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991.
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993.
Ruifu Wang Jie Li Yaping Duan Hongjun Cao Yingjie Zhao 《Journal of the Indian Society of Remote Sensing》2018,46(9):1413-1421
To maintain national socio-economic development and maritime rights and interests, it is necessary to obtain the space location information of various ships. Therefore, it is important to detect the locations of ships accurately and rapidly. At present, ship detection is mainly carried out by combining satellite remote sensing imaging with constant false alarm rate (CFAR) detection. However, with the rapid development of satellite remote sensing technology, remote sensing data have gradually begun to show the characteristics of “big data”; additionally, the accuracy and speed of ship detection can be improved by analysing big data, such as by deep learning. Thus, a ship detection algorithm that combines CFAR and CNN is proposed based on the CFAR global detection algorithm and image recognition with the CNN model. Compared with the multi-level CFAR algorithm that is based on multithreading, the algorithm in this paper is more suitable for application to ship detection systems. 相似文献
994.
Yuan Zhao Shugang Cao Yong Li Hongyun Yang Ping Guo Guojun Liu Ruikai Pan 《Natural Hazards》2018,90(3):1201-1221
Coalbed methane is a kind of clean energy source and also a kind of hazardous gas threatening the safety of coal mine production. Permeability is a key parameter to evaluate gas migration capability. However, the permeability is influenced by moisture content. Here, a series of seepage experiments were conducted to analyze the development tendency of flux and permeability to reveal the impact mechanism. Experimental results show that permeability tends to be a sharp drop with increasing moisture, but it had a slight fluctuation with relative gas pressure increasing under the constant mean effective stress. Considering the effect of moisture and gas sorption, a new gas–solid coupling model was developed based on experimental results and theoretical analysis and was implemented into FEM software for simulation. The numerical results of the new gas–solid coupling model were in good accordance with the experimental results and have a priority to cube law in precision. This study reveals that, on the one hand, the moisture can influence the adsorption-induced strain and, on the other hand, it can lead to a significant decrease in porosity due to pore volume occupation. 相似文献
995.
Wenxin Cao Dangpeng Xi Mihaela C.Melinte-Dobrinescu Tian Jiang Sherwood W.Wise Jr. Xiaoqiao Wan 《地学前缘(英文版)》2018,9(5):1465-1478
The Paleocene-Eocene Thermal Maximum(PETM) event was a dramatic global warming w55.93 Ma ago that resulted in biological extinction events, lithological changes, and major deviations in σ13 C and σ18 O.The southwestern Tarim Basin of China exposes successive Paleogene strata as a result of Tethys evolution and is considered an ideal region for PETM research.Based on calcareous nannoplankton biostratigraphy, we also used stable isotopes and XRD to analyse the Paleocene-Eocene transition in the Tarim Basin. At the Bashibulake Section, the PETM interval is characterized by(1) an abrupt negative shifts in σ13 C_(org), σ13 C_(carb) and σ18 O(-3%, -4.5% and -3%respectively);(2) an obvious negative correlation between the K-mode(Discoaster, Fasciculithus, Ericsonia, Sphenolithus and Rhomboaster) and r-mode(Biscutum, Chiasmolithus, Toweius) nannofossil taxa coincident with a robust Rhomboaster-Discoaster assemblage; and(3) a significant increase in the percentage of detrital input along with an increase in gypsum content. In the upper part of the Qimugen Formation Micrantholithus and Braarudosphaera are commonly found right up to the top where most of the nannofloras suffer a sharp decrease. In the overlying Gaijitage Formation, calcareous nannofossils disappear completely. These events indicate that the southwestern Tarim Basin was a warm shallow continental shelf during the deposition of the Qimugen Formation. From the early Eocene, the environment changed conspicuously. Evaporation increased and sea level fell, which led to an acid climate.This climate mode continued within the youngest unit studied, the Gaijitage Formation, characterized by the deposition of thick evaporates. Consequently, most of the marine plankton, i.e. calcareous nannoplankton, became disappear, because of the significant climate shift. 相似文献
996.
Tempe cell with a self-developed horizontal hanging column attachment was used to measure the soil water characteristic curves (SWCCs) of granular materials initially saturated with either water or polymer solutions. For SWCCs of six poorly graded granular materials with d 50 ranging from 0.04 to 0.7 mm in water, it was found that (1) as grain size decreases, air entry value increases, and matric suction (ψ) for the funicular and pendular regimes increases and that (2) steep desaturation curves over narrow ψ range in the funicular regime were observed. Air entry values obtained from the fitting parameter 1/α in van Genuchten SWCC equation fall in the boundaries calculated from the pore throat sizes in both simple cubic and face-centered cubic packings. A toroidal meniscus water model, which incorporates the measured surface tension and contact angle values between aqueous solutions and solid surfaces, was proposed for the SWCC in pendular regime and was compared to well-received numerical methods. This toroid model successfully depicts SWCC of poorly graded granular materials in water. However, SWCCs predicted by this toroid model underestimate the degree of saturation in the pendular regime for Ottawa 20–30 sands in polymer solutions. Herschel–Bulkley fluid, which is a type of non-Newtonian fluids, is postulated to increase the ψ needed to drain the polymer solution due to the nonzero shear stress intercept. In addition, it is also postulated by scanning electron microscopy and optical confocal imaging results that the rough surfaces of Ottawa 20–30 sand, which have many micron-sized “kinks”, together with the possible chemical attractions, help retain the polymer solutions on the solid surfaces, or water film. 相似文献
997.
Jing Wang Xin Wen Fan Yang Zhanfang Cao Shuai Wang Hong Zhong 《Environmental Earth Sciences》2018,77(12):472
A novel two-dimensional carbon material using phytic acid-functionalized graphene oxide was successfully synthesized by a simple hydrothermal method. Properties of the material were characterized by SEM, FT-IR, FITR-Rama and BET. Some factors like contact time, pH, and temperature were studied to investigate the adsorption characteristics on Cu(II) ions of the material. Experiment results showed that the material can reach equilibrium adsorption in 20 min and get maximum adsorption capacity (316.586 mg g) under the condition of pH 4.0, 304 K. The adsorption of Cu(II) ions was an exothermic and spontaneous process, and could be better simulated by the pseudo-second-order kinetics and Freundlich isotherm model. 相似文献
998.
Jiang-Feng Liu Hong-Yang Ni Yong-Gui Chen Yu Wu Shuai-Bing Song Xu-Lou Cao Wen-Bo Bao Hai Pu Xian-Biao Mao 《Environmental Earth Sciences》2018,77(16):583
In this study, water retention tests under free swelling conditions were performed to investigate the water intake (or loss) behaviour of compacted GMZ bentonite. First, the water retention characteristics were investigated, and then the microscopic pore structure was observed by environmental scanning electron microscope (ESEM). The results indicate that GMZ bentonite has a strong swelling (or a limited shrinkage ability) due to water intake (loss). The suction behaviour of GMZ bentonite is similar to MX80 bentonite and FEBEX bentonite. We also find that the confinement conditions can affect the suction behaviour of the material, especially at high relative humidity (RH). Additionally, a mathematic model can fit the mass change data very well. Microscopic tests show that the granular sensation of GMZ bentonite is obvious for a sample at low RH. With the increase in RH, the surface of GMZ bentonite becomes more smooth. The differences in the porosities calculated by the macroscopic and microscopic tests can be attributed to image resolution. The inter-laminar pores and intra-aggregate pores cannot be observed by the ESEM method. In addition, ESEM observation can provide an intuitive basis for the further research of the seepage property of GMZ bentonite. 相似文献
999.
Chunye Lin Yumeng Xue Xuan Zhang Duanzhi Renqin Xueli Zhou Yuanxin Cao Bobo Guo Xitao Liu 《Environmental Earth Sciences》2018,77(4):153
Lake Qinghai in the Qinghai-Tibet plateau is the largest lake in China. This study firstly reported the geochemistry of Cd in the lake. Water samples were collected from Lake Qinghai (n = 69) and Buha River (n = 12), while sediment (n = 22) and topsoil (n = 45) samples were collected from the lake and around the lake area, respectively. In addition, pore water samples (n = 20) were separated from sediment samples. Water samples were analyzed for pH, K, Na, Ca, Mg, Cl, S, and Cd, while sediment and topsoil samples were analyzed for K, Na, Ca, Mg, Al, Fe, Mn, S, Sc, and Cd. The average concentration of Cd was 0.014 μg L?1 in the water of Lake Qinghai and 0.007 μg L?1 in the water of Buha River. However, the average concentration of Cd was 0.320 μg L?1 in the sediment pore water, much higher than that in the lake water and river water. Cadmium concentration in the lake water might be mainly controlled by salinity, while it in the pore water might be mainly controlled by carbonate minerals. Cadmium concentration in the river water might be controlled by alkalinity and pH. The average concentration of Cd in the sediment was 0.284 mg kg?1. The enrichment of Cd in the lake sediment was significantly higher than that in the topsoil around the lake. Anthropogenic atmospheric deposition of Cd did not led to the increase in dissolved Cd level in the lake water, but led to its enrichment in the lake sediment. 相似文献
1000.
Investigations were undertaken in the riparian zone near Shangba village, an AMD area, in southern China to determine the effects that river–groundwater interactions and groundwater residence time have had on environmental quality and geochemical evolution of groundwater. Based on the Darcy’s law and ionic mass balances as well as the method of isotopic tracer, the results showed that there were active interactions between AMD-contaminated river water and groundwater in the riparian zone in the study area. River water was found to be the main source of groundwater recharge in the northwestern part of the study area, whereas groundwater was found to be discharging into the river in the southeastern part of the study area throughout the year. End-member mixing analysis quantified that the contributions of river water to groundwater decreased gradually from 35.9% to negligible levels along the flow path. The calculated mixing concentrations of major ions indicated that water–rock reactions were the most important influence on groundwater quality. The wide range of Ca2+?+?Mg2+ and HCO3? ratios and the change of groundwater type from Ca2+–SO42? type to a chemical composition dominated by Ca2+–HCO3? type indicated a change of the major water–rock reaction process from the influence of H2SO4 (AMD) to that of CO2 (soil respiration) along a groundwater flow path. Furthermore, the kinetics interpretation of SO42? and HCO3? concentrations suggested that the overlapping time of their kinetics triggered the hydrochemical evolution and the change of major weathering agent. This process might take approximately 8 years and this kinetic time will be continued when a steady source of contamination enter the aquifer. 相似文献