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daryani--mohammad
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Evaluation of ceramic/ceramic joint interface prepared via brazing
, Article Materials Forum, 18 October 2011 through 20 October 2011 ; Volume 35 , October , 2011 , Pages 20-30 ; 08832900 (ISSN) ; 9781876855369 (ISBN) ; Nemati, A ; Sharif University of Technology
2011
Abstract
Recent investigations show that ceramic/ceramic joints have high potential for applications in industry. Cost and difficulty in manufacturing complex components, either in one step or by joining of ceramic-metal and ceramic-ceramic, have inhibited more widespread use. It is important to know how to join components without problems and to understand the role of the interface as the main factor controlling the properties in these joints. The purpose of this paper was to investigate the joining of two ceramics with metal fillers (SiC to SiC and Al2O3 to Al2O3) and to investigate the interface of SiC/SiC and Al2O3/Al 2O3 with the same metal interlayer (Ag-Cu-Ti) and the effects on the...
An Efficient Algorithm for Graph Sum Coloring Problem
, M.Sc. Thesis Sharif University of Technology ; Eshghi, Kourosh (Supervisor)
Abstract
Graph sum coloring problem is a special case of graph vertex coloring. Because of its applications in practical areas, especially in scheduling, many researchers have been attracted to it. In recent years, several heuristic and metaheuristic algorithms were applied to sum coloring problem. In this research a heuristic algorithm based on mini-max ant system and simulated annealing metaheuristics is used for graph sum coloring problem. This algorithm is tested on random graphs used in the literature and compared with prior algorithms. Results show that in many cases our proposed algorithm reaches the best known results or improves them
Interfacial microstructure and properties of SiC/SiC joint brazed with Ag-Cu-Ti alloys
, Article 11th International Conference and Exhibition of the European Ceramic Society 2009, 21 June 2009 through 25 June 2009 ; Volume 1 , 2009 , Pages 212-214 ; 9781617823848 (ISBN) ; Kokabi, A. H ; Daryani, A. G ; Sharif University of Technology
2009
Abstract
SiC Ceramic was joined to itself using active brazing alloys, like Ti in shape of sheet filler of Ag-cu and Ti-6AI-4V. This operation occurred in an inert gas furnace. Interfacial microstructure was studied with scanning electron microscopy and X-Ray diffraction. Variation of Electrical Specific Resistance measured by 4 pin astute multimeter and strength of these joints was measured by fracture shear loading. This joint happened at 900°C and upper temperature with 90 minutes and upper time. Electrical specific resistance goes up with the joint in low temperature and time but this variation is very little. The microstructure showed excellent bonding at the interfaces. The data showed also...
Dynamic Analysis & Control of a Biomimetic Robotic Fish Employing the Bond Graph Approach
, M.Sc. Thesis Sharif University of Technology ; Selk Ghafari, Ali (Supervisor) ; Meghdari, Ali (Supervisor)
Abstract
In this thesis, a dynamic model of the biomimetic robotic fish with a flexible tail is developed. In this model, the oscillating frequency of the tail controls the forward velocity, and the body spline offset parameter controls the heading angle. The robotic fish were divided to two parts: a rigid body, and a flexible tail. The rigid body includes the head and the electrical and mechanical equipment. The bond graph model was developed and the numerical values were extracted from constructed robotic fish have also been hydrodynamically analyzed. Simulation results were quantitatively compared and verified with Matlab Simmechanics simulations. These simulations described the lateral movement...
Effects of Ti-based catalysts on hydrogen desorption kinetics of nanostructured magnesium hydride
, Article International Journal of Hydrogen Energy ; Volume 39, Issue 36 , December , 2014 , Pages 21007–21014 ; ISSN: 03603199 ; Simchi, A ; Sadati, M ; Hosseini, H. M ; Targholizadeh, H ; Khakbiz, M ; Sharif University of Technology
2014
Abstract
In the present work, the synergetic effect of Ti-based catalysts (TiH2 and TiO2 particles) on hydrogen desorption kinetics of nanostructured magnesium hydride was investigated. Nanostructured 84mol% MgH2-10%mol TiH2-6%mol TiO2 nanocomposite powder was prepared by high-energy ball milling and subjected to thermal analyses. Evaluation of the absorption/desorption properties revealed that the addition of the Ti-based catalysts significantly improved the hydrogen storage performance of MgH2. A decrease in the decomposition temperature (as high as 100°C) was attained after co-milling of MgH2 with the Ti-based catalysts. Meanwhile, solid-state chemical reactions between MgH2 and TiO2 nanoparticles...
Effect of Titanium Compounds on H-kinetics of Nanostructured Magnesium Hydride
, M.Sc. Thesis Sharif University of Technology ; Simchi, Abdolreza (Supervisor) ; Maddah Hosseini, Hamid Reza (Supervisor)
Abstract
Magnesium hydride (MgH2) is an attractive candidate for solid-state hydrogen storage applications. Scanning Electron Microscopy observations showed that during cyclic absorption and desorption considerable micro-crack was formed at the reaction interface and reduced the nucleation time. To improve the kinetic properties of MgH2 during dehydrogenation a nanostructured MgH2-10%mol TiH2-6%mol TiO2 material system was prepared by high-energy ball milling. Isothermal analysis with commercial volumetric sievert demonstrated that the addition of titanium compounds significantly improved the kinetics of dehydrogenation compared to commercial MgH2
Construction of an Experimental Device for Foaming Agent and an Experimental Study of the Properties of Foaming Agent
, M.Sc. Thesis Sharif University of Technology ; Bazargan, Mohammad (Supervisor)
Abstract
The primary purpose of acidizing operations in the oil and gas industry is to enhance hydrocarbon production. Acidizing has been a common and conventional method for years, especially when production engineers face issues like declining reservoir pressure leading to reduced production rates. Initially, the treatment solution is referred to as matrix acidizing. In acidizing operations, different additives are combined with the acid to control its behavior in the reservoir. These additives may include iron control agents, corrosion inhibitors, friction reducers, and more. Incompatibility among these additives, the acid, and reservoir fluids can lead to severe damage to the reservoir....
Numerical Analysis of An Annular Gas Turbine Combustor
, M.Sc. Thesis Sharif University of Technology ; Farshchi, Mohammad (Supervisor)
Abstract
The goal of this research is the simulation of the annular combustion chamber of the turbine engine utilized by liquid fuel. The achievement to this goal will lead to create numerical tools for parametric study, analysis and combustion chamber designing.For this reason simple geometry has been considered. This simplicity of geometry causes to facilitate in parametric study and decrease in saving time for modeling and meshing. This combustion chamber is a simplified model of engine CF6. In recent study, the k – ε realizable model has been used for turbulence modeling. For non-adiabatic condition, chemical reaction is dissolved by utilizing probability density function along with laminar...
Theoretical and Experimental Study to Conversion of AUC to UO2 by Microwave Heating
, Ph.D. Dissertation Sharif University of Technology ; Otukesh, Mohammad (Supervisor) ; Ghannadi Maragheh, Mohammad (Co-Advisor) ; Ghasemi, Mohammad Reza (Co-Advisor)A misbehavior‐tolerant multipath routing protocol for wireless Ad hoc networks [electronic resource]
, Article International Journal of Research in Wireless Systems (IJRWS) ; Vol. 2, Issue 9, pp. , Sep. 2013 ; Pakravan, Mohammad Reza ; Aref, Mohammad Reza ; Sharif University of Technology
Abstract
Secure routing is a major key to service maintenance in ad hoc networks. Ad hoc nature exposes the network to several types of node misbehavior or attacks. As a result of the resource limitations in such networks nodes may have a tendency to behave selfishly. Selfish behavior can have drastic impacts on network performance. We have proposed a Misbehavior-Tolerant Multipath Routing protocol (MTMR) which detects and punishes all types of misbehavior such as selfish behavior, wormhole, sinkhole and grey-hole attacks. The protocol utilizes a proactive approach to enforce cooperation. In addition, it uses a novel data redirection method to mitigate the impact of node misbehavior on network...
SAR Imaging Using the TomoSAR Technique to Resolve Multiple Scatterers
, M.Sc. Thesis Sharif University of Technology ; Bastani, Mohammad Hassan (Supervisor) ; Karbasi, Mohammad (Co-Supervisor)
Abstract
During the last few years, the study of urban environment structures is considered as a research field of interest in remote sensing. In satellite observations of the earth's surface, continuous imaging in terms of time and space has caused the remote sensing technique to be proposed as a useful and efficient tool for the analysis of urban areas. Obtaining quantitative spatial information from the urban environment in fields such as determining the height of buildings plays an essential role in urban planning, monitoring damage to buildings, establishing communication bases and digital cities. During the last two decades, the use of Tomosar approach in order to reconstruct the structures of...
Joint Optimization of Computation Offloading and Resource Allocation in Mobile Edge Computing Networks
, M.Sc. Thesis Sharif University of Technology ; Pakravan, Mohammad Reza (Supervisor) ; Hadi, Mohammad (Co-Supervisor)
Abstract
Mobile edge computing (MEC) is a promising technology that aims to resolve cloud computing’s issues by deploying computation resources at the edge of mobile network and in the proximity of users. The advantages of MEC include reduced latency, energy consumption, and load on access and mobile core networks, to name but a few. Despite all the aforementioned advantages, the mobility of mobile network users causes the traditional MEC architecture to suffer from several issues, such as decreased efficiency and frequent service interruption. One of the methods to manage users’ mobility is virtual machine (VM) migration, where the VM containing the user’s task is migrated to somewhere closer to...
Estimating Possible Effects of Subsidies in Competition and Development of Fixed Broadband Internet
, M.Sc. Thesis Sharif University of Technology ; Vesal, Mohammad (Supervisor) ; Rahmati, Mohammad Hossein (Supervisor)
Abstract
In this work, the dynamic competition between firms providing internet services is studied. The framework is Markov equilibrium whereby structural parameters are obtained using two-step estimations, allowing for analyzing the situation in case of subsidies for service upgrade. The results show that such subsidy has little effect on the number of firms while increasing the number of fast firms
Simulation and Control of an Aromatic Extractive Distillation Column
,
M.Sc. Thesis
Sharif University of Technology
;
Shahrokhi, Mohammad
(Supervisor)
Abstract
In this study steady state and dynamic simulation of an NFM extractive distillation unit for seperation of aromatics and non-aromatic components has been carried out. Column output composition obtained with experimental binary coefficients is compared with those obtainded by UNIFAC equation. The results indicate that using UNIFAC for all binrary coefficients results in an unacceptable error in concentration of benzene. If the experimental binary coefficents of benzene with NFM are used and the rest are calculated by UNIFAC equation, the simulation results will be very close to those obtained via experimental binary coefficients. Also it is shown that considering a constant efficiency for all...
Investigation of Transport Phenomena in Clarification of Beer by Membrane Using CFD Method
, M.Sc. Thesis Sharif University of Technology ; Soltanieh, Mohammad (Supervisor)
Abstract
During the brewing process, beer alternately goes through different chemical and biochemical reactions and solid–liquid separation stages. The clarification at the final step of brewing is a highly critical stage when it comes to producing a clear and bright beer. Recently, membrane technology has been successfully used in beer clarification, wherein Kieselguhr (diatomaceous earth) filtration is replaced by cross-flow microfiltration. The most important disadvantages of using microfiltration in clarification of beer is the fouling and flux decline during the process. The phenomenology of fouling mechanisms is still undefined and selection of an appropriate technique for flux enhancement in...
Design and Manufacture of a Burner for Transforming Natural Gas to Reduction Gas
, M.Sc. Thesis Sharif University of Technology ; Halali, Mohammad (Supervisor)
Abstract
Different methods can be used to produce reduction gas. One example is using coal. But today there’s a tendency to use natural gas. One way of transforming natural gas to reduction gas is to burn it with gases produced by combustion, such as or vapor; usually a catalyst is used in this method. Another method is burning natural gas directly with oxygen or air. The recent method is of benefit especially in Iran, because of available natural gas resources and avoiding catalyst problems. Designing a burner for this purpose is an important step in reaching this goal. In this project such a burner is designed and manufactured. The burner manufactured in this project burns natural gas with...
Investigation the Effects of Parking Pricing and Improving Public Transportation Policies on Private Car Use Reduction in Central Business District
, M.Sc. Thesis Sharif University of Technology ; Kermanshah, Mohammad (Supervisor)
Abstract
Nowadays, with population growth and vehicle traffic increase, only providing transportation supply couldn’t answer the transportation demand. One of the most important solutions to reduce traffic is transportation demand management (TDM). In this research, the effects of parking pricing and improving public transportation services on private car demand reduction in city center are examined. The data are collected from private cars users in the city center of Isfahan through interviews. By stated preference method, the impacts of parking price and public transit travel time and other related factors were investigated. For this purpose, binary logit, multinomial logit and nested logit models...
Guarding Polygons with Sliding k-modem Cameras
, M.Sc. Thesis Sharif University of Technology ; Ghodsi, Mohammad (Supervisor)
Abstract
In this thesis, we study the problem of guarding art galleries with sliding cameras and k-transmitter. This problem is a new version of classic art gallery problem, which the goal is covering the entire region with minimum number of guards. In early version of art gallery problem, usually point guards with 360 degree vision were used, but in this thesis we use sliding cameras instead. This new guards specified by an orthogonal segment which entirely settled interior of polygon and can see up to k walls. Based on this two notions (sliding camera and k-transmitter) we say that a guard can see point p, if the intersections number of normal segment through p to corresponding segment of guard...
Application of Adaptive Fuzzy Logic Systems in Controller Design of Nonlinear Processes
, M.Sc. Thesis Sharif University of Technology ; Shahrokhi, Mohammad (Supervisor)
Abstract
Most of dynamical models in the real world, have various restrictions and complexities in their structures. These constraints make the controller design much more difficult. In this work, it has been tried to design the controller for two kinds of common dynamical systems in the presence of these restriction by using the fuzzy logic systems. Several restrictions are investigated in this project such as unknown dynamic of the model, unmeasured state variables, unknown control directions, existence of time delay in the input and the state variables, input saturation and controller singularity.The backstepping technique and the dynamic surfaces control approach have been used to design the...
Synthesis and Characterization of Cu2ZnSnS4 (CZTS)Thin Films Prepared by Pulsed Laser Deposition Technique
, M.Sc. Thesis Sharif University of Technology ; Mahdavi, Mohammad (Supervisor)
Abstract
The Cu2ZnSnS4 (CZTS) quaternary compound, with suitable optical and electrical properties, is one of the most interesting materials for absorber layer of thin film solar cell. Since all constituents of CZTS, are abundant in earth’s crust and non-toxic, it is a proper replacement for the materials like CdTe and CuInSe2. The CZTS pellet was synthesized by the solid-state reaction and deposited on soda lime glass substrates by pulsed laser deposition (PLD) method. PLD technique has the advantages of offering stoichiometric preservation during the materials transformation from target to substrate and good crystallinity due to the highly energetic species. CZTS has was deposited in order to...