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We address the problem of repeated coverage of a target area, of any polygonal shape, by a team of robots having a limited visual range. Three distributed Clusterbased algorithms, and a method called Cyclic Coverage are introduced for the problem. The goal is to evaluate the performance of the repeated coverage algorithms under the effects of the variables: Environment Representation, and the Robots' Visual Range. A comprehensive set of performance metrics are considered, including the distance the robots travel, the frequency of visiting points in the target area, and the degree of balance in workload distribution among the robots. The Cyclic Coverage approach, used as a benchmark to compare the algorithms, produces optimal or near-optimal solutions for the single robot case under some criteria. The results can be used as a framework for choosing an appropriate combination of repeated coverage algorithm, environment representation, and the robots' visual range based on the particular scenario and the metric to be optimized.

Data Envelopment Analysis is used to determine the relative efficiency of Decision Making Units as the ratio of weighted sum of outputs by weighted sum of inputs. To accomplish the purpose, a DEA model calculates the weights of inputs and outputs of each DMU individually so that the highest efficiency can be estimated. Thus, the present study suggests an innovative method using a common set of weights leading to solving a linear programming problem. The method determines the efficiency score of all DMUs and rank them too.

Bismuth selenide, Bi 2 Se 3 , nanoparticles were synthesized by a new precursor complex, [bis(salicylate)bismuth(II)]; [Bi 2 (Hsal) 3 ], via a sonochemical method in an aqueous solution. The average diameter of the Bi 2 Se 3 nanoparticles was 25 nm. The efficiency of the Bi 2 Se 3 nanoparticles as a photocatalyst for the decolorization of rhodamine-B and methylene blue using ultraviolet light irradiation has been evaluated. Furthermore, a preliminary study on the possibility of developing a solar cell having the FTO/TiO 2 /Bi 2 Se 3 /Pt-FTO structure was also investigated to produce an inexpensive solar cell by Bi 2 Se 3 nanoparticles. Products were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, photoluminescence, and EDX analysis.

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