Sharif Digital Repository

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... 

In recent years, dust storms have turned into one of the most prominence environmental issues, existing in Tehran. The infiltration of dust through west borders has led to significant increase in the concentration of Tehran’s pollutants. The main abroad source of these dusts are deserts located in Middle East. The contribution of Middle East deserts in daily concentration of PM10, without the inclusion of local emission sources, was analyzed in previous studies. In this study, we analyzed the contribution of dust storms, formed in Middle East, in Tehran’s PM10 and PM2.5 concentration, using CMAQ model. Dust periods between 2012 and 2014, was identified using observation data and satellite... 

The purpose of the present study is to model and control a 6DOF satellite dynamics with a rigid body in the Earth’s orbit including the fuel slosh. The satellite manages and controls its attitude and position by twelve ON-OFF thrusters installed alongside the principal body axes. Moreover, due to using the liquid fuel to feed these thrusters, fuel slosh may have a strong dynamical effect on the satellite translational and rotational dynamics and control. The thrusters’ activation may result in fuel slosh and the impact of their frequent switching ON-OFF on fuel is considered in this study. The thrusters force magnitude, switching intervals, and their frequencies can affect the magnitude of... 

Named entity recognition (NER) is one of important tasks in natural language processing (NLP). Named entities consist of specific nouns such as personal names, organizations, locations, etc., which refer to important entities in text. NER contributes towards other NLP tasks such as machine translation, text summarization ,and text classification. In the recent decade, with respect to development of deep learning (DL) methods, considerable progress has been made in this field. The objective here is to propose an efficient method for NER in Farsi (Persian) text through DL methods. Since deep neural networks require a great deal of training data, and due to the fact that Farsi lacks such data,... 

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... 

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...