网衣对波浪传播影响的三维数值模拟          下载免费PDF全文

曾启东  董国海  赵云鹏  张晓明  汪睿 《海洋工程》2014,32(6):98-104

为研究网衣对波浪传播的影响,采用多孔介质模型模拟网衣,建立了模拟网衣与波浪相互作用的三维数值波浪水槽模型。基于该数值模型研究了波浪经过网衣作用后波高衰减的变化规律,并与物理模型试验结果进行比较。通过对比数值模拟和物理模型试验的结果,证明了该三维数值模型模拟网衣对波浪传播影响的可行性。  相似文献   

A Study of Resource Curse Effect of Chinese Provinces Based on Human Developing Index   总被引：1，自引：1，他引：0  

HUANG Yue  FANG Yangang  ZHANG Ye  LIU Jisheng 《中国地理科学(英文版)》2014,(6):732-739

Traditional opinion considers that natural resources play an important positive role in economic development, while resource curse theory holds that natural resources usually obstruct economic increase. This debate needs further exploration. In most of empirical studies on resource curse theory, the economic development of an area is mainly evaluated by the Gross Domestic Product （GDP）, however, the social and cultural contents of economic development are seldom considered. Thus, the Human Developing Index （HDI） was chosen to describe the comprehensive developing situation of an area in our study. Based on the panel data from the year of 2000 to 2011, the relationship between Human Developing Index and resource exploitation degree （RED） of 30 provinces in China （Tibet, Tai- wan, Hong Kong and Macao were not included because of the restriction of data acquisition） was investigated by correlation coefficient analysis and regression analysis. We found that resource curse did exist over the entire country and its effect on 30 provinces were not exactly the same. According to the effects of resource curse, these provinces could be classified into four types： no resource curse prov- inces, slight resource curse provinces, severe resource curse provinces, and extreme resource curse provinces. Testing from two short time periods 2000-2005, and 2006-2011, the resource curse effect was not prominent. However, testing from the entire period of 2000-2011, the effect was obvious among each province.  相似文献   

Might electricity consumption cause urbanization instead? Evidence from heterogeneous panel long-run causality tests     

《Global Environmental Change》2014

The share of a population living in urban areas, or urbanization, is both an important demographic, socio-economic phenomenon and a popular explanatory variable in macro-level models of energy and electricity consumption and their resulting carbon emissions. Indeed, there is a substantial, growing subset of the global modeling literature that seeks to link urbanization with energy and electricity consumption, as well as with carbon emissions. This paper aims to inform both modelers and model consumers about the appropriateness of establishing such a link by examining the nature of long-run causality between electricity consumption and urbanization using heterogeneous panel methods and data from 105 countries spanning 1971–2009. In addition, the analysis of the time series properties of urbanization has implications both for modelers and for understanding the urbanization phenomenon. We consider total, industrial, and residential aggregations of electricity consumption per capita, three income-based panels, and three geography-based panels for non-OECD countries. The panel unit root, cointegration, and causality tests used account for cross-sectional dependence, nonstationarity, and heterogeneity – all of which are present in the data set. We cannot reject pervasively Granger causality in the urbanization to electricity consumption direction. However, the causality finding that is both the strongest and most similar across the various panels is that of long-run Granger causality from electricity consumption to urbanization. In other words, the employment and quality of life opportunities that access to electricity afford likely encourage migration to cities, and thus, cause urbanization. Also, nearly all countries’ urbanization series contained structural breaks, and the most recent post-break annual change rates suggested that nearly all countries’ rates of urbanization change were slowing. Lastly, future modeling work on energy consumption or carbon emissions should consider subnational scales of analysis, and focus on measures of urban density or urban form rather than national urbanization levels.  相似文献   

Prediction of non-cavitation propeller noise in time domain     

叶金铭  熊鹰  肖昌润  毕毅 《中国海洋工程》2011,25(3):531-538

The blade frequency noise of non-cavitation propeller in a uniform flow is analyzed in time domain. The unsteady loading (dipole source) on the blade surface is calculated by a potential-based surface panel method. Then the time- dependent pressure data is used as the input for Ffowcs Williams-Hawkings formulation to predict the acoustics pressure. The integration of noise source is performed over the true blade surface rather than the nothickness blade surface, and the effect of hub can be considered. The noise characteristics of the non-cavitation propeller and the numerical discretization forms are discussed.  相似文献   

开发区土地要素对经济增长的贡献——基于江苏省面板数据的估计与测算     

陈伟  严长清  吴群  李永乐 《地域研究与开发》2011,30(5)

通过构建含有土地要素的生产函数,并与面板数据模型相结合,分析了土地要素对江苏省开发区经济增长的作用。结果显示:(1)江苏省开发区整体正处于规模报酬递增阶段,苏南处于规模报酬不变阶段,苏中、苏北处于规模报酬递增阶段;(2)土地要素对开发区经济增长有正面的推动作用,但开发区经济增长对资本要素更为敏感;(3)土地要素容易被其他要素替代,尤其容易被资本替代;(4)固定资产投资仍是开发区经济增长的主要推动力。未来一段时间内,土地要素的作用将继续削弱,资本要素仍然起到主要作用,土地集约利用水平将不断提高。  相似文献   

黄河流域旅游生态安全的动态演变特征及驱动因素     

穆学青  郭向阳  明庆忠  胡程 《地理学报》2022,77(3):714-735

科学测度与审视旅游生态安全对促进黄河流域旅游经济和生态环境协调可持续发展具有重要的理论和实践价值。从流域可持续发展视角,基于DPSIR系统模型构建黄河流域旅游生态安全理论框架和指标体系,采用改进TOPSIS法、核密度曲线、空间自相关、传统和空间马尔可夫链及面板分位数回归方法对其动态演化特征和驱动因素进行探析。结果表明：① 时间上,旅游生态安全均值波动下降后上升,呈收敛趋势,且有向“双核”形态演变的趋势。空间上,旅游生态安全值整体较低（0~0.55）,由2008年以风险级为主（占89.04%）转变为2017年以风险级和恶化级为主（分别占60.27%和31.51%）,且仍存在较大下行转移风险。② 动态演化特征上,不考虑邻域条件下,旅游生态安全风险级、敏感级转移具有“路径依赖”与“自身锁定”效应。而恶化级、临界安全级保持初始状态概率较小,且类型转移通常发生在相邻等级递次转移。邻域背景在其动态变化过程中起着重要作用,且其动态演化特征具有显著时空异质性。③ 影响因素方面,环境污染对低层级单元的旅游生态安全负向抑制作用较为明显,旅游负荷水平对较高层级地区旅游生态安全的正向边际效应略大,而旅游发展水平、经济发展水平等变量则对较低等级单元旅游生态安全的正向边际效应较大。  相似文献   

中国省际高技能人才迁移的时空演化机制     

古恒宇  沈体雁 《地理学报》2022,77(10):2457-2473

高技能人才迁移是推进新型城镇化建设的重要议题,也是影响地区创新产出和高质量发展的关键要素。针对人才迁移数据中蕴含的零膨胀和网络自相关特性,本文将特征向量空间滤波（ESF）技术和“两阶段”Hurdle模型结合,构建空间Hurdle引力模型,结合2000—2015年中国省际高技能人才迁移面板数据,研究人才迁移的时空演化格局和驱动机制。研究结论显示：① 2000—2015年人才迁移的跨省迁移比例先升后降;人才迁移表征出集聚格局,维系了其空间分布的不均衡性;随时间推移,人才迁移格局呈现分散趋势,人才空间分布集聚性下降;人才迁移和空间分布均呈现出持续显著的网络与空间自相关性特征。② 引力因素（人口规模、空间距离）、地区经济和科技发展水平（工资、科教投入）、自然舒适度（平均温差、空气质量）、城市舒适度（医疗及教育公共服务、城市绿化）以及其他因素（社会网络、生活成本、人口密度）共同驱动了跨世纪以来中国省际人才迁移过程。③ 人才迁移可被看作一个“两阶段”过程,影响其迁移概率和迁移规模的因素呈现一定差异。④ 经济增速、科教投入、自然舒适度和基础公共服务对人才迁移的影响随时间增强,而工资和城市绿化的影响随时间减弱。本文的研究结论为地区人才治理及实现地区均衡发展提供政策参考。  相似文献   

西南喀斯特石漠化深度贫困县的贫困影响 因素分析     

杨人懿  钟昌标  杨子生  刘凤莲  彭海英 《世界地理研究》2022,31(6):1298-1309

中国西南喀斯特石漠化地区人口-资源-环境-经济矛盾十分突出,严重制约了地区的可持续发展。基于该地区的深度贫困县——广西德保县的2014—2019年各乡镇社会、经济、人口等维度的面板数据,以空间贫困为理论导向,运用空间动态面板模型和GWR模型探索了石漠化地区县域贫困影响因素及溢出效应。空间动态自回归模型结果表明,各乡镇当年的贫困发生率表现出较大的惯性;农村居民恩格尔系数的下降、农村医疗卫生水平的提高、就业水平的提升、少数民族占比的下降、人口密度的降低均可明显地促进地区减贫。空间动态杜宾模型估计结果不仅支持了空间动态自回归模型结果,而且表明农村居民恩格尔系数、农村医疗卫生水平、人口密度分别表现出显著的有益、不利和有益的外溢效应,长期影响更深远。GWR模型结果表明其影响效果具有明显的空间差异性。  相似文献   

1978~2014年中国城市化与经济增长关系研究——基于省域面板数据     

管卫华  姚云霞  彭鑫  魏也华  张惠 《地理科学》2016,36(6):813-819

利用省域面板数据进行单位根检验和协整检验,对1978~2014年中国(不包括港澳台地区)经济增长和城市化的关系,以及不同省域经济增长与城市化作用程度进行研究,同时运用Mann-Kendall方法将中国城市化增长分成1978~1995年和1996~2014年两个阶段,并对不同阶段中国省域经济增长和城市化的相互作用关系进行研究,结果表明：① 1978~2014年中国经济增长对城市化具有促进作用,从各省域的相互作用程度来看呈现中东部较低,西南和东北部较高的区域格局,同时此阶段城市化对于经济增长的作用并没有得到证实。② 1978~1995年中国城市化和经济增长之间的相互作用关系没有得到证实。③ 1996~2014年中国城市化与经济增长相互促进,从各省域城市化对经济增长的作用强度来看呈现出中东部低,而周边内陆省区高的区域格局,而经济增长对城市化作用的区域格局与之相反。  相似文献   

中国城乡福祉差距及其影响因素研究     

李萱  杨庆媛  毕国华 《地域研究与开发》2021,40(2):1-6

从教育、医疗、收入和消费水平4个维度构建城乡福祉差距测度指标体系并测算城乡福祉差距指数,揭示中国城乡福祉差距的时空变化;利用2008—2017年中国内地除西藏以外30个省份的面板数据,分析城镇化对中国城乡福祉差距的影响及其区域差异。结果表明:2008—2017年,中国城乡福祉差距指数增大但城乡福祉差距的空间差异逐渐减小;城镇化对全国以及西部地区的城乡福祉差距具有显著负向作用,对东部与中部影响作用甚微;加大财政支农力度、提高农村社会保障水平、引导资本下乡均能缩小城乡福祉差距。  相似文献