Sharif Digital Repository

The Concept of causation plays a major role in Hume’s philosophy and as yet has been debated between philosophers. This Thesis aims to Consider the main part of Hume’s view about Causation, but it also Ventutes into more recent approaches in this subject. In first chapter, we attend to Consider The project of Hume named "Seience of man" and The associative mechanism of causation is expressed. In Second chapter, We turn to three famous interpretations of Hume’s view and the meaning of two definitions of Causation is discussed. In third chapter, we try to analyse the real nature of necessary Connection. According to fourth chapter, we again attend to three interpretations and recognize the... 

The purpose of this research is to study the behavior of some kind of conventional and retrofitted Khorjini connections, such as stress and strain concentration and eventually strain-jumping phenomenon. Thus the software ABAQUS 2019 was used to fabricate the FEM models of the connections with experimental prototypes. In analytical studies, 21 specimens with different sizes of the connection components were analyzed. True stress-strain curves for steel and weld materials were used and damage initiation and revolution were considered in the weld material. Also cracking of the welds was considered by a micromechanical method. The main defects of the connection are severe initial stiffness... 

The Riemann- Hilbert correspondence theorem is a higher dimensional generalization of Hilbert’s 21st problem. The main problem was about existence of differential equations with regular singularities on Riemann sphere with a specific monodromy group. Deligne generalized the problem to algebraic connections with regular singularities. Kashiwara and Mebkhout independently generalized the theorem for derived category of D-modules. In this thesis, we will begin by studying this theorem in simple cases.In chapter 3 generalized version of the theorem by Deligne,will be introduced. At the end of the third chapter a proof of Riemann-Hilbert correspondence for the special case of projective curves... 

On average there are to resistance spot welding connections per vehicle. The quality of these welding directly affects the quality of the finished product and the strength of the vehicle against various loads, including road roughness, different maneuvers and even sudden impacts from accidents. During the spot welding process, unintentional failures occur due to the wrong choice of current, force and time. The aim of this study is to investigate the fatigue strength of three-sheets welding joints in numerical and laboratory methods, considering the defects of (Undersize weld, Stick, edge of sheet metal and Edge of sheet metal-SECANT) . For this purpose, a healthy spot welding model was first... 

Steel structures are one of the most common structures in the world. One of the main parts of these structures is the connections, which are divided into three main categories of fixed, semi-rigid and joints, according to
the different criteria provided in the guidelines and codes. Perhaps the main challenge facing civil engineers has been designing efficient connections against lateral loads (seismic loads, wind loads). This issue has received more and more attention from designers due to the poor performance of the fasteners against lateral loads. Investigating and evaluating semi-rigid connections as one of the main part of steel structures against various loads, especially lateral... 

Existing design methods for steel frames has been improved over the last three decades in order to incorporate the behavior of semi-rigid steel connections in furtherance of frame design and since the analysis and design of structures is often done based on the assumption of completely rigid or pinned behavior,therefore, the actual behavior of connections and their modeling can help to understand the actual behavior of structures.Knowledge of the initial rotational stiffness of the connection is important for elastic analysis of structures. Investigations show that structures with semi-rigid connections have many features which are the causes to prefer these kinds of connections to the... 

Today steel tubular systems are used more than before, especially in recent years. A difficulty with this type of systems is making beam to column connections using bolts due to no access to holes of bolts from the inside of tube or hollow circular column. Reverse channel connection is devised and introduced to prevail this problem. Access to holes in this connection is from the inside of channel. In this connection, the web of the channel is connected to steel beam using bolts and the two legs of channel is welded to face of tube column.
This type of connection does include some innovations; not too many researchers work on different versions of this connection. This thesis provides an... 

The human brain can be described as a dynamic system with multiple subsystems interacting with one another and multi-channel observations of these subsystems are available. The modeling of a system from its observations allows us to gain insight into how its various components interact with one another and also provides intuition about the desired system. Hidden Markov Model (HMM) is a probabilistic model with hidden states that is suitable for modeling these types of systems. Multi-channel observations are available from several subsystems interacting with each other within a general system. In this case, it may be necessary to develop more comprehensive models incorporating multi-channel... 

The study of bolted moment end-plate connections, both beam to column and beam to beam connections, is quite general and standard nowadays. Buildings which utilize such connections are widely being used and the reorganization of their significant benefits is growing. The research work reported in this thesis presents the results of several parametric analyses to determine the moment–rotation curve of bolted moment end-plate connections utilizing Rectangular Hollow Sections (RHS) and two rows of bolts using Finite Element Modeling (FEM). Previous experimental studies have focused on the moment-rotation relationship under pure bending. This project particularly involves further numerical... 

Autonomous Vehicles have received much consideration in different trends in recent two decades. Autonomous Vehicles refer to vehicles that can drive without a driver and perform all driving tasks automatically, so eliminating the driver's role can affect various aspects. In this research, the effects of Autonomous Vehicles on the improvement of the traffic condition is studied. To this end, freeway’s performance parameters including travel time and traffic speed at the time of a traffic accident in mixed traffic conditions have been simulated. Considering that the braking behavior, acceleration, and speed changes of the Autonomous Vehicle are effective on the evaluation parameters, five... 

The use of concrete and steel composite structural systems has been extensively studied both numerically and experimentally. Composite concrete and steel beams consist of a steel beam on which the concrete slab is constructed using shear connections. The performance of concrete slabs and steel beams in steel composite concrete structures is generally provided by welded shear connectors on the upper flange of the steel beam. In this study, a more accurate model in numerical form will be conducted to investigate the effect of shear connectors installed in the composite beam in the critical area of beam to column connection, which is considered as a protected zone. The main objective of this... 

In this thesis we study Manin’s proof of Mordel conjecture for function fields in characteristic 0 and restate it using modern algebraic geometry language. First we define an important tool for study of geometry of varieties over function fields: Gauss-Manin connection. Then we study Picard-Fuchs equations as a tool for translating geometric information about variety to arithmetic information. Finally we study height functions over function fields and their relations with Picard-Fuchs equations  

In this thesis, we consider a simple layered structure grown along [001] direction. Based on the previous works we show that the energy spectrum contains linear Dirac spectrum of type II tilted in some direction. We also investigate the anomalous transport phenomena in the bilayer structures grown along [111] direction of a class of perovskites. The crystal field splits the d orbitals into two classes dubbed as eg and t2g described by different Hamiltonians within each manifold. An applied magnetic field breaks the time reversal symmetry and we show that the tight-binding bands acquire non-zero Chern numbers underlying the existence of non-trivial band topology in these structures. Again... 

A quasi-Z-source inverter is a beneficial structure in photovoltaic applications. In a transformerless grid-connected inverter system, the common-mode voltage fluctuations cause the leakage current flow through the ground. The low-frequency harmonics of the common-mode voltage results in the malfunction of the residual current device. On the other hand, the high-frequency harmonics of the common-mode voltage cause EMI problems, additional loss and disturbance in the output currents. In this thesis, some methods are presented to reduce the leakage current in a three-phase quasi-Z-source inverter. First, different shoot-through implementation methods are investigated. By modifying the number... 

In addition to improving on current services, future mobile networks will need to support new services types. Two of the envisioned services are enhanced mobile broadband (eMBB) and ultra-reliable low-latency communication. The unprecedented requirements of the new services are out of the reach of current networks, moreover, the diverse characteristics of the new services poses great challenges to the network designers. One of these challenges is designing an efficient resource allocation algorithm that effectively deals with different timescales that the URLLC and eMBB services operate at. A promising enabling technology is multi-connectivity. Multi connectivity is defined as using spatial... 

The purpose of the current study is to investigate the base metal capacity of stiffened seated angle connections and to inspect their behaviour. The effect of different parameters on the capacity of connections is examined, considering the damage in the column. This research is important since for welding design, codes require the designer to control the base metal capacity to check the connection capacity, while the method of calculating this capacity is not provided, and this issue is not considered in the design. In this research, ABAQUS finite element software was used to model and analyze the results. A total of 90 stiffened seated angle connections, which were connected to the flange... 

Distributed generation (DG) technologies have achieved an intense progress during the last years. One of the appropriate ways to enter a DG system in the electrical network is through the use of microgrids. Because the majority of DG units are connected to the grid with power electronic converters, specific control strategies have been developed for these converters. Control strategies of DGs in microgrid differ in the grid-connected and the islanded states of operation. Changing the control modes from one state to another requires a reliable islanding detection method, and results in unwanted transients. It is, therefore, desirable to devise an integrated control approach for both states.... 

In the present study an air supply system of a connected-pipe ramjet test facility for liquid fuel ramjet engine in theoretical and numerical base designed and optimized that the purpose is for performance test of a ramjet engine combustor in flight condition. The flight condition gained from previous assessment that is 1.5 kg air in 10 bars and 550 K. Air supply subsystems consist of air tanks, compressors, valves, regulators, preheater, and fuel and oxygen systems that are designed in a preliminary process and then valves, orifices, and fuel and oxygen systems optimized by HYSYS program. In the last step preheater that is a gas turbine combustor investigated and possible changes made by... 

In recent years, composite systems comprised of reinforced concrete columns and steel beams, have taken consideration. This system took its own advantages both from steel and concrete systems. Joints of this system categorized into through-beam-type and through-column-type. In this research, after reviewing past studies, two kinds of the joints were modeled in ABAQUS finite element program and seismic performance of these two joints were evaluated. These two selected joints were tested by Chin-Tun Chen and Cheng-Chih Chen ( ) and also Hiroshi Kuramoto and Isao Nishiyama ( ). After verifying the finite element model with the experimental studies, a parametric study were conducted on the steel...