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Search Results: 1 - 10 of 411631 matches for " J Wang "
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A Control Strategy for Smoothing Active Power Fluctuation of Wind Farm with Flywheel Energy Storage System Based on Improved Wind Power Prediction Algorithm  [PDF]
J. C. Wang, X. R. Wang
Energy and Power Engineering (EPE) , 2013, DOI: 10.4236/epe.2013.54B075
Abstract: The fluctuation of active power output of wind farm has many negative impacts on large-scale wind power integration into power grid. In this paper, flywheel energy storage system (FESS) was connected to AC side of the doubly-fed induction generator (DFIG) wind farm to realize smooth control of wind power output. Based on improved wind power prediction algorithm and wind speed-power curve modeling, a new smooth control strategy with the FESS was proposed. The requirement of power system dispatch for wind power prediction and flywheel rotor speed limit were taken into consideration during the process. While smoothing the wind power fluctuation, FESS can track short-term planned output of wind farm. It was demonstrated by quantitative analysis of simulation results that the proposed control strategy can smooth the active power fluctuation of wind farm effectively and thereby improve power quality of the power grid.
A Comparative Study of Two Schools: How School Cultures Interplay the Development of Teacher Leadership in Mainland China  [PDF]
Feiye Wang, Sally J. Zepeda
Creative Education (CE) , 2013, DOI: 10.4236/ce.2013.49B013
Abstract:

This article seeks to gain an understanding of the interrelated relationship between school cultures and the teacher leadership development by comparing the experience of teacher leaders’ from two middle schools in China that exhibited different kinds of school culture. The researchers argue that the better the school culture was, the more prospective Teacher leaders would develop and the better Teacher leaders would enact their leadership, which further would reinforce the building of a healthy school culture.

 

Historical earthquake investigation and research in China
J. Wang
Annals of Geophysics , 2004, DOI: 10.4401/ag-3337
Abstract: China is one of the countries with the longest tradition of culture and has suffered many earthquake disasters, so many earthquake documents have therefore been conserved. In this paper we try to outline some basic information of historical earthquake investigation and research in China, such as collection of historical earthquake data from archives, historical earthquake catalogues, seismic intensity scales. We introduce briefly the huge accomplishments of historical research and discuss some problems encountered. Through examples, we illustrate the solutions to some typical problems. There are some suggestions on further work.
Role of Feedback in AGN-HOST Coevolution: A Study from Partially Obscured Active Galactic Nuclei
J. Wang
Physics , 2014, DOI: 10.1016/j.newast.2014.11.004
Abstract: Partially obscured AGNs within a redshift range $z=0.011\sim0.256$ are used to re-study the role of feedback in the AGN-host coevolution issue in terms of their [OIII]$\lambda$5007 emission line profile. The spectra of these objects enable us to determine the AGN's accretion properties directly from their broad H$\alpha$ emission. This is essential for getting rid of the "circular reasoning" in our previous study of narrow emission-line galaxies, in which the [OIII] emission line was used not only as a proxy of AGN's bolometric luminosity, but also as a diagnostic of outflow. In addition, the measurement of $D_n(4000)$ index is improved by removing an underlying AGN's continuum according to the corresponding broad H$\alpha$ emission. With these improvements, we confirm and reinforce the correlation between $L/L_{\mathrm{Edd}}$ and stellar population age. More important is that this correlation is found to be related to both [OIII] line blue asymmetry and bulk blueshift velocity, which suggests a linkage between SMBH growth and host star formation through the feedback process. The current sample of partially obscured AGNs shows that the composite galaxies have younger host stellar population, higher Eddington ratio, less significant [OIII] blue wing and smaller bulk [OIII] line shift than do the Seyfert galaxies .
Evidence of Contribution of Intervening Clouds to GRB's X-ray Column Density
J. Wang
Physics , 2013, DOI: 10.1088/0004-637X/776/2/96
Abstract: The origin of excess of X-ray column density with respect to optical extinction in Gamma-ray bursts (GRBs) is still a puzzle. A proposed explanation of the excess is the photoelectric absorption due to the intervening clouds along a GRB's line-of-sight. We here test this scenario by using the intervening \ion{Mg}{2} absorption as a tracer of the neutral hydrogen column density of the intervening clouds. We identify a connection between large X-ray column density (and large column density ratio of $\mathrm{\log(N_{H,X}/N_{HI})}\sim0.5$) and large neutral hydrogen column density probed by the \ion{Mg}{2} doublet ratio (DR). In addition, GRBs with large X-ray column density (and large ratio of $\mathrm{\log(N_{H,X}/N_{HI})}>0$) tend to have multiple saturated intervening absorbers with $\mathrm{DR<1.2}$. These results therefore indicate an additional contribution of the intervening system to the observed X-ray column density in some GRBs, although the contribution of the host galaxy alone cannot be excluded based on this study.
Rank three Nichols algebras of diagonal type over fields of positive characteristic
J. Wang
Mathematics , 2015,
Abstract: Over fields of arbitrary characteristic we classify all rank three Nichols algebras of diagonal type with a finite root system. Our proof uses the classification of the finite Weyl groupoids of rank three.
Jitter Self-Compton Process: GeV Emission of GRB 100728A
J. Mao,J. Wang
Physics , 2012, DOI: 10.1088/0004-637X/748/2/135
Abstract: Jitter radiation, the emission of relativistic electrons in a random and small-scale magnetic field, has been applied to explain the gamma-ray burst (GRB) prompt emission. The seed photons produced from jitter radiation can be scattered by thermal/nonthermal electrons to the high-energy bands. This mechanism is called jitter self-Compton (JSC) radiation. GRB 100728A, which was simultaneously observed by the Swift and Fermi, is a great example to constrain the physical processes of jitter and JSC. In our work, we utilize jitter/JSC radiation to reproduce the multiwavelength spectrum of GRB 100728A. In particular, due to JSC radiation, the powerful emission above the GeV band is the result of those jitter photons in X-ray band scattered by the relativistic electrons with a mixed thermal-nonthermal energy distribution. We also combine the geometric effect of microemitters to the radiation mechanism, such that the "jet-in-jet" scenario is considered. The observed GRB duration is the result of summing up all of the contributions from those microemitters in the bulk jet.
Application of Jitter Radiation: Gamma-ray Burst Prompt Polarization
J. Mao,J. Wang
Physics , 2013, DOI: 10.1088/0004-637X/776/1/17
Abstract: A high-degree of polarization of gamma-ray burst (GRB) prompt emission has been confirmed in recent years. In this paper, we apply jitter radiation to study the polarization feature of GRB prompt emission. In our framework, relativistic electrons are accelerated by turbulent acceleration. Random and small-scale magnetic fields are generated by turbulence. We further determine that the polarization property of GRB prompt emission is governed by the configuration of the random and small-scale magnetic fields. A two-dimensional compressed slab, which contains stochastic magnetic fields, is applied in our model. If the jitter condition is satisfied, the electron deflection angle in the magnetic field is very small and the electron trajectory can be treated as a straight line. A high-degree of polarization can be achieved when the angle between the line of sight and the slab plane is small. Moreover, micro-emitters with mini-jet structure are considered to be within a bulk GRB jet. The jet "off-axis" effect is intensely sensitive to the observed polarization degree. We discuss the depolarization effect on GRB prompt emission and afterglow. We also speculate that the rapid variability of GRB prompt polarization may be correlated with the stochastic variability of the turbulent dynamo or the magnetic reconnection of plasmas.
Gamma-ray Burst Prompt Emission: Jitter Radiation in Stochastic Magnetic Field Revisited
J. Mao,J. Wang
Physics , 2011, DOI: 10.1088/0004-637X/731/1/26
Abstract: We revisit the radiation mechanism of relativistic electrons in the stochastic magnetic field and apply it to the high-energy emissions of gamma-ray bursts (GRBs). We confirm that jitter radiation is a possible explanation for GRB prompt emission in the condition of a large electron deflection angle. In the turbulent scenario, the radiative spectral property of GRB prompt emission is decided by the kinetic energy spectrum of turbulence. The intensity of the random and small-scale magnetic field is determined by the viscous scale of the turbulent eddy. The microphysical parameters $\epsilon_e$ and $\epsilon_B$ can be obtained. The acceleration and cooling timescales are estimated as well. Due to particle acceleration in magnetized filamentary turbulence, the maximum energy released from the relativistic electrons can reach a value of about $10^{14}$ eV. The GeV GRBs are possible sources of high-energy cosmic-ray.
Using Optimized Distributional Parameters as Inputs in a Sequential Unsupervised and Supervised Modeling of Sunspots Data  [PDF]
K. Mwitondi, J. Bugrien, K. Wang
Journal of Software Engineering and Applications (JSEA) , 2013, DOI: 10.4236/jsea.2013.67B007
Abstract:

Detecting naturally arising structures in data is central to knowledge extraction from data. In most applications, the main challenge is in the choice of the appropriate model for exploring the data features. The choice is generally poorly understood and any tentative choice may be too restrictive. Growing volumes of data, disparate data sources and modelling techniques entail the need for model optimization via adaptability rather than comparability. We propose a novel two-stage algorithm to modelling continuous data consisting of an unsupervised stage whereby the algorithm searches through the data for optimal parameter values and a supervised stage that adapts the parameters for predictive modelling. The method is implemented on the sunspots data with inherently Gaussian distributional properties and assumed bi-modality. Optimal values separating high from lows cycles are obtained via multiple simulations. Early patterns for each recorded cycle reveal that the first 3 years provide a sufficient basis for predicting the peak. Multiple Support Vector Machine runs using repeatedly improved data parameters show that the approach yields greater accuracy and reliability than conventional approaches and provides a good basis for model selection. Model reliability is established via multiple simulations of this type.

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