Low-to-medium temperature geothermal fluids in the granite regions of southeastern China are an important renewable energy resource, but they are also a source of contamination containing highly toxic elements such as fluoride and arsenic. This study analyzed the origin of the geothermal fluids in a regional-scale hydrogeological unit in the city of Xiamen, China, based on isotope and hydrochemical analyses. The Br/Cl ratios suggested that the inland geothermal fluid is merely recharged by rainwater from the mountain edge, while the coastal geothermal fluid is originally recharged by the seawater and later mixed with rain-derived groundwater. The geothermal water featured high SiO2 and detectable Zn concentrations. The former reflects the significant water–granite interaction along the flow path, and the latter indicates the active hydraulic connection between surface waters, shallow aquifers and deep geothermal fluids. High radon content was detected near the deep conductive fault adjacent to a geothermal well, demonstrating that the fault damage zone acts as a major conduit for upward transport of the deep geothermal fluid. As a result, the fault damage zones developed in the granite are necessary for the formation of geothermal water, which leads to the uneven distribution of geothermal water in the subsurface. High-temperature geothermal water can be found in those regions with fairly sparse fault damage zones. In contrast, in the region with high-density fault activities, the active communication between shallow cool water and deep geothermal fluids can decrease the water temperature.
To discover the characteristics, distribution and potential of shallow geothermal energy in the Beijing-Tianjin-Hebei Plain area. This paper, based on a large amount of data collection and field investigations, evaluateed the shallow-layer geothermal energy in the study area through the analytic hierarchy process and comprehensive index method. Based on suitability zoning results superimposed with 1:100 000 land use data, the study area is divided into encouraged, controlled, restricted and prospective mining areas regarding the development of shallow geothermal energy, and the economic availability of shallow geothermal energy in the encouraged and controlled areas are evaluated. The results show that the shallow geothermal energy in the Beijing-Tianjin-Hebei Plain can meet the heating and cooling demand of 6×108 m~2 of buildings, equivalent to 1.15×10~7 t of standard coal, thus reducing carbon dioxide emissions by 2.73×10~7 t and reducing sulfur dioxide emissions by 1.95×10~5 t. According to the development and utilization mode, the energy demand level and the Beijing-Tianjin-Hebei coordinated development plan, the development and utilization of geothermal resources in the plain area has two types: Urban concentrated mining areas and rural scattered mining areas. The scale and level of intensive utilization of regional geothermal resources are of great significance. 相似文献
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
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
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