Sharif Digital Repository

the gravitational wave (GW) which is a prediction of General Relativity has entered a new era after being detected by Ligo observatory in 2015. new discoveries are still being made. the discovery of GW is a new opportunity for studying gravity, astrophysical sources of GWs like binary black-holes or binry neutron stars as well as testing cosmology models.on the other hand, it should be mentioned that the astronomy of gravitational waves is in its dawn stage. in future having numerous precise detectors and by accumulation of data, speaking about exact phenomena and statistical analysis will become meaningful. as in the case of cosmic microwave background physics, in which researchers started... 

Nowadays binary sensors such as infrared sensors are vastly employed in industrial, commercial and general applications due to their simplicity and low price. Beam sensors are common type of these sensors which can detect objects when they cross its beam. Sequence of sensors which are crossed in a time order is called sensor word. Consider an object, produced sensor word shows the order which it has crossed the beams. If we have more than one object then sensor word is combination of all sensor words produced by all object. We need to separate each sensor word. In this research, sensor word is developed to Fixed-Charge Minimum Cost Maximum Flow Network type.In this case, the consequent... 

In present thesis, the effect of cosmological constant, Λ, in bending of light by spherical symmetric mass has been studied. At first we obtain the Schwarzschild-de Sitter solution as spherical symmetric solution of General relativity field equations with cosmological constant, without we suppose the solution is static. Then we obtain gravitational lens equation by considering the space geometry and we benefited from several approach to specify the contribution of cosmological constant to the deflection angle. Furthermore we put new upper bounds on the value of the lambda independently of cosmological constraints. Finally for study the contribution of lambda in gravitational lensing... 

Gravitational lensing affects not only the position and number of images of cosmic objects but also their shapes. In the so-called weak gravitational lensing effects related to shape of the cosmic objects are studied. These require high quality images and wide field of view. Because of technology development and production of multi-chip CCD cameras in recent decades, we are witnessing an increase in the number of projects using weak lensing techniques. Taking instrumental errors into account, the first step in weak lensing studies should be the proper data reduction to produce final images in which instrumental errors are removed and have sufficient precision to be processed. In This thesis... 

In recent years, the use of embedded processors has grown increasingly in wide range of computer systems; so that most of manufactured CPUs are used in emebedded systems many of which are safty-critical systems such as medical devices, aircraft flight control, space systems, nuclear systems, etc. The incidence of failure in these systems can cause irreversible damages on human life, financial or environmental matters. Silicon process technology trends, such as reducing the threshold voltage, increasing the frequency and decreasing the size of transistors, not only caused increase in single-bit fault rate but also caused occurance of multi-bit faults. Due to importance ofcorrect operation of... 

We have tried this for the first time to reperesent a comprehensive description of the evolution of a perfect fluid in inhomogeneous relativistic models.We solve Einstein equations using numerical methods.In this procedure we can evaluate the effect of pressure in perfect fluid evolution.Also we look at the behavior of the various horizons, and in the end we will present a cosmological model to a black hole  

In this research, steady state and transient performance of a single spool axial turbojet engine (without afterburner) is studied. Performance maps of main components such as; compressor, combustor and turbine are extracted from a similarity (geometry independent) approach.Then using nested loops method, steady state model of the turbojet engine is developed and using shaft dynamics and volume packing equations, transient model of the turbojet engine is analyzed. Steady state and transient simulations results of an engine are validated by experimental data and then effect of changes on input parameters such as; polar moment of inertia, Mach number, fuel heating value, pressure and... 

Over the past two decades, several studies have been investigated on synthesis and properties of semi-conductor quantum dots because of their applications in sensors, LEDs, detectors, solar cells, etc. One of challenging issues in synthesizing these nano-particles is their size distribution. In this study, Cadmium Selenide was synthesized by the method of colloidal synthesis. X-ray diffraction showed that the crystalline nano-particles have wurtzite structure. For obtaining a uniform size distribution, effect of various parameters such as molar ratio of components and reaction temperature on the growth kinetics of these particles, were studied. Results showed that molar ratio of Selenium to... 

Studing the Scattering Amplitudes has a crucial importance in Quantum Field Theory; and nowadays; there have been many progress in computing these observables: Scattering amplitudes respect the symmetries of a theory: However; it is possible for them to have more symmetries than ones can be seen from the lagrangian of the theory: On the other hand; Feynman diagrams which manifest the locality and unitarity of the theory are not applicable in these kind of theories; since for computing the easiest scattering amplitudes thousends of these diagrams must be computed: In this work; we are going to see using BCFW recursion relation and onshell diagrams how it is easy to compute the scattering... 

In the most cosmological models which already have putted forth, metric has a spherical symmetry; however, according to the galaxy’s shape is not a real approximation. In order to build a more acqurate model, by applying a particular conformal transformation on the static vacuum solution, we introduce a new metric which is axially symmetric and also it approaches to FLRW metric at space infinity. The cosmological model according to this metric has especial features;The solution we have found represent a spacetime which is axially symmetric although it leads to a spherically symmetric Einstein tensor. Therefore, we have found a solution of Einstein equations representing a spherically... 

Although villagers and nomads are an important part of Iran's population, the growth of cities has led to neglecting them and their needs including traveling and transportation needs. The aim of this study is to recognize and to study the transportation demands in a pastoral nomadic society. For this purpose, the theory of activity-based modeling was studied. Sequential modeling was chosen which considers the daily activities of each person as a result of five sequential decisions: a) choosing daily activity pattern; b) choosing primary tour time; c) choosing primary tour mode choice; d) choosing secondary tour time; and e) choosing secondary tour mode choice. In order to conduct a survey... 

Inflation is the leading paradigm for the theory of early universe and the mechanism for generating the seeds of perturbation in cosmic microwave background and large scale structure. In this thesis various aspects of primordial anisotropies and the effects of long mode during inflation are studied. There exist two powerful tools in studying the effects of super-horizon inflationary perturbations, namely, Maldacena’s consistency condition and Weinberg’s theorem. However, there are inflationary models, such as solid inflation and non-attractor inflation, which evade these theorems and in this thesis we study their consequences and features. At first we study statistical anisotropy in the... 

Undoubtedly, energy is one of the most important components of progress in any country. Despite some existing imagery about the future of human access to new and non-renewable energy sources, it is now safe to say that energy is a limited resource that is becoming increasingly difficult to access over time. Utilizing the experiences of developed countries in the field of optimal management and advancing strategic goals in the field of energy is one of the necessities of the country today. In this dissertation, using the meta-combined method, the experiences of the United States of America, China, Saudi Arabia, Norway, Singapore and India as countries that each have one of the advantages in... 

The concept of mass is considered as a fundamental concept in physics. There are, however, ambiguities in its definition in different areas of physics. Specifically, in general relativity we are facing many quasi-local mass definitions for structures leading to different numerical values for astrophysical objects. Our aim is to study the relevance of the concept of mass in astrophysics and cosmology. Astrophysicists use different mass concepts for different applications. We have studied all these defi- nitions and tried to find out how relevant they are. It seems the fundamental concept used in all these definitions is the energy density, which is a local concept and has a unique definition in general... 

Smart heat-sensitive polymers play a unique role in drug delivery systems due to reversible behavior in response to environmental changes, especially temperature changes. Among the heat-sensitive polymers, UCST polymers due to their specific behavior and very little-known polymers with this feature are the subject of many new researches. In the present study, New designed temperature-sensitive polymers with UCST capability based on acrylamide and vinyl acetate were synthesized. These copolymers were synthesized in different percentages of acrylamide by free radical polymerization in solution conditions. All polymers compounds were characterized by H-NMR, FT-IR, DSC and GPC measurements. The...