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New evaluations of ant colony optimization start nodes

100%

Fidanova S. , Marinov P. , Atanassov K.

2014

tom Vol. 43, no. 3

471--485

Ant Colony Optimization (ACO) is a stochastic search method that mimics the social behavior of real ant colonies, managing to establish the shortest route to the feeding sources and back. Such algorithms have been developed to arrive at near-optimal solutions to large-scale optimization problems, for which traditional mathematical techniques may fail. In this paper, the semi-random start procedure is applied. A new kind of evaluation of start nodes of the ants is developed and several starting strategies are prepared and combined. The idea of semi-random start is related to a better management of the ants. This new technique is tested on the Multiple Knapsack Problem (MKP). A Comparison among the strategies applied is presented in terms of quality of the results. A comparison is also carried out between the new evaluation and the existing one. Based on this comparative analysis, the performance of the algorithm is discussed. The study presents the idea that should be beneficial to both practitioners and researchers involved in solving optimization problems.

Plasmaspheric electron density reconstruction based on the topside sounder model profiler

89%

Kutiev I. , Marinov P. , Belehaki A. , Jakowski N. , Reinisch B. , Mayer C. , Marinov P. , Galkin I. , Tsaqouri I.

Acta Geophysica

2010

tom Vol. 58, no. 3

420-431

We apply a model-assisted technique to construct the topside electron density profile based on Digisonde measurements. This technique uses the Topside Sounder Model (TSM), which provides the plasma scale height, O+-H+ transition height, and their ratio Rt = HT/hT, derived from topside sounder data of Alouette and ISIS satellites. The Topside Sounder Model Profiler (TSMP) incorporates TSM and uses the model quantities as anchor points for the construction of topside density profiles. TSMP provides its model ratios with transition height and plasmaspheric scale height. The analysis carried out indicates that Digisonde derived F-region topside scale height Hm is systematically lower than one derived from topside sounder profiles. To construct topside profiles by using Hm, a correction factor of around 3 is needed to multiply the neutral scale height in the ?-Chapman formula. It was found that the plasmaspheric scale height strongly depends on latitude and its ratio with the F-region scale height expresses large day-to-day variability.

Verification of the TSMP-assisted digisonde topside profiling technique

63%

Belehaki A. , Kutiev I. , Reinisch B. , Jakowski N. , Marinov P. , Galkin I. , Mayer C. , Tsaqouri I. , Herekakis T.

Acta Geophysica

2010

tom Vol. 58, no. 3

432-452

The purpose of this paper is to evaluate the performance of the TSMP-assisted Digisonde (TaD) topside profiling technique. We present systematic comparisons between electron density profiles and TEC parameters extracted from TaD model with (a) CHAMP-derived TEC parameters, (b) CHAMP reconstructed profiles, (c) ground based GPSderived TEC parameters, and (d) profiles reconstructed from RPI/ IMAGE plasmagrams. In all cases, TaD follows the general trend of plasmaspheric observations derived from the above datasets. Especially during storm cases, TaD shows remarkable agreement with the variations of the ground based GPS-derived TEC parameters. Overall, the comparison results shows that TaD method can be adopted by EURIPOS to provide the electron density distribution up to plasmaspheric heights in real-time.