消费级惯性传感器动态系统误差分析与建模

针对传统的系统误差转台标定方法耗时耗力且受限于实验地点的问题,该文从载体运动特征的角度,使用高精度战术级惯性导航设备作为参考,采集车载动态数据,通过传统传感器信号误差模型对消费级低成本惯性导航设备在线标定后,对标定后的观测值残差分别与载体运动角速度、角加速度、角冲击(加速度导数)、线性加速度、线性加速度冲击进行相关性分...     

A combined ToF‐SIMS and EMP/SEM study of a three‐phase symplectite in the Los Angeles basaltic shergottite

Abstract— A rare three‐phase symplectite consisting of Ca‐rich pyroxene, Fe‐rich olivine, and a silica phase is frequently found rimming pyroxene in the Martian meteorite Los Angeles. This assemblage is usually interpreted as the breakdown product of metastable pyroxferroite, a very rare pyroxenoid mineral itself. However, its origin is not entirely understood, mainly because the extremely small average size of the constituent phases represents a challenge for precise high‐resolution analysis. In addition to electron microbeam methods, the present study uses time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) to overcome the limits of spatial resolution and to comprehensively study this mineral assemblage. The prevailing breakdown hypothesis is supported by the following results: (1) The three symplectite phases are very homogenous in composition from 100 μm down to the micrometer scale. (2) The silica phase could be shown to be almost pure SiO². (3) The symplectite bulk composition is consistent with pyroxferroite. Sub‐micrometer sized Ti‐oxide grains are found within the symplectite (but not within the Ca‐rich pyroxene) and probably represent a minor breakdown phase in addition to the three main phases.     

顾及f3项的电离层延迟模型

给出了顾及f3项时消除电离层延迟的两种方法:用三频观测值来消除电离层延迟,直接用地磁场模型来计算f3项。提出了一种用一个三次曲面来拟合30°×40°的区域内的场强H的简化算法。用两种方法求得的电离层延迟之差小于0.5 mm。     

GNSS电离层延迟模型的数学统一与方法扩展

总结了当前广泛研究的利用GNSS观测数据建立电离层延迟模型的基本理论,并从数学上利用第一类算子方程统一现有的模型。着重分析了电离层VTEC的数学模拟和逼近方法,提出了建立模型的方法上的一系列扩展,从数学角度分析模型各种处理方式上的潜在问题,并给出了简单的单站模型计算实例,实证了理论的正确性。     

Lithostratigraphy of the Kalahari Group in northeastern Namibia

The Kalahari Group in northeastern Namibia consists of terrestrial sediments deposited in a tectonically active basin that was formed by flexural uplift of the African continental margin and independent structures related to rifting. The thickness of the sequence varies from a few meters to around 400 m. Greatest thicknesses occur where the NW–SE trending Kalahari basin axis conjugates with NE–SW trending grabens.Repeated phases of flooding and desiccation dominate the depositional environments of the Kalahari Group in northeastern Namibia. Associations of lithofacies allow recognition of distinct depositional settings such as proximal debris flows, braided streams and sand fans, and pans and sandflats.The northeastern Namibian Kalahari Group rests unconformable on the pre-Kalahari surface which showed a relatively pronounced relief in the Epukiro area. The succession starts with conglomerates, breccias and pebbly sandstones, followed by carbonates, sandstones of various maturities, and silcretes. Ferruginous sandstones and ferricretes occur locally. The onset of Kalahari Group deposition was likely a basin-wide event and therefore the basal lithostratigraphic units can be correlated with confidence. Conversely, the correlation of the succeeding lithostratigraphic units remains fairly speculative.     

Response spectrum method for multi-support seismic excitations

A new response spectrum method is developed for seismic analysis of linear multi-degree-of-freedom, multiply supported structures subjected to spatially varying ground motions. Variations of the ground motion due to wave passage, loss of coherency with distance and variation of local soil conditions are included. The method is based on fundamental principles of random vibration theory and properly accounts for the effects of correlation between the support motions as well as between the modes of vibration of the structure.     

单频伪距差分模型用于动动目标监控的研究与实现

给出了相位平滑伪距进行相对定位的数学模型,基于该模型编写了单频GPS接收机用于实时米级动动目标监控的相对定位的程序,试验结果表明此单频伪距差分模型完全可以用于米级实时动动目标监控.     

导航卫星自主定轨星座旋转误差的地面校正算法

目的 基于星间测距的导航卫星自主定轨不可避免地会出现星座旋转,导致轨道精度下降并对造成用户定位系统误差。对星座旋转现象的原因和影响进行了分析,指出轨道升交点赤经的系统偏差ΔΩ和地球定向参数EOP的预报误差是星座旋转的主要误差源,主要表现为星座绕地球自转轴(犣轴)的旋转。在此基础上,提出一种独立、实用的星座旋转的地面校正算法,利用区域地面站的伪距观测值估计并校正星座旋转误差。仿真结果表明,使用两个测站可以估计旋转误差的三个分量,较为完善地消除星座旋转误差,显著提高用户定位的精度;使用一个测站,仅考虑关于犣轴的旋转分量,也可以校正大部分旋转误差,但校正效果略差。     

北斗天线相位中心改正策略及其对定位精度的影响分析

当前尚未有权威机构发布北斗接收机天线相位中心改正信息,从而影响和限制了北斗系统的高精度定位应用。针对这一亟待解决的问题,采用以GPS天线相位中心改正（PCO和PCV改正）模型代替BDS天线相位中心改正来提高北斗定位精度的处理策略。结果表明,采用上述处理策略,PPP高程方向偏差从1 dm减小到cm级,相对定位的高程方向偏差从cm级减小到mm级,验证了此处理策略的有效性和可行性。     

Revising the shock classification of meteorites

The current shock classification scheme of meteorites assigns shock levels of S1 (unshocked) to S6 (very strongly shocked) using shock effects in rock‐forming minerals such as olivine and plagioclase. The S6 stage (55–90 GPa; 850–1750 °C) relies solely on localized effects in or near melt zones, the recrystallization of olivine, or the presence of mafic high‐pressure phases such as ringwoodite. However, high whole rock temperatures and the presence of high‐pressure phases that are unstable at those temperatures and pressures of zero GPa (e.g., ringwoodite) are two criteria that exclude each other. Each type of high‐pressure phase provides a minimum shock pressure during elevated pressure conditions to allow the formation of this phase, and a maximum temperature of the whole rock after decompression to allow the preservation of this phase. Rocks classified as S6 are characterized not by the presence but by the absence of those thermally unstable high‐pressure phases. High‐pressure phases in or attached to shock melt zones form mainly during shock pressure decline. This is because shocked rocks (<60 GPa) experience a shock wave with a broad isobaric pressure plateau only during low velocity (<4.5 km s^?1) impacts, which rarely occur on small planetary bodies; e.g., the Moon and asteroids. The mineralogy of shock melt zones provides information on the shape and temporal duration of the shock wave but no information on the general maximum shock pressure in the whole rock.