Iterative Reconstruction for Transmission Tomography on GPU Using Nvidia CUDA

The iterative reconstruction algorithms for X-ray CT image reconstruction suffer from their high computational cost.Recently Nvidia releases common unified device architecture(CUDA),allowing developers to access to the processing power of Nvidia graphical processing units(GPUs),in order to perform general purpose computations.The use of the GPU,as an alternative computation platform,allows decreasing processing times,for parallel algorithms.This paper aims to demonstrate the feasibility of such an implement...     

Method of Stabilizing the Surface Energy of Fabrics Coated with Silicone

Silicone coatings have been used in this study. The method adopted was the liquid drop analysis on the coated fabrics. The contact angle between a liquid drop and the fabric surface was measured with two liquids continuously and recorded by a computer. The surface energy was calculated by means of Owens method. Kinetic measurement was adopted. The contact angle of liquids on the fabric coated silicone decreased with time was found. A compound solution DX has been found, so that the contact angle of the liquids on the fabric washed with DX becomes constant, and the surface energy of the fabric can be reduced to below 15 mJ/m2.     

Accretion of low-metallicity gas by the Milky Way

Models of the chemical evolution of the Milky Way suggest that the observed abundances of elements heavier than helium ('metals') require a continuous infall of gas with metallicity (metal abundance) about 0.1 times the solar value. An infall rate integrated over the entire disk of the Milky Way of approximately 1 solar mass per year can solve the 'G-dwarf problem'--the observational fact that the metallicities of most long-lived stars near the Sun lie in a relatively narrow range. This infall dilutes the enrichment arising from the production of heavy elements in stars, and thereby prevents the metallicity of the interstellar medium from increasing steadily with time. However, in other spiral galaxies, the low-metallicity gas needed to provide this infall has been observed only in associated dwarf galaxies and in the extreme outer disk of the Milky Way. In the distant Universe, low-metallicity hydrogen clouds (known as 'damped Ly alpha absorbers') are sometimes seen near galaxies. Here we report a metallicity of 0.09 times solar for a massive cloud that is falling into the disk of the Milky Way. The mass flow associated with this cloud represents an infall per unit area of about the theoretically expected rate, and approximately 0.1-0.2 times the amount required for the whole Galaxy.