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Demetris T. Christopoulos

Publications and source records attributed to Demetris T. Christopoulos.

6 recordsLinked to original sources
arXiv2014

Developing methods for identifying the inflection point of a convex/concave curve

We are introducing two methods for revealing the true inflection point of data that contains or not error. The starting point is a set of geometrical properties that follow the existence of an inflection point p for a smooth function. These properties connect the concept of convexity/concavity before and after p respectively with three chords defined properly. Finally a set of experiments is presented for the class of sigmoid curves and for the third order polynomials.

math.NA↗
arXiv2014

Inflection point analysis for Greek seismicity 1900-2006

The seismicity of Greek region is studied under the prism of ESE & EDE methods for finding the inflection point of cumulative energy released. Main shocks are chosen from 106 years data. The result is that with both methods a critical time region exist at the end of 1982 to early 1983. After this time the seismicity tends to increase and gives remarkable events, like Athens Sep 1999 earthquake.

physics.gen-ph↗
arXiv2013

On the effective radius of convergence for a given truncated power series expansion

An effective radius of convergence is defined and computed for any truncated Taylor series. Applications to well known series are performed and is shown that a range of good coincidence for actual and approximative plot can always be found. For sufficient large degree of approximation the effective radius is also an estimation of the true non-infinite radius of convergence.

math.FA↗
arXiv2013

Linear Regression without computing pseudo-inverse matrix

We are presenting a method of linear regression based on Gram-Schmidt orthogonal projection that does not compute a pseudo-inverse matrix. This is useful when we want to make several regressions with random data vectors for simulation purposes.

math.ST↗