Model Definition and 1000 Threads

Hi, English is not my native language. I manage first time a competition on social media, where: 1. people bring a photo and gather like on it. The top 3 likes will go to final, 2. in the final, they play with a small robot as a vacuum cleaner to clean an area of 1mX1.5m which has 1 pin in...

Hey guys! First time posting on this site. Been reading for quite a while and really loving it! :thumbs:! I'm a chemistry student and reading my book in general chemistry I couldn't understand two things about Sommersfeld's atomic model. I believe i understand the whole concept but what...

Hi everyone, hopefully someone can help For an vector AR(1) model of the form y(t)=Ay(t-1) + et How does one estimate the variance of the white noise input. I was under the impression that one can simply use the residual of the model fit and estimate the variance from this, when I do a...

Homework Statement At the bottom of this linked-to screen below is an equation for E = - ... = - .... = - 13.6 Z^2 / n^2 eV https://en.wikipedia.org/wiki/Bohr_model#Electron_energy_levelsHomework Equations I'm using the following values for the formula Z=1 n=1 K sub e = 8.987 x 10^9...

I am a programmer and physics fan. A speaker (Lawrence Krauss?) at https://origins.asu.edu/events/great-debate-parallel-realities-probing-fundamental-physics (not on youtube yet) said physics theories beyond the standard model are an under-determined problem. There are 7,000 theories that fit...

Here is the question: I have posted a link there to this thread so the OP can view my work.

Hi all, I need a model of a pneumatic pressure regulator. The model should be as simplest as possible and use an optimization solver to identify the regulator parameters in order to fit the performance I find in the datasheet of a commercial pressure regulator. I have already done a model...

I am a MSc student and I am looking for a place to do my PhD in Physics Beyond the Standard Model (Theoretical side). Any suggestions for a place to apply?. I know that there are the traditional elite places like MIT, Standford, Berkeley and so on but I am looking for other suggestions given...

Hi everybody, I have participated in a course about solid state physics and have been introduced with Kronig-Penny model. Now in this model, so far I understood we solve the nature of wave function of an electron inside an array of potential barrier. It very nicely explains the concept of...

Hello Everyone, I understand that sometimes in physics we make a model of some physical system purely for theoretical convenience, as it allows us to calculate certain properties of the system very easily; although, sometimes these models aren't actually what is going on, but it doesn't matter...

Homework Statement The circuit in the diagram utilizes three identical diodes having I_S = 10−16 A. Find the value of the current I required to obtain an output voltage V_o = 2.4 V. If a current of 1 mA is drawn away from the output terminal by a load, what is the change in output...

Please excuse for my less knowledge in the subject.But I have genuine inquisitiveness. My Question is: If we assume electrons traveling in the orbit around nucleus like planets by inverse square law then electron must always be in the plannar path i,e. never coming out of plane of motion.Then...

We all know that photons are the particle representation of an EM 2-D wavefront and as the front expands the space between photons increases. We also know that particles of matter can exhibit wave properties. So in an analogous fashion to light, I'm thinking that each of the fundamental...

Hello, I am graduate student in NE within the US. I am working on a grant that examines a small (10-100 microns) ceramic film region on the outside of the cladding region. I have assessed the neutronic impact, as well as a thermal impact (heat transfer coefficients, etc.) of the additional...

Homework Statement For a problem I'm doing, I am considering a universe in which k=0, and I'm told that I can consider most of the expansion to have happened during a phase when only one of the density parameters was dominant (I know which one, as well), but I don't know the scale factor or...

In every source I've checked so far, we make the assumption that we can neglect electron-electron interaction in this model but they always fail to give any reason to answer why this is plausible. Does anyone know how physicists convinced themselves of this at the time and even now (other than...

Hello I am interesting in transformers lately, and I noticed that most commonly used method for representing transformers in power systems is by symmetrical components. Now, I am wondering - is there any way that we can represent and calculate transformer in phase system, totally without...

Hi, Please see the attached Excel file. I have a sample of 70 data pairs. The correlation between X and Y is -0.68. The OLS regression coefficient is statistically significant as shown in the file. However, with a R^2 of 0.40, I am not sure if my model would be good enough to forecast Y...

Hi All, Have the following given and would like some help with the 3 questions below. Any help will be greatly appreciated :) City 1 TOTAL POPULATION CITY 1 100,000 Avg Age of Population 27.8 Median Age (Male) 20.5 Median Age (Female) 27.8 % Male Population 46.43% % Female Population 53.57%...

Homework Statement See attachment. Only struggling with (ii). Homework Equations The Attempt at a Solution So ultimately after doing everything, calculating B(ε)-B(0) & assuming z>>1 and z2/A > 47 I find that B(ε)-B(0) > 0.048ε2A2/3 I don't really see how this tells me if the nuclei will...

I have a question regarding symmetry groups. I've often heard that the Standard Model is a SU(3) x SU(2) x U(1) theory. From what I understand these groups contain the symmetries under which the Lagrangian function is invariant. If so, what does every one of the 3 groups above contain (what...

Hey guys. I have some trouble understanding how the F-test is used for testing the viability of a regression model. Before I delve into the background/question, just wanted to post a link that discusses the topic briefly: http://www.stat.yale.edu/Courses/1997-98/101/anovareg.htm So, coming...

Hi I chose a Monte Carlo simulation of the 2D Ising model as my Computational Physics course project. Unfortunately, I ran intro problems when formulating the exact problem since my professor probably wants me to simulate a real life material and extract magnetization curve M(T,H) out of it...

Hello guys, I am quite unsure in how to start the modeling for population. If I define y as the number of infected persons and y' as the rate of spread is it correct? I see the number of contacts between infected and non infected persons to be equal to the number of infected persons. Otherwise I...

In other words, can dark matter be reconciled with GR without drastically changing the idea that force is due to space-time curvature? and in the case of the standard model is there any thoughts of how the force of dark matter is transmitted via the exchange of a particle? It seems that this...

I have a difficult problem on my research exploration for math. I am modeling the convection currents of boiling water in a pot, which is heated by an electric stove. There is a constant supply of energy at 8000 watts (the average for a stove) that heats the pot from the bottom of the pot...

I have a difficult problem on my research exploration for math. I am modeling the convection currents of boiling water in a pot, which is heated by an electric stove. There is a constant supply of energy at 8000 watts (the average for a stove) that heats the pot from the bottom of the pot...

Hi, I am currently researching methods available for manufacturing a half-span wing model (approx 0.5m span, low sweep delta wing of varying cross section) to be used in wind tunnel experiments. A recent paper suggested the use of epoxy and micro glass beads injected into an aluminium mold...

Homework Statement Consider the following statement: "The temperature of a gas is a measure of the speed of its particles (atoms and molecules). Now suppose that I mix two gases together, for example oxygen and carbon dioxide, which are initially at different temperatures; if I wait long...

"Summing over spins" in Ising model. I don't understand this concept very well. Is it like taking the energy each possible configuration and adding them together? For example, if we had a 2D lattice gas and wanted to sum over the "white" the spins in a "checkerboard pattern": What are we...

I have three elements, A, B, C, that under certain conditions (rapid heating and cooling) form one ABC phase solid. Sometimes when I add a fourth element, D, I get two phase (AB,CD) solid. Obviously this phenomena is thermodynamically favourable. My guess (still undergraduate) is that there...

I read recently in my old ugrad 2012 solid state physics textbook, in its discussion of the attractive force between electrons in cooper pairs (in superconductors), that the attractive force between cooper pairs is explained mostly by the exchange of phonons (a quasiparticle associated with the...

Hi, I'm new posting to these forums, so I'm not sure if this is in the right place. Anyway, here it goes: I've done a lot of research (on my own and in college; academic articles, educational videos, etc.) about astrophysics, and I've always been fascinated by the concept of gravity...

Hello, Does anybody know/had experience with software that can turn 2D images to 3D models in CAD program, preferably in an offline environment (not on cloud)? The resulting model has to be accurate enough for aerospace engineering purposes. from looking online, I really didn't find...

Hi Just a quick question that I have been wondering about ... how do nucleons fill energy levels, and what is the maximum number of nucleons that can occupy each level? The given pattern is: 1s, 1p, 1d, 2s, 1f, 2p, 1g, etc I can see no obvious pattern here. Can anyone explain? I...

Calculate the 3 missing values from the system above assuming that it is in equilibrium i) Plant uptake = 196940 ii) Ocean deposition = iii) Weathering of calcium phosphate minerals = I can't seem to understand how you find the missing parts of the model image attached I know the...

As far as I understand: In the Drude model we take the electron to be moving in a random direction after each collision (*), such that the mean velocity is simply the average of -eEt/m, which is just -eEτ/m, where τ is the relaxation time. But I am very confused about this basic assumption...

HI, i have a set of data that i want to plot with matlab, using an equation. i have all x data points and want to generate y values for each x data point. function y =marko(x) y= (4.11/1.98)*{(1/4*((1-x/L).^2))-(1/4)-(x/L)}; x=(218+data points) from the command window i have...

αℓєєиα♥'s question at Yahoo! Answers regarding the logistic population growth model Here is the question: I have posted a link there to this topic so the OP can see my work.

Homework Statement A hydrogen atom in an excited state absorbs a photon of wavelength 410 nm. What were the initial and final states of the hydrogen atom. Homework Equations Rydberg equation: \frac{1}{λ}=R_∞(\frac{1}{n{_l}{^2}}-\frac{1}{n{_u}{^2}}) The Attempt at a Solution...

Hi, I'm attempting to make a model of a DC motor capable of calculating the efficiency of the motor for different values for torque. I have managed to make a code to generate the torque-speed-power plots for given inputs, however I have been unable to figure out how to calculate the...

For example say you got an E_8 X E_8 heterotic string theory and you compactify it on a Calibi Yau with SU(3) holonomy it breaks one of the chiralities down to an E_6 G.U.T. So you have something like E_6 X E_8. What do you do with that other copy of E_8? How is that interpreted? I don't...

Veltman states that the cosmological constant in the Higgs model takes the form C= m2M2 / 8g2 , which is way too large. In fact, the universe should be about the size of a theorists head or a football. http://igitur-archive.library.uu.nl/...temVeltman.pdf He states that "since the energy of...

Homework Statement 1) Which U(1), SU(2) and SU(3) gauge invariances are implemented in nature according to the Standard Model? What are the related quantum numbers? 2) The SU(2) symmetry is referred to as a non-abelian symmetry. What does this imply for the interactions between the force...

Hello Physics Forums. Our professor asked us to do a program on constructing the band diagram of BCC and FCC for nearly free electron approximation. what is the best algorithm i can use? i can program a bit, it's just the step-by-step method i am not sure of. thank you

If I could use any polynomial up to degree ∞, then can I get a close fit to any continuous function? I know that with a 4th degree polynomial you can get a pretty close fit to the sine function between 0 and 2pi...

Hello. Just started learning about how to model a DC motor. A simple model consists of the input Voltage in series with an inductor, a resistor and a back emf. I have two questions. Why have both the inductor and the back emf (voltage source)? If you know that at a voltage V and a load L1...

OK so I am not sure if this should be on a physics forum, a maths forum or a biology forum. All I know is I am stuck. A little back ground: Researchers have modeled how various animals can see depending on their visual sensor cells, namely cones (colours vision) and rods (luminance)...

Hello guys, I'm having some trouble reading two circuits : Here they are : In the first one I need to Determine the Thevenin then the Norton Equivalent of the circuit. For the second one I have to find expressions of the current I1 flowing through the R1 resistor, I2 in R2 and then...

I noticed that using the Laue equations reflections from some of the planes in the fcc and bcc crystal are not allowed. Now using the (maybe too naive?) Bragg model we can always find Bragg peaks whichever plane we hit with waves. So is the Bragg model too simple for these planes? And what is it...