基于单片机和GPS信号的校频系统   总被引：5，自引：0，他引：5  

李展  张莹  周渭 《时间频率学报》2005,28(1):68-75

介绍一种基于INTEL 80C196KC单片机的校频系统,包括系统的设计原理、硬件组成和软件实现。该系统通过利用GPS接收机得到的1PPS秒脉冲信号,实现对晶体振荡器频率的校准,从而获得一个短期及长期稳定度都比较优良的时间频率标准。该系统采用了量化时延原理进行短时间间隔比对,对测量数据进行卡尔曼滤波处理。  相似文献   

基于能值的科尔沁沙地不同农牧比例村落发展可持续性对比     

韩丹  李玉霖  詹瑾  杨红玲 《中国沙漠》2021,41(3):235-244

为评估和比较科尔沁沙地不同生产经营模式自然村落的发展可持续性,通过能值分析方法,定量分析了分别以种植业和养殖业为主的2个自然村落的能值投入与产出情况,建立能值分析指标体系,对2种模式系统的可持续性进行评估.结果表明:在资源投入方面,村落外部辅助能约占总能值投入的39.17％,说明2种生产经营模式对外部资源依赖较小,能值...  相似文献   

宜昌地区下寒武统水井沱组黑色页岩地球化学特征及其地质意义     

万蒙蒙  冯明石  孟万斌  刘四兵  芦云飞  聂应  赵瞻  过敏 《矿物岩石地球化学通报》2021,40(4):946-957

宜昌地区下寒武统水井沱组黑色页岩是一套重要的区域性烃源岩,探讨其沉积古环境及沉积模式有助于对地质历史演化的认识,推动油气勘探进展,为页岩气勘探提供科学依据.本文通过对宜昌地区水井沱组野外剖面观测,利用薄片鉴定、扫描电镜、全岩X射线衍射(XRD)、总有机碳(TOC)及主微量元素等分析测试,分析其地球化学特征,探讨其沉积古...  相似文献   

阿尔金山南缘断裂带的分段分带特征及其构造演化   总被引：4，自引：1，他引：3  

伍跃中  王战  陈守建  张转 《地质学报》2008,82(9):1195-1209

通过卫星遥感图像分析和野外调查,参考最新的地质调查和前人研究成果,系统总结了阿尔金山南 缘断裂带的构造特征,表明该断裂带具有沿走向上的多级分段性、横向上的多级分带性,其构造活动性质和运动方 向具有多级周期性反复的演化特点。这是地壳波浪状构造运动在阿尔金山南缘断裂带的具体体现。因此任何单 一的左行、右行或逆冲、正滑作用模式都不能全面、合理地解释其构造演化过程。  相似文献   

基于FTP协议的地震数据共享技术研究   总被引：1，自引：0，他引：1  

马中华  朱小毅  段天山  薛兵  陈阳  林湛  彭朝勇  杜则澄 《地震》2008,28(3):79-84

随着互联网技术的广泛应用, 为地震数据共享提供了必要的外部条件, 但是怎样提供优质的地震数据共享方案一直是地震观测技术的一个研究课题。 文中研究了一种基于FTP协议的地震数据共享方案, 该方案不仅可以提供传统的数据下载、 上载功能, 而且还可以根据用户需求, 提供采样率变换、 数据格式转换等服务, 可以方便地为地震数据用户提供服务, 从而使地震数据得到更加广泛的共享应用。 该文重点介绍了该基于FTP协议的数据共享技术的模型设计和实现。  相似文献   

Correction to: An integrated framework of coastal flood modelling under the failures of sea dikes: a case study in Shanghai     

Ke  Qian  Yin  Jiangshan  Bricker  Jeremy D.  Savage  Nicholas  Buonomo  Erasmo  Ye  Qinghua  Visser  Paul  Dong  Guangtao  Wang  Shuai  Tian  Zhan  Sun  Laixiang  Toumi  Ralf  Jonkman  Sebastiaan N. 《Natural Hazards》2021,109(1):705-706

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Public attention to the great smog event: a case study of the 2013 smog event in Harbin,China     

Wei  Jiuchang  Zhan  Wanling  Guo  Xiumei  Marinova  Dora 《Natural Hazards》2017,89(2):923-938

Natural Hazards - The 2013 outbreak of smog in China triggered unprecedented public attention in the country, which played a critical role in crisis communication and management. This study...  相似文献   

Underdamped slug tests with unsaturated‐saturated flows by considering effects of wellbore skins          下载免费PDF全文

Xiuyu Liang  Hongbin Zhan  You‐Kuan Zhang  Jin Liu 《水文研究》2018,32(7):968-980

An analytical solution is presented for the slug tests conducted in a partially penetrating well in an unconfined aquifer affected from above by an unsaturated zone. The solution considers the effects of wellbore skin and oscillatory responses on underdamped slug tests. The flow in the saturated zone is described by a two‐dimensional, axially symmetric governing equation, and the flow in the unsaturated zone above the water table by a linearized one‐dimensional Richards' equation. The unsaturated medium properties are represented by the exponential constitutive relationships. A Laplace domain solution is derived using the Laplace and finite Fourier transform and the solution in the real‐time domain is evaluated using the numerical inverse Laplace transform method. The solution derived in this study is more general and reduces to the most commonly used solutions for slug tests in their specified conditions. It is found that the unsaturated flow has a significant impact on the slug test conducted in an unconfined aquifer. The impact of unsaturated flow on such a slug test is enhanced with a larger anisotropy ratio, a shorter well screen length, a shorter distance between the well screen and the water table, or a larger well screen radius. The impact of unsaturated flow on slug tests decreases as the degree of penetration (the length of well screen) increases. For a fixed well screen length, the impact of unsaturated flow on slug tests decreases as the distance between the centre of screen and the water table increases. A large dimensionless well screen radius (>0.01) leads to significant effects of unsaturated flow on slug tests. The unsaturated flow reduces the oscillatory responses to underdamped slug tests. The unsaturated zone has significant impact on slug test under high‐permeability wellbore skin.  相似文献   

Chief sources of brachiopod recovery from the end Ordovician mass extinction with special references to progenitors   总被引：2，自引：1，他引：1  

Jiayu Rong  Renbin Zhan 《中国科学D辑(英文版)》1999,42(5):553-560

Survivor, Lazarus and progenitor taxa are sources of biotic recovery following mass extinction. Investigations of the benthic brachiopods through the latest Ordovician mass extinction shows that progenitors developed many evolutionary novelties and successful surviving mechanisms. They are superior to survivors and Lazarus taxa in their ability to adapt to environmental changes. They are the primary source of macroevolution and the ancestors of a number of new taxa. Three kinds of progenitors are recognized based on the Ordovician-Silurian brachiopods from South China: survivor-progenitors, crisis-progenitors and Lazarus-progenitors; the last has the strongest ability to resist adverse environments, and is the most diverse and abundant. Project supported by the National Natural Science Foundation of China (Grant No. 49672083) and Major Project of the Chinese Academy of Sciences (CAS) (Grant KZ952-51-023).  相似文献   

黑龙江五大连池火山群大地电磁探测和研究初步结果   总被引：2，自引：0，他引：2  

詹艳  赵国泽  白登海  晋光文  王继军  宣飞  江钊  任锦章  曲家志  郭德明 《地质论评》1999,45(7):400-408

对黑龙江五大连池火山群新近观测的7条大地电磁测深剖面资料进行了处理、解释和分析。研究表明,在地下约几百米深度至15～20 km左右,存在一个上宽下窄似铆钉状的高阻异常体,推测为固结过程中的火山岩浆体。该高阻体一直穿过地壳与上地幔连接,有向深处延伸的通道,并随着深度的加大,其电阻率逐渐减小。该火山群属于岩浆直接来自上地幔的火山类型,在地壳内没有明显的低阻岩浆囊存在。火山区的构造走向为近南北方向。  相似文献