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

A non-parametric hysteresis model for magnetorheological

In this paper a new non-parametric hysteresis model is offered for simulation of behaviors of magneto-rheological dampers. The offered model takes the excitation frequency, amplitude and current as variables and because of that it is capable of estimating the hysteresis force in different stimulation conditions with a good level of accuracy. Also, the model has the required level of flexibility for simulation of different dampers. The model completion is free of all complications observed in other models. Finally, the accuracy of simulations provided by this model are compared with experimental data as well as two parametric and non-parametric models

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

Cardiovascular effect of nifedipine in morphine dependent rats: hemodynamic, histopathological, and biochemical evidence

Aim To investigate whether administration of nifedipine has considerable therapeutic effect in morphine-dependent rats. Methods Sixty animals were randomized into control, morphine, morphine plus nifedipine, and morphine plus dimethyl sulfoxide (DMSO, as nifedipine soluble) groups. Each group consisted of two subgroups, with and without heart injury. The groups were treated with incremental doses of morphine or morphine plus nifedipine daily for 7 days. Myocardial injury was induced by isoproterenol (50 mg/kg i.p.) on the day 7. On the day 8, the heart rate (HR), blood pressure (BP), rate-pressure product (RPP), and the plasma level of cardiac troponin I were measured and the hearts were histopathologically examined. Results In morphine-dependent rats, nifedipine administration was associated with a significantly higher decrease in the plasma level of cardiac troponin I than the administration of morphine alone. This finding was also significant in dependent animals that received only DMSO. HR, BP, RPP, and histopathological indices did not show significant changes in the presence of nifedipine. Conclusion Administration of nifedipine failed to show a significant therapeutic effect in morphine-dependent rats, especially in the group with myocardial injury

Treatment of Recurrent Corneal Epithelial Defect by Autologous Serum Eye Drop

Background: The aim of the present study was to evaluate the efficacy of autologous serum eye drop in treatment of recurrent corneal epithelial defect.Materials and Methods: Fourteen patients with recurrent corneal epithelial defect were studied. Autologous serum was prepared from the patients and diluted in 20% normal saline. The patients were instructed to use the autologous serum every six hours. Patients were followed for a mean period of 18 months.Results: Four males (28.6%) and 10 females (71.4%) entered the study. Four patients stopped the treatment after three months with complete satisfaction from treatment. Patients reported a reduction in frequency and severity of attacks 4.6±2 weeks after the start of treatment. The mean number of attacks before the procedure was 7.6±0.9 per year which was reduced to 2.2±0.9 per year after treatment (p<0.001). The main side effects in patients were eye pruritus and redness which were well tolerated by patients.Conclusion: Autologous serum application seems to be a safe and effective method to treat recurrent corneal epithelial defect

An evidence for lack of pseudoneglect in patients with schizophrenia:An ERP study

Studies have reported an altered expression of pseudoneglect in patients with schizophrenia, but no study has examined pseudoneglect in schizophrenia at the neural level. We investigated pseudoneglect using the visual P3 event-related potential and the mental number bisection (MNB) task in 21 patients and 25 controls. Using an oddball task, participants were asked to discriminate an infrequent (‘one’ or ‘nine’) from a frequent written number (‘five’). The P3 ERP components were delayed to the targets on the right of the MNL (‘nine’) compared to the targets on the left (‘one’) in controls. The effect of number magnitude on the P3 latency was not observed in the patients. In MNB task, the patients did not show the normal leftward bias observed in healthy individuals. Our findings indicate a lack of pseudoneglect and the presence of an anomalous brain asymmetry in schizophreni

Strategy to manage T-Wave Oversensing in a Biventricular ICD

T-wave oversensing is a relatively prevalent cause of intracardiac signals oversensing in patients with Implantable Cardioverter Defibrillator (ICD). Some of these oversensings are typically corrected with device reprogramming. If reprogramming fails to resolve the issue, invasive options such as repositioning the implanted lead may be necessary. We present a patient with dilated cardiomyopathy and intermittent T wave oversensing by a cardiac resynchronization therapy (CRT) that was managed by altering V-V timing