This study analyses physicochemical properties of soils from coal waste piles at the Naluozhai Coal Mine that were dumped 5, 15, 25 and 35 years ago, respectively. The soil at a 20-year old coal waste site where Vetiveria Zizanioides was cultivated was taken as a control. Principal components were analysed to determine their weights, and the weighted summation method was used to calculate soil quality integrated index (SQI). Eight indices were considered to assess land suitability for vegetation restoration, namely pH value, soil layer depth, field moisture capacity, stable infiltration, volume weight, total porosity, organic matter content and vegetation coverage. The results showed that vegetative restoration depends primarily on the organic matter content of the coal waste pile; the control pile recorded the highest SQI and it was satisfactory for vegetation restoration; the 35-year old pile was encouraging for vegetation restoration, second only to the control pile. 相似文献
The NiS2 nanosheet array on Ni foil (NiS2/NF) was prepared using an in situ growth strategy and sulfidation method and was used as the cathode of lithium sulfur battery. The unique nanostructure of the NiS2 nanosheet array can provide abundant active sites for the adsorption and chemical action of polysulfides. Compared with the sulfur powder coated pure NF (pure NF-S) for lithium sulfur battery, the sulfur powder coated NiS2/NF (NiS2/NF-S) electrode exhibits superior electrochemical performance. Specifically, the NiS2/NF-S delivered a high reversible capacity of 1007.5 mAh g−1 at a current density of 0.1 C (1 C= 1675 mA g−1) and kept 74.5% of the initial capacity at 1.0 C after 200 cycles, indicating the great promise of NiS2/NF-S as the cathode of lithium sulfur battery. In addition, the NiS2/NF-S electrode also showed satisfactory electrochemical performance when used as the cathode for sodium sulfur battery.
Very high resolution (VHR) remote-sensing imagery can reveal ground objects in great detail, depicting the colour, shape, size and structure of the objects. However, VHR also leads to a large amount of noise in the spectra, which may reduce the reliability of the classification result. This article presents an extension of the mean filter (MF), which is named ‘modified mean filter (MMF)’, for smoothing the noise of VHR imagery. First, the MMF is a shape-adaptive filter that is constructed by gradually detecting the spectral similarity between a kernel-anchored pixel and its contextual pixels through an extension detector with eight neighbouring pixels. Then, because pixels of an objective are usually homogeneous with spatial continuity, the pixels located at the hollow area within an extended region are rectified to enhance the smoothing effect. Finally, the spectral value of the kernel-anchored pixel is determined by the mean of the group of pixels within the adaptive region. Despite the proposed filter is a simple extension of MF, it has an advantage in preserving the edge between different classes, and smoothing the noise of intra-class. The MMF approach is investigated through comparing with the classification of VHR images based on filter processing, including the traditional mean filter (MF), the median filter (MedF) and the recursive filter (RF) which has been proposed for image classification in Kang, Li, and Benediktsson (2014). The experimental results obtained by considering two VHR images show the effectiveness of the proposed of MMF, which improves the performance of the classification and implies more potential applications. 相似文献
Source localization accuracy is very sensitive to sensor location error.This paper performs analysis and develops a solution for locating a moving source using time difference of arrival(TDOA)and frequency difference of arrival(FDOA)measurements with the use of a calibration emitter.Using a Gaussian random signal model,we first derive the Cram′er-Rao lower bound(CRLB)for source location estimate in this scenario.Then we analyze the differential calibration technique which is commonly used in Global Positioning System.It is indicated that the differential calibration cannot attain the CRLB accuracy in most cases.A closed-form solution is then proposed which takes a calibration emitter into account to reduce sensor location error.It is shown analytically that under some mild approximations,our approach is able to reach the CRLB accuracy.Numerical simulations are included to corroborate the theoretical developments. 相似文献