Sharif Digital Repository

Continuous variation of electrical loads in the power grid results in fluctuations of voltage frequency and. Accordingly, the need to the dynamic stability of the power grid would necessitates a constant balance between the production and consumption rates of electric power. In the same vein, given the launch of Bushehr nuclear power plant and its connection to the national electricity network, an investigation of the power plant’s capabilities in changing the produced power seems to be an important necessity.
Therefore, modeling the Bushehr reactor core in the DynCo code, the present thesis is aimed at investigating the reactor behavior during the power change periods with the... 

Identification of different hazards in a UF6 production process, and evaluation of the risk originated from these hazards is the main objective of this project. A number of hazards are present in a typical UF6 production process, such as leakage of chemical gases like HF and F2 and also radioactive UF6 gas release. In order to evaluate risk due to these hazards, probabilistic approach has been used. Due to lack of probabilistic safety criteria (PSC) for chemical releases, only for UF6 gas release risk assessment has been done. As a first step in PSA of this process eight groups of initiating events have been identified using HAZOP study, and for each initiating event, event tree analysis... 

Airline scheduling is a dynamic process in nature such that it changes not only during one year period but also in smaller intervals due to the economic, political, religious, and social factors. Basically, airlines schedule planners through using mathematical models decide which flights are to be served in what periods of time and at what costs. This has to be done considering a set of constraints of different nature, from airspace and airport congestion up to climatic conditions or even crews working conditions. Such a complex problem requires different methods for an efficient solution. In this study by using network optimization method and applying different operational constraints on... 

Efforts to model and control surge, as the underlying instability of centrifugal compressors, were conducted. Of the three major instabilities in compressors, namely chokage, stall and surge, the latter has a significant role in limiting the available range of operation in centrifugal compressors, which are the most common devices for the transportation of Natural gas. The customary method to circumvent surge, which if occurred, could impose severe, catastrophic and irreversible damages to the machine, is to avoid the zones in which it is likely to develop by means of a recycling system. These often called "surge avoidance" or "surge prevention" schemes have the benefit of high reliability,... 

In order to manage a complex system, one way is to divide it into smaller parts. That’s the reason airspace in each country should be divided into sectors. Currently, these sectors have fixed areas and each is controlled by a number of air traffic controllers. However, the traffic crossing these sectors is considerably dynamic, which means the traffic density and its distribution varies seasonally, weakly and even through the 24 hours of a day. Moreover, weather conditions and security and military issues make constraints to some of these sectors. This sometimes results in some high traffic sectors while some others have very low traffic density which causes two main problems. One is that,... 

Brain computer interfaces (BCI) are systems designed to understand the brain function from activation patterns and dynamics recorded from the brain activity and use this knowledge to give disabled people the ability to communicate with their surroundings. Features are extracted from recorded signals from the brain while occupied in a mental task and classified into categories related to the task given. These classifiers are then used for the estimation of user anticipation. Usually, the tasks defined are meant to evoke or induce a potential in the pattern of the brain. Awareness of error responses is one of the cognitive functions of the brain which occurs when a response is in conflict with... 

This work, with the help of FUZZY DEMATEL and FUZZY TOPSIS methods investigates the behavior of a general transportation system. In fact, we have been able to develop a cause and effect model to describe why in an unsustainable system any increase in the so called “human value” would not help increase the overall system’s sustainability. Moreover, we have been able to analyze the new role of the key stakeholders as “insurance companies”. in fact, such companies receives a guaranteed flow of money without providing any extra services in the current unstable situation which help widen the gap and increase the rate of instabilities. Further investigations might be necessary to examine the role... 

Supply chains are socio-technical engineering systems which now days perform in more uncertain operational environment than before. These systems have been vulnerable because of increasing the number of natural disasters, competitiveness and changing the demand. So these systems in order to be survived in such high uncertain environment need to enhance some capabilities in their structure. In this research by considering an assumed auto supply chain, we try to develop an approach to cover uncertainties in operational environment of this system. At the next step, we use design structure matrix modeling to model the interactions between system elements before and after scenario occurring.... 

In this study, the thermal-hydraulic analysis of prismatic HTGR’s core with natural convection has been studied using porous media approach. VHTR are the new generation reactors which due to special neutron and thermo physical properties have highly inherent safety. In lose of forced circulation accident, decay heat is transferred from core to pressure vessel wall and then to water tubes in concrete wall at reactor cavity with conduction, convection and radiation automatically. In this case the high volume of decay heat is stored in graphite block with high thermal capacity and is prevented the instantaneous temperature rising.
The aim of this study is justifying inherent safety of HTGR... 

In the class of unmanned air vehicles (UAV), there is a class entitled as Quad-rotor that engineers pay much attention due to specific features to them. Main applications of this class are because of vertical take-off and landing capability and high controllability. This class has high controllability in environments with high barriers because of the inherent imbalance. All of the Quad-rotors have already studied, had a fixed structure. So the designer's main focus was on improving the guidance and control systems and almost all forms of linear and nonlinear control methods and fuzzy, adaptive and robust control have been investigated. In this study variable structure is examined instead... 

Inadvertent opening safety valve of pressurizer (SVP) is one of the most common initiator events in Booshehr nuclear reactors with occurrence frequency of 1.1E-0.2. This event has the third rank in initiator event among 16 other events (Loop and Compensated LOCA were ranked as first and second respectively). So special attention must be paid to SVP and the operators need to have specific trainings on this matter. In this thesis, the SVP as initiator event is being considered and the sequence which lead to core damage (CD), according to design informations is being modeled moreover the qualitative and quantitative analysis is carried out. In the modeling process we have used the SAPHIRE... 

The purpose of this thesis is to present a novel approach in Terrain Following/Terrain Avoidance (TF/TA) flight using Fuzzy Logic. The fuzzy logic can decide where and how the aircraft needs to change its altitude and/or heading angle. The method due to its fast decision making algorithms would be useful for on-line operation. It could also help design trajectories in an off-line manner. To achieve the above goal, the method effectively incorporates the dynamics of the aircraft and could handle tough terrains in terms of shape and peculiarities. The mathematical method basically, uses a special relationship among existing slope and slope derivative of the terrain together with aircraft... 

This work presents a novel approach to redefine a safe aircraft based on systems engineering fundamentals. Its aim is to prescribe a “Safe-Functional-Aircraft” instead of currently used procedures that is based on “Physically-defined-Safe-Aircraft”. The current work is much more consistent with increasing number of flights. It basically suggest that any aircraft that can complete its mission should not declare emergencies due to any physical malfunction. With proper simulations, have investigated the feasibility of replacing a “physically safe” aircraft with an “operationally/functionally safe” one. The process makes use of well-known documents such as FTA and FMEA ; which are produced... 

Following Three Mile Island (TMI) accident in 1979, first severe accident (SA) in Nuclear Power Plants (NPPs), Accident Management Support Tools (AMSTs) were developed and installed in a number of NPPs. Lessons learned from Fukushima accident highlighted importance of Accident Management (AM) in mitigation severe radiological consequences after a SA and suggested reconsiderations of AM program which in turn created the need for AMSTs adaption and modernization. An efficient AMSTs should have the following principal capabilities: (1) Identification of accidents and diagnosis of the plant damage state (PDS), (2) Prediction of accident progress path and (3) Source term analysis and prediction... 

In this study, a model for the optimal routes for the recovery of space debris is expressed. The dynamic model using a binary system consisting of satellites and orbital debris containment space is extracted. Trastrhay available on satellite and aerodynamic drag on the system circuit changes the whole system and the entry of debris into the thick atmosphere began to burn.This circuit must be optimized. The thrusters are assumed as variable optimization problem. After simulation of optimization, it follows that by changing the initial value thrusters, Trastrhay the optimal cost function changes. Also, indicating the final height of system affects on parameters, thrusters and the cost... 

Due to nuclear power plants’ growing roll in providing energy, analyzing probable accidents and their prevention is of vital importance. The thermal-hydraulic shock accident which happened in Bushehr nuclear power plant deaerator has been simulated in this study. Steam bubble collapsing which takes place in two phase medium by mixing steam and subcooled water leads to this kind of shock causing financial and physical irreparable damage in nuclear power plants. For carrying out this simulation, first an steady state model of the deaerator was run using RELAP5 code and then using this model and other plant’s data such as the ropert of the accident and plant’s Final Safety Analysis Report... 

Loose parts in the primary circuit of a nuclear power plant, causing damage to the fuel rods and other equipment, so early localization and mass estimation of this pieces can provide context of safety measures for the reactor after an event.Acoustic signals emitted by the location of these parts provide enough information to estimate their location and mass. So with obtain time-of-arrival differences between sensors and sound velocity can be estimate loose part location. In this thesis signals of the sensors in Bushehr power plant monitoring system are analyzied. To estimate the loose part locations, the time delays between sensors must be calculated. The time difference between the sensors... 

In this study, the determination of the distribution and the differences concentration of hydrogen in containment of Bushehr power plant by modeling of containment and Hydrogen removal system of Bushehr power plant during LB-LOCA accident is accomplished. In Bushehr nuclear power plant, which has a unique design, the containment is similar to PWR power plants with a metal sphere, but the installed reactor is a VVER-1000. After a full study on the containment and its systems, the required data for modeling is gathered and afterwards, the engineering handbook is prepared for MELCOR input code and then the modeling and size classification of the containment is done in 4 different ways,... 

The existing trend in air transportation growth, clearly shows that aviation industries need to profoundly look at “formation flights” in a more efficient manner and without complex computations. This work describes a new efficient Logic to accept or reject a possible formation among all available. The approach considers each airplane as an agents that “sees” the current traffic environment and then selects the best “Action” to satisfy its desired objectives. The logic, although simple, considers the location and time to join a formation or to create one; and the position to leave the original formation. Different Mathematical model have been investigated to find-out which one is more... 

This work describes a new approach to the so called “Engineering Requirements Process” based on abilities to develop a meaningful task. We first describe how a meaningful is created from scratch and then we explain how requirements could be added to a level where the predefined task is no-longer doable. The process is then applied to design of an aircraft wing to show how requirements could be avoided during a design process. The method is expected to be applicable to all aircraft sub-systems and parts. The process is particularly useful where all design requirements are not available at once, rather they increase as time goes on and new stakeholders become apparent. In this work, we have...