Sharif Digital Repository

Gorgan Bay and Miankaleh Wetland have been exposed to various environmental risks in the past years due to the decrease in the Caspian water level and the subsequent decrease in the water level of these water bodies. 2 channels, Chapgoli and Ashuradeh, are the only ways connecting the Gulf with the Caspian Sea. If the water level of the Caspian Sea and the Gulf continue to decrease, these 2 channels will be completely blocked and the connection between the Gulf and the sea will be completely closed. Due to the low depth of the bay and high evaporation on this water body, the blockage of these 2 channels will eventually lead to drying up of the bay or changing the flora and fauna of the area.... 

High level of safety, environmental issues, economic efficiency and on-line refueling give the potential to pebble bed reactors to have a unique significance among the new generation of reactors. Here the reactor core is an assembly of the fuel pebbles and moderators which are randomly located in the core. This feature makes it difficult and ingenious for simulating, moreover this kind of distribution makes us unable to know the exact structure of the core. Fuel pebble is made of many tiny particles called TRISO which are again randomly located in the graphite lattice, therefore makes the reactor's simulation too difficult. Due to these problems, simulation of this reactor with certain codes... 

In this thesis, first we simulate the needle penetration in the soft tissues via finite element and adaptive finite elemet methods. Then, we design a proper controller for the model of tissue-needle interaction model considering some uncertain parameters and conditions in the needle-tisuue model. Needle penetration speed into the soft tissue and the applied force to needle are supposed to be the system’s inputs in the model. Deformations of tissue particles are modeled based on the tissue particles’ velocities through a set of equations. To solve these equations, numerical methods are used which are conceptually based on finite element methods. In the control step, the needle’s velocity and... 

The Machinable Austempered Ductile Iron (MADI), a new group of Austempered Ductile Iron (ADI), has been developed to remove the problems (hardness and cost) of ADI cast iron. MADI is a special kind of ductile iron which has proper machinabilty properties. This kind of ductile iron can be produced using a specific chemical composition and defined heat treatment process. By providing these conditions, the hardness of the cast iron will be in the range of as-cast cast iron. On the other hand, because of the especial production process, the cost of the final shape casting will be lower than ADI cast iron. In the present work, firstly the effect of heat treatment parameters, including the time... 

A highly reliable tool for transient simulation is vital in the safety analysis of a nuclear reactor. Despite this fact most tools still use diffusion theory and point-kinetics that involve many approximations such as discretization in space, energy, angle and time. However, Monte Carlo method inherently overcomes these restrictions and provides an appropriate foundation to accurately calculate the parameters of a reactor. For this reason, in this thesis, a dynamic Monte Carlo code named MCSP (Monte Carlo dynamic Simulation of Particles tracking) is developed for both the steady state and time-dependent simulation of particle (neutrons, photons and electrons) tracking in an arbitrary 3D... 

Prostate cancer is the second most common cancer in men and the fourth leading cause of death in the world. In this study, the 188Re-HYNIC-PSMA radiolabeled compound was produced as a compound for use in the treatment of prostate cancer and its metastases under optimal labeling conditions and its radiochemical purity was obtained above 98% using RTLC and HPLC chromatographic methods. This compound is stable at room temperature and in human blood serum for at least 48 hours after preparation. The biological distribution of this compound was investigated in each rat tissue and the amount of injected activity per unit mass of each tissue (%ID/g) was determined. The bio-distribution of 188... 

In this work 1-(2-hydroxyethyl)-3-methylimidazoliumbis{(trifluoromethyl) sulfonyl}imide ([hemim][NTf2]) and 1-benzyl-3-methylimidazoliumbis{(trifluoromethyl) sulfonyl}imide ([bzmim][NTf2]) ionic liquids were used to study the effect of introducing hydroxyl and benzyl groups to the imidazolium cation on aliphatic/aromatic separations. Toluene separation from heptanes has been investigated by extraction using ionic liquids. Finally, a realistic model for survey the data was used. The liquid-liquid equilibrium (LLE) data for the {heptane + toluene + [hemim][NTf2]}, {heptane + benzene + [hemim][NTf2]} , {heptane + toluene + [bzmim][NTf2]} systems were measured at 313.2 K and atmospheric... 

Positron Emission Tomography (PET) is a cutting-edge medical imaging technique that enables the examination of functional activities in different regions of the body, particularly the brain. This technique involves injecting a radiopharmaceutical into the body, which emits gamma rays that are subsequently detected by the PET scanner to generate images. However, a significant challenge in PET imaging is the degradation of image quality due to noise and photon scattering, which can lead to diagnostic errors, especially in sensitive applications such as detecting brain diseases. Various image reconstruction techniques have been developed in the past to mitigate attenuation and scattering... 

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... 

In this thesis, two-level optimal control of uncertain and non-uncertain large-scale systems is presented. In the proposed two-level approach, using a decomposition/coordination framework, the large-scale system is first decomposed into several interactive subsystems, at the first-level, where a smaller optimization problem is solved at each subsystem. At the second-level, a substitution type prediction method, as a coordination strategy, is used to predict the interaction between subsystems. The coordinator mainly evaluates the next update for the coordination parameters and continues to exchange information with the first-level, so that the overall optimum solution is obtained. It is shown... 

Regard to high temperature and using dry fuel in engines with CNG (Compressed Natural Gas), wear problems and instability of valve seat insert (VSI) in these types of engines have been increased. Today some of high alloy steel (consist of Cr,Ni,Co,W,Mo, . . .), Ni-base alloy or Co-base alloy are used in manufacturing VSI. It's clear these materials have high price. In powder metallurgy methods high percentage alloy is used for manufacturing VSI. These are the reasons why casting method for VSI manufacturing has been pleasant to be used.
In this project the cast iron has been used for CNG engine VSI, by adding some elements like Mo,V,W, and Nb. The graphite has been used as solid... 

The analysis of gamma-ray spectra of low resolution detectors is difficult and sometimes impossible, as a result of photo peak’s overlapping. The usual methods of radiation spectra analysis based on fitting of peaks to mathematical curves or detecting of peaks with numerical calculation, are valid for high resolution detectors. However these methods are less successful for lower resolution detectors such as the common scintillators. The wide peaks in the spectrum maybe overlap and make it difficult to analysis. To solve this problem, we test here a method, based on the use of the artificial neural network. At first spectra of elements are converted to the patterns which are suitable for the... 

Radiation detection techniques have important applications including prompt gamma neutron activation analysis (PGNAA), radiotherapy dose measurement, medical imaging and homeland security. Pulse height distribution is also a useful parameter in Radionuclide identification. Gamma ray spectroscopy analysis is a common technique in measuring of radiation field to identify the radioactive source.
Probabilistic methods are commonly used for numerical simulation of Pulse height distribution. In Monte Carlo methods, each history is individually tracked and details of interactions are available. Using the Monte Carlo methods for calculation of pulse height distribution leads to more real... 

Sequencing and scheduling of jobs are decision making processes that are used in many manufacturing and service industries. In the traditional scheduling models, it is assumed that the values for all the problem parameters are constant and known in advance. However, production environments in the real world are subject to many sources of uncertainty or randomness. This research investigates three different types of stochastic scheduling problems. In the first case, the problem is minimizing the number of tardy jobs in the class of static list policies, where the job processing times are random variables. For this case, the stochastic problems in single machine and flow shop environments are...