期刊：
Journal of Software,2012年7(6):1219-1226 ISSN：1796-217X
通讯作者：
Fang, K.(fk@hunau.Net)
作者机构：
[Jing Song; Kui Fang] Institute of Information Science and Technology, Hunan Agricultural University, Changsha, China;[Xiang-Yang Xu] Institute of Computer Science, Changsha University, Changsha, China;[Lu-Ming Shen] Science College, Hunan Agricultural University, Changsha, China
关键词：
local convexity;global convexity;gauss curvature;the second fundamental form
摘要：
Based on a geometrical method, the internal relationships between locally parameterized curves and the local parameterized surfaces are analyzed. A necessary and sufficient condition is derived for the local convexity of parameterized surfaces and functional surfaces. A criterion for local convexity (concavity) of parameterized surfaces is found, also, the criterion condition of binary function convex surfaces is obtained. Finally, the relationships between a globally parameterized curves surfaces is discussed, a necessary condition is presented for the global convexity of parameterized surfaces , and it is proved that locally convex parameterized surfaces are also globally convex.
关键词：
Titanium dioxide;mesoporous material;dye-sensitized solar cells
摘要：
Pure anatase TiO2 spheres with mesoporous structure were prepared by a simple urea assisted hydrothermal process at low temperature. X-ray Diffractometer, Scanning Electron Microscope, Transmission Electron Microscope, and N2 adsorption-desorption were used to characterize TiO2. The dye-sensitized solar cells results show that an overall light conversion efficiency of 6.96% which is 36.7% higher than that of the overall efficiency (5.09%) obtained from the P25 photoanode owing to the superior light scattering effect and the high level of dye loading capacity of microspheres.
摘要：
Two mild alkaline oxidative pretreatments of rice straw followed by enzymatic hydrolysis were investigated. In addition to measuring the composition variance, the pretreated rice straw solutions were analysed by the UV/Vis spectra. These two mild oxidative pretreatment of rice straw cause the removal of lignin, hemicellulose and neutral detergent solubles (NDS), where the H <inf>2</inf>O<inf>2</inf>/NaOH pretreatment solubilize the lignin and the O <inf>3</inf>/NaOH pretreatment oxidative degrade the lignin. These two mild oxidative pretreatment of rice straw enhance susceptibility to enzymatic hydrolysis, and speed-up the enzymatic hydrolysis. The conversion yield of cellulose and hemicellulose presented in the O<inf>3</inf>/NaOH pretreated rice straw was 92.6%, compared to 82.3% and 52.5% in the H<inf>2</inf>O <inf>2</inf>/NaOH pretreated and untreated rice straw, respectively.
期刊：
Applied Mechanics and Materials,2012年212-213:1062-1066 ISSN：1660-9336
通讯作者：
Zou, Ruibiao
作者机构：
[Zou, Ruibiao] Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.;[Yi, Wei; Mou, Zouxin] Sany Heavy Ind Co Ltd, Changde 415001, Peoples R China.
会议名称：
International Conference on Civil, Architectural and Hydraulic Engineering (ICCAHE 2012)
会议时间：
AUG 10-12, 2012
会议地点：
Zhangjiajie, PEOPLES R CHINA
会议主办单位：
[Zou, Ruibiao] Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.^[Yi, Wei;Mou, Zouxin] Sany Heavy Ind Co Ltd, Changde 415001, Peoples R China.
作者机构：
[Jia, Zhengyuan; Fan, Zhou] School of Economics and Management, North China Electric Power University, Baoding 071003, China;[Zhao, Liang] Beijing Gas and Heating Design Institute, Beijing 100032, China
通讯机构：
School of Economics and Management, North China Electric Power University, China
摘要：
The paper proposes several mathematical models of the multidirectional associative memory (MAM) neural network by analyzing its structure. A model of MAM with distributed delays is studied. Under some new assumptions on activation functions, $${2^{n_0[m/2]}}$$ invariant subsets of MAM are constructed. Then the existence and the exponential stability of $${2^{n_0[m/2]}}$$ periodic solutions located on invariant subsets are obtained by constructing a suitable Liapunov function and a Poincaré mapping. An estimating method of the exponential convergence rate is given. The obtained results are new to MAM neural networks. An example is given to illustrate the effectiveness of the results. The paper proposes several mathematical models of the multidirectional associative memory (MAM) neural network by analyzing its structure. A model of MAM with distributed delays is studied. Under some new assumptions on activation functions, $${2^{n_0[m/2]}}$$ invariant subsets of MAM are constructed. Then the existence and the exponential stability of $${2^{n_0[m/2]}}$$ periodic solutions located on invariant subsets are obtained by constructing a suitable Liapunov function and a Poincaré mapping. An estimating method of the exponential convergence rate is given. The obtained results are new to MAM neural networks. An example is given to illustrate the effectiveness of the results.
关键词：
Yeast lipid;Lignocellulosic biomass;Detoxification of hydrolyzate;Inhibition;Biodiesel
摘要：
Microbial lipid produced using yeast fermentation with inexpensive carbon sources such as lignocellulosic hydrolyzate can be an alternative feedstock for biodiesel production. Several inhibitors that can be generated during acid hydrolysis of lignocellulose were added solely or together into the culture medium to study their individual inhibitory actions and their synergistic effects on the growth and lipid accumulation of oleaginous yeast Rhodosporidium toruloides. When the inhibitors were present in isolation in the medium, to obtain a high cell biomass accumulation, the concentrations of formic acid, acetic acid, furfural and vanillin should be lower than 2, 5, 0.5 and 1.5 g/L, respectively. However, the synergistic effects of these compounds could dramatically decrease the minimum critical inhibitory concentrations leading to significant growth and lipid production inhibitions. Unlike the above-cited inhibitors, sodium lignosulphonate had no negative influence on biomass accumulation when its concentration was in the range of 0.5-2.0 g/L; in effect, it was found to facilitate cell growth and sugar-to-lipid conversion. The fatty acid compositional profile of the yeast lipid was in the compositional range of various plant oils and animal tallow. Finally, the crude yeast lipid from bagasse hydrolyzate could be well converted into fatty acid methyl ester (FAME, biodiesel) by enzymatic transesterification in a tert-butanol system with biodiesel yield of 67.2% and lipid-to-biodiesel conversion of 88.4%.
作者机构：
[温芝元] College of Science, Hunan Agricultural University, Changsha 410128, China;[曹乐平] Office of Academic Affairs, Hunan Biological and Electromechanical Polytechnic, Changsha 410127, China
通讯机构：
Office of Academic Affairs, Hunan Biological and Electromechanical Polytechnic, China
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+.
