Problem of energy scale in rigid triaxial rotor model

The problem of mismatching of the level energies, in the ground band and the [Formula: see text]-band of triaxially deformed atomic nuclei, as predicted in the rigid triaxial rotor (RTR) approximation of Davydov and Filippov (DF) model, with experiment, is well known. Here, we illustrate the solutions suggested in the literature, and the deviations observed in the converted energy values, from the experiment. We analyze the source of problem of this mismatch with experiment. This enables a physical picture of the DF (or RTR) model spectra. Our analysis will help in understanding the merits and the limitation of the RTR model in this respect.

Interrogating the Lead-up to a Critical Speed in Rotordynamics

This paper presents a new approach to predicting an incipient critical speed in a rotating shaft. Based on the classical governing equations of motion for an eccentric mass on a flexible shaft (the Jeffcott rotor model), the approach is centered on examining the behavior of small perturbations or random disturbances to infer the approach of a critical speed (resonance). Such disturbances, that may be based on intentional probing, or simply the result of naturally occurring fluctuations, cause small transients. It is the changing nature of these transients (as characterized by their associated eigenvalues) that is used to assess the proximity to a critical speed. In this paper the material developed is based on analysis, but generating the data from simulations or experiments will be the next step. The approach is a kind of stress-test, conceptually not dissimilar to structural health monitoring and damage detection, but here directed toward the lead-up to resonance.

Parametric Study of Flexure Pivot Bearing Induced Thermal Bow-Rotor Instability (Morton effect)

This paper investigates the journal asymmetric temperature induced thermal bow vibration of a rotor, as supported by a flexure pivot journal bearing (FPJB). Thermal bow induced vibration, known as Morton effect (ME) is caused by non-uniform viscous heating of the journal, and the resulting thermal bow often causes increasing vibration amplitudes with time-varying phase. Full FJPB's structural and thermal finite element models are developed and integrated into the flexible rotor model. The model is validated by comparing its predicted ME response with experimental results. A FPJB model, which uses predicted “equivalent” radial and tilting stiffness of the bearing is compared with the full FEM-based model. The impact of FPJB's design parameters such as web thickness, bearing material, and housing thicknesses are investigated with parametric studies. The results show that FPJB parameter values may have a major effect on the speed range of ME vibration, and its severity.

Generalized abelian gauge field theory under rotor model

Gauge field theory with rank-one field [Formula: see text] is a quantum field theory that describes the interaction of elementary spin-1 particles, of which being massless to preserve gauge symmetry. In this paper, we give a generalized, extended study of abelian gauge field theory under successive rotor model in general [Formula: see text]-dimensional flat spacetime for spin-1 particles in the context of higher-order derivatives. We establish a theorem that [Formula: see text] rotor contributes to the [Formula: see text] fields in the integration-by-parts formalism of the action. This corresponds to the transformation of gauge field [Formula: see text] and gauge field strength [Formula: see text] in the action. The [Formula: see text] case restores back to the standard abelian gauge field theory. The equation of motion and Noether’s conserved current of the theory are also studied.

Study of signature inversion in 123,125I using Particle Rotor Model calculations

The phenomenon of signature inversion in positive parity yrast states of [Formula: see text]I nuclei has been studied using the Particle Rotor Model (PRM) calculations. The experimentally observed signature inversion is well reproduced from the PRM calculations. The change in the value of a triaxial parameter [Formula: see text] was observed after the inversion. The PRM calculations were also used to describe the reduced transition probabilities. The derived change in the value of “[Formula: see text]” (in Lund convention) after inversion is interpreted as the change in nuclear shape from near triaxial to tending towards noncollective oblate.