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Molecular dynamics simulation of ion selectivity traits of nickel hexacyanoferrate thin films

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中国有色金属学会会刊：英文版 2006年第4期16卷 897-902页

作者：郝晓刚 YU Qiu-ming JIang Shao-yi d. T. SCHWARTZ department of Chemical Engineering Taiyuan University of Technology Taiyuan 030024 China department of Chemical Engineering University of Washington Seattle Washington 98195-1750 USA

The ion selectivity of nickel hexacyanoferrate thin film to alkali cations in ESIX (electrochemically switched ion exchange) processes was investigated using molecular dynamics(Md) techniques; water and cation (Na+ and Cs+) intercalation, configuration, and dynamics in reduced nickel hexacyanoferrate structures with different cation combinations were studied and compared with the experimental results. In the simulations, water was represented by an extended simple point-charge(SPC/E) model, and all other atomic interactions were represented by a universal force field(UFF). The potential energies of various cations combination (Cs+ and Na+) in reduced i-NiHCF and 1 mol/L Cs/NaCl mixed solution were obtained. In most cases, the total potential energy of the solid is reduced when water is intercalated into the various reduced NiHCF structures. Combining the solid and the solution simulation results, it is shown that the solid composition of 3Cs+/1Na+ is the stablest structure form (NaCs3Ni4[Fe(CN)6]3) over a range of solution compositions.

关键词：镍分子动力学模拟离子选择性薄膜离子交换

Particle-in-cell simulations of laser–plasma interactions at solid densities and relativistic intensities: the role of atomic processes

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High Power Laser Science and Engineering 2018年第3期6卷 112-126页

作者： d. Wu X. T. He W. Yu S. Fritzsche State Key Laboratory of High Field Laser Physics Shanghai Institute of Optics and Fine Mechanics Shanghai 201800 China Helmholtz lnstitut Jena D-07743 Jena Germany Key Laboratory of HEdP of the Ministry of Education Center for Applied Physics and Technology Peking University Beijing 100871 China Theoretisch-Physikalisches lnstitut Friedrich-Schiller-University Jena D-07743 Jena Germany

direct numerical simulation of intense laser-solid interactions is still of great challenges, because of the many coupled atomic and plasma processes, such as ionization dynamics, collision among charged particles and collective electromagnetic fields, to name just a few. Here, we develop a new particle-in-cell （PIC） simulation code, which enables us to calculate laser-solid interactions in a more realistic way. This code is able to cover almost ＇all＇ the coupled physical processes. As an application of the new code, the generation and transport of energetic electrons in front of and within the solid target when irradiated by intense laser beams are studied. For the considered case, in which laser intensity is 1020 W. cm-2 and pre-plasma scale length in front of the solid is 10 Izm, several quantitative conclusions are drawn：（i） the collisional damping （although it is very weak） can significantly affect the energetic electrons generation in front of the target, （ii） the Bremsstrahlung radiation will be enhanced by 2-3 times when the solid is dramatically heated and ionized, （iii） the ＇cut-off＇ electron energy is lowered by an amount of 25% when both collision damping and Bremsstrahlung radiations are included, and （iv） the resistive electromagnetic fields due to Ohmic heating play nonignorable roles and must be taken into account in such interactions.

关键词： high energy density physics laser plasmas interaction

Molecular dynamics Simulation of Tensile deformation and Fracture of γ-TiAl with and without Surface defects

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Journal of Materials Science & Technology 2016年第10期32卷 1033-1042页

作者： H.N.Wu d.S.Xu H.Wang R.Yang Institute of Metal Research Chinese Academy of Sciences

Molecular dynamics simulation of uniaxial tension along [001] has been performed to study the influence of various surface defects on the initiation of plastic deformation and fracture of γ-TiAl single *** results indicate that brittle fracture occurs in perfect bulk; surfaces and edges will be detrimental to the strength of materials and provide dislocation nucleation site. The defects on surfaces and edges cause further weakening with various effects depending on defect type, size, position and orientation,while the edge dimples are the most influential. For γ-TiAl rods with surface dimples, dislocations nucleate from an edge of the rod when dimples are small, dimple dislocation nucleation occurs only when the dimples are larger than a strain rate dependent critical size. The dislocations nucleated upon [001]tension are super dislocations with Burger vectors 〈011] or 1/2 〈 112] containing four 1/6 〈 112 〉 partials. The effects of surface scratches are orientation and shape sensitive. Scratches parallel to the loading direction have little influence, while sharp ones perpendicular to the loading direction may cause crack and thus should be avoided. This simulation also shows that, any type of surface defect would lower strength,and cause crack in some cases. But some may facilitate dislocation nucleation and improve ductility of TiAl if well controlled.

关键词： Intermetallic compounds Superdislocation Fracture Surface defects Molecular dynamics

On the Simulation of Industrial Gas dynamic Applications with the disconti- nuous Galerkin Spectral Element Method

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Journal of Thermal Science 2016年第3期25卷 250-257页

作者： F. Hempert M. Hoffmann U. Iben C.-d. Munz Robert-Bosch GmbH Robert-Bosch Campus 1 71272 Renningen Germany Institute of Aerodynamics and Gas dynamics Pfaffenwaldring 21 70569 Stuttgart Germany

In the present investigation, we demonstrate the capabilities of the discontinuous Galerkin spectral element method for high order accuracy computation of gas dynamics. The internal flow field of a natural gas injector for bivalent combustion engines is investigated under its operating conditions. The simulations of the flow field and the aeroacoustic noise emissions were in a good agreement with the cxperirnental data. We tested several shockcapturing techniques for the discontinuous Galerkin scheme. Based on the validated framework, we analyzed the development of the supersonic jets during different opening procedures of a compressed natural gas injector. The results suggest that a more gradual injector opening decreases the noise emission.

关键词： discontinuous Galerkin natural gas injection supersonic under-expanded jet high performance computing

A novel estimation algorithm for torpedo tracking in undersea environment

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Journal of Central South University 2019年第3期26卷 673-683页

作者： d.V.A.N.RAVI KUMAR S.KOTESWARA RAO K.PAdMA RAJU department of ECE GVPCEW department of ECE KLEF department of ECE JNT University

A novel estimation algorithm is introduced to handle the popular undersea problem called torpedo tracking with angle-only measurements with a better approach compared to the existing filters. The new algorithm produces a better estimate from the outputs produced by the traditional nonlinear approaches with the assistance of simple noise minimizers like maximum likelihood filter or any other algorithm which belongs to their family. The introduced method is extended to the higher version in two ways. The first approach extracts a better estimate and covariance by enhancing the count of the intermediate filters, while the second approach accepts more inputs so as to attain improved performance without enhancement of the intermediate filter count. The ideal choice of the placement of towed array sensors to improve the performance of the proposed method further is suggested as the one where the line of sight and the towed array are perpendicular. The results could get even better by moving the ownship in the direction of reducing range. All the results are verified in the MATLAB environment.

关键词： estimation algorithm torpedo tracking angle-only measurements line of sight maximum likelihood filter

Nitrogen enhanced drainage of CO2 rich coal seams for mining

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International Journal of Mining Science and Technology 2017年第5期27卷 755-761页

作者： Luke d.Connell Regina Sander Michael Camilleri deasy Heryanto Zhejun Pan Nicholas Lupton CSIRO Energy ClaytonVictoria 3169Australia

Coal seams with high CO_2 gas contents can be difficult to drain gas for outburst management. Coal has a high affinity for CO_2 with adsorption capacities typically twice that of CH_4. This paper presents an analysis of nitrogen injection into coal to enhance drainage of high CO_2 gas contents. Core flooding experiments were conducted where nitrogen was injected into coal core samples from two Australian coal mining basins with initial CO_2 gas contents and pressures that could be encountered during underground mining. Nitrogen effectively displaced the CO_2 with mass balance analysis finding there was only approximately 6%–7% of the original CO_2 gas content residual at the end of the core flood. Using a modified version of the SIMEd II reservoir simulator, the core flooding experiments were history matched to determine the nitrogen and methane sorption times. It was found that a triple porosity model(a simple extension of the Warren and Root dual porosity model) was required to accurately describe the core flood observations. The estimated model properties were then used in reservoir simulation studies comparing enhanced drainage with conventional drainage with underground in seam boreholes. For the cases considered, underground in seam boreholes were found to provide shorter drainage lead times than enhanced drainage to meet a safe gas content for outburst management.

关键词： Gas drainage High CO2 ECBM Reservoir simulation

Effect of Hydrogen on Corrosion and Stress Corrosion Cracking of AZ91 Alloy in Aqueous Solutions

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Acta Metallurgica Sinica(English letters) 2016年第1期29卷 1-7页

作者： Jian Chen Jian-Qiu Wang En-Hou Han Wei Ke d.W.Shoesmith department of Chemistry Western University Surface Science Western Western University Key Laboratory of Nuclear Materials and Safety Assessment Institute of Metal ResearchChinese Academy of Sciences

The effect of hydrogen on the corrosion and stress corrosion cracking of the magnesium AZ91 alloy has been investigated in aqueous solutions. Hydrogen produced by corrosion in water diffuses into, and reacts with the Mg matrix to form hydride. Some of the hydrogen accumulates at hydride/Mg matrix （or secondary phase） interfaces as a consequence of slow hydride formation and the incompatibility of the hydride with the Mg matrix （or secondary phase）, and combines to form molecular hydrogen. This leads to the development of a local pressure at the hydride/Mg matrix （or secondary phase） interface. The expansion stress caused by hydride formation and the local hydrogen pressure due to its accumulation result in brittle fracture of hydride. These two combined effects promote both the corrosion rate of the AZ91 alloy, and crack initiation and propagation even in the absence of an external load. Hydrogen absorption leads to a dramatic deterioration in the mechanical properties of the AZ91 alloy, indicating that hydrogen embrittlement is responsible for transgulanar stress corrosion cracking in aqueous solutions.

关键词： AZ91 alloy Corrosion Hydrogen Secondary ion mass spectroscopy (SIMS) Transgulanarstress corrosion cracking (TGSCC)

Trajectory sampling and finite-size effects in first-principles stopping power calculations

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npj Computational Materials 2023年第1期9卷 238-246页

作者： Alina Kononov Thomas W.Hentschel Stephanie B.Hansen Andrew d.Baczewski Center for Computing Research Sandia National LaboratoriesAlbuquerqueNMUSA School of Applied&Engineering Physics Cornell UniversityIthacaNYUSA Pulsed Power Sciences Center Sandia National LaboratoriesAlbuquerqueNMUSA

Real-time time-dependent density functional theory(TddFT)is presently the most accurate available method for computing electronic stopping powers from first ***,obtaining application-relevant results often involves either costly averages over multiple calculations or ad hoc selection of a representative ion *** consider a broadly applicable,quantitative metric for evaluating and optimizing trajectories in this *** methodology enables rigorous analysis of the failure modes of various common trajectory choices in crystalline *** randomly selecting trajectories is common practice in stopping power calculations in solids,we show that nearly 30%of random trajectories in an FCC aluminum crystal will not representatively sample the material over the time and length scales feasibly simulated with TddFT,and unrepresentative choices incur errors of up to 60%.We also show that finite-size effects depend on ion trajectory via“ouroboros”effects beyond the prevailing plasmon-based interpretation,and we propose a cost-reducing scheme to obtain converged results even when expensive core-electron contributions preclude large *** work helps to mitigate poorly controlled approximations in first-principles stopping power calculations,allowing 1–2 order of magnitude cost reductions for obtaining representatively averaged and converged results.

关键词： size prevailing selecting

Offshore fears and onshore risk: exchange rate pressures and bank volatility contagion in China

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Economic and Political Studies 2020年第3期8卷 374-393页

作者： Jennifer Lai Paul d.McNelis School of Finance Guangdong University of Foreign StudiesGuangzhouP.R.China Gabelli School of Business Fordham UniversityNew YorkUSA

This paper shows that signals from the offshore China spot market for the Chinese renminbi of the Hong Kong SAR(listed as CNH)directly affect the volatility of share prices of Chinese banks and the overall risks of Chinese banking *** is especially so amid heightened uncertainty about global trade or the People’s Republic of ***,the CNH market volatility is a leading indicator of onshore Chinese banking sector *** results suggest that further offshore exchange market movements arising out of news such as increasing trade friction with the United States will generate greater volatility in the Chinese banking *** from being a shock absorber for the Chinese financial system,the CNH market appears to be a shock transmitter of risk from offshore economic policy uncertainty to the Chinese banking system.

关键词： Chinese banking stability offshore exchange markets exchange rate pressures Chinese currency CNH market