The effect of strength anisotropy on the bearing capacity of spudcan foundations

The vertical bearing capacity of spudcan foundations in strength anisotropic soils is investigated numerically using the MIT-S1 model implemented in the AFENA finite element package. The model in AFENA is validated against existing laboratory test data of normally consolidated soil. The bearing capacities of spudcans in soils with isotropic and anisotropic strengths are compared. Soil with isotropic strength is simulated using an elasto-plastic model. It is found that the bearing capacity of a spudcan in an anisotropic soil is reduced by about 9% for a rough spudcan and 3% for a smooth spudcan on average. There is a combined effect of soil anisotropy and spudcan roughness on the spudcan bearing capacity. Moreover, the effect of the pressuremeter strength of an anisotropic soil on foundation capacity can’t be ignored.     

Vertical amplitude reduction of Rayleigh waves by a row of piles in a poroelastic half‐space

A row of rigid piles is addressed as the countermeasures for isolating Rayleigh waves in a poroelastic half‐space. The complex characteristic equations for Rayleigh waves are derived via Biot's theory and their existence conditions are given. The piles are modeled as Euler–Bernoulli beams with longitudinal displacements and the diffracted field by each pile is constructed only with Rayleigh waves. Six infinite linear systems of algebraic equations are obtained in terms of the equilibrium of forces and continuity of displacements at the pile–soil interfaces. The systems are subsequently solved in the complex least‐squares sense. The influence of certain pile and soil characteristics such as the permeability of poroelastic soil, spacing between the piles and length of the piles on the isolating performance of a pile barrier is investigated. Computed results show that the permeability of poroelastic soil displays a significant effect on the vertical amplitude reduction of Rayleigh waves. Copyright © 2009 John Wiley & Sons, Ltd.     

Experimental study of extreme shear stress for shallow flow under simulated rainfall

The raindrop impact and overland flow are two major factors causing soil detachment and particle transportation. In this study, the turbulent characteristics of the shallow rain‐impacted water flow were investigated using a 2‐D fibre‐optic laser Doppler velocimetry (FLDV) and an artificial rainfall simulator. The fluctuating turbulent shear stress was computed using digital data processing techniques. The experimental data showed that the Reynolds shear stress follows a probability distribution with heavy tails. The tail probability increases with an increase of rainfall intensity or raindrop diameter, and it decreases with an increase of Reynolds number. A modified empirical equation was derived using both the raindrop diameter and rainfall intensity as independent variables to provide a better prediction of the Darcy‐Weisbach friction coefficient f under rainfall conditions. Copyright © 2009 John Wiley & Sons, Ltd.     

微带发夹型滤波器的设计

微带发夹型滤波器具有结构紧凑,尺寸小、重量轻和成本低等优点.根据微波电路设计的基本理论,利用微波电路ADS软件,设计了一个微带发夹型滤波器,其中心频率为2.3GHz时,通带带宽为200MHz,通带内插损小于1.7dB.仿真结果表明所设计的滤波器不仅尺寸小,而且性能优越,具有很高的实用价值.     

Survey of cyanomyovirus abundance in Shantou coastal waters by g20

To understand the genetic diversity and population changes in cyanophages in the coastal waters of Shantou,northeast South China Sea,we used the capsid assembly protein gene g 20 as a marker of the abundance and phylogeny of natural cyanomyovirus communities. The abundance of total viruses,heterotrophic bacteria,and picophytoplankton in the coastal waters was monitored with flow cytometry. Hydrological parameters(NO ˉ 3,NO ˉ 2,NH 3,soluble reactive phosphorus,total dissolved nitrogen,total dissolved phosphorus,dissolved oxygen,chemical oxygen demand,temperature,salinity,and chlorophyll a concentration) and microbial abundance(total viruses,total bacteria,P rochlorococcus,Synechococcus,and eukaryotes) were measured in the upper and lower layers at four sampling sites in the research area. In the direct viral counts,cyanomyoviruses accounted for 1.92% to 10% of the total viral community. A phylogenetic analysis showed that the g 20 sequences in the Shantou coastal waters were very diverse,distributed in eight distinct operational taxonomic units,including the newly formed Cluster W. The g 20 gene copies inferred from real time PCR assay indicated that cyanomyoviruses were correlated significantly with the heterotrophic bacteria numbers and the nitrate and chlorophyll a concentrations. These results suggest that cyanomyoviruses are ubiquitous and are an abundant component of the virioplankton in Shantou coastal waters.     

时空过程网络可视化模拟与分析服务——以溃坝洪水为例

洪水溃坝等复杂灾害现象的时空过程模拟分析,是当前国际地理信息科学热点研究方向之一。随着网络的普及化,公众对GIS时空分析模型的网络实时集成和可视化分析提出了迫切的需求。本文以溃坝洪水为例开展了时空过程网络可视化模拟与分析服务研究,利用Web GL、HTML5、Ajax、Web Service、GPU并行计算等技术手段,通过探讨溃坝洪水时空模型计算优化、网络三维可视化模拟与动态交互分析等关键技术,研发了原型系统并进行应用实验。实验结果表明,本文研究成果有助于实现时空过程信息的网络发布,在线影响分析及动态可视化服务,可为分布式网络环境下溃坝洪水等时空过程信息管理和应急决策提供科学依据和技术支持。     

基于电子鼻的青蛤(Cyclina sinensis)软组织多氯联苯的快速检测方法研究

为建立一种简单快捷的水产品中多氯联苯(PCBs)检测方法,本研究应用电子鼻对青蛤(Cyclina sinensis)软组织中富集的多氯联苯进行检测,并采用HS-SPME-GC-MS(顶空固相微萃取-气质联用)对结果进行了验证。首先利用电子鼻制作PCB15浓度梯度模版,检测PCB15处理72h以及144h的青蛤软组织中残留量,采用LDA和PCA两种方法统计并同模板的浓度进行比较。结论:青蛤软组织中PCB15浓度能明显分开,并随着处理时间的延长,区分效果愈加明显,区分度愈大。PCA的分辨效果明显优于LDA。运用欧氏距离、马氏距离、判别函数法和相关性对含有PCB15的样品浓度分别进行鉴别和验证,四种方法总的鉴别率均达到90%以上,能够较准确地对样品进行验证。电子鼻检测青蛤软组织中的多氯联苯的最低检测限为0.05μg/L,GC-MS为0.5μg/L。     

福建东山岛地质灾害特征与成因初探

海岛是海上陆地国土和人类开发海洋的远涉基地及前进支点。海岛大幅度地快速增长的开发活动与工程建设使脆弱的海岛生态环境正遭受到严重威胁。东山岛是福建第二大岛,近10年随着水产养殖与育苗、风电建设、环岛公路和房地产开发等海岛利用和开发强度的加大,海岛地质灾害及潜在风险陡增。基于现场调查和遥感影像解译,分析东山岛赋存的地质灾害类型及其分布,初步探究了主要地质灾害的诱因,为更有效地保护和可持续性开发东山岛,制定合理长效规划、防灾与减灾对策提供准确依据,并为福建及周边基岩岛的地质灾害调查与防治提供实测数据参考。     

南极半岛东北海域表层沉积有机质来源及其沉积环境

采用气相色谱-质谱技术对南极半岛东北海域海底表层沉积物的总有机碳、有机质碳同位素(δ13 Corg)和生物标志化合物等进行了测试分析。研究区表层沉积物总有机碳TOC平均值高于现代深海沉积物中的平均含量。δ13 Corg的变化说明该海域有机碳来源呈海洋水生生物来源和陆源混合的特征。正构烷烃的峰型分布、主峰碳、饱和烃轻重比C-21/C+22和(C21+C22)/(C28+C29)、甾烷组合和藿烷组合证实研究区西部表层沉积物有机质来源以陆源高等植物为主,其陆源可能来自于附近的南极半岛和南舍得兰群岛;研究区东部表层沉积物有机质来源偏以海源为主,且以低等浮游生物、藻类及细菌生物等海源输入为主。碳优势指数(Carbon preference index,CPI)、奇偶优势指数(Odd-even Predominance,OEP)和甾烷C29ααα20S/(20S+20R)比值显示研究区D1-7站位和D5-9沉积物有机质演化程度较高,D5-2和D2-4站位的有机质演化程度低,其他站位介于中间状态。饱和烃中姥鲛烷、植烷及其比值(Pr/Ph)等组合显示研究区西部以氧化-弱还原的沉积环境为主,其可能是受高温低盐别林斯高晋海水流和附近火山喷发的影响所致;研究区东部以还原—强还原沉积环境为主,可能是受低温高盐的威德尔底层水(WSBW)和威德尔海深层水(WSDW)影响所致。     

南海西北部沉积物捕获器中颗石藻通量和属种组成变化记录

本文利用沉积物捕获器回收的连续时间序列沉降颗粒物样品,研究了南海西北部海南岸外陆坡外缘海域颗石藻的通量和属种组成变化及其环境意义。研究发现,东亚夏季风引起的海南岸外上升流以及冬季风导致的混合层深度增加都会刺激该区域颗石藻的生长,其中夏季上升流的影响尤为显著。从颗石粒属种组成来看,Florisphaera profunda是南海西北部中深层(1 000m)水体中主要的颗石粒优势种,此外Emiliania huxleyi,Gephyrocapsa oceanica和Gephyrocaps ericsonii等属种含量也颇高。然而在将颗石粒折算成颗石球数量后,Emiliania huxleyi则成为主要优势种。沉积物捕获器中F.profunda的相对百分含量与颗石粒总通量呈显著的负相关,表明F.profunda的相对含量与总的颗石藻生产力有着密切联系。本结果对于利用沉积物中的颗石藻记录,尤其是F.profunda相对含量变化,恢复和重建古海洋环境尤其是古海洋生产力的研究提供了直接的理论证据。