Distribution of vertical turbulent mixing parameter caused by internal tidal waves and solitary waves in the South Yellow Sea

Many observations show that in the Yellow Sea internal tidal waves (ITWs) possess the remarkable characteristics of internal Kelvin wave, and in the South Yellow Sea (SYS) the nonlinear evolution of internal tidal waves is one of the mechanisms producing internal solitary waves (ISWs), which is different from the generation mechanism in the case where the semidiurnal tidal current flows over topographic drops. In this paper, the model of internal Kelvin wave with continuous stratification is given, and an elementary numerical study of nonlinear evolution of ITWs is made for the SYS, using the generalized KdV model (GKdV model for short) for a continuous stratified ocean, in which the different effects of background barotropic ebb and flood currents are considered. Moreover, the parameterization of vertical turbulent mixing caused by ITWs and ISWs in the SYS is studied, using a parameterization scheme which was applied to numerical experiments on the breaking of ISWs by Vlasenko and Hutter in 2002. It is found that the vertical turbulent mixing caused by internal waves is very strong within the upper layer with depth less than about 30m, and the vertical turbulent mixing caused by ISWs is stronger than that by ITWs.     

Plant Species Richness Affected Nitrogen Retention and Ecosystem Productivity in a Full‐Scale Constructed Wetland

The effects of plant species richness (SR; i.e., 1, 2, 4, 8, and 16 species per plot) on substrate nitrate and ammonium retention and ecosystem productivity in a full‐scale constructed wetland (CW) with high nitrogen (N) input were studied. Substrate nitrate (0.1–16.4 mg kg^?1) and ammonium concentrations (1.3–9.2 mg kg^?1) in this study were higher than those in other comparable biodiversity experiments. Substrate nitrate concentration significantly increased while ammonium concentration significantly decreased with the increase of plant SR (p = 0.008 and 0.040, respectively). The response of ecosystem productivity to increasing SR was unimodal with four species per plot achieving the greatest productivity. Transgressive overyielding, which was compared to the most productive of corresponding monocultures, did not occur in most polycultures. We conclude that substrate N retention was enhanced by plant SR even with high N input, and plant SR could be managed to improve the efficiency of N removals in CWs for wastewater treatment.     

土地出让价格信号引起的房价变化时空扩散效应

从信号传递角度出发,研究土地出让事件冲击带来的房价变化在时间和空间上的扩散效应。利用杭州2006年1月-2010年3月177宗住宅用地成交数据和251个新建商品住宅楼盘交易数据,借助GIS相关软件展开实证研究,结果发现:①土地出让价格信号引起房价的变化,对房价的影响具有“不对称性”;②房价变化以出让地块为中心往外扩散,呈现“波纹效应”;③房价变化具有“持续性”,土地出让价格信号对房价的影响持续四个月,影响范围达3 km以上;④房价波动强度随时间推移和空间延伸不断渐弱。对此,政府应尽量保持地价平稳,规避地价信号所产生的市场波动风险。     

中国南方大陆海岸线时空变迁

海岸线变迁对于海岸带生态环境变化乃至全球变化研究具有重要意义。通过对5个时相TM影像的人机交互解译,获取1990年,1995年,2000年,2005年和2010年中国南方大陆海岸线信息,分析了各时段岸线变迁特征及变迁原因。结果表明:(1)中国南方大陆海岸线的长度和分形维度保持相对稳定,但岸线长度存在总体缩短和局部增长的演化趋势。(2)岸线海向推进的岸段占据主要部分,陆向缩退岸线仅发生在少部分岸段。(3)长江口—杭州湾南岸和珠江三角洲两个典型岸段的分析表明中国南方大陆岸线的时空变化速率与强度在不断加强。(4)在1990—2010年期间,引起中国南方大陆海岸线时空变迁的人为因素的作用比自然因素显著,并导致人工岸线比重不断增大,自然岸线比重不断下降。     

数字化前兆设备防雷技术应用分析

根据雷电危害的类型及台站不同设备的特点和布局,在充分分析雷电入侵观测系统途径的基础上,应用适用于数字化前兆台站的防雷技术,全面采取电源线路防护、信号线路防护、电磁屏蔽、接地等措施,可取得综合性防雷保护。通过对使用徕信防雷技术10个台站的防雷效果进行分析,说明综合防雷安全性效果明显。     

L21雷电预警系统在前兆防雷中的应用

L21雷电预警系统在呼和浩特基准地震台防雷击试运行发现,雷电到来发出预警并自动切换电源,对前兆设备防雷击起到关键作用,为替代人工断电措施提供安全保障,保证观测记录的正常运行。     

城市地下管线共享平台建设模式探讨

针对地下管线信息孤立建设、分散管理的现状,提出了省、市、县三级地下管线信息共享建设的设计模式,深入分析了不同级别的地下管线信息管理和应用的需求,设计了省、市、县三级地下管线共享平台的建设框架,对地下管线信息集成管理、共享应用具有一定的指导意义。     

Bioremediation and fodder potentials of two Sargassum spp. in coastal waters of Shenzhen,South China

In this study, the bioremediation potentials of two seaweeds (Sargassum hemiphyllum and S. henslowianum) against pollution in a coastal mariculture area of Shenzhen, South China, were investigated by comparing the growth, nutrient bioaccumulation capacity of plants from the seaweed bed (control site) with plants from the fish farm. Results indicated that both species are potential candidates for bioremediation in the fish farm areas in terms of their high growth rates and high bioaccumulation capacities on inorganic nutrients. Both Sargassum spp. contain high levels of crude protein (11.7–14.0%) and crude fat (2.2–2.7%), suggesting high nutritional values. The S. hemiphyllum may serve as a good aquaculture fodder with high nutritional compositions and low heavy metal contents. However, heavy metals (Cr, Pb and Cd) of S. henslowianum exceed the maximum allowable concentrations as aquatic feed, which restricts its fodder application. In general, the results of this study may contribute to the marine pollution bioremediation in the coastal areas of South China, especially in mariculture zones.     

毛乌素沙地现代沙丘沙的粒度特征及其意义

对毛乌素沙地不同类型41个现代沙丘的沙粒度分析结果表明,流动沙丘沙主要由细沙和中沙组成,平均粒径为2.17 Φ;固定-半固定沙丘沙的主要粒级是细沙和极细沙,平均粒径为3.09 Φ。流动沙丘沙平均粒径整体自西北到东南减小,而分选性总体表现为中等-较好,无明显空间变化规律。概率累计曲线和粒度特征参数散点图表明,毛乌素沙地沙丘沙以跃移搬运方式为主,存在着就地起沙和就地堆积的可能。平均粒径和分选性空间变化规律的差异,是在频繁强烈的风沙活动环境下物源和大气环流共同作用的结果。     

Vertical impedance of tapered piles considering the vertical reaction of surrounding soil and construction disturbance

The pile–soil system is divided into layers of sufficient number such that the shear stiffness at the pile–soil interface can be determined based on the complex stiffness transfer method. The vertical reaction of surrounding soil on the annular projections at the interface of adjacent pile segments is simplified using Voigt model, whose spring and damping coefficients are derived afterward, allowing an amended impedance function transfer method to be proposed. Using the amended impedance function transfer method, the dynamic equilibrium equation of the pile is solved to give an analytical solution for the impedance function at the pile top. By comparing the solution proposed in this paper with other solutions, the superiority of the bearing capacity of a tapered pile is further confirmed. A parameter study is then conducted to give insight into the coupled interaction of the vertical reaction of the surrounding soil with construction disturbance in the low-frequency range concerned in the seismic design of the pile foundations.