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Solving the 2-D Elliptic Monge-Ampère Equation by a Kansa's Method

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Acta Mathematicae Applicatae Sinica 2017年第2期33卷 269-276页

作者： Qin LI zhi-yong liu School of Science Beijing Technology and Business University Beijing 100048 China School of Mathematics and Statistics Ningxia University Yinchuan 750021 China

In this paper, a Kansa＇s method is designed to solve numerically the Monge-Ampere equation. The primitive Kansa＇s method is a meshfree method which applying the combination of some radial basis functions （such as Hardy＇s MQ） to approximate the solution of the linear parabolic, hyperbolic and elliptic problems. But this method is deteriorated when is used to solve nonlinear partial differential equations. We approximate the solution in some local triangular subdomains by using the combination of some cubic polynomials. Then the given problems can be computed in each subdomains independently. We prove the stability and convergence of the new method for the elliptic Monge-Ampere equation. Finally, some numerical experiments are presented to demonstrate the theoretical results.

关键词： radial basis functions Kansa's method Monge-Amp^re equation finite element methods mesh-free methods interpolation

Cognitive Study of the Linear Order of the English Construction“X and Y”

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Journal of Electronic Science and Technology 2017年第1期15卷 20-24页

作者： yong-zhi liu Fan Fan College of Foreign Languages&Cultures Chengdu University of TechnoiogyChengdu 610059China

The English construction “X and Y ”refers to the coordination of two words with and as conjunction, X and Y being of the same part of speech and parallel meanings. This paper is a cognitive study of the linear order of the English construction “X and Y ”from the perspectives of cognitive salience, cognitive iconicity, and cognition of formal rules. The linear characteristics of “X and Y ” are revealed as follows： 1）salience-downgrading order; 2） chronological iconicity;3） cognition of alphabetic order and prosodic order.

关键词： cognition conjunction syntactic linguistics salient formal bread X and Y discussion father

Refinement of primary Si grains in Al–20%Si alloy slurry through serpentine channel pouring process

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International Journal of Minerals,Metallurgy and Materials 2016年第5期23卷 572-580页

作者： zhi-kai Zheng Wei-min Mao zhi-yong liu Dong Wang Rui Yue School of Materials Science and Engineering University of Science and Technology Beijing Beijing 100083 China School of Mechanics Jinzhong University Jinzhong 030600 China

In this study, a serpentine channel pouring process was used to prepare the semi-solid A1-20%Si alloy slurry and refine primary Si grains in the alloy. The effects of the pouring temperature, number of curves in the serpentine channel, and material of the serpentine channel on the size of primary Si grains in the semi-solid A1-20%Si alloy slurry were investigated. The results showed that the pouting temperature, number of the curves, and material of the channel strongly affected the size and distribution of the primary Si grains. The pouring tempera- ture exerted the strongest effect, followed by the number of the curves and then the material of the channel. Under experimental conditions of a four-curve copper channel and a pouring temperature of 701℃, primary Si grains in the semi-solid A1-20%Si alloy slurry were refined to the greatest extent, and the lath-like grains were changed into granular grains. Moreover, the equivalent grain diameter and the average shape coefficient of primary Si grains in the satisfactory semi-solid A1-20%Si alloy slurry were 24.4 μm and 0.89, respectively. Finally, the re- finement mechanism and distribution rule of primary Si grains in the slurry prepared through the serpentine channel pouring process were analyzed and discussed.

关键词： aluminum silicon alloys serpentine channel pouring process semi-solid process morphology grain refinement

Non-detection of pulsed radio emission from magnetar Swift J1834.9-0846: constraint on the fundamental plane of magnetar radio emission

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Research in Astronomy and Astrophysics 2013年第7期13卷 835-840页

作者： Hao Tong Jian-Ping Yuan zhi-yong liu Xinjiang Astronomical Observatory Chinese Academy of Sciences

The magnetar Swift J1834.9-0846 is observed using the Nanshan 25 m radio telescope. No pulsed radio emission is detected. The upper limit on the pulsed radio emission from this source is 0.5 mJy. According to the ＂fundamental plane＂ for radio magnetars, this source should have radio emission. Therefore, our results put constraints on the existence of a fundamental plane of magnetar radio emission. We argue that a magnetar＇s ability to emit radio emission may have little to do with the spin down luminosity and is related to the magnetar＇s X-ray luminosity. The only necessary condition is a relatively low X-ray luminosity.

关键词： pulsars: individual (Swift J1834.9-0846) - stars: magnetars - stars:neutron

Investigation of rheo-diecasting mold filling of semi-solid A380 aluminum alloy slurry

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International Journal of Minerals,Metallurgy and Materials 2017年第6期24卷 691-700页

作者： zhi-yong liu Wei-min Mao Wei-pan Wang zhi-kai Zheng Rui Yue School of Materials Science and Engineering Tsinghua University Beijing 100084 China School of Materials Science and Engineering University of Science and Technology Beijing Beijing 100083 China Beijing Nanshan Institute of Aeronautical Materials Beijing 100048 China National Engineering Research Center of Light Alloy Net Forming Shanghai Jiao Tong University Shanghai 200240 China

The rheo-diecasting mold filling capacity and the microstructure of the semi-solid A380 aluminum alloy slurry were investigated. The results show that the mold filling capacity was strengthened with increasing pouring temperature or increasing injection pressure. Under certain process parameters, the mold cavity was fully filled. However, the mold filling capacity decreased with increasing holding time. The mold filling capacity was improved with increasing shape factor of primary α(Al) grains; however, the solid fraction and the grain size significantly increased at the same time. In addition, the microstructures along the route of the spiral samples obviously differed. The grain size decreased gradually from the near-end to the far-end, whereas the shape factor increased gradually.

关键词： aluminum alloys semi-solid slurry rheo-diecasting mold filling microstructure

One and two dimensional chloride ion diffusion of fly ash concrete under flexural stress

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2011年第9期12卷 692-701页

作者： Yun-sheng ZHANG Wei SUN zhi-yong liu Shu-dong CHEN Jiangsu Key Laboratory for Construction Materials Southeast University Nanjing 211189 China

A preloading frame is firstly designed to accurately apply external flexural stress to concrete specimens. Then a method is developed to measure one and two dimensional (1D and 2D) chloride ion concentrations at different distances from the surface of concrete under flexural stress. Using this method and the preloading frame, 1D and 2D stress-diffusion is systematically investigated for fly ash concretes made with different fly ash contents (0%, 10%, 20%, 40%, and 60%), and water to binder ratios (0.3, 0.35, and 0.4). The stress accelerating effect on 1D and 2D chloride ion diffusion is also quantitatively analyzed through a comparison between stress-diffusion and nonstress-diffusion. A diffusion accelerating effect caused by external flexural stress can clearly be observed through the comparison. In order to quantify the stress accelerating effect, a stress accelerating factor is proposed in this paper. The relationship between stress accelerating factor and external stress-to-ultimate stress ratio is given as an exponential function. Finally, the process of the initiation, prorogation, and distribution of microcracks on the tensile face of specimen is observed in-situ by using a small-sized loading frame and scanning electron microscope (SEM). The above research provides an insight into chloride attack on the edge reinforcing bars of concrete structures under flexural stress, such as large-span beam and board in the field of civil engineering.

关键词： Fly ash Concrete Flexural stress Chloride ion One and two dimension

Stress corrosion cracking of X80 pipeline steel exposed to high pH solutions with different concentrations of bicarbonate

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International Journal of Minerals,Metallurgy and Materials 2013年第7期20卷 645-652页

作者： Lin Fan Cui-wei Du zhi-yong liu Xiao-gang Li School of Materials Science and Engineering University of Science and Technology Beijing

Susceptibilities to stress corrosion cracking （SCC） of X80 pipeline steel in high pH solutions with various concentrations of HC03 at a passive potential of-0.2 V vs. SCE were investigated by slow strain rate tensile （SSRT） test. The SCC mechanism and the effect of HC03 were discussed with the aid of electrochemical techniques. It is indicated that X80 steel shows enhunced susceptibility to SCC with the concentration of HCO3 increasing from 0.15 to 1.00 mol/L, and the susceptibility can be evaluated in terms of current density at -0.2 V vs. SCE. The SCC behavior is controlled by the dissolution-based mechanism in these circumstances. Increasing the concentration of HCO3 not only increases the risk of rupture of passive films but also promotes the anodic dissolution of crack tips. Besides, little susceptibility to SCC is found in dilute solution containing 0.05 mol/L HCO3 for X80 steel. This can be attributed to the inhibited repassivation of passive films, manifesting as a more intensive dissolution in the non-crack tip areas than at the crack tips.

关键词： pipeline steel stress corrosion cracking bicarbonate passive films

Relationship between chloride diffusivity and pore structure of hardened cement paste

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2011年第5期12卷 360-367页

作者： Guo-wen SUN Wei SUN Yun-sheng ZHANG zhi-yong liu Jiangsu Key Laboratory of Construction Materials.Southeast University Nanjing 211189china

Based on effective media theory, a predictive model, relating chloride diffusivity to the capillary pores, gel pores, tortuosity factor, and pore size distribution of hardened cement, is proposed. To verify the proposed model, the diffusion coefficient of chloride ions, the degree of hydration, and peak radius of capillary pores of cement paste specimens were measured. The predicted results for chloride diffusivity were compared with published data. The results showed that the predicted chloride diffusivity of hardened cement paste was in good agreement with the experimental results. The effect of the evolution of pore structures in cement paste on chloride diffusivity could be deduced simultaneously using the proposed model.

关键词： Hardened cement paste Chloride diffusivity Porosity Tortuosity factor Constrictivity Key words: Hardened cement paste, Chloride diffusivity, Porosity, Tortuosity factor, Conslrictivity

Flow-accelerated corrosion behavior of 13Cr stainless steel in a wet gas environment containing CO_2

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International Journal of Minerals,Metallurgy and Materials 2018年第7期25卷 779-787页

作者： yong Li Min-dong Chen Jian-kuan Li Long-fei Song Xin Zhang zhi-yong liu Corrosion and Protection Centre Key Laboratory for Corrosion and Protection（MOE）National Environmental Corrosion Platform（NECP）University of Science and Technology BeijingBeijing 100083China Nuclear and Radiation Safety Center Ministry of Environmental Protection of P.R.ChinaBeijing 100082China

This work investigated the flow-accelerated corrosion （FAC） behavior of 13Cr in a wet CO2-containing environment at different flowing gas velocities mid impinging mlgles, with the natural-gas pipeline environment simulated by a self-assembled impingement jet sys- tem. Surface molphology determination, electrochemical measurements, mid hydromechaziics numerical analysis were cmlied out to study the FAC behavior. The results demonstrate that pitting corrosion was the primary mode of corrosion in 13Cr stainless steel. High-flow-rate gas destroyed the passive film mid decreased the pitting potential, resulting in more serious corrosion. The corrosion degree witk various im- pact mlgles showed the following order： 90~ 〉 60~ 〉 45~. The shear force and the electrolyte from the flowing gas were concluded to be the determinm^t factors of FAC, whereas the shear force was the main factor responsible for destroying the passive film.

关键词： flow-accelerated corrosion jet loop flowing velocity impact magle C02