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以陶瓷原料中常见的高岭土和围场土为研究对象,考察粒度、升温速率对两种矿物差热分析(DTA)曲线的影响。实验结果表明:不同矿物的粒度、升温速率对差热分析曲线有较明显的影响,即随着试样粒度的增大,差热分析曲线的峰形越来越低,越来越平坦,反应温度滞后;而随着升温速率的提高,差热分析曲线的峰形越来越高,越来越尖锐,反应温度也会发生滞后。 相似文献
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何方奕 《鞍山师范学院学报》1996,(4)
本文以同时蒸馏萃取法(SDE)提取了药用皖鄂鼠尾草精油,用毛细管GC/MS/DS联用仪分离并初步鉴定了其中的35种化合物,占总峰面积的87%,再用气相色谱-富里叶红外光谱联用技术、双柱程序升温保留指数和标样核对等方法鉴定了19种化合物,占总峰面积的25%.含量较高的组份是Epi-2-pupukeanone(19%),去氢白菖烯(7.7%),δ-荜澄茄烯(6.7%),(十)-δ-瑟林烯(4.3%). 相似文献
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本文采用高温固相法制备蓝色长余辉发光材料Sr2 Al6 O11:Eu2+,Dy3+,研究了不同的升温速率对其性能的影响.用X射线衍射仪对所合成的材料进行物相分析,用荧光分光光度计记录样品的发射光谱,用亮度计记录其余辉衰减曲线.结果表明:随着升温速率从3℃/min提高到7℃/min,材料物相由富锶相逐渐向富铝相转变;发射光谱首先发生微弱蓝移,如果继续调高升温速率,发射光谱又会红移;材料发光性能不断提高.在烧结温度为1200℃,升温速率为4℃/min附近条件下制备的样品峰值波长达到最短(468 nm),其余辉时间(≥1 mcd/m2)可达240 min以上. 相似文献
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黄李健 《河北职业技术学院学报》2014,(2):38-40,46
针对几种经典的降低均峰比的方法进行了研究,通过MATLAB对改进的限幅滤波法、选择映射法(SLM)、部分传输序列法(PTS)三种算法进行仿真分析。仿真结果表明三种算法都有效地降低了OFDM系统的均峰比。限幅滤波法实现简单但引入了噪声;选择性映射法可无失真地降低系统的均峰比,但引入了冗余而导致系统的有效传输效率降低;部分传输序列法效果优于选择性映射算法,但是计算量大,实现复杂度较高。 相似文献
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苯乙烯-马来酸酐共聚物热降解动力学研究 总被引：1，自引：0，他引：1
冯才敏 《顺德职业技术学院学报》2007,5(2):34-37
利用热重分析技术(TG-DTG),在5、10、15和20K/min线性升温速率和氮气气氛条件下,考察了苯乙烯-马来酸酐共聚物(SMA)的热降解过程和动力学。实验发现,随着升温速率的增大,降解温度呈线性升高。运用Freeman-Carroll方法、Flynn-Wall方法和Kissinger方法分别对SMA的热降解反应进行了模拟,求取了热降解反应的活化能和反应级数,发现三种方法所求得的活化能基本一致,并确定SMA的热降解反应为非一级反应。 相似文献
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设计了核磁共振氟谱法(~(19)F NMR)测定氟他胺含量的实验。此实验以三氟甲苯为内标,化学位移δ=-61. 10×10~(-6)处的氟他胺的特征峰作为定量峰。实验结果表明,氟他胺的~(19)F NMR检测方法在其浓度0. 2～10. 0 mg/mL范围内,样品与内标物的积分面积比与浓度比具有良好的线性关系(R~2=0. 996)。实验方法的定量限和检出限分别为18μg/mL和5μg/mL;同一标准品溶液重复实验5次,相对标准偏差(RSD)为1. 94%,证明该方法重复性比较好。此实验不仅为氟他胺的定量分析提供了一种实用、快速有效的方法,而且培养了学生的创新思维和科研能力。 相似文献
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《洛阳师范学院学报》2019,(2):31-34
利用四水醋酸锰,[1, 10]-邻菲罗啉, 4-(4-羟基吡啶基)-1, 2-邻苯二甲酸,通过水热合成法合成了一种新型金属有机配合物[Mn(L)(phen)(H_2O)]·H_2O,并对其结构进行了分析.结果表明,该晶体属三斜晶系,空间群P-1,晶胞参数为:a=10.5357(4)?,b=10.7779(6)?,c=12.2105(6)?,α=72.990(5)°,β=65.808(4)°,γ=65.339(5)°,V=1136.99(9)?~3, Z=1,M_r=1084.71.配合物每个结构单元由两个Mn离子,两个邻菲罗啉,两个4-(4-羟基吡啶基)-1, 2-邻苯二甲酸配体,两个配位水和两个结晶水分子组成.配合物在空间堆积之后形成了一个超分子化合物. 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