Spatial distribution and temporal variation of reference evapotranspiration in arid and semi‐arid regions of Iran

Analysis of spatial and temporal variations of reference evapotranspiration (ET_o) is important in arid and semi‐arid regions where water resources are limited. The main aim of this study was to analyse the spatial distribution and the annual, seasonal and monthly trends of the Penman–Monteith ET_o for 21 stations in the arid and semi‐arid regions of Iran. Three statistical tests the Mann‐Kendall, Sen's slope estimator and linear regression were used for the analysis. The analysis revealed that ET_o increased from January to July and deceased from July to December at almost all stations. Additionally, higher annual ET_o values were found in the southeast of the study region and lower values in the northwest of the region. Although the results showed both positive and negative trends in annual ET_o series, ET_o generally increased, significantly so in six (～30%) of the stations. Analysis of the impacts of meteorological variables on the temporal trends of ET_o indicated that the increasing trend of ET_o was most likely due to a significant increase in minimum air temperature, while decreasing trend of ET_o was mainly caused by a significant decrease in wind speed. At the sites where increasing ET_o trends were statistically significant, the rate of increase varied from (+)8·36 mm/year at Mashhad station to (+)31·68 mm/year at Iranshahr station. On average, an increasing trend of (+)4·42 mm/year was obtained for the whole study area during the last four decades. Seasonal and monthly ET_o have also tended to increase at the majority of the stations. The greatest numbers of significant trends were observed in winter on the seasonal time‐scale and in September on the monthly time‐scale. Copyright © 2011 John Wiley & Sons, Ltd.     

基于网格模板的最小欧式距离准则图像自动拼接技术

提出一种结合网格模板和最小欧式距离准则的图像自动拼接方法。方法选取图像重叠部分作为处理对象，运用边缘检测自动获取基准图像特征块，并提出基于网格模板的最小欧式距离准则用于计算匹配点，最后使用图像融合技术消除接缝。应用证明该方法拼接准确快速，实现简单，适合大部分图像拼接应用的需要。     

后门检测系统的Win32应用程序设计与实现

介绍了后门检测系统的设计,以及各模块实现拟采用的方案,包括:网卡数据包的截获,进程和端口号的映射,截获包的解码与分析和数据库设计等.     

一种新的超声波心动图像分割算法

针对超声心动图像噪声大,边界模糊,灰度分布不均匀等特点,提出了一种新的图像分割算法.首先对超声图像进行滤波和边缘锐化等预处理,然后再使用GVFSnake模型对预处理后的图像进行分割,从而提取出心室的边界.经试验证明,这种新的超声心动图像分割算法,比传统的超声图像分割算法在图像分割精度上有显著的提高.     

基于合成孔径雷达交叉极化通道数据的海上目标探测

Azimuth ambiguities(ghost targets) discrimination is of great interest with the development of a synthetic aperture radar(SAR). And the azimuth ambiguities are often mistaken as actual targets and cause false alarms. For actual targets, HV channel signals acquired by a fully polarimetric SAR are approximately equal to a VH channel in magnitude and phase, i.e., the reciprocity theorem applies, but shifted in phase about ± for the first-order azimuth ambiguities. Exploiting this physical behavior, the real part of the product of the two cross-polarized channels, i.e.(S S)HV VH, hereafter called A12 r, is employed as a new parameter for a target detection at sea. Compared with other parameters, the contrast of A12 r image between a target and the surrounding sea surface will be obviously increased when A12 r image is processed by mean filtering algorithm. Here, in order to detect target with constant false-alarm rates(CFARs), an analytical expression for the probability density function(pdf) of A12 r is derived based on the complex Wishart-distribution. Because a value of A12 r is greater/less than 0 for real target/its azimuth ambiguities, the first-order azimuth ambiguities can be completely removed by this A12r-based CFAR technology. Experiments accomplished over C-band RADARSAT-2 fully polarimetric imageries confirm the validity.     

Dose of truth—Monitoring marine non-indigenous species to serve legislative requirements

Non-indigenous species (NIS) are recognized as a global threat to biodiversity and monitoring their presence and impacts is considered a prerequisite for marine environmental management and sustainable development. However, monitoring for NIS seldom takes place except for a few baseline surveys. With the goal of serving the requirements of the EU Marine Strategy Framework Directive and the EU Regulation on the prevention and management of the introduction and spread of invasive alien species, the paper highlights the importance of early detection of NIS in dispersal hubs for a rapid management response, and of long-term monitoring for tracking the effects of NIS within recipient ecosystems, including coastal systems especially vulnerable to introductions. The conceptual framework also demonstrates the need for port monitoring, which should serve the above mentioned requirements but also provide the required information for implementation of the International Convention for the Control and Management of Ships Ballast Water and Sediments. Large scale monitoring of native, cryptogenic and NIS in natural and man-made habitats will collectively lead to meeting international requirements. Cost-efficient rapid assessments of target species may provide timely information for managers and policy-advisers focusing on particular NIS at particular localities, but this cannot replace long-term monitoring. To support legislative requirements, collected data should be verified and stored in a publicly accessible and routinely updated database/information system. Public involvement should be encouraged as part of monitoring programs where feasible.     

我国海洋声学探测技术竞争力分析

海洋声学探测技术用于海洋物理及海洋特定目标特性探测,是人类认识海洋、开发和利用海洋丰富资源必不可少的海洋高技术。文中全面介绍了海洋声学探测技术的技术结构以及致力于此技术研究的国内外主要研究机构,着重对比分析了国内外海洋声学探测技术的发展现状与趋势,并总结出我国该领域现存在的问题。结果表明我国海洋声学探测技术水平与国外相差10 a左右,未来需靠长期稳定支持、按需开展研究、加大基础工业投资以及提高材料与工艺水平等措施推进我国海洋声学技术的良性发展。     

轨道扣件病害自动化检测研究及应用

传统扣件检查基本采用人工检查方式,不仅工作效率低、劳动强度大,而且人为干扰因素多、检查采样率低。针对以上问题,本文提出了一种基于线结构光传感器的轨道扣件损伤和松动检测方法,并开发了轨道扣件智能监测系统以实现扣件病害自动检测。最终将研究成果应用于徐州市某地铁区间轨道扣件检测,验证了该方法的可行性和准确率,为地铁轨道扣件检查提供了新方法。     

基于卷积神经网络的无人机影像违章建筑检测应用

无人机航拍影像具有分辨率高、回访周期短等特点,利用无人机遥感技术手段对城市范围的建设进行动态监测,可及时、有效地发现涉嫌违法的建设活动。本文结合实际项目需求,研究通过卷积神经网络方法进行违章建筑的自动检测,替代过去靠大量人力检查的模式,目前测试区域无人机影像试验取得了较好的效果,在样本数据不足5000份的情况下,准确率和召回率分别达到了71%和88%。随着样本数据的不断增多,基于该深度学习方法将较大程度上持续提升检测准确率和召回率,能够更精准地发现违法活动,具有较大的实际应用价值及潜力。     

利用结构面对象的高分遥感影像建筑物变化检测

根据建筑物具有丰富的角点和规则的外观形状的特点,本文提出了依据线段信息生成建筑物变化检测基本单元——结构面对象的建筑物变化检测方法。从高分遥感影像中提取出建筑物的边缘线及屋顶外形线条,生成结构面对象并提取其在两时相影像中相应的特征信息,通过监督分类获取变化建筑区域。试验结果表明,利用结构面对象进行建筑物变化检测能较完整地覆盖变化建筑物表面且对象边缘检测效果较好。