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Search Results: 1 - 10 of 127017 matches for " LI Zhenghua "
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Investigation of Patch Antenna Based on Photonic Band-Gap Substrate with Heterostructures
Zhenghua Li,Yan Ling Xue,Tinggen Shen
Mathematical Problems in Engineering , 2012, DOI: 10.1155/2012/151603
Abstract: The characteristics of the patch antenna based on photonic band-gap (PBG) substrate with heterostructures were studied numerically by using the method of finite difference time domain (FDTD). The results indicate that, comparing to the conventional patch antennas, the expansion of working frequency band of the new patch antenna can be realized and its radiation efficiency also can be improved notably with the influence of PBG. In addition, for this new kind of patch antenna, its return loss is much less and there are two minimum values for return loss corresponding to the resonant frequency of the two different photonic crystals made of the substrate. Its physical mechanism lies on the PBG which suppresses the surface waves propagating along the surface of the substrate and reflects most of electromagnetic wave energy radiated to the substrate significantly.
Effects of Ce concentrations on ignition temperature and surface tension of Mg-9wt.%Al alloy
Deng Zhenghua,Li Huaji,Zhao Wanjun
China Foundry , 2013,
Abstract: Magnesium alloys are well known for their excellent properties, but the potential issues with oxidation and burning during melting and casting largely limit its industrial applications. The addition of Ce in magnesium alloys can significantly raise ignition-proof performance and change the structure of the oxide film on the surface of the molten metal as well as the surface tension values. Surface tension is an important physical parameter of the metal melts, and it plays an important role in the formation of surface oxide film. In this present work, the ignition temperature and the surface tension of Mg-9wt.%Al alloy with different Ce concentrations were studied. Surface tensions was measured using the maximum bubble pressure method (MBPM). Ignition temperature was measured using NiCr-NiSi type thermocouples and was monitored and recorded via a WXT-604 desk recording device. The results show that the ignition point of Mg-9wt.%Al alloy can be effectively elevated by adding Ce. The ignition temperature reaches its highest point of 720 ℃ when the addition of Ce is 1wt.%. The surface tension of the molten Mg-9wt.%Al alloy decreases exponentially with the increase of Ce addition at the same temperature. Similarly, the experiment also shows that the surface tension of Mg-9wt.%Al alloy decreases exponentially with the increase of temperature.
Aqua{6,6′-dimethoxy-2,2′-[ethane-1,2-diylbis(nitrilomethylidyne)]diphenolato}nickel(II)
Zhenghua Guo,Lianzhi Li,Tao Xu,Jinghong Li
Acta Crystallographica Section E , 2009, DOI: 10.1107/s1600536809034278
Abstract: The title complex, [Ni(C18H18N2O4)(H2O)], lies on a mirror plane with the NiII ion coordinated by two N and two O atoms of a tetradentate Schiff base ligand and one water O atom in a distorted square-pyramidal enviroment. The –CH2–CH2– group of the ligand is disordered equally over two sites about the mirror plane. The dihedral angle between the mean planes of the two symmetry-related chelate rings is 37.16 (6)°. In the crystal structure, intermolecular O—H...O hydrogen bonds link complex molecules into one-dimensional chains along [100] and these chains are linked, in turn, by very weak intermolecular C—H...O hydrogen bonds into a two-dimensional network.
Bis[μ-N-(3-methoxy-2-oxidobenzylidene-1:2κ2O2:O2)-l-isoleucinato-2κ2N,O]bis(1,10-phenanthroline-1κ2N,N′)dinickel(II) methanol tetrasolvate trihydrate
Yan Li,Zhenghua Guo,Jianfang Dong,Lianzhi Li
Acta Crystallographica Section E , 2012, DOI: 10.1107/s1600536812008987
Abstract: In the title complex, [Ni2(C14H17NO4)2(C12H8N2)2]·4CH3OH·3H2O, the two NiII ions are bridged by two Schiff base anions, leading to a dinuclear complex. One NiII ion is six-coordinated by four O atoms and two N atoms of two tridentate Schiff base ligands derived from the condensation of l-isoleucine and o-vanillin. The other NiII ion is six-coordinated by four N atoms of two 1,10-phenanthroline ligands and two O atoms of the Schiff base ligands. In the crystal, intermolecular O—H...O and C—H...O hydrogen bonds lead to a three-dimensional structure. Intramolecular C—H...O hydrogen bonds are also present. One of the methyl groups of the l-isoleucinate moieties is disordered over two sets of sites with an occupancy ratio of 0.687 (19):0.313 (19) and two methanol molecules are half-occupied.
{N-[(2-Oxido-1-naphthyl)methylidene]serinato-κ3O,N,O′}(1,10-phenanthroline-κ2N,N′)copper(II)
Jinghong Li,Zhenghua Guo,Lianzhi Li,Daqi Wang
Acta Crystallographica Section E , 2010, DOI: 10.1107/s1600536810012675
Abstract: In the title complex, [Cu(C14H11NO4)(C12H8N2)], the tridentate Schiff base ligand is derived from the condensation of 2-hydroxy-1-naphthaldehyde and l-serine. The CuII atom is five-coordinated by one N atom and two O atoms from the Schiff base ligand and by two N atoms from a 1,10-phenanthroline ligand in a distorted square-pyramidal geometry. In the crystal structure, the combination of intermolecular O—H...O and C—H...O hydrogen bonds results in a two-dimensional network structure parallel to (001).
Di-μ-oxido-bis[(4-formyl-2-methoxyphenolato-κO1)oxido(1,10-phenanthroline-κ2N,N′)vanadium(V)]
Zhenghua Guo,Lianzhi Li,Tao Xu,Jinghong Li
Acta Crystallographica Section E , 2009, DOI: 10.1107/s1600536809032516
Abstract: The title complex, [V2(C8H7O3)2O4(C12H8N2)2], is a centrosymmetric dimer formed by two VV complex units bridged by two μ2-oxido groups. The VV atom is six-coordinated by three oxide O atoms, one O atom from a vanillinate ligand and two N atoms from a 1,10-phenanthroline ligand in a significantly distorted octahedral geometry. In the crystal structure, weak intermolecular C—H...O hydrogen bonds connect the molecules into a three-dimensional network.
Bis[1-(2-naphthyliminomethyl)-2-naphtholato-κ2N,O]copper(II)
Zhenghua Guo,Lianzhi Li,Chengyuan Wang,Jinghong Li
Acta Crystallographica Section E , 2009, DOI: 10.1107/s1600536809030694
Abstract: In the title complex, [Cu(C21H14NO)2], the CuII atom, lying on an inversion center, is coordinated by two bidentate 1-(2-naphthyliminomethyl)-2-naphtholate ligands in a trans arrangement, forming a slightly distorted square-planar coordination geometry. The mean planes of two naphthyl systems of the ligand make a dihedral angle of 40.32 (11)°.
Flow injection chemiluminescence determination of levofloxacin in medicine and biological fluids based on its enhancing effect on luminol–H2O2 reaction
Xiaodong Shao,Ying Li,Yangqin Liu,Zhenghua Song
Spectroscopy: An International Journal , 2009, DOI: 10.3233/spe-2009-0379
Abstract: Levofloxacin{(–)-(S)-9-fluoro-2,3-dihydro-3-methyl-10-(4-methyl-1-piperazinyl)-7-oxo-7H-pyrido[1,2,3-de]-1,4-benzoxazine-6-carboxylic acid} is a synthetic fluorinated quinolone derivative, having activity against both Gram (+) and Gram (–) bacteria (aerobic and anaerobic) through inhibition of their DNA gyrase. In this paper, a simple flow injection chemiluminescence with luminol–hydrogen peroxide system was described for determining levofloxacin. The chemiluminescence intensity in the presence of levofloxacin was remarkably enhanced compared with that in the absence of it. Under the optimum reaction conditions the chemiluminescence increment produced was proportional to the concentration of levofloxacin in the range of 1.0–700.0 ng ml–1 (R2═0.9992), with a detection limit of 0.3 ng ml–1 (3σ). At the flow rate of 2.0 ml min–1, the whole process including sampling and washing could be completed in 0.5 min offering the sampling efficiency of 120 times h–1 accordingly, and the relative standard deviation (RSD) was less than 3.0% (n═5). The recovery for the levofloxacin samples was from 95.9% to 104.5%. It was satisfactory for the application to determine levofloxacin in pharmaceutical preparations, human urine and serum samples.
(Methanol-κO)(methanolato-κO)oxido[N-(2-oxidobenzylidene)isoleucinato-κ3O,N,O′]vanadium(V)
Chengyuan Wang,Zhenghua Guo,Jianfang Dong,Lianzhi Li
Acta Crystallographica Section E , 2012, DOI: 10.1107/s1600536812028231
Abstract: In the title complex, [V(C13H15NO3)O(CH3O)(CH3OH)], the VV atom is six-coordinated by a tridentate O,N,O′-donor ligand, derived from the condensation of salicylaldehyde and l-isoleucine, a vanadyl O atom, a methanolate O atom and a methanol O atom in a distorted octahedral geometry. The asymmetric unit contains two complex molecules. In the crystal, intermolecular O—H...O and C—H...O hydrogen bonds connect the molecules into a one-dimensional chain along [100].
(Methoxo-κO)oxidobis(quinolin-8-olato-κ2N,O)vanadium(V)
Zhenghua Guo,Lianzhi Li,Chengyuan Wang,Tao Xu
Acta Crystallographica Section E , 2009, DOI: 10.1107/s1600536809031560
Abstract: In the title complex, [V(C9H6NO)2(CH3O)O], the central VV atom is coordinated by the O atoms from the oxido and methoxo ligands and the N and O atoms of two bis-chelating quinolin-8-olate ligands, forming a distorted octahedral environment. In the crystal structure, weak intermolecular C—H...O hydrogen bonds connect molecules into centrosymmetric dimers which are, in turn, linked by weak C—H...π interactions into chains along the b axis.
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