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针对乙醇偶合制备C4烯烃的影响因素问题,建立了多元线性回归模型、灰色预测模型和优化模型,分析了催化剂组合乙醇转化率、C4烯烃的选择性与温度的关系,解决了不同催化剂组合及温度对乙醇转化率以及C4烯烃选择性大小的影响以及或反应温度变化与乙醇加入速度对C4烯烃收率的影响等问题。通过微元分析法、改进粒子群算法和最小二乘法等建立数学模型,并调用Matlab软件中的函数计算、微分方程计算模块和Simulink仿真等模块结合编程实验得出温度与乙醇转化率及C4烯烃选择性成正相关;Co/SiO2和HAP质量比越高、乙醇加入速度越快和温度越高,对乙醇转化率和C4烯烃选择性影响越大;或反应温度变化与乙醇加入速度成反比时C4烯烃收率增加。 相似文献
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用延迟匹配样本任务来考察时距记忆,在实验中相继呈现标准刺激和比较刺激,操纵标准和比较刺激的延迟时间,发现随着延迟时间的增加,更多被试作出选择短时距或选择长时距的反应,出现选择短现象或选择长现象。对选择偏差的理论解释目前主要有主观缩短假设、相对时距假设、模糊假设和觉察假说。训练与呈现形式、实时距和空时距、不同种群、不同通道以及计时策略等是影响时距选择偏差的主要因素。今后应根据时间分段综合模型,结合脑机制进行研究。 相似文献
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将乙醇与污泥加入到高压反应釜中,利用乙醇的超临界特性和供氢性,实现污泥的液化制油反应,然后分别利用真空抽滤装置和旋蒸装置提取渣产物和油产物。主要考察反应温度、停留时间、污泥添加量及催化剂对产油率的影响。研究发现,当反应温度290℃,停留时间60 min,污泥/乙醇的固液比为1/20时油产率最高,且加入氢氧化钠时油产率可提升至45. 5%。通过分析发现,液化油中C元素含量比污泥原料提升了105. 8%,H元素含量相比提升了71. 8%,O元素含量则大幅降低,液化油的热值比污泥高20. 12 MJ/kg。液化油中各组分的碳链集中在C16～C20,主要为酯类,占56. 36%,而烷烃类化合物含量较低,仅为6. 32%,后续应对酯类化合物进行脱氧来进一步提升油品质。 相似文献
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目的:优化沙棘中总黄酮提取工艺,明确其抗氧化性能。方法:以沙棘为研究对象,以沙棘黄酮得率为指标值,使用乙醇溶液作为提取剂,采用超声波辅助萃取法,对提取时间(A)、提取温度(B)、乙醇体积分数(V乙醇/V_总)(C)、料液比(D)进行单因素试验和响应面分析,考察4个因素对总黄酮得率的影响,并对沙棘黄酮的体外抗氧化活性进行检测。结果:在提取时间23 min、提取温度80℃、50%乙醇、料液比1∶20条件下沙棘黄酮得率最高,为2.316 mg/g。各因素对沙棘黄酮得率的影响大小依次为：料液比、乙醇体积分数、提取时间、提取温度。体外抗氧化结果表明,沙棘黄酮具有很好的DPPH自由基和羟自由基清除能力,当沙棘黄酮粗提取物质量浓度达到5 mg/mL时,沙棘黄酮对DPPH自由基的清除率达87.5%,对羟自由基的清除率达到了77.7%。结论:沙棘中含有丰富的黄酮类物质,且具有较好的抗氧化性能。 相似文献
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本文利用实验室自主开发的计算机数据采集、处理系统和无纸记录仪器,对以草酸铵为底物,硫酸铈铵为催化剂,溴酸钾为氧化剂,硫酸为介质的化学振荡体系进行了研究,描述了该体系的振荡特性。研究了各物质初始浓度、反应温度、还原性物质、双氧水、乙醇、Ag^＋和CCL等对振荡行为的影响。实验结果表明,升高温度,振荡周期、寿命均显著缩短;Ag^＋、H2O2、C2H5OH等共存时,或使振荡周期增长,或具有显著的抑制作用。本文还对该振荡反应的机理进行了深入研究。 相似文献
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以乙醇为溶剂,采用浸提方法,通过单因子试验确定影响火龙果果皮色素提取的主要因素及其最佳水平;通过L。（3。）正交试验确定其最优提取工艺;同时对色素在不同pH,Ca2＋、Mn2＋、Cu2＋、Fe2＋等金属离子,不同温度、H2O2条件下的稳定性,以及清除DPPH自由基活性等方面进行了研究．结果表明,料液比、提取时间、提取温度对色素的提取影响较大,而在低浓度的乙醇作溶剂时,其影响不大,但当乙醇浓度超过30％提取受到影响;提取的最佳工艺为料液比l：20,提取时间60min,提取温度40℃,提取pH6．0;火龙果果皮色素在酸性环境中较稳定,在碱性环境中色素分解较快,温度的增加可影响其稳定性,Ca2＋对其影响较大,而Mn2＋,Cu2＋,Fe2＋的影响较小,对H2O2有一定的抗性和具有清除DPPH自由基活性的作用． 相似文献
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选取乙醇和异戊醇两种具有不同分子结构的含氧燃料,采用生成速率和敏感性分析的方法,研究了醇类含氧燃料分子结构对燃料热解过程的影响.结果表明:两种醇类含氧燃料热解的主要反应有两类,一类是由脱水反应和断键反应组成的单分子解离反应,另一类是氧化过程中H、OH等小分子自由基的氢提取反应.与乙醇相比,异戊醇具有能量密度更高、水溶性更低、与传统燃料的混合性更好,与传统发动机适应性更强和运输存储更方便等优点. 相似文献
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渣油热转化过程中吡啶等四种含氮化合物热转化规律及反应机理研究 总被引：1，自引：0，他引：1
姜兆波 《山东教育学院学报》2006,21(2):115-117
本文采用微型反应器,以吡啶、喹啉、吖啶、吲哚为模型化合物,四氢萘、甲苯为溶剂,研究了反应温度、时间、进料状况等因素对含氮化合物热反应的影响。实验结果表明,反应时问、温度、体系的供氢能力等因素都对含氮化合物的热反应历程和程度有明显影响。含氮化合物的裂解与缩合生焦同时进行且存在竞争;与单、双环含氮化合物相比,多环含氮化合物更易于缩合生焦。含氮化合物的热反应按自由基机理进行,反应受生成自由基的难易程度限制,芳香环自由基活性较小,较难断裂,而主要是相互缩合生成多环化合物,再进一步缩合生成焦。 相似文献
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小叶女贞果实抗氧化活性研究 总被引：1，自引：0，他引：1
以乙醇为溶剂提取小叶女贞果实,经减压浓缩后,依次用乙酸乙酯和正丁醇进行萃取。用DPPH自由基的清除能力来评价两个部位的抗氧化活性。结果表明,乙酸乙酯部位浓度为500μg/mL时自由基清除率大于75%,IC50=302.818μg/mL,正丁醇部位浓度为300μg/mL时自由基清除率大于75%,IC50=189.241μg/mL。正丁醇部位抗氧化能力比乙酸乙酯部位更好,是乙酸乙酯部位的1.6倍。 相似文献
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《海外英语》2007,(5):10-11
Many college freshmen arrive woefully unprepared to do college work, and as disadvantaged populations continue to grow, the share of the American work force that has made it through college is expected to plummet. Many experts blame that educational failure not just on high schools but also on colleges. School & College, a special report by The Chronicle, looks at efforts to fix the system. What reforms would better prepare students for college? What should schools and colleges be doing differently? How should state and federal officials help? 相似文献
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《海外英语》2007,(4):36
There are numbers of crossroads on our long and unpredictable life journey where we totally have no idea about which direction to choose. No matter what our decision is, we should not turn back, but face the music and go ahead instead. I am this kind of girl who always does try without regretting, one example is how I dealt with my love. 相似文献
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Migration occurs behind a variety of reasons and has a great effect on the whole world. People may migrate in order to improve their economic situation, or in order to escape civil strife, persecution, and environmental disasters. The impact of migration is complex, bringing both benefits anddisadvantages. This paper briefly talks about the causes of migration, the allocation of benefits, and the ways in which individual countries and the international community deal with this important subject. 相似文献
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Sister Carrie is one of the most controversial characters in American literature.Thought as a "fallen woman" firstly,she was defined as a "new woman" by some critics later. However, by digging into the motivaton behind the whole process of Carrie's "success", the relationship between Carrie and her creator (the author), the social conditions of then American, it can be found that Carrie has never been free-standing on her thought and she has never found her real-sdf even after becoming a famous actress. In a society dominated by mass consumerism Carrie is only an adherent of her own desires. She also is a representative of all those country girls flooded into cities, a symbol and a sacrifice of the urbanization of America in a time countryside was overcome by cities. 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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唐芳 《读与写:教育教学刊》2008,5(6)
During interview with English majors, it was found that a majority of students expressed disappointment with their experience of English literature classes. Students' dislike of learning English literature appears to be the major problem of teaching English literature in China. Reader response approach is a good way to solve this problem. In this paper, I explain the rationale behind the reader response approach, such as its origin, definition, features, assumptions, and strategies. Then I illustrate how reader response approach works as a teaching strategy by presenting several teaching models. At last I evaluate its usefuiness for teachers and present the advantages of reader response approach in Chinese context. 相似文献