Sharif Digital Repository

Purpose: The purpose of this paper is to investigate the English for publication purpose practices of doctoral students in Iran. The overall objective was to explore their motives, hurdles and strategies in academic writing. Design/methodology/approach: This case study draws on a narrative inquiry to explore nine science and engineering doctoral students’ perceptions of academic publication. The data were analyzed through a hybrid process of inductive and deductive thematic analysis. Findings: The qualitative results showed three dominant themes, namely: motives for publication, hurdles to publication and strategies for dealing with these challenges were extracted. The main sources of... 

Due to the increased flexibility of modern multi-megawatt wind turbine structures, more advanced analyses are needed to investigate the effects of geometric nonlinearities originating from large blade deformations under operational loads. The main objective of this paper is to study the related dynamics and the aeroelastic effects of these nonlinearities by using a multi-flexible-body aeroelastic model of an entire three-bladed wind turbine assembly instead of a more conventional single-blade model. A geometrically-exact beam formulation is employed to model the rotating blades connected to the wind turbine tower tip via hub and nacelle components; and the revolute joint constraint is... 

Human tracking is an essential step in many computer vision-based applications. As single view tracking may not be sufficiently robust and accurate, tracking based on multiple cameras has been widely considered in recent years. This paper presents a distributed human tracking method in a smart camera network and introduces a particle filter design based on Histogram of Oriented Gradients (HOG) and color histogram. The proposed adaptive motion model also estimates the target speed from the history of its latest displacement and improves the robustness of the tracker by decreasing the probability of missing targets. In addition, a distributed data fusion method is proposed which fuses the... 

Proteins possess a variety of nucleophiles, which can carry out different reactions in the functioning cells. Proteins endogenously and synthetically can be modified through their nucleophilic sites. The roles of these chemical modifications have not been completely revealed. These modifications can alter the protein folding process. Protein folding directly affects the function of proteins. If an error in protein folding occurs, it may cause protein malfunction leading to several neurodegenerative disorders such as Alzheimer's and Parkinson's. In this study, Hen Egg White Lysozyme (HEWL) and bovine insulin, as model proteins for studying the amyloid formation, were covalently attached with... 

This research investigates a three dimensional parametric risk assessment model considering the 3rd factor to be the impact on business. In order to represent the 3rd order risk assessment matrix monitoring the impact of safety reports on the continuous economical performance of the airline, the other two factors, probability of safety and severity are redefined. Introducing two quantitative and qualitative assessment methodologies, the overall risk of the organization can be studied by means of Analytical Hierarchy Process (AHP). providing an adequate background to define the safety goals of the organization  

Permanent magnet synchronous motor (PMSM) drives have many advantages over other drives, i.e. high efficiency and high power density. Particularly, PMSMs are epoch-making and are intensively studied among researchers, scientists and engineers. This paper deals with a novel high performance controller based on genetic algorithm. The scheme allows the motor to be driven with maximum torque per ampere characteristic. In this paper assuming an appropriate fitness function, the optimum values for d-axis current of motor set points at each time are found and then applied to the controller. Simulation results show the successful operation of the proposed controller  

An Al-5 wt% Ti composite was fabricated via powder metallurgy and hot extrusion from initial pure Al and Ti powders. The effect of subsequent heat treatment at 600 °C for different time intervals on microstructure and mechanical properties was investigated. XRD and EDS analyses showed the in-situ formation of Al3Ti intermetallic. SEM micrographs demonstrated the formation of core-shell structured particles in Al matrix for composites heat treated up to moderate heating times (4 h). Generation of voids and pores in the heat treated composites was considered as a result of the Kirkendall effect. Mechanical properties of composites were studied by hardness and tensile testing methods at room... 

An Al-5 wt% Ti composite was fabricated via powder metallurgy technique and hot extrusion. The produced composite samples were heat-treated subsequently at 600 °C for various time durations of 0, 4 and 10 h to achieve different volume fractions of the intermetallic Al3Ti phase. Pure aluminum sample was produced as a benchmark specimen to be compared to the composite samples. SEM studies were used to investigate the microstructure of the composite samples, and it was revealed that core-shell structured particles were formed in the composite heat-treated for 4 h. Triple point bending test was performed on the single edge notched beam specimens of the heat-treated Al-5 wt% Ti composite and the... 

Permanent magnet synchronous motor (PMSM) drives have many advantages over other drives, e.g. high efficiency and high power density. Particularly, permanent magnet synchronous motors are epoch-making and are intensively studied among researchers, scientists and engineers. This paper deals with a novel high performance controller based on genetic algorithm. The scheme allows the motor to be driven with maximum torque per ampere characteristic. In this paper assuming an appropriate fitness function, the optimum values for d-axis current of motor set points at each time are found and then applied to the controller. Simulation results show the successful operation of the proposed controller. ©... 

The study reported in this paper deals with the problem of developing a controller with tolerance to current sensor faults. To achieve this goal, two control strategies are considered. In the first method, field oriented control and a developed observer are used in case of no fault. The second approach is concerned with fault tolerant strategy based on an observer for faulty conditions. Current sensors failures are detected and the current will be estimated successfully in order to allow continuous operation of the vector control. Based on the motor model, currents can be estimated using a nonlinear observer. A decoupling current vector control strategy is developed to ensure high... 

The equalizing wake flow into the propeller behind the ship is important from the hydrodynamic performance viewpoint. In this study, numerical simulations of the DTMB4119 propeller with two symmetric and asymmetric duct types behind the KRISO Container Ship (KCS) are performed using Computational Fluid Dynamics (CFD). In order to improve the wake equaling flow, a combined duct and stators' configurations are installed before the propeller in the stern of the ship and its hydrodynamic performance is studied using CFD. A duct with the NACA4415 section and two types of stator configurations are selected. The STAR-CCM+ software using the finite volume discretization method was used to solve the... 

In this paper, the modal-based indices are used in damage identification of the wind turbine blade. In contrast of many of previous researches, the geometric nonlinearity due to the large structural deformation of the modern wind turbines blade is considered. In the first step, the finite element model (FEM) of the rotating blade is solved to obtain the modal features of the deformed structure under operational aerodynamic loading. Next, the accuracy and efficiency of the various modal-based damage indices including the frequency, mode shape, curvature of mode shape, modal assurance, modal strain energy (MSE) and the difference of indices (between the intact and damaged blades) are... 

In this paper, a reduced order model for the nonlinear dynamic analysis of the wind turbine blade under operational loading is presented. The accuracy and efficiency of the proposed model are investigated through various static and dynamic analyses. A comprehensive straightforward formulation for the nonlinear beam model is developed based on different large deformation strain theories. Also, the fluid-structure coupling effects due to quasi-steady aerodynamics and gravitational forces are included. The new matrix expressions are introduced for direct conversion of the developed formulation into the reduced order model (ROM). Thereafter, the ROM based on the Galerkin method is developed... 

In this paper, an aeroelastic analysis of a rotating wind turbine blade is performed by considering the effects of geometrical nonlinearities associated with large deflection of the blade produced during wind turbine operation. This source of nonlinearity has become more important in the dynamic analysis of flexible blades used in more recent multi-megawatt wind turbines. The structural modeling, involving the coupled edgewise, flapwise and torsional DOFs, has been performed by using a nonlinear geometrically exact beam formulation. The aerodynamic model is presented based on the strip theory, by applying the principles of quasi-steady and unsteady airfoil aerodynamics. Compared to the... 

Research in the choice behavior of air travelers has evolved to include an analytical focus on variation in the sensitivities of travelers to factors influencing itinerary choice. Some choice studies have moved beyond a focus on assumed representative, mean-level sensitivities toward a goal of representing the distribution of preferences across a sample. The mixed multinomial logit model has served as a valuable means of estimating such distributions of air travel preferences, including studies of business travelers, impacts of airport level-of-service attributes, distributions of willingness-to-pay (WTP), and information-processing strategies. Does the insight gained in previous studies,... 

We develop an analytical framework for queueing and delay analysis in the case of a number of distinct flows arriving at a network node, where asynchronous partial network coding is applied for an efficient packet transmission. In order to perfectly model and analyze the practical communication networks, the arriving flows are assumed to be general Markovian arrival processes. As a key example, we apply the proposed model to the problem of coded caching in single bottleneck caching networks. In addition, we verify the accuracy of the proposed model through simulations and real trace-driven experiments. © 1967-2012 IEEE  

In this paper, we try to develop and implement the HRV signal processing into a Field Programmable Gate Array (FPGA) for extracting this signals feature  

Since the development of data centers, power management (i.e., assessment, consumption and monitoring) has been a great challenge among scientists and engineers. By emerging a new generation of data center in the form of Hyperscale cloud data centers (HCDC), this concern has become more devastating than ever. The huge physical scale and the high level of system utilization through large power compensating system are some of the main characteristics of today's HCDC. The lack of appropriate power assessment from available power estimation models, prevents professionals from designing an accurate HCDCcapacity planning. In particular, during steady state workload processing at the high... 

In this article, we propose a software-hardware system to improve the quality of image recovery in millimeter-wave (MMW) imaging systems, which aims to benefit from copolarization and cross-polarization scatterings from the target. The proposed dual-polarized antenna array structures consist of two orthogonal subarrays with the same phase center, where each subarray is comprised of 2 imes 1 or 4 imes 1 rectangular edge fed patches and the optimized ground defects. These compact structures, which support radiation of two orthogonal linear polarizations, are designed on a single-layer board using crossover technique. The dual-polarized scattering from the target is captured by the orthogonal... 

This study investigates the effect of the variation of the properties of unreinforced brick masonry walls, such as aspect ratio, prism strength, and axial load ratio, on determining the post-earthquake damage states of the walls using fragility curves. A database comprising 245 damaged unreinforced masonry walls is collected that have been tested under the quasi-static cyclic loads up to more than three percent drift ratios. The collected walls are categorized into four damage states according to the resisting lateral force during the cyclic loading obtained from the backbone of the hysteresis curves. Then, multivariable fragility surfaces based on the drift ratio and design properties of...