期刊：
JOURNAL OF PHYSICS-CONDENSED MATTER,2011年23(39):395004 ISSN：0953-8984
通讯作者：
Yang, Jianyu
作者机构：
[Yang, Jianyu] Hunan Inst Engn, Dept Math & Phys, Xiangtan 411104, Peoples R China.;[Hu, Wangyu] Hunan Univ, Dept Appl Phys, Changsha 410082, Hunan, Peoples R China.;[Tang, Jianfeng] Hunan Agr Univ, Dept Appl Phys, Changsha 410028, Hunan, Peoples R China.
通讯机构：
[Yang, Jianyu] H;Hunan Inst Engn, Dept Math & Phys, Xiangtan 411104, Peoples R China.
摘要：
The diffusion of single tungsten adatoms on the surfaces of rhombohedral clusters is studied by means of molecular dynamics and the embedded atom method. The energy barriers for the adatom diffusing across and along the step edge between a {110} facet and a neighboring {110} facet are calculated using the nudged elastic band method. We notice that the tungsten adatom diffusion across the step edge has a much higher barrier than that for face-centered cubic metal clusters. The result shows that diffusion from the {110} facet to a neighboring {110} facet could not take place at low temperatures. In addition, the calculated energy barrier for an adatom diffusing along the step edge is lower than that for an adatom on the flat (110) surface. The results show that the adatom could diffuse easily along the step edge, and could be trapped by the facet corner. Taking all of this evidence together, we infer that the {110} facet starts to grow from the facet corner, and then along the step edge, and finally toward the {110} facet center. So the tungsten rhombohedron can grow epitaxially along the {110} facet one facet at a time and the rhombohedron should be the stable structure for both large and small tungsten clusters.
关键词：
college physics;agricultural university;explore independently;teaching method;teaching efficiency
摘要：
China is a big agricultural country, and training qualified agricultural talents relates to long-term development of our country. College physics is one of the important foundation courses in agricultural university, but the classroom teaching current faces severe challenges. To improve the efficiency of college physics teaching, we propose to a new type of teaching mode which explored independently by the students themselves. It can change the boring classroom atmosphere, and effectively stimulate students’ learning enthusiasm. So it can improve the teaching efficiency and promote agricultural talent training.
摘要：
The surface diffusion of Pt dimers on Wulff polyhedral clusters with 586-12934 atoms was studied by the embedded atom method. The minimum energy diffusion path and the corresponding energy barrier for dimer diffusion on cluster surfaces were determined through a combination of the quenched Molecular Dynamics and the Nudged Elastic Band method. It was found that the diffusion of a dimer across the step-edge by dissociation and consecutive single-atom exchange with the edge atoms, rather than diffusion over the edge as a unit. Therefore, the step can enhance the dissociation of the dimer. For small Wulff polyhedral clusters containing up to 2000 atoms, the energy barrier for dimer diffusion from the {111} to the {100} facet is almost equal to that for the single adatom diffusion on the flat {111} surface. From the calculated cluster size dependence of the energy barrier, we conclude that the Wulff polyhedral cluster is stable, as the cluster has more than about 2000 atoms.
期刊：
Computers & Mathematics with Applications,2011年61(6):1687-1699 ISSN：0898-1221
通讯作者：
Chen, Haibo
作者机构：
[Chen, Haibo; Liu, Zhisu] Cent S Univ, Dept Math, Changsha 410075, Hunan, Peoples R China.;[Zhou, Tiejun] Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.
通讯机构：
[Chen, Haibo] C;Cent S Univ, Dept Math, Changsha 410075, Hunan, Peoples R China.
关键词：
dirichlet boundary value problem;impulsive effects;variational methods;critical points
摘要：
In this paper, we study the existence of solutions for a class of second-order impulsive differential equation. By using the critical point theorem of Y. Jabri and an even functional theorem, we give some new criteria to guarantee that the impulsive differential equation has at least one solution, infinitely many solutions under the assumption that a nonlinear term satisfies sublinear, superlinear, asymptotically linear, respectively. Some recent results are extended and conditions of assumptions are simplified. Finally, some examples are presented to illustrate our main results.
摘要：
A series of novel water soluble quinoline derivatives 1a∼1d were synthesized from 8-hydroxyquinoline and the fluorescence of these compouds had been quenched by Cu2+ or Fe3+ in absolute water. It was seen that the fluorescence of 1a was quenched by 93% with addition of 50 μM of Cu2+ in absolute water and 75% in the presence of 50 μM of Fe3+ with the quenching ratio (Cu2+ :Fe3+) of 1:0.80, showing much higher sensitivity and selectivity of Cu2+ to Fe3+. In addition, the presence of some other metal ions such as K+, Ca2+, Zn2+, Al3+, Mn2+, Fe2+, Ba2+, Co2+, Ni+, Cr3+, Cd2+, Cu2+, Hg2+, Pb2+, Sn2+, Na+ and Mg2+ had little influence on the selectivity and sensitivity of Cu2+. The easily availabe 1a could be considered a potential fluorescence sensor for Cu2+.
期刊：
Journal of Global Optimization,2011年50(2):221-227 ISSN：0925-5001
通讯作者：
Miao, Yu
作者机构：
[Miao, Yu] Henan Normal Univ, Coll Math & Informat Sci, Xinxiang 453007, Henan, Peoples R China.;[Shen, Luming] Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.
通讯机构：
[Miao, Yu] H;Henan Normal Univ, Coll Math & Informat Sci, Xinxiang 453007, Henan, Peoples R China.
关键词：
Iterative scheme with errors;Hemicontractive mapping;Common fixed points
摘要：
In this paper, we are concerned with the study of an iterative scheme with errors involving two hemicontractive mappings. We approximate the common fixed points of these two mappings by weak and strong convergence of the iteration process in Hilbert space.
摘要：
Humic acid (HA)-coated Fe3O4 (Fe3O4/HA) superparamagnetic nanoparticles were synthesized by a chemical co-precipitation method with cheap and environmental friendly iron salts and HA. The as-synthesized samples were characterized by X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FTIR) and vibrating sample magnetometer (VSM). The Fe3O4/HA nanoparticles showed faster adsorption rate and higher removal capacity of cationic organic dye Methylene blue (MB) in neutral water. Moreover, the MB desorption could be easily completed. And the reused performance of Fe3O4/HA nanoparticles was also excellent.
关键词：
penalized function;weak solution;nematic liquid crystals model
摘要：
In this paper, we are concerned with a simplified hydrodynamic equation, proposed by Ericksen and Leslie, modeling the flow of nematic liquid crystals. For a bounded domain in R(3), under the assumption that initial density belongs to L(gamma)(Omega), gamma>3/2, we show the global existence of weak solutions to the nematic liquid crystals model with a penalized system. Furthermore, we also obtain the energy inequality for weak solutions. Copyright (C) 2011 John Wiley & Sons, Ltd.
关键词：
Homoclinic orbit;nonlinear difference equation;p-Laplacian;variational structure;critical point
摘要：
The paper proves the existence of nontrivial homoclinic orbits for second order nonlinear p-Laplacian difference equations without assumptions on periodicity using the critical point theory. Moreover, if the nonlinearity is an odd function, the existence of an unbounded sequence of nontrivial homoclinic orbits is proved.
摘要：
Two-year-old seedlings of trifoliate orange (Poncirus trifoliata (L.) Raf.) and lemon (Citrus limonia Osbeck.) were sprayed with 0.1 mmol.L-1 abscisic acid (ABA) and then their leaves were collected randomly to expose to freezing stress. Specifically, these detached leaves were treated at 0, -3, -6, -9 and -12°C for 1 h respectively.The concentration of malondialdehyde (MDA), percentage of electrolyte leakage (EL) and the activities of several antioxidant enzymes (superoxide dismutase, catalase and peroxidase) were determined spectrophotometrically. The results show that the percentage of electrolyte leakage in trifoliate orange was lower than that in lemon, while the MDA concentration and the antioxidant activities of antioxidant enzymes in trifoliate orange were higher than those in lemon. Pretreatment with the abscisic acid can significantly reduce the membrane damage caused by freezing stress. However, the lipid peroxidation damage caused by low temperature and the activities of antioxidant enzymes were irregularly influenced by ABA pretreatment. We were thus able to infer that exogenous ABA can enhance the cold tolerance of citrus by a process rather than by activating antioxidant enzymes.
Abbreviation
ABA, Abscisic acid; POD, peroxidase; CAT, catalase; SOD, superoxide dismutase; EL, electrolyte leakage; MDA, malondialdehyde; ROS, reactive oxygen species.
