Sharif Digital Repository

Monopiles are large-diameter with a typical diameter of 2 to 10 meters that are used for the base of offshore wind turbines. During its life, this structure is subjected to wind, wave, and sea currents, and due to the lateral displacement of the monopile, the wind turbine base structure with a considerable height can create the effect of "P-Δ". Therefore, accuracy in modeling and accurate estimation of monopile displacements and rotations is important. At present, the lateral design of monopiles is based on force-displacement (p-y) curves. P-y curves are semi-empirical curves based on experimental results obtained on piles with a diameter of less than one meter in different soils and under... 

Regarding the existing contrary in the literature in relation to the effect of plastic fine on sand liquefaction behaviour, we decided to study this effect. Amounts of 5, 15, and 25 percent of two types of plastic fine, Kaolinite with PI=19 and Bentonite with PI=116 added to Firoozkooh Sand and 68 stress controlled tests were conducted using cyclic simple shear apparatus. In all teste the frequency of shear loading and consolidating vertical effective stress were constant and 0.1 Ht and 100 kPa respectively. Reaching excess pore water pressure ratio to the maximum value (r_u=Max) and reaching double amplitude shear strain to the value of 5% have been considered as liquefaction critera. In... 

increased cohesion up to 4H pencil. Results of immersion test in water showed stability of coatings. Polarization test in naphtha and water mixture for stainless steel, copper and aluminum meshes demonstrated 98.89%, 86.25% and 66.6% protection efficiency respectively. In order to study of oil and water separation efficiency, mixtures of water and naphtha with different content of naphtha were used. Separation test for 200μm St.St mesh in different slopes demonstrated that changing of slop increase separation efficiency up to 95.5% for water and up to 100% for naphtha. Separation test for meshes with different pore size demonstrated that meshes with small pore size are more appropriate for... 

The railroad blocking problem emerges as an important issue at the tactical level of planning in freight rail transportation. This problem consists of determining the paths of each shipment which minimize the total cost subject to the key constraints such as limitation on travel time, limitation on number of dispatched trains, and limitation on the number of cars classified at each station. The multi-path railroad blocking model is developed and then a new heuristic algorithm based on the Lagrangian relaxation technique to solve the realistic rail network is introduced.To consider the uncertainty which is inherent in the demand and travel time (as a supply indicator of rail system), a... 

Optimum railroad alignment, which can be categorized into continuous problems, has been a conundrum for engineers because of two reasons: At the first, there is a wide variety of information that is necessary for finding optimum one. Secondly, the major costs of a railway, such as length-dependent, traffic-dependent, volume-dependent and location-dependent are affected by the numerous factors so that, it may be difficult to formulate them. In order to solve large scale continuous optimization problems, there are two approaches: firstly, such problems may be tackled with a combinatorial optimization algorithm, e.g. ant colony optimization (ACO), by the continuous range of allowed values are... 

Vortex-induced vibration is a known phenomenon in fluids flow that is being studied in different fields of engineering and usually, we want to reduce the harmful effects of this phenomenon on the subjected structures. Also, it is possible to use this phenomenon for harvesting clean energy from fluids flow. Energy harvesting from vortex-induced vibrations is based on the maximizing of flow instead of its reduction, and the utilization of these vibrations instead of their suppression. Vortex induced vibrations occur in any ranges of Reynolds numbers. Only in three transient regions cause a reduction in vortex-induced vibrations; therefore, even in streams with a velocity less than 0.2 m/s, it... 

The aim of this work is to design, build and test a laboratory scale flameless combustion chamber. Also, a theoretical model is developed to simulate flameless combustion with a simple model. Flameless combustion is a combustion type with transparent flame which consumes less fuel than typical premix and diffusion flames and emits very low level of NOx. In flameless combustion, recirculation ratio is higher than typical diffusion flames so the flow field is highly turbulent. High recirculation ratio causes low oxygen concentration in combustion zone; thus requiring inlet air to be preheated for flame stabilization at low equivalence ratio and oxygen concentration. We have designed a... 

Solid State Drives (SSDs) have an electronic architecture based on non-volatile memories. The unique merit of a SSD is its internal parallelism. Thus, adopting SSDs as the storage media in the storage systems in various devices, such as smart phones, personal computers, large workstations, and etc., improves the performance of the device, substantially. However, the conventional host interface protocols in SSDs, i.e. SATA and SAS, have critical limitations, like low bus bandwidth (maximum 12Gbps), and a single shared request queue. With such limitations, the host interface turns into a performance bottleneck in conventional SSDs. Therefore, the high performance provided by such SSDs cannot... 

Nowadays, surveillance cameras are an integral part of the transportation management center. On one hand, developing of surveillance cameras around the cities and on the other hand, increasing costs of driving accidents, makes it necessary to use the automatic behavior analyzing systems on video sequences. The scientists’ focuses on detecting unusual events as one of the most important usage of video analysis, and recently, the algorithms of unusual action detecting had an impressive development by using the machine learning methods. In this research, the existing unusual event detection methods and in special, traffic unusual activities will place under scrutiny, and we suggest an algorithm... 

In recent years, utilizing the colloidal gas aphron (CGA) drilling fluids is getting more and more commonplace due to their little formation damage and filtration loss. This study tries to investigate the effect of presence of nanoparticles and their type (hydrophobicity) on stability and performance of water and oil based CGA drilling fluids. This is done through analyzing stability, filtration, rheology, and pore blockage tests. Water and oil based CGA drilling fluids consisted of stabilizer, surfactant, and nanoparticles are generated and through examining of the effects of polymer, surfactant, and nanoparticle concentrations, the optimum formulation is obtained. High pressure-high... 

This dissertation proposes a new platform and a new software for evaluation of urban Water Distribution Network (WDN) resilience. Resilience is considerd as the ability of an infrastructure to come back to steady state after being affected by any environmental or man-made disturbance. WDN, as an essential infrastructure, has major role on resilience and sustainability of cities and communities. Today, uninterrupted performance of WDN is a basic need of people who live in cities. This uninterrupted performance becomes bolder in face of man-made or natural disasters like earthquake. The uninterrupted performance of a system is dependent on the system’s resilience. Majority of researchers... 

In this thesis, the Artificial Neural Networks (ANN) will be used in Automatic Speech Recognition (ASR) instead of Hidden Markov Models (HMM). Hidden Markov Model is one of the most dominant Bayesian network technologies and is the most successful model in current ASR systems. However, excessive training time is a major issue in speech recognition based on Hidden Markov Model (HMM). This thesis presents an Artificial Neural Network language model for human speech by mapping the spectral features of speech namely the formants, cepstrum (Mel-Frequency Cepstral Coefficients (MFCCs)) and Power Spectral Density (PSD) as features of samples of specific words into a discrete vector space. The... 

Recent developments in space industry and the great tendency for definition of efficient, precise and low cost missions are the main reasons for the growing interest in satellites formation flight. Regarding the aforementioned, the study of the multiple satellite control methods is the subject of the present project. In this project, the governing equations of motion of satellite formation flight are developed. Based on this development, it is shown that the satellite linear equations of motion like many other linear system presentations, can not sufficiently model the real system. Therefore, some of the most famous uncertainties in space dynamics such as semimajor axis and eccentricity...