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It is well known that the dry/wet boundaries of land surface temperature fractional vegetation coverage (LSTfc) trapezoid framework vary linearly with vegetation coverage (fc). In this study, the theoretical end-members algorithm is modified to continuously estimate the dry/wet end-members under varying vegetation conditions, causing the theoretical dry/wet boundaries to become non-linear. The findings revealed that the non-linear dry/wet boundaries were generally below the conventional linear dry/wet boundaries. Furthermore, the non-linear boundary scheme adopted herein provided better performance in estimating the latent heat flux (LE) and vegetation latent heat flux fraction (LEv/LE) compared to the linear boundary scheme. The parametric schemes of aerodynamic and thermodynamic roughness length and the aerodynamic resistance were the major drivers that result in dry/wet boundaries characteristics being highly non-linear. This study enhanced the physical process description in the LST-fc trapezoid framework and improved the prediction accuracy of regional LE and its components. [ABSTRACT FROM AUTHOR]

Water-quality monitoring for small urban waterbodies by remote sensing gets to be difficult due to the coarse spatial resolution of remote-sensing imagery. The recently launched Sentinel-2 produces imagery with a spatial resolution of 10 × 10 m and a temporal resolution of 5 days. It provides an opportunity to conduct high-frequency water-quality monitoring for small waterbodies. Since illegal discharges are an important issue for urban water management, total phosphorous (TP), total nitrogen (TN), and chemical oxygen demand (COD) were chosen as the target water-quality parameters. TP, TN and COD, however, are non-optically active parameters. There are fairly limited previous studies on retrieving these parameters in comparison with optically active parameters, e.g. Chlorophyll-a etc. Based on the fact that non-optically active parameters may be highly correlated with optically active parameters, this study compared 255 possible Sentinel-2 imagery band compositions to identify the most appropriate ones for TP, TN and COD retrieval. Three machine-learning models, namely Random Forest (RF), Support Vector Regression (SVR) and Neural Networks (NN), were compared to seek the most robust ones for retrieving the above non-optically active parameters. Results showed that the most appropriate band (hereafter termed as ' B i n d e x ' for brevity) compositions for TP, TN, and COD retrieval were ' B 3 + B 4 + B 5 + B 6 + B 7 + B 8 ', ' B 3 + B 4 + B 5 \breAK + B 6 + B 7 + B 8 ', and ' B 2 + B 3 + B 5 + B 6 + B 7 + B 8 ' respectively. The coefficient of determination (R2) of TP, TN, and COD estimations by NN, RF and SVR was 0.94, 0.88, and 0.86, respectively. The retrieval performances of these non-optically active parameters were hence significantly improved by the optimized machine-learning models and imagery band selection. The developed models have limitations in applying to other areas, thus band selection and tuning parameters with new data are necessary for different areas. The water-quality mapping obtained from Sentinel-2 imagery provided a full spatial coverage of the water-quality characterization for the entire water surface, and helped identify illegal discharges to urban waterbodies. This study provides a new practical and efficient water-quality monitoring strategy for managing small waterbodies. [ABSTRACT FROM AUTHOR]

Surface sediment samples were collected from 10 typical locations throughout the Dongting Lake, China, in January 2009. Samples were assayed by atom absorption spectrophotometer and cold atomic fluorescent spectrophotometer for Pb, Cd, As, Hg. In order to investigate the spatial distribution characteristics, sources, and potential ecological risks of heavy metals, the geostatistics method, potential ecological risk index, and multivariate statistical analysis were applied. The results showed that except for the content of Hg, the contents of Pb, Cd, and As had similar spatial distribution characteristics. The average contents of Cd and As exceeded the second class contents of the National Standard for Soil Environment Quality (GB15618-1995), especially that for Cd. The potential ecological risk posed by these heavy metals decreased in the order of the outlet of the Dongting Lake > the East Dongting Lake > the South Dongting Lake > the West Dongting Lake spatially. From the results of multivariate statistical analysis, Pb and Cd, as the first group, were considered to be rooted in mining smelting processes for developed mining and heavy industry. And Hg, as the second group, was mainly derived from parent material weathering, while As was probably considered to originate from both sources above. [ABSTRACT FROM PUBLISHER]

The junction temperature of LED (light emitting diode) has a significant impact on its performance and lifetime. In this paper, a simplified model based on the finite element analysis is developed to simulate the temperature distribution of the 200 W LED module using software ANSYS. The model contains LED package, the heat pipe radiator, as well as TIM (thermal interface material) between the LED package and radiator. The temperature distribution of the simulation agrees with that of the experimental measurement. Thickness of TIM affects the heat dissipation significantly, the chips temperature and the maximum temperature difference of chips increases sharply with TIM thickness increasing. Substituting aluminum fins with copper fins cannot improve the heat dissipation performance of heat pipe radiator, and the air velocity of heat pipe radiator plays a key role in the heat dissipation. Thermal conductivity of package submount directly affects the chip temperature and the uniformity of temperature distribution of package submount. [ABSTRACT FROM AUTHOR]