剖线强度梯度变化的作物软硬变化区精确划分

[目的]软硬变化区的划分是进行遥感变化检测技术识别农作物的基础。为解决人工判读方法中存在人为主观因素影响以及自动判别和交互式判别方法对不同研究区的适用性问题,该文提出基于剖线梯度变化(Profile based Gradient Change Magnitude,PGCM)进行软硬变化区划分的方法。[方法]该研究选择破碎农业景观种植区域为研究区,计算拔节期Quick Bird影像和播种期模拟影像两个时相的变化强度,从作物地块内部向外绘制剖线,利用剖线强度的梯度变化确定硬变化区(Hard change region,HCR)、软变化区(Soft change region,SCR)和未变化区(Non change region,NCR)3者间的划分阈值。[结果]从识别结果来看,PGCM能够有效在地块边界处探测到软变化像元,进而确定HCR、SCR。像元分辨率在5~60 m不同尺度下,识别HCR区混入比例为11%~16%,混入比例随着分辨率下降而降低;NCR区混入比例为3%~4%,受分辨率尺度影响不大;SCR区识别比例为74%~86%,识别精度较高,识别结果与冬小麦空间分布结果保持一致。[结论]PGCM方法能够自动、便捷地确定阈值,摆脱人工判定的主观性,有效地划分出HCR、SCR和NCR 3个区域,为进一步HCR、SCR区内的作物识别提供基础。     

Residential mobility and the local context: Comparing long-term and short-term spatial trends of population movements in Greece

Residential mobility is a key dimension of population dynamics shaping urban growth and rural development at different spatio-temporal scales. Assuming spatial mobility as increasingly dependent on the intrinsic characteristics of local contexts, the present study investigates long-term and short-term population movements in a European country (Greece), in light of regional urbanization processes and socioeconomic development. A multidimensional analysis of indicators of residential stability and background variables was carried out with the aim at evaluating the influence of local contexts on more general processes of population mobility. Different typologies of spatial mobility associated to factors (directly or indirectly) dependent on demographic dynamics, economic performances and urban cycles were identified. The empirical findings of this study evidence (more or less traditional) paths of internal migration and a latent process of population relocation across metropolitan regions, together with more recent international migrations at both working and retirement age. While short-range population movements were the ultimate result of late suburbanization in Greece, medium- and broad-range mobility consolidated the country's divide in urban and rural areas, evidencing the attractive role of Athens. Spatial direction and intensity of population movements reflect complex socioeconomic transformations, whose knowledge provides innovative visions for a better understanding of future demographic dynamics in Mediterranean Europe.     

激电中梯和激电测深在寻找铜锌多金属矿中的应用

目前在多金属矿床勘查的物探方法中,激电中梯和激电测深是一种最有效的物探方法之一,在分析勘查区的地质资料的基础之上,合理布设测线,合理选取电极装置,通过分析整理激发极化法电测深数据,得到能够较准确地反映地下矿体的赋存、分布等特征的地质成果资料,预测成矿有利区段,所圈定锌多金属矿找矿靶区在后来的地质找矿工作中得到了证实。     

Compliance of land cover changes with municipal land use planning: Evidence from the Lisbon metropolitan region (1990–2007)

In the past few decades, urbanisation has become a major phenomenon in European cities, thus representing one of the key human land cover changes with socio-economic and environmental impacts. In the Lisbon metropolitan region it is estimated that 17% of natural and farmland have been transformed into artificial areas. Since the end of 1990s, specific EU guidelines have been issued to contain urban sprawl and preserve agricultural land. Spatial planning in Portugal obviously is integrating these assumptions into the statutory land-use master plans. But what is the performance of this land use planning system regarding land cover evolution itself? Based on the Lisbon metropolitan region (LMR), one of the major areas of urban growth in Portugal, we examine spatio-temporal land cover patterns between 1990 and 2007 by integrating cross-matrix analysis, spatial metrics, and gradient analysis. Additionally, we overlay these land cover dynamics with municipal master plans that regulate land development in order to assess the compliance levels of this land-use regulatory system. Results indicate that: artificial areas are growing by coalescence and/or by scattered development along an urban–rural gradient; agricultural land is reducing and fragmentation is increasing to enlarge peri-urban spaces; there are high levels of conversion of agricultural land into urban land in protected areas, thus showing a lack of compliance to the land use regulatory system visible in the existing gaps between the original land-use assignments of the master plan and the actual developments.     

特低渗透油藏间歇式生产油井产能预测分析

特低渗透油藏产能低,开发难度大已成为共识。为了对特低渗透油藏油井产能和油藏产量进行准确的预测,本文在达西公式的基础上,考虑到特低渗透油藏的渗流受到启动压力梯度的影响,推导出了具有启动压力梯度的间歇式生产的油井产能的预测模型,得出油井间歇式生产过程中采油量与时间存在指数递减关系;还推导得出油井关井时间段井底压力变化的数学模型,分析出其井底压力变化与采油时间段的采油速度有关,并给出了进行计算机迭代运算的求解方法和计算步骤。     

东北地区土壤活性有机碳对水热梯度变化的反映S152.4+2S153.6

基于样区20年气象资料统计结果和2006年土壤有机碳实测值,分析了东北样区内土壤活性有机碳各组分的空间分布格局及其与年均温(t)、降雨量(p)、有效积温和p/t(降雨量/年均温)之间的关系。结果表明:样区内土壤活性有机碳各组分沿纬度呈现出南低北高的分布趋势;活性有机碳各组分与土壤有机之间具有显著的正相关性;活性有机碳组分之间具有较强的相关性;活性有机碳各组分与气候因素之间存在良好的相关性。活性有机碳各组分与年均温之间的相关性大于活性有机碳各组分与降雨量之间的相关性。     

社会嵌入视角下的能力构建研究

在分析社会网络中不同企业的能力差异后,本文提出了以梯度转移为形式的能力构建模式。社会嵌入机制可以通过强化企业间的网络联结来提供支撑,其中结构嵌入是基于网络特性来拓展联结广度,关系嵌入则基于企业行为来增强联结深度,两者的融合会进一步促进企业的跨组织边界知识互动,以维持能力梯度转移的持续和稳定。     

互通式立交桥的设计要点

本文对互通式立交桥设计阶段进行分析,明确适合的技术指标,匝道设计、平曲线半径、纵坡大小、超高的设计合理与否,都决定线型好坏。     

中部地区承接加工贸易梯度转移探讨

我国加工贸易存在的地区发展不平衡问题,日益成为阻碍中国经济协调发展的重要因素。如何顺应国内、国际经济发展趋势,使加工贸易在地区分布上进行科学合理地调整,形成地区协调梯级发展的态势,是目前亟待研究和解决的问题。     

我国住房公积金制度运行的绩效、问题及对策

住房公积金制度建立至今，已成为我国住房保障体系的重要组成部分，为我国住房建设和住房金融提供发展的动力，尤其在推动廉租房建设方面发挥了重要作用。但是，住房公积金制度在现实运行中还是存在覆盖面有限、运行效率低、保障作用有限以及治理结构设计、决策机制和监管机制不健全等问题。文章对以上问题进行了归纳和深入分析。并在此基础上，提出了规范和完善住房公积金制度的对策和建议。