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Short cycle structures for graphs on surfaces and an open problem of Mohar and Thomassen

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Science china Mathematics 2006年第2期49卷 212-224页

作者： REN Han & DENG Mo department of Mathematics, East china normal University, Shanghai 200062, china college of Mathematics & Information Science, Northwest normal University, lanzhou 730070, china department of Mathematics East China Normal University Shanghai China college of Mathematics & Information Science Northwest Normal University Lanzhou China

In this paper we investigate cycle base structures of a (weighted) graph and show that much information of short cycles is contained in an MCB (i.e., minimum cycle base). After setting up a Hall type theorem for base-transformation, we give a sufficient and necessary condition for a cycle base to be an MCB. Furthermore, we show that the structure of MCB in a (weighted)graph is unique. The property is also true for those having a longest length (although much work has been down in evaluating MCB, little is known for those having a longest length). We use those methods to find out some unknown properties for short cycles sharing particular properties in (unweighted) graphs. As applications, we determine the structures of short cycles in an embedded graph and show that there exist polynomially bounded algorithms in finding a shortest contractible cycle and a shortest two-sided cycle provided such cycles exist. Those answer an open problem of B. Mohar and C. Thomassen.

关键词： cycle base facial cycle graph embedding.

(2+1)-Dimensional Electron Acoustic Solitary Waves in an Unmagnetized Collisionless Plasma with Vortex-Like Hot Electrons

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Communications in Theoretical Physics 2007年第2期47卷 339-342页

作者： LIN Mai-Mai DUAN Wen-Shan department of Physics,Northwest,normal University,lanzhou 730070,china department of Physics Northwest Normal University Lanzhou 730070 China

In this paper,(2+1)-dimensional electron acoustic waves (EAW) in an unmagnetized collisionless plasmahave been studied by the linearized method and the reductive perturbation technique,*** dispersionrelation and a modified Kadomtsev Petviashvili (KP) equation have been obtained for the EAW in the plasma consideringa cold electron fluid and a vortex-like hot *** is found from some numerical results that the parameter β (theratio of the free hot electron temperature to the hot trapped electron temperature) effects on the amplitude and thewidth of the electron acoustic solitary waves (EASW).It can be indicated that the free hot electron temperature andthe hot trapped electron temperature have very important effect on the characters of the propagation for the EASW.

关键词： electron acoustic solitary wave vortex-like hot electrons reductive perturbation method

Determination of Trace Amount of Yttrium with Bromopyrogallol Red by solid-phase Spectrophotometry

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Rare Metals 2001年第3期20卷 202-204页

作者： Jinzhang Gao,Gang Ni, Li Yuan, Jingwan Kang department of Chemistry, Northwest normal University, lanzhou 730070, china 西北师范大学甘肃兰州 730070

A simple and sensitive method for the determination of trace amount of yttrium by solid-phase spectrophotometry has been studied. Yttrium can form a 1 : 1 complex with bromopyrogallol red (BPR) on resin, which was determined directly at 605 nm, pH=6.5. It has a highly sensitivity (epsilon = 6.3 x 10(6)) which is 300-fold higher than the corresponding spectrophotometry in solution. The method was applied to the determination of yttrium in churchite.

关键词： solid-phase spectrophotometry bromopyrogallol red (BPR) yttrium

Molten solvent extraction behavior of trivalent La, Sm, Dy, and Yb with tri-n-butyl phosphate into molten paraffin wax at 60 ℃

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Rare Metals 2002年第1期21卷 7-11页

作者： PENG Bo, GAO Jinzhang, FAN Haiyan, KANG Jingwan, and YANG Wu department of Chemistry, Northwest normal University, lanzhou 730070, china department of Chemistry Northwest Normal University Lanzhou 730070

The extraction behavior of La^3+, Sm^3+, Dy^3+, and Yb^3+ insodium acetate-acetic acid medium was studied with tri-N-butylphosphate (TBP) at 60 deg. C using paraffin wax as a diluent. Theextraction percentage is greater than 85/100 in the pH range of 6 to8. The result of slope analysis method indicates that thecompositions of the extracted species are different between the lightand heavy rare ear this. The formula of the extracted species isfound to be La (TBP) (OH) (Ac)_2 for La^3+ and Yb (TBP) (OH)_3 forYb^3+. The effects of extracting time, the concentration of TBP inthe organic phase and salts on the extraction efficiency were alsodiscussed.

关键词： solvent extraction rare earth TBP Paraffin wax

Focalizations and Their Functions in Heart of Darkness

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兰州大学学报（社会科学版） 2000年第S1期28卷 109-113页

作者： Dong Xiaohua (Foreign Languages department, Northwest normal University, lanzhou, 730070, china)

As an important technique involved in the novel writing,the focalization is studied in detail in *** paper is an attempt to analyze the arrangement of focalizations and their functions in Heart of Dartness according t... 详细信息

关键词： focalizations narratology functions

Anderson's Cognitive Theory and Learning Strategy Studies in Second Language Acquisition

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兰州大学学报（社会科学版） 2000年第S1期28卷 228-231页

作者： Lu Wenpeng (Foreign Languages department, Northwest normal University, lanzhou, 730070, china)

Second language acquisition can not be understood without addressing the interaction between language and cognition. Cognitive theory can extend to describe learning strategies as complex cognitive skills. Theoretical developments in Anderson’s production systems cover a broader range of behavior than other theories, including comprehension and production of oral and written texts as well as comprehension, problem solving, and verbal *** Anderson’s cognitive theory can be served as a rationale for learning strategy studies in second language acquisition.

关键词： Anderson’s cognitive theory Anderson’s production systems learning strategy studies second language acquisition

The Justification of the Unjustifiable in Hawthorne's The Scarlet Letter

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兰州大学学报（社会科学版） 2000年第S1期28卷 39-43页

作者： Xiang Weiyi (Foreign Languages department, Northwest normal University, lanzhou, 730070, china)

A young nation, the United States in nineteenth century went on an experiment on the national identity, value, performance and destiny. Hawthorne, as a writer, took part in this experiment. In his The Scarlet Letter, he justifies what seems unjustifiable: that is Hester’s transgression of both religious and social laws. By Hester’s “social experiment,” Hawthorne advocates the Enlightenment idea that natural law takes precedence over God’s law; as well as the humanistic idea that human being is more important than social conventions. In Hester’s destiny, Hawthorne expressed his hope that the newborn nation should develop on a more healthy and natural way.

关键词： Hawsthorne The Scarlet Letter Hester

Robustness and breakup of the spiral wave in a two-dimensional lattice network of neurons

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Science china(Physics,Mechanics & Astronomy) 2010年第4期53卷 672-679页

作者： MA Jun 1,2, TANG Jun 2 , ZHANG AiHua 3 & JIA Ya 2 1 department of Physics, lanzhou University of Technology, lanzhou 730050, china 2 department of Physics, Central china normal University, Wuhan 430079, china 3 college of Electrical and Information Engineering, lanzhou University of Technology, lanzhou 730050, china department of Physics Lanzhou University of Technology Lanzhou China department of Physics Central China Normal University Wuhan China college of Electrical and Information Engineering Lanzhou University of Technology Lanzhou China

The robustness and breakup of spiral wave in a two-dimensional lattice networks of neurons are investigated. The effect of small- world type connection is often simplified with local regular connection and the long-range connection with certain probability. The network effect on the development of spiral wave can be better described by local regular connection and changeable long-range connection probability than fixed long-range connection probability because the long-range probability could be changeable in realistic biological system. The effect from the changeable probability for long-range connection is simplified by multiplicative noise. At first, a stable rotating spiral wave is developed by using appropriate initial values, parameters and no-flux boundary conditions, and then the effect of networks is investigated. Extensive numerical studies show that spiral wave keeps its alive and robust when the intensity of multiplicative noise is below a certain threshold, otherwise, the breakup of spiral wave occurs. A statistical factor of synchronization in two-dimensional array is defined to study the phase transition of spiral wave by checking the membrane potentials of all neurons corresponding to the critical parameters(the intensity of noise or forcing current)in the curve for factor of synchronization. The Hindmarsh-Rose model is investigated, the Hodgkin-Huxley neuron model in the presence of the channel noise is also studied to check the model independence of our conclusions. And it is found that breakup of spiral wave is easier to be induced by the multiplicative noise in presence of channel noise.

关键词： spiral wave factor of synchronization breakup multiplicative noise robustness

The Love of “The Lost Generation” inThe Sun Also Rises

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兰州大学学报（社会科学版） 2000年第S1期28卷 49-54页

作者： Liu Jianfeng (Foreign Languages department, Northwest normal University, lanzhou, 730070, china) [HT5SS][CD=36]

This article shows us the multiplicity and perplexity of the Lost Generations love and thus exposes that the evil war destroys lives and civilization of human beings;ruins the life,youthfulness,happiness,future and ... 详细信息

关键词： Hemingway The Sun Also Rises the Lost Generation