Sharif Digital Repository

Magnesium and its alloys have been used as biodegradable implements in recent years. However Magnesium implements may corrode in the body before the natural healing process of the damaged tissue. MAO process was studied in order to reduce primary corrosion of Magnesium alloy in Simulated Body Fluid (SBF). MAO coating was created on AZ31 alloy in a nontoxic alkaline-silicate solution at DC current densities of 5, 10, 15 and 20 mA/cm2 for 30 minutes and the current was in form of 20-10-5 mA/cm2 steps that each were applied for 10 minutes. The maximum corrosion resistance was observed for the mentioned step applied current in a 30g/l Sodium Silicate solution. Furthermore the effects of adding... 

catalyzed oxidation of organic compounds such as olefins, sulfides, benzylics alcohols and phenolics. Cyanide-catalyzed aldimine coupling was employed to senthesize compounds with a-imineamine structural motifs : 2,3-di-(2-hydroxyphenyl)-1,2-dihydroquinoxaline, that way for synthesized NONO tetra-dentate Schiff-base ligands. With attention to solid geometry these ligands are possible to synthesize homo and hetronuclear mixed-ligand complexes. we are also synthesized homonuclear mixed-ligand Mn(III) and hetronuclear Mn(III)-Fe(III) with tetradentate Schiff-base ligand quinoxaline and acetyl acetone ligand. These complexes and ligands are characterized by FT-IR, 1H NMR, 13C NMR, UV and... 

In this work, a non-isothermal model of natural gas in pipelines including mass, momentum and energy balance equations are used as model equations for modeling and state estimation in gas pipeline systems. An algorithm is proposed to handle the discontinuities that appear in the dynamic model of a GTN. The states of GTN are estimated using the continuous/discrete form of the extended Kalman filter for two benchmarks and some heuristic rules for sensor placement in a GTN are concluded. Also, a framework for distributed and decentralized state estimation in high-pressure and long-distance gas transmission networks (GTNs) is proposed. Some heuristic rules are suggested for system decomposition... 

Orthogonal Frequency Division Multiplexing (OFDM) is a digital transmission method developed to meet the increasing demand for higher data rates in communications which can be used in both wired and wireless environments. This thesis describes the issue of the Peak to Average Power Ratio (PAPR) in OFDM system, based on compressed sensing at the receiver of a peak-reducing sparse clipper applied to an OFDM signal at the transmitter. By choosing proper clipping threshold, clipping signal will be sparse so locations, magnitudes, and phases of the clipping signal can be recovered by compressed sensing method. We demonstrate that in the absence of optimization algorithms at the transmitter,... 

Localization of electrical activity in the brain is one of the major problems in cognitive science and neuroscience. Indeed, Source localization is the inverse processing procedure on brain signals to estimate the location and position of resources in the human brain. Current technics for neurological imaging is included fMRI، PET، MEG and ERP. These methods is not appropriated to answer the question that when does each of different components of the brain begin their activity. The EEG signals could be useful to eliminate some of limitations of above methods. The problem with EEG signals collected from the skull is that they don’t refer directly to the location of active neurons. The... 

Redundant number systems provide for carry-free arithmetic, where the result of arithmetic operations is achieved, in redundant format, without the need for latent carry propagation. However conversion of the result to a conventional nonredundant representation, always, requires carry propagation. Therefore, efficient use of redundant number systems is feasible when a series of arithmetic operations is to be performed before the need arises to obtain the result in a nonredundant representation. Redundant number systems have been used in several special purpose integrated designs (e.g., DSP applications) and also as intermediate number representation in complex arithmetic operations... 

Industrial water systems often allow efficient water uses via water reuse and/or recirculation. The design of the network layout connecting water-using processes is a complex problem which involves several criteria to optimize. The general problem can be formulated as a non-convex nonlinear program (NLP), but due to the presence of bilinear terms, it may be difficult for local optimization solvers to attain global optimal solutions. To overcome this difficulty, this paper presents a hybrid approach combining the global optimization power of evolutionary algorithms and speed and accuracy of mathematical programming technics.By this strategy, local solutions can be avoided and the... 

Because of the Complexity in Calculating the Probability of Failure of the System, This Computation is Done by the Software Have Been Developed for this Purpose. Of Course, When We Use Them, We See That Each of Them Have Their Advantages and Disadvantages. One of the disadvantages that have been tried to be resolved over time, the type of programming and algorithm for calculation of it is the fault tree Because new techniques like modularization which have been designed in recent years, a significant improvement in accuracy and speed performance computing applications that use this method have been obtained.In This Thesis Has Developed Software That is Able to Calculate the Probability of... 

The importance of transfer learning in image-related problems comes from its many advantages that are sometimes undeniable. Previous researches have well shown the success of transfer learning in this area using deep neural networks. However, transfer learning for time series data has not yet been done in a conventional and automated manner. The main reason for avoiding transfer learning in this domain relates to the dynamic and stochastic nature of the time series, where they show a time-varying behavior. Previous experiments have shown that transfer learning between two heterogeneous time series could harm the forecasting accuracy of a model. Therefore, in this thesis, we aim to explore... 

Concepts and ideas of a society, formed by its discourse and ideology, are mainly manifested through language. Therefore, language has always been the subject of studies and research of many scholars such as linguists. As the languages of different countries are different, in order to transfer the thoughts of a writer, a deep examination of the source text as well as the translation of the work itself seems to be of much importance. Since translation is not an independent phenomenon and depends on the interpreter's perception, it is in relation with ideological concepts and power like the work itself. In order to be able to examine the structural effects of a work on the foundation of the...