Visualizing Patterns of Genetic Landscapes and Species Distribution of Taxus wallichiana (Taxaceae), Based on GIS and Ecological Niche Models

The Chinese yew (Taxus wallichiana), which is widely distributed in the Himalayas and in southern China, is now on the edge of extinction. In order to understand the evolutionary processes that control the current diversity within this species at the genetic and ecological levels, its genetic patterns and range dynamics must first be identified and mapped. This knowledge can then be applied in the development of an effective conservation strategy. Based on molecular data obtained from 48 populations of T. wallichiana, we used GIS-based interpolation approach for the explicit visualization of patterns of genetic divergence and diversity, and a number of potential evolutionary hotspots have been specifically identified within the genetic landscape maps. Within the maps of genetic divergence and diversity, five areas of high inter-population genetic divergence and six areas of high intra-population genetic diversity have been highlighted in a number of separate mountain regions, and these evolutionary hotspots should have the priority to be protected. Furthermore, four geographical barriers have been identified: the eastern Himalayas, the Yunnan Plateau, the Hengduan Mountains and the Taiwan Strait. According to ecological niche modeling (ENM), the populations of T. wallichiana within the Sino-Himalayan Forest floristic subkingdom experienced westward expansion from the periods of Last Inter-glacial to Last Glacial Maximum (LGM). Following the LGM, the distribution range overall became reduced and fragmented. These findings challenge the classic mode of contraction-expansion in response to the last glaciation. In conclusion, our findings suggest that the changes in geographical landscapes and climate that occurred during the Quaternary resulted in current genetic landscape patterns.     

3D GIS支持下的盐腔三维表面拓扑重建技术研究

在分析了盐岩特性和盐腔作为地下能源储备库等应用可行性和重要性的基础上,详细阐述了利用声纳探测技术进行盐腔测量的原理及测腔数据的组织方式。利用HalfEdge数据结构和边界表示模型,对声纳测腔数据进行了盐腔三维表面拓扑重建技术的研究。并对构建的表面模型进行了有效性检查和可能存在的缺陷进行了修复,得到了正确、有效的盐腔三维表面模型,为盐腔的稳定性分析、蠕变特性分析等数值模拟过程,提供了有效的数据基础。该方法具有重要的经济意义和社会意义,可以为盐腔的建造,尤其是安全合理地利用盐腔提供科学依据和技术支持。     

一种大规模倾斜摄影模型三维可视化方案

提出了一种基于四叉树结构的大规模倾斜摄影模型三维可视化方案：首先采用二次误差测度（QEM）的半边折叠算法对三角网格模型进行分层几何简化;然后对分层简化的模型进行纹理映射和分块,分块结果采用Morton编码命名;最后将场景按金字塔结构进行LOD（多细节层次结构）组织。选取某一试验区域的真实倾斜模型数据进行了试验,结果表明,该方案能依据模型在计算机屏幕上所占的像素大小,动态加载倾斜模型数据,完成大规模场景的实时可视化。     

Paleovalley-related uranium deposits in Australia and China: A review of geological and exploration models and methods

The features and similarities in the geology of paleovalley-related uranium mineralizing systems in Australia and China can be used to refine strategies for exploration. Paleovalley-related uranium resources include sandstone-, lignite- and calcrete-style deposits that are developed within the host sediments deposited in paleovalleys. The paleovalleys incise either crystalline bedrock or older sedimentary rocks, and uranium was deposited and concentrated by the influx of oxidized/reduced groundwaters flowing in aquifers within the paleovalley fill. The critical features of paleovalley-related uranium deposits include sediment and uranium sources, geological setting, depositional environment, age and relative timing of mineralization, aquifer characteristics, availability and distribution of reductants, and preservation potential of the uranium mineral system. This set of information provides a basis to establish the uranium mineralization model, which can then be used to assist with generating targets for uranium exploration and prospectivity analysis of a region. With respect to Sino-Australian examples, paleovalley-related uranium deposits form mostly around the margins of sedimentary basins and the mineralization is commonly hosted within channel fills contained within paleovalleys developed upon, or proximal to, Precambrian crystalline rocks that contain primary uranium sources. The deposits that have been well studied show remarkably similar factors that controlled the formation of paleovalley-related uranium deposits. Basement/bedrocks with above-background (2.8 ppm U) levels of uranium (10–100 ppm) that are linked to, and/or, incised by paleovalleys are associated with these deposits and are the inferred source of the uranium. In these regions, extensive fluvial systems developed particularly during Mesozoic and Cenozoic times, uranium from the bedrock was first dispersed into the sediments, and then concentrated to form deposits through successive chemical remobilization, precipitation and concentration. The deposits formed in continental or marginal marine environments, and commonly are associated with reduced lithologies, containing pyrite and dispersed organic matter and/or seams of lignite, or show evidence of infiltrated hydrocarbons. The mineralization is developed where oxidizing fluids (carrying dissolved U) reacted with reductants in the sediments. Geological, geophysical and geochemical features of the paleovalleys and related uranium deposits are used to construct models to understand host sediment distribution, fluid flow and ore genesis that can assist exploration for paleovalley-hosted uranium deposits. Precise geometric definition of the basin margin and paleovalley architecture is important in identifying exploration targets and improving the effectiveness of drilling. Refinements in remote sensing, geophysical and data processing techniques, in combination with sedimentological and depositional interpretations, provide an efficient approach for outlining the principal drainage patterns and channel dimensions. To help reduce risk, an exploration strategy should combine these technologies with a detailed understanding of the physicochemical parameters controlling uranium mobilization, precipitation and preservation.     

Development and testing of a physically based,three-dimensional model of surface and subsurface hydrology

We present a numerical, catchment-scale model that solves flow equations of surface and subsurface flow in a three-dimensional domain. Surface flow is described by the two-dimensional parabolic approximation of the St. Venant equation, using Manning’s equation of motion; subsurface flow is described by the three-dimensional Richards’ equation for the unsaturated zone and by three-dimensional Darcy’s law for the saturated zone, using an integrated finite difference formulation. The hydrological component is a dynamic link library implemented within a comprehensive model which simulates surface energy, radiation budget, snow melt, potential evapotranspiration, plant development and plant water uptake. We tested the model by comparing distributed and integrated three-dimensional simulated and observed perched water depth (PWD), stream flow data, and soil water contents for a small catchment. Additional tests were performed for the snow melting algorithm as well as the different hydrological processes involved. The model successfully described the water balance and its components as evidenced by good agreement between measured and modelled data.     

大质量X射线双星脉冲星4U 1901+03的脉冲轮廓研究

大质量X射线双星脉冲星4U 1901 03在沉寂30多年后,于2003年1月爆发.利用罗西X射线时变探索者卫星RXTE为期5个月的观测数据,对其脉冲轮廓进行了系统研究,得到了该源的脉冲轮廓演化以及能量相关性,脉冲比例演化和脉冲比例对能量的依赖关系.研究发现,4U 1901 03的脉冲轮廓和脉冲比例随双星系统的吸积率变化呈现阶段性的演化,脉冲比例在十几keV处达到峰值.这些脉冲轮廓的复杂变化表明,脉冲轮廓不能用单一的几何或物理模型解释,而是与观测角度以及X射线源的辐射机制相关.利用标准的脉冲星辐射模型讨论了4U 1901 03脉冲轮廓的观测现象.     

Performance of operational systems with respect to water level forecasts in the Gulf of Finland

This paper is devoted to the validation of water level forecasts in the Gulf of Finland. Daily forecasts produced by four setups of operational, three-dimensional Baltic Sea oceanographic models are analyzed using statistical means and are compared with water level observations at three Finnish stations located on the northern coast of the Gulf of Finland. The overall conclusion is that the operational systems were skillful in forecasting water level variations during the study period from November 1, 2003, to January 31, 2005. The factors causing differences between the water level forecasts of different models are discussed as well. An important task of operational sea level forecasting services is to provide accurate and early information about extreme water levels, both positive and negative surges. During the study period, two major winter storms occurred which caused coastal flooding in the region. According to our analysis, the operational models forecast the rise of water levels during these events rather successfully. Nowadays, operational forecasts can provide early warnings of extreme water levels at least 1 day in advance, which may be regarded as a minimum requirement for an operational forecasting system. The paper concludes that the models generally performed very well, with over 93% of the hourly water level forecasts found to be within the range of ±15 cm of the observed water levels, and with the timing of the water level peaks accurately predicted. Further discussion and studies dealing with the assessment of the skills of both operational meteorological and oceanographic forecasts, especially in connection with rare surge events, will be necessary. Skill assessment of operational oceanographic models would be relatively easy if acceptable error limits or a quality system was developed for the Baltic Sea operational models.     

CMIP5模式对ENSO现象的模拟能力评估

针对参与耦合模式比较计划(CMIP5)的17个海-气耦合模式对20世纪气候的模拟结果,从热带太平洋海表温度和大气海平面气压变化的综合分析角度较详细评估了模式对厄尔尼诺-南方涛动(ENSO)现象的模拟能力。结果表明,这些模式基本上能模拟出ENSO现象的一些主要特征,包括热带太平洋海温的空间分布及其时空演变特征、与海平面气压变化的关联、ENSO周期变化及锁相特征等,但不同模式的模拟结果仍然差异较大。(1)从模拟的热带太平洋年平均海温的偏差来看,多模式集合平均值与观测的均方根误差小于1.0℃,但单个模式的误差相对要大一些。误差较小的为1.2—1.3℃,多数模式在1.6℃以下,但也有个别模式的误差超过2.0℃。(2)从经验正交函数分解结果来看,热带太平洋实测月平均海表温度距平和海平面气压距平的年际尺度变化第1模态主要表现为ENSO变化特征,第2模态反映的是海温的长期变化趋势。只有少数几个CMIP5模式能够再现这种特征,多数模式所模拟的海温距平/海平面气压距平时空变化的第1、第2特征向量分布顺序与观测分析正好相反,ENSO变成了第2模态,趋势成了最主要的模态。尽管如此,所有模式都能模拟出南方涛动变化与热带太平洋海温距平时空变化的密切关联,无论是作为第1还是第2特征模态,所有模式模拟的南方涛动与热带太平洋海温距平时空变化都有密切相关。(3)谱分析结果表明,ENSO现象具有2—7年的周期,其中,4年的周期最明显。大多数模式模拟的ENSO周期在此范围内,但有些模式的主要周期偏短,为2年左右。个别模式的ENSO主要周期为11年,已超出2—7年的范围。(4)多数模式模拟的厄尔尼诺及拉尼娜的峰值出现在冬季(11—2月),与观测基本吻合。另有少数模式模拟的峰值出现在9—10月,比观测略提前。只有个别模式模拟的峰值出现在夏季,与观测相差太大。     

面向对象高分遥感影像典型自然地物半自动提取

针对目前高空间分辨率遥感影像(简称高分遥感影像)地物全自动提取无法完全实现的现实,本文结合自然地物的光谱和纹理特征,提出一种面向对象的高分遥感影像典型自然地物半自动提取方法.首先构建最小生成树(Minimum Spanning Tree,MST)进行影像初始分割,根据影像灰度平均归一化值和标准差统计对象的光谱、纹理等特...     

Efficient multivariable submarine depth-control system design

An efficient solution for the multivariable submarine control design at low-depth conditions under the influence of wave disturbances is presented. The analysis and control design process is carried out under the framework of individual channel analysis and design (ICAD), which is based on the multivariable structure function (MSF). Classical frequency-domain control techniques based on Bode and Nyquist plots are used. Robustness is stated in terms of gain and phase margins. The closed-loop system includes low-order diagonal controllers facilitating its implementation, assessment, and tuning. ICAD discloses new physical insights of the submarine dynamical behaviour. Previous designs based on diagonal controllers consider the input–output channels defined by pairing the bow hydroplane angle with the depth and the stern hydroplane angle with the pitch angle. The alternative input–output pairing leads to unstable closed-loop systems. This phenomenon is associated with hydroplane reverse control. Here it is shown that MSF-based diagonal controllers can be applied effectively for both sets of channel configurations. Emphasis is placed on satisfying design specifications aiming at maintaining the depth low. The solution presented is more feasible and clearer to apply in practice than those so far reported in the literature.