河南省农民工务工地选择及影响因素分析

规模巨大的农民工流动是当前中国最重要的社会经济现象之一,而其微观基础是农民工对务工地的选择.基于河南省33个样本村1091位农民工田野调查数据,对农民工微观个体务工地选择及影响因素进行了研究.结果发现,区域农民工的流动方向和务工地选择具有分散与集中相结合的特征,距离决定着社会网络密度和家务管理成本,经济发展水平影响着工资水平的高低和就业机会的多少,二者成为决定农民工整体流动方向的基本因素.影响农民工务工地选择的显著因子为:务工者年龄、教育程度、婚姻状况、家庭劳动力数量、人均耕地面积、所在村庄经济发展水平等.其中,年龄较小者、教育程度较低者、已婚者、家庭劳动力数量较多者、村庄经济发展水平较低者选择在较大空间范围内务工的概率较大,由于地形、交通状况因素的影响,人均耕地面积较大者在较大空间范围内务工的概率亦较大,反之亦然.家务管理是务工地选择的重要机制.     

农业结构调整与中国乡村转型发展——以河南省巩义市和鄢陵县为例

农业转型升级是中国乡村转型发展的主要引擎。而规模化、专业化生产是国际农业转型升级的方向。本文以两个不同乡村转型道路的典型县域(工业化转型的巩义市和农业现代化转型的鄢陵县)为例,利用区位熵、结构变化指数和专业化指数,在乡镇尺度深入分析新世纪以来乡村经济转型发展背景下乡村农业结构调整状况,以及由此带来的乡村景观再造。主要结论为：①基于市场需求的农业结构调整与乡村转型之间的相互作用是农产品提质增效倒逼耕地利用方式的现代化转变,并引致乡村景观的多功能再造。未来中国农业的转型方向将是规模化大宗农业与专业化精细农业并存;②无论是乡镇的非农化转型还是农业现代化转型,均可带来乡镇耕地的规模化、专业化利用以及农业内部的结构调整,并引致乡村的进一步转型。工业转型县农业结构以粮食作物为主要调整方向,农业现代化转型县以粮食和特色农作物为主要调整方向,并形成了特色专业村或产业集群;③农业结构调整方向更加与自然条件和资源禀赋相匹配,空间配置更加合理。     

“一带一路”国家粮食贸易网络空间格局及其演化机制

农产品贸易是“一带一路”沿线国家间经贸合作的重要内容,但现有贸易理论无法很好地解释“一带一路”国家间粮食贸易网络的格局演化。该文构建了一个四维菱形分析框架,并将社会网络分析与空间计量分析相结合,基于1993—2016年联合国商品贸易数据,分析了“一带一路”国家间粮食贸易网络的空间结构特征及其演化机制。结果表明：① “一带一路”国家间的粮食贸易网络密度不断提高,贸易关系和贸易强度不断加深,在全球粮食贸易网络中的地位呈波动上升态势,并出现明显的贸易俱乐部现象;② 该粮食贸易网络呈现由无核到多核再到重塑的演化历程;③ 中国与其他“一带一路”国家间的粮食贸易经历了从出口导向到进口导向的演化历程,“一带一路”倡议提高了中国在全球粮食贸易网络中的地位;④ “一带一路”国家间粮食贸易网络的演化是受资源禀赋、经济环境、文化认同和政治博弈4个因素共同作用的结果,各因素在不同阶段所起的作用不同;粮食贸易较其他贸易而言特色鲜明,其稳定性更强。研究结果对促进“一带一路”国家农业贸易的健康繁荣,建设开放包容的经济环境具有指导意义。     

特色种植的空间持续性及其影响因素研究——以河南省封丘县树莓产业为例

以河南省封丘县树莓产业为例,基于实地调查,从特色种植的空间扩散网络、村域种植规模变化、不同类型村空间分布特征、整体参与村空间集聚特征4方面对特色种植的空间持续性进行分析发现：特色种植空间扩散网络密度低,空间持续性不强,但其变化的空间范围一定,集聚特征明显。运用AMOS21.0对以上现象的影响因素进行分析发现：① 农户自身特性,尤其是冒险性精神对其持续种植时长影响较大;② 资金、技术、信息等生产条件获取越便利,农户持续种植时间越长;③ 政府推动对农户持续种植具有正向作用;④ 资源环境,尤其是土壤特性和能人带动对村域种植规模影响深刻;⑤ 距离区位对村域持续种植的影响弱于基础设施条件。     

1989-2009年河南省农作物地理集聚及其演化机制

以河南省17 种农作物为对象,采用1989-2009 年的地市级数据,对农作物的集聚特点、专业化格局及其演化机制进行分析。研究结果表明:河南省农作物的集聚水平低且整体增长缓慢,尤其是遍在农作物;部分农作物有分散化的趋向,而水稻的集聚程度一直很高,较大程度上影响了河南省农作物整体的集聚水平;经济作物的集聚与区域专业化程度均高于粮食作物,且分布格局变化不大,仍集聚于研究时段初始时的优势区域;蔬菜类作物专业化程度较低,其空间分布与城市化水平高度相关,不断向郑汴地区集聚;水果类作物不断向豫西山地尤其是三门峡市集中,而部分水果类作物如葡萄、桃等则出现分散化的趋势。总体来说,各市域间农作物结构相似度高,分工与专业化生产初现雏形。在此基础上,构建了基于演化经济地理学的“稳定—变化—选择—适应”过程分析框架,对河南省农作物集聚与专业化格局的形成演化机制进行阐释。     

Numerical Analyses of the Influence of Blast-Induced Damaged Rock Around Shallow Tunnels in Brittle Rock

Most of the railway tunnels in Sweden are shallow-seated (<20 m of rock cover) and are located in hard brittle rock masses. The majority of these tunnels are excavated by drilling and blasting, which, consequently, result in the development of a blast-induced damaged zone around the tunnel boundary. Theoretically, the presence of this zone, with its reduced strength and stiffness, will affect the overall performance of the tunnel, as well as its construction and maintenance. The Swedish Railroad Administration, therefore, uses a set of guidelines based on peak particle velocity models and perimeter blasting to regulate the extent of damage due to blasting. However, the real effects of the damage caused by blasting around a shallow tunnel and their criticality to the overall performance of the tunnel are yet to be quantified and, therefore, remain the subject of research and investigation. This paper presents a numerical parametric study of blast-induced damage in rock. By varying the strength and stiffness of the blast-induced damaged zone and other relevant parameters, the near-field rock mass response was evaluated in terms of the effects on induced boundary stresses and ground deformation. The continuum method of numerical analysis was used. The input parameters, particularly those relating to strength and stiffness, were estimated using a systematic approach related to the fact that, at shallow depths, the stress and geologic conditions may be highly anisotropic. Due to the lack of data on the post-failure characteristics of the rock mass, the traditional Mohr–Coulomb yield criterion was assumed and used. The results clearly indicate that, as expected, the presence of the blast-induced damage zone does affect the behaviour of the boundary stresses and ground deformation. Potential failure types occurring around the tunnel boundary and their mechanisms have also been identified.     

Formation of baotite - a Cl-rich silicate - together with fluorapatite and F-rich hydrous silicates in the Kval?ya lamproite dyke, North Norway

Baotite occurs as a late phase in the Kval?ya lamproite dyke and in the fenitized granite adjacent to the dyke, suggesting that baotite formed during reactions between rock and fluids derived from a volatile-rich lamproitic magma. Most of the analyzed grains of baotite from the Kval?ya lamproite show compositions close to the ideal Nb-free end-member Ba₄Ti₈Si₄O₂₈Cl. Compilation of all published baotite analyses suggests that the major compositional variations of baotite occur between the Nb-free end member Ba₄Ti₈Si₄O₂₈Cl, and a Nb-rich end member Ba₄Ti₂Fe2⁺ ₂Nb₄Si₄O₂₈Cl. However, a Pb-bearing baotite, showing significant concentrations of Ca, Sr, Pb and K, and approximately 3 Ba p.f.u., was also identified from the Kval?ya lamproite. Euhedral fluorapatite formed as an early phase during crystallization of the lamproite magma, while anhedral REE-rich fluorapatite overgrowths on the euhedral grains formed during reactions with the late magmatic fluid. Fluorapatite contains up to 1.2?F p.f.u., but only traces of Cl. Other F-rich, but Cl-poor minerals of the lamproite include fluoro-potassic-magnesio-arfvedsonite, fluoro-phlogopite, and yangzhumingite. The presence of baotite together with a range of high-F, but low-Cl mineral phases suggests that the minerals formed in equilibrium with a high-F, Cl-bearing hydrous fluid. The high Cl-content of baotite demonstrates that Cl is strongly partitioned into this mineral in the presence of a Cl-bearing F-rich hydrous fluid. We suggest that a combination of high a_Si, a_Ti, a_Ba, and f_O2, but low a_Ca of the fluid enabled baotite formation.     

地理邻近、关系邻近对农业产业集群创新影响——基于山东省寿光蔬菜产业集群实证研究

以寿光蔬菜产业集群为例,运用ArcGIS 10.0软件的空间邻近分析,Ucinet软件的社会网络分析以及多元线性回归模型从多维邻近性视角探究蔬菜集群企业的地理邻近、关系邻近特征及两者在集群企业创新中的影响。研究表明：① 蔬菜集群企业具有明显的地理集聚特征,企业的空间邻近有利于集群创新氛围的形成;② 集群企业及各创新主体间拥有紧密的关系邻近网络,关系网络中多核心节点,促使创新资源、隐性知识、新技术等的扩散与传播;③ 进一步回归分析表明,关系邻近对蔬菜产业集群创新作用更显著,永久性地理邻近在寿光蔬菜产业集群创新中仍然起到正向作用,但作用要弱于关系邻近。说明多元关系邻近在集群创新过程中能够对消除过度的地理邻近、单一关系邻近造成的创新锁定起到作用,同时还为全球化背景下农业集群创新提供新的渠道。