船舶螺旋桨射流对湘江河床底泥扰动影响分析

船舶航行时螺旋桨产生的射流会对河道水流产生扰动,这种扰动是否能引起河床底泥的再悬浮需要更深入的论证分析。通过对比分析螺旋桨射流发展规律的研究成果,以湘江典型河段为研究对象,结合实船测量结果和此段河流地质资料,探讨了螺旋桨射流对湘江长株潭段河床底泥扰动的影响,并对此段河床底泥起动和悬浮条件进行了理论分析。结果表明:在周围环境流速较低的条件下,螺旋桨射流初始速度、河床水深及泥沙粒径是决定泥沙是否运动的主要因素。湘江长株潭河段已基本库区化,大部分河道平均水深远大于航道的标准水深2.8 m,河床泥沙平均粒径大于0.87 mm,其中细颗粒泥沙很少,由于螺旋桨射流断面平均流速小于泥沙起动流速,悬浮指标计算值远大于4,因此可以判断船舶正常航行在该段河流时底泥难以起动和再悬浮。     

不同好氧预处理方式对餐厨垃圾产甲烷的影响

为了研究不同好氧预处理方式对餐厨垃圾厌氧消化产甲烷的影响,通过建立3个模拟厌氧生物反应器,研究了传统厌氧生物反应器C1、上层好氧预处理-厌氧生物反应器C2和底部好氧预处理-厌氧生物反应器C3 3种不同操作条件下的产甲烷过程.结果表明,挥发性有机酸的累积使C1始终处于产甲烷滞后阶段;而C2、C3的好氧预处理通过加快易水解酸化组分和过量挥发性有机酸的好氧降解,有效缓解了酸性抑制,产甲烷滞后时间明显缩短至10 d内.第32天C2停止上层曝气后,在27 d内甲烷浓度达到了50％以上,同时,产甲烷速率迅速上升,并在第81天可达到峰值773 mL/(kg·d).C3在第11天停止底部曝气后,虽然经过22 d的时间甲烷浓度即上升至50％,但之后产甲烷速率经历回落阶段后再次逐渐上升,在实验结束时仅达到517 mL/(kg·d).上层曝气的好氧预处理方式所需曝气时间相对较长,但其产甲烷启动快,与底部曝气相比,其后期的甲烷化过程更稳定并可达到较高的产甲烷速率.     

综合拉底、扩漏和出矿全过程的底部结构安全性颗粒流模拟技术研究

为探明自然崩落法从拉底崩落至出矿全过程中底部结构节理连续扩展过程与破坏过程规律，采用PFC2D软件，结合RocLab软件反演节理岩体参数，建立229 m×129 m的岩体扩大模型，对拉底崩落至出矿过程进行连续综合计算。研究结果表明:模拟结果及破坏现象与现场监测结果相近，建模与细观参数反演方法适用于该类岩体工程研究；裂纹扩展贯通导致岩体失稳破坏，破坏过程与裂纹扩展具有相对应的阶段特征，裂纹扩展分为崩落前稳定扩展期，崩落与聚矿槽开挖过程加速扩展期和后续持续扩展期；结构破坏分为蕴育过程，扰动失稳过程和宏观破坏过程；较大范围的宏观破坏主要在出矿阶段。该模拟方法与结果可为底部结构维护以及节理岩体长期稳定性研究提供参考。     

长大区间隧道抽出式串联通风机排烟能力实验研究*

为实现有效通风以降低隧道火灾带来的损失和伤亡,依托青岛市地铁8号线大洋站至青岛北站区间隧道,建立线性比尺为1∶15的隧道通风排烟模型实验系统,针对通风机串联单抽,围绕3种通风机频率匹配组合,测定单机的变频频率值、电功消耗、排烟道与行车道的断面平均风速以及右侧行车道静压。研究结果表明:在相同功率消耗下,不同频率匹配的串联通风机排烟效果存在差异;针对此差异,利用气体挡烟墙性能及其计算欧拉数值比较发现,风井近端的通风机频率较大时,下游对污染气流的抵抗力更强,拥有更好的排烟效果。研究结果可为隧道火灾提供更有效率的防灾救灾数据支持,并从欧拉数方面为研究隧道临界风速提供新角度。     

鄱阳湖典型湿地沉水植物的分布格局及其水环境影响因子

沉水植物是湖泊湿地生态系统中关键组分,调查研究沉水植物分布格局及其水环境影响因子,对于沉水植被的恢复与重建具有重要的指导意义。2013年5月初期分别对鄱阳湖典型湿地区域中有沉水植物的25个样地进行群落结构调查,采用系统取样方法对沉水植物进行调查采样并监测水环境因子,在野外调查的基础上运用GIS软件制作鄱阳湖典型区域沉水植物的生物量分布图,并采用主成分分析(PCA)和典范对应分析(CCA)方法分析其主要影响因子。结果表明:鄱阳湖湿地沉水植物以苦草(Vallisneria natans)为广布种,其中蚌湖及白沙湖以黑藻(Hydrilla verticillata)为优势种,白沙洲及乐安河龙口段以苦草为优势种,伴生种主要有金鱼藻(Ceratophyllum demersum)、马来眼子菜(Potamogeton malaianus)、菹草(P.crispus)、小茨藻(Najas minor)、大茨藻(N.marina)、刺苦草(V.spinulosa)和水车前(Ottelia alismoides)等。采用双向指示种分析法将研究区沉水植物分为6个群落;5月初大部分沉水植物尚处于生长季初期,生物量相对较低,仅菹草的生物量较大;沉水植物与浮叶植物共存现象明显。主成分分析(PCA)结果显示,第一主成分中水深、总磷和溶解氧等因子的系数值较大,第二主成分中pH值、化学需氧量和水体透明度等因子的系数值较大,是影响沉水植物分布的关键因子;典范对应分析(CCA)结果显示,水深、总磷和总氮对苦草和黑藻的影响显著,水体透明度是马来眼子菜的主要影响因子。     

臭氧+曝气生物滤池深度处理工艺试验研究

针对某污水厂出水不达标的情况,本研究采用臭氧(O3)和曝气生物滤池(BAF)组合工艺对其进行深度处理.结果表明,当采用两级臭氧+曝气生物滤池工艺时,出水COD在31～46 mg/L,色度在13～29倍,均达到一级A排放标准.在最佳运行条件下,臭氧氧化使相对分子质量大于50 000的有机物含量减少10％,小于1 000的有机物含量增加14％.曝气生物滤池工艺使相对分子质量小于1 000的有机物含量降低了24％.     

A critical and empirical analysis of the national-local ‘gap’ in public responses to large-scale energy infrastructures

A national-local ‘gap’ is often used as the starting point for analyses of public responses to large scale energy infrastructures. We critique three assumptions found in that literature: the public's positive attitudes, without further examining other type of perceptions at a national level; that local perceptions are best examined through a siting rather than place-based approach; that a gap exists between national and local responses, despite a non-correspondence in how these are examined. Survey research conducted at national and local levels about electricity transmission lines in the UK confirm these criticisms. Results do not support a gap between national and local levels; instead, both differences and similarities were found. Results show the value of adopting a place-based approach and the role of surveys to inform policy making are discussed.     

Mini-review on river eutrophication and bottom improvement techniques,with special emphasis on the Nakdong River

Water quality in rivers is vital to humans and to maintenance of biotic and ecological integrity. During the Four Major Rivers restoration of South Korea, remarkable attempts have been made to decrease external nutrient loads and moveable weirs were designed to discharge silt that may deposit in pools. However, recently eutrophication of the Nakdong River, which was limited to the lower reaches, is seen to be spreading upstream. The reduction of external nutrient loads to rivers is a long-term goal that is unlikely to lead to reductions in algal blooms for many years because of the time required to implement effective land management strategies. It would therefore be desirable to implement complementary strategies. Regulating the amount of water released is effective at preventing algae blooms in weir pools; so, the relationship between discharge, stratification and bloom formation should be understood in this regard. However, pollutants are likely to accumulate in the riverbed upstream from release points. Thus, to control phosphorus levels, total phosphorus density should be lowered by applying in-river techniques as well. As many ecosystem properties are controlled by multiple processes, simultaneous river bottom improvement techniques, such as combined dissolved oxygen supply and nutrient inactivation, are likely to be effective. The purpose of this review is to present a series of technological approaches that can be used to improve the river bottom area and hence sediment nutrient release, and to illustrate the application of these techniques to the Nakdong River.     

Irrigation Water Allocation Using an Inexact Two‐Stage Quadratic Programming with Fuzzy Input under Climate Change

Agricultural irrigation accounts for nearly 70% of the total water use around the world. Uncertainties and climate change together exacerbate the complexity of optimal allocation of water resources for irrigation. An interval‐fuzzy two‐stage stochastic quadratic programming model is developed for determining the plans for water allocation for irrigation with maximum benefits. The model is shown to be applicable when inputs are expressed as discrete, fuzzy or random. In order to reflect the effect of marginal utility on benefit and cost, the model can also deal with nonlinearities in the objective function. Results from applying the model to a case study in the middle reaches of the Heihe River basin, China, show schemes for water allocation for irrigation of different crops in every month of the crop growth period under various flow levels are effective for achieving high economic benefits. Different climate change scenarios are used to analyze the impact of changing water requirement and water availability on irrigation water allocation. The proposed model can aid the decision maker in formulating desired irrigation water management policies in the wake of uncertainties and changing environment.     

罐底含油泥热解动力学参数计算方法的优选

在化学反应设计中反应动力学是较重要的因素。为得到更合理的污泥热解动力学参数计算方法,利用热重分析仪,在氮气气氛下对罐底含油污泥的热解特性进行研究。根据热重实验数据,分别采用Coats-Redfern法、Kissinger法、FWO法和Popescu法计算污泥热解动力学参数,并获取罐底泥热解制油的主要阶段(第2阶段)的反应活化能E、频率因子A并分析各种方法反应机理。通过对比不同计算方法得到动力学参数及拟合曲线与实验曲线的相关性,确定了最佳罐底含油污泥热解动力学参数计算方法。研究表明,Popescu法得到罐底泥的热解过程符合Jander方程,活化能E为101.43 kJ/mol,与FWO法得到的91.20 kJ/mol相近,且预测曲线与实验曲线有较好的相关性(0.9816),说明Popescu法计算罐底泥热解动力学参数更合适。