Sharif Digital Repository

Target recognition is one of the widespread applications of today's radars that requires obtaining target signatures using radar measurements. High-resolution range profile (HRRP) is one of these signatures that provides a one-dimensional radar image of the target. There are several methods for radar target's HRRP synthesis , all of which require a large bandwidth. One of these methods is the use of stepped frequency radar. One of the advantages of this method is providing a wide bandwidth by sending pulses with small bandwidths, thus obviating the need for broadband receivers and transmitters and making implementation easier. In many cases HRRP of target is sparse, because the number of... 

This study presents a facile sol-gel template-assisted route to prepare CNT-TiO2 hybrid structures (CTH) for dye-sensitized solar cell (DSSC) applications. Non-covalent functionalized multi-walled carbon nanotubes (CNTs) with average diameter of 80 nm are used as the template for TiO2 deposition. The X-ray diffraction reveals that the hybrid structures are composed of primary anatase TiO2 nanoparticles with the average crystallite size of 12 nm, after heat treatment at 450°C in air atmosphere. TEM and FESEM images show that the shell thickness of the coated TiO2 on CNTs’ outmost walls varies between 60 to 120 nm, when the ratio of CNTs:TiO2 is 10wt. %. Photovoltaic measurements demonstrate... 

This study investigates consumers’ response to changing the household electricity meter from single stroke case to three stroke case. Existence of different prices in different hours during the day is the advantage of three stroke electricity meters compared to single stroke ones. Electricity bill data of 19,742 subscribers, in Tehran Interior Region 2, during the period 1387 to 1393, has been used to evaluate this policy. Subscribers who always use only single stroke electricity meters or three stroke ones are considered as the control group; and subscribers who have experienced electricity meter change during the period are considered as the experimental group. Changing electricity meters... 

Identifying fractional systems and designing controllers for these systems is one of the leading challenges due to their limitations. Systems can have constraints on output, input, and states. These constraints make it difficult to design a controller. In this project, controller design methods for fractional-order systems with output constraints are investigated. A controller is designed for a strict feedback nonlinear system with unknown dynamics subject to asymmetric and variable output constraints, unknown direction of the controller, and unmeasurable states. To design the controller, the direct and backstepping technique is used and the Lyapunov barrier function is applied for the first... 

In the study of heat transfer in micro-channels, free and force convections are two limit cases and these two methods of heat transfer are combined together generally, so to achieve the most accurate informations about the flow field they should be considered in combination. In the first part of the thesis the fully developed slip flow mixed convection in vertical micro-ducts of arbitrary shapes is investigated.Uniform axial heat flux and uniform peripheral wall temperature (H1) is considered. The method considered is analytical-numerical in which the governing equations and three of the boundary conditions are exactly satisfied but the remaining slip boundary condition on the duct wall... 

Engineering, Procurement and Construction (EPC) contracts commonly used in the construction of oil and gas production facilities in Iran. These projects are subjected to many uncertainties. Because in these projects contractor is responsible for most of the activities related to the Engineering, Construction and Procurement, EPC contractors often assume most of project risks. Therefore, project risk management is very essential for achieving project goals. Several studies have focused on the identification and analysis of EPC project risks. However, they fail to identify appropriate risk management strategies. The objective of this study is to identify fair and efficient risk allocation and... 

Lean premixed flames bring both benefits and challenges to combustion systems. While they have low emission levels and high efficiencies, they are also very susceptible to combustion instabilities. Low swirl burners have been shown to be very capable in stabilizing lean premixed flames.
In this thesis, behavior of low swirl flames under conditions of variable equivalence ratio (0.6 – 0.8), mean flow velocity (3.5 – 5.5 m/s), and excitation frequency is investigated. In static stability diagram of the flame, a region is observed in which stability mode of the flame is dependent on the path that takes the flame to its operating point (hysteresis region). Increasing the recess distance of... 

Because of deregulation and economic issues, power systems operate closer to their stability limits than before. So, security assessment of power system has gained a lot of attention in power system studies. Transient stability and its real time assessment is a great concern in power system security. Among all different methods for transient stability assessment, Automatic Learning methods are used the most in real time assessment problems. These methods can provide fast assessment of transient stability, sensitivity analysis and means of control of the transient stability phenomena. In this paper Adaboost algorithm is used as a brand new method in transient stability assessment of a medium... 

The use of unbonded post-tensioned precast concrete walls with horizontal joints as the primary lateral load resisting system in seismic zones has been considered in several previous studies. These walls are constructed by post-tensioning precast wall panels across horizontal joints using post-tensioning steel which is not bonded to the concrete. The behavior of the unbounded post-tensioned precast structural wall under lateral loads strongly depends on base panel geometry and concrete confinement properties. In this research an analytical parametric investigation on base panel design parameters is conducted using DRAIN-2DX software. Fiber beam-column elements are used to represent the... 

Despite major environmental and economic benefits of cold recycled asphalt mixtures, many agencies have not yet made widespread use of this technology due to its so-called poor field performance and lack of accurate information on mechanical properties of cold recycled mixtures. Fiber is one the additives that is sometimes used to enhance asphalt mixture properties. Using fibers to improve the performance of cold recycled asphalt mixture has been studied by a few researchers with somehow contradictory results. In this research, the effects of adding four synthetic fibers (Polypropylene, A-glass, Para-Aramid, and Polyester) and two waste fibers (Waste Polyester and Waste Nylon) with different... 

In this project, different types of optical frequency selector devices are compared with each other and the factors limiting their behavior (losses, throughput, quality factor, etc.) are precisely analyzed. Change this behavior in near-field and far-field scales as well as the behavior of these devices in nano-dimensions are analyzed. Also, the main theoretical and technological limitations of different types of optical filters in far-field and near-field regimes are compared. In the following, the scaling behavior of different filter families in passing to nanometric dimensions is investigated and finally the limitations of the possibility of making the selected sample are analyzed. For... 

Domain shift is an inevitable issue when histopathological images are analyzed in a standard laboratory. This is due to the variations in tissue handling, manual procedures for sample preparation, and differences in scanners. This can result in reduced performance of machine learning algorithms trained on images from one laboratory when applied to another. In this framework, the goal of utilizing domain generalization techniques in machine learning is to develop models that perform well in different domains. This research examines various methods of dealing with the domain shift challenges within the context of detecting mitotic cells, and proposes algorithms to improve domain generalization... 

In recent years, advances have been made in the field of miniaturization of the devices (in order to increase their efficiency, lessen the materials needed for the constructions and experiments, reduce costs and energy usage) resulting in the dramatic increase of surface to volume ratio in these devices. This progress has led to the dominance of surface forces which can be used to control very important interface phenomena having a special application such as electrokinetic. Using today’s manufacturing technology; it is possible to construct micro-nanochannels made from different materials such as silicon, glass, quartz, polydimethylsiloxane (PDMS), polymethyl methacrylate (PMMA) whose... 

In this project, the goal is to form gold nanoparticles on glass surface using Sol-Gel method, to create the appropriate physical and optical properties. To reach this purpose, the main point is to form the stable gel as a network of nanoparticles on glass surface. After coating, physical properties, surface properties and morphology were investigated. To investigate the absorption rate, the optical spectrum reflex had been appeared through 500-550 nm using UV-Visible test. Also, to observe morphology, particle size and distribution on the surface, the thin films have been tested via FESEM. Using a polymer template for gold nanoparticles, the structure of nanoparticles optimized... 

This paper studies a multi-product, multi-period, multi-allocation hub location problem based on real case in domestic automotive industry. As 3PL companies spread, using dynamic hubs in a contractual manner becomes passible; So in this paper the hub set is the combination of both static and dynamic hubs. The nodes are suppliers, sites and dealers of a supply chain that have certain demand of each product in each period. In this problem backlogging is allowable and causes penalty. Different transportation modes like road and railroad are usable just in hub network. Direct transmission is possible and candidate hubs are capacitated with multi suggested capacities. A mixed integer programming... 

Superconducting SQUID sensors are one of the most sensitive magnetic sensors that have been ever produced. Due to their high sensitivity, these sensors have many applications in different fields. Magnetic Imaging and far away targets detections are of these applications. In this project, a magnetic imaging system based on Superconducting SQUID sensors have been designed and implemented. In SQUID applications one of the most important problems is the cancelation of the unwanted fields including background low frequency and high frequency fields. In residential and urban areas the interference of Electricity network is considered as one of the major noise sources. While the high frequency...