Variable Definition and 1000 Threads

An interesting and well presented new paper by Kumar and Xu: "Observational constraints on a cosmological model with variable equation of state parameters for matter and dark energy" http://arxiv.org/abs/1207.5582 The idea of a variable equation of state for matter and dark energy is not...

I have an ode function which is of the form: function [output]=Fun[input1,input2,input3] which is solving a set of non-linear differential equations. input1 and 3 are fixed but input2 is a variable. Say: input1=3; % a constant input3=20; input2=[2 4 6 8]; function Fun is being...

Can I use excel to make an equation for 4 variables (x,y,z,w) e.g a,b,c,d,3,f,g,h,i, would be constants w = ax + by + cz + dx^2 + ey^2 + fz^2 + gxy + hyz + iyz What are these equations called ? What literature can I study to better understand the procedure of making these tye of...

Homework Statement An oscillating LC circuit is designed to operate with a maximum current of 31 mA. The inductance is fixed at 42 mH, and the frequency is changed by means of a variable capacitor C. (a) If the highest voltage that the capacitor can handle is 50 V, can the circuit be operated...

Typical VC: http://goo.gl/Z4Dbg I have that guy there or one very similar. My question is how does one hook this up to the inductor? Forget, for now, the rest of the circuit. How do these two piece fit together? The bottom feet (there are two on each side) I assume take the positive...

Homework Statement http://img12.imageshack.us/img12/1176/img20120713190506.jpg Homework Equations V_{C}' = dv/dt I_{L}' = di/dt The Attempt at a Solution I did KCL at the centre node: I_{L} + i_{2} = \frac{V_{C}'}{5} (Vc'/5 is basically the current coming from the capacitor...

Homework Statement Suppose X is a discrete random variable whose probability generating function is G(z) = z^2 * exp(4z-4) Homework Equations No idea The Attempt at a Solution I'm thinking that due to the exponent on the z term, that the exp(4z-4) would be the P[X=3] =...

Homework Statement In the electric circuit shown in the figure, when the value of the variable resistor R3 is 25Ω, the current which flows into the power supply is 2A. Moreover, when the value of the variable resistor R3 is 5Ω a current of 1A flows into the resistance R2. Q1.Find the value of...

Homework Statement First, there's a slender rod with length L that has a mass per unit length that varies with distance from the left end, where x=0, according to dm/dx = yx where y has units of kg/m^2. (a) Calculate the total mass of the rod in terms of y and L (Which I've already done and...

Homework Statement A line charge in the x directio has a variable charge density given by the equation λ=4 λnot((1-x)/2L), where λnot is a constant. The rod has a length of L. i)What is the net charge of the rod? Hint-the net charge is calculated by integrating the charge density with respect...

Homework Statement I just need to know how to access an arraylist that was created in a class (call it Company). In class CompanyTest, I need to access a list of employees that was created in Company. This is Company class: public ArrayList<Employee> list = new ArrayList<Employee>()...

the problem is as follows: [1-(12*x*(y^2))]*(dy/dx)=y^3 we need to solve this equation such as x=5 & y=2 by regarding y as the independent variable. Here is my work for the first attempt: Step 1)separation & integration Step 2)ln(x)= (-1/(2y^2))-12ln(y)+C...

Dear all, I have a question about the variable substitution in Langevin equation and Fokker-Planck equation and this has bothered me a lot. The general Langevin equation is: $$\frac{dx}{dt}=u(x)+\sqrt{2 D(x)}\eta(t)$$ and the corresponding Fokker-Planck equation is thus: $$\frac{\partial...

Hi Maybe I don't see the wood because of all the trees, but: You have a second derivative \frac{\mathrm{d}^2}{\mathrm{d}x^2} e^{-ax} \cdot u(ax) Now you make the variable transformation w=ax How to express \frac{\mathrm{d}^2}{\mathrm{d}w^2} Thanks Greetings

Homework Statement A racing car of mass 20000kg accelerates with a driving force of 480(t-10)^2 Newtons until it reaches its maximum speed after 10 seconds. Find its maximum speed, and the distance it travels in reaching this speed. The Attempt at a Solution Again, I can't seem to...

EDIT: Oh and I forgot that $p_Y(y) = 0$ otherwise.

Homework Statement A car of mass 1200kg is at rest on a level road. Two people push it, producing a total force given by (240-12t) Newtons, where t is the time in seconds, until this becomes zero after 20 seconds. How fast is the car then moving, and how far does it move while it is being...

You are given a random exponential variable X: f(x) = λ exp(-λ x). Suppose that X = Y + Z, where Y is the integral part of X and Z is the fractional part of X: Y = IP(X), Z = FP(X). Which is the following conditional probability: P(Z < z | Y = n) for 0 ≤ z < 1 and n = 0, 1, … ?

I want to calculate \int_a^b \frac{1}{\sqrt{2 \pi \sigma^2}} e^{(-(x-\mu)/\sigma^2)} log_2 (1 + e^{-x}) dx

Homework Statement An open-topped railway wagon of mass M is rolling freely along straight level frictionless track at a constant velocity v0. At time t=0 the wagon enters a heavy rain shower and starts to collect rainwater. The rain falls vertically. As a consequence the wagons mass increases...

Homework Statement A 2kg bucket containing 10kg of water is hanging from a vertical ideal spring of force constant 125N/m and oscillating up and down with amplitude 3cm. Suddenly the bucket springs a leak in the bottom such that water drops out of the bucket at a steady rate of 2g/s...

Hi, I have a random variable X with some zero-mean distribution. I have a function Y of this r.v. given by something complicated Y=(a+X)^\frac{2}{3} Is there an explicit way of finding the distribution of Y or even its mean? Thanks

hello! I am interested to know if a tube can be created that with some kind of mechanism, its diameter will increase on demand the range of the diameter should start at the smallest possible (0.01 mm or less if possible, even if the walls of the tube virtually concur) and increase up to...

Homework Statement So I came across the integral \int^{1}_{0}x\sqrt{1-x^2} and I tried to solve it in two ways using the change of variables theorem for integration, however both ways are supposed to give me the same result, but they differ in the sign and I cannot find what I am doing...

Hi Iknow that if we have delta function of one variables function, then we can write it as: \delta (f(x)) = \sum \frac{\delta(x-x0)}{f'(x0)} but how we can write a function of two variables: \delta (f(x,y))

what is log of z=X+JY? Thanks

Hello all, I have a 3 phase Variable frequence drive that requires an input voltage of 380-480VAC. I would like to test what would happen if I apply 300VAC to the drive. I have access to 208V and 440V. Is there anything I can do to obtain 300V? I have thought about a variable power supply...

Hi All, I need to train an HMM using data with sequences of variable length (5 - 500 symbols per input sequence). From what I've seen thus far, all (or most) trainings are perfirmed on data-sets of a fixed size, although there is no explicit demand for this in the HMM structure. So...

Homework Statement http://img716.imageshack.us/img716/7453/28042782.jpg The Attempt at a Solution What I do not understand is how the Jacobian suddenly gets inverted when doing the integral, I have looked over my other tutorial problems for similar solutions and I do not recall doing...

Hello guys, First of all, thanks for looking at this post and trying to help me. I have function which is shown below, F1= (ε1-√(1+(ε1 μ1-1)x^2))/(ε1+√(1+(ε1 μ1-1)x^2)); F2= (ε2-√(1+(ε2 μ2-1)x^2))/(ε2+√(1+(ε2 μ2-1)x^2)); F=F1*F2; Here, F is a function of x --> F(x) I...

Well, I am now trying to figure out a single variable expression for Sin. I have a couple ideas using some pieces of geometric formulas I have played with recently but this is still new to me. I'm not talking about sin x, but an algebraic expression for the sin wave. Any thoughts?

What I am looking for is a cheap, lightweight way to generate a range of specific frequencies. To expand a little, a microwave uses a constant frequency but may vary its power to cook the food. I've heard it tries to match the resonant frequency of the water molecule in order to agitate it...

Homework Statement A car is stopped at an intersection with a red light and a biker (in a bike lane) with velocity v is approaching the car. When the biker is a distance d from the intersection, the light turns green and the car begins to accelerate at a constant acceleration a. If the biker...

Homework Statement e^2x * e^2 Homework Equations The Attempt at a Solution Really, I'm just a little bit confused on how I would go about adding the exponent. None of the examples in the book cover that. Is it simply e^2x+2?

For some non-linear 3D function, let's say I want to take the partial derivative for x where y is constant. Each point for Z will be different of course since it's non-linear. So let's say I plug in an X of 3 where Y is constant for some function and I get a slope of 5 as my answer. Is it...

How are described in the Industry those transformers able to operate with a variable frequency? These transformers will be used downstream of a Frequency Drive. Anyone knows? Any specific characteristics? Thanks

Hello, how do you define a function or make a list with n elements, where n is any? More precisely there is a function in mathematica, BellY BellY[n,k,\{x_{1},...x_{n-k+1}\}] which gives the partial Bell polynomial. I would like to define in mathematica the complete Bell polynomial defined...

About the definition of "discrete random variable" Hogg and Craig stated that a discrete random variable takes on at most a finite number of values in every finite interval (“Introduction to Mathematical Statistics”, McMillan 3rd Ed, 1970, page 22). This is in contrast with the assumption that...

It has been a while since I have done limis now, and I want to make sure I am doing this correctly. I have the problem listed below (x-y)/(x+y) as (x,y) -> (0,0) In my mind I can gather that it will asymptote as you approach from either (-1,1) or (1,-1) I also know that it will...

Hi, I have an equation: \frac{q-\bar{q}}{w_{i}^{2}+w'_{j}^2}=\sum^{n}_{i=0}\sum^{m}_{j=1}F_{0}\cdot a_{ij}\cdot cos(w_{i}\cdot x)\cdot cos(w'_{j}\cdot y) I'm trying to solve for a_{ij} I have the solution, but I'm not sure how they came up with it. The solution is...

Hi all, I have a MIMO system which I have developed in Simulink and I have also work out the Model predictive control for it. Now I have a manipulated variable which I want to be used during night and remained turned off during day. I have tried but could not figure out how to do this in...

I ran into a kind of strange thing today while coding. I needed Pi in a program, so I used 2*accos(0.0) to pull it out, but my answers were slightly off. I checked the Pi calculated and it was off after a few decimal places. "Odd", I thought, and just decided to put in Pi as an assigned number...

Homework Statement Problem: Find the limit if it exists, or state that it does not exist for: lim (x,y)→(0,0) [2x^3 + 6y^3]/[x^2 + y^2]. Answer: lim (x,y)→(0,0) [2x^3 + 6y^3]/[x^2 + y^2] = 0 Homework Equations r^2 = x^2 + y^2 The Attempt at a Solution I know I can replace...

Homework Statement I'm trying to understand the equations given in my textbook (Principles of Physics, Ninth International Edition) for finding the center of mass. The equations are given below. They're used to find the x, y, and z components of the center of mass for objects. I'm trying to...

Can somebody give me a scenario when chilled beams would be the preferred method of conditioning and ventilation as opposed to the variable refrigerant flow systems? I have heard a lot about chilled beams, but I'm not sure they are ever going to really get popular in the US, because I don't...

let x=r^2. if we have already d/dr, how to find d/dx? I was saying, d/dr=(d/dx)*(dx/dr)=(d/dx)*2r ? But am doubting it?

Hi, I want to select my variable automatically in MATLAB so I used the following commands: (may variable for example are: Mpoint1,Mpoint5,Mpoint14,...) for i=1:50 if exist (eval(['Mpoint' num2str(i)])); statements else...

Homework Statement Solve the following equation in N^3: x^2+y^2+z^2=xyz-1 The Attempt at a Solution I moved all the terms to one side, but I don't know what to do from there on.

Considering U1 and U2 which both follow Uniform (0 , A), then after the transformation of variable, i can find x=(U1+U2)/2 has f(x)=2/A(both my classmates and me get this result). However i am confused that when i integrate x by it range from 0 to A (because U1 and U2 both ranged from 0 to...

Homework Statement http://img706.imageshack.us/img706/263/hwstatement.png Homework Equations KCL/Node voltage method Ideal op-amp rules The Attempt at a Solution I solved a previous, similar problem where the gain was fixed and the resistor mass going into the inverting and noninverting...