FEATURE-BASED GEOMETRIC MODELLING AND ANALYSIS OF MULTIBODY MECHANICAL SYSTEM BEHAVIOUR

The aim of this paper is to present a modelling system and an application to analyse the mechanical behaviour of a gear-box. Designing a new type of gear-box, there is a real need for the concurrent engineering activities of the designers of geometric modelling, mesh generation and mechanical analysis. In this system own developed contact types of finite elements (FEM) have been used. The new system contains some programs of the earlier system ASSYM (CASM Lab.) for modelling the casing as the superstructure of a gear-box and its bearings as FEM contact-macroelements. In the proposed system the designers can use the modeller CAEDS (IBM Corp.) for feature-based geometric modelling and for generating the global mesh model of casing, the FEM analysis processor Mac/NASTRAN (MacNeal-Schwendler Corp.) and the new version of the N_SIM program (CASM Lab.) for modelling the pairs of gears and the bearings, furthermore the New Grid (N.G.) preprocessor (CASM Lab.). The N.G. can introduce the local mesh models of macroelements to the global mesh of gear-box casing

Study of a high spatial resolution 10B-based thermal neutron detector for application in neutron reflectometry: the Multi-Blade prototype

Although for large area detectors it is crucial to find an alternative to detect thermal neutrons because of the 3He shortage, this is not the case for small area detectors. Neutron scattering science is still growing its instruments' power and the neutron flux a detector must tolerate is increasing. For small area detectors the main effort is to expand the detectors' performances. At Institut Laue-Langevin (ILL) we developed the Multi-Blade detector which wants to increase the spatial resolution of 3He-based detectors for high flux applications. We developed a high spatial resolution prototype suitable for neutron reflectometry instruments. It exploits solid 10B-films employed in a proportional gas chamber. Two prototypes have been constructed at ILL and the results obtained on our monochromatic test beam line are presented here

Measurement of the complex Faraday angle in thin-film metals and high temperature superconductors

A sensitive polarization modulation technique uses photoelastic modulation and hetrodyne detection to simultaneously measure the Faraday rotation and induced ellipticity in light transmitted by semiconducting and metallic samples. The frequencies measured are in the mid-infrared and correspond to the spectral lines of a CO2 laser. The measured temperature range is continuous and extends from 35 to 330K. Measured samples include GaAs and Si substrates, gold and copper films, and YBCO and BSCCO high temperature superconductors.Comment: 12 pages of text, 6 figures, fixed typos in formulas, added figur

Insectivorous bats in Indian rice fields respond to moonlight, temperature, and insect activity

ABSTRACT: Context - Rice, India’s most widely grown crop, suffers substantial and increasing yield loss to insect pests. Insectivorous bats are known suppressors of insect pests, providing significant economic value to agricultural systems worldwide, yet their ecology in Indian agricultural landscapes is poorly understood. Objectives - We assess the influence of key biotic and abiotic factors on the activity of insectivorous bats over the growing season and within a night in a rice cultivation landscape. Methods - Passive acoustic recorders were used to track bat activity in a rice field in the Sonitpur district of Assam, India. We used generalised linear mixed models to analyse the effect of temperature, insect activity, and moonlight intensity on the activity of six bat sonotypes. We also used a multimodal analysis to describe the within-night activity patterns of these sonotypes. Results - Minimum nightly temperature and moonlight intensity had a positive and negative influence, respectively, on the activity of six bat sonotypes, while the activity of four bat sonotypes increased with insect activity. Within-night activity showed one of two patterns: three sonotypes displayed a dusk peak in activity, while the three other sonotypes were active through the night. Conclusion - The potential to maximise natural pest control in agricultural landscapes can only be realised through understanding the ecology of natural enemies in these landscapes. Our findings suggest that bats in rice fields are tracking insects over a season and within a night, pointing to a valuable ecosystem service in Indian agriculture that is yet to be quantified.info:eu-repo/semantics/publishedVersio

Optical Conductivity and Hall Coefficient in High-Tc Superconductors: Significant Role of Current Vertex Corrections

We study AC conductivities in high-Tc cuprates, which offer us significant information to reveal the true electronic ground states. Based on the fluctuation-exchange (FLEX) approximation, current vertex corrections (CVC's) are correctly taken into account to satisfy the conservation laws. We find the significant role of the CVC's on the optical Hall conductivity in the presence of strong antiferromagnetic (AF) fluctuations. This fact leads to the failure of the relaxation time approximation (RTA). As a result, experimental highly unusual behaviors, (i) prominent frequency and temperature dependences of the optical Hall coefficient, and (ii) simple Drude form of the optical Hall andge for wide range of frequencies, are satisfactorily reproduced. In conclusion, both DC and AC transport phenomena in (slightly under-doped) high-Tc cuprates can be explained comprehensively in terms of nearly AF Fermi liquid, if one take the CVC's into account.Comment: 5 page

Functional biogeography of oceanic islands and the scaling of functional diversity in the Azores

Analyses of species-diversity patterns of remote islands have been crucial to the development of biogeographic theory, yet little is known about corresponding patterns in functional traits on islands and how, for example, they may be affected by the introduction of exotic species. We collated trait data for spiders and beetles and used a functional diversity index (FRic) to test for nonrandomness in the contribution of endemic, other native (also combined as indigenous), and exotic species to functional-trait space across the nine islands of the Azores. In general, for both taxa and for each distributional category, functional diversity increases with species richness, which, in turn scales with island area. Null simulations support the hypothesis that each distributional group contributes to functional diversity in proportion to their species richness. Exotic spiders have added novel trait space to a greater degree than have exotic beetles, likely indicating greater impact of the reduction of immigration filters and/or differential historical losses of indigenous species. Analyses of species occurring in native-forest remnants provide limited indications of the operation of habitat filtering of exotics for three islands, but only for beetles. Although the general linear (not saturating) pattern of trait-space increase with richness of exotics suggests an ongoing process of functional enrichment and accommodation, further work is urgently needed to determine how estimates of extinction debt of indigenous species should be adjusted in the light of these findings