Browsing by Author "Yılmaz, Melek"
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Atomic collisions and free lepton pair production
In this work we have calculated the total cross sections of electronpositron pair production for the collisions of fully stripped gold ions for various energies. We have also compared our calculation with other methods.

Cosmic ray intensity variation during a CME
Authors:Kandemir, Gulcın; Geçkinli, Melih; Firat, Coşkun; Yılmaz, Melek; Ozugur, B
Publisher and Date:(PergamonElsevier Science Ltd, 2002)The June 6 2000 coronal mass ejection was an exceptional full halo which made it possible to measure cosmic ray (CR) decrease with a simple experimental setup. Variation in the local secondary cosmic ray density has been investigated by means of gamma rays. The experiment site was located in Istanbul (41.1N 29.0E). CR electrons and slow gamma rays have been eliminated. The CR density has dropped drastically starting on June 8 2000. The counts have been compared with the preshock levels and some ...

Coulomb corrections in the leptonpair production in ultrarelativistic nuclear collisions
Authors:Guclu, Mehmet C.; Kovankaya, G.; Yılmaz, Melek
Publisher and Date:(Amer Physical Soc., 2005)We solve the perturbative electronpositron pair production exactly by calculating the secondorder Feynman diagrams. We compare our result with Born methods that include Coulomb corrections. We find that a smallmomentum approximation is not adequate to obtain exact Coulomb corrections and higherorder terms should also be included. We also compare the impact parameter dependence cross sections.

Design of lowpass ladder networks with mixed lumped and distributed elements by means of artificial neural networks
In this paper, calculation of parameters of lowpass ladder networks with mixed lumped and distributed elements by means of artificial neural networks is given. The results of ANN are compared with the values that are desired. It has been observed that the calculated and the desired values are extremely close to each other. So this algorith can be used to obtain the parameters that will be used to synthesize such circuits.

On the inverse pointsource problem of the Poisson equation
In this work, a basic inverse heat conduction problem of a simple 2D model with steady state heat source is taken into view. The physical problem is for a square region with uniform thermophysical properties and a point heat source of unit magnitude. To obtain boundary data , temperature probes are placed at the midpoints of the sides of the square domain. The objective of the inverse problem is to estimate the coordinates of the point source with the least amount of data. Initially, the ...

On the inverse pointsource problem of the poisson equation
Authors:Yılmaz, Melek; Şengül, Metin Y.; Geçkinli, Melih
Publisher and Date:(Istanbul University, 2005)In this work a basic inverse heat conduction problem of a simple 2D model with steady state heat source is taken into view. The physical problem is for a square region with uniform thermophysical properties and a point heat source of unit magnitude. To obtain boundary data temperature probes are placed at the midpoints of the sides of the square domain. The objective of the inverse problem is to estimate the coordinates of the point source with the least amount of data. Initially the inverse ...