由58Fe 和209Bi 熔合后的相关衰变过程得到的109号元素的证据

本文报导了合成109号元素的实验。用能量为4.95,5.05和5.15MeV/u 的~(58)Fe 束轰击~(209)Bi 靶,研究了全熔合产物衰变模式的特性。总辐照剂量为7×10~(17)粒子。所用的实验方法是:用静电场速度过滤器在飞行过程中分离向前方向成峰的反应产物,经过飞行时间装置后注入到位置灵敏固态探测器中,测量其动能,估算出质量、入射的时间和位置。以所有的出射粒子的能量和时间来记录很有限的反应产物发生级联α粒子和(或)自发裂变的继发衰变。在5.15 MeV/u 时的一个特别的衰变过程是:在5ms 和22ms 先分别发射两个α粒子,最后,在13s 后发生自发裂变。第一个α粒子的动能为11.10±0.04MeV。对各种可能的解释进行了详细的分析,例如纯属偶然的信号相关,转移反应产物的衰变和从能量上看允许的余核蒸发等。最后表明质量数为266的109号元素的同位素、即全熔合后的单中子蒸发道、从统计的观点看是最好的指定。本文同时也讨论了合成新元素的前景。     

Precision Mass Measurements of Short-lived Nuclides at the Heavy-ion Storage Ring in Lanzhou

Recent commissioning of the Cooler Storage Ring at the Heavy Ion Research Facility in Lanzhou enabled us to conduct high-precision mass measurements at the Institute of Modern Physics in Lanzhou (IMP). In the past few years, mass measurements were performed using the CSRe-based isochronous mass spectrometry employing the fragmentation of the energetic beams of 58Ni, 78Kr, 86Kr, and 112Sn projectiles. Masses of short-lived nuclides on both sides of the stability valley were addressed. Relative mass precision of down to 10−6 ~ 10−7 is routinely achieved. The mass values were used as an input for dedicated nuclear structure and astrophysics studies, providing for instance new insights into the rp-process of nucleosynthesis in X-ray bursts. In this contribution, we briefly review the so far conducted experiments and the main achieved results, as well as outline the plans for future experiments.     

Impact of counter-rotating-wave term on quantum heat transfer and phonon statistics in nonequilibrium qubit–phonon hybrid system

Counter-rotating-wave terms(CRWTs)are traditionally viewed to be crucial in open small quantum systems with strong system–bath dissipation.Here by exemplifying in a nonequilibrium qubit–phonon hybrid model,we show that CRWTs can play the significant role in quantum heat transfer even with weak system–bath dissipation.By using extended coherent phonon states,we obtain the quantum master equation with heat exchange rates contributed by rotating-waveterms(RWTs)and CRWTs,respectively.We find that including only RWTs,the steady state heat current and current fluctuations will be significantly suppressed at large temperature bias,whereas they are strongly enhanced by considering CRWTs in addition.Furthermore,for the phonon statistics,the average phonon number and two-phonon correlation are nearly insensitive to strong qubit–phonon hybridization with only RWTs,whereas they will be dramatically cooled down via the cooperative transitions based on CRWTs in addition.Therefore,CRWTs in quantum heat transfer system should be treated carefully.     

Properties of ground state and anomalous quantum fluctuations in one-dimensional polaron-soliton systems—the effects of electron-two-phonon interaction and non-adiabatic quantum correlations

Based on the Holstein model Hamiltonian of one-dimensional molecular crystals, by making use of the expansion approach of the correlated squeezed-coherent states of phonon instead of the two-phonon coherent state expansion scheme, the properties of the ground state and the anomalous quantum fluctuations are investigated in a strongly coupled electron-phonon system with special consideration of the electron-two-phonon interaction. The effective renormalization (αi) of the displacement of the squeezed phonons with the effect of the squeezed-coherent states of phonon and both the electron-displaced phonon and the polaron-squeezed phonon correlations have been combined to obtain the anomalous quantum fluctuations for the corrections of the coherent state. Due to these non-adiabatic correlations, the effective displacement parameter αi is larger than the ordinary parameter α (0) i . In comparison with the electron-one-phonon interaction (g) corrected as αig, we have found the electron-two-phonon interaction (g1) corrected as αi2 g1 is enhanced significantly. For this reason, the ground state energy (E(2) 0 ) contributed by the electron-two-phonon interaction is more negative than the single-phonon case (E(1) 0 ) and the soliton solution is more stable. At the same time, the effects of the electron-two-phonon interaction greatly increase the polaron energy and the quantum fluctuations. Furthermore, in a deeper level, we have considered the effect of the polaron-squeezed phonon correlation (f-correlation). Since this correlation parameter f > 1, this effect will strengthen the electron-one and two-phonon interactions by fαig and f2αi2 g1, respectively. The final results show that the ground state energy and the polaron energy will appear more negative further and the quantum fluctuations will gain further improvement.     

Investigation on performance of all optical buffer with large dynamical delay time based on cascaded double loop optical buffers

Optical buffers are critical for optical signal processing in future optical packet-switched networks. In this paper, a theoretical study as well as an experimental demonstration on a new optical buffer with large dynamical delay time is carried out based on cascaded double loop optical buffers (DLOBs). It is found that pulse distortion can be restrained by a negative optical control mode when the optical packet is in the loop. Noise analysis indicates that it is feasible to realise a large variable delay range by cascaded DLOBs. These conclusions are validated by the experiment system with 4-stage cascaded DLOBs. Both the theoretical simulations and the experimental results indicate that a large delay range of 1-9999 times the basic delay unit and a fine granularity of 25 ns can be achieved by the cascaded DLOBs. The performance of the cascaded DLOBs is suitable for the all optical networks.     

Generalized unscented Kalman filtering based radial basis function neural network for the prediction of ground radioactivity time series with missing data

On the assumption that random interruptions in the observation process are modeled by a sequence of independent Bernoulli random variables, we firstly generalize two kinds of nonlinear filtering methods with random interruption failures in the observation based on the extended Kalman filtering (EKF) and the unscented Kalman filtering (UKF), which were shortened as GEKF and GUKF in this paper, respectively. Then the nonlinear filtering model is established by using the radial basis function neural network (RBFNN) prototypes and the network weights as state equation and the output of RBFNN to present the observation equation. Finally, we take the filtering problem under missing observed data as a special case of nonlinear filtering with random intermittent failures by setting each missing data to be zero without needing to pre-estimate the missing data, and use the GEKF-based RBFNN and the GUKF-based RBFNN to predict the ground radioactivity time series with missing data. Experimental results demonstrate that the prediction results of GUKF-based RBFNN accord well with the real ground radioactivity time series while the prediction results of GEKF-based RBFNN are divergent.     

The NUBASE2020 evaluation of nuclear physics properties

The NUBASE2020 evaluation contains the recommended values of the main nuclear physics properties for all nuclei in their ground and excited,isomeric(T1/2≥100 ns)states.It encompasses all experimental data published in primary(journal articles)and secondary(mainly laboratory reports and conference proceedings)references,together with the corresponding bibliographical information.In cases where no experimental data were available for a particular nuclide,trends in the behavior of specific properties in neighboring nuclei were examined and estimated values are proposed.Evaluation procedures and policies that were used during the development of this evaluated nuclear data library are presented,together with a detailed table of recommended values and their uncertainties.     

毛细现象公式的导出

液体表面分子间的吸引力、液体表面的分子有一种使其面积缩成最小的力,或称一种抵抗表面积扩张的力,此力称“表面张力”．液体表面是指液体与空气或其他液体相接触的自由面．若不指明,即可认为相对于空气而言．表面张力的大小与接触面的物质有密切关系．此外,表面张力还与温度有关,温度越高,表面张力越小．表面张力的方向总是与液面相切,与分界线相垂直．若在液面作一长为L的直线,将液面分成两部分,这两部分之间的相互牵引力为F,即表面张力F=σL．其中σ为液体表面张力系数．单位为N/m．由于表面张力的作用,液滴表面有收缩到最小的趋势,而使液滴成近似球形的状态．     

Lump,lumpoff and predictable rogue wave solutions to a dimensionally reduced Hirota bilinear equation

We study a simplified(3+1)-dimensional model equation and construct a lump solution for the special case of z=y using the Hirota bilinear method.Then,a more general form of lump solution is constructed,which contains more arbitrary autocephalous parameters.In addition,a lumpoff solution is also derived based on the general lump solutions and a stripe soliton.Furthermore,we figure out instanton/rogue wave solutions via introducing two stripe solitons.Finally,one can better illustrate these propagation phenomena of these solutions by analyzing images.     

Arbitrary full-state hybrid projective synchronization for chaotic discrete-time systems via a scalar signal

In this paper we present a new projective synchronization scheme,where two chaotic(hyperchaotic) discretetime systems synchronize for any arbitrary scaling matrix.Specifically,each drive system state synchronizes with a linear combination of response system states.The proposed observer-based approach presents some useful features:i) it enables exact synchronization to be achieved in finite time(i.e.,dead-beat synchronization);ii) it exploits a scalar synchronizing signal;iii) it can be applied to a wide class of discrete-time chaotic(hyperchaotic) systems;iv) it includes,as a particular case,most of the synchronization types defined so far.An example is reported,which shows in detail that exact synchronization is effectively achieved in finite time,using a scalar synchronizing signal only,for any arbitrary scaling matrix.     

Model-independent Veltman condition,naturalness and the little hierarchy problem

We adopt a bottom-up Effective Field Theory(EFT)approach to derive a model-independent Veltman condition to cancel out the quadratic divergences in the Higgs mass.We show using the equivalence theorem that all the deviations in the Higgs couplings to the W and Z from the SM predictions should vanish.We argue based on tree-level unitarity that any new physics that naturally cancels out the quadratic divergences should be ≤19 TeV.We show that the level of fine-tuning required is unless the O(0:1%-1%) UV sector has a symmetry that forces the satisfaction of the model-independent Veltman condition,in which case all fine-tuning is eliminated.We also conjecture that,if no new physics that couples to the Higgs is observed up to~19 TeV,or if the Higgs couplings to the SM particles conform to the SM predictions,then the Higgs either does not couple to any UV sector or is fine-tuned.     

Research on the field emission mechanism of nano-structured carbon film

The field emission(FE) characteristics of nano-structured carbon films(NSCFs) are investigated.The saturation behaviour of the field emission current density found at high electric field E cannot be reasonably explained by the traditional Fowler-Nordheim(F-N) theory.A three-region E model and the curve-fitting method are utilized for discussing the FE characteristics of NSCFs.In the low,high,and middle E regions,the FE mechanism is reasonably explained by a modified F-N model,a corrected space-charge-limited-current(SCLC) model and the joint model of F-N and SCLC mechanism,respectively.Moreover,the measured FE data accord well with the results from our corrected theoretical model.     

High-speed polarization mode dispersion compensation in a 43-Gb/s RZ-DQPSK transmission system over 1200 km of standard single-mode fibre

This paper reports that the designed optical polarization mode dispersion compensator shows a good performance under the real-time variation of differential group delay, state of polarization and principal state of polarization in a (40 × 43)-Gb/s dense-wavelength-multiplexing, 1200-km enhanced return-to-zero differential-quadrature-phase-shift-keying (RZ-DQPSK) system. The polarization mode dispersion tolerance of the system is improved by 26 ps using the optical polarization mode dispersion compensator. The short and long time stabilities are tested with the bit error ratio recorded.vspace1mm     

Sampling strong tracking nonlinear unscented Kalman filter and its application in eye tracking

The unscented Kalman filter is a developed well-known method for nonlinear motion estimation and tracking. However, the standard unscented Kalman filter has the inherent drawbacks, such as numerical instability and much more time spent on calculation in practical applications. In this paper, we present a novel sampling strong tracking nonlinear unscented Kalman filter, aiming to overcome the difficulty in nonlinear eye tracking. In the above proposed filter, the simplified unscented transform sampling strategy with n+2 sigma points leads to the computational efficiency, and suboptimal fading factor of strong tracking filtering is introduced to improve robustness and accuracy of eye tracking. Compared with the related unscented Kalman filter for eye tracking, the proposed filter has potential advantages in robustness, convergence speed, and tracking accuracy. The final experimental results show the validity of our method for eye tracking under realistic conditions.     

SSRF中BPM支撑的机械稳定性分析

主要对上海光源(SSRF)束流位置监视器(BPM)支撑的机械稳定性进行了研究.受有限元计算与初始设计方案的振动测试结果不一致的启发,对BPM支撑与地面的连接考虑了三种方案:膨胀螺母、半灌浆与全灌浆连接.通过采用改进的全灌浆连接来代替初始设计的膨胀螺母连接,BPM支撑的横向最低共振频率由20.2Hz增加到50.2Hz,支撑顶部与地面的横向均方根位移(4-50Hz)之比由4.36降低到1.32,机械稳定性能得到大大的提高.     

The geometric phase in nonlinear frequency conversion

The geometric phase of light has been demonstrated in various platforms of the linear optical regime, raising interest both for fundamental science as well as applications, such as flat optical elements. Recently, the concept of geometric phases has been extended to nonlinear optics, following advances in engineering both bulk nonlinear photonic crystals and nonlinear metasurfaces. These new technologies offer a great promise of applications for nonlinear manipulation of light. In this review, we cover the recent theoretical and experimental advances in the field of geometric phases accompanying nonlinear frequency conversion. We first consider the case of bulk nonlinear photonic crystals, in which the interaction between propagating waves is quasi-phase-matched, with an engineerable geometric phase accumulated by the light. Nonlinear photonic crystals can offer efficient and robust frequency conversion in both the linearized and fully-nonlinear regimes of interaction, and allow for several applications including adiabatic mode conversion, electromagnetic nonreciprocity and novel topological effects for light. We then cover the rapidly-growing field of nonlinear Pancharatnam-Berry metasurfaces, which allow the simultaneous nonlinear generation and shaping of light by using ultrathin optical elements with subwavelength phase and amplitude resolution. We discuss the macroscopic selection rules that depend on the rotational symmetry of the constituent meta-atoms, the order of the harmonic generations, and the change in circular polarization. Continuous geometric phase gradients allow the steering of light beams and shaping of their spatial modes. More complex designs perform nonlinear imaging and multiplex nonlinear holograms, where the functionality is varied according to the generated harmonic order and polarization. Recent advancements in the fabrication of three dimensional nonlinear photonic crystals, as well as the pursuit of quantum light sources based on nonlinear metasurfaces, offer exciting new possibilities for novel nonlinear optical applications based on geometric phases.     

A type of new conserved quantity deduced from Mei symmetry for Nielsen equations in a holonomic system with unilateral constraints

<正>A type of new conserved quantity deduced from Mei symmetry for Nielsen equations in a holonomic system with unilateral constraints is investigated.Nielsen equations and differential equations of motion for the holonomic mechanical system with unilateral constraints are established.The definition and the criterion of Mei symmetry for Nielsen equations in the holonomic systems with unilateral constraints under the infinitesimal transformations of Lie group are also given.The expressions of the structural equation and a type of new conserved quantity of Mei symmetry for Nielsen equations in the holonomic system with unilateral constraints are obtained.An example is given to illustrate the application of the results.     

10BaF₂:NaF,Na₃AlF₆/TiO₂ composite as a novel visible-light-driven photocatalyst based on upconversion emission

A rare-earth free upconversion luminescent material, 10BaF 2 :NaF, Na 3 AlF 6 , is synthesized by a hydrothermal method. The study of fluorescent spectrum indicates that it can convert visible light (550 nm–610 nm) into ultraviolet light (290 nm–350 nm), and two emission peaks at 304 nm and 324 nm are observed under the excitation of 583 nm at room temperature. Subsequently, 10BaF 2 :NaF, Na 3 AlF 6 /TiO 2 composite photocatalyst is prepared and its catalytic activity is evaluated by the photocatalytic reduction of CO 2 under visible light irradiation (λ > 515 nm). The results show that 10BaF 2 :NaF, Na 3 AlF 6 /TiO 2 is a more effective photocatalyst for CO 2 reduction than pure TiO 2 , their corresponding methanol yields are 179 and 0 μmol/g-cat under the same conditions. Additionally, the mechanism of photocatalytic reduction of CO 2 on 10BaF 2 :NaF, Na 3 AlF 6 /TiO 2 is proposed.     

Observation of lateral long range order in superconducting FeTe thin films

<正>We find that the superconductivity in the thin films of the formerly believed non-superconducting parent compound FeTe is accompanied by an emergence of second order with a correlation length of 742 nm and 258 nm at 10 K and 300 K,respectively.The structural phase transition found in iron pnictide superconductors,in non-superconducting FeTe bulk samples,and in FeSe superconducting thin films is not observed in the superconducting FeTe thin films.The interplay between superconductivity and long range order may suggest the crucial role of competition between electronic localization and itinerancy which leads to strong quantum fluctuations in the FeTe system.     

Approximate analytic solutions for a generalized Hirota—Satsuma coupled KdV equation and a coupled mKdV equation

<正>This paper applies the variational iteration method to obtain approximate analytic solutions of a generalized Hirota-Satsuma coupled Korteweg-de Vries(KdV) equation and a coupled modified Korteweg-de Vries(mKdV) equation. This method provides a sequence of functions which converges to the exact solution of the problem and is based on the use of the Lagrange multiplier for the identification of optimal values of parameters in a functional.Some examples are given to demonstrate the reliability and convenience of the method and comparisons are made with the exact solutions.