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1.
低温水热合成金红石二氧化钛纳米棒 总被引：1，自引：0，他引：1
在低温水热条件下,以离子液体1-丁基-3-甲级溴化咪唑([C4mim]Br)为添加剂,制备出了金红石二氧化钛纳米棒.XRD分析证明,所得样品为纯金红石相结构;SEM和TEM结果表明,金红石纳米棒直径为20 nm,长度为200 nm,而且这些纳米棒有自发组装成棒束的趋势.当温度升高时,金红石纳米棒的尺度变大,而且生成了规整的纳米棒束.研究表明,离子液体的存在不仅有利于金红石的生成,而且有效控制了金红石棒的过度生长. 相似文献
2.
以Zn（NO3）2.6H2O和NaOH为原料,采用改进的水热法通过控制反应溶液的浓度、反应温度和反应时间等沉积参数,合成了包括氧化锌纳米棒阵列、蜂窝状氧化锌纳米棒、花状氧化锌纳米棒等纳米结构.用XRD、SEM和HR-TEM对样品进行了表征,结果表明所制样品为六方纤维锌矿结构的ZnO晶体;SEM测试结果显示ZnO晶体的形貌呈花状和蜂窝棒状等形貌,HR-TEM结果表明单晶纳米棒沿[0001]方向生长.研究了玻璃衬底上装配的花状氧化锌纳米棒的场发射特性,测试结果表明花状氧化锌纳米棒具有优良的场发射;开启场强为4.3V/μm,当场强为8V/μm时,发射电流密度达到2.2mA/cm2. 相似文献
3.
采用热蒸发法系统研究了影响氧化锡纳米结构形貌的主要因素。结果发现改变反应中衬底的温度以及氧气的流量或分压所制备的氧化锡纳米结构形貌有较大的变化。在低温、低的氧流量或氧压下所合成的氧化锡为线状结构,在相对高温、高的氧流量或氧压下所合成的氧化锡为棒状形貌。 相似文献
4.
本文利用离散偶极子近似法,研究T型排列的金纳米棒双聚体的表面等离子体耦合共振特性,发现金纳米棒双聚体间距变化时表面等离子体共振消光峰发生红移或者蓝移,适当间距的T型排列金纳米棒双聚体结构可以产生更强的局域表面增强电场.本文对于金纳米棒双体结构的计算结果对于金纳米棒在生物传感方面应用具有一定的参考价值. 相似文献
5.
本文利用离散偶极子近似法,研究T型排列的金纳米棒双聚体的表面等离子体耦合共振特性,发现金纳米棒双聚体间距变化时表面等离子体共振消光峰发生红移或者蓝移,适当间距的T型排列金纳米棒双聚体结构可以产生更强的局域表面增强电场.本文对于金纳米棒双体结构的计算结果对于金纳米棒在生物传感方面应用具有一定的参考价值. 相似文献
6.
《实验技术与管理》2019,(11):55-59
对氨水溶液体系中种子层法制备ZnO纳米棒的生长机理进行研究。采用溶胶-凝胶法制备出具有002择优取向的ZnO种子层薄膜,利用XRD研究旋涂速度和热处理温度对薄膜取向性的影响;采用密闭高压的氨水溶液体系制备出具有高比表面的ZnO纳米棒,利用SEM对Zn O的微观形貌进行表征,并说明了氨水体系下ZnO纳米棒薄膜的生长机理。测试果表明,4000r/min及300℃的热处理温度制备的ZnO种子层薄膜具有显著的002择优取向,有利于后续ZnO纳米棒沿002方向择优生长。氨水体系下,所获得的ZnO纳米棒长径比大于50,且顶部呈六角锥形,棒与棒之间的空隙较大,有利于敏感气体和量子点的吸附。 相似文献
7.
1温度当一个设备从高温环境移至低温环境使用时,一般出问题的可能性不大,只有在从低温环境移至高温环境使用时,较容易出故障。这是因为高温环境下空气中的水蒸汽极易在遇到低温 相似文献
8.
利用水热法分别制备了α-FeO3纳米棒和立方体,并以其作为前驱物制备了α-Fe2O3/SnO2复合材料.样品的成份、结构、形貌和尺寸采用X-ray粉末衍射(XRD)和扫描电镜(SEM)等测试手段进行了表征.分析结果发现,α-Fe2O3前驱物的形貌能够影响α-Fe2O3/SnO2的最终形貌和结构.以α-Fe2O3纳米棒作为前驱物时,α-Fe2O3/SnO2复合材料是由棒状结构组成的团聚体;而以α-Fe2O3立方体作为前驱物时,在相同的制备条件下能够得到α-Fe2O3/SnO2球形粒子.最后对α-Fe2O3前驱物的形貌对α-Fe2O3/Sno2复合材料生长过程中的影响机理进行了探讨. 相似文献
9.
研究了充电模式、放电模式、温度对镍氢（三圈霸道）电池和镍镉（天球360）电池性能的影响.采用标准充电模式时综合性能最佳;相同充放电模式下,镍氢电池的放电容量约为镍镉电池的2倍;放电电流从100mA升高到1 000 mA时,循环性能下降,对镍隔电池的影响尤为明显;镍氢电池对高温较为敏感,在50℃时的循环性能大幅度下降,而镍镉电池对低温较为敏感. 相似文献
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11.
扩张时期研究生教育科类结构的特点及变化分析 总被引：1，自引：0，他引：1
20世纪90年代末以来,我国高等教育进入了规模扩张时期。研究生规模的迅速扩大、研究生人数的急剧增加,使得研究生教育成为我国高等教育的重要组成部分。伴随着数量的发展,研究生教育的科类结构形成了如下特征:(1)工学、理学、管理学、医学所占比例较大,相加起来达到总数的70%;而哲学、历史学、农学、教育学所占比例较小,均在4%以下。(2)理科与文科的比例约为6∶4。(3)硕士生的科类结构与博士生的科类结构存在着一定的差别。对研究生教育科类结构发生直接影响的因素似乎主要来自高等教育内部。 相似文献
12.
陈文联 《衡阳师范学院学报》2001,22(2):86-91
近代中国不缠足思潮，肇始于19世纪末的戊戌维新时期。维新人士从多方面挟击缠足，为倡天足，并身体力行，笃诚实践，推动了不缠足习潮的产生。戊戌不缠足思潮是在尖锐复杂的社会环境中产生的，对近代的社会文化结构造成巨大的冲击，对正在兴起的妇女运动也产生了深远的影响，但思潮在某些方面也表现出无法掩饰的局限性。 相似文献
13.
Emer Smyth 《牛津教育评论》2018,44(1):37-55
AbstractYoung people in Irish schools are required to choose whether to sit secondary exam subjects at higher or ordinary level. This paper draws on a mixed methods longitudinal study of students in 12 case-study schools to trace the factors influencing take-up of higher level subjects within lower secondary education. School organisation and process are found to shape the extent to which young people actually have a ‘choice’. Streaming practices, which are more prevalent in schools serving socio-economically disadvantaged communities, constrain the degree of choice young people have over their subject levels, with those in lower stream classes usually allocated to ordinary level. Even where schools have mixed ability base classes, schools influence access to higher level subjects. In the middle-class and socially mixed schools, teachers are more likely to expect and encourage all students to take higher level. In contrast, in working-class schools there are sharp declines in the proportion taking higher level subjects as they approach the national exam taken at the end of lower secondary education. Early decisions about not pursuing higher level are found to have long-term consequences. The findings contribute to our understanding of how curriculum differentiation reinforces social class differences in educational pathways. 相似文献
14.
张丁非 《重庆大学学报(英文版)》2004,3(2):12-15
IntroductionFe-C-Si-Mnalloyisamaterialusedforcommonbladesinhydroelectricgenerators.Itscurrentchemicalcompositionintermsofmassfractionwisasfollows:w(C)withintherangefrom0.17%to0.25%,w(Si)0.40%to0.8%,w(Mn)1.2%to1.6%,w(S)≤0.045%andw(P)≤0.045%.Thebladeserviceconditionrequiresgoodstrength,ductilityandwearresistance.AnormalprocessingandheattreatingprocedureofFe-C-Si-Mnalloybladesincludesinsequence:casting,920°Cnormalizing,600°Ctempering,andwelding.Thevolumeofabladeissohugethatitscentralare… 相似文献
15.
美国的大学、学院、社区学院形成的高等教育体系中,社区学院承担了转学教育、职业教育、继续教育等重要职能。美国社区教育在其发展历程中形成了鲜明特色,其中有许多值得我国高职院校借鉴、学习的做法。结合我国的现实,提出了基础课教学改革的想法和思路。 相似文献
16.
Lydia Schaap Henk G. Schmidt Peter P.J.L. Verkoeijen 《Assessment & Evaluation in Higher Education》2012,37(7):875-887
The purpose of this study was to gain insight into determinants of knowledge growth among first-year psychology students in a curriculum that uses the Progress Test (an assessment method for long-term retention of knowledge and knowledge growth) as its main assessment tool. To that end, the relation between the level of initial learning, prior knowledge, class attendance and individual study time, and Progress Test scores was analysed. The data showed that level of initial learning was positively associated with prior knowledge and class attendance. Further, level of initial learning was positively related to knowledge growth at the end of the first year of the curriculum. Students with higher levels of initial learning had a more extended knowledge base at the end of the first year of their curriculum than students with lower levels of initial learning. Prior knowledge, class attendance and individual study time did not have a significant relation with knowledge growth. 相似文献
17.
The relationship between motivation to read and reading comprehension in chilean elementary students
Orellana Pelusa Melo Carolina Baldwin Paula De Julio Samuel Pezoa José 《Reading and writing》2020,33(10):2437-2458
This study examined the role of reading motivation in reading comprehension achievement of 1070 Chilean third, fourth, and fifth-grade students enrolled in public and private schools. Students were assessed in Spanish reading comprehension and were administered the Motivation to Read Profile from Gambrell, Palmer, Codling and Mazzoni (1996), at the beginning and end of the school year. Results showed that motivation to read at the beginning of the school year was significantly associated with gains in reading comprehension skills. When disaggregating motivation into self-concept and value of reading, only self-concept of reading significantly predicted gains in reading comprehension. Moderation analyses showed that students that started the year with lower reading comprehension and higher motivation to read, had significantly better reading comprehension at the end of the school year, than their peers who started with lower reading motivation. The pedagogical implications are discussed.
相似文献18.
测量了烧结SrRuO3 的零场冷却 (ZFC)和加场冷却 (FC)的直流磁化强度和交流磁化率 .交流磁化率 -温度曲线的峰随外加直流偏场的增加向低温方向移动 .继续增加直流偏场 ,一个峰分裂成两个峰 ,其中低温下的一个峰继续向低温方向移动 ,另一个高温处的峰却向高温方向移动 .在不同频率下测量零偏场下的交流磁化率 .随频率的增加 ,峰值减小 ;但峰的位置并没有像以前报道的那样向高温方向移动 .可见 ,烧结SrRuO3 并没有显示自旋玻璃行为 . 相似文献
19.
A repulsive vortex-vortex interaction model was used to numerically study the melting transition of the two-dimensional vortex system with Monte Carlo method. Then a δ-function-like peak in the specific heat was observed and the internal energy showed a sharp drop at the melting temperature, which indicated that there exists a first-order melting transition at finite temperatures. The Lindemann criterion was also investigated and valid, but different from previous simulation results. 相似文献
20.
This longitudinal study aimed at examining the relationship between children's task persistence, mothers' academic help, and the development of children’s literacy skills (reading and spelling) at the beginning of primary school. The participants were 870 children, 682 mothers, and 53 class teachers. Data were collected three times – at the beginning and the end of Grade 1 and at the end of Grade 2. Better literacy skills predicted higher persistence in completing school tasks and, correspondingly, higher persistence was related to better subsequent skills. Also, lower task persistence at the end of Grade 1 corresponded to more frequent academic help from mothers in Grade 2. Moreover, children’s literacy skills predicted mother’s later academic help via task persistence: the lower the children’s literacy skills were, the less task persistence children exhibited, and the more mothers engaged in academic help later on. 相似文献