城市滨湖整治探讨

通过对南宁市内河现状、功能和存在问题的分析 ,得出造成内涝灾害的成因 ,对城市滨湖整治进行探讨。     

Diel changes in vertical overlap between Cyclops strenuus (Copepoda; Cyclopoida) and its prey in oligotrophic Lake Toya, Hokkaido, Japan

The vertical distribution of Cyclops strenuus and its prey, and the gut contents of C. strenuus were investigated at 3 h intervals over 24 h periods in the pelagic area of oligotrophic Lake Toya in May, August and October 1992. C. strenuus showed slight diel vertical migration (DVM) in May, but did not migrate and was always distributed below 15 m in August and October, the thermally stratified period. This suggests that the DVM is strongly influenced by the development of the thermocline, which the copepod may not be able to cross. Gut content analyses revealed that in Lake Toya it is omnivorous, and that the dominant prey are cladocerans and Filinia longiseta. The number of prey remains in the gut varied with time, and the diel changes did not follow changes in prey density that take the vertical overlap between predator and prey into account. We argue that very low prey density associated with the oligotrophic nature of the lake would mask the relationship between prey density and the number of prey in the gut of the predator.     

Succession of the ecosystems of the Aral Sea during its transition from oligohaline to polyhaline water body

During 22 field trips from 1990 to 2002 (mainly the western basin of the Large Aral) data on salinity, phytoplankton, zooplankton, zoobenthos and fish fauna have been collected. In 2002, the salinity of the western basin reached 75 ppt, while that in the eastern basin, 150 ppt. In 1999–2002, 159 species of planktonic algae have been recorded. This is approximately twice as low as recorded before. The diversity of Cyanophyta, Pyrrhophyta and Chlorophyta in particular has dropped in the past few years. As before, currently Bacillariophyta is the most diverse plankton. However, the composition of dominants has changed. Once previously dominant species, Actinocyclus ehrenbergii, vanished from the plankton of the Aral Sea and was replaced by such diatoms as Amphora coffeaformis, A. coffeaformis var. acutiuscula and Synedra tabulata var. parva.Since 1970s, a gradual decrease in the diversity of zooplankton has been taking place. Since 1997, the formerly dominant Calanipeda aquaedulcis vanished, which apparently was the reason for the emergence of Moina salina and Artemia parthenogenetica. Since 2000, artemia has been dominant in the plankton of the Aral Sea, constituting 99% of the zooplankton biomass.In the 1970–1980s, a rapid decrease in the biodiversity of the zoobenthos was observed. In the 1990s, most aboriginal and introduced species became extinct. Currently, the bivalve mollusk Syndosmya segmentum, the ostracod Cyprideis torosa and larvae of the dipteran Chironomus salinarius can still be recorded in the western basin. In the eastern basin no benthos is observed.By 1998, in the Large Aral, only five fish species survived: baltic herring Clupea harengus membras, flounder Platichthys flesus luscus, atherine Atherina boyeri caspia and bullheads Neogobius fluviatilis and Potamoschistus caucasicus. Since 2002, only flounder and atherina have been recorded in the western basin of the Large Aral. No fish have been recorded in the eastern part of the Aral Sea in 2002.With increasing salinity and transition of the Aral Sea from an oligohaline to a polyhaline water body, its biota is becoming drastically poorer. Almost all local species became extinct in the Aral; however, some still survive (including some endemics) in some lakes around the Aral Sea. In the near future, artemia will be the only animal in the Aral Sea.     

深水峡谷库区高桩承台钢吊箱围堰设计与施工技术研究

针对太平湖特大桥主墩基础施工特点,且受外部施工环境影响较大,工期紧张,经过高桩承台钢吊箱围堰施工方案的比选(原位拼装下放和整体浮运到位下放),并结合钻孔桩钢平台施工需求,提出较为快捷的施工方案,即"钻孔桩施工平台与承台钢围堰合二为一";对工厂化作业、整体组装、下水浮运、定位以及搭建平台等施工策略予以探究,切实有效应对了高桩承台基础施工时间紧迫、作业难度高,同时提高工程质量,节约施工成本,最终取得了良好施工效果。     

36100 DWT大湖型散货船结构设计特点

介绍了36 100 DWT大湖型散货船结构设计中遇到的有关总纵强度、局部强度、重量控制等问题。通过大湖型散货船与常规散货船的对比,着重分析了在总纵强度计算中的差异;货舱槽型舱壁在考虑部分灌装时,晃荡压力的校核;首次航行工况下,首部抗拍击强度的合理减免,以及减免的前提条件。因此在全船结构设计中,经优化布置及结构形式,有效地控制了结构重量。