Research on mass loss and nose shape evolution of kinetic energy projectiles penetrating concrete at high velocity

The high-speed penetration of concrete targets by kinetic energy projectiles results in apparent mass loss,which blunts the nose of the projectile and decrease its penetration performance.The friction work between the projectile and the concrete target,the plastic deformation of the projectile,and the cutting of aggregates to the projectile significantly affect the mass loss of the projectile.To address these effects,a discrete iterative model is developed for the mass loss and nose shape evolution of the projectile by coupling three mechanisms based on the effect of temperature on strength.In the model,both friction work and plastic work increase the temperature of the projectile's surface layer,thereby weakening the strength of this part and rendering it easier for mass loss to occur due to aggregate cutting.The model discretizes the projectile and penetration process with respect to the space and time dimensions,respectively.The mass loss and nose shape evolution of the projectile are obtained by iteratively calculating a point-by-point regression.The predicted depth of penetration(DOP),mass loss,and residual projectile profile are compared with experimental data to validate the model.The comparison shows satisfactory agreement between the calculated results and experimental data.Additionally,the deceleration,velocity,DOP,and mass loss during penetration are analyzed with respect to time.Finally,based on the model,the effects of projectile strength,caliber-radius-head(CRH),and concrete target strength on penetration are discussed.

Overpotential-dependent shape evolution of gold nanocrystals grown in a deep eutectic solvent

This paper reports an overpotential-dependent shape evolution of gold nano-crystals （Au NCs） in a choline chloride-urea （ChCl-urea） based deep eutectic solvent （DES）. It was found that the growth overpotentials play a key role in tuning the shape of Au NCs. The shape evolution of Au NCs successively from concave rhombic dodecahedra （RD） to concave cubes, octopods, cuboctahedral boxes, and finally, to hollow octahedra （OH） was achieved by carefully controlling the growth overpotentials in the range from -0.50 to -0.95 V （vs. Pt quasi-reference electrode）. In addition, the presence of urea was important in the shape evolution of Au NCs. The surface structure of the as-prepared Au NCs was comprehensively characterized by scanning electron microscopy （SEM）, transmission electron microscopy （TEM） and electrochemical studies. It was demonstrated that the electrocatalytic activity of the as-prepared Au NCs for D-glucose electrooxidation was sensitively dependent on their morphologies. The results illustrated that the dehydrogenated glucose adsorbed on concave RD and concave cubic Au NCs was preferentially transformed to gluconolactone at low electrode potentials. Subsequent gluconolactone oxidation occurred favorably on octopods with {111}-truncated arms and hollow OH at high electrode potential. This study opens up a new approach to develop the surface-structure-controlled growth of Au NCs by combining DES with electrochemical techniques. In addition, it is significant for the tuning of the electrocatalytic properties of NCs.

Shape evolution and test of the critical-point symmetry X(5) in ^(176)Os

The lifetimes of excited states in the yrast band of 176Os have been measured up to I = 20 level using the Doppler shift attenuation method. The high-spin states of 176Os were populated via fusion evaporation reaction 152Sm(28Si,4n)176Os at a beam energy of 140 MeV. The results support an X(5) structure for 176Os at low spin. This structure disappears at high spin and shows a symmetry rotor character. The shape change of 176Os is similar to that of 178Os.

Shape evolution of 72,74Kr with temperature in covariant density functional theory

The rich phenomena of deformations in neutron-deficient krypton isotopes, such as shape evolution with neutron number and shape coexistence, have attracted the interest of nuclear physicists for decades. It is interesting to study such shape phenomena using a novel way, e.g. by thermally exciting the nucleus. In this work, we develop the finite temperature covariant density functional theory for axially deformed nuclei with the treatment of pairing correlations by the BCS approach, and apply this approach for the study of shape evolution in 72,74Kr with increasing temperature. For 72Kr, with temperature increasing, the nucleus firstly experiences a relatively quick weakening in oblate deformation at temperature T-0.9 MeV, and then changes from oblate to spherical at T-2.1 MeV. For 74Kr, its global minimum is at quadrupole deformation β2--0.14 and abruptly changes to spherical at T-1.7 MeV. The proton pairing transition occurs at critical temperature 0.6 MeV following the rule Tc =0.6△p （0）, where △p（0） is the proton pairing gap at zero temperature. The signatures of the above pairing transition and shape changes can be found in the specific heat curve. The single-particle level evolutions with temperature are presented.

Shape Co-Existence in the Transitional Nuclide ^(157)yb

High-spin states in 157Yb have been populated in the 144Sm（160, 3n）157yb fusion- evaporation reaction at a beam energy of 85 MeV, and two rotational bands have been established for the first time. Within the framework of the triaxial particle-rotor model, the energy spectra and single-particle configurations of 157Yb are investigated. The calculated energy spectra agree well with the experimental data. The newly observed vf7/2 band, and the previously known vi13/2 band in 157Yb, are also discussed by means of Total-Routhian-Surface methods. The structural characters observed in 157Yb provide evidence for the shape coexistence of three distinct shapes： prolate, triaxial and oblate. At higher spins, both the vf7/2 band and the vi13/2 band in 157Yb undergo a shape evolution with sizable alignments occurring.

Effective shape-controlled growth of monolayer MoS2 flakes by powder-based chemical vapor deposition

In the recent years, transition-metal dichalcogenides such as MoS2 have attracted considerable attention owing to their unique structure and electronic properties. Chemical vapor deposition （CVD） is a popular method for producing MoS2 flakes with different shapes. Here, we report an effective method for achieving a broad range of shape evolution in CVD-grown monolayer MoS2 flakes. By controlling the S and MoO3 temperatures, the shape of the monolayer MoS2 flakes was varied from hexagonal to triangular via intermediate shapes such as truncated and multi-apex triangles. The shape evolution of the MoS2 flakes can be explained by introducing the term “nominal Mo：S ratio”, which refers to the amount of loaded MoO3 and evaporated S powders. By using the nominal Mo：S ratio, we predicted the potential reaction atmosphere and effectively controlled the actual proportion of MoO3-x with respect to S in the growth region, along with the growth temperature. From the systematic investigation of the behavior of the shape evolution, we developed a shape-evolution diagram, which can be used as a practical guide for producing CVD-grown MoS2 flakes with desired shapes