基于地性线的不规则三角网优化构建算法   总被引：1，自引：0，他引：1  

江帆  王志伟  朱长青  安敏 《武汉大学学报(信息科学版)》2007,32(2):124-127

提出了利用自动增加特征点消除平三角形的方法，并通过重构等高线验证了构网算法的实用性和有效性。实验表明，本文算法能很好地消除不合理的平三角形，优化三角网结构。  相似文献   

Diurnal atmospheric forcing and temporal variations of the nutation amplitudes     

C. Bizouard  A. Brzeziński  S. Petrov 《Journal of Geodesy》1998,72(10):561-577

A 29-year time-series of four-times-daily atmospheric effective angular momentum (EAM) estimates is used to study the atmospheric influence on nutation. The most important atmospheric contributions are found for the prograde annual (77 μas), retrograde annual (53 as), prograde semiannual (45 as), and for the constant offset of the pole (δψsinɛ₀=−86 as, δɛ=77 as). Among them only the prograde semiannual component is driven mostly by the wind term of the EAM function, while in all other cases the pressure term is dominant. These are nonnegligible quantities which should be taken into account in the new theory of nutation. Comparison with the VLBI corrections to the IAU 1980 nutation model taking into account the ocean tide contribution yields good agreement for the prograde annual and semiannual nutations. We also investigated time variability of the atmospheric contribution to the nutation amplitudes by performing the sliding-window least-squares analysis of both the atmospheric excitation and VLBI nutation data. Almost all detected variations of atmospheric origin can be attributed to the pressure term, the biggest being the in-phase annual prograde component (about 30 as) and the retrograde one (as much as 100200 as). These variations, if physical, limit the precision of classical modeling of nutation to the level of 0.1 mas. Comparison with the VLBI data shows significant correlation for the retrograde annual nutation after 1989, while for the prograde annual term there is a high correlation in shape but the size of the atmospherically driven variations is about three times less than deduced from the VLBI data. This discrepancy in size can be attributed either to inaccuracy of the theoretical transfer function or the frequency-dependent ocean response to the pressure variations. Our comparison also yields a considerably better agreement with the VLBI nutation data when using the EAM function without the IB correction for ocean response, which indicates that this correction is not adequate for nearly diurnal variations. Received: 10 September 1997 / Accepted: 5 March 1998  相似文献   

滇池草海底泥疏挖对水体水质及底泥影响分析研究   总被引：22，自引：1，他引：22  

安琪  李发荣 《云南地理环境研究》2002,14(2):65-69

1998年 5月起 ,滇池草海经过近 1年的疏挖 ,清除底泥约 4 0 0× 10 4 m3,使内草海水体质量有明显改善。内湖底质的有机污染物及金属污染物得到有效去除 ,减少了泥层中污染物向水体的扩散 ;大部分水体透明度达到 0 .8m ,已超过沉水植物恢复的需补偿深度 ,为草海水生态恢复创造了条件 ;疏浚区水深增加 ,湖容扩大 ,提高了草海的调蓄能力。但与外草海及外滇池对照点底泥相比 ,草海底泥金属污染物含量仍处较高水平  相似文献   

北京-萨哈林剖面的地幔纵向速度结构   总被引：3，自引：0，他引：3       下载免费PDF全文

宋仲和  朱介寿  安昌强  张丽娟 《地球物理学报》1981,24(3):310-318

本文根据北京台网、大连、长春、牡丹江、海参威等26个台站的记录,选用了从北京地区到阿留申群岛西端的300多个地震,研究了北京-萨哈林剖面的地幔纵向速度分布。 用Herglotz-Wiechert公式计算得出的V-h作为初始模型,计算理论走时曲线,找出了与实际走时曲线符合较好的速度结构。其特点为:上地幔顶部的速度为7.8公里/秒;高速盖层中有正速度梯度;在约60-120公里深度范围内为低速层;130公里以下速度缓慢增大;在370-440公里、600-740公里有两个速度梯度较大的过渡层,其中以370-440公里的正速度梯度最大,与之相应的震中距为19°。在1060公里以下有微弱的正梯度。 用Kaila方法计算了深度为400公里左右的地震震源深度处的速度值,与上述结果一致。  相似文献   

新疆西克尔地区微震波谱的初步研究          下载免费PDF全文

朱传镇  石汝斌  罗胜利  安镇文 《地球物理学报》1975,18(4):256-268

为探索大地震发生前孕震区内微震辐射波谱的变化,在新疆西克尔地区,用选频测震仪对微震波谱进行了观测和研究。选频测震仪分为6个频道,各道中心频率分别为6.0周、8.1周、15.7周、30.0周、50.0周、75.0周。初步结果表明:在一个地震系列中,随着临近较强地震（M_L≥3.2）的发生,微震P波在10周-60周频率范围内的谱值增高,其置信水平一般在70％以上。较强地震发生以后,微震P波在相应频率范围内的谱值下降。 文中还简要地分析了选频地震记录的物理意义,并对较强地震前,微震辐射波谱变化的原因作了初步说明。  相似文献   

RESEARCH ON EARTHQUAKE EMERGENCY MAPPING METHOD BASED ON TEMPLATE MATCH          下载免费PDF全文

XU Jing-hai  ZHOU Hai-jun  NIE Gao-zhong  AN Ji-wen 《地震地质》1979,42(3):748-761

After an earthquake, earthquake emergency response and rescue are important ways to mitigate earthquake-induced losses. Various earthquake emergency maps can provide effective references and guidance to those actions. Currently, related studies include the investigation on symbols of emergency maps, remote sensing emergency mapping and GIS-based mapping methods. However, the existing studies overlook the characteristics of rapidity, dynamicity and variety of presentation methods in making earthquake emergency maps. In this paper, a map template matching method is used to quickly make earthquake emergency maps considering their characteristics. We take investigations on the service objects(users)of the earthquake emergency maps to understand the needs of making earthquake emergency maps. The audience theory in mass media field and map information transmission theory are adopted to classify the users of the earthquake emergency maps into four categories: earthquake emergency commanders, technical staffs for decision-making, earthquake emergency rescuers, and the public. The components of different types of users are described and then their diverse demands in earthquake emergency maps are analyzed, such as the needs of on-field disaster information maps, earthquake information maps, physical geography and social economic maps. Following those needs, we introduce the representation methods of the earthquake emergency maps according to their formats(vector or raster)and contents, such as point symbolization method, kilometer grid method, line symbolization method and range method. Then, we study the rapid plotting method of earthquake emergency map based on map template matching method. The core steps of the method include: 1)before earthquake, the templates of different earthquake emergency maps are designed, prepared and connect the earthquake emergency features with their related spatial database. The map layout and map elements are stored in the templates. 2)After earthquake, the earthquake emergency features will be generated from seismic models(such as attenuation model of earthquake magnitude and seismic intensity)or the information obtained from field investigation. 3)Corresponding earthquake emergency map template is selected in accordance with the generated seismic features. And the features are used to update related features inside the selected template. 4)Minor adjustments are made such as to the map scale and some map annotations to finally generate the formal earthquake emergency map. Architecture of template system of the earthquake emergency maps is designed, including map user level, map template level, template layer level and map element level. Regrading to the architecture, the general map template of earthquake emergency is presented which includes four main regions: title region, main picture region, auxiliary region and annotation region. The main picture region is the essential, which lays geographic background maps and earthquake emergency features. Finally, an earthquake emergency mapping system is developed. Based on the system, a case study is presented, which demonstrates making a simulated seismic intensity influence map. From three aspects, the case presents the application of the template-matching method including: generating earthquake emergency features, substituting the features inside the template with the generated features, and revising map annotations. Therefore, the map template matching method is verified so that it can be used to quickly generate various earthquake emergency maps.  相似文献   

轨道调谐建立洛川黄土地层的时间标尺   总被引：5，自引：0，他引：5       下载免费PDF全文

鹿化煜  杨文峰 《地球物理学报》1998,41(6):804-810

对黄土高原中部洛川厚140m黄土剖面进行了黄土层间隔5cm、古土壤层间隔3cm的采样,在室内测量了全部样品的磁化率．以磁化率变化作为东亚夏季风气候变化的替代性指标,利用轨道调谐方法建立了黄土－古土壤序列的时间标尺．结果表明,B／M界线处的年龄是772KaB．P,午城黄土与离石黄土分界线的年龄为1348KaB．P,黄土堆积底界的年龄为2471KaB．P．．通过和古地磁场倒转点绝对年龄对比以及与太阳辐射量变化时间序列进行交叉谱分析,证明了新时间标尺的可信性．  相似文献   

公路收费系统通用通信组件设计与实现     

安海平  陶宏才 《成都信息工程学院学报》2007,22(2):226-230

介绍了公路收费系统中所需的实时数据通信功能的设计,并通过组件方式,将其制作成具有一定安全性的通用组件,提供给应用系统调用,从而提高开发效率.  相似文献   

河北省近海有害藻华灾害分级、时空分布和优势藻华生物变化特征     

安鑫龙  李雪梅  李志霞 《海洋技术学报》2015,34(1):69-75

为研究1989—2013年河北省近海有害藻华灾害分级、时空分布和优势肇事生物变化特征,对河北省近海累计58次有害藻华记录的发生时间、位置与范围、面积和优势有害藻华生物种类进行了统计分析。结果表明:小型(面积0~100 km2)、中型(100~1 000 km2)、大型(≥1 000 km2)和面积不详的有害藻华中,小型藻华为多发性藻华,发生次数占全省海域累计发生次数的60.35%;5-8月份是藻华多发期,发生次数占累计发生次数的86.21%;2000年后藻华发生频率大增,由原来年均发生1次演变为年均发生4次;秦皇岛海域发生藻华次数最多,占全省海域累计发生次数的57.14%,沧州海域次之,唐山海域最少;秦皇岛海域发生藻华累计面积最大,占全省海域累计发生面积的64.25%,沧州海域次之,唐山海域最小。河北省优势海洋有害藻华生物共计15种,易发性藻华生物夜光藻Noctiluca scintillans引发藻华次数最多,占全省海域累计发生次数的44.83%,2009年前是河北省近海最主要的藻华肇事生物;高发性藻华生物抑食金球藻Aureococcus anophagefferens引发有害藻华累计面积最大,占全省海域累计发生面积的55.57%,2009年后该藻和夜光藻共同成为河北省近海优势藻华肇事生物。  相似文献   

不同截止高度角下BDS-3SPP精度分析     

朱玉香  陈永贵  安春华 《测绘通报》2021,(3):23-27

针对卫星可见数与历元可用率较低情况下的BDS-3定位性能,本文基于MEGX跟踪站BDS-3与GPS实测数据,分析了不同高度角（10°、20°、30°、40°）下BDS-3卫星B1I、B1C、B2a、B3I,以及GPS系统L1频率的单点定位（SPP）精度。研究发现,BDS-3平均卫星可见数与卫星空间几何构型优于GPS,且随着高度角的增加呈线性变化。BDS-3的4个频率的SPP精度随着高度角的增加呈先增加后降低的趋势,高度角为20°时,定位精度最高,高度角达到40°时,定位精度最低,且历元可用率也最低;但B1I和B3I历元可用率仍大于90%,而B1C和B2a历元可用率大于70%;不论是SPP定位精度还是历元可用率,均优于GPS系统L1频率。  相似文献