1980年以来黄土高原半干旱区乡村人居环境系统脆弱性时序演变——以陕西省佳县为例   总被引：1，自引：1，他引：1  

杨晴青  杨新军  高岩辉 《地理科学进展》2019,38(5):756-771

从人地系统脆弱性视角切入,遵循“演变轨迹刻画—阶段情景描绘—演化路径与机理剖析”的逻辑轴线,结合“ground-truthing”质性研究方法,探索了1980年以来以陕西省佳县为代表的黄土高原半干旱区乡村人居环境系统演变历程与路径。主要结论如下：① 定量测度了1980—2016年佳县乡村人居环境综合系统及子系统脆弱度值。其中,自然系统脆弱性由干旱主导转向雨涝灾害主导;21世纪以来,居住系统脆弱性全面减轻,支撑系统脆弱性反弹加剧;近10 a,社会系统脆弱性逐渐减轻,人类系统已走向重度脆弱等级,综合脆弱性停滞于中度脆弱等级。② 提出了乡村人居环境系统脆弱性情景转化阈值规则,界定了顽固脆弱、不受控制的脆弱、可控的脆弱、稳定健康、易变的系统等5类脆弱性情景。案例区脆弱性演变经历4个阶段,但徘徊于顽固脆弱的系统与不受控制的脆弱性系统情景之间。③ 建构了乡村人居环境系统脆弱性阶段性演化动力机制,梳理了5大子系统脆弱性阶段性演化路径,提炼了涉及气候变化、城市化扰动、市场变化、政策干预及农户行为适应等5大驱动因素的20件关键影响事件。  相似文献   

P–T evolution of glaucophane–omphacite bearing HP–LT rocks in the western Tianshan Orogen, NW China:new evidence for 'Alpine-type' tectonics     

R. Klemd  F. C. Schröter  T. M. Will  J. Gao 《Journal of Metamorphic Geology》2002,20(2):239-254

The late Palaeozoic western Tianshan high‐pressure /low‐temperature belt extends for about 200 km along the south‐central Tianshan suture zone and is composed mainly of blueschist, eclogite and epidote amphibolite/greenschist facies rocks. P–T conditions of mafic garnet omphacite and garnet–omphacite blueschist, which are interlayered with eclogite, were investigated in order to establish an exhumation path for these high‐pressure rocks. Maximum pressure conditions are represented by the assemblage garnet–omphacite–paragonite–phengite–glaucophane–quartz–rutile. Estimated maximum pressures range between 18 and 21 kbar at temperatures between 490 and 570 °C. Decompression caused the destabilization of omphacite, garnet and glaucophane to albite, Ca‐amphibole and chlorite. The post‐eclogite facies metamorphic conditions between 9 and 14 kbar at 480–570 °C suggest an almost isothermal decompression from eclogite to epidote–amphibolite facies conditions. Prograde growth zoning and mineral inclusions in garnet as well as post‐eclogite facies conditions are evidence for a clockwise P–T path. Analysis of phase diagrams constrains the P–T path to more or less isothermal cooling which is well corroborated by the results of geothermobarometry and mineral textures. This implies that the high‐pressure rocks from the western Tianshan Orogen formed in a tectonic regime similar to ‘Alpine‐type’ tectonics. This contradicts previous models which favour ‘Franciscan‐type’ tectonics for the southern Tianshan high‐pressure rocks.  相似文献   

同步卫星伪码测距系统设计     

韩学义  张挥 《时间频率学报》1993,16(1):20-31

根据伪码测距技术和卫星通讯的特点,针对我国已发射的或将要发射的以及我国目前租用的C波段和Ku波段卫星,设计了用高精密传输终端(或MITREX)进行伪码测距时卫星地面站的参数,并估算出了伪码测距精度。  相似文献   

逐步线性回归法实现中华虎头蟹(Orithyia sinica) 形态指标与体重的通径分析   总被引：2，自引：0，他引：2  

来守敏  王仁杰  姜令绪  秦浩  李玉全 《海洋与湖沼》2015,46(6):1438-1443

为探讨中华虎头蟹(Orithyia sinica)形态指标与体重的关系, 为良种选育提供最佳的测量指 标, 实验以中华虎头蟹为材料, 测量甲宽、甲长、眼间距、侧齿间距、大螯不动指长、大螯宽、步足 长节长、体高、体重等26 个指标, 借助逐步线性回归、相关分析和通径分析等方法, 分析形态指标 与体重的关系。结果表明, 除第Ⅳ侧齿间距(A₈)外, 实验所测形态指标与体重的相关系数均达到了显 著水平(P<0.05); 采用逐步线性回归的方法建立了多元回归方程Y=-273.841+10.4X₁+2.867X₂, 其中 Y 为体重(g), X₁ 为右大螯宽(mm), X₂ 为第Ⅱ侧齿间距(mm), 定量分析了形态指标对体重的影响结果。  相似文献   

An automated method for the calculation of P–T paths from garnet zoning,with application to metapelitic schist from the Kootenay Arc,British Columbia,Canada     

D. P. Moynihan  D. R. M. Pattison 《Journal of Metamorphic Geology》2013,31(5):525-548

An automated method for the calculation of P–T paths based on garnet zoning is presented and used to interpret zoning in metapelitic schist from the southern Canadian Cordillera. The approach adopted to reconstruct the P–T path is to match garnet compositions along a radial transect with predictions from thermodynamic forward models, while iteratively modifying the composition to account for fractional crystallization. The method is applied to a representative sample of garnet‐ and staurolite‐bearing schist from an amphibolite facies Barrovian belt in the southern Canadian Omineca belt. Garnet zoning in these schists is concentric and largely continuous from core to rim. Three zones are present, the first two of which coincide with sector‐zoned cores of garnet crystals. Similar zoning is developed in rocks that contain or lack staurolite, respectively, suggesting garnet growth was restricted to the initial part of the prograde P–T path prior to the development of staurolite. Growth zoning in large garnet crystals has not been significantly modified by diffusion. This interpretation is based on zoning characteristics of garnet crystals and is further supported by results of a forward model incorporating the effects of simultaneous fractional crystallization and intracrystalline diffusion. The P–T path calculated for this rock includes an initial, linear stage with a high dP/dT, and a later stage dominated by heating. The approach adopted in this study may have application to other garnet‐bearing rocks in which growth zoning is preserved.  相似文献   

基于快照方式的面向对象模型探讨     

李国斌  武法东  赵俊美 《地球信息科学学报》2006,8(2):91-94

TGIS(Spatial-TemporalGIS)是GIS的重要分支,是实现动态数字地球的关键技术。静态3DGIS的技术已基本成熟,而其加上时间维的4DTGIS的关键技术是时空数据库的建立及其操作,它们与时空数据模型有关,主要处理超海量数据的存取和查询。本文结合快照模型的简单易行性和面向对象模型的方便灵活性,同时避开快照模型的不一致性和冗余性,以及面向对象的复杂性,探讨基于快照方式的面向对象模型,是一种实用的TGIS数据模型。它在对时间属性的处理方面采用独到的方法,首先建立一个基数据,然后通过快照方式产生缓冲数据,经过比较形成一个以对象变化为主的带有时间戳的新数据层。这样,在数据存储方面,节省了很多空间;在查询分析方面,以对象变化分层的数据算法更容易实现。此理论方法有效解决了TGIS的“瓶颈”问题,并通过自动元胞机理论(CA)予以证明。  相似文献   

粤港澳大湾区建设国际科技创新中心的全球视野与理论模式   总被引：3，自引：0，他引：3  

王云  杨宇  刘毅 《地理研究》2020,39(9):1958-1971

建设国际科技创新中心是粤港澳大湾区新时代最有共识、最有优势、最富挑战的战略方向,亟需国际科技创新中心建设的理论探索。国内外经典创新系统理论更加专注于创新系统内部,注重单一空间的创新要素与创新活动组织问题,忽视了全球和区域之间要素的关联模式,缺乏在全球视野下宏观与微观结合的综合观察。由此,本文在总结国内外经典创新系统理论的基础上,构建了全球视野下的以“科技”和“人才”为核心,以“科技-产业-全球生产网络”和“人才-环境-世界城市网络”为链条的国际科技创新中心理论模式,认为国际科技创新中心是全球创新网络、全球生产网络和世界城市网络三重网络结构的核心节点,建设国际科技创新中心需要实现三重网络的协同效应。在这样的理论框架下,分析了粤港澳大湾区双核心与双链条的发展情况,并以此提出了粤港澳大湾区建设国际科技创新中心的路径和相关建议。  相似文献   

演化经济地理学视角下旅游目的地研究述评及启示     

赵政原  刘志高 《地理科学进展》2019,38(1):101-110

由于旅游目的地系统的多元和综合属性,其研究内容往往呈现跨学科的属性,涵盖地理学、经济学、管理学、社会学等多个领域。20世纪90年代以来,以进化论和复杂系统论为理论基础,强调历史过程和空间异质性的演化经济地理学,因其超越原有的单线逻辑的叙事而受到旅游研究者的关注。作为旅游目的地研究的新范式和新理论,演化经济地理学被应用于旅游目的地的演化路径和演化动力机制,并为其提供了“结构—过程”分析视角。而另一方面,中国旅游目的地的发展及演变,和西方发达国家的经验有着较大区别,只有在充分立足于中国旅游目的地的实际状况和基本国情的基础上,才能够更好地构建“中国特色”的旅游目的地理论体系,探索更为多元化的旅游研究方法。加强与政治经济学和制度经济学研究的结合能够为中国的旅游实践提供较为宏观尺度的政策分析视角,进而有助于旅游公共服务体系的转型升级;加强中微观层面的多尺度耦合机制和多元主体行为研究,将有助于探索不同利益相关者参与下中国旅游目的地的可持续发展路径。  相似文献   

基于地形图分析的空间数据挖掘系统的设计与实现     

张小朋  葛文  王鹏波  蔡畅 《海洋测绘》2008,28(4):60-62

在对地形图进行分析的基础上，设计了一套功能较为完善的空间数据挖掘系统，分析并解决了功能实现过程中遇到的难点问题。该系统主要完成了基本的空间计算、地形特征提取、障碍路径分析、空间聚类分析等功能模块。参照一般的GIS结构，系统结构分为数据源、数据挖掘和用户界面三层，各层相对独立。系统在Visual C＋＋6．0的语言环境下进行开发，具有可扩充性。经过调试，系统运行良好，具有较好的实用性。  相似文献   

P–T path of high-pressure/low-temperature rocks and tectonic implications in the western Tianshan Mountains, NW China     

Gao  Klemd  Zhang  Wang  & Xiao 《Journal of Metamorphic Geology》1999,17(6):621-636

The Chinese western Tianshan high-pressure/low-temperature (HP–LT) metamorphic belt, which extends for about 200 km along the South Central Tianshan suture zone, is composed of mainly metabasic blueschists, eclogites and greenschist facies rocks. The metabasic blueschists occur as small discrete blocks, lenses, bands, laminae or thick beds in meta-sedimentary greenschist facies country rocks. Eclogites are intercalated within blueschist layers as lenses, laminae, thick beds or large massive blocks (up to 2 km² in plan view). Metabasic blueschists consist of mainly garnet, sodic amphibole, phengite, paragonite, clinozoisite, epidote, chlorite, albite, accessory titanite and ilmenite. Eclogites are predominantly composed of garnet, omphacite, sodic–calcic amphibole, clinozoisite, phengite, paragonite, quartz with accessory minerals such as rutile, titanite, ilmenite, calcite and apatite. Garnet in eclogite has a composition of 53–79 mol% almandine, 8.5–30 mol% grossular, 5–24 mol% pyrope and 0.6–13 mol% spessartine. Garnet in blueschists shows similar composition. Sodic amphiboles include glaucophane, ferro-glaucophane and crossite, whereas the sodic–calcic amphiboles mainly comprise barroisite and winchite. The jadeite content of omphacite varies from 35–54 mol%. Peak eclogite facies temperatures are estimated as 480–580 °C for a pressure range of 14–21 kbar. The conditions of pre-peak, epidote–blueschist facies metamorphism are estimated to be 350–450 °C and 8–12 kbar. All rock types have experienced a clockwise P–T path through pre-peak lawsonite/epidote-blueschist to eclogite facies conditions. The retrograde part of the P–T path is represented by the transition of epidote-blueschist to greenschist facies conditions. The P–T path indicates that the high-pressure rocks formed in a B-type subduction zone along the northern margin of the Palaeozoic South Tianshan ocean between the Tarim and Yili-central Tianshan plates.  相似文献