跨地区生计及其变迁视角下流动人口城镇住房分层的特征及其影响因素   总被引：1，自引：0，他引：1  

林李月  朱宇  林坤 《地理研究》2022,41(7):1948-1962

在跨地区生计及其变迁的视角下,将流动人口在流入地和流出地城镇的住房状况有机结合,借助2016年中国流动人口动态监测调查数据和相匹配的城市特征数据,运用描述统计和多层次回归模型,探究流动人口城镇住房分层的特征及其影响因素。结果发现,流动人口的城镇住房已形成了一个从低到高依次由无城镇产权房、有城镇产权房（流出地或流入地城镇产权房）和多区域城镇产权房构成的“三阶四级式”的“金字塔型”结构。模型结果显示,流动人口个体及家庭的社会经济条件和流出地的区位禀赋是其实现城镇住房自有的重要基础和财务支撑,流入城市的经济发展水平、房价和城市规模仅对流入地和多区域城镇产权房有显著影响。因此,本文挑战了流动人口住房条件差的刻板印象,并吸引人们关注流动人口跨地区生计及其变迁对其城镇住房的影响,拓展了当代中国城镇住房分层研究的视角。  相似文献   

Submesoscale motions and their seasonality in the northern Bay of Bengal     

Lanman Li  Xuhua Cheng  Zhiyou Jing  Haijin Cao  Tao Feng 《海洋学报(英文版)》2022,41(4):1-13

The unbalanced submesoscale motions and their seasonality in the northern Bay of Bengal(BoB) are investigated using outputs of the high resolution regional oceanic modeling system. Submesoscale motions in the forms of filaments and eddies are present in the upper mixed layer during the whole annual cycle. Submesoscale motions show an obvious seasonality, in which they are active during the winter and spring but weak during the summer and fall. Their seasonality is associated with the mixed layer...  相似文献   

Global stability for convection induced by absorption of radiation     

B. Straughan   《Dynamics of Atmospheres and Oceans》2002,35(4)

We study the linear instability and nonlinear stability of a model, for convection induced by selective absorption of radiation, due to Krishnamurti. The nonlinear analysis yields critical Rayleigh numbers very close to the critical ones of linear instability theory and this demonstrates that linear theory effectively captures the physics of the onset of convection. Realistic boundary conditions appropriate to fixed surfaces are analysed and these reflect the experiments performed by Krishnamurti. The results obtained here lend much credence to use of the model of Krishnamurti for convection in a fluid layer stably stratified when the heat source depends on the concentration of the stratifying agent.  相似文献   

Improved topographic mapping through high-resolution SAR interferometry with atmospheric effect removal     

《ISPRS Journal of Photogrammetry and Remote Sensing》2013

The application of SAR interferometry (InSAR) in topographic mapping is usually limited by geometric/temporal decorrelations and atmospheric effect, particularly in repeat-pass mode. In this paper, to improve the accuracy of topographic mapping with high-resolution InSAR, a new approach to estimate and remove atmospheric effect has been developed. Under the assumptions that there was no ground deformation within a short temporal period and insignificant ionosphere interference on high-frequency radar signals, e.g. X-bands, the approach was focused on the removal of two types of atmospheric effects, namely tropospheric stratification and turbulence. Using an available digital elevation model (DEM) of moderate spatial resolution, e.g. Shuttle Radar Topography Mission (SRTM) DEM, a differential interferogram was firstly produced from the high-resolution InSAR data pair. A linear regression model between phase signal and auxiliary elevation was established to estimate the stratified atmospheric effect from the differential interferogram. Afterwards, a combination of a low-pass and an adaptive filter was employed to separate the turbulent atmospheric effect. After the removal of both types of atmospheric effects in the high-resolution interferogram, the interferometric phase information incorporating local topographic details was obtained and further processed to produce a high-resolution DEM. The feasibility and effectiveness of this approach was validated by an experiment with a tandem-mode X-band COSMO-SkyMed InSAR data pair covering a mountainous area in Northwestern China. By using a standard Chinese national DEM of scale 1:50,000 as the reference, we evaluated the vertical accuracy of InSAR DEM with and without atmospheric effects correction, which shows that after atmospheric signal correction the root-mean-squared error (RMSE) has decreased from 13.6 m to 5.7 m. Overall, from this study a significant improvement to derive topographic maps with high accuracy has been achieved by using the proposed approach.  相似文献   

On inviscid stratified parallel flows varying in two directions     

Y. T. Fung 《地球物理与天体物理流体动力学》2013,107(1-4):57-69

Abstract

A stratified parallel flow in a potential force field is investigated. The density, the velocity, and the potential field of the flow are allowed to vary in two directions. Three sufficient conditions are derived for guaranteed stability of the flow. Two are the classical stability conditions in their respective directions. The third, measured by a newly defined Richardson number, is a result of the shear interaction and the pressure balance condition for stability. Like the classical Richardson number which is always positive preceding stability, this new number acts as a constraint on the other two stability conditions. In addition to the above stability criteria, a semi-ellipse theorem is derived for the present flow.  相似文献   

三角洲平原高弯曲分流河道内部结构单元三维建模   总被引：1，自引：0，他引：1  

尹艳树  张昌民  尹太举  俞宸 《地质论评》2013,59(3):544-550

以大庆萨尔图油田北三区西部西块SⅡ12小层典型三角洲平原高弯曲分流河道为例,进行了三角洲平原高弯曲分流河道内部结构单元建模。首先根据高弯曲分流河道沉积层次性,以及河流弯曲机理,解剖了分流河道内部结构,识别出点坝以及侧积层单元,提取了侧积层形态参数和统计参数。其次采用椭球形方程建立了侧积层平面数学函数表达式,采用直线方程描述侧积层剖面形态,从而建立侧积层空间三维几何形态。最后,分两步建立了高弯度分流河道内部结构单元三维地质模型。首先采用序贯指示建模建立分流河道微相模型;随后根据侧积层数学模型描述侧积层空间分布。并在分流河道微相内部将侧积层模型嵌入,形成精细的高弯曲分流河道内部结构模型。以此思路为指导建立了SⅡ12小层结构模型,以此结构模型为基础的储层参数模型很好地再现了点坝内部侧积层对流体渗流的遮挡,为油藏数值模拟和剩余油挖潜奠定了基础。  相似文献   

Modeling residual circulation and stratification in Oujiang River estuary     

林伟波  王义刚  阮晓红  徐群 《中国海洋工程》2012,26(2):351-362

A 3D,time-dependent,baroclinic,hydrodynamic and salinity model was implemented and applied to the Oujiang River estuarine system in the East China Sea.The model was driven by the forcing of tidal elevations along the open boundaries and freshwater inflows from the Oujiang River.The bottom friction coefficient and vertical eddy viscosity were adjusted to complete model calibration and verification in simulations.It is demonstrated that the model is capable of reproducing observed temporal variability in the water surface elevation and longitudinal velocity,presenting skill coefficient higher than 0.82.This model was then used to investigate the influence of freshwater discharge on residual current and salinity intrusion under different freshwater inflow conditions in the Oujiang River estuary.The model results reveal that the river channel presents a two-layer structure with flood currents near the bottom and ebb currents at the top layer in the region of seawater influenced on north shore under high river flow condition.The river discharge is a major factor affecting the salinity stratification in the estuarine system.The water exchange is mainly driven by the tidal forcing at the estuary mouth,except under high river flow conditions when the freshwater extends its influence from the river’s head to its mouth.  相似文献   

Glauconitic coating on a gastropod,Fusitriton laudanum,from the Chatham rise,New Zealand (note)     

G. P. Glasby 《新西兰海洋与淡水研究杂志》2013,47(3):383-386

Superficial coatings of glauconite grains have been observed on the gastropod mollusc, Fusitriton laudanum, from the Reserve Bank, Chatham Rise. The glauconite predates the shell on which it accretes and is incorporated on to the shell surface by agglutination of sand‐size material by mucus secreted by epizoic anemones.  相似文献   

太平洋不同海水层结条件下的内波波致声场起伏研究     

李佳讯  张韧  金宝刚  陈奕德 《海洋学报》2013,35(3):78-86

基于Argo资料对太平洋海域海水层结进行分类区划,利用内波动力学方法对内波致声起伏进行数值求解,对不同层结状况下的内波致声起伏进行模拟试验。结果表明:垂直方向海水层结的不均匀和跃层的存在,使海洋内波斜压模态受到了歪曲变形。层结峰的个数和深度与声速起伏存在很好的对应关系。有内波的声传播特征总体上与没有内波时的相似。不同层结情况下,声场对内波扰动的响应不一致。  相似文献   

The diel verticalmigration of sound scatterers observed by an acoustic Doppler current profiler in the Luzon Strait from July 2009 to April 2011     

YANG Chenghao  LIAO Guanghong  YUAN Yaochu  CHEN Hong  ZHU Xiaohua 《海洋学报(英文版)》2013,32(11):1-9

Acoustic Doppler current profiler （ADCP） receives echoes from sound scatterers, then their speed is calcu- lated by the Doppler effect. In the open ocean, most of these backscatterers are from the plankton. The sound scatterers descend down to depth at around dawn, their mean speed is 2.9 cm/s, then they ascend up to the surface layer at around dusk with a mean speed of 2.1 cm/s, in the Luzon Strait. The descending speed is faster, which suggests that this zooplankton population may accelerate its downward migration under the action of the gravity. The vertical distribution of a mean volume backscattering strength （MVB- S） in the nighttime has two peaks, which locate near the upper and lower boundary layers of halocline, respectively. However, the backscatterers only aggregate near the surface layer in the daytime. The diel ver- tical migration （DVM） of sound scatterers has several characteristic patterns, it is stronger in summer, but weaker in winter, and the maximum peak occurs in September. The DVM occurrence is synchronous with the seawater temperature increasing at around dawn and dusk, it may affect the ocean mixing and water stratification,  相似文献