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Search Results: 1 - 10 of 43020 matches for " Zhijun Xu "
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Absolute cross-section normalization of magnetic neutron scattering data
Guangyong Xu,Zhijun Xu,J. M. Tranquada
Physics , 2013, DOI: 10.1063/1.4818323
Abstract: We discuss various methods to obtain the resolution volume for neutron scattering experiments, in order to perform absolute normalization on inelastic magnetic neutron scattering data. Examples from previous experiments are given. We also try to provide clear definitions of a number of physical quantities which are commonly used to describe neutron magnetic scattering results, including the dynamic spin correlation function and the imaginary part of the dynamic susceptibility. Formulas that can be used for general purposes are provided and the advantages of the different normalization processes are discussed.
C@Ag/TiO2: A Highly Efficient and Stable Photocatalyst Active under Visible Light  [PDF]
Bei Jin, Xiaosong Zhou, Xuyao Xu, Lin Ma, Zhijun Wu, Yingshan Huang
World Journal of Nano Science and Engineering (WJNSE) , 2013, DOI: 10.4236/wjnse.2013.31001
In this paper, preparation and characterization of C@Ag/TiO2 nanospheres compound photocatalysts was reported. C@Ag nanosphere was firstly synthesized via hydrothermal reaction, and followed by a sol-gel process to obtain the functionalized C@Ag/TiO2 nanosphere which has highly efficient visible light catalytic ability towards methyl orange (MO). The morphology of the obtained compound was characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) technologies. From which we can see that the as-prepared samples show a spherical structure with a diameter of approximately 200 nm, and the silver particle in core was about 10 nm. The catalytic ability of the synthesized photocatalysts under visible light irradiation shows that C@Ag/TiO2 possesses higher photocatalytic activity towards MO degradation than that of N-P25 (TiO2). Furthermore, the C@Ag/TiO2 photocatalysts exhibited excellent reusability with almost no change after five runs. Finally, the possible photocatalytic mechanism of catalyst under visible light was discussion and proposed.
A finite-dimensional integrable system associated with a polynomial eigenvalue problem
Taixi Xu,Weihua Mu,Zhijun Qiao
International Journal of Mathematics and Mathematical Sciences , 2006, DOI: 10.1155/ijmms/2006/13479
Abstract: M. Antonowicz and A. P. Fordy (1988) introduced the second-order polynomial eigenvalue problem Lφ=(∂2
First-principles calculations of current-induced spin-transfer torques in magnetic domain walls
Ling Tang,Zhijun Xu,Zejin Yang
Physics , 2013, DOI: 10.1142/S0217979213500926
Abstract: Current-induced spin-transfer torques (STTs) have been studied in Fe, Co and Ni domain walls (DWs) by the method based on the first-principles noncollinear calculations of scattering wave functions expanded in the tight-binding linearized muffin-tin orbital (TB-LMTO) basis. The results show that the out-of-plane component of nonadiabatic STT in Fe DW has localized form, which is in contrast to the typical nonlocal oscillating nonadiabatic torques obtained in Co and Ni DWs. Meanwhile, the degree of nonadiabaticity in STT is also much greater for Fe DW. Further, our results demonstrate that compared to the well-known first-order nonadiabatic STT, the torque in the third-order spatial derivative of local spin can better describe the distribution of localized nonadiabatic STT in Fe DW. The dynamics of local spin driven by this third-order torques in Fe DW have been investigated by the Landau-Lifshitz-Gilbert (LLG) equation. The calculated results show that with the same amplitude of STTs the DW velocity induced by this third-order term is about half of the wall speed for the case of the first-order nonadiabatic STT.
Dielectric and piezoelectric properties of Ba(Zr xTi1-x)O3 lead-free ceramics
Li, Wei;Xu, Zhijun;Chu, Ruiqing;Fu, Peng;Zang, Guozhong;
Brazilian Journal of Physics , 2010, DOI: 10.1590/S0103-97332010000300018
Abstract: lead-free ceramics ba(zrxti1-x)o3 (x = 0.02-0.2) were prepared using a solid-state reaction technique. the structural and electrical properties were systemically investigated. crystalline structures and microstructures were analyzed by x-ray diffraction and scanning electron microscope (sem) at room temperature. all the samples possess pure perovskite structure. a small amount of zr content has great effect on the microstructure of ba(zrxti1-x)o3 ceramics. the homogeneous microstructure with grain size about 30μm is obtained for the sample at x = 0.05. the phase transitions merge together in one peak for the samples at x = 0.10 and the highest dielectric constant 15900 is obtained for the sample at x = 0.15. the ba(zrxti1-x)o3 ceramics at x=0.05 exhibit excellent piezoelectric properties of high d33 = 208 pc/n, kp = 31.5% and qm = 500.
Preparation and luminescence characteristics of Sr3SiO5:Eu2+ phosphor for white LED
PanLai Li,ZhiPing Yang,ZhiJun Wang,QingLin Guo,Xu Li
Chinese Science Bulletin , 2008, DOI: 10.1007/s11434-008-0044-8
Abstract: The Sr3SiO5:Eu2+ phosphor was synthesized by high temperature solid-state reaction. The emission spectrum of Sr3SiO5:Eu2+ shows two bands centered at 487 and 575 nm, which well agree with the theoretic values of emission spectrum. The excitation spectrum for 575 nm emission center has several excitation bands at 365, 418, 458 and 473 nm. And the results show that the emission spectrum of Sr3SiO5:Eu2+ is influenced by the Eu2+ concentration. The relative emission spectra of the white-emitting InGaN-based YAG:Ce3+ LED and Sr3SiO5:Eu2+ LED were investigated. The results show that the color development of InGaN-based Sr3SiO5:Eu2+ is better than that of InGaN-based YAG:Ce3+, and the CIE chromaticity of InGaN-based Sr3SiO5:Eu2+ is (x=0.348, y=0.326).
Performance Study of IEEE 802.11 Broadcast Protocols in Vehicular Networks
Luobei Kuang,Zhijun Wang,Ming Xu,Yingwen Chen
Information Technology Journal , 2011,
Abstract: Vehicular networks are becoming an important way to provide various services. As the broadcast is highly used in vehicular networks, there is a need to study the performance of the broadcast protocols. This study aims to investigate the IEEE 802.11 broadcast protocol performance in the highly mobile vehicular network environments. In this study, we firstly propose a zone based system model to catch up the vehicle mobility and then develop performance models based on analysis of vehicle DCF broadcast behaviors. Based on the models, we figure out the impact of the mobility. The effectiveness validation of the developed models is also verified by simulations.
Synthesis and Characterization of Sodium N,N'-dioctyl-ethylenediamine Diacyl Propionate
Jian Xu,Xiujun Liu,Bin Wang,Zhijun Qiao
International Journal of Chemistry , 2010, DOI: 10.5539/ijc.v2n1p194
Abstract: Sodium N,N'-dioctyl-ethylenediamine diacyl propionate, an anionic gemini surfactant, was synthesized by ethylenediamine with n-octyl bromide, followed by reaction with succinic anhydride, cesium hydroxide and triethylamine as catalyst, through N-alkylation and N-acylation. Structure of the intermediate and final product was characterized by infrared spectrometer and nuclear magnetic resonance apparatus. The influences of material ratio and reaction time on the N-alkylation product yield were investigated. Experimental results showed that the yield of the N-alkylation product reached up to 64% under the optimum reaction conditions, the yield of the N-acylation product was 39%.
Quality Assessment for Systematic Review /Meta-Analysis on Antidepressant Therapy Published in Chinese Journals
Zhijun Xiao,Ye Zhang,Yan Wang,Feng Xu
International Journal of Pharmacology , 2012,
Abstract: A lot of systematic reviews/meta-analyses compiled by Chinese professionals and published in Chinese medical journals bring a lot of perplexity as they help to a certain extent to make decision in some conflicting clinical results. This study aims to assess the quality of systematic reviews and meta-analyses on antidepressant therapy published in Chinese journals. The reviews/meta-analyses on antidepressant therapy were identified by searching three main Chinese data banks i.e., Chinese National Knowledge Infrastructure (CNKI), Wanfang Data (WF) and Chinese Biomedical Literature Database (CBM). A pre-stated criterion was used for review/meta-analysis selection. All reviews were evaluated by two reviewers separately. Data in qualified reviews were extracted into a Microsoft Excel database for analysis. Two assessment tools were used: (1) the Overview Quality Assessment Questionnaire (OQAQ) and (2) Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA). Sixty eight reviews/meta-analyses were included in this study. More than 50% of them had methodological and reporting defects which could have reduced the reliability of the review/meta-analysis results. The flaws were mainly low quality of search strategy, inappropriate bias control and absence of quality assessment for original study.
Chern semi-metal and Quantized Anomalous Hall Effect in HgCr2Se4
Gang Xu,Hongming Weng,Zhijun Wang,Xi Dai,Zhong Fang
Physics , 2011, DOI: 10.1103/PhysRevLett.107.186806
Abstract: In three dimensional (3D) momentum space of solid crystal, a topological phase boundary separating the Chern insulating layers from normal insulating layers may exist, where the gap must be closed, resulting in a "Chern semi-metal" state with topologically unavoidable band-crossings at fermi level. This state, if found to exist, is a condensed-matter realization of chiral fermions (or called Weyl fermions) in (3+1)D, and should exhibit remarkable features, like magnetic monopoles in the bulk and fermi arcs on the surface. Here we predict, based on first-principles calculations, that such novel quantum state can be realized in a known ferromagnetic compound HgCr2Se4, with a single pair of Weyl fermions separated in momentum space. The characteristic feature of this state in HgCr2Se4 is the presence of quantum Hall effect without external magnetic field in its quantum-well structure.
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