Зависимость свойств вариативных градиентно-пористых структур кремния от метода формирования

A series of samples of gradient-porous silicon structures with crystallographic orientations (100) and (111) by deep anode etching was obtained. Dependences of the rate of deep anodic etching and the depth of the porous layer of the samples on the anode current density are shown. The absorption and reflection coefficients of the samples were investigated by optical spectrometry depending on their crystallographic orientation and the depth of the porous layer. The influence of water solutions on the optical properties of the samples was determined.

Attenuation of solar radiation in Arctic snow: field observations and modelling

Solar radiation was measured above and in the snowpack on Svalbard using a spectroradiometer and a quantum meter measuring average photosynthetically active radiation (PAR). In order to specify the effect of melting on the snow’s radiation properties, all measurements were performed before and during the melt season in May and June 1997 and 1998. Along with the radiation measurements, physical and structural snow properties were logged in snow pits. A physically based model was used to simulate the penetration of radiation into the snow The model formulation accounts for the spectrally dependent interactions between the radiation and snow grains, and requires inputs of the incoming solar radiation spectrum and the vertical snow density and grain-size. The vertical radiation-flux profile was computed using a two-stream radiation approximation where the absorption and reflection coefficients are related to the surface albedo, solar spectrum, grain-size and number of grains per unit volume. In general, snow before the onset of melt attenuates solar radiation more than coarser-grained snow that has been exposed to melting conditions. Quantum-meter measurements of PAR before and during melt can be explained by model outputs using both constant and variable extinction coefficients. Spectroradiometer measurements at fixed depth levels showed, in addition, that impurities in the snow reduce its transparency and therefore have the opposite effect to aging.

Further Studies of the Infrared Absorption of Rubber

The transmission spectrum of natural rubber has been studied in the region between 1µ and 15 µ and the effects of linear and radial stretch have been observed. Linear extension greater than 400 per cent of the original length produces an increase in the C—C vibrational frequency. Both linear and radial stretch produce an increase in absorption coefficient and a decrease in reflection coefficient. The changes in absorption and reflection coefficients are greatest at short wave-lengths.