Sharif Digital Repository

The fast growth of social networks and their wide range of applications have made the anal-ysis of them an interesting field of research. The growth of concern in modeling large social networksand investigation of their structural features leads studies towards community detec-tion in such networks. In recent years, a great amount of effort has been done for introducing community detection algorithms, many of which are based on optimization of a global cri-terion which needs network’s topology. However, because of big size of most of the social networks , accessing their global information tends to be impossible. Hence, local commu-nity detection algorithms have been introduced. In this... 

Liquid jet behavior in an intense electric field is studied experimentally and numerically.Imaging is used in experiments to charactrize jet behavior. Electrospray of ethanol using a simple needle in a wide range of operating conditions is investigated. Liquid meniscus is captured using a high-speed camera and different electrospray modes are described based on involved forces. A new nozzle is invented that broadens the stability margins of the useful cone-jet mode. The physical mechanisms of the new cone-jet is discussed and it is characterized using appropriate dimensionless parameters. A simple jet in presence of a gaseous crossflow and a normal electric field is also studied. The liquid... 

In this project, tomato processing waste has been considered as a raw material for bio-refinery applications. Some products from tomato wastes that are usable, economical and environmentally friendly have chosen after lots of studying on researches in regards of producing valuable materials from tomato waste. I’ve used “Superpro designer” software for economical evaluation and determining the possibility of this practice for industrial applications. Beside the tomato paste factory, the process includes one unit of Lycopene production. In addition to Lycopene production, it is possible to produce fertilizer from residues and using them as livestock food or producing energy for the output... 

Considering the widespread applications of amides, synthesis of these compounds is of great importance. The one pot oxidative addition of amines to aldehydes is one of the most simple and appealing approaches to synthesis amides. With the aim of developing a mild and convenient approach towards preparation of amides, numerous methods have been reported for this important process over the past few decades. These improvements have been mostly related to the optimization of reaction conditions and the use of more challenging substrates including diverse derivatives of aldehydes, and also design a novel and effective catalytic systems. Due to the various advantages of supported heterogeneous... 

Considering the widespread applications of α-aminonitriles, their synthesis is of great importance. The Strecker reaction represents a direct and appealing approach for the preparation of α-aminonitriles. With the aim of developing a mild and convenient approach towards the construction of α-aminonitriles, numerous methods have been reported for this important process over the past few decades. These have been mostly related to the optimization of reaction conditions and the use of more challenging substrates including ketimines and ketiminium salts and design of novel and effective catalytic systems. Due to the various advantages of supported heterogeneous catalysts and in our aim to... 

Considering the advantages of heterogeneous catalysts for the easy work up procedure, being eco-friendly, and the reusability, herein, two projects are carried out by metal-supported SBA-15 catalysts. The first one is the oxidative deprotection of trimethylsilyl ethers catalyzed Cr (VI) in the presence of TBHP as oxidant. In this project, trimethylsylil ethers are oxidized in good to high yields. The second project is the oxidative coupling of thiols to disulfides catalyzed by Fe (III) in the presence of hydrogenperoxide. This catalyst/oxidant system convets different aromatic thiols to corresponding disulfides efficiently  

This projct includes the following sections: In the first section, Michael addition reaction of anthrone to nitroolefins is described in water without using any catalyst to prepare 9-(2-nitro-1-arylethyl)anthracene-10(9H)-ones. This method is green, efficient and gives high yields of products. The solvent effect is also investigated. In the second section, Considerable efforts have been directed in recent years towards the transition metal complex catalyzed oxidation of organic compounds such as olefins, sulfides, benzylics alcohols and phenolics. And due to the various advantages of supported heterogeneous catalysts and in our aim to develop a simple, more efficient and eco-friendly... 

Compression systems are widely used in industry. Dynamic Modeling is a necessary step in design procedure of a safe compression system. A dynamic model should be adequate and simulate dominant elements of system. One important element of industrial compression systems is downstream pipelines. In this work, a dynamic model including pipeline acoustics is developed. It is accepted that changes of working gas molecular weight can cause inception of instabilities in compression systems. The dynamic model used to study mechanisms of these instabilities. A conventional control system is modeled and tuned for the compression system. The ability of this control system to prevent such instabilities... 

Resonance acoustic spectroscopy (RAS) is one of the techniques used for monitoring the production quality and evaluation of mechanical properties of cylindrical components, due to their non-destructivity, high precision and quickness.
In this technique, the resonance effects are caused by the excitation of eigenvibrations of structure by an incident acoustic wave located in far-field. The resonance spectroscopy (isolation and identification of the resonance features) is performed on the far-field scattered pressure field which contains valuable information about the characteristics of the target. Appropriate exploitation of these resonance informations from the theoretical model and... 

Titania is one of the photocatalytic materials , but low quantum yield and relatively high band gap of TiO2 limited its applications.There are several ways to improve the photocatalytic properties of this material relied on narrowing the band gap,by doping TiO2 with other metals and oxides or increasing its specific surface area.In this work ,TiO2-SiO2-Ni coating have been made by sol-gel process and deposited on quartz substrate by using of dip-coating method .Effect of increasing Nickel content in nanocomposite and primary sol on crystalline structure,morphol ogy, photocatalytic properties and specific surface area have been investigated by means of X-Ray diffraction method, FT-IR, SEM,... 

Distributed generation (DG) and its utilization have some benefits and risks for its owner and power network. From owner perspective, benefits of DG include selling energy, reducing costs related to fuel, and other economic benefits. However, there are some risk factors for the owner including risk of supplying fuel, risk of selling generated power, and other risk factors related to establishment of the DG unit. Utilizing risk-reduction tools such as signing agreements for selling power, purchasing fuel, and related economic tools are necessary for risk management of the owners of DG units. The purpose of this thesis is to investigate the economic situation of the DG units and optimize the... 

The bis(cyclometalated) platinum(II) complexes of the type [Pt(ppy)(p′py)], in which ppy = p′py = 2-(p-tolyl)pyridine, 6; ppy = 2-(3-bromophenyl)pyridine, p′py = 2-(p-tolyl)pyridine, 7; ppy = 2-(2,4-difluorophenyl)pyridine, p′py = 2-(p-tolyl)pyridine, 8; ppy = 2-(2,4-difluorophenyl)pyridine, p′py = 2-(2,4-difluorophenyl)pyridine, 9, have been prepared from the reaction of the cyclometalated platinum(II) complex [Pt(ppy)Me(SMe2)] with one equiv p′py and one equiv B(C6F5)3. The structure of 6, 7 and 10 determined using X-ray crystallography in solid state. However NMR spectroscopy methods have been used for structural characterization of the complexes in solution phase. The bis(cyclometalated)... 

Clustering presents valuable information in discovery of the climatic zones. To use clustering approaches, similarity measure, clustering algorithm, and clustering validity index should be determined. To find climatic zones over Middle East nad North Africa (MENA), this study performs k-means clustering with Euclidean distance as the similarity measure on four monthly precipitation datasets (CRU, GPCC, UDEL, and PREC/L) and two monthly temperature datasets (CRU, NOAA GHCN-CAMS). This study aims to validate clustering results and find a proper number of clusters. For this purpose, five traditional validity indices are examined on experimental datasets. Results show significant differences... 

Causal discovery is of utmost importance for agents who must plan and decide based on observations. Since mistaking correlation with causation might lead to un- wanted consequences. The gold standard to discover causal relation is to perform experiments. However, experiments are in many cases expensive, unethical or impossible to perform. In these situations, there is a need for observational causal discovery. Causal discovery in the observational data setting involves making significant assumptions on the data and on the underlying causal model. This thesis aims to alleviate some of the assumptions and tries to identify the causal relationships and causal mechanisms using generative neural... 

Hard disk drives are the main component of computers for permanent data storage. The security of the stored data is related closely to the air gap between the read-write head and the surface of disk. This gap which is created by the aerodynamic force between head and the disk is altered continually by lateral oscillations of disk. In the extreme condition of zero gap and contact between the protective coating layer and subsequently the magnetic material of the disk with the head, the disk will be scratched and damaged. Therefore, the active or passive control of these vibrations has a particular importance in the technology of manufacturing of hard disks. The first step in active control...