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Search Results: 1 - 10 of 28591 matches for " Xiaojing Zhu "
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First Principles Calculations of Hydrogen Storage on Calcium-Decorated, Boron-Doped Bilayer Graphene  [PDF]
Xiaojing Zhu
Journal of Materials Science and Chemical Engineering (MSCE) , 2018, DOI: 10.4236/msce.2018.611001
Abstract: In this paper, the adsorption and storage of hydrogen on calcium-decorated, boron-doped bilayer graphene was investigated using first principles calculation. The calcium-decorated bilayer graphene was investigated and it was shown that the binding energy of H2 molecule adsorbed on the calcium-decorated bilayer graphene is 0.02 eV and the energy does not belong to reversible usage range of 0.2 - 0.6 eV. Substitutional boron doping can improve the adsorption energy of Ca to bilayer graphene with the empty pz orbital of boron atoms. Our calculations show that calcium atoms can be solidly adsorbed on the interlayer (Ca/B/Graphene) and outerlayer (2Ca/B/Graphene and 3Ca/B/Graphene) of B-doped bilayer graphene. Hydrogen molecule binds with Ca/B/Graphene, 2Ca/B/Graphene and 3Ca/B/Graphene system with an energy that belongs to reversible usage range of 0.2 - 0.6 eV. The overlap between Ca 3d and H2σ orbitals just below the Fermi energy demonstrates the charge transfer between the Ca atom and the H atom and the role of hybridization of the 3d orbita of Ca with the σ orbitals of H2 in efficient adsorption of hydrogen molecules. The charge from hydrogen bonding orbital transfers to empty 3d orbitals of the Ca atom, and then from the 3d orbitals of the Ca atom donated to H2σ* antibonding orbital. Hydrogen moleculars can be adsorbed on the interlayer and outerlayer of Ca-decorated B-doped bilayer graphene.
Matrix Padé-Type Method for Computing the Matrix Exponential  [PDF]
Chunjing Li, Xiaojing Zhu, Chuanqing Gu
Applied Mathematics (AM) , 2011, DOI: 10.4236/am.2011.22028
Abstract: Matrix Padé approximation is a widely used method for computing matrix functions. In this paper, we apply matrix Padé-type approximation instead of typical Padé approximation to computing the matrix exponential. In our approach the scaling and squaring method is also used to make the approximant more accurate. We present two algorithms for computing and for computing with many espectively. Numerical experiments comparing the proposed method with other existing methods which are MATLAB’s functions expm and funm show that our approach is also very effective and reliable for computing the matrix exponential . Moreover, there are two main advantages of our approach. One is that there is no inverse of a matrix required in this method. The other is that this method is more convenient when computing for a fixed matrix A with many t ≥ 0.
A new double trust regions SQP method without a penalty function or a filter
Xiaojing Zhu,Dingguo Pu
Computational and Applied Mathematics , 2012, DOI: 10.1590/s1807-03022012000200011
Abstract: A new trust-region SQP method for equality constrained optimization is considered. This method avoids using a penalty function or a filter, and yet can be globally convergent to first-order critical points under some reasonable assumptions. Each SQP step is composed of a normal step and a tangential step for which different trust regions are applied in the spirit of Gould and Toint [Math. Program., 122 (2010), pp. 155-196]. Numerical results demonstrate that this new approach is potentially useful. Mathematical subject classification: 65K05, 90C30, 90C55.
Cyclic DNA codes over F2+uF2+vF2+uvF2
Shixin Zhu,Xiaojing Chen
Mathematics , 2015,
Abstract: In this work, we study the structure of cyclic DNA codes of arbitrary lengths over the ring R=F2+uF2+vF2+uvF2 and establish relations to codes over R1=F2+uF2 by defining a Gray map between R and R1^2 where R1 is the ring with 4 elements. Cyclic codes of arbitrary lengths over R satisfied the reverse constraint and the reverse-complement constraint are studied in this paper. The GC content constraint is considered in the last.
Robust Distributed Maximum Likelihood Estimation with Dependent Quantized Data
Xiaojing Shen,Pramod K. Varshney,Yunmin Zhu
Mathematics , 2012,
Abstract: In this paper, we consider distributed maximum likelihood estimation (MLE) with dependent quantized data under the assumption that the structure of the joint probability density function (pdf) is known, but it contains unknown deterministic parameters. The parameters may include different vector parameters corresponding to marginal pdfs and parameters that describe dependence of observations across sensors. Since MLE with a single quantizer is sensitive to the choice of thresholds due to the uncertainty of pdf, we concentrate on MLE with multiple groups of quantizers (which can be determined by the use of prior information or some heuristic approaches) to fend off against the risk of a poor/outlier quantizer. The asymptotic efficiency of the MLE scheme with multiple quantizers is proved under some regularity conditions and the asymptotic variance is derived to be the inverse of a weighted linear combination of Fisher information matrices based on multiple different quantizers which can be used to show the robustness of our approach. As an illustrative example, we consider an estimation problem with a bivariate non-Gaussian pdf that has applications in distributed constant false alarm rate (CFAR) detection systems. Simulations show the robustness of the proposed MLE scheme especially when the number of quantized measurements is small.
Distributed Bayesian Detection Under Unknown Observation Statistics
Xiaojing Shen,Pramod K. Varshney,Yunmin Zhu
Mathematics , 2012,
Abstract: In this paper, distributed Bayesian detection problems with unknown prior probabilities of hypotheses are considered. The sensors obtain observations which are conditionally dependent across sensors and their probability density functions (pdf) are not exactly known. The observations are quantized and are sent to the fusion center. The fusion center fuses the current quantized observations and makes a final decision. It also designs (updated) quantizers to be used at the sensors and the fusion rule based on all previous quantized observations. Information regarding updated quantizers is sent back to the sensors for use at the next time. In this paper, the conditional joint pdf is represented in a parametric form by using the copula framework. The unknown parameters include dependence parameters and marginal parameters. Maximum likelihood estimation (MLE) with feedback based on quantized data is proposed to estimate the unknown parameters. These estimates are iteratively used to refine the quantizers and the fusion rule to improve distributed detection performance by using feedback. Numerical examples show that the new detection method based on MLE with feedback is much better than the usual detection method based on the assumption of conditionally independent observations.
Stabilization of Neoclassical Tearing Modes by rf Current  [PDF]
Xiaojing Wang, Xiaodong Zhang, Qingquan Yu, Yang Zhang, Sizheng Zhu, Xiaoguang Wang, Bin Wu
World Journal of Engineering and Technology (WJET) , 2017, DOI: 10.4236/wjet.2017.54B011
Abstract:
Neoclassical tearing mode (NTM) can degrade plasma confinement or even cause disruptions in existing tokamaks. Stabilization of the NTMs by radio frequency (rf) current is investigated by the modified Rutherford equation (MRE) in this paper. In a range of parameters, the required rf current for mode stabilization is obtained, which is linearly proportional to the bootstrap current density for both modulated current drive (MCD) and non-modulated current drive (NMCD), linearly (quadratically) to the radial width of the rf current for MCD (NMCD), and quadratically to the radial deviation of the rf current from the rational surface for both MCD and NMCD.
Microfinance in Fisheries in China  [PDF]
Xiaojing Wang
Open Journal of Social Sciences (JSS) , 2015, DOI: 10.4236/jss.2015.35001
Abstract:

Because of lack of collateral and formal financial information, family aquacultures and small boat owners find it difficult to get loans from formal financial institutions. Fishery microfinance can partly solve the information asymmetry and incomplete contract problems in rural financial market, and it is an effective complement to formal fishery finance. The service object of fishery microfinance is mainly micro-enterprises in fisheries, including family aquacultures and small fishing boats. Fishery microfinance providers include formal financial institutions and many kinds of micro-financial institutions, among which China Fishery Mutual Insurance Association (FMIA) is the most famous one. Although micro-finance has a 20-year-history in China, there are still some problems that block its advance. The market is huge, but the existing providers are not providing good services and most are not sustainable. There is still a long way towards commercial operation and financial sustainability.

Research on the Innovation of Employment Guidance in Universities under the Integrate Innovation & Entrepreneurship Education Background
—Based on the Survey of Universities in North Henan
 [PDF]

Xiaojing Liu
Creative Education (CE) , 2017, DOI: 10.4236/ce.2017.815170
Abstract: The background of “Innovation and Entrepreneurship” education puts forward higher requirements for employment guidance in colleges and universities. This paper investigates the current status of employment guidance in Local Universities in North Henan by questionnaire and interview. It indicates that several problems exist in the content and method, ideas and team of university employment guidance. Therefore, on the base of investigation, practice and rethink, this article summarizes?and drawson the experiences of employment guide, and puts?forward the innovational suggestions and strategies of employment guide in domestic colleges and universities. Employment guidance will be better by constructing a diversified employment guidance platform, enriching the contents and methods of employment guidance, building high-quality of instructors and establishing employment guidance ideas form government, enterprises and colleges.
Oscillation Theorems for a Class of Nonlinear Second Order Differential Equations with Damping  [PDF]
Xiaojing Wang, Guohua Song
Advances in Pure Mathematics (APM) , 2013, DOI: 10.4236/apm.2013.31A032
Abstract:

The oscillatory behavior of solutions of a class of second order nonlinear differential equations with damping is studied and some new sufficient conditions are obtained by using the refined integral averaging technique. Some well known results in the literature are extended. Moreover, two examples are given to illustrate the theoretical analysis.

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