The dynamical origin of physiological instructions used in birdsong production

In this work we report experimental measurements of pressure patterns used in canary song. We find that these patterns are qualitatively similar to the subharmonic solutions of a simple dynamical system. This is built to account for the activities of subpopulations of neurons arranged in a simple architecture compatible with anatomical observations. The consequences of Hebbian plasticity in the coupling between the driving and the driven systems are outlined.      

系统生物学中的物理问题

在20世纪末到21世纪初的十多年里,生命科学,特别是分子生物学发生了令世人瞩目的变化.生命科学研究飞速发展使人们相信21世纪是生命科学的世纪.与此同时,人们也越来越清楚地意识到生命科学研究的质的飞跃不可能由生物学家独立完成.数学、物理、化学、力学、信息科学在生物学研究中必将担任越来越重要的角色.文章通过介绍几个作者参与的系统生物学研究工作,探讨物理学在系统生物学中应该并能担任的角色.     

系统生物学中的物理问题

在20世纪末到21世纪初的十多年里,生命科学,特别是分子生物学发生了令世人瞩目的变化.生命科学研究飞速发展使人们相信21世纪是生命科学的世纪.与此同时,人们也越来越清楚地意识到生命科学研究的质的飞跃不可能由生物学家独立完成.数学、物理、化学、力学、信息科学在生物学研究中必将担任越来越重要的角色.文章通过介绍几个作者参与的系统生物学研究工作,探讨物理学在系统生物学中应该并能担任的角色.     

A Borel Transform Method for Locating Singularities of Taylor and Fourier Series

Given a Taylor series with a finite radius of convergence, its Borel transform defines an entire function. A theorem of Pólya relates the large distance behavior of the Borel transform in different directions to singularities of the original function. With the help of the new asymptotic interpolation method of van der Hoeven, we show that from the knowledge of a large number of Taylor coefficients we can identify precisely the location of such singularities, as well as their type when they are isolated. There is no risk of getting artefacts with this method, which also gives us access to some of the singularities beyond the convergence disk. The method can also be applied to Fourier series of analytic periodic functions and is here tested on various instances constructed from solutions to the Burgers equation. Large precision on scaling exponents (up to twenty accurate digits) can be achieved.     

与地震预测预报有关的几个物理问题

文章简要介绍了与地震预测预报有关的几个物理问题,包括地震活动性问题、地球深部物质的物理性质及其变化问题、地球深部的流体问题、地震破裂问题、地球深部的形变和应力问题.这些问题的研究涉及当代物理学的一些前沿领域,唐山大地震后30年来有诸多重要进展.     

厄尔尼诺大气物理机理的周期解

运用重合度理论探讨了一类非线性问题的周期解.然后将其应用于一个厄尔尼诺大气物理机理振荡,简捷地得到了该模型的周期解. 关键词： 非线性 厄尔尼诺现象 周期解     

Complex network analysis in inclined oil--water two-phase flow

Complex networks have established themselves in recent years as being particularly suitable and flexible for representing and modelling many complex natural and artificial systems. Oil--water two-phase flow is one of the most complex systems. In this paper, we use complex networks to study the inclined oil--water two-phase flow. Two different complex network construction methods are proposed to build two types of networks, i.e. the flow pattern complex network (FPCN) and fluid dynamic complex network (FDCN). Through detecting the community structure of FPCN by the community-detection algorithm based on K-means clustering, useful and interesting results are found which can be used for identifying three inclined oil--water flow patterns. To investigate the dynamic characteristics of the inclined oil--water two-phase flow, we construct 48 FDCNs under different flow conditions, and find that the power-law exponent and the network information entropy, which are sensitive to the flow pattern transition, can both characterize the nonlinear dynamics of the inclined oil--water two-phase flow. In this paper, from a new perspective, we not only introduce a complex network theory into the study of the oil--water two-phase flow but also indicate that the complex network may be a powerful tool for exploring nonlinear time series in practice.     

物理参数对光限幅效应的影响

为了对抗日益严重的激光武器威胁，需要了解激光防护材料的光学性能。该文根据非线性吸收模型，推导出光限幅阈值表达式。并以表达式为理论依据，利用配位聚合物［Cd(L4)(SO4)(H2O)2］n在波长532nm、脉冲宽度为40ps的条件下所获得的实验数据，分析研究非线性吸收参数、线性透过率和有效激发态吸收截面等物理参数对光限幅效应的影响。以此为基础，研究了激光防护材料的非线性光学特性和光限幅特性，为制备光限幅材料提供了理论和实验依据。     

Bifurcations and Dynamics of Traveling Wave Solutions to a Fujimoto-Watanabe Equation

In this paper, we study the bifurcations and dynamics of traveling wave solutions to a Fujimoto-Watanabe equation by using the method of dynamical systems. We obtain all possible bifurcations of phase portraits of the system in different regions of the parametric space. Then we show the sufficient conditions to guarantee the existence of traveling wave solutions including solitary wave solutions, periodic wave solutions, compactions and kink-like and antikink-like wave solutions. Moreover, the expressions of solitary wave solutions and periodic wave solutions are implicitly given,while the expressions of kink-like and antikink-like wave solutions are explicitly shown. The dynamics of these new traveling wave solutions will greatly enrich the previews results and further help us understand the physical structures and analyze the propagation of the nonlinear wave.     

在大学物理教学中引入非线性物理的探索与实践

总结了在大学物理教学中引入非线性物理的实践与体会 ,对引入内容、引入方法等问题进行探讨 ,并指出存在和需要解决的问题 .     

α-铁中位移级联过程中缺陷的生成和He-空位复合物的形成

运用分子动力学方法研究了不同He浓度和不同级联能下含He的α-Fe低温时的位移级联过程.模拟的主要撞击原子(PKA)的能量(E_P)(即级联能)从500eV变化到5keV，辐照温 度为100K，He的浓度从1%变化到5%.比较了不同He浓度下的Fe-He混合物和纯α-Fe的位移级 联过程，发现在含有He的α-Fe中总的Fe和He的Frenkel对与纯的α-Fe的Frenkel对的数目相 当.当He的浓度较低时，含有He的α-Fe中的Frenkel对比α-Fe的要低，随He的浓度增加，有 He的α-Fe中的Frenkel对比α-Fe中的高，这主要与He在金属中的性质有关.本研究证明了位 移级联过程可以直接导致He泡的成核.对不同级联能和不同He浓度下Fe的位移级联过程的模 拟，发现在同样的级联能下，随着He浓度的增加，He成团的几率增大；在同样的He浓度下, 随着级联能的增加,He成团的几率也同样增加，并分析了级联下He泡的形成机制. 关键词： Fe 位移级联 He-空位复合物 分子动力学     

Transition to chaos in a driven pendulum with nonlinear dissipation

The Melnikov-Holmes method is used to study the onset of chaos in a driven pendulum with nonlinear dissipation. Detailed numerical studies reveal many interesting features like a chaotic attractor at low frequencies, band formation near escape from the potential well and a sequence of subharmonic bifurcations inside the band that accumulates at the homoclinic bifurcation point.     

物理学中的全量子化效应与新的探索

在一般的第一性原理计算中,原子核总是被近似成经典粒子.然而,在一些特殊的体系中,原子核的量子效应对体系的物理性质和物理过程有着至关重要的影响.在相关问题的模拟中,考虑了原子核量子效应的全量子化计算,展示了其独有的准确性.目前,路径积分分子动力学是被广泛采用的全量子化计算方法.而第一性原理的路径积分分子动力学不仅保留了第一性原理计算中电子结构和电子基态能量计算的方法,同时还应用费恩曼（Feynman）路径积分原理,得到了包含原子核量子信息的运动方程.张千帆等人应用第一性原理路径积分分子动力学,计算了BaZrO3中氢核的输运情况.结果表明,原子核的量子化对输运中两个不同的子过程有不同程度的影响,它使得有氢氧键断裂的T过程的势垒下降更多,使T过程成为快过程,从而验证了红外光谱实验的结果,同时否定了传统计算给出的T过程是慢过程的结论.     

物理学中的全量子化效应与新的探索

在一般的第一性原理计算中,原子核总是被近似成经典粒子.然而,在一些特殊的体系中,原子核的量子效应对体系的物理性质和物理过程有着至关重要的影响.在相关问题的模拟中,考虑了原子核量子效应的全量子化计算,展示了其独有的准确性.目前,路径积分分子动力学是被广泛采用的全量子化计算方法.而第一性原理的路径积分分子动力学不仅保留了第一性原理计算中电子结构和电子基态能量计算的方法,同时还应用费恩曼(Feynman)路径积分原理,得到了包含原子核量子信息的运动方程.张千帆等人应用第一性原理路径积分分子动力学,计算了BaZrO3中氢核的输运情况.结果表明,原子核的量子化对输运中两个不同的子过程有不同程度的影响,它使得有氢氧键断裂的T过程的势垒下降更多,使T过程成为快过程,从而验证了红外光谱实验的结果,同时否定了传统计算给出的T过程是慢过程的结论.     

我们的"非线性物理"课

提出了对理工科大学开设“非线性物理”课的课程体系的设计思路，介绍了该课程教学内容的具体安排。     

Special purpose computers in physics

This talk describes a new approach for large-scale computational problems which is particularly effective when a relatively simple algorithm is used. We demonstrate that it is possible to design and construct, at modest cost, special purpose computers for various classes of problems. By exploiting the principles of pipelining and parallel processing, and by adapting the hardware design to the specific structure of a particular algorithm, one can obtain a device which is as fast as or faster than general-purpose commercial supercomputers. The user of a such a processor has the double advantage of its speed and of its continuous availability for the particular problem for which it was constructed. In statistical mechanics special purpose computers have been built recently (i) for Monte Carlo simulation of the Ising model, and (ii) for the molecular dynamics of classical many-particle systems with short-range interactions. The design and performance of these machines are discussed and compared to those of commercial computers.     

复杂网络思想方法在大学物理教学中的应用

复杂网络是近年来复杂性研究的热点领域,与物理学的发展有密切的联系.让学生了解该领域的基本概念、方法及其与物理之间的关系大有裨益.本文对复杂网络中的一些基本概念和思想进行了简要介绍,并利用复杂网络的基本概念和思想对物理教学中两个较复杂的典型问题进行了分析.     

Statistical physics of shear flow: a non-equilibrium problem

Complex fluids are easily and reproducibly driven into non-equilibrium steady states by the action of shear flow. The statistics of the microstructure of non-equilibrium fluids is important to the material properties of every complex fluid that flows, e.g. axle grease on a rotating bearing; blood circulating in capillaries; molten plastic flowing into a mould; the non-equilibrium onion phase of amphiphiles used for drug delivery; the list is endless. Such states are as diverse and interesting as equilibrium states, but are not governed by the same statistics as equilibrium materials. I review some recently discovered principles governing the probabilities of various types of molecular re-arrangements taking place within a sheared fluid. As well as providing new foundations for the study of non-equilibrium matter, the principles are applied to some simple models of particles interacting under flow, showing that the theory exhibits physically convincing behaviour.     

Existence and Dynamics of Bounded Traveling Wave Solutions to Getmanou Equation

In this paper, we study the existence and dynamics of bounded traveling wave solutions to Getmanou equations by using the qualitative theory of differential equations and the bifurcation method of dynamical systems. We show that the corresponding traveling wave system is a singular planar dynamical system with two singular straight lines, and obtain the bifurcations of phase portraits of the system under different parameters conditions. Through phase portraits, we show the existence and dynamics of several types of bounded traveling wave solutions including solitary wave solutions, periodic wave solutions, compactons, kink-like and antikink-like wave solutions. Moreover, the expressions of solitary wave solutions are given. Additionally, we confirm abundant dynamical behaviors of the traveling wave s olutions to the equation, which are summarized as follows: i) We confirm that two types of orbits give rise to solitary wave solutions, that is, the homoclinic orbit passing the singular point, and the composed homoclinic orbit which is comprised of two heteroclinic orbits and tangent to the singular line at the singular point of associated system. ii) We confirm that two types of orbits correspond to periodic wave solutions, that is, the periodic orbit surrounding a center, and the homoclinic orbit of associated system, which is tangent to the singular line at the singular point of associated system.