In mathematics and computational science, the Euler method (also called forward Euler method) is a first-order numerical procedure for solving ordinary differential equations (ODEs) with a given initial value. It is the most basic explicit method for numerical integration of ordinary differential equations and is the simplest Runge–Kutta method. The Euler method is named after Leonhard Euler, who treated it in his book Institutionum calculi integralis (published 1768–1870).The Euler method is a first-order method, which means that the local error (error per step) is proportional to the square of the step size, and the global error (error at a given time) is proportional to the step size.
The Euler method often serves as the basis to construct more complex methods, e.g., predictor–corrector method.
(This is from W. Greiner Quantum Mechanics, p. 293 from the topic of Ritz Variational Method)
1) Are ##\frac{\delta}{\delta \psi^{*}}## derivatives in equations 11.35a and 11.35b? If this is so, we can differentiate under the integral sign to get ##\int d^3x (\hat{H}\psi)## in equation 11.35a...
(I do understand there are many ways to formulate the FE method, but I wish to understand this one.)
I understand that Hamilton's Principle is just that: a principle ( a law the recapitulates the equations of motion)
I also understand that the Principle of Virtual Work (PVW) is a reformulation...
So I was looking at this example problem in my textbook and I don’t understand how they got -168.1 degrees. The part I’m confused with is the first part of the 2nd picture, there’s a coma in the inverse tan, I don’t know what that means.
I wish to set up the node equations for a 2D heated plate with boundary conditions. I understand how to do this in 1D but have not found a suitable example problem worked out in 2D and examples I have seen are very involved and complex. @pasmith showed me you to set up the 1D problem as follows...
Hello.
I'am practicing circuit analisis about the norton and thevenin's circuits and I can't seem to manage to get the right thevenin's voltage using the node voltage for a)
resolution
1) I did source transformation turning the current source(2A) into a voltage source (10V)
applied node voltage...
McCabe - Thiele method is used to find minimum number of separation stages or theoretical plates for a given efficiency of separation in distillation for two - component mixture if components have similar enthalpy of vaporization.
If components have similar enthalpy of vaporization ,than on...
Taking the moments about points A and C, why is a distance of 3 meters used in Fhc and Fhg? Isn’t it supposed to be 1.5 meters for both?
I acknowledge that Fhc and Fhg have x and y components, but were we considering the horizontal or vertical component (or both components) of either Fhc and Fhg...
Hello,
This problem comes just prior to introducing change of variables with Jacobian.
Given the following region in the x-y plane, I have to choose (with justification) the correct change of variables associated, for ##u\in [0,2]## and ##v \in [0,1]##.
The correct choice here is a), but I do...
I wanted to declare a local variable inside a static method main().
My code looks like this -
class Operator
{
static int a;
public static void input() {
Scanner in=new Scanner(System.in);
System.out.println("Enter the number:");
a=in.nextInt(); //this is...
I was just checking out this experiment for finding focal length of a lens that I did few years back. the method used was called as the u-v method(https://www.concepts-of-physics.com/pdf/uv-method.pdf), and here in this method, object distance u and image distance v is measured from the sharp...
Disclaimer: This is not a repost.
The problem wants me to calculate the force of a p.c. , that is isolated by itself (this p.c. is the only charge this problem starts with in this problem) inside a capacitor, a distance h/4 from the bottom plate.
This is what I have though of so far but I...
Before I can find the force on q I must balance the charges. This problem starts of with -q and q inside the capacitor. I have added image charges on the opposite side of each plate. Would this work?
The code I have for solving the diffusion equation on the spherical domain. The solution seems to differ drastically depending on the refinement of the mesh which obviously shouldn't be the case. I have checked and double checked my derivation and code and I can't seem to find an error. One...
Hello,
I wrote a code to solve a non-linear PDE using Canrk nicolson method, but I'm still not able to get a correct final results. can anyone tell me what wrong with it?
Hi,
I was looking at the following example, and I cannot really understand the justification for why this function is positive semi-definite.
Example Problem: We are looking at the function: ## f(x, y) = \frac{x^2}{y}, x \in \mathbb{R} , y > 0 ##. Is this function positive semi-definite...
I am trying to understand how to apply the finite element method for a simple 1D wave equation with four elements for learning purposes.
$$\frac{d^2 T(x)}{dx^2} = -f(x)$$
I am stuck because the structure of the equations set up in Numerical Methods for Engineers by Chapra and Canale as shown...
Gradient descent is numerical optimization method for finding local/global minimum of function. It is given by following formula: $$ x_{n+1} = x_n - \alpha \nabla f(x_n) $$ There is countless content on internet about this method use in machine learning. However, there is one thing I don't...
Hi PF
Not every function works when we try to compute the root with this method
The following theorem guarantees that the method of fixed point iteration will work for a particular class of functions
A fixed point theorem
Suppose that ##f## is defined on an interval ##I=[a,b]## and...
Hi, PF
Sometimes it is not easy to find roots of functions. Newton gave a nice clue: the Newton's Method formula: ##x_{n+1}=x_n-\dfrac{f(x_n}{f'(x_n)}##. My concern is, now that I have understood and practiced it, comprehend what I've sketched in the summary. This is all taken from "Calculus...
Anton Zeilinger, wrote, " "We always implicitly assume the freedom of the experimentalist... This fundamental assumption is essential to doing science. If this were not true, then, I suggest, it would make no sense at all to ask nature questions in an experiment, since then nature could...
https://scholar.harvard.edu/files/schwartz/files/7-ensembles.pdf
https://mcgreevy.physics.ucsd.edu/s12/lecture-notes/chapter06.pdf
On page 3 of both the notes above, the author merely claims that $$P \propto \Omega_{\text{reservoir}}$$
But isn't $$P \propto...
Hello! Consider this circuit
Now I want to calculate the current Ik. The values are given as follows;
Uq1 = 12 V
Uq2 = 18V
R1 = R2 = 8 Ohm
R3 = R4 = 20 Ohm
My approach was using the Superposition theorem. First I deactived Uq2 and left Uq1 active.
Now if I am not mistaken the resistors R2 R3...
I am going to give up a bit more on the given problem. We start with polynomial ## x^27 -x ## over GF(3)[x] and we factorize it using a well known theorem it turns out it factorises into the product of monic polynomials of degree 1 and 3, 11 of them all together.
We then choose one of those...
Hi there, I've been stuck on this issue for two days. I'm hoping someone knowledgeable can explain.
I'm working through the construction of the quantum path integral for the free electrodynamic theory. I've been following a text by Fujikawa ("Path Integrals and Quantum Anomalies") and also...
A very "meta" idea crossed my mind today, and I'd like some feedback. Apologies in advance in case the half-formedness of said idea results in a meandering post.
The specific connection I made was that the creation-versus-evolution "debate" could be characterized, at its most basic, as the...
I've been struggling, no matter what I try to do I can't come up with a solution. The answer is in situ, but in my mind it would work perfectly fine. The only thing we would do is just use an RNA probe complementary to the gene we are trying to detect and it should light up the moment the gene...
This method calculates surface tension based on force balance acting on the ring placed on the liquid surface: $$ F = G + \gamma L $$
where ##G## is weight of the ring, ##L## is wetted length of the ring which is equal to its circumference, ##F## is outer force of tensiometer acting on the ring...
Good Morning
I am "comfortable" with formulating Hamilton's Principle with a Lagrangian (KE - PE), conducting the calculus of variations and obtaining the Euler Lagrange Equations. Advanced mathematical theory, is beyond me.
I also have a minimal understanding of using Lagrange multipliers...
There's a classic physics problem that is:
If Earth is orbiting the Sun at 1 au from and is suddenly stopped. How long does it take to fall into the Sun (neglecting the size of the Sun/Earth)?
I know that a clever way to solve this problem is by using degenerate ellipses and an object...
I'd like to compare 2 or more near-infrared spectra. The data consists of measured light intensity in different wavelengths (range 600 nm to 1100 nm).
I'm wondering which statistical method would be appropriate? I noticed when searching online that pearson correlation might be inaccurate as...
There is an entry in Wikipedia at this link: https://en.wikipedia.org/wiki/Pythagorean_triple
Under elementary properties of primitive Pythagorean triples, general properties,sixth bullet from the bottom of this section, there is this generalized Diophantine equation:
x^2p + y^2p = z^2
Where: p...
Hi,
I was watching a video where the following formula, for expected value, was presented for a discrete probability distribution which cannot take negative values:
E[X] = \sum_{j = 1}^{\infty} P(X \geq j)
and I never saw this formula before and am trying to develop an intuition for it. I am...
Hello,
I am wondering if it is possible to calculate the B-field of a conductor above an iron plate just using the complex image method. To keep it simple let’s consider a 2D calculation, the metal plate is infinitely deep and wide and the conductor is infinitely long and thin. If the metal...
Books that teaches classical mechanics through a discourse method ie asking interesting questions and answering them maybe a similar one to
Understanding Basic Chemistry Through Problem Solving: The Learner's Approach
Book by Jeanne Tan and Kim Seng Chan. Not exactly asking numerical questions...
Hey! 😊
We have the matrix $A=\begin{pmatrix}1 & 4 & -1 \\ 2 & 2 & 7 \\ 2 & -4 & 7\end{pmatrix}$ and we want to calculate the $QR$ factorisation using the Householder method.
First we take the first column of the matrix $a_0=\begin{pmatrix}1 \\ 2 \\ 2\end{pmatrix}$.
We have that $\alpha=\pm...
Hey! :giggle:
We have the matrix $\begin{pmatrix}2 & 1/2 & 1 \\ 1/2 & 3/2 & 1/2 \\ 1 & 1/2 & 2\end{pmatrix}$.
We take as initial approximation of $\lambda_2$ the $1.2$. We want to calculate this value approximately using the inverse iteration (2 steps) using as starting vector...
rall)?
What I mean is, suppose I were to spend 1 hour total in the sun. If I spent it in "3 chunks" of 20 minutes with 10 minutes between each chunk (in the shade), would that reduce my sunburn damage chances vs. spending the full 1 hour entirely in the sun?
I was mowing grass in 90...
I have implemented steganography encryption and decryption process, and I wondered if someone could decrypt the message in these conditions;
(a) without having the original image
(b) having the original image. The encryption starts from the first color code and the first pixel.
(c) having the...
I have been working on a problem for a while and my progress has slowed enough I figured I'd try reaching out for some more experience. I am trying to map a point on an ellipsoid to its corresponding point on a sphere of arbitrary size centered at the origin. I would like to be able to shift any...
https://reason.com/wp-content/uploads/2021/07/b49101a8-ad23-44dc-9500-ecec551c08b8.pdf
This was unexpected. In a 55 page decision from the Superior Court of DC, the judge said the following.
The scientist litigator, and his expert witnesses said:
It seems to me that the judge gets it, and...
Summary:: Require to determine the designated forces using principle of virtual work ( unit force method )
I have no idea how to determine the multispan beam using virtual work, if I start to analyse the subsidiary portion BC member, the Yc can be calculated and following by the Ma... it seems...
I would like any tips about a Maple ''home made'' program that I received for a project but this program seems to stop before the very end of the code. I want to find de lift of an airfoil with Boundary finites elements method. I have this error at the very end :
Error, (in fprintf) number...
dx/dt =1, x(0,s)=0, dy/dt=x, y(0,s) = s, du/dt=(y-1/2x^2)^2, u(0,s)=e^s
I did well at the beginning to get x(t,s) =t and y(t,s)=1/2t^2 + s, but got stuck with the du/dt part.
You can sub in x=t and y=1/2t^2 +s for x and y to get du/dt = s^2. But that's still three variables, and I can't see...