Characteristic analysis of journal bearing under thin film lubrication—Layered Viscosity Model
Journal bearing is a kind of widely used bearing and its study never stops. The analysis is carried to journal bearing with layered viscosity model in this paper. Layered Viscosity Model regards viscosity as piecewise function and averages every segment in order to get more accurate expression, and the pressure distributing, load capacity and friction are obtained for journal sliding bearing under thin film lubrication. The condition of thin film lubrication actualizing is made certain. The theoretical base is provided for the analysis of aggradation and liniment surface layer lubrication. This work could promote the understanding and research of the mechanism of the nano - scale thin film lubrication.
Experimental Study of Microtextured Surfaces Operating Under Thin-Film EHD Lubrication Conditions
The effect of microdents within thin elastohydrodynamics (EHD) contacts has been studied by two measurement techniques. Phase-shifting interferometry was used to obtain topography of microtextured surface and thin-film colorimetric interferometry provided detailed information about film thickness changes within a lubricated contact. The behavior of microdents has been observed for positive slide-to-roll ratios when the disk is moving faster than the microtextured ball. The depth of microdents has been found to play significant role as to the lubrication films efficiency. The presence of deep microdents within lubricated contact results in film thickness reduction downstream that can even cause lubrication film breakdown. As the depth of microdents is reduced, this effect diminishes and beneficial effect of microdents on film thickness formation has been observed. No such an effect of microdent depth on lubricant film shape has been observed in case of negative slide-to-roll conditions when microdents do not cause film thickness reduction regardless of their depths. Obtained results suggest that surface texturing using microdents of an appropriate depth could help to increase lubrication films capabilities.
In search of optimum chest radiography techniques.
A nation-wide study of chest radiography in Sweden had previously revealed a large variation in the physical and technical factors involved, in particular the radiation dose. In this study the image quality could not be assessed unambiguously. The aim of the present study was to try to establish a correlation between visual grading of radiographs and physical and technical factors in order to find the optimum chest X-ray system. The physical and technical performance of 24 chest units was evaluated. Radiographs were taken of an anthropomorphic chest phantom supplied with test structures simulating various pathologies. Image quality was assessed by visual grading analysis of the radiographs. The physical and technical parameters of the units rated best were used to exemplify good radiographic practice. The results were in agreement with the recommendations issued by the Commission of the European Communities (CEC). It was also shown that low radiation dose is compatible with high-quality radiographic imaging of the chest.