HOMFLY-PT skein module of singular links in the three-sphere

For a ring $R$, we denote by $R[\mathcal L]$ the free $R$-module spanned by the isotopy classes of singular links in $\mathbb S^3$. Given two invertible elements $x,t \in R$, the HOMFLY-PT skein module of singular links in $\mathbb S^3$ (relative to the triple $(R,t,x)$) is the quotient of $R[\mathcal L]$ by local relations, called skein relations, that involve $t$ and $x$. We compute the HOMFLY-PT skein module of singular links for any $R$ such that $(t^{-1}-t+x)$ and $(t^{-1}-t-x)$ are invertible. In particular, we deduce the Conway skein module of singular links

An experimental study of the high speed interaction between a labyrinth seal and an abradable coating in a turbo-engine application

A new high-speed test rig was designed to simulate the interactions between labyrinth seals and abradable coatings in similar turbo-engine operating conditions. To determine a solution for turbo-engine efficiency enhancement, we investigated the clearance reduction between the rotary parts in air systems, the successive starts and stops, the thermal expansion and the vibrations that might cause direct rub interactions between a rotary seal, known as a labyrinth seal, and a turbo-engine housing coated with a sacrificial abradable material. High interaction speeds from 0 to 130 m s−1 were obtained using a 5-axis milling machine fitted with a unique magnetic bearings spindle developed specifically for the study. The purpose of this paper is to study the interaction phenomena between an abradable material (Al–Si 6%) and a nickel alloy (Alloy 718) to obtain a first contact assessment under different turbo-engine operating conditions. The experimental results are first presented by visual observations of the posttest samples, as specified by accurate profile measurements. A quantitative approach to the interaction forces recorded during the tests and micrographic observations complete the preliminary study. This work provides new basic data for a preliminary study of the interaction between labyrinth seal teeth tips and abradable coatings in turbo-engine applications

Técnicas de manejo agropecuário sustentável

The competitiveness in the rural sector and the need to make viable and sustainable property, direct the farmer to seek new production strategies. In this sense, the book Techniques of sustainable agricultural management has as objective contributed information on concepts, management practices, technological innovations, which are applicable in the agricultural production. The same is composed of 13 chapters, topics covered in aquaculture production, management and dairy production, as general aspects of hematology fish; dynamics of decision-making and adaptive flow dairy production systems; importance of performance measures and body biometrics in small ruminants; milk production in beef cows; parasitism in beef cattle; performance of dairy cows in production; efficiency of cross beef cattle in finishing phase; development of Marchangus: five years; and, bovine growth efficiency. In vegetable production area are addressed matters relating on management and olive cultivation, species of great economic importance and diversification as alternative on the property; functional foods in fruit and vegetables; influence of environmental factors, harvesting and drying in the production and composition of essential oils of Mentha spp; and, implication of the contamination of corn grain by mycotoxins in livestock production. At the end of the book, the expectation of the authors is to have contributed with relevant themes of Brazilian agriculture, which could reflect positively on knowledge, values and quality of available material.A competividade no setor rural e a necessidade de tornar a propriedade viável e sustentável, direcionam o agricultor a buscar novas estratégias de produção. Nesse sentido, o livro Técnicas de manejo agropecuário sustentável tem como objetivo contribuir com informações sobre conceitos, práticas de manejo e inovações tecnológicas que sejam aplicáveis na produção agropecuária. O mesmo é composto de 13 capítulos, sendo abordados assuntos na área de piscicultura, produção, manejo e raças de produção leiteira e de corte, como aspectos gerais de hematologia de peixes; dinâmica do processo decisional e fluxo adaptativo de sistemas de produção leiteiros; importância das medidas de desempenho e biometria corporal em pequenos ruminantes lactentes; produção de leite em vacas de corte; parasitismo na bovinocultura de corte; performance de vacas leiteiras em produção; eficiência dos cruzamentos na bovinocultura de corte sobre a fase de terminação dos animais; desenvolvimento do composto Marchangus: cinco anos; e, eficiência do crescimento dos bovinos. Na área de produção vegetal são abordados assuntos relacionados sobre o manejo e cultivo de oliveira, espécie de grande importância econômica e como alternativa de diversificação na propriedade; alimentos funcionais em frutas e vegetais; influência dos fatores ambientais, colheita e secagem na produção e na composição de óleos essenciais de Mentha spp; e, implicações da contaminação de grãos de milho por micotoxinas na produção pecuária. Ao finalizar o livro, a expectativa dos autores é ter contribuído com temas relevantes da agropecuária brasileira, e que pudessem refletir positivamente em conhecimento, valores e qualidade do material disponibilizado

Fatigue crack initiation detection by an infrared thermography method

In this paper, the study of the temperature variation during fatigue tests was carried out on different materials (steels and aluminium alloys). Tests were performed at ambient temperature using a piezoelectric fatigue system (20 kHz). The temperature field was measured on the surface of the specimen, by means of an infrared camera. Just at the beginning of the test, it was observed that the temperature increased, followed by a stabilization which corresponds to the balance between dissipated energy associated with microplasticity and the energy lost by convection and radiation at the specimen surface and by conduction inside the specimen. At the crack initiation, the surface temperature suddenly increases (whatever the localization of the initiation), which allows the determination of the number of cycles at the crack initiation and the number of cycles devoted to the fatigue crack propagation. In the gigacycle fatigue domain, more than 92% of the total life is devoted to the initiation of the crack. So, the study of the thermal dissipation during the test appears a promising method to improve the understanding of the damage and failure mechanism in fatigue and to determine the number of cycles at initiation

Short Communication: Performance of steers fed on pasture receiving different seeding rates of vetch in an integrated crop-livestock system

Aim of study: To evaluate the performance of beef calves fed black oat and Italian ryegrass pasture seeded with several different seeding rates (SR) of common vetch in a crop-livestock integrated system.Area of study: The experiment was carried out in Dois Vizinhos city, Paraná, Brazil.Material and methods: An area of 8.3 ha was used, which was divided into 11 paddocks, 0.75 ha each. Nellore calves (n = 22), 7 ± 2 months old and with initial body weight of 134 ± 27 kg were used for the tests. The experimental design was completely randomised. Vetch (Vicia sativa L., ‘Amethyst’) SR treatments included 0, 15, 30, and 45 kg ha-1, in a mixture with black oat (Avena strigosa Schreb. ‘IPR 61’ and Italian ryegrass (Lolium multiflorum Lam.) pastures.Main results: There was no effect of SR on pasture productivity parameters. The increase in vetch seed in the seed mixture resulted in an increase in crude protein and neutral detergent fibre, but decreased in vitro digestibility of vetch. However, these changes did not affect the nutritional value of the pasture. Vetch SR of 30 kg ha-1 or higher allowed greater share of the legume in the pasture, thereby enhancing greater individual animal performanceResearch highlights: Vetch SR of 30 kg ha-1 or higher allowed greater share of the legume in the pasture, thereby enhancing greater individual animal performance

Deep Reef Benthos of Bermuda: Field Identification Guide

Deep Reef Benthos of Bermuda builds on the video and imagery data collected during Nekton’s Mission – the XL Catlin Deep Ocean Survey - and provides a photographic guide for the visual identification of many of the corals, marine plants and other common invertebrates that inhabit Bermuda’s outer deep reefs.This guide is designed to aid marine biologists, divers and naturalists with the identification of organisms as seen in underwater footage or live in the field.</div

Low connectivity between shallow, mesophotic and rariphotic zone benthos

© 2019 Massachussetts Medical Society. All rights reserved. Worldwide coral reefs face catastrophic damage due to a series of anthropogenic stressors. Investigating how coral reefs ecosystems are connected, in particular across depth, will help us understand if deeper reefs harbour distinct communities. Here, we explore changes in benthic community structure across 15-300 m depths using technical divers and submersibles around Bermuda. We report high levels of floral and faunal differentiation across depth, with distinct assemblages occupying each depth surveyed, except 200-300 m, corresponding to the lower rariphotic zone. Community turnover was highest at the boundary depths of mesophotic coral ecosystems (30-150 m) driven largely by taxonomic turnover and to a lesser degree by ordered species loss (nestedness). Our work highlights the biologically unique nature of benthic communities in the mesophotic and rariphotic zones, and their limited connectivity to shallow reefs, thus emphasizing the need to manage and protect deeper reefs as distinct entities

Tribological characterization of a labyrinth-abradable interaction in a turbo engine application

To enhance the efficiency of a turbo engine, one solution is reducing the clearance between the rotary parts in the secondary air system. This clearance reduction causes direct interactions in the secondary air system of a turbo engine when a rotary seal, called a labyrinth seal, rubs against the turbo engine casing as a result of successive starts and stops, thermal expansions and vibrations. To protect sealing systems from severe damage, abradable coatings are used on the inner periphery of the casing. The purpose of the present paper is to study the labyrinth-abradable interaction during high speed contacts through a detailed tribological characterization. The labyrinth-abradable interaction experiments were conducted on a dedicated test rig that was able to reproduce representative turbo engine operating conditions. A complete tribological analysis based on a third body approach and on accommodation flows was investigated using high speed imaging of the interaction. A schematic description of the interaction, with the addition of images extracted from recorded videos, is proposed to define two types of third body formation and their evolution during labyrinth-abradable interactions. Finally, the labyrinth-abradable interaction life cycle was used as a basis to discuss the coating subject to a labyrinth tip speed increase

The wear mechanisms occurring in a labyrinth seal/abradable contact depending on the incursion depth parameter

The contact behavior of an abradable coating (Al-Si 6%) and a labyrinth seal tooth (stainless steel) in a turbo-engine application was studied as a function of the incursion depth parameter, during labyrinth seal/abradable interaction. A controlled and a gradual increase of the labyrinth seal incursion (by step of 50 μm) is performed to obtain the chronological contact evolution under severe operating tribological conditions. The labyrinth seal/abradable contact experiments were conducted on a dedicated test rig able to reach high contact speeds from 0 to 130 m.s−1. To complete contact forces measurement during tests, a suitable instrumentation (acoustic emission sensor, accelerometer, thermocouples, etc.) is developed and coupled as close as possible of the interaction area. The experimental results from the both severe tribological conditions are presented by an analysis of signals recorded during contact tests. Macrographic and micrographic rub-groove observations of post tests samples, coupled with recorded signals from the contact complete the Al-Si 6% behavior study. A wear process description using the third body approach has been proposed to sum up the whole tribological results. Two different varieties of particles production have been identified; a ductile and an adhering layer on the rub-groove bottom and pulverulent fine powder particles, thus providing two different kind of third body and two different material flows