两种功率倒置阵列天线调零模型的等效性分析

在对卫星导航接收系统中两种常见的功率倒置阵列天线调零模型：基于参考信号的最小均方误差模型和线性约束条件下的最小功率模型,利用分块矩阵求逆特性从理论上证明了这两种模型之间的等效性,并针对不同模型的特点指出了这两种模型各自不同的应用场合,通过仿真对理论分析的有效性进行了验证,从而为卫星导航接收系统中的抗干扰调零天线的理论建模、仿真设计和实际应用提供了新的参考。     

太阳辐射短时临近预报R模型的构建及验证

提高太阳辐射短时临近预报（<6 h）的准确率是确保电网调度的重要举措,也是极具挑战性的技术瓶颈之一。基于云-辐射关系,利用地面观测的太阳辐照度反演的云相对辐射强迫比值,构建了太阳辐射短时临近预报模型（R模型）,并用美国南部大平原中心站16 a的辐照度观测数据,对R模型的预报性能进行了评估。结果表明：（1）有云存在的个例中,R模型较传统的简单持续性模型（Simple模型）的预报性能有很大提升,相比于预报性能较高的智能持续性模型（Smart模型或RCRF模型）仍有2%～25%的改进。（2）在16 a包含2.9×105个8类云状个例的总体检验中,当预报时效超过1 h时,R模型的预报性能显著优于Simple模型和RCRF模型。相对于RCRF模型,R模型在6 h预报时效下,对总辐射和直接辐射的预报性能可分别提高25%和19%,预报时效分别延长了1.5 h和1 h。（3）R模型为太阳辐射短时临近预报提供了准确率更高的基准模型。同时,该模型可仅依靠地面短期的辐照度观测资料即可预报,为缺少同期气象要素观测的光伏电厂的辐射预报提供了新的途径或新的可能。     

海潮改正模型对GPS基线的影响

利用GAMIT软件解算了2011年前200天国内9个IGS站的数据,解算时考虑采用未加入和分别加入4种不同的海潮改正模型等情况,对4种不同海潮改正模型在基线分量上的影响进行了比较,说明了不同模型对GPS基线的影响差异较小;并对含沿海地区GPS测站和只含内陆地区GPS测站的基线进行了分析,结果表明含沿海地区GPS测站的基线比只含内陆地区GPS测站的基线受海潮改正模型的影响大;最后重点采用功率谱分析了海潮改正对GPS基线分量影响的周期,得到其3个方向的变化周期。     

MÉTHODE D'ÉTUDE DES NAPPES LIBRES DANS LES AQUIFÈRES ANISOTROPES

Abstract

The necessary and sufficient conditions for non-zero phase shift and non-zero attenuation in linear flood routing can be derived from the continuity equation alone and are found to depend on the existence of an imaginary part in the expression for frequency or in the expression for wave number. It is shown that in linear flood routing the phase lag between flow rate and area of flow is directly related to the attenuation per unit wave length. The effects of using various forms of the momentum equation, in addition to the continuity equation, are exemplified by deriving analytical expressions in terms of the frequency, both for attenuation per unit channel length and for phase shift, for the kinematic wave, the general diffusion analogy, and the complete St. Venant equation.     

台站电源远程管理单元的实现

由电源测控单元、短信平台及远程控管平台构成的上海市地震局台站电源远程管理单元,实现了对台站市电、UPS、电池组等设备状态的实时监控,对台站电池组的远程充放电功能,以及对台站电源故障的短信告警,为用户提供了可视化的台站电源状态报表,提高了用户对电源故障的处理效率和台站设备运行率。     

岷县漳县M_s6.6地震前平凉台地电场变化

应用2013年甘肃岷县漳县M_s6.6地震前263天及震后9天的平凉台观测数据研究了该台地电场在时间域、频率域内的变化,得到:(1)在岷县漳县M_s6.6地震以及在2013年四川芦山M_s7.0地震前平凉台地电场观测记录了显著的自然电场变化,在近距离的岷县漳县地震前自然电场变化更显著,异常变化的持续时间长;(2)平凉台地电场最大熵功率谱密度在4月20日四川芦山地震前发生连续增大的现象,并持续到甘肃岷县漳县地震后。最后讨论了本次地震地电场极低频成分异常变化的机理。     

Improvement of streams hydro‐geomorphological assessment using LiDAR DEMs

Hydro‐geomorphological assessments are an essential component for riverine management plans. They usually require costly and time‐consuming field surveys to characterize the spatial variability of key variables such as flow depth, width, discharge, water surface slope, grain size and unit stream power throughout the river corridor. The objective of this research is to develop automated tools for hydro‐geomorphological assessments using high‐resolution LiDAR digital elevation models (DEMs). More specifically, this paper aims at developing geographic information system (GIS) tools to extract channel slope, width and discharge from 1 m‐resolution LiDAR DEMs to estimate the spatial distribution of unit stream power in two contrasted watersheds in Quebec: a small agricultural stream (Des Fèves River) and a large gravel‐bed river (Matane River). For slope, the centreline extracted from the raw LiDAR DEM was resampled at a coarser resolution using the minimum elevation value. The channel width extraction algorithm progressively increased the centerline from the raw DEM until thresholds of elevation differences and slopes were reached. Based on the comparison with over 4000 differential global positioning system (GPS) measurements of the water surface collected in a 50 km reach of the Matane River, the longitudinal profile and slope estimates extracted from the raw and resampled LiDAR DEMs were in very good agreement with the field measurements (correlation coefficients ranging from 0 · 83 to 0 · 87) and can thus be used to compute stream power. The extracted width also corresponded very well to the channel as seen from ortho‐photos, although the presence of bars in the Matane River increased the level of error in width estimates. The estimated maximum unit stream power spatial patterns corresponded well with field evidence of bank erosion, indicating that LiDAR DEMs can be used with confidence for initial hydro‐geomorphological assessments. Copyright © 2013 John Wiley & Sons, Ltd.     

前兆定点形变观测数据噪声分析

地球物理研究表明,可以构造或选择合适的统计模型模拟观测噪声,从而了解噪声特性,获得噪声谱及其含量.对吉林省5个台站的倾斜观测共18个测项产出的时间序列进行噪声分析,结果表明,长期观测噪声可用带通噪声和随机游走噪声的组合模型模拟,短时间观测噪声可用谱指数介于-1至-2的幂律噪声模型模拟.该结论对定点形变观测噪声的认识、噪声源的研究以及地壳构造信息的提取具有参考意义.     

Beach morphodynamic characteristics and classifications on the straight coastal sectors in the west Guangdong

Journal of Geographical Sciences - Currently beach morphodynamic classification is the most important foundation to conduct associated coastal geomorphological studies. This paper carried out beach...     

Evaluation of the half‐power bandwidth method to estimate damping in systems without real modes

The objective of this work was to assess the significance of the values of damping obtained applying the half‐power bandwidth method to the frequency response records of the steady‐state response of a system that does not possess real modes either because the damping matrix does not satisfy the orthogonality condition or because its parameters are functions of frequency. A multi‐degree of freedom system with real modes and different types of damping is considered first. A two degree of freedom system with an arbitrary damping matrix, a rigid mass on an elastic foundation subjected to vertical and coupled horizontal/rocking vibrations, and a single degree of freedom model of a building accounting for inertial soil structure interaction effects are considered next in more detail. The results show that the predictions of the method, when applicable compare very well with those provided by approximate formulae and procedures used in practice. Copyright © 2010 John Wiley & Sons, Ltd.