Sharif Digital Repository

The brain is constantly anticipating the future of sensory inputs based on past experiences. When new sensory data is different from predictions shaped by recent trends, neural signals are generated to report this surprise. Surprise leads to garnering attention, causes arousal, and motivates engagement. It motivates the formation of an explanation or updating of current models. Three models have been proposed for quantifying surprise as the Shannon, Bayesian, and confidence-corrected surprises. In this thesis, we analyze EEG and MEG signals recorded during oddball tasks to examine and statistically compare the value of temporal/ spatial components in decoding the brain’s surprise. We... 

One of the most efficient and effective methods of water and wastewater treatment is the use of membranes and can be a good alternative to traditional methods such as adsorption, chemical coagulation and .... One of the limitations of this method is membrane fouling, which limits its use in industry.In this study, ultrafiltration membrane made by phase inversion method from a combination of PVDF and SPES polymers and surface modified with hyperbranched polyethylene imine and its performance in cationic coating paint purification was investigated. Also, the performance of this membrane has been investigated by calculating the separation rate, pure water flux, contact angle and specifications... 

Cellular automata is a model for physical systems that has homogenous and simple components. Simple components, which are called cells, have local interactions creating complicated global emergent of behaviour. In the field of cellular automata, there are two basic problems: forward and inverse problems. Characterizations of cellular automata rule are studied in forward problem, but in inverse problem, there exists a description of cellular automata and we should find a rule or a set of rules that satisfy the given description. This problem belongs to the class of NP problems and hence heuristic algorithms such as evolutionary algorithms have been used for solving it. Since rules space and... 

A new microfluidic device is introduced for sorting the particles based on the hydrodynamic resistance induced in a microchannel which is not needed for additional detection or sorting modules. Hydrodynamic resistance affects physical properties, such as size and deformability of the particle. This device could apply application in cell sorting for remedies, diagnostics, and industrial applications. The device design is performed using an equivalent resistance model, and also numerical simulations are performed. For validation of the results, they are compared with experimental results. Moreover, we will discuss threshold particle size and will introduce a way to approximate it to ... 

Current research studies the effect of electromagnetic field on reducing precipitation on membrane surface in reverse osmosis. Reverse osmosis is one of the most widely applied methods for water desalinization. Despite its advantages over other desalinization techniques, suffers from shortcomings such as blockage of membrane surface. Use of magnetic fields for reducing precipitation in process equipment, the so-called magnetic treatment, has been studied and practiced for decades. This research intends to study the effect of electromagnetic field on water and its mineral content, and the possibility of its application as a method for reducing precipitation and blockage in reverse osmosis... 

In the present research the methods and challenges to ocular drug delivery have been investigated with more emphasis on ocular diseases that do not have any approved treatment. Periocular route is a promising alternative to the common routes of ocular drug delivery especially for treatment of posterior eye diseases. Based on barriers for efficient drug delivery to the eye, magnetic drug targeting revealed to be influential to eliminate some obstacles of this route which has not been worked before. It is hypothesized that the particles can pulled into the eye or will be trapped inside the sclera tissue or even if it is not happened, they can stay behind the sclera and magnetic force can... 

In this study, modification of Polyvinylidene fluoride membrane in order to reduce membrane fouling in membrane bioreactors is investiged. To achieve this goal, chemical modification and grafting methods were used. Initially, by chemical modification, the reaction was made to make hydroxyl groups on the membrane surface. The hydroxyl functional groups were used as a site for connecting of subsequent monomers. Finally, the lysozyme enzyme was used as the main modifier to improve the hydrophilicity and antibacterial properties of the membrane surface. To evaluate the performance of the modified membrane in comparison with the pristine membrane, different tests, such as water contact angle... 

Wind power is site dependent and is by nature partially dispatchable. Furthermore, good wind sites are far from grid. Due to these problems, and along with the existing limitations in the transmission networks, a comprehensive analysis over an extended time is needed to properly explore all potential wind sites for wind capacity allocation. This problem is computationally expensive and decomposition methods are required to break down this problem. Here Benders decomposition approach is used, which is a popular technique for solving large-scale problems, to decompose the original problem into a master and a subproblem. The master problem is a linear problem, which allocates wind capacity to... 

For many years of tall buildings with regard to the development and progress towns are necessary for the urbanite of the city and are considered as progress of the symbols societies. These buildings because of high wore their features special treatment under the influence lateral loads like the earthquake. In a way that today is an important issue in seismology and Earthquake Engineering all the powerful movements of the earth and its effect on the performance of the workforce special buildings as tall. Two points in this important subject. First modeling and simulations of the Most Powerful Earthquakes that in general occur in the field of near source earthquake generator. The earthquake of... 

Nowadays best using of fossil fuels sources of the country (and) importance of comparison against lack of capacity in petrol production make determined the programmers and the directors to foresee and design expanded programs of the goals, to use natural gas for car fuels. To reach fulfillment of these programs, the confirmed needs of the natural gas cylinders are improved and make it essential to invest on producing compressive natural gas cylinders. In this way economical and technical change researches has been done in order to construct on department to produce 200,000 compressive natural gas cylinders in a year during two sets.(shifts) According to the results of technical researches... 

This study analyzes determinants of customers’ switching intentions. The context of this study is service area and we have studied customers’ behavior of internet service providers. In this research we focus both on transactional and relational variables. We have tried to clarify the role of consumers’ commitment on their intentions to switch. Drawing from literature and based on previous service switching research we have developed a switching model. This includes two component of customer commitment and the antecedents of commitment. We have developed our hypothesis according to this model and the literature review. The survey was administered to ADSL internet home users. A sample of 130... 

Dynamic impedance functions method is most recent approach in the analysis of soil-foundation dynamic interaction, and presented for massless rigid foundations. Impedance functions are frequency dependent functions, and used to obtain dynamic response of foundation with arbitrary mass subjected to dynamic loading of any frequency and magnitude. The important assumptions for appropriate useof mentioned method are rigidity of foundation and visco-elastic behavior of the soil beneath the foundation. In this study, experimental vertical impedance functions of square and circular foundations have been investigated,using physical modeling tests. A granular soil layer with finite thickness... 

Phased array systems which are used for sending and receiving electromagnetic signals in mandatory directions are widely used in today’s wireless communication, satellite communication, and radar systems. Phased array systems are composed of units called transmitter/ receiver (TR) modules. These units are connected to antennas in one end and to the combiner/divider at the other end and are playing a major role in determining the quality of phased arrays. Transmitter/Receiver units include a phase shifting circuit for controlling the phase and an attenuator circuit for amplitude control of the signal being sent or received, solid state switches and a number of amplifiers. The aim of this... 

Drop penetration into the capillary tube, as a classical problem, has been studied over 100 years. But there are a few studies that investigate forced impregnation of capillary tubes, which has major application in coating, inkjet printing and rain drop penetration into the soil, have been made. A comprehensive numerical investigation on millimeter droplet impact dynamics on a thick capillary tube with micrometer sized pore is conducted and validated against experimental data. This work is extended to oblique impact of drops into pores and normal impact on nanoscaled pores. We apply the finite volume numerical method to solve the time-dependent governing equations of continuity, momentum in... 

Optimal investment strategies are often derived in continuous time models, but have to be implemented in discrete time. It has been shown that in models with stochastic volatility or jumps; this could lead to significant utility loss, for an investor who utilizes ‘Derivatives’ in his/her portfolio. In this study, we determine the optimal investment strategies with discrete trading explicitly taken into account, through ‘Stochastic Dynamic Programming’. These strategies are in the form of optimal factor exposures for portfolio. The investor, then, needs to use sufficient non-redundant Derivatives in addition to the ‘Stock’ to gain the desired exposures in each point of state space he meet.... 

The systemic approach to innovation plays a central and somewhat unifying role within the field of innovation studies. The main tenets of the approach were developed during the last decades of twentieth century by a bunch of researchers who were tackling with the problem of the economic nature of innovation and its role in growth and competitiveness. The innovation systems approach spread out rapidly throughout the globe and established itself as a framework for studying and policy making in academia and national and supranational organizations. This vast and fast expansion, however, was accompanied by a set of critical contemplations on the theoretical soundness of the approach and also by... 

Optimization of heat transfer in vehicle's underhood which contains radiator, cylidir block, cylinder head and … with minimum pressure loss on engine is one of the most important problems of the car companies in all over the world.To design some cooling parts like simple radiators which doesn’t have a effective cooling effect, we can use equations.but for more complicated geometries which is morte efficient we have many complicated solutions.So in this condition computationl analysis and laboratories play an important role.in this condition we should consider that producing a sample and the process of verifying the result of test is too expensive.So recently the car companies prefare... 

Linear structure of polypropylene, which is a direct result of Ziegler-Natta catalysts, led to the melt strength of the polymer is low and it does not show hardness strain. This defect is cause to the use of polypropylene in some processes, such as thermoforming, making foam etc. are limited. A main methods to solve this defect are branching structure of the polymer. There are three general methods for this purpose, which are modified by chemical, electron beam irradiation and polymerization in the presence of metallocene catalyst. The first two methods that past processing, polypropylene branching using linear type is produced, while the third method branching occurs during polymerization....