862 research outputs found
Effects of Component Model Fidelity Level on Dynamic Analysis Accuracy of a Multi-MW Wind Turbine Drivetrain
Wind farms can incur major expenses due to turbine gearbox component failure that often occurs within five years of deployment. Turbine testing facilities such as Energy Innovation Center (EIC) in Charleston, SC are a growing resource used by the wind energy industry to improve our understanding of turbines in the field and accelerate turbine development. In the meantime, a multibody dynamics model has been developed in EIC for a mutli-MW wind turbine to carry out performance and life assessments to understand the influence of high-frequency mass and misalignment imbalance forces and gear transmission forces.
This thesis aims to investigate multibody dynamics modeling options and understand how modeling fidelity level of four components of interest influences the simulated response of the entire drivetrain under load. The components of interest were the main shaft, bed plate, first planetary carrier, and gearbox housing. The model fidelity levels of these bodies were varied from flexible body representations containing many component modes to rigid body representation with few degrees of freedom. The system was subjected to ramped unidirectional loading input at the nose of the rotor hub, which emulates testing conditions that are periodically run on drivetrains at EIC. Campbell analysis was then performed on a subsystem gearbox model to understand how component flexibility affects the speed-dependent vibration of gearbox components.
Activating more component modes was found to improve the relative accuracy in the motion of the high-speed shaft. This benefit was judged against the relative computational cost for activating each of the components\u27 modes. The bedplate\u27s dynamic modes had the greatest influence on the motion of the high-speed shaft. Representing all drivetrain bodies as rigid bodies leads to a significant overprediction of the internal motion and forces of the drivetrain. Activating the four components\u27 first thirty dynamic modes caused a computational cost increase of 5 times. Carrier and gearbox housing flexibility softens the vibration frequencies of the gearbox subsystem across the turbine operating speed range. Strategic recommendations are contributed according to some differing purposes in design and testing of turbine
drivetrains
Film in Staffordshire - special report
An introduction to the film industry and services available in Staffordshir
Determination of the resistivity anisotropy of SrRuO by measuring the planar Hall effect
We have measured the planar Hall effect in epitaxial thin films of the
itinerant ferromagnet SrRuO3 patterned with their current paths at different
angles relative to the crystallographic axes. Based on the results, we have
determined that SrRuO3 exhibits small resistivity anisotropy in the entire
temperature range of our measurements (between 2 to 300 K); namely, both above
and below its Curie temperature (~150 K). It means that in addition to
anisotropy related to magnetism, the resistivity anisotropy of SrRuO3 has an
intrinsic, nonmagnetic source. We have found that the two sources of anisotropy
have competing effects
The F-Landscape: Dynamically Determining the Multiverse
We evolve our Multiverse Blueprints to characterize our local neighborhood of
the String Landscape and the Multiverse of plausible string, M- and F-theory
vacua. Building upon the tripodal foundations of i) the Flipped SU(5) Grand
Unified Theory (GUT), ii) extra TeV-Scale vector-like multiplets derived out of
F-theory, and iii) the dynamics of No-Scale Supergravity, together dubbed
No-Scale F-SU(5), we demonstrate the existence of a continuous family of
solutions which might adeptly describe the dynamics of distinctive universes.
This Multiverse landscape of F-SU(5) solutions, which we shall refer to as the
F-Landscape, accommodates a subset of universes compatible with the presently
known experimental uncertainties of our own universe. We show that by
secondarily minimizing the minimum of the scalar Higgs potential of each
solution within the F-Landscape, a continuous hypervolume of distinct minimum
minimorum can be engineered which comprise a regional dominion of universes,
with our own universe cast as the bellwether. We conjecture that an
experimental signal at the LHC of the No-Scale F-SU(5) framework's
applicability to our own universe might sensibly be extrapolated as
corroborating evidence for the role of string, M- and F-theory as a master
theory of the Multiverse, with No-Scale supergravity as a crucial and pervasive
reinforcing structure.Comment: 15 Pages, 7 Figures, 1 Tabl
Paramagnetic anisotropic magnetoresistance in thin films of SrRuO3
SrRuO3 is an itinerant ferromagnet and in its thin film form when grown on
miscut SrTiO3 it has Tc of ~ 150 K and strong uniaxial anisotropy. We measured
both the Hall effect and the magnetoresistance (MR) of the films as a function
of the angle between the applied field and the normal to the films at
temperatures above Tc. We extracted the extraordinary Hall effect that is
proportional to the perpendicular component of the magnetization and thus the
MR for each angle of the applied field could be correlated with the magnitude
and orientation of the induced magnetization. We successfully fit the MR data
with a second order magnetization expansion, which indicates large anisotropic
MR in the paramagnetic state. The extremum values of resistivity are not
obtained for currents parallel or perpendicular to the magnetization, probably
due to the crystal symmetry.Comment: 3 pages, 3 figure
Recommended from our members
Spring 1985
The New England Sod Industry (page 3) New Trends and Research in Turfgrass Culture (5) Fifty-Fourth Annual Turf Conference and Ninth Industrial Show Irrigation Programming (13) Landscape Development in Large Residential Communities (17
Introduction
Vertebrate species have been introduced to almost all parts of the world for thousands of years. Within the United States and its territories alone, over 1000 vertebrate species have been introduced since the early sailing ships explored the world. This includes at least 86 species of mammals, 127 species of birds, 126 species of reptiles, 53 species of amphibians, and over 673 species of fish (Witmer and Fuller 2011). Many of these species were native to the United States, but were moved to novel regions, often unintentionally or intentionally by humans. While invasive vertebrates have been introduced to all parts of the world, in this book, we focus on introduced terrestrial vertebrates in the United States and its territories, and the intention is to provide an overview of the complexity and challenges associated with managing invasive species within the United States. Often, the management of invasive species and the prevention of new species becoming established is largely a function of the regulatory framework established within a specific country. In this book, although historical management successes and failures are discussed, the focus is on current effective management options and potential future developments to minimize the effects of invasive species and prevent their spread into new areas.
Although plants and animals have been introduced into new areas for centuries, the increased volume of worldwide trade and transportation has accelerated the rate of species introductions over the last 150 years. Animals are introduced for many reasons, both purposeful and accidental. Intentional introductions include both legal and illegal activities such as the production of food and fur, work animals, sport hunting opportunities, companion animals, aesthetics, pets, pet trade propagation, religious purposes, and pest control. Accidental introductions occur because of stowaways in transport vehicles, hitchhikers or stowaways in or on other commodities, escapees, and, in some cases, because of range expansion of a species, often facilitated by human activities and land use. For example, a tropical storm is thought to have brought the cattle egret Bubulcus ibis to North America (Florida initially) from the Caribbean islands after they had crossed the Atlantic Ocean from Europe and Africa. However, it may have been agricultural land use that allowed its subsequent rapid range expansion westward across North America. Likewise, habitat fragmentation stemming from anthropogenic land use has facilitated the expansion of coyotes (Canis latrans) across the Eastern United States and far south into Central America over the last several decades, reaching areas where the species formerly did not occur
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