Observation of twisting growth of branched polyethylene single crystals formed from the melt

The twisting growth of a branched polyethylene single crystal formed from the melt was observed directly by means of transmission electron and atomic force miscroscopy. The surface stress asymmetry arising from the asymmetry of the surface-fold structure and, chain tilting resulted in the twisting growth of the single crystals. The handedness of the twisting lamellae was consistent With the chain-tilting direction. When multilayer lamellae piled up in a thicker film, the lamellar twist would be inevitably causing screw dislocations.

Organic template-directed crystallization of the complex fluoride NH4MnF3 with perovskite structure

(100)-oriented NH4MnF3 perovskite with different morphologies have been obtained in situ via an organic template; experimental results can be rationalized in terms of electrostatic interactions and lattice matching between the organic template and the ions undergoing nucleation.

Synthesis and structure of alpha-B-Keggin type heteropoly complex K5H[Co-4(VW9O33)(2)]center dot 5H(2)O

A new complex K5H[Co-4(VW9O33)(2)]. 5H(2)O was prepared and its structure was determined by X - ray diffraction analysis. The anion has alpha - beta - Keggin structure. Two (VW9O33)(7-) moieties (alpha - B isomers) are linked via four Co(11)O-6 groups. The single crystal of the title complex is monoclinic P2(1/n) with a = 1.2307(3) nm, b = 2.1250(4) nm, c = 1.5817(3) nm, beta = 91.86(3)degrees, V = 4.1343 (14) nm(3), R = 0.0895, R-w = 0.2180.

α-B-Keggin型杂多化合物K_5H[Co_4(VW_9O_(33))_2]·5H_2O的合成和结构

合成了新化合物K_5H[Co_4(VW_9O_(33))·5H_2O,并运用IR,UV-ViS,DTA和单晶X射线衍射对其结构进行了表征.测定结果证实标题化合物具有α-B-Keggin型结构,两个(VW_9O_(33)~(7-)结构单元由四个Co(Ⅱ)O_6 八面体连接.杂多化合物属单斜晶系P2_(1/n),a=1.2307(3)nm,b=2.1250(4)nm,c=1.5817(3)nm,β=91.86(3)°,V=4.1343(14)nm~3,R=0.0895,R_w=0.2180.

PREPARATION AND MICROSTRUCTURAL CHARACTERIZATION OF SURFACE-MODIFIED NANOSIZED SNO2 PARTICLES

Nanosized stannic oxide particles modified with a layer of DBS were successfully prepared through the colloidal chemical method and their microstructures were characterized. FTIR and XPS were used for the determination of the main components. It can be proved that the nanosized SnO2 particles were capped by DBS. The sizes of particle were determined by TEM and XRD. By the investigation of XPS, we can conclude that there are a lot of oxygen vacancies in the surface of the nanoparticulates. Based on this conclusion, the ESR signal of the sample can be explained.

表面修饰的二氧化锡纳米粒子的制备及微结构表征

采用胶体化学法制得表面包覆有ＤＢＳ的二氧化锡纳米粒子，并运用一系列手段对其微结构进行了表征。结果表明：样品为表面包覆有ＤＢＳ的二氧化锡纳米粒子的集合体，粒度表面有大量氧空位，粒度分布均匀且单分散性好，其平均粒径为１．５ｎｍ，表面修饰以后的二氧化锡纳米粉体是以无定形结构为主的纳米微晶结构，体相二氧化锡为抗磁性物质，而表面修饰后的纳米微晶的顺磁共振谱中出现一条顺磁信号，根据纳米微晶的结构特点对此信号进行了解释。

数字模拟在电化学中的应用

本文通过列举大量文献评述了数字模拟在电化学中的进展,包括了模拟的基本方法,边界值的处理及其在电化学中的应用情况。数字模拟已成为了解电化学过程的极好方法。

自旋置换对称体系多脉冲及二维核磁共振实验的密度算符描述(Ⅱ)——多量子积算符方法

在对称化乘积算符(简称SAPO)方法基础上提出了多量子积算符(简称MQCPO)方法。改进的密度算符理论对I_nS(I=1/2,S=1/2;n为任意正整数)自旋体系多脉冲及二维核磁共振实验的描述普遍适用。MQCPO与SAPO从不同角度反映了自旋体系的对称性,故它们之间存在简单线性关系。文中给出I_n(I=1/2,n=2,3)自旋体系MQCPO的SAPO表示。MQCPO有利于自由演化过程的描述,而脉冲作用的描述则是SAPO为佳;利用MQCPO与SAPO的线性关系及SAPO笛卡儿分量的坐标轮换性质,“z”表象下脉冲作用的描述变得简单而直观。对异核谱剪辑及自旋拓扑滤波(spin topology filtration)等实验脉冲序列的分析,该方法是方便的。

Determination of five pharmacologically active compounds extracted from Rhodiola for natural product drug discovery with HPLC-APCI-MS

A rapid and sensitive liquid chromatography-atmospheric pressure chemical ionization mass spectrometry (HPLC-APCI-MS) assay for the determination of five pharmacologically active compounds (PAC) extracted from the traditional Chinese medicine, Rhodiola , namely salidroside, tyrosol, rhodionin, gallic acid, and ethyl gallate has been developed. In this method, PAC could be baseline separated and detected with DAD at 275 nm. The validation of the method, including sensitivity, linearity, repeatability, and recovery, was examined. The linear calibration curves were acquired with correlation coefficient >0.999 and the limits of detection LOD (at a signal-to-noise ratio=3:1) were between 0.058 and 1.500 mu mol/L. It was found, that the amounts of PAC varied with different species of Rhodiola . The established method is rapid and reproducible for the separation of five natural pharmacologically active compounds from extracts of Rhodiola with satisfactory results.

Fuzzy层次神经网络

本文提出和归纳了Ｆｕｚｚｙ前馈神经网络模型，并提出了Ｆｕｚｚｙ前馈神经网络的反向传播学习算法，模拟结果表明利用ＦｕｚｚｙＢＰ学习算法训练的Ｆｕｚｚｙ前馈神经网络具有较好的非逻辑归纳能力和Ｆｕｚｚｙ规则表达能力。

巢湖沉积物δ^13C（org）和δ^15N记录的生态环境演化过程

通过对巢湖2处柱状沉积物样品中δ^13Corg、δ^15N、C/N比值、TOC和TN含量的测定,分析了近百年来巢湖沉积物有机质的来源,探讨受人类活动影响的湖泊生产力变化和富营养化过程.结果表明,巢湖沉积物有机质的主要来源是水生藻类,陆生有机质的输入量较少,但是城市污染物的输入与农业面源污染的影响是不可忽视的.巢湖沉积物剖面上,δ^13Corg、δ^15N、TOC和TN含量变化按沉积深度可以明显划分为2个阶段：①10 cm以下,H3点δ^13Corg波动在-21.74‰- -19.34‰的范围内,其余数据表现相对平缓,湖泊内的生物物种是固氮植物和非固氮植物共存,2个采样点具有不同的湖泊营养化进程;②10 cm至表层段,2个剖面的δ^13Corg迅速减小,δ^15N、TOC和TN则是显著增大,巢湖闸的建成使得内源营养物质快速积累,湖泊初始生产力水平迅速提高,富营养化加剧.

Using hybrid knowledge engineering and image processing in color virtual restoration of ancient murals

IEEE Transactions on Knowledge and Data Engineering, vol. 15, no. 5, pp. 1338-1343, 2003.

Asistencia técnica de ingeniería y diseño industrial. Adecuación de equipos y herramientas.

27 hojas : ilustraciones, planos.

Development of a general internet attitude scale and internet self-efficacy scale

The measurement of users’ attitudes towards and confidence with using the Internet is an important yet poorly researched topic. Previous research has encountered issues that serve to obfuscate rather than clarify. Such issues include a lack of distinction between the terms ‘attitude’ and ‘self-efficacy’, the absence of a theoretical framework to measure each concept, and failure to follow well-established techniques for the measurement of both attitude and self-efficacy. Thus, the primary aim of this research was to develop two statistically reliable scales which independently measure attitudes towards the Internet and Internet self-efficacy. This research addressed the outlined issues by applying appropriate theoretical frameworks to each of the constructs under investigation. First, the well-known three component (affect, behaviour, cognition) model of attitudes was applied to previous Internet attitude statements. The scale was distributed to four large samples of participants. Exploratory factor analyses revealed four underlying factors in the scale: Internet Affect, Internet Exhilaration, Social Benefit of the Internet and Internet Detriment. The final scale contains 21 items, demonstrates excellent reliability and achieved excellent model fit in the confirmatory factor analysis. Second, Bandura’s (1997) model of self-efficacy was followed to develop a reliable measure of Internet self-efficacy. Data collected as part of this research suggests that there are ten main activities which individuals can carry out on the Internet. Preliminary analyses suggested that self-efficacy is confounded with previous experience; thus, individuals were invited to indicate how frequently they performed the listed Internet tasks in addition to rating their feelings of self-efficacy for each task. The scale was distributed to a sample of 841 participants. Results from the analyses suggest that the more frequently an individual performs an activity on the Internet, the higher their self-efficacy score for that activity. This suggests that frequency of use ought to be taken into account in individual’s self-efficacy scores to obtain a ‘true’ self-efficacy score for the individual. Thus, a formula was devised to incorporate participants’ previous experience of Internet tasks in their Internet self-efficacy scores. This formula was then used to obtain an overall Internet self-efficacy score for participants. Following the development of both scales, gender and age differences were explored in Internet attitudes and Internet self-efficacy scores. The analyses indicated that there were no gender differences between groups for Internet attitude or Internet self-efficacy scores. However, age group differences were identified for both attitudes and self-efficacy. Individuals aged 25-34 years achieved the highest scores on both the Internet attitude and Internet self-efficacy measures. Internet attitude and self-efficacy scores tended to decrease with age with older participants achieving lower scores on both measures than younger participants. It was also found that the more exposure individuals had to the Internet, the higher their Internet attitude and Internet self-efficacy scores. Examination of the relationship between attitude and self-efficacy found a significantly positive relationship between the two measures suggesting that the two constructs are related. Implication of such findings and directions for future research are outlined in detail in the Discussion section of this thesis.