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. P

    Dimension of a graphical model

    Can someone tell me what is the "dimension" of a model? For example, the dimension of a saturated model. thanks
  2. powerof

    Solving for v_y max in a Spin-Friction Free Tennis Ball Model

    Homework Statement Title might be unclear since I had little space to explain. I'll state my problem from the beginning: I don't know how to determine one of the constants in formula for the velocity (the maximum velocity on the y-axis to be precise). I need that constant because I want to...
  3. T

    Re-Examining Black Holes and the Standard Model

    I was thinking about this and either I have a misunderstanding of black holes or they are simply not how the standard model proposes them to be. Lets start out by setting a few a statements from the standard model that you agree with. If you disagree about any of these points please comment so...
  4. J

    Is this the model that all the big-name tech companies follow?

    From what I can tell, here's what Google, Amazon, Facebook, Microsoft and all the other big-name tech companies of today do: Keep a lean force of developers on staff. The hiring process is very selective. While these workers will have amazing pay and benefits, they also will work long hours...
  5. N

    How Do Horizontal and Vertical Movements Differ in Subducted Plates?

    For my homework I was given a velocity diagram of the Juan de Fuca plate similar to this: The first question is as follows: Measurements indicate that the Juan de Fuca plate is moving at a speed of ~40 mm/year. Calculate, and draw diagrams that show, the horizontal and vertical components...
  6. R

    Unit Circle and Quantum Predictions [hidden variable model agrees with QM?]

    I would like to reopen a discussion on assertions made by David Mermin such as: “There is no conceivable way to assign such instruction sets to the particles from one run to the next that can account for the fact that in all runs taken together, without regard to how the switches are set, the...
  7. B

    How Did We Develop Early Models of the Atom?

    In my studies, I find myself coming back to the same question.How do we know all these things about matter. Its quantized, it has mass and, charge and blah blah blah. I understand that these models of the building blocks of "physical things" are well tested mathematical models that attempt to...
  8. V

    Is the Energy Change in a Bohr Atom Always Equal to One Photon?

    From Wikipedia, the following diagram explains the energy emitted when an electron jumps from a higher-energy shell to a lower-energy shell: I already know that the energy of a single photon is equal to ##hf## and in this diagram, ##\Delta E=hf##. Does that mean that ##\Delta E## is only one...
  9. Lolligirl

    MHB Writing a Mealy model for the 2's complement of subtracting 1101?

    This question is worded in a confusing way: Question: Write a Mealy finite state machine that produces the 2’s complement result of subtracting 1101 from a binary input stream (assuming at least 4 bits of input). So our input here is e.g. 10010101 or 001011 or something similar, and we want to...
  10. H

    Mathematical model for pearlite interlamellar spacing

    It is seen that interlamellar spacing in pearlite becomes finer by increasing rate of cooling. theoretically this is because the rapid cooling rate produces more nucleation sites for lamella percipitation. so i tried to create a mathematical model using gibbs free energy change during...
  11. T

    Question about the "Bounce" model of BH and Anisotropy

    I have some doubts/questions about the new BH model. This model gains popularity, but does it make any sense? Q1. Assuming the extreme time dilation inside BH, even tiny anisotropy after the bounce leads to HUGE (billion years) differences in the time of the visible explosion. One can argue...
  12. B

    Oscillation frequency of electrons in atoms (Bohr model)

    Homework Statement Here is a picture: http://puu.sh/bZtAu/82bdc201bc.png Homework Equations For force, F = (Ze^2)/4 * pi * e0 * R^3) * r f = sqrt(k/m) * 1/2pi Where e0 = vacuum permeability, 8.854 x 10^-12m and r = radius of hydrogen atom, 5.3 x 10^-11m The Attempt at a Solution I...
  13. B

    How Should Manage Be Represented in an ER Diagram for a Video Rental Company?

    I am doing a ER Diagram for a class and having a lot of trouble with a specific piece of the sentence. Anyway, here is the business requirements we are diagramming: The video rental company has several branches throughout the USA. The data held on each branch is the branch address made up of...
  14. M

    Exploring the Interaction Model of a 3D Hypersurface

    Homework Statement This is not homework but relevant to an interaction model that I am developing. I assume an even distribution of sources on a spherical 3d-hypersurface, the sources having a potential as a function of pairwise 4-distance between any two sources. I wish to obtain the sum...
  15. M

    Critical Exponents in the 1D Ising Model

    Homework Statement Obtain the critical exponents for specific heat, susceptibility, and the order parameter (magnetization). Homework Equations $$A = -k_B T N \ln \left[e^{\beta J} \cosh (\beta h) +\sqrt{ e^{2\beta J}\sinh^2 \beta h + e^{-2\beta J} }\right]$$ $$\left<m \right> \propto...
  16. fluidistic

    Ising model without spin-spin interaction

    Homework Statement Hey guys! I'm not convinced by what I obtained so far, please tell me whether I'm in the right or wrong direction. The Hamiltonian has the form ##H=-h\sum _i s_i## where ##s_i=\pm 1## and ##h=kT##. 1)Calculate the partition function and the Gibbs free energy. 2)Calculate the...
  17. J

    Model an FPGA FM Radio Demodulator in Python

    I am trying to model an FPGA FM radio demodulator in Python. I will have a mixer that converts an FM channel to 36MHz IF, and I plan on undersampling this IF signal. If in the digital world (my Python model), I have a high sample rate FM signal at 1.2MHz, should I be able to resample to a...
  18. P

    Why Does the Hopping Term in the Hubbard Model Project to Zero at Half-Filling?

    This is a question from Altland and Simons book "Condensed Matter Field Theory". In the second exercise on page 64, the book claims that if we define \hat P_s, \hat P_d to be the operators that project onto the singly and doubly occupied subspaces respectively, then at half-filling the...
  19. A

    How Do You Use the Incremental Model to Analyze Diode Circuits?

    Homework Statement Homework Equations r_d= V_T/I_D, V_T=25mV The Attempt at a Solution i alreayd find the operation of diodes, D1 off and D2 on (2nd circuit). the current through this diode i also calculate as 34mA, also r_d=0.7353 ohm. I am having trouble using incremental model, in my book...
  20. U

    Need guidance on Proof theory and Model theory

    Hi, I'm planning to start my Master programme this december. I am very interested in philosophy of logic. And i am inclined to read more proof theory rather than model theory. And i really wanted to engage in proof theory as my first reading materials towards mathematical logic area...
  21. D

    Converting Pressure to Power in a Scale Model Boat

    I have built a model boat, ( http://schoolroad.weebly.com/rpgmodel_11.html ) and am trying to find out the amount of Power - maybe in Watts, that it takes to propel it at different speeds while it is running on the water. I have a rough sketch of the mechanism principle attached. When the...
  22. S

    NPN transistor model for use with differential equations-LC oscillator

    Hello, I am trying to get a better understanding of how oscillator circuits (clapp, hartley, colpitts etc) work, so I have been trying to solve the differential equation for a very simple one--the one most the way down the page here...
  23. H

    De Broglie wavelength - model for comparing photons and electrons

    Hello, I'm thinking about the wavelength of a freely propagating photon vs. a freely propagating electron. For the photon, we have the classical picture of oscillating E and B fields perpendicular to the direction of propagation, and we call the wavelength of the photon, which can be...
  24. C

    Understanding Kaon Notations on Chart Before Standard Model

    I was looking at this old chart (before the standard model was completed) and this thing with Kaon notations was confusing. So I understand that the top right number on a particle denotes charge, but what is subscript? Does that denote the number, as in which exact particle it refers to? Because...
  25. M

    How to model the flight kinematics of an airplane with air resistance?

    I want to derive some equations for a 2-D airplane's motion, specifically when it lifts off and lands. Can someone show me where I can start and how I can use differential equations to develop equations like the speed/position of the airplane in its x and y components? Also, if anyone is...
  26. H

    Discrete logistic equation, restricted growth model

    Homework Statement I need to write \begin{align*} N_{k+1} = \frac{\lambda N_{k} }{1+aN_{k} } \end{align*} in the form \begin{align*} N_{k+1} = N_{k} + R(N_{k})N_{k} \end{align*} Homework Equations As above The Attempt at a Solution I know that \begin{align*} N_{k+1} = N_{k} +...
  27. R

    Thrust from model engine exhaust

    I’m interested in your views on whether any significant thrust could be obtained using the cooling air and exhaust gases from a model aircraft engine. International class control line speed models (known as F2A) achieve speeds of around 300 km/hr using 2.5cc engines and tuned pipe exhausts that...
  28. T

    MATLAB Model a circle using finite difference equation in matlab

    hello. I have a MATLAB skeleton provided because i want to model a distribution with a circular geometry. all in all, i want the 3d graph of the code to be some type of cylinder. This is the code: % flat step condition for ii=1:nHi, for jj=1:nHj, if (X(ii)/R_P)<1 &...
  29. M

    Understanding the 4-Stage Doppler Model: Exploring Sound Waves in Air

    Hi, I was hoping that somebody might be able to help me better understand/verify a Doppler model from the perspective of both a stationary and moving reference frame. For the current purpose, this Doppler model might be generally described in terms of sound waves in air, where air is assumed to...
  30. U

    Renormalizability of the Standard Model

    Why is it such a big deal? According to the "modern" (Wilsonian) viewpoint, non-renormalizability is not such a "sickness" of a quantum field theory, as long as one adopts the viewpoint that the theory is not UV complete, aka, the theory is simply an effective field theory with a finite cut-off...
  31. Warpspeed13

    Would it be possible to build a model tokamak

    Would it be possible to just get a swirling plasma in an acrylic tube kind of like the arc reactor in iron man? I'm not talking about anything close to the temperatures or pressures required for fusion just kind of a demo piece to show the general idea.
  32. P

    Can I prevent setting up standing waves in my COMSOL model?

    Can I prevent setting up standing waves in my COMSOL model? I'm using integration over two opposing faces to get the pressure at the 'outlet' - but it seems that no matter what I do to prevent the standing waves, they won't go away. Any help would be great, Thanks
  33. P

    EPQ: Mathematical model of tea bag diffusion

    I've done some research, and I've looked at the derivation of the diffusion equation, but I don't want to reproduce even a more simple version of it. I'd like something that can I do almost exclusively myself. The point of this is not to plot some graphs, and extract some line of best fit or...
  34. S

    Renormalization of the non-linear [itex]\sigma[/itex] model

    I have some questions about this paper:http://users.phys.psu.edu/~radu/extra_strings/freedman_sigma_model.pdf In section 3, they renormalize the bosonic non-linear \sigma model at one loop level. The action is given by I_B[\phi]=\frac{1}{2}\int...
  35. Austine-J5

    What type of motor is best for powering a homemade helicopter?

    Hello guys, I have a project I intend to embark on,actually it a helicopter,but I still can't figure out the best type of motor to power the blades of my design. I need something light,small and POWERFUL. I look forward to your contribution. Thanks in advance.
  36. Y

    Intro Quantum Mechanics: Neils Bohr Model Explained

    Recently, I saw a video on Introductory Quantum Mechanics. Here's the link : https://www.youtube.com/watch?v=5Gnqpbge3Yk I failed to understand the explanation of de Broglie's model. He mentions that the waves interfere with each other but how do we know the properties like amplitude etc. of...
  37. B

    Error by Model import sab. Modeltyp in Ansoft 15.

    I try to import a sab. Modeltyp in Ansoft 15. but i receive an error that translation for the model is failed or saved file is from a later version. how can i fix the problem. Thank you .
  38. E

    When does the Debye-Gru model become unacceptable to use?

    So the Debye-Gruneisen model seems to work quite well for most solids at low tempeartures, and in many cases at room or higher temperatures. But is there a good overview of when this would fail for a condensed phase? Such as van hove singularities that are unexpected compared to a "standard"...
  39. T

    Fitting a mixture model when component priors are known

    I have a list of scores between 0 and 1 generated by an information retrieval system - 1 being very relevant and 0 being completely non-relevant. I do not know whether the scores correspond to relevant or non-relevant items or not but I do know that the distribution of scores is generated by a...
  40. I

    What Is the Most Current Model in Solid State Physics?

    Hi Everyone, I was curious as to what the most current model in solid state physics is. I've studied the Einstein and Debye Models in Stat Mech, as well as free electron and tight binding models in an intro solid state class, but these models are rather old(which does not imply they are...
  41. R

    Coudln't find Steven Weinberg's "a model of leptons"

    i searched Steven weinberg in google scholar. it returns many articles but "a model of leptons" why does "a model of leptons" not appear in google scholar? is there some mistake or some reason for it not to appear? it seems odd that the famous articles is not found Phys. Rev. Lett. 19, 1264...
  42. W

    Why is the mathematical model favored over the mechanical model?

    In theoretical physics, why is the mathematical model favored over the mechanical model? Awhile back, I posted a thread asking about what each theory posits as real. For example, quantum field theory might limit the set of real things to fields, field quanta, the universe, and causality. It...
  43. duhuhu

    Glued Versus Solid Model in Modal Analysis

    I am performing Modal analysis on a fairly simple structure (a square aluminum rod with some pillars attached to the top of it) and need to get some basic modal analysis results. Making a solid aluminum piece would be rather expensive and time consuming to design and then mill out, so the...
  44. M

    Symmetries of the Standard Model: exact, anomalous, spontaneously brok

    There are a number of possible symmetries in fundamental physics, such as: Lorentz invariance (or actually, Poincaré invariance, which can itself be broken down into translation invariance and Lorentz invariance proper), conformal invariance (i.e., scale invariance, invariance by...
  45. A

    Designing a far flying catapult launched model glider

    Many of you are familiar with the catapult launched profile fuselage gliders that are sold in hobby stores. Since these tend to rather fragile, I am designing gliders with better durability out of card, and also with a full fuselage. These will have a 20 cm wingspan typically. Given that low...
  46. A

    Develop Model Emulating Given Wave Pattern

    Question: Develop a model for producing a repeating pattern of 8 waves, with 6 smaller waves of approx. the same size and the second and sixth waves much larger. The sketch below gives a general indication of the eight wave pattern. (Sorry for large image) I would like to know how to "take...
  47. Serious Max

    Word problem involving sinusoidal model

    Homework Statement Homework Equations y=30\sin(\dfrac{2\pi}{20}t)+270 General principal solutions: t=\left(\dfrac{\arcsin(\dfrac{1}{3}) 20}{2\pi}\right)+20k, k\in \mathbb{Z} t=1.08173+20kGeneral symmetry solutions: t=\left(-\dfrac{(\arcsin(\dfrac{1}{3})-\pi)20}{2\pi}\right)+20k, k\in...
  48. M

    Questioning 3D Model views of effect of large bodies on curving space.

    Hi everyone. I am not a physicist or scientist but this is a question I have pondered for a while now. Everytime I see a model of how large bodies (eg Earth and sun) bend the planar representation of space (creating a "cup" or "dip") I always feel that this is not completely representative...
  49. S

    Build a Model Hadron Collider at Home!

    Hi guys, I have the idea of putting together a model collider that fires two smashable objects (eggs or whatever) at each other and show a high speed camera footage of the objects hitting each other - this is all as an analogy of what the hadron collider does at CERN. Any ideas what I...
  50. lfqm

    Identical atoms in the Dicke model

    Hey guys, I've recently read about the Tavis-Cummings and Dicke models and I got a little bit confused about them. They are suppoused to model N identical atoms interacting with a one-mode EM field, however the atomic operators are defined in the basis (for the case of two atoms)...
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