# Questions tagged [modeling]

Questions about approaches for simulating physical systems or phenomena by building from related understanding and basic principles.

165 questions
Filter by
Sorted by
Tagged with
459 views

### Large deformation of solids

Link to notebook with this question and code I'd like to understand how large deformations of solid mechanics work and how they are implemented. For this am looking at the following reference problem: ...
73 views

### NDSolve not finding the right solution for a mass hanging of a thread

My NDSolve isn't predicting the right trajectory for one particular case of a problem. System Consider a mass vertically hanging by an almost inelastic thread. The ...
64 views

### How to model the following system of ODE's in Mathematica with plots of the solution?

Consider the following (i) \begin{align} \frac{d S}{dt} &= -\frac{\beta S I}{N}\\[2ex] \frac{dI}{dt} &= \frac{\beta S I}{N} \end{align} Where $N=S+I$ is the total population. (ii) \begin{align}...
51 views

### Help with plotting the bifurcation diagram $R_0$ vs $I.$ [closed]

I am working on the paper "A short study of an SIR model with inclusion of an alert class, two explicit nonlinear incidence rates and saturated treatment rate" by Kumar, Nilam and Kishor and ...
397 views

### Mass Transport Model

I've asked similar questions before about Mathematica's Mass Transport model. My aim is to model these systems and show how they change by manipulating various parameters. This time it's the following ...
145 views

### Solving time dependent Schrodinger equation for a wavefunction and harmonic oscillator [closed]

How can I obtain a GIF/graph similar to these ones here by solving the time-dependent Schrodinger equation $$i\hbar\frac{\partial ψ(x,t)}{\partial t} = -\frac{\hbar^2}{2m}\nabla^2ψ(x,t) + V(x)ψ(x,t)$$...
123 views

### Mass Transfer Value

I'm trying to model the following boundary condition using MassTransferValue.  D_A \frac{\partial[A]} {\partial x} + D_B \frac{\partial[B]} {\partial x}+ D_C \...
206 views

### How to add an attractive potential (migration term) named component to Mass Transport PDE

Wolfram Mathematica 12.2 now features "Named Partial Differential Equation Terms" For specific physics fields, relevant PDE terms have been packaged as components and augmented with ...
60 views

### 2D transient heat equation resolution

I'm writing a code to get the analytical solution mentioned in Sun et al., 2013. I will copy here the passages needed to solve the equation. The 2D transient heat equation is: First of all, I set the ...
63 views

### Graph embedding constrained to a surface?

Have been contemplating it for a while, but did not dare to post as I felt like this must be a major undertaking to implement. Then saw the excellent answers to a recent question RegionPlot3D KnotData ...
47 views

### Microcontrollerembedcode unable to connect to Arduino Yun

Hi Mathematica enthusiasts, I am trying to follow this tutorial off Wolfram reference for microcontrollers Real Time Data Acquisition I have an Arduino Yun Rev2 hooked up exactly as it is from the ...
36 views

### finding FWHM of a dataset with unknown mathematical equation

I have a dataset. I have plotted using "Listloglinearplot". Now I need to find the FWHM (full width half maxima) of the same, However I dont know which mathematical eqution describes best to ...
78 views

### NDSolve for ODE-PDE Problem

happy holidays, I am solving a coupled ODE - PDE system -for simplicity all coefficients are taken as 1-. I checked other questions on the issue but couldn't find any suitable answer or comparison. ...
49 views

### How to formulate NDSolve[…] for a two-sector SIR model

The following Code aims to simulate the employment effects of a pandemic, drawing on the conventional SIR model. I extended the SIR model with two economic sectors (...
82 views

### Does mathematica have support for mixture models?

Does Mathematica have support mixture models? Similar to the R language libraries mclust or ...
519 views

### Time dependent Schrödinger equation in 2D

I have the following Schrödinger equation in $2D$: \begin{cases} \partial_t \Psi(x,t) = V(x,t) \Psi(x,t) \quad x \in [-10,10]^2\\ \Psi(x,0)=\exp( \frac{1}{2} (-x^2+y^2)) \end{cases} where the ...
80 views

### Equation Plotting

I'm using the mean field theory approximation and the Ising Model for magnetization to come up with the following equation: m(T) = tanh(m(T)/T) where T is an ...
166 views

### Nonlinear Difference Equations [closed]

How can I plot the nonlinear difference equations?
77 views

142 views

### FindFit problem, some models work — and some do not

I asked this question. Answers and comments were appreciated. But (some) of the comments did not make satisfied. [Maybe due to my bad English I did not describe my problem very well]. Let me try ...
133 views

### FindFit, FindFormula, Fit, NonlinearModelFit - Which one to use? (I got no good curves & plots)

See this code, what mistake I did? (I got no plot) ...
38 views

### Having trouble with NDSolve [closed]

I'm trying to plot the solutions to the following set of differential equations, I'm doing this through NDSolve with the following code, ...
73 views

### FindFit low speed when fitting polynomial coefficients: is it possible to significantly increase the speed?

I work in Mathematica with a Butterworth filter, the transfer function of which depends on the selected order and cutoff frequency. I want to evaluate the change in the location of the roots on the ...
116 views

### How to model the movement of a mass over a dome?

I'm trying to replicate the graphs and animation found in this page that studies the movement of a mass over a dome solving numerically the differential equation ...
76 views

### Trying to recreate a plot which tracks the age of individuals inside a compartment model

I am using a compartment model from this paper. I am trying to recreate Figure 6. I will be honest, I have no clue how to approach this. The paper doesn't give information on how to achieve the ...
240 views

### Find best equation for data and the area under curve

How can I find the best formula that describe the following Figure and also find the area under the curve (the numerical value): The data for the figure can be found here: https://pastebin.com/...
54 views

### How can I get a plot of “surface area coverage” of a parametric plot?

I have a parametric function defined by the x and y functions: ...
60 views

### Why do I keep getting these error messages?

I am trying to fit a parametric differential equation system to the data of the infection cases in Hungary. I keep getting the error messages: ParametricNDSolveValue::ndcf: Repeated convergence ...
67 views

### Simple neural network with feedbacks in state-space form

Having studied more or less in detail the mechanisms of working with the state-space that Mathematica provides us with, I asked myself: can these tools be applied to neural networks? This article ...
148 views

### Conditional Random Walk

I am attempting to model a physical process I'm observing in the lab with a random walk generator. I need to find a way to impose a condition such that when the random walk runs into a point in the ...
60 views

### Count data fitting with Nonhomogeneous Poisson process

Following is count data needed to model with a nonhomogeneous Poisson process (NHPP). For each row-wise e.g. 8:15-8:30, every 12 intervals of 15 minutes size and 15 days of data collected. I have ...
82 views

### Changing a parameter by specific time in NDSolve in a COVID-19 spread simulation

I'm trying to create a mathematical model for COVID-19, to help my city, using the follow system of equations: ...
111 views

### 3D Plotting and optimising on the surface area of a spherical gyroid [closed]

*this is an equation of a shperical gyroid emphasized texti want to plot it in mathematica and obtain the shapes like those on the picture below. sinxcosy + sinycosz + sinzcosx = 0 i also want to know ...
95 views

### How to turn a collection of contour lines into a printable object (mesh, etc)?

Inspired by Henry Segerman's developing fractal curves, I decided to try to convince Mathematica to do something similar. The inspiration for cf, f, and g below came from How to make this Dragon Curve?...
33 views

### Export and Printout3D missing pieces in STL file

I'm experiencing some strange behavior when using Export and Printout3D on the entire object created below. Exporting each part individually or using Printout3D work just fine. Also, for some reason ...
419 views

### Help with “Coordinate should be a pair of numbers, or a Scaled or Offset form.”

I am plotting the pair of recurrence relations: ...
271 views

### Lagrangian of three-mass system with Mathematica

Before proceeding to calculations in Mathematica, I would like to clarify with knowledgeable people. There is an ordinary linear three-mass system. If we write its Lagrangian, we get the following ...
89 views

### Plotting fibre direction at each node

I was wondering if there was a way to plot the direction vector of a fibre family at each node in AceGen/AceFem? Below is an example of exactly what I want to do but I do not know how to recreate it. ...
199 views

### Logistic fit of data

I would like to use LogitModelFit to find the logistic function to my data. The error I obtain is LogitModelFit::binrsp: The response values are expected to be ...