Robustness of the octupole collectivity in 144Ba within the cranking covariant density functional theory in 3D lattice

The octupole deformation and collectivity in octupole double-magic nucleus 144Ba are investigated using the Cranking covariant density functional theory in a three-dimensional lattice space.The reduced B(E3)transition probability is implemented for the first time in semiclassical approximation based on the microscopically calculated electric octupole moments.The available data,including the I-ωrelation and electric transitional probabilities B(E2)and B(E3)are well reproduced.Furthermore,it is shown that the ground state of 144Ba exhibits axial octupole and quadrupole deformations that persist up to high spins(I≈24h).

Nuclear charge radius predictions by kernel ridge regression with odd-even effects

The extended kernel ridge regression(EKRR)method with odd-even effects was adopted to improve the description of the nuclear charge radius using five commonly used nuclear models.These are:(i)the isospin-dependent A^(1∕3) formula,(ii)relativistic continuum Hartree-Bogoliubov(RCHB)theory,(iii)Hartree-Fock-Bogoliubov(HFB)model HFB25,(iv)the Weizsacker-Skyrme(WS)model WS*,and(v)HFB25*model.In the last two models,the charge radii were calculated using a five-parameter formula with the nuclear shell corrections and deformations obtained from the WS and HFB25 models,respectively.For each model,the resultant root-mean-square deviation for the 1014 nuclei with proton number Z≥8 can be significantly reduced to 0.009-0.013 fm after considering the modification with the EKRR method.The best among them was the RCHB model,with a root-mean-square deviation of 0.0092 fm.The extrapolation abilities of the KRR and EKRR methods for the neutron-rich region were examined,and it was found that after considering the odd-even effects,the extrapolation power was improved compared with that of the original KRR method.The strong odd-even staggering of nuclear charge radii of Ca and Cu isotopes and the abrupt kinks across the neutron N=126 and 82 shell closures were also calculated and could be reproduced quite well by calculations using the EKRR method.

Low-energy spin dynamics in a Kitaev material Na_(3)Ni_(2)BiO_(6) investigated by nuclear magnetic resonance

We perform ^(23)Na nuclear magnetic resonance(NMR) and magnetization measurements on an S=1,quasi-2D honeycomb lattice antiferromagnet Na_(3)Ni_(2)BiO_(6).A large positive Curie-Weiss constant of 22.9 K is observed.The NMR spectra at low fields are consistent with a zigzag magnetic order,indicating a large easy-axis anisotropy.With the field applied along the c*axis,the NMR spectra confirm the existence of a 1/3-magnetization plateau phase between 5.1 T and 7.1 T.The transition from the zigzag order to the 1/3-magnetization plateau phase is also found to be a first-order type.A monotonic decrease of the spin gap is revealed in the 1/3-magnetization plateau phase,which reaches zero at a quantum critical field H_(C)≈8.35 T before entering the fully polarized phase.These data suggest the existence of exchange frustration in the system along with strong ferromagnetic interactions,hosting the possibility for Kitaev physics.Besides,well below the ordered phase,the 1/T_(1) at high fields shows either a level off or an enhancement upon cooling below 3 K,which suggests the existence of low-energy fluctuations.

Non-Markovian entanglement transfer to distant atoms in a coupled superconducting resonator

We investigate the non-Markovian effects on the entanglement transfer to the distant non-interacting atom qubits,which are embedded in a coupled superconducting resonator.The master equation governing the dynamics of the system is derived by the non-Markovian quantum state diffusion(NMQSD)method.Based on the solution,we show that the memory effect of the environment can lead to higher entanglement revival and make the entanglement last for a longer time.That is to say,the non-Markovian environment can enhance the entanglement transfer.It is also found that the maximum entanglement transferred to distant atoms can be modified by appropriately selecting the frequency of the modulated intercavity coupling.Moreover,with the initial anti-correlated state,the entanglement between the cavity fields can be almost completely transferred to the separated atoms.Lastly,we show that the memory effect has a significant impact on the generation of entanglement from the initial non-entangled states.

具有未知参数的机器人-摄像机系统的自适应动态反馈跟踪控制（英文）

The tracking problem of nonholonomic mobile robots with uncertainties is investigated in this paper. An uncertain model of the nonholonomic kinematic system is presented based on the visual feedback and the state and input transformations for a kind of mobile robots in chained form with uncertainties. Two transformations are exploited based on the idea of backstepping and the structure of tracking error system. Then, both an adaptive control law and a dynamic feedback robust controller are designed to track the desired trajectory by using Lyapunov direct method and the extended Barbalat Lemma. The asymptotic convergence of a closed-loop error system is proved rigorously. Finally, simulation results demonstrate the effectiveness of the proposed strategies.

Thermal Stability and Degradation of Chitosan Modified by Cinnamic Acid

The reaction of chitosan with cinnamic acid gave the corresponding N-cinnamoyl chitosan (NCC) polymer. The chem-ical structure of the modified polymer was characterized by IR, 1H-NMR and elemental analysis. Thermogravim- etric analysis reveals that the thermal stability of chitosan polymer is greater than NCC polymer. The activation energies of thermal degradation of chitosan and NCC polymers were determined using Arrhenius relationship. Thermal degradation of NCC polymer was studied and the products of degradation were identified by GC-MS technique. It seems that the mechanism of degradation of NCC polymer is characterized by elimination of low-molecular weight radicals. Combination of these radicals and random scission mechanism along the backbone chain are the main source of the degradation products.

Thermomagnetic effect with microtemperature in a semiconducting photothermal excitation medium

The main goal of this paper is to focus on the investigation of interaction between a magnetic field and elastic materials with microstructure, whose microelements possess microtemperatures with photothermal excitation. The elastic-photothermal prob- lem in one-dimension is solved by introducing photothermal excitation at the free surface of a semi-infinite semiconducting medium （semiconductor rod）. The integral transform technique is used to solve the governing equations of the problem under the effect of the microtemperature field. The analytical expressions for some physical quantities in the physical domain are obtained with the heating boundary surface and free traction. The numerical inversion technique is used to obtain the resulting quantities in the physical domain. The obtained numerical results with some comparisons are discussed and shown graphically.

Adsorption-controlled transition of the electrical properties realized in Hematite(alpha-Fe_2O_3) nanorods ethanol sensing

Alpha-Fe203 nanorods are synthesized through a hydrotherrnal method with no surfactant introduced and ethanol sensors are fabricated from these nanorods. The device can respond to ethanol vapour in a concentration range from 1 to 1500 parts per million and shows both p-type and n-type responding characteristics during the investigation of the ethanol sensing. The sensor displays a p-type characteristic when the ethanol concentration is low and converted into an n-type characteristic as the concentration exceeds a certain value. Such a phenomenon is attributed to the chemisorbed oxygen, which leads to different modifications of the energy band at the surface, namely, depletion layer or inversion layer.

NMR Evidence of Antiferromagnetic Spin Fluctuations in Nd_(0.85)Sr_(0.15)NiO_(2)

Despite the recent discovery of superconductivity in Nd_(1-x)Sr_(x)NiO_(2) thin films,the absence of superconductivity and antiferromagnetism in their bulk materials remains a puzzle.Here we report the 1H NMR measurements on powdered Nd0.85Sr0.15NiO2 samples by taking advantage of the enriched proton concentration after hydrogen annealing.We find a large full width at half maximum of the spectrum,which keeps increasing with decreasing the temperature T and exhibits an upturn behavior at low temperatures.The spin-lattice relaxation rate ^(1)T_(1)^(-1) is strongly enhanced when lowering the temperature,developing a broad peak at about 40 K,then decreases following a spin-wave-like behavior ^(1)T_(1)^(-1)∝T^(2) at lower temperatures.These results evidence a short-range glassy antiferromagnetic ordering of magnetic moments below 40 K and dominant antiferromagnetic fluctuations extending to much higher temperatures.Our findings reveal the strong electron correlations in bulk Nd_(0.85)Sr_(0.15)NiO_(2),and shed light on the mechanism of superconductivity observed in films of nickelates.

Generalized Square Conservative Multistep Finite Difference Scheme Incorporating Historical Observations

In this paper,a multistep finite difference scheme has been proposed,whose coefficients are determined taking into consideration compatibility and generalized quadratic conservation,as well as incorporating historical observation data.The schemes have three advantages:high-order accuracy in time,generalized square conservation,and smart use of historical observations.Numerical tests based on the one-dimensional linear advection equations suggest that reasonable consideration of accuracy,square conservation,and inclusion of historical observations is critical for good performance of a finite difference scheme.

Controlling the entanglement of mechanical oscillators in composite optomechanical system

A controllable entanglement scheme of two mechanical oscillators is proposed in a composite optomechanical system.In the case of strong driving and high dissipation,the dynamics of the movable mirror of the optomechanical cavity is characterized by an effective frequency in the long-time evolution of the system.Considering the classical nonlinear effects in an optomechanical system,we investigate the relationship between the effective frequency of the movable mirror and the adjustable parameters of the cavity.It shows that the effective frequency of the movable mirror can be adjusted ranging fromωm（the resonance frequency of the coupling oscillator） to-ωm.Under the condition of experimental realization,we can generate and control steady-state entanglement between two oscillators by adjusting the effective frequency of the movable mirror and reducing the effective dissipation by selecting the parameter of the cavity driving laser appropriately.Our scheme provides a promising platform to control the steady-state behavior of solid-state qubits using classical manipulation,which is significant for quantum information processing and fundamental research.

Study on Mott-Insulator-Superfluid Phase Transition in Symmetric and Unsymmetric Double-Chain Bose-Hubbard Model

The symmetric and the asymmetric double-chain Bose-Hubbard Models( BHMs) are studied by the mean-field theory. By using Landau's quantum phase transition theory,phase diagrams for systems with different hopping energies and repulsive interactions are obtained. Thereby,Mott-insulator-superfluid( MISF)phase transition boundaries are determined. Our results show that tunneling effects between two chains provide additional channels for particles hopping between corresponding optical lattice sites of different chains,which makes easier for systems to transit from MI to SF phase. The two-site parity function is also utilized to investigate the properties of the system near the quantum phase transit point.We found that the increase of inter-chain hopping will reinforce the tunneling effects between two chains,and reduce the intrachain tunneling effects within the same chain.

Fractional-order Generalized Principle of Self-support (FOGPSS) in Control System Design

This paper reviews research that studies the principle of self-support U+0028 PSS U+0029 in some control systems and proposes a fractional-order generalized PSS framework for the first time. The existing PSS approach focuses on practical tracking problem of integer-order systems including robotic dynamics, high precision linear motor system, multi-axis high precision positioning system with unmeasurable variables, imprecise sensor information, uncertain parameters and external disturbances. More generally, by formulating the fractional PSS concept as a new generalized framework, we will focus on the possible fields of the fractional-order control problems such as practical tracking, U+03BB-tracking, etc. of robot systems, multiple mobile agents, discrete dynamical systems, time delay systems and other uncertain nonlinear systems. Finally, the practical tracking of a first-order uncertain model of automobile is considered as a simple example to demonstrate the efficiency of the fractional-order generalized principle of self-support U+0028 FOGPSS U+0029 control strategy. © 2014 Chinese Association of Automation.

Double-passage mechanical cooling in a coupled optomechanical system

We consider a three-mode optomechanical system where two cavity modes are coupled to a common mechanical oscillator. We focus on the resolved sideband limit and illustrate the relation between the significant parameters of the system and the instantaneous-state mean phonon number of the oscillator cooled to the ground state, particularly at the early stage of the evolution. It is worth noting that the optical coupling sets up a correlation between the two cavity modes,which has significant effect on the cooling process. Using numerical solutions, we find that the inter-cavity coupling will decrease the cooling effect when both cavities have the same effective optomechanical coupling. However, when the effective optomechanical couplings are different, the cooling effect will be strongly improved by selecting appropriate range of inter-cavity coupling.

Quantum steering in Heisenberg models with Dzyaloshinskii–Moriya interactions

In this work, we study the quantum steering in two-qubit Heisenberg models with Dzyaloshinskii–Moriya(DM)interaction and an external magnetic field. We find that the steerable weight(SW) and the critical temperature where SW → 0 can be enhanced by the DM interactions. In the special case where the magnetic field is vanishing and the two spins are ferromagnetically coupled, the DM interaction can tune the zero-temperature SW from zero to a finite value. In addition to the SW, some other measurements used to identify the quantum entanglement and quantum correlations are investigated, i.e., the concurrence, the quantum discord, and the robustness of coherence. In the strong magnetic field limit,our results show that the SW is dramatically different from the other measurements.

Glassy behaviour of random field Ising spins on Bethe lattice in external magnetic field

The thermodynamics and the phase diagram of random field Ising model （RFIM） on Bethe lattice are studied by using a replica trick. This lattice is placed in an external magnetic field （B）. A Gaussian distribution of random field （hi） with zero mean and variance （hi2 = H2RF is considered. The free-energy （F）, the magnetization （M） and the order parameter （q） are investigated for several values of coordination number （z）. The phase diagram shows several interesting behaviours and presents tricritical point at critical temperature Tc = J/k and when HRF = 0 for finite z. The free-energy （F） values increase as T increases for different intensities of random field （HRE） and finite z. The internal energy （U） has a similar behaviour to that obtained from the Monte Carlo simulations. The ground state of magnetization decreases as the intensity of random field HRF increases, The ferromagnetic （FM） paramagnetic （PM） phase boundary is clearly observed only when z →∞. While FM PM-spin glass （SG） phase boundaries are present for finite z. The magnetic susceptibility （X） shows a sharp cusp at Tc in a small random field for finite z and rounded different peaks on increasing HRF.

Glassy phase and thermodynamics for random field Ising model on spherical lattice in magnetic field

Phase diagram and thermodynamic parameters of the random field Ising model （RFIM） on spherical lattice are studied by using mean field theory. This lattice is placed in an external magnetic field （B）. The random field （hi） is assumed to be Gaussian distributed with zero mean and a variance （hi2） = HRF2. The free energy （F）, the magnetization （M） and the order parameter （q） are calculated. The ferromagnetic （FM） spin-glass （SG） phase transition is clearly observed. The critical temperature （Tc） is computed under a critical intensity of random field HRF = V/2/πJ. The phase transition from FM to paramagnetic （PM） occurs at TC = J/k in the absence of magnetic field. The critical temperature decreases as HRF increases in the phase boundary of FM-to-SG. The magnetic susceptibility （X） shows a sharp cusp at TC and the specific heat （C） has a singularity in small random field. The internal energy （U） has a similar behaviour to that obtained from the Monte Carlo simulation.

Robustness of coherence between two quantum dots mediated by Majorana fermions

We study three important measurements used to identify the quantum correlations between two quantum dots （QDs） mediated by a pair of Majorana fermions （MFs） in a superconducting quantum wire. We find that, in addition to the quantum discord, the robustness of coherence （ROC） can also be considered as a quantity to measure the quantum correlation for the special case where the quantum entanglement is vanishing. For comparison, we study the quantum correlation between two QDs mediated by other fermions, i.e., regular fermions and superconducting fermions. We find that, when the quantum entanglement is not vanishing, i.e., the concurrence is finite, the detailed difference between the concurrence and ROC can be considered as an important implication for the existence of MFs.

Dust Acoustic Solitary Waves in Saturn F-ring's Region

Effect of hot and cold dust charge on the propagation of dust-acoustic waves （DAWs） in unmagnetized plasma having electrons, singly charged ions, hot and cold dust grains has been investigated. The reductive perturbation method is employed to reduce the basic set of fluid equations to the Kortewege-de Vries （KdV） equation. At the critical hot dusty plasma density Nho, the KdV equation is not appropriate for describing the system. Hence, a set of stretched coordinates is considered to derive the modified KdV equation. It is found that the presence of hot and cold dust charge grains not only significantly modifies the basic properties of solitary structure, but also changes the polarity of the solitary profiles. In the vicinity of the critical hot dusty plasma density Nho, neither KdV nor mKdV equation is appropriate for describing the DAWs. Therefore, a further modified KdV （fmKdV） equation is derived, which admits both soliton and double layer solutions.

Three-Step Difference Scheme for Solving Nonlinear Time-Evolution Partial Differential Equations

In this paper, a special three-step difference scheme is applied to the solution of nonlinear time-evolution equations, whose coefficients are determined according to accuracy constraints, necessary conditions of square conservation, and historical observation information under the linear supposition. As in the linear case, the schemes also have obvious superiority in overall performance in the nonlinear case compared with traditional finite difference schemes, e.g., the leapfrog(LF) scheme and the complete square conservation difference(CSCD) scheme that do not use historical observations in determining their coefficients, and the retrospective time integration(RTI) scheme that does not consider compatibility and square conservation. Ideal numerical experiments using the one-dimensional nonlinear advection equation with an exact solution show that this three-step scheme minimizes its root mean square error(RMSE) during the first 2500 integration steps when no shock waves occur in the exact solution, while the RTI scheme outperforms the LF scheme and CSCD scheme only in the first 1000 steps and then becomes the worst in terms of RMSE up to the 2500th step. It is concluded that reasonable consideration of accuracy, square conservation, and historical observations is also critical for good performance of a finite difference scheme for solving nonlinear equations.