单频GPS接收机天线扼流圈的研制与测试   总被引：2，自引：0，他引：2  

高玉平  刘子懿  徐劲松  王正明 《时间频率学报》2006,29(1):51-57

讨论了多路径效应对GPS共视比对的影响及削弱其影响的方法。结合综合原子时项目的需求,研制了适用于单频GPS接收机的天线扼流圈,并用零基线比对方法进行了测试。结果表明,研制的天线扼流圈可有效地削弱多路径效应的影响,并可明显地改善单频GPS接收机NTSCGPS-1的抗干扰能力。  相似文献   

Contributions to the Ring Current Energy During Geomagnetic Storms     

Van Zele  María Andrea 《Studia Geophysica et Geodaetica》2002,46(1):33-41

The purpose of this research was to study the complexity of the energization of the ring current during a geomagnetic storm, produced during southern Bz(IMF) by the injection of plasma sheet ions, accelerated by enhanced convective electric fields. This model assumes that the plasma sheet is continuously populated by H⁺ from the sun and the ionosphere, and sporadically by ionospheric O⁺, making the ring current a coupled system whose energy can hardly be expressed analytically. When Bz(IMF) turns north, the ring current becomes uncoupled, and the energy decays exponentially if the storm is weak, or can be expressed as a combination of exponentials during strong storms representing the quick decay of O⁺ and the slower decay of H⁺, as has been shown.  相似文献   

湖北省土壤侵蚀景观空间异质性及驱动因子分析     

张志  王少军 《中国地质灾害与防治学报》2004,15(4):49-53

地域分异是地球表层大小不等、内部具有一定相似性地段之间的相互分化以及由此产生的差异。为了研究不同区位土壤侵蚀问题，从土壤生态景观及系统论出发，运用地质学、地理学、景观生态学、环境学的理论和研究方法，研究湖北省土壤侵蚀景观空间格局及其驱动因子，使土壤侵蚀问题研究提高到一个新的水平。湖北省土壤侵蚀景观具有南北分带、东西分区，为一不对称的断块一环组合，土壤流呈现向长江、江汉盆地中心轴带辐聚、单流向特点。景观空间异质性形成的首要驱动因子是大地构造背景，以房县一襄樊一广济断裂带为界，南北两侧地壳物质组成和构造发展史存在较明显的差异，现代气候带、降雨量、温热程度及土地利用等差异，造成了湖北省区域土壤地理、土壤生态的分异，形成湖北省土壤生态带、区具有南北分带，东西分区的宏观格局；其次大兴安岭一武陵山深部构造陡变带两侧新构造运动强度差异、大别造山带构造强烈隆升，导致土壤侵蚀强度的西强东弱、南北强中间弱的态势；成土母岩差异性决定了土壤可蚀性的多变；空间上“土壤侵蚀内城区”分布在湖北省的周边地区，经济贫困、管理落后，这一地区的经济水平与水土流失间形成“自反馈作用”，这一现象在我国水土保持、生态建设工作中应该引起重视。  相似文献   

波,流联合作用下的近岸海底沙波稳定性研究进展   总被引：3，自引：0，他引：3  

程和琴  王宝灿 《地球科学进展》1996,11(4):367-371

近岸海底大型沙波是一种研究较为薄弱的地貌单元，但它的迁移对港口、航道和海底电缆及钻井平台、输油管道等海洋工程设施建设造成的危害极大。在综述目前国内外有关研究文献的基础上，概要地介绍了作者提出的一种较为简便、省力和有效的沙波迁移速率和沙波稳定性定量评价和预测方法，旨在提高航道通航能力和海洋工程建设的灾害防治和预测能力  相似文献   

Impact of the Mass Parameter on Particle Dynamics in a Ring Configuration of N Bodies     

F.?E.?PsarrosEmail author  T.?J.?Kalvouridis 《Astrophysics and Space Science》2005,298(3):469-488

Parameters play a very important and determinative role in the dynamics of a dynamical system as well as in the formation of its particular characteristics. In this paper we investigate the way in which a large scale variation of the mass parameter, influences the behavior of a mass-less particle which moves in the vicinity of a ring arrangement of N-bodies. More precisely, we study the impact of this parameter on periodic motions and their characteristics.  相似文献   

高温高压下水的剪切粘滞度的平衡分子动力学计算   总被引：3，自引：1，他引：2  

郭永贵  张毅刚 《岩石学报》1998,14(1):1-10

本项工作用ＴＩＰ４Ｐ模型对水分子进行了平衡分子动力学模拟。根据Ｇｒｅｅｎ－Ｋｕｂｏ理论,计算了温度从６５２Ｋ到８１４Ｋ,密度从０．５３６０ｇ／ｃｍ３到０．８６３８ｇ／ｃｍ３六个不同温度和密度水的剪切粘滞度,并和实验值进行了对比。在所计算的温度和密度范围,平衡分子动力学计算结果与实验值的平均绝对值差别为１５％,好于使用非平衡分子动力学方法获得的粘滞度值。平衡分子动力学的方法将是获得地学中高温高压下流体输运性质的重要途径。  相似文献   

Equilibrium Evaporation and the Convective Boundary Layer   总被引：2，自引：1，他引：1  

M. R. Raupach 《Boundary-Layer Meteorology》2000,96(1-2):107-142

A theory is developed for surface energy exchanges in well-mixed, partlyopen systems, embracing fully open and fully closed systems as limits.Conservation equations for entropy and water vapour are converted intoan exact rate equation for the potential saturation deficit D in a well-mixed, partly open region. The main contributions to changes in D arise from (1) the flux of D at the surface, dependent on a conductance g_q that is a weighted sum of the bulk aerodynamic and surface conductances; and (2) the exchange flux of D with the external environment by entrainment or advection, dependent on a conductance g_e that is identifiable with the entrainment velocity when the partly open region is a growing convective boundary layer (CBL). The system is fully open when g_e/g_q , and fully closed when g_e/g_q 0. The equations determine the steady state surface energy balance (SEB) in a partly open system, the associated steady-state deficit, and the settling time scale needed to reach the steady state. The general result for the steady-state SEB corresponds to the equations of conventional combination theory for the SEB of a vegetated surface, with the surface-layer deficit replaced by the external deficit and with g_q replaced by the series sum (g_q ^-1 + g_e ^-1)^-1. In the fully open limit D is entirely externally prescribed, while in the fully closed limit, D is internally determined and the SEB approaches thermodynamic equilibrium energy partition. In the case of the CBL, the conductances g_q and g_e are themselves functions of D through short-term feedbacks, induced by entrainment in the case of g_e and by both physiological and aerodynamic (thermal stability) processes in the case of g_q. The effects of these feedbacks are evaluated. It is found that a steady-state CBL is physically achievable only over surfaces with at least moderate moisture availability; that entrainment has a significant accelerating effect on equilibration; that the settling time scale is well approximated by h/(g_q + g_e), where h is the CBL depth; and that this scale is short enough to allow a steady state to evolve within a semi-diurnal time scale only when h is around 500 m or less.  相似文献   

Variations of Seismicity in the Avachinsky Gulf (Kamchatka, Russia)     

V. Saltykov  V. Chebrov  J. Kugaenko 《Natural Hazards》1999,19(2-3):87-96

Variations of seismic mode in the region of the Avachinsky Gulf (Kamchatka, Russia) are considered. Observed anomalies (seismic quiescence, the ring seismicity, reduction of the slope of the earthquake recurrence diagram) provide a basis to consider this region as a place of strong earthquake preparation. The Kamchatka regional catalogues of earthquakes between 1962–1995 were used in the analysis. A reduced seismicity rate is observed during 10 years in an area of 150 km × 60 km in size. During the last five years, in the vicinity of the area considered, earthquakes with M > 5 occurred three times more often than the average over thirty years. It is interpreted as ring seismicity. The block of 220 km × 220~km in size, including the quiescence zone, is characterized by a continuous decrease of the recurrence diagram slope, which has reached a minimum value for the last 33 years in this region.  相似文献   

树轮纤维素中氧同位素温度意义     

陈拓  秦大河  任贾文 《冰川冻土》1999,(3)

树轮作为自然档案中的一种, 其同位素研究是较为新颖的领域文章比较系统地从树轮纤维素的提取、氧的来源、植物体内氧的分馏、与温度变化的关系等４ 个方面评述了树轮纤维素氧同位素组成的气候学意义已有的研究结果表明, 树轮纤维素氧同位素组成的变化是温度变化的良好载体, 但在定量恢复古温度变化时遇到了不少限制, 有待于进一步完善分馏模型  相似文献   

福州平安大厦深基坑支护设计与施工          下载免费PDF全文

阮广招  黄金灿 《探矿工程》1999,(4):14-15,21

深基坑支护设计与施工是当前城市高层、超高层建筑突显的技术难题。通过工程实例,从设计方案的选择到施工、监测,提供了有益的经验。  相似文献