应用P—S曲线分析非线弹性地基上的欧拉——伯努利梁

在较大外荷载下,搁置在地基上的Bernoulli—Euler梁下部的土体会发生塑性变形。在使用有限差分法离散了文克勒地基梁（Winkler）的控制方程后,形成了线性代数方程组,然后调用计算机Fortran程序进行了求解。利用p-s曲线,通过迭代,使用有限差分法求解了考虑土体塑性的变基床系数的Winkler地基梁的位移。计算结果表明：通过p-s曲线和变基床系数的Winkler地基梁模型,可近似分析出地基在外荷载作用下是进入弹性阶段还是弹塑性阶段,并给出较为合适的地基沉降值。最后,讨论了算法的应用范围。     

Contrasting local retention and cross-shore transports of the East Australian Current and the Leeuwin Current and their relative influences on the life histories of small pelagic fishes

Transport between shelf and offshore environments supports a significant proportion of ocean primary productivity and is critical to the life cycle of many marine species. While fundamental differences in the underlying dynamics of eastern and western boundary currents have been recognized and studied for more than half a century, the implications for physical dispersal rates have received much less attention. In this study we explore how Australia’s two major boundary current systems, the East Australian Current and the Leeuwin Current, differ in their local retention and cross-shore transports in the upper water column and how these differences favor contrasting life histories of small pelagic fishes. The results suggest that the East Australian Current forms a partial barrier to onshore transport, but is effective in entraining shelf waters and transporting them offshore, particularly in the region where the current separates from the coast. Blue mackerel (Scomber australasicus) spawn on the outer-shelf in this separation region and may thereby maximize the dispersion of eggs and larvae in the mainly oligotrophic waters of the southern Coral Sea. In contrast, the Leeuwin Current system promotes onshore transport through the combined effects of mean onshore flow and eddy-induced mixing. In the Great Australian Bight, sardine (Sardinops sagax) and anchovy (Engraulis australis) may exploit the high coastal retention of the Leeuwin Current system by spawning on the inner-shelf during summer when the current is weakest and winds assist retention and enhance production through local upwelling.     

Logistic曲线在涠洲油田群含水规律研究中的应用

含水上升规律研究是油田动态分析的重要内容,应用Logistic生长曲线统一表征油田含水上升规律,并建立了涠洲油田群不同主力产层的油田含水上升模式。研究表明以涠洲组为主力产层的油田在生产过程中具有凸型的含水率上升规律,以角尾组为主力产层的油田在生产过程中具有s型的含水率上升规律,而以流沙港组为主力产层的油田在生产过程中则具有凹型的含水率上升规律。应用涠洲油田不同主力产层典型的含水率上升方程,结合区域产量规划研究,预测了涠洲油田群的产水量情况,为油田群水处理设施的建设规划提供了基础。研究方法对油田开发管理及区域规划具有一定的借鉴意义。     

水化学性质对蒙脱石悬浮液膨胀性的影响

实验研究了NaOH、HCl、NaCl和CaCl2等电解质加入量对蒙脱石悬浮液膨胀性的影响,并通过离子色谱、体视显微镜和激光粒度分析技术,研究了蒙脱石粒度变化与体积膨胀之间的关系。实验结果表明,NaOH、HCl对蒙脱石悬浮液膨胀性影响不明显,而NaCl和CaCl2对蒙脱石悬浮液的膨胀有明显的抑制作用;而且CaCl2对蒙脱石膨胀的抑制作用明显强于NaCl,CaCl2浓度比NaCl少了1个数量级时即可达到相同的膨胀抑制效果。离子色谱分析显示,CaCl2溶液与蒙脱石混合后,悬浮液上清液中的Ca2+浓度减少,而Na+浓度增加,分析存在离子交换过程。经激光粒度分析仪和体视显微镜观察,电解质的加入使颗粒之间产生了团聚作用,改变了颗粒的粒径,从而在宏观上表现为蒙脱石悬浮液体积的减少。     

基于激光云高仪反演全天边界层高度的两步曲线拟合法

大气边界层高度是天气、气候、大气环境研究中的一个重要参数,目前尚缺少基于激光雷达探测系统反演全天边界层高度的有效方法。文中利用北京朝阳站、大兴站的激光云高仪数据,首先评估了梯度法、标准偏差法、曲线拟合法和小波协方差法反演边界层高度的适用性和局限性,发现梯度法容易受环境噪声的影响,曲线拟合法稳定性较好,但在夜间弱湍流条件下会将残留层高度误判为夜间边界层高度。提出两步曲线拟合法,将一天中边界层结构划分为白天的对流边界层、夜间的残留层和稳定边界层,通过用不同的理想曲线对其进行两步拟合,获取全天边界层高度的变化。将两步曲线拟合法的反演结果与基于L波段探空雷达的位温梯度法的探测结果进行比较发现:两者相关系数为0.91,证明了两步曲线拟合法的可行性以及激光云高仪探测边界层高度的应用潜力。采用该方法反演2017年5—6月朝阳站与大兴站边界层高度,对比发现:城区特殊的下垫面性质使朝阳站日间对流边界层发展更早,边界层高度更高,全天朝阳站边界层高度的变化在308—1391 m,大兴站在197—1302 m。      

城市化速度曲线及其政策启示——对诺瑟姆曲线的讨论与发展

诺瑟姆提出的城市化S形曲线是城市地理学的经典理论成果,对它在中国的应用却存在曲解。根据诺瑟姆原文,不是所有国家的城市化水平都能达到100%,城市化水平在30%到70%之间也不是一直处于加速状态;进而推导出城市化速度变化的四阶段倒"U"形曲线:孕育阶段、加速阶段、减速阶段、趋零阶段。其政策含义和启示在于:城市化速度变化有其规律,不能拔苗助长;中国已经迈过城市化速度的拐点,加速城市化不应是长期的主旋律;城市化依然是主要发展方向和趋势;中国城市化理念与重点均需转型;城市化与包容性增长、城乡统筹和农民工市民化是"十二五"时期的主要任务。     

经济增长与环境污染的库兹涅茨曲线分析与预测——以宁夏为例

根据环境库兹涅茨曲线假说,选取1991—2007年宁夏经济与环境数据,建立经济发展与工业"三废"排放量以及生活污水排放量的计量模型,分析它们的环境库兹涅茨曲线特征及其成因。研究发现,宁夏工业废水排放量的环境库兹涅茨曲线呈"U"形曲线,工业废气和固体废弃物排放量的环境库兹涅茨曲线均呈倒"N"形曲线,第一次下降的拐点分别出现在2015年和2007年,生活污水排放量的环境库兹涅茨曲线呈正"N"型。结果表明,宁夏工业废水、废气以及生活污水排放量随着经济的发展仍处于上升期,环境污染物排放量EKC的转折点尚未达到。参照发达国家经验,同时结合宁夏"十二五"规划,预计到2020年宁夏人均GDP达到10 000美元时,工业废气和固体废弃物将出现EKC的拐点,工业废水排放量和生活废水排放量不能出现拐点。同时,根据污染物和经济发展的分析结果,提出了不同污染物的防治措施及建议。     

明清时期河南回族分布格局研究

明清时期,回族移居河南又出现高潮,不仅人数与年俱增,分布区域也逐渐扩展到省内各个村落.在分布格局上由小集中向大分散变迁,由相对独立的封闭性寺坊聚居区转变为开放性象征聚居区,是今天河南回族分布格局产生的基础.其分布模式的形成受文化融合、民族文化认同、文化与经济互动、地理等因素的影响.同时,也与社会历史背景、民族政策以及国家与社会关系的特点有关.     

Extracting fair-weather data from atmospheric electric-field observations at Syowa Station, Antarctica

At Syowa Station (69.0°S, 39.6°E), located on East Ongul Island near the continent of Antarctica, atmospheric electric-field observations started in 1968 and had been carried out intermittently. An improved electric-field mill at Syowa Station had and obtained better-quality atmospheric electric-field data from February 2005 to January 2006. After a 1-year interruption, the observations resumed in January 2007.The atmospheric electric-field data from Syowa Station are often contaminated due to local disturbances caused by near-ground meteorological phenomena. We examined correlations between the atmospheric electric field and near-ground weather from February 2005 to January 2006 and from February 2007 to January 2008, and proposed a criterion to extract “fair-weather” electric-field data based on wind speed and cloud coverage data. The diurnal variation of fair-weather data in January followed the shape of the so-called Carnegie curve. Fair-weather data obtained during a substorm showed some correspondence between the atmospheric electric field and variations in the geomagnetic field. This newly developed extraction method may enable the use of atmospheric electric-field data for studying the solar terrestrial environment.     

Predicting and forecasting flow discharge at sites receiving significant lateral inflow

Two models, one linear and one non‐linear, were employed for the prediction of flow discharge hydrographs at sites receiving significant lateral inflow. The linear model is based on a rating curve and permits a quick estimation of flow at a downstream site. The non‐linear model is based on a multilayer feed‐forward back propagation (FFBP) artificial neural network (ANN) and uses flow‐stage data measured at the upstream and downstream stations. ANN predicted the real‐time storm hydrographs satisfactorily and better than did the linear model. The results of sensitivity analysis indicated that when the lateral inflow contribution to the channel reach was insignificant, ANN, using only the flow‐stage data at the upstream station, satisfactorily predicted the hydrograph at the downstream station. The prediction error of ANN increases exponentially with the difference between the peak discharge used in training and that used in testing. ANN was also employed for flood forecasting and was compared with the modified Muskingum model (MMM). For a 4‐h lead time, MMM forecasts the floods reliably but could not be applied to reaches for lead times greater than the wave travel time. Although ANN and MMM had comparable performances for an 8‐h lead time, ANN is capable of forecasting floods with lead times longer than the wave travel time. Copyright © 2007 John Wiley & Sons, Ltd.