Sharif Digital Repository

Primary visual cortex plays a paramount role in processing visual information. Visual information after the primitive processing by LGN and Thalamus, will be sent to the primary visual cortex which is called V1 area. According to the fact that V1 neurons have the definitive sensitivity to the edge and contrast of visual stimuli so their behavior are very selective to the certain features, specially contrast, of visual stimuli. These neurons have different response behavior to contrast. In fact most of them have some nonlinear behavior to this feature. Normally we expect that response of them or spiking rate of them grow linearly by the contrast increases but in most many cases they have some... 

Improvement of semiconductors photocatalytic activity by different means has always been one of the challenges for researchers. Semiconductors doping for band-gap engineering and changing morphology to increase specific surface area and photocatalytic reaction sites are amongst these efforts. In this research simultaneous effect of these two parameters for three morphologies containing nanoparticle, nanowire and micro dandelion, simultaneously doped with carbon and nitrogen has been investigated. Final purpose of this thesis is to decrease the band-gap energy close to soft UV photon energies to make surface photodynamic therapy possible. Nanoparticle morphology with size distribution between... 

The representation of data influences the explanation factors of data variations. Thus,the success of learner algorithms depends on the data representation. Our main contribution in this thesis is learning of high level and abstract representation using deep structure. One of the fundamental examples of representation learning is the AutoEncoders. The auto-encoder is a rigid framework that doesn’t consider explanation factors in terms of statistical concepts. So, the auto-encoders can be re-interpreted by seeing the decoder as the statistical model of interest. The role of encoder is a mechanism for inference in the model described by the decoder. Our purpose is to design such model with... 

Using microbial electrolysis cells (MEC) for hydrogen production has been considered in recent years. So far, synthetic wastewaters containing substances such as glucose and acetate have been mainly used in MECs and industrial wastewaters have not been widely studied. Food industry wastewater is a suitable choice for application in microbial electrolysis cell due to its biodegradable materials. In present research, dairy wastewater and sludge collected from UASB reactor of Iran Dairy Industries company, Tehran were initially used in a dual chamber microbial fuel cell until a stable voltage was generated .Afterward, the system was converted to a MEC applying a predetermined voltage. The... 

Hi-C is a new technology invented to record the amount of interaction between all chromatin fragments. Chromatin interactions are manifestations of chromatin's 3D structure. It has been proved that different 3D structures of different cell types, despite having the same DNA, causes in different functionalities of cells. Therefore knowing chromatin structure, the factors affecting it and the way it affects cells' behaviors such as gene co-expression, sheds more light on the knowledge about cells and the methods that can change their fates. Finding the causes of diseases, designing more efficient drugs and progressing the conversion of different cell types into each other used for amending... 

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... 

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... 

In the competitive facility location problem, two service providers fight over winning consumers by establishing a series of well-located facilities on the line. The consumers seek their required services from the facility which is closest to them. The order in which service providers locate and build their facilities is as follows: the first service provider establishes k facilities after which the second service provider locates another k facilities and this goes on for m rounds. The payoff of each service provider equals the number of consumers that choose that provider’s facilities to seek service from. In this dissertation, we address different types of this problem and try to analyze... 

Thermal protection systems are ablative composite coatings that, through endothermic reactions, protect the main structure or underlying layers under high thermal loads. Under these conditions, various phenomena occur, such as pyrolysis, char formation and char cracking, surface recession, as well as different modes of heat transfer including conduction, convection, and radiation. Successful simulation of the ablation phenomenon will lead to the development of a tool that greatly assists in the design of thermal protection systems for atmospheric re-entry vehicles.The primary focus of this dissertation is the experimental investigation of the ablation process, or surface recession, of... 

High efficiency and low-emission fuel cells have the capacity to replace fossil fuels for energy supply concerns. Solid oxide fuel cells operate in relatively high temperature and have power plant applications. Hence, they are acquainted to be coupled with cycle gas turbine to reduce the cost and increase the overall system efficiency. The control of these hybrid systems is so important. Due to the system nonlinearity and having more than one controlled variable, its control with classic methods would be difficult. The model based predictive control is used as an alternative to mitigate these difficulties. In addition to their high performance, their extension to the multivariate case would... 

With the progression of technology demands for novel method of heat cooling is increased so the old method of cooling such as heat removal by air stream with force convection and even single phase method was not sufficient for today’s industry need. Nowaday, spray cooling method which belongs to two phase cooling method is one of the most popular method. In this study two method of spray cooling: spray cooling with flow blurring nozzle and electrospray cooling were investigated. For both method, at first the physics of phenomena and morphology of spray is studied experimentally then the efficiency of heat removal in each method is evaluated by the assessment of variation of temperature and... 

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... 

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... 

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... 

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.... 

The classification of different tumor types is of great importance in cancer diagnosis and drug discovery. However, most previous cancer classification studies are clinical based and have limited diagnostic ability. Cancer classification using gene expression data is known to contain the keys for addressing the fundamental problems relating to cancer diagnosis. The recent advent of DNA microarray technique has made simultaneous monitoring of thousands of gene expressions possible. With this abundance of gene expression data, researchers have started to explore the possibilities of cancer classification using gene expression data and quite a number of Pattern Recognition approaches have been... 

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...