Finite element modeling of a wind turbine blade

Wind energy is a sustainable source of power that has a much lower environmental impact than conventional energy sources. One of the important stages in developing the modern wind turbines is studying the dynamic behavior of the flexible blades. In this article, a finite element beam model of a 150 kW horizontal axis wind turbine blade is presented. The beam elements of the present model are linear with 14 DOF and arbitrary cross sections that consider rotational velocity, shear center, warping and gyroscopic effects, stiffening due to the rotation, and all the couplings. In the present model, the cross-sectional properties along each element are variable that decreases number of the needed elements, size of the model and hence the analyses running time. By using the present model, natural frequencies, mode shapes and frequency and transient responses of the blade are extracted. The modal properties are compared with another finite element beam code BModes, and with a shell finite element model of the same blade in ABAQUS. The blade frequency and transient responses in the flap and edge directions under a turbulent wind loading are also compared with ABAQUS. Furthermore, the effects of the rotational speed and pitch angle on the blade modal properties are studied

Adaptive interval type-2 fuzzy logic systems for vehicle handling enhancement by new nonlinear model of variable geometry suspension system

This research examines the emerging role of adaptive interval type-2 fuzzy logic systems (AIT2FLS) versus adaptive type-1 fuzzy logic system (AT1FLS) in vehicle handling by a new nonlinear model of the variable geometry suspension system (VGS) as a vehicle active suspension system. A proper controller is needed in order to have soft response and robustness against challenging vehicle maneuvers. Two controllers, including AT1FLS and AIT2FLS have been used in the paper. The proposed AIT2FLS can efficiently handle system uncertainties, especially in the presence of most difficult challenging vehicle maneuvers in comparison with AT1FLS. The interval type-2 fuzzy adaptation law adjusts the consequent parameters of the rules constructed on the Lyapunov synthesis approach. For this purpose, the kinematic equations are obtained for the vehicle double wishbone suspension system and they are substituted in a nonlinear vehicle handling model with eight degrees of freedoms (8DOFs). Thereby, a new nonlinear model for the analysis of VGS is obtained. The results indicate that between the two controllers, the proposed AIT2FLS has better overall vehicle handling, robustness and soft response

Investigation of damage detection in blade root joints of a 100 kW wind turbine using frequency tracking

With the increasing need for more power production by wind turbines and thus increasing in their sizes, importance of accurate designing of wind turbines has substantially increased. One of the major aspects related to the reliability of operation of wind turbines concerns the safe and adequate performance of the blades. It is important that damage to blades is detected before they fail or cause the turbine to fail. Root joints are located in blade root and join blades to the hub. They are significantly affected by fatigue and extreme loads, so damage detection in root joints is vital. In this article a 100 kW wind turbine model was developed and damages in root joints were modeled by reducing their stiffness and the possibility of damage detection in blade root joint was investigated by tracking the dominant frequencies in nacelle and blades. The model considers structural dynamics of the turbine and includes dynamic coupling between the blades and the tower and consists of 11 degree of freedom (two in each of the blades, two for tower and one for each root joint). Finally, numerical simulations were carried out to evaluate the effectiveness of the method for damage detection. Simulation results showed the dominant frequency tracking method has an appropriate capability of detecting damages in the root joints of the wind turbine

An Energy-Efficient Generic Accuracy Configurable Multiplier Based on Block-Level Voltage Overscaling

Voltage Overscaling (VOS) is one of the well-known techniques to increase the energy efficiency of arithmetic units. Also, it can provide significant lifetime improvements, while still meeting the accuracy requirements of inherently error-resilient applications. This paper proposes a generic accuracy-configurable multiplier that employs the VOS at a coarse-grained level (block-level) to reduce the control logic required for applying VOS and its associated overheads, thus enabling a high degree of trade-off between energy consumption and output quality. The proposed configurable Block-Level VOS-based (BL-VOS) multiplier relies on employing VOS in a multiplier composed of smaller blocks, where applying VOS in different blocks results in structures with various output accuracy levels. To evaluate the proposed concept, we implement 8-bit and 16-bit BL-VOS multipliers with various blocks width in a 15-nm FinFET technology. The results show that the proposed multiplier achieves up to 15% lower energy consumption and up to 21% higher output accuracy compared to the state-of-the-art VOS-based multipliers. Also, the effects of Process Variation (PV) and Bias Temperature Instability (BTI) induced delay on the proposed multiplier are investigated. Finally, the effectiveness of the proposed multiplier is studied for two different image processing applications, in terms of quality and energy efficiency.Comment: This paper has been published in IEEE Transactions on Emerging Topics in Computin

The prevalence of pediculosis capitis and its associated risk factors in primary schools of girls in rural district

زمینه و هدف: آلودگی به شپش سر یکی از بیماری های شایع در تمام سنین و دارای انتشار جهانی است. آلودگی به شپش سر در مراکز تجمعی مانند مدرسه‌ها، پادگان‌ها و خوابگاه ها زیاد و در مدارس، بویژه مدرسه‌های ابتدایی دخترانه در حد قابل توجهی می باشد. این مطالعه با هدف تعیین شیوع آلودگی به شپش سر و عوامل موثر بر آن در دانش آموزان مدارس ابتدایی دخترانه مناطق روستایی استان قم در سال 1390 انجام شد. روش بررسی: این مطالعه توصیفی- تحلیلی بر روی 900 نفر از دانش آموزان دختر ساکن در مناطق روستایی استان قم که به روش نمونه گیری تصادفی چند مرحله ای انتخاب شدند، انجام شد. داده ها با استفاده از پرسشنامه و معاینه موی سر از نظر آلودگی به شپش جمع آوری شدند و با آزمون های آماری کای اسکور و رگرسیون لجستیک چندگانه مورد تجزیه و تحلیل قرار گرفتند. یافته‌ها: در بین 900 دانش آموز مورد بررسی، 120 نفر (3/13) آلوده به آلودگی با شپش سر تشخیص داده شدند. در آنالیز بین متغیرهای محل سکونت، شغل و تحصیلات پدر، میزان تحصیلات مادر، تعداد افراد خانوار، وجود حمام در منزل، تعداد دفعات استحمام، تعداد دفعات شانه‌زنی، سابقه ابتلا به شپش سر، وجود یا عدم وجود مربی بهداشت در مدرسه، دسترسی یا عدم دسترسی به خدمات بهداشتی درمانی و ابتلا به آلودگی با شپش سر ارتباط معنی دار آماری مشاهده شد (05/0>P). نتیجه گیری: علل شیوع این بیماری در بین دانش آموزان استان قم با عواملی مثل عدم وجود مربی بهداشت در مدرسه، عدم دسترسی کافی به خدمات بهداشتی درمانی، عدم توجه کافی به رعایت بهداشت فردی مرتبط بود. بنابراین رعایت بهداشت فردی، آموزش دادن در مورد راه های آلودگی و پیشگیری از بیماری و فراهم کردن امکانات بهداشتی می تواند در کاهش آلودگی و عوارض ناشی از آن نقش مهمی داشته باشد

Mathematical Modeling of Transmission Dynamics and Optimal Control of Vaccination and Treatment for Hepatitis B Virus

Hepatitis B virus (HBV) infection is a worldwide public health problem. In this paper, we study the dynamics of hepatitis B virus (HBV) infection which can be controlled by vaccination as well as treatment. Initially we consider constant controls for both vaccination and treatment. In the constant controls case, by determining the basic reproduction number, we study the existence and stability of the disease-free and endemic steady-state solutions of the model. Next, we take the controls as time and formulate the appropriate optimal control problem and obtain the optimal control strategy to minimize both the number of infectious humans and the associated costs. Finally at the end numerical simulation results show that optimal combination of vaccination and treatment is the most effective way to control hepatitis B virus infection

Study and analysis of the functions of al-Urf in understanding and inferring the religious rules

Religious rules in Shiite jurisprudence are inferred from the four sources of the Qur'an, Sunnah, reason and consensus. But, in addition to these sources, some foundations such as common law (al-urf) are also mentioned. Referring to common law is widely used in the words of jurists. Based on it, the question arises here: what are the roles of common law and Irtikazat in common law in understanding and inferring the religious rules? This article seeks to answer this question and tries to study and analyze the functions of common law in understanding and inferring the religious rules. The research hypothesis is that common law and Irtikazat in common law are used in understanding the words of religious arguments, subjecting and de-subjecting of common law for the religious documents, proving or denying some rights and other issues that are used by jurists and lawyers in the process of inferencing. One of the findings of the present study is that most scholars of the Islamic jurisprudence and law have not distinguished between these two foundations. But, it is more correct that common law is considered from the category of objective matter in the practical life of people, while Irtikazat in common law are from the category of subjective matter

Dibromido{N′-[1-(pyridin-2-yl)ethyl­idene]picolinohydrazide-κ2 N′,O}cadmium

The title compound, [CdBr2(C13H12N4O)], was obtained from the reaction of Cd(NO3)2·4H2O with meth­yl(pyridin-2-yl)methanone picolinoylhydrazone and sodium bromide. The Cd2+ cation is ligated by one O atom and two N atoms of the tridentate ligand and two bromide anions, forming a Br2CdN2O polyhedron with a distorted trigonal–bipyramidal coordination geometry. In the crystal, non-classical C—H⋯Br hydrogen bonds are observed. In addition, π–π stacking inter­actions [centroid–centroid distance = 3.7455 (19) Å] contribute to the stabilization of the crystal structure

Low-rank and sparse recovery of human gait data

Due to occlusion or detached markers, information can often be lost while capturing human motion with optical tracking systems. Based on three natural properties of human gait movement, this study presents two different approaches to recover corrupted motion data. These properties are used to define a reconstruction model combining low-rank matrix completion of the measured data with a group-sparsity prior on the marker trajectories mapped in the frequency domain. Unlike most existing approaches, the proposed methodology is fully unsupervised and does not need training data or kinematic information of the user. We evaluated our methods on four different gait datasets with various gap lengths and compared their performance with a state-of-the-art approach using principal component analysis (PCA). Our results showed recovering missing data more precisely, with a reduction of at least 2 mm in mean reconstruction error compared to the literature method. When a small number of marker trajectories is available, our findings showed a reduction of more than 14 mm for the mean reconstruction error compared to the literature approach

The Relationships between Mental Health Status, Achievement Motivation, Job Satisfaction and Oxidative Stress in Subjects Exposed to Nickel Welding Fumes

This study was conducted on 27 male welding workers who worked in a company that manufactures road construction machinery and is located in an industrial part of Iran, in the Central province. In the serum, total antioxidant capacity (TAC), lipid peroxidation (LPO), DNA damage (8-OH-dG)was measured. Mental health status was evaluated by General Health Questionnaire (GHQ-28) and achievement motivation was evaluated by Herman’s achievement motivation Test (ACMT), and job satisfaction was measured by Dennett Job Satisfaction Test. The results of this study showed that there was a reverse significant relationship between nickel and TAC with ACMT and job satisfaction. The oxidative stress of Ni ended up in psychological disorders. As oxidative stress causes psychological disorders, the welding workers suffered from more psycho- pathology and were in need of greater care