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STRESS-STRAIN HySTERESIS OF Cu-Zn-Al pOLyCRySTALLINE SMAs─Ⅱ: EXpERIMENTS AND NUMERICAL SIMULATIONS

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Acta Metallurgica Sinica(English Letters) 1999年第3期12卷 211-215页

作者： y. Chen y. Huo X. Zu M. Tu and y. Gou ( Department of Metal Materials, Sichuan University, Chengdu 610065, China)( Department of Metal Materials, Sichuan University, Chengdu 610065, China)( Department of Metal Materials, Sichuan University, Chengdu 610 Sichuan Univ Chengdu China

In this paper, the stress-strain bys torests at various temperatures was investigated experimentally for Cu-Zn-Al polycrystalline shape memory alloys (SMAs). Numerical simulations of the pseudoelastic hysteresis were performed based on a model, which had been proposed by the authors. As observed in the experiments, the shapes of the outer loops of the hysteresis varied strongly from specimen to specimen, which have the same chemical composition but different heat-treatment. Rather complicated inner hysteretic curves were obtained at testing temperatures higher than Af. The numerical simulations of the stress-strain hysteresis and the inner hysteretic curves agreed quite well with the experimental results.

关键词： shape memory alloys (SMAs) hystcresls inner hysteretic Beavior pseudoelasticity numerical simulations

Elastic field near the tip of an anticrack in a decagonal quasicrystalline material

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Applied Mathematics and Mechanics(English Edition) 2020年第3期41卷 401-408页

作者： Xu WANG p.SCHIAVONE School of Mechanical and power Engineering East China University of Science and TechnologyShanghai 200237China Department of Mechanical Engineering 10-203 Donadeo Innovation Centre for EngineeringUniversity of AlbertaEdmontonAlberta T6G 1H9Canada

We investigate the elastic field near the tip of an anticrack in a homogeneous decagonal quasicrystalline material subject to plane strain deformations. The phonon and phason stresses exhibit a square root singularity at the anticrack tip. Two realvalued phonon stress intensity factors and two real-valued phason stress intensity factors are introduced to scale four separate modes of deformation. We obtain four analytic functions which completely characterize the induced phonon and phason stresses as well as the displacement field. In particular, we derive a concise yet elegant representation of the anticrack contraction force.

关键词： decagonal quasicrystal anticrack elastic field anticrack contraction force analytic continuation

初夏东北冷涡指数的建立与分析(1961-2010)

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全球变化数据学报（中英文） 2024年第1期8卷 104-109,V0104-V0109页

作者：何丽烨马宁郭军天津市气候中心天津300074

东北冷涡是东亚中高纬度地区的重要天气系统,其频繁活动能够导致明显的气温和降水异常,具有显著的“气候效应”。使用水平分辨率为2.5°×2.5°、时间分辨率为逐日的NCEp/NCAR(美国国家环境预报中心和国家大气研究中心)再分析资料,研究... 详细信息

东北冷涡是东亚中高纬度地区的重要天气系统,其频繁活动能够导致明显的气温和降水异常,具有显著的“气候效应”。使用水平分辨率为2.5°×2.5°、时间分辨率为逐日的NCEp/NCAR(美国国家环境预报中心和国家大气研究中心)再分析资料,研究时段取1961–2010年。根据东北冷涡天气学定义,将符合下述条件的天气系统定义为一次冷涡天气过程:(1)在500hpa等压面上至少能分析出一根闭合等高线,并有冷中心或明显冷槽配合的低压环流系统;(2)冷涡中心出现在(35°N–60°N,115°E–145°E)范围内;(3)冷涡在上述地区的生命史为3天或3天以上。考虑海河流域的地理位置,根据逐年东北冷涡低压中心在西涡范围(115°E–125°E)达到的最南位置,界定对初夏(6月,下同)海河流域降水有显著影响的东北冷涡活动关键区域(38°N–48°N,115°E–125°E),统计出冷涡中心频次标准化值,形成初夏东北冷涡指数数据集(1961–2010)。数据集包括:(1)初夏标准化东北冷涡活动指数;(2)逐年初夏东北冷涡500 hpa位势高度低压中心在115°E–125°E区域的最南位置。该数据集存储为1个Excel文件(.xlsx格式),数据量约12.5 KB。

关键词：东北冷涡初夏降水海河流域气候效应

prediction of grain structure in direct-chill cast Al–Zn–Mg–Cu billets using cellular automaton-finite element method

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progress in Natural Science:Materials International 2021年第3期31卷 434-441页

作者： Min-Seok Kim Sang-Hwa lee Jae-Gil Jung Kwangjun Eah Department of Materials Science and Engineering Gachon University Metallic Materials Division Korea Institute of Materials Science Department of Materials Science and Engineering Yonsei University

A cellular automaton-finite element(CA-FE) model was used to predict the solidification grain structure of permanent mold cast A7086 alloy. In this model, a Gaussian distribution of nucleation sites was adopted, and the Kurz-Giovanola-Trivedi model was extended to a multicomponent Al–Zn–Mg–Cu alloy system to determine the growth kinetics of the dendrite tip. For describing the Gaussian distribution of nucleation sites on the mold surface, an empirical relationship between the initial cooling rate of the melt and the nucleation density was proposed. Under various casting conditions, the calculated grain structures agreed well with the experimental results. Subsequently, the model was applied to the direct-chill(DC) cast billets, and the simulated grain structures reproduced well the experimental results. This confirmed that the current CA-FE model can be used practically and effectively in DC casting processes.

关键词： Cellular automaton-finite element (CA-FE) model Direct-chill casting Al–Zn–Mg–Cu alloy A7068 alloy Grain structure

腹侧海马CA1区HCN2通道功能下调参与慢性炎症痛

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中国疼痛医学杂志 2024年第1期30卷 51-51页

作者：刘风雨(译) 北京大学神经科学研究所

海马作为边缘系统的重要结构,在疼痛感知和疼痛慢性化中起关键作用。近期对人类和啮齿类的研究表明,腹侧海马CA1 (ventral hippocampal CA1,vCA1)的功能失调,包括神经元兴奋性降低以及与其他脑区功能连接度降低,参与调控疼痛慢性化。然... 详细信息

海马作为边缘系统的重要结构,在疼痛感知和疼痛慢性化中起关键作用。近期对人类和啮齿类的研究表明,腹侧海马CA1 (ventral hippocampal CA1,vCA1)的功能失调,包括神经元兴奋性降低以及与其他脑区功能连接度降低,参与调控疼痛慢性化。然而,vCA1调控疼痛的分子机制不清。超极化激活环核苷酸门控阳离子通道(hyperpolarization-activated cyclic nucleotide-gated channels,HCN),尤其是HCN1和HCN2亚型,在CA1区锥体神经元表达丰富,具有稳定膜电位等作用。该研究采用完全弗氏佐剂(complete Freund’s adjuvant,CFA)小鼠模型,探讨vCA1区HCN通道是否参与调节慢性炎症痛。

关键词：超极化激活环核苷酸门控阳离子通道神经元兴奋性腹侧海马慢性化完全弗氏佐剂边缘系统 CA1区功能失调

A Jacobian-Free Newton Krylov Implicit-Explicit Time Integration Method for Incompressible Flow problems

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Communications in Computational physics 2013年第5期13卷 1408-1431页

作者： Samet y.Kadioglu Dana A.Knoll Department of Mathematical Engineering Yildiz Technical University34210 Davutpasa-EsenlerIstanbulTurkey Fuels Modeling and Simulation Department Idaho National LaboratoryP.O.Box 1625MS 3840Idaho FallsID 83415USA Theoretical Division Los Alamos National LaboratoryP.O.Box 1663MS B-216Los AlamosNM87545USA

We have introduced a fully second order IMplicit/EXplicit(IMEX)time integration technique for solving the compressible Euler equations plus nonlinear heat conduction problems(also known as the radiation hydrodynamics problems)in Kadioglu et al.,***[22,24].In this paper,we study the implications when this method is applied to the incompressible Navier-Stokes(N-S)*** IMEX method is applied to the incompressible flow equations in the following *** hyperbolic terms of the flow equations are solved explicitly exploiting the well understood explicit *** the other hand,an implicit strategy is employed for the non-hyperbolic *** explicit part is embedded in the implicit step in such a way that it is solved as part of the non-linear function evaluation within the framework of the Jacobian-Free Newton Krylov(JFNK)method[8,29,31].This is done to obtain a self-consistent implementation of the IMEX method that eliminates the potential order reduction in time accuracy due to the specific operator *** employ a simple yet quite effective fractional step projection methodology(similar to those in[11,19,21,30])as our preconditioner inside the JFNK *** present results from several test *** each test,we show second order time ***,we present a study for the algorithm performance of the JFNK solver with the new projection method based preconditioner.

关键词： Incompressible flow Navier-Stokes equations IMEX method JFNK method preconditioner

Identification of the active sites and mechanism for partial methane oxidation to methanol over copper-exchanged CHA zeolites

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Science China Chemistry 2020年第6期63卷 850-859页

作者： yu Mao p.Hu School of Chemistry and Chemical Engineering The Queen’s University of BelfastBelfastUK

To make methane a suitable energy carrier and transport less costly,it is an urgent and challenging task for us to convert methane to liquid under mild conditions *** this study,we explored partial methane oxidation to methanol by density functional theory(DFT)calculations using a hybrid functional(HSE06)with van der Waals(vdW)*** stabilities of different active sites over SSZ-13 and SApO-34,two CHA type zeolites,are thoroughly investigated by ab initio molecular dynamics(AIMD)simulations and ab initio thermodynamics *** possible active sites,namely[CuOHCu]2+,[Cu(OH)2Cu]2+,[CuOCu]2+and[CuOH]+,are identified ***-to-methanol reaction mechanisms are further studied upon these most stable active sites,among which[CuOCu]2+and[CuOH]+are proved to be *** migration of species among zeolite pores are also discussed,which accounts for the activity on[CuOH]+*** concept may represent a more complete picture of catalytic reactions over zeolites in general.

关键词： DFT heterogeneous catalysis methane-to-methanol CHA zeolites

Thermoelectric field for a coated hole of arbitrary shape in a nonlinearly coupled thermoelectric material

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Applied Mathematics and Mechanics(English Edition) 2022年第11期43卷 1691-1700页

作者： Xu WANG p.SCHIAVONE School of Mechanical and power Engineering East China University of Science and TechnologyShanghai 200237China Department of Mechanical Engineering University of Alberta10-203 Donadeo Innovation Center for EngineeringEdmonton T6G 1H9Canada

We study the thermoelectric field for an electrically and thermally insulated coated hole of arbitrary shape embedded in an infinite nonlinearly coupled thermoelectric material subject to uniform remote electric current density and uniform remote energy flux.A conformal mapping function for the coating and matrix is introduced,which simultaneously maps the hole boundary and the coating-matrix interface onto two concentric circles in the image *** analytic continuation,we derive a general solution in terms of two auxiliary *** general solution satisfies the insulating conditions along the hole boundary and all of the continuity conditions across the perfect coating-matrix *** the two auxiliary functions have been obtained in the elementary-form,the four original analytic functions in the coating and matrix characterizing the thermoelectric fields are completely and explicitly *** design of a neutral coated circular hole that does not disturb the prescribed thermoelectric field in the thermoelectric matrix is achieved when the relative thickness parameter and the two mismatch parameters satisfy a simple ***,the neutrality of a coated circular thermoelectric inhomogeneity is also accomplished.

关键词： thermoelectric material nonlinear coupling coated hole of arbitrary shape complex variable method analytic solution neutral coated hole

N_(2)and Ar dilution on the premixed biogas jet flame under external acoustic enforcement

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propulsion and power Research 2023年第4期12卷 486-504页

作者： Bugrahan Alabas Ilker yılmaz yakupÇam Department of Aeronautical Engineering Faculty of Aeronautics and AstronauticsErciyes UniversityKayseri 38039Turkey Department of Energy Systems Engineering Faculty of TechnologyGazi UniversityAnkara 06560Turkey Department of Aircraft Maintenance and Repair Faculty of Aeronautics and AstronauticsErciyes UniversityKayseri 38039Turkey

In this study,combustion instabilities and flue gas emission changes under different dilutions of N_(2)(nitrogen)and Ar(argon)of a promising biogas mixture(70%CH4-30%CO_(2))in the fight against greenhouse gas emissions were *** the experiments,additions were made from 0%to 50%at intervals of 10%for both *** order to detect the instability of the flame,external acoustic enforcements at different frequencies was applied through the speakers placed in the combustion chamber *** dynamic pressure fluctuation values were *** results showed that low dilution ratios were effective in reducing flame instability for both inert ***,as the dilution ratio increased,the fuel/air mixture became leaner and blowoff *** the case of comparing two different gases,it has been observed that the effect of argon gas on reducing dynamic pressure fluctuation is *** outlet temperature and brightness values of the flame decreased in both Ar and N_(2)*** and NOx emissions increased with increasing diluent volume for all dilution *** the emissions of the two diluent gases are compared,the CO emission,which was 3134 ppm in the undiluted condition,increased up to 4949 ppm in 50%Ar dilution,while it increased to 4521 ppm in 50%N_(2)dilution.

关键词： Biogas Combustion instabilities pollutant emissions Gas turbine combustor Dilution