Application of Dynamic Subgrid-scale Models for Large-eddy Simulation of the Daytime Convective Boundary Layer over Heterogeneous Surfaces

The sensitivity of large-eddy simulation (LES) to the representation of subgrid-scale (SGS) processes is explored for the case of the convective boundary layer (CBL) developing over surfaces with varying degrees of spatial heterogeneity. Three representations of SGS processes are explored: the traditional constant Smagorinsky–Lilly model and two other dynamic models with Lagrangian averaging approaches to calculate the Smagorinsky coefficient (C _S ) and SGS Prandtl number (Pr). With initial data based roughly on the observed meteorology, simulations of daytime CBL growth are performed over surfaces with characteristics (i.e. fluxes and roughness) ranging from homogeneous, to striped heterogeneity, to a realistic representation of heterogeneity as derived from a recent field study. In both idealized tests and the realistic case, SGS sensitivities are mostly manifest near the surface and entrainment zone. However, unlike simulations over complex domains or under neutral or stable conditions, these differences for the CBL simulation, where large eddies dominate, are not significant enough to distinguish the performance of the different SGS models, irrespective of surface heterogeneity.     

威海市杨家滩水源地地下水资源评价

本文分析了威海市杨家滩不源地第四系冲洪积－海相沉积物分规律和水文地质特征；在此基础上，应用有限单元方法进行了地下水量评价和预测水源地地下水位的变化趋势；提出了最优开采方案。     

海南昌江沿岸海域石珊瑚的物种多样性及其分布

2009年3月,采用水下照相及摄像方法,对海南昌江沿岸海域的石珊瑚物种多样性、分布及覆盖度进行了调查.结合历史资料,共发现石珊瑚10科15属28种和1未定种.其中鹿角珊瑚属（Acropora）、角蜂巢珊瑚属（Favites）、叶状珊瑚属（Lobophyllia）等为优势类群,常见分布珊瑚种类有角孔珊瑚（Gonioporasp.）、标准蜂巢珊瑚（Favia speciosa）、五边角蜂巢珊瑚（Favites pentagona）、多孔鹿角珊瑚（Acropora millepora）、十字牡丹珊瑚（Pavona decussata）、伞房叶状珊瑚（Lobophyllia corymbosa）等.石珊瑚主要分布于海尾镇三联村以南海域,覆盖率最高为12%.本次调查在海南昌江沿岸海域记录的珊瑚种类数多于以前的记录,但少于海南南岸的三亚鹿回头,也少于北部的广西涠洲岛、广东徐闻、香港等海域,随着调查次数的增加,预计会有更多的种类被发现.该海域是北部湾珊瑚幼虫交流的中间过渡区,对珊瑚礁的保护与恢复具有重要意义.     

几种网络体系结构中数据包的效率比较分析

介绍了一种新型网络体系结构SUNA，并将它的数据包与其它两种层次型网络体系结构中的数据包进行了组成和效率上的比较分析。说明了在这方面，SUNA的数据处理效率的优势。     

Isolation, distribution and evaluation of cytotoxic and antioxidant activity of cultivable actinobacteria from the Oman Sea sediments

Screening bioactive natural products from bacteria is a determinative step in the drug discovery programs. The present study aim to isolate actinobacteria from the Oman Sea sediments for determining the effects of different culture media and treatments on the yield of the isolation process, and measure the DPPH radical scavenging and Artemia cytotoxic activity of culture extracts of the actinobacterial isolates. A total of 290 actinobacterial isolates were collected from 14 sediment samples. Heat treatment(40.68%) and M_4 medium(29.31%) exhibited the maximum isolation rates of actinobacteria. Streptomyces isolates were dominantly distributed in all of the investigated stations according to 16 S rRNA gene sequencing. The distribution pattern of Streptomyces followed a depth-dependent frequency trend, whereas the members of rare genera including Micromonospora, Nocardia Actinoplanes, Nocardiopsis, Saccharopolyspora and Crossiella were distributed in deeper stations. Approximately,25% of the examined isolates could scavenge 90% of 10~(–4) mol/L DPPH solutions at 1 250 μg/mL final concentration of their ethyl acetate culture extracts. Furthermore, the most potent extracts could scavenge DPPH radicals with IC50 ranges from 356.8 to 566.4 μg/mL. Brine shrimp cytotoxicity tests showed that 38.88% of the examined culture extracts exhibited LC_(50) lower than 1 000 μg/mL against the Artemia cells. Moreover, the most potent culture extracts exhibited LC_(50) range from 335.4 to 534.4 μg/mL. Phylogenetic analysis by 16 S rRNA gene sequence revealed that the OS 005, OS 263 and OS 157 closely related to Streptomyces djakartensis, Streptomyces olivaceus and Nocardiopsis dassonvillei respectively. These results suggested the widespread distribution of the antioxidant and cytotoxic producing actinobacteria in the Oman Sea sediments, which could be considered as promising candidates for the discovery of microbial bioactive compounds.     

脂类分析在海洋微藻化学分类学上的研究进展

总结了目前脂类研究在海洋微藻化学分类学上的研究进展。所有的海洋微藻脂类都含一定的脂肪酸和甾醇,而不同种类的海洋微藻都有其特殊的脂肪酸和甾醇组成特征,我们可以运用这些特性来判别微藻可能所处的化学分类学地位：如果运用从某些藻类中发现的部分罕见脂类成分,还有可能对微藻的个别种类进行确定。随着对微藻中脂类物质分离,提取、纯化技术研究的不断深入,加上质谱、核磁共振等结构分析手段和脂类衍生化技术的日益完善,可以构建海洋微藻脂类物质组成结构快速查询信息库,并使其成为微藻化学分类的一个重要辅助手段。     

Paleo‐fires and Atmospheric Oxygen Levels in the Latest Permian: Evidence from Maceral Compositions of Coals in Eastern Yunnan,Southern China

Inertinite maceral compositions of the Late Permian coals from three sections in the terrestrial and paralic settings of eastern Yunnan are analyzed in order to reveal the paleo-fire events and the atmospheric oxygen levels in the latest Permian. Although the macerals in the studied sections are generally dominated by vitrinite, the inertinite group makes up a considerable proportion. Its content increases upward from the beginning of the Late Permian to the coal seam near the Permian-Triassic boundary. Based on the microscopic features and the prevailing theory that inertinite is largely a by-product of paleo-fires, we suggest that the increasing upward trend of the inertinite abundance in the latest Permian could imply that the Late Permian peatland had suffered from frequent wildfires. Since ignition and burning depend on sufficient oxygen, a model-based calculation suggests that the O2 levels near the Wuchiapingian/Changhsingian boundary and the Permian-Triassic boundary are 27% and 28% respectively. This output adds supports to other discoveries made in the temporal marine and terrestrial sediments, and challenges the theories advocating hypoxia as a mechanism for the Permian-Triassic boundary crisis.     

Enhancing the mechanical properties of marine clay using cement solidification

Abstract

The use of soft clay and dredged marine clays as the construction material is challenging. This is because the high water content, high compressibility and low permeability of the clay causing the instability of ground and structure. This detrimental effect of soft clay can be improved by the cement solidification process, which is relatively cheap and efficient. This paper mainly focuses on the study of improvement on the mechanical behavior of cement mixed marine clay. The soil is reconstituted by using ordinary Portland cement of 5%, 10%, 15% and 20% by its mass. The study reveals that cementation of clay significantly improves the peak and residual strength of soil. Similarly, the primary yield stress of the soil is also improved from 16 to 275?kPa as cement content increases from 5% to 20%, respectively. By using statistical tools, the relationships between various parameters are established, which are very important to define the mechanical behavior of the clay. This study reveals that the yield surface of the solidified marine clay is not a smooth elliptical surface. Rather it is composed of two linear surfaces followed by a log-linear surface which can be modeled by using simple parameters obtained from triaxial tests.     

Tides in the Tongan Region of the Pacific Ocean

Tidal levels and currents in the Tongan region of the Pacific were simulated using a two-dimensional frequency-domain finite element model. The eight major diurnal and semidiurnal tidal constituents were modeled successfully, using open boundary conditions taken from a global tidal model based on the Topex/Poseidon satellite altimeter. Comparison of model results with observations from the single tide gauge site in the area were later used to adjust the boundary conditions. The validity of omitting horizontal eddy viscosity from the finite element model was checked by running an equivalent finite difference model. The results show that although the submarine Tongan ridge does not appear to trap tidal energy, there are residual tidal currents and possible recirculations which are capable of influencing biological productivity around Tonga. The model results are reduced to a simple method for predicting tidal heights in outlying areas, based only on the tidal calendar for the capital, Nuku'alofa.     

Influence of salinity on permeability characteristics of marine sediments

Abstract

Laboratory tests were conducted on compacted marine sediments to study the effect of salt concentration of permeating fluid on its permeability characteristics. Deep sea sediment samples were collected from water depths varying from 3700 to 4500 m off Mauritius coast. Liquid limit and plasticity index varied widely from 45 to 75 and 10 to 35, respectively. Permeability was found at different void ratios with distilled water and 0.2, 0.4, and 0.8 N NaCl solutions as permeating fluid. It was found that permeability increases with an increase in salt concentration for a given void ratio. This is explained by diffused double layer theory. Also, the rate of increase in permeability decreases with increase in salt concentration. The effect of salt concentration seemed to be less at higher void ratios.