Sharif Digital Repository

During production from gas condensate reservoirs, reservoir pressure decreses to lower than dew point pressure of the reservoir fluid. Consequently, condensates will form in near wellbore regions, which significantly decrease well productivity. One of the remediations that is recently proposed for solving this problem is wettability alteration of near wellbore region to gas wetting condition. In comparison to other methods, it provides a better permanency, which is its key advantage. The main purpose of this thesis is, quantitative, qualitative and modeling study of wettability alteration of rock to gas wetting condition and verification of modeling rsults for a reservoir rock sample. Also,... 

Nowadays, the use of microreactors is receiving a great deal of attention due to the unique characteristics of such systems, such as high surface-to-volume ratio, low material loss, greater safety, and minimizing mass and heat transfer limitations. In this study, the optimization of the continuous-flow synthesis of Plavix by Cu-MOF heterogeneous catalyst utilizing a glass microreactor was investigated. Structural characteristics of the catalyst were investigated using X-ray diffraction spectroscopy (XRD), Fourier-transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), and BET surface area studies to describe the structure and morphology of the catalyst. In order to build... 

During the recent years, the emerging technology of photonic, on-chip communication has been widely explored to resolve the problems of traditional electrical communication in terms of performance and power consumption. Micro-Resonator (MR) as the photonic building block for optical comunication is very sensitive to temperature and process variation. Variation of resonance wavelength of a micro-resonator as a result of temperature fluctuations causes tremendous error for optical data routing through the waveguides, and reduce the reliability of network. A temperature-aware routing algorithm enables the network to tolerate fault and continue working properly. Temperature variation of MRs is a... 

Tubular sections and consequently tubular joints in construction of steel structures in the form of space frames is widely used in ground and marine structures, including offshore jacket platforms. The passage of part of the life of the existing offshore platforms has caused cracks in various parts of the joints of these structures due to various reasons, the most important of which is fatigue. In this thesis, by adopting numerous numerical studies and validations with some cited experimental papers, the principles governing the proper buckling behavior of tubular members focusing on the conventional geometries of Persian Gulf platforms as well as the behavior and local flexibility of... 

In the past few years, many research works on the controllable integration of metal nanoparticles and metal-organic frameworks were done, since the obtained composite material shows a synergism effect in catalysis and photocatalysis, drug delivery applications, gas, and energy storage, as well as sensing. For the first time, in this study, we employed template-assisted growth to synthesize Au-HKUST-1 Nanocomposite. XRD analysis entirely confirms that employing this strategy in synthesizing Au-HKUST-1 was wholly successful, and the plasmonic properties of this nanostructure were studied via UV-visible spectroscopy. In the course of synthesis, gold nanoparticles with 70nm diameter were... 

Single nucleotide polymorphs, There are changes caused by a mutation in a nucleotide in the Dena sequence. Mononucleotide polymorphisms are the most common type of genetic variation. Some of these changes have little or no effect on cells, while others cause significant changes in the expression of cell genes that can lead to disease or resistance to certain diseases. Because of the importance of these changes and their effect on cell function, the relationships between these changes are also important. Over the past decade, thousands of single disease-related mononucleotide polymorphisms have been identified in genome-related studies. Studies in this field have shown that the expression of... 

Nowadays, video streaming over peer-to-peer networks has become an interesting field to deliver video in large scale networks. As multi-channel live video streaming networks increase,distributing video with high quality among channels faces many challenges. The most significant challenges cause from frequent channel churns, unbalanced channel resources, network heterogeneity and diversity of users’ bandwidths. They include: nodes’ unstability, low users participations, large startup and playback delays, low video quality received by users and lack of resources in unpopular channels.In order to solve the above problems, we have proposed several solutions such as: 1- using distribution groups... 

Semi-supervised Learning (SSL) is an extremely useful approach in many applications where unlabeled data can be easily obtained. Graph based methods are among the most studied branches in SSL. Since neighborhood graph is a key component in these methods, we focus on methods of graph construction in this project. Graph construction methods based on Euclidean distance have the common problem of creating shortcut edges. Shortcut edges refer to the edges which connect two nearby points that are far apart on the manifold. Specifically, we show both in theory and practice that using geodesic distance for selecting and weighting edges results in more appropriate neighborhood graphs. We propose an... 

At first the killing vector fields will be investigated. Conditions are introduced for the hypersurface of a Riemannian manifold with a killing vector field to be equipped with the same killing vector field. Then 2-killing vector field is studied and its relation with killing vector fields and monotone vector fields is presented. After that conformal vector fields are discussed and conditions are introduced in order that the Riemannian manifold equipped with a conformal vector field, isisometric to n-dimensional sphere with constant curvature. Finally we will present the conditions which conformal vector field is a 2-killing vector field. Then we will present the results in which the... 

During the last decade, there have been a great number of researches on complex networks.Data aggregation is the first step in the analysis of these networks. However, due to the large scale of them, almost never is there complete information about a network’s different aspects. Therefore, analysis of a complex network is usually done based on the incomplete data. Al-though a good sampling approach in a way that the achieved sample is a good representative of the whole network has its own challenges, analysis of incomplete data causes a significant alternation in the estimation results. Consequently, one of the first problems emerging after sampling is the possibility of predicting the... 

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... 

A great deal of information are continuously generated by users in different contexts such as social networks and online service providers in terms of temporal marked events. These events indicate that what happened to who by when and where.Modeling such events and predicting future ones has interesting applications in different domains such as item recommendation in online service providers and trending topic prediction in online social networks. However, complex longitudinal dependencies among such events makes the prediction task challenging. Moreover, nonstationarity of generative model of events and large size of events, makes the modeling and learning the models challenging.In this... 

Nowadays many of us spend a big part of our daily times on social media.One of the most important research problems in social media analysis is how to engage users. The trace of user activity over these websites is a valuable resource for user understanding and engagement, but this data is very huge and unstructured. An approach to deal with this problem is user behavior modeling. In this process, first a behavioral model is considered for users, then using the activity data and the behavioral model, some parameters are learned. Finally, using the learned parameters, a user profile is constructed for each user. This profile can be used for user engagement and many other applications.... 

In fact knot theory is working by an elastic string. A knot is A smooth embedding of in . We say that two knots are equivalent if there is an ambient isotopic between them. In knot theory we study equivalent classes of knots. As it seems from its name, a dynamical system is the study of motions, mechanics and dynamics of a system. We will observe some systems and stability of orbits in theme. Then we define templates which contain orbits in themselves. At last, we observe relations between discrete dynamical systems and knot theory. Then for any arbitrary chaotic knot we observe that there exist an universal template that contain a copy of any kind of not. Finally we will study some open... 

Multimedia applications which exploit the network resources are best provided in broadband networks. Additionally, broadband wireless access systems enable broadband access in places where the wired solutions are not applicable. The IEEE 802.16 standard is designed to provide broadband wireless access and addresses the PHY and MAC layers of wireless metropolitan area networks. This standard has been designed to support quality of service for different applications, and due to their various requirements has considered four classes of service for connections. However, quality of service support mechanisms (such as admission control and packet scheduling), are out of the scope of the standard....