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Swarm intelligence algorithm based on competitive predators with dynamic virtual teams

100%

Yang S. , Sato Y.

tom Vol. 7, No. 2

87--101

In our previous work, Fitness Predator Optimizer (FPO) is proposed to avoid premature convergence for multimodal problems. In FPO, all of the particles are seen as predators. Only the competitive, powerful predator that are selected as an elite could achieve the limited opportunity to update. The elite generation with roulette wheel selection could increase individual independence and reduce rapid social collaboration. Experimental results show that FPO is able to provide excellent performance of global exploration and local minima avoidance simultaneously. However, to the higher dimensionality of multimodal problem, the slow convergence speed becomes the bottleneck of FPO. A dynamic team model is utilized in FPO, named DFPO to accelerate the early convergence rate. In this paper, DFPO is more precisely described and its variant, DFPO-r is proposed to improve the performance of DFPO. A method of team size selection is proposed in DFPO-r to increase population diversity. The population diversity is one of the most important factors that determines the performance of the optimization algorithm. A higher degree of population diversity is able to help DFPO-r alleviate a premature convergence. The strategy of selection is to choose team size according to the higher degree of population diversity. Ten well-known multimodal benchmark functions are used to evaluate the solution capability of DFPO and DFPO-r. Six benchmark functions are extensively set to 100 dimensions to investigate the performance of DFPO and DFPO-r compared with LBest PSO, Dolphin Partner Optimization and FPO. Experimental results show that both DFPO and DFPO-r could demonstrate the desirable performance. Furthermore, DFPO-r shows better robustness performance compared with DFPO in experimental study.

Optimization of injection pressure for fuel consumption and exhaust emissions in a dimethyl ether (DME) engine with a common rail type injection system

70%

Yanai T. , Konno M. , Sato Y. , Oikawa H. , Nozaki S.

tom Vol. 17, No. 2

511-518

Morphological, developmental, and ecological characteristics of the suctorian ciliate Ephelota gigantea (Ciliophora, Phyllopharyngea, Ephelotidae) found on cultured wakame seaweed in Northeastern Japan

51%

Sato Y. , Muto T. , Endo Y. , Kobayashi T. , Nakano N. , Sato H. , Nishitani G. , Sato-Okoshi W.

nr 4

Selection of rub trees by brown bears (Ursus arctos) in Hokkaido, Japan

51%

Sato Y. , Kamiishi C. , Tokaji T. , Mori M. , Koizumi S. , Kobayashi K. , Itoh T. , Sonohara W. , Takada M. B. , Urata T.

tom 59

nr 1

Tree rubbing by brown bears (Ursus arctos) is a well-known behavior throughout the animal’s distribution. There is still insufficient information on the characteristics and function of the behavior. We investigated seasonal frequency of tree rubbing by brown bears, characteristics and reasons for selection of rub trees, and characteristics of bear signs on and around rub trees in a mixed coniferous–broad-leaved deciduous forest in Hokkaido, Japan. Between 1998 and 2009, we found 172 rub trees and confirmed 995 tree rubbings. We found that the rub trees were used repeatedly by bears within a year and for multiple years (more than 10 years). Tree rubbing by brown bears was observed from April to November, with a peak between May and June that corresponds to the mating season of brown bears. Abies sachalinensis was selected and broad-leaved trees were avoided for tree rubbing based on estimated availability in natural forest. The preference for Abies sachalinensis might be because the strong odor of resin attracts bears for rubbing their head and neck in resinous substances and for increasing the detectability of their markings by receptor bears. Selected trees for rubbing were located right beside the trail on relatively level ground among trees along roads or trails. Trees had a relatively large diameter at breast height. These characteristics would also serve to increase the access and detectability of their markings. Series of pad-shaped depressions was the most frequently observed (70 %) indication of bear rubbing, followed by debarking (51 %) and clawing (30 %). In terms of visual and olfactory signal amplification, physical damage by bears to the trees might have a function to enhance the smell as a result of increase in outflow of the resin. We conclude that tree rubbing behavior is associated with the mating season of brown bears and that the main purpose of this behavior is scent marking to communicate intraspecifically during the mating season.