Performance of computer-optimized tapered-roller bearings to 2.4 million DN

The performance of 120.65 mm bore high speed design tapered roller bearings was investigated at shaft speeds to 20,000 rpm under combined thrust and radial load. The test bearing design was computer optimized for high speed operation. Temperature distribution and bearing heat generation were determined as a function of shaft speed, radial and thrust loads, lubricant flow rates, and lubricant inlet temperature. The roller bearing operated successfully at shaft speeds up to 20,000 rpm under heavy thrust and radial loads. Cup cooling was effective in decreasing the high cup temperatures to levels equal to the cone temperature

Lubrication of optimized-design tapered-roller bearings to 2.4 million DN

The performance of 120.65 mm (4.75 in.) bore high speed design, tapered roller bearings was investigated at shaft speeds to 20,000 rpm (2.4 million DN) under combined thrust and radial load. The test bearing design was computer optimized for high speed operation. Temperature distribution bearing heat generation were determined as a function of shaft speed, radial and thrust loads, lubricant flow rates, and lubricant inlet temperature. The high speed design, tapered roller bearing operated successfully at shaft speeds up to 20,000 rpm under heavy thrust and radial loads. Bearing temperatures and heat generation with the high speed design bearing were significantly less than those of a modified standard bearing tested previously. Cup cooling was effective in decreasing the high cup temperatures to levels equal to the cone temperature

Validity of the Adiabatic Approximation

We analyze the validity of the adiabatic approximation, and in particular the reliability of what has been called the "standard criterion" for validity of this approximation. Recently, this criterion has been found to be insufficient. We will argue that the criterion is sufficient only when it agrees with the intuitive notion of slowness of evolution of the Hamiltonian. However, it can be insufficient in cases where the Hamiltonian varies rapidly but only by a small amount. We also emphasize the distinction between the adiabatic {\em theorem} and the adiabatic {\em approximation}, two quite different although closely related ideas.Comment: 4 pages, 1 figur

Endurance tests with large-bore tapered-roller bearings to 2.2 million DN

Endurance life tests were run with standard design and optimized high-speed design 120.65-mm-(4.750-in.-) bore tapered-roller bearings at shaft speeds of 12,500 and 18,500 rpm, respectively. Standard design bearings of vacuum melted AISI 4320 and CBS-1000M, and high-speed design bearings of CBS-1000M and through-hardened AISI M-50 were run under heavy combined radial and thrust load until fatigue failure or until a preset cutoff time of 1100 hours was reached. Standard design bearings made from CBS 1000M material ran to a 10 percent life approximately six times rated catalog life. Twelve identical bearings of AISI 4320 material ran to ten times rated catalog life without failure. Cracking and fracture of the cones of AISI M-50 high-speed design bearings occurred at 18,500 rpm due to high tensile hoop stresses. Four CBS 1000M high-speed design bearings ran to twenty-four times rated catalog life without any spalling, cracking or fracture failures

A group model for stable multi-subject ICA on fMRI datasets

Spatial Independent Component Analysis (ICA) is an increasingly used data-driven method to analyze functional Magnetic Resonance Imaging (fMRI) data. To date, it has been used to extract sets of mutually correlated brain regions without prior information on the time course of these regions. Some of these sets of regions, interpreted as functional networks, have recently been used to provide markers of brain diseases and open the road to paradigm-free population comparisons. Such group studies raise the question of modeling subject variability within ICA: how can the patterns representative of a group be modeled and estimated via ICA for reliable inter-group comparisons? In this paper, we propose a hierarchical model for patterns in multi-subject fMRI datasets, akin to mixed-effect group models used in linear-model-based analysis. We introduce an estimation procedure, CanICA (Canonical ICA), based on i) probabilistic dimension reduction of the individual data, ii) canonical correlation analysis to identify a data subspace common to the group iii) ICA-based pattern extraction. In addition, we introduce a procedure based on cross-validation to quantify the stability of ICA patterns at the level of the group. We compare our method with state-of-the-art multi-subject fMRI ICA methods and show that the features extracted using our procedure are more reproducible at the group level on two datasets of 12 healthy controls: a resting-state and a functional localizer study

Effet de la prédation et des nutriments sur les réseaux microbiens planctoniques

Les effets de l'ajout de nutriments et de poissons planctonophages sur le réseau trophique microbien (protozoaires, phytoplancton, zooplancton) ont été évalués lors d'une étude expérimentale utilisant des enclos de grande taille (8 m diam., 12 m prof.), placés dans un lac humique du Bouclier Canadien. Un plan factoriel avec 4 traitements, C (contrôle), N (ajout de nutriments), P (ajout de poissons planctonophages) et NP (ajout de nutriments et poissons) a été appliqué. L'abondance et la biomasse du zooplancton (Rotifères, Cladocères, Copépodes), des Protozoaires Ciliés et du phytoplancton (Chl. a) ont été déterminées pendant 6 semaines dans chaque strate (épi-, méta- et hypolimnion). La présence de poissons planctonophages a entraîné une baisse de la biomasse du zooplancton de grande taille (Cladocères), mais a favorisé le développement du zooplancton de petite taille (Rotifères). La diminution de biomasse des Cladocères dans les enclos avec poissons s'associait avec une hausse de l'abondance des Protozoaires Ciliés et du phytoplancton pour les enclos NP. L'ajout de nutriments a augmenté la biomasse des Cladocères, des Ciliés et du phytoplancton qui présentait une tendance monospécifique. L'étude a montré que dans un lac humique riche en carbone organique dissous, les nutriments ne sont pas le seul facteur déterminant la structure des communautés microbiennes. Celles-ci subissent également les effets en cascade de la prédation des poissons planctonophages situés au sommet de la chaîne alimentaire.An experimental study was conducted using large enclosures (8 m diam., 12 m depth.) set up in a humic lake on the Canadian Shield to determine the effects of nutrients and planktivorous fish on the microbial food web (protozoans, phytoplankton and zooplankton). A four treatments factorial design was applied as following: C (control), N (nutrients), P (planktivorous fish) and NP (nutrients and fish). Zooplankton, ciliate and phytoplankton abundance and biomass were measured for six weeks in the epi-, meta- and hypolimnion. In the fish enclosure, the decrease of cladoceran biomass produced an increase in ciliate abundance and phytoplankton biomass when both fish and nutrients were present. Nutrient loading increased the biomass of cladocerans, phytoplankton and ciliates. This study showed that, in humic lakes, the microbial community is regulated not only by nutrients, but top-down effects, via fish predation, must also be considered

Giant magnetic anisotropy at nanoscale: overcoming the superparamagnetic limit

It has been recently observed for palladium and gold nanoparticles, that the magnetic moment at constant applied field does not change with temperature over the range comprised between 5 and 300 K. These samples with size smaller than 2.5 nm exhibit remanence up to room temperature. The permanent magnetism for so small samples up to so high temperatures has been explained as due to blocking of local magnetic moment by giant magnetic anisotropies. In this report we show, by analysing the anisotropy of thiol capped gold films, that the orbital momentum induced at the surface conduction electrons is crucial to understand the observed giant anisotropy. The orbital motion is driven by localised charge and/or spin through spin orbit interaction, that reaches extremely high values at the surfaces. The induced orbital moment gives rise to an effective field of the order of 103 T that is responsible of the giant anisotropy.Comment: 15 pages, 2 figures, submitted to PR

Thin GaAsSb Diodes With Low Excess Noise

Thin avalanche layers have been adopted to achieve low excess noise and high gain bandwidth products in InP and InAlAs avalanche photodiodes. In this work we report the excess noise characterization in a series of Al1-xGaxAs0.56Sb0.44 (x = 0, 0.05, 0.1, 0.15) diodes with avalanche layer thickness of 110-116 nm. These alloys, lattice matched to InP, showed lower excess noise than InP and InAlAs. Dark current, most probably originating from surface leakage, was observed to be lower in composition with higher Ga concentration. Avalanche gain and excess noise measurements using lasers of 543 and 633 nm wavelengths indicated that at a given electric field, the electron ionization coefficient is larger than the hole ionization coefficient. Using the 543 nm laser, low excess noise data corresponding to an effective ionization coefficient ratio of k = 0.1 in the conventional excess noise theory was measured in Al1-xGaxAs0.56Sb0.44 (x = 0.05, 0.1, 0.15), although pure electron injection was not achieved. Our results demonstrated the potential of using Al1-xGaxAs0.56Sb0.44 (x = 0.05, 0.1, 0.15) as replacement for InP and InAlAs for high speed and low excess noise avalanche photodiodes. The data reported in this paper is available from the ORDA digital repository (https://doi.org/10.15131/shef.data.5155822)

Exposure to Household Air Pollution from Biomass-Burning Cookstoves and HbA1c and Diabetic Status Among Honduran Women

Household air pollution from biomass cookstoves is estimated to be responsible for more than two and a half million premature deaths annually, primarily in low and middle‐income countries where cardiometabolic disorders, such as Type II Diabetes, are increasing. Growing evidence supports a link between ambient air pollution and diabetes, but evidence for household air pollution is limited. This cross‐sectional study of 142 women (72 with traditional stoves and 70 with cleaner‐burning Justa stoves) in rural Honduras evaluated the association of exposure to household air pollution (stove type, 24‐hour average kitchen and personal fine particulate matter [PM2.5] mass and black carbon) with glycated hemoglobin (HbA1c) levels and diabetic status based on HbA1c levels. The prevalence ratio (PR) per interquartile range increase in pollution concentration indicated higher prevalence of prediabetes/diabetes (vs normal HbA1c) for all pollutant measures (eg, PR per 84 μg/m3 increase in personal PM2.5, 1.49; 95% confidence interval [CI], 1.11‐2.01). Results for HbA1c as a continuous variable were generally in the hypothesized direction. These results provide some evidence linking household air pollution with the prevalence of prediabetes/diabetes, and, if confirmed, suggest that the global public health impact of household air pollution may be broader than currently estimated