120°E磁赤道上空电离层电子浓度总含量的混沌特性分析及非线性预测初探

本文利用120°E磁赤道上空电离层TEC1996～2004年的观测数据讨论电离层TEC参量的混沌特性,并探讨利用混沌理论对电离层参量进行预报的可能性. 实际计算表明,在指定经纬度的TEC时序数据中存在混沌特性,其关联维数为36092,李雅普诺夫指数为03369. 采用混沌“加权一阶局域法”进行预测较为成功. 对预测误差分析表明,预测点在1～144之间误差相对较小,标准差约为76438 TECU,相关系数约为09172.     

Trophic structure and functioning in a eutrophic and poorly flushed lagoon in southwestern Taiwan

Tapong Bay, a eutrophic and poorly flushed tropical lagoon, supports intensive oyster culture. Using the Ecopath approach and network analysis, a mass-balanced trophic model was constructed to analyze the structure and matter flows within the food web. The lagoon model is comprised of 18 compartments with the highest trophic level of 3.2 for piscivorous fish. The high pedigree index (0.82) reveals the model to be of high quality. The most-prominent living compartment in terms of matter flow and biomass in the lagoon is cultured oysters and bivalves, respectively. The mixed trophic impacts indicate that phytoplankton and periphyton are the most-influential living compartments in the lagoon. Comparative analyses with the eutrophic and well-flushed Chiku Lagoon and non-eutrophic tropical lagoons show that high nutrient loadings might stimulate the growth and accumulation of phytoplankton and periphyton and therefore support high fishery yields. However, net primary production, total biomass, fishery yields per unit area, and mean transfer efficiency of Tapong Bay were remarkably lower than those of Chiku Lagoon. The lower transfer efficiency likely results from the low mortality of cultured oysters and invasive bivalves from predation or the lower density of benthic feeders constrained by the hypoxic bottom water as a result of poor flushing. This might therefore result in a great proportion of flows to detritus. However, the hypoxic bottom water might further reduce the recycling of the entering detritus back into the food web. In contrast to many estuaries and tropical lagoons, poor flushing of this eutrophic tropical lagoon might induce a shift from detritivory to herbivory in the food web.     

“绿道-邻里”视角下建成环境对城市绿道使用的影响——以广州为例

基于“绿道-邻里”视角,采集了广州典型城市绿道上的市民使用人数与类型等属性,并运用多元线性回归模型探讨绿道周边建成环境（人口密度和土地类型混合度）与绿道使用之间的关系。结果表明：绿道周边建成环境作为绿道使用的潜在来源地和目的地,影响着城市绿道使用效果,步行和骑行可达范围内的居住区人口密度和绿道周边土地利用混合度均可作为绿道使用强度的解释因子,两者的增加均会带来绿道使用强度的提高;除此之外,周边居民区收入水平、年龄和时间等变量对城市绿道使用也会造成影响。研究结果可为城市绿道建设提供直接参考。     

天气因素对武汉市出租车出行活动的影响

天气状况作为人们生活环境的组成要素之一,对居民日常出行可产生显著的影响,具体可表征为特定空间位置和用地类型范围内出行活动的需求量以及道路交通路线选择的变化。高效、智能化的交通应急管理和城市规划建设亟需理解天气因素影响交通出行时空分布的基本规律。本文选取武汉市作为典型研究区域,基于出租车、气象和空气质量等数据,对不同天气下的居民出行模式和司机路径选择模式进行时空分析,并解释2类模式产生变化的原因和机制。结果表明：① 从时间上看,工作日的出租车需求量更容易受到天气变化的影响,其中降雨、气温的升高和风速的增强会显著降低居民对出租车的需求;② 从全市域空间尺度上看,降雨使得居民对出租车的需求量在工作日时段减少,而在周末时段增加,其中降雨主要刺激短距离出租车出行需求而抑制中长距离出行需求;③ 从城郊区空间尺度上看,雨天时段主城区内部的中距离流量减少,郊区内部的短距离流量增加,往返于主城区和郊区的中长距离流量在工作日减少、在周末增加;④ 从功能区空间尺度上看,下雨使得行政办公用地的出租车需求量减少,商业金融用地的出租车需求量在工作日减少、在周末增加,工业用地的出租车需求量在工作日增加、在周末减少;⑤ 从行驶路径上看,出租车司机在晴天时偏好根据距离来判断最佳路线,而在雨天倾向于改变原先路线选择策略,将距离和车速共同作为最佳路线的指标,选择用时最少的最佳路线。本文研究成果可帮助城市和交通管理部门更加深入地理解城市居民出行规律及其时空分布特征。     

Hydrochemical characteristics and controlling factors of natural water in the border areas of the Qinghai-Tibet Plateau

Journal of Geographical Sciences - The special geography and human environment of the Qinghai-Tibet Plateau has created the unique hydrochemical characteristics of the region’s natural water,...     

中国海洋环境规制对海洋技术创新的影响研究——基于环渤海和长三角地区的比较

文章运用中国沿海11个省、市、自治区2006—2015年的面板数据为样本,将海洋环境规制划分为命令控制型和经济激励型两类,对比分析了环渤海和长三角地区海洋环境规制对海洋技术创新的影响差异。研究发现:从沿海地区整体来看,命令控制型和经济激励型环境规制对海洋技术创新的影响作用均显著为正;在试点城市环境规制对技术创新的促进作用优于非试点城市;在环渤海地区,命令控制型环境规制对海洋技术创新的影响作用显著为正,经济激励型不显著;在长三角地区,经济激励型环境规制对海洋技术创新的影响作用显著为正,命令控制型不显著。基于实证结果提出了制定差异化的环境规制、加大政府对研发资金的支持等有针对性的政策建议。     

海洋油田平台水下安防系统航迹融合与报警技术

多传感器信息融合技术是对各个传感器的观测数据进行综合处理的过程,是多学科、多领域的高层次共性关键技术。以多源信息融合技术为基础,对 AIS、雷达与声呐多源探测信息融合算法进行了较为深入地研究,提出适应水下安防系统的多源信息融合与报警技术的工程化应用方案,对实际应用情况做了简要总结,经验证该技术能够较好应用于水下安防系统的数据分析和分级报警中。     

A deep learning approach for detecting candidates of supernova remnants

Detecting supernova remnant(SNR) candidates in the interstellar medium is a challenging task because SNRs have weak radio signals and irregular shapes. The use of a convolutional neural network is a deep learning method that can help us extract various features from images. To extract SNRs from astronomical images and estimate the positions of SNR candidates, we design the SNR-Net model composed of a training component and a detection component. In addition, transfer learning is used to initialize the network parameters, which improves the speed and accuracy of network training. We apply a T-T plot(of the different brightness temperatures of map pixels at two different frequencies) to calculate the spectral index of SNR candidates. To accelerate the scientific computing process, we take advantage of innovative hardware architecture, such as deep learning optimized graphics processing units, which increases the speed of computation by a factor of 5. A case study suggests that SNR-Net may be applicable to detecting extended sources in the images automatically.     

基于深度卷积神经网络的高分辨率遥感影像场景分类

场景分类对于高分辨率遥感影像的理解和信息提取具有重要意义。传统方法利用低、中级或语义特征来对影像的场景进行判别,但是针对高分影像涵盖的细节多、类别复杂等特点,中低层特征无法对影像语义进行准确描述。本文提出了一种基于深度卷积神经网络DCNN场景分类模型。首先利用卷积层对影像的纹理、颜色等低阶特征进行提取,然后利用池化层对重要特征进行筛选,最后将提取到的特征进行组合,形成高阶语义特征,利用高阶语义特征对高分影像进行场景分类。为了解决模型的过拟合问题,使用了数据增广、正则化及Dropout提高模型的泛化能力。本文方法在UC Merced-21取得了91.33%的准确率,相比于传统方法,有效地提高了分类精度,同时证明了深度卷积神经网络在遥感影像分类领域优越性。     

Physiological changes of submerged macrophytes in response to a floating filamentous green algae bloom in clear-water conditions

The aim of this study was to evaluate the physiological responses of a submerged macrophyte to a floating fi lamentous green algal bloom in clear-water conditions.Elodea nuttallii was grown with floating Cladophora sp.at four diff erent levels(0,control;140,280,560 g FW/m ~2)in an outdoor experimental system,and its photosynthetic and antioxidant systems were evaluated.The presence of floating Cladophora sp.signifi cantly changed the water environment by decreasing light intensity and increasing dissolved oxygen and the pH value.The photosynthetic parameters of E.nuttallii(e.g.?F/F _m~￠,F _v/F _m,total chlorophyll)were higher in the presence of floating Cladophora sp.than in the control at the beginning of experiment.Because of the increasing dissolved oxygen concentration and pH value,the values of these indicators decreased(except for photosynthetic pigments)during the experiment.Compared with E.nuttallii in the control,E.nuttallii growing in the presence of floating Cladophora sp.showed higher malondialdehyde content,catalase activity,and peroxidase activity.The biomass of E.nuttallii was decreased by about 30% in the presence of high biomasses of floating Cladophora sp.(280 and 560 g FW/m ~2).These results suggest that floating Cladophora had complex eff ects on the biomass of E.nuttallii and that changes in water quality resulting from floating Cladophora sp.may be more important than its direct shading eff ect.