卡尔曼滤波算法的灰色理论模型在变形监测中的应用

本文针对灰色理论模型在建模过程中受到随机扰动影响这一问题,提出了利用卡尔曼滤波处理建模数据的方法.经过实例检验,证明基于滤波算法的灰色理论模型在一定程度上可以提高预测值的精度,更好地反映了观测目标的变形趋势,在变形监测中具有一定的优势.     

梯形面片数据模型及其空间运算应用

提出一种新的基于梯形面片的空间运算方法,该方法将多边形要素预先分解成一系列的梯形面片,后续的空间运算将不再基于原始多边形要素进行操作,而是对分解产生的梯形面片进行更为简便的计算处理。梯形面片模型结合了常见矢量数据模型数据精度高、栅格数据模型运算简单等优点,在执行相关空间运算中与常见矢量和栅格模型相比具有优势。详述了该数据模型,并以点面包含分析和多边形叠置分析等实例探讨了其在空间运算中的应用,测试与分析表明该方法兼具数据精度高、算法实现简单等优点,能较有效地提高空间运算的执行效率。     

一种高效的三维GIS数据库引擎设计与实现

针对大规模三维城市建模与数据库协同应用,设计实现了一种高效的三维GIS数据库引擎,支持基于Oracle 11g的多模式数据库管理;提出了顾及语义的三维空间数据库模型,为地上下室内外三维空间数据的一体化组织管理奠定了基础。介绍了该引擎涉及的多层次三维空间索引、多级缓存、多线程调度以及异步通信传输等关键技术,并用武汉市三维城市模型数据进行了试验分析,验证了该引擎的有效性和可靠性。     

GPS天线相位转绕误差及其对GPS精密单点定位的精度影响分析

对于GPS精密单点定位,天线相位转绕误差无法通过星间求差法消除或者减弱,因此必须通过适当的模型加以改正。本文详细分析该误差的特性及其改正方法,并采用自编软件通过计算实例分析其对GPS精密单点定位的精度影响。     

The GRAPES Variational Bias Correction Scheme and Associated Preliminary Experiments

The variational assimilation theory is generally based on unbiased observations. In practice, however, almost all observations suffer from biases arising from observational instruments, radiative transfer operator, precondition of data, and so on. Therefore, a bias correction scheme is indispensable. The current scheme for radiance bias correction in the GRAPES 3DVar system is an offline scheme. It is actually a static correction for the radiance bias before the process of cost function minimization. In consideration of its effects on forecast results, this kind of scheme has some shortcomings. Thus, this study provides a variational bias correction (VarBC) scheme for the GRAPES 3DVar system following Dee’s idea. In the VarBC scheme, the observation operator is modified and a new control variable is defined by taking the predictor coefficients as the control parameters. According to the feature of the GRAPES-3DVAR, an incremental formulation is applied and the original bias correction scheme is maintained in the actual process of observations. The VarBC is designed to co-exist with the original scheme, because it is a dynamic revision to the observational operator on the basis of the old method, i.e., it adjusts the model state vector along with the control parameters to an unbiased state in the process of minimization and the assimilation system remains consistent with available information automatically. Preliminary experimental results show that the mean departures of background-minus-observation and analysis-minus-observation are reduced as expected. In a case study of the heavy rainfall that happened in South China on 11–13 June 2008, the 500-hPa geopotential height is better simulated using the analyzed field from the VarBC as the initial condition.     

Relationship of photosynthetic carbon fixation with environmental changes in the Jiulong River estuary of the South China Sea, with special reference to the effects of solar UV radiation

Phytoplankton cells in estuary waters usually experience drastic changes in chemical and physical environments due to mixing of fresh and seawaters. In order to see their photosynthetic performance in such dynamic waters, we measured the photosynthetic carbon fixation by natural phytoplankton assemblages in the Jiulong River estuary of the South China Sea during April 24-26 and July 24-26 of 2008, and investigated its relationship with environmental changes in the presence or the absence of UV radiation. Phytoplankton biomass (Chl a) decreased sharply from the river-mouth to seawards (17.3-2.1 μg L⁻¹), with the dominant species changed from chlorophytes to diatoms. The photosynthetic rate based on Chl a at noon time under PAR-alone increased from 1.9 μg C (μg Chl a)⁻¹ L⁻¹ in low salinity zone (SSS < 10) to 12.4 μg C (μg Chl a)⁻¹ L⁻¹ in turbidity front (SSS within 10-20), and then decreased to 2.1 μg C (μg Chl a)⁻¹ L⁻¹ in mixohaline zone (SSS > 20); accordingly, the carbon fixation per volume of seawater increased from 12.8 to 149 μg C L⁻¹ h⁻¹, and decreased to 14.3 μg C L⁻¹ h⁻¹. Solar UVR caused the inhibition of carbon fixation in surface water of all the investigated zones, by 39% in turbidity area and 7-10% in freshwater or mixohaline zones. In the turbidity zone, higher availability of CO₂ could have enhanced the photosynthetic performance; while osmotic stress might be responsible for the higher sensitivity of phytoplankton assemblages to solar UV radiation.     

2011年3月24日缅甸孟帕亚M7.2级地震地震构造浅析

本文简要论述了2011年3月24日缅甸孟帕亚M7.2级地震的发震构造,孟帕亚断裂的活动特征、活动时代,以及断裂与历史地震活动的关系.     

2010年2月27日智利Mw8.8地震前全球地震活动特征分析

通过对智利地震前全球不同时空范围地震活动特征分析,发现:①智利地震前出现了两类地震空区:第一类空区为1900年以来形成的360 km长的Mw≥8.0地震空段,第二类空区为震前5年形成的780 km长的M≥5.5地震空段;②1986-2010年,智利中南部仅发生1次Mw7.1地震,表现为显著的Mw≥7.0地震平静异常;③...     

Sedimentary records of natural and artificial Huanghe (Yellow River) channel shifts during the Holocene in the southern Bohai Sea

Two gravity cores collected off the modern Huanghe (Yellow River) delta in the southern Bohai Sea were analyzed for grain size, the total organic carbon (TOC)/total nitrogen (TN) ratio, color diffraction, magnetic susceptibility, ¹⁴C dating and ¹³⁷Cs and ²¹⁰Pb isotope contents to clarify changes in the sedimentary environment during the Holocene. In particular, the effect of natural and artificial river-course shifts of the Huanghe on the Bohai Sea sediment was investigated. A peat layer, scouring surface and sharp changes in the grain size, TOC/TN ratio, sediment color (L^?, a^?) and magnetic susceptibility were identified and are likely to be due to the early-Holocene sea-level rise resulting in environmental changes from coastal to shelf environments in the Bohai Sea. After the sea level reached its maximum at 6-7 ka BP, the lateral shifts in the river course of the Huanghe formed 10 superlobes, and superlobe 7 (11-1048 AD) and superlobe 10 (1855-present) of the Huanghe delta affected the core sites. The northern site of BH-239 has been more affected by the Huanghe since the middle Holocene. Notably, in the superlobe 10 period, the reshaping of the northern Huanghe delta due to an artificial river-course shift from northward to eastward in 1976 (e.g., a∼10 km shoreline retreat due to coastal erosion) was recorded in the core sediments, particularly in terms of the TOC/TN ratio, sediment color (L^? and a^?) and magnetic susceptibility, owing to the huge sediment supply from coastal erosion of the former river mouth area.     

水温前兆台网观测井条件研究

从水温前兆台网的现状入手,对观测井的类型、条件、传感器的观测深度及观测部位的温度特征等条件进行了分析总结,发现不同的水温正常动态类型与观测条件密切相关,并对正常动态与观测条件的关系作了初步分析,研究表明,传感器应在离开含水层和温度波动最小的层位进行观测.最后分析了水温前兆观测仪器的安装方法与观测条件,进而说明观测层位可...