Sharif Digital Repository

Circular polarization (CP) is one of the common polarization types used in wireless systems for frequency identification (RFID), global positioning (GPS) and wireless local area networks (WLAN), since it can provide greater flexibility in orientation angle between transmitter and receiver, and better mobility and weather penetration than the linearly polarized antennas. Magnetic permeability in ferrites can be tuned by external magnetic field ; So ferrites can be good candidates for new reconfigurable CP antenna technology. In this project, we will consider circularly polarized slot antenna with a wide axial ratio beamwidth that consists of a normally magnetized ferrite substrate mounted... 

In this thesis, light transmission in dielectric slit arrays on metallic and magneto-optical material has been analyzed by mode matching method together with numerical simulations on commercial softwares such as Comsol Multiphysics and CST microwave studio. It has been shown that light transmission can be attributed to either the Fabry-Perot resonances or a collective resonance phenomenon across the array. In the first case, the transmission resonance is related to the slit depth and is confined to a single slit. In the second case; however, the resonant mechanism affects several neighboring slits. Surprisingly the former is converted to the latter by increasing the slit depth. Furthermore... 

Subwavelength localization of electromagnetic energy with intense local fields, also known as electromagnetic hotspots, has received significant attention over the past few decades. In most cases the hotspot is achieved through the resonant concentration of electromagnetic fields. One way recently considered to get hotspot is through reflection of electromagnetic waves in nonreciprocal one-way structures, in plasmonics and via magneto optic effect.However these hotspots are less confined compared to hotspots caused by resonances. So combining nonreciprocal structures with resonance can provide better hotspots.Our aim in this thesis is to study nonreciprocal resonant structures using coupled... 

This thesis formulates Green's function of periodic arrays of two-dimensional rectangular holes Perforated on a PEC film. Green's function of two-dimensional periodic free space in the spectrum domain is computed. Using Floquet theory and considering the holes as rectangular waveguides, Green's function of the structure is presented.For sub-wavelength holes in cut-off and propagating cases, numerical results are presented. The effects of changing the aperture's thickness and the number of required modes have been reported. The structure under a normal and oblique incident wave is investigated, and the high conformity of the presented model results and full-wave simulations is observed.In... 

Due to its extensive applications in imaging, data security, medication, etc., Terahertz has attaracted an ever-inceasing attention. Design and implementation of Terahertz sources and circuits as waveguide, filters, etc. in this band have attracted attention. The unique elec-tric characteristics of graphene, like showing plasmonic characteristics in Terahertz frequency band, made this recently recognized matter a promising one to build super-integrated plas-monic circuits in Terahertz band. In this text, the first section represents an introduction for a number of graphene waveguides as well as studying the effective refractive index method to analyze graphene waveguides. Due to the small... 

Nitrogen compounds are becoming increasingly important in wastewater management, because of the many effects that nitrogenous material can have on the environment that need nitrogen removal. In this study, the performance of a submerged fixed bed reactor in nitrogen removal, constructed two anoxic and aerobic sections under Modified Ludzack-Ettinger process was investigated. Laboratory experiments were conducted at a constant COD concentration of 350 mg/lit, hydraulic retention times of 8, 12 and 18 hours and influent ammonia loading rate between 0.128 and 0.955 g NH3/m2.day. Nitrogen removal efficiency was obtained between 80.4 and 97.3%, and COD removal efficiency was achieved between 88.9... 

Distribution power systems are undergoing a fundamental transition with the introduction of microgrids (MGs) and proliferation of renewable energy sources inspired mainly by privacy and environmental concerns. In this regard, energy management methods employed by utilities should take into account the intermittent nature of RESs power production while coping with the independent operation of MGs. Transactive energy (TE) is an emerging concept which utilizes economic-based mechanisms to facilitate the dynamic and decentralized management of active agents of the system. However, the energy transactions between transactive agents could have adverse impacts on the technical aspect of the system... 

Let C(S) and C(T) denote the sup-normed Banach spaces of real or complex-valued continuous functions on the compact Hausdorff spaces S and T, respectively. A linear map H:C(T)→C(S) is called separating if, for x,y∈C(T), xy≡0 implies HxHy≡0. In the second chapter of this thesis, we will show that any continuous separating map is a continuous multiple of a composition map. Moreover, it will be proved that any linear separating isomorphism of C(T) onto C(S) is continuous. We will also define separating and biseparating maps on the rings of continuous functions equipped with the compact-open topology. In addition, vector-valued separating maps will be investigated. For example, assume that C(T)... 

In this dissertation, transportation networks with two classes of vehicles, including conventional vehicles and autonomous vehicles, have been studied. Four problems, including traffic assignment problem with two classes, congestion pricing problem for conventional vehicles, network design problem for autonomous vehicles, and simultaneous congestion pricing and network design problem, have been modeled and algorithms to solve them are presented. In this study, a dynamic penalty function algorithm is used to solve the congestion pricing problem, and a heuristic algorithm is used to solve the network design problem. Besides, the two-class traffic assignment problem is solved using the... 

Three-dimensional (3D) computational fluid dynamics (CFD) was used in this study to investigate single and multi phase flow behavior related to three stages of ESP pump. Compared to experimental measurements, the numerical prediction for single phase flow of water is matched very well. Furthermore, the effects of viscosity and pump rotational speed for oil were investigated and the results show that by increasing oil viscosity and decreasing rotational speed, the pump head and efficiency reduced. ESP performance under two phase oil-methane flow and the effect of oil viscosity, rotational speed, intake pressure, gas bubble diameter, oil rate and gas volume fraction were studied. ESP boosting... 

Nowadays anaerobic treatment of wastewater has been gaining more and more popularity. This process is usually used for waste sludge and wastewater with high concentrations of organic pollutants. One bioreactor that uses the anaerobic process to treat wastewater is the Anaerobic Baffled Reactor (ABR). This reactor was studied in the present study. The Anaerobic Baffled Reactor is composed of a series of up flow anaerobic sludge reactors. A simple design, low process cost, low sludge production and the lack of a need for a separator of the gas and sludge are some of the important characteristics of this reactor. Furthermore, ABRs are resistant against temperature and pH and can separate... 

CMOS technology has reached two digit nanometer dimensions. This scaling trend improves performance and power consumption on the one hand, and reduces noise margin and circuits reliability on the other. Along with downscaling, sensitivity to radiation induced soft errors is increasing. As CMOS dimensions are shrinking, node capacitance of circuits become smaller. Consequently, particles with smaller charge could induce parasitic voltages in some nodes and result in soft errors. There are more particles with smaller charge than the ones with larger. Therefore, soft error rate is rapidly increasing with technology advances. Single Event Multiple Effects (SEMEs) is a new challenge emerged in... 

In elliptic curves equation, if the number of solution is infinite, complication of calculation increase quickly. Even the simplest solutioncan be large. y2 + y = x35115523309x − 140826120488927 The x-coordinate number of smallest solution has 5454 digits. The theorem of Mordell and Weil states that “The set E(Q) of rational solutions has the structure of an infinitely generated abelian group.” E(Q) = (Z)rankE(Q) ⊕T Can the rank be arbitrary large? The current record is rank(E)=28.Manjul Behargava has recently made progress on the study of the average rank for all elliptic curves with rational coefficient. Every such curve has a unique equation of the form y2 = x3 +Ax+B, where A and B are...