Author Archives: Shuhua Zhang

About Shuhua Zhang

Born in Anhui, China. Awarded a doctor's degree in electronic engineering from Tsinghua University. Now a postdoc researcher working on audio and speech signal processing, especially source separation, in gipsa-lab, Grenoble-INP, France.

Monotonically increasing intervals

Problem  A real sequence satisfies for all , where . Let be the length of the th interval. Show that there exists a unique such that for all . Remark  This is a problem that arises from nonlinear quantization in … Continue reading

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3D Matrix Multiplication Tricks

Recently, I came across times 3D matrix multiplication in Matlab. It is for frequency domain signal processing, specifically, frequency-dependent multi-channel Wiener filter. Here, 3D matrix multiplication means 2D matrix multiplication at each frequency (or other parameters):  Given and which are … Continue reading

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Dense Circle

Proposition 1. Let be an irrational number and denote the set of fractional parts of for all . Then is dense in . Proof. We shall first prove that is dense at , then proceed to the whole range of … Continue reading

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Originally posted on What's new:
I’ve just uploaded to the arXiv my paper “Every odd number greater than 1 is the sum of at most five primes“, submitted to Mathematics of Computation. The main result of the paper is…

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Blacklist IPs that attack SSH and FTP services on a Linux machine

I manage a Linux server (Redhat EL4, kernel version 2.6.9-34). Yesterday,  I found the server was attacked relentlessly from It seemed to be a brutal force dictionary attack. What to do then? The obvious way is to manually add that IP … Continue reading

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