Most of this review is devoted to a description of the interacting boson model in its different forms and to a discussion of its applications to a range of nuclei. Possible relations between the interacting boson model and the collective model are described and some attempts to derive the interacting boson model from the shell model are reviewed. To help the non-specialist reader the article begins with a survey of the more firmly established nuclear models.

http://iopscience.iop.org/article/10.1088/0034-4885/48/2/001/pdf

The interacting boson model of nuclear structure

Inelastic scattering exciting the ${2}^{+}$ and ${4}^{+}$ members of the ${K}^{\ensuremath{\pi}}$${=2}^{+}$ \ensuremath{\gamma}-vibrational band in $^{152}$,154Sm, $^{160}\mathrm{Gd}$, $^{164}\mathrm{Dy}$, $^{166}$,168Er, $^{176}\mathrm{Yb}$, $^{182}$,184W, and $^{192}\mathrm{Os}$ has been measured with 65-MeV polarized protons. Coupled-channel analyses have been performed assuming the \ensuremath{\gamma}-vibrational model or the asymmetric rotor model. A large hexadecapole (${Y}_{42}$) term in the \ensuremath{\gamma} motion is necessary in both models in order to reproduce the experimental data. The quadrupole (${Y}_{22}$) and hexadecapole (${Y}_{42}$) transition strengths to the \ensuremath{\gamma}-vibrational band have been extracted systematically from the optical potential parameters and the deformation parameters for the first time. These show a strong mass number dependence, and can be understood qualitatively by a simple geometrical picture together with the quadrupole (${Y}_{20}$) and hexadecapole (${Y}_{40}$) moments. The experimental ${Y}_{22}$ and ${Y}_{42}$ strengths have been compared with a random-phase-approximation calculation. This suggests the importance of the hexadecapole degree of freedom in the \ensuremath{\gamma} vibration. A density-dependent Hartree-Fock calculation explains the quadrupole (${Y}_{20}$) moments and the trend of the hexadecapole (${Y}_{40}$) moments of the deformed optical potentials very well. The effect of the density dependence of the effective interaction is also discussed through the ${Y}_{20}$ moments and ${Y}_{22}$ strengths.

Inelastic proton scattering exciting the gamma -vibrational band in deformed nuclei (152 <= A <= 192) at 65 MeV and the systematics of the hexadecapole (Y42) strength of the gamma vibration.

Group theoretical aspects of the extended interacting boson model (gIBM) with s, d, and g bosons are discussed. The basis states and branching rules are given for the seven dynamical symmetries. Casimir operators and their eigenvalues are obtained and enable one to write down energy formulas.

Group theoretical aspects of the extended interacting boson model

On the influence of the O(5) symmetry on shape coexistence in atomic nuclei

Anharmonicities of γ-vibrations in 168Er

The g-boson and the collective states of 168Er

Group theoretical study of s-d-g interacting boson model and 168Er spectrum

Effect of workpiece microstructure on tool wear behavior and surface quality during machining Inconel 718 alloy

The infiltration and cooling effect of lubricant droplets in the cutting zone largely depend on setting minimum quantity lubricant (MQL) system parameters appropriately. The study determines the optimal spray angle and spray distance relying on the geometric position relationship between the nozzle and the overall cutting zone. A numerical model that combines computational fluid dynamics (CFD) and discrete phase model (DPM) is presented to simulate droplet transport process for dynamic milling and one-tooth milling by flow field distribution and droplet characteristics. The influences of different spray distances and spray angles on the infiltration process and cutting tool temperature are analyzed. The experiments aimed at verifying the results of the analysis are conducted by measuring cutting force, cutting temperature, surface roughness, surface microtopography and tool wear. The result indicates that the spray distance has a significant impact on the jet divergence, and insufficient lubrication or excessive lubrication is effectively avoided with the optimal cutting distance. Spraying in the direction of cutting-out promotes the accessibility of the lubricant and greater concentration of droplets in the cutting zone, especially later in the cutting process, which results in increased infiltration, reduced friction, and improved heat dissipation. Moreover, experiments demonstate that the optimal state of jetting in the direction of cutting-out is 46 °C lower than that of dry cutting, the surface roughness is reduced by 19.8%, and the wear amount is reduced by roughly 34%. This study has a better understanding of the setting of spray distance and spray angle in MQL milling and the development of equipment, which provides theoretical guidance for the optimization of MQL system parameters in practical applications. 

Xiao-Qian Zhou

Papers

The g-boson and the collective states of 168Er

Group theoretical study of s-d-g interacting boson model and 168Er spectrum

Effect of workpiece microstructure on tool wear behavior and surface quality during machining Inconel 718 alloy

Analysis of droplet characteristics and cooling lubrication effects in MQL milling of 316L stainless steel

Experimental characterization of the performance of MQL-assisted turning of solution heat-treated and aged Inconel 718 alloy