布达拉宫旅游商业化的社区治理研究

以社区为出发点,综合旅游商业化、社区治理等相关理论,在布达拉宫及周边社区旅游商业化表征分类的基础上,梳理其社区旅游商业化的治理成效及治理困境。再运用静态博弈模型与决策树,分析布达拉宫及周边社区旅游商业化的治理中各利益主体博弈的过程,并探析治理困境的原因。研究发现,旅游商业化的社区治理受到各利益主体间权力大小和利益选择的影响。政府及相关部门处于强势地位,主导并采取措施治理旅游商业化。布达拉宫的各空间圈层在商业化治理过程和难度上都存在明显差异。引起治理困境的原因主要是“权”与“利”的纠葛、商业化控制的阈限不清晰、利益主体之间的沟通不畅。在主要利益相关者的博弈中,各治理主体共同重构一个相对均衡的“利益－权力”关系结构,以保证社区旅游商业化得以有效治理。     

中国县域乡村地域多功能格局及影响因素识别

论文以中国大陆县域为研究单元,构建乡村地域多功能评价指标体系,利用熵权法、半变异函数和地理探测器等模型,对2000—2015年中国乡村多功能指数进行综合测评,揭示中国县域乡村地域多功能的空间分异特征,定量识别乡村地域多功能空间分异的影响因素。研究结果表明：① 中国乡村地域多功能在空间上呈现出平原、东部沿海等地区高值集聚,高原、山地等地区低值集聚,各县域乡村地域多功能整体呈现出逐渐提升态势;② 经济发展功能和社会保障功能对乡村地域多功能的贡献率逐渐增大,农业生产功能和生态保育功能对乡村地域多功能的贡献率逐渐减小;③ 2000—2015年,中国大陆范围内县域乡村地域多功能空间自相关范围和强度总体呈现减小的趋势,随机性因子成为乡村地域多功能空间分异的主要驱动力;④ 县域经济整体发展水平和财政收入是影响乡村地域多功能空间分异的主导因素;各影响因素之间的两两交互作用会增强乡村地域多功能的空间分异;社会环境因素对乡村地域多功能空间分异的影响程度逐渐上升,自然环境因素的影响程度逐渐下降。     

基于DEM分形特征的坡度尺度变换模型

利用DEM提取坡度具有明显的尺度依赖性,探求DEM在不同尺度下表现出的规律关系,建立多尺度变换模型,以实现不同尺度间的转换是地形分析研究的热点和难点。本文阐释了DEM表面与地表粗糙度分形维数值的地学意义及内在关系,并利用分形对象的自相似性原理,建立了一种基于DEM分形特征的坡度尺度变换模型。选取四川丘陵地区某小流域为研究区,进行坡度尺度变换实验和误差分析,结果表明该模型能有效实现坡度尺度变换:在非平坦地区(坡度>1°)一般重采样方法变换得到的坡度误差为该方法的1.86倍;从信息熵理论分析,经该方法转换后的坡度信息得到了显著恢复。对于无1︰1万及以上精度地形数据的西南山区,利用该方法获取高精度坡度数据具有重要的理论价值和现实意义。     

Predictability of Chinese Summer Extreme Rainfall Based on Arctic Sea Ice and Tropical Sea Surface Temperature

Chinese summer extreme rainfall often brings huge economic losses, so the prediction of summer extreme rainfall is necessary. This study focuses on the predictability of the leading mode of Chinese summer extreme rainfall from empirical orthogonal function(EOF) analysis. The predictors used in this study are Arctic sea ice concentration(ASIC) and regional sea surface temperature(SST) in selected optimal time periods. The most important role that Arctic sea ice(ASI) plays in the appearance of EOF1 may be strengthening the high pressure over North China, thereby preventing water vapor from going north. The contribution of SST is mainly at low latitudes and characterized by a significant cyclone anomaly over South China. The forecast models using predictor ASIC(PA), SST(PS), and the two together(PAS) are established by using data from 1980 to 2004. An independent forecast is made for the last 11 years(2005-2015). The correlation coefficient(COR) skills between the observed and cross-validation reforecast principal components(PC) of the PA, PS, and PAS models are 0.47, 0.66, and 0.76, respectively. These values indicate that SST is a major cause of Chinese summer extreme rainfall during 1980-2004. The COR skill of the PA model during the independent forecast period of 2004-2015 is 0.7, which is significantly higher than those of the PS and PAS models. Thus, the main factor influencing Chinese summer extreme rainfall in recent years has changed from low latitudes to high latitudes. The impact of ASI on Chinese summer extreme rainfall is becoming increasingly significant.     

Case Study of Fog Predictability for an Event with Cold-Front Synoptic Pattern

Fog has recently become a frequent high-impact weather phenomenon along the coastal regions of North China. Accurate fog forecasting remains challenging due to limited understanding of the predictability and mechanism of fog formation associated with synoptic-scale circulation. One frequent synoptic pattern of fog formation in this area is associated with cold front passage(cold-front synoptic pattern, CFSP). This paper explored the predictability of a typical CFSP fog event from the perspective of analyzing key characteristics of synoptic-scale circulation determining fog forecasting performance and the possible mechanism. The event was ensemble forecasted with the Weather Research and Forecasting model. Two groups of ensemble members with good and bad forecasting performance were selected and composited. Results showed that the predictability of this case was largely determined by the simulated strengths of the cold-front circulation(i.e., trough and ridge and the associated surface high). The bad-performing members tended to have a weaker ridge behind a stronger trough, and associated higher pressure over land and a weaker surface high over the sea, leading to an adverse impact on strength and direction of steering flows that inhibit warm moist advection and enhance cold dry advection transported to the focus region. Associated with this cold dry advection, adverse synoptic conditions of stratification and moisture for fog formation were produced, consequently causing failure of fog forecasting in the focus region. This study highlights the importance of accurate synoptic-scale information for improved CFSP fog forecasting, and enhances understanding of fog predictability from perspective of synoptic-scale circulation.     

Dynamic hydraulic jump and retrograde sedimentation in an open channel induced by sediment supply: experimental study and SPH simulation

Mountainous torrents often carry large amounts of loose materials into the rivers, thus causing strong sediment transport. Experimentally it was found for the first time that when the intensive sediment motion occurs downstream over a gentle slope, the siltation of the riverbed is induced and the sediment particles can move upstream rapidly in the form of a retrograde sand wave, resulting in a higher water level along the river. To further study the complex mechanisms of this problem, a sediment mass model in the framework of the Smoothed Particle Hydrodynamics(SPH) method was presented to simulate the riverbed evolution, sediment particle motion, and the generation and development of dynamic hydraulic jump under the condition of sufficient sediment supply over a steep slope with varying angles. Because the sediment is not a continuous medium, the marker particle tracking approach was proposed to represent a piece of sediment with a marked sediment particle. The twophase SPH model realizes the interaction between the sediment and fluid by moving the bed boundary particles up and down, so it can reasonably treat the fluid-sediment interfaces with high CPU efficiency. The critical triggering condition of sediment motion, the propagation of the hydraulic jump and the initial siltation position were all systematically studied. The experimental and numerical results revealed the extra disastrous sediment effect in a mountainous flood. The findings will be useful references to the disaster prevention and mitigation in mountainous rivers.     

Assessing effects of “source-sink” landscape on non-point source pollution based on cell units of a small agricultural catchment

Ascertaining the relationship between "source-sink" landscape and non-point source(NPS) pollution is crucial for reducing NPS pollution, however, it is not easy to realize this target on cell unit scale. To reveal the relationships between "sourcesink" landscape and NPS pollution based on cell units of a small catchment in the Three Gorges Reservoir Region(TGRR), the runoff and nutrient yields were simulated first by rainfall events on a cell unit scale based on the Annualized AGricultural Non-Point Source Pollution Model(AnnAGNPS). Landscape structure and pattern were quantified with "sourcesink" landscape indicators based on cell units including landscape area indices and locationweighted landscape indices. The results showed that:the study case of small Wangjiagou catchment highlighted a good prediction capability of runoff and nutrient export by the AnnAGNPS model. Throughout the catchment, the spatial distribution trends of four location-weighted landscape indices were similar to the trends of simulated total nitrogen(TN) and total phosphorus(TP), which highlighted the importance of spatial arrangement of "source" and "sink" landscape types in a catchment when estimating pollutant loads. Results by Pearson correlation analysis indicated that the location-weighted landscape index provided a more comprehensive account of multiple factors, and can better reflect NPS-related nutrient loss than other landscape indices applied in single-factor analysis. This study provides new findings for applying the "source-sink" landscape indices based on cell units in small catchments to explain the effect of "source-sink" landscape on nutrient export based on cell unit, and helps improve the understanding of the correlation between "source-sink" landscape and NPS pollution.     

基于拓扑关系的BIM室内封闭空间边界建筑要素搜索方法研究

BIM作为工程建设领域的热门新兴技术,包含建筑物全生命周期内的各种数字化信息,但其对要素间空间关系的描述限于建筑领域的专业性表达,以及建模过程中的预定义。基于BIM数据的几何-语义特点,提出一种自动化构建BIM建筑要素拓扑关系的方法,并以此为基础搜索室内封闭空间的边界建筑要素,得到以建筑要素为单元的室内空间划分;以整层建筑物空间作为实验数据,通过实验结果验证了算法的准确性,实现BIM室内三维空间分割,为基于BIM的空间分析提供数据支撑。     

鄂尔多斯盆地前寒武纪末期古地貌恢复及其对烃源岩的控制作用

鄂尔多斯盆地前寒武纪末期古地貌控制着后期沉积体系的空间配置与古地理展布。通过野外剖面、岩芯分析、测井数据等建立鄂尔多斯盆地寒武系层序地层格架;选取寒武纪SS1最大海泛面(徐庄组沉积晚期地层)为标志层,通过残余厚度印模法,并结合古地质图分析,对研究区前寒武纪进行古地貌恢复,明确了前寒武纪沉积背景、构造格局及物源方向。总体上,前寒武纪鄂尔多斯盆地南、北濒临秦祁海和兴蒙海,东、西被贺兰和晋豫陕坳拉槽所夹持,古地貌东北高、西南低,受秦祁海影响最大,可将其划分为3个古构造地貌单元:高地剥蚀区、受古构造控制形成的坳陷区以及处于剥蚀与沉积过渡地带的斜坡阶地区。通过研究前寒武纪末期古地貌与寒武纪早期烃源岩分布认为,拉张活动背景下的坳陷带以及斜坡带是鄂尔多斯盆地寒武纪早期烃源岩发育的有利区块,前寒武纪古地貌格局影响了寒武纪早期烃源岩发育与分布。恢复古地貌形态对于揭示物源供给,研究沉积物搬运、平面和纵向展布特征,探究沉积、沉降中心的迁移规律,以及进一步揭示生储盖组合和分布具有重大意义。     

内含裂隙角的恐龙化石轴向受压数值试验及裂纹扩展机理研究

面临众多古生物化石遭受风化破坏的现实,恐龙化石保护是一项世界性难题。化石的风化原因多种多样,其中化石内部裂隙是导致恐龙化石风化、破坏的重要因素。该文以岩石断裂力学为理论依据,模拟分析内含裂隙的恐龙化石在压力作用下的破坏情况。通过数值模拟的方法,进行了内含裂隙恐龙化石数值压缩试验,并对内含裂隙的恐龙化石裂纹扩展机理进行了研究。研究结果表明,随着裂隙角度增大,开裂角逐渐减小,裂隙处特别是两端应力集中,其他部位应力较低、分布均匀;裂纹扩展是从裂纹尖端起裂,最终裂纹扩展到边缘。此研究结果为揭示恐龙化石风化机理和开展保护提供了基础参考资料。