Sharif Digital Repository

A geometric network is a weighted undirected graph whose vertices are points in the plane and edge weights are equal to the Euclidean distance of its endpoints. Routing is one of the important problems in graph theory and if the underlying graph is a geometric network,it has applications in different fields including transportation, communication networks and robotics. In many applications the graph data is not accessible or finding the optimal path is costly. Therefore local routing is used. In local routing the goal is that at each vertex,the routing must be done only given the neighbours of the current vertex, the origin and the destination of the route. Geometric spanner is a subgraph of... 

The effect of alloying elements such as Chrome, Molybdenum and Chrome-Molybdenum on microstructure and mechanical properties of submerged-arc weld of structural St37 and 4135 Chromoly Steel was investigated. Addition of alloying elements was done through flux and slag-weld metal reactions. Bonded flux was used to achieve this purpose. Mechanical properties were studied by means of Longitudinal Tensile, Hardness and Charpy V-notch tests. Microstructure was studied by means of Optical and Scanning Electron Microscope. The results show that chromium increase Ultimate Tensile Strength (UTS) and impairs Impact Toughness (IT), although it increases the percentage of acicular ferrite (AF). In the... 

In this thesis, we investigate some problems in Sublinear field. We designed an algorithm that approximate the minimum distance of a shape to be a disk. In the first algorithm, we assumed that its input is a matrix and 1s in the matrix represent black pixels and 0s in the matrix represent white pixels. Also, we designed another algorithm that its input is a data structure contains the positions of a convex shape and we can sample uniformly from its pixels. In this problem similar to the first problem we must approximate the minimum distance of a shape to be a disk. Finally, we designed an algorithm for counting disks in a matrix. The input is a matrix that it contains some disks which have... 

Multiscale modeling is performed within the framework of homogenization methods for problems in which the scales are separated. The existence of representative volume element (RVE) is one of the main ingredients of homogenization methods. Due to non-existence of RVE and macroscale mesh sensitivity, the continuous homogenization method is not applicable for softening materials. Despite the non-existence of RVE for softening materials, it has been demonstrated that by performing the average over the active damage zone rather than the entire domain, objective responses with respect to RVE size could be obtained. That is why discontinuous homogenization is used instead of continuous... 

Presently, a wide range of devices operate at supercritical condition. In fact, supercritical condition refers to a condition in which both temperature and pressure of injected fluid exceed the critical point. In the case of modern internal combustion engine, the temperature and pressure of combustion chamber is high enough that can be considered as supercritical condition, whilst the fuel injected may be subcritical or transcritical.It has been widely accepted that in supercritical state, vaporization enthalpy is vanished and there is no distinction between gas and liquid. Hence, only a single state will remain which is neither liquid nor gas and referred to as fluid. Moreover, many... 

The robot considered in this project is to test parts and equipment installed in marine vessels under sea movements and waves. After a thorough assessment amongst common solutions to problems of this kind, a Stewart-Gough based manipulator has been chosen so that all the requirements could be satisfied. Therefore, according to the information obtained through relevant organisations, the purpose of this project is to work on dynamics, control, and design of the structure of a 6DOF Stewart platform – based hydraulic motion simulator for heavy payloads for samples weighing up to 2.5 tons which can handle linear accelerations up to 10 m/s2, rotary accelerations up to 150 º/s2 performing at a... 

According to the increasing need of the world to increase the speed of existing technologies such as computers, cars, urban transport, etc. The need to carry goods at higher speeds is also a concern that due to its cost It can make a significant contribution to the economy. In the maritime industries, in addition to the commercial and economic orientation, there is also military capability the speed factor and the ability to navigate is very important for military vessels. The power in the sea is inevitably dependent to speed, so for Increasing the speed of vessels with regard to military and economic objectives needs optimized Propulsion systems which There are also limitations for them.... 

During the operation of a nuclear power plant, the reactor pressure vessel (RPV) is exposed to a variety of pressure and thermal stresses and neutron radiations. This will cause the loss of the initial strength of the reactor vessel component. During the occurrence of some of accidents, an excessive cooling of the coolant inside the RPV takes place which in the term is called overcooling transients. In addition, in some of these events, a break in a section of the circuit will reduce the water level at the core of the reactor. By reducing the water level, the existing emergency makeup water systems are activated and inject water into the reactor. The temperature of the added water is much... 

In this dissertation, a proper closed-form representation has been presented for the site specific indoor radio-wave propagation. Characteristic Green’s function (CGF) technique is used to obtain the integral representation of the Green’s function of a rectangular 2D room with dielectric slab walls. Based on numerical simulations, this method provide quite accurate results for wave propagation in the interior region (away from the walls) but the error increases for source or field points near the walls. The presented integral form of Green’s function has slow convergence and computed using Real images, complex images and rational function fitting methods. An error of less than 20 percent is... 

This thesis presents the seismic performance evaluation of steel MRFs with nonlinear replaceable links. Although existing MRFs can provide life safety during a design level earthquake, they are expected to sustain significant damage at the locations of flexural yielding fuses in the beams .These drawbacks can be mitigated by introducing replaceable links at the locations of expected inelastic action. Codes require that the span-to-depth ratio of the beams in moment resisting frames (MRF) should be limited to guarantee the development of plastic hinges with a sufficient length at beam ends. To overcome the abovementioned limits, in this paper a new replaceable shear structural fuse is... 

The popularity of Internet-based video services has grown dramatically in recent years, with the figure now estimated to be around 75 percent of total bandwidth consumption and it will increase to 82 percent by 2021. The growth of video services, as well as the advent of 360-degree videos and more real-world experience in it than conventional videos, have led companies such as Google, Facebook, and others to embark on this field of research and implementation to make it an epidemic. One of the major issues that will challenge the implementation of this video service on the network is the high volume of these videos that do not make it possible for everyone to use them. It is necessary to... 

Optical telecommunications, and especially optical fiber-based telecommunications, have been one of the most important leading factors in advancing information technology. This age seems to have an insatiable appetite for information in a way that every two years we see a two-fold increase in the traffic of optical networks.The focus of this thesis is in the area of backbone optical networks. We know that companies operating in this field spend a huge amount of money to set up and maintain optical networks. One aspect of reducing costs in optical networks is the use of grooming to reduce the cost of using network equipment.Different heuristic algorithms for optimization are proposed for this... 

Human blood is a valuable and scarce product which is only produced by human body. There is no replaceable material for our blood and there has always been a constant need to donors and blood products in societies. Like every other product, blood has to be transfused to patients after it is donated and this process requires a complete and effective blood supply chain. Considering all properties, complexities and uncertainties of a blood supply chain, we need to develop stable methodologies in order to simplify decision making in blood supply chain. In this research, we develop a novel blood distribution system from a regional blood center (RBC) to its nearby hospitals. It helps RBCs plan the... 

In this study, a fully coupled thermo-hydro-mechanical model for two-phase fluid flow and heat transport in fractured/fracturing porous media is introduced using the extended finite element method (XFEM) for numerical solution. The subject is important in the environmental and industrial fields such as hydraulic fracturing in petroleum industry, CO2 geo-sequestration, geothermal energy extraction and radioactive waste disposal in unsaturated porous media. In the fractured porous media, there are couplings of traction and heat and mass transfer between the fracture space and the surrounding media. Therefore, consideration of the fracture geometry explicitly in the modeling is important to... 

Titanium dioxide (TiO2) is a transparent n-type semiconductor with wide band gap which makes it suitable for applications such as solar cells. TiO2 dye-sensitized solar cells (DSSCs) transform the visible light energy to the electrical energy by excitation of absorbed dye. In the present study, TiO2 nanowires and nanoparticles were synthesized by hydrothermal and sol-gel methods, respectively. The effect of TiO2 morphology on photovoltaic performance of the cells was studied by fabrication of single layer DSSCs containing pure nanowires, pure nanoparticles and mixture of nanowires and nanoparticles with various weight ratios. The results revealed that, DSSC made of 10 wt% nanowires and 90... 

In recent years, energy storage systems have received widespread attention from researchers to increase the reliability of the power grid. These systems have different types that compressed air system is of special importance due to its high stored energy and long life. In this system, the surplus of electricity generated from renewable energy sources or grid electricity at low power consumption is compressed and stored in a tank. When there is a need for power consumption or peak power consumption, compressed air will generate electricity by passing through the turbine and will help the network. Large-scale type of the system requires special geographical location for air storage; for this... 

Companies are facing increasingly faster pace of technological evolution. Running a business with a large supply chain without considering the technological changes in the environment might provoke a difficult situation and result in competitive disadvantage. The field of hybrid and electric vehicles has developed a lot in the last decade in the world and the technologies of this field are developing in a dynamic circumstance. Iran Khodro, as the largest automaker in Iran, cannot be indifferent to this reality. Despite the huge oil and gas resources in the country, is it necessary to develop hybrid and electric vehicles in Iran? This is the main question we are trying to answer in the first... 

Much research has been done in the field of queuing or forecasting aircraft routes. These methods have been implemented mainly for commercial aircraft, and little research has been done on electric birds. In this research, we intend to extend these methods to the field of electric birds and create a database based on the existing records of successful flights that electric birds have had in the landing phase. Next, design an intelligent learning system that adjusts its parameters and has the ability to predict the route for birds planning to land at an airport. This intelligent system can manage the birds that are going to land with high computational speed and keep it up to date by adding... 

The purpose of this study is to introduce a new indicator to estimate the amount of irrigation water in excess of the need and also to determine the optimal irrigation pattern to reduce water loss in agriculture. According to the Food and Agriculture Organization of the United Nations, the major loss of fresh water takes place in agriculture, and the reduction of water resources is more significant in developing countries that do not have advanced agricultural equipment. One of the challenges in the studies related to reducing the amount of water used in agriculture is a lack of knowledge on the spatial distribution and temporal changes in water loss in a region. Although estimation of... 

In recent years, Deep Neural Networks have become essential tools, surpassing human capabilities in various applications, leading to their widespread integration into various everyday applications. However, a fundamental challenge of these networks lies in their substantial energy consumption, particularly concerning constrained electronic devices. To address this issue, numerous solutions have been proposed, encompassing software-based approaches such as network pruning, knowledge distillation, and network quantization. Moreover, hardware-oriented enhancements have also emerged, including the utilization of approximate circuits and approximate calculations within neural network...