Mo-Fe催化剂中Mo含量对SWCNTs的制备影响

以“柠檬酸法”制备的Mo-Fe-MgO为催化刑，在850℃下，以Ar为载气，CH4为碳源，制备生成单壁碳纳米管．重点研究了催化剂中Mo的含量对单壁碳纳米管制备质量的影响．实验结果显示，Ar载气中，提高Mo-Fe-MgO催化刑中的Mo载量可以提高碳产率，但同时也造成产物中单壁碳纳米管含量的大幅下降．依据碳产率以及产物中单壁碳纳米管含量的变化，给出了Mo-Fe催化刑的最佳组分比例．     

碳纳米管储氢的分子动力学模拟

应用分子动力学方法(MD)对单壁碳纳米管(SWCNT)储氢的物理吸附过程进行模拟.系统地研究了单壁碳纳米管的物理吸附储氢量与管径、温度、压力之间的关系.作出典型管径碳纳米管的吸附等温线.实现了分子动力学方法在巨正则系综(GCE)中的应用.     

单壁碳纳米管在阴离子表面活性剂溶液中的分散悬浮和团聚沉降性能研究

纳米颗粒在水中的悬浮和团聚性能是决定它们在环境中迁移行为及潜在健康和环境风险影响范围的关键。表面活性剂不仅在环境中普遍存在,而且是工业制备纳米颗粒稳定悬浮液的主要分散剂。本文以单壁纳米碳管为代表,研究震荡扰动及稀释等模拟环境条件下其在阴离子表面活性剂溶液中的分散悬浮和团聚沉降性能,为评价纳米颗粒排放进入环境后的潜在风险提供依据。创新要点：现有研究认为,纳米颗粒由于能在水中稳定悬浮,其排放到环境中会产生长距离迁移并存在造成大范围污染的可能性和生态健康风险。在本文中,震荡扰动及稀释等模拟环境条件的研究表明,单壁碳纳米管在环境中长距离迁移并造成大范围污染的可能性和风险较小。研究方法：通过比较震荡扰动（模拟环境条件）和超声辅助两种分散悬浮方式及有无添加十二烷基苯磺酸钠（SDBS）阴离子表面活性剂条件下的单壁碳纳米管在水中的悬浮性能（图1）,研究单壁碳纳米管能否在环境中被分散悬浮。通过研究 Na＋,K＋,Ca2＋和 Mg2＋等环境主要阳离子存在时 SDBS 稳定悬浮的单壁碳纳米管悬浮性能及与 SDBS 浓度等的相关性（图6和8）,探明稳定悬浮的单壁碳纳米管能否在环境稀释过程中和环境阳离子存在下保持稳定悬浮。重要结论：在超声辅助下,单壁碳纳米管可以在 SDBS阴离子表面活性剂溶液中稳定分散悬浮,但不能在水中稳定分散悬浮。在无超声辅助、仅通过机械震荡的情况下,单壁碳纳米管无法在水中和 SDBS溶液中稳定分散悬浮。对于已经在 SDBS溶液中稳定悬浮的单壁碳纳米管,它们在 Na＋,K＋,Ca2＋和 Mg2＋等环境主要阳离子存在时也会脱稳形成团聚沉降,且该团聚沉降行为取决于悬浮溶液中 SDBS的浓度。当 SDBS稳定悬浮的单壁碳纳米管在环境中被稀释?     

碳纳米管结构概述

本文通过对碳纳米管的分类的描述、碳纳米管的合成方法、碳纳米管结构的表征、不规则碳纳米管的结构和欧拉定律、多壁碳纳米管概述、单壁碳纳米管的管束及管束环、碳纳米管结构的稳定性以及碳纳米管结构的观察等8各方面 ,综述了碳纳米管的一般特点 ,同时提供了较详细的参考资料。文章重点描述了碳纳米管结构的表征。     

氩在单壁碳纳米管中扩散的分子动力学模拟

利用分子动力学模拟方法模拟了氩在不同直径的单壁碳纳米管(SWCNTs)中的扩散。通过利用公式     

Stone-Wale缺陷对单壁碳纳米管的电子结构和光学性质的影响

文章在简单阐述碳纳米管的几何结构特征、基本物理特性的基础上,结合Universal力场和紧束缚方法,研究在单壁碳纳米管中,由于Stone-Wale缺陷的存在对系统电子结构和光学性质的影响。结果表明Stone-Wale缺陷的出现使得碳纳米管中的电子受到缺陷的散射,从而极大的修改了费米面附近系统的性质,使态密度和线性光学发生明显的改变,并具体分析了在缺陷附近局域态的分布情况。     

单壁碳纳米管膜在转动电解质中的电学性质

单壁碳纳米管膜在转动电解液中诱导的电流随电解液转动角速度、浓度和温度的变化而变化。实验结果表明：该诱导电流随电解液的转动角速度的增加而增加,并与电解液的浓度和温度密切相关。碳纳米管的这种效应可作为一种新型的流体角速度传感器和能量转换器。     

单壁开口碳纳米管的Randic指数

针对单壁开口碳纳米管的规则性,当给定纳米管的周长(或直径)和长度时,得出了常见的锯齿型开口纳米管和扶手椅型开口纳米管的Randi'c指数的计算公式。并比较出具有相同直径和长度的纳米管,扶手椅型的Randi'c指数较小。     

我国首次合成单一手性碳纳米管的长共轭链段

中国科学技术大学杜平武教授课题组通过精确分子设计,在世界上合成了首例单一手性指数单壁碳纳米管的长共轭链段。该成果以封面文章的形式发表于《美国化学会志》杂志。碳纳米管可被认为是仅包含sp^2键合原子的全碳基管状共轭聚合物,然而直径特定的碳纳米管片段长共轭聚合物尚无研究报道。具有单一直径和手性的纯碳纳米管材料,在纳米科技和电子学领域有着重要的应用潜力,但合成这样的碳纳米管是合成化学和材料化学领域的一个重要挑战。催化剂表面介导生长的方法在制备碳纳米管方面表现出巨大的潜力,然而纳米管纯度始终是一个难以克服的问题。     

海藻酸钠修饰的碳纳米管吸附水溶液中Zn(Ⅱ)的研究

借助新型偶联剂,通过海藻酸钠(SAL)对碳纳米管(CNTs)进行修饰和改性,制备海藻酸钠-碳纳米管复合物,利用TEM表征了修饰后的MWNTs的表面形貌,借助全自动快速比表面积及孔隙度分析仪表征了MWNTs的比表面积和孔结构。考察了溶液p H值、温度、吸附时间、吸附剂的量等因素对海藻酸钠-碳纳米管复合物吸附水溶液中锌离子行为的影响。表征结果显示,利用海藻酸钠对多壁碳纳米管进行改性,提高了分散性、比表面积和孔径。实验结果表明:中性条件下的吸附效果均较酸性条件下的好,而在偏碱性条件下,溶液会发生沉淀,吸附不再是主要作用。在室温25℃,p H=6条件下,SAL-MWCNTs复合物对锌离子吸附平衡时间为60min,由Langmuir模型计算可知改性碳纳米管对Zn^(2+)的最大吸附量为84.50 mg/g。     

The rocky road of teachers becoming action researchers

This paper describes an action research project conducted in the course of teaching about action research. Eight doctoral students and a professor co-taught the course. We organized it to demonstrate aspects of action research and conducted our research as an example of action research methodology. We shared our proposal, data collection strategies, and beginning data analyses with our students. Our action research project thus served two purposes: (1) it helped us to study our own teaching and the emerging understandings of our students, and (2) it demonstrated action research for our students while they designed their own research proposals.     

数据挖掘技术研究

数据挖掘就是从大量的数据中提取隐含信息和知识,利用数据库,人工智能和数理统计等多方面的技术,是一类深层次的数据分析方法。     

ASPIRATIONS AND YOUNG PEOPLE’S CONSTRUCTIONS OF THEIR FUTURES: INVESTIGATING SOCIAL MOBILITY AND SOCIAL REPRODUCTION

The United Kingdom’s Coalition government has introduced an education policy that is focused on increasing the opportunities to promote and advance social mobility for all children within state education. Raising young people’s aspirations through school-based initiatives is a prominent theme within recent policy texts, which are focused on improving educational outcomes and thus advancing social mobility. This article draws on qualitative data from paired interviews with 32 students in two academies to first investigate if our participants’ aspirations indicate a desire for intragenerational social mobility and second, to explore our participants’ perceptions of the influences of their family background on their aspirations for the future. Analysis of our data highlights the mismatch between our participants’ aspirations for the future and the government’s constructions of what they should aspire to, as articulated in policy texts. By investigating aspirations, as part of a wider project to understand social mobility qualitatively, our data shows the important role of family in shaping our participants’ varied and diverse aspirations that are frequently at variance with government policy.     

Performance Analytics: The Missing Big Data Link Between Learning Analytics and Business Analytics

Big data analytics technology is changing the human capital development landscape. Global benchmarking trends reveal a gap between what executives expect from our profession and what we are currently capable of delivering. Emerging big data performance analytics technology offers our profession the capability to answer this growing executive expectation to diagnose the current and projected strengths and vulnerabilities of their workforce. It provides real‐time evidence that our performance improvement solutions optimize human and organizational performance.     

Toward Improving the Modeling of MTMM Data: A Response to Geiser,Koch, and Eid (2014)

Geiser, Koch, and Eid (2014) expressed their views on an article we published describing findings from a simulation study and an empirical study of multitrait–multimethod (MTMM) data. Geiser and colleagues raised concerns with (a) our use of the term bias, (b) our statement that the correlated trait–correlated method minus one [CT–C(M–1)] model is not in line with Campbell and Fiske’s (1959) conceptualization of MTMM data, (c) our selection of a data-generating model for our simulation study, and (d) our preference for the correlated trait–correlated method (CT–CM) model over the CT–C(M–1) model. Here, we respond to and elaborate on issues raised by Geiser et al. We maintain our position on each of these issues and point to the interpretational challenges of the CT–C(M–1) model. But, we clarify our opinion that none of the existing structural models for MTMM data are flawless; each has its strengths and each has its weaknesses. We further remind readers of the goal, findings, and implications of our recently published article.     

我国上市公司的盈利能力与资本市场关系的动态分析——以方正科技为例

以净资产收益率代表我国上市公司的盈利能力,以上证收盘综合指数代表我国的资本市场,以1991～2010年的数据为研究对象,通过VEC模型分析表明：我国上市公司的盈利能力与我国的资本市场之间存在着长期的均衡关系;我国的上市公司和我国的资本市场之间彼此存在着负向的影响;我国的上市公司主要是受自身因素的影响,我国的资本市场在短期内主要是自身因素的影响,在长期内会受到我国上市公司的影响。     

我国企业年金供给能力评估

企业年金计划的运行关键是一个"资金"问题。本文以我国企业的财务数据和与职工生活相关的经济数据为基础,重点选取法定公益金、净利润、人均剩余收入、人均可支配收入等指标,运用实证分析的方法对我国企业年金的供给能力做出评估,量化我国企业年金的供给能力。     

Mental deficiency,a challenge to education

The purpose of this article is to expose the politics that arise in the research and evaluation of school reform efforts. We draw on qualitative data gathered in a study of comprehensive school reform to elucidate methodological issues in several areas. We discuss how we were perceived as researchers, how participants used our research and our presence in political ways, and how we questioned our own role in the research process. We discuss challenges in the data-gathering process, including the selection of interviewees for the study. Finally, we discuss challenges in the interpretation of data, including the representation of multiple perspectives and how to portray data on schools where reform appears to be a nonevent.     

Response to comment on estimating school efficiency

After correcting errors in our paper ([Bifulco and Bretschneider, 2001]), [Ruggiero, 2003]) finds that efficiency estimates provided by DEA and COLS have higher correlations with true efficiency values than indicated in our analysis. However, because Ruggiero only considers cases without measurement error, his analysis leaves the primary question of our study unanswered. Using the corrected data generation process proposed by Ruggiero, we find that the presence of measurement error substantially reduces the correlations between estimates of efficiency provided by DEA and COLS and true efficiency. Thus, the primary conclusions of our original study remain. If the administrative data sets used in school accountability programs have significant amounts of measurement error, and if the methods used to estimate efficiency require exogenous inputs, than measures of school efficiency can be quite misleading.     

Novel algorithm for complex bit reversal: employing vector permutation and branch reduction methods

We present novel vector permutation and branch reduction methods to minimize the number of execution cycles for bit reversal algorithms. The new methods are applied to single instruction multiple data （SIMD） parallel implementation of complex data floating-point fast Fourier transform （FFT）. The number of operational clock cycles can be reduced by an average factor of 3.5 by using our vector permutation methods and by 1.1 by using our branch reduction methods, compared with conventional implementations. Experiments on MPC7448 （a well-known SIMD reduced instruction set computing processor） demonstrate that our optimal bit-reversal algorithm consistently takes fewer than two cycles per element in complex array operations.