Sharif Digital Repository

There are different kinds of ownership structures. In every economy special kinds of these structures are common. These structures include Pyramidal ownership, cross-ownership, etc. These structures empower shareholders to make a gap between their cash flow right and ownership right in a special firm so they could control more firms with the same capital. These structures have their pros and cons, like the internal capital market and tunneling. Of important factors affecting these structures are Legal protection of minor shareholders, shareholder concentration, and largest shareholder. In this research, we find that, unlike most countries, there is a negative relationship between a firm's... 

As the crowded cities require public transportation and because of lack of space on the ground, Subway and boring underground tunnels encountered. In this thesis the interaction of boring the line 7 of Tehran metro with the existing station of line 1 of Tehran metro (Molavi station) is studied. By changing the soil specification, The surface settlement is significant so the soil specification is one of the important parameters of the interaction. For comparinf the effect of these parameters, the soil settlement and bending moments is investigated in different parts of station while the lower tunnel is passing beneath it. The 3D Abaqus software is used for modeling this interaction. In... 

Recently, Needs for construction of rock structures and underground ones such as tunnels, dam foundations, power plants and caverns built to keep oil, gas and nuclear waste has increased dramatically. In order to design, construct and excavate these underground structures safely and economically, full understanding of rock mass properties, suitable tools and practical techniques of drilling are necessary. Because of existing this discontinuities, including joints and layered rock masses and their effects on mechanical behavior of rock mass, it is necessary for the geomechanical profile, shear strength and failure mechanism of rock mass to be accurately indentified. Shear strength criterions... 

In recent years, numerous companies in various industries apply supply-chain management to improve their market competitiveness. Advances in information technology bring new approaches for managing supply chain activities. Consequently, emphasis on supply-chain coordination has increased in recent years. Vendor managed inventory (VMI) is an important coordination initiative. In VMI, the vendor assumes responsibility for managing inventories at retailers using advanced online messaging and data-retrieval systems. In this dissertation we investigate the effect of VMI on supply chain performance under make-to-order and make-to-stock environment. By using renewal reward theorem, we derive the... 

Nowadays, air pollution has become one of the biggest problem of large cities and has numerous negative effects on the environment and people's health. The present research examines how various types of pollutants are distributed in an urban environment, depending on the type of arrangement in different places. Razaviyeh town (including nine 15-story buildings) in the 9th phase of Pardis new city in Tehran has been studied three-dimensionally here. The dimensions of each building in this complex are 12 x 13.5 meters and their height is about 45 meters. Thus, the dimensions of the computational domain used are estimated to be less than 0.02 square kilometers. In this research, computational... 

In this thesis, we study monadic second order logic and the languages of graphs. We introduce the notion of ∆- regular graph automaton. Then we designed this finite automaton for processing on labeled graphs. Definability of graph languages which are recognizable by this automaton is shown. To do this, we first briefly introduced monadic second order logic, and then we studied definability of regular string and tree languages in monadic second order logic. In the last section of thesis, ∆- regular graph automaton is introduced  

Uranium is the most important element in the nuclear fuel cycle. Recovery of uranium from waste produced at every stage of the fuel cycle is not only economically important, but also environmentally important. In the production phase of uranium hexafluoride, certain amount of solid waste is produced in the bottom of the fluorination reactor. In order to extract the uranium from this waste, we have to eliminate the fluorine contained in the waste. This is because the fluorine forms strong complex with uranyl ions during the extraction process, and prevents from efficient extraction of uranium. In the current thesis؛ first, we examined the characteristics of the waste ... 

This project evaluates the feasibility of using waste salmon fish bones as the reusable and low cost solid catalyst support for synthesis of biodiesel from waste sunflower oil via transestrification method. Calcinated waste fish bone derived hydroxyapatite (HAP) was employed as the supporter for KOH & K2CO3 to prepare an efficient solid base catalyst for biodiesel production. The catalyst were characterized by SEM-EDS, XRD, FTIR, BET, TGA, ICP. The effects of catalyst preparation conditions (such as fish bone and KOH or K2CO3 calcination temperature, loading of KOH or K2CO3 on the support), reaction conditions (such as reaction time, methanol/oil molar ratio, reaction temperature and... 

Liquefaction of gases is one of the applications of cryogenic science. Among the gases, Helium has the lowest boiling point, which at a pressure of 1atm is approximately 4.2K. Liquid helium can be used to cool superconductors in transportation equipment, military radars, and medical imaging equipment. For helium liquefaction, various cycles are used; these cycles have different parameters in their structure such as of input mass fraction to expanders, heat exchanger effectiveness, expander arrangement and ... which their analysis for improving the performance of the cycle is important. In this research, the aim is to study 2, 3 and 4 expander cycle with various parameters and structure. For... 

Estimation of demand, for example, for transportation is an important issue for the planning and programming of various systems. Thus, enhancing the predictability power of such models is of high value. Demand stems from choices of individuals, and choice is subject to uncertainty and fuzziness. Uncertainty comes from many factors including incomplete information of decision-maker, and fuzziness comes from many other factors including personal perception regarding the value of the variables affecting choice. This study tries to introduce a new approach in building choice models, in which variables are transformed into another variable by the help of a global wisdom. This wisdom shows the... 

In Persian language, there are some special uncertainties and complexities regarding the extraction of phonemes due to its flexible structure. In this work, we try to solve two problems caused by this issue, homographs disambiguation and Ezafe recognition in Persian text to speech systems.
In this work, two methods are presented for solving the two problems. The first one is a pattern recognition method based on Aho-Corasick algorithm that has the best performance according to the execution time. The second method is a hidden Markov model tagger based on Viterbi algorithm that uses bigram and trigram statistics. These methods are run on 10 million word corpus and the results are compared... 

Airplanes usually experience minor position change and height loss during cruise flight, but under normal circumstances the aircraft total energy is adequately acceptable to maintain the trajectory and the desired performance without severe oscillations. On the other hand, if the airplane encounters a wind-shear or microburst during take-off or landing phases, it would be a dangerous situation, as the aircraft kinetic and potential energy levels are not as high.
In this research, a model predictive controller is designed and investigated to allow a transport category aircraft to either escape or penetrate the microburst. In this regard, initially a DMC controller is designed for 6-DoF... 

Despite adoption of HR analytics and the recognition of its importance by senior managers, its effective implementation in organizations remains a challenge. Given the benefits of HR analytics for organizations and the relative readiness of organizational structures to leverage it, this study seeks to answer the question: “How can HR analytics processes be effectively implemented in organizations?” Establishing an empirical foundation for improving existing theoretical models can significantly contribute to advancing this field. Using a single-case study approach, this research investigates the implementation of an employee engagement system through Officevibe software in a startup operating... 

According to the impossible trinity, countries can only enjoy from two of the following choices simultaneously: fixed exchange rate, free capital flow and independent monetary policy. A part of the economics literature has tried to verify the theory empirically. Some of the researches like Klein and Shambugh(2015) has concluded that the trilemma is valid on the occasion of transferring the effect of base countries interest rate changes to other countries. On the other side, a few papers like Ray(2013) has shown that an independent monetary policy can just be obtained by a closed capital flow and a float exchange rate system can not necessarily give central banks the autonomy of monetary... 

Nanopositioning is the technology to control position of the objects with precision of the scale of nanometers. Nowdays, This technology emerged as one of the components of research and production in the micro and nanometer dimensions, helping researches and producers to carry out many state of the art projects. A nanopositioning device, consists of a support to path guidance, an actuator to apply force and motion, a driving circuit for communication with the actuator, a sensor for measuring displacement, a circuit for reading sensor’s data, a controlling algorithm to reach the desired precision, a controlling hardware to enforce controlling logic, a power supply and a graphical user...