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Ren, Xiao-Yan,Niu, Chun-Yao,Chen, Wei-Guang,Tang, Ming-Sheng,Cho, Jun-Hyung The Royal Society of Chemistry 2016 Physical chemistry chemical physics Vol.18 No.27
<P>Exploring the properties of noble metal atoms and nano- or subnano-clusters on the semiconductor surface is of great importance in many surface catalytic reactions, self-assembly processes, crystal growth, and thin film epitaxy. Here, the energetics and kinetic properties of a single Cu atom and previously reported Cu magic clusters on the Si(111)-(7 x 7) surface are re-examined by the state-of-the-art first-principles calculations based on density functional theory. First of all, the diffusion path and high diffusion rate of a Cu atom on the Si(111)-(7 x 7) surface are identified by mapping out the total potential energy surface of the Cu atom as a function of its positions on the surface, supporting previous experimental hypothesis that the apparent triangular light spots observed by scanning tunneling microscopy (STM) are resulted from a single Cu atom frequently hopping among adjacent adsorption sites. Furthermore, our findings confirm that in the low coverage of 0.15 monolayer (ML) the previously proposed hexagonal ring-like Cu-6 cluster configuration assigned to the STM pattern is considerably unstable. Importantly, the most stable Cu-6/Si(111) complex also possesses a distinct simulated STM pattern with the experimentally observed ones. Instead, an energetically preferred solid-centered Cu-7 structure exhibits a reasonable agreement between the simulated STM patterns and the experimental images. Therefore, the present findings convincingly rule out the tentative six-atom model and provide new insights into the understanding of the well-defined Cu nanocluster arrays on the Si(111)-(7 x 7) surface.</P>
An Investigation into the Prevalence of Voice Strain in Chinese University Teachers
( Gang Zhou ),( Xiao Chun Niu ) 범태평양 응용언어학회 2015 Journal of Pan-Pacific Association of Applied Ling Vol.19 No.1
Vocal disorders are very common occupation-related disease in teachers, though it has never been given enough attention in China. As a result, the occupational health care of professional voice users is surprisingly undeveloped compared to the attention given to occupational hearing disorders or many other occupational symptoms. The aim of the present study was to assess the prevalence of voice problems in the general population of Chinese university teachers, and explore whether their voice problems affected their daily life, their social life and their work. A voice strain and voice handicap index questionnaire was administered to university instructors of English (N = 156) in six Chinese universities. Results indicated that voice strain is prevalent among Chinese university instructors. The respondents`` self-perceptions revealed that voice strain was significantly correlated with their job and their daily activities.