基于GIS的黄河上游龙羊峡库区生态环境遥感监测研究

本项研究以黄河上游生态环境严重退化的龙羊峡库区为研究区，应用遥感与GIS一体化的方法，建立了库区生态环境动态监测信息系统。在系统的支持下，利用多时相、多波段TM遥感数据，对库区近十年来生态环境变化进行监测分析，揭示了库区土地沙漠化、水土流失、土地利用／土地覆盖的现状，以及建库近十年来生态环境时空演化的过程与发展趋势，为库区生态环境治理提供科学依据。本项研究利用遥感和GIS技术，采用生态环境综合分类系统，在一次分类处理中通过多层次不同级别的组合获得了基于同一信息源的土地沙漠化、草场盖度、土地利用处地覆盖等多种环境类型信息，并利用环境信息模型对库区的土壤侵蚀进行了评价。基于GIS的分类后再处理使遥感分类精度有了一定程度的提高。研究表明，在GIS的支持下充分利用遥感信息监测与评价生态环境，是区域生态环境定量化研究的有效途径。     

1992—2018年中国旱作农田土壤湿度的时空模式及气象驱动因素

土壤湿度作为影响陆气水热交换的重要变量,指示了干旱的演变特征。为揭示中国旱作农田土壤湿度的变化特征及其气象驱动要素,本文利用站点数据研究了1992—2018年中国旱作农田土壤湿度变化趋势的时间和空间特征,采用相关性、敏感性分析等方法探究了土壤湿度的驱动机制。结果表明：2001年中国旱作农田土壤湿度的变化趋势发生转折,土壤湿度年际变化普遍由下降趋势变为上升趋势,主要由夏季和秋季土壤湿度主导。而且土壤湿度的变化存在空间异质性,2001年后东北地区的土壤湿度在显著增加,而西南地区在显著下降。降水量和蒸散发的时空变化是土壤湿度趋势发生时空变化的主要原因,二者存在协同作用,北方地区由降水主导,南方地区由蒸散发主导。     

作为体积目标的舰船辐射噪声建模

舰船辐射噪声是由舰船上机械运转和舰船运动产生并辐射到水中的噪声,是水下目标探测系统对运动舰船进行探测、识别的基础,亦是扫雷装备需重构的重要物理场信息,具有重要的理论和应用价值。 基于舰船辐射噪声的来源和时频空域特点,将作为体积目标的舰船辐射噪声源简化为 3 个主要噪声辐射源,建立了“三亮点” 的体积目标辐射噪声模型,在保留目标主要特征的基础上,简化了重构算法的复杂性,提高了模型的实用性,可以为实验室目标探测、识别研究和扫雷装备提供较为逼真的目标数据来源。     

A model test system with a dynamic load device for geotechnical engineering in cold regions

A model test system with a dynamic load device for geotechnical engineering in cold regions is presented. This system consists of a model test tank, a refrigeration device and temperature controller, a dynamic load device, together with sensors and data loggers for detecting stress, deformation, and temperature changes. The system can accommodate soil blocks up to 3 m in length, 2.5 m in width, and 1 m in height. The lowest temperature provided by the refrigeration device is -20 °C. The maximum load provided by the dynamic load device is 100 kN and the vibration frequency of the dynamic load can range from 0.1 to 10 Hz. A number of waveforms, such as sine waves, rectangular waves, triangle waves, and other user-defined waves can be generated by the dynamic load device controller.     

毛乌素沙区沙漠化土地防治区划

毛乌素沙区在自然条件、沙漠化程度和变化趋势及产业经济发展特征等方面具有明显的空间异质性,合理地进行区域沙漠化土地防治区划是因地制宜开展土地沙漠化防治工作的重要基础。选取自然条件、沙漠化发展过程及人类活动等方面12个指标,将毛乌素沙区划分为黄土高原与鄂尔多斯高原过渡区、毛乌素沙地腹地典型草原区和西鄂尔多斯荒漠草原区3个区、7个亚区、12个小区。在区域可持续发展战略的实施过程中,要根据亚区和小区的特点有针对性地进行沙漠化土地的防治,充分利用区域资源优势,优化产业结构,确保经济效益、社会效益和生态效益的稳步提升。     

晋北沙漠化地区起沙风风况与输沙势

利用10个气象站点2001、2005、2010,2014年风速数据,计算并分析了晋北沙漠化地区起沙风风况及输沙势时空变化。结果表明：研究区年均起沙风频率和起沙风平均风速均为春季最大,冬季次之,夏季最小,各季节和全年年际变化均表现为大致减小趋势;输沙势显示研究区春季处于中风能环境,是最主要的风沙活动期,其他季节和全年整体上均处于低风能环境;春季风能环境总体呈减弱趋势,这可能是导致研究区2000年以来沙漠化逆转的重要因素之一;受地势影响,研究区春季风能环境呈北高南低、东高西低趋势,最高值位于东北部的大同盆地。     

NUMERICAL SIMULATION OF INTERANNUAL AND INTERDECADAL VARIABILITY OF SURFACE WIND OVER THE TROPICAL PACIFIC

A global atmospheric general circulation model (L9R15 AGCMs) forced by COADS SST was integrated from 1945 to 1993. Interannual and interdecadal variability of the simulated surface wind over the tropical Pacific was analyzed and shown to agree vey well with observation. Simulation of surface wind over the central-western equatorial Pacific was more successful than that over the eastern Pacific. Zonal propagating feature of interannual variability of the tropical Pacific wind anomalies and its decadal difference were also simulated successfully. The close agreement between simulation and observation on the existence of obvious interdecadal variability of tropical Pacific surface wind attested to the high simulation capability of AGCM.     

南沙群岛景观及区域古地理

本文论述了南沙群岛的海底地形、海底表层沉积、珊瑚礁景观、区域新生代古地理、以永暑礁为代表的古气候与古海面，以及本区古海洋等自然地理特征。     

Investigation of insulation layer dynamic characteristics for high-speed railway

Dynamic performance of insulation is one of the key parameters during the insulation application for high-speed railway subgrade. This paper conducted laboratory and field tests for the materials and dynamic load,especially for thermal performance, elastic deformation, and accumulated deformation of insulation materials.Experiment results show that mechanical properties of insulation layer structure are stable, which satisfies the requirements of the high speed railway.     

Problems with biogenic silica measurement in marginal seas

Surface sediment samples from the Bohai, Yellow Sea, and the Pacific were used to assess biogenic silica (BSi) content and to study uncertainties in BSi measurements. The contents of BSi in the Bohai and Yellow Sea are all less than 1%. The dissolution of BSi in sediments from the Bohai and Yellow Sea is very important to maintain high levels of silicate in the water column. The non-biogenic silica from clay minerals has an obvious effect on BSi of sediment samples in the Bohai and Yellow Sea with low BSi and high clay minerals. The solid to solution ratio was found to have a great influence on BSi measurement, which can induce uncertainties up to 75%. The effect of loss by sorption and centrifugation is negligible. Interlaboratory comparison of techniques for BSi measurement by the wet alkaline extraction technique of Mortlock and Froelich [Deep-Sea Res. 36 (1989) 1415-1426] with clay correction was suggested to give no significant differences. However, differences in sediment compositions and reagent to sample ratio may limit the application of the wet alkaline extraction method.