Spherical to deformed shape transition in the nucleon-pair shell model

A study of the shape transition from spherical to axially deformed nuclei in the even Ce isotopes using the nucleon-pair approximation of the shell model is reported. As long as the structure of the dominant collective pairs is determined using a microscopic framework appropriate to deformed nuclei, the model is able to produce a shape transition. However, the resulting transition is too rapid, with nuclei that should be transitional being fairly well deformed, perhaps reflecting the need to maintain several pairs with each angular momentum.Comment: 7 pages, 5 figure

Thermal Logic Gates: Computation with phonons

Logic gates are basic digital elements for computers. We build up thermal logic gates that can perform similar operations as their electronic counterparts. The thermal logic gates are based on the nonlinear lattices, which exhibit very intriguing phenomena due to their temperature dependent power spectra. We demonstrate that phonons, the heat carriers, can be also used to carry information and processed accordingly. The possibility of nanoscale experiment is discussed.Comment: 5 pages, 5 figures. To appear in Phys. Rev. Let

Counting statistics of tunneling through a single molecule: effect of distortion and displacement of vibrational potential surface

We analyze the effects of a distortion of the nuclear potential of a molecular quantum dot (QD), as well as a shift of its equilibrium position, on nonequilibrium-vibration-assisted tunneling through the QD with a single level ($\epsilon_d$) coupled to the vibrational mode. For this purpose, we derive an explicit analytical expression for the Franck-Condon (FC) factor for a displaced-distorted oscillator surface of the molecule and establish rate equations in the joint electron-phonon representation to examine the current-voltage characteristics and zero-frequency shot noise, and skewness as well. Our numerical analyses shows that the distortion has two important effects. The first one is that it breaks the symmetry between the excitation spectra of the charge states, leading to asymmetric tunneling properties with respect to $\epsilon_d>0$ and $\epsilon_d<0$. Secondly, distortion (frequency change of the oscillator) significantly changes the voltage-activated cascaded transition mechanism, and consequently gives rise to a different nonequilibrium vibrational distribution from that of the case without distortion. Taken in conjunction with strongly modified FC factors due to distortion, this results in some new transport features: the appearance of strong NDC even for a single-level QD with symmetric tunnel couplings; a giant Fano factor even for a molecule with an extremely weak electron-phonon interaction; and enhanced skewness that can have a large negative value under certain conditions.Comment: 29 pages, 11 figures, published versio

New axial laminated-structure flux-switching permanent magnet machine with 6/7 poles

In this paper, one new axially laminated-structure flux-switching permanent magnet machine (ALSFSPMM) with 6/7 (stator/rotor) poles is proposed. Different from the conventional flux-switching permanent magnet machine (FSPMM), the stator and rotor of ALSFSPMM are laminated parallel to the axial direction, which can make full use of PM flux linkage, decrease part magnetic saturation, and reduce the iron loss particularly in the range of high speed. By the 2-D model prediction of finite element algorithm (FEA), ALSFSPMM has lower cogging torque, stronger flux weakening ability, greater torque density, higher efficiency, etc., and hence it is an ideal candidate for the drive system of plug-in hybrid electrical vehicle (PHEV). © 2011 IEEE

Nuclear pairing reduction due to rotation and blocking

Nuclear pairing gaps of normally deformed and superdeformed nuclei are investigated using the particle-number conserving (PNC) formalism for the cranked shell model, in which the blocking effects are treated exactly. Both rotational frequency $\omega$-dependence and seniority (number of unpaired particles) $\nu$-dependence of the pairing gap $\tilde{\Delta}$ are investigated. For the ground-state bands of even-even nuclei, PNC calculations show that in general $\tilde{\Delta}$ decreases with increasing $\omega$, but the $\omega$-dependence is much weaker than that calculated by the number-projected Hartree-Fock-Bogolyubov approach. For the multiquasiparticle bands (seniority $\nu> 2$), the pairing gaps keep almost $\omega$-independent. As a function of the seniority $\nu$, the bandhead pairing gaps $\tilde{\Delta}(\nu,\omega=0)$ decrease slowly with increasing $\nu$. Even for the highest seniority $\nu$ bands identified so far, $\tilde{\Delta}(\nu,\omega=0)$ remains greater than 70% of $\tilde{\Delta}(\nu=0,\omega=0)$.Comment: 15 pages, 5 figure

Optimal design of high-frequency magnetic links for power converters used in grid-connected renewable energy systems

© 2014 IEEE. Recently high-frequency common magnetic links with cores of advanced magnetic materials, such as nanocrystalline and amorphous materials, have been considered as viable candidates for the development of medium-voltage power converters. This offers a new route of step-up-transformer-less compact and lightweight direct grid integration of renewable generation systems. Most importantly, it minimizes the voltage imbalance and common mode issues of the converter systems. However, the electromagnetic design of high-frequency common magnetic links is a multiphysics problem and thereby affects the system efficiency and cost. In this paper, an optimization technique is proposed and verified by prototype magnetic links. The design optimization, implementation, test platform, and experimental test results are analyzed and discussed

An assessment of wetland nature reserves and the protection of China’s vertebrate diversity

Evaluación de los humedales declarados reserva natural y protección de la diversidad de vertebrados de China Se evaluaron las reservas naturales existentes en China y se estudió la distribución de los cuatro taxones de vertebrados terrestres endémicos y amenazados, que comprenden los reptiles, los anfibios, las aves y los mamíferos. Con vistas a determinar la riqueza de las especies, se combinó la evaluación anterior de los 148 humedales declarados reserva natural con la lista de los vertebrados endémicos y amenazados elaborada por el gobierno. Dicha riqueza de especies se clasificó en tres categorías: alta, media y baja mediante un análisis factorial y se seleccionaron 31 ecosistemas de humedales como zonas de alta protección. Asimismo, se analizó la relación existente entre las especies amenazadas y las endémicas en las reservas, y se observó que ambos modelos de riqueza eran parecidos. Se espera que, sobre la base del estudio de la riqueza, se pueda crear un sistema de clasificación de las reservas naturales, con su gestión correspondiente, con el objetivo de proteger la diversidad de las especies en China.We assessed all 148 wetland nature reserves in China and the distribution of the four taxa of endemic and threatened terrestrial vertebrates, reptiles, amphibians, birds and mammals. Assessment of the wetland nature reserves was combined with the governmental list of the endemic and threatened vertebrates to identify the richness of the species. Species richness was scored as high, medium or low using a factor analysis method, and 31 wetland ecosystems were marked as high protection areas. The relationship between the threatened species and the endemic species in the reserves was also analyzed. We found that both richness patterns were similar. Based on the richness study, a nature reserve classification system with correspondingEvaluación de los humedales declarados reserva natural y protección de la diversidad de vertebrados de China Se evaluaron las reservas naturales existentes en China y se estudió la distribución de los cuatro taxones de vertebrados terrestres endémicos y amenazados, que comprenden los reptiles, los anfibios, las aves y los mamíferos. Con vistas a determinar la riqueza de las especies, se combinó la evaluación anterior de los 148 humedales declarados reserva natural con la lista de los vertebrados endémicos y amenazados elaborada por el gobierno. Dicha riqueza de especies se clasificó en tres categorías: alta, media y baja mediante un análisis factorial y se seleccionaron 31 ecosistemas de humedales como zonas de alta protección. Asimismo, se analizó la relación existente entre las especies amenazadas y las endémicas en las reservas, y se observó que ambos modelos de riqueza eran parecidos. Se espera que, sobre la base del estudio de la riqueza, se pueda crear un sistema de clasificación de las reservas naturales, con su gestión correspondiente, con el objetivo de proteger la diversidad de las especies en China