Sharif Digital Repository

Concrete gravity dams are one of the most important infrastructures therefore their performance under seismic load is an important issue of concern for dam owners. It is necessary that these infrastructures to be able to continue their function after a disaster such as earthquake, as any damage can cause huge cost. For analysis of dams linear and nonlinear analyses are used. Because even operating loads will create cracks in the body of the dam, dam behavior can not always be considered linear. It is remarkable that these surface cracks can join together under seismic loads and this question the safety of dams. It is important to note that nonlinear analysis of concrete gravity dams is... 

Ramjets have many applications and in the speed range of Mach numbers 2 to 5 show the best performance in terms of specific fuel consumption. In many applications, including some anti-air missiles, cannon and mortars, solid fuel ramjet can be used to improve the system performance.
In this thesis, two activities are performed:
A) One dimensional simulation of the internal flow field of solid fuel ramjet by development of available softwares.
B) Optimization of design parameters of a specific ramjet motor based on the above simulation.
The main target of this thesis is simulation of internal ballistics, design and optimization of a solid fuel ramjet for a particular... 

The purpose of this project is to survey the created kind of inclusion in super alloyed based nickel. primarily, for this matter for the preparing of super alloyed based nickel, the vacuum induction melting furnace has been designed and built , then for surveying the kind of inclusion the effective parameters such as temperature , timing and material of crucible has been considered accordingly , the material of crucibles was considered based on mud-clay- graphitic- pure graphitic- aluminum- zirconium. From the obtained analysis samples of SEM has been distinguished which, with increasing of the temperature and the time ,the percentage of impurity will go up in super- alloyed and the... 

The environmental concerns in today's world, encourage the people involved in the plastic industry, along with the development of recycling culture, to produce and consume bio-based and biodegradable plastics. In this regard, during the last two decades, polylactic acid (PLA), which is a bio-based and biodegradable polymer, has experienced a high growth rate of production and is used in various applications such as packaging, textile and additive manufacturing. Along with the growth of the consumption of this polymer, the knowledge and development of its recycling methods have also been considered by researchers. Considering the expansion of the use of PLA blended with another biodegradable... 

Due to the intensification of competition in real markets and the increase in customer needs, manufacturers are forced to implement value-adding techniques in their production management. Many companies begin their improvement efforts without considering the need for a comprehensive plan. As a result, their improvement efforts are not carried out in an integrated and complete manner and do not lead to complete and desirable results. The main objective of this study is to provide a framework that proposes a detailed vision of lean implementation in the machine-woven carpet industry, considering the value stream map as a tool to achieve improvement strategies in this industry. This framework... 

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... 

Technology advancement in feilds of wireless communication and energy-efficient designs also more tendencies toward applicable low price devices lead to emergence of a very popular type of networks named Wireless Sensor Network (WSN). WSNs have multiple applications in different areas such as military, spying, medical, surveilance, traffic control, security, robotic, data accumulation from dangreous areas, intelligent houses and etc. Most WSN applications are in harsh and unreliable environments, hence there are some challenges to provide a reliable connection in this kind of networks, especially as they are infrustructueless, autonoms and distributed using traditional methods may not lead... 

The term "data-driven" was first introduced in computer science and has entered the vocabulary of controlled engineering in recent years. So far, several classes of data-driven-control (DDC) methods have been introduced, which are identified by different names in the literature such as data-driven control, data-based control, modeless control, model-free adoptive control, iterative feedback tuning and virtual reference feedback tuning.Data-driven control includes all control theories and methods in which the controller directly and using the input-output data of the control system or knowing the processed data and without explicit knowledge of the mathematical model of the system (unlike... 

Train scheduling is one of the most complicated stages of railway planning. In this stage, the arrival and departure times of trains at stations are determined. In this thesis, we studied train scheduling on a two-way and single track railway in order to minimize the total travel times of trains subject to a set of operational constraints and prayer time related constraints that determines the optimal station for prayer. In this project, we tried to simulate the real constraints exist in IRAN railway network and the objective function considers customer’s and railway management’s satisfaction, simultaneously. First, a mathematical programming is proposed for this problem. After demonstrating... 

The present ph.D. thesis consists of three sections including the static calculation, neutron noise calculation and neutron noise source unfolding in VVER-1000 reactor core. The multi-group, two dimensional neutron diffusion equations and corresponding adjoint equations are solved in the static calculation. The spatial discretization of equations is based on Galerkin Finite Element Method (GFEM) using unstructured triangle elements generated by Gambit software. The static calculation is performed for both linear and quadratic approximations of shape function; baesd on which results are compared. Using power iteration method for the static calculation, the neutron and adjoint fluxes with the... 

Process of casting with evaporative patterns and unbonded sand is a new method that due to different economic, environmental and technological benefits is considered to large and small industrial parts manufacturing in recent years. Different parameters are effective on the surface and metallurgical quality in this process, such as foam density, sand type and size, level and mode of vibration, sand compaction, coating and pouring time and temperature. If coating permeability that is function of type, thickness and concentration of coating is chosen improper, pyrolysis vapor of foam don’t exit completely and in this condition carbon of vapor deposit on the metal surface and produces defect... 

Nurse scheduling problem has received a great amount of attention during recent years. In this problem number of needed nurses from different skill levels is given for each Location-shift during planning horizon, and the goal is to allocate each nurse to shifts, such that the demand of each location-shift is satisfied. Many researches have been done with the aim of minimizing the number of needed nurses to satisfy the demand of locationshifts or maximizing nurses preferences to work in desired shifts. In this research an integer programming model is proposed to minimize the number of needed nurses and maximize nurses preferences simultaneously. The proposed mathematical model is appropriate... 

In this research the risk of oil price for Iran and Opec basket is studied. Several methods in order to estimate Value at Risk (VaR) such as Standard Historical Simulation, Historical Simulation with Autoregressive Forecast, Historical Simulation with moving average forecast, and ARMA are examined. The experiment is performed based on daily oil prices, from January 2005 to December 2009. The data is divided into two smaller time periods. The first, from 2005 to 2008, was used to estimate the model coefficients. The second part of data, i.e., the data gathered in 2009, was used for forecasting purposes. The result of experiment show that Historical Simulation with Autoregressive Forecasts... 

Wireless mesh networks (WMN) appeared as popular communication networks supporting high speed and high throughput applications. They consist of mesh routers and mesh clients and they have unique characteristics like self organizing and self configuring of the mesh nodes that bring a great deal of efficiency, reliability and robustness to networks and decreases networks maintenance cost notably. Also WMNs provide an integration of different types of wireless networks by exploiting the gateway involvement. One of the important group communication technologies that offers high level of bandwidth conservation and efficiency is multicasting. It also decreases the cost of communication compared to...