BP人工神经网络在青藏铁路南段地壳稳定性定量评价中的应用

将BP人工神经网络方法引入区域构造活动性、区域地壳稳定性研究领域,对青藏铁路南段沿线的构造活动性进行定量分析.选用断层运动速率、地震震级、温泉温度及剪切应变4个关键影响因子作为BP人工神经网络的输入向量,构造活动强度(α)作为输出向量,以α为定量判据,将全区划分为相对稳定区(α＜0.22)、较不稳定区(α≈0.22～0.38)、不稳定区(α≈0.38～0.69)、极不稳定区或强烈构造活动区(α≥0.69).在青藏铁路南段沿线划分出格仁错、崩错、当雄-羊八井、错那湖、唐古拉山口南、聂荣东北、聂荣西北、雅鲁藏布江断裂沿线、萨迦等不稳定区,在不稳定区内部进一步划分出申扎、蓬错、尼木、桑雄、羊八井5个极不稳定区.     

隧道地震响应数值模拟研究

在进行隧道地震响应的数值模拟研究时, 横向计算范围和人工边界等对计算结果有很大的影响。本文以黄草坪隧道为研究对象, 应用有限差分程序FLAC3D对其进行地震响应的数值模拟研究, 将横向计算范围分别取为隧道洞径的5倍、6倍、7倍、8倍、9倍和10倍, 并分别采用FLAC3D中的截断边界、自由场地边界和粘性边界进行计算。研究结果表明, 当地震波为P波时, 横向计算范围取为洞径的7至8倍, 人工边界采用自由场地边界或粘性边界是比较合理的。      

潜在地震灾害预测和评价神经网络系统及其若干问题

结合人工神经网络自身的特性和地震灾害预测研究的特点,本文应用神经网络模型,建立了潜在地震灾害预测和评价系统。针对网络模型参数设置、数据归一化、中间层神经元最优数目以及泛化分类评价指标等若干实际问题给出了实际可行的解决方案。通过大样本数据对网络的训练,形成了有识别和记忆功能的非线性预测和评价系统。对网络的测试和检验,论证了该系统在预测潜在地震灾害上的可行性和有效性。同时,从测试精度出发,探讨了这种预测网络存在的不足,并给出了相应的改进建议,为开展进一步的研究工作提供了参考。     

天然气水合物的声学探测模拟实验

在人工岩心中进行天然气水合物的生成和分解实验,同时获取了体系的温度、压力、声学特性(Vp和Vs、幅度和频率)及含水量等参数。经研究发现,温压法、超声探测法和TDR探测法都能灵敏探测沉积物中天然气水合物的形成和分解过程。分析认为,本次实验中水合物形成速率过快,只能宏观研究水合物对沉积物声学特性的影响,建议采用长岩心进一步研究沉积物中水合物的声学特性。     

Floating and fixed artificial habitats: Spatial and temporal patterns of benthic communities in a coral reef environment

While natural marine habitats with motion capabilities, e.g., kelps and seaweeds, have been studied alongside their associated fouling communities, little is known of the effect of motion on the communities of floating artificial habitats such as buoys, rafts, and pontoons, particularly in tropical systems. Hydrodynamic features greatly differ between floating and fixed artificial substrata, which in turn affect the structure of their associated communities. This study tested the hypothesis that floating and fixed artificial installations in a tropical reef system (Eilat, Red Sea) would support different benthic communities throughout space and time. Specifically, we examined differences in communities recruited onto settlement plates between floating and fixed installations deployed at three different sites, along a two-year monitoring period. The three sites exhibited distinct differences in species assemblages between the monitoring dates (6, 12, 18 and 24 months post deployment), mainly between the first and the last two dates. The average level of dissimilarity between floating and fixed installations increased over time at all sites. Over 50% of the dissimilarity between the floating and fixed installations resulted from five taxonomic groups i.e., bryozoans, bivalves, barnacles, sponges, including the amount of bare space on the settlement plates. The contribution of these groups to the dissimilarity changed both temporally within each site, and spatially among sites. The observed differences were related to the hydrodynamic characteristics of floating and fixed habitats, interacting with biotic features such as predation, successional processes and seasonality; and abiotic features including small-scale spatial changes, light, and position in the water column.     

The onset of fish colonization in a coastal defence structure (Chioggia,Northern Adriatic Sea)

Coastal defence structures constitute the most extensive hard substrates of the Northwestern Adriatic Sea and are known to sustain rich benthic and nektonic communities. To appreciate the pattern of colonization, we studied the fish assemblage of a recently deployed breakwater. We compared observations from two years, the different sides (landward and seaward) of the barrier, and the two fringes, characterized by timing of work completion. The results indicate that colonization, still in process, follows different patterns among species. Benthic and necto-benthic species presented a striking increase in abundance and richness in the second year of colonization, while more mobile species did not evince any variation between years. Differences in mobility among species suggest that the latter group may have reached the breakwater from nearby artificial substrates, whereas the former colonized the new structure as recruits. In addition, fish assemblages differed between the two sides, likely due to variation in the environmental characteristics, and according to depth, reflecting species preferences.     

海州湾海域赤潮灾害与成因探讨

2004～2006年海州湾海域共发生有记录的赤潮7起,涉及海域面积近2000 km2,海洋生态环境受到严重威胁.本文根据近年来海州湾赤潮发生的情况和相关资料,阐述了海州湾赤潮的发生及其影响、赤潮主要藻种,从物理、化学、气候、生物等因素上分析和讨论了海州湾赤潮发生的原因,并在此基础上提出了相应的防治对策:(1)加强赤潮的研究工作;(2)控制陆源污染物的入海,防止海水富营养化;(3)加强赤潮监测.     

防海胆食害藻礁的设计及实验研究

人工藻礁是进行藻场建设的重要手段,但由于海胆等食藻类生物的摄食,将会影响藻类的生长,从而影响人工藻场的建设效果.为解决人工藻场建设中海胆的食害问题,从礁体自身设计出发,实验设计了8种不同形状的藻礁,选用光棘球海胆和中间球海胆为实验对象,观察比较了不同形状藻礁对海胆攀爬的阻碍效果,实验发现:侧周面为锯齿形或侧周面缠挂多孔柔性材料的礁型可有效阻止海胆攀爬,起到防止海胆摄食礁顶藻类的目的.研究结果为人工藻礁的设计提供了参考依据.     

Research on red tide occurrences using enclosed experimental ecosystems in west Xiamen Harbor, China—Relationship between various factors and red tide occurrences

A series of enclosed ecosystem experiments were conducted in a land-based tank near the seaside of West Xiamen Harbor. The results of experiments conducted in different seasons and years showed a repeatable phytoplankton succession. In this relatively stable ecosystem with added nutrients and trace metals, diatoms dominated initially, dinoflagellates dominated in the later stage, and dinoflagellate red tides eventually occurred. Vitamin B₁₂ enrichment may speed up this succession process. Stirring the water column could stop this process. Soluble Mn at a level of 3–4 μg/L in seawater, which also is the existing concentration of soluble Mn in Xiamen Harbor seawater, is sufficient for the multiplication of algae and occurrence of red tide. The present study showed that excessive soluble Mn in Xiamen Harbor cannot cause red tide, and that Fe was one of the important factors causing diatiom red tide in this present study. Project 39570145 supported by NSFC.     

Study of red tide prediction model for the Changjiang Estuary

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