Sharif Digital Repository

The predator – prey model is arises when the growing rate of one type decreased and the growing rate of another type increased. In this project, in chapters 2,3,4 and 5 we will describe the existence of periodic solutions for predator-prey systems and introduce some classical techniques for finding this solutions which the most important of them is the continuation theorem, for using this theorem we must find the open set Ω which by the conditions on Fredholm mapping L and the mappings Q , N we solve the equation Lx=Nx . In chapter 2 we study the periodic solutions of the below systemx2(k)






 

Prevalence of Multiple Drug Resistant Tuberculosis and use of Yersinia-Pestis in bioterrorism warrants synthesis of new antimicrobial agents. Although Pyrazoline derivatives were first synthesized as antimicrobial drugs, but they also had Mono Amine Oxidase inhibitory effects. In this Quantitative Structure – Activity Relationship (QSAR) study, MAO-I activity of pyrazoline derivatives were evaluated. By applying semi-empirical quantum calculations at AM1 level, optimum 3D geometry of 32 molecules were obtained.After descriptor generation, Principal Component Analysis (PCA) was performed to fiind out 5 outliers. After omitting outliers and sorting molecules according to IC50 values, Stepwise... 

The removal of ethylene glycol, one of the most widely used antifreez, with moving bed biofilm reactor (MBBR) was studied. Beside of ethylene glycol, the synthetic wastewater contained molasses and other salts as nutrient source. The packings were composed of polyethylene and shaped like small cylinders with a surface area of 500 m2 per m3 bulk volume of carriers(KMT). The COD of the feed was adjusted by varying the ratio of ethylene glycol to molasses. The total COD was 1252.5, 1345 and 1500 mg/L. The resulted showed that when the biofilm grows on the packings and its thickness is good enough, the removal efficiency increased. The increase was attributed to higher concentration of biomass... 

In 1917 Einstein used Λ as a cosmological constant in his theory of general relativity, but after a while he receded for some reasons. This constant has been reconsidered again recently. But using it in general relativity has caused some problems. In this thesis, after a short review of important elements in studying cosmological constant problem, like a short introduction to general relativity and cosmology in the first chapter as well as a short review of quantum field theory and supersymmetry in the second chapter, we will study the history and introduction of the problem in the third chapter.in the third chapter , different solutions to this problem ,like supersymmetry,anthropic... 

The purpose of this research is theoretical and numerical investigations on centrifugal compressor. A computer code has been developed to simulate single-zone and two-zone model, based on the revised formulation for real gas, using Peng-Robinson equations. Single-zone modeling, also known as meanline method, established based on 1-D equations of fluid dynamics considering ideal gas relations, empirical loss correlations, slip factors, impeller efficiency and no wake or separation regions. Considering usual significant separated regions in the gas path of impellers, two-zone (jet and wake zone) model has been developed to achieve a more reliable simulation by using fewer correlations based on... 

The Sudoku puzzle is played on a 9 × 9 grid which is divided into nine boxes each with 3 × 3 cells. Initially, some digits between 1 and 9 are given on the grid as the clues. Generalized Sudoku (a table of n2 by n2 that includes n2 blocks with n cells and in each of its rows, columns and blocks has all numbers from 1 to n2 appeared once and only once) can be considered too. Millions of people around the world are tackling one of the hardest problems in computer science without even knowing it. The first such puzzle appeared in the May 1979 edition of Dell P encil P uzzles and W ord Games and, according to research done by W ill Shortz, the crossword editor of the N ew Y ork T imes, was... 

On track to achieve heat transfer methods for small-scale, this research describes the design process of fabrication and experimental analysis of micro heat pipes with a rectangular section. First, the overview of micro-fluid systems and conventional mechanisms of heat transfer in these systems is discussed. Then, in order to describe the research theory and principles of heat pipe, various types of heat pipes micro scale and macro scaled are analyzed. After that, the method used for fabrication of a micro heat pipe without grooves is described. A new method for fabrication of MHP is investigated in this study. By using this method, one fiber glass board is fabricated by printed circuit... 

Since little attention has been given to multiattribute compared to multivariate control charts, this research is concerned with developing a new methodology to employ the multivariate exponentially weighted moving average (MEWMA) charts for multi-attribute processes. Moreover, since the variable sample size and sampling interval (VSSI) MEWMA charts detect small process mean-shifts faster than the traditional MEWMA, an economic design of VSSI MEWMA chart is proposed to obtain the optimum design parameters of the chart. The sample size, the sampling interval, and the warning/action limit coefficients are obtained using a genetic algorithm such that the expected total cost per hour is...