Sharif Digital Repository

Recently, due to the restructuring of power systems and the high penetration level of local renewables, distribution systems have encountered with the complexity of power management. Therefore, the modern systems would be operated in a multi-agent structure which facilitates the power management as well as privacy protections of independent entities. In this structure, the distribution system is assumed to compose of several agents who independently schedule their local resources in order to maximize their own profits. Consequently, this paper provides an efficient peer-to-peer (P2P) active power management framework in a multi-agent distribution system while considering network constraints... 

In recent years, distributed structures have been developed in distribution networks as a result of privatization as well as integration of independently operated distributed energy resources (DERs) into the grid. In this context, effective management techniques seem to be necessary to enable decentralized operation of systems that have been consisted of multiple agents. Accordingly, novel management schemes should be applied in such systems to enable the distributed reactive power management, which would finally improve voltage profile in the network. As a result, this paper develops a distributed algorithm for reactive power management in multi-agent distribution systems with the aim of... 

The KASUMI block cipher is used for the cellular communications networks and safety of many wireless standards. Third generation cellular network technology (3G) permits to transmit information, voice and video at very high data rates never seen before that will revolutionize personal communications and information exchange. On the other hand, Residue Number System (RNS) is a modular representation and is evidenced to be serviceable equipment in many applications which need high-speed computations and high-performance components. RNS is a non-weighted and integer number system that can support secure, highspeed, low-power, parallel and carry-free arithmetic. For attaining the most... 

Third generation cellular network technology (3G) can revolutionize communications and data exchanges between many people in a more overwhelming fashion than 2G and 2.5G networks did. The 3G UMTS, the 3G GSM and the 3G GPRS rely on the KASUMI block cipher. Therefore, increasing speed, decreasing power consumption and error detection/correction are the major concerns of the KASUMI algorithm and its generation. On the other hand, Residue Number System is a non-weighted number system and it is currently considered as an important method for high-speed, low-power, parallel and carry-free arithmetic realizations. Redundant Residue Number System is an extension of RNS that also supports error... 

In this paper, we examine fluid flow and associated dispersion around a circular cylinder under progressive surface wave motion. The flow field and vortex shedding patterns were studied using flow visualization and Particle Image Velocimetry (PIV). Several patterns of vortex shedding were identified around a single cylinder. The vortex shedding patterns under progressive wave motion are similar to those observed in planar oscillatory flow, except in the way the vortices form and in the orientation they take. The observed vortex patterns in progressive wave motion are more unstable than those in planar oscillatory flow. Using particle tracking and the Lagrangian dispersion method, the... 

In this paper a saturable absorber medium is employed as an optical limiter to reduce the spot size to the range of several tens of nanometres. The characteristics of a Gaussian beam are theoretically analysed upon propagation through the saturable absorber medium. Based on Maxwell equations a system of coupled nonlinear ordinary differential equations for intensity, beam radius and beam curvature is obtained. Theoretical analyses and numerical results show that the behaviour of a Gaussian beam in a saturable absorber medium strongly depends on the initial characteristics of the laser beam. Numerical results indicate that, depending on the initial conditions and a suitable saturable absorber... 

In this paper, the transient response of a double coupler fiber ring resonator containing an erbium-doped fiber amplifier (EDFA) in half part of the fiber ring resonator and a quantum dot-doped fiber (QDF) saturable absorber in the other half, is investigated. It is demonstrated that, depending on the device parameters and the input power of the signal and pump, various types of dynamic behaviors (such as bistability, monostability, and regenerative pulsation) can be observed in this intrinsic, optical bistable device. The proposed device can be exploited by optical communication networks to realize all-optical functionalities  

We show that, in a nonlinear centrally coupled circular array of evanescently coupled fibers, the coupling dynamics of a weak signal beam can be efficiently influenced by a high-power control beam that induces nonlinear defects. When the intense control beam is launched into the central core and one core in the periphery, then localized solitons are formed and cause the fibers with induced defects (defected fibers) to decouple from the other array elements. In the presence of a high-intensity control beam, the propagation of weak signal is restricted to the defected optical fibers. The weak signal periodically couples between the induced defects. This oscillatory behavior depends on the sign... 

The non-paraxial and vectorial effects have an important role in the dynamics of highly confined beam in nonlinear medium. In this paper, we study the vectorial non-paraxial propagation of Gaussian field in the saturable absorber media numerically with the aim of nano-lithography. It is shown that in the optimal regimes for nanolithography, the mutual coupling between components of optical field and mode coupling between different orders of Hermite-Gaussian mode lead to generation of various patterns upon propagation through saturable absorber media. The vectorial effect is responsible for the symmetry breaking. For converging input beam, while the intense part of the beam goes toward the... 

The laser interferometric gravitational-wave detectors are sensitive to the quantum state of light employed in the dark port of interferometric system. In this paper a general quantum state for the dark input port is assumed. The quantum state of light is expanded versus the Fock states. The quantum noise of interferometric system is computed as a function of the quantum state of light. The variational method and the genetic algorithm are employed to determine the coefficients of the dark input port and the laser input power for the minimization of the quantum noise. Calculation shows that the optimum quantum state for the dark input port is very close to the vacuum squeezed state. For this... 

This paper addresses the problem of recovering sparse link vectors with network topological constraints that is motivated by network inference and tomography applications. We propose a novel framework called UCS-NT in the context of compressive sensing for sparse recovery in networks. In order to efficiently recover sparse specification of link vectors, we construct a feasible measurement matrix using this framework through connected paths. It is theoretically shown that, only O(k log(n)) path measurements are sufficient for uniquely recovering any k-sparse link vector. Moreover, extensive simulations demonstrate that this framework would converge to an accurate solution for a wide class of... 

In analysing the structural organization of a social network, identifying important nodes has been a fundamental problem. The concept of network centrality deals with the assessment of the relative importance of a particular node within the network. Most of the traditional network centrality definitions have a high computational cost and require full knowledge of network topological structure. On the one hand, in many applications we are only interested in detecting the top-k central nodes of the network with the largest values considering a specific centrality metric. On the other hand, it is not feasible to efficiently identify central nodes in a large real-world social network via... 

In transition from concept design to detail design, designers and engineers need to find specific materials to optimize performance of the systems. The large number of materials and the wide range of manufacturing processes cause engineers always to seek new materials selection methods. In this research work a new method so called QFD method, which employs materials indices, is introduced. The method enjoys a combination of Ashby's materials selection concepts with the Quality Function Deployment (QFD) tool. The QFD method, which is modified here to fit the materials selection field, provides the designer with the required weighting factors for the material indices. Incorporation of House of... 

In this research, the effect of surface characteristics on boiling heat transfer has been investigated experimentally. For this purpose, a device with the ability to automatically record the liquid temperature of the inlet and outlet of the test area, calculate the coefficient of boiling heat transfer, and heat flux has been developed. The automatic temperature stability of the working fluid and the ability to investigate the effect of surfaces with different characteristics (in terms of material and surface structure) on the boiling heat transfer parameters are the most important features of this device. The performance of the experimental setup was evaluated by the modified "Chen" equation...