Sharif Digital Repository

Block shear failure in the parent material is considered as a common potential failure mode in welded connections used in steel structures. However, there is only little research reported on the block shear failure of welded connections under multiaxial loading. Multiaxial loading is defined as loading not parallel or perpendicular to weld lines and in the case of in planar eccentricity results in torsional loads. In this research a nonlinear finite element model is developed to study the effect of connection geometry, weld group configuration, and eccentricity of lap splice connection on block shear capacity. The case studied concerns a 3 milimeter thick structural steel plate (CSA G40.21... 

One of the biggest problems in improving the performance of submersible propellers is the acoustic standard in conventional propellers. Recently, new solutions in propellers geometry have been used to reduce non-cavitation noise. Designing CRP licenses is one of these methods. This research includes numerical analysis. Numerical analysis in this research solves RANS equations of flow and extraction of hydrodynamic parameters and impeller noise in Ansys software. The results of numerical hydrodynamic solution are validated by laboratory results.DTMB 4119 three-blade propeller is used for hydrodynamic and hydroacoustic validation. The solution of Lighthill equations by FW-H method is... 

There are many different opinions about the mass transfer contribution during jet formation in liquid - liquid extraction columns, and this could impact on their design. In this work, using experimental data obtained in two RDC columns and unpublished data of the jet mass transfer coefficients, mass transfer can be predicted during jet formation. The jet length and diameter were anticipated by using existing relations, and then the jet mass transfer coefficient was predicted, jet mass transfer rate and total column mass transfer rate were calculated and finally the contribution of mass transfer during jet formation in the column was predicted. Mass transfer contribution in the jet in various... 

Knowing the exact position of the robot in real world is one of crucial and important aspects of its navigation process. For this purpose, several inertial sensors such as gyroscope, accelerometer and compass have been used; however, each one of these sensors has its own drawbacks which cause some inaccuracies in some specific situations. Moreover, the Global Positioning System (GPS) is not available in indoor environments and also not accurate in outdoor places. All of these reasons have persuaded researchers to use camera frames captured from the top of robot as new information for estimating motion parameters of the robot. The main challenge for vision aided localization algorithms is... 

Ni-SiC composite coatings are widely used in industry (equipment high wear resistance coatings, corrosion resistant coatings, ship and boiler coatings, . . . ). Its unique properties in high wear resistance, corrosion resistance and tribological properties, researchers tend to investigate this coating. This study covers Ni-SiC composite coating under pulsed current using a rotating disk electrode to achieve optimal conditions in synthsis process, increaseing hardness and resistance to corrosion in coatings.waats' bath established for electrodeposition in this research. Bath parameters, current parameters and hydrodynamic of solution is examined. Changing of current type from direct current... 

Epilepsy is one of the most common non-communicable neurological disorders, characterized by recurrent seizure symptoms. Although much progress has been made in the diagnosis, control, and treatment of epilepsy in recent years, the exact mechanism of seizures, the specific method for early diagnosis of epilepsy and related syndromes, and definitive treatment for all patients are not yet known. In a type of seizure known as focal seizure, the electrical activity of neurons at the epilepsy focus synchronizes abnormally, and this synchronization can propagate to other regions of the brain in a process called secondary generalization, which finding a method for its prevention is our essential goal... 

The physical description of particles states in the quantum theory are characterized by means of theirs mass and spin. The inertial and gravitational properties of mass are already well known in mechanics and gravitation theories as well as their quantum counterparts. In spite of mass, the inertial and gravitational properties of intrinsic spin are not studied that much.In this thesis we review the inertial and gravitational properties of intrinsic spin. Initially we explore the general procedure to formulate Dirac equation in arbitrary curved spacetime. Then we write Dirac equation in Kerr spacetime to draw physical conclusions about the interaction of Dirac particles with the Kerr... 

In this study, stability as well as linear and nonlinear vibrations of coaxial rotating cylindrical shells conveying annular incompressible fluid medium are investigated. To this aim the inner isotropic and elastic rotating cylindrical shell along with the rigid and stationary outer cylinder are considered. Equations of motion for the inner cylinder are determined according to the Hamilton’s principle and using the Sanders-Koiter theory assumptions. In order to generalize the boundary condition implementation, some translational and rotational springs are attached to the boundaries at the mid-plane. The final system of equations are solved by means of the extended Galerkin method – being an... 

This thesis presents the development of a Finite Element Model (FEM) for a new type of Beam-Column Semi-Rigid steel connection. This connection consists of a steel semi cylinder connected to a plate and inserted on the top and bottom of the beam connecting it to the column by welding. It seems that changing the geometry of the semi cylinders and their weld lengths can have a great influence on the rigidity or flexibility of the connection. Therefore, meaningful categories of the connection with different semi cylinder geometries and weld lengths have been modeled and investigated by means of a Finite Element Modeling software ABAQUS, and their moment-rotation curves were driven. Also 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... 

Connections have a crucial role in the behavior of every structure. Amongst various types of connections used in steel structures are those used to connect the columns to the foundations, namely Base Plates. As other types of connections, base plates control the behavior of the structure in various respects including affecting the effective length of columns. The main task of any base plate is to distribute the forces of the column on the foundation in such a manner that the stresses in concrete are below their allowable values. Different configurations, with or without various attachments, are used for designing the base plates hence achieving various types of behavior with various levels... 

In this study the concept of the origin of life, as an important question, is investigated and reviewed.Then the possibility of the beginning of life from an extraterrestrial origin is studied via spectroscopy methods to analyze the role of the cosmic waves.Moreover, by considering the similarity between the chirality of the essential amino acids and extraterrestrial amino acids, found in meteors the various methods for studying the structure of molecules, as well as the possibility of the transfer of the central elements of life from space to the earth are reviewed in details.Finally, we suggest how chirality might be emerged due to the interaction of the molecule with the environment,... 

A special steel beam-to-column connection, named Khor-jini, is commonly used for steel framing system in Iran. In this system, two continuous beams are passed next to the columns and are connected to the column side using seated brackets.This type of connection has been common in Iran from the late past. Unfortunately, the seismic behavior of Khorjini frames had not been sufficiently studied prior to Manjil Earthquake of 1990. Due to very large damages which occurred in steel structures especially in connections during the said earthquake, the seismic behavior of this type of connection was studied and some of its weak points were recognized.In this study non-linear... 

The purpose of this research is to study the behavior of conventional and retrofitted Khorjini connections. Thus the software ABAQUS 6.11 was used to fabricate the FEM models of the connections with experimental prototypes. In analytical studies, 21 specimens with different size 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 were considered by a micromechanical method. Behavioral characteristics of the conventional connections are specified and appropriate relations are suggested, using Stability equations of the connection... 

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... 

Due to the important role of base plates, both in transferring forces from the structure to the foundation, and also in transferring vibrations from soil to the structure, it is necessary to have sufficient knowledge on their behaviour and performance under monotonic and cyclic loading regimes. In fact, the behaviour of the supports of any structure cannot be identified without identifying the behaviour of its base plates. Numerous configurations with/without various types of attachments have been proposed and used for base plates. In this work, altogether six commonly-used types of base plates were studied and their behaviour under monotonic and cyclic loadings was obtained using commercial... 

Labneh is a semisolid product that is produced by concentrating milk to approximately 23% total solids (wt/vol) by the traditional cloth bag method, ultrafiltration and direct reconstitution. For ultrafiltration membrane processing is carried out either before or immediately after fermentation. The effect of storage time on the flow properties of concentrated yogurt (labneh) was investigated using a rotational viscometer. Experiments were performed at after 0, 2, 5 and 14 days after production. The apparent viscosity of fresh sample was then measured as a function of shear rate. For a given shear rate, the apparent viscosity was measured as a function of shearing time. The increase in the... 

Aiming to improve the extraction performance of wind energy has led to the noticeable increase of the structural dimensions in the modern wind turbines. The larger blade with more flexibility experiences large structural deformation even under nominal operational loading, so the nonlinear modeling and analysis of these structures have become as important subject of the recent wind turbine researches. In this dissertation, the geometrical exact model of the rotating wind turbine blade under the effects of the tower tip's motion, and also the operational loading comprising the aerodynamic and gravitational loadings is presented. In this way, the geometrical exact beam formulation is developed... 

The objective of this research is to investigate the basic design challenges of a first stage turbine nozzle in a constant volume combustion (CVC) gas turbine engine. In general, CVC cycles have higher thermal efficiency and specific power despite their unstable combustion phenomenon which is due to moving as well as oscillating shock waves with a specific frequency and amplitude and resulting in a challenge to the engine designer. In this thesis, first, the performance parameters of CPC and CVC cycles are introduced and compared. Further, a model is developed to examine the flow non-uniformity, entropy generation, cycle thermal efficiency, and specific fuel consumption of a flow through the... 

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...