			Home About us Contact

Outer Ring (outer + ring)

Distribution by Scientific Domains

Engineering	42%

Selected Abstracts

Friction reduction in rolling bearing by using polymer additives,

LUBRICATION SCIENCE, Issue 8 2009
Maria Bercea
Abstract The friction torque on the outer ring of a tapered roller bearing has been experimentally measured for a mineral oil (base oil), as well as for samples of the base oil additived with low-density polyethylene. The data show an important reduction of friction by introducing the polymer into the base oil due to the film formed by the adsorption of macromolecular coils on the solid surface. The effectiveness of macromolecular additive contribution to friction behaviour is described in terms of polymer efficiency, which shows maximum values at low polymer concentrations. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Repellency of deet to nymphs of Triatoma infestans

MEDICAL AND VETERINARY ENTOMOLOGY, Issue 1 2000
R. A. Alzogaray
Summary The repellency of N,N-diethyl-3-methylbenzamide (deet) to Triatoma infestans (Klug) (Hemiptera: Reduviidae) was evaluated using third-instar nymphs and a video tracking technique. Three experimental designs were used: (a) the test arena floor was divided into two halves, only one of which was treated with deet; (b) the arena floor was divided into an inner circle and an outer ring, only the latter treated with deet; (c) half of the test arena was covered by a filter paper roof treated with deet (out of reach of the nymphs). In all three types of experiment, a repellent effect was demonstrated proportional to the dose of deet. When a host (pigeon) was shielded by deet-treated gauze, the rate of blood-feeding by the nymphs was inhibited. Topical pre-treatment of the nymphs with N-ethylmaleimide, to block chemoreception, inhibited the repellency. [source]

Probing the origin of the dark material on Iapetus

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2010
F. Tosi
ABSTRACT Among the icy satellites of Saturn, Iapetus shows a striking dichotomy between its leading and trailing hemispheres, the former being significantly darker than the latter. Thanks to the Visual and Infrared Mapping Spectrometer (VIMS) imaging spectrometer on-board Cassini, it is now possible to investigate the spectral features of the satellites in Saturn system within a wider spectral range and with an enhanced accuracy than with previously available data. In this work, we present an application of the G-mode method to the high resolution, visible and near-infrared data of Phoebe, Iapetus and Hyperion collected by Cassini/VIMS, in order to search for compositional correlations. We also present the results of a dynamical study on the efficiency of Iapetus in capturing dust grains travelling inwards in Saturn system with the aim of evaluating the viability of the Poynting,Robertson drag as the physical mechanism transferring the dark material to the satellite. The results of spectroscopic classification are used jointly with the ones of the dynamical study to describe a plausible physical scenario for the origin of Iapetus' dichotomy. Our work shows that mass transfer from the outer Saturnian system is an efficient mechanism, particularly for the range of sizes hypothesized for the particles composing the newly discovered outer ring around Saturn. Both spectral and dynamical data indicate Phoebe as the main source of the dark material. However, due to considerations on the collisional history of the Saturnian irregular satellites and to the differences in the spectral features of Phoebe and the dark material on Iapetus in the visible and ultraviolet range, we suggest a multisource scenario where now extinct prograde satellites and the disruptive impacts that generated the putative collisional families played a significant role in supplying the original amount of dark material. [source]

The first named Ediacaran body fossil, Aspidella Terranovica

PALAEONTOLOGY, Issue 3 2000
James G. Gehling
Aspidella terranovica Billings, 1872 was first described from the late Neoproterozoic Fermeuse Formation (St. John's Group) on the Avalon Peninsula of eastern Newfoundland, approximately 1km stratigraphically above the famous Ediacaran biota at Mistaken Point, and several kilometres below the base of the Cambrian. Aspidella has been reinterpreted perhaps more than any other Precambrian taxon, and has variously been regarded as a fossil mollusc or ,medusoid', a gas escape structure, a concretion, or a mechanical suction mark. Our studies indicate that Aspidella includes a wide variety of preservational morphs varying from negative hyporeliefs with a raised rim and ridges radiating from a slit (Aspidella -type preservation), to flat discs with a central boss and sharp outer ring (Spriggia preservation), to positive hyporeliefs with concentric ornamentation (Ediacaria preservation). Specimens occur in a continuum of sizes, with preservational styles dependent on the size of the specimen and the grain size of the host lithology; the elongation of specimens is tectonic. Aspidella is confirmed as a body fossil from observations of complex radial and concentric ornamentation, mutually deformed borders in clusters of specimens, and occurrence on the same bedding planes as certain distinctive Ediacaran taxa. Aspidella is indistinguishable from, and has priority over, several of the most common genera of late Neoproterozoic discoidal body fossils worldwide. Similar fossils from Australia are interpreted as holdfasts of frond-like organisms. The density of specimens in the Aspidella beds suggests levels of benthic biomass in the Neoproterozoic that could rival those of modern marine communities. The serial growth forms, PalaeopascichnusIntrites, Neonereites renariusYelovichnus, associated with Aspidella, are interpreted as body fossils of unknown affinities rather than trace fossils. A new, trilobed, Ediacaran body fossil, Triforillonia costellae gen. et sp. nov., is described from the Aspidella beds of the Fermeuse Formation. [source]

Design Optimization of Blood Shearing Instrument by Computational Fluid Dynamics

ARTIFICIAL ORGANS, Issue 6 2005
Jingchun Wu
Abstract:, Rational design of blood-wetted devices requires a careful consideration of shear-induced trauma and activation of blood elements. Critical levels of shear exposure may be established in vitro through the use of devices specifically designed to prescribe both the magnitude and duration of shear exposure. However, it is exceptionally difficult to create a homogeneous shear-exposure history by conventional means. This study was undertaken to develop a Blood Shearing Instrument (BSI) with an optimized flow path which localized shear exposure within a rotating outer ring and a stationary conical spindle. By adjustment of the rotational speed and the gap dimension, the BSI is designed to generate shear stress magnitudes up to 1500 Pa for exposure time between 0.0015 and 0.20 s with a pressure drop of 100 mm Hg. Computational fluid dynamics (CFD) revealed that a flow path designed by first-order analysis and intuition exhibited unfavorable pressure gradient, vortices, and undesirable regions of reverse flow. An optimized design was evolved utilizing a parameterized geometric model and automatic mesh generation to eliminate vortices and reversal flow and to avoid unfavorable pressure gradients. Analysis of the flow and shear fields for the extreme limits of the shear gap demonstrated an improvement in homogeneity due to shape optimization and the limitations of an annular shear device for achieving completely uniform shear exposure. [source]

Heat transfer characteristics between inner and outer rings of an angular ball bearing

HEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 1 2003
Keiji Mizuta
Abstract Heat transfer between the inner and the outer rings of an angular ball bearing is investigated experimentally and heat transport by balls is analyzed theoretically. The bearing used is lubricated by oil and rotated in the range from 600 to 4000 rpm. Considering heat generation by friction, the net heat flow between the rings is evaluated. The results show that balls are the dominant heat carrier and their conductance depends on rotational speed and thrust force. The other heat transfer route is supposed mainly to be between the rings based on the fact that its heat flow rate depends on the rotational speed. © 2002 Wiley Periodicals, Inc. Heat Trans Asian Res, 32(1): 42,57, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.10070 [source]