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해당되는 게시물 6건
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2008/12/21 10:13
My handwriting
2008/12/21 10:13 2008/12/21 10:13
For 2008 Fall, I took Analysis I, measure theory. This is my cheat sheet that I made for the final, just for studying purposes. It's written on a letter paper with a HITEC-C 0.3 black pen.
User imageUser image
2008/08/12 15:56 2008/08/12 15:56
Let there be two identical, symmetrically coupled oscillators, denote the phase as LaTeX equation. Let us denote the phase response curve (PRC) as LaTeX equation. The PRC represents the change in phase for infinitesimal perturbation at phase LaTeX equation.
If the coupling is pulse coupled with some sort of transfer function LaTeX equation, the effective coupling function (or effective PRC in [3]), LaTeX equation.
The phase dynamics can be described by,
LaTeX equation,
LaTeX equation.
Now, in case of phase synchrony, LaTeX equation.
Therefore,
LaTeX equation.
is the key function to consider. If this function is 0 at 0, it means there exist a stable synchronizing solution. And 0 at other phase differences implies phase synchrony.
Note that this function has the same sign and solution as the odd portion of LaTeX equation.

As LaTeX equation, the alternative expression,
LaTeX equation,
says the second derivative of LaTeX equation has the same sign and solution.

[1] Dong-Uk Hwang, Sang-Gui Lee, Seung K Han, Hyungtae Kook, "Phase-model analysis of coupled neuronal oscillators with multiple connections", Physical Review E (Statistical, Nonlinear, and Soft Matter Physics), Vol. 74, No. 3. (2006) [doi]
[2] Hyungtae Kook , Sang-Gui Lee , Dong-Uk Hwang and Seung Kee Han Synchronization of a Neuronal Oscillator Network with multiple connections of time delays Journal of the Korean Physical Society, 2007 50:341-345.
[3] Hideyuki Cateau, Katsunori Kitano, Tomoki Fukai, "Interplay between a phase response curve and spike-timing-dependent plasticity leading to wireless clustering", Physical Review E (Statistical, Nonlinear, and Soft Matter Physics), Vol. 77, No. 5. (2008) [doi]

2008/08/05 12:45
Street-Fighting Mathematics
2008/08/05 12:45 2008/08/05 12:45

When I was a teenager, I used to use these kinds of tricks to do well on tests. Especially useful for multiple choices but works very well otherwise. The course material is inspiring and well organized. I highly recommend to take a look.

http://ocw.mit.edu/OcwWeb/Mathematics/18-098January--IAP--2008/CourseHome/index.htm

Sanjoy Mahajan, course materials for 18.098 / 6.099 Street-Fighting Mathematics, IAP 2008. MIT OpenCourseWare (http://ocw.mit.edu/), Massachusetts Institute of Technology. Downloaded on [5 Aug 2008].

TAG :
2008/02/15 10:24 2008/02/15 10:24
Let LaTeX equation be the transition probability from state i to state j in time t of a discrete state Markov process, that is:
  1. LaTeX equation (transition probability is always non-negative)

  2. LaTeX equation (the total out going probability from a state is 1)

  3. LaTeX equation (the probability through state k is consistent)

  4. LaTeX equation (for infinitesimal time the probability of staying at the current state is 1)
Theorem
For every i

LaTeX equation

exists but may be infinite.

Proof (adapted from Karlin and Taylor 1981)
First we define LaTeX equation,

LaTeX equation

LaTeX equation

It is easy to see LaTeX equation therefore LaTeX equation for all t. Now we put

LaTeX equation

LaTeX equation and if it is not infinite, there for every LaTeX equation, there exists a LaTeX equation such that LaTeX equation.

For each t, we decompose as LaTeX equation via division with natural number n and reminder LaTeX equation. Then,

LaTeX equation

LaTeX equation

The equality is because as LaTeX equation, LaTeX equation. Since LaTeX equation was arbitrary, we have

LaTeX equation

for when LaTeX equation, the limit is also infinite.
Finally,

LaTeX equation.

Reference
  • Samuel Karlin, Howard M. Taylor. A second course in stochastic processes, Academic press 1981 (ISBN 0-12-398650-8)
2006/12/24 09:33
Algorithm 1
2006/12/24 09:33 2006/12/24 09:33
This is the algorithm I have been working on for a few days.
Guess what it is before I publish it. BTW, Merry Christmas, everyone.

User inserted image

update 2008 Feb: This algorithm is published as
Il Park, António R. C. Paiva, José Príncipe, Thomas B. DeMarse. An Efficient Algorithm for Continuous-time Cross Correlogram of Spike Trains, Journal of Neuroscience Methods, Volume 168, Issue 2, 15 March 2008, 514-523
2006/09/29 07:36
Series sum of n^m x^n
2006/09/29 07:36 2006/09/29 07:36
LaTeX equation
where LaTeX equation.
This summation converges for LaTeX equation and for all integers LaTeX equation.
You can solve this my differentiating the following easy sum LaTeX equation times
LaTeX equation
however, it is always convenient to know the short cut answer.

BTW, I wonder why nobody makes equation search engine for the web.
Searching equations with reordering and change of variables would be very helpful.
I know mathworld supports a little bit of search but it is not enough.
If I only had some time, I would start implementing for Wikipedia formulas with Prolog.

Reference: http://www.jstor.org/view/07468342/di020761/02p0031j/0
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