Studies on the Structures and Hydrogen-bonding Interactions in Aqueous Glycine Solutions Using All-atom Molecular Dynamics Simulations and NMR Spectroscopy

All-atom molecular dynamics （MD） simulations and chemical shifts were used to study interactions and structures in the glycine-water system. Radial distribution functions and the hydrogen-bond network were applied in MD simulations. Aggregates in the aqueous glycine solution could be classified into different regions by analysis of the hydrogen-bonding network. Temperature-dependent NMR spectra and the viscosity of glycine in aqueous solutions were measured to compare with the results of MD simulations. The variation tendencies of the hydrogen atom chemical shifts and viscosity with concentration of glycine agree with the statistical results of hydrogen bonds in the MD simulations.

Solvation of halogen ions in aqueous solutions at 500 K–600 K under 100 atm

Structural properties of the pure water and halogen solutions at high temperatures and pressures are studied by using the molecular dynamics simulations and quantum molecular simulations. The related characters are calculated as functions of temperature and pressure. The results show that the hydrogen bonded networks become looser as temperature increases,with the collapse of the traditional tetrahedral structure. It is similar to the concentration-dependent collapse in the Na Cl solutions. However, adding other halogen elements has no further effects on the already weakly bonded water molecules.At the phase changing points, the process of hydration is evident for the bigger ions, so that the bigger the ion is, the smaller a cluster is formed.

Investigation of the solute transportation coupled with heat transfer and fluid flow during twin-roll strip casting process

Mathematical model of solute [C] distribution in twin-roll strip casting process has been setup successfully with Calcosoft for the first time. Simulation result shows that in the center of the molten steel pool between the two rolls there is a vortex flow, which is a solute enriched area. But the highest solute concentration position is at the solidification front of the columnar grain zone near the cooling roll surface. Another solute enriched position is in the back flow above the nip point. Combined with the formation mechanism of microstruoture in final as cast strip, analysis shows that solute enriched area is in the transitional area between columnar and equiaxed grain zone.

Comparison of corrosion mechanisms of 510L low alloy steel treated by ACS and EPS techniques under various service environments

The corrosion mechanism of 510L low alloy steel treated by acid-cleaned surface(ACS)and eco-pickled surface(EPS)techniques in three simulated solutions(S0:atmospheric environment;S1:soil environment;S2:industrial environment)and the influence of interaction between different corrosive anions on corrosion were investigated.The results show that the total corrosion rates of samples in three simulated solutions were in order of S2>S0>S1,which is simultaneously correlated with initial corrosion dissolution processes as well as after the formation of corrosion products.HCO3−will inhibit the initial corrosion owing to the formation of films,whereas HSO3−will accelerate the dissolutions of the matrix based on the synergistic action of HSO3−and Cl−.On the other hand,there is no significant difference in corrosion rates between the samples treated by ACS and EPS techniques.The EPS technique that is safe,reusable and environmentally friendly can be further widely used in future work.

BIFURCATIONS AND NEW EXACT TRAVELLING WAVE SOLUTIONS OF THE COUPLED NONLINEAR SCHRDINGER-KdV EQUATIONS

By using the method of dynamical system, the exact travelling wave solutions of the coupled nonlinear Schrdinger-KdV equations are studied. Based on this method, all phase portraits of the system in the parametric space are given. All possible bounded travelling wave solutions such as solitary wave solutions and periodic travelling wave solutions are obtained. With the aid of Maple software, the numerical simulations are conducted for solitary wave solutions and periodic travelling wave solutions to the coupled nonlinear Schrdinger-KdV equations. The results show that the presented findings improve the related previous conclusions.

碳酸物种和氯离子对生物磷灰石磷酸钙成核的影响

磷灰石是骨骼和牙齿等生物硬组织的主要无机成分,对脊椎动物至关重要.生物系统的体液中普遍存在碳酸物种和Cl^(-)离子,了解这些阴离子对生物磷灰石成核过程的影响有助于解释生物矿化的控制作用.理论研究表明,Ca-O配位数在CaP成核和CaP与添加剂的界面相互作用中是一个重要描述符.CaP团簇最外层的Ca^(2+)离子能够通过静电作用吸引碳酸物种和Cl^(-)离子,从而促进CaP相的形成.在碳酸物种和Cl^(-)离子存在的情况下,钙磷石(DCPD)可以转化为羟基磷灰石(HA).平衡氧同位素分馏和振动光谱分析结果表明,Cl^(-)离子掺杂的B型HA是最有可能的生物磷灰石.上述结果可以指导阴离子掺杂的具有生物功能的磷灰石材料的合成.

High corrosion resistance film on rebar by cerium modification

A cerium film was prepared on the surface of rebar by chemical conversion method to enhance its corrosion resistance.The film in the simulated concrete pore solution was measured by electrochemical method,transmission electron microscope(TEM)and X-ray photoelectron spectroscopy(XPS).The effect of temperature on film formation was studied,and the optimum temperature was determined at 35℃.The film produced by too high formation temperature has more defects,resulting in the lower corrosion resistance.The Ce film resistance increased with time evolution until 800 h,then decreased and stabilized.The Ce film layer has a double-layer film structure,the upper layer is an oxide of cerium,and the underlayer is an oxide of iron.Results revealed that after being immersed in the simulated concrete pore solution,the corrosion resistance of the Ce film was enhanced by self-densification.

Lattice Boltzmann model for simulation on leaching process of weathered elution-deposited rare earth ore

The lattice Boltzmann model with coupled chemical reaction was proposed to simulate the ion exchange process of rare earth leaching and verified by comparison with both empirical correlation of mass transfer coefficient and unreacted-core shrinking model. By simulation, the zonation phenomenon of leaching reagent in the leaching column was presented, and the breakthrough curve of leaching reagent was obtained. When t=50 s, there existed the saturated and exchange zones, and the leaching reagent concentration decreased gradually from 20 to 9.3 g/L. In accordance with the breakthrough curve, the breakthrough capacity of ion-type rare earth ore and the adsorbed ion concentration of leaching reagent were derived, the time of t=25 s was the breakthrough point of ammonium ion in leaching reagent and the breakthrough capacity of the rare earth ore was 125 g/L. Besides, the chemical kinetics parameters used for the solute transfer process of rare earth leaching were obtained by the simulation and then were used to determine the rate-limiting steps of rare earth leaching process.