高位滑坡的运动转化形式

高位滑坡剪出口高于坡脚,它一旦滑离滑坡发生区,运动可能转化成四种形式:1.崩塌:由滑体经分级解体滑过剪出口处依次向前倾倒而成;2.碎屑流动或3.碎屑滑动:由滑动块体经碎屑化而成;4.泥石流:在适当的细粒物质量和水体条件下生成的碎屑流动。     

区域交通网络分形的DBM特征--交通网络Laplacian分形性质的实证研究

城镇体系在理论状态下的三角点阵格局暗示着现实中的交通网络在一定时空条件下具有ＤＢＭ模型的某些特征。从形态分析和维数对比两个方面论证了区域交通网络扔Ｌａｐｌａｃｉａｎ分形性质,认为可用ＤＢＭ模型模拟城镇体系－交通网络的形成和演化过程,从而揭示其动力学机制。     

榆林蟒坑滩的自然资源合理利用及沙漠化土地整治意见

本文对榆林地区沙化的一般规律进行了叙述,提出当地现代沙漠化的主要表现形式是固定和半固定沙丘的活化;提出了恢复沙地植被和生产力的设想.对滩地进行了成因划分,对湖沼洼地型滩地的生产条件作了重点分析,初步计算了蟒坑滩的地下水资源,提出为了改变滩地沼泽土"冷板田"土壤水分潴积的状况,应当充分利用滩区丰富的地下水,井灌井排。对蟒坑沙漠化土地的治理和滩地的合理利用也提出了比较切合实际的意见,可供生产部门参考。     

基于居民认知视角的小城镇群网化影响因素分析——以常州市为例

伴随着市场经济的发展,小城镇群网化对区域间要素流动和城乡一体化发展的重要性逐渐显现。利用2011年7月对常州市小城镇镇区常住居民的随机抽样调查数据,对调查样本和居民认知情况进行了统计分析;运用累积Logistic模型,分析了居民认知视角下小城镇群网化发展的影响因素。结果显示:居民出行交通方式、居民月消费水平、保障房制度、产业发展和集贸市场的健全程度5个因素对小城镇群网化发展影响显著,并反映出市民对小城镇群网化发展具有强烈的主观诉求,但促进小城镇群网化发展的政策供给存在不足。最后提出了促进常州市小城镇群网化发展的具体建议。     

DUST FALL IN THE TAKLA MAKAN DESERT OF CHINA

The Takla Makan Desert is one of the supposed sources of eolian deposits in the eastern China and the North Pacific Ocean. Lack of direct measurements hinders the theoretical interpretation of material exchange between the atmosphere and land surface as well as the sediment budget of the region. From 1992 to 1994, four measuring sites were established in the vicinity of 84°E meridian along a 380 km observation traverse from the northern margin to the central desert. Data were collected on quantities of dust fall and sedimentary characteristics of airborne sediments, including grain-size distributions as well as chemical and mineral compositions. The quantities of annual dust fall were 10² to 10³ tons km^-2 yr^-1, increasing from the margin toward the central desert. Monthly concentrations of particles finer than 0.02 mm in diameter ranged from 0.06 to 1.25 mg m^-3 over the three-year observation period. The elemental ratio and the element enrichment factor ruled out the Takla Makan Desert as possible sources of the dust in Hawaii and Alaska. The mean geometric diameter of airborne sediments in the 4 to 8 m surface layer from the Luntai oasis was 0.038 mm and from the interior ranged 0.064 to 0.067 mm being moderately to poorly sorted. Weight percent of particles finer than 0.063 mm in diameter were from 83.5% to 47.7%, decreasing toward the central desert. Distributions of the airborne particles were unimodal with peak diameters of 0.06 to 0.07 mm in the central desert and 0.02 to 0.06 mm in the sites toward the edge of the desert. [Key words: dust fall, sedimentary characteristics, Takla Makan Desert.]     

Extended FRAG-BASE schema-matching method for multi-version open GIS Web services retrieval

The OGC Web Service (OWS) schemas have the characteristics of a complex element structure, are distributed and large scale, have differences in element naming, and are available in different versions. Applying conventional matching approaches may lead to not only poor quality, but also bad performance. In this article, the OWS schema file decomposition, fragment presentation, fragment identification, fragment element match, and combination of match results are developed based on the extended FRAG-BASE (fragment-based) schema-matching method. Different versions of Web Feature Service (WFS) and Web Coverage Service (WCS) schema-matching experiments show that the average recall of the extended FRAG-BASE matching for the schemas is above 80%, the average precision reaches 90%, the average overall achieves 85%, and the matching efficiency increases by 50% as compared with that of the COMA and CONTEXT matcher. The multi-version WFS retrieval under the Antarctic Spatial Data Infrastructure (AntSDI) data service environment demonstrates the feasibility and superiority of the extended FRAG-BASE method.     

A Voronoi neighborhood-based search heuristic for distance/capacity constrained very large vehicle routing problems

Local search heuristics for very large-scale vehicle routing problems (VRPs) have made remarkable advances in recent years. However, few local search heuristics have focused on the use of the spatial neighborhood in Voronoi diagrams to improve local searches. Based on the concept of a k-ring shaped Voronoi neighbor, we propose a Voronoi spatial neighborhood-based search heuristic and algorithm to solve very large-scale VRPs. In this algorithm, k-ring Voronoi neighbors of a customer are limited to building and updating local routings, and rearranging local routings with improper links. This algorithm was evaluated using four sets of benchmark tests for 200–8683 customers. Solutions were compared with specific examples in the literature, such as the one-depot VRP. This algorithm produced better solutions than some of the best-known benchmark VRP solutions and requires less computational time. The algorithm outperformed previous methods used to solve very large-scale, real-world distance constrained capacitated VRP.     

大城市边缘区农村居民点用地空间布局优化研究——对上海南汇地区的考察

大城市边缘区农村居民点用地存在用地粗放、布局散乱、难于规范管理等问题。以大城市边缘区农村居民点用地整理为契机,优化空间布局不仅有利于形成农村经济新增长点,还可促进农村居民点土地集约节约利用。在分析当地农村居民点用地现状及其分布状况的基础上,以典型地区——上海南汇地区为例,对其空间分布的随机性进行了检验,对农村居民点用地按标准偏差分类,并进一步按欧氏空间距离对大于2.25标准偏差的地块进行聚类分析。结果显示:南汇地区农村居民点用地的空间分布并不是随机分布,可分为远离中心类和集聚中心类两种类型。依据结果,提出了"远离中心方案"和"集聚中心方案"两种不同的农村居民点用地整理方案。     

Monitoring Mongolia Gobi dust transport using OMI data

The characteristics of long-distance dust transport from Asia to the United States over the Pacific Ocean are statistically analyzed using OMI AI (Ozone Monitoring Instrument Aerosol Index) data during 2005–2007. The results show that there is a high correlation of AI (the correlation coefficients are as high as 0.83 in March, 0.62 in April and 0.54 in May) between the Mongolia Gobi Desert and the west coast region of the United States (40°–50°N, 120°–130°W), indicating a strong source-receptor area relationship. Through calculating the lag correlation coefficient of the dust propagation time, we determined that the dust propagation time from the Mongolia Gobi Desert to the west coast of the United States is about 6–7 days at the 99% confidence level.     

The impact of land use change on quality evolution of soil genetic layers on the coastal plain of south Hangzhou Bay

Land use change plays an important part in the studies of global environmental change and regional sustainable development. The change of soil quality can particularly reflect the impacts of human socio-economic activities on environment. Taking the coastal plain of south Hangzhou Bay as a study case, we analyzed the effects of land use changes on organic matter (OM), total nitrogen (TN), total phosphorus (TP), available phosphorus (AP), available potassium (AK), total salinity (TS), pH value in soil genetic layers, and assessed soil quality change related to different land use types from 1982 to 2003. The results show that: (1) The general change tendency of soil quality in the coastal plain of south Hangzhou Bay declined obviously in A layer and slightly rise in B (or P) layer and C (or W) layer. The contents of TP decreased generally in all soil genetic layers, but the variety difference of other soil quality indices was relatively great. (2) The change of soil quality in the areas where land use changed is far more remarkable than that with land use unchanged. The value of quality variety is A layer >B (or P) layer >C (or W) layer. (3) The changes of soil tillage, cultivation, fertilization, irrigation and drainage activities related to land use may make some soil-forming processes disappeared and bring in other new processes which will affect the soil quality and soil genetic layers directly.