Loading...
Search for:
ebrahimi--ali-reza
0.155 seconds
Total 4500 records
A Gluing Construction for Calabi-Yau Metrics of Kummer Surfaces
, M.Sc. Thesis Sharif University of Technology ; Esfahanizadeh, Mostafa (Supervisor) ; Seyyed Ali, Reza (Co-Supervisor)
Abstract
let T4 = C2/ be a complex torus with induced flat Kähler metic. The quotient X = T4/Z2 (where the generator of Z2 acts by multiplication by −1) is an orbifold with 24 singularities, called a singular Kummer Surface. Locally any of the singularities are modelled on the singularity of C2/Z2. We can describe the minimal resolution X of X by resolving all of the singularities as : TCP1 ! C2/Z2.There is a well known Calabi–Yau metric on TCP1 named the Eguchi–Hanson metric, with the important property that far from the exceptional divisor −1(0) the metric is asymptotically locally Euclidean (ALE). We identify a small annulus around any singular point of X/Z2 with a large annulus over TCP1 far...
Investigating the Effect of Patent Activities on the Centrality Indices of Scientific Collaboration Network of Faculty Members in Selected Iranian Universities
, M.Sc. Thesis Sharif University of Technology ; Mirnezami, Reza (Supervisor)
Abstract
Scientific collaboration and the resulting outputs have been always of interest to the scientific community. Specifically, drawing and understanding the elements of scientific collaboration network and identifying its determinants are important step in prescribing and implementing policies in various fields and disciplines of science. Focusing on the Iran context, this study examines the scientific collaborations of faculty members in selected Iranian universities (Sharif University of Technology, University of Tehran, Iran University of Science and Technology, Amirkabir University of Technology, Isfahan University of Technology, and Ferdowsi University of Mashhad). We have drawn the...
Design and Construction of Fluorescent Confocal Microscopy Setup for Detection of Single Photon Emitters in 2d Materials
, M.Sc. Thesis Sharif University of Technology ; Esfandiar, Ali (Supervisor)
Abstract
The main goal of this research is to detect and characterize single-photon emitters in two-dimensional hexagonal boron nitride crystal with the help of fluorescence confocal microscope and Hanbury-Brown and Twiss interferometer. The origin of single-photon radiation in this crystal is not precisely known. It seems that the transition between energy levels, which occurs due to the presence of point defects in the crystal structure of this material, in the distance between the conduction and valence bands, is the source of single-photon radiation. This material does not require low temperature for single-photon radiation, which is an important advantage for it. In a confocal microscope, the...
Cracked Rotors Modeling for Vibration Analysis and Control
, Ph.D. Dissertation Sharif University of Technology ; Behzad , Mehdi (Supervisor) ; Meghdari, Ali (Supervisor)
Abstract
The main aim of this thesis is to develop a mathematical model for vibration analysis of cracked rotors. This model should be a simple and precise model for prediction of the cracked rotor vibration behavior and suitable for vibration control. In order to create such model, the pure bending of a cracked beam is analyzed at first. This analysis is performed for two different orientations of the crack with respect to the beam and the bending vector. In this section a continuous bending model with continuous model for crack is developed which can predict the full deformation of the cracked beam in bending and can estimate the stress distribution in the beam with good approximation. Comparison...
Investigating Effects of Interphase on Mechanical Properties of Particulate Metal-Matrix Nanocomposites Using Surface Elasticity
, M.Sc. Thesis Sharif University of Technology ; Naghdabadi, Reza (Supervisor)
Abstract
Due to ignoring the effect of length scale and neglecting the details at nanosize, classical methods are not sufficiently accurate to determine the properties of nanostructured materials. More reliable results can be obtained, using surface elasticity theory. Lots of analytical, experimental and numerical investigations have been done on the effect of interphase on the mechanical properties of polymer nanocomposites whereas metal matrix nanocomposites are in the first stages of analytical and numerical researches and have attracted so much attention.
The main objective of this research is to investigate the effects of interphase as well as coating, on the mechanical behavior of metal...
The main objective of this research is to investigate the effects of interphase as well as coating, on the mechanical behavior of metal...
Evaluation and Simulation of using Magnetite as Heat Transfer Medium in Direct Solar Absorption Collectors
, M.Sc. Thesis Sharif University of Technology ; Mohammadi, Mohammad Reza (Supervisor)
Abstract
In this study, application of a Magnetic Nanofluid consisting of Magnetite as Nanoparticle and Water as base fluid in DASC systems is investigated. The DASC system is modeled theoretically and behavior of such system is predicted.In this study a comparison between magnetite Nanofluid and some other common Nanofluids is conducted. The study shows that Magnetite Nanofluid has a better performance and efficiency than Water, Al2O3 Nanofluid and SiO2 Nanofluid. Also magnetite Nanofluid and TiO2 Nanofluid function are almost similar.Also effect of external magnetic field on the performance of magnetite Nanofluid is investigated. It is showed that when the magnetic Nanofluid is subjected to an...
Feedback control of the neuro-musculoskeletal system in a forward dynamics simulation of stair locomotion [electronic resource]
, Article Proc. of IMechE Part H: Journal of Engineering in Medicine ; 2009, Vol. 223, No. 6, pp. 663-675 Journal of NeuroEngineering and Rehabilitation ; Volume 11, Issue 1, 30 April 2014, Article number 78 ; Meghdari, Ali ; Vossough, Gholam Reza ; Sharif University of Technology
Abstract
The aim of this study is to employ feedback control loops to provide a stable forward dynamics simulation of human movement under repeated position constraint conditions in the environment, particularly during stair climbing. A ten-degrees-of-freedom skeletal model containing 18 Hill-type musculotendon actuators per leg was employed to simulate the model in the sagittal plane. The postural tracking and obstacle avoidance were provided by the proportional—integral—derivative controller according to the modulation of the time rate change of the joint kinematics. The stability of the model was maintained by controlling the velocity of the body's centre of mass according to the desired centre of...
Direct Numerical Simulation of Heat and Fluid Flow through Porous Channel
, M.Sc. Thesis Sharif University of Technology ; Nouri Boroujerdi, Ali (Supervisor)
Abstract
In this project, direct numerical simulation of fluid flow inside the porous channel is carried out. The flow channel is containing uniform array of solid blocks with square cross sections in an staggered scheme. Two thermal boundary conditions of constant temperature and constant heat flux of solid blocks were applied to the problem. The Navier-Stokes equations directly applied to the fluid region with no assumption of volume-averaging. Governing equations of two-dimensional flow with constant properties were discretized with control volume method. Energy equations for solid and fluid phases were solved separately. The results show that for solid block lengths over channel height, a/H=0.05,...
Simulation of the Local Strain Effect on Deformation of a Steel Part
, M.Sc. Thesis Sharif University of Technology ; Karimi Taheri, Ali (Supervisor)
Abstract
One of the methods of forming the metal parts is to apply a localized strain field to the workpiece. This field can be generated by creating a deformation in an actuator connected to the workpiece, or directly by a localized imposing heat (thermal localized strain) to the workpiece. For example in laser forming process, the workpieces in the forms of sheet and tube can be deformed by creating localized strain field induced from thermal field caused by laser irradiation. The main mechanisms in laser forming are temperature gradient mechanism, upsetting mechanism and buckling mechanism. It is worth mentioning that until now, the localized strain field induced by laser irrediation is...
Simulation of Retrogression Process Effect on Mechanical Properties and Formability of Precipitation-Hardenable Aluminum Alloys
, Ph.D. Dissertation Sharif University of Technology ; Karimi Taheri, Ali (Supervisor)
Abstract
A common heat treatment used for hardenable aluminum alloys is the retrogression process. In this process, by dissolving a specific precipitate in the alloys (η'), the strength of the alloys is reduced and their formability is enhanced. However, by applying the retrogression process and deforming the alloy, followed by an aging cycle, the strength returns to its original state. In this project the microstructural evolution during the retrogression process in 7075-aluminum alloy has been primarily studied experimentally with the help of a transmission electron microscope and the effect of retrogression time on the microstructural evolution has been assessed. In addition, since the simulation...
Nonlinear Modelling of Return and Volatility in IRANs Auto Industry
, M.Sc. Thesis Sharif University of Technology ; Keshavarz Hadad, Golam Reza (Supervisor)
Abstract
Long memory in assets return is important on the theoretical as well as the practical aspects and since it is a special form of nonlinear dynamics, in this study an ARFIMA model was used with the aim of considering the long memory in the return conditional average of automobile industry index. Then, due to the observation of ARCH effects, the simultaneous conditional average modeling and turbulences in the automotive industry index return using an ARFIMA-FIGARCH model was considered in the residuals of the best fitted model and results were that for modeling the returns and turbulences of automobile industry stocks which has a special long memory, FIGARCH will provide better and more...
Feasibility Study of RFID Application for Items Tracking and Identification in Chain Stores
,
M.Sc. Thesis
Sharif University of Technology
;
Akbari Jokar, Mohammad Reza
(Supervisor)
Abstract
Today, using Radio Frequency Identification (RFID) technology is of a remarkable interest to the industry and services sectors. Application of this technology could result in higher levels of productivity and effectiveness. On the other hand, department stores are increasing in number and size in the country. Application of RFID technology could play an undeniable role in both reducing the time each customer must spend in order to complete their purchase, and accelerating the logistics operations of these stores.
Through literature review, this research studies application of RFID technology instead of other identification technologies such as Bar-Code, reveals strengths and weaknesses...
Through literature review, this research studies application of RFID technology instead of other identification technologies such as Bar-Code, reveals strengths and weaknesses...
Developing an Applied Model for Energy Management in Dairy Production Industry
, M.Sc. Thesis Sharif University of Technology ; Mokhtar, Ali Reza (Supervisor) ; Miremadi, Ali Reza (Supervisor)
Abstract
Reviewing trends of energy consumption in the world reveals that sooner or later energy resources will be depleted. This concerning rate of consumption has brought about more greenhouse gases (GHG) emission influencing deleteriously on environment and climate. Human has continued energy consumption to maintain and improve the quality of his life through industrial production. Industry as a significant energy user owns considerable contribution to this consumption. Several attempts have been carried out to develop energy management systems in order to improve the energy efficiency of industrial sectors. Whilst they are comprehensive and could be applied to any sector, there is lack of...
Simulation of Structure Formation in The Presence of Fuzzy Dark Matter Using Gevolution Code
,
M.Sc. Thesis
Sharif University of Technology
;
Abolhasani, Ali Akbar
(Supervisor)
Abstract
n this thesis, the formation of cosmic structures in the presence of fuzzy dark matter (FDM) is investigated using the Gevolution code. In the FDM model, dark matter is composed of ultralight bosons. In fact, the mentioned bosons are the remnants of a scalar field present in the early universe. Simulations of structure formation in the presence of FDM that have been carried out so far (for example with Gadget and RAMSES) are based on Newtonian gravity, which have a number of limitations. The Gevolution code is an N-Body simulation that, unlike other existing simulations, is based on General Relativity, which can lead to interesting results. In fact, in this simulation, the weak field limit...
Developing an Analytical Model with Experimental Verification of Tapered Cantilevered Piezoelectric Vibration Energy Harvester
, M.Sc. Thesis Sharif University of Technology ; Hosseini Kordkhaili, Ali (Supervisor)
Abstract
Evolution of electrical devices and the need for wireless sensor and remote control has led to extensive research in field of energy harvesting. Regarding this approach, most studies devoted to use of piezoelectric effect in converting the dissipative vibration energy into usable electrical energy. Despite extensive progress made in this field of engineering, there were no significant growth in analytical solution and implementation of mathematical equations related to dynamic and electricity of piezoelectric harvester of beams with different geometries. The main focus of this thesis is solving constitutive and coupled electromechanical equations of piezoelectric harvester related to a...
An Experimental Study of the Effects of Sweep Wing on the Boundary Layer of 2D Wing
, M.Sc. Thesis Sharif University of Technology ; Soltani, Mohammad Reza (Supervisor) ; Davari, Ali Reza (Co-Advisor)
Abstract
The behavior of boundary layer under the effect of the sweep angle is considered. The measurements were performed by a pitot tube rake. Three models with various sweep angels at angles of attack -2, 0 and 2 degree were tested. Both tip and root of all wings were closed by flat plates in order to prevent the flow to roll-up. However the flow field on the wing was still three-dimensional because of the sweep angle. The velocity on the wing has two components; longitudinal and lateral. The cross flow emerges due to the non-equilibrium of pressure and centrifugal forces. The velocity profiles showed that the magnitude of cross flow was stronger near the leading edge of the wing. The cross flow...
Optimal Batch Production for a Single Machine System with Rework
, M.Sc. Thesis Sharif University of Technology ; Haji, Ali Reza (Supervisor)
Abstract
This research attempts to develop the optimal solution for an inventory problem consisting of a single machine which produces items some of which may be defective. We assume that no shortages are allowed and all defective items are to be reworked. Setup cost for rework and waiting time of defectives are considered. This research consists of two different parts. In the first part we consider two different policies where in the first policy in each cycle after the regular production the machine is setup for the rework of defectives of the same cycle. In the second policy several cycles constitute a period. All the defectives produced in the period are reworked in the last cycle of that period....
Improving the Reliability of Energy Harvesting Wireless Sensor Networks
, M.Sc. Thesis Sharif University of Technology ; Ejlali , Ali Reza (Supervisor)
Abstract
Energy harvesters are used in today’s Wireless Sensor Networks (WSNs) to harvest the energy from the environment. One of the important advantages of the energy harvesting sensor networks over battery-operated sensor networks is that the use of the energy harvester prolongs the life time of the nodes, while a battery-operated node becomes useless once its energy runs out. Although an energy harvester can provide a supply source with a lifetime much greater than a battery, the amount of available energy for an energy harvesting system is a random variable and is not as predictable as the energy of a battery. This unpredictability may cause reliability problems. In order to solve the existing...
Energy Management in Energy Harvesting Wireless Sensor Nodes
, M.Sc. Thesis Sharif University of Technology ; Ejlali, Ali Reza (Supervisor)
Abstract
Wireless Sensor Networks have become widespread because of their flexibility, applicability and ability to precept data with high accuracy. However, the most limiting factor in their usage is the amount of available energy in nodes since energy depletion in a node means that it is dead, therefore many efforts have been done for optimum energy management in Wireless Sensor Networks. In many cases, the key solution to prolong the network lifetime is load balancing. In this way, all the nodes will die (approximately) together and the lifetime of network will be maximized. Load balancing can be implemented in all layers from physical layer to application. It should be noted that it is not always...
Gaining Competitive Advantage through Marketing Strategies in Container Terminal: A Case Study on Shahid Rajaee Port in Iran
, M.Sc. Thesis Sharif University of Technology ; Miremadi, Ali Reza (Supervisor)
Abstract
The competitiveness of a port convinced shipping lines and shippers with a significant basis in selecting a port. Port authorities and port operators can make use of the competitive advantage as a parameter for counter measures by grasping the advantages and disadvantages of the ports and be a prime factor of opportunities and threats of the ports. Ports have a significant role in today’s networked business environment. They are being regarded as hubs that are part of various logistic systems. The very essence of a seaport is to link maritime networks and land network. These networks for the port are means of analyzing its competitiveness. A port overall competitiveness is determined by it’s...