Urbanization in China Based on International Comparison:A Discussion with Two Prevalent Views

Two prevalent views are reviewed on China's urbanization firstly.Then,this article highlights the characteristics and pattern of urbanization in the world based on the quadrants map,using data of 118 countries or areas.The results indicate that the process of urbanization in the world excluding the data of China has slowed down gradually.A further exploration examines China's urbanization process and economic development over time,which reveals that both urbanization level and the level of economic development belong to the low-grade coordination pattern.The low level of urbanization is closely connected with the low level of economic development.Actually,China's urbanization gap appeared during 1985-1995,but it has been eliminating this urbanization gap since 1995 as a result of rapid urbanization growing.The complicated realities revealed in this analysis challenge the existing two prevalent views.

大坝混凝土早龄期变温条件下拉伸徐变研究

为解决大坝混凝土早龄期拉伸徐变确定困难的问题,本文综合考虑大坝混凝土早龄期水化发展进程和约束状态,采用温度-应力试验技术,测试获得粉煤灰掺量分别为35%和80%掺量的两种大坝混凝土在两种不同温度养护模式下约束试件和自由试件的温度、变形和应力的发展曲线,由此确定两种大坝混凝土的早龄期拉徐变及其发展规律。结合温度-应力试验和绝热温升试验数据,提出变温条件下的改进开尔文模型的大坝混凝土早龄期拉徐变模型,并对模型进行验证。结果表明:粉煤灰掺量为80%的大坝混凝土早龄期拉伸徐变度较大,可减小约束应力的发展,对混凝土早龄期抗裂有利。基于水化发展进程的改进开尔文模型可较好地预测约束状态下大坝混凝土的早龄期拉伸徐变,从而用于其早龄期开裂风险评估。