Fatigue Behavior of Unbonded Partially Prestressed Concrete Beams with Flexure

A study on fatigue behavior of unbonded partially prestressed concrete beams is presented.Model tests have been carried out in static loading and cyclic compressive loading on 15 beams withflexure.The ratios of the lower limit to the upper limit of fatigue load are 0.5 and 0.3 respectively,and thefrequencies of cyclic loading are 8 Hz and 4.5 Hz respectively.The experimental results of the strains of theconcrete and steel bars,the deflection of test beams,and the crack width of normal section are analyzed.According to statistics and analysis of test results,the corresponding calculation models are developed andpresented.     

沙尘和霾气溶胶的物理特征比较

粒子尺度谱和复折射率指数是描述大气气溶胶的基本物理参数,也是遥感大气气溶胶光学厚度的基本假定量,决定了光学厚度遥感的准确程度。本文分析了中国气溶胶遥感网反演的北京周边的沙尘和霾天气下大气气溶胶的体积谱和复折射指数,结果表明:沙尘和霾天气下气溶胶的体积谱均呈现双峰对数正态分布,霾气溶胶粒子体积谱在细模态(0.1～1μm)和粗模态(1～10μm)的占比大体相当,沙尘气溶胶粒子体积谱中粗模态占比远远高于细模态,以粗粒子为主;将实际测量的复折射率同HITRAN 2008数据库中各种类型的气溶胶复折射率光谱数据相比,类沙尘粒子的复折射指数同沙尘气溶胶最为接近,水溶性粒子同霾气溶胶最为接近,在大气气溶胶遥感中如果缺少复折射率的光谱数据,可考虑将类沙尘粒子和水溶性粒子的复折射率光谱数据(0.2～40μm)外推近似代替沙尘和霾气溶胶用于紫外和红外遥感。本研究可为利用紫外光谱和红外光谱定量遥感沙尘和霾气溶胶研究提供参考和依据。     

中国绿色发展效率的空间特征及溢出分析

提高绿色发展效率是建设生态文明、促进经济转型发展的重要途径。基于Super-SBM模型对中国（除港、澳、台、西藏地区）2005~2015年绿色发展效率进行测度,从空间异质、空间关联与空间机理3个方面分析绿色发展效率的空间特征,运用空间杜宾模型验证绿色发展效率的溢出效应并探讨各要素的空间传导机制。结果表明：① 2005~2015年,中国绿色发展效率表现为“先平稳再快速再稳定”的阶段性变化规律,地区间差异较大,形成了“东-中-西”阶梯式递减和“南-中-北”对称式分布的空间分异特征,“T”字型发展格局逐渐凸显。② 绿色发展效率存在显著的空间正相关,空间集聚程度逐步降低,热点区域增加,东部沿海地区形成稳定的热点区,中西部形成稳定的冷点区。③ 绿色发展效率的空间自组织性逐渐增强,空间差异不断扩大,由空间自相关导致的结构化分异更加明显,随机成分引起的空间异质性正逐渐减弱,西北-东南是空间差异的主要方向。④ 绿色发展效率存在较强的空间溢出效应,经济水平、技术创新和能源强度产生明显正向效应,产业结构则具有显著负向效应。     

河南省社会发展综合实验区建设的实践与成效

通过实施调查研究，深入地总结了河南省竹林，孟庄，林州等社会发展综合实验区建设以来的主要成就，经验与存在问题，并进行了具体的科学分析。     

滇池富营养化时空特征评价

1IntroductionEutrophication is the most widespread water quality problem in China and many other countries. Symptoms such as high levels of chlorophyll a, excessive seaweed blooms, occurrence of anoxia and hypoxia have occurred in many areas. Water-qualit…     

完善职工持股制度是地勘单位产权制度改革的有效途径

论述了职工持股制度是地勘单位产权制度改革的途径。提出实行职工持股体现各种生产要素按贡献参与分配的要求和职工持股的基本内容。     

Systematic documentation of landslide events in Limbe area (Mt Cameroon Volcano,SW Cameroon): geometry,controlling, and triggering factors

Limbe town and surrounding areas, on the SE foot slopes of the active Mt Cameroon Volcano, have experienced numerous small-scale shallow landslides within the last 20 years. These resulted in the loss of ~30 lives and significant damage to farmland and properties. Landslides and their scars are identified in the field, and their geometry systematically measured to construct a landslide inventory map for the study area. Specific landslides are investigated in detail to identify site-specific controlling and triggering factors. This is to constrain key input parameters and their variability for subsequent susceptibility and risk modeling, for immediate local and regional applications in land-use planning. It will also enable a rapid exploration of remediation strategies that are currently lacking in the SW and NW regions of Cameroon. Typical slides within the study area are small-scale, shallow, translational earth, and debris slides though some rotational earth slides were also documented. The depletion zones have mean widths of 22 m ± 16.7 m and lengths of 25 ± 23 standard deviation. Estimated aerial extents of landslide scars and volume of generated debris range from 10¹ to 10⁴ m² and 2 to 5 × 10⁴ m³, respectively. A key finding is that most slope instabilities within the study area are associated with and appear to be exacerbated by man-made factors such as excavation, anarchical construction, and deforestation of steep slopes. High intensity rainfall notably during localized storms is the principal triggering factor identified so far. The findings from this case study have relevance to understanding some key aspects of locally devastating slope instabilities that commonly occur on intensely weathered steep terrains across subtropical Africa and in the subtropics worldwide and affecting an ever denser and most vulnerable population.     

Seismic design and shake table tests of a steel post‐tensioned self‐centering moment frame with a slab accommodating frame expansion

Post‐tensioned (PT) self‐centering moment frames were developed as an alternative to welded moment‐resisting frames (MRFs). Lateral deformation of a PT frame opens gaps between beams and columns. The use of a composite slab in welded MRFs limits the opening of gaps at the beam‐to‐column interfaces but cannot be adopted in PT self‐centering frames. In this study, a sliding slab is used to minimize restraints to the expansion of the PT frame. A composite slab is rigidly connected to the beams in a single bay of the PT frame. A sliding device is installed between the floor beams and the beams in other bays, wherever the slab is allowed to slide. Many shaking table tests were conducted on a reduced‐scale, two‐by‐two bay one‐story specimen, which comprised one PT frame and two gravitational frames (GFs). The PT frame and GFs were self‐centering throughout the tests, responding in phase with only minor differences in peak drifts that were caused by the expansion of the PT frame. When the specimen was excited by the 1999 Chi‐Chi earthquake with a peak ground acceleration of 1.87g, the maximum interstory drift was 7.2% and the maximum lateral force was 270 kN, equal to 2.2 times the yield force of the specimen. Buckling of the beam bottom flange was observed near the column face, and the initial post‐tensioning force in the columns and beams decreased by 50 and 22%, respectively. However, the specimen remained self‐centering and its residual drift was 0.01%. Copyright © 2011 John Wiley & Sons, Ltd.     

Holocene peatland development along the eastern margin of the Tibetan Plateau

Knowledge of peatland initiation, accumulation, and decline or cessation is critical in understanding peatland development and the related carbon source/sink effect. In this study, we investigated the development of three peat profiles along the eastern margin of the Tibetan Plateau (ETP) and compared the results with those of our previous work along this transect. Our work showed that the initiation over the northern ETP is later and the slowdown/cessation earlier than in the middle to southern ETP. The timing of optimum peatland formation over the northern ETP lags the Holocene climatic optimum. These spatio-temporal differences are likely to be related to the intensity of Asian summer monsoon. Our work suggests that some peatlands along the ETP transect have returned or are now returning their previously captured carbon to the atmosphere and thus act as carbon sources. Some peatlands still have net accumulation at present, but the rates have been reduced concomitant with the decreasing summer monsoon intensity. We speculate that more of the previously stored carbon in the ETP peatlands will be re-emitted to the atmosphere if the aridity continues, as might occur under a continuous global-warming scenario.