In situ determination of organic compounds in liquid samples using a combined UV-Vis/fluorescence submersible sensor

In order to improve the in situ evaluation and quantitative analysis of complex contaminations of liquid media such as ground-, surface, and wastewaters, an integrated submersible sensor probe has been developed. It is especially characterized by the option of simultaneously measuring ultraviolet/visible (UV/Vis) and fluorescence spectra. Owing to the compact construction with light sources, flow cell, detection system, and data acquisition/processing unit in the waterproof case, the data transfer to the surface can be realized electrically, and the operation depth is practically not limited. The variability in the measuring techniques allows a wide variety of chemical compounds to be analysed within a broad concentration range. The performance of the new submersible sensor probe was tested ex situ in laboratory scale, and the performance was comparable with that of stationary measuring instruments. As an example for an in situ application, the sensor probe was successfully used to monitor the migration of chemical substances during a tracer experiment in groundwater. The concentration of the tracer compound uranin (sodium fluorescein) was measured in the range of 5–500 µg L^?1 using fluorescence spectroscopy, while at the same time the contents of toluene were continuously detected in the same groundwater wells using the UV/Vis sensor channel.     

基于TSFS结合高阶张量特征提取方法的海水半潜油种类鉴别研究

半潜油是一种隐藏于海面之下并呈现悬浮状态的溢油,其长期毒害并侵蚀着海洋生态环境。然而,针对半潜油污染到目前还未形成有效地监测手段和处理方式,致使其污染的突发性和危害性更甚于海面溢油。因此,研究有效地半潜油鉴别方法对保护海洋生态环境具有重要意义。三维荧光光谱技术中的总同步荧光光谱(TSFS)在油类污染物检测与鉴别中具有不存在瑞利散射干扰以及冗余数据少的优势,但由于TSFS数据本身不具备三线性结构,使得多维校正分析方法在其应用上受到了一定的限制。基于此,开展基于TSFS结合高阶张量特征提取方法的海水半潜油种类鉴别研究。首先,利用有机分散剂和六种不同种类的油品配制了90个半潜油实验样本;然后,利用FS920荧光光谱仪采集实验样本的TSFS数据,并对该数据进行标准化预处理;最后,通过高阶张量特征提取方法二维线性判别分析(2D-LDA)以及二维主成分分析(2D-PCA)分别建立了半潜油样本的鉴别模型;并将所建模型与常规方法多元曲线分辨率交替最小二乘法(MCR-ALS)结合线性判别分析(LDA)以及多维偏最小二乘判别分析(NPLS-DA)进行了对比。分析结果表明,2D-LDA和2D-PCA所建立的半潜油样本鉴别模型具有可靠的性能,鉴别模型的精确率、灵敏度及特异性分别为100%,100%和100%。并且,2D-LDA和2D-PCA能够直接提取TSFS光谱图像矩阵在空间、统计学以及图形学上的精细光谱特征,为区分半潜油样本带来更为精准的鉴别依据。因此,相较于常规的基于展开或分解数据的方法,高阶张量特征提取方法所建立鉴别模型所得到的预测结果更加精确。该研究为半潜油种类鉴别提供了一种参考。     

Global warming and coral reefs: modelling the effect of temperature on Acropora palmata colony growth

Data on colony growth of the branching coral Acropora palmata from fringing reefs off Discovery Bay on the north coast of Jamaica have been obtained over the period 2002-2007 using underwater photography and image analysis by both SCUBA and remotely using an ROV incorporating twin lasers. Growth modelling shows that while logarithmic growth is an approximate model for growth, a 3:3 rational polynomial function provides a significantly better fit to growth data for this coral species. Over the period 2002-2007, involving several cycles of sea surface temperature (SST) change, the rate of growth of A. palmata was largely proportional to rate of change of SST, with R(2)=0.935. These results have implications for the influence of global warming and climate change on coral reef ecosystems.     

低温容器夹层真空度对内罐压升率的影响研究

针对低温容器夹层真空失效工况,建立了低温容器夹层真空度与通过内罐壁面热流密度的理论模型,结合ANSYS-FLUENT软件对某立式低温容器内的液氮蒸发过程进行了仿真模拟,研究了初始充满率为50%时,低温容器内罐空间温度及压力随夹层真空度变化的规律。结果表明,随着夹层真空度降低,通过低温容器内罐壁面的平均热流密度增大,内罐中液体温度升高速率增大;当夹层真空完全失效时,内罐压升率分别是夹层真空度为10-3 Pa、1 Pa和10 Pa时的10.4倍、5倍和1.2倍。     

南海夏季海洋环境噪声与海面风速相关特性分析

海洋环境噪声是影响潜艇作战及远程目标探测和定位的重要参数,由于海洋环境噪声具有很强的时空变异性,因此只能通过试验数据测量和处理了解环境噪声的统计特性。本文以2013年4月30日至8月1日,南海典型海域布放海洋环境噪声测量潜标系统所收录的环境噪声为研究对象,数据处理结果表明,在整个频率范围内,海洋环境噪声与对数风速具有很好的线性关系,但环境噪声随风速变化的斜率与频率相关,在1kHz附近达到最大值。本文通过波束形成分析了海洋环境噪声的垂直指向性,并给出了“垂直方向噪声”、“水平方向噪声”和“全向噪声”与风速相关性分析结果,可以看出,在风浪噪声与远处航船噪声都有贡献的中频段,“垂直方向噪声”与海面风速的相关性好于“全向噪声”和“水平方向噪声”与海面风速的相关性,且“垂直方向噪声”随风速变化的斜率略大于“全向噪声”随风速变化的斜率。     

Miniature flow injection analyser for laboratory, shipboard and in situ monitoring of nitrate in estuarine and coastal waters

A miniature, submersible flow injection analyser, with solid-state spectrophotometric detection, for the in situ determination of nitrate is described. It utilises the standard laboratory chemistry of cadmium reduction followed by diazotisation. The detection limit was 2.8 μg l⁻¹ N and the linear range could be varied from 2.8 to 100 μg l⁻¹ N up to 100–2000 μg l⁻¹ N to suit local environmental conditions. The versatility of the instrument is demonstrated by results from laboratory, shipboard (North Sea IMPACT Cruise) and in situ (Tamar Estuary, UK) deployments. They show the excellent temporal and spatial resolution that can be achieved for studying dynamic processes in estuarine and coastal waters. The results acquired during the IMPACT Cruise map the transport of nitrate from the Humber Estuary into the North Sea and show that nitrate uptake was more pronounced in areas of shallow and clear waters (Dogger Bank) than in the coastal mixing zone with higher suspended solids. A key feature of the analyser is its portability and ease of deployment due to the small size and weight and low buoyancy. Accuracy was assessed by participation in an international intercomparison exercise and the results were within the assigned tolerance interval of the consensus mean (Z<2).     

Flutter instability of a fluid-conveying fluid-immersed pipe affixed to a rigid body

A set of simplified boundary conditions for a flexible beam connected to a rigid body at one end and free at the other end is presented and applied to the case of a fluid-conveying, fluid-immersed pipe. These boundary conditions represent an analytically tractable approximation to those of a submersible which uses a combination of jet action and flutter instability induced tail motion to produce thrust. The boundary conditions are made non-dimensional, and the effect of the non-dimensional mass of the rigid body on system stability is assessed. The neutral stability of this system is determined within a two-parameter space consisting of the velocity of the fluid within the tail, and the forward speed of the submersible. Equations in the literature, derived using slender-body theory, were used to compute the sign of the thrust produced by the tail and the tail's Froude efficiency for the neutrally stable waveforms of the beam.