The measurement of lubricant-film thickness using ultrasound

Ultrasound is reflected from a liquid layer between two solid bodies. This reflection depends on the ultrasonic frequency, the acoustic properties of the liquid and solid, and the layer thickness. If the wavelength is much greater than the liquid-layer thickness, then the response is governed by the stiffness of the layer. If the wavelength and layer thickness are similar, then the interaction of ultrasound with the layer is controlled by its resonant behaviour. This stiffness governed response and resonant response can be used to determine the thickness of the liquid layer, if the other parameters are known. In this paper, ultrasound has been developed as a method to determine the thickness of lubricating films in bearing systems. An ultrasonic transducer is positioned on the outside of a bearing shell such that the wave is focused on the lubricant-film layer. The transducer is used to both emit and receive wide-band ultrasonic pulses. For a particular lubricant film, the reflected pulse is processed to give a reflection-coefficient spectrum. The lubricant-film thickness is then obtained from either the layer stiffness or the resonant frequency. The method has been validated using fluid wedges at ambient pressure between flat and curved surfaces. Experiments on the elastohydrodynamic film formed between a sliding ball and a flat surface were performed. Film-thickness values in the range 50-500 nm were recorded, which agreed well with theoretical film-formation predictions. Similar measurements have been made on the oil film between the balls and outer raceway of a deep-groove ball bearing

How can field margin management contribute to invertebrate biodiversity?

Farmland invertebrates are vital for healthy ecosystem functioning. Many groups have declined due to agricultural intensification. Arable field margins potentially can increase food resources and provide winter refuges for invertebrates. They might also buffer them from agrochemical applications and farm operations. This chapter describes a series of field and farm-scale experiments which show that ways in which arable field margins are established and managed can have profound effects on their invertebrate assemblages. Field margin swards established by sowing with a grass and wildflower seed mixture attracted more butterflies than naturally regenerated swards. In the short term, larger and more species-rich invertebrate assemblages were fostered on unmanaged margins than on those managed by cutting. The timing of cutting was critical, with mid-summer cutting having the most persistent, negative effects on invertebrates, while cutting in spring and autumn was generally less damaging and may help maintain sward species richness. Fallowed land (set-aside) configured as blocks rather than margins constituted qualitatively different habitats for invertebrates. Margin width had complex effects on invertebrate abundance and species richness. Boundary hedgerows increased numbers of most invertebrate groups in the adjacent margin. The chapter suggests that blanket management approaches for invertebrates at the farm scale are not optimal. A diverse farmed landscape, with margins of different sizes and different sward structures, will provide for the different ecological requirements of invertebrate populations, and promote their diversity in the characteristically unstable environment of arable systems

Auto-calibration of ultrasonic lubricant-film thickness measurements

The measurement of oil film thickness in a lubricated component is essential information for performance monitoring and design. It is well established that such measurements can be made ultrasonically if the lubricant film is modelled as a collection of small springs. The ultrasonic method requires that component faces are separated and a reference reflection recorded in order to obtain a reflection coefficient value from which film thickness is calculated. The novel and practically useful approach put forward in this paper and validated experimentally allows reflection coefficient measurement without the requirement for a reference. This involves simultaneously measuring the amplitude and phase of an ultrasonic pulse reflected from a layer. Provided that the acoustic properties of the substrate are known, the theoretical relationship between the two can be fitted to the data in order to yield reflection coefficient amplitude and phase for an infinitely thick layer. This is equivalent to measuring a reference signal directly, but importantly does not require the materials to be separated. The further valuable aspect of this approach, which is demonstrated experimentally, is its ability to be used as a self-calibrating routine, inherently compensating for temperature effects. This is due to the relationship between the amplitude and phase being unaffected by changes in temperature which cause unwanted changes to the incident pulse. Finally, error analysis is performed showing how the accuracy of the results can be optimized. A finding of particular significance is the strong dependence of the accuracy of the technique on the amplitude of reflection coefficient input data used. This places some limitations on the applicability of the technique. © 2008 IOP Publishing Ltd

Thermal Imaging and Physiological Analysis of Cold-Climate Caribou-Skin Clothing

Protective clothing is essential for human existence in the Arctic, and caribou-skin clothing has played a pivotal role for millennia. Although people with northern experience often extol caribou-skin clothing, few scientific studies have investigated its properties. We used infrared thermal imaging in a pilot study to compare authentic caribou-skin clothing sewn by traditional Inuit seamstresses with two other types of cold-weather clothing: a standard-issue, Canadian army, winter uniform and an ensemble of modern retail clothing designed for extreme cold (a down anorak and snowmobile pants). To make the comparison, two subjects sequentially wore the three types of clothing—caribou skin, army uniform, and modern retail—in a still air, uniform thermal environment (where radiant temperatures of all environmental surfaces were equal to air temperature) at −21°C to −23°C (−6°F to −10°F). Thermal imaging quantifies the temperature of the outer surface of clothing, thereby providing key, functionally relevant information on the interface where clothing and environment meet. Under otherwise similar conditions, a low clothing surface temperature indicates superior clothing performance and a reduced rate of heat loss from the body to the environment. Caribou-skin clothing was similar to modern extreme-cold retail clothing: the whole-body composite surface temperature of our subjects wearing caribou-skin clothing was −22.1°C to −22.7°C, compared with −21.6°C in both subjects wearing the modern retail clothing. The army winter uniform (−18.9°C to −20.0°C) was inferior. These quantitative results were mirrored by the subjects’ subjective impressions. A particular advantage of thermal imaging is that it pinpoints locations in clothing where heat leaks occur. Although the two types of modern clothing exhibited heat leaks at zippered structures (even though fully closed), the caribou-skin clothing evaded such heat leaks by lacking such structures, because it is donned over the head. The integral hood characteristic of a caribou-skin parka was also superior in comparison to the detachable hood of the army uniform.Les vêtements de protection sont essentiels à l’existence humaine dans l’Arctique, et les vêtements en peau de caribou y jouent un rôle vital depuis des millénaires. Même si les gens qui ont évolué dans le Nord vantent souvent les mérites des vêtements en peau de caribou, peu d’études scientifiques ont été réalisées au sujet de leurs propriétés. Nous nous sommes servi d’imagerie thermique infrarouge dans le cadre d’une étude pilote visant à comparer les vêtements en peau de caribou authentique cousus par des couturières inuites traditionnelles à deux autres types de vêtements pour temps froid : un uniforme d’hiver standard de l’Armée canadienne et un ensemble de vêtements modernes du détail conçus pour des froids extrêmes (un anorak en duvet et des pantalons de motoneige). À des fins de comparaison, deux sujets ont porté, dans l’ordre séquentiel, les trois types de vêtements — vêtement en peau de caribou, uniforme de l’armée et vêtements modernes du détail — dans des conditions de vent nul thermique uniforme (où les températures radiatives de toutes les surfaces environnementales sont égales à la température de l’air) moyennant des températures allant de −21 °C à −23 °C (de −6 °F à −10 °F). L’imagerie thermique quantifie la température de la surface extérieure du vêtement, ce qui permet d’obtenir de l’information fonctionnellement pertinente et essentielle sur le point de rencontre du vêtement et de l’environnement. Dans des conditions par ailleurs semblables, la faible température du vêtement en surface indique un rendement supérieur pour ce vêtement et un taux réduit de perte de chaleur du corps à l’environnement. Les vêtements en peau de caribou ont donné des résultats semblables aux vêtements pour froid extrême modernes du détail : la température composite du corps entier de nos sujets portant les vêtements en peau de caribou variait de −22,1 °C à −22,7 °C, comparativement à −21,6 °C chez les deux sujets portant les vêtements modernes du détail. Les températures de l’uniforme d’hiver de l’armée étaient inférieures (de −18,9 °C à −20,0 °C). Ces résultats quantitatifs cadraient avec les impressions subjectives des sujets. Un des avantages particuliers de l’imagerie thermique, c’est qu’elle permet de repérer là où les pertes de chaleur se produisent dans les vêtements. Bien que les deux types de vêtements modernes perdaient de la chaleur à l’endroit des fermetures éclair (même si elles étaient fermées complètement), les vêtements en peau de caribou n’affichaient pas de telles pertes de chaleur en raison de l’absence de structures de ce genre parce que ces vêtements s’enfilent par la tête. Par ailleurs, il y a lieu de noter que la caractéristique intégrale du capuchon du parka en peau de caribou était également supérieure à celle du capuchon amovible de l’uniforme militaire

Positron interactions with water-total elastic, total inelastic, and elastic differential cross section measurements

9 págs.; 5 figs.; 4 tabs.© 2014 AIP Publishing LLC. Utilising a high-resolution, trap-based positron beam, we have measured both elastic and inelastic scattering of positrons from water vapour. The measurements comprise differential elastic, total elastic, and total inelastic (not including positronium formation) absolute cross sections. The energy range investigated is from 1 eV to 60 eV. Comparison with theory is made with both R-Matrix and distorted wave calculations, and with our own application of the Independent Atom Model for positron interactions.This work has been supported by the Australian Research Council’s Centre of Excellence Program. G.G. and F.B. would like to acknowledge the Spanish Ministerio de Economıa y Competitividad (project FIS2012-31230). Some financial support through COST Action “Nano-IBCT” is also gratefully acknowledged.Peer Reviewe

Heteromysis cocoensis n. sp. (Crustacea: Mysida: Mysidae) from coastal waters of Isla del Coco, Costa Rica

A survey of the invertebrate fauna of coral reef hard bottom communities in the shallow waters of Isla del Coco yielded a new species of mysid belonging to the genus Heteromysis S. I. Smith, 1873. Heteromysis (Olivemysis) cocoensis, n. sp. was collected from coral rubble at depths of 8 to 34 m. It differs from its congeners by having male pleopods 1, 3, and 4 with modified setae. Within the subgenus Olivemysis Băcescu, 1968, the new species is morphologically most similar to Heteromysis. ekamako Wittmann and Chevaldonne, 2017 from the Pacific, Heteromysis. gomezi Băcescu, 1970, H. mayana Brattegard, 1970, and H. rubrocinta, Băcescu, 1968 from the Western Atlantic, and Heteromysis. dardani Wittmann, 2008, Heteromysis. wirtzi Wittmann, 2008, and Heteromysis. sabelliphila Wittmann and Wirtz, 2017 from the Eastern Atlantic. However, H. cocoensis n. sp. is distinguished from these six apparently closely related species by the following combination of characters: flagellate, modified setae on articles 1 and 3 of the antennular peduncle, and setation of thoracic endopod 3, male pleopods 1, 3 and 4, uropodal endopods, and the apical and lateral margins of the telson. A diagnostic table separating these eight species is given.Universidad de Costa Rica/[]/UCR/Costa RicaUCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Biologí