Development mechanism for the landslide at Xinlu Village,Chongqing, China

Due to the continuous and intense rainfall from June 26 to 28, 2016, Xinlu Village in Ganshui Town, Qijiang District, Chongqing, experienced a unitary-slip landslide at approximately UTC+8 19:30 on June 28. This landslide disrupted the Chuan-Qian railway and damaged four residential buildings. To analyze and rehabilitate the landslide, the engineering geology, hydrological conditions, and deformation instability mechanism of this landslide were investigated and comprehensively analyzed based on an in situ survey, geophysical drilling, and a laboratory quick-shearing test. The results show that the landslide is a typical gradual progressive landslide.     

II型超新星瞬发爆炸模型的对流不稳定性

本文研究ＩＩ型超新星瞬发爆炸模型中的铁星核在坍缩、反弹和激波传播过程中的对流不稳定性．发现在铁星核内区出现中子指状对流,外区出现Ｓｃｈｗａｒｚｓｃｈｉｌｄ对流,而在声速点和中微子俘陷球之间的过渡区出现Ｌｅｄｏｕｘ对流．在０．７４－０．９１Ｍ间的区域是对流不稳定的活跃区域．     

Rocky desertification poverty in Southwest China: Progress,challenges and enlightenment to rural revitalization

Journal of Geographical Sciences - Rocky desertification poverty (RDP) refers to rural poverty triggered or exacerbated by rocky desertification, which deprives farmers of opportunities for...     

我国旅游地理研究格局及热点分析

以国家自然科学基金2000—2019年资助的560项旅游类课题为数据来源,对课题立项的时空分布、承担单位、负责人等进行统计分析,构建由6个主类和15个亚类组成的旅游地理问题分类体系,运用词频统计和内容分析法,总结我国旅游地理研究格局和热点发展态势。研究发现：2000年至2019年间,自然基金委对旅游类课题的资助力度不断加强,总体呈先缓慢、后迅速增长、再大幅提升后保持平稳发展的态势,资助空间分布呈“东高西低”的特点,课题依托单位明显优势集中,课题承担人则呈离散分布;旅游流、旅游产业发展、旅游交通等研究主题热度逐渐减弱,旅游者行为和感知、旅游的社会文化影响、旅游地空间、典型旅游地保护和开发、旅游生态环境等主题热度明显上升,在此基础上对各热点主题历年变化特征和规律进行归纳总结。本文更新和拓展了以往同类研究发现,对旅游学者进行研究选题和课题申报有参考和指导意义。     

黄海近岸锋面的时空变化及其对沉积物输运和沉积的影响

利用2010和2012年黄海海域不同季节的航次观测数据与HYCOM模式再分析数据进行了比对,检验了HYCOM模式的水体温度数据在黄海海域的适用性。据此分析了黄海海域的温度锋面和混合锋面的时空变化。结果显示,温度锋通常在秋季开始出现,在冬季最为发育,在春季逐渐消失;黄海混合锋面与季风活动密切相关,主要在秋季开始出现,在冬季发育。悬浮沉积物基本上集中在温度锋的向岸一侧,难以跨越锋面输运。山东半岛成山头海域的温度锋在形态及空间位置上与泥质沉积区相对应,沉积中心(厚度40 m)主要分布在温度锋的西侧,而在其东侧泥质沉积厚度快速减小。研究结果发现,秋冬季节混合锋与温度锋的空间位置并不一致,混合锋位于温度锋的西侧,强烈混合使得沉积物不易沉降,对应泥质沉积厚度小;而在混合锋东侧,悬浮沉积物浓度高且水体层化显著,沉积物易于沉降堆积,与泥质沉积中心对应。混合锋与温度锋的空间分布差异与共同作用可能是该区域泥质沉积体"Ω"形态发育的动力学机制。     

Generating GPS satellite fractional cycle bias for ambiguity-fixed precise point positioning

With the development of precise point positioning (PPP), the School of Geodesy and Geomatics (SGG) at Wuhan University is now routinely producing GPS satellite fractional cycle bias (FCB) products with open access for worldwide PPP users to conduct ambiguity-fixed PPP solution. We provide a brief theoretical background of PPP and present the strategies and models to compute the FCB products. The practical realization of the two-step (wide-lane and narrow-lane) FCB estimation scheme is described in detail. With GPS measurements taken in various situations, i.e., static, dynamic, and on low earth orbit (LEO) satellites, the quality of FCB estimation and the effectiveness of PPP ambiguity resolution (AR) are evaluated. The comparison with CNES FCBs indicated that our FCBs had a good consistency with the CNES ones. For wide-lane FCB, almost all the differences of the two products were within ±0.05 cycles. For narrow-lane FCB, 87.8 % of the differences were located between ±0.05 cycles, and 97.4 % of them were located between ±0.075 cycles. The experimental results showed that, compared with conventional ambiguity-float PPP, the averaged position RMS of static PPP can be improved from (3.6, 1.4, 3.6) to (2.0, 1.0, 2.7) centimeters for ambiguity-fixed PPP. The average accuracy improvement in the east, north, and up components reached 44.4, 28.6, and 25.0 %, respectively. A kinematic, ambiguity-fixed PPP test with observation of 80 min achieved a position accuracy of better than 5 cm at the one-sigma level in all three coordinate components. Compared with the results of ambiguity-float, kinematic PPP, the positioning biases of ambiguity-fixed PPP were improved by about 78.2, 20.8, and 65.1 % in east, north, and up. The RMS of LEO PPP test was improved by about 23.0, 37.0, and 43.0 % for GRACE-A and GRACE-B in radial, tangential, and normal directions when AR was applied to the same data set. These results demonstrated that the SGG FCB products can be produced with high quality for users anywhere around the world to carry out ambiguity-fixed PPP solutions.     

基于直方变差图的土地覆盖数据集多尺度精度评价

针对目前精度评价尺度单一的问题,提出基于直方变差图的多尺度精度评价方法,分别在像元尺度和亚像元尺度进行土地覆盖数据集精度评价。在像元尺度利用驻点作为采样工具直接评价数据集精度;亚像元尺度上,则利用非严格定义的驻点和驻点直方变差图对不同面积和空间结构的优势类进行精度评价。并以浙江北部典型区域为实验区,Landsat TM/ETM+为参考数据,对UMD、IGBP DISCover、MOD12Q1-2001、GLC2000、GlobCover2009等5种大尺度土地覆盖数据集进行多尺度精度评价实验。结果表明,多尺度精度评价方法能够全面地评价土地覆盖数据集的精度,提供更加丰富的多尺度精度信息。像元尺度精度评价可在一定程度上消除由于参考数据与数据集间的空间匹配造成的误差,评价结果更加客观;亚像元尺度精度评价能有效反映亚像元尺度优势地物面积及空间结构与精度的关系。     

A geochemical survey of trace elements in agricultural and non-agricultural topsoil in Dexing area,China

In China, soil pollution is very serious, which has jeopardized the ecology, food safety, the people's health, and even the sustainable development of agriculture. In order to investigate the soil pollution situation, a total of 874 agricultural and non-agricultural topsoil samples were collected from Dexing area, northeast of Jiangxi Province, China. The total elemental concentrations of 17 elements (As, Hg, Mo, Cd, Cr, Zn, Cu, Mn, Ti, Pb, Fe, Ca, K, Si, Al, Mg, and Na) were determined. The geochemical background and threshold was predicted with the method of the median ± median absolute deviation (MAD). The agricultural soil median concentration of trace elements was similar to that of the non-agricultural soil. In contrast to Jiangxi soil background of trace elements, the geochemical background of the study area was obviously higher. The maps of the pollution indices for As, Cd, Cr, Cu, Hg, Mn, Mo, Pb, Ti and Zn of non-agricultural soil and agricultural soils in the study area, showed that the highest level of pollution is distributed near and along the Lean River, especially in the neighboring and surrounding Dexing and Leping mining area.     

江西南部鸡笼嶂组研究的新进展

分析了江西南部鸡笼嶂组划分的现状及存在的问题,提出了龙南盆地和石马剖面的“鸡笼嶂组”属中侏罗世－晚侏罗世早期余田群上部菖蒲组的一部分;菖蒲盆地的“鸡笼嶂组”属早白垩世晚期－晚白垩世早期版石群优胜组。鉴于安远、河岭、蔡坊、岩背等盆地的鸡笼嶂组属晚侏罗世,为火山喷发期的产物,而且整合于鸡笼嶂组之下的上丁组为火山初始期的产物,建议将赣南地区晚侏罗世火山活动形成的上丁组和鸡笼嶂组统称为莲花寨群。指出安远莲     

川滇黔桂地区二叠纪不同成因盆地层序地层模型

通过不同类型沉积盆地层序界面性质、层序类型、结构、组成、完整性、对称性以及层序发育特征和控制因素研究表明,不同成因沉积盆地,其层序内部构型及成因格架各异.克拉通盆地层序发育主要受全球海平面变化及碳酸盐自旋回控制,LST以陆上暴露不整合面及其上风化残积相为特征,TST以海侵上超不整合面上相对薄的超覆型退积准层序组为特色,HST表现为厚层加-进积丘礁滩组合;对于被动陆缘裂谷盆地,主控因素包括全球海平面变化和同沉积断裂活动,LST期,孤台以陆上暴露不整合面及残积相为标志,台盆表现为水下间断不整合面及上覆混屑浊积岩,TST以台盆硅灰岩-硅岩退积准层序组不断向斜坡和孤台上超为特征,HST期,孤台以加积-进积丘礁滩组合为主,台盆为加积型钙屑重力流沉积,弧后裂谷盆地层序特征与被动陆缘裂谷盆地相似,但其台盆加深加宽,层序以硅质岩及火山碎屑浊积岩为主,揭示层序发育主要受同沉积断裂活动、全球海平面变化及火山活动控制;被动陆缘走滑盆地层序发育主要受控于不同沉积断裂活动及全球海平面变化,层序组成以放射虫硅质岩和深水泥岩为主;前陆盆地LST以造山侵蚀不整合面及盆底扇沉积为特征,TST表现为巨厚层浊积扇-扇三角洲弱进积-弱退积充填型准?