共查询到20条相似文献，搜索用时 93 毫秒
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张秀芬 《黄河之声(科教创新)》2007,(3)
试验研究了在模拟平流沉淀池中,设置挡板、溢流堰对浊度去除效果的影响,以及在沉淀区中投放短管填料对浊度去除效果的提高。通过控制不同进水流态、短管填料不同投加方式、不同投放位置、不同投放量的对比,提出提高浊度去除率的最优方法。 相似文献
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比色管色谱法测定食品中甜蜜素的探讨 总被引：1，自引：0，他引：1
采用比色管为顶空瓶，顶空气相色谱法测定食品中甜蜜素含量。样品在比色管中保温，用氢火焰离子化检测器检测，食品中甜蜜素的最低检出浓度为1.9mg／kg，在样品中加标浓度为0.2-0.4g／kg时，平均回收率为92.4％一97.6％，高、中、低三种浓度的变异系数均小于5％。 相似文献
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对过硫酸钾消解法绘制污水中总磷标准曲线方法进行改进,水样取样量和所加入试剂的用量均同步缩小至1/10,并于北京双晖京承公司的CM-05型多功能水质监测仪的COD消解管中进行显色反应,另在与之配套的分光光度计上直接比色测定,消解时间仅为15 min,具有快捷、简便、高效等优点. 相似文献
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<正> 麝香草酚浊度试验(TTT)是临床常用的肝功能试验。在急性肝细胞损伤早期,是继血清谷丙转氨酶升高后最早出现阳性的一个指标,也是观察肝细胞损伤后治疗效果的一个指标。由于麝香草酚絮状试验(TFT)易受温度、时间等影响,已被卫生部列为淘汰项目,但麝香草酚浊度试验仍被保留,为广大医院继续使用。该试验的标准浊度液一般采用 相似文献
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胡献舟 《中国教育技术装备》2002,(6):29-30
在“空气中二氧化硫测定”的实验教学时,笔者发现,按《空气和废气监测分析方法》(第三版)(以下简称“规范”)一书中规定的方法进行操作,学生很难控制显色反应的显色时间,利用比色管调配试剂进行显色反应时,也很难达到操作要求,在一定程度上影响了实验结果的精确性。近年来,笔者对测定条件及实验器皿加以控制和改进后,既保证了测定结果的准确性,又大大降低了实验操作难度,缩短了操作时间,提高了教学效率。 相似文献
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以铝箔酸、铝盐水和铝酸钙粉为主剂,亚铁酸为助剂．酸溶一步法合成聚合氯化铝铁．采用多因素正交试验研究了投料温度、加铁时间和保温时间对产品中铝含量、盐基度及其在处理污水过程中对污水中COD、TP和浊度的去除效果影响．结果表明,保温时间对产品中铝含量和盐基度及COD去除率影响最大,投料温度对浊度的去除效果最为明显,加铁时间对产品中铝含量、COD及浊度的去除率影响不大． 相似文献
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主位推进模式是文学语篇构建的重要形式手段。文学语篇比其它类型的语篇呈现出较为复杂的主位推进模式,常常是多种模式的交叉配合使用;主位同一型、主位派生型、述位分裂型和延续型是文学语篇中最为常用的主位推进模式。主位推进模式在文学语篇的构建和解读过程中发挥着重要作用,恰当的主位推进模式可以帮助作者实现其语篇目的;利用主位推进模式对文学语篇进行分析,有助于深刻理解语篇内容以及作者组织语篇信息的方法。为了从更高的层面上来描述和分析语篇中的主位推进模式,还引入了句群主位的概念。 相似文献
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This study addresses heat transfer performance of various configurations of coiled non-circular tubes, e.g., in-plane spiral ducts, helical spiral ducts, and conical spiral ducts. The laminar flow of a Newtonian fluid in helical coils made of square cross section tubes is simulated using the computational fluid dynamic approach. The effects of tube Reynolds number, fluid Prandtl number, coil diameter, etc., are quantified and discussed. Both constant wall temperature and constant heat flux conditions are simulated. The effect of in-plane coil versus a cylindrical design of constant coil, as well as a conical coil design is discussed. Results are compared with those for a straight square tube of the same length as that used to form the coils. Advantages and limitations of using coiled tubes are discussed in light of the numerical results. 相似文献
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This article applies Goldratt's thinking process (TP) to problems associated with an engineering consulting firm's invoicing system and the need to increase productivity to maintain demand. The core problem found was the company was not maximizing the use of project management personnel. Results of the TP are an effect‐cause‐effect analysis that considers undesirable effects associated with increasing productivity. By identifying the core problem, we determined what to change, what to change to, and how to cause the change. 相似文献
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介绍了一种用于强化管壳式换热器壳侧传热和支撑管束的螺旋折流片新型结构,该结构是对换热器管子相间地套上螺旋折流片以产生旋涡流动.研究模型是在正方形布置的4个管子中的2个对角管子套上螺旋折流片后形成的通道,利用FLUENT软件对该上述四管通道模型的流场和温度分布情况进行了数值模拟;分析了四管通道模型中螺旋折流片对强化传热和流动阻力随雷诺数的变化关系的影响.算例结果显示该新型结构可比相同尺寸的光管通道中的情形传热系数提高约40%～55%,同时也将伴随较高的流动阻力.可以相信螺旋折流片式换热器将会在许多工业领域有良好的应用前景. 相似文献
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采用离体花粉培养技术,研究了不同浓度的细胞外钙对百合花粉萌发和花粉管生长的影响.结果表明：在0.01％ Ca2＋度下花粉萌发和花粉管生长速率最快,高于或低于这个浓度,花粉管生长速率和萌发速率都显著被抑制.将快速生长的花粉管,转入Ca2＋浓度为03％的培养基中,花粉管的生长在几秒种内就被抑制.长时间0.3％ Ca浓度培养导致花粉管呈波浪形状.这种改变是不可逆的,当用pectinase处理或降低培养基中的钙浓度时,花粉管破裂.这些结果说明钙作为花粉管生长调节信号,对花粉管的生长具有直接作用和间接作用. 相似文献
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In this article the author explores the policy discourse on teacher professionalism (TP) in Singapore. Various types of relevant policy texts are collected and analysed, considering the three different perspectives of TP discussed in the existing literature – the managerial view, the professional view and the transformative view. The author argues that the current discourse presents a hybrid notion of TP that integrates managerial and professional views to serve policymakers’ intentions, but this is a constrained view that may de-professionalise the teaching profession by narrowing TP to faithful alignment and effective implementation of the national curriculum. 相似文献
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Brian C. Poncy Christopher H. Skinner Elizabeth McCallum 《Psychology in the schools》2012,49(8):744-755
An adapted alternating treatments design was used to compare the effects of class‐wide applications of Taped Problems (TP) and Cover, Copy, and Compare (CCC) procedures designed to enhance subtraction fact fluency in an intact third‐grade classroom. During the TP procedure, a tape provided an auditory prompt (i.e., the problem), followed by a 2‐second delay and then the correct answer. Students attempted to supply the correct answer before the answer was provided by the tape. During the CCC procedure, students would cover a math‐fact family triangle, attempt to write one of two possible problems and answer, write the reciprocal fact and answer, and evaluate their responses. Results show that TP caused greater increases in subtraction fact fluency than CCC or a control condition. Discussion focuses on preventing student math deficits, issues regarding alternating treatments designs, and future directions for research. © 2012 Wiley Periodicals, Inc. 相似文献
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Namin Shin Jason K.Y. Chan 《British journal of educational technology : journal of the Council for Educational Technology》2004,35(3):275-288
This paper presents an exploratory study that investigates the effects of online learning on distance education students in an open university context. Two hypotheses are posited: (1) a direct relationship exists between students’ involvement in online learning and distance learning outcomes, and (2) an indirect relationship exists between these two domains via the mediating variable of an institutional Transactional Presence (TP), that is, a student's sense of the availability of and connectedness with an educational institution. Student learning achievement, satisfaction and intent‐to‐persist are used as indicators of outcomes of distance learning. The analysis of data garnered from 285 distance students reveals multifaceted relationships between students’ engagement in online learning, their perceptions of institutional TP and the three learning outcome variables. Besides the findings, the paper will discuss factors affecting students’ engagement in online learning in relation to different requirements, that is, optional or compulsory online use as well as the level of the course (undergraduate or postgraduate). 相似文献
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The desalination of brackishor sea wateris widelyap-plied to the water supply in China and around theworld[1—4]. The common desalination methods , such asmultistage flesh, multi-effect distillation and reverse osmo-sis, usually require high initial costs and skill oper-ation[5 ,6]. For this reason,these desalination techniquesare mostlyreliable for large capacity of fresh water produc-tion but not economical in the water-shortage areas wherewater demand is decentralized or proper infrastructu… 相似文献
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对自由圆管在其中心部位经受刚性平头弹体横向冲击时的动力学行为进行了实验研究和计算机仿真.研究了不同管径、管长以及不同材质的自由圆管在3种不同直径和质量的平头弹体的横向冲击下的变形历程、最终的变形模态以及能量的分配方式,得到了自由圆管被穿透时子弹的临界速度和临界动能.并把实验和模拟的结果与自由梁模型的情况作了比较和分析. 相似文献