ALMA observations of the circumstellar envelope around EP Aqr

Atacama Large Millimetre/sub-millimetre Array(ALMA) observations of CO(1–0) and CO(2–1) emissions from the circumstellar envelope of the asymptotic giant branch(AGB) star EP Aqr have been made with four times better spatial resolution than previously available. They are analysed with emphasis on the de-projection in space of the effective emissivity and flux of matter using as input a prescribed configuration of the velocity field, assumed to be radial. The data are found to display an intrinsic axisymmetry with respect to an axis making a small angle with respect to the line of sight. A broad range of wind configurations, from prolate(bipolar) to oblate(equatorial) has been studied and found to be accompanied by significant equatorial emission. Qualitatively, the effective emissivity is enhanced near the equator to produce the central narrow component observed in the Doppler velocity spectra and its dependence on star latitude generally follows that of the wind velocity with the exception of an omni-present depression near the poles. In particular, large equatorial expansion velocities produce a flared disc or a ring of effective emissivity and mass loss. The effect on the determination of the orientation of the star axis of radial velocity gradients, and possibly competing rotation and expansion in the equatorial disc, is discussed. In general,the flux of matter is found to reach a broad maximum at distances of the order of 500 AU from the star.Arguments are given that may be used to favour one wind velocity distribution over another. As a result of the improved quality of the data, a deeper understanding of the constraints imposed on morphology and kinematics has been obtained.     

Fine-scale responses of phytoplankton to freshwater influx in a tropical monsoonal estuary following the onset of southwest monsoon

In May of 2007, a study was initiated by the National Institute of Oceanography (NIO), Goa, India, to investigate the influence of monsoonal rainfall on hydrographic conditions in the Mandovi River of India. The study was undertaken at a location ∼2 km upstream of the mouth of this estuary. During the premonsoon (PreM) in May, when circulation in the estuary was dominated by tidal activity, phytoplankton communities in the high saline (35–37 psu) waters at the study site were largely made up of the coastal neritic species Fragilaria oceanica, Ditylum brightwellii and Trichodesmium erythraeum. During the later part of the intermonsoon (InterM) phase, an abrupt decline in salinity led to a surge in phytoplankton biomass (Chlorophyll a ∼14 mg m^− 3), of a population that was dominated by Thalassiosira eccentricus. As the southwest monsoon (SWM) progressed and the estuary freshened salinity and Chlorophyll a (Chl a) concentrations decreased during the MoN, Skeletonema costatum established itself as the dominant form. Despite the low biomass (Chl a <2 mg m^− 3), the phytoplankton community of the MoN was the most diverse of the entire study. During the postmonsoon (PostM), the increase in salinity was marked by a surge in dinoflagellate populations comprising of Ceratium furca, Akashiwo sanguinea, and Pyrophacus horologium.     

光谱影像的灰度矢量相关特征与边缘特征提取

提出了多光谱图像像元特征矢量之间的极小互相关系数，极大互相关系数及互相关差值和相关密度的概念，在对模拟图像进行矢量相关分析及其对边缘提取的有效性分析基础上，提出对多光谱图像采取像元特征矢量相关分析并提取边缘信息的方法，对TM图像进行试验分析的结果说明了此方法的有效性。     

电子地图设计课程多媒体情境教学研究

以对武汉大学通识课“电子地图设计”建设为背景,分析了综合性大学中通识课程的建设理念和途径,重点总结了多媒体情境教学方法在课程全环节的运用,对于多学科背景的受众取得了良好的教学效果。     

高光谱影像能量边缘提取

高光谱影像的能量边缘提取方法的本质是利用高光谱信号的能量相似性与能量分布特征来寻找边缘，从能量边缘图可以提取属于不同地物类别的主要边缘，这些边缘都比较明显与完整。实验结果表明，能量边缘对噪声信号不敏感，与用其他方法寻找边缘的结果相比，能量边缘具有更好的效果。     

EDM高程导线测量软件的使用

介绍EDM数据采集软件的安装与使用,阐述野外采集数据时应该注意的问题,提出程序改进的建议。     

越南北部岩溶特征及其相关环境问题

越南北部属热带季风气候,受东南亚季风影响明显,雨量充沛,气温高,植被发育。它们地处特提斯海槽和环太平洋带两个全球性的构造带交汇处,碳酸盐岩受构造改造强烈,岩溶广泛发育,岩溶地貌类型齐全。与中国西南亚热带、热带岩溶区相比,岩溶发育特征有许多类似之处,但其岩溶泉水有更高的碱度,反映出更强烈的溶蚀作用。随着越南经济发展,岩溶区中的一些环境问题也日益突出,不合理的土地利用,已开始造成土地石漠化等环境问题。      

电法测量接地电阻计算方法及影响因素仿真分析

采用电法测量时,为提高观测精度和质量,增强电磁耦合抗干扰能力,须合理计算和减小接地电阻。接地电阻可根据电流场性质和导线电阻定义来计算。针对棒状电极,运用MATLAB软件仿真分析其接地电阻随电极半径、入土深度、电极表面附近土壤覆盖距离的变化规律,确定棒状电极的主要尺寸。由于电极尺寸一般相对固定,减小接地电阻主要通过减小电极附近的土壤电阻率和多根电极并联接地。通过仿真分析接地电阻随更换土壤覆盖半径及集合屏蔽效应系数随电极间隔变化规律,指出更换土壤覆盖半径一般取在100~150 cm范围内,电极间隔大于2倍入土深度,此时接地效果最佳。      

Intertidal mangrove boundary zones as nursery grounds for the mud crab Scylla serrata

The demand for mud crab Scylla serrata (Forsskål 1775) in the global market has increased, hence there is growing momentum to farm the species in Africa. Aquaculture production in Kenya and elsewhere in East Africa currently relies on juvenile seeds sourced from the wild. Wild-seed collection calls for management of the juvenile crab industry founded on knowledge of the species’ ecology, so as to achieve a sustainable seed supply and recruitment to the capture fishery. This study investigated the tidal, diurnal and seasonal occurrence of juvenile crabs in three habitats (intertidal-flat boundary zones, inside the mangroves, and in channels) in small creeks (Mida, Kilifi and Mtwapa) and Gazi Bay, on the coast of Kenya. Sampling was done with scoop nets and seining at receding tides and via burrow searches at low spring tides (day and night). Juveniles in the mangrove/intertidal-flat boundary zone were found sheltered under mangrove leaves or debris, or in shallow burrows during low spring tides, whereas at receding tides they could be seen moving out with the tide or searching for sheltering substrate or burrows. Catch per unit effort at high-abundance sites varied between 59 and 68 crabs fisher^?1 day^?1. More juvenile crabs, sized 10–80 mm internal carapace width (ICW), occurred at night during the receding tide. Net-seining was effective in the collection of juvenile mud crabs <30 mm ICW, whereas burrow sampling was effective for gathering larger crabs. However, collection of juveniles by seining reduced the quality of the crabs caught due to frequent loss of chelipeds, as compared with retrieving individual crabs by searching burrows. Some juveniles collected in the intertidal-flat boundary-zone habitat were either in the process of moulting or had just moulted, indicating the significance of this habitat for mud crabs at this physically delicate life stage.