Sharif Digital Repository

In this work, inertial guidance and control of an axisymmetric flying vehicle with a spinning part is performed based on dynamic modeling and seven degree of freedom simulation. Flying vehicle is composed of front and aft bodies and these bodies are connected to each other via a hydrodynamic bearing. Front body is roll isolated from the aft body and includes all necessary guidance and control equipments such as sensors, canard set and so on. The control fins, located on the nose, is used to control the roll angle of the nose and to execute the lateral acceleration commands. Also, the aft body is freely rolling and includes the stabilizing fins. In this project, the translational and... 

In this study a new Ni(II)-¬oxazoline complex was synthesized by reaction of Ni(CH3COO)2.4H2O and 2-(2׳-hydroxyphenyl)-2-oxazoline ligand in MeOH solvent. The resulting complex bis[2-(2׳-hydroxyphenyl)-2-oxazolinato]Ni(II), was characterized by different spectroscopic methods. X-ray diffraction showed that this complex is four coordinated with a square planner geometry. The complex was applied as an efficient homogeneous catalyst in C-C coupling Heck reaction of arylhalides with olefins such as methylacrylate. Investigation of the catalytic activity of the complex in Heck reaction between arylhalides and olefins showed high yield and selectivity. For example reaction between iodobenzene and... 

In this study, electrochemical oxygen reduction reaction (ORR) was studied on Cu, Pd, Rh, Pd-Cu and Rh-Cu alloys in alkaline solution. Pd-Cu and Rh-Cu alloys were prepared by electrochemical methods. On copper electrode it is found that direct oxygen reduction is accompanied by the electrochemical reductions of copper oxides. Also, mechanism and kinetics of reaction change as the amount of copper oxides increase on the surface. For electrodeposited alloys, it is indicated that the reactivity of Pd-Cu and Rh-Cu alloys toward oxygen reduction is higher than pure Pd and pure Rh. The maximum reactivity among Pd-Cu alloys is related to the sample with 24.5% copper content while the maximum... 

Cavity Quantum Electro-Dynamics (CQED) in Weak, Strong and Ultra-Strong coupling Regimes are studied. A MATLAB m-file is written which is able to solve any arbitrary CQED configuration. This program demands input data such as number of Quantum Dots, number of energy levels of each Quantum Dot, energies of each energy level of Quantum Dots, Number of cavity modes, eign-frequency of each cavity mode, coupling constant, dipole strength of each allowed transition of Quantum Dots and initial state of system from user and begins to solve the Schrodinger equation for annihilation and atomic ladder operators. In addition, coefficients of each possible ket will be calculated. Since, any approximation... 

Strongly correlated materials are kind of materials in which novel electric and magnetic properties will appear as a result of strong correlations among their electrons like “heavy fermion materials”. Kondo lattice model is a model to describe heavy fermion materials. If we are merely interested in the magnetic properties of heavy fermions we can replace the Kondo lattice Model with the simpler model called the Kondo-necklace model which consists of the interactions only among the spins of the itinerant (conduction) and localized electrons (magnetic impurities) and also the interactions between the spins of the itinerant electrons. In this thesis we investigate the properties of the one... 

Given the complex structure of electronic waste and the difficulty of recycling it by traditional methods, the focus is mainly on biohydrometallurgy method, and in particular on bioleaching. To recover metals, various microorganisms are utilized in this method. In light of previous studies, cyanogenic bacteria have been widely used for the extraction of basic and precious metals. Among the species, indigenous microorganisms have a higher ability to resist toxic environments in the bioleaching of metals due to their adaptation by rapid changes in their metabolic system over time. The main objective of this study is to isolate indigenous microorganisms from electronic waste landfill for their... 

This study investigates the effect of titanium dioxide and magnesium oxide additives on hydroxyapatite synthesized by sol-gel and composite with the predominant phase of hydroxyapatite by in situ method to improve mechanical properties. Scaffold samples were synthesized with nanometer-sized hydroxyapatite and composite powder particles by gel casting and sintered at 1200 ° C. Then, to evaluate the synthesized powders, simultaneous thermal analysis (STA), X-ray diffraction test, FTIR test, FESEM, EDS, and MAP analysis were used. Also, to evaluate the mechanical properties of the scaffolds, a compressive test was used, and to evaluate the scaffolds' density, the Archimedes method was used.... 

Due to the prominence of the evaluation of the consequences of rising temperatures, this paper examines the effects of temperature variation on mortality across different demographic groups in Iran. I use a rich weekly data set from 2009 to 2017 across different demographic groups to understand the potential health impacts of climate change in a developing country. Using several fixed effect regressions, I discover that for an additional day with a mean temperature over 25°C, mortality rate increases by 2.56% relative to the effects of an extra day in 0-5 °C, in the weekly temperature exposure horizon. I test for the harvesting effect by comparing the estimates at weekly and monthly... 

The importance of power consumption in high performance multiprocessors, combined with power reduction capability of on-chip optical interconnects, offers optical network-on-chip (ONoC) as a new technology solution which can deliver considerably higher bandwidth and lower latencies with significantly lower power dissipation than an interconnection network based only on electronic signaling. An on-chip network should be able to support multicast communications efficiently whether it is an optical or electrical network. On the other hand, multicast communications in optical networks-on-chip has been implemented using shared bus which is not scalable. Moreover, most of optical on-chip... 

Having the high strength to weight ratio has been made the composites special materials very important these days. The low density of aluminum and its appropriate corrosion properties make it a good choice for metallic matrix. Also, the high tensile strength of stainless steel fibers can helps as a reinforcement in the composite to improve its mechanical properties. Enhancing the bonding of composite’s components can helps it to develop its properties. Casting is an appropriate process for making an aluminum matrix containing steel fibers as reinforcement in a structural composite. In addition, rolling process can remove so many defects made by casting, and improve joining of fibers and... 

In this study, flexural vibration of a functionally graded nanotube under an initial stress is investigated. The small scale effect is taken into consideration based on Eringen’s nonlocal elasticity theory. The material properties are assumed to vary exponentially along the depth direction. The complete effect of the initial stress is taken into account in the problem formulation. The governing equations of motion are derived by using the Hamilton’s principle on the basis of the nonlocal Timoshenko beam theory. An analytical solution of the governing equations, for free vibration of a simply-supported nanotube is presented. Numerical results are presented to investigate the effect of the... 

let Mn n be a positive semmi definite matrix and M:= (U; B) be a matroid. Consider the problem of finding S 2 B such that det(MS;S) is maximized, in witch MS; S is the submatrix of M, restricted to rows and columns of S. This problem has a variety of applications including page ranking algorithms. The problem above is an NP-hard problem in the general case. However, there are several approximating and estimating algorithms for some special cases, which are interesting. Also, exactly solving the problem is NP-hard, even for some special matroids. As an example, one can consider the uniform matroids. Khachiyan introduced a greedy algorithm with dd approximation factor. Afterward, Di summa et... 

Equal Channel angular pressing (ECAP) is one of the most applicable Severe Plastic Deformation (SPD) Procedures which results in improvement of strength and ductility through grain refinement and an appropriate texture development. In this study, in order to achieve a proper orientation and microstructure, ECAP was performed in different routes and temperatures up to 4 passes on AZ31 magnesium alloy. Microstructure and mechanical properties were studied. X-ray diffraction analysis was performed to study the basal orientation variation and calculation of sub-grain size. In addition, cold rolling at room temperature was done on the fourth pass specimens, in order to study the effect of ECAP... 

In this research a no-wait flowshop sequence dependent setup time scheduling problem with weighted earliness-tardiness penalties as the criterion (F_m |nwt,S_ijk |∑▒〖w_j^' E_j+w_j^" T_j 〗) is investigated. It is assumed that n jobs are assigned to a flowshop with m machines. The jobs are not allowed to wait between two successive machines according to no-wait requirement. Moreover each machine needs a setup time before processing a new job. The value of this setup time is dependent on the previous processed job on that machine.
A mixed integer linear programming model is proposed to solve the problem. As the problem is shown to be strongly NP-hard, a particle swarm optimization (PSO)... 

One of the most important issues that an organization faced with is resource management. The proper resource management has the great rule in organization cost reduction. One of the most efficient processes in resource allocation is auction and there is different auction with different mechanism and goals. In an auction there is a set of items and a set of bids, and the task of auctioneer is matching items with suitable bids. Each bid consist of desirable items and the bidder value of that items. In an auction process, after mechanism design of auction and auction implementation we must identify the winners of auction and this is a hard problem even in simple auction.
In this study we...