一种潜艇装备作战能力比较研究方法     

罗浩  宁云晖  陶伟  尤岳 《数字海洋与水下攻防》2020,3(6):494-498

对潜艇装备作战能力评估问题进行了研究，发现运用定量评估方法的过程中存在指标评价所需数据无法完全获取的问题。结合美弗吉尼亚潜艇改进情况，分析了影响潜艇作战能力的一些关键因素，重点基于潜艇武器装载能力，对国外典型潜艇进行了作战能力比较分析，最后对分析结果进行了评价，并讨论了未来潜艇作战能力评估方法的发展方向。  相似文献   

GPS/PWV时间序列特征提取方法的研究     

胡广保  叶世榕  张彦祥  夏朋飞  夏凤雨 《大地测量与地球动力学》2019,39(1):36-40

针对GAMIT/GLOBK软件解算得到的4 a GPS/PWV时间序列的特征提取问题，提出基于滤波辅助的部分集成经验模态分解（PEEMD）与Hilbert谱分析相结合的特征提取方法。首先，在PEEMD方法的基础上,结合滤波辅助的PEEMD方法与Hilbert谱分析，建立GPS/PWV时间序列特征提取模型；然后，将所提出的方法应用于TNML测站4 a的GPS/PWV长时间序列和7 d的GPS/PWV短时间序列分析中，并将滤波辅助的PEEMD结果与传统的小波分解结果进行对比。结果表明，该特征提取方法能准确有效地提取出 GPS/PWV时间序列中的周年周期和日周期特征分量，滤波辅助的PEEMD分解结果与小波分解结果一致，且提取的特征分量与原始信号更加吻合。  相似文献   

基于伽马射线的类轴子粒子探测及暗物质子晕搜寻研究          下载免费PDF全文

夏子晴 《天文学报》2021,62(2):21-112

目前已经有很多观测证据表明宇宙中存在着大量暗物质,其能量密度占据了目前宇宙总能量密度的1/4.根据高精度的数值模拟和引力透镜观测,我们已经对从矮星系到星系团中的暗物质空间分布有了较好的理解,但是对于暗物质究竟是什么我们还一无所知.由此,物理学家提出了很多假想的粒子模型.  相似文献   

Seismogenic Structures of the 2006 ML4.0 Dangan Island Earthquake Offshore Hong Kong     

XIA Shaohong  CAO Jinghe  SUN Jinlong  LV Jinshui  XU Huilong  ZHANG Xiang  WAN Kuiyuan  FAN Chaoyan  ZHOU Pengxiang 《中国海洋大学学报(英文版)》2018,(1)

The northern margin of the South China Sea, as a typical extensional continental margin, has relatively strong intraplate seismicity. Compared with the active zones of Nanao Island, Yangjiang, and Heyuan, seismicity in the Pearl River Estuary is relatively low. However, a ML4.0 earthquake in 2006 occurred near Dangan Island(DI) offshore Hong Kong, and this site was adjacent to the source of the historical M5.8 earthquake in 1874. To reveal the seismogenic mechanism of intraplate earthquakes in DI, we systematically analyzed the structural characteristics in the source area of the 2006 DI earthquake using integrated 24-channel seismic profiles, onshore–offshore wide-angle seismic tomography, and natural earthquake parameters. We ascertained the locations of NW-and NE-trending faults in the DI sea and found that the NE-trending DI fault mainly dipped southeast at a high angle and cut through the crust with an obvious low-velocity anomaly. The NW-trending fault dipped southwest with a similar high angle. The 2006 DI earthquake was adjacent to the intersection of the NE-and NW-trending faults, which suggested that the intersection of the two faults with different strikes could provide a favorable condition for the generation and triggering of intraplate earthquakes. Crustal velocity model showed that the high-velocity anomaly was imaged in the west of DI, but a distinct entity with low-velocity anomaly in the upper crust and high-velocity anomaly in the lower crust was found in the south of DI. Both the 1874 and 2006 DI earthquakes occurred along the edge of the distinct entity. Two vertical cross-sections nearly perpendicular to the strikes of the intersecting faults revealed good spatial correlations between the 2006 DI earthquake and the low to high speed transition in the distinct entity. This result indicated that the transitional zone might be a weakly structural body that can store strain energy and release it as a brittle failure, resulting in an earthquake-prone area.  相似文献   

Coordinative similitude law considering fluid‐structure interaction for underwater shaking table tests     

Zhong‐Xian Li  Kun Wu  Yundong Shi  Ning Li  Yang Ding 《地震工程与结构动力学》2018,47(11):2315-2332

Generally, when a model is made of the same material as the prototype in shaking table tests, the equivalent material density of the scaled model is greater than that of the prototype because mass is added to the model to satisfy similitude criteria. When the water environment is modeled in underwater shaking table tests, however, it is difficult to change the density of water. The differences in the density similitude ratios of specimen materials and water can affect the similitude ratios of the hydrodynamic and wave forces with those of other forces. To solve this problem, a coordinative similitude law is proposed for underwater shaking table tests by adjusting the width of the upstream face of the model or the wave height in the model test to match the similitude ratios of hydrodynamic and wave forces with those of other forces. The designs of the similitude relations were investigated for earthquake excitation, wave excitation, and combined earthquake and wave excitation conditions. Series of numerical simulations and underwater shaking table tests were performed to validate the proposed coordinative similitude law through a comparison of coordinative model and conventional model designed based on the coordinative similitude law and traditional artificial mass simulation, respectively. The results show that the relative error was less than 10% for the coordinative model, whereas it reached 80% for the conventional model. The coordinative similitude law can better reproduce the dynamic responses of the prototype, and thus, this similitude law can be used in underwater shaking table tests.  相似文献   

基于SPEI的渭河流域干旱时空变化特征分析          下载免费PDF全文

邹磊  余江游  夏军  王飞宇 《干旱区地理》2020,43(2):329-338

以标准化降水蒸散指数（SPEI）作为评估指标，基于渭河流域28个气象站点1961—2017年实测降水量和气温数据，采用Mann-Kendall（M-K）趋势检验、经验正交函数以及小波变换等方法分析渭河流域干旱时空变化特征，并研究渭河流域干旱与6种大尺度气候因子之间的相关关系，进一步探讨主要气候因子对流域干旱时空分布特征的潜在影响。研究表明：渭河流域在1961—2017年间整体呈现出变旱的趋势。通过经验正交函数分解，渭河流域干旱分布场主要有3种典型模态类型，分别为全局型、西北—东南反向分布型以及东—西反向分布型；同时，大尺度气候因子南方涛动指数SOI与流域干旱分布场具有更好的相关关系，对该区域内干旱变化有较强的影响。  相似文献   

“一带一路”沿线国家石油资源流动类型演变     

孙琪  赵媛  张新林  夏四友 《世界地理研究》2020,29(2):337-345

综合运用石油自给率、流动比率等方法，以“一带一路”沿线国家为研究对象，对1995—2014年各国石油资源流动类型时空演变进行研究。结果表明：1）1995—2014年石油净补给型国家数量较为稳定，无产型或低产型国家的石油贸易倾向变化相对较小；基本自给型国家数量占比最大，1995年占比1/2，其余四个年份占比稳定在1/3；净支出型国家数量显著增加，至2014年其中有5个国家保持不变，表明这些国家的石油产量具有较大的优势。2）1995年和2014年汇地国家均为39个国家，其中有34个国家一直保持汇地职能，空间分布上呈东多西少，南多北少，东西分化以西亚、中亚、东欧为界；有14个国家一直保持源地职能，其空间分布格局与汇地相应，西多东少，南多北少，主要分布于西亚、东欧及中亚；交流地数量较少，呈分散分布，且分布地不稳定。3）从数量变化来看，研究期内汇地略有增加，源地略有减少，交流地略有增加；“一带一路”源地总出口量与汇地总进口量的比呈逐年降低趋势。  相似文献   

Cryosphere evapotranspiration in the Tibetan Plateau: A review     

KunXin Wang  YinSheng Zhang  Ning Ma  YanHong Guo  YaoHui Qiang 《寒旱区科学》2020,12(6):355-370

Land surface actual evapotranspiration is an important process that influences the Earth's energy and water cycles and determines the water and heat transfer in the soil-vegetation-atmosphere system. Meanwhile, the cryosphere's hydrological process is receiving extensive attention, and its water problem needs to be understood from multiple perspectives. As the main part of the Chinese cryosphere, the Tibetan Plateau faces significant climate and environmental change. There are active interaction and pronounced feedback between the environment and ET_a in the cryosphere. This article mainly focuses on the research progress of ET_a in the Tibetan Plateau. It first reviews the ET_a process, characteristics, and impact factors of typical underlying surfaces in the Tibetan Plateau (alpine meadows, alpine steppes, alpine wetlands, alpine forests, lakes). Then it compares the temporal and spatial variations of ET_a at different scales. In addition, considering the current greening of cryosphere vegetation due to climate change, it discusses the relationship between vegetation greening and transpiration to help clarify how vegetation activities are related to the regional water cycle and surface energy budget.  相似文献   

基于Sentinel-1A合成孔径雷达数据和全卷积网络的城市建设用地监测方法研究          下载免费PDF全文

卢文路  刘志锋  何春阳  夏沛 《干旱区地理》2020,43(3):750-760

Sentinel-1A合成孔径雷达数据不受云、雾等天气条件的影响并具有丰富的纹理信息，为提取城市建设用地信息提供了一种新的数据源。本文发展了一种基于Sentinel-1A合成孔径雷达数据和全卷积网络的城市建设用地监测方法。该方法的优势主要在于可以有效复合不同极化方式下的Sentinel-1A合成孔径雷达数据和综合集成多尺度特征。在甘肃省张掖市甘州区的应用表明，该方法的提取结果总体精度为92.50%，Kappa系数为0.85。与现有方法“KTH-Pavia城市提取器”相比，Kappa系数提高了37.10%，总体精度提高了11.50%。因此，该方法具有良好的应用潜力。  相似文献   

南沙他国侵占岛礁战略价值及空间格局评价     

闵开付  程亮  周晓  夏南  李宁  李满春 《热带地理》2020,40(4):684-693

从建岛潜力、岛礁辐射能力和岛礁承载能力3个方面选取26个指标，采用主客观综合赋权法确定各因子权重，利用线性加权法获得被越南、菲律宾、马来西亚、文莱等国所侵占的南沙44个岛礁的战略价值，并对结果进行空间插值，分析其空间格局特征。结果表明：1）被马来西亚侵占的弹丸礁、越南侵占的南威岛、以及菲律宾侵占的中业岛，其战略价值位列前3，评价得分分别为100、98.42和97.09。2）岛礁辐射能力空间分布格局呈现“NW—SE条带式”，“最高”和“高”等级的区域由研究区西北延伸至东南，然后向东北、西南两侧递减，辐射能力格局中有2个核心区域和2个次级核心区域。承载能力空间分布格局呈现“横向条带式”，由北向南越来越低，有1个核心区域和2个次级核心区域。建岛潜力空间分布格局有3个核心区域及2个次级核心区域。3）岛礁战略价值空间分布格局有3个核心区域，分布于研究区中部、北部及南部，与越南、菲律宾、马来西亚密切相关的核心区域各有1个。越南侵占岛礁最多且空间分布较广，有2个次级核心区域也与越南密切相关，越占岛礁若进一步建设，将形成多核心协同的战略格局，需密切关注。  相似文献