Sharif Digital Repository

In this paper the problem of cooperative tracking of multiple targets for multi-agent systems is investigated. Defining problem of target tracking as gathering maximum rewards associated with the targets, an optimization-based algorithm is presented. A cooperative receding horizon controller for reaching moving targets is proposed. Agents are controlled by adjusting their headings toward the moving targets. A notable advantage of the proposed approach is the estimations of target's motion and planning the agent's heading based on them. Simulation results are provided to verify the efficiency of the proposed method  

In this paper, we study the problem of leader selection in the presence of selfish nodes in mobile ad-hoc networks (MANETs). In order to encourage selfish nodes to assume the leadership role, some form of incentive mechanism is required. We present an incentive-based leader selection mechanism in which incentives are incorporated in the form of credit transfer to the leader, which motivates nodes to compete with each other for assuming the leadership role. The competition among nodes is modeled as a series of one-on-one incomplete information, alternating offers bargaining games. Furthermore, we propose an efficient algorithm in order to reduce the communication overhead imposed on the... 

Task-based self-organizing algorithms have been proposed as a solution for the management of mobile ad-hoc networks (MANETs). Such algorithms assign tasks to nodes by sequentially selecting the best nodes as leaders. Since the correct functionality of such algorithms depends on the truthfulness of participant nodes, any misbehavior can disrupt the operation of the network due to absence of a centralized monitoring unit. In this paper, we consider the problem of malicious behavior in leader-based MANETs. Current solution analyzes the behavior of the leader by means of some checker nodes. This approach is vulnerable since a malicious checker can ruin the character of a normal behaving leader,... 

Short term hydrothermal scheduling (STHTS) is a non-linear, multi-modal and very complex constrained optimization problem which has been solved using several conventional and modern metaheuristic optimization algorithms. A number of research articles have been published addressing STHTS using different techniques. This article presents a comprehensive review of research published for solving the STHTS problem in the last four decades. © 2013 IEEE  

Short-term hydrothermal scheduling (STHTS) is a highly non-linear, multi-model, non-convex, and multi-dimensional optimization problem that has been worked upon for about 5 decades. Many research articles have been published in solving different test cases of STHTS problem, while establishing the superiority of one type of optimization algorithm over the type, in finding the near global best solution of these complex problems. This paper presents the implementation of an improved version of a variant of the Particle Swarm Optimization algorithm (PSO), known as Accelerated Particle Swarm Optimization (APSO) on three benchmark test cases of STHTS problems. The adaptive and variable nature of... 

Several semi-analytical models are considered for a double-gyre problem in a turbulent flow regime for which a reference fully numerical eddy-resolving solution is obtained. The semi-analytical models correspond to solving the depth-averaged Navier–Stokes equations using the spectral Galerkin approach. The robustness of the linear and Smagorinsky eddy-viscosity models for turbulent diffusion approximation is investigated. To capture essential properties of the double-gyre configuration, such as the integral kinetic energy, the integral angular momentum, and the jet mean-flow distribution, an improved semi-analytical model is suggested that is inspired by the idea of scale decomposition... 

Single cell gel electrophoresis was used to observe the effect of bifenthrin and chlorpyrifos on Labeo rohita. The present work was planned to study the genotoxic effect of pesticide mixture on the major indian carp, L. rohita at sub-lethal concentration 33% LC50. First of all, 96-hr LC50 was determined for L. rohita, then fish was given sub-lethal environment for 70 days. Erythrocytes from blood were taken after each fortnight for the assessment of time dependent DNA damage (% damage), aggregate tail length of comets and genomic destruction. There was increase in damage up to 56 days and after that a slight decrease was observed in next fourteen days. After statistical analysis, it was... 

Ca-doped Ni–Mg–Mn spinel ferrites with compositions of Ni0·5Mg0·3Mn0.2CaxFe2-xO4 (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5) were prepared via sol-gel auto-ignition technique. TGA/DTA, FTIR, XRD, FESEM, and VSM were employed to evaluate the thermal, spectral, structural, morphological, and magnetic features of Ca-doped Ni–Mg–Mn spinel ferrites. TGA/DTA curves show the weight loss in the sample. This weight loss was attributed to the oxidation and decomposition of the sample contents at a temperature of 500 °C. XRD reveals a single-phase structure of the Ni–Mg–Mn nano ferrites. A single-phase orthorhombic structure was confirmed for Ca-doped Ni–Mg–Mn ferrites. Structural parameters such as lattice... 

Intermittency of height fluctuations in stationary state of the Kardar-Parisi-Zhang (KPZ) equation with infinitesimal surface tension in 1+1 dimensions was discussed. Stochastic differential equations were used for the study. It was found that the probability density function [in 1+1] is independent of the coefficient of the linear term. When the random force with smooth spatial correlation was considered, the problem changed to a more complicated one  

The Kardar-Parisi-Zhang (KPZ) equation with infinitesimal surface tension, dynamically develops sharply connected valley structures within which the height derivative is not continuous. We discuss the intermittency issue in the problem of stationary state forced KPZ equation in [Formula presented] dimensions. It is proved that the moments of height increments [Formula presented] behave as [Formula presented] with [Formula presented] for length scales [Formula presented]. The length scale [Formula presented] is the characteristic length of the forcing term. We have checked the analytical results by direct numerical simulation. © 2004 The American Physical Society  

We report a simple and inexpensive synthesis route of TiO2 nanoparticles using electrical arc discharge between titanium electrodes in oxygen bubbled deionized (DI) water followed by heat treatment. The resulting nanoparticles were characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), dynamic light scattering (DLS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). XRD patterns demonstrate formation of TiO2 phase in oxygen bubbled water after heat treatment and dominance of rutile to anatase phase. The size and morphology of TiO2 nanoparticles were studied using different arc currents as a crucial parameter in properties of final... 

In this study, the Polyaniline/Polyvinyl Alcohol (PANi/PVA) composite was examined for arsenite (As(III)) removal from aqueous solution. The effect of several parameters including PVA concetration (0–5 g/L), pH (1–13), adsorbent dosage (0.5–6 g/L), contact time (0–120 min), initial As(III) concentration (0.5–100 mg/L), and As(III) oxidation were evaluated on the adsorption efficiency. The results indicated that PVA has an effective role in increasing adsorptive capacity of PANi, by changing its morphology and extending its active surface sites. The adsorption process was pH dependent and As(III) removal consistently improved by increasing solution pH. Adsorption reached equilibrium within... 

The unsaturated small strain shear modulus, Gmax, is a key reference value in predicting relationships between dynamic shear modulus and shear strain amplitude and is thus a key quantity to properly model the behavior of dynamically-loaded geotechnical systems such as pavements, rail beds, and machine foundations. From the interpretation of the experimental Gmax results for unsaturated soils, different definitions of trends between Gmax and the stress state of the unsaturated soils and material properties are proposed. However, in most of trends, the relationship between the stress state and void ratio is considered and the effect of void ratio on the unsaturated small strain shear modulus... 

Alterations in the structure of a magnetron, e.g., the A6 relativistic magnetron, are proposed, which considerably increase the device's build-up speed. We cover the magnetron vane surfaces with semiconductor layers of nonzero electric conductivity, with an exact geometrical design. Semiconductor layers with considerable mechanical strength also provide excellent shielding for the vanes against the high-energy relativistic electrons' bombardment. The novel structure introduces several new free parameters to the magnetron design procedure and considerably increases the design flexibility. A multistage exact optimization procedure, performed by extensive computer simulations, shows that... 

Malaysian secondary schools are facing a shortage of male teachers. Almost 70% of the teaching profession is dominated by female teachers. There is an obvious gap in the reason why teaching is not preferred by the male gender. This study intends to find the determinants of career success among male teachers with the hope of revealing the career success factors that are associated with male teachers. A survey was done among 140 male teachers in secondary schools in the state of Malacca, Malaysia. Results showed that 4out of 5 of the determinants factors are significantly explaining career success among the teachers (Emotional Intelligence, Person-Job-Fit, Career Adaptability & Work-Life... 

In this study, a series of highly swelling hydrogels based on sodium alginate (NaAlg) and polymethacrylamide (PMAM) was prepared through free radical polymerization. The graft copolymerization reaction was performed in a homogeneous medium and in the presence of ammonium persulfate (APS) as an initiator andN,N′-methylenebisacrylamide (MBA) as a crosslinker. The crosslinked graft copolymer, alginate-graft-polymethacrylamide (Alg-g-PMAM), was then partially hydrolyzed by NaOH solution to yield a hydrogel, hydrolyzed alginate-graft-polymethacrylamide (H-Alg-g-PMAM). During alkaline hydrolysis, the carboxamide groups of Alg-g-PMAM were converted into hydrophilic carboxylate anions. Either the... 

Engineered water (EW) flooding is one of the enhanced oil recovery (EOR) techniques in carbonate reservoirs. In this method, the wettability of reservoir rock is altered by controlling the amount of various ions in the injected brine. The thermodynamics of wettability is related to the surface interactions and stability of water film on a rock surface. It can be identified by calculating disjoining pressure isotherms. In this study, core flooding tests, contact angle and zeta potential measurements along with the disjoining pressure isotherm calculation by the DLVO theory were used to investigate the wettability alteration of dolomite rock. Four brines include reservoir formation water...