美国出口管制下中国外贸风险的省域地理差异     

姜辉 《地理科学》2020,40(10):1618-1626

从总贸易、出口、进口、外资和人员5个视角构建对美风险系数，测度和比较各省区市对美外贸风险的地理差异。结果表明：上海、浙江和福建与美国的进出口贸易规模最大，对美国市场的依赖程度最高，面临的综合外贸风险最大；河南尤其需要防范对美国的出口风险；海南、新疆、天津和西藏等需要加强从美国进口的风险管理；重庆除了需要防范对美出口风险外，还因为实际利用美资最多且依赖程度最大，亟需加强外资风险管理。宁夏和山西虽然从美国的引资规模不大，但是对美资的依赖程度最高，亟需提升外资多元化水平。从人员跨境流动风险来看，上海、北京和浙江面临的风险最大。中国各省区市在应对美国出口管制时应该加强外贸风险的识别和管理，针对不同的风险采取差别化的防范和化解措施。  相似文献   

利用GLAS激光测高数据评估DSM产品质量及精度优化   总被引：2，自引：0，他引：2  

胡柳茹  唐新明  李国元  付冬暇  窦显辉  赵世湖 《测绘通报》2019,(11):39-43

提出了一种利用卫星激光测高数据直接优化提升数字表面模型（DSM）产品精度的方法。选取境外中亚地区的资源三号DSM开展试验，通过采用多准则约束方法提取激光高程控制点，分别利用偏度、中值、线性、二次多项式等进行DSM误差修正，发现4种模型均能有效消除DSM系统误差，其中基于二次多项式的方法更适用于平地和丘陵地貌，线性模型更适用于高山地貌。试验验证了采用卫星激光测高数据优化境外DSM技术流程的可行性，最终可提高DSM的绝对高程精度。  相似文献   

Three-dimensional active earth pressure from cohesive backfills with tensile strength cutoff     

Zheng-Wei Li  Tian-Zheng Li  Xiao-Li Yang 《国际地质力学数值与分析法杂志》2020,44(7):942-961

Most of previous analyses on the active earth pressure were performed in two-dimensional cases using the Mohr-Coulomb (M-C) failure function to describe the soil strength. However, all failures of retained slopes indicate a somewhat three-dimensional (3D) feature, and the M-C function is found to overestimate the tensile strength of cohesive soil. In this work, a kinematic limit analysis–based approach is developed for computing the 3D active earth pressure resulting from cohesive backfills. The concept of tensile strength cutoff is adopted to implement the reduction or elimination of tensile strength from the strength envelope. An extended 3D horn failure mechanism that is associated with the modified strength envelope is developed to characterize the collapse of retained slopes. The resultant of active earth pressure is evaluated from the work rate balance equation and expressed as an unfactored coefficient. The obtained results indicate that less support provided by the wall is required when allowing the existence of soil cohesion and 3D effects and that eliminating the tensile strength can observably increase the active earth pressure, especially for the backfill with a great level of cohesion.  相似文献   

郯庐断裂带南段继承性断裂构造控矿模式研究及其应用效果——以皖东北五河金矿整装勘查为例     

汪青松  张顺林  张金会  张家嘉  尤淼 《地质学报》2020,94(10):2965-2977

郯庐断裂带南段的皖东北地区地质构造复杂，多为厚覆盖区，找矿难度大。由于控矿条件难以调查清楚，缺乏具有区域特色的勘查理论指导，区内金矿勘查长期没有取得突破成果。笔者依托五河金矿整装勘查项目，进行了区域重磁异常特征和成矿规律分析研究，发现皖东北地区北东- 北北东向重力低异常具有弧形条带特征，并以郯庐断裂带为界，大致具有旋转对称性。重磁异常保存印支期构造格架痕迹信息，反映了郯庐断裂带南段时空演化特征，显示了北东- 北北东向主要断裂构造具有继承性，形成于印支期，燕山期继续活动，控制白垩纪“红层盆地”和燕山期成岩成矿作用。中低温热液型金多金属矿床和矽卡岩型铜金矿床是皖东北地区主要矿床类型，均受继承性断裂构造控制。结合郯庐断裂的演化特征，利用物探成果引领地质理论创新，提出了郯庐断裂带南段矿床的“继承性断裂构造控矿模式”。根据继承性断裂构造形成机理分析其空间分布规律，总结了矿化蚀变构造带的物探异常标志，解决了皖东北覆盖区成矿预测与找矿靶区圈定难题，在五河金矿整装勘查区应用取得了重要找矿成果，圈定6个金矿找矿靶区，得到了钻探验证，已发现中型规模金矿床2处、小型3处，估算潜在资源量可达特大型规模，实现了安徽省境内郯庐断裂带金矿找矿的重大突破。  相似文献   

基于专利的石漠化治理技术分析     

宁宝英  马建霞  姜志德 《中国沙漠》2019,39(5):135-142

石漠化是发生面积仅次于沙漠化的荒漠化类型，已成为中国西南喀斯特山区可持续发展的主要障碍，其治理与恢复是复杂的系统工程。从治理技术层面，以1 159组简单专利族为数据基础，揭示国内石漠化治理技术类别分布和主要领域。在对专利进行简要计量分析以提供概貌认识的基础上，通过阅读专利摘要内容，采用自下而上的聚类方法将当前专利划分为石漠化判断、治理、产业经济3个大类，监测与评价、科研仪器、生物治理、工程治理、化学治理、综合治理、综合产业、农业和工业9个中类，更细分至雨水搜集净化等42个小类。根据专利数量认定的四大主要技术领域为：工程治理（8.63%）、水分利用（12.51%）、栽培种植（27.52%）、植物资源加工（9.67%），占总量的58.33%，专利领域分布相对集中。对主要技术领域采用内容分析法，提取工程治理具体措施、集雨工具、植物、加工制品等的信息并对其进行了详细阐述，指出目前专利技术中的问题：石漠化地区特有的植物资源众多，但目前加工层次偏低，应在拓展加工类型、延长加工产业链条、发掘植物药用和日用价值方面加大研发力度；防止土壤漏失技术、设施农业技术和生命基因技术亟待发展。分析可为全面认识国内石漠化治理技术提供专利视角的参照。  相似文献   

基于STIRPAT模型的内蒙古沙漠化地区环境压力分析     

樊胜岳  刘文文  周宁 《中国沙漠》2019,39(3):117-125

实现经济与生态环境的协调发展，已经成为当前治理沙漠化的巨大挑战。如何定量分析人类活动和自然条件对环境的影响，是当前环境经济学界研究的热点问题。以内蒙古自治区71个沙漠化县为研究对象，以1986—2010年为研究区间做面板空间计量实证分析。选取了人口、富裕度、技术水平、风速和降水作为环境基础指标构建STIRPAT模型，从环境压力内在驱动角度定量分析不同的自然因素和人为因素对沙漠化地区环境的综合影响。结果表明：在观测数据范围内，富裕度、技术水平、风速和降水是内蒙古自治区环境压力的主要驱动因素；富裕度每增加1%，环境压力显著增加0.096%；技术水平每变化1%，将引起环境压力相应发生0.084%的变化；风速和降水每变动1%分别使得沙漠地区环境压力显著地增加0.640%和减少0.216%。  相似文献   

Experimental investigation on a cabin-suspended catamaran in terms of motion reduction and wave energy harvesting by means of a semi-active motion control system     

《Applied Ocean Research》2019

A novel concept catamaran equipped with a suspended cabin, named Wave Harmonizer Type 4 (WHzer-4), is proposed and evaluated. The mass-spring-mass system is constructed by mounting four sets of suspensions in-between the cabin and the twin-hull. Two sets of dual motor/generators (M/Gs) are attached on the center beam of the cabin's deck fore and aft. Each shaft-end of the dual M/Gs is connected to the twin-hull through a rack-pinion gear unit. In this way the vertical relative motion between the cabin and the twin-hull can be transferred into the rotational motion of the M/Gs, and vice versa. A semi-active motion control system, which contains a proportional-integral (PI) controller, is designed and applied to each of the dual M/Gs for the aim of absorbing wave energy under the condition of suppressing the local vertical velocity of the cabin as much as possible. A 1/5 scale model ship with a length of 1.6 m is built, and a forced-oscillation bench test is implemented to validate the performance of the control system. Then, a series of towing tank tests is carried out in regular head waves. The heave and pitch responses of the cabin, those of the twin-hull and the corresponding wave energy capture width ratio (CWR) at five control scenarios and two reference scenarios are investigated. Discussion on the results of the tank test shows that the motion reduction of the cabin and the wave energy harvesting can be achieved simultaneously at a few wave conditions. However, at other conditions, although noticeable amount of wave energy is harvested, motion reduction of the heave and pitch of the cabin could not be obtained at the same time. It is suggested that varying the gain settings of the PI controllers according to the location of the controllers may improve the effectiveness of the proposed control system.  相似文献   

Effects of long-term cyclic horizontal loading on bucket foundations in saturated loose sand     

《Applied Ocean Research》2019

A 1-g model experimental study was conducted to investigate the accumulated rotations and unloading stiffness of bucket foundations in saturated loose sand. One-way horizontal cyclic loading was applied to model bucket foundations with embedment ratios 0.5 and 1.0. Up to 10⁴ cycles of loading were applied at a frequency of 0.2 Hz varying load amplitudes. The accumulated rotation of the bucket foundations increased with the number of cycles and the load amplitudes. Empirical equations were proposed to describe the accumulated rotation of the foundations. The unloading stiffness of foundations increased with the number of cycles but decreased with an increase in load amplitude. The initial unloading stiffness of L/D = 1.0 (L is skirt length; D is foundation diameter) was approximately twice that of L/D = 0.5. Excess pore water pressure difference of 50% was observed between L/D = 0.5 and 1.0. The suction and static capacity of the bucket increased with increase of bucket embedment ratio with a difference of 69.5% and 73.6% respectively between L/D = 0.5 and 1.0.  相似文献   

大气负荷对新疆地区地壳形变和地面重力变化的影响     

王海涛  王斌  王伟  章传银 《大地测量与地球动力学》2019,39(2):189-194

基于ECMWF全球大气模型和中国地面气候资料日值数据集中新疆及周边的气象站气压数据，根据弹性地壳形变理论，采用移去-恢复法，利用负荷格林函数法和球谐函数法，计算新疆及周边区域2011~2015年大气负荷变化对地壳垂直、水平形变的影响，同时采用大气导纳方法计算大气变化对地面重力的影响。结果表明，大气负荷对新疆地区垂直形变的影响达到cm级，对地面重力的影响可达10 μGal；大气负荷影响具有明显的季节性。  相似文献   

Hydrological management strategies for the control of algal blooms in regulated lowland rivers     

Jian Li  Wei Yin  Haiyan Jia  Xiaokang Xin 《水文研究》2021,35(6):e14171

Reservoirs of lowland floodplain rivers with eutrophic backgrounds cause variations in the hydrological and hydraulic conditions of estuaries and low-dam reservoir areas, which can promote planktonic algae to proliferate and algal bloom outbreaks. Understanding the ecological effects of variations in hydrological and hydraulic processes in lowland rivers is important for algal bloom control. In this study, the middle and lower reaches of the Han River, China, a typical regulated lowland river with a eutrophic background, are selected. Based on the effect of hydrological and hydraulic variability on algal blooms, a hydrological management strategy for river algal bloom control is proposed. The results showed that (a) differences in river morphology and background nutrient levels cause significant differences in the critical threshold flow velocities for algal bloom outbreaks between natural river and low-dam reservoir sections; there is no uniform threshold flow velocity for algal bloom control. (b) There are significant differences in the river hydrological/hydraulic conditions between years with and without algal blooms. The average river flow, water level and velocity in years with algal blooms are significantly lower than those in years without algal blooms. (c) For different river sections where algal blooms occur and to meet the threshold flow velocities, the joint operation of cascade reservoirs and diversion projects is an effective method to prevent and control algal blooms in regulated lowland rivers. This study is expected to deepen our understanding of the ecological significance of special hydrological processes and guide algal bloom management in regulated lowland rivers.  相似文献