基于声场模型的猎雷声呐探测成像仿真方法

针对猎雷声呐对水雷目标探测仿真问题,提出一种基于运动学信息与水下声场传播耦合分析的探测成像仿真方法。利用 Bellhop3D 声场分析方法对水下声信道信号冲击响应进行计算,结合信号复分析方法得到信号传播信道参数以构建声散射模型,以运动耦合方式综合分析声呐搭载平台位置、姿态及速度等因素对回波信号的影响,通过综合考虑上述因素来模拟目标回波信号,从而利用较为真实的等效回波信号进行图像重构。 以高频前视声呐为例,对声呐探测沉底水雷目标情况进行了仿真,结果表明,该方法能够得到高频声呐对沉底水雷目标的探测图像,与实际情况具有一致性,可为进一步构建反水雷相关模拟仿真训练系统提供参考。     

Adaptation strategies for mitigating agricultural GHG emissions under dual-level uncertainties with the consideration of global warming impacts

Agriculture plays a central role in maintaining food security and achieving sustainable development for human society. It is a challenge for the agricultural sector to mitigate greenhouse gas (GHG) emissions and maintain agricultural production. However, dual-level uncertainties exist in the processes of agricultural GHG accounting and emission reduction management. In this research, an integrated approach for identifying adaptation strategies in agricultural GHG emission reduction management was developed through incorporating life cycle analysis (LCA) of agricultural production into a general mathematical programming model. This approach strengthened the applicability of LCA and the comprehensiveness of programming models in generating agricultural adaptive actions under different GHG emission restriction targets. Also, dual-level uncertainties of LCA and adaptation management can be effectively addressed. A case study was proposed to illustrate application of the approach in Dalian City, China. The results indicated that farming patterns in eight districts would change significantly. The total area of maize fields would account for the primary proportion (i.e., 40–45 %) in its agricultural sector. Rice, peanut and cabbage fields would be the minor contributors in terms of GHG emissions. In addition to effective rainfall (i.e., [156, 259] mm/ha), a certain amount of water would be supplied for agricultural irrigation to maximize the city’s agricultural yields. Compared with other agricultural crops, rice fields would need the largest amount of irrigation water (i.e., [153.72, 277.98] Mt) to meet the requirements of local government plans.     

基于Landsat与DMSP-OLS的非监督城区提取方法研究

夜间灯光数据DMSP-OLS经常被用作区域范围监测城市区域,但是其低空间分辨率和"溢出"效应容易导致产生较差的结果。经过分辨率更高的Landsat数据能够得到更精确的结果,但所需的大量人力限制了其在大尺度下应用。本文利用非监督机器学习,提出了一种结合Landsat和DMSP-OLS的30 m分辨率城市提取方法。基于城市像元常常同时拥有两种特性(如更高的夜间灯光强度和位于不透水面区域),分类学习的训练样本被自动提取。然后,两种数据提供的4种互补的特征(光谱、纹理、不透水面指数和夜间灯光强度)被用作城市/非城市分类。实验结果表明:相对于仅仅使用单一数据源,结合两种数据能够得到更好的城市提取结果,因此,本文提出的方法能可靠且高效地提取大范围城市区域。     

Identification of optimal strategies for agricultural nonpoint source management in Ulansuhai Nur watershed of Inner Mongolia,China

In this study, an environmental-friendly modeling system was developed and applied to an agriculture nonpoint source (AGNPS) management in Ulansuhai Nur watershed. In this system, water environmental capacity, credibility-based chance-constrained programming (CCCP), and AGNPS optimization models were integrated into a general modeling framework. It could be used to calculate water environmental capacity of total nitrogen and total phosphorus in Ulansuhai Nur watershed, which could consequentially provide input data for the developed AGNPS optimization model. Also, the inherent uncertainties in estimating water environmental capacities that can be expressed as possibilistic distributions were reflected and addressed based on computational results of three widely used methods. Such uncertainties were consequentially transferred to the proposed CCCP model based on the adoption of multiple credibility satisfactory levels, significantly facilitating objectivity reflection of decision alternatives. The developed modeling system was then applied to Ulansuhai Nur watershed of Inner Mongolia, a semi-arid river basin in northwestern China. Optimal strategies for AGNPS management in Ulansuhai Nur watershed were generated with consideration of the maximum total agricultural income under multiple policy scenarios. The results showed that the total agricultural income would increase with point source pollution being cut down, and would decrease with rising credibility levels, representing decreasing system violation risks. It was indicated that the higher of total nitrogen/phosphorus discharge being less than water environmental capacity of Ulansuhai Nur, the lower the total agriculture incomes. The proposed methods could help decision makers establish various production patterns with cost-effective agriculture nonpoint source management schemes in the basin of Ulansuhai Nur, and gain in-depth insights into the trade-offs between total agricultural incomes and system reliabilities.     

SIFT与粗差剔除算法相结合的机载SAR影像匹配研究

SAR影像匹配是SAR数据处理的重要环节,但是,SAR影像匹配成功率、正确率及精度较低。通过SAR影像匹配,建立SAR匹配像对,对雷达立体观察和立体测量有重要的意义。在机载SAR影像匹配中,应用SIFT 算法,获得较稳定的特征,并结合2D单应变换的RANSAC算法剔除误匹配点对;选取三组不同类别的机载SAR影像数据,利用SIFT 和粗差剔除相结合的算法,通过VC++和OpenCV编程,提取出特征稳定且均匀分布的同名点对,完成机载SAR影像匹配实验。结果表明,对于含有人工建筑物的机载SAR影像,SIFT 算法可有效地提取大量稳定的匹配点对,其正确率高;对于含有自然植被的机载SAR影像,SIFT 算法可有效地提取较多稳定的匹配点对,其正确率较高;由于SIFT 算法实质上是基于局部灰度匹配的算法,对于纹理信息缺乏的机载SAR影像,只可提取少量稳定的匹配点对,其正确率相对前两者较低。总体而言,在机载SAR影像中SIFT 算法能够提取到稳定的匹配点对,并结合基于2D单应变换的RANSAC算法,可有效剔除误匹配点对,提高匹配正确率及精度。     

东海黑潮暖舌对热带气旋“派比安”(1807)强度的影响

通过使用天气研究与预报(Weather Research and Forecasting,WRF)模式对热带气旋(Tropical Cyclone,TC)个例“派比安”(1807)进行了一组数值试验,分析了东海黑潮暖舌对“派比安”强度的影响。研究结果表明,东海黑潮暖舌高海面温度(以下简称“海温”)导致TC区域内海气界面热通量显著增加,并造成TC边界层不稳定特征发展,形成了有利于垂直对流发展的边界层环境。因此TC内特别是TC眼墙处对流更为活跃,TC强度显著提高,同时黑潮暖舌对TC的局部加热还会引起TC内部对流活动的非对称分布。根据数值试验的结果,黑潮暖舌为“派比安”整体动能增加做出约24.7%的贡献,中心气压变化对东海黑潮暖舌高海温特征的响应时间约为10 h。此外,在黑潮暖舌作用下,“派比安”7级风圈半径扩张16.3%,最大风速半径收缩10.7%。     

热带气旋预报的人工神经网络方法

根据１９４９－１９８８年登陆珠江口的热带气旋资料，运用了人工神经网络的一个典型模型－“反向传播”模型，建立了该地区３５－４９小时热带气旋登陆地点的预报模型，并应用于热带气旋登陆地点的预报，即珠江口的热带气旋登陆地点预报，其拟合最大相对误差不超过０．７％。结果表明，神经网络预报模型具有容错能力强、预报速度快的特点，可望成为望带气旋预报的有效辅助手段。     

Diversity and community structure of eukaryotic microalgae in surface sediments in the central Bohai Sea,China, based on a metabarcoding approach

Sediment samples were collected at 17 stations in the central Bohai Sea, China, and the diversity and community structure of eukaryotic microalgae were assessed by metabarcoding the V4 region of 18S rDNA. A total of 930 operational taxonomic units (OTUs) were detected for microeukaryotes, including 98 algal OTUs. The algal communities comprised 42 genera belonging to 19 classes of six phyla, and they were dominated by chrysophytes and dinoflagellates. Dinoflagellates were also the most diverse microalgal group. The nano-sized dinoflagellates Biecheleria halophila and Azadinium trinitatum occurred abundantly in the study area; however, they have not been reported previously, as they may be overlooked or misidentified in light microscopy. Many pico-sized chlorophytes were detected in the sediment samples. Sixteen of the detected OTUs were assigned to potentially harmful and/or bloom-forming microalgae, suggesting some potential risks of harmful algal blooms in the central Bohai Sea. The capacity of metabarcoding to detect morphologically cryptic and small species makes this method a sufficiently sensitive means of detection for assessing eukaryotic microalgae in sediments.

     

基于改进SWAT模型的灌溉—施肥—耕作对乌梁素海流域营养物负荷及作物产量的影响

不合理的灌溉、施肥和耕作是导致乌梁素海流域农业面源污染的主要根源,乌梁素海作为我国北方地区重要的生态安全屏障,多年来面临着湖泊水环境污染、水生态退化等问题,科学开展湖泊水环境综合治理首先要解决流域内农业面源污染问题.研究通过修改土壤水平衡、溶质平衡、地下水平衡和作物生长等模块对SWAT 2012原始版本进行改进,并采用改进的SWAT模型构建了乌梁素海流域分布式水文模型,利用实测径流、硝态氮与总磷排放量、地下水埋深以及作物产量校正和验证模型.基于现状情景,以玉米、葵花和小麦3种主要作物为研究对象,设置了削减灌水量、施肥量及调整耕作方式3种农田管理情景.基于改进SWAT模型不同情景的模拟结果,计算分析各管理情景下的硝态氮与总磷负荷及对各作物产量的影响.结果表明,改进SWAT模型具有良好的模拟效果.不同作物削减5%夏灌水量增产最多达8.41%～10.32%,削减10%秋浇水量均明显减少硝态氮和总磷负荷.不同作物营养物负荷均随着氮磷施肥削减比例的增大呈现逐渐降低的趋势,但下降曲线逐渐趋于平缓;各作物产量随氮磷施肥削减比例的增加呈先增加后减少的趋势,其中玉米、小麦氮磷施肥削减比例达20%时产量开...     

基于BiLSTM-CRF的中文地质时间信息抽取

时间信息贯穿于地质现象和事件产生、发展、消亡的整个过程中,反映了地质现象和事件的状态和演变过程.特别是,地质时间表达通常与成矿内在机制和时空演化规律有关.设计并实现了基于深度学习的通用时间和地质时间信息抽取方法.结合地质矿产文本中时间信息的描述特点,将时间信息划分为通用时间信息与地质时间信息两种类型,并对两种时间信息类型进行细分;基于自主研发的“交互式矿产信息标注软件”,采用交叉验证及意见反馈模式构建了地质时间信息语料库;实现了基于双向长短期记忆神经网络—条件随机场(BiLSTM-CRF)的时间信息抽取方法;并与主流的卷积神经网络(CNN)和条件随机场(CRF)模型的抽取结果进行了比较.实验结果表明,基于双向长短期记忆神经网络—条件随机场的时间信息抽取效果最好,对总体时间抽取的F1值达到95.49％,较好地解决了地质文本中时间信息的规范化表达和结构化抽取问题.