Conditions Definition and 1000 Threads

I'm modeling a physical system described by a second-order ODE with LOTS of parameters. Using SciLab, I sucessfully implimented the model using a while loop with time. Because of the loop structure, every time I called the DE solver (ode), I updated the intial conditions for the current...

Hi folks, I was wondering how to code a Maxwell solver for a problem with time-dependent boundary conditions. This is not my homework, but I love programming and would like to implement what I learned in my physics undergrad course to get a better understanding. More precisely, if I have an...

Let me see if I can line out my question a little better to hopefully get some sort of input. I am trying to understand where a type of boundary condition approx. called stiff spring BCs. I have, among a couple of other examples, an example comsol "dialysis" model that uses it. I have been...

Hey! I'm an international student - thinking of pursuing an Aerospace Engg. Bachelors' degree in US. What are the job opportunities in US in this field for international students? I've heard that US companies that offer Aerospace jobs for non-American citizens are quite rare. Is this true...

What are the minimal conditions to have a non-relativistic quantum theory like Schrödinger theory?

Are there general boundary conditions for the wave equation PDE at infinity? If there is, could someone suggest a book/monograph that deals with these boundary conditions? More specifically, if we have the following wave equation: \[ \nabla ^2 p = A\frac{{\partial ^2 p}}{{\partial t^2...

Homework Statement Consider the following cantilevered beam: The beam has a mass of m = 25 kg and is 2.2 meters long. The suspended block has a mass M = 280 kg and the supporting cable makes an angle of 30 degrees with the beam. Determine the force that the wall exerts on the beam at the...

Homework Statement Let u(x,t) be the solution of the following initial value problem for the nonhomogeneous wave equation, u_{x_1x_1}+u_{x_2x_2}+u_{x_3x_3}-u_{tt}=f(x_1,x_2,x_3,t) u(x,0)=0 and u_t(x,0)=0 x\in\Re^3 , t>0 Use Duhamel's Principle and Kirchoff's formula to show that...

Equations of motion! the conditions pleasezz What are the conditions that enable the equations of motion to be used except from the fact that acceleration must be uniform ?

The total energy of a particle is given by: E_{tot} = 2 \dot{x}^{2} - cos(\frac{1}{2} \pi x) and I'm told that the particle passed through the point x=1 [m] with a velocity of \vec{v}=-\frac{1}{2} \hat{x} [m/sec]. I'm required to find the maximum velocity of the particle during its motion...

The alternating series test contains two conditions for convergence. The first condition is that the nth term (extracting the power of -1) is always positive and monotonically decreasing. The second is that the limit of that nth term goes to 0 as n goes to infinity. I've seen a proof...

Homework Statement I'm getting through a paper and have a few things I can't wrap my head around. 1. In defining the boundary conditions for a membrane (a function of vector 'r'), the author claims that for a small displacement (u) and a boundary movement (f), the boundary condition can be...

I have this, probably quite simple, problem. In the RNS superstring, when varying the action, we obtain in general a term \int d\tau [X'_{\mu}\delta X^{\mu}|_{\sigma=\pi}-X'_{\mu}\delta X^{\mu}|_{\sigma=0} + (\psi_+ \delta \psi_+ - \psi_- \delta \psi_-)|_{\sigma=\pi}-(\psi_+ \delta \psi_+ -...

Hello, what are the conditions that a continuous even function f must satisfy in order to have \int_{-\infty}^{+\infty}f(x)dx < \infty ?

Homework Statement (a) A siren emits a frequency of 900 Hz. Wind is blowing at a steady speed of 15.0 ms-1. The speed of sound in calm air is 343 ms-1. What is the frequency heard by someone approaching at 15.0 ms¹, (i) when the wind blows from the person to the siren, (ii) when the wind...

I'm trying to understand how to set up the problem of a 1D wire that is insulated at one end and has a heat source at the other. I know the heat law, from my textbook: du/dt = B d2u/dx2 + q(x,t) 0 < x < L, t > 0 Where q(x,t) is the source of heat. The problem is, I want the heat...

Hallo Every one, Homework Statement y(x,t)=sin(x)cos(ct)+(1/c)cos(x)sin(ct) Boundary Condition: y(0,t)=y(2pi,t)=(1/c)sin(ct) fot t>0 Initial Condition : y(x,0)=sin(x),( partial y / Partial t ) (x,0) = cos(x) for 0<x<2pi show that y(x,t)=sin(x)cos(ct)+(1/c)cos(x)sin(ct)...

Homework Statement So using the D'Alembert solution, I know the solution of the wave equation is of the form: y(x,t) = f(x-ct) + g(x+ct) I'm told that at t=0 the displacement of an infinitely long string is defined as y(x,t) = sin (pi x/a) in the range -a<= x <= a and y =0...

Hello everybody, I've been puzzling over something (quite simple I assume). Take S^1. Now consider the action of a Z_2 which takes x to -x, where x is a natural coordinate on the cylinder ( -1< x <1). Now we mod out by this action. The new space is an orbifold: smooth except at x=0. It...

Consider an aluminum cylindrical rod 1.0 meter long connecting two heat reservoirs. Both of the reservoirs are maintained at T=300 K. Initially, the cylinder is at 300 K, except for the center point of the cylinder which has been rapidly irradiated to a temperature of 600 K. There is no heat...

1. I have a rod of length 4,cross section 1 and thermal conductivity 1.Nothing is mentioned about the end at the origin x=0, but at the opposite end x=4, the rod is radiating heat energy at twice the difference between the temperature of that end and the air temperature of 23 celcius. Find the...

Homework Statement A hot air balloon has a volume of 2000m^3, and air is always at atmospheric pressure due to large opening. What is the mass of the air if the temp is 120*c. Assume a molecular weight of 28.8g/mol for the air) Homework Equations PV=nrt The Attempt at a Solution...

One of the conditions for oscillation is that the (regenerative) feedback loop must provide a 180 degree phase shift. This is due to the fact that, for a regenerative effect, the signal must undergo n*360 degrees phase shift: 180 from the amplifier and another 180 from the feedback network...

Homework Statement The steady state temperature distribution, T(x,y), in a flat metal sheet obeys the partial differential equation: \frac{\partial^2{T}}{\partial{x}^2}+{\frac{\partial^2{T}}{\partial{y}^2}}=0 Separate the variables and find T everywhere on a square flat plate of sides S with...

Homework Statement Attached question Homework Equations The Attempt at a Solution I tried rearranging S1 for Z then using Maple to plot it, which gave me a cone extending from the point z=1. For S2, would I have to plot it twice? once for <1 and once for =1? I have no...

Hello everybody, This is just a general question I have, and probably the title did a very bad job at explaining it, so here it goes. Is there any material that is available, or even if its still in research (as long as you have some links), that bends/flexes or contracts in certain...

Homework Statement Let n be a nonzero integer and let a be an integer with gcd(a, n) = 1. We have two equivalent conditions which characterize primitive roots: (i) a is primitive modulo n if the order of a is \phi(n). (ii) a is primitive modulo n if for every element b with gcd(b, n) = 1 we...

Homework Statement A surface at z = 0 is held at potential V (x, y) = V0 cos(qx) sin(qy). Find the potential in the region z > 0. Homework Equations Laplace's equation in Cartesian coordinates The Attempt at a Solution I wrote at least a page of my past 2 attempts at a solution...

the general equation of a circle has 3 constants , so it is said that 3 conditions , like 3 points (on the circle) are required to specify a circle , but , we require only the center and radius to specify a circle , so how many conditions are actually required ??

Homework Statement Consider the Heat Equation： du/dt=k(d2u/dx2), where d is a partial and d2 is the second partial. The B.C.'s are u_x(0,t)=u(0,t) and u_x(L,t)=u(L,t), where u_x is the partial of u with respect to x. The I.C is u(x,0)=f(x) Now, consider the Boundary Value Problem...

I just started CM (I had 2 classes until now) and the professor said that if you know the position and velocity of say all the particles, then you know how the system will evolve. This, I already read and knew. I've probably a common question so feel free to redirect me to any similar...

Why is it that change in enthalpy (h=e + pv) depends upon pressure as they say, we should measure at standard pressure, while pv=nrt so no matter da presure nrt is the same the product p by change in volume is constant so accordin 2 me we should specify only da temperature change...

For a string with one endpoint attached to a wall and the other to an oscillator (so that it is under boundary conditions), what is the character of waves that are not at a harmonic frequency?

Homework Statement A high temperature, gas cooled nuclear reactor consists of a composite cylindrical wall for which a thorium fuel element (Ka=57 W/m*K) is encased in graphite (Kb= 3 W/m*K) and gaseous helium flows through an annular coolant channel. Consider conditions for which the helium...

Homework Statement Solve the equation u_{x}+2xy^{2}u_{y}=0 with u(x,0)=\phi(x) Homework Equations Implicit function theorem \frac{dy}{dx}=-\frac{\partial u/\partial x}{\partial u/\partial y}The Attempt at a Solution -\frac{u_x}{u_y}=\frac{dy}{dx}=2xy^2 Separating variables...

Hi there, I recently read that the equations of motion for an classical open string naturally give rise to two boundary conditions, namely Dirichlet and Neumann boundary conditions. (i) Could someone explain to me what do these boundary conditions physically mean, in particular for open...

Homework Statement 2) Given a cubic equation y = (x+5)(ax^2 + bx - 2). Give conditions on a and b for the equation to represent the following curve. The curve is attached to the email. http://img35.imageshack.us/img35/8246/question2o.png Homework Equations The Attempt at a Solution...

Greetings all, I have a question in regards to my initial conditions. The problem as given is: ut=uxx with u' = 0 at x=0 and u=0 at x=L I was also given u={1 0<x<L/2, 0 L/2<x<L I understand the set up of the problem and the solving of it for the most part, however I'm having...

Homework Statement du/dt = (d^2)u/d(x^2), t>0, 0<x<1 u(0,t) = 0 = u(1,t) , t>0 u(x,0) = P(x), 0<x<1 P(x) = {0 , if abs(x-1/2) >epsilon/2 {u/epsilon, if abs(x-1/2) <= epsilon/2 i need to find u(1/2,1/pi^2) Homework Equations i have u(x,t) = SUM{ 2/(n*pi)...

Homework Statement The problem can be found http://whites.sdsmt.edu/classes/ee382/homework/382Homework4.pdf" . It is the first one. Note: The subscript x = 0 is supposed to be y = 0 (the teacher typed it in wrong). Homework Equations \vec{\boldsymbol{D}}_{2t} =...

Hello all, This is to do with forced longitudinal vibration of a rod (bar). It's basically a problem to do with the linearised plane wave equation (1d). The rod is fixed firmly at one end, and excited at the other by a harmonic force. The wave equation (with constant rho/E instead of...

Homework Statement d20/de2+1=0 and the boundry condition is -d0/de(evaluated at e=+/- 1)=+/-H0(evaluated at +/-1). The final result yields 0(e)=(1/2)(1-e2)+1/H. What i don't understand is how to use this boundary condition and where the 1/H comes from. The Attempt at a Solution...

Homework Statement Find the potential outside of a long grounded conducting cylindrical rod of radius R placed perpendicular to a uniform electric field E0. Homework Equations V(s,\phi) = a_{0}+b_0{}ln(s) + \sum(A_n{}cos(n\phi)+B_n{}sin(n\phi))*(C_n{}s^n{}+D_n{}s^{-n}) The sum being...

hello all, We live in a hot part of the world with the extra bonus of high humidity - around 90%. We don't have A/C, and don't really want to get it (energy use). Evaporative cooling won't do much (towel on head) becuase of water saturation in air. Would a cold wet towel + fan force water...

http://i48.tinypic.com/1o4ow9.jpg why in this circuit they say that in t<0 the voltage on both capacitators is 12 volts?? if both points of each capacitators is connected to the voltage source directy then 12 volts is ok. but here we have a resistor between them this resistor drops...

Homework Statement The problem is given as follows: Solve dy/dt + y = 0.5, y(t=0)=1Homework Equations The Attempt at a Solution I separate the y terms from the t terms, which gives me dy(-y+0.5)=dt I integrate both sides to get -ln(-y+0.5)=t+C C is the constant, I combine the constants from...

For a Sturm-Liouville problem, as in: \frac{d}{{dx}}\left[ {r(x)\frac{{dy}}{{dx}}} \right] + [\lambda p(x) + q(x)]y = 0 I've read in several books that one assumes that p, q and r are continuous, real-valued and bounded in the interval I, r' is continuous, and p>0. But I've never seen...

what is the solution for y in this peculiar ODE ? A\left(y,x\right)=\frac{dy}{dx}+B(x)(1-y) with initial conditions : \frac{dy}{dx}=\left0 \ldots , y=0 \frac{dy}{dx}=\delta(x-x_{0})\ldots,y=1 moreover \int^{\infty}_{-\infty}Adx=\int^{\infty}_{-\infty}Bdx=1

I own an old and small car with only 30HP and a very poor aerodynamic coefficient, Cx=0.51. Based on this and on the rolling coefficient, I just solved out what would be the maximum speed when driving on a leveled road and there is no wind at all. It came out to be 120Kms/hr which can be...

A partial differential equation requires boundary conditions. Consider a 2-dimensional problem, where the variables are 'x' and 'y'. The boundary is the line x=0 and you are given all sorts of information about the function on that line. If you are given just the values of the function on the...