Effect of mixing on microbial communities in the Rhone River plume

The biological processes involved during mixing of a river plume with the marine underlying water were studied off the Rhone River outlet. Samples of suspended and dissolved matter were collected while tracking a drifting buoy. Three trajectories were performed, at 2-day intervals, under different hydrological and meteorological situations. A biological uptake was evidenced from ammonium (NH₄) and phosphate (PO₄) shortage, indicating an early “NH₄-dependent” functioning occurring before the well-known “NO₃-based” cycle. The different ratios between NH₄, NO₃ and PO₄, as a function of salinity, were discussed to detail the preferential use in PO₄ and NH₄. Salinity zones with enhanced bacterial production, high chlorophyll a concentration, as well as DOC, NH₄ and PO₄ consumption were evidenced from 20 to 35 in salinity. It was shown that the successive abundance of bacteria and phytoplankton during transfer reflected the competition for PO₄ of both communities. On the Rhone River plume, the role played by temperature, light conditions and suspended matter upon biological activity seems relatively minor compared to salinity distribution and its related parameter: nutrient availability. It can be concluded that biological uptake in the Rhone River plume was closely related to the dilution mechanism, controlled itself by the dynamics of the plume. In windless conditions and close to the river mouth, the density gradient between marine and river water induced limited exchanges between the nutrient-rich freshwater and the potential consumers in the underlying marine water. Consequently, little biological activity is observed close to the river mouth. Offshore, mixing is enhanced and a balance is reached between salinity tolerance and nutrient availability to form a favourable zone for marine phytoplankton development. This can be quite far from the river mouth in case of a widely spread plume, corresponding to high river discharge. Under windy and wavy conditions, the plume freshwater is early and rapidly mixed, so that the extension of the “enhanced production zone” is drastically reduced and even bacteria could not benefit from the fast mixing regime induced.     

碳交易背景下集装箱港区地下物流系统运输网络分析

为减少以集装箱卡车运输为主的港口公路集疏运给城市交通和环境带来的不良影响,集装箱港区逐步提出一种新的可持续 发展运输模式———地下物流系统,以解决当前港口城市发展面临的共性问题。 针对上海外高桥至嘉定线的地下物流系统布局方 案,根据预测的外高桥港区港口公路集疏运交通量,从碳交易、时间、成本3个角度,建立综合运输网络优化模型,以此分析在集装 箱港区实行地下物流系统的合理性; 利用Lingo12求解获得综合运输网络运量的分配,得到引入地下物流能够降低成本支出的结 果,同时达到节能减排和缓解交通拥堵的目的。 此外,对碳交易价格和地下物流系统运输单价的合理区间进行讨论。 试验结果可 为地下物流系统建成后货物配送计划和实现综合运输网络提供一些参考。     

碳纤维复合材料在钢筋混凝土公路桥翻修中的应用

介绍了一座三跨钢筋混凝土公路高架桥翻修过程中新材料和新技术的应用。在分析桥梁结构、加固和拓宽桥面的过程中,充分考虑了能够满足新的设计要求的新型复合材料的使用。文章描述了为达到设计强度、黏结力和锚固力而采用的加固方法和碳纤维增强聚合物的应用技术。     

Influence of the Mackenzie River plume on the sinking export of particulate material on the shelf

We examined the influence of the Mackenzie River plume on sinking fluxes of particulate organic and inorganic material on the Mackenzie Shelf, Canadian Arctic. Short-term particle interceptor traps were deployed under the halocline at 3 stations across the shelf during fall 2002 and at 3 stations along the shelf edge during summer 2004. During the two sampling periods, the horizontal patterns in sinking fluxes of particulate organic carbon (POC) and chlorophyll a (chl a) paralleled those in chl a biomass within the plume. Highest sinking fluxes of particulate organic material occurred at stations strongly influenced by the river plume (maximum POC sinking fluxes at 25 m of 98 mg C m^− 2 d^− 1 and 197 mg C m^− 2 d^− 1 in 2002 and 2004, respectively). The biogeochemical composition of the sinking material varied seasonally with phytoplankton and fecal pellets contributing considerably to the sinking flux in summer, while amorphous detritus dominated in the fall. Also, the sinking phytoplankton assemblage showed a seasonal succession from a dominance of diatoms in summer to flagellates and dinoflagellates in the fall. The presence of the freshwater diatom Eunotia sp. in the sinking assemblage directly underneath the river plume indicates the contribution of a phytoplankton community carried by the plume to the sinking export of organic material. Yet, increasing chl a and BioSi sinking fluxes with depth indicated an export of phytoplankton from the water column below the river plume during summer and fall. Grazing activity, mostly by copepods, and to a lesser extent by appendicularians, appeared to occur in a well-defined stratum underneath the river plume, particularly during summer. These results show that the Mackenzie River influences the magnitude and composition of the sinking material on the shelf in summer and fall, but does not constitute the only source of material sinking to depth at stations influenced by the river plume.     

双积分对单车型动力系统应用影响分析

为分析节能动力系统在不同车型上应用的合理性,本文以满足双积分管理办法为边界,分析采用不同动力系统的传统车对新能源车型数量需求,主要结论包括:同一动力系统在不同车型应用,为满足双积分需求,所需的新能源车型数量差别很大;大型高油耗车辆,为满足双积分管理办法需要大量新能源车型。     

汽车发动机积炭分析及控制措施

现今的发动机技术虽然相当的成熟,但燃烧的效率也仅达25%—30%而已,因此积炭主要是由机械本身所造成的现象,以及汽油品质不佳所引起,汽车行驶一段时间后,燃油系统就形成一定积炭。行驶在二万公里以上汽车积炭特别严重,就会出现发动机怠速不稳、忽高忽低;加油时,加速不良,有发闷的现象;行驶无力,尤其超车时,提速反应慢,无法达到原车动力;尾气刺眼、刺鼻,严重超标;油耗也比以往增加。     

公路交通服务能力的绿色安全指标研究

国际上公路交通服务能力皆以道路拥堵情况(V/C 值)及行车顺畅程度为评估 标准,缺乏对交通安全潜在社会成本、时间成本及环境保护的测量.根据国际社会对绿色 经济、绿色交通运输的重视与发展趋势,本文以台湾电子收费系统的数据为基础,针对不 同交通流需求量、路段平均行驶速率衍生的时间成本与污染排放、交通安全等因子,分别 构建出行时间延滞成本、碳排放增量成本、潜在肇事概率成本等3 个参数指标,利用这3 个指标构建综合型绿色安全交通服务指标(Green and Safety Index for traffic levels of service, GSI),作为划分交通服务水平的评估标准,并通过实时在线软件,提供出行者道路 出行延滞、碳排放及安全等社会成本信息.     

基于交通结构发展情景分析的城市交通碳排放测算研究

随着我国城市化和机动化进程的不断加快,在满足居民出行需求的同时,需要更加合理的出行结构来促进交通环境的改善.本文利用不同方法分析测算了城市交通碳排放现状,结合低碳目标的城市客运交通结构优化模型探讨了交通出行比例不变、交通出行比例优化和交通出行比例失衡三种发展情景.分析表明,不同情景下的城市交通碳排量的平均年增长率分别为13.1%、7.3%和15.3%.公共交通是交通结构优化的主要推动力,只有在公共交通分担率不断上升的同时,控制并降低小汽车交通出行比例,才能降低碳排放总量的增长速度.     

跨临界CO2制冷系统气体冷却器分布参数仿真

运用分布参数法建立了船用跨临界CO2制冷系统的关键部件之一-气体冷却器的稳态仿真模型,用此模型分析了气体冷却器变工况、变结构参数特性,并与集中参数模型进行了对比.此外,还分析了主要特性参数的空间分布情况,得出了一些可供系统设计及调试参考的结论.     

"壁可"注入法与碳纤维材料在铁路桥梁修复加固中的应用

通过在百济坡大桥中采用“壁可”注入法修补梁体裂缝和碳纤维材料加固梁体,介绍了此次修复加固过程中所用材料的性能和具体的施工技术,为今后桥梁修复补强提供了技术参考.