多维邻近性对流动人口回流意愿的影响——基于中国流动人口动态监测数据的实证

随着城市产业转型升级和县域经济快速发展,人口回流已成为现阶段中国人口迁移与流动过程中的重要组成部分,回流劳动力是乡村振兴和新型城镇化的重要力量,对于区域协调发展意义重大。距离是人口流动空间选择的核心解释变量,在多维邻近性视角下探究多种距离对流动人口回流的影响,有利于深化对人口回流机制的理解。论文借鉴多维邻近性分析框架,基于2016年中国流动人口动态监测调查数据,采用二元Logistic回归模型探究地理、制度和社会邻近性对流动人口回流意愿的影响。研究表明：① 回流群体主要是受教育水平较低的大龄已婚流动人口,其在劳动力市场不占优势,但家庭对其情感需求与依赖较大,回流意愿明显。② 不同维度邻近性均对流动人口回流意愿有较强解释力,地理、制度和社会邻近性对回流意愿均有显著负向影响,长距离跨省或跨方言区迁移的劳动力回流意愿更为强烈。③ 不同邻近性对回流意愿的影响存在群体异质性。高学历群体回流意愿受其所在流入地参保情况的抑制,同时受到方言和地理距离的不同影响;新生代流动人口则较易受非正式制度邻近性影响而选择回流;长期外出劳动力的回流意愿会因其已熟悉流入地方言并在流入地积极参保而降低。     

基于气象因子及机器学习回归算法的夏季空调负荷预测

气温、气压、相对湿度等气象因子对夏季用电负荷的影响非常显著。为了定量研究气象因子导致用电负荷的变化,本文将夏季用电负荷与当年4月及9月用电平均值之差定义为夏季空调负荷,并利用2014年1月到2016年12月南京市逐时气温、气压、相对湿度、水汽压、降雨量、风速、露点温度等气象资料,以及逐日逐时用电负荷数据资料,采用多元线性、K近邻法,决策树,bagging回归、随机森林等5种机器学习回归算法进行建模,并对其分别进行参数调优工作,进而得到空调负荷预测结果。结果表明:多元线性回归方法是5种回归算法里效果最差的一种,但通过增加特征量的种类和样本数,可以提高预测精度;随机森林回归算法是5种回归算法里效果最好的一种,较多元线性回归算法减小误差达44%,并且较好描述了空调负荷高值区的极端情况并减少了对于训练数据的过拟合现象。     

基于偏最小二乘回归的区域模式风速预报订正技术研究

利用偏最小二乘回归技术,将预报产品作为自变量,相应的自动气象站观测资料作为因变量,对2013—2016年冬季浙江省中尺度区域模式预报近地面风速进行订正和评估。所选956站中多数站点风速订正后有所改善,通过定量分析可知浙江西部地区整体改善效果最好,其中效果明显站点占91. 7%;中部地区改善效果明显站点占86. 5%;东部沿海地区改善效果略差,明显改善的站点占67%。各地级市整体表现均不错,除舟山地区为49.9%外,其他地区风速改善比例均超过50%。选取2017年1月20日浙江东北地区沿海大风过程分析发现订正后的风速与观测风速更为接近,在定海大岛站点(靠里)中表现尤为明显,订正后的结果具有显著参考价值。     

Shell use by sympatric hermit crab species in a seasonally open coastal lagoon in Northeastern Brazil

There are gaps in what is known about the patterns of gastropod shell use by hermit crabs in Brazilian lagoon areas, especially in Northeastern Brazil. However, this is important because the understanding of selection patterns provides information on life history and eco‐evolutionary conceptions of paguroids. The present study investigated the use of gastropod shells occupied by Pagurus criniticornis and Clibanarius sclopetarius in a coastal lagoon seasonally connected to an estuary and to the sea, correlating eco‐evolutionary aspects and hydrodynamic characters. The study was carried out between February 2013 and January 2014. Hermit crabs and their shells were identified and measured (hermit crabs’ cephalothorax shield length and width, major propodus length and height, weight, shell total length and width, shell aperture length and width). Partial least squares regression was used to analyse the morphometric data. Additionally, a multinomial proportions test was performed to infer patterns (inter‐/intra‐specific) of shells’ occupation. Hermit crab species occupied a total of 13 types of shells, predominantly those of Neritina virginea (67.83%). The shell weight was the most important determinant of shell occupancy in the morphometric model (variable importance in projection >1). The proportions of N. virginea shells used were similar in both species of hermit crabs, except between the sexes of P. criniticornis. Presumably, the high utilization rate of N. virginea shells is related to its abundance and dispersal, and to the shells’ suitability for hermit crabs, which is reflected by the morphometric model, as well as by the hydrodynamics of the lagoon‐estuarine environment. The relative occupation of different types of shells for each species of hermit crabs studied appears to be associated with regulation by inter‐/intra‐specific competition, which fosters the co‐occurrence of those populations. These results endorse coastal lagoons as a refuge and recruitment area for aquatic fauna. In addition, it highlights a challenge in the management and conservation of paguroid species whose population dynamics depend on the resources coming from the Gastropoda community.     

北京市城区扩展的空间格局与影响因素

2000年以来北京市持续推进产业结构升级,由此引发了经济活动的空间重构,伴随着住宅郊区化、职住分离以及交通基础设施的配套建设,将引起新一轮城市空间扩展。构建顾及综合可达性因素、邻域因素、自然因素、规划因素以及社会经济因素的城市空间扩展模型,分析诊断北京城区扩展进程中的主要影响因素及问题,从而为指导与管治北京市城市空间的有序扩展提供科学支撑。研究表明：① 综合交通静态可达性（单一年份）与城市扩展呈显著负相关;综合交通动态可达性（年份之间的可达性变化）则在引导北京市城市空间发展方面并无显著影响。② 邻域建设用地百分比与城市扩展呈正相关,而农用地、林业用地及水域用地的比例将减少土地开发的概率。③ 城市总体规划在指导城市空间扩展的纲领性地位逐渐受到重视,其对城区扩展的影响程度最为显著。④ 常住人口的分布现状、第二产业企业数量、第三产业企业数量分布现状对土地开发无显著影响。⑤ 认为北京市静态可达性与土地利用变化呈负相关,即可达性条件较差的地区,土地开发的可能性越小,这与北京市“摊大饼式”空间蔓延和居住郊区化的发展现实相符;北京市动态可达性与土地利用变化亦呈负相关,表明可达性提高程度越大的区域并不一定带来更高的土地开发几率,这从侧面传递了沿着既有建成区进行土地扩展的概率远远大于由于诸如轨道交通建设而带来可达性极大改善区域的概率。因此,重视与发挥综合交通动态可达性指标对城市扩展的引导作用,将是有效破解城市蔓延式扩张、优化城市扩展的重要手段。     

汶上东平沉积变质型铁矿床磁性铁品位回归模型

汶上-东平地区沉积变质型铁矿床磁性铁品位与可溶铁品位呈线性关系,相关系数0.965,经筛选,选取了2 030组样品建立了汶上-东平带沉积变质型磁铁矿品位与可溶铁的一元回归方程,经过与样品测试的分析结果对比,证明一元回归方程具有代表性、客观性。     

基于地理加权回归模型的典型山地卫星反演降水产品降尺度研究

降水是陆地水循环的关键变量,高分辨率降水数据的获取是准确模拟陆地水循环过程的前提。虽然卫星反演降水产品具有较强的空间代表性和连续性,但其空间分辨率较低的问题限制了它的应用。以太行山、横断山和喀斯特山区为研究对象,基于降水与高程(DEM)、植被指数(NDVI)之间存在较好相关关系的假设,构建了GPM降水(Global Precipitation Measurement Mission)与高程、植被指数的地理加权回归模型,得到了2014—2016年研究区1km分辨率GPM降水数据。研究结果表明:地理加权回归模型能有效地提高GPM数据的空间分辨率。降尺度后,GPM数据精度在太行山和横断山区略有提高。年尺度上,相比于原始GPM数据,太行山和横断山区降尺度数据站点实测数据的确定系数分别提高了0.06和0.08,RMSE分别降低了0.45%和3.89%,MAE分别降低了0.16%和1.70%;月尺度上,太行山区67%的月份,横断山区83%的月份GPM产品降尺度后更加接近于站点实测数据。喀斯特地区GPM数据降尺度后精度略有下降,降尺度后,年尺度的降雨数据与实测数据的RMSE和MAE分别增加了10.00%和8.00%,R^2降低了0.06,月尺度上仅8月和9月降尺度后的精度更高。降雨与地形和NDVI的关系较弱是喀斯特地区降尺度效果较差的主要原因。     

大连城市绿地可达性对房价影响的差异性分析

研究房价、遥感影像等多源数据,采用邻域分析法和地理加权回归模型分析大连市中山区绿地可达性及其与房价之间的空间相关性。结果表明：① 房价均价14 745.35元/m²,呈环状分布,由沿海向内陆衰减、桂林街道起中心向外围递减;② 研究区内可达性最好的绿地类型是街旁绿地,绿地可达性总体水平最高街道是桂林街道;公园绿地可达性最好的住宅区分布在昆明街道和桃源街道,街旁绿地可达性最好的住宅区分布在桂林街道,附属绿地可达性最好的分布在老虎滩街道,其他绿地可达性最好的分布在桃源街道。③ 不同类型绿地可达性对房价影响作用程度递减排序为：附属绿地、街旁绿地、公园绿地和其他绿地;附属绿地、街旁绿地和其他绿地与房价呈现空间正相关,随着到达绿地距离降低,房价呈现增长趋势;公园绿地与房价呈现负相关,随着到达公园绿地的距离降低,房价呈现衰减趋势。     

尼罗罗非鱼体重与体维可量性状之间的关系

以尼罗罗非鱼为研究对象,通过测量和回归分析,研究体重与体维可量性状之间的相关关系。结果表明:体重与体长、身长、全长、体高、体厚等形态特征性状的相关性均高于0.85,呈较高的正相关关系;多元回归方程lnW=a+b1lnLS+b2lnDB和lnW=a+b1lnLC+b2lnDB对于全体数据的拟合度分别为0.958和0.955,拟合度较高,且在实际检验中效果较好,超过88%的个体误差范围在5.0%之内,可有效反映出不同体维性状对鱼类体重的影响。     

Diatoms as indicators of climatic and limnological change in Swedish Lapland: a 100-lake calibration set and its validation for paleoecological reconstructions

This study investigated the distribution of subfossil diatom assemblages in surficial sediments of 100 lakes along steep ecological and climatic gradients in northernmost Sweden (Abisko region, 67.07° N to 68.48° N latitude, 17.67° E to 23.52° E longitude) to develop and cross-validate transfer functions for paleoenvironmental reconstruction. Of 19 environmental variables determined for each site, 15 were included in the statistical analysis. Lake-water pH (8.0%), sedimentary loss-on-ignition (LOI, 5.9% and estimated mean July air temperature (July T, 4.8%) explained the greatest amounts of variation in the distribution of diatom taxa among the 100 lakes. Temperature and pH optima and tolerances were calculated for abundant taxa. Transfer functions, based on WA-PLS (weighted averaging partial least squares), were developed for pH (r² = 0.77, root-mean-square-error of prediction (RMSEP) = 0.19 pH units, maximum bias = 0.31, as assessed by leave-one-out cross-validation) based on 99 lakes and for July T (r² = 0.75, RMSEP = 0.96 °C, max. bias = 1.37 °C) based on the full 100 lake set. We subsequently assessed the ability of the diatom transfer functions to estimate lake-water pH and July T using a form of independent cross-validation. To do this, the 100-lake set was divided in two subsets. An 85-lake training-set (based on single limnological measurements) was used to develop transfer functions with similar performance as those based on the full 100 lakes, and a 15-lake test-set (with 2 years of monthly limnological measurements throughout the ice-free seasons) was used to test the transfer functions developed from the 85-lake training-set. Results from the intra-set cross-validation exercise demonstrated that lake-specific prediction errors (RMSEP) for the 15-lake test-set corresponded closely with the median measured values (pH) and the estimations based on spatial interpolations of data from weather stations (July T). The prediction errors associated with diatom inferences were usually within the range of seasonal and interannual variability. Overall, our results confirm that diatoms can provide reliable and robust estimates of lake-water pH and July T, that WA-PLS is a robust calibration method and that long-term environmental data are needed for further improvement of paleolimnological transfer functions.