课程文献中心 更多>>

摘要： We give a classification of compact solitons for the pluriclosed flow on complex surfaces. First, by exploiting results from the Kodaira classification of surfaces, we show that the complex surface underlying a soliton must be Kahler except for the possibility of steady solitons on minimal Hopf surfaces. Then, we construct steady solitons on all class 1 Hopf surfaces by exploiting a symmetry ansatz.

关键词： Urbanization   Multiple stressors   Stream flow   Contamination   Biological quality   Traits  

摘要： Urban streams provide important ecosystem services to cities' population, from the maintenance of urban biodiversity, temperature, humidity and air quality to improving aesthetics and provision of natural areas for recreation. However, these streams are under multiple-stressors, including artificialization of the channel and flow, poor water quality and cut of riparian vegetation which puts in risk their ecological integrity and consequently their services. In this study, we aimed to understand variations in macroinvertebrate communities and in biological condition as a response to flow and water quality, by following a Mediterranean urban stream over 8 months (December-July). With a monthly periodicity, we sampled invertebrate communities and characterized in situ water physicochemical parameters. The urban stream studied showed a high variation of environmental factors over time. Invertebrate communities were generally poor, with some Ephemeroptera (Baetis sp.) but was dominated by Chironomidae and Oligochaeta that changed over time alongside with environmental conditions. Biological quality based on the Portuguese Invertebrates Index (IPtIS) varied between poor and bad. Multivariate community patterns (at genus level) showed variations in communities over time, as well as in their biological trait patterns (invertebrates' maximal size, reproduction mode, resistance form, feeding habits and locomotion mode). Periods displaying worse biological quality, less diverse communities and lower functional richness corresponded to peaks of discharge, higher conductivity and hardness while the best quality communities were found under lower nitrate concentrations. Our study points out that the detection of impacts or recovery in urban streams through invertebrate communities might require at least the use of genus level as family level does not detect smoother changes. Communities reflect the complex interplay of environmental variables affecting structural and functional n

关键词： Fluidization   MRI   Jets  

摘要： Rapid magnetic resonance imaging (MRI) was used to characterize properties of a single central gas jet injected into a 3D gas fluidized bed under incipient fluidization conditions. Snapshots of both particle concentration and particle velocity are provided. The average jet height, oscillations in jet height and the size of bubbles breaking off from the jet increased with increasing jet velocity. The frequency of bubble breakoff from the jet decreased with increasing jet velocity. The jet height measurements are compared with various correlations in the literature, and the quantitative data provided here can be compared directly with that from numerical simulations and theoretical predictions for validation purposes. (C) 2019 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.

摘要： 886

摘要： 5175

摘要： 2094

关键词： 表面改質   濕潤性   冷凝   結霜   表面張力  

摘要： 本研究利用一冷板进行冷凝、结霜实验，透过网版印刷制作荆棘形状之亲疏水混合表面，利用其湿润性梯度差异，达到表面冷凝水快速排除及抗结霜之特性。结冰实验结果显示，超亲水荆棘型表面结构的湿润性过大，冷凝水覆盖铁氟龙图形区域，导致排水机制运作不完全，延缓冰层冻结冻效益，与抛光红铜样本相比仅增加7.9%。而红铜荆棘型样本的液滴吸附合并及排除效果则非常显着，使其表面刷新率提高，抑制冰层生长效益与抛光红铜相比增加了52.4%，结冰期间热传系数相比於抛光红铜提高约16.2%。除冰实验结果则指出，红铜荆棘型样本因整体接触角较高，对融化的水排斥力较大，导致其除霜效率相比於超亲水荆棘型样本提升20%，但除冰後大液滴容易因接触角迟滞现象而停滞在结构交界处。

关键词： Pipeline magnetic flux leakage   Convolution neural network   Feature extraction   Sparse self coding   Convolution kernel image   Entropy similarity constraint  

摘要： In order to intelligently classify magnetic flux leakage signals, this study proposes a method of magnetic flux leakage image classification based on sparse self-coding. With inputting with the magnetic flux leakage image of the pipe weld, it extracts features automatically from the Convolutional Neural Network (CNN) rather than the artificial extraction process. The network classification ability can be improved through pre-training of the convolution kernel and introducing the sparse constraints and the image entropy similarity constraint rules. The experiment uses 500 images of magnetic flux leakage signals to classify the girth welds and spiral welds. The accuracy of classification is 95.1%, which is superior to the traditional convolution neural network model. Experimental results show that the improved model has good feature extraction ability and generalization ability. (C) 2019 Elsevier B.V. All rights reserved.

关键词： 表面活性剂   水成膜泡沫灭火剂   表面张力   泡沫性能  

摘要： 由于含氟表面活性剂具有较长的氟碳链,难以降解,实验采用两种不含氟的碳氢表面活性剂复配,同时也添加3种辅助添加剂,配置出3%型水成膜泡沫灭火剂,并对其性能进行测试,结果表明:新配制出的水成膜泡沫灭火剂表面张力降低到了20.85 mN/m、发泡倍数达到了6.4倍,25%析液时间为4.1 min、在丙酮上的稳泡时间为5.8 min、灭火时间为0.18 min,各项性能指标均能达到国家标准,是一种环境友好型的水成膜泡沫灭火剂。

关键词： 肺动脉高压   动脉性肺动脉高压   平均肺动脉压   肺血管阻力   对钙离子通道阻滞剂   长期有反应的肺动脉高压   伴有明显肺静脉或肺毛细血管受累的肺动脉高压  

摘要： 肺动脉高压(pulmonary hypertension)既往被定义为仰卧位静息状态下右心导管测得平均肺动脉压(m PAP)≥25mmHg。第六届肺动脉高压大会(WSPH)建议用mPAP>20 mmHg定义肺动脉压的异常升高,而要定义毛细血管前肺动脉高压需要加上PVR≥3 WU。关于肺动脉高压的临床分类,此次大会在第一大类动脉性肺动脉高压中新增了"1.5对钙离子通道阻滞剂(CCBs)长期有反应的肺动脉高压"并且用"1.6伴有明显肺静脉或肺毛细血管受累的PH"代替原有的"1’肺静脉闭塞病(PVOD)或肺毛细血管瘤样增生症(PCH)"。