Effect of blade contamination on power production of wind turbines

Wind turbines suffer from considerable power losses because of contamination ontheir blades, that can be due to erosion, wear, smog, insect, sand and dust particle impact.Blade contamination, its effects on the flows over the wind turbine blades and consequentpower production losses form the main focus of the present study. These effects are mainlydue to increased roughness on the blades leading to earlier laminar-turbulent transition andconsequently, thicker boundary-layers on the blades. Early laminar-turbulent transition leadsto a larger part of the flow over a blade being turbulent, thus increasing skin friction drag.Thicker boundary-layer on a blade results in blade profile being effectively modified, renderingthe flow over the blade depart from ideal. In the present study, the effects of blade contaminationon power output of contaminated wind turbine blades is investigated numerically using an inhousecomputational tool. Blade Element Momentum Method (BEM) combined with the PanelMethod is used to calculate the local velocity and angle of attack at the blade sections, togetherwith the power produced by the blade. Trajectories of particles causing contamination arecalculated using Lagrangian approach, also yielding the impingement pattern of the particleson the blade surface, i.e. particle collection efficiency distribution. The effects of roughness onthe boundary-layer flow are investigated by using an Integral Boundary-Layer Method, whichyields the characteristics of the boundary-layer, i.e. laminar-turbulent transition location,increased skin-friction and thickening of the boundary-layer. The blade shape is modifieddue contamination thickness, the local height of which is assumed to be proportional to thelocal collection efficiency. Also, the roughness height distribution used in the boundary-layercalculations is assumed to be equal to the contamination thickness distribution on the blades.Power production and consequent losses of wind turbines with contaminated wind turbine bladesare studied with respect to variations in particle size, wind speed and roughness height

OXIDATIVE STRESS AND SERUM S100B LEVELS IN ADOLESCENTS WITH FIRST-EPISODE DRUG-NAIVE UNIPOLAR DEPRESSION

Background: Unipolar depression is common among adolescents and has high recurrence rates. Studies conducted with adults show that oxidative stress plays a role in etiology of depression but studies with adolescent patients are limited. In addition, baseline S100B level in adult patients with depression is considered as a marker of response to treatment. The purpose of this study was to measure the levels of serum S100B, Malondialdehyde (MDA), total oxidant status (TOS), and total antioxidant status (TAS), which have not been previously investigated in adolescent patients with first-episode, drug-naïve unipolar depression, and to investigate the relationship of these parameters with disease severity and patient-specific variables. Subjects and methods: This study was conducted with 37 adolescents diagnosed with unipolar depression and 37 healthy peers. Participants were asked to fill out the Beck Depression Scale, Screen for Child Anxiety Related Disorders, and suicide probability questionnaires. After this procedure, 5 cc blood was collected from the adolescents and serum S100B, MDA, TOS, and OSI levels measured. Results: Serum S100B, MDA, TOS, and OSI levels were higher and TAS level was lower in patients than their healthy peers. There was no relationship between the patients\u27 severity of depression or suicide probability and these parameters. The serum S100B, MDA, TOS, and OSI levels of female patients were higher than their healthy peers, but the TAS level was not different. Male patients had higher TOS and OSI levels and lower TAS levels than their healthy peers. Conclusions: The results show that increased serum S100B, MDA, TOS and OSI levels may contribute to etiology of depression regardless of gender. The gender-specific increase in S100B and MDA levels, which were significantly increased in female adolescent patients but not in males, should be supported by further follow-up studies

The Effect of the Rate of Waste Tire Powder Substitution on the Physical and Mechanical Properties of CEM II Cement

Recycling of waste has a great importance in preservation of the energy and decreasing the global impact that has been created by production of new materials. There is an increasing debate about the use of waste tires because of their environmental and health affects. Waste tires can be used for a range of civil engineering applications. This study investigates the physical and mechanical properties of CEM II (reference) and waste tire powder substituted cements. For this purpose, waste tire powder was substituted as a replacement for CEM II cement in amounts of 0, 2.5, 5, 7.5 and 10 weight %. The effects of waste tire powder on compressive and flexural strength, setting time, water demand and volume expansion were determined by standard tests of cement. As a result, a relative increase according to reference cement pastes was determined in the setting time of the waste tire powder substituted cement pastes. Besides these, a decrease were identified with the 2, 7, 28 and 56 days flexural and compressive strength tests for the waste tire powder substituted cement mortars according to reference cement mortars

Long-term evaluation of laser retinopexy in retinal breaks: a review and the importance of lifetime follow-up

Purpose: To evaluate the effects of laser retinopexy in retinal breaks and the recurrence cases.Materials and Methods: 45 eyes of 25 patients who underwent laser retinopexy in retinal breaks between the period of July 2009 and January 2013 are included. All the breaks and suspicious areas for possible breaks are treated with laser photocoagulation. The breaks were surrounded with three rows of laser spots. After the routine controls, the patients are called every 6 months and advised to come immediately to our clinic if new flashing or floaters occur.Results: The patients were followed-up for an average period of 29.65 ± 10.45 months. New breaks were treated again and evaluated for the possible reasons. We found in three patients new breaks after an average period of 27.33 ± 2.03 months. No specifications are observed in these subjects.Conclusion: Retinal breaks can occur even a long time after. It is not known why this process is progressing and new tears develop. For this reason, patients who underwent a laser therapy because of retinal breaks should followed-up for a lifetime. We advise that, unsymptomatic patients who underwent laser retinopexy, should be examined every 6 months and every new complaint of flashing and big floaters should be carefully taken into consideration to prevent retinal detachments.Keywords: Laser retinopexy, posterior vitreous detachment, retinal break

Increased P-wave dispersion in patients with newly diagnosed lichen planus

OBJECTIVE: Lichen planus is a chronic inflammatory autoimmune mucocutaneous disease. Recent research has emphasized the strong association between inflammation and both P-wave dispersion and dyslipidemia. The difference between the maximum and minimum P-wave durations on an electrocardiogram is defined as P-wave dispersion. The prolongation of P-wave dispersion has been demonstrated to be an independent risk factor for developing atrial fibrillation. The aim of this study was to investigate P-wave dispersion in patients with lichen planus. METHODS: Fifty-eight patients with lichen planus and 37 age- and gender-matched healthy controls were included in this study. We obtained electrocardiographic recordings from all participants and used them to calculate the P-wave variables. We also assessed the levels of highly sensitive C-reactive protein, which is an inflammatory marker, and the lipid levels for each group. The results were reported as the means ± standard deviations and percentages. RESULTS: The P-wave dispersion was significantly higher in lichen planus patients than in the control group. Additionally, highly sensitive C-reactive protein, LDL cholesterol, and triglyceride levels were significantly higher in lichen planus patients compared to the controls. There was a significant positive correlation between highly sensitive C-reactive protein and P-wave dispersion (r = 0.549,

The initial part of polymorphic ventricular tachycardia as a clue for the sustainability of tachycardia and ablation success: A varying degree of purkinje–Myocardial complicity?

The cardiac Purkinje system is capable of very rapid burst activity suggestive of its potential role in being a driver of polymorphic ventricular tachycardia (VT) (PMVT) or ventricular fibrillation (VF). It plays a pivotal role, however, not only in the triggering of but also the perpetuation of ventricular arrhythmias. A varying degree of Purkinje–myocardial complicity has been blamed in determining not only the sustained or non-sustained nature of PMVT but also the pleomorphism of the non-sustained runs. The initial part of PMVT before cascading to the whole ventricle to establish disorganized VF can give important clues for ablation of PMVT and VF. We present a case of an electrical storm after acute myocardial infarction that was successfully ablated after identifying Purkinje potentials that triggered polymorphic, monomorphic, and pleiomorphic VTs and VF

Özel Yetenekli Öğrencilerin Oyunlaştırma Sürecinde Tercih Ettikleri Oyuncu Tiplerinin Çeşitli Değişkenlere Göre İncelenmesi

Bu araştırmada özel yetenekli öğrencilerin oyunlaştırma sürecinde oyuncu%252Fkullanıcı tiplerini çeşitli değişkenler açısından tespit edilmesi amaçlanmıştır. Tarama modellerinden genel tarama modelinin kullanıldığı bu araştırmanın çalışma grubunu 2018-2019 eğitim öğretim yılı İstanbul İlinde yer alan Bilim ve Sanat Merkezinde öğrenim gören 202 Özel Yetenekli Öğrenciler oluşturmaktadır. AraştırmadaTondello ve diğerleri (2016) tarafından hazırlanan ve Akgün ve Topal (2018) tarafından Türkçeye uyarlanan Oyunlaştırma için Oyuncu Tipleri Ölçeği kullanılmıştır. Araştırmada elde edilen bulgular doğrultusunda özel yetenekli kız öğrencilerin oyunlaştırma sürecinde en çok başaranlar tipini seçtikleri tespit edilmiştir. Bununla birlikte özel yetenekli kız öğrencilerin sosyalleşenler ve özgür ruhlar tipini diğer oyuncu tiplerine oranla daha çok tercih ettikleri sonucuna verilmiştir. Ayrıca elde edilen bulgular doğrultusunda özel yetenekli erkek öğrencilerinde özel yetenekli kız öğrenciler gibi oyunlaştırma sürecinde başaranlar stilini tercih ettikleri ve aynı zamanda sosyalleşenler ile özgür ruhlar stilini tipini tercih ettikleri sonucuna varılmıştır. Araştırmaya katılan 10 , 11, 12 ve 13 yaşındaki özel yetenekli öğrencilerin en çok başaranlar tipini seçtikleri tespit edilmiştir