Sharif Digital Repository

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... 

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... 

Numerical study of the interaction mechanism of the premixed flame and the acoustic field is performed in this work. The geometry similar to those used in experiments, is a two-dimensional tube in which flame travels form open end towards the closed end. The numerical study is done using PPM method. Results show that the shape and speed of laminar flame is strongly affected by the induced acoustic field. Stronger interaction is observed in the closed-end tube with no slip boundary conditions. The effect of the Lewis number on the interaction mechanism is also investigated. Premixed flame- accelerated flame – interaction of flame and acoustic field  

Translation quality assessment (TQA) as a systematic field of inquiry has been under scholarly investigation over the past decades. In spite of the challenges appeared in the path to success, theoretical and practical developments have already been made in translation studies. One of the unsettled and challenging problems concerning translation assessment, yet, is the subjectivity that is inherent in the process of scoring test-takers’ translation performances. In the absence of any granular objective criteria which includes all the subcomponents of translation as a multi-layer rather than unitary construct, the raters inevitably bring their intuition and will to the act of measurement.... 

Knowing the location and time of oil accidents and trying to track the pollution caused by these accidents is very important for the purpose of monitoring and protecting the environment. The occurrence of large oil spills in the marine environment can have serious environmental, social and economic consequences. In this research, oil spills in the Persian Gulf were first identified using remote sensing method and Sentinel-1 satellite images. The images of this satellite were called for the processes needed to identify oil spills in Google Earth Engine space. After detecting the oil spills, it is necessary to determine the duplicate spills and remove these types of spills, as well as estimate... 

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 ... 

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... 

In this thesis, we focus on some internal organization issues of the supply chain; in particular, we analyze some network design problems which are typical of producer companies. The aim is to optimize the flow of goods through the literature distribution network, from the plants where the goods are produced (supply points) to the demand points, which are essentially distributors such as wholesalers or retailers. The system addresses a class of distribution network design problems, which is characterized by multiple product families, a central manufacturing plant site, multiple central warehouses and distribution center, and retail outlets (customer zones) which demand multiple units of... 

The purpose of this research has been measuring how much studied companies use different levers of controls. Management control system has been described as the system which ensures the organization about implementing its strategy (Antony, 2004; Simons, 1995). In this research we chose Levers of Control framework (Simons, 1995) as the proper model to describe management control systems in organizations. Using related literatures, we developed a questionnaire to measure how much different organizations use each levers of control. The proposed questionnaire was distributed in three businesses with different Value Creation Logics (Stabell & Fjeldstad, 1998), to provide a ... 

Popular usage of composite materials in aerospace, civil and defense industries in the last decades has been the cause for paying more attention to optimization of composites tailoring. Due to inherent complexity of composite problems, i.e. discrete nature, complex interrelationship of design variables, existence of so many local optimum points, and etc., gradient base methods of optimization are found to be incapable and as a result using other powerful methods seems inevitable. Nowadays Genetic algorithm (GA) as an evolutionary technique is used for tackling composite problems. The success of a genetic algorithm can be quantified by estimating the cost, time required and the quality of... 

Nowadays, despite the special position of power electronic converters in the world, and the fact that they become an integral part of human life, still in the wake of a serious necessity the development process has not stopped and the increasingly fast pace, it opens up new horizons. This important necessity emerges from the environmental concerns regarding consumption of fossil fuels and their limited and imbalanced distribution which can be effectively addressed with the use renewable energy systems. By improving the quality of the semiconductor switches and offering new topologies in different functions as well as using new control methods, scholars try to develop enhanced converters in... 

With the progression of technology demands for novel method of heat cooling is increased so the old method of cooling such as heat removal by air stream with force convection and even single phase method was not sufficient for today’s industry need. Nowaday, spray cooling method which belongs to two phase cooling method is one of the most popular method. In this study two method of spray cooling: spray cooling with flow blurring nozzle and electrospray cooling were investigated. For both method, at first the physics of phenomena and morphology of spray is studied experimentally then the efficiency of heat removal in each method is evaluated by the assessment of variation of temperature and... 

Nowadays, concerns about the reduction of fossil fuels and environmental issues, have made renewable resources more important. Among these resources, photovoltaic (PV) systems are more popular than others, due to their environmental compatibility and unlimited availability of sunlight. Increasing the penetration level of PV systems in electricity networks presents various technical and control challenges such as voltage and frequency variations; and protection and harmonics issues. In this thesis, voltage rise problem due to reverse power flow in distribution feeders is discussed. This is one of the main obstacles to the expansion of these resources in distribution networks.Various solutions... 

Today, the correct management of construction projects in IRAN's water industry has become a severe concern for its managers. Construction projects of the water industry constitute a considerable part of the country's construction industry. Several significant Issues such as operation management, water industry projects, correct management of resources, crisis management in the water industry, increased productivity and useful life of structures, increasing productivity, and preventing water loss are among the determinative challenges in construction projects in Iran. One of the new methods for the correct management of the life cycle of projects in this area is the use of Building... 

The distinction between SOEs and private firms in access to loans is essential from the viewpoint of policy-making. This distinction is more crucial when we know that the difference is caused by factors other than natural market forces and has emerged merely by government ownership. In this paper, we investigate a unique intervention in privatization and identify the causal effect of government ownership on access to loans. In this respect, we study Sahamedalat in Iran by using DID approach and estimate the effect of giving up the treatment firm's cashflow right on the amount and composition of the loans. The results show the intervention significantly decreases the long-term loan of the... 

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...