Estimates of reynolds stress and TKE production in the seasonally stratified East China Sea

During the two cruises in March and July of 2011, the tidal cycling of turbulent properties and the T/S profiles at the same location in seasonally stratified East China Sea (ECS) were measured synchronously by a bottom-mounted fast sampling ADCP (acoustic Doppler current profiler) and a RBR CTD (RBR-620) profiler. While focusing on the tide-induced and stratification’s impact on mixing, the Reynolds stress and the turbulent kinetic energy (TKE) production rate were calculated using the ‘variance method’. In spring, the features of mixing mainly induced by tides were clear when the water column was well-mixed. Velocity shear and turbulent parameters intensified towards the seabed due to the bottom friction. The components of the velocity shear and the Reynolds stress displayed a dominant semi-diurnal variation related to velocity changes caused by the flood and ebb of M₂ tide. Stratification occurred in summer, and the water column showed a strongly stratified pycnocline with a characteristic squared buoyancy frequency of N² ～ (1–6) × 10^?3 s^?2. The components of the velocity shear and the Reynolds stress penetrated upwards very fast from the bottom boundary layer to the whole water column in spring, while in summer they only penetrated to the bottom of the pycnocline with a relatively slow propagation speed. In summer, the TKE production within the pycnocline was comparable with and sometimes larger than that in the well-mixed bottom layer under the pycnocline. Considering the associated high velocity shear, it is speculated that the mixing in the pycnocline is a result of the local velocity shear.     

Gravity field and tectonic features of Block L2 in the Lamu basin,Kenya

A gravity survey on the scale of 1: 250 000 was carried out in Block L2 located in the Lamu basin of south‐east Kenya in order to study tectonic features and find out favourable petroleum prospects in the block. This paper, through data processing and synthetic interpretation of the measured gravity data in the block, discusses characteristics of the gravity field and their geological implications, determines the fault system and the basement depth, analyses features of the main strata, divides structure units and predicts favourable petroleum zones. In the block, the regional gravity anomaly is mainly caused by the inclined Moho surface that rises in the east and subsides in the west topographically and the Bouguer gravity anomaly primarily reflects the superimposition of the gravity effect derived from the Moho surface and the basement relief. Two groups of faults extending NW (NWW) and NE (NEE) respectively are dominant in the block and their activities resulted in the framework of east‐west zoning and south‐north blocking. The basement depth greatly changes in an alternative high and low pattern. The Permian‐Triassic, Jurassic and Tertiary strata are extensively developed, while the Cretaceous is only developed in the east of the block. Structurally, the block can be divided into five units, of which the Tana sag shows excellent source‐reservoir‐seal associations and is a favourable target for future petroleum exploration.     

Discussion of paper ‘Simulation of floor response spectra in shake table experiments’ by G. Maddaloni,K. P. Ryu and A. M. Reinhorn,Earthquake Engineering and Structural Dynamics 2011; 40(6): 591‐604

Three main topics including the floor motion action mechanism, the test frame design, and the target spectrum simulation presented in the paper are discussed specifically. Floor motion action mechanism is critical in understanding the seismic performance of architectural nonstructural components. Seismic sensitiveness and earthquake response properties of the nonstructural components should be considered in the design of the test frame for the shaking table test. Target spectrum simulation is also a challenging job in the shaking table test, in which dynamic characteristics of the specimen, performance of the shaking table facilities, and the control techniques should be all considered. Copyright © 2011 John Wiley & Sons, Ltd.     

土壤有机质含量估测及其影响因素的光谱分析

 土壤颗粒大小差异使土壤反射光谱产生相应变化,影响土壤有机质含量等属性的光谱预测精度。本研究准备了颗粒粒径分别为2、0.25和0.15mm的土样,测定土壤有机质(Soil Organic Matter,SOM)含量,并于室内模拟条件下测定其反射光谱。通过分析不同粒径土样的原始(Raw)、多次散射校正(Multiple scattering correction, Msc)、一阶微分(First derivative, Fd)、连续统去除(Continuum removal, Cr)光谱与SOM含量之间的关系,筛选出与SOM含量相关性最强的Fd光谱单波段(2250nm, r=0.82, P<0.01),并建立线性回归模型;利用全波段光谱反射率,以偏最小二乘回归(Partial least square regression, PLSR)方法,确立2mm土样Msc处理光谱的PLSR模型为最优模型(RPD=3.56、R²=0.90、RMSEP=1.96g/kg)。土壤颗粒粒径对土壤光谱反射率变化有明显影响,但二者之间并非简单的线性关系,可能存在一个转折点;单变量(单波段光谱反射率)线性回归模型的预测能力,明显低于全波段反射光谱(Msc处理)-PLSR模型;土样样本容量对SOM含量预测精度有显著影响。因此,根据样本容量大小,选择合适的土壤颗粒粒径与光谱预处理方法组合可以提高预测精度。     

Influences of Al,Mg, and K on Calculating Concentrations of Other Formation Elements and Their Corrections in Geochemical Logging

In geochemical logging, the standard capture gamma-ray spectra of Al, Mg, and K have no distinct characteristic energy peaks. This feature easily influences the spectral bands of characteristic peaks of other elements and thus affects the accuracy of calculating their concentrations. To study this influence, we constructed a model formation containing Al, Mg, and K, and employed the Monte Carlo N Particle Transport Code (MCNP) program to simulate their capture spectra. The results indicate that the calculated dry weights of Si are almost free from the influences of Mg, K, and Al. The ones of Ca and Fe are influenced, but only to a minor extent. The dry weight of S is concurrently influenced. Specifically, the K concentration causes S concentration to deviate significantly from its real concentration. By correcting for such influences, we can obtain relatively accurate values. Data processing for a real well validates the finding that Mg, Al, and K in the formation influence the precision of calculation of other elements and also testifies to the effectiveness of the correction method.     

石家庄铁四局北国-开元广场岩土工程勘察实录

通过石家庄铁四局北国-开元广场工程勘察实例介绍,总结出一套成功进行岩土工程分析的有效办法和技术途径,分析结果通过实测验证,可供同行们参考。     

西部大地形变数据库设计与建设

介绍西部大地形变数据库的设计与建设.     

渗流应力耦合分析在溪洛渡电站坝址区的应用

把裂隙岩体概化为等效连续介质,建立了统一的渗流－弹塑性应力全耦合控制议程。坝区耦合分析表明耦合和不耦合分析所得的坝区渗流场有一定差别,耦合分析的厂房地下洞室顶部的水压力值增大,且洞室壁面的出渗量也增大。考虑耦合作用的地下洞室群区域的渗探优化布置仍需进一步的研究。     

渤海海峡断面温度结构及流量的季节变化

作者采用 POM模式 ,利用从卫星遥感资料反演的风和海表温度 (SST)数据并考虑 M2分潮作用 ,对渤海海域的温度、流场的三维结构进行数值计算。根据数值模式的计算结果 ,重点分析渤海海峡温度结构和水交换的季节变化特征。结果表明风应力和 SST的季节性变化导致渤海海峡的水交换流型、温度结构和流量有明显的季节性变化。