Sharif Digital Repository

let T4 = C2/ be a complex torus with induced flat Kähler metic. The quotient X = T4/Z2 (where the generator of Z2 acts by multiplication by −1) is an orbifold with 24 singularities, called a singular Kummer Surface. Locally any of the singularities are modelled on the singularity of C2/Z2. We can describe the minimal resolution X of X by resolving all of the singularities as : TCP1 ! C2/Z2.There is a well known Calabi–Yau metric on TCP1 named the Eguchi–Hanson metric, with the important property that far from the exceptional divisor −1(0) the metric is asymptotically locally Euclidean (ALE). We identify a small annulus around any singular point of X/Z2 with a large annulus over TCP1 far... 

During the last few years, utilization of distributed generation (DG) in power systems has been widely increased. This trend has magnified studying the effects and impacts of DG on such systems. One of the benefits of DGs in a power system is loss reduction. If determining DG size and place is done properly, the loss of the network can be minimized. Another way of reducing loss in distribution network is by reconfiguring the network. During the reconfiguration, constraints like being radial, avoiding load isolation as well as voltage/current limitations must be taken into consideration. Taking these constraints into account makes reconfiguration an optimization problem. In this project, the... 

Particulate ceramic reinforced aluminum matrix composites have high specific strength and stiffness; however, low fracture toughness and deformability have restricted their industrial applications. Among the methods introduced to overcome this shortcoming is fabricating the layered composites which contain alternative layers of aluminum (Al) and discontinuously reinforced aluminum (DRA). In this study, two different routes; i.e., "Powder extrusion - Casting - Rolling" and "Powder extrusion - Roll bonding" were employed to produce layered Al-DRA composites. After production of Al6061/SiCp composites via hot powder extrusion, mentioned processes were utilized to make DRA-Al-DRA laminate. In... 

low-molecular-weigth aminothiols such as cysteine (Cys), homocysteine (Hcy) and glutathione (GSH) play a critical role in many biochemical pathways . Their level in biological fluids such as human plasma and urine are important for clinical diagnostics of a variety of diseases.
We report herein the development of a highly sensitive colorimetric method for detection of cysteine and glutathione using the citrate capped gold nanoparticles (Au-NPs). This thiol containing molecules exhibit intriguing reactivities with Au nanoparticles. The reactivity involves the displacement of the citrate shell by the thiolate shell which is followed by intermolecular electrostatic interactions or... 

Today, base lead piezoelectrics are the center of attention due to their very good electrical properties, and low cost of production. Among these ceramics are PZT which is a combination of Pb(ZrxTi1-x)O3 and PCN which is a combination of Pb(CoxNb1-x)O3. PZT is a normal piezoelectric whose dielectric properties would be improved if relaxor is added. PCN is ferroelectric with perovskite structure and curie temperature -27℃ which is known as a relaxor with high constant dielectric properties. In this research, adding PCN to PZT was done by sol-gel seeding method. Calcination at a temperature of 900℃ was causing the creation of single-phase perovskite powder. After that, conventional sintering... 

The aim of this study is to investigate the effect of Copper oxide on the microstructure, properties, and grain growth kinetic in Tin oxide- Based varistors. Copper oxide was mixed in Tin oxide with different concentration, including 0, 0.1, 0.25, 0.5, and 1 mol% and the samples were sintered at 1250, 1300, and 1350 oC. Then, phase and microstructural characterization was investigated and consequently, electrical properties were evaluated. According to results, Copper Oxide with forming the liquid phase through the sintering process, accelerated grain growth. It was found that, by increasing concentration of CuO, mean grain size was increased from 2.6 µm in 1250 oC and 5 hours to 17.1 µm... 

In this thesis the behavior of a 3D wing has investigated by Flow visualization and pressure acquisition test. The goal of this tests was considering changes in 3D wing section parameter in comparison with 2D airfoils. The performed Tests showed that variation in 3D wing treatment is affected by finite aspect ratio and sweep angle and also indicate changes in pressure profile, increasing pressure peak and decreasing effective speed. CFD studies has conducted to investigate special effect of sweep angle and show that lift and drag coefficient decrease with increasing sweep angle. Also different section pressure profile near the wing tip and intersection of wing/fuselage varies and miss... 

In this research, the surface of multi-walled carbon nanotubes (CNTs), as template, were coated by Lead zirconate titanate (PZT) with composition of Pb(Zr0.52Ti0.48)O3 via sol-gel process. The final product is called PZT-CNT hybrid material. For functionalizing of CNTs, benzyl alcohol was used. Simultaneous thermal analysis (STA) proved that the as-derived amorphous material crystallized at 520 ˚C. Scanning Electron Microscope (SEM) images verified the deposition of a uniform coating of PZT on the surface of CNTs and proved that the functionalizing treatment was done successfully. X-ray diffraction (XRD) showed that the crystal structure of the hybrid was tetragonal perovskite.... 

F-BAR protein is one of the Bin/Amphiphysin/Rvs (BAR) superfamily proteins which contributes in curvature generation and stabilization of lipid membranes. These proteins usualy form lattices on the membrane and can sculpt the membrane. In this project the interaction of F-BAR protein with a lipid membrane is modeled using coarse grained molecular dynamics approach. In order to describe the curvature generation and stabilization we would need an appropriate coarse grained model for the lipid membrane. In this project the proposed model for the membrane describes a membrane in liquid phase with a lateral diffusion in the lipid bilayer. Depth and width of the lipids potential is determined in... 

Last generation of solar cells which are organo-metal halide perovskite solar cells (PSCs) with power conversion efficiency over 20% are increasingly comparable to the silicon types, these PSCs are poorly stable under working environment. Carbon-based PSCs with lower cost and more stability seem a better choice for commercialization in future. In these PSCs TiO2 and NiO are working as electron and hole transporting materials, respectively. In addition, ZrO2 film between two mentioned layers works as a buffer layer to prevent direct contact. In this thesis, the initial powder, necessary for fabricating the buffer layer is synthesized at the first place. Then, since the printing method is a... 

TLP diffusion bonding method refers to a method in which two metal pieces can be bonded by putting an interlayer between two pieces and heating to a temperature lower than base metal melting point. Theoretically, this process shows that the bonding line disappears completely at the end of the process and it is not possible to recognize it. However, these assumptions were not accomplished in practice. Therefore, various parameters such as material of interlayer, thickness of interlayer, temperature and time of bonding, temperature and time of homogenizing and applied pressure on metal pieces should be controlled to achieve the best shearing strength results. Aluminum based composites have... 

In the present research, transient liquid phase bonding of dissimilar st52 low carbon manganese steel to 304 stainless steel by pure Cu foil, in induction furnace and SIC furnace, was investigated. Samples were bonded in induction and SIC furnace at 1150 0C for different bonding times. Samples were then cut transversely and cross section of samples was examined by optical and scanning electron microscope. Complete isothermal solidification time was more than 9 hours and 90 minutes for SIC and induction furnace, respectively. Micro hardness and shear strength tests were done on samples bonded in optimum condition. Shear strength of none homogenized samples which had been bonded in SIC... 

Reviewing trends of energy consumption in the world reveals that sooner or later energy resources will be depleted. This concerning rate of consumption has brought about more greenhouse gases (GHG) emission influencing deleteriously on environment and climate. Human has continued energy consumption to maintain and improve the quality of his life through industrial production. Industry as a significant energy user owns considerable contribution to this consumption. Several attempts have been carried out to develop energy management systems in order to improve the energy efficiency of industrial sectors. Whilst they are comprehensive and could be applied to any sector, there is lack of... 

Many efforts have been put into increasing the efficiency of dye-sensitized solar cells that part of it has been devoted to structure and chemical composition of photoanode electrode. In this thesis, the effect of changes in the composition and its influence on light scattering ability in photoanode of dye sensitized solar cells was studied.First, the nanoparticles of titanium dioxide powder through solvothermal method as well as spherical particle and barium titanate powder by sol-gel method were synthesized. XRD and FE-SEM analyses indicated that synthesized powders are in good size and morphology regarding the intended chemical composition. Optical properties of TiO2 particles were... 

The behavior of boundary layer under the effect of the sweep angle is considered. The measurements were performed by a pitot tube rake. Three models with various sweep angels at angles of attack -2, 0 and 2 degree were tested. Both tip and root of all wings were closed by flat plates in order to prevent the flow to roll-up. However the flow field on the wing was still three-dimensional because of the sweep angle. The velocity on the wing has two components; longitudinal and lateral. The cross flow emerges due to the non-equilibrium of pressure and centrifugal forces. The velocity profiles showed that the magnitude of cross flow was stronger near the leading edge of the wing. The cross flow... 

This research attempts to develop the optimal solution for an inventory problem consisting of a single machine which produces items some of which may be defective. We assume that no shortages are allowed and all defective items are to be reworked. Setup cost for rework and waiting time of defectives are considered. This research consists of two different parts. In the first part we consider two different policies where in the first policy in each cycle after the regular production the machine is setup for the rework of defectives of the same cycle. In the second policy several cycles constitute a period. All the defectives produced in the period are reworked in the last cycle of that period.... 

Energy harvesters are used in today’s Wireless Sensor Networks (WSNs) to harvest the energy from the environment. One of the important advantages of the energy harvesting sensor networks over battery-operated sensor networks is that the use of the energy harvester prolongs the life time of the nodes, while a battery-operated node becomes useless once its energy runs out. Although an energy harvester can provide a supply source with a lifetime much greater than a battery, the amount of available energy for an energy harvesting system is a random variable and is not as predictable as the energy of a battery. This unpredictability may cause reliability problems. In order to solve the existing... 

Wireless Sensor Networks have become widespread because of their flexibility, applicability and ability to precept data with high accuracy. However, the most limiting factor in their usage is the amount of available energy in nodes since energy depletion in a node means that it is dead, therefore many efforts have been done for optimum energy management in Wireless Sensor Networks. In many cases, the key solution to prolong the network lifetime is load balancing. In this way, all the nodes will die (approximately) together and the lifetime of network will be maximized. Load balancing can be implemented in all layers from physical layer to application. It should be noted that it is not always... 

The competitiveness of a port convinced shipping lines and shippers with a significant basis in selecting a port. Port authorities and port operators can make use of the competitive advantage as a parameter for counter measures by grasping the advantages and disadvantages of the ports and be a prime factor of opportunities and threats of the ports. Ports have a significant role in today’s networked business environment. They are being regarded as hubs that are part of various logistic systems. The very essence of a seaport is to link maritime networks and land network. These networks for the port are means of analyzing its competitiveness. A port overall competitiveness is determined by it’s...