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Search Results: 1 - 10 of 36124 matches for " Kai Sun "
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Task-based Approach in College English Teaching of Digital-based Context
Ling Jiang,Kai Sun
International Journal of Modern Education and Computer Science , 2010,
Abstract: With the wide employment of modern educational technology, college English teaching is going on a process of replacing traditional educational media with modern ones, which are closely connected with multimedia computers and internet technology to raise its efficiency and quality. However, some problems and challenges still exist in the college English teaching. In order to solve the problems, this article designs a test and collects data to check the effectiveness of the task-based approach within the Internet-assisted multimedia in college English teaching. The results show that Linguistic form was analyzed and practiced with task-based approach which may help the learners notice the linguistic problems and try out new language forms and structures, and that Internet-assisted multimedia has been effective in intriguing learners' interests and greatly enhanced their self-esteem.
Generalized Fuzzy Metric Spaces with Properties
Guangpeng Sun,Kai Yang
Research Journal of Applied Sciences, Engineering and Technology , 2010,
Abstract: In this study, the notion of Q-fuzzy metric space is introduced and some properties are obtained. Two new common fixed point theorem s are proved in Q-fuzzy metric spaces under some suitable conditions.
The Construction of China’s Environmental Public Interest Litigation Mechanism
Canadian Social Science , 2012, DOI: 10.3968/j.css.1923669720120806.8085
Abstract: The environmental public interest litigation could promote the execution of environmental law and provide the public a way to anticipate. In order to protect the public participation in environmental justice, before public interest litigation, we should establish a consultation mechanism. Key words: Public participation; Public interest litigation; Consultation mechanism
Time-Reversal Symmetry Breaking and Spontaneous Anomalous Hall Effect in Fermi Fluids
Kai Sun,Eduardo Fradkin
Physics , 2008, DOI: 10.1103/PhysRevB.78.245122
Abstract: We study the spontaneous non-magnetic time-reversal symmetry breaking in a two-dimensional Fermi liquid without breaking either the translation symmetry or the U(1) charge symmetry. Assuming that the low-energy physics is described by fermionic quasiparticle excitations, we identified an "emergent" local $U(1)^N$ symmetry in momentum space for an $N$-band model. For a large class of models, including all one-band and two-band models, we found that the time-reversal and chiral symmetry breaking can be described by the $U(1)^N$ gauge theory associated with this emergent local $U(1)^N$ symmetry. This conclusion enables the classification of the time-reversal symmetry-breaking states as types I and II, depending on the type of accompanying spatial symmetry breaking. The properties of each class are studied. In particular, we show that the states breaking both time-reversal and chiral symmetries are described by spontaneously generated Berry phases. We also show examples of the time-reversal symmetry-breaking phases in several different microscopically motivated models and calculate their associated Hall conductance within a mean-field approximation. The fermionic nematic phase with time-reversal symmetry breaking is also presented and the possible realizations in strongly correlated models such as the Emery model are discussed.
Power System Dynamic State Estimation by Unscented Kalman Filter with Guaranteed Positive Semidefinite State Covariance
Junjian Qi,Kai Sun
Mathematics , 2014,
Abstract: In this paper an unscented Kalman filter with guaranteed positive semidefinite state covariance is proposed by calculating the nearest symmetric positive definite matrix in Frobenius norm and is applied to power system dynamic state estimation. The proposed method is tested on NPCC 48-machine 140-bus system and the results validate its effectiveness.
Power System Differential-Algebraic Equations
Bin Wang,Kai Sun
Computer Science , 2015,
Abstract: This document presents an introduction of two commonly used power system differential algebraic equations for studying electromechanical oscillation and transient stability. Two types of generator models are used to formulate the power system model, respectively: the second-order classical model and the fourth-order generator model. An example is provided on the IEEE 9-bus system.
Finding Semi-Analytic Solutions of Power System Differential-Algebraic Equations for Fast Transient Stability Simulation
Nan Duan,Kai Sun
Computer Science , 2014,
Abstract: This paper studies the semi-analytic solution (SAS) of a power system's differential-algebraic equation. A SAS is a closed-form function of symbolic variables including time, the initial state and the parameters on system operating conditions, and hence able to directly give trajectories on system state variables, which are accurate for at least a certain time window. A two-stage SAS-based approach for fast transient stability simulation is proposed, which offline derives the SAS by the Adomian Decomposition Method and online evaluates the SAS for each of sequential time windows until making up a desired simulation period. When applied to fault simulation, the new approach employs numerical integration only for the fault-on period to determine the post-disturbance initial state of the SAS. The paper further analyzes the maximum length of a time window for a SAS to keep its accuracy, and accordingly, introduces a divergence indicator for adaptive time windows. The proposed SAS-based new approach is validated on the IEEE 10-machine, 39-bus system.
An Analytical Formulation of Power System Oscillation Frequency
Bin Wang,Kai Sun
Computer Science , 2015,
Abstract: This letter proposes an analytical approach to formulate the power system oscillation frequency under a large disturbance. A fact is revealed that the oscillation frequency is only the function of the oscillation amplitude when the system's model and operating condition are fixed. Case studies also show that this function is damping-insensitive and could be applied to an inter-area model of a multi-machine power system.
Ultrasensitive Detection of Glyphosate Using CdTe Quantum Dots in Sol-Gel-Derived Silica Spheres Coated with Calix[6]arene as Fluorescent Probes  [PDF]
Tao Li, Yunyou Zhou, Junyong Sun, Kai Wu
American Journal of Analytical Chemistry (AJAC) , 2012, DOI: 10.4236/ajac.2012.31003
Abstract: We have developed a simple method for the preparation of highly fluorescent and stable, water-soluble CdTe quantum dots in sol-gel-derived composite silica spheres which were coated with calix[6]arene. The resulting nanoparticles (NPs) were characterized in terms of UV, fluorescence and FT-IR spectroscopy and TEM. The results show that the new NPs display more intense fluorescence intensity and are more stable than its precursors of the type SiO2/CdTe. Under the optimum, the novel NPs exhibit a higher selectivity and ultrasensitive fluorescence probes for the determination of gly-phosate over other pesticides, the fluorescence intensity increase with the concentration of glyphosate in the range from 1.0 to 25.0 nmol/L and the detection limit is low to 0.0725 nmol/L. A mechanism is suggested to explain the inclusion process by a Langmuir binding isotherm.
Small-Signal Stability Analysis of Wind Power System Based on DFIG  [PDF]
Bin Sun, Zhengyou He, Yong Jia, Kai Liao
Energy and Power Engineering (EPE) , 2013, DOI: 10.4236/epe.2013.54B081
Abstract: This paper focuses on the small-signal stability of power system integrated with DFIG-based wind farm. The model of DFIG for small-signal stability analysis has built; the 3-generator 9-bus WECC test system is modified to investigate the impacts of large scale integration of wind power on power system small-signal stability. Different oscillatory modes are obtained with their eigenvalue, frequency and damping ratio, the results from eigenvalue analysis are presented to demonstrate the small-signal stability of power system is enhanced with the increasing output of the wind farm.
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