Formation of glacier tables caused by differential ice melting

Glacier tables are structures frequently encountered on temperate glaciers. They consist of a rock supported by a narrow ice foot which forms through differential melting of the ice. In this article, we investigate their formation by following their dynamics on the Mer de glace glacier (Alps, France). We report field measurements of four specific glacier tables over the course of several days, as well as snapshot measurements of a field of 80 tables performed on one given day. We develop a simple analytical 1-D heat conduction model accounting for the various mechanisms of the heat transfer on the glacier using local meteoreorological data, and which displays excellent agreement with the field measurements. We show that the formation of glacier tables results from a competition between two effects: on the one hand, a geometrical amplification of the heat flux received by the rock and transmitted to the ice underneath on the one hand, and on the other hand, a shielding effect resulting from the warmer temperature of the rocks compared to that of the ice (reducing the sensible and net infrared incident fluxes). The latter is greatly amplified by direct solar irradiation, which induces a strong temperature gradient across the thickness of the rock.

Synthesis of CuO/ZnO Nanocomposites and Their Application in Photodegradation of Toxic Textile Dye

CuO/ZnO composites are synthesized using a simple mechanochemical combustion method. X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and Fourier transform infrared (FTIR) are used to characterize the prepared oxides. X-ray diffraction reveals that the prepared CuO/ZnO exhibit a wurtzite ZnO crystal structure and the composites are composed of CuO and ZnO. The strong peaks of the Cu, Zn, and O elements are exhibited in the EDX spectrum. The FTIR spectra appear at around 3385 cm−1 and 1637 cm−1, caused by O–H stretching, and 400 cm−1 to 590 cm−1, ascribable to Zn–O stretching. The photocatalytic performances of CuO/ZnO nanocomposites are investigated for the degradation of methylene blue (MB) aqueous solution in direct solar irradiation. The degradation value of MB with 5 wt % CuO/ZnO is measured to be 98%, after 2 h of solar irradiation. The reactive •O2− and •OH radicals play important roles in the photodegradation of MB. Mineralization of MB is around 91% under sunlight irradiation within 7 h. The photodegradation treatment for the textile wastewater using sunlight is an easy technique—simply handled, and economical. Therefore, the solar photodegradation technique may be a very effective method for the treatment of wastewater instead of photodegradation with the artificial and expensive Hg-Xe lamp.

Modeling and Thermal Performance Analysis of Parabolic trough Solar Field with Single-Axis Tracked

In this paper, a model of parabolic trough solar field with single-axis tracked was developed based on detailed mathematical derivation. A software tool is also developed for its performance calculation. By the model and software, the direct solar irradiation (DNI) intercepted by the collectors and the thermal output can be obtained for a given solar field under different tracking mode. To obtain the characters of the solar field performance with different tracking modes and regions, the annual performance of the solar field is evaluated for different sites in China such as Beijing, Lhasa. Besides that, the effect of the space between collector rows on thermal output of a solar field is also discussed.

Using Artificial Neural Networks to Predict Direct Solar Irradiation

This paper explores the possibility of developing a prediction model using artificial neural networks (ANNs), which could be used to estimate monthly average daily direct solar radiation for locations in Uganda. Direct solar radiation is a component of the global solar radiation and is quite significant in the performance assessment of various solar energy applications. Results from the paper have shown good agreement between the estimated and measured values of direct solar irradiation. A correlation coefficient of 0.998 was obtained with mean bias error of 0.005 MJ/m2 and root mean square error of 0.197 MJ/m2. The comparison between the ANN and empirical model emphasized the superiority of the proposed ANN prediction model. The application of the proposed ANN model can be extended to other locations with similar climate and terrain.

Habitat requirements of Cardaminopsis petraea — Rare and relict species of the Czech Republic

Vegetation with Cardaminopsis petraea was sampled by phytosociological relevés at almost all the known Czech sites, and characterized by indicator values, influence of potential direct solar irradiation, and bedrock type with the aid of multivariate methods. It has been declared that C. petraea prefers open natural or seminatural drier to mesophilous habitats without some preference to the bedrock. It occupies habitats with various slopes, but it prefers more extreme slants and northerly exposed slopes. The classification and ordination methods showed clear distinction between Moravian and Bohemian habitats. Apart from other types, in Bohemia this species occurs uniquely in acidophilous rock communities, whereas in Moravia it grows uniquely within calcareous grasslands. Relictness of the species was discussed in relation to the specific site conditions (light supply, disturbance regime, and geographical isolation) and to the occurrence of other rare taxa and habitats. Occurrence on some man-made habitats was also observed.