Sharif Digital Repository

Black holes are theoretically significant because they are (ideal) entities fully described by just three properties: mass, charge, and spin. Their importance also stems from their unique status as spacetime entities with universal properties, including the event horizon and—when including the singularity—representing the boundary of space and time. Beyond their spacetime properties, black holes are also thermodynamic systems. Their behavior requires a theory that integrates both spacetime and thermodynamics. A black hole is something that requires both a theory of spacetime and a theory of thermodynamics to describe and explain its behavior. A consistent description of time, spacetime, and... 

Zeolite membranes are of interest due to their special properties; thermal and mechanical resistances and non-plasticization property in gas separations. Therefore, separation of H2S from natural gas by these membranes is the main goal of this thesis which is not investigated in the world. After some theoretical investigations including diffusion mechanisms of gases in the zeolites and adsorption mechanism of H2S on the zeolites, pure silica CHA-type (Si-CHA) zeolite was selected. After successful synthesis of Si-CHA zeolite, adsorption isotherms of H2S, CO2, and CH4 on the Si-CHA zeolite were measured over pressure range of 0-190 kPa and temperatures of 25 °C, 50 °C, and 75 °C. Acid gases... 

Energy harvesting from wasted environmental energy to power low-power electronic devices has emerged as an enabling technology for wireless applications in the past decade. The purpose of this technology is to provide remote power sources and/or recharge storage devices such as batteries and capacitors. This concept has environmental implications in reducing chemical waste produced by replacing batteries and potential monetary benefits that also reduce maintenance costs.Energy harvesting (EH) from untapped natural energy sources is common nowadays due to the increasing demand for electricity. Sources have the potential to generate micro to milliwatt power, depending on environmental... 

General Relativity is a generally covariant and deterministic theory of space-time. The Hole Argument requires that there is no substantivalist interpretation of general relativistic space-time. In this thesis, I am intended to show that this conclusion is not compelling. Through this, a deeper understanding of philosophical and mathematical content of General Relativity is investigated  

Think of an Alpine hiker who because of avalanche and a blinding blizzard, is stranded on a desolate, mountain path facing a chasm. The hiker cannot return the way he came because of the avalanche, yet, if he stays where he is, he will freeze as the temperature plummets. The hiker’s only real hope is to jump the chasm. Knowing that exertion generally follows belief, the hiker realizes that his attempt will be half-hearted, diminishing his chance of survival, unless he brings himself to the belief that he can make the jump. In circumstances like these, one is clearly justified both in forming beliefs motivated by pragmatic reasons, and in suppressing beliefs (I cannot make the jump) motivated... 

The thesis at hand provides a comparative study of Kantian and Fichtean ethics. In the course of this study, the ethical theory of these philosophers will be analyzed through three stages of “Foundation of Ethics,” “System of Ethics,” and “Application of Ethics”: Foundation of Ethics seeks out human will as the sole possible ground for ethical theory of both Kant and Fichte; System of Ethics follows the endeavors of the two thinkers in deducing concept of ethics from this sole ground; and lastly, Application of Ethics introduces the ethical thoughts resulting from a Fichtean account of ethics. This thesis is mostly based upon studies of Allen W. Wood of the ethical thoughts of Kant and... 

In this thesis a smart anticorrosive pH-responsive coat was developed with layer by layer (LbL) technique in the assembly of SiO2/CTAB/PSS/HMTA/PSS/PEI/PSS. SiO2 nanoparticles were prepared from Matland Company (Iran) with average size of 24 nm. At first, the corrosion inhibition of HMTA for API 5L Grade B steel in 3.5 wt.% NaCl solution was investigated. Tafel polarization technique showed the optimum concentration of HMTA was 0.08 M with 92% corrosion inhibition efficiency as the morphology of coverage and adsorption on the steel surface was confirmed by SEM and EDS. AFM results showed the roughness of the surface decreased from 241 nm to 56 nm that is attributed to HMTA adsorption on the... 

In recent years, sparse representation has had a variety of applications in computer vision such as noise reduction, image reconstruction, classification and dimension reduction. In this project, we aim to provide a method of matching the keypoints obtained from the Scale Invariant feature Transform (SIFT) algorithm. In this algorithm is used descriptor instead of intensity . The proposed method, first, extracts the salient points from the images and learns a dictionary-based descriptors corresponding to the points. Then, using the dictionary, it obtains the sparse coefficients for each salient point by which, it determines the correspondence of the salient points in the two images using SVD... 

This study investigates the possibility of knowledge transfer from military industries, with a focus on the missile industry, to other sectors in the country, particularly the automotive industry, from the perspective of technological capabilities. The objective of this research is to conduct a comparative analysis of the technological capabilities of these two industries and to evaluate the potential and challenges associated with the process of knowledge and technology transfer. The research methodology involves qualitative analysis through interviews with experts and the review of relevant documents and records. The conceptual framework has been developed based on existing models of... 

The present work has been planned to elaborately investigate the key parameters which affect the formation of shrinkage porosities during centrifugal casting of ductile cast iron pipes. The porosity defects can be mostly found in the Hot Mould centrifugal casting products and adversely affect the final mechanical properties of ductile iron pipes namely Ultimate Tensile Strength and Elongation.
In the first point of view, the created defects were detected through microstructural observations and the corresponding responsible mechanisms were also discussed. The results showed that the inner porosity is produced because solidification occurs from both the inner and outer surfaces... 

Xanthan gum is a water-soluble exo-polysaccharide. It is produced industrially from carbon sources by fermentation using the gram-negative bacterium Xanthomonas campestris. There have been various attempts to produce xanthan gum by fermentation method using bacteria and yeast by using various cheap raw materials. In this study the cultural conditions for xanthan gum production by Xanthomonas campestris were investigated and optimized by response surface methodology, to maximize cell and xanthan production in batch experiments using YM broth without pH control. The individual and interactive effects of three independent variables (carbon source concentration (40-80 g/l), nitrogen source... 

The search for an empirically proven quantum theory of gravity is one of the greatest open problems of fundamental physics. Obstacles are formal and conceptual in nature. Our goal is to find a theory that somehow unites general relativity (Einstein's classical field gravity theory) and quantum field theory. In this research work, the problem of quantum gravity and the reason for its importance are investigated, as well as the proposed solutions; and what philosophical issues do these approaches and the issue itself create. Research has been carefully selected to remain managed in terms of size and content, however, some basic formalism is introduced to enter physics and the philosophy of...