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Effects of the extrusion parameters on microstructure,texture and room temperature mechanical properties of extruded Mg-2.49Nd-1.82Gd-0.2Zn-0.2Zr alloy

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International Journal of Minerals,Metallurgy and Materials 2025年第1期32卷 136-146页

作者： Chenjin Zhang Guangyu Yang Lei Xiao Zhiyong Kan jing guo Qiang Li Wanqi Jie State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi’an 710072China College of Materials Science and Engineering Fuzhou UniversityFuzhou 350108China College of Chemistry and Environmental Science Qujing Normal UniversityQujing 655011China

Microstructure,texture,and mechanical properties of the extruded Mg-2.49Nd-1.82Gd-0.2Zn-0.2Zr alloy were investigated at different extrusion temperatures(260 and 320℃),extrusion ratios(10:1,15:1,and 30:1),and extrusion speeds(3 and 6 mm/s).The experimental results exhibited that the grain sizes after extrusion were much finer than that of the homogenized alloy,and the second phase showed streamline distribution along the extrusion direction(ED).With extrusion temperature increased from 260 to 320℃,the microstructure,texture,and mechanical properties of alloys changed *** dynamic recrystallization(DRX)degree and grain sizes enhanced as the extrusion ratio increased from 10:1 to 30:1,and the strength gradually decreased but elongation(EL)*** the extrusion speed increased from 3 to 6 mm/s,the grain sizes and DRX degree increased significantly,and the samples presented the typical-rare-earth(RE)*** alloy extruded at 260℃ with extrusion ratio of 10:1 and extrusion speed of 3 mm/s showed the tensile yield strength(TYS)of 213 MPa and EL of 30.6%.After quantitatively analyzing the contribution of strengthening mechanisms,it was found that the grain boundary strengthening and dislocation strengthening played major roles among strengthening *** results provide some guidelines for enlarging the industrial application of extruded Mg-RE alloy.

关键词： Mg-rare earth alloys extrusion temperature extrusion ratio extrusion speed strengthening mechanisms

A NEW WELL TEST MODEL FOR A TWO-ZONE LINEAR COMPOSITE RESERVOIR WITH VARIED THICKNESSES

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Journal of Hydrodynamics 2010年第6期22卷 804-809页

作者： ZHANG Lie-hui guo jing-jing LIU Qi-guo State Key Laboratory of Reservoir Geology and Exploitation Southwest Petroleum University Chengdu 610500China

This article presents a new well test model for two-zone linear composite reservoirs, where the rock and fluid properties as well as the formation thicknesses on both sides of the discontinuity are distinctly different. An analytical solution of pressure-transient behavior for a line-source, constant-rate well in this type of reservoir configuration is obtained with Fourier space transformation and Laplace transformation. By applying Duhamel principle, the wellbore storage and skins effects can easily be included. A set of type curves are generated and the sensitivities of the relevant parameters are discussed. A new correlating parameter MhDl√ηD is proposed to identify the pressure response in the pressure derivative curve. The model as well as the corresponding type curves are quite general that they are useful in predicting the production performance or analyzing the production data from this type of well-reservoir systems.

关键词： non-uniform thickness linear composite well test model type curve

Stable NiPt-Mo_(2)C active site pairs enable boosted water splitting and direct methanol fuel cell

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Green Energy & Environment 2023年第2期8卷 559-566页

作者： jing Li Zhu guo Wenjie Zhang jing guo Konggang Qu Weiwei Cai Sustainable Energy Laboratory Faculty of Materials Science and ChemistryChina University of GeosciencesWuhan430074China Shandong Provincial Key Laboratory/Collaborative Innovation Center of Chemical Energy Storage&Novel Cell Technology Liaocheng UniversityLiaocheng252059China

Sluggish kinetics of methanol oxidation reaction(MOR)and alkaline hydrogen evolution reaction(HER)even on precious Pt catalyst impede the large-scale commercialization of direct methanol fuel cell(DMFC)and water electrolysis *** both of MOR and alkaline HER are related to water dissociation reaction(WDR),it is reasonable to invite secondary active sites toward WDR to pair with Pt for boosted MOR and alkaline HER activity on ***_(2)C and Ni species are therefore employed to engineer NiPt-Mo_(2)C active site pairs,which can be encapsulated in carbon cages,via an in-situ self-confinement *** activity of Pt in NiPt-Mo_(2)C@C toward HER is boosted to11.3 A mg_(pt)^(-1),33 times higher than that of Pt/***,MOR catalytic activity of Pt in NiPt-Mo_(2)C@C is also improved by 10.5 times and the DMFC maximum power density is hence improved by *** considering the great stability,NiPt-Mo_(2)C@C exhibits great practical application potential in DMFCs and water electrolysers.

关键词： Hydrogen evolution reaction Methanol oxidation reaction Direct methanol fuel cell Active site pair Self-confinement

Differential quadrature time element method for structural dynamics

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Acta Mechanica Sinica 2012年第3期28卷 782-792页

作者： Yu-Feng Xing jing guo The Solid Mechanics Research Center Beihang University100191 BeijingChina

An accurate and efficient differential quadrature time element method （DQTEM） is proposed for solving ordi- nary differential equations （ODEs）, the numerical dissipation and dispersion of DQTEM is much smaller than that of the direct integration method of single/multi steps. Two methods of imposing initial conditions are given, which avoids the tediousness when derivative initial conditions are imposed, and the numerical comparisons indicate that the first method, in which the analog equations of initial displacements and velocities are used to directly replace the differential quadra- ture （DQ） analog equations of ODEs at the first and the last sampling points, respectively, is much more accurate than the second method, in which the DQ analog equations of initial conditions are used to directly replace the DQ analog equations of ODEs at the first two sampling points. On the contrary to the conventional step-by-step direct integration schemes, the solutions at all sampling points can be obtained simultaneously by DQTEM, and generally, one differential quadrature time element may be enough for the whole time domain. Extensive numerical comparisons validate the effi- ciency and accuracy of the proposed method.

关键词： Differential quadrature rule Direct integrationmethod Time element Phase error. Artificial damping

Dynamic stress concentration of an elliptical cavity in a semi-elliptical hill under SH-waves

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Earthquake Engineering and Engineering Vibration 2021年第2期20卷 347-359页

作者： Qi Hui Chu Fuqing guo jing College of Aerospace and Civil Engineering Harbin Engineering UniversityHarbin 150001China

The method of wave-function expansion in elliptical coordinates,elliptical cosine half-range expansion and Mathieu function were applied to obtain an exact analytical solution of the dynamic stress concentration factor(DSCF)around an elliptical cavity in a shallow,semi-elliptical *** infinite system of simultaneous linear equations for solving this problem was established by substituting the wave expression obtained by the Mathieu function including the standing wave expression of elliptical lining given herein into the boundary condition obtained by the region-matching *** finite equations system with unknown coefficients obtained by truncation were solved numerically,and the results in the case of an ellipse degenerating into a circle were compared with previous results to verify the accuracy of the *** effects of different aspect ratios,incident wave angles and aperture ratios on the dynamic stress concentration around the elliptical cavity were *** numerical results,when the elliptical hill was changed into a circular one,were analyzed and compared in *** engineering,this model can be regarded as a semi-cylindrical hill with an elliptical cylindrical unlined tunnel under the action of SH waves,and the results are significant in aseismic design.

关键词： SH waves dynamic stress concentration factor(DSCF) elliptical coordinate Mathieu function

WELL TESTING ANALYSIS FOR HORIZONTAL WELL WITH CONSIDERATION OF THRESHOLD PRESSURE GRADIENT IN TIGHT GAS RESERVOIRS

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Journal of Hydrodynamics 2012年第4期24卷 561-568页

作者： guo jing-jing ZHANG Su ZHANG Lie-hui QING Hairuo LIU Qi-guo State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation Southwest Petroleum UniversityChengdu 610500 China Central Sichuan Mining District PetroChina Southwest Oil and Gas Field Company Suining 629000 China Department of Geology University of Regina Regina SK S4S 0A2 Canada

A fundamental solution for homogeneous reservoir in infinite space is derived by using the point source function with the consideration of the threshold pressure gradient. The fundamental solution of the continuous point source function is then derived based on the Green function. Various boundary conditions of the reservoirs are considered for this case and the corresponding solutions are obtained through the mirror image reflection and the principle of superimposition. The line source solution is obtained by integration. Subsequently, the horizontal-well bottom hole pressure response function for a non-linear gas flow in the homogeneous gas reservoir is obtained, and the response curve of the dimensionless bottom hole pressure and the derivative for a horizontal well in the homogeneous gas reservoir are obtained. In the end, the sensitivities of the relevant parameters are analyzed, The well test model presented in this paper can be used as the basis of the horizontal well test analysis for tight gas reservoirs.

关键词： horizontal well non-linear gas flow threshold pressure gradient tight gas reservoir

Band Gap of Strained Graphene Nanoribbons

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Nano Research 2010年第3期3卷 189-199页

作者： Yang Lu jing guo Department of Electrical and Computer Engineering University of FloridaGainesvilleFL 32611USA

The band structures of strained graphene nanoribbons(GNRs)are examined using a tight-binding Hamiltonian that is directly related to the type and magnitude of *** to a two-dimensional graphene whose band gap remains close to zero even if a large strain is applied,the band gap of a graphene nanoribbon(GNR)is sensitive to both uniaxial and shear *** effect of strain on the electronic structure of a GNR depends strongly on its edge shape and structural *** an armchair GNR,a weak uniaxial strain changes the band gap in a linear fashion,whereas a large strain results in periodic oscillation of the band *** the other hand,shear strain always tends to reduce the band *** a zigzag GNR,the effect of strain is to change the spin polarization at the edges of GNR,and thereby modulate the band gap.A simple analytical model,which agrees with the numerical results,is proposed to interpret the response of the band gap to strain in armchair GNRs.

关键词： Graphene nanoribbons(GNRs) band gap strain

Assessment of High-Frequency Performance Limits of Graphene Field-Effect Transistors

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Nano Research 2011年第6期4卷 571-579页

作者： Jyotsna Chauhan jing guo Department of Electrical and Computer Engineering University of Florida Gainesville FL 32611-6130 USA

High frequency performance limits of graphene field-effect transistors （FETs） down to a channel length of 20 nm have been examined by using self-consistent quantum simulations. The results indicate that although Klein band-to-band tunneling is significant for sub-100 nm graphene FETs, it is possible to achieve a good transconductance and ballistic on-off ratio larger than 3 even at a channel length of 20 nm. At a channel length of 20 nm, the intrinsic cut-off frequency remains at a few THz for various gate insulator thickness values, but a thin gate insulator is necessary for a good transconductance and smaller degradation of cut-off frequency in the presence of parasitic capacitance. The intrinsic cut-off frequency is close to the LC characteristic frequency set by graphene kinetic inductance （L） and quantum capacitance （C）, which is about 100 GHz-um divided by the gate length.

关键词： Field effect transistor (FET) radio frequency (RF) carbon nanotube (CNT) intrinsic cut-off frequency transconductance

Theoretical Study on the Catalytic Activity and Sulfur Resistibility of Amorphous Alloy Ni-B-P

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Chinese Journal of Structural Chemistry 2007年第3期26卷 273-280页

作者： FANG Zhi-Gang guo jing-Xue School of Chemical Engineering University of Science and Technology Liaoning Anshan 114051 China

In the present paper, one hundred cluster models NinBP （n = 1-6） have been designed and studied by density functional theory （DFT） to get an insight into the local structure, catalytic properties and sulfur resistibility of amorphous alloy Ni-B-P. The configurations in triplet state are found more stable than those in the singlet state. It is found： that as the content of Ni in the clusters increases, the value of Fermi level in clusters fluctuated, which shows that the content of Ni can influence the Fermi level to a certain extent. Based on the Fermi level and DOS, we consider the activity of catalyst in hydrogenation reaction is the best in cluster Ni3BP. On the basis of the charge of clusters NinBP （n = 1 -6）, we conclude the amorphous alloy Ni-B-P with high Ni content has better sulfur resistibility and the best hydrogenation activity, strong sulfur resistibility appears in clusters Ni3BP, and the amorphous alloy Ni60B20P20 with similar proportion is expected to prepare in the future.

关键词： amorphous alloy Ni-B-P DFT catalytic activity sulfur resistibility