The effects of sinusoidal leading edge of turbine blades on the power coefficient of horizontal-axis wind turbine (HAWT)

In order to improve the aerodynamic performance of horizontal-axis wind turbine (HAWT), a sinusoidal shape is applied to turbine blade. In this study, four types of modified blades were chosen based on variations in amplitude and wavelength of protuberance along the leading edge. Compared with the baseline model, the power coefficients (C_p) of HAWT with modified blades were improved, especially at low tip speed ratios. At low wind speed (V = 6 m/s), blades with short wavelength obtain significant improvement in C_p compared with the baseline model. As wind speed increases, this improvement decreases. In addition, turbine blade with large amplitude and long wavelength obtains better C_p values at higher wind speeds than lower ones, which have a great potential to be more superior at relatively higher wind speeds.     

Transport infrastructures,environment impacts and tourists' welfare: a choice experiment to elicit tourist preferences in Siena–Italy

Transport infrastructures have been investigated as drivers of tourist demand. Specific attention has been devoted to air transport infrastructure and services. However, the literature on this issue is scanty. Moreover, few studies focus on ex-ante valuation of tourists' preferences for mobility systems. This study contributes to this literature by presenting a case study on the re-organization of the mobility system to access the city of Siena, Italy. A choice experiment is carried out to elicit tourists' preferences for distance, time, cost, travel mode, along with the environmental impact of infrastructure. The latter factor turns out to be particularly relevant in explaining tourists' choices and welfare. Furthermore, the results appear to be robust and not significantly dependent on design settings (specifically the number of alternatives). While these results only refer to a single case study, they seem to suggest that new transportation facilities do not necessarily cause an increase in tourism flows.     

鸟粪石法回收制肥工业废水中氨氮的中试研究

制肥工业废水中氨氮浓度高,难以直接进行生化反应,采用鸟粪石沉淀法可有效去除并回收氨氮。利用中试反应器回收某制肥工业废水中的氨氮,采用氯化镁与氧化镁作为联用镁源,通过考察不同进料方式、搅拌速度、停留时间等因素的影响,确定了鸟粪石法回收氨氮的最佳工况:采用间歇进水、固体投加镁源的投料方式,搅拌速度300 r/min,停留时间2 h。最佳条件下,氨氮去除率达到93.5%,磷残余率小于0.3%,生成的鸟粪石纯度可达85.6%,砷和铅的质量分数分别为0.0036和0.0008,符合肥料中重金属限值(GB/T 23349-2009),其他重金属均未检出。因此,回收产品有很好的利用价值。经济分析表明磷源是此方法处理成本较高的主要原因。     

堆石料强度和变形性质的大型三轴试验及模型对比研究

在饱和试样大型三轴试验成果基础上,对两种堆石料(垫层料、次堆石)的变形与强度特性变化规律进行了总结。认为围压是影响堆石料强度和变形特性的最重要因素;堆石料的非线性应力应变关系用邓肯张模型和指数模型来拟合都基本令人满意,但指数模型会高估初始剪切模量;堆石料的径向应变与轴向应变关系可以分成两段,并能够依次用双曲线和直线来模拟;随着围压的升高,堆石料的剪胀性会急速降低,颗粒破碎可能性会增加,因此相应的最大主应力比和内摩擦角会随之发生明显的减小,并且可以用幂函数关系很好的拟合它们与围压的关系。     

不同吊顶材料对燃烧室内和狭长走廊中烟气危害性的影响

选取建筑用材中几种常用的吊顶材料,研究火源以及火势迁移等因素对狭长走廊中烟气危害性的影响.试验在小尺寸实验台上进行,研究了采用不同吊顶材料时燃烧室和走廊中烟气的体积分数峰值、峰宽时间及到达峰值的时间,揭示了烟气的危害程度.试验表明,不同吊顶材料对火灾中烟气的危害性有明显影响.复合板吊顶材料能够显著增加烟气体积分数峰值并缩短到达峰值的时间,其烟气体积分数峰值约为单纯钢板吊顶情况下的两倍.PVC吊顶材料在同样火灾载荷下的塌落倾向最明显.     

Effect of application of phosphate and organic manure-based fertilizers on arsenic transformation in soil columns

The mobility of arsenic in Cambisol under the influence of added barnyard manure and application of a phosphate solution to the soil was described on the basis of column experiments. A soil sample containing 126 mg/kg total As and 3.72 mg/kg specifically-sorbed As was extracted using demineralized water (DIW) or a 28 μmol/l phosphate solution in a column containing untreated soil and in a column with added barnyard fertilizer. The pH, Eh, alkalinity, main components, including DOC, and selected trace elements (Al, Mn, Pb, Cu, Zn, Cd, Cr, Co, Ni, Ba and As) were determined in the extracts. Hydrodynamic tests of the flow and transport of the substances in the columns were carried out. The addition of barnyard manure was manifested in elevated concentrations of the main inorganic components, DOC and Al and a decrease in the Eh value and Mn concentration. Application of a phosphate solution was manifested in a decrease in the NO₃ and SO₄ concentrations, probably as a result of the effect of increased biological fixation. The As concentration in extracts varied from 8.8 to 15.5 μg/l and was not dependent on the composition of the extracting solution or the addition of barnyard fertilizer.     

改性尿素的肥效及淋溶特性研究初探

在普遍尿素的生产工艺中分别加入一定比例的无机矿物改性剂,研制出３种改性尿素。盆栽结果显示,在等质量及等Ｎ施肥条件下,３种改性尿素均有较大幅度的增产。淋溶实验表明,改性尿素与德国缓释尿素的淋溶曲线相似。     

基于高压电容器振动试验夹具材料的选用与设计

介绍了一种基于高压电容器性能检测及振动试验所需的夹具,从夹具材料的选取、结构设计和刚度要求进行了设计,分析了该夹具在制造过程中存在的关键问题及解决方法,并在振动试验中加以验证。     

不锈钢钢渣单颗粒成分分析及用于烟气脱硫的模拟试验

为研究不锈钢钢渣化学成分及用于烟气脱硫的可行性,采用电子探针微区分析技术对太原钢铁(集团)有限公司不锈钢钢渣进行单颗粒形貌和组分分析,然后测定钢渣中游离氧化钙含量和浆液的pH,在此基础上,开展了将其用于烟气脱硫的模拟试验,研究了钢渣干湿状态、粒径对脱硫效率和失效时间的影响。结果表明,不锈钢钢渣颗粒呈不规则形状,主要成分包括CaO、MgO、Al2O3、SiO2等,其中游离氧化钙占4%~7%;钢渣浆液呈碱性。浸湿状态下80目以上钢渣脱硫率大于60%,失效时间170min。表明不锈钢钢渣具备一定的烟气脱硫潜力,可以考虑用来"以废治废"。     

九曲桥行人运动实验与模拟研究

公共场所中的人群疏散是行人疏散动力学研究中的重要内容。基于九曲桥行人运动观测实验对转角区域的行人运动特征进行研究,并利用人员疏散模拟软件Pathfinder模拟了因激励作用所导致的行人速度提高对通行效率的影响。结果表明,由于行人的停留、拍照行为导致转角内区域出现了明显的行人变换走道现象;行人在转角内区域出现的停留、超越行为导致行人速度出现大幅度波动,最低速度约为0.2 m/s,最高速度约为0.7 m/s;与转角后区域相比,行人密度变化对转角内区域的行人速度的影响更小,单位流量的影响更大;由于观测实验中行人停留、拍照等行为的存在,相同密度下转角后区域行人运动速度、单位流量均低于P&M平直通道模型;适当的激励作用有助于减轻行人拥堵,提高通行效率,当行人速度达到较高水平后效果不再显著。