First-Principles Calculations of the Quantum Size Effects on the Stability and Reactivity of Ultrathin Ru (0001) Films

We carry out first-principles calculations of Ru（0001） films up to 30 monolayers （MLs） to study the quantum size effect （Q, SE） of Ru films for two cases： the freestanding Ru films and Ru films on Pt（111） substrates. Our studies show that the properties of these films （surface energy, work-function, charge density decay length in a vacuum and chemical reactivity） exhibit pronounced oscillatory behavior as a function of the film thickness, with an oscillation period of about four MLs for both cases due to the relationship of the match between the Fermi wave vector and the film thickness. Due to the localization of d-electron of Ru films, these quantum oscillations almost disappear when the thickness of the film is more than -20 ML for the free standing Ru films, while for the Ru films on Pt substrates the oscillations disappear quickly when the thickness of the film is beyond -13 ML. Our results reveal that the stability and reactivity of the Ru films could be tailored through Q, SE and the Ru bilayer grown on Pt substrates observed in the experiment is also related to the effect.

A process-oriented approach for identifying potential landslides considering time-dependent behaviors beyond geomorphological features

Geomorphological features are commonly used to identify potential landslides.Nevertheless,overemphasis on these features could lead to misjudgment.This research proposes a process-oriented approach for potential landslide identification that considers time-dependent behaviors.The method integrates comprehensive remote sensing and geological analysis to qualitatively assess slope stability,and employs numerical analysis to quantitatively calculate aging stability.Specifically,a time-dependent stability calculation method for anticlinal slopes is developed and implemented in discrete element software,incorporating time-dependent mechanical and strength reduction calculations.By considering the time-dependent evolution of slopes,this method highlights the importance of both geomorphological features and time-dependent behaviors in landslide identification.This method has been applied to the Jiarishan slope(JRS)on the Qinghai-Tibet Plateau as a case study.The results show that the JRS,despite having landslide geomorphology,is a stable slope,highlighting the risk of misjudgment when relying solely on geomorphological features.This work provides insights into the geomorphological characterization and evolution history of the JRS and offers valuable guidance for studying slopes with similar landslide geomorphology.Furthermore,the process-oriented method incorporating timedependent evolution provides a means to evaluate potential landslides,reducing misjudgment due to excessive reliance on geomorphological features.

基于人工边界条件的波面相位解析重建

At present,the measurement of the near wave field of ships mostly relies on shipborne radar.The commonly used shipborne radar is incoherent and cannot obtain information on wave surface velocity.Therefore,the mathematical model of wave reconstruction is remarkably complex.As a new type of radar,coherent radar can obtain the radial velocity of the wave surface.Most wave surface reconstruction methods that use wave velocity are currently based on velocity potential.The difficulty of these methods lies in determining the initial value of the velocity integral.This paper proposes a wave surface reconstruction method based on an artificial boundary matrix.Numerical simulation data of regular and short-crest waves are used to verify the accuracy of this method.Simultaneously,the reconstruction stability under different wave velocity measurement errors is analyzed.The calculation results show that the proposed method can effectively realize the reconstruction of wave field.

Photo-induced athermal phase transitions of HgX(X= S,Se,Te) by ab initio study

Ab initio calculations of lattice constants, lattice stabilities of HgX（X = S, Se, Te） at different electronic temperatures（T_e） have been performed within the density functional theory（DFT）. We find that the lattice constants of HgX increase and the phonon frequencies reduce as T_e increases. Especially the transverse-acoustic（TA） phonon frequencies of HgX gradually become negative with the elevation of the electron temperature. That is to say ultrafast intense laser induces lattice instabilities of HgX and athermal melting appears for the increase of laser intensity. What is more, with the X atom number increasing, the critical electronic temperatures of HgX are decreased in sequence. This result would be helpful for understanding the athermal melting processes for femtosecond laser micromachining.

The influence of wave surge force on surf-riding/broaching vulnerability criteria check

This study focuses on the influence of the wave surge force on the assessments of the surf-riding/broaching vulnerability criteria according to the new proposal of the IMO Second Generation Intact Stability Criteria. A code is developed for the criteria check and the sample ship calculations show that the accuracy of the wave surge force estimation has a significant influence on the assessment result. For further investigation, the wave surge force measurement through a captive model test is made for a purse seiner to validate the numerical model, the effects of the wave steepness and the ship forward speed on the wave surge force responses are also discussed. It is demonstrated that the diffraction effect is important for the correct estimation of the wave surge force. Therefore, it is recommended to include this effect in the assessment procedure.

Density functional theory study on the influence of cation ratio on the host layer structure of Zn/Al double hydroxides

A density functional theory （DFT） study has been carried out for [Zn-1AI（OH2）n＋6（OH）2n-2]^3＋ （n=3-6） and [Znn-1AI（OH2）2n-2（OH）2n-2]^3＋ （n = 7） clusters, which include the basic structural information of the brucite-like lattice structure of Zn/Al layered double hydroxides （LDHs） with Zn/AI molar ratio （R） in the range 2-6, in order to understand the effect of the Zn/Al ratio on the structure and stability of binary Zn/Al LDHs. Based on systematic calculations of the geometric parameters and formation energies of the cluster models, it was found that it is possible for Zn^2＋ and Al^3＋ cations to replace Mg^2＋ isomorphously in the brucite-like structure with different R values, resulting in differences in microstructure of the clusters and unit cell parameter a of the Zn/Al LDHs. Analysis of the geometry and bonding around the trivalent Al^3＋ or divalent Zn^2＋ cations reveals that Al^3＋ plays a more significant role than Zn^2＋ in determining the microstructure properties, formation and bonding stability of the corresponding ZnRAl clusters when R〈5, while the influence of Zn^2＋ becomes the dominant factor in the case of R〉 5. These findings are in good agreement with experiments. This work provides a detailed electronic-level understanding of how the composition of cations affects the microstructure and stability of Zn-containing binary LDH layers.