Rhythm dynamics of complex neuronal networks with mixed bursting neurons

The spatiotemporal order and rhythm dynamics of a complex neuronal network with mixed bursting neurons are studied in this paper. A quantitative characteristic, the width factor, is introduced to describe the rhythm dynamics of an individual neuron, and the average width factor is used to characterize the rhythm dynamics of a neuronal network. An r parameter is introduced to denote the ratio of the short bursting neurons in the network. Then we investigate the effect of the ratio on the rhythm dynamics of the neuronal network. The critical value of r is derived, and the neurons in the network always remain short bursting when the r ratio is larger than the critical value.     

密度矩阵重正化群的异构并行优化

密度矩阵重正化群方法（DMRG）在求解一维强关联格点模型的基态时可以获得较高的精度,在应用于二维或准二维问题时,要达到类似的精度通常需要较大的计算量与存储空间.本文提出一种新的DMRG异构并行策略,可以同时发挥计算机中央处理器（CPU）和图形处理器（GPU）的计算性能.针对最耗时的哈密顿量对角化部分,实现了数据的分布式存储,并且给出了CPU和GPU之间的负载平衡策略.以费米Hubbard模型为例,测试了异构并行程序在不同DMRG保留状态数下的运行表现,并给出了相应的性能基准.应用于4腿梯子时,观测到了高温超导中常见的电荷密度条纹,此时保留状态数达到10⁴,使用的GPU显存小于12 GB.     

锂玻璃探测器中子探测效率的刻度

为了精确测量keV能区的中子俘获截面,中国原子能科学研究院正在建造一台4π 全吸收型γ 探测装置---GTAF,锂玻璃探测器将会作为中子束流监视器测量中子能谱。利用5SDH-2 加速器刻度了锂玻璃探测器在两个入射中子单能点(250 和565 keV) 的探测效率,并使用EANT4 和MCNP 程序模拟计算了锂玻璃探测器的相对探测效率。通过归一化实验数据和模拟结果,得到了锂玻璃探测器在10keV~1 MeV 能区的中子探测效率曲线。对于把锂玻璃探测器测量得到的飞行时间谱转化为中子束流能谱,是一项非常重要的工作,同时为探测器效率刻度提供了新方法。In order to accurately measure the neutron capture cross section in the energy range of keVMeV, 4 πgamma-ray total absorption facility (GTAF) is being constructed at China Institute of Atomic Energy (CIAE). The lithium glass detector will be used as a neutron beam monitor for GTAF. The detection efficiency of the lithium glass detector at two incident neutron energy points (250, 565 keV) was calibrated in 5SDH-2 accelerator, and the relative detection efficiency was simulated by GEANT4 and MCNP code. By the normalization of the experimental data and simulation result, the neutron detection efficiency curve of the lithium glass detector between 10 keV and 1 MeV was obtained. This work will be important to convert the Time-of-flight spectrum that be measured by Li-glass detector to the energy spectrum of neutron beam, and provide the new method for calibration of detection efficiency.     

15波长输出的布里渊掺铒光纤激光器

多波长布里渊掺铒光纤激光器是一种新型的多波长光纤激光器,其原理是利用受激布里渊增益和掺铒光纤的线性增益,可以在常温下得到波长间隔约为0．08nm(～10GHz)的多波长输出。报道的布里渊掺铒光纤激光器,在布里渊抽运功率为1．7mW、980nm抽运功率为300mW的情况下得到稳定的15个波长(间隔～10GHz)的输出,这种激光器用作光传感器、光谱分析仪以及密集波分复用系统的光源。实验发现,输出波长的个数随着980nm抽运功率的增大而增加。另外,布里渊掺铒光纤激光器的信号功率主要来自于掺铒光纤的增益,而布里渊增益对它的影响不大。     

含纳米棒银溶胶的制备及其光谱性质研究

以CTAB表面活性剂胶束为模板用化学还原法制备出含有银纳米棒的银胶体,用透射电镜(TEM)对颗 粒形貌进行了表征.UV Vis吸收谱显示,含银纳米棒溶胶有两个吸收蜂,其中长波长吸收峰位置随胶粒长径比增 加迅速红移和宽化.用多尺寸统计平均的Mie散射模型计算了纳米棒银胶体的吸收谱,较好地解释了长波长吸收 峰的宽化.以此胶体为衬底材料,测量了染料分子的表面增强拉曼散射(SERS),结果显示,SERS强度随胶体中 所含纳米棒长径比的增加呈现先显著增强后缓慢减弱的变化规律,用电磁增强理论对有关现象进行了分析.     

Measured local heat transport in turbulent Rayleigh-Bénard convection

Local convective heat flux in turbulent thermal convection is obtained from simultaneous velocity and temperature measurements in an aspect-ratio-one convection cell filled with water. It is found that fluctuations of the vertical heat flux are highly intermittent and are determined primarily by the thermal plumes in the system. The experiment reveals a unique mechanism for the heat transport in turbulent convection.     

潘宁源放电的全三维电磁粒子模拟/蒙特卡罗碰撞数值算法研究

深入研究潘宁放电的物理机制, 研制了全三维高品质算法粒子模拟软件(PIC), 设计并添加了相应物理情景的蒙特卡罗碰撞模块(MCC), 并对电子、氢分子离子(H₂⁺)、氢正离子(H⁺)、氢三正离子(H₃⁺)同时进行了跟踪, 成功研制了全三维电磁PIC/MCC数值算法. 结合国内研究较热的潘宁放电模型, 对该算法进行模拟验证. 模拟结果显示: 采用有效的滤波算法能抑制电磁数值噪声, 电子能量呈麦克斯韦分布, 由于电子的径向漂移和加速导致离子源顶端H₂⁺产量较大. 关键词： 潘宁离子源 高品质算法 粒子模拟/蒙特卡罗     

Comparison of entanglement trapping among different photonic band gap models

We investigate the roles of different qubit-environment decoherence models on the entanglement trapping of two qubits. By considering three environmental models （the single photonic band gap model, the common photonic band gap model, and the two independent photonic band gaps model）, we note that the final values of entanglement trapping are determined by these different models. We also give the conditions of obtaining the larger entanglement trapping by comparing two-qubit entanglement dynamics in different decoherence models. Moreover, the comparison of entanglement trapping between two Bell-like states in the same decoherence model are also carried out.     

更正:质子束治疗中非均匀组织的等效水厚度修正研究[物理学报2013,62,068701]

《物理学报》2013年第62卷第6期第068701页《质子束治疗中非均匀组织的等效水厚度修正研究》一文中,因作者疏忽导致几处错误,特此更正,并诚挚地向读者致歉.期刊网上此文的电子版已做相应的更正.将3.1节中三个公式做如下更正:将(1)式:"WET=R介质/R水×b"改成:"WET=R水/R介质×b"将(2)式:"WET=R1/R水×d1+R2/R水×d2+···+Rn/R水×dn"改成:"WET=R水/R1×d1+R水/R2×d2+···+R水/Rn×dn"     

Effects of delayed recovery and nonuniform transmission on the spreading of diseases in complex networks

We investigate the effects of delaying the time to recovery (delayed recovery) and of nonuniform transmission on the propagation of diseases on structured populations. Through a mean-field approximation and large-scale numerical simulations, we find that postponing the transition from the infectious to the recovered states can largely reduce the epidemic threshold, therefore promoting the outbreak of epidemics. On the other hand, if we consider nonuniform transmission among individuals, the epidemic threshold increases, thus inhibiting the spreading process. When both mechanisms are at work, the latter might prevail, hence resulting in an increase of the epidemic threshold with respect to the standard case, in which both ingredients are absent. Our findings are of interest for a better understanding of how diseases propagate on structured populations and to a further design of efficient immunization strategies.