Generalized Korn's inequality and conformal Killing vectors

Korn's inequality plays an important role in linear elasticity theory. This inequality bounds the norm of the derivatives of the displacement vector by the norm of the linearized strain tensor. The kernel of the linearized strain tensor are the infinitesimal rigid-body translations and rotations (Killing vectors). We generalize this inequality by replacing the linearized strain tensor by its trace free part. That is, we obtain a stronger inequality in which the kernel of the relevant operator are the conformal Killing vectors. The new inequality has applications in General Relativity.Comment: 8 page

Sher 25: pulsating but apparently alone

The blue supergiant Sher25 is surrounded by an asymmetric, hourglass-shaped circumstellar nebula, which shows similarities to the triple-ring structure seen around SN1987A. From optical spectroscopy over six consecutive nights, we detect periodic radial velocity variations in the stellar spectrum of Sher25 with a peak-to-peak amplitude of ~12 km/s on a timescale of about 6 days, confirming the tentative detec-tion of similar variations by Hendry et al. From consideration of the amplitude and timescale of the signal, coupled with observed line profile variations, we propose that the physical origin of these variations is related to pulsations in the stellar atmosphere, rejecting the previous hypothesis of a massive, short-period binary companion. The radial velocities of two other blue supergiants with similar bipolar nebulae, SBW1 and HD 168625, were also monitored over the course of six nights, but these did not display any significant radial velocity variations.Comment: 9 pages, 7 figures. Accepted for publication in MNRA

Understanding Climate Feedback Contributions to Surface Warming: TOA Versus Surface Perspective

The global-mean surface temperature has warmed by approximately 1.04oC from 1880-2016, primarily driven by the anthropogenic increase of carbon dioxide (CO2). Since Earths temperature is tied to a multitude of physical processes, the increase of CO2 triggers climate feedbacks that modulate the surface warming response. Thus, to understand the surface warming response to increasing CO2, we must also understand how the different climate feedbacks it triggers modify the surface temperature. Most climate feedback studies evaluate radiative feedbacks using a top-of-atmosphere perspective, but a few use a surface perspective instead. The effects of radiative feedbacks on surface temperature should be insensitive to the perspective chosen; past studies, however, have shown conflicting results between the TOA and surface perspectives

Unmasking the Negative Greenhouse Effect over the Antarctic Plateau

A paradoxical negative greenhouse effect has been found over the Antarctic Plateau, indicating that greenhouse gases enhance energy loss to space. Using 13 years of NASA satellite observations, we verify the existence of the negative greenhouse effect and find that the magnitude and sign of the effect varies seasonally and spectrally. A previous explanation attributes this effect solely to stratospheric CO2; however, we surprisingly find that the negative greenhouse effect is predominantly caused by tropospheric water vapor. A recently developed principle-based concept is used to provide a complete account of the Antarctic Plateaus negative greenhouse effect indicating that it is controlled by the vertical variation of temperature and greenhouse gas absorption. Our findings indicate that unique climatological conditions over the Antarctic Plateaua strong surface-based temperature inversion and scarcity of free tropospheric water vaporcause the negative greenhouse effect

A finite point method in computational mechancis. Applications to convective transport and fluid flow.

The paper presents a fully meshless procedure fo solving partial differential equations. The approach termed generically the ‘finite point method’ is based on a weighted least square interpolation of point data and point collocation for evaluating the approximation integrals. Some examples showing the accuracy of the method for solution of adjoint and non‐self adjoint equations typical of convective‐diffusive transport and also to the analysis of compressible fluid mechanics problem are presented

A stabilized finite point method for analysis of fluid mechanics problems

flow type problems is presented. The method is based on the use of a weighted least square interpolation procedure together with point collocation for evaluating the approximation integrals. Some examples of application to convective trasport and compressible flow problems are presented

KINETIC AND KINEMATIC ANALYSIS OF THE BACKSTROKE START

Race start technique in competitive swimming has developed considerably in recent years and is thought to be an important factor governing the outcome of a race. The purpose of this study was to measure the reliability of a new analysis system for swimming (PAS-S), as well as to analyse the backstroke start kinetics and kinematics and to compare the normal backstroke start with the backstroke start with a new start device. 16 high level competitive swimmers were examined in this study, which revealed that the measurements with the PAS-S are reliable. The analysis of the backstroke start showed the importance of a high preload force just before the start signal. Furthermore, if available, swimmers should use the new backstroke start device since the 15 m times were significantly faster even without considerable training with the new start device

KINETIC AND KINEMATIC ANALYSIS OF THE LEG POSITIONING IN THE FREESTYLE TRACK START IN SWIMMING

In swimming competitions, the track start is an important part of the race. The aim of this study was to assess and compare the relative positioning of the dominant leg in the preferential freestyle track start. The data was collected using the (Kistler) Performance Analysis System for Swimming (PAS-S) that includes a force measurement and motion analysis system. The results taken from 15 high level competitive swimmers showed that 67.7 % of the subjects naturally position their dominant leg in front. Starting with the dominant leg in front (6.67±0.24) was significantly (p < 0.001) faster than in the rear position (7.25±0.23). However swimmers had faster starts when using their preferential track start. Detailed analysis of the swimming start and the footedness allows coaches and athletes to train the fastest starting technique

Service-oriented simulation using web ontology

Copyright © 2012 Inderscience Enterprises Ltd.Commercial-off-the-Shelf (COTS) Simulation Packages (CSPs) have proved popular in a wider industrial setting. Reuse of Simulation Component (SC) models by collaborating organisations or divisions is restricted, however, by the same semantic issues that restrict the inter-organisation use of other software services. Semantic models, in the form of ontology, utilised by a web-service-based discovery and deployment architecture provide one approach to support simulation model reuse. Semantic interoperation is achieved using domain-grounded SC ontology to identify reusable components and subsequently loaded into a CSP, and locally or remotely executed. The work is based on a health service simulation that addresses the transportation of blood. The ontology-engineering framework and discovery architecture provide a novel approach to inter-organisation simulation, uncovering domain semantics and providing a less intrusive mechanism for component reuse. The resulting web of component models and simulation execution environments present a nascent approach to simulation grids