改善气液传质效率实现丝状菌膨胀污泥控制的方法

为了研究活性污泥系统中丝状菌的存在与污泥气液传质的关系,实验测量了不同絮体结构丝状菌污泥对体积溶氧传质系数(kLa)的影响,并考察了改善气液传质效率对控制丝状菌膨胀的影响。实验结果表明,丝状菌对气液传质的影响主要取决于丝状菌的沉淀性能而不是丝状菌的数量。在由于溶氧不足导致丝状菌膨胀的条件下,可以通过改善丝状菌絮体结构提高系统的气液传质效率,即通过絮体结构调控消除溶氧不足的外在条件,从而实现了控制丝状菌膨胀的目的。研究成果以改善丝状菌结构为手段,从微生物本身出发提高系统曝气效果,为控制丝状菌膨胀提供了新的思路。     

农民农地转出意愿及影响因素的性别差异——基于天津市578份调查问卷的实证分析

基于2015年对天津市农民的调查数据,运用二元Logistic回归模型,在性别差异的视角下,分析了农民农地转出意愿的影响因素。研究发现:对男性和女性农地转出意愿均有显著影响的主要是年龄、家庭农业收入比重、家庭劳动人口数量、非农就业年工资水平、对农地的态度、对政府土地流转服务评价、对农民工子女入学政策的评价。只对男性农地转出意愿有显著影响的是农地经营成本、农地经营收益、是否签订劳动合同、外出找工作途径、农地转出程序评价、对开展就业技能培训的评价、是否参与新农保、对新农保保障能力评价。只对女性农地转出意愿有显著影响的是文化程度、婚姻状况、对非农就业工作生活环境的感知、所在地区。基于上述结论,提出了相关对策建议。     

基于Ti/SnO2阳极氧化法的典型染料废水电化学氧化规律

采用Ti／SnO2电极间接阳极氧化法处理直接深棕M和活性艳蓝KNR模拟染料废水，研究电解质种类、pH、电压、NaCl投加量及电解时间对其降解效果的影响；在最佳组合条件下，通过分析uV—Vis光谱以及降解过程中氮元素的存在形式，研究上述2种染料的降解规律。结果表明，在pH为3，电压20V，NaCl投加量为2．5g／L的条件下，电解30min后，直接深棕M和活性艳蓝KNR的脱色率分别达到80％和95％，60min后直接深棕M的COD去除率可达75％，活性艳蓝KNR的COD去除率达到90％；电解60min后，直接深棕M的偶氮双键完全破坏，萘环和苯环结构被逐步降解，活性艳蓝KNR溶液电解2min，其分子结构中的蒽醌共轭体系被破坏，随反应的进行，蒽醌结构逐渐被破坏，染料逐步降解。     

填料塔中Na2CO3吸收高浓度H2S的传质特性

在填料吸收塔中考察了Na2CO3溶液吸收高浓度H2S气体的气液传质特性。通过测量填料塔进出口气体中H2S浓度计算了Na2CO3溶液吸收高浓度H2S气体的总体积传质系数（KGa），并研究了进气流速、吸收液流量、吸收温度和吸收液浓度对KGa的影响。结果表明，KGa随Na2CO3浓度、吸收液流量的增加而增加，随吸收温度、进气流速的升高而降低；在高浓度H2S吸收过程中液相传质阻力不能忽略。     

离子液体[BMIm][PF6]增强抗性质粒RP4介导的接合转移基因mRNA的表达水平

环境中广泛存在的抗生素和抗生素抗性基因会导致很严重的人类健康风险。在我们前期研究中发现,离子液体1-丁基-3-甲基咪唑六氟磷酸盐([BMIm][PF6])作为环境选择性压力可以促进抗生素抗性基因的水平转移。本研究以E.coli DH5α(RP4)和同属的E.coli HB101,以及E.coli DH5α(RP4)和跨属的Salmonella enterica之间的纯菌接合转移体系为考察对象,从mRNA基因表达调控水平角度阐明离子液体[BMIm][PF6](0.001~2.5 g·L-1)影响质粒RP4接合转移的机理。结果表明,离子液体[BMIm][PF6]通过抑制基因kor A,kor B和trb A的mRNA表达水平来提高接合和跨膜转运基因trb Bp和trf Ap的表达;增强水平转移基因tra F的mRNA表达水平,并通过增强负调控基因kil A和kil B的mRNA表达水平抑制质粒的垂直传递过程;通过抑制基因trb K的mRNA表达水平降低接合转移体系的排斥效果,从而促进质粒RP4的接合转移。该结果有助于为抗生素抗性基因在环境中水平转移扩散的机理研究提供理论依据。     

应对气候变化关键技术创新差异的时空格局——以“一带一路”沿线国家为例

技术是应对气候变化的重要手段,关键技术创新差异的扩大将不利于各国应对气候变化的协同发展。以技术产出的专利为数据源,运用大数据挖掘工具、泰尔熵指数及空间计量学的方法和理论,分析了"一带一路"沿线国家应对气候变化关键技术创新差异的时空格局演变情况。研究结果表明:(1)沿线国家应对气候变化关键技术创新差异整体上呈现下降态势,并以初期震荡向后期平稳有升过度。(2)按地理位置划分的区域技术创新差异呈现高的空间集聚效应,且强强集聚与弱弱集聚具有一定时期内的稳定性,部分地区面临陷入技术贫困陷阱风险。(3)沿线各国应对气候变化技术创新差异存在趋同俱乐部现象,个别国家随时间推移可能经历不同俱乐部过度。针对这种趋同特征及各国技术需求特点可划分为4种类别:技术转出区、技术转入区、技术扩散区和技术承接区。技术转出区多集中在东欧某些经济发达、能源依存度高的国家。为此,本文提出如下建议:(1)各国根据自身情况制定减排政策的同时,需要国际社会制定与其相适应的差异化且有侧重的援助方案。(2)技术创新强国在涉及应对气候变化技术转移知识产权等事项上应该给予技术需求国让步。同时,技术转移应考虑区域协同及地理邻近的扩散。(3)中国应发挥好南南合作援助基金的作用,加强特定区域内共性技术的帮扶力度,建立与适宜国家间关键技术联合研发与示范机制,树立大国形象。(4)中国应加快沿线战略布局,根据不同区域各国应对气候变化的现状及其技术能力制定差异化的产业和技术转移的政策,加强与沿线国家的技术合作与贸易往来,形成优势互补的产业链。     

选择性转移、转移成本与中国城乡收入差距变动

本文通过构建由城镇正规、非正规与农村农业部门组成的农村劳动力择优向城镇转移情形下的三部门经济生产和分配模型,对我国20世纪90年代初期以来存在极强选择性和具有高昂转移成本下的城乡劳动力转移对我国城乡收入差距可能产生的影响进行了理论分析,并根据模型对影响进行了数值模拟实验。研究结果表明,农村劳动力的择优转移和转移成本会内生性地引致我国城乡收入差距的扩大。究其原因,主要在于农村中相对优质的劳动力进入到城镇就业,在给城镇居民带来更多回报率较高投资机会的同时,而农业则由于优质人力资本的流出而大大延滞了其发展速度,这种"一促一抑"、"一荣一损"的内在机制势必引致城乡收入差距的扩大,同时转移成本的存在会放大收入差距扩大的程度。进一步地,通过把劳动力选择性转移与随机转移和劣者淘汰不同情形下我国可能出现的城乡收入差距进行对比的反事实分析表明,20世纪90年代初期以来在我国农村大量劳动力不断向城镇转移就业的过程中,劳动力很强择优转移的特性在城乡收入差距进一步扩大中贡献了约1/3的份额,而往返流动的转移成本在城乡收入差距扩大中产生了大约1.2倍的乘数效应,这是本研究得到的两个重要量化结果。为了缩小我国城乡收入差距,文章建议要为农民工市民化创造便利条件,为城乡间资本要素自由流动提供便利渠道,需要将城镇化建设与新农村建设很好地结合,特别是要最大限度地释放农村经济社会发展的自身活力以让农村能人能够在当地更好地施展才干。     

Numerical studies on the thermal regimes of the horizontal tube falling film evaporation under varying feeder height

ABSTRACT

This paper discusses about the effect of feeder height and heat flux on the heat transfer characteristics of horizontal tube falling film evaporation in the thermal regimes. In order to investigate this, a two- dimensional CFD model was developed to perform simulation and results were compared and validated with published data available in the literature. Heat transfer co-efficients in the thermal regimes were determined from the CFD simulation and the results were recorded, analyzed and validated with the mathematical models available in the literature. The novelty of the current study is to predict the commencement of the fully developed thermal region over the tube from the simulation model under varying feeder height and heat flux. An effort was also made to measure the liquid film thickness around the tube from the CFD model in the thermal regimes. It is observed that angle of thermally developing region contracts and fully developed thermal region extends with the increase of the feeder height and heat flux. It is observed from the study that increase of heat flux by 10 kW/m² resulted in increase of heat transfer co-efficient value by 10–12% average in thermally developing region and 12–15% average in fully developed region. Thinnest liquid film thickness observed between 85 and 127°angle. Shifting of thinnest region of liquid film upward from the mid tube with the increase of the feeder height and heat flux is noted.     

Spatiotemporal trends of illegal activities from ranger‐collected data in a Ugandan national park

Within protected areas, biodiversity loss is often a consequence of illegal resource use. Understanding the patterns and extent of illegal activities is therefore essential for effective law enforcement and prevention of biodiversity declines. We used extensive data, commonly collected by ranger patrols in many protected areas, and Bayesian hierarchical models to identify drivers, trends, and distribution of multiple illegal activities within the Queen Elizabeth Conservation Area (QECA), Uganda. Encroachment (e.g., by pastoralists with cattle) and poaching of noncommercial animals (e.g., snaring bushmeat) were the most prevalent illegal activities within the QECA. Illegal activities occurred in different areas of the QECA. Poaching of noncommercial animals was most widely distributed within the national park. Overall, ecological covariates, although significant, were not useful predictors for occurrence of illegal activities. Instead, the location of illegal activities in previous years was more important. There were significant increases in encroachment and noncommercial plant harvesting (nontimber products) during the study period (1999–2012). We also found significant spatiotemporal variation in the occurrence of all activities. Our results show the need to explicitly model ranger patrol effort to reduce biases from existing uncorrected or capture per unit effort analyses. Prioritization of ranger patrol strategies is needed to target illegal activities; these strategies are determined by protected area managers, and therefore changes at a site‐level can be implemented quickly. These strategies should also be informed by the location of past occurrences of illegal activity: the most useful predictor of future events. However, because spatial and temporal changes in illegal activities occurred, regular patrols throughout the protected area, even in areas of low occurrence, are also required.     

基于换乘人耐受限的对向公交换乘生存距离模型研究

为揭示对向公交换乘距离与换乘乘客横穿道路的相互关系,约请272名受试者,完成城市公交汽车换乘试验。基于换乘试验统计出横穿马路人数,采用非参数估计方法估计换乘乘客的最大忍耐换乘距离,利用SPSS软件,构建拟合程度最高的对向换乘生存距离二次项函数模型,并对模型的有效性进行验证。结果表明,违规过街行人数随公交换乘距离的增大而增多;生存率随换乘距离的增大呈现"缓慢减小-迅速减小-平缓减小"的变化趋势,换乘距离增加至126 m后,越来越多的乘客难以接受这样的距离;换乘距离相同时,男性相比女性更容易横穿马路;根据构建的对向公交换乘生存距离模型,85%的换乘乘客可接受的换乘距离为124 m,50%的换乘乘客可接受的换乘距离为174 m。