Locational specificities of fertility transition in Sri Lanka     

Lakshman Yapa  Padmasiri Siddhisena 《GeoJournal》1998,45(3):177-188

Sri Lanka has one of the lowest fertility rates among poor countries of the world. The fertility decline which began in the 1950s has held steady during the last four decades, despite low levels of economic development. Widespread use of contraception is the primary cause of the fertility decline. However, there is no one single homogenous body of people that can be characterized as a ‘modern’ contracepting population through which new methods of family planning have spatially diffused. There is evidence that the overall fertility decline began even before the establishment of the modern family planning program in Sri Lanka. Our analysis showed four broad regional regimes of fertility transition with considerable social and place-to-place differences in method-specific rates of contraception among them. Non-modern ‘traditional techniques’ of contraception which are widely used are an important part of fertility regulation. Sterilization is the most common method of modern contraception in all regions. Less than a tenth of the protected couples use methods such as the pill and the IUD; moreover, these methods are often discontinued after initial use. Traditional methods are an important part of the contraceptive mix in Sri Lanka, and it would be inadvisable to discourage the use of such practices. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

鲁西地区中生代沂南超单元基本特征     

王世进  张成基  吕明英 《山东国土资源》1998,(4)

“七五”以来,鲁西地区开展的１∶５万和１∶２０万区调工作,对中生代侵入岩的研究逐步深入,建立了济南、铜石、埠村、沂南等超单元。本文对重新厘定的沂南超单元的基本特征及所属单元典型侵入体（命名地点）的特征作了初步介绍,并对这套中基性杂岩体的形成时代、就位机制、岩浆演化及与铜、铁、金矿化的关系进行了探讨。  相似文献   

涉及分担一个非零值的亚纯函数的正规定则     

谢东 《成都信息工程学院学报》2009,24(4):414-417

设F为区域D内的亚纯函数族n(≥3),m(≥1)为两正整数,6为非零有穷复数,若对 f,g∈F,在D内f"(f"-1)f'与g"(g"'-1)g'IM分担b.则F在D内正规.  相似文献   

Capitalising the farm family entrepreneur: negotiating private equity partnerships in Australia     

Alexandra Langford 《The Australian geographer》2019,50(4):473-491

ABSTRACT

Research on the financialisation of land and agribusiness has highlighted major shifts in agri-food systems globally. Yet these accounts tend to focus on the activities of financial actors, and few take seriously the role of farmers in negotiating investments in land and agribusiness. Farmers in the global North may be well placed to benefit from partnerships with financial investors, although little is known about the way that such partnerships are formed. Australian studies of farmer agency have been productive in examining farm family entrepreneurs and globally engaged farmers who work beyond the farm gate to organise supply chains. This paper adds to these studies by providing insights about a capitalising farm family entrepreneur, who successfully negotiated and entered into a direct equity partnership with a large foreign pension fund. Several observations are significant: the exceptional skill, time and expense required to negotiate these partnerships; the role of consultants and non-human actors in structuring them; and the spatially- and temporally divergent farm development practices that are enabled by a shift from debt to equity financing. These observations are indicative of a new adaptive strategy of family farmers to shifting financial landscapes and of emergent family, corporate, and financial farm hybridity.  相似文献   

家庭化迁移对流动人口职住关系的影响——以广州为例     

文萍  周素红 《地理研究》2022,41(4):1212-1226

流动人口家庭化迁移可能对其在城市的职住关系产生影响。本研究基于广州市居民日常出行调查数据,考察流动人口在不同家庭化迁移状态下的职住关系,并与本地市民进行比较。研究发现：广州市流动人口职住临近特征明显,但随着家庭化迁移程度提高,职住距离增长,并接近本地市民水平。相较于个体单独迁移,夫妻共同迁移由于难以同时实现职住临近,职住距离更长;子女和老人随迁情境下,流动人口职住区位郊区化特征明显,因为郊区能以较低成本满足家庭生活对住房和住区环境的更高要求,但该情境下整体职住距离增幅较小且不显著。多数家庭化迁移的流动人口仍存在不稳定流动特征,以租房为主,租金规避需求与环境提升需求并存,需要相关政策加以关注。  相似文献   

阿尔金成矿带成矿单元划分及成矿系列探讨   总被引：2，自引：0，他引：2  

乔耿彪  ;杨合群  ;杜玮  ;赵晓健 《西北地质》2014,(4):209-220

阿尔金成矿带地处新疆、青海和甘肃三省的衔接部位,是我国西部重要的铁、铅、锌、金、铜等矿产资源重点勘查区之一,也是全国矿产资源潜力评价项目划分的Ⅲ级成矿单元之一。笔者以地层、构造、岩浆岩带和相关的成矿作用为标志,将阿尔金成矿带进一步划分为3个Ⅳ级成矿单元(成矿亚带),并概述了各Ⅳ级成矿单元的地质矿产特征;在此基础上,按照杨合群等(2012)提出的与各类地质建造有关的成矿系列细化为同生成矿系列、准同生成矿系列、后生成矿系列和表生风化成矿系列,构建了阿尔金成矿带的11个成矿系列家族和16个成矿(或矿化)系列,这将对该区域今后的找矿和勘查工作具有一定的指导作用。  相似文献   

基于多源激光点云融合的建筑物BIM建模     

刘亚坤  刘会云  李永强  赵上斌  杨亚伦 《地球信息科学学报》2021,23(5):763-772

墙体、窗户等单元构件是建筑物重要组成部分,精细提取其几何参数及位置信息对于完整表达建筑物整体模型具有重要意义。针对单一点云数据源无法获取建筑物单元构件相关参数并完整表达室内外模型重建问题,本文提出一整套融合室内外多源点云数据的BIM模型重建技术。为验证方法的有效性,选取河南理工大学测绘与国土信息工程学院教学楼为实验区域,室内外数据采集时间为2019年5月。在对实验区域机载、车载和地面点云数据进行预处理的基础上,分别选取各点集共轭特征点,以高精度的地面点云为基准,将机载和车载点云融合到地面点云。为提高后期模型重建精度及处理效率,以点云间最小空间距离的方式剔除重叠区域冗余数据。对建筑物进行整体平面与立面剖切,将剖切面在CAD中进行跟踪绘制二维线划图,将二维线划图导入Revit软件中绘制轴网与标高,并利用提取到的墙体几何参数编辑墙体族类型进行BIM模型重建。根据提取到的窗户几何参数统计其类型并编辑窗户族,将其归为有规律性和无规律性两类,有规律性窗户单元找出其重复性规律及位置控制参数,无规律性窗户单元逐个放置,二者结合优化BIM模型。为验证模型重建精度,选取建筑物代表性立面,以人工实测立面边长为参照,将由点云数据提取到的相对应立面边长及模型边长与之对比分析,其误差集中分布在0.0~0.2 m之间,存在0.2 m以上误差,但大部分在0.3 m以下。实验结果证明了该方法的准确性。  相似文献   

Weiwoboidae fam.nov.of 'Higher' Fulgoroidea (Hemiptera:Fulgoromorpha) from the Eocene Deposits of Yunnan,China     

Lin Qibin  Jacek Szwedo  Huang Diying  Adam Stroiński 《《地质学报》英文版》2010,84(4):751-755

<正>A new family of so-called‘higher' planthoppers,Weiwoboidae fam.nov.,from the Lower Eocene of Yunnan is described.A new monotypic genus,Weiwoboa gen.nov.,with Weiwoboa meridiana sp.nov.is also described and illustrated.The characters of tegmen venation of the new family,its evolution,and supposed relationships are briefly discussed.  相似文献   

虾夷扇贝Smad基因家族的鉴定及表达分析     

潘好远  戴晓婷  胡乃娜  曾启繁 《中国海洋大学学报(自然科学版)》2021,(3)

Smad基因介导的细胞信号在调节动物发育和细胞干性方面起着至关重要的作用。由于其功能的多样性和重要性,Smad基因家族一直受到广泛的研究。然而,双壳贝类Smad基因家族缺乏系统的鉴定和分析。为了理解双壳贝类Smad基因家族的进化和生物学功能,本文在虾夷扇贝基因组鉴定出4个Smad基因,并对其遗传和表达特征进行了分析。时空表达谱显示,Smad3基因在虾夷扇贝受精卵和2~8细胞时期有较高的表达量,而在胚胎及幼虫阶段该基因表达量迅速降低,推测其在胚胎早期细胞分裂和分化过程中发挥重要作用。Smad6在胚胎发育早期表达量较低,在囊胚期及原肠胚时期表达量显著升高,可能与母源调控向合子型调控过渡的“中期囊胚转换”有关。Smads基因在各组织中也呈现了独特的表达模式,其中Smad3、Smad5和Smad6分别在肌肉、血细胞和鳃中表达量最高。而Smad4在各个组织内均有表达且表达量相似。实验结果暗示了Smad基因在虾夷扇贝中不仅参与协调了早期胚胎的发育,也与组织器官的形成和稳态有关。本研究有助于理解贝类Smad基因的进化及功能,为深入研究该基因家族在贝类中的生物学功能和调控机制奠定基础。  相似文献   

一个新的正规定则     

王柳  张庆德 《成都信息工程学院学报》2006,21(Z1):98-103

证明了单位圆内亚纯函数族F,若不正规,则存在一个函数列在开平面上的任意紧子集上一致收敛于一个非常数的亚纯函数,并应用它得到一个新的正规定则:设F为区域D内的一亚纯函数族,若对每一f∈F,fnf′≠1(n≥2),则F在区域D内正规.  相似文献