Sharif Digital Repository

The Kakeya needle problem was stated by a Japanese mathematician, Kakeya, in 1917 as follows: \What is the least area of a planar shape in which a needle of unit length can be turned 180 degrees?" Later, this problem was closely related to some problems in Fourier analysis and harmonic analysis, theory of partial dierential equations, theory of arithmetic combinatorics, and analytic number theory. In this thesis, after stating some elementary considerations in chapter one, we describe the Kakeya needle problem and Besicovitch's solution in chapter two. In chapter three there will be some discussions about the Fourier multiplier operator and in particular, disk multiplier operator, and we... 

In this thesis, we study diffusive heterogeneous predator-prey system with Holling type-II functional response in the presence of harvesting in prey equation i.e.8>>>>><>>>>>: Δu = u a(x)u2 buv1 + mu ch(x) inΩ;Δv = v v2 +duv1 + muinΩ;@u = @v = 0 on @Ω,where Ω is a smooth bounded region in RN and a(x) is a nonnegative continuous function on Ω, with Ω0 a region such that Ω0 Ω and a(x) > 0on ΩnΩ0. We show that in the case of weak prey growth rate, i.e. less than the first eigenvalue of Δ in Ω0 with Dirichlet boundary condition,the system has a positive solution for the values of in a bounded interval and c > 0 sufficiently small. We also investigate the multiplicity of positive solutions... 

The efficiency of acidizing operation is usually assessed through Build up or Drawdown test (calculation of skin). These methods are performed only after the acidizing operation, so it is impossible to evaluate the efficiency of acidizing during the real time operation. Analysis of the acidizing efficiency during the operation by using the acidizing operation data is a viable approach to this costly and challenging process. In this project, it has been tried to present a well testing method for calculating changes of skin value of a carbonate reservoirs during acidizing operation by using the real field data (surface pressure, injection rate and etc.).
The estimation of skin changes... 

Nowadays millions of images are shared on social media every day , So image inpainting has become an important issue . After advent of Generative adversarial network image inpainting methodes based on deep learning has been revived and significant progress has been made . For a proper image inpainting , The inpainted image must benefit from the appropriate structure and texture in the missing regions . Therefore, in this project , an attempt is made to use a two-stage structure by using Generative adversarial network .in first stage first by using Gabor filters , the image structure is extracted and then the image structure is completed , while the second stage focuses only on the... 

The main purpose of my research is to present a predictive E-Commerce plan for Iran. For many people the term "electronic commerce" means shopping on the part of the Internet called the World Wide Web, but other technologies such as wireless transmissions on mobile telephone and personal digital assistant devices are also included. In our thesis the term Electronic Commerce or (E-Commerce) is used in its broadest sense, and includes all business activities conducted using electronic data transmission technologies. In Iran e-commerce has achieved an important role and is facing remarkable acceptance in trade operations, therefore my study focuses on the development of E-Commerce model in... 

In this work, a comprehensive dynamic model has been used for styrene emulsion polymerization in a semi-batch reactor to predict the evolution of product particle size and molecular weight distributions under non-isothermal condition. Method of moments has been applied for solving the population balance equations and the results are compared with the results obtained from finite-volume method as a precise technique. A sensitivity analysis respect to perturbation in initial values of various reagents, species and the reactor temperature has been performed to identify suitable manipulated variables for closed-loop control of the reactor. The detailed model is used to generate optimal feed... 

Today, due to the decline of drinkable water, many desalination plants have been established and operated around the world. Disposal of these brines, which have higher density and temperature than receiving water, causes many environmental impacts. Industrial power plants discharge these effluents into the seawater body mostly as submerged jets due to their higher effectiveness. Many experimental researches have been done on the negative and positive buoyant jet that discharged form desalination plants. But a few numerical studies have been done with investigating the full Navior-Stokes equations and they have been flawed in modeling. For example, some of these models have been able to... 

In this research, self-optimizing method has been used to design a plant-wide control structure for processes containing purge and recycle streams. The method is based on the concept of self-optimizing variables to maximize the process profitability in the presence of possible disturbances. The purpose of this thesis is to perform this procedure on ammonia and methanol processes containing purge and recycle streams.Using the results obtained for the ammonia process and considering the constraints and operating conditions of the problem, the active constraints of this process were detected which were cooling water flow rates to exchangers. According to local analysis method, self-optimizing... 

Purple phototropic bacteria (PPB) are a potential mechanism for wastewater treatment and recovering materials. Purple phototropic bacteria is one of the microorganisms that use infrared light energy and carbon contained in volatile fatty acids (VFA), in addition to eliminating nitrogenous compounds, it has a high ability to recover nutrients in wastewater. In this project, a photobioreactor is investigated, in which the purple phototropic bacteria by absorbing nutrients (phosphate and nitrate) and substances present in the wastewater, provides the possibility of releasing these substances in the open environment without the environmental hazards. The mathematical modeling and control of this... 

In light of rising energy costs and restricted access to energy resources, enhancing energy efficiency in process industries has become increasingly important. One effective method for reducing energy consumption in chemical industries is the use of thermal integration in distillation columns. This study examines the thermal integration of a benzene-toluene distillation column with the aim of analyzing and improving energy performance from a dynamic intensification perspective. Initially, the internal thermal integration of the distillation column was modeled. Subsequently, a mathematical analysis of the model was conducted to identify conditions of multiplicity. Following this, steady-state... 

One of the model based control strategies that has been proposed in recent years for the control of process systems is the one based on the economic models, in which objective functions with an economic basis are used along with the equations and constraints to perform control calculations. In this work, the control of a multiproduct continuous stirred reactors is discussed, in which, it is possible to produce different products based on changes in the market demand, the price of the products or the primary raw materials according to a specific schedule. One of the recently used methods is the economic predictive control method based on the Lyapunov function. In this method a quadratic... 

Emulsion polymerization is a multiphase process which produces dispersions of polymeric particles in water called polymeric latexes. When instead of surfactants solid particles stabilize the latex, the process is called Pickering emulsion polymerization. Latexes produced in this way exhibit better mechanical and optical properties. In this work, a model for styrene Pickering emulsion polymerization in the presence of Laponite RDS given in the literature was simulated. The results of simulation were unsatisfactory. A procedure was developed to separately check different parts of the code which was written for the task. Also, another emulsion polymerization system, in which the monomer was... 

In today’s business world, team working as one of the most useful solutions to improve organizational performance and efficiency is used by different organizations and companies. Many experts and academic researchers are focused on teams and team based organizations in their studies and tried to find its cause and effect on organizational performance in the past two decades. Also different variables are recommended as influencing factor on team performance by different authors, In spite of all these researches, no fixed list of these factors, which are been acceptable by reasonable number of researchers and experts, can be find yet. This study tries to present the results of an experimental...