地球密度模型研究进展与热平衡估计

地球科学最新研究成果表明,地表物质运动与核幔边界的大规模能量交换过程密切相关,地球动力系统平均温度的演变具有由高到低的整体趋势。越来越多的证据表明,地球内部处于非绝热状态,正在持续进行的地球冷却过程将对地表环境产生重大影响。人类对地球内部热源的开发尽管可以使地表短时期迅速增强,但也造成地球内部长期加速变冷的严重后果。     

地铁变形监测中曲线拟合与自回归模型的综合应用

曲线拟合与自回归是变形监测数据分析的常用方法。本文首先给出曲线拟合和自回归模型的模型形式以及模型正确性的检验方法,然后结合广州某地铁的部分实际监测资料,综合使用两种模型进行变形曲线的拟合与分析,结果表明:该综合模型对变形数据的处理有着显著的优越性。     

Hydraulic modelling of subglacial tunnel channels,south‐east Alberta,Canada

One of the key issues associated with the hypothesis of catastrophic subglacial drainage of the Livingstone Lake event is whether flows of such large magnitudes are physically feasible. To explore this issue, a one‐dimensional hydraulic network flow model was developed to investigate the range of peak discharges and associated flow parameters that may have been carried by a tunnel channel network in south‐east Alberta, Canada. This tunnel channel network has been interpreted elsewhere to carry large discharges associated with subglacial meltwater flows because of the convex longitudinal profiles of individual channels. This computational modelling effort draws upon established and verified engineering principles and methods in its application to the hydraulics of this problem. Consequently, it represents a unique and independent approach to investigating the subglacial meltwater hypothesis. Based on the modelling results, it was determined that energy losses resulting from friction limit the maximum peak discharge that can be transported through the tunnel channel network to 10⁷ m³ s⁻¹, which is in reasonable agreement with previous estimates of flood discharges for proposed megafloods. Results show that flow through channels with convex longitudinal profiles occurs when hydraulic head exceeds 910 m (Lost River) and 950 m (Sage Creek) , respectively. These are considerably below the maximum head capable of driving flow through the system of 1360 m, beyond which ice is decoupled from the bed across the pre‐glacial drainage divide. Therefore, it is concluded that these model results support the hypothesis of catastrophic subglacial drainage during the Livingstone Lake event. Copyright © 2000 John Wiley & Sons, Ltd.     

联合不确定度的多期水深剖面分析方法及应用

单波束测深技术在近海及河口水深测量中被广泛应用,但受动态海洋环境的影响,很难有效获取不同时期同一位置的水深数据,这给快速变化的近海地形的准确对比与分析造成很大困难。针对该技术问题,本文提出了一种联合不确定度的多期水深剖面分析方法。通过初始不确定度计算、水深及不确定度传递、卡尔曼滤波更新等步骤构建时序地形剖面,并基于假设检验完成剖面地形演变分析。用两期次河口区单波束数据对算法进行了验证。结果表明,本文方法获取了可与实际地形剖面有效对比的水深剖面,并可对地形骤变区域作出准确评估,对于快速变化的河口水下三角洲尤其是航道区域的演变分析具有实际的应用价值。     

动态海面上方船舶六自由度运动仿真

在Fudide-Krylov假设条件下,依据船舶分离建模理论在固定和运动坐标系中计算海面船只六自由度运动数学模型。主要包括:对风、浪、流的单独建模并进行矢量叠加,并在风浪流联合作用下对船舶六自由度运动构建简化的数学建模,完成实时仿真。基于Simulink和V-Realm Builder虚拟现实技术创建船舶运动模型、海洋表面环境及船只的几何模型,对船舶六自由度运动进行视景仿真,给出了有风无浪、有浪无风和风浪兼有三种情况下船只旋回路径和船舶运动轨迹。在VR视景浏览器中创建动态海面上船舶六自由度运动模型,不仅易于实现且结果逼真。得到的结果为进一步研究动态船只目标声散射特性的精确预报提供基础。     

旅游建构城市群“乡土—生态”空间的理论框架及研究展望

城市群“乡土—生态”空间是国土空间的重要组成部分和城市群空间的有机组成部分,是城市群优化城乡空间结构、维持传统人文活动、传承地域历史文化、维系生态系统健康的战略空间。关注旅游建构城市群“乡土—生态”空间的过程、格局和机制对满足国家战略需求和旅游地理学科建设具有重要意义。系统梳理城市群空间、旅游发展影响、城市群“乡土—生态”空间基本属性等研究领域的相关成果,发现已有研究对城市群内部及周边的边缘地带关注不足,有待进一步探索和诠释新的功能地域空间;对旅游显著影响中国经济社会空间的事实关注不够,有待进一步强化旅游助推中国现代化经济体系建设、生态文明建设、优秀传统文化传承创新的典型“空间性”研究;对城市群“乡土—生态”空间的利用方式关注较少,有待进一步开展城乡空间利用和城乡关系演变研究。研究认为,以旅游作为新的产业路径、新的利用方式科学引导主体功能区规划落地,推动城市群“乡土—生态”空间转型升级,发挥旅游在城市群空间结构优化和城市群可持续发展过程中的作用是探索国土整治与国土空间优化中国特色道路的重要举措。在构建旅游建构城市群“乡土—生态”空间的“三阶段”理论假说的基础上,指出未来应该重点开展的研究内容：遵循“过程—格局—机制—效应”的研究路线,探讨旅游建构城市群“乡土—生态”空间的实践路径,提出旅游建构城市群“乡土—生态”空间的政策保障体系研究的技术路径,探索旅游建构城市群“乡土—生态”空间在不同尺度空间上的一般特征和规律。     

Particulate organic matter and ballast fluxes measured using time-series and settling velocity sediment traps in the northwestern Mediterranean Sea

Prompted by recent data analyses suggesting that the flux of particulate organic carbon sinking into deep waters is determined by fluxes of mineral ballasts, we undertook a study of the relationships among organic matter (OM), calcium carbonate, opal, lithogenic material, and excess aluminum fluxes as part of the MedFlux project. We measured fluxes of particulate components during Spring and Summer of 2003, and Spring of 2005, using a swimmer-excluding sediment trap design capable of measuring fluxes both in a time-series (TS) mode and in a configuration for obtaining particle settling velocity (SV) profiles. On the basis of these studies, we suggest that distinct OM–ballast associations observed in particles sinking at a depth of 200 m imply that the mechanistic basis of the organic matter–ballast association is set in the upper water column above the Twilight Zone, and that the importance of different ballast types follows the seasonal succession of phytoplankton. As in other studies, carbonate appears to enhance the flux of organic matter over opal. Particles must be at least half organic matter before their settling velocity is affected by ballast concentration. This lack of change in ballast composition with SV in particles with <40% OM content suggests that particle SV reaches a maximum because of the increasing importance of inertial drag. Relative amounts of OM and opal decrease with depth due to decomposition and dissolution; carbonates and lithogenic material contribute about the same amount to total mass, or increase slightly, throughout the water column. The high proportion of excess Al cannot be explained by its incorporation into diatom opal or reverse weathering, so Al is most likely adsorbed to particulate oxides. On shorter time scales, dust appears to increase particle flux through its role in aggregation rather than by nutrient inputs enhancing productivity. We suggest that the role of dust as a catalyst in particle formation may be a central mechanism in flux formation in this region, particularly when zooplankton fecal pellet production is low.     

调和分析法应用于编制地壳垂直运动速率面等值线图的可靠性讨论

对有关文献提出的“地壳垂直运动调和分析”模型的建立过程作了全面分析 ,指出 :该模型建立过程中所做的一些处理是不合理的 ,由此建立的模型不是地壳垂直运动规律的客观反映 ,因而尚不足以成为编制地壳垂直运动速率面等值线图的可靠手段。     

论鸟类飞行起源的“树栖”与“地栖”假说之争

简要介绍了鸟类飞行起源的2种假说:"树栖起源"假说与"地栖起源"假说。详细讨论了2种假说的理论支撑点及存在的问题,认为鸟类的祖先和原始鸟类可以借助自然界中任何有利的地形和地物来帮助滑翔和起飞,而不是仅仅依赖直立高大的树木。"地栖起源"假说更合乎情理,也更接近或更符合客观事实,同时提出了"地栖起源"假说的新模式图。     

昆明市县区收入差距的时空演进及其成因分析

以昆明市各县区为研究单位,对收入差距问题作了实证分析。采用统计法和建立绝对β-收敛模型测度了县区收入差距,描述其时序过程和空间演替特征;利用Theil指标法揭示区域差距的构成与来源,并运用回归法探讨其影响因素。结论证实,昆明市区域差异演进并没有偏离收敛性假说:县区收入差距以2003年为拐点呈阶段性律动,总体差距趋小而梯度间差距和城乡间差距深化,社会消费、储蓄、财政支出是其影响因素,而普遍认为有促进作用的市场因素在概念模型分析中却不显著。为此,发挥市场力量势在必行。