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1.
《China Geology》2021,4(3):421-432
The Badain Jaran Desert is the third largest desert in China, covering an area of 50000 km2. It lies in Northwest China, where the arid and rainless natural environment has a great impact on the climate, environment, and human living conditions. Based on the results of 1∶250000 regional hydrogeological surveys and previous researches, this study systematically investigates the circulation characteristics and resource properties of the groundwater as well as the evolution of the climate and ecological environment since the Quaternary in the Badain Jaran Desert by means of geophysical exploration, hydrogeological drilling, hydrogeochemistry, and isotopic tracing. The results are as follows. (1) The groundwater in the Badain Jaran Desert is mainly recharged through the infiltration of local precipitation and has poor renewability. The groundwater recharge in the desert was calculated to be 1.8684×108 m3/a using the water balance method. (2) The Badain Jaran Desert has experienced four humid stages since the Quaternary, namely MIS 13-15, MIS 5, MIS 3, and the Early–Middle Holocene, but the climate in the desert has shown a trend towards aridity overall. The average annual temperature in the Badain Jaran Desert has significantly increased in the past 50 years. In detail, it has increased by about 2.5°C, with a higher rate in the south than in the north. Meanwhile, the precipitation amount has shown high spatial variability and the climate has shown a warming-drying trend in the past 50 years. (3) The lakes in the hinterland of the Badain Jaran Desert continuously shrank during 1973–2015. However, the vegetation communities maintained a highly natural distribution during 2000–2016, with the vegetation cover has increased overall. Accordingly, the Badain Jaran Desert did not show any notable expansion in that period. This study deepens the understanding of groundwater circulation and the climate and ecological evolution in the Badain Jaran Desert. It will provide a scientific basis for the rational exploitation of the groundwater resources and the ecological protection and restoration in the Badain Jaran Desert.© 2021 China Geology Editorial Office.  相似文献   
2.
Historical aerial photographs are an invaluable tool in shoreline mapping and change detection in coastal landscapes. We evaluate the extent to which structure-from-motion (SfM) photogrammetric methods can be applied to quantify volumetric changes along sandy beaches, using archival imagery. We demonstrate the application of SfM-derived digital surface models (DSMs) at East Beach and Lady Bay in southwest Victoria, Australia, using photographic datasets taken in 1969, 1977 and 1986, and compare them to LiDAR-derived DSMs acquired at both sites in 2007. The SfM approaches resulted in two entire and two partial suitable DSMs out of six datasets. Good-quality DSMs were spatially continuous with a good spread of ground control points (GCPs) near the beach at Lady Bay, whereas unsuitable DSMs were mostly restricted by poor distribution and number of GCPs in spatially segmented areas of East Beach, due to limited overlapping of images, possible poor quality of GCPs and also the propagation of errors in the derived point clouds. A volume of approximately 223 000 ± 72 000 m3 was deposited at Lady Bay between 1969 and 2007, despite minimal erosion observed near the breakwater. The partially suitable dataset of East Beach indicated that beach erosion of at least 39 m3 m−1 occurred immediately to the east of the seawall after 1977. We also discuss the drawbacks and strengths of SfM approaches as a benchmark of historical erosion assessments along sandy beaches. © 2020 John Wiley & Sons, Ltd.  相似文献   
3.
在通常的四分块矩阵求广义逆矩阵和凯利逆矩阵公式基础上,分析左上角子矩阵为秩亏、右下角子矩阵为零的特殊四分块矩阵的凯利逆矩阵存在条件,应用广义逆矩阵法和矩阵变换法推导该类特殊四分块矩阵的凯利逆矩阵显性表达公式,并用于解算约束秩亏间接平差模型的参数估计。实验数据表明,当满足存在性条件时,应用分块矩阵求逆公式解算约束秩亏间接平差模型的结果与间接平差模型的解算结果一致,表明推导的显性表达公式具有可行性。  相似文献   
4.
《China Geology》2021,4(4):673-685
The widely-developed, mixed clastic-carbonate succession in the northern Qaidam Basin records the paleo-environment changes under the glacial activity during the Late Paleozoic icehouse period in the context of regional tectonic stability, however, the depositional environment and sequence stratigraphy characteristics of the mixed deposits is rarely reported and still not clear. Combined the latest drilling wells data, we analyzed the sedimentary and stratigraphic characterization of the mixed strata via detailed field outcrops and core observations and thin section microscopic observations and recognized three depositional systems, including progradational coastal system, incised valley system, and carbonate-dominated marine shelf system, and identified four third-order sequences, SQ1, SQ2, SQ3 and SQ4, consisting of LST, TST, and HST. The depositional environment is overall belonged to marine-continental transition context and shifted from marine to continental environment frequently, showing an evolutionary pattern from marine towards terrestrial-marine transition and then back into the marine environment again in the long-term, which was controlled by the regional tectonic subsidence and the high-frequency and large-amplitude sea-level changes due to the Late Paleozoic glacial activity. The result is of significance in understanding the evolution of the Qinghai-Tibet Plateau and the sedimentation-climate response.©2021 China Geology Editorial Office.  相似文献   
5.
蒋太平  李果民  肖华  沈林江 《探矿工程》2021,48(S1):269-274
为了获取参数井压裂设计的相关参数,需要对井眼进行阵列声波测井和微侧向电阻率测井,需要采取大直径岩心进行力学实验。采用固体岩心钻探取心工艺,钻孔口径难以达到物探测井仪器入井要求,岩心直径也不能满足实验要求,必须采用大口径取心工艺才能满足设计要求。同时,常规取心工艺难以满足页岩气勘探对岩心(页岩或者煤心)提升时间的要求,绳索取心工艺在这方面优势明显。本篇介绍了大口径绳索取心工艺在页岩气地质调查井川蔺参1井的成功应用,根据大口径绳索取心钻具的结构特点,结合目的层岩性特征,总结了合理的取心钻进工艺参数和技术保障措施,取得了较好的效果。  相似文献   
6.
Cropland fallows are the next best-bet for intensification and extensification, leading to increased food production and adding to the nutritional basket. The agronomical suitability of these lands can decide the extent of usage of these lands. Myanmar’s agricultural land (over 13.8 Mha) has the potential to expand by another 50% into additional fallow areas. These areas may be used to grow short-duration pulses, which are economically important and nutritionally rich, and constitute the diets of millions of people as well as provide an important source of livestock feed throughout Asia. Intensifying rice fallows will not only improve the productivity of the land but also increase the income of the smallholder farmers. The enhanced cultivation of pulses will help improve nutritional security in Myanmar and also help conserve natural resources and reduce environmental degradation. The objectives of this study was to use remote sensing methods to identify croplands in Myanmar and cropland fallow areas in two important agro-ecological regions, delta and coastal region and the dry zone. The study used moderate-resolution imaging spectroradiometer (MODIS) 250-m, 16-day normalized difference vegetation index (NDVI) maximum value composite (MVC), and land surface water index (LSWI) for one 1 year (1 June 2012–31 May 2013) along with seasonal field-plot level information and spectral matching techniques to derive croplands versus cropland fallows for each of the three seasons: the monsoon period between June and October; winter period between November and February; and summer period between March and May. The study showed that Myanmar had total net cropland area (TNCA) of 13.8 Mha. Cropland fallows during the monsoon season account for a meagre 2.4% of TNCA. However, in the winter season, 56.5% of TNCA (or 7.8 Mha) were classified as cropland fallows and during the summer season, 82.7% of TNCA (11.4 Mha) were cropland fallows. The producer’s accuracy of the cropland fallow class varied between 92 and 98% (errors of omission of 2 to 8%) and user’s accuracy varied between 82 and 92% (errors of commission of 8 to 18%) for winter and summer, respectively. Overall, the study estimated 19.2 Mha cropland fallows from the two major seasons (winter and summer). Out of this, 10.08 Mha has sufficient moisture (either from rainfall or stored soil water content) to grow short-season pulse crops. This potential with an estimated income of US$ 300 per hectare, if exploited sustainably, is estimated to bring an additional net income of about US$ 1.5 billion to Myanmar per year if at least half (5.04 Mha) of the total cropland fallows (10.08 Mha) is covered with short season pulses.  相似文献   
7.
Abstract

A super-resolution enhancement algorithm was proposed based on the combination of fractional calculus and Projection onto Convex Sets (POCS) for unmanned aerial vehicles (UAVs) images. The representative problems of UAV images including motion blur, fisheye effect distortion, overexposed, and so on can be improved by the proposed algorithm. The fractional calculus operator is used to enhance the high-resolution and low-resolution reference frames for POCS. The affine transformation parameters between low-resolution images and reference frame are calculated by Scale Invariant Feature Transform (SIFT) for matching. The point spread function of POCS is simulated by a fractional integral filter instead of Gaussian filter for more clarity of texture and detail. The objective indices and subjective effect are compared between the proposed and other methods. The experimental results indicate that the proposed method outperforms other algorithms in most cases, especially in the structure and detail clarity of the reconstructed images.  相似文献   
8.
为实现对用海项目施工期悬浮泥沙扩散的实时跟踪监测,尝试采用无人机携带可见光、多光谱传感器对古雷围填海项目的围堰区进行遥感探测。利用Pix4d软件对无人机携带的可见光及多光谱照片进行处理,结果表明,可见光及多光谱影像对水体中的悬浮泥沙分布均具有一定的识别能力。通过研究分析多光谱影像的光谱特征发现,近红外波段对悬浮泥沙含量的升高较为敏感,运用波段比值公式计算结果显示,围堰内含沙水体经溢流口排入海域后浓度明显降低,并可向南继续扩散约300 m。该方法可克服遥感卫星影像时空分辨率低的特点,为用海项目资源环境影响跟踪监测提供新的技术手段。  相似文献   
9.
李飞 《地质与勘探》2020,56(3):566-579
本文依据江苏如东滩涂区综合地球物理调查工作,对小洋口地区断裂构造空间展布进行了解译,分析了解译断裂与栟茶河断裂的关系。解译结果主要参考实测无人机航磁资料,辅以浅层地震和电磁法资料。综合两个子测区的断裂构造解译结果,同时参考华东地区航磁和重力资料,对栟茶河断裂的空间展布位置进行了推断,认为其是近EW向大型断裂,延伸距离长,同时控制测区其他断裂的展布。实测数据未发现金坛—如皋断裂在测区范围内存在的地球物理证据,分析认为其未发育至栟茶河断裂以北。  相似文献   
10.
中国海域及邻区是建设“21世纪海上丝绸之路”、打造海洋命运共同体和推动可持续发展的关键地区,也是地球科学最具有典型性和代表性的研究区域之一。中国管辖海域1:100万区域地质调查是一项以国家需求为导向、以解决重大地球系统科学问题为目标的基础性公益性工作。中国地质调查局通过近20年的持续调查,实现了对中国管辖海域1:100万区域地质调查的全面覆盖,系统地获取了海洋地质和地球物理基础数据,形成了基于实测数据的“一图一库一报告”,大幅提升了中国海洋地质调查工作程度。这项工作填补了中国小比例尺海洋地质国情调查的空白,初步摸清了中国管辖海域地质环境条件和资源环境潜力,取得了一批原创性的认识,为建设海洋强国提供了详实可靠的地质资料,为提升区域地质科学的认知水平奠定了坚实基础。  相似文献   
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