Sharif Digital Repository

A high percentage of reinforced concrete buildings are not earthquake resistant because they are often designed based on old regulations, which do not satisfy the requirements of new earthquake codes. Construction weaknesses make buildings more vulnerable, and thus, different approaches are needed to strengthen structures to resist lateral forces. 3D Panel system brings together the best qualities of in-situ and precast systems and improves their shortcoming. It includes the advantages of precast systems, such as having relatively low labor costs, less waste material and machinery, reducing implementation time and improving quality control. At the same time, serious problems related to... 

In this thesis the behavior of a 3D wing has investigated by Flow visualization and pressure acquisition test. The goal of this tests was considering changes in 3D wing section parameter in comparison with 2D airfoils. The performed Tests showed that variation in 3D wing treatment is affected by finite aspect ratio and sweep angle and also indicate changes in pressure profile, increasing pressure peak and decreasing effective speed. CFD studies has conducted to investigate special effect of sweep angle and show that lift and drag coefficient decrease with increasing sweep angle. Also different section pressure profile near the wing tip and intersection of wing/fuselage varies and miss... 

Combination of 3D IC technology and network on chip (NoC) is an effective solution to increase system scalability, and also alleviate the interconnect problem in large scale integrated circuits. However, due to the increased power density in 3D NoC systems and the destructive impact of high temperatures on chip reliability, applying thermal management solutions becomes crucial in such circuits. Since hardware thermal control techniques, such as DVFS, can cause significant degradation on chip performance, in this thesis we propose a runtime distributed migration algorithm based on game theory to balance the heat dissipation among processing elements (PEs) in 3D NoCs. The objective of this... 

Fatigue crack is one of the most important causes of defect for gear systems. This effect results tooth fracture and failure of other elements of the power transmission systems. As a result, much effort has been devoted to the modeling of fatigue crack and improving the methods of crack detection. Simulations of three dimensional crack growth in spur gears due to misalignment and examination of this effect on vibration response of gear system are the main goals of this research. To model the crack growth, a new method of gear meshing modeling was proposed. In this method, the effects of pinion on the gear and vice-versa are modeled by a finite set of virtual interconnected springs. The... 

In this research, a novel quasi-3D design method is developed for the centrifugal compressor impeller on the blade-to-blade plane. In this method, an iterative inverse design method called Ball-Spine Algorithm (BSA) is incorporated into the quasi-3D analysis code solving the Euler equations on the blade-to-blade and meridional planes at each shape modification step. In design procedure, the difference between the target and current pressure distribution along the suction or pressure sides of the impeller causes the blade-to-blade profile to be changed and the target pressure distribution to be satisfied. In order to validate the quasi-3D analysis code, the centrifugal compressor of a gas... 

Combination of 3D stacking and network-on-chip (NoC), known as 3D NoC, has some advantages such as reduced propagation delay, chip area and interconnect, and power consumption, and bandwidth increase. Despite these advantages, the increased power density per chip area due to area decrease causes thermal problems in 3D NoCs to be more critical than 2D NoCs. Therefore, design of temperature management algorithms is essential for these systems. One of the dynamic thermal management techniques is task migration that balances generated thermal among cores.In this thesis, we propose a task migration scheme using feedback control for 3D NoCs. The main purpose of this scheme is to decrease the peak... 

The purpose of this research is theoretical and numerical investigations on centrifugal compressor. A computer code has been developed to simulate single-zone and two-zone model, based on the revised formulation for real gas, using Peng-Robinson equations. Single-zone modeling, also known as meanline method, established based on 1-D equations of fluid dynamics considering ideal gas relations, empirical loss correlations, slip factors, impeller efficiency and no wake or separation regions. Considering usual significant separated regions in the gas path of impellers, two-zone (jet and wake zone) model has been developed to achieve a more reliable simulation by using fewer correlations based on... 

In this study some experiments were performed to investigate the effect of sweep angle on the transition location of laminar flow to turbulent flow. Three half wing models were used, each having a different sweep angle but with the same aspect ratio in various angles of attack. Two flat plates were used at the ends of the swept wing models to prevent the flow from rolling up over the wing. By simulating flow over infinity swept wing by eliminating tip vertices, the effect of sweep angle on flow transition phenomenon was investigated.
The experiments included the study of transition flow via hot-film sensors, which were glued on the wing surface. We found that the small leading-edge... 

Due to the physical limitations of the conventional 2D ICs at Giga-Scale Integration, modern technologies have been emerged. Among them, through silicon via (TSV) - based 3D ICs have been used to continue Moore’s law in the interconnect era. In these systems, dies are stacked at z-direction after wafer thinning. Electrical connections between stacked dies are done by TSVs. One important advantage of 3D integration technology is their ability to stack heterogeneous systems with different technologies on a single chip. This will not only increase interconnect density but also will reduce the delay and power consumption. However, nowadays, fabrication and optimum design of TSVs are still big... 

Passive energy dissipation systems are mechanical devices which could spread input energy, reduce response and decrease possible damage of the structure. Dampers were identified as a strong energy dissipation devices with cost efficiency and easy installation and maintanance. In this study, effects of using friction and metallic yield dampers to reduce structural responses are investigated. In addition, a comparison between these devices for reducing responses are conducted. Two 5 and 10 stories buildings with intermediate steel moment frames with and without damper are modeled and designed. It is seen, using of dampers could be reduce sections’ sizes. Seven pairs of earthquake records... 

Today many videos in an interval of a particular scene in a different view angle to each other are filmed. Use these videos are used in numerous fields. Time synchronization between the video, is the basis for their use. In order to provide an automated process for creating time synchronization between the video, numerous studies have been conducted that each requires specific conditions are to achieve the desired result. The biggest challenge of this problem, which appears when the camera recorded video viewing angles, high and low, and when filming the shared vision between them, jump frames is taken. Players are coordinated. In experiments conducted on different data sets, the average... 

The main subject of this thesis is to improve conventional CFD algorithms applied in numerical simulation of inviscid unsteady flows around moving boundaries with large relative motions, on unstructured grids. All challenges in this regard are reviewed, and appropriate efficient schemes are introduced to address them. A new scheme is presented for valid grid generation during grid movement and is implemented for 2D and 3D problems. Customary three dimensional convergence acceleration techniques such as implicit time stepping and multigriding have been applied. For implicit solution of the flow equations a new algorithm is used. Via a special renumbering algorithm, the approximate... 

Isogeometric Analysis method is a newly introduced method for the analysis of problems governed by partial differential equations.The major difference between classic finite element method and isogeometric method is that FEA uses piecewise polynomial shape functions for analysis while the Non-Uniform Rational B-Splines (NURBS) functions are applied as basis function in isogeometric method. To model strong discontinuities like cracks in classical finite element method , very fine mesh near the crack tip must be used. Application of eXtended Finite Element Method (X-FEM) avoid making very fine mesh near crack tip which is a time consuming task. In the extended finite element method , a... 

Object recognition is a field of image processing with the purpose of object detection and determining its pose. There was a wide research of object recognition using 2d information. These methods are less efficient due to their sensitivity to view and scale. Today with development of 3d technology, 3d reconstruction of objects has been eased, thus there is a new trend of 3d methods. 3d object recognition uses 3d data and model to recognize objects more efficiently in different views and in occlusion and clutter. The related works are classified in three category of view-based, feature matching, and classification. In this research we attempted to improve one of the best feature matching... 

Today, the use of carbon nanostructures hybridized with noble metals has attracted considerable attention for the fabrication of bio-electrochemical sensors. Since the specific surface area has an immense effect on the sensing response, three-dimensional structures of graphene have a great capability to utilize in these sensors. In this research, three-dimensional graphene was provided on the porous nickel foam by chemical vapor deposition technique. By evaluation of raman spectroscopy, the time period of 20 minutes for solving of the carbon atoms into the nickel foam was selected as the main parameter of optimized conditions for the synthesis of graphene. Afterward, production of few-layer... 

Conventional two-dimensional photos are images of a three-dimensional scene. In fact, since the recording medium record only the intensity of the incoming light, information about the phase of the light couldn't be recorded and this results in making 2D photos from a real 3D scene.
In this research a mechanism for getting three-dimensional images in endoscopy and laparoscopy by Digital Holography has been designed based on the criteria standards in this field.
 

Conventional two-dimensional photos are images of a three-dimensional scene. In fact, since the recording medium record only the intensity of the incoming light, information about the phase of the light couldn't be recorded and this results in making 2D photos from a real 3D scene.
In this research a mechanism for getting three-dimensional images in endoscopy and laparoscopy by Digital Holography has been designed based on the criteria standards in this field.
 

Holography is a lensless process with a unique characteristic of recording a 3D image on a 2D plate! From the first hologram constructed by Gabor, the development of holography found several techniques. For the aim of fabricating holograms of Sharif University of Technology, International Campus-Kish Island’logo, we have chosen transmission and rainbow techniques because of their accuracy and applicability. A recording material is needed for the process. Photoresist was found more appropriate to work on. Besides He-Cd and He-Ne lasers are mostly in use in general holography. The laboratory work is an inseparable part which is achieved at laser and hologram unit of Atomic Energy... 

In this essay we focus on the question of whether a 3-manifold (possibly with bound- ary) like M supports a codimension-1 transversely oriented foliation like F , such that F is transverse to ∂M and does not have Reeb components. If such foliation exists, then ∂M is necessarily a (possibly
empty) union of tori and (based on the works of Novikov, Reeb and Rosenberg) M is either S2 × S1(with F being the prod- uct foliation) or M is irreducible. In a paper by David Gabai, which we discuss, the sufficiency of these conditions is proved in case of non-trivial second homology group.Furthermore, from the works of Thurston it is concluded that compact leaves of such foliation are norm minimizing... 

The goal of this thesis is to survey natural frequencis of nanostructures such as nanobeams and nanoplates using nonlocal theory of elasticity by finite element method. In nonlocal theory of elasticity,the constitutive relation appears as an integral form so that the stress of a point is a function of the strain of all points in the field such that by getting away from the assumed point, the effect of strains on the stress of that point decreases. In fact, the stress on a point is an average of stress in the field and the effect of stress of other points in determined by a function called the kernel function. In order to achieve natural frequencies and shape modes of a structure, we need to...