检索结果-南通市图书馆

Operators on Differential Form Spaces for Riemann Surfaces

在线全文

学校读者我要写书评

暂无评论

Acta Mathematica Sinica,English Series 2007年第5期23卷 925-934页

作者： guang Fu CAO xiao Feng WANG Department of Mathematics Guangzhou University Guangzhou 510405 P. R. China

In the present paper, a problem of Ioana Mihaila is negatively answered on the invertibility of composition operators on Riemann surfaces, and it is proved that the composition operator Cp is Predholm if and only if it is invertible if and only if p is invertible for some special cases. In addition, the Toeplitz operators on ∧1 2, a（M） for Riemann surface M are defined and some properties of these operators are discussed.

关键词： Riemann surface Composition operator Toeplitz operator

High-temperature oxidation behavior of DZ125 Ni-based superalloy under tensile stress

在线全文

学校读者我要写书评

暂无评论

Rare Metals 2022年第12期41卷 4188-4193页

作者： Hong-Yu Qi xiao-Bo Liang Shao-Lin Li xiao-guang Yang School of Energy and Power Engineering Beihang UniversityBeijing 100191China Collaborative Innovation Center of Advanced Aero-Engine Beijing 100191China

The key in antioxidant capacity of aero-engine hot components is the protective oxide *** factors can affect the performance of oxide *** effect of tensile stress on high-temperature oxidation behavior of directionally solidified DZ125 Ni-based superalloy was investigated by thermogravimetric analysis(TGA).Tensile samples were subjected to stress of 100 MPa,and the oxidation behavior was studied at 980℃in *** surface and cross-sectional morphologies of the oxidized coating were analyzed by scanning electron microscope(SEM).The influence of tensile stress on the oxidation behavior of directionally solidified DZ125 Ni-based superalloy at high temperature was *** show that an applied tensile stress generally leads to larger Cr/Ni mass ratio in the oxide scales,greater overall chromium depletion values directly under the oxide scales,lower specific weight gain values and thinner oxide *** factors are attributed to the formation of fast diffusion paths for Cr atoms to diffuse to the surface under tensile stress,thus causing a reduction in the duration of the less protective transient oxidation period and promoting a faster formation of the protective Cr_(2)O_(3)layer.

关键词： DZ125 Ni-based superalloy High-temperature oxidation Tensile stress Diffusion

Free cupric ions in contaminated agricultural soils around a copper mine in eastern Nanjing City, China

在线全文

学校读者我要写书评

暂无评论

Journal of Environmental Sciences 2006年第5期18卷 927-931页

作者： LUO xiao-san ZHOU Dong-mei WANG Yu-jun State Key Laboratory of Soil and Sustainable Agriculture Institute of Soil Science Chinese Academy of Sciences Nanjing 210008 China Graduate School of the Chinese Academy of Sciences Beijing 100039 China

To determine the environmental free metal ion activity was a recent hot issue. A method to measure low-level free cupric ion activity in soil solution extracted with 0.01 mol/L KNO3 was developed by using cupric ion-selective electrode （ISE） and calibrating with Cu-buffer solution. Three copper buffers including iminodiacetic acid （IDA）, ethylenediamine （EN）, and glycine （Gly） were compared for calibrating the Cu-ISE curves in the range of free cupric ions （pCu^2＋） 7-13. The Cu-EN buffer showed the best electrode response and thus was applied as the calibration buffer. The pCu^2＋ of 39 contaminated agricultural soils around a copper mine was measured, ranging from 5.03 to 9.20. Most Cu in the soil solutions was found to be complexed with dissolved soil organic matters, averaging 98.1%. The proportion of free Cu^2＋ ions in the soil solutions decreased with the increasing of solution pH. Soluble Cu and free Cu^2＋ ions concentrations were analyzed by multiple linear regressions to evaluate the effects of soil properties on metal levels and speciation. The results showed that soil solution pH was the most significant factor influencing pCu^2＋（with R^2 value of 0.76）, while not important for the soluble Cu concentration.

关键词： copper ion selective electrode (Cu-ISE) free metal ion activity soil solution metal speciation bioavailability

ATR-FTIR and XPS study on the structure of complexes formed upon the adsorption of simple organic acids on aluminum hydroxide

在线全文

学校读者我要写书评

暂无评论

Journal of Environmental Sciences 2007年第4期19卷 438-443页

作者： GUAN xiao-hong CHEN guang-hao SHANG Chii School of Municipal and Environmental Engineering Harbin Institute of Technology Harbin 150090 China. Department of Civil Engineering Hong Kong University of Science and Technology Hong Kong China

Information on the binding of organic ligands to metal （hydr）oxide surfaces is useful for understanding the adsorption behaviour of natural organic matter on metal （hydr）oxide. In this study, benzoate and salicylate were employed as the model organic ligands and aluminum hydroxide as the metal hydroxide. The attenuated total reflectance Fourier transform infrared （ATR-FTIR） spectra revealed that the ligands benzoate and salicylate do coordinate directly with the surface of hydrous aluminum hydroxide, thereby forming innersphere surface complexes. It is concluded that when the initial pH is acidic or neutral, monodentate and bridging complexes are to be formed between benzoate and aluminum hydroxide while bridging complexes predominate when the initial pH is alkalic. Monodentate and bridging complexes can be formed at pH 5 while precipitate and bridging complexes are formed at pH 7 when salicylate anions are adsorbed on aluminum hydroxide. The X-ray photoelectron （XP） spectra demonstrated the variation of C 1 s binding energy in the salicyate and phenolic groups before and after adsorption. It implied that the benzoate ligands are adsorbed through the complexation between carboxylate moieties and the aluminum hydroxide surface, while both carboxylate group and phenolic group are involved in the complexation reaction when salicylate is adsorbed onto aluminum hydroxide. The information offered by the XPS confirmed the findings obtained with ATR-FTIR.

关键词： adsorption aluminum hydroxide benzoic acid complexation natural organic matter salicylic acid

A physically based methodology for predicting anisotropic creep properties of Ni-based superalloys

在线全文

学校读者我要写书评

暂无评论

Rare Metals 2016年第8期35卷 606-614页

作者： Jia Huang Duo-Qi Shi xiao-guang Yang School of Energy and Power Engineering Beihang University

This paper is focused on developing suitable methodology for predicting creep characteristics （i.e., the minimum creep strain rate, stress rupture life and time to a specified creep strain） of typical Ni-based directionally solidified （DS） and single-crystal （SC） superalloys. A modem method with high accuracy on simulating wide ranging creep properties was fully validated by a sufficient amount of experimental data, which was then developed to model anisotropic creep characteristics by introducing a simple orientation factor defined by the ultimate tensile strength （UTS）. Physical confidence on this methodology is provided by the well-predicted transitions of creep defor- mation mechanisms. Meanwhile, this method was further adopted to innovatively evaluate the creep properties of different materials from a relative perspective.

关键词： Wilshire equations Anisotropic creepproperties Ni-based superalloy Prediction methodologyCreep mechanism

Adsorption behavior of condensed phosphate on aluminum hydroxide

在线全文

学校读者我要写书评

暂无评论

Journal of Environmental Sciences 2007年第3期19卷 312-318页

作者： GUAN xiao-hong CHEN guang-hao SHANG Chii School of Municipal and Environmental Engineering Harbin Institute of Technology Harbin 150090 China Department of Civil Engineering Hong Kong University of Science and Technology Hong Kong China

Sodium pyrophosphate （pyro-P, Na4P2OT）, sodium tripolyphosphate （tripoly-P, Na3P3O10）, and sodium hexametaphosphate （meta-P, （NaPO3）6） were selected as the model compounds of condensed phosphate to investigate the adsorption behavior of condensed phosphate on aluminum hydroxide. The adsorption was found to be endothermic and divisible into two stages：（1） fast adsorption within 1 h; and （2） slow adsorption between 1 and 24 h. The modified Freundlich model simulated the fast adsorption stage well; the slow adsorption stage was described well by the first-order kinetics. The activation energies of pyro-P, tripoly-P, and meta-P adsorption on aluminum hydroxide were determined to be 20.2, 22.8 and 10.9 kJ/mol P adsorbed, respectively, in the fast adsorption stage and to be 66.3, 53.5 and 72.5 kJ/mol P adsorbed, respectively, in the slow adsorption stage. The adsorption increased the negative charge of the aluminum hydroxide surface. Transmission electron microscopy and energy dispersive X-ray analysis analyses provided evidence that the adsorption was not uniform on the surface and that the small crystals contributed more to the fast adsorption than the normal sites did. The results from X-ray fluorescence spectrometry and X-ray photoelectron spectroscopy tests also revealed the uneven adsorption of condensed phosphate as a function of the penetration depth. More condensed phosphates were adsorbed on the outer surface of aluminum hydroxide than in its inner parts.

关键词： activation energy aluminum hydroxide condensed phosphate eutrophication surface charge

Influence of electronic structure on Compton scattering through comparing Cu-Ni alloys with Cu-Ni powder mixtures

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2012年第1期25卷 55-64页

作者： guang LUO Xianquan HU guangyu xiao Chunyang KONG College of Physics and Electronic Engineering Chongqing Normal UniversityChongqing 400047China

The application fields of Compton scattering have been further broadened through the studies of theories and experiments as well as the electronic structure of the scatters. The relationship between the contents of binary alloys （also binary powder mixtures） and the number of Compton scattered photons has been thoroughly examined. The linear expression of the relationship has been obtained approximately according to the Compton scattering theory. And the relationship has been validated well through the Compton scattering experiments with the scatters of Cu-Ni binary alloys or Cu- Ni binary powder mixtures. Furthermore, it is found that the slope of Cu-Ni powder mixture series is steeper than that of Cu-Ni alloy series, and through the pseudopotential plane wave theory of DFT the microscopic principles of Compton scattering of Cu-Ni alloy and Cu-Ni powder mixture series have been discussed and compared with each other. The results show that the electronic structure is the main reason for the difference of the linear slopes, and the line slope of Cu-Ni powder mixtures series is steeper than that of Cu-Ni alloy series.

关键词： Compton scattering Microscopic principle Cu-Ni Line slope

Design and Properties of Fluoroelastomer Composites via Incorporation of MWCNTs with Varied Modification

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Polymer Science 2020年第9期38卷 983-992,I0007页

作者： guang-Yao Yang Li-Fen Tong xiao-Bo Liu Research Branch of Advanced Functional Materials School of Materials and EnergyUniversity of Electronic Science and Technology of ChinaChengdu 610054China

Multi-walled carbon nanotubes(MWCNTs)modified with silane coupling agent A-1120(MWCNTs-A1120)were *** with the raw MWCNTs,acidified MWCNTs(MWCNTs-COOH),and MWCNTs grafted with EDA(MWCNTs-NH2),MWCNTs-A1120 have the best dispersion in fluoroelastomer at the same doping ***,fluoroelastomer/MWCNTs-A1120 composite has the best mechanical properties with tensile strength of 13.92 MPa and elongation at break of 111.78%.Then,the effects of doping amount of MWCNTs-A1120 on the electrical properties of the composites were *** dielectric constant of the composite increases with the increase of MWCNTs-A1120,and the dielectric loss does not change much at the low doping amount such as 0.5 wt%.When the doping amount of MWCNTs-A1120 is 5 wt%,the dielectric constant and the dielectric loss value are greatly increased,and the volume resistivity is greatly decreased,which proves that the conductive network is formed in the composite,so the filling amount of 5 wt%is the percolation *** tensile deformation of the sample also affects the electrical properties of the *** the tensile deformation increases,the dielectric constant and dielectric loss of the composite *** the composite with 5 wt%MWCNTs-A1120,excessive tensile deformation will destroy the conductive network structure of the composite,so the composite will change from conductive material to dielectric ***,such composite is a good candidate for flexible conductive material or flexible dielectric material used in harsh environments such as high temperatures and various aggressive solvents.

关键词： Modified-MWCNTs Fluoroelastomer nanocomposite Interface compatibility Dielectric properties Volume resistivity

Forming and growing mechanisms of homogenization-solution pores in a single crystal superalloy

在线全文

学校读者我要写书评

暂无评论

Rare Metals 2018年第5期37卷 399-406页

作者： xiao-Dai Yue Jia-Rong Li xiao-guang Wang Zhen-Xue Shi Science and Technology on Advanced High Temperature Structural Materials Laboratory Beijing Institute of Aeronautical Materials

The forming and growing mechanisms of homogenization-solution pores in a single crystal superalloy were investigated. The microstructures were observed with optical microscope （OM） and field emission microscope （FEM） after homogenization-solution heat treated at 1328℃ and 1350 ℃ for 2 h, 6 h and 9 h. Results indicate that when heat treated at 1328 ℃, pores appear at the interface of eutectic and matrix at first and then leave in the matrix with the shrink of eutectic. When heat treated at 1350 ℃, incipient melting happens at first, and some of them have a pore in the center. After that, with the homogenization-solution process, incipient melting microstructure fades away gradually. By analyzing the results with thermodynamics and kinetics methods, it is concluded that some pores nucleate during directional solidification and then become larger and visible during homogenization-solution heat treatments; some pores are generated by incipient melting, yet such pores are difficult to be distinguished from other pores; imbalanced elements cross-diffusion induces to the forming and growing of pores too, and such imbalanced diffusion also plays an important part on the growth of all preexisting pores.

关键词： Single crystal superalloy Pore Homogenization Solution Heat treatment Incipient melting