The one-point PDF of the initial conditions of our local Universe from the IRAS PSC redshift catalogue

The algorithm ztrace of Monaco & Efstathiou is applied to the IRAS PSCz catalogue to reconstruct the initial conditions of our local Universe with a resolution down to ~5  h ¹ Mpc. The one-point probability distribution function (PDF) of the reconstructed initial conditions is consistent with the assumptions that: (i) IRAS galaxies trace mass on scales of ~5  h ¹ Mpc and (ii) the statistics of the primordial density fluctuations are Gaussian. We use simulated PSCz catalogues, constructed from N -body simulations with Gaussian initial conditions, to show that local non-linear bias can cause the recovered initial PDF (assuming no bias) to be non-Gaussian. However, for plausible bias models, the distortions of the recovered PDF would be difficult to detect using the volume finely sampled by the PSCz catalogue. So, for Gaussian initial conditions, a range of bias models remain compatible with our PSCz reconstruction results.     

An Empirical Method to Make Oil Production Models Tolerant to Anomalies

Modeling oil production is of interest to society and hotly debated. Often anomalies have occurred which makes modeling oil production via a particular theory (e.g., Hubbert’s bell curve) difficult. The empirical method described here allows for such historic anomalies to be incorporated while still using the underly theory. This method is explained using Hubbert’s bell curve and Former Soviet Union oil production as an example.     

基于CPT资料的土性参数随机场特性研究

通过CPT资料研究土性参数随机场特性是一种比较理想的方法。土性参数随机场的平稳性是后续研究的先决条件之一,可以通过Bartlett统计量进行检验,但采用不同的模型拒绝域相差比较大,这样给实际应用造成困难,新模型LGS由于适应范围广可以解决这一问题。从随机场的基本理论出发,介绍了新相关模型LGS的数值模拟方法。基于LGS相关模型,采用修正的Bartlett统计量对随机场平稳性进行检验,统一了拒绝标准。用两组数据进行了实例分析,通过编制的程序进行计算,结果表明,这种相关模型对不同形式的相关函数有较好的适应性,可以解决拒绝域不统一的问题。     

利用探索式空间数据解析北京城市空间经济发展模式

城市经济空间结构是城市研究和城市规划基本内容之一。利用其探索式空间数据分析方法,根据1949-2004年企业登记就业数据在邮政区尺度上对北京市1949年以来城市空间经济发展进行了探讨。基于空间邻近矩阵和不同距离矩阵的Global Moran'sI和Local Moran'sI都表明解放后市区并没有明显的经济集聚,50多年来空间经济发展模式几乎都是以市区为核心集聚式发展;尽管郊区一些重要乡镇呈现出发展势头,但几乎没有和周边地区形成互动关系,而是和市中心或其它地区保持较强的联系。分析还表明,北京地区经济的空间相互作用在计划经济时代大体在60km以内,市场经济时代(1983-2002年)提高到75km。北京经济空间模式经历了以下6个阶段:①1957-1982年,中心集中发展;②1983-1987年,沿京津廊道空间组织;③1988-1992年,北部为主的城市中心发展;④1993-1997年,城市中心集中扩张模式;⑤1998-2002年,城市中心填充发展;⑥2002-2004年,出现了城市空心化结构态势,空间经济组织面临新一轮重组。     

Diagnostic study and modeling of the annual positive water temperature onset

A data-driven model is designed using artificial neural networks (ANN) to predict the average onset for the annual water temperature cycle of North-American streams. The data base is composed of daily water temperature time series recorded at 48 hydrometric stations in Québec (Canada) and northern US, as well as the geographic and physiographic variables extracted from the 48 associated drainage basins. The impact of individual and combined drainage area characteristics on the stream annual temperature cycle starting date is investigated by testing different combinations of input variables. The best model allows to predict the average temperature onset for a site, given its geographical coordinates and vegetation and lake coverage characteristics, with a root mean square error (RMSE) of 5.6 days. The best ANN model was compared favourably with parametric approaches.     

The amphipod Orchomenella pinguis – A potential bioindicator for contamination in the Arctic

Indigenous organisms can be used as bioindicators for effects of contaminants, but no such bioindicator has been established for Arctic areas. Orchomenella pinguis is a benthic amphipod, ubiquitous in the Arctic and can be found in high numbers. We collected O. pinguis at sites with different contamination levels. Population characteristics (body length distribution, average dry weight and amphipod organic content) were related to sediment contaminant concentrations, in order to identify suitable endpoints for using this species as a bioindicator. We show that O. pinguis was prevalent in both clean and contaminated areas, easy to sample and that its population characteristics could be linked to both contamination and sediment organic content. We suggest that O. pinguis is a suitable bioindicator for the Arctic, but that endpoints such as reproductive effects and phenotypic and genotypic responses are needed together with population characteristics to assess impacts of contamination.     

A Bayesian hierarchical modeling approach for analyzing observational data from marine ecological studies

We introduce the Bayesian hierarchical modeling approach for analyzing observational data from marine ecological studies using a data set intended for inference on the effects of bottom-water hypoxia on macrobenthic communities in the northern Gulf of Mexico off the coast of Louisiana, USA. We illustrate (1) the process of developing a model, (2) the use of the hierarchical model results for statistical inference through innovative graphical presentation, and (3) a comparison to the conventional linear modeling approach (ANOVA). Our results indicate that the Bayesian hierarchical approach is better able to detect a “treatment” effect than classical ANOVA while avoiding several arbitrary assumptions necessary for linear models, and is also more easily interpreted when presented graphically. These results suggest that the hierarchical modeling approach is a better alternative than conventional linear models and should be considered for the analysis of observational field data from marine systems.     

GPS RTK技术在全野外数字化地形图测绘中的应用

主要介绍了RTK技术在地形图图根测量、碎部测量中的可行性和操作步骤及注意事项;并详细分析了该方法的测量精度。     

基于最大顺序统计量的P波初动极性自动读取方法的小震震源机制反演及在云南小江地区的应用研究

地震P波震相到时与初动极性的精确读取是地震资料分析处理的重要步骤之一.本研究采用了一种新的高精度自动确定地震波P波震相到时与初动极性的概率分布的方法(POI方法,后同),在此基础上研究开发了一套自动化小震震源机制解的反演流程,并将其应用在云南小江断裂带周边区域的小震震源机制和构造应力场反演中.得到的震源机制与应力场反演结果与前人的研究一致,且与区域GPS观测结果和构造背景吻合度较好,显示该方法具有良好的应用前景,为高效分析密集台阵地震观测资料,开展小震震源参数测量与区域应力场反演提供了新的研究思路和技术手段.