遗传优化神经网络方法在桥梁震害预测中的应用

本文将遗传算法与神经网络相结合,从而建立了一种高效的、实用的桥梁震害预测方法。根据遗传算法具有局部寻优的特点,为避免BP神经网络陷入局部极小值,本文将二者结合起来形成GA-BP混合算法,以GA优化神经网络的初始权值和阈值,对网络进行训练。在大量收集梁式桥震害资料的基础上,将此算法引入桥梁的震害预测中,并与传统的单独BP神经网络相比较,结果表明该方法能够有效、准确地对桥梁结构进行震害预测。     

Tidal effects on diel variations of picoplankton and viruses in the Changjiang estuary

Spatial distributions and seasonal variations of picoplankton (i.e. Synechococcus spp., Prochlorococcus spp., picoeukaryotes and heterotrophic bacteria) and viruses in the Changjiang estuary have been reported in the past. However, short-term variations (e.g. at a tidal timescale) of these organisms and their regulating factors remain unclear. We determined the time-series of fluctuations of picoplankton and viruses with tide simultaneously in flow cytometry in the Changjiang estuary during a cruise in June 2006, in which a tidal model based rectangle equation was applied. The results indicate that high cell abundances of picoplankton and viruses occurred during flood tide and low cell abundances during ebb tide. The period of the surface cell abundance variations was about 13 h, suggesting the surface cell abundances in the Changjiang estuary were largely regulated by tide. However, cell abundances in middle and bottom waters varied in different periods due to influences of tidal induced physical forces such as resuspension and stratification. Therefore, tidal action is an important factor for the diel variations of picoplankton and viruses in the Changjiang estuary.     

“4S”技术支持下的土地利用决策

4S"技术是全球定位系统(Global Positions System,缩写为GPS)、遥感(Romote Sensing 缩写为RS)、地理信息系统(Geographical Information System, 缩写为GIS)和专家系统(Expert System, 缩写为ES)的合称.     

流式细胞术在海洋浮游植物研究中的应用

流式细胞术在海洋浮游植物研究中的应用张利华（华东师范大学,河口海岸国家重点实验室,上海,２０００６２）生物学的研究已进入细胞分子研究的新纪元,从传统的定性描述发展到对细胞的各种形态参数与生物学特征、生化组成以及细胞功能等方面进行定量研究,其研究手段在...