New bifurcations of basin boundaries involving Wada and a smooth Wada basin boundary

This paper demonstrates and analyses double heteroclinic tangency in a three-well potential model, which can produce three new types of bifurcations of basin boundaries including from smooth to Wada basin boundaries, from fractal to Wada basin boundaries in which no changes of accessible periodic orbits happen, and from Wada to Wada basin boundaries. In a model of mechanical oscillator, it shows that a Wada basin boundary can be smooth.     

An alternating periodic－chaotic ISI sequence of HH neuron under external sinusoidal stimulus

A study of Hodgkin－Huxley (HH) neuron under external sinusoidal excited stimulus is presented in this paper. As is well known, the stimulus frequency is to be considered as a bifurcate parameter, and numerous phenomena, such as synchronization, period, and chaos appear alternatively with the changing of the stimulus frequency. For the stimulus frequency less than 2f_B (f_B being the base frequency in this paper), the simulation results demonstrate that the single HH neuron could completely convey the sinusoidal signal in anti-phase into interspike interval (ISI) sequences. We also report, perhaps for the first time, another kind of phenomenon, the beat phenomenon, which exists in the phase dynamics of the ISI sequences of the HH neuron stimulated by a sinusoidal current. It is shown furthermore that intermittent transition results in the general route to chaos.     

理论研究F2BN3多聚体的结构特色和热力学稳定性

在密度泛函理论（DFT）B3LYP/6-311+G*水平上计算研究了叠氮二氟硼多聚体(F2BN3)n (n=1-4),获得了它们的结构和热力学性质,讨论了几何参数随聚合度的变化趋势。多聚体(F2BN3)2-4的优化构型均为由不同子体系的叠氮基α−N和B原子相连形成的环状结构。三聚体的船扭式构象比椅式构象的结合能低10.54 kJ•mol-1;四个新获得的四聚体的结合能差异较大,大小为3.1~45.65 kJ•mol-1。由焓变可知,单体形成二聚体在热力学上是不利的,而形成三聚体和四聚体在高达1200 K的温度下是有利的,同时分析比较了后续反应的热力学参数。     

基于腔面非注入区的半导体激光器的热特性分析

利用Ansys有限元分析软件模拟了宽条形激光器腔面在不同生热率条件下对有源区温度的影响,并对带有腔面非注入区的激光器结构进行了热分析,比较了不同长度的非注入区结构的器件的温度特性。腔面的温升对器件可靠性影响极大,计算结果表明随着非注入区宽度的增加,芯片前腔面有源区的温度明显降低。结果为采用非注入区结构提高COD阈值功率提供了设计参考。     

The isolated critical value phenomenon in local－global riddling bifurcation

A chaotic synchronized system of two coupled skew tent maps is discussed in this paper. The locally and globally riddled basins of the chaotic synchronized attractor are studied. It is found that there is a novel phenomenon in the local－global riddling bifurcation of the attractive basin of the chaotic synchronized attractor in some specific coupling intervals. The coupling parameter corresponding to the locally riddled basin has a single value which is embedded in the coupling parameter interval corresponding to the globally riddled basin, just like a breakpoint. Also, there is no relation between this phenomenon and the form of the chaotic synchronized attractor. This phenomenon is found analytically. We also try to explain it in a physical sense. It may be that the chaotic synchronized attractor is in the critical state, as it is infinitely close to the boundary of its attractive basin. We conjecture that this isolated critical value phenomenon will be common in a system with a chaotic attractor in the critical state, in spite of the system being discrete or differential.     

基于多曝光图像融合的沙尘图像增强

针对沙尘图像存在细节模糊、对比度低和颜色偏移等问题,提出了基于多曝光图像融合的沙尘图像增强算法.首先对蓝通道进行补偿,以弥补沙尘图像的蓝光损失;其次对图像的RGB三通道分别进行标准化,以减小通道直方图之间的偏离,从而去除偏色.为了提高图像中不同区域的细节,采用线性参数控制的方法生成多幅曝光图像.通过用对比度、饱和度和良...     

LOW-FREQUENCY INTERNAL FRICTION STUDY FOR SrBi2Ta2O9 FERROELECTRIC CERAMICS

Low-frequency internal friction (IF) of SrBi₂Ta₂O₉(SBT) ceramics has been measured at temperatures ranging from 293 to 623 K. Two IF peaks, with their locations around 393 K (P1) and 569 K (P2) (f≈1.58 Hz), respectively, are observed. P1 is found to be associated with a relaxation process with activation energy of 0.97 eV and pre-exponential factor of 3.58×10^-14 s. Peak shape analyses reveal that P1 can be well described by a broadened Debye peak with the width parameter β from 2.70 to 2.92. The mechanism responsible for P1 is proposed to be relaxation of oxygen vacancies near domain walls(DWs). P2 is considered to arise from viscous motion of DWs since it shows characteristics of static hysteresis type. Comparisons for the IF behavior between SBT and Pb(Zr, Ti)O₃(PZT) suggest that in SBT oxygen vacancies are much less localized near DWs than that in PZT. This result provides a possible explanation for the weak DW pinning due to oxygen vacancies in SBT.     

Geometric quantities of lower doubly excited bound states of helium

Expectation values of single electron and interelectronic geometric quantities such as $\langle r\rangle$, $\langle r_{12}\rangle$, $\langle r_<\rangle$, $\langle r_>\rangle$, $\langle \cos\theta_{12}\rangle$ and $\langle \theta_{12}\rangle$ are calculated for doubly excited $2{\rm p}n{\rm p}\,{}^1P^{\,\rm e}\,(3\leq n\leq5),\, 2{\rm p}n{\rm p}\,{}^3\!P^{\,\rm e}\,(2\leq n\leq5)$ and $2{\rm p}n{\rm d}\,{}^{1,3}D^{\,\rm o}\,(3\leq n\leq5)$ states of helium using Hylleraas-$B$-spline basis set. The energy levels converge to at least 10 significant digits in our calculations. The extrapolated values of geometric quantities except for $\langle \theta_{12}\rangle$ reach 10 significant digits as well; $\langle \theta_{12}\rangle$ reaches at least 7 significant digits using a multipole expansion approach. Our results provide a precise reference for future research.     

970nm高功率光栅外腔可调谐半导体激光器

宽条形半导体激光器广泛应用于激光泵浦、激光加工等领域。针对宽条型半导体激光器输出光谱宽、调谐范围小的问题,采用衍射效率分别为28%和55%的反射式衍射光栅作为反馈元件构建了宽条形970 nm波长光栅外腔半导体激光器。研究了Littrow结构激光器参数对其性能（调谐范围、功率、阈值电流、线宽）的影响。实验结果表明,通过结构优化可得到窄线宽可调谐激光输出,适当地提高温度和使用较高衍射效率的光栅可增加激光器调谐范围,并且较高衍射效率的光栅可降低激光器的阈值电流。基于S偏振入射方式的光栅外腔激光器最大可实现27.87 nm的波长调谐范围,光谱线宽压窄至0.2 nm,输出功率可达1.11 W。     

分光光度法研究在氯化钠-四丁基溴化铵体系中Au(Ⅲ)与U(Ⅵ)、Ce(Ⅲ)、Mg(Ⅱ)和Cu(Ⅱ)的浮选分离

用分光光度法研究了氯化钠和四丁基溴化铵浮选分离金的行为及与一些金属离子分离的条件。结果表明,当溶液中氯化钠和四丁基溴化铵的浓度分别为2.5×10-3mol/L和4.0×10-4mol/L,pH3.0时,Au(Ⅲ)可与U(Ⅵ)、Ce(Ⅲ)、Mg(Ⅱ)和Cu(Ⅱ)离子定量分离,对合成水样中Au(Ⅲ)的分离和测定,结果满意。