共查询到20条相似文献，搜索用时 265 毫秒
1.
采用全电子从头计算法,对丙二烯分子的两种不同构型进行计算．结果表明：丙二烯分子来取Ｄ２ｄ对称结构比Ｄ２ｈ对称结构更稳定 相似文献
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基于密度泛函理论和非平衡格林函数方法,研究了铝或磷原子掺杂对锯齿型硅烯纳米带输运特性和自旋热电效应的影响.发现通过改变铝或磷原子掺杂位置,其费米面处的自旋极化率可以达到100%或-100%,同时其自旋向上(对于-100%)和自旋向下(对于100%)对于塞贝克效应也得到明显加强.甚至在特殊的掺杂位置和电子能量时,其自旋塞贝克系数可以远大于相应的电荷塞贝克系数.表明用铝或磷掺杂后的锯齿型硅烯纳米带可以用作制备理想的热自旋器件. 相似文献
3.
能带结构在固体物理/半导体物理的教学及相关科研活动中占有重要地位.本文从理论上推导了体硅的价带E～k色散关系模型，利用MATLAB语言编程绘制了体硅价带E～k色散关系图及等能面图，通过对价带顶处色散曲线进行抛物线拟合，获得了体硅各晶向空穴有效质量，所得有效质量结果与其他理论计算及实验测量结果符合较好. 相似文献
4.
β-榄香烯立体结构的分子力学研究 总被引：1，自引：0，他引：1
利用分子力学计算方法研究了β-榄香烯的构型和构象．通过能量最小化,对所有构象空间进行烯基取代基旋转势能极小点的全面搜索,确定了β-榄香烯的优势空间构象;并且与β-榄香烯衍生物的单晶X-射线衍射结构测定的有关结果做了比较和讨论 相似文献
5.
邝代治 《衡阳师范学院学报》1999,20(6):40-44
研究了三羰基（五甲二硅基）环戊二烯基羰基卤-钼［（η5-C5H4SiMe2SiMe5）（CO）3Mo－XX=Cl、Br、I]和（五甲二硅基）环戌二烯基双三苯基膦羰基溴钼[（η5-C5H4SiMe2SiMe5）（PPh3）2（CO）Mo—Br]以及二羰基（五甲二硅基）环成二烯基环氧亚成基卤钼{η5-C5SH4SiMe2SiMe5）（CO）2[CO（CH2）3]Mo－XX=Br、I}化合物的红外光谱,硅与茂环发生电子反馈作用表现在红外光谱振动吸收发生位移,从而讨论硅甲基取代环成二烯后对化合物的红外光谱的影响。并对标题化合物的主要红外吸收带进行归属。 相似文献
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利用密度泛函理论(DFT)中的B3LYP方法,在6-31+G(d,p)理论水平上对丙烯与氧原子的反应机理进行了研究.对反应物、产物、中间体及过渡态进行了优化,并通过内禀反应坐标(IRC)计算和振动分析对反应过渡态进行了确认.计算结果表明,氧原子与丙烯可以快速复合形成多种中间体,然后经历异构化、解离反应生成各种产物如CH3CH2CHO、CH3COCH3、不饱和烃以及H2O、OH、H.丙烯与氧原子反应通道主要有异构化、置氢和脱水反应3个过程. 相似文献
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宋爱春 《数理化学习(高中版)》2011,(19):55-57
中学化学教材介绍,二氧化硅是原子晶体,空间网状结构,存在硅氧四面体结构,硅原子处于四面体中心,氧原子处于四面体四个顶角.其中,最小环为12元环,含有6个硅原子和6个氧原子.硅酸盐和二氧化硅一样,都是以硅 相似文献
9.
该文以热负荷较大的2135型柴油机的硅铝合金活塞为研究对象,通过有限元分析软件MSC.Patran和MSC.Nastran进行有限元模拟计算,结合试验测得值对活塞进行温度场分析计算,以得出活塞在热负荷作用下的温度分布,进而为活塞的结构改进和优化提供重要依据。 相似文献
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《赣南师范学院学报》2019,(6):58-61
硅基深槽刻蚀是槽栅IGBT器件的基本结构,也是确保器件性能的关键工艺,氮化硅硬掩蔽膜质量对于硅基深槽刻蚀起着重要的作用.本文采用低压化学气相淀积(LPCVD)工艺淀积氮化硅薄膜,具有均匀性好,而且呈现较大的张应力,可以补偿二氧化硅缓冲层的压应力,有效地解决了硅-二氧化硅-氮化硅夹心结构的应力问题.分析比较了工艺参数,如气体流量、淀积环境的压强、温度等,对氮化硅薄膜生长速率及膜厚的影响,获得了氮化硅薄膜淀积的优化工艺参数. 相似文献
11.
Laura Hirsto 《Scandinavian Journal of Educational Research》2013,57(2):99-108
In this study, the strategies teachers use in home and school collaboration were surveyed. The subjects were early education teachers in Helsinki, Finland. Questionnaires were used for the data collection. Factor analysis resulted in the extraction of six strategy types. Strategies representing parents as the recipients of information were most frequently used. Strategies representing two‐way communication were also quite often in evidence. The most rarely used strategies included parents as decision makers, volunteers, or resources in the elaboration of learning. Teachers who had children who were approximately the same age as their pupils were more active in using strategies involving teachers as supporters of parenting and parents as a resource for the elaboration of learning. The strategies found and the implications of the Finnish data are discussed. 相似文献
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This study focused on the drivers of online child sexual exploitation and abuse (OCSEA) among Filipino children and youth, with emphasis on community norms. An ethnographic qualitative study was conducted in two communities in MetroManila that are considered “hotspots” for child sexual abuse. One hundred and forty-four (144) males and females from various age groups served as key informants. Political officials, Internet shop managers, professionals and police officers were also interviewed. Non-participant observations and mapping were used to provide context regarding OCSEA in the communities.The results revealed that OCSEA was committed online by heterosexual and same sex attracted men in their 40s–50s. The usual victims were girls aged 13–17 years, although boys were also noted. The victims came from poor families and were out-of-school. The various forms of online activities leading to OCSEA included sexual chatting, showing of child sex photos and live videos as well as sextortion. The online transactions were usually initiated by the peer group and some enablers. In general, online sexual activities were perceived as “normal” among young people, although regarded as “disgusting”. Online sex activities had become a source of “easy money” for the child and family. They were perceived as not harmful because of anonymity and the absence of any actual physical contact. People in the community tolerate these online practices and do not report the incidence to authorities. The effects on children and youth were predominantly social and psychological, albeit perceived as economically beneficial. Some preventive and mitigating actions were recommended to curb the incidence of OCSEA in the communities. 相似文献
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Peer tutoring is effective in increasing academic skills with both the regular and special education populations. Studies also have reported significant findings in the social/affective realm, such as social acceptance. In spite of the numerous studies investigating the effects of tutoring on social benefits, results are inconclusive. It is important to establish the extent to which peer tutoring can be used, especially as a technique for social change. The purpose of this study was to investigate the effects of a structured peer tutoring program on the social acceptance of students. Students perceived as not socially accepted were paired with students who were rated as well liked. Both had the opportunity to serve as tutors and tutees. Participants were administered a questionnaire, pre-and postintervention. The results were significant for type of student, distinguishing between those students rated as liked and those rated as disliked. The results also showed that students in the control group were rated higher on the “dislike” category than were those in the treatment conditions. Significance was obtained for the experimental groups on a time variable, suggesting that regardless of role (tutor vs. tutee) change in acceptance would occur over time. However, evaluation by mean analysis suggested that the students who were rated as disliked and served as tutors were rated as liked more following treatment. 相似文献
15.
以二甘醇和卤代烷为原料,用相转移催化法合成了７种二甘醇单烷基醚,均获得较高产率。讨论了二甘醇单醚合成的应用历程,并对其物理常数,水溶液的表面张力,起泡性能,临界胶束浓度进行了测试和分析。 相似文献
16.
Sonja Laine 《High Ability Studies》2010,21(1):63-76
The purpose of this paper is to present the results of research in which the Finnish public discussion of giftedness and gifted children, and conceptions of giftedness and gifted children presented in it, were examined. The research was conducted by analyzing articles from the Finnish newspaper Helsingin Sanomat and the teachers’ periodical Opettaja, using the content analysis method. The results show that giftedness is seen as multidimensional, and both intrapersonal and environmental contributions are recognized as essential in talent development. The conceptions of gifted children were quite diverse, and gifted children’s possible problems were frequently discussed. Moreover, misunderstandings were revealed as well as areas that have not been adequately addressed. 相似文献
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刘向明 《江西师范大学学报(哲学社会科学版)》2006,39(4):79-84
从睡虎地秦简中可知,秦代以法律形式保障布的货币功能及其顺利流通,也把禀衣作为重要的统治手段,从而确认衣布为重要财产加以保护。秦代还对衣布相关行业加强了控制,甚至对人们的衣着也作出了相应的规定,而使衣着体现社会等级关系,这成为当时社会的一个明显特征。 相似文献
18.
The cognitive abilities of a group of dysphasic children in a special school in Finland were examined in this study to answer the following questions: Can we categorize their cognitive processing as planning, arousal-attention, simultaneous and successive processing (PASS)? The second question was concerned with detecting subgroups within the dysphasic sample in terms of PASS processes. The subjects were 60 dysphasic children in a special school. Their ages ranged from 7 to 19 years. All subjects were administered tests of planning, arousal-attention as well as simultaneous and successive processing. They were also administered the Wechsler test of intelligence for children and adults according to their ages, two sub-scales of Wechsler memory scale, as well as three ad hoc tests, cancellation task, KS persons and Rey Osterrieth copy task. The results of the factor analysis generally confirmed the emergence of the four PASS factors. As a results of cluster analysis, two subtypes of dysphasics emerged categorized as clearly high and low in the successive factor as well as relatively high and low on the simultaneous factor scores. The low-simultaneous/low-successive group was significantly lower in WISC verbal IQ the Wechsler memory scale for logical memory, and the ad hoc test of KS persons. The results were discussed, in terms of the importance of understanding the language problems typically associated with the two subtypes as well as the remedial program which will take into account their cognitive differences in spite of the fact that both groups had significant language impairment. 相似文献
19.
华定存 《新疆职业大学学报》2008,16(2):10-13
本文阐述了发展少数民族地区旅游业的意义和作用、现状与问题,考察了制约少数民族地区旅游业发展的因素,并在此基础上,对少数民族地区旅游业的开发应采取的对策和措施进行了分析,以期使少数民族地区旅游业得以持续发展。 相似文献
20.
109 Children were classified using the Ainsworth Strange Situation at 18 months. 81 children who were unequivocally classified as insecure/avoidant (A1, A2) or securely attached (B1, B2, B3) were used in this study. The children's parents reported on occurrences of problem behaviors at 24 months, 27 months, 30 months, and 48 months using several methods. The children were observed at 18 and 30 months in their homes with their families and in toddler playgroups during the same period. The only significant effect for attachment classification was that teachers and observers of the playgroups rated girls classified as insecure/avoidant as more difficult to deal with and as having more difficulty with peers than girls rated as securely attached. 相似文献