Recent content by makris

Can anybody tell a few good sources for 1dimentional signal decimation? Either books or URLs? I know how to use the "decimate" function in MATLAB thus perform decimation, but my goal is to code a function in MATLAB (or C) to perform the same process. That is why I need the theory behind...

I would like to solve a problem of the type (da/dt)^2 + f(a)* (da/dt) = g(a) (1) a=a(t) unknown function f(a), g(a) = known functions of a. This differential equation is a first order ODE but (da/dt)^2 makes it different compared to a typical first order ODEs (at least to my...

Hi all, I have the following question. A = nxn non singular matrix I = nxn identity matrix li = eigevalues of A i=1,2...n ui = eigenvectors corresponding to the previous eigenvalues. It true that ( A - l1 * I ) * x =0 is satisfied by any vector of the form x = a1 * u1...

This is a reply to the message by gvk. Sorry I am replying this late... The book by Wilhelm Flugge gives an introduction to tensors assuming minimum prerequisites. It explains very well the following (pages 2-8 or a little bit more): 1.)Covariant and contravariant base vectors...

Even though I am posting this quite late, I have decided to post it hopping that I will save some people's time. I have found the most lucid explanation on the covariant - contravariant issue in the book "Tensor Analysis and Continuum Mechanics" by Wilhelm Flugge. (pages 2-7). The...

The Laplacian operator can be applied to a function of two variables. I agree that we should not see the action of the Laplacian as taking a function find the partial derivatives and add them… In my question I assume that x, t are independent variables. To see the Laplacian as V*V (which is...

Consider a function U(x,y) where x, and y are spatial variables (have units of length) Assume that the symbol V^2 corresponds to the Laplacian operator. Then V^2U= Uxx + Uyy where the subscript indicates partial differentiation. Consider now a function F(x,t) where x is spatial...

Exactly! I have done the same both for Dy/Dx and Dy/Dt to verify that Dy/Dt=-c*Dy/Dx Thanks.

I have concluded that Dy/Dx=F'(x-ct) after working with some examples. So I wrote down several functions with (x-ct) as an argument and I took the partial derivative with respect to x. Then I took the derivative with respect to the argument as a whole (z=(x-ct) ) to form F'(x-ct). They are...

Assume the well known PDE of an infinite length string D^2(y)/Dt^2 = c^2* ( D^2(y)/Dx^2) where y=y(x,t) is the transverse displacement of the string. D/Dx= partial derivative with respect to x D/Dt= partial derivative with respect to t c= velocity of the wave According to Morse and...