鱼游泳能力对体长的响应及其在鱼道设计中的应用

为了探讨鱼类体长对游泳能力的影响并为鱼道水流的设计提供参考,该研究在封闭水槽中使用"递增流速法"测试了海南省某水利枢纽鱼道目标对象的游泳能力,并用Origin软件进行了数据统计分析,得到了试验鱼感应流速、临界游泳速度和爆发游泳速度的直线回归方程和Kaplan-Meier曲线.结果表明:1)随着试验鱼体长增大,相对感应流...     

大兴县荒漠化生态安全评价研究

根据大兴县荒漠化地区的环境特点,提出了生态安全评价的具体指标体系和构建原则,并采用数量化原理与方法,对各指标进行了具体量级划分,同时利用关联度分析方法,确定了指标的系数,并提出了衡量生态安全程度的数量化指标、生态安全系数及其计算方法.以土壤养分、水分条件、植被状况和风力4个影响生态安全因子确定了指标体系.以土壤有机质含量、林草地覆盖度、降水量和土壤粘沙比为生态安全评价的具体指标,计算了各个因子对生态安全影响程度.根据土地利用情况,确定了大兴县624个土地利用单元的生态安全系数,采用GIS平台得到了大兴地区的生态安全评价图.研究成果可直接为环北京治沙防沙重点工程的实施提供指导,研究方法可供区域生态安全评价借鉴.     

秸秆还田对土壤脱氢酶和多酚氧化酶活性动态变化的影响

通过旱田试验研究了冬小麦生长期内,秸秆还田与肥料配施对土壤脱氢酶活性和多酚氧化酶活性动态变化的影响.结果表明,土壤脱氢酶活性在冬小麦生长期内波动较大,出现多个峰值;秸秆还田和厩肥的施入均能显著提高土壤脱氢酶活性.在冬小麦生长后期,尿素能显著提高土壤脱氢酶活性,而过磷酸钙的施入一定程度上降低了土壤脱氢酶活性.土壤多酚氧化酶活性表现为在冬小麦生长前期和中期活性较低,4、5月份活性迅速升高,出现高峰值,随后在收获期迅速降低;秸秆还田和过磷酸钙对土壤多酚氧化酶活性的影响不显著.在冬小麦生长中期,厩肥和尿素对土壤多酚氧化酶活性有一定的抑制作用,在冬小麦生长旺盛期,厩肥和尿素对多酚氧化酶活性的抑制作用不明显.     

110 kV变电站电动接地刀闸自动误合原因分析

通过对一起变电站电动接地刀闸自动误合事件原因查找、分析、处理,从设计、施工、验收、运行维护等方面提出防范措施。     

喹烯酮的研究及其在生产中的应用

喹烯酮是一种新型药物饲料添加剂,具有抑制有害菌,保护有益菌的作用,能够促进动物机体生长,提高饲料转化效率。文章对喹烯酮的物理和化学性质、作用机理、检测方法、代谢、毒性等以及在动物养殖生产中的应用进行了论述,以期为喹烯酮在生产中更加合理、广泛的应用提供依据。     

芬兰林业税的改革及启示

芬兰自1922年起对林业实行立地生产力税制, 根据土地面积和土地生产力征税, 成为有效促进木材供应增长和鼓励林业投资的重要工具。1993年, 芬兰开始实行按实际收入征税的新税制。新税制操作简便, 并与其他欧盟国家税制接轨, 适应了芬兰经济发展的现实需要。文中讨论了芬兰林业税改革对中国的启示:立地生产力税制对于中国而言, 操作难度大; 中国应借鉴芬兰经验, 结合我国林业特点, 设计适应国情的林业税制。     

Organic chlorine and chloride in submerged paddy soil: a case study in Anhui province, southeast China

Abstract. Efforts to understand the fate of organochlorine compounds in arable soil have concentrated on anthropogenic compounds, in spite of the fact that organochlorine compounds are both produced and mineralized in soil through natural processes. In order to understand the fate of chlorinated pesticides, it is necessary to take account of the natural chlorine cycle. The present study is a first attempt to illuminate the relationship between the natural chlorine cycle and agricultural practices. The concentration and storage of organic chlorine (Cl_org) and chloride (Cl_inorg) were determined in topsoil of a paddy field compared to an adjacent afforested hill at a sampling site in the Meicun area, Anhui Province, China. The concentration of Cl_org, as well as the chlorine-to-carbon ratio, was significantly lower in the paddy field samples than in the forest soil samples. A weak relationship between the concentration of Cl_org and the organic carbon content was observed in the paddy field, in contrast to the observations made in the adjacent forest soil as well as those made in previous studies, which have suggested a positive correlation between organic carbon content and Cl_org. The similarity between our results at the forest site and the previous studies, which have been carried out in temperate regions, suggests that it is the land use rather than the climate that makes the current paddy soil results different. Our results suggest that the contribution of Cl_org to the paddy soil from above-ground litter and from production within the soil are small or negligible compared with the contribution from pesticide application and wet and dry deposition.     

M85甲醇燃料在EQ6100发动机上应用的试验研究

为了缓解汽车对石油的依赖,改善我国大气污染,适应我国能源开发的需要,对保有量大、应用面广的ＥＱ６１００汽车发动机进行了高掺烧比例甲醇燃料（Ｍ８５）的技术改造和试验研究。通过对原发动机的结构改装和有关参数的调整,试验结果表明Ｍ８５甲醇发动机与原发动机相比,其动力性、经济性和尾气排放均有大幅度的改善和提高。甲醇燃料完全可以在现有改装的汽油机上使用。     

基于网络集成的弧齿锥齿轮数字化闭环制造技术

为突破弧齿锥齿轮数字化闭环制造过程信息继承性与集成性低的局限,实现弧齿锥齿轮齿面数字化闭环过程的集成运行和齿面制造信息的集成管理,该文提出了一种弧齿锥齿轮的网络化闭环制造模型,建立了网络化闭环制造的运行机制,采用基于TCP/IP(transmission control protocol/internet protocol,传输控制/网络通讯协定)的分布式集成控制模式构建网络化闭环制造模型的通信网络,利用Web服务应用集成方法建立闭环制造过程信息集成机制,并通过设计开发闭环制造集成系统实现网络化闭环制造信息的集成统一管理。应用结果表明:该模型及其实现技术可行实用,实现了齿面制造过程的数字化和集成化运行,使齿轮副的齿面精度和啮合性能都得到明显提高。以该文的准双曲面齿轮副滚动检测试验为例,辐射噪声降低约7%,振动加速度幅值降低约15%。该研究为弧齿锥齿轮的网络化和集成化制造提供参考。     

Lipid oxidation in corn oil-in-water emulsions stabilized by casein,whey protein isolate,and soy protein isolate

Proteins can be used to produce cationic oil-in-water emulsion droplets at pH 3.0 that have high oxidative stability. This research investigated differences in the physical properties and oxidative stability of corn oil-in-water emulsions stabilized by casein, whey protein isolate (WPI), or soy protein isolate (SPI) at pH 3.0. Emulsions were prepared with 5% corn oil and 0.2-1.5% protein. Physically stable, monomodal emulsions were prepared with 1.5% casein, 1.0 or 1.5% SPI, and > or =0.5% WPI. The oxidative stability of the different protein-stabilized emulsions was in the order of casein > WPI > SPI as determined by monitoring both lipid hydroperoxide and headspace hexanal formation. The degree of positive charge on the protein-stabilized emulsion droplets was not the only factor involved in the inhibition of lipid oxidation because the charge of the emulsion droplets (WPI > casein > or = SPI) did not parallel oxidative stability. Other potential reasons for differences in oxidative stability of the protein-stabilized emulsions include differences in interfacial film thickness, protein chelating properties, and differences in free radical scavenging amino acids. This research shows that differences can be seen in the oxidative stability of protein-stabilized emulsions; however, further research is needed to determine the mechanisms for these differences.