Application of acoustic Doppler current profiler combined with a scientific echo sounder for krill Euphausia pacifica density estimation

ABSTRACT:   An application of the acoustic Doppler current profiler (ADCP, 153.6 kHz) in combination with a scientific echo sounder (EK60, 38 and 200 kHz) was investigated to estimate the density of krill Euphausia pacifica . The acoustic backscattering strength from sound scattering layers was compared with biomass estimates from midwater trawls. Euphausia pacifica was targeted among mixed species populations in the sound scattering layer in the offshore Funka Bay area of Hokkaido, Japan. The frequency characteristics of acoustic backscattering by krill were calculated using a distorted wave Born approximation scattering model at three frequencies. Krill aggregations identified from the EK60 data were extracted as the mean volume backscattering strength difference between two frequencies. They were then used to identify similar aggregations in the ADCP data by matching observation times and depths for the two methods, which were applied simultaneously. Results from the comparison of the mean volume backscattering strength and the density calculated from the ADCP and EK60 showed that ADCP can be used to measure density and spatial–temporal distribution of krill aggregations. Current speed and direction at the study site were found to be 16.1 cm/s and 187.0°, respectively, and krill speed and direction (including the current component) were found to be 19.8 cm/s and 172.2°, respectively. Based on the ADCP data, the net speed and direction of the krill aggregations were found to be 5.9 cm/s and 128.0°, respectively.     

西部少数民族贫困山区扶贫模式研究——以四川省昭觉县为例

西部民族贫困山区是我国扶贫攻坚的重点和难点地区,其扶贫工作的好坏直接关系：我国民族团结、全面建设小康社会目标的实现。在分析西部民族贫困山区县——四川省昭觉县农村贫困与扶贫工作现状的基础上,总结了适合民族贫困山区县的扶贫模式——“三集中”扶贫模式,提出通过发展县域循环经济和建立健全生态环境补偿机制来推广发展“三集中”扶贫模式的对策建议。     

遂川天然次生林干材收获模型

根据天然次生林中收集的样本资料,以样地中检尺乔木树干材积为基准变量Ｙ,以平均林龄,平均胸径,株数、乔木种数、郁闭度为说明变量,建立不同的干材收获模型。『     

不同DEM分辨率下的坡面土壤侵蚀模型的坡长因子提取对比研究

采用基于GIS的非累计流量的坡长直接提取算法(NCSL)和空间分析提取法(SAC)对陕北省安塞县10个样区的坡长进行提取,并计算相应的坡长因子。对不同DEM分辨率下的坡长提取结果对比,结果表明:NCSL对坡长的提取精度明显好于SAC的提取结果,其中DEM在5、10 m分辨率下的提取精度最好,且二者计算的坡长因子值差异不大,因此,可采用10 m分辨率NCSL方法提取坡长。     

ECK2007模型与其他密钥协商协议模型安全强弱关系的形式化证明

比较了安全性模型Extended Canetti＆Krawczyk 2007（ECK 2007）与其他4个安全模型（Bellare＆Rogaway 1993（BR93）,Bellare＆Rogaway 1995（BR95）,Bellare,Pointcheval＆Rogaway 2000（BPR 2000）和Canetti＆Krawczyk 2001（CK2001））的不同点,并形式化地分析了这些模型之间的强弱关系,对模型间存在的蕴含关系提供了形式化证明,对非蕴含关系提供了反例。     

Relation of soil organic matter concentration to climate and altitude in zonal soils of China

With a total of 886 data sets distributed in different regions of China, the relation of soil organic matter (SOM) concentration to climate and altitude was investigated. These data sets were obtained from the 2nd National Soil Survey of China that was completed in early 1980s. According to climate gradient and vegetation community succession, six geographical regions, including eastern, southern, northern, northeastern, northwestern and southwestern China, were divided to identify the key factors regulating surface SOM concentration in different geographical regions. Correlation analysis indicates that surface SOM concentration is in general negatively correlated with annual mean temperature (T) and positively correlated with annual mean precipitation (P) and altitude (H). A further investigation suggested that multiple regression models with different combination of T, P and H could explain 41.5%–56.2% of the variability in surface SOM concentration for different geographical regions, while the driving variables are different. Variables of T and P determined surface SOM concentration in northern, northeastern and northwestern China. In eastern and southern China, variables of P and H are key factors regulating surface SOM concentration. Surface SOM concentration in southwestern China is determined by a linear combination of T, P and H.     

基于遥感技术的气象因素变化影响水稻单产定量研究

以黑龙江省五常市为研究区域,应用在水稻移栽期至成熟期选择的系列MODIS影像反演NDVI,通过NDVI间接反演LAI,并逐日拟合水稻全生育期的LAI,结合SIMRIW模型,计算研究区域2006年低温影响下的水稻单产。经演算,水稻单产值为5411．74kg／hm^2,是实际值的84％。研究结果表明应用高时间分辨率MODIS图像能够准确反演并拟合逐日LAI,可以为冷害影响下水稻单产的研究提供参考。