共查询到20条相似文献，搜索用时 140 毫秒
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微波辐射全氟磺酸树脂催化合成柠檬酸三丁酯的研究 总被引：1，自引：0，他引：1
以柠檬酸和正丁醇为原料,废弃的全氟磺酸树脂为催化剂,在微波辐射条件下合成柠檬酸三丁酯,对影响合成柠檬酸三丁酯的因素进行研究。结果表明：微波辐射条件下,醇酸摩尔比为6：1、催化剂用量为0．315g、微波辐射时间为40min、微波辐射功率为500W,柠檬酸三丁酯的最高产率可达93．9％。该催化剂绿色环保且易于回收,重复使用六次以上产率仍可达到90％以上。 相似文献
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载铁(Ⅲ)树脂催化合成柠檬酸三丁酯 总被引：4，自引：1，他引：4
报道了阳离子树脂负载FeCl3催化合成柠檬酸三丁酯，研究了反应时间、醇酸摩尔比、催化剂用量等因素对反应的影响．结果表明，该催化剂对柠檬酸三丁酯的合成具有良好的催化活性，酯收率可达90．7％。 相似文献
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用正丁醇和柠檬酸为原料,WO3/MoO3/SiO2为催化剂催化合成柠檬酸三丁酯.通过考察醇与酸的物质的量比,反应温度和反应时间,催化剂用量和溶剂用量对酯化反应的影响.确定合成柠檬酸三丁酯的最佳反应条件为n(正丁醇)/n(柠檬酸)=4.5,催化剂用量为反应物柠檬酸质量的6%,反应温度130 -140℃,反应时间3.5h,... 相似文献
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以柠檬酸和正丁醇为原料,硫酸铝为催化剂,合成柠檬酸三丁酯,考察了其酸醇比对酯化率的影响,并与在超声催化条件下反应对酯化率的影响进行了对比.确定了实验最佳反应条件为:以柠檬酸用量为基准,酸醇摩尔比为1∶4.0,催化剂用量为4%,在超声波振荡温度为0℃,振荡时间为20 min条件下合成柠檬酸三丁酯,酯化率为92.6%. 相似文献
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以柠檬酸和正丁酵为原料,以纳米Sm2O3为催化剂催化合成无毒增塑剂柠檬酸三丁酯.探讨了催化剂用量、酸醇物质的量比、反应时间、反应温度对反应的影响.结果表明,纳米Sm2O3催化合成柠檬酸三丁酯的最佳条件为n(柠檬酸):n(正丁醇)=1:5.0,催化剂用量为柠檬酸质量的4.5%,反应时间为3.0h,反应温度为114～147℃,酯化率可达90.83%,并对合成的产品进行了红外光谱分析. 相似文献
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PLA／TBC的等温结晶动力学研究 总被引：1，自引：0，他引：1
田怡 《乐山师范学院学报》2008,23(12):40-41
采用差示扫描量热（DSC）方法对柠檬酸三丁酯（TBC）增塑聚乳酸的等温结晶动力学进行了研究．结果表明,TBC的加入明显提高了聚乳酸的结晶速度．对所得数据用Avrami方程进行了处理,并计算了其等温结晶活化能． 相似文献
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宋少华 《读与写:教育教学刊》2008,5(5):3-5
This essay mainly studies the linguistic features of News English on stylistics.The study is made mainly on three aspects of News English.They are lexical features.sentence features and grammar features of News English.Through the study we find that News English,as a distinctive and new language.has its own lin-guistic features in words, sentences and grammar. 相似文献
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GUO Bao-feng Xiao Da-wei 《重庆大学学报(英文版)》2005,4(3):129-133
Using virtual reality for interactive design gives a designer an intuitive vision of a design and allows the designer to achieve a viable, optimal solution in a timely manner. The article discusses the process of making the Virtual Reality System of the Humble Administrator＇s Garden. Translating building data to the Virtual Reality Modeling Language （VRML） is by far unsatisfactory. This creates a challenge for computer designers to do optimization to meet requirements. Five different approaches to optimize models have been presented in this paper. The other methods are to optimize VRML and to reduce the file size. This is done by keeping polygon counts to a minimum and by applying such techniques as object culling and level-ofdetail switching. 相似文献
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邱崇丙 《唐山师范学院学报》2014,(1):21-23
汉字的六书,《说文》对“转注”一类,语焉不详。后世学者提及转注,也仅限于许慎所举出的例字。《汉字例说》一文,作者从转注的角度综合考虑,对部分现代常用字作了分析,跟传统的解释有所不同。希望能抛砖引玉,互相切磋,以推进学术研究。 相似文献
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西方传统哲学对人的思考严格遵循主—客的思维模式,大力弘扬主体性原则,崇尚“人类中心主义”。而自西方现当代人文思潮产生以来,对人的理解发生了转向,弘扬非理性,倡导人与自然的融合。海德格尔就是这种思潮的代表。文章从本体论和认识论两个维度对海氏“人（此在）是澄明”这一哲学命题作出了新的解释。 相似文献
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Rajesh Kanoi 《海外英语》2007,(1):52
Today, Sunday morning, I sit thinking and typing at my computer. My thoughts are in my homeland, India and my body is in China. The body is here and mind there for a good reason. Mr. Hu is president and I am resident and both are in each other's countries (what a difference the absence of one small letter makes!). Mr. Hu will return in a few days and I will stay on longer. 相似文献
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民主是个好东西,然而,民主并不是解决当前所有问题的万能钥匙。在中国政治民主化的进程中,需要正确解读民主与集中,民主、自由与纪律,民主与党的领导,民主与选举,民主与决策,民主与效率,民主与民众文化素质这几对重要关系,深刻剖析民主的生命力及弱点,澄清国民在民主认识上的误区,才能清晰定位目前民主政治发展的目标。 相似文献
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刘晓臻 《昆明师范高等专科学校学报》2011,(5):37-39,45
《型世言》中＂虚撮脚＂、＂撇呆＂、＂找截＂、＂间壁＂、＂隔夜＂、＂锅边秀＂等六条没被解释或解释不确的词语,其义当为：1.＂虚撮脚＂的本义是＂空拉架势,作出要干某事的样子＂,引申义是＂敷衍,虚于应付＂和＂阿谀奉承,假奉承＂;2.＂撇呆＂即＂发呆＂;3.＂找截＂即＂简捷,利索＂;4.＂间壁＂即＂隔壁＂之意;5.＂隔夜＂意为＂昨天＂,＂前一天＂或＂前一天晚上＂;6.＂锅边秀＂也做＂锅边转＂,本义指厨房中烧火做饭的人,后引申指＂粗使丫头＂、＂女孩＂等。 相似文献
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RUZBEHANI Mohsen 《重庆大学学报(英文版)》2004,3(1):20-25
1.IntroductionOne-cyclecontrolmethod,whichwasproposedaboutonedecadeago[1],hasbecomeanattractivemethodinspecialfieldssuchaspowerfactorcorrection[2-6],switchingamplifiers[7,8],etc.Themainideaofthiscontrollerisbasedonintegrationofdiodevoltageinone-cycleandforcesittobeexactlyequaltothereferencevalue.Themainadvantageofthiscontrollerisitsrealtimeabilitytorejectthevariationofinputvoltage[1].Despitethisgreatability,ithasnogoodperformancesinrejectingofloaddisturbanceandfollowingreferencecommands.Espec… 相似文献
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Stephen Petrina 《Interchange》2004,35(1):81-126
What should be learned? How should it be organized for teaching? These seemingly simple questions are deceivingly political. Curriculum theorists are preoccupied with the politics of the first question at the expense of the realpolitik of the second. Instructional designers are preoccupied with the realpolitik of the second question at the expense of the politics of the first. I argue that conceptual distances between curriculum theory and instructional design are based on divisions of labour established during the 1960s. After decades of neglect, curriculum theorists, and specifically critical theorists, appear clueless when it comes to curriculum design and the realpolitik of their causes. When it comes to the realpolitik of practice their political causes are formless. Quite the opposite of critical theorists, instructional theorists nearly mastered the realpolitik of form but have no political causes. I argue that, to contradict the status quo of C&;I, curriculum theorists will have to dirty their hands with the realpolitik of form and instructional designers will have to clutter their heads with theory. 相似文献
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Clarence W. Joldersma 《Interchange》2008,39(1):21-47
This article explores the question: Why are students of worth? Educationally, an answer often involves a Kantian response:
They are of worth because they are always ends and never means. This response is usually connected to a notion of autonomy
interpreted as individual, rational self-determination. The article argues for a different answer. The essay begins with a
recent educational example of construing worth as rational autonomy. Meira Levinson, in her book The Demands of Liberal Education (1999), argues for a version of rational autonomy which is taken in the essay as a Kantian response to the question. The
essay then turns to Kant’s own understanding of intrinsic human worth as ends. Although the essay agrees in general with the
notion of end, it criticizes Kant’s version of rational autonomy. Instead, it argues for a notion of worth as irreplaceable
singularity. Both the critique of the Kantian answer and theessay’salternative are shaped by the philosophy of Emmanuel Levinas.
Here technical notions of “the other,” proximity and singularity are brought to bear on the question of human worth. The Levinasian
alternative, so the essay argues, better answers the question of student worth by highlighting the incomparability of the
student as a singular other. 相似文献