} \right) \right) $$, where the plot then has a sort of break, something like this: But this is not the...
  43. nomadreid

    I Measurable cardinal to get inner model, also in cumulative hierarchy

    If κ is a(n inaccessible) measurable cardinal, then there exists an elementary embedding j:(V,∈)→(M,∈), with critical point κ, whereby (M,∈) is an inner model of ZFC and the construction of j can follow through taking a κ-complete, non-principal ultrafilter U and constructing κV/U. In the von...
  44. Leo Liu

    Understanding the Tomlinson Model of Sliding Friction

    I have just watched a video lecture about the Tomlinson model (aka Prandtl–Tomlinson Model) which explains the friction mechanism at a nanoscale by analogy with a tip dragged by a spring. The video has prompted me to ask several questions. The spring is dragged over a corrugated substrate, as...
  45. nughii

    The Mathematical Model of a DC Bus Voltage on a Microgrid

    I want to compute the dc bus voltage using a programming language, but I doubt the initial value that I should enter. I use the model from this document. This is the explanation about this model Based on my understanding, ##v## is the grid voltage. This value can change. What is the initial...
  46. Jehannum

    Gap in the market for a book on the Standard Model

    Summary:: Is there a primarily non-technical book covering all aspects of the Standard Model of particle physics? The Standard Model comes up a lot in YouTube videos. There must be a decent amount of public interest. I think there would be a market for a semi-technical but accessible for the...
  47. FourEyedRaven

    Particle What are the best resources for studying physics beyond the standard model?

    Hi. I'm looking for recommendations of books, surveys, or lecture notes, that deal with physics beyond the standard model all in one place. The starting point is someone who already knows QFT and the SM at the level of Schwartz's book on QFT and the SM...
  48. fresh_42

    Quantum Article about the Standard Model

    I thought this might be worth a read: https://iopscience.iop.org/article/10.1088/1361-6552/aa5b25/pdf
  49. TachyonLord

    A Books/Resources related to the thermal model for particle production

    I can only find papers relating to how they've used the model but nothing about the model.
  50. bland

    I Why isn't the Goldstone boson on the Standard Model map?

    They seem to have something to do with Z or W particles, maybe, and they have something to do with mediating weak iso spin, I think, and they may be related to the Higgs field. But they don't have a box dedicated to them on the Standard Model of particle physics. Can someone tell me why this is...
Back
Top