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Search Results: 1 - 10 of 34101 matches for " ZHU Pei "
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Microscopic description of neutron emission rates in compound nuclei
Yi Zhu,Junchen Pei
Physics , 2014, DOI: 10.1103/PhysRevC.90.054316
Abstract: The neutron emission rates in thermal excited nuclei are conventionally described by statistical models with a phenomenological level density parameter that depends on excitation energies, deformations and mass regions. In the microscopic view of hot nuclei, the neutron emission rates can be determined by the external neutron gas densities without any free parameters. Therefore the microscopic description of thermal neutron emissions is desirable that can impact several understandings such as survival probabilities of superheavy compound nuclei and neutron emissivity in reactors. To describe the neutron emission rates microscopically, the external thermal neutron gases are self-consistently obtained based on the Finite-Temperature Hartree-Fock-Bogoliubov (FT-HFB) approach. The results are compared with the statistical model to explore the connections between the FT-HFB approach and the statistical model. The Skyrme FT-HFB equation is solved by HFB-AX in deformed coordinate spaces. Based on the FT-HFB approach, the thermal properties and external neutron gas are properly described with the self-consistent gas substraction procedure. Then neutron emission rates can be obtained based on the densities of external neutron gases. The thermal statistical properties of $^{238}$U and $^{258}$U are studied in detail in terms of excitation energies. The thermal neutron emission rates in $^{238, 258}$U and superheavy compound nuclei $_{112}^{278}$Cn and $_{114}^{292}$Fl are calculated, which agree well with the statistical model by adopting an excitation-energy-dependent level density parameter. The coordinate-space FT-HFB approach can provide reliable microscopic descriptions of neutron emission rates in hot nuclei, as well as microscopic constraints on the excitation energy dependence of level density parameters for statistical models.
Quantum phase transition and von Neumann entropy of quasiperiodic Hubbard chains

Zhu Xuan,Tong Pei-Qing,

中国物理 B , 2008,
Abstract: The half-filled Hubbard chains with the Fibonacci and Harper modulating site potentials are studied in a self-consistent mean-field approximation. A new order parameter is introduced to describe a charge density order. We also calculate the von Neumann entropy of the ground state. The results show that the von Neumann entropy can identify a CDW/SDW (charge density wave/spin density wave) transition for quasiperiodic models.
Relationship between micro-porosity and tensile properties of 6063 alloy
Li Xiehua,He Lizi,Zhu Pei
China Foundry , 2013,
Abstract: The micro-porosity is usually present in the as-cast microstructure, which decreases the tensile strength and ductility and therefore limit the application of cast aluminum parts. Although much work has been done to investigate the effects of various casting parameters on the formation of porosity in various aluminum alloys, up to now, little information has been available for the relationship between micro-porosity and tensile properties of 6063 alloy. In this study, the influences of size and area fraction of micro-porosity on the tensile properties and fracture behavior of 6063 aluminum alloy were investigated by means of tensile testing, optical microscopy (OM), and scanning electron microscopy (SEM). The tensile tests were conducted in air at 100 ℃, 200 ℃ and 300 ℃, respectively. Results show that the large micro-porosity with sizes between 100 μm and 800 μm located at the center and top of the ingot, while the small micro-porosity with size between 2 μm and 60 μm distributed at the edge and bottom of the ingot. The area fraction of micro-porosity at the center of the ingot is much bigger than that at the edge of the ingot. When tested at 100 ℃, with the decrease in the area fraction of micro-porosity from the top of the ingot to the bottom of the ingot, the ultimate tensile strength, yield strength and the elongation are increased from 82 to 99 MPa, 32 to 66 MPa and 7% to 11%, respectively. When the temperature is no more than 200 ℃, the strain hardening exponent decreases with an increase in the area fraction of micro-porosity; while the deviation disappears when the temperature reaches 300 ℃. The fracture mode of the alloy is greatly influenced by the size and area fraction of the micro-porosity.
LED Modulation Characteristics in a Visible-Light Communication System  [PDF]
Yanrong Pei, Shaoxin Zhu, Hua Yang, Lixia Zhao, Xiaoyan Yi, Junxi Junxi Wang, Jinmin Li
Optics and Photonics Journal (OPJ) , 2013, DOI: 10.4236/opj.2013.32B034
Abstract:

This paper conducts a research on modulation characteristics of blue light-emitting diodes (LEDs) used in a visible-light communication (VLC) system. Through analysis of the modulation characteristics of LEDs with different emitting sizes, we find that there is a similar linear relationship between LED’s 3dB bandwidth and the operation current density. This experiment also shows that high series resistance is one major issue that limits our LED's modulation speed. To further improve the LED bandwidth, the resistance can be reduced by optimizing device layout as well as reducing material bulk resistance. Clearly, this study provides an approach to increase the modulation bandwidth of GaN-based LEDs for VLC systems.

Interlayer Coupling in Magnetic/Pd Multilayers
Zhu-Pei Shi,Barry M. Klein
Physics , 1995,
Abstract: The Anderson model of local-state conduction electron mixing is applied to the p roblem of interlayer magnetic coupling in metallic multilayered structures with palladium (Pd) spacer layers. An oscillation period of $5$ spacer monolayers and the tendency towards ferromag netic bias of the interlayer magnetic coupling that we obtain are consistent with the experimental data.
Lie bialgebra structures on the twisted Heisenberg-Virasoro algebra
Dong Liu,Yufeng Pei,Linsheng Zhu
Mathematics , 2010,
Abstract: In this paper we investigate Lie bialgebra structures on the twisted Heisenberg-Virasoro algebra. With the classifications of Lie bialgebra structures on the Virasoro algebra, we determined such structures on the twisted Heisenberg-Virasoro algebra. Moreover, some general and useful results are obtained. With our methods and results we also can easily to determine such structures on some Lie algebras related to the twisted Heisenberg-Virasoro algebra.
Bis(μ-4-hydroxybenzoato-κ2O:O′)bis[triaquabis(4-hydroxybenzoato)-κO;κ2O,O′-terbium(III)] decahydrate
Yi-Min Zhu,Pei-Pei Feng,Yang-Yi Yang,Seik Weng Ng
Acta Crystallographica Section E , 2010, DOI: 10.1107/s1600536809052489
Abstract: The title dinuclear compound, [Tb2(C7H5O3)6(H2O)6]·10H2O, lies on a center of inversion and the two TbIII atoms are bridged by two 4-hydroxybenzoate anions; each metal atom is further coordinated by one monodentate anion and chelated by the third anion. The eight-coordinate geometry approximates a square antiprism. Hydrogen bonds of the O—H...O type connect the uncoordinated water molecules to the dinuclear species, forming a three-dimensional network.
Identification of a Key Amino Acid of LuxS Involved in AI-2 Production in Campylobacter jejuni
Paul Plummer,Jinge Zhu,Masato Akiba,Dehua Pei,Qijing Zhang
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0015876
Abstract: Autoinducer-2 (AI-2) mediated quorum sensing has been associated with the expression of virulence factors in a number of pathogenic organisms and has been demonstrated to play a role in motility and cytolethal distending toxin (cdt) production in Campylobacter jejuni. We have initiated the work to determine the molecular basis of AI-2 synthesis and the biological functions of quorum sensing in C. jejuni. In this work, two naturally occurring variants of C. jejuni 81116 were identified, one producing high-levels of AI-2 while the other is defective in AI-2 synthesis. Sequence analysis revealed a G92D mutation in the luxS gene of the defective variant. Complementation of the AI-2? variant with a plasmid encoded copy of the wild-type luxS gene or reversion of the G92D mutation by site-directed mutagenesis fully restored AI-2 production by the variant. These results indicate that the G92D mutation alone is responsible for the loss of AI-2 activity in C. jejuni. Kinetic analyses showed that the G92D LuxS has a ~100-fold reduced catalytic activity relative to the wild-type enzyme. Findings from this study identify a previously undescribed amino acid that is essential for AI-2 production by LuxS and provide a unique isogenic pair of naturally occurring variants for us to dissect the functions of AI-2 mediated quorum sensing in Campylobacter.
A soluble polymer-supported NADH model: Synthesis and application
LianRui Mei,Xiao-Qing Zhu,Jin-Pei Cheng
Chinese Science Bulletin , 2010, DOI: 10.1007/s11434-010-3205-5
Abstract: A polyethylene glycol (PEG)-supported NADH model as a novel organic reductant was designed and synthesized. The reductions of various α, β-unsaturated ketones by the PEG-supported NADH model were examined, and the results showed that the reductions completely and quickly proceed with no catalyst at ambient temperature. The main advantages of this liquid-like PEG-supported NADH model are easy workup, and an optimal potential for recycling use and solvent-free for use in reactions.
On the Structure and Nature of Glass
论玻璃结构及其本质

ZHU Pei-Nan,
诸培南

无机材料学报 , 2003,
Abstract: The author reveiws the works on study of the structure and nature of glass, done by the author and his colleagues, in the past 20 years. Some important conclusions indicated that glass as the non-crystalline solid, its structure may contain two types of agglomerated atoms or atomic groups, i.e., disorder groups and ordered orientated (one dimensionally prefered) groups. In addition, a little quantity (negligible) of nano-crystals may appear as a particular role in real glass and this characteristic may distinguish it from ideal glass. A table is shown for interpretating more briefly. A schematic diagram of fused silica glass structure is designed by the author and provided here, so, it may express the stucture and nature of glass with its reasonable scientific recognition.
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