BPL时码发播和自主授时方法

在对国际上普遍采用的3种罗兰-C数字调制方法分析比较的基础上,对我国BPL长波授时发播系统技术改造中选用的数字调制方法、时码发播和自主授时方法进行了介绍,并提出了实现BPL时码发播和自主授时后宜采用的闰秒方案.     

Preliminary assessment of the navigation and positioning performance of BeiDou regional navigation satellite system

BeiDou regional navigation satellite system(BDS)also called BeiDou-2 has been in full operation since December 27,2012.It consists of 14 satellites,including 5 satellites in Geostationary Orbit(GEO),5 satellites in Inclined Geosynchronous Orbit(IGSO),and 4 satellites in Medium Earth Orbit(MEO).In this paper,its basic navigation and positioning performance are evaluated preliminarily by the real data collected in Beijing,including satellite visibility,Position Dilution of Precision(PDOP)value,the precision of code and carrier phase measurements,the accuracy of single point positioning and differential positioning and ambiguity resolution(AR)performance,which are also compared with those of GPS.It is shown that the precision of BDS code and carrier phase measurements are about 33 cm and 2 mm,respectively,which are comparable to those of GPS,and the accuracy of BDS single point positioning has satisfied the design requirement.The real-time kinematic positioning is also feasible by BDS alone in the opening condition,since its fixed rate and reliability of single-epoch dual-frequency AR is comparable to those of GPS.The accuracy of BDS carrier phase differential positioning is better than 1 cm for a very short baseline of 4.2 m and 3 cm for a short baseline of 8.2 km,which is on the same level with that of GPS.For the combined BDS and GPS,the fixed rate and reliability of single-epoch AR and the positioning accuracy are improved significantly.The accuracy of BDS/GPS carrier phase differential positioning is about 35 and 20%better than that of GPS for two short baseline tests in this study.The accuracy of BDS code differential positioning is better than 2.5 m.However it is worse than that of GPS,which may result from large code multipath errors of BDS GEO satellite measurements.     

Implications of next generation attenuation ground motion prediction equations for site coefficients used in earthquake resistant design

Proposals are developed to update Tables 11.4‐1 and 11.4‐2 of Minimum Design Loads for Buildings and Other Structures published as American Society of Civil Engineers Structural Engineering Institute standard 7‐10 (ASCE/SEI 7–10). The updates are mean next generation attenuation (NGA) site coefficients inferred directly from the four NGA ground motion prediction equations used to derive the maximum considered earthquake response maps adopted in ASCE/SEI 7–10. Proposals include the recommendation to use straight‐line interpolation to infer site coefficients at intermediate values of (average shear velocity to 30‐m depth). The NGA coefficients are shown to agree well with adopted site coefficients at low levels of input motion (0.1 g) and those observed from the Loma Prieta earthquake. For higher levels of input motion, the majority of the adopted values are within the 95% epistemic‐uncertainty limits implied by the NGA estimates with the exceptions being the mid‐period site coefficient, F_v, for site class D and the short‐period coefficient, F_a, for site class C, both of which are slightly less than the corresponding 95% limit. The NGA data base shows that the median value of 913 m/s for site class B is more typical than 760 m/s as a value to characterize firm to hard rock sites as the uniform ground condition for future maximum considered earthquake response ground motion estimates. Future updates of NGA ground motion prediction equations can be incorporated easily into future adjustments of adopted site coefficients using procedures presented herein. Published 2014. This article is a U.S. Government work and is in the public domain in the USA. Earthquake Engineering & Structural Dynamics published by John Wiley & Sons Ltd.     

一种SINS/GPS深组合导航系统技术问题分析

为了满足高动态用户及强干扰条件下的应用需求,提出了一种基于卫星信号矢量跟踪的SINS/GPS深组合导航方法,设计了基于FPGA硬件平台的实施方案。利用组合卡尔曼滤波器反馈回路取代了传统接收机中独立、并行的跟踪环路,能够同时完成所有可视卫星信号的跟踪和导航信息处理;通过矢量跟踪算法对所有可视卫星信号进行集中处理,能够增强跟踪通道对信号载噪比变化的适应能力,从而提高接收机在强干扰或信号中断条件下的跟踪性能;根据SINS导航参数和星历信息推测GPS伪码相位和多普勒频移等参数,用以辅助卫星信号的捕获和跟踪,能够大大缩短接收机的搜索捕获时间,并增强接收机在高动态条件下的跟踪性能。基于矢量跟踪的深组合方法不仅在GPS信号短暂中断期间,能够保证系统的导航精度和可靠性,而且在强干扰环境中能够维持较好的伪码相位和载波频率跟踪性能。     

大比例尺地形图分幅统一编号的构想

在分析比较现行国家基本比例尺地形图和大比例尺地形图分幅编号的相关规定的基础上,提出了一种全国范围内大比例尺地形图的分幅编号规则,并结合分幅编号与地理坐标的关系,以实例解析了2个通用的应用模型。     

CASS环境下高程点检查修改算法与实现

主要介绍了CASS环境下地形图生产中遇到的高程点Z值与高程值不一致问题的检查与修改的方法,并详细阐述了适用于程序代码快捷实现的有效算法。     

开源GIS软件安装使用方式综述

开源GIS软件的安装使用有源代码编译,可执行文件,USBGIS,GIS CDROM/DVD,GISVM,LiveGIS等多种方式,利用开源GIS软件可以集成搭建企业级通用GIS方案平台,对比研究了多种安装使用方式,充分满足GIS教学、科研和生产的需要。     

Hybrid Simulation of Collisionless Shock Formation in Support of Laboratory Experiments at Unr

The problem of producing collisionless shocks in the laboratory is of great interest for space and astrophysical plasmas. One approach is based on the idea of combining strong magnetic field (up to 100 Tesla) created during a Z-pinch discharge with a plasma flow produced in the process of the interaction of a laser pulse with a solid target. In support of laboratory experiments we present hybrid simulations of the interaction of the plasma flow with frozen in it magnetic field, with the spherical obstacle. Parameters of the flow correspond to a laser plasma ablation produced in the laboratory during irradiation of the target by a 3 J laser. Magnetic fields in the plasma flow and around the obstacle are created by the currents produced by the pulse power ZEBRA voltage generator. With the appropriate set of initial conditions imposed on the flow collisionless shocks can be created in such a system. Using independent generators for plasma flow and magnetic field allows for the exploration of a wide range of shock parameters. We present simulations of the formation of supercritical collisionless shock relevant to the experiment, performed with the 2D version of the hybrid code based on the CAM-CL algorithm [Planet. Space Sci. 51, 649, 2003].     

闽西晚中生代基性岩脉的地球化学研究

对闽西三个地区基性岩脉的地球化学研究发现,该区域的基性岩脉为亚碱性岩石系列,具有高 Al、低 Ti、Na2O > K2O的特征;相对富集大离子亲石元素,亏损高强场元素.半村辉绿岩脉和拔里角闪辉长岩脉以 Nb、Ta、Ti负异常为特征,林子坟辉长辉绿岩脉具有 Nb、Ta负异常和 Ti弱正异常.半村和拔里的岩脉稀土元素总量高,明显富集轻稀土元素,(La/Yb)N=6.8～8.4;林子坟的岩脉稀土元素总量相对较低,轻稀土元素弱富集,(La/Yb)N=2.0.结合基性岩脉的地球化学特征和区域构造演化分析,初步认为半村和拔里的基性岩脉来自与俯冲作用有关的富大离子亲石元素流体交代的富集地幔;林子坟基性岩脉是软流圈地幔部分熔融的产物,地壳混染作用是其相对富集大离子亲石元素的原因.结合玄武岩构造环境判别图解可知,半村和拔里岩脉具有的大陆边缘弧的特征并不指示基性岩脉形成的构造环境,而是说明其源区受到俯冲板片派生出来的流体交代作用.半村和拔里岩脉形成于大陆板内拉张带,林子坟岩脉形成于板内裂谷环境.与华南其他地区的基性岩脉对比表明,虽然晚中生代华南地区处于拉张的构造背景下,但是岩脉形成的构造环境与微量元素地球化学特征均有明显的差异,反映了各地区构造环境演变和地幔演化的复杂性.     

Crust and upper mantle structure in east China and sea areas

Introduction Rayleigh wave is a kind of seismic wave propagating along the surface of the Earth, its propagation speed depends chiefly on the S-wave velocity structure of the Earth. Rayleigh wave energy of different periods concentrated in different depth ranges. The layered structure of the Earth causes the phenomenon of dispersion of surface waves, that is, surface waves of different periods are propagated with different speeds. By measuring the dispersion curves of surface waves the S-wav…