Experimental investigations of pressures, temperatures, and film thicknesses in pure rolling elastohydrodynamic contacts have been made in a two-disk apparatus. Transducers for pressure, gap, and temperature measurements were applied by an evaporation technique. Measurements were made over a range of speeds, loads, and oil inlet temperatures with oils having various pressure-viscosity coefficients. The predicted film thicknesses and shape of the pressure profile (including the secondary pressure peak) agree well with the experimental observations as inlet viscosity, pressure viscosity coefficient, and load are varied.
An experimental platform was designed to study the effects of laser accelerated protons (LAPs) on mammalian cells. The protons, in the MeV energy range, originate from the rear side of a thin 5 µm Ti foil target following the interaction with a high power laser pulse and are accelerated by the target normal sheath mechanism. A tape Ti foil target was developed, allowing a shot repetition rate of up to 5 Hz, which corresponds to the rate of the laser system. A dipole magnet arrangement was used for energy dispersion and to separate the proton burst from electrons and x rays. The absorbed radiation dose at the cell port was measured with CR39 plastic detectors and calibrated imaging plates. An epifluorescence microscope with compact open-beam optics was developed to image live cells and their spatiotemporal properties during and after irradiation. To demonstrate the functionality of all components of the platform, biological proof of concept experiments were carried out using two suspension (Jurkat and Ramos) and two adherent (HeLa and A-549) cell lines. A multitude of biological procedures and analytical techniques were established on-site or in laboratories nearby. For example, we analyzed DNA double-strand break (DSB) induction and repair by detecting the γH2A.X signal by fluorescence microscopy and flow cytometry. The observed dose-dependent increase in DSB induction confirms that DNA damage is induced in cells after exposure to LAPs.
The purpose of this study is to develop a model for the albedo of a cloud bar array over a reflecting surface. The model is based on the discrete-ordinates method for evaluation of radiant exchange between surfaces separated by a radiatively transparent medium. The model assumes that the clouds are opaque and accounts for the cloud geometry, the separation between the clouds, the height of the clouds above the ground, and the ground reflectance. The cloud bar array is irradiated by direct and diffuse components of solar energy. Cloud albedos are greater than the ground reflectance for ground surfaces with low reflectances and are less than the ground reflectance for highly reflecting ground surfaces but may be greater than the albedo for a plane layer cloud. In view of these findings, care must be exercised to account properly for the effects of cloud geometry and ground reflectance when cloud albedos are determined.
One of the difficultiesinvolved with radiative transfer analysis between surfaces separated by a radiatively nonparticipating medium is the evaluation of geometric factors, commonly referred to as view factors. For a nonreflecting ground, evaluation of the view factors is manageable. However, for a reflecting ground, evaluation of view factors between an area on the ground and an area on the side of a cloud becomes tedious because the ground may see many sides in the cloud bar array and partial obstruction due to blockages occurs. In an attempt to circumvent the problems of finding view factors for complex geometries, Stlnchez and Smith [1992] developed a radiant exchange model using the discrete-ordinates method (DOM). The model was shown to produce accurate heat fluxes for geometries involving shadowing and obstruction. For application to the cloud bar array, the model must be extended to account for a collimated radiant energy source. Ol LIIIb lb LU albedo for a cloud bar a•ay over a reflecting surface. The model uses the discrete-ordinates method to determine radiant exchange between surfaces. Emphasis is placed on examining the effect of the cloud bar geomet• and ground reflectance on the cloud alb•o. The cloud bar system, governing radiative transfer equations, and the numerical solution of these equations using the DOM •e presented in the next two sections. To veri• the accuracy of the model based on the DOM, a second model based on the radiosity/i•adiation method (RIM) is also developed. Results for the cloud albedo as a function of the cloud geometric parameters, ground reflectance, and direction of incident sol• energy are then examined. Conclusions follow the results section.
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