This paper deals with multi-period project portfolio selection problem. In this problem, the available budget is invested onthe best portfolio of projects in each period such that the net profit is maximized. We also consider more realisticassumptions to cover wider range of applications than those reported in previous studies. A novel mathematical model ispresented to solve the problem, considering risks, stochastic incomes, and possibility of investing extra budget in each timeperiod. Due to the complexity of the problem, an effective meta-heuristic method hybridized with a local search procedureis presented to solve the problem. The algorithm is based on genetic algorithm (GA), which is a prominent method to solvethis type of problems. The GA is enhanced by a new solution representation and well selected operators. It also ishybridized with a local search mechanism to gain better solution in shorter time. The performance of the proposedalgorithm is then compared with well-known algorithms, like basic genetic algorithm (GA), particle swarm optimization(PSO), and electromagnetism-like algorithm (EM-like) by means of some prominent indicators. The computation resultsshow the superiority of the proposed algorithm in terms of accuracy, robustness and computation time. At last, theproposed algorithm is wisely combined with PSO to improve the computing time considerably.

The concept of super line graph was introduced in the year 1995 by Bagga, Beineke and Varma. Given a graph with at least r edges, the super line graph of index r, Lr(G), has as its vertices the sets of r-edges of G, with two adjacent if there is an edge in one set adjacent to an edge in the other set. The line completion number lc(G) of a graph G is the least positive integer r for which Lr(G) is a complete graph. In this paper, we  nd the line completion number of grid graph Pn  Pm for various cases of n and m.

In this paper some properties of a generalization of Fibonacci sequence are investigated. Then we solve the Diophantine equations x2±kxy-y2±x=0, where k is a positive integer, and describe the structure of solutions.

Many studies have been conducted in the last decades on cellular polypropylene (Cell-PP) films. Most of them focus on theoptimisation of the material for sensor applications. Processed under Gas Diffusion Expansion (GDE), Cell-PP films showhigh piezoelectric activity and low stiffness/density, properties that make them ideal for sensors. GDE increases the heightand decreases the length over height ratio (aspect ratio) of individual voids within the material. This change in voidmorphology, and eventually stiffness, results in a nonlinear piezoelectric response of these materials. In this study, a Cell-PP sample was tested under static, quasi-static and low-frequency compressive stress. The main aim is to evaluate itsmechanical and piezoelectric properties in the nonlinear region of its response over strain. The load– deflection curves aswell as the piezoelectric responses were obtained for stresses up to 270 kPa (engineering strain close to 0. 26). It is shownthat both the magnitude of the initial load and the strain rate have a critical effect on the creep/stress relaxation of the filmand eventually on its piezoelectric response. Finally, it is shown that under dynamic conditions, and for the sameengineering strain region, it is more relevant to present the piezoelectric response, in terms of strain rather than stress.

Facility location problem (FLP) is a mathematicalway to optimally locate facilities within a set of candidatesto satisfy the requirements of a given set of clients. This study addressed the uncapacitated FLP as it assuresthat the capacity of every selected facility is finite. Thus, even if the demand is not known, which often is the case, inreality, organizations may still be able to take strategicdecisions such as locating the facilities. There are differentapproaches relevant to the uncapacitated FLP. Here, thecuckoo search via Le´ vy flight (CS-LF) was used to solvethe problem. Though hybrid methods produce betterresults, this study employed CS-LF to determine first itspotential in finding solutions for the problem, particularlywhen applied to a real-world problem. The method wasapplied to the data set obtained from a department store inDavao City, Philippines. Results showed that applying CSLFyielded better facility locations compared to particleswarm optimization and other existing algorithms. Although these results showed that CS-LF is a promisingmethod to solve this particular problem, further studies onother FLP are recommended to establish a strong foundationof the capability of CS-LF in solving FLP.

In the present study, the effect of size distribution of magnetite nanoparticles in a PVDF matrix on the magnetic propertiesof PVDF? Fe3O4 nanocomposites was experimentally and theoretically investigated. The size distribution of nanoparticlesin polymer matrix and morphology of the nanocomposites were studied by the means of scanning electron microscopyand atomic force microscopy. It was found that when the Fe3O4 nanoparticles are introduced into the polymermatrix, their coagulation takes place. The increase in the size of the particles depends on their concentration in the polymermatrix, the type of polymer (polar, non-polar, its viscosity, etc. ), reaction temperatures, etc. In addition, when Fe3O4nanoparticles are introduced into the polymer network, the oxidation of the surface layer of particles occurs and themagnetic size decreases. Consequently, the reduced magnetic properties may also be observed. The hysteresis loops havebeen recorded in small magnetic field range. It was found that the magnetic hysteresis parameters depend on the size andconcentration of Fe3O4 nanoparticles. Theoretical calculations were compared with experimental results obtained fromM(H) measurements. The reasons of differences between theoretical and experimental results have been explained.

A cooperativity is observed between CH/p and hydrogen bond interactions in HF···Py^X1benX2 complexes. The cooperativity is more influenced by the inductive effects in comparison with the resonance effects. Increase in the electron withdrawing nature of substituents is accompanied by decrease in the cooperativity energy (Ecoop). The vital effect of the reactivity centre on the Ecoop is determined through the good relationship between spara+ (the substituted constant estimated for the para placed reactivity center) and Ecoop values.

Silver (Ag) nanolayers were deposited on nickel oxide (NiO) thin films by DC magnetron sputtering. The thickness of Aglayers was in range of 20– 80 nm by variation of deposition time between 10 and 40 s. X-ray diffraction results showed thatthe crystalline properties of the Ag/NiO films improved by increasing the Ag film thickness. Also, atomic force microscopyand field emission scanning electron microscopy images demonstrated that the surface morphology of the films was highlyaffected by film thickness. The film thickness and the size of particles change by elevating the Ag deposition times. Thecomposition of films was determined by Rutherford back scattering spectroscopy. The transmission of light was graduallyreduced by augmentation of Ag films thickness. Furthermore; the optical band gap of the films was also calculated from thetransmittance spectra.