Sharif Digital Repository

In a centralized power system, the system operator, derives a maintenance scheduling plan that maximizing reliability of system and minimizing operating cost. But in a restructured power system the goals of GENCOs and independent system operator (ISO) are separate and each of them optimize its own goal. The goal of each GENCO is to maximize its annual benefits and the goal of ISO is to maximize the reliability of system throughout the year. Therefore there are two objective functions for finding an optimum maintenance schedule in restructured power system. This thesis proposes a new method for maintenance scheduling of generation units in a restructured power system. Firstly each GENCO... 

Software Product Line Engineering (PLE) and Agile Software Development are two leading approaches in the software industry. Despite the inherent differences between the two approaches, they are intended to fulfill common goals, such as: Reducing time to market, increasing customer satisfaction, promoting product quality, managing changes in requirements, and lowering the costs of development. In addition, each of them has certain positive features which address the other’s weaknesses. As a result, it seems reasonable to integrate the two approaches in order to produce a combined method which fulfills the common goals while addressing the weaknesses. Agile Product Line Engineering (APLE) is a... 

Stress whitening is a type of discoloration that can occur in variety of polymers used in automotive and household industries. The current research tries to investigate the effective microstructural parameters such as strain rate, rubber second phase, and branched polypropylene (PP) on the stress whitening in polypropylene in order to propose toughed PP blends with limited stress whitening. It is shown that increasing the strain rate in tensile test results in formation of more visible whitened area within the plastically deformed zone. This is the consequence of further growth of micro-voids at higher strain rates. The results are in accordance with the Mie scattering concepts. Besides, the... 

The problem of linear prediction is one of the traditional issues in signal processing. With the genesis of graph signal processing, the prediction of signals defined on graphs has been recently addressed. Some existing methods provide approaches for predicting samples of a graph signal based on a known adjacency matrix among nodes. On the other hand, some studies have used graph smoothing technique, which ensures that the estimated signals remain smooth on the graph. Furthermore, graph neural networks have been proposed recently, and some research has considered methods for predicting graph signals using a graph neural network, which is possible by using extracted features from the training... 

Heartbeat is the result of contractions of over 10 billion cardiac cells. These cells’ cytoplasms are connected to each other by gap junctions which are arrays of intercellular protein channels. Thus action potential can propagate from one cell to another and cause its contraction. In core-conductor model, one-dimensional microscopic representation of cardiac tissue, cells are attached to each other to form a ladder network. The parallel elements are connected to each other by series resistors which represent gap junctions. These resistors are nearly always considered as static elements. In this thesis I have investigated the effects of incorporating the dynamicity of gap junction resistors... 

In this research we study multi-commodity inventory-location problem under disruption risk that is formulated to a nonlinear integer-programming model. The objective function of this model is minimization of inventory and location costs simultaneously under disruption risk. These disruptions may be caused by natural events such as earthquake, flood, fire and man-made sources like labor strike or terrorist attack. The structural design of a supply chain greatly affects how these kinds of disruption risks influence the network. In this regard, this study proposes a strategy to reduce the impacts of disruption risk by considering substitute commodity in the multi-commodity inventory-location... 

The aim of this investigation is the experimental study of nozzle exhaust jet flow effects on aerodynamic behavior of an air vehicle at transonic speeds. For this sake, a secondary jet injection is used by the ejector into test model. The ejector total pressure for jet injection varies between 0 (jet off) to 4 bar for simulating nozzle exhaust jet flow and supplying intake’s required mass flow rate. All tests were conducted at QRC Trisonic wind tunnel and at Mach number of 0.5 to 0.85 and angles of -4 to 6 deg. The aerodynamic force and pressure results were recorded in order to analyze the exhaust jet flow. This study revealed that the aerial vehicle drag becomes bigger than its free flight... 

This study aims to evaluate aerodynamic coefficients of an airplane with air breathing engine experimentally. In these experiments, an ejector is used to better simulate flying conditions and aerodynamic interferences generated in inlet and exhaust engine. Therefore, at first, an ejector was designed for simultaneous simulation of exit cold flow and inlet flow of engine. All tests were conducted at QRC Trisonic wind tunnel and at Mach number of 0.5 to 0.85, angles of -4 to 6 deg. and for various amounts of pressure ejector and control surfaces angles. Finally, for the Mach number of 0.5, effect of roughness on the aerodynamic coefficients was examined. The results showed that, drag... 

Bracing Systems are usually a set of inclined members that are embedded in structures to resist lateral forces and control lateral displacements. There are different types and behaviors for Bracing Systems depending on the way of assembling and locating them in the structure. Braced Frames, such as Concentrically Braced Frames (CBFs), generally have high stiffness and low ductility. Another Type of Braced Frames is Eccentrically Braced Frames (EBFs) which improves CBFs by establishing suitable ductility as well as stiffness. Inelastic behavior of Links involved with EBFs caused this in EBFs. Nevertheless, these systems have no efficiency in next earthquake, because links are parts of beams... 

High-altitude simulation lab of chemical thrusters is one of the most important infrastructures for the development of space thrusters technology. In these laboratories, different sections are designed according to the requirements for simulation of the thrusters at specific pressure and temperature. The purpose of this research is to design a subset of the creation and preservation of vacuum for the purpose of ground testing of chemical thrusters. Vacuum preservation is more comprehensive than the vacuum creation and is usually the bottleneck of design, so the design of this subset is intended in the present study. To illustrate this, after introducing the basic concepts required, two... 

Inlets must decelerate the air with lowest loss and drag together with a given pressure and Mach number with best quality and uniformity to the engine. This is done based on flight Mach number, by an arrangement of shock waves and surfaces gradient in the inlet. Any distortion in the flow field and the inlet geometry parameters may disrupt such arrangement and influence on the inlet performance, in addition, under critical conditions, it might affect the stability of the intakes. Any distortion in the flow field and the inlet geometry parameters may disrupt such arrangement and influence on the inlet performance, in addition, under critical conditions, it might affect the stability of the... 

As an essential laboratory instrument in aerospace engineering, wind tunnels need to be calibrated. Therefore, this thesis takes into account the calibration of the subsonic wind tunnel at the Sharif University of Technology, with the test section dimensions of 90 × 42 × 30 cm3. It is necessary to accurately and correctly determine the effective parameters for the wind tunnel results to be reliable. A pitot-static tube, a standard wing, pressure sensors, a force balance, a turbulence sphere, rake, yawhead, a digital level, a protractor, and a data acquisition system were used for this experiment. For calibration, variables including flow uniformity, flow Angularity, turbulence intensity,...