海水循环水系统中环境因子对大西洋鲑体内土腥味物质含量的影响

为获知不同时期封闭式海水循环水养殖系统中水质因子、浮游植物和细菌群落结构对大西洋鲑(Salmo salar)体内土腥味物质含量变化的影响,于2018—2019年4次采集封闭式海水循环水养殖系统的水样和大西洋鲑。测定水体的氨氮、亚硝氮、硝氮、活性磷酸盐等指标,分析水体浮游植物群落结构并通过16S高通量测序测定水体中细菌群落结构,通过微波蒸馏-固相微萃取-气相色谱-质谱联用(MD-SPME-GC-MS)方法,分析大西洋鲑背肌中土臭素(Geosmin,GSM)和二甲基异冰片(2-methylisoborneol,MIB)的含量。研究发现:测定水质指标中温度、溶解氧、盐度、pH、氨氮、亚硝氮、硝氮、活性磷酸盐、总氮、总磷、总悬浮物和溶解性总有机碳在不同时期差异显著。共鉴定出浮游植物7门、13目、26属,蓝藻门(Cyanophyta)、硅藻门(Bacillariophyta)和绿藻门(Chlorophyta)为优势门;不同时期细菌群落中的优势菌门均为变形菌门(Proteobacteria)和拟杆菌门(Bacteroidetes),但细菌群落结构存在差异,这主要是由水质差异引起的。在不同时期,鱼体MIB含量均高于GSM含量,MIB为鱼体中主要的土腥味物质,在7和10月MIB含量较高。鱼体土腥味物质含量受浮游植物和细菌群落影响,而水质因子可能通过影响浮游植物和细菌群落的结构,来影响养殖鱼体内土腥味物质的含量。     

亚像素定位的关键问题研究

分析了控制点标志的选择与设计,采用了图像处理、Hough变换、角点与直线高精度定位算子等方法,实现了中南大学近景摄影测量二维控制场1 350个人工标志点的自动识别和亚像素定位,仿真图检测平均精度达到±0.05像素。     

中国沿海HY-2A校正微波辐射计水汽含量数据精度检验方法

为评价“海洋二号”卫星（HaiYang-2A, HY-2A）校正微波辐射计（Calibration Microwave Radiometer, CMR）近海水汽产品精度,以中国沿海全球导航卫星系统（Global Navigation Satellite System, GNSS）业务观测站数据和欧洲中期天气预报中心（European Centre for Medium-Range Weather Forecasts, ECMWF)发布的第五代大气再分析资料（ECMWF Reanalysis 5, ERA5）作为验证数据。首先对选取的GNSS业务观测站数据和CMR水汽含量数据进行时空匹配,两者的观测时间一致、空间范围取为100 km;然后利用精密单点定位方法反演GNSS业务观测站上空的大气可降水量（Precipitable Water Vapor, PWV）,同时对1 h分辨率的ERA5再分析资料内插计算,得到CMR水汽数据点处的ERA5 PWV;最后以GNSS PWV和ERA5 PWV为参考,分析2015年CMR水汽产品精度和偏差时空分布。结果表明,CMR水汽含量和GNSS PWV、E...     

凤眼莲根对东海原甲藻生长的抑制作用及机制研究

观察凤眼莲Eichhornia crassipes根粉末及丙酮提取物对东海原甲藻Prorocentrum donghaiense生长的影响,比较分析根系丙酮提取物中的化学成分以及不同成分抑藻效果,探讨凤眼莲根对藻类生长的抑制作用及其化学基础。结果显示,1.5g.L-1以上的凤眼莲根粉末可完全抑制东海原甲藻的生长。实际浓度0.019g.L-1的凤眼莲根丙酮提取物对东海原甲藻可产生50%的抑制率。N-苯基-2-萘胺浓度为1mg.L-1时,第6天对东海原甲藻的抑制率超过60%。浓度50μl.L-1时,亚油酸对东海原甲藻的抑制率超过80%。气相色谱-质谱联用(GC-MS)或高效液相色谱(HPLC)检测显示,凤眼莲根丙酮提取物中含有一定量的亚油酸和N-苯基-2-萘胺,同时还有大量的长链脂肪酸如十六酸、9-十六碳烯酸等。结果表明,凤眼莲根可显著抑制东海原甲藻的生长,N-苯基-2-萘胺、亚油酸可能是凤眼莲根抑藻的主要因子。     

基于数值模拟的汾河二库对晋祠泉岩溶水系统渗漏补给作用研究

汾河二库的下闸蓄水,改变了晋祠泉域汾河地表水对岩溶水的渗漏补给条件,对区域岩溶水流场变化有着长远的影响。本研究通过系统梳理库区水文地质条件,勾画地表水渗漏补给岩溶水范围,考虑地层岩性、蓄水高度等因素,确定二库不同蓄水水位下晋祠泉域获渗漏量占比;构建晋祠泉三维岩溶地下水流模型,研究二库渗漏对泉域岩溶地下水补给作用,并预测不同蓄水情景下晋祠泉口水位变化趋势。结果表明：晋祠泉域获渗漏量占比随二库蓄水位非线性变化,最低为92.8%,在二库蓄水位达902 m后稳定在93.7%,而渗漏量与二库蓄水高度呈正相关;泉域岩溶水径流区受渗漏补给作用最显著,其次为排泄区、北部补给区;渗漏补给作用下,地下水位回升值受二库水位和补水距离影响;维持设计水位（905.7 m）和2017年水位（895.9~902.4 m）时,预计晋祠泉口水位分别在2021年7月和2023年1月达到泉口高程。     

Identification of Convective and Stratiform Clouds Based on the Improved DBSCAN Clustering Algorithm

A convective and stratiform cloud classification method for weather radar is proposed based on the density-based spatial clustering of applications with noise (DBSCAN) algorithm. To identify convective and stratiform clouds in different developmental phases, two-dimensional (2D) and three-dimensional (3D) models are proposed by applying reflectivity factors at 0.5° and at 0.5°, 1.5°, and 2.4° elevation angles, respectively. According to the thresholds of the algorithm, which include echo intensity, the echo top height of 35 dBZ (ET), density threshold, and ε neighborhood, cloud clusters can be marked into four types: deep-convective cloud (DCC), shallow-convective cloud (SCC), hybrid convective-stratiform cloud (HCS), and stratiform cloud (SFC) types. Each cloud cluster type is further identified as a core area and boundary area, which can provide more abundant cloud structure information. The algorithm is verified using the volume scan data observed with new-generation S-band weather radars in Nanjing, Xuzhou, and Qingdao. The results show that cloud clusters can be intuitively identified as core and boundary points, which change in area continuously during the process of convective evolution, by the improved DBSCAN algorithm. Therefore, the occurrence and disappearance of convective weather can be estimated in advance by observing the changes of the classification. Because density thresholds are different and multiple elevations are utilized in the 3D model, the identified echo types and areas are dissimilar between the 2D and 3D models. The 3D model identifies larger convective and stratiform clouds than the 2D model. However, the developing convective clouds of small areas at lower heights cannot be identified with the 3D model because they are covered by thick stratiform clouds. In addition, the 3D model can avoid the influence of the melting layer and better suggest convective clouds in the developmental stage.     

Characterization of Regional Combustion Efficiency using ΔXCO: ΔXCO2 Observed by a Portable Fourier-Transform Spectrometer at an Urban Site in Beijing

Measurements of column-averaged dry-air mole fractions of carbon dioxide and carbon monoxide, CO₂ (XCO₂) and CO (XCO), were performed throughout 2019 at an urban site in Beijing using a compact Fourier Transform Spectrometer (FTS) EM27/SUN. This data set is used to assess the characteristics of combustion-related CO₂ emissions of urban Beijing by analyzing the correlated daily anomalies of XCO and XCO₂ (e.g., ΔXCO and ΔXCO₂). The EM27/SUN measurements were calibrated to a 125HR-FTS at the Xianghe station by an extra EM27/SUN instrument transferred between two sites. The ratio of ΔXCO over ΔXCO₂ (ΔXCO:ΔXCO₂) is used to estimate the combustion efficiency in the Beijing region. A high correlation coefficient (0.86) between ΔXCO and ΔXCO₂ is observed. The CO:CO₂ emission ratio estimated from inventories is higher than the observed ΔXCO:ΔXCO₂ (10.46 ± 0.11 ppb ppm^?1) by 42.54%–101.15%, indicating an underestimation in combustion efficiency in the inventories. Daily ΔXCO:ΔXCO₂ are influenced by transportation governed by weather conditions, except for days in summer when the correlation is low due to the terrestrial biotic activity. By convolving the column footprint [ppm (μmol m^–2 s^–1)^–1] generated by the Weather Research and Forecasting-X-Stochastic Time-Inverted Lagrangian Transport models (WRF-X-STILT) with two fossil-fuel emission inventories (the Multi-resolution Emission Inventory for China (MEIC) and the Peking University (PKU) inventory), the observed enhancements of CO₂ and CO were used to evaluate the regional emissions. The CO₂ emissions appear to be underestimated by 11% and 49% for the MEIC and PKU inventories, respectively, while CO emissions were overestimated by MEIC (30%) and PKU (35%) in the Beijing area.     

二维层状介质中衍射波的计算

本文讨论了衍射波的计算,它是文献[5]的继续和发展,是为了应用射线法解决二维地震人机联作工作的一部分。根据波的物理性质,引入了等效炮点、等效检波点和等效界面等概念,将Berryhill导出的衍射波计算公式推广到倾斜界面和楔形结构等情形。这一工作与文献[1—3]中的工作相结合,在实用上解决了二维地震人机联作解释中的正演计算方法问题。     

密肋复合墙体非线性数值分析及抗剪承载力研究

结合课题组前期的研究成果,通过对墙体中不同材料的本构模型、墙体中裂缝、多种材料的联结以及墙体边界条件的研究与探讨,运用通用有限元程序ANSYS对密肋复合墙体进行非线性有限元分析;并在试验结果与有限元模拟的基础上,依据极限平衡理论,建立起来复合墙体的斜截面抗剪极限承载力公式。理论分析与试验研究表明:复合墙体非线性有限元模型能够较好地模拟墙体内力和变形发展的全过程,描述裂缝的形成和扩展,对于实际工程和科学研究具有足够的精度;墙体斜截面抗剪承载力公式与实测值吻合较好,具有一定的精度,满足工程设计需要。     

松辽盆地深层地震资料叠前时间偏移连片处理技术研究

为了建立松辽盆地等时地层格架,深入认识松辽盆地地质特征和结构以及油气聚集规律,本文开展了松辽盆地不同工区、不同时期采集的二维和三维地震资料叠前连片处理技术研究.本文针对叠前连片处理过程中不同区块的非一致性, 采用了相应的处理方法和手段, 使得连片处理后数据的相位达到一致,区块间拼接带的频率、能量(或振幅)变化自然合理.处理后的资料地质现象丰富,地层齐全,具有较高的信噪比和连续性.资料反映的区域构造合理,有利于对松辽盆地区域地质规律进行统一的认识.