14,409 research outputs found
Effective field theory for triaxially deformed nuclei
Effective field theory (EFT) is generalized to investigate the rotational
motion of triaxially deformed even-even nuclei. A Hamiltonian, called the
triaxial rotor model (TRM), is obtained up to next-to-leading order (NLO)
within the EFT formalism. Its applicability is examined by comparing with a
five-dimensional collective Hamiltonian (5DCH) for the description of the
energy spectra of the ground state and band in Ru isotopes. It is
found that by taking into account the NLO corrections, the ground state band in
the whole spin region and the band in the low spin region are well
described. The results presented here indicate that it should be possible to
further generalize the EFT to triaxial nuclei with odd mass number.Comment: 21 pages, 9 figure
Behavior of the collective rotor in nuclear chiral motion
The behavior of the collective rotor in the chiral motion of triaxially
deformed nuclei is investigated using the particle rotor model by transforming
the wave functions from the -representation to the -representation. After
examining the energy spectra of the doublet bands and their energy differences
as functions of the triaxial deformation, the angular momentum components of
the rotor, proton, neutron, and the total system are investigated. Moreover,
the probability distributions of the rotor angular momentum (-plots) and
their projections onto the three principal axes (-plots) are analyzed. The
evolution of the chiral mode from a chiral vibration at the low spins to a
chiral rotation at high spins is illustrated at triaxial deformations
and .Comment: 21 pages, 6 figure
Doublet bands in Cs in the triaxial rotor model coupled with two quasiparticles
The positive parity doublet bands based on the configuration in Cs have been investigated in the two
quasi-particles coupled with a triaxial rotor model. The energy spectra ,
energy staggering parameter , and
values, intraband ratios,
ratios, and orientation of the
angular momentum for the rotor as well as the valence proton and neutron are
calculated. After including the pairing correlation, good agreement has been
obtained between the calculated results and the data available, which supports
the interpretation of this positive parity doublet bands as chiral bands.Comment: Phys.Rev.C (accepted
A subject-specific EMG-driven musculoskeletal model for applications in lower-limb rehabilitation robotics
Robotic devices have great potential in physical therapy owing to their repeatability, reliability and cost economy. However, there are great challenges to realize active control strategy, since the operator’s motion intention is uneasy to be recognized by robotics online. The purpose of this paper is to propose a subject-specific electromyography (EMG)-driven musculoskeletal model to estimate subject’s joint torque in real time, which can be used to detect his/her motion intention by forward dynamics, and then to explore its potential applications in rehabilitation robotics control. The musculoskeletal model uses muscle activation dynamics to extract muscle activation from raw EMG signals, a Hill-type muscle-tendon model to calculate muscle contraction force, and a proposed subject-specific musculoskeletal geometry model to calculate muscular moment arm. The parameters of muscle activation dynamics and muscle-tendon model are identified by off-line optimization methods in order to minimize the differences between the estimated muscular torques and the reference torques. Validation experiments were conducted on six healthy subjects to evaluate the proposed model. Experimental results demonstrated the model’s ability to predict knee joint torque with the coefficient of determination (R2) value of 0.934±0.0130.934±0.013 and the normalized root-mean-square error (RMSE) of 11.58%±1.44%11.58%±1.44%
Reexamine the nuclear chiral geometry from the orientation of the angular momentum
The paradox on the previous interpretation for the nuclear chiral geometry
based on the effective angle has been clarified by reexamining the system with
the particle-hole configuration
and rotor with deformation parameter . It is found that the
paradox is caused by the fact that the angular momentum of the rotor is much
smaller than those of the proton and the neutron near the bandhead. Hence, it
does not support a chiral rotation interpretation near the bandhead. The
nuclear chiral geometry based on the effective angle makes sense only when the
angular momentum of the rotor becomes comparable with those of the proton and
the neutron at the certain spin region.Comment: 14 pages, 4 figure
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