Non-linear Definition and 340 Threads

  1. R

    MATLAB Newton-Raphson Method for Non-linear System of 3 variables in Matlab

    I am trying to solve 3 non-linear system of 3 variables using the Newton-raphson method in matlab. Here are the three equations: \begin{equation} c[\alpha I+ k_f+k_d+k_ns+k_p(1-q)]-I \alpha =0 \end{equation} \begin{equation} s[\lambda_b c P_C +\lambda_r (1-q)]- \lambda_b c P_C =0 \end{equation}...
  2. J

    Solution of system of non-linear equations

    1. Is there a general condition for the existence and uniqueness of solution of a system of simultaneous non-linear equations similar to the determinant test for a system of linear equations. 2. What are the solution methods (theoretical and numerical) for solving a system of simultaneous...
  3. R

    MHB How to Solve Non-Linear Equations of 3 Variables Using Newton-Raphson Method?

    The three non-linear equations are given by \begin{equation} c[(6.7 * 10^8) + (1.2 * 10^8)s+(1-q)(2.6*10^8)]-0.00114532=0 \end{equation} \begin{equation} s[2.001 *c + 835(1-q)]-2.001*c =0 \end{equation} \begin{equation} q[2.73 + (5.98*10^{10})c]-(5.98 *10^{10})c =0 \end{equation} Using the...
  4. M

    How to Solve a System of Non-Linear ODEs in Physics?

    Hello everybody. Solving a problem in Physics I run into a system of equations that I do not know how to solve, I would appreciate some help. Here is the system: \ddot{x}+4\dot{x}^2=C_1e^{y} \dot{y}^2=C_2\ddot{x} The dependent variables are x,y. C_1 and C_2 are some constants. I try...
  5. MarkFL

    MHB David's Math: Solving a Non-Linear System in 2 Variables

    Here is the question: I have posted a link there so the OP can view my work.
  6. ETBunce

    MHB Non-linear function with two unknown constants and one variable

    Am am presented with the problem: h(t) = c - (d - 4t)^2 At time t = 0, a ball was thrown upward from an initial height of 6 feet. Until the ball hit the ground, its height, in feet, after t seconds was given by the function h above, in which c and d are positive constants. If the ball reached...
  7. J

    Condition for a vector field be non-linear

    If a vector field ##\vec{v}## is non-divergent, so the identity is satisfied: ##\vec{\nabla}\cdot\vec{v}=0##; if is non-rotational: ##\vec{\nabla}\times\vec{v}=\vec{0}##; but if is "non-linear" Which differential equation the vector ##\vec{v}## satisfies? EDIT: this isn't an arbritrary...
  8. J

    Non-linear acceleration in swim cap for data consistency(help)

    Dear Experts! I am currently try to measure the drag of an buoyant object. I did 10 replicates, in general terms 10 tests all with the same set-up and same release mechanisms. To start off with I will explain my project: Drag reduction in swim cap First of all I got one accelerometer...
  9. V

    Uncertanty in a non-linear regression with least squares method

    Homework Statement Ok, so I'm trying to fit a set of data (21000 points to be exact) to a sine function. Homework Equations Y = A*sin(ωt) The Attempt at a Solution I used NumPy to get the parameters A and ω with the least squares method. So far, so good. However, i appear to...
  10. D

    Ohm's Law & Non-Linear Circuits

    Ohm's law only applies to linear circuits. If most loads in life are non-linear, what use is ohm's law?
  11. C

    First order non-linear differential equation

    Homework Statement Hello, I was given an extension problem in a Dynamics lecture today and am struggling to solve it. It is a simple scenario: a particle of mass m is accelerating due to Galilean gravity, but is subject to a resistive force that is non-linear in the velocity of the particle...
  12. 5

    Second order non-linear differential equation involving log

    EDIT: my problem is solved, thank you to those who helped Homework Statement Solve: x y^{\prime \prime} = y^{\prime} \log (\frac{y^{\prime}}{x}) Note: This is the first part of an undergraduate applications course in differential equations. We were taught to solve second order...
  13. P

    A system of 2 non-linear equations with 2 unknowns

    Homework Statement i'm trying to find a solution for these two equations, p & q are variables and c is known constant (it's given randomly) : $$ \begin{align}...
  14. I

    How can I solve a non-linear functional problem numerically?

    Hello, I'm not really sure where does this question fit and what title should it bear, but here is my problem: \psi(x) \exp (a\psi(x)^2) = C f(x) given a positive definite f(x), find ψ(x) and the constant C, subject to the condition \int \psi(x)\, dx = 1 I want to solve this numerically...
  15. ajayguhan

    Understanding Normal Modes of Objects - Linear vs Non-Linear Particles

    What does one mean by normal mode of an object? Why is it 3n-5 for linear particles, 3n-6 for non linear particle where n is the number of particle.
  16. D

    MHB First Order Non-Linear Ordinary D.E.

    Hello people, I couldn't solve the given D.E by using exact d.e & substitution method :( Thanks in advance. (x*y*sqrt(x^2-y^2) + x)*y' = (y - x^2*(sqrt(x^2-y^2) ) gif file of d.e can be found in the attachments part.
  17. M

    MATLAB Polymath or Matlab non-linear algebraic solver

    Hello, I am having difficulty inputting a non linear algebraic equation into polymath to solve for reference the equation is x*(100-.5*x)^0.5/(15-x)/(20-.5 * x)^0.5 - 87.824 == 0 and I want to solve for x, but haven't gotten anything. Also I don't know how to program it into matlab...
  18. H

    [Wolfram Mathematica] Using Newton's method to solve non-linear system

    Hi. This is not actually not part of the homework; but it's something I'd like to do. I have to solve the following system using Newton-Raphson's method: $$\begin{matrix} \frac{X}{\mu }+Y=1 \\ X=\left( \lambda -\left( K-1 \right)X \right)Y \\ \end{matrix}$$ Surfing the...
  19. M

    Non-linear multivariable functions

    I wanted to know if there is any way of classifying the set of all non-linear multivariable functions. I wish to analyse something over all possible non linear functions with 4 variables. In fact these variables are binary variables. for example f(x,y,u,v)= x.y - u\oplusv
  20. B

    Non-linear convolution and power series

    Homework Statement Hi, suppose we have the summation \sum_{i=0}^{n-1} \sum_{j=0}^{n-1} a_j b_{i-j}^{j} x^i, where the subscripts are taken modulo n, and a_i^n = a_i, b_i^n = b_i for each i. Write the above power series as a product of two power series modulo x^n - x.Homework Equations I'm...
  21. L

    Coupled non-linear differential equations

    Homework Statement x'= E - sin x + K sin (y-x) y'= E + sin y + K sin (x-y) E and K >0 Find fixed points for this system of equations Homework Equations This system is the form of coupled oscillators described in Strogatz. θ1'= ω1 + K sin (θ2-θ1) θ2'= ω2 + K sin (θ1-θ2)...
  22. D

    Programs Best path to Non-Linear Dynamics/Chaos theory for non-science major?

    Hi, I think some background is necessary: I'm a Psychology undergraduate student. I also really love math. I've incorporated some pure math into my studies - next semester I'll have room for a course on "Foundational Mathematics" (I'm not sure if that's exactly what they call it outside my...
  23. J

    Non-linear second order from calculus of variation I can't solve

    Hi, I derived the equation: 1+(y')^2-y y''-2y\left(1+(y')^2\right)^{3/2}=0 Letting y'=p and y''=p\frac{dp}{dy}, I obtain: \frac{dp}{dy}=\frac{1+p^2-2y(1+p^2)^{3/2}}{yp} I believe it's tractable in p because Mathematica gives a relatively simple answer: p=\begin{cases}\frac{i...
  24. L

    Non-linear difference equation transformation

    Homework Statement The problem is tough to type out correctly. Pasting problem statement image http://postimg.org/image/a0r92a0wl/ http://postimg.org/image/a0r92a0wl/ The Attempt at a Solution I just need to know how to proceed with the problem. Not the answer. This is the scan...
  25. dexterdev

    How to find the input output relation of an unknown non-linear system?

    Hi friends, I have a system (with unknown properties) which takes an input vector of length 10 and outputs a vector with length 6. I select Inputs vector 'I' which is a 1000x10 matrix, : 1000 samples of 10 elements. And outputs vector 'O' is a 1000x6 matrix,: 1000 samples of 6...
  26. Z

    MHB What are the fixed points and stability of a non-linear system of ODEs?

    I need help with the following so please help me -- Consider the following non-linear system X’ = x² - ay Y’ = y² - y(a) Find the fixed points of this system. (depending on a, there may be different fixed points!) (b) Study stability of each fixed point via linearization. In the case the...
  27. B

    Scaling Invariant, Non-Linear PDE

    Homework Statement Consider the nonlinnear diffusion problem u_t - (u_x)^2 + uu_{xx} = 0, x \in \mathbb{R} , t >0 with the constraint and boundary conditions \int_{\mathbb{R}} u(x,t)=1, u(\pm \inf, t)=0 Investigate the existence of scaling invariant solutions for the equation...
  28. S

    Shooting method for non-linear equation

    shooting method for non-linear equation(urgent) Homework Statement for shooting method , in non-linear equation, we're find $$t_{k}=t_{k-1}-\frac{[y(b,t_{k-1})-β](t_{k-1}-t_{k-2})}{y(b,t_{k-1})-y(b,t_{k-2})}$$ but how can we find the $$y(b,t_{k})$$ ? I am suppose to use Euler method for...
  29. F

    How can I solve a first-order non-linear ODE?

    Hi! I'm having a lot of trouble solving the following ODE: dx/dt = A - B*sin(x) where A and B are constants. My ODE skills are a bit rusty, and I wasn't able to find anything on the Internet that could help me, so could someone please show me how to solve for x in terms of t? I've...
  30. J

    Solving Non-linear Problem for x between 0 and L

    Assume we have a straight piece of wire with two end points A and B and with length L where x_{A}=0 and x_{B}=L. The wire has non-ohmic resistance and hence the current is not proportional to the potential difference, i.e. \left(V_{A}-V_{B}\right). In fact the current is a function of the...
  31. anemone

    MHB Solving a Non-Linear System: Approaches and Techniques

    Hi members of the forum, I am given to solve the following non-linear system: Solve (1+4^{2x-y})(5^{1-2x+y})=1+2^{2x-y+1} and y^3+4x+\ln(y^2+2x)+1=0 I'm interested to know how you would approach this problem because I don't see a way to do so. Thanks!
  32. P

    Can we apply non-linear smoothing to a linear looking like data ?

    My doubt is that whether we can apply non-linear smoothing to a almost linear data ( without one or 2 discontinuity) I have attached the pic in which the red data is the smoothed one. Blue is the original one. I multiplied each point with an increasing like 1, 1.1, 1.2, 1.3, 1.4...so on...
  33. Ackbach

    MHB A Method for Proving Some Non-Linear Limits

    I received permission from my father to post this from his (unpublished) Calculus text. Note that this method will, I believe, work for proving existence of a limit for a nonlinear function at any point that is not a local extremum. My father thought it would be good to give you this proviso...
  34. E

    Is this PDE linear or non-linear?

    hello, guys Below is the equation I am concerned with: Is the above equation non-linear because of (delta P/delta x)^2 term assuming other variables are constant and don't change with pressure , P?
  35. C

    How to find error between non-linear plot and data points?

    Is there a formal way to measure the error between some arbitrary points and a non-linear curve in order to minimize it?
  36. S

    Thoughts on a non-linear second order problem

    h''(t)=-\frac{1}{h(t)^2}, h(0) = h_0, h'(0)=v_0 The first step is to, I think, reduce this to a fist-order problem: h'(t)h''(t)=-h'(t)\frac{1}{h(t)^2} --- Multiply both sides by h'(t) h'(t)^2=\frac{1}{h(t)}+c_1 --- Integrate both sides 1/h'(t) = \sqrt{\frac{h(t)}{c_1 h(t)+1}} ---...
  37. E

    Can Fourier Series Simplify Solving Nonlinear ODEs with Oscillatory Inputs?

    Hi all, I have a nonlinear ODE in the following form: a x'' + b |x'|x' + c x' + d x = y where x and y are functions of time and a,b,c and d are constants. As far as I can tell the only way to solve this is numerically, something I've managed to do successfully using a Rung-Kutta scheme...
  38. D

    Sigma Plot, Non-linear regression, fitting a line to a set of points

    I model arterial baroreflex data that I have collected in humans using the Kent equation which is: y=p1/(1+exp((x-p3)*p2))+p4; where Y=heart rate, X= estimated carotid sinus pressure, p1=range of Y, p2=slope coeff, p3=centerpoint on X, p4 = minimum Y. I use Sigma Plot to do a best fit line...
  39. G

    Maths behind non-linear dynamics, driven damped oscillator more specifically.

    I am investigating the mathematics behind driven damped oscillators, I will then simulate it in MATLAB and observe the unpredictable long term behavior of the system. In order to create non-linearity in a oscillating spring I can no longer use hookes law but a form of it by introducing a...
  40. G

    MATLAB Is fortran 90 or matlab better for simulating non-linear dynamics (Chaos)?

    I am going to be simulating damped driven oscillators for my project and I was wondering if someone could give me a definitive answer on the matter. I know MATLAB is more of a 'tool' than a language so I'm thinking the maths behind damped driven oscillators might be easier to implement into...
  41. W

    MHB Four Non-Linear Simultaneous Equations

    4 equations, 4 unknowns: \[\frac{u(r^2 - u^2)}{r^2 + u^2}=156~~~~~~~~~~(1)\] \[\frac{v(r^2 - v^2)}{r^2 + v^2} = 96~~~~~~~~~(2)\] \[\frac{w(r^2 - w^2)}{r^2 + w^2} = 63~~~~~~~~~~(3)\] \[\frac{315uvw + 24336vw + 9216uw + 3969uv}{2r} = 943488~~~~~~~~~(4)\] Who can solve that mess?
  42. D

    How to Model Droplet Vaporization Using Coupled Non-linear Equations?

    Hi,I'd really appreciate any help on this as I've spent many many hours trying to get my head around it. I am simulating the vaporization of a droplet in hot air and I have two equations to use: m_lc_l\frac{dT_l}{dt} = \widetilde{h}A_0(T_\infty - T_l) + \dot{m}_l(h_v-h_l) \dot{m_l} = -\frac{\pi...
  43. M

    Linear or Non-Linear Differential Equations

    (d4x)/(dt4) + (1/(1+t))*(d2)/(dt2) = x(t) Is this differential equation linear or non-linear? I don't understand the difference.
  44. M

    System of non-linear partial differential eqs from electrostatics

    I have an electrostatics problem (shown here: https://www.physicsforums.com/showthread.php?t=654877) which leads to the following system of differential equations: \frac{\partial E_z}{\partial z}=\frac{\rho}{\epsilon_0} (1) Z_i E_r \frac{\partial \rho}{\partial r}+(u_g+ Z_i E_z)...
  45. B

    Substitution to turn a non-linear least squares problem into a linear one

    Hi, I want to solve an overdetermined non-linear equation with the method of least squares. Assume it's f(x) = 1 + ax + a^2 + b, and I want to estimate a and b. This is non-linear, as I said, so the derivatives of the squared residuals involve a^3 terms and are difficult to solve. Now I thought...
  46. A

    Cubic non-linear inequality (HELP)

    I just can't figure this out one question from my review test. I don't know hot to express it graphically or algebraically.
  47. F

    How to transform non-linear frequency vibration to constant frequency?

    How to transform non-linear frequency vibration to constant frequency of vibration of 2 Hz? Such as transform the different frequency of waves to constant frequency and then maintain it..
  48. mnb96

    How the inner product changes under non-linear transformation

    Hi, if we suppose x and y are two elements of some vector space V (say ℝn), and if we consider a linear function f:V→V', we know that the inner product of the transformed vectors is given by: \left\langle f\mathbf{x} , f\mathbf{y} \right\rangle = \left\langle \mathbf{x} ...
  49. G

    Solving Non-Linear Differential Equation with Fourier Transforms

    Hiya. I have to solve this bad boy under the assumptions that f, f' and f'' tend to 0 as |x| tends to infinity: 1/2(f')^2 = f^3 + (c/2)f^2 + af + b where a,b,c are constants. My thoughts are use Fourier Transforms to use the assumptions given, but not sure how to do them on these terms...
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