高激发态核的多重碎裂

中能重离了反应后期高激发态核的多重碎裂可用量子统计模型来处理。不稳定的中等质量碎片将再次衰变成新的碎片多重性分布。由反应所发射的各种带电粒子数目间的比率标志的碎裂度可确定系统的熵，而由粒子不稳定碎片衰变的产额，可确定核系统的温度。     

Chaotifying a stable linear controllable system by single input state feedback

In this paper, an approach for chaotifying a stable controllable linear system via single input state-feedback is presented. The overflow function of the system states is designed as the feedback controller, which can make the fixed point of the closed-loop system to be a snap-back repeller, thereby yields chaotic dynamics. Based on the Marotto theorem, it proves theoretically that the closed-loop system is chaotic in the sense of Li and Yorke. Finally, the simulation results are used to illustrate the effectiveness of the proposed method.     

干涉学在高激发核性质研究中的应用

简单介绍了干涉学的发展历史,综述了利用粒子关联（干涉）测量高激发核衰变中轻粒子和中等质量碎片的发射时标、发射次序以及核温度的实验结果．这些结果表明,热核由相继衰变逐渐向多重碎裂的过渡． A brief introduction of interference development has been made.The experimental results of the time scale, emission order and temperature of light charged particles and intermediate mass fragments emitted from hot nuclear systems have been reviewed. These results indicate the transition from sequential decay to multifragmentation for hot nuclear decay.     

高激发核相继裂变的限制

高温核衰变是当前中能重离子核物理中研究最热烈的课题.理论上对高温核的衰变进行了各种预言,相继裂变就是其中之一.本文从有关核裂变的时间尺度、裂前中子发射、裂变截面等随激发能的变化和多重碎裂的实验结果以及复杂碎片发射时间的实验结果分析了对高温核相继裂变的限制,提出了从复杂粒子蒸发向多重碎裂过渡的可能性. Sequential fission is one of the several kinds of theoratical production for hot nucleus de-cay.By analysing relevant experimental results such as fission time scale,prescission neutron emission,fission cross sections and their variation with excitation energy,the results of multifragmentation andthe time scale of complex fragment emission,a limit to the sequential fission of the hot nucleus is sug-gested in this paper.A transition from intermediate mass fragment evaporation to..     

New exact solutions of the Einstein-Maxwell equations for magnetostatic fields

The symmetry reduction method based on the Fr′echet derivative of differential operators is applied to investigate symmetries of the Einstein-Maxwell field equations for magnetostatic fields, which is a coupled system of nonlinear partial differential equations of the second order. The technique yields invariant transformations that reduce the given system of partial differential equations to a system of nonlinear ordinary differential equations. Some of the reduced systems are further studied to obtain the exact solutions.     

Existence of horseshoe maps in voltage-mode controlled buck converters

In this paper, chaos in a voltage-mode controlled buck converter is studied. The existence of chaos is proven theoretically in this system. The proof consists of showing that the dynamics of the system is semiconjugate to that of a one-sided shift map, which implies positive entropy of the system and hence chaotic behaviour. The essential tool is the horseshoe hypotheses proposed by Kennedy and Yorke, which will be reviewed prior to the discussion of the main finding.     

Analysis of Chaotic Dynamics in a Two-Dimensional Sine Square Map

We study an N-dimensional system based upon a sine map, which is related to the simplified model of an opto-electronic system. The system behavior is analyzed with the tools of nonlinear dynamics （bifurcations in the parameter plane, critical manifolds, basins of attraction, chaotic attractors）. Our study relies on a two-dimensional system （N=2）. It is interesting that this system shows the existence of bounded chaotic orbits, which can be considered for secure transmissions.     

关于合成265Bh实验的可行性分析

分析了目前关于超重核研究的现状,结合现有的设备及条件,在合成259Db以后,下一次实验的目标核初步确定为107号元素的新同位素265Bh.描述了对MG转轮收集探测系统的实验检验结果.实验中成功地观察和测量了24Mg+232Th的产物252No的母子体的α衰变谱,为下一步合成265Bh完成了部分预实验工作.另外,也给出了下一个目标核的衰变特性的理论预言值,同时也选择了产生该目标核的弹靶组合及反应道,并对生成截面进行了粗略估计,给出了该核的可观测性产额及可行性分析. The present status of investigation on the surperheavy nuclei are analyzed. After 259Db synthesized, the next objective nuclide is determined to be265Bh, a new isotope of Z=107 element, according to our existing available equipment and conditions.The test result of the MG rotating wheel collection and detection system is described. The α decay spectra of mother daughter of the product252No from24Mg +232Th reaction are observed and measured successfully in this test experiment. It is regarde...     

Upgrade of Control System for the BEPCII

The BEPC will increase its luminosity ten times with upgrade of both the machine and detector,which is the project BEPCII,The project will be started at beginning chine and detector,which is the project BEPCII.The project will be started at beginning of 2002 and finished within 3-4 years.In order to reach the goal of the BEPCII,a number of new equipment will be added in the system,such as the superconducting RF cavities,new magnet power supplies and beam feedback system,and the BEPC control system has to be upgraded.The BEPC control system was built in 1987 and was upgraded in 1994.It is an Open VMS and CAMAC based-system,some equipment is controlled by PCs.We are going to upgrade the existing system by EPICS.Several VME IOCs will be added in the system with feildbus,PLCs for the new equipment control.And we will keep the existing system in use,such as CAMAC hardware ,PC based sub-control and application programs,which will be merged into the EPICS system.Recently the development of the EPICS prototype has been started.Regard some slow control,commercial SCADA product can be chosen as the development tool.We have just finished a prototype with the SCADA product Wizcon.This paper will describe the system design and development issues.     

核温度的动力学计算

介绍了测量热力学微正则系综中哈密顿动力学系统温度的一种新的动力学途径,即在各态历经性的假设下,温度可作为函数（Ｈ／‖Ｈ‖２）在能量面上的时间平均算出．这一方法不仅给出了确定温度的一种有效的计算途径,而且也提供了动力学系统理论和哈密顿系统的统计力学之间的内在联系． A new dynamical approach for measuring the temperature of a Hamiltonian dynamical system in the microcanonical ensemble of thermodynamics is presented. It shows that under the hypothesis of ergodicity the temperature can be computed as a time average of the function, ·(H/‖H‖ 2) , on the energy surface. This method not only yields an efficient computational approach for determining the temperature, but also provides an intrinsic link between dynamical system theory and the statistical...     

A First Order Generalized Thomas-Fermi Approximation for the Electron Density in Inversion Layers

An operator evaluation of the one-particle density matrix of a degenerate system of independent particles in first order with respect to the gradient of the potential developed by Macke and Rennert yields an analytic expression for the particle density. This method is extended here to potentials with an infinite step and to finite temperatures – a situation which is characteristic for inversion electrons in MIS-systems. The resulting density can be expressed as the Airy transform of the zeroth order (local density approximation). The first order yields both the tunneling into the classically forbidden region and oscillations of the density near the step of the potential. The operator evaluation of the density matrix is shown to be equivalent to solving a Schrödinger like equation. The first order density yields results for the subband structure of (100)Si inversion and accumulation layers at OK in remarkable agreement to density functional calculations of Ando.     

Linking quantum discord to entanglement in a measurement

We show that a von Neumann measurement on a part of a composite quantum system unavoidably creates distillable entanglement between the measurement apparatus and the system if the state has nonzero quantum discord. The minimal distillable entanglement is equal to the one-way information deficit. The quantum discord is shown to be equal to the minimal partial distillable entanglement that is the part of entanglement which is lost, when we ignore the subsystem which is not measured. We then show that any entanglement measure corresponds to some measure of quantum correlations. This powerful correspondence also yields necessary properties for quantum correlations. We generalize the results to multipartite measurements on a part of the system and on the total system.     

Driving potential and fission-fragment charge distributions

We propose an efficient approach to describe the fission-fragment charge yields for actinides based on the driving potential of the fissioning system. Considering the properties of primary fission fragments at their ground states, the driving potential, which represents the potential energies of the system around scission configuration and closely relates to the yields of fragments, can be unambiguously and quickly obtained from the Skyrme energy-density functional together with the Weizsäcker–Skyrme mass model. The fission-fragment charge distributions for thermal-neutron-induced fission and spontaneous fission of a series of actinides, especially the odd–even staggering in the charge distributions, can be well reproduced. Nuclear dynamical deformations and pairing corrections of fragments play an important role in the charge distributions.     

Hadron production in relativistic nuclear collisions: thermal hadron source or hadronizing quark-gluon plasma?

Measured hadron yields from relativistic nuclear collisions can be equally well understood in two physically distinct models, namely a static thermal hadronic source vs. a time-dependent, nonequilibrium hadronization off a quark-gluon plasma droplet. Due to the time-dependent particle evaporation off the hadronic surface in the latter approach the hadron ratios change (by factors of ) in time. Final particle yields reflect time averages over the actual thermodynamic properties of the system at a certain stage of the evolution. Calculated hadron, strangelet and (anti-)cluster yields as well as freeze-out times are presented for different systems. Due to strangeness distillation the system moves rapidly out of the , plane into the -sector. Strangeness to baryon ratios prevail during a considerable fraction (50%) of the time evolution (i.e. -droplets or even -droplets form the system at the late stage: The possibility of observing this time evolution via two-particle correlations is discussed). The observed hadron ratios require MeV and MeV. If the present model is fit to the extrapolated hadron yields, metastable hypermatter can only be produced with a probability for . Received: 15 April 1997 / Revised version: 5 June 1997     

The influence of selective sputtering on surface composition

The time dependence of the surface composition of a one-phase, two-component homogeneous system is calculated assuming different sputter yields for the two components. It is shown for a special case that the amount of material which has to be removed before a steady state situation is obtained, is approximately one monolayer. Signals obtainable with different modern surface analytical methods under steady state conditions are discussed.     

One-dimensional approximation to stochastic lattice system with strong coupling

One-dimensional approximation to stochastic lattice system with strong coupling is derived. For a special periodic coupling, the existence of a rotation number is proved, which yields the frequency locking of the system. And by the one-dimensional approximation system, an approximation to the rotation number is also derived.     

Planar diagrams

We investigate the planar approximation to field theory through the limit of a large internal symmetry group. This yields an alternative and powerful method to count planar diagrams. Results are presented for cubic and quartic vertices, some of which appear to be new. Quantum mechanics treated in this approximation is shown to be equivalent to a free Fermi gas system.ENS, Paris. On leave of absence from INFN-Frascati     

Exact results on random bond Ising Chains in magnetic fields

In this contribution we present exact results on the random bond Ising Chain in a magnetic field. The original problem is reduced to the solution of a functional equation for a certain probability distribution, which can be used to evaluate thermodynamics and correlation functions. We give a sufficiently accurate solution for low temperatures, which yields the complete low-temperature behaviour. Comparison is made with different Monte-Carlo-calculations performed on this system.Work supported in part by the Deutsche Forschungs-gemeinschaft     

Symmetries and conservation laws of the classical Boussinesq equation

A recursion operator for the classical Boussinesq equation is given, which yields infinitely many symmetries and conservation laws. It is also shown that these symmetries define a hierarchy of the classical Boussinesq equation each of which is a hamiltonian system.