智能群体环绕运动控制

自然界中,鸟类迁徙、鱼类群游等群体智能运动具有一定的规律.例如,鸟类迁徙以领导者和跟随者模式的直线运动为主,鱼类中以环绕运动为主.自然界的这种群体直线运动与环绕运动具有十分重要的理论研究价值和广泛的工程应用前景.本文针对群体环绕运动进行研究,考虑个体只能获取局部目标信息这一特性,设计均值估计器进行群体目标状态估计,建立环绕运动算法,确保实现群体圆形编队且保持队形.通过李雅普诺夫理论分析,证明每个个体在有限时间内能获取所有目标平均位置信息,且能基于群体圆形编队队形进行目标环绕和追踪,队形随目标状态变化.有关结果通过仿真得到进一步验证.     

Finite-time rotating target-encirclement motion of multi-agent systems with a leader

This paper investigates the finite-time rotating target-encirclement control problem for multi-agent systems with a leader, in which the leader can obtain the state information of the target, whereas followers cannot. A novel finite-time rotating encirclement protocol is proposed, containing the state estimators of the target and the leader. Besides, some sufficient conditions are given for achieving finite-time rotating encirclement target-tracking. The validity of the achieved results is eventually assessed by a numerical example.     

Proximity-Encirclement of Multiple Exceptional Points in Non-Hermitian Photonic Waveguides

Conventionally, dynamical encirclement of exceptional points in non-Hermitian systems is known to manifest a counterintuitive chiral state conversion. However, the prerequisite of such traits enclosing an exceptional point is broken when only encircling its proximity, preserving a still chiral switching. Research on the proximity-encirclement in multistate systems is lacking. In this paper, a photonic-waveguide-array non-Hermitian system is proposed to investigate the dynamics by encircling two exceptional points or their proximity. A series of encircling trajectories defined by the parametric equations are designed to steer the evolution of photonic modes in waveguides. The wave propagating along the waveguides is also simulated to capture this non-Hermitian physics. The chiral behavior in proximity-encirclement contrasts with the familiar encirclement of one exceptional point and exhibits the unexpected occurrence of nonadiabatic transitions. Furthermore, if two exceptional points are sufficiently encircled, the system will evolve to a stable final state earlier, as a symbol of the occurrence of the nonadiabatic transition. Such novel chiral conversion is maintained only if the encircling trajectories are located at adequate proximity.     

原子核振动与转动模型（Ⅰ）推转玻尔─莫特逊哈密顿量和偶偶核正常转动谱分析

从推转壳模型出发，导出了转动频率未量子化的集体振动－转动哈密顿量，称为推转玻尔－莫特逊哈密顿量（ＣＢＭＨ）．引入合理的集体运动位势，由ＣＢＭＨ可以得到解析形式的转动谱公式．应用这一振动－转动模型，对偶偶变形核的正常转动能谱进行了分析，取得了满意的结果．     

中心集体流对带电粒子关联函数的影响

讨论了中心集体流对带电粒子关联函数的影响,采用蒙特卡罗方法研究了热源发射出的单粒子能谱与双粒子关联谱受中心集体流的影响. 利用QMD模型计算了100MeV/u的Ni+Ni系统在b=0fm条件下的双质子关联函数. 在计算中发展了一种交换粒子计算方法并证实了在100MeV/u Ni+Ni的中心碰撞中存在中心集体流. 计算结果表明,在中重系统中关联函数对中心集体流是灵敏的,为在100MeV/u以上能区研究中重系统中心碰撞形成的中心集体流提供了一种可行的方法.     

Collective properties of the final state in processes involving the production of hadron jets

Experimental results obtained by studying soft hadron jets in pion-proton and pion-nucleus reactions at intermediate energies with the aid of traditional collective variables are presented. Analytic approximations that describe, at a qualitative level, the dependences of collective parameters on the energy and multiplicity are proposed. Estimates obtained for strong coupling constant by studying collective variables are in reasonable agreement with its world-average value and with the results extracted by using different methods. The behavior of traditional collective variables as functions of the multiplicity in various interactions makes it possible to obtain a universal estimate for the lower boundary of the region of experimental manifestations of jets in multiparticle-production processes.     

Vibrational and Rotational Motions Model of Nucleus(Ⅰ) Cranking Bohr-Mottelson Hamiltonian and Analyses of the Rotational Bands of Even-Even Nuclei

Starting from cranking shell model,a collective vibrational and rotational Hamiltonian(cranking Bohr-Mottelson Hamiltonian CBMH)is derived,in which the rotational frequency is not quantized.Introducing a reasonable collective potential,the formula for the rotational spectrum can be obtained.The formula is applied to analyze the rotational bands of even-even nuclei with satisfactory results.     

Microscopic calculation of the collective motion in76Kr

A microscopic calculation of Bohr's collective Hamiltonian is used to describe the collective motion in the⁷⁶Kr isotope. A single-particle basis calculated in a deformed Woods-Saxon potential leads to the potential energy surface obtained by the Strutinsky renormalization procedure, and to the inertial functions determined in the cranking model approximation. The collective Schrödinger equation is solved numerically. The low-energy, even parity states in⁷⁶Kr are analyzed in the frame of this model. The theoretical results involve the potential energy and the inertial parameters as functions of intrinsic quadrupole deformations, the collective levels and wave functions including their transitions and electromagnetic moments. A good agreement between experiment and theory is obtained without adjusting specifically for this nucleus any parameter in the model. Some results regarding statical and dynamical characteristics of even-even^{74, 78, 80}Kr isotopes are also presented.     

核多体系统输运现象的微观理论

首先回顾了描写核多体系统输运现象的一些主要模型和方法,然后介绍了输运现象微观动力学基础研究上一些新的结果,强调了单粒子运动动力学特征在建立集体输运方程和理解超重核合成机制上的重要作用。能量耗散和熵产生的数值计算结果表明,集体运动耗散过程可分为退相干、弛豫和定态等3 个阶段,弛豫过程通常表现为非常复杂的反常扩散过程。在这些理论工作的基础上,提出了一种自洽地分离核多体系统集体和单粒子变量的可能途径。In this article, I provide a simple review on conventional methods and models on the transport phenomenon of nuclear many-body systems. By exploiting the basic idea of time-dependent projection operator, I recommend a novel method to derive the transport equation for collective motion which is embedded on the microscopic dynamics of timedependent single-particle motion. It is emphasized that the microscopic dynamics of single-particle motion should play an important role for understanding the dynamics of nuclear reaction and the synthesis mechanisms of new superheavy elements. The numerical results of energy dissipation and entropy production indicate that the collective motion passes through three stages, such as dephasing/decoherence, statistical relaxation and stationary state. The statistical relaxation is a complex anomalous diffusion process in general. With the aid of above analysis and results, a possible way to define the collective and single-particle variables for the realistic nuclear many-body systems is proposed.     

Irreducible U(3) tensor interactions in the symplectic collective model

The potential V(β, γ) of the Bohr-Mottelson and symplectic collective models is expressed as a linear combination of U(3) irreducible tensor operators in the symplectic enveloping algebra. This many-body collective potential is then projected onto the symplectic two-body tensor operators. The projected two-body potential is shown to give results similar to the many-body potential in ²⁰Ne. Hence, in the symplectic shell model, one has obtained a collective model with two-body forces.     

Disappearance of Collective Rotation in Heavy Ion Collisions

A theoretical analysis of collective rotation is performed in heavy ion collisions below 100 MeV/nucleon in the quantum molecular dynamics approach. Both methods are contributed to this analysis, one is based on the shapes of azimuthal distribution, and the other is based on the numerical semiclassical calculation of rotation. The collective rotation becomes weaker with the increasing of beam energy, and tends to fade out at a certain beam energy. The impact parameter dependence of collective motion is also discussed. In connection with recent experiments, theoretical results and experimental data are compared by taking into account the fluctuation of experimental reaction plane determination.     

An agent-based model of collective emotions in online communities

We develop an agent-based framework to model the emergence of collective emotions, which is applied to online communities. Agent’s individual emotions are described by their valence and arousal. Using the concept of Brownian agents, these variables change according to a stochastic dynamics, which also considers the feedback from online communication. Agents generate emotional information, which is stored and distributed in a field modeling the online medium. This field affects the emotional states of agents in a non-linear manner. We derive conditions for the emergence of collective emotions, observable in a bimodal valence distribution. Dependent on a saturated or a superlinear feedback between the information field and the agent’s arousal, we further identify scenarios where collective emotions only appear once or in a repeated manner. The analytical results are illustrated by agent-based computer simulations. Our framework provides testable hypotheses about the emergence of collective emotions, which can be verified by data from online communities.     

Damping of collective modes in DIC: Quantal versus statistical fluctuations

A model is developed to describe the transformation of relative kinetic energy into intrinsic excitation energy in DIC. Energy dissipation is viewed as an indirect process, in which collective vibrational modes are first excited coherently and then damped due to the coupling to the remaining non-collective degrees of freedom. Both collective and intrinsic degrees of freedom are included explicitly, and the coupling between them is treated in a random-matrix model. Under certain assumptions it is shown that, in the weak-coupling limit, the collective probability distribution in phase space obeys a Fokker-Planek equation. This transport equation is used to derive equations of motion for the expectation values of some “macroscopic” quantities characterizing the process. Some numerical results are presented and a qualitative comparison with the Copenhagen model is attached.     

高能重离子碰撞中末态粒子的关联度与集合侧向流

提出了关联度概念,采用粒子群关联函数方法对Bevalac流光室1.2A GeV Ar+BaI₂碰撞事件中关联度不同的粒子对集合侧向流的作用进行了研究.研究表明:关联度是描述集合侧向流性质的一个重要参量.少数关联度较大的粒子(或碎片)可以产生集合侧向流效应,但高阶集合流关联却不受其支配,而是关联度不同的多数粒子(或碎片)集体贡献的结果.     

Landau damping of collective mode in a quasi-two-dimensional repulsive Boseben Einstein condensate

We investigate the Landau damping of the collective mode in a quasi-two-dimension repulsive Bose—Einstein condensate by using the self-consistent time-dependent Hatree—Fock—Bogoliubov approximation and a complete and orthogonal eigenfunction set for the elementary excitation of the system. We calculate the three-mode coupling matrix element between the collective mode and the thermal excited quasi-particles and the Landau damping rate of the collective mode. We discuss the dependence of the Landau damping on temperature, on atom number in the condensate, on transverse trapping frequency and on the length of the condensate. The energy width of the collective mode is taken into account in our calculation. With little approximation, our theoretic calculation results agree well with the experimental ones and are helpful for deducing the damping mechanics and the inter-particle interaction.     

On a correlation between the properties of low lying collective levels and fission process observables in even nuclei

Effective polynomial potentials for one-dimensional nuclear collective motion leading to fission make it possible to obtain a relation between the spontaneous fission rate, the height of the barrier and the energies of low-lying collective levels. The results are compared with experiment.     

Evidence of electromagnetic absorption by collective modes in the heavy fermion superconductor UBe(13)

We present results of a microwave surface impedance study of the heavy fermion superconductor UBe(13). We clearly observe an absorption peak whose frequency and temperature dependence scales with the BCS gap function Delta(T). Resonant absorption into a collective mode, with energy approximately proportional to the superconducting gap, is proposed as a possible explanation. Fits to the data provide a simple relation between Delta(T) and the collective mode frequency.