Model Definition and 1000 Threads

Hello all, I've been tasked with developing a model for dose received from the Chernobyl Accident. I'm struggling a little to find dose estimates from which I can extrapolate back to find the initial dose received. Does anyone have any references that they can point me towards? I believe there...

Homework Statement Consider an electron in the n = 4 level of Li ++. According to the Bohr model, what is the radius of the orbit of the electron? Homework Equations r = .0529 nm r(n) = (.0529 nm) x (n2) The Attempt at a Solution I thought this was pretty obvious? We want to know the radius...

Hi all, Does anyone know of, or can anyone point me in the right direction for where to find a small, low rpm generator? RPM can be anywhere in the range of 100-300RPM, and size would be around 50mm long. To put this into context, I am building a small turbine (~300mm diameter), which will...

I want to know how can I begin to exercise the representation of a phenomenon in a mathematical model.

Urs Schreiber submitted a new PF Insights post Spectral Standard Model and String Compactifications Continue reading the Original PF Insights Post.

After reading some materials on Bohr model, I understand the model is more or less incorrect, especially in terms of "orbital". I just wonder if the energy expression is also wrong or not. In my text for general quantum theory, the energy about two neighboring level is given as ##\Delta E =...

Hi, I am a student in the Netherlands, currently 17 years old and at the end of my 'middelbare school', meaning that next year I'll be a bachelor student at a university. I am doing an extended essay/research thing that is custom you do in your last year, with a friend of mine. We picked the...

Homework Statement In the earliest circular planetary model of the atom the electron and proton orbited a common centre. The electrostatic forces alone provided the force field. However an accelerating charged body will send out electromagnetic waves and the orbiting charges would consequently...

A simple harmonic oscillator model consisting of two masses connected with a massless spring is provided in [edit] I hate cut and past on the mac. Always seems broken Slide 30 http://webs.um.es/bussons/GW_lecture_KG.pdf The left hand side of the equation of motion is simply the classical one...

Hi, I am reading about this symmetry but I'm struggling to have a deep understanding of it. Would somebody please explain this symmetry to me from a conceptual point of view? Thanks in advance, Luca

Why do axisymmetric FEA models of magnets and their fields make the field farther from the axis appear denser than it really is when the flux line mode is enabled? I'm using the F.E.M.M. system at the moment. All integrals and graphs give correct values, but the depicted lines of flux appear...

Hey everyone. I thought about this problem the other day, but I don't know what theory I need to solve this problem. Given a 2D rectangle with a known, varying resistance, and a known voltage drop across the length, how would one calculate the current density at each point on the surface. By...

Homework Statement State and use simple assumptions to show that ' Power is proportional to V^5' is the expected relationship for a pure tungsten filament bulb. Homework Equations V=IR I=dq/dt Q=mcT The Attempt at a Solution I tried to use a simple model where the rate of heat loss is...

This has turned out to be a long question to type out so I apologise, but I don't think it's too hard to follow or read through quickly and I believe the actual question itself may not be too complicated once I get round to asking it. You can possibly skip to the last few paragraphs and still be...

Homework Statement (linear combination of atomic orbitals): Lets consider two atoms which are bond together with a covalent bond. Let's consider any sets of wavefunctions |n\rangle for n=1,2,...,N. Let's call orbital |1\rangle around nucleus 1 and orbital |2\rangle around nucleus 2 and so on...

How can we make a mathematical model for tracking micronutrients in an anaerobic system (Bioreactor) that has different chambers. The feeding ( Sargassum spp.) inters in the first chamber and should pass through the system 'til the last chamber. We know the concentration of micronutrients( Fe...

It is often said that science is a 'model' of reality out there. I think this statement is wrong. It presupposes that there is a reality that is beyond 'modelling'. Suppose, someone really finds out the reality 'as it really is'. ( I am not saying there surely is). She would first of all...

Hi everyone, I've been working on developing a crypto-currency called eQualityCoin for a while now and hoped someone here might be able to help me "classify" the system in a formal mathematical sense. The system's main feature is a simple rule for how it determines a purchaser's exchange...

Is there anywhere in physics textbooks , or anywhere else, a section on KINETICS OF ROTATING FLEXIBLE, CONSTRAINED BODY BY GRAVITY ( TURBINE ROTOR IN BEARINGS), NON-INVARIANT (Time -translation invariance by Noether’s theorem), WITH ECCENTRIC MASSES, TORQUE DRIVEN AT NON-CENTROIDAL AXIS...

i am finding it difficult to get insight about modelling of non linear system (electrical). my queries are, consider the system is DC DC converter... 1) I read that to study the dynamics of the system we linearise the non-linear system...why do we want to linearise it?... 2)can some one please...

Homework Statement I want to diagonalize the quadratic form $$ m_0((m_u+m_d)\pi^3\pi^3+\frac{2}{\sqrt{3}}(m_u-m_d)\pi^3\pi^8+\frac{1}{3}(m_u+m_d+4m_s)\pi^8\pi^8)$$ which can be found under equation 5.47, in order to get the mass of the η and ##\pi^0## pions. This quadratic form is produced by...

Hi, I am trying to work out how the electron would oscillate about a mean position in the plum pudding model. Plum pudding model; -1 electron atom. -Positive charge of ##+e## distributed evenly about the volume of the atom of radius ##R##. -Electron (charge ##-e##) is free to move within the...

I've read a few resources on ARIMA, and I still have a few outstanding questions. Here is what I know, and let me know if I am incorrect: Given any set of data, before I can do any forecast, I can use ARIMA to assess the model and make it stationary first. Before I start, I should plot out the...

Could someone tell me an application of the model of free fall to industry or more generally by using Newton's second law and the law of gravitation, construct a model similar to the free fall one, that has an application in industry

Homework Statement Suppose that we observe ##i=1,2,\ldots,n## independent observations that can be modeled as follows: $$Y_i = i(\theta+\epsilon_i) \quad \text{where} \; \; \epsilon_i \sim N(0,\sigma^2).$$ 1. Write the above as a regression model, ##E(Y) = X\theta##, ##\text{Cov}(Y) =...

I have some newbie kind of confusion The model in question is taken from wikipedia: and If, in the first model, the light ray is reflected back to its source, could there be some kind of detectable interference at the midpoint (where the blue arrows are)? If the answer is yes, would this...

I'm trying to understand a 3 phase induction machine model used as a generator in a Doubly Fed Induction Generator (DFIG) arrangement in Simulink. In this model for the induction generator component, they have stated that the model is a "Positive sequence model" of the induction generator...

Homework Statement Nearly free electron model in a 2D lattice. Consider a divalent 2D metal with a square lattice and one atom per primitive lattice cell. The periodic potential has two Fourier components V10 and V11, corresponding to G = (1,0) and (1,1). Both are negative and mod(V10) >...

Hello Everyone, I am designing Simulink model for HIL testing. Basic concept: Input: Throttle angle ----> Injection timing from that I have calculated requested torque (% of max torque)(chekced and correct) Real torque follows requested torque with delay. (long list of conditions depending on...

Hello! I am predicting the peak altitude of a model rocket based on some ground tests. I know that Total Force on the rocket=Thrust-mg-kv^2 but am stuck as to which value for 'v' to use? Is it the velocity of the rocket with the effects of gravity and air resistance taken into account or the...

Homework Statement a gemoetrical similar open chanel model is constructed with 10: 1 , if the model discharged 7m^3 /s , what is the corresponding discharge in prototype? Homework EquationsThe Attempt at a Solution Q = (L^3) / T , [ (Lp^3)/ (Tp) ] / [ (Lm^3) / Tm ] = (Lr^3) / Tr [/B] but...

I know to describe Quantum Mechanical systems we can use: -Schrodinger equation -Feynman Path Integral method -Heisenberg Matrix formulation Well my question is, if you want to calculate molecular properties, and want to understand biochemistry (protein), you have a system with several...

Hello everyone, I am predicting the altitude of a model rocket based on some testing I did where I found the impulse of a little single stage model rocket motor. I am wondering how to incorporate drag into my calculations to make it more accurate. I know D=Cd*rho*v^2*A and I can definitely find...

The following is from my notes: In 1972, a model was proposed by Georgi and Glashow as a candidate theory describing W bosons and photons with Lagrangian $$\mathcal L = -\frac{1}{2} \text{Tr} F^{\mu \nu}F_{\mu \nu} + (D_{\mu} \phi)^T (D^{\mu} \phi) - \mu^2 \phi^T \phi - \lambda(\phi^T...

Homework Statement Modify the model d = 12 sin (30(t-5)) + 14 to match the new data which is as follows; maximum water depth is 22 m minimum is 6 m, and the first high tide occurs at 5:00am. Homework EquationsThe Attempt at a Solution The answer is y= 8 sin (30(t-2)) + 14 Ik it's 8 b/c...

A recent discussion at the Expanding from and eventually to a singularity thread has been both interesting and informative, and it has shown me very clearly that I would benefit from a few good books, rather than the piecemeal approach I've been taking to understanding singularities and the Big...

Homework Statement Assume that there is a deviation from Coulomb’s law at very small distances, the Coulomb potential energy between an electron and proton is given by V_{mod}(r)=\begin{cases} -\frac{q^{2}}{4\pi\varepsilon_{0}}\frac{b}{r^{2}} & 0<r\leq b\\...

Homework Statement Not exactly a homework problem but I tried to predict the spin and parity of (the ground states of) ##^{89}Sr##,##^{97}Zr## and ##^{137}Ba## using the shell model and my results seem to differ from the tables. Homework Equations Parity ##\pi = (-1)^l## Figure 4 seems to...

Hi people, I'd like to simulate a 2d array of atoms/ions under a magnetic field H via the Ising's model. I've read http://fraden.brandeis.edu/courses/phys39/simulations/AsherIsingModelReport.pdf to get an idea on how to proceed. I'm not sure I got the correct ##\Delta E## values though. I'm...

I'm curious about contact forces, such as the normal reaction force on a book resting on a table. I've read that it's actually the electromagnetic force, but atoms are electrically neutral and there is no ostensible repulsive force between electrons and the nucleus, so I have some doubts. Has...

Homework Statement In the kinetic model of an ideal gas, it is assumed that: A. The forces between the gas and the container are zero B. The intermolecular potential energy of the molecules of the gas is constant. C. The kinetic energy of a given gas molecule is constant D. The momentum of a...

I have been struggling to solve the following problem for days. I was given the state space model of a circuit and asked to determine the system elements. So basically, I think I have to find a suitable circuit which describes the state space equation. I am not really sure how to approach this...

<< Moderator's note: thread spun off from https://www.physicsforums.com/threads/radiation-from-a-square-loop-of-current.868648/ >> But Sir, then why was Rutherford's atomic model rejected by physicists?

The problem is a simple n-body problem: there is n charged particles - electrons, protons, or other particles; we have the initial parameters: a mass, charge, position, velocity, at a time t = 0. In a standard (classical) numerical computation of the n-body problem I can use any numerical...

I'm using the general Hubbard model (H = U \sum n_{i,\uparrow} n_{i,\downarrow} - t \sum (c^{\dagger}_{i,\sigma} c_{i+1,\sigma} + c^{\dagger}_{i+1,\sigma} c_{i,\sigma})) to solve for eigenstates of simple quantum dot configurations. For the case of a double dot with two electrons in singlet...

Hey folks. I've done a little bit of research into model rocketry and I'm stuck with the idea of designing and projecting a rocket to put into practice all the engineering I'm learning in college - I'm into MechE. I want to start simple, doing a few tests and learning the basics - types of...

Homework Statement Two objects are connected by a light string passing over a light, frictionless pulley as shown in the figure below. The object of mass m1 = 4.80 kg is released from rest at a height h = 4.40 m above the table. (a) Using the isolated system model, determine the speed of the...

I have to make an oil rig model with the size of 60x50x50cm by using recycled materials and weight will be added from 1 kg to 10 kg depends on its stability. How can I make this model float? thank you

Homework Statement There are several parts to this question, however I could complete these parts. It is just an equation used in the prior part to the question that is need to solve this: If we define \begin{equation} \sigma_{n}^{-}=\sigma_{n}^{x}+i\sigma_{n}^{y} \end{equation} and with the...

Hello everyone i want to model viscoplasticity using Ansys APDL, Perzyna and Peirce or Anand model offer us to do this modeling, and each modèle Contains different parameters. the question is: how to determine the parameters (if we can determine them experimentally, what is the concerned test...