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Search Results: 1 - 10 of 58007 matches for " Yan Zheng "
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Closure for Spanning Trees with k-Ended Stems  [PDF]
Zheng Yan
Open Journal of Discrete Mathematics (OJDM) , 2014, DOI: 10.4236/ojdm.2014.43008

Let T be a tree. The set of leaves of Τ is denoted by Leaf(Τ). The subtree Τ—Leaf(Τ) of T is called the stem of Τ. A stem is called a k-ended stem if it has at most k-leaves in it. In this paper, we prove the following theorem. Let G be a connected graph and k≥2 be an integer. Let u and ν be a pair of nonadjacent vertices in G. Suppose that |NG(u)∪NG(v)|≥|G|-k-1. Then G has a spanning tree with k-ended stem if and only if G+uv has a spanning tree with k-ended stem. Moreover, the condition on |NG(u)∪NG(v)|

The Study on New Solid-State Breaker and Its Over-voltage Suppression Technique  [PDF]
Longji Zhu, Yan Zheng
Energy and Power Engineering (EPE) , 2013, DOI: 10.4236/epe.2013.54B237

A design scheme of the intelligent SSB (Solid State Breaker) based on the IGCT (Integrated Gate Commutated Thyris- tor) is presented. The topology of switch module and the structure of the SSB are proposed. Firstly, to the IGCT’s over-voltage sensitivity problem, a new technique of reducing the over-voltage is introduced, which releases the elect romantics energy of faulty line by a capacitive current branch to reduce the amplitude of over-voltage. Secondly, the principle of over-voltage suppression with current release branch is analyzed, and the overall control scheme of solid- state breaker is put forward. Finally, the simulation results also demonstrate its obvious effectiveness in over-voltage suppression after adding a current release branch into the SSB.

A Study on the Development of Eco-tourism Resources Based on Scientific Development Philosophy
Yan Zheng
International Journal of Business and Management , 2009,
Abstract: Eco-tourism represents the new tendency of the development of the present-day tourism. The following essay brings forward the strategic options of the development of the eco-tourism resources in China by means of the analysis of their present-day eco-tourism. The essay also provides information into the designs of the ecological tourist products in China.
Self-Organizing Molecular Field Analysis on a New Series of COX-2 Selective Inhibitors: 1,5-Diarylimidazoles
Shunlai Li,Yan Zheng
International Journal of Molecular Sciences , 2006, DOI: 10.3390/i7070220
Abstract: Self-organizing molecular field analysis (SOMFA), a simple three-dimensionalquantitative structure–activity relationship (3D-QSAR) method is used to study the correlationbetween the molecular properties and the anti-inflammatory biological activities of a new series of1,5-Diarylimidazoles that act as selective COX-2 inhibitors. The statistical results, cross-validated rCV2 (0.507) and non cross-validated r2 (0.546), show a satisfied predictive ability.
Magnetic properties of street dust and topsoil in Beijing and its environmental implications
Yan Zheng,ShiHong Zhang
Chinese Science Bulletin , 2008, DOI: 10.1007/s11434-007-0450-3
Abstract: Environmental magnetic measurements were carried out on the samples of street dust and topsoil, which were collected along the roadway in the urban and suburb of Beijing, including magnetic susceptibility (χ), anhysteretic remanent magnetization (ARM), isothermal remanent magnetization (IRM) of all samples and temperature-dependence of magnetic susceptibilities and magnetic hysteresis parameters of representative samples. Obvious differences exist between the samples of street dust and those of topsoil. Compared with topsoil samples, the concentration of magnetic particles and high-coercivity components in street dust samples are higher, and the magnetic grains are coarser. Both dust and topsoil samples are dominated by ferrimagnetic minerals, and iron particles are only detected in some dust samples. These results suggest that street dust samples reflect the characteristic of particles produced by industrial and traffic activities, and the magnetic property of topsoil samples represents the characteristic of particles from both anthropogenic and natural sources. The distribution of magnetic parameters is influenced by the environment where the samples are collected, like industry, traffic density and other road conditions. Hard isothermal remanent magnetization (HIRM) may be used as an indicator of particles produced by traffic activity. Dust storm samples collected on 17 and 18 April, 2006 have different magnetic properties from street dust and natural particles, like loess and paleosol, which indicate that the dust storm might be mixed with anthropogenic particulates during transport and falling.
Journal of Engineering Science and Technology , 2011,
Abstract: We have developed an innovative hybrid problem-based learning (PBL) methodology. The methodology has the following distinctive features: i) Each complex question was decomposed into a set of coherent finer subquestions by following the carefully designed criteria to maintain a delicate balance between guiding the students and inspiring them to think independently. This learning methodology enabled the students to solve the complex questions progressively in an inductive context. ii) Facilitated by the utilization of our web-based learning systems, the teacher was able to interact with the students intensively and could allocate more teaching time to provide tailor-made feedback for individual student. The students were actively engaged in the learning activities, stimulated by the intensive interaction. iii) The answers submitted by the students could be automatically consolidated in the report of the Moodle system in real-time. The teacher could adjust the teaching schedule and focus of the class to adapt to the learning progress of the students by analysing the automatically generated report and log files of the web-based learning system. As a result, the attendance rate of the students increased from about 50% to more than 90%, and the students’ learning motivation have been significantly enhanced.
Monoliths with Proteins as Chiral Selectors for Enatiomer Separation
Yan Zheng,Yibing Ji
Lecture Notes in Engineering and Computer Science , 2011,
Using Renyi Cross Entropy to Analyze Traffic Matrix and Detect DDoS Attacks
Ruoyu Yan,Qinghua Zheng
Information Technology Journal , 2009,
Abstract: In this study, we propose Renyi cross entropy to analyze matrix traffic and detect anomaly rather than other entropy metrics, such as Shannon entropy, used extensively in many earlier studies. At first, we introduce a new type of traffic termed IF-flow (internal flow) collected in router. IF-flow can make the attack traffic more conspicuous in a large number of normal traffics, which makes attacks, especially DDoS attacks, spotted more easily. Then, the analysis of Renyi cross entropy of IF-flow matrix traffic, Abilene matrix traffic confirms that matrix traffic distribution has local stability in time. This conclusion provides a guidance to accurately detect anomaly. Finally, Renyi cross entropy is used to detect DDoS attacks existed in IF-flow testing data set and Abilene testing data set. The results of detection experiments show Renyi cross entropy based method can detect DDoS attacks at the beginning with higher detection rate, lower false alarm than Shannon entropy based method.
Modeling the Implied Volatility Surface-: A Study for S&P 500 Index Option
Jin Zheng,Yan Cai
Research Journal of Applied Sciences, Engineering and Technology , 2013,
Abstract: The aim of this study is to demonstrate a framework to model the implied volatilities of S&P 500 index options and estimate the implied volatilities of stock prices using stochastic processes. In this paper, three models are established to estimate whether the implied volatilities are constant during the whole life of options. We mainly concentrate on the Black-Scholes and Dumas’ option models and make the empirical comparisons. By observing the daily-recorded data of S&P 500 index, we study the volatility model and volatility surface. Results from numerical experiments show that the stochastic volatilities are determined by moneyness rather than constant. Our research is of vital importance, especially for forecasting stock market shocks and crises, as one of the applications.
Research of the Export Rebates Mode for Production Enterprises
Dazhu Yan,Kexin Zheng
Asian Social Science , 2010, DOI: 10.5539/ass.v6n8p183
Abstract: The export rebates is a kind of tax policy usually used in the international trading to enhance the international competitive force of the export goods of native country. In 25 years’ practice, through continual reform and perfection, the export rebates policy of China has exerted very important function to develop the foreign trade and increase the foreign exchange through exports for China. However, with the continual development of economy, the current export rebates mechanism still has some conflicts and problems. The deficiencies existing in the computation mode of “exemption, set off and refund” of export goods of current production enterprises are analyzed and discussed from the view of value added tax, and some improved suggestions are proposed from the tax basis to more scientifically and reasonably exert of the positive function of the export rebates policy in the international trading.
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