一种等效声速梯度的迭代计算方法          下载免费PDF全文

辛明真  阳凡林  闫循鹏  卜宪海 《海洋测绘》2015,(5):28-31

等效声速剖面法将实际复杂的声速剖面用一个简单的声速剖面等效替代,在声线跟踪时可以提高计算效率。但在多波束测深系统归位计算中,由于地形的起伏,对每ping各个波束使用单一的等效声速剖面会影响计算精度。通过仿真实验分析了地形起伏对等效声速剖面法计算精度的影响,提出了一种等效声速迭代算法,通过实验发现,相比于常梯度声线跟踪算法,迭代算法可达到同等精度水平,并有更高的计算效率。  相似文献   

Energy economy system and risk management: a contribution toward China meeting its goals for the Paris climate accord     

Ding  Zhihua  Wu  Jy S.  Shi  Xunpeng  Wang  Qunwei 《Natural Hazards》2019,95(1-2):1-5

  相似文献   

The economic impact of climate risks in China: evidence from 47-sector panel data, 2000–2014     

Sun  Yongping  Zou  Xin  Shi  Xunpeng  Zhang  Ping 《Natural Hazards》2019,95(1-2):289-308

Climate risks have significant economic impacts on the various sectors of an economy through direct and indirect channels. When aggregated, their impact can be underestimated or overestimated. This paper examines the impact of five types of climate risks on 47 sectors in China from 2000 to 2014 through the application of a threshold model. We find that: (1) the impact of the integrated climate risks index on sector output is linear. While rainstorms show a U-shaped relationship with output, the other four types of risks—droughts, typhoons, high temperatures and low temperatures freezing—have an inverted U-shaped relationship. (2) Climate risks indirectly influence sector output through capital stock in a significantly positive way. (3) The proportion of intermediate inputs leads to significant differences in the impact of climate risks on sectors. The results suggest that climate policies need to be sector- and risk-specific, as well as dynamic.

  相似文献   

新生儿头部CT检查261例分析     

陈雪鹏  谢了武 《CT理论与应用研究》1995,4(4):29-31

笔者报道应用ＣＴ扫描对２６１例围产期窒息儿进行头部扫描，发现有二种颅内病变；颅内出血和脑缺氧缺血性脑病共２３０例，其阳性率为８８．１％，就其ＣＴ表现，病理基础及脑损伤程度与预后关系进行论述。  相似文献   

海平面上升—夹河断流背景下烟台套子湾海滩砂粒度变化          下载免费PDF全文

刘立新  王昕  陈浩宇  李训鹏 《山东国土资源》2022,38(5):63-70

将烟台套子湾2021年与2005—2006年夹河口东西两侧海滩砂的粒度特征进行对比分析,揭示了近16年来套子湾海滩沉积物粒度特征变化对全球海平面上升—夹河入海水沙减少等过程的具体响应。研究表明,现代套子湾海滩砂样品以中砂、细砂为主,分选极好或好,标准偏差介于0.23~0.4,夹河口东侧的海滩砂平均粒径（Mz：1.39~1.64Φ）比西侧海滩砂平均粒径（Mz：1.47~1.91Φ）粗,主要组分中的粗砂和中砂含量比西侧高,表明现代夹河口东侧区域水动力较夹河口西侧强,该区海滩砂受到海洋动力的长期改造分选较好。近16年夹河口两侧海滩砂粒度明显粗化,表现在海滩砂平均粒径变粗、主要组分粒度变粗约0.5Φ、概率累积曲线的粗细截点变粗0.5~1Φ及滚动、跃移、悬移组分含量明显变化。夹河入海物质减少,海平面快速上升,导致海洋动力增强是研究区海滩砂粒度粗化、海滩侵蚀的主要原因,该研究结果可以为套子湾海滩防护提供科学指导。  相似文献