基于精选基准消秩亏的GNSS参考网数据处理方法

全球导航卫星系统（GNSS）参考网多用于估计卫星轨道/钟差、监测地表形变和速度场、确定精密地球自转参数等方面。相关数据处理模式包括：双差基线解（DD）和非差精密单点定位（PPP）等。本文首先从GNSS基本观测方程出发,通过选取两组基准参数,导出了上述两模式下的列满秩观测方程,然后分析了它们的不足,例如：相位偏差在DD模式中吸收了钟差,丧失了时不变特性;模糊度在PPP模式中吸收了相位偏差,失去了整数性。基于上述分析,本文提出了一种新的参考网数据处理方案,以充分融合DD和PPP模式的优势。它的关键策略是精选基准参数,以达到消秩亏的目的,具体优点体现在：相位偏差独立可估,若合理约束为时不变参数,可充分减少参数个数,提高网解精度;待估模糊度具备整周特性,经由模糊度固定,可改善网解可靠性。     

GPS-RTK测定坐标转换到地方独立坐标的方法及其适用性分析

GPS-RTK技术已经广泛应用于测绘工程的各个领域,特别是在城市测量和工程测量的应用中,因其使用的地方独立坐标系统的特殊性,GPS-RTK坐标转换参数求取方法也具有特殊性。本文从实际工作应用的角度出发,论述了GPS-RTK技术在城市测量和工程测量中坐标转换的不同方法及其适用性。     

Is rainfall intensity significant in the rainfall–runoff process within tropical rainforests of northeast Queensland? The Hewlett regression analyses revisited

Following the statistical analyses of long‐term rainfall‐runoff records from research basins in humid temperate latitudes, Hewlett and co‐workers extended the global challenge to disprove their findings that rainfall intensity was non‐significant. This paper responds to Hewlett's challenge as no preceding analyses have involved forested basins in a tropical cyclone‐prone area. Based on a 7 year rainfall‐runoff record, quickflow (QF), peak flow (QP) and quickflow response ratios (QRR) were regressed as dependent variables against rainfall parameters (intensity, P_i, amount, P), storm duration, D and antecedent flow, I. These data sets were categorised into total streamflow (Q) classes and stratified into three seasons, (monsoon, post‐monsoon and dry) for forested and cleared catchments. Where rainfall variable collinearity met acceptable levels, the addition of P_i to regression models including P, D, I contributed up to 9% and 66% of the respective variations in quickflow and peak flow. For the highest Q storm classes (monsoon), P_i alone accounted for up to 67% and 91% of the variation in Q_F and Q_P respectively and was the dominant influence on Q_P for all seasons. The very high rainfall intensities experienced in the monsoon season is a causal factor why these results differ from those of other research drainage basins. Surprisingly, P_i continued to have a significant influence on Q_F for dry season classes when less‐intense rainfall occurs. Further the results were similar for both catchments across all seasons. P was the dominant independent variable affecting Q_F above a threshold Q of 50 mm (monsoon), as rainfall contributes directly to saturation overland flow and return flow under saturated conditions. Further although QRR increased with increasing Q for each season, the regression results for that parameter were poor possibly due to the non‐linearity of the rainfall‐runoff relationship. Copyright © 2010 John Wiley & Sons, Ltd.     

Estimation of Nash's IUH parameters using stochastic search algorithms

In rainfall–runoff studies, it is often necessary to change the duration of a given unit hydrograph. Nash's Instantaneous Unit Hydrograph (IUH) is an ideal method that eliminates the hydrograph duration. This paper presents the results of the application of search algorithms, namely a genetic algorithm and hill climbing, to develop the IUH that minimizes the error between the observed and generated hydrographs. Also the performance of these methods has been compared with that of the classical method used for estimation of IUH, namely the method of moments. The genetic algorithm is a popular search procedure for function optimization that applies the mechanics of natural genetics and natural selection to explore a given search space. Hill climbing is an optimization technique that belongs to the family of local search and algorithms can be used to solve problems that have many solutions, with some solutions better than others. The results obtained from both the genetic algorithm and hill climbing algorithm for estimation of Nash's IUH parameters were compared with the results obtained by the method of moments for storms from two river basins that are located in different climatic regions. It was found that both the genetic algorithm and hill climbing provided improved and consistent results. Copyright © 2008 John Wiley & Sons, Ltd.     

等离子体背景参数对尖峰辐射的影响

本文在电子回旋脉塞不稳定性理论的基础上,着重讨论了等离子体背景参数ω_(pe)/Ω_e对尖峰辐射性质的影响,内容包括:该参数的物理意义、取值范围,以及在尖峰辐射性质中,对ω_(pe)/Ω_e的变化比较敏感的偏振和谐波结构,等等。     

An investigation of gravitational lens determinations of H0 in quintessence cosmologies

There is growing evidence that the majority of the energy density of the Universe is not baryonic or dark matter, but rather it resides in an exotic component with negative pressure. The nature of this 'quintessence' influences our view of the Universe, modifying angular diameter and luminosity distances. Here, we examine the influence of a quintessence component upon gravitational lens time-delays. As well as a static quintessence component, an evolving equation of state is also considered. It is found that the equation of state of the quintessence component and its evolution influence the value of the Hubble constant derived from gravitational lenses. However, the differences between evolving and non-evolving cosmologies are relatively small. We undertake a suite of Monte Carlo simulations to examine the potential constraints that can be placed on the universal equation of state from the monitoring of gravitational lens systems, and demonstrate that at least an order of magnitude more lenses than currently known will have to be discovered and analysed to accurately probe any quintessence component.     

双基地激光测风雷达回波信号仿真研究

本文针对传统的体散射模型并未考虑大气不均匀性对信号传输的影响等问题,通过引入垂直非均匀的大气参数改进了模型,并利用其建立了体目标的双基地激光测风雷达方程,仿真了侧向散射回波信号,并与单基地雷达进行了对比分析。研究表明:水平方向上,双基地激光测风雷达的回波信号分布特征与单基地雷达差异较大,其回波信号等值线在近地面为卵形线,随着探测高度的增加,回波信号等值线逐渐变为以主、被动雷达为焦点的椭圆形,并最终趋近于圆形;垂直方向上,双基地激光测风雷达的回波信号随高度衰减剧烈,近地面的回波能量约为10^-10 J,4 km高度的回波能量约为10^-15J,在中低层大气(0~10 km),回波信号中气溶胶散射占比大,在高层大气(10 km以上),分子散射占比大。