Search results for "Lead"

Minimum Leading Edge Protection Application Length to Combat Rain-Induced Erosion of Wind Turbine Blades

2021

Leading edge erosion (LEE) repairs of wind turbine blades (WTBs) involve infield application of leading edge protection (LEP) solutions. The industry is currently aiming to use factory based LEP coatings that can applied to the WTBs before they are shipped out for installation. However, one of the main challenges related to these solutions is the choice of a minimum LEP application length to be applied in the spanwise direction of the WTBs. Generally, coating suppliers apply 10–20 m of LEP onto the blades starting from the tip of the blade using the “rule of thumb”, and no studies in the literature exist that stipulate how these LEP lengths can be calculated. In this study, we extend the sc…

Effects of Onshore and Offshore Environmental Parameters on the Leading Edge Erosion of Wind Turbine Blades: A Comparative Study

2021

Abstract The presence of rain-induced leading edge erosion of wind turbine blades (WTBs) necessitates the development of erosion models. One of the essential parameters for erosion modeling is the relative impact velocity between rain droplets and the rotating blade. Based on this parameter, the erosion damage rate of a WTB is calculated to estimate the expected leading edge lifetime. The environmental conditions that govern this parameter have site-specific variations, and thus, rain and wind loading on a turbine differ for onshore and offshore locations. In addition, there are wave loads present in the offshore environment. The present paper tries to provide guidelines for erosion modelin…

Numerical investigation of rain droplet impact on offshore wind turbine blades under different rainfall conditions: A parametric study

2020

The leading edge of a fiber composite wind turbine blade (WTB) is prone to erosion damages due to repeated rain droplet impact during its service life. Such damages are critical to the blade's aerodynamic as well as structural performance, ultimately resulting in substantial repair costs. An effective design of a coating material for WTB is necessary and its analysis must include variables associated with erosive rain droplets such as (1) droplet diameter, (2) impact velocity, and (3) droplet impact angle. The present paper develops and validates a coupled fluid structure interaction (FSI) computational model for simulating rain droplet impact on WTBs, where the structure domain is modelled…

Poleward range expansion without a southern contraction in the ground beetle Agonum viridicupreum (Coleoptera, Carabidae)

2011

We investigated the extent of poleward shifts in the distribution range of Agonum viridicupreum due to climate change in the western Palaearctic. Species' records were obtained from extensive literature sources as well as from collections, and consistent amateur entomologists' recordings. Within the general geographic range of the species, we analyzed in detail two parts of both, the northern and southern distribution range boundaries: (1 and 2) north-western Germany (leading or high-latitude edge), (3) Israel and (4) southern Italy (rear or low-latitude edge). Temporal changes in the occurrence data of the species indicated a northward shift of the leading edge of a minimum of 100 km withi…

Leading Edge Erosion of Wind Turbine Blades: Effects of Environmental Parameters on Impact Velocities and Erosion Damage Rate

2021

Abstract Leading edge erosion (LEE) of a wind turbine blade (WTB) is a complex phenomenon that contributes to high operation and maintenance costs. The impact between rain droplets and rotating blades exerts cyclic fatigue stresses on the leading edge — causing progressive material loss and reduced aerodynamic performance. One of the most important parameters for erosion modelling and damage prediction is the relative impact velocity between rain droplets and rotating blade and depends upon the environmental conditions. The environmental condition, in general, could vary for onshore and offshore wind turbines (OWTs) — for instance, the presence of wave-induced loads along with less turbulen…

Polarization tensors of planar domains as functions of the admittivity contrast

2014

(Electric) polarization tensors describe part of the leading order term of asymptotic voltage perturbations caused by low volume fraction inhomogeneities of the electrical properties of a medium. They depend on the geometry of the support of the inhomogeneities and on their admittivity contrast. Corresponding asymptotic formulas are of particular interest in the design of reconstruction algorithms for determining the locations and the material properties of inhomogeneities inside a body from measurements of current flows and associated voltage potentials on the body's surface. In this work we consider the two-dimensional case only and provide an analytic representation of the polarization t…

Letter to the Editor Regarding “First Report of Extraspinal Lead Migration Along a Thoracic Spinal Nerve After Spinal Cord Stimulation”

2021

Un nou enfocament en el lideratge del segle XXI

2012

La noció segons la qual algunes persones poden ser primus inter pares (primer/a entre iguals) és potser el pilar fonamental de la nostra societat actual. La pregunta sobre qui hauria de ser el primer ha estat font de curiositat i inspiració per a religions, filòsofs i artistes. Malgrat això, la veritable pregunta no és tan sols qui ha de ser el primer, sinó també quines qualitats, valors o creences permeten que algú es destaque sobre els altres per guiar-los. En aquest treball desenvolupem teòricament certes característiques dels líders i de les organitzacions i l'impacte que tenen en la salut psicològica dels individus, i tot seguit presentem alternatives teòriques en funció dels avanços e…

La dirección orquestal y su dimensión social: hacia la inclusión de la mujer

2022

Por influencia de las teorías freudianas suele decirse que, en el contexto de una orquesta, la batuta representa la virilidad, al ser un elemento usado única y exclusivamente por quien ostenta el liderazgo de aquella. El director, batuta en mano, se transforma en un mediador entre el conjunto musical, la obra y el público. Sin embargo, esta analogía únicamente funciona a nivel de recepción musical y social cuando estamos ante un líder varón. El presente artículo analiza con perspectiva de género el rol del director de orquesta partiendo de su origen, como figura que surge en el siglo XIX y evoluciona hasta la actualidad. En concreto se exponen los resultados de una investigación cuyo objeti…

Estilo de liderazgo en un órgano de control externo. El caso de la Sindicatura de Comptes de la Comunitat Valenciana

2019

Este artículo analiza los patrones de liderazgo en la Sindicatura de Comptes de la Comunitat Valenciana durante sus tres décadas de existencia. Como organización pública de relevancia estatutaria ha experimentado una modernización sostenida para adecuar sus estructuras al entorno sociopolítico. Uno de los factores que explican el calado de los cambios de la Sindicatura es el liderazgo y el modelo directivo (Bass 1985) de sus síndicos mayores en las distintas fases del ciclo de vida (Levitt, 1965; Adizes, 1994). Por consiguiente, partiendo de un estudio longitudinal de la caracterización de los liderazgos de los síndicos mayores entre 1985-2015 se expondrán los principales rasgos que han car…