上海职住优化效应的代际差异

城市的职住关系一直为研究者广泛关注。过剩通勤概念以实际通勤与理论最短通勤的差距反映城市职住关系与通勤状态,是衡量通勤效率和优化潜力的常用指标。国内的过剩通勤研究数量有限,且鲜有从年龄视角考察。本文利用2017年9月上海市手机网格数据,分析不同年龄段居民的职住与通勤状态,采用模拟个人换居的方法测度过剩通勤,并探讨职住关系优化效应的代际差异。结果表明：上海居民的职住关系存在明显的代际差异,青年人是劣势群体,老年人是优势群体,中年人介于其间;上海全市过剩通勤率为69%,职住关系优化的潜力和效应巨大,可使得通勤距离显著减少,代际分异缓和,青年人的获得感最大,城市年龄空间结构更加均衡。提出上海的空间规划和政策应以理想的城市年龄空间结构为目标,以提高人的居住和就业空间的流动性、青年化城市中心、中老年化城市外围为途径。     

Impact assessment of modified clay on embryo-larval stages of turbot Scophthalmus maximus L.

Using modified clay is one of the most promising methods for the mitigation of harmful algal blooms(HABs). However, the environmental impact of modified clay has become a subject of global concern. In this study, turbot(Scophthalmus maximus L.) embryos were used as a model to assess the effect of modified clay on this sensitive stage of fish development. Results show that the 24 and 48 h LC_(50)(median lethal concentrations) of the modified clay were 1.70 and 1.65 g/L, and the safe concentration was 0.47 g/L, which is much higher than the concentration used to treat HAB. The modified clay did not affect significantly the hatchability of turbot embryos but when the concentration exceeded 0.50 g/L, the deformity rate of newly hatched larvae increased significantly. The total length, specific growth rate(SGR)and yolk sac absorption rate of larvae reached their peaks at 0.50 g/L and then gradually decreased as the concentration of modified clay increased. Therefore, a moderate amount of modified clay does not harm the survival and hatching of turbot embryos, or the growth and development of newly hatched larvae.     

Variations in Dissolved Methane in the Yellow Sea During the Spring Algal Blooms of 2009

Methane(CH_4) is an important greenhouse gas and oceans are net sources of atmospheric CH_4. The effects of environmental factors on the CH_4 variation during different phases of the spring algal blooms were examined during two cruises conducted in the Yellow Sea(YS) from February to April of 2009. During the pre-bloom period from February to March, low CH_4 saturation( 134%) was observed in the surface water, except at two nearshore stations where the CH_4 levels were above 140% in March due to mixing with the coastal water. During the bloom period, CH_4 increased obviously at two bloom-tracking stations, especially at the surface with mean saturations of 140% and 170%. The increase in CH_4 concentration/saturation is thought to be the result of in situ CH_4 production. The particulate organic carbon(POC) and chlorophyll a contents were believed to be important factors that influenced the CH_4 production. In addition, the presence of different dominant phytoplankton species and the grazing pressure may have stimulated the CH_4 production by supplying potential methanogenic substrates(such as dimethylsulphoniopropionate(DMSP)). Both the incubation data and the in situ estimations further evidenced the significant influence of the spring blooms on the CH_4 production. The calculated sea-to-air CH_4 fluxes during the bloom period were not significantly higher than those during the pre-bloom period despite the bloom-increased CH_4 saturation. This is due to the variation in physical forcing(such as wind speed), which is the main driver for determining the CH_4 flux. Finally, we estimated the annual CH_4 flux in the YS as 9.0 μmol m~(-2) d~(-1); the findings suggest that the YS is a natural source of atmospheric CH_4.     

智能优化方法与粒子滤波技术融合的分析与展望

智能优化算法通过模拟自然生态系统机制以解决复杂优化问题,粒子滤波成为解决非线性及非高斯动态系统最优估计问题的研究热点。若将多种优化算法结合使用,设计更好的滤波器参数寻优步骤,将会极大改善现有非线性滤波的估计性能。介绍了几种智能计算方法和粒子滤波方法,在此基础上,对智能优化方法与粒子滤波技术的融合进行了分析和讨论,并加以总结和展望。     

土地调查运行数据库质量评价研究

在分析土地调查数据组织管理模型、数据库运行模型的基础上,从应用的角度建立土地调查运行数据库的质量评价模型,并进行模型示例和分析,得出一些有益的结论。     

跨断层隔震管道分析

埋地管道在断层错动作用下的内力分析及其抗震措施一直是生命线工程的一个重要问题与研究热点。对地下管道在断层错位下的响应计算,取得的成果较多,比较经典的有Newmark-Hall方法和Kennedy方法。后来又出现基于壳模型的简化方法,如高田至郎提出的简化计算方法等。相对来讲,关于管道抗震措施的研究成果较少。本文提出一种抗震措施,进行了基于壳模型的有限元动力数值模拟,并与4种松到中密场地土条件下的埋地管道断层错位响应进行对比分析。计算结果表明,本方法中三种长度管道的最大轴向拉应变远小于埋地管道的最大轴向拉应变,而且最大轴向压应变亦不大。     

南京栖霞山铅锌多金属矿成矿特征及找矿方向

在分析矿床地质特征的基础上,结合前人资料探讨了栖霞山铅锌多金属矿的成矿物质来源、控矿因素和矿床成因。成矿流体主要由来自深部的含矿热液、源自石炭—二叠系碳酸盐岩的有机流体和地表渗流雨水组成。其中,有机流体在矿物沉淀富集过程中起到较为重要的作用。矿体主要受纵向断裂F2、上下构造层之间不整合面和石炭—二叠系碳酸盐岩地层控制,认为在栖霞山深部,沿纵向断裂F2的延伸方向仍有较大找矿空间。