# Search results

1. ### Transfer of Quantum State

Thanks for your help, I really appreciate it. The reason i ask about the transfer of states, is because that I plan to write a story which involved a "stolen" quantum states ie experimenter B steal the quantum states of photons from A and make the original photons randomly oriented. I am...
2. ### Transfer of Quantum State

Hmm....so would it be safe to say that, experimenter B can't "steal" the information from A without exchanging the photon or ask the information from A like you said?
3. ### Transfer of Quantum State

Hmm..that means if they aren't entangled before, there isn't anyway to make them entangled? Meaning that, if the photons are not prepared from the same source, there is absolutely no change for the transfer to occur?
4. ### Transfer of Quantum State

An experimenter, A, has prepared four photons with known polarization states. In another lab, experimenter B has prepared four photons with random orientation. Is it possible, for the photons prepared by B, to take the polarization states of the photons prepared by A, without B knowing the...
5. ### Coefficient of (1+x+x^2)^n

I am fine with that expression. The only thing is I don't quite understand the derivation (like how you express the right hand theorem). Or maybe I am just being too sleepy..:)
6. ### Coefficient of (1+x+x^2)^n

I have looked into it as well. The formula doesn't express the function in terms of x^k alone, and i have problem converting the expression...
7. ### Coefficient of (1+x+x^2)^n

I need to find a formula that describe the sequence shown above. (The sequence is highlighted.) I am aware that the sequence is the coefficient of the polynomial (1+x+x^2)^n, and have tried using Taylor's expansion. Still, I can't get a nice formula that describe the sequence. Any help/hint...
8. ### Modelling of Car Impact

I have done some googling online, and there are fair bit of journals and articles describing how to define the contact force and the changes during the collision. Haven't manage to look through all of those thoroughly, but from first glance, the articles on impact modelling that i have read...
9. ### Modelling of Car Impact

I know that real car would crumple, and it is hard to estimate to what extend would a particular vehicle crumple in an impact. For simplicity, i would assume rigid body case first. In such case how can i proceed with my modelling?
10. ### Modelling of Car Impact

I am trying to model the following situation: Let say i have an obstacle with known mass, and I know the coefficient of static and dynamic friction between the obstacle material and the floor. A car travelling at a fixed velocity is to impact the obstacle. For simplicity i will first consider...
11. ### Hyperplane math homework

[PLAIN]http://img823.imageshack.us/img823/1883/questiona.png [Broken] Thanks for your help. I am stuck with the next part of the question though. I know that a and b will lies on the different side of the line/plane/hyper plane, but I am not too sure how to provide a rigorous proof for that...
12. ### Hyperplane math homework

Homework Statement [PLAIN]http://img835.imageshack.us/img835/1108/question.png [Broken] The Attempt at a Solution I understand that the determinant represents the set of points, x in R_k which lies in the hyper plane passing through the points p1, p2.....p_k. I also know, that if the...
13. ### Wavefront Simulation using Geometry Optics and Physical Optics

I am required to simulate the propagation of a the wavefront produced by a laser light (about 633 nm) passing through a system of lens and undergoes a few reflection. What I did at the moment is to do ray tracing, record the optical path length of each ray, then connect every point of the same...
14. ### Solving Laplacian Equation Analytically

Yes, I read about that. But the problem is, there are so many possible combinations (different products of function y and function x), and how should i use the boundary condition to find the one I need?
15. ### Solving Laplacian Equation Analytically

I wish to solve a 2D steady state heat equation analytically. The boundary is a square. The top side is maintained at 100 C, while the other sides are maintained at 0 C. The differential equation governing the temperature distribution will be the laplacian equation. To solve the equation...
16. ### Calculate the change in entropy of the universe

Thanks a lot Mapes! I never realize that it is heat capacity instead of specific heat capcity (as they give us mass in the question). :)
17. ### Calculate the change in entropy of the universe

Homework Statement Calculate the change in entropy of the universe as a result of the following process: A copper block of mass 0.4 kg and heat capacity 150 JK-1 at 1000C is placed in a lake at 100C. 2. The attempt at a solution change in entropy (copper) = mc ln (T2 / T1)...
18. ### Reversibility of Otto Cycle

I refer to the first process, but a hypothetical ideal one where it is reversible. After some thought, I think that in order for an ideal gas to expand under constant volume and yet be reversible, there will have to be many heat reservoir, with infinitesimal small difference in temperature...
19. ### Reversibility of Otto Cycle

Theoretically, we can have reversible isochoric expansion and isochoric compression. Is Otto Cycle reversible then? I read that the efficiency of all reversible engine between two heat reservoir would have the same efficiency. However, since the efficiency of an Otto Cycle is lower than...
20. ### Infinitesimal Strain Tensor

I read that http://img196.imageshack.us/img196/1705/71301190.png [Broken] I am not so sure about the last term. Shouldn't it be http://img10.imageshack.us/img10/3962/88484785.png [Broken] instead?
21. ### Del Operator for Cylindrical Coordinate

http://img208.imageshack.us/img208/5153/12802868.png [Broken] Why is the del operator for cylindrical coordinate the upper one and not the lower one? How does the 1/r term arises?
22. ### Divergence Theorem

http://img60.imageshack.us/img60/9696/21249035.jpg [Broken] I am stuck at the last step. Can anyone give some hints? Thanks in advanced.
23. ### Magnetic moment

Quote from "Spin Stabilized Magnetic Levitation of Horizontal Rotors", L. A. Romero, from SIAM Journal of Applied Mathematics. "Suppose we have a rotor that has two equal dipoles on the axis of symmetry, each pointing in the direction of the axis of symmetry. We suppose that the magnets are...
24. ### The commercial toy, Levitron, can achieve stable magnetic levitation

True, the magnetic configuration of Levitron doesn't allow it to rotate on horizontal axis. I did try other magnetic configuration but it doesn't work out as well. However, can we generalize, that for ANY magnetic configuration, the system wouldn't be able to levitate stably and rotating on...
25. ### The commercial toy, Levitron, can achieve stable magnetic levitation

The commercial toy, Levitron, can achieve stable magnetic levitation due to gyroscopic stabilization and axis precesion. The Levitron toy sold in market has a vertical spinning axis, and so far I have not found a variation with horizontal axis. Is it allowed in Earnshaw's theorem, for a...
26. ### Visualization of Magnetic Field

Suppose I have an electric motor, and I wish to visualize how the magnetic field change by time. Is it possible for me to visualize the magnetic field line without using iron powder or ferrofluid? Is it possible to have multiple hall sensors to detect magnetic field strength in various location...
27. ### N-doped region tend to flow to the p-doped region

When a diode is first manufactured, the electrons in the n-doped region tend to flow to the p-doped region due to diffusion effect. In the process, a depletion region is formed until the electric field in the depletion region cancel out the diffusion effect. Hence an equilibrium is reached. (or...
28. ### Earnshaw's Theorem and a photon

Thanks for the prompt reply. Yeah, I forgot that this is in uniform field, hence the field strength decrease by 1/r rather than 1/r^2. Suppose if I substitute the proton with a sphere attached by many magnet with the same polarity facing up, and similarly, attach many magnet on the interior...
29. ### Earnshaw's Theorem and a photon

Imagine there is a hollow sphere charged with positive charge, distributed evenly. Then a proton is placed in the cavity. Would the proton levitate stably in the middle of the cavity? By Earnshaw Theorem, any configuration of system with fixed field strength which obey inverse square law will...
30. ### Demagnetization of a permanent magnet

When we magnetize a ferromagnetic material, we provide an input of energy. Is it possible to demagnetize a magnet, and convert a fraction of the energy to usable work? (Of course, this is not a useful way to generate work, and some fraction of the input energy is lost)