一类厄尔尼诺/拉尼娜-南方涛动海-气振子的奇摄动解

厄尔尼诺/拉尼娜-南方涛动是涉及赤道太平洋中的一个海-气交互的年际现象.本文的目的是建立一类海-气振子模型的非线性奇摄动问题的渐近求解方法.并在一类海-气振子模型的基础上,借用奇摄动方法研究了对应问题的近似解.由奇摄动方法得到的结果分析厄尔尼诺/拉尼娜-南方涛动海-气振子模型的赤道太平洋的海表温度异常和气-海振子的温度深度异常.     

B元素添加对Co-Zr-Mo合金薄带的磁性能及结构的影响

利用X射线和磁性测量研究了Co_77Zr（18-x）Mo₅B_x合金薄带的结构和磁性.实验发现,在Co-Zr-Mo合金中添加适当含量的B,可以使其矫顽力显著提高,当x=2.0时,制备出具有迄今为止Co-Zr基永磁合金最大矫顽力H_c=7.0 kOe（1 Oe=79.5775 A/m）的快淬薄带.随着B元素添加,Co₇₇Zr_18-xMo₅B_x合金薄带的晶粒逐渐细化,并根据Henkel plot模型计算得出软磁相fcc-Co与硬磁相Co₅Zr相之间的交换耦合作用逐渐增强.合金薄带的矫顽力主要受硬磁相Co₅Zr相的晶粒尺寸控制,并随着晶粒尺寸的减小先升高后降低.另一方面,Co₇₇Zr₁₈Mo₅合金薄带的矫顽力机理为反磁化核形核模型,添加B元素之后矫顽力机理变为畴壁钉扎模型.通过X射线衍射和热磁分析发现,B元素并没有进入到Co₅Zr相的晶格中,而是存在于非晶相中.     

Identifying Radix Curcumae by using terahertz spectroscopy

The absorption spectra from 0.2 THz to 1.6 THz of four kinds of similar Chinese herbs, including huangyujin, lvyujin, guiyujin and wenyujin, have been investigated by terahertz time-domain spectroscopy (THz-TDS). Furthermore, by using support vector machines (SVM) method, the linear kernel function, the polynomial kernel function, and the radial basis kernal function are employed for separating four kinds of Radix Curcumae. The calculated results show that the accuracy of discrimination for these four kinds of Chinese herbs is 100%.     

Self-mixing effect in Yb3+ doped DBR fiber laser with different linewidth enhancement factor

We present a self-mixing interference model approach to stimulate the self-mixing interference in YDBR fiber laser with optical self-mixing interference operating in the weak feedback regime. The self-mixing interference model includes Yb³⁺ doped fibers pumped at 920 nm, with distributed Bragg reflector mirrors at both fiber ends and external reflector. Using the quasi-analytical YDBR fiber laser model and self-mixing three-mirror cavity model, the output power expression is deduced and the Peak-to-Peak values and asymmetry values of self-mixing waveform at different linewidth enhancement factor have been studied in detail.     

Thermodynamic and physical properties of FeAl and Fe3Al: an atomistic study by EAM simulation

With this work we present a newly developed potential for the Fe–Al system, which is based on the analytical embedded atom method (EAM) with long range atomic interactions. The potential yields for the two most relevant phases B2-FeAl and D0₃-Fe₃Al lattice constants, elastic constants, as well as bulk and point defect formation enthalpies, which are in good agreement with experimental and other theoretical data. In addition, the phonon dispersions for B2-FeAl and D0₃-Fe₃Al show a good agreement with available experiments. The calculated lattice constants and formation enthalpy for disordered Fe–Al alloys are in good agreement with experimental data or other theoretical calculations. This indicates that the present EAM potentials of Fe–Al system is suitable for atomistic simulations of structural and kinetic properties for the Fe–Al system.     

Electronic structure and enhanced visible‐light absorption of N,B‐codoped TiO2

We present GGA+U calculations to investigate the electronic structure and visible‐light absorption of N,B‐codoped anatase TiO₂. The N_sB_i (substitutional N, interstitial B) codoped TiO₂ produces significant Ti 3d and N 2p mid‐gap states when the distance of N and B atoms is far, whereas the N_iB_i (interstitial N and B) and N_sB_s (substitutional N and B) codoped TiO₂ prefer to form localized p states at 0.3–1.2 eV above the valence band maximum. Further, the optical band edges of the three codoped systems shift slightly to the visible region, but only the far‐distance N_sB_i codoped TiO₂ clearly shows an optical transition. These results indicate that N_sB_i codoped TiO₂ has a dominant contribution to the optical absorption of N,B‐codoped TiO₂. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

一种混沌密码序列周期特性检测新方法

针对数字混沌密码序列发生器产生的二值序列局部范围内存在的周期特性评价难问题,提出一种新的周期特性分析方法——BSPD(binary sequence’s periodic detection)方法,用于评价二值序列具有的周期特性.该方法除可用于检测二值序列是否存在精确周期,或在部分时域范围内存在周期现象;还可检测出序列局部出现的周期性重叠模板,用于具体分析二值序列中周期现象的统计特征.一个基于经典Logistical映射的BSPD检验表明,该方法可以有效地定位一个类似随机混沌二值序列中蕴含的周期现象.     

油水两相流水包油流型多尺度排列熵分析

采用多尺度排列熵算法研究了垂直油水两相流水包油流型的多尺度动力学特性.首先,在内径为20 mm的垂直管道内采集了油水两相流水包油流型电导传感器波动信号,然后计算了不同流动工况下电导波动信号的多尺度排列熵值.研究发现多尺度排列熵率与均值可定量刻画水包油流型动力学复杂性;此外,提出了通过增量时间序列累积量与多尺度排列熵率联合分布识别三种不同水包油流型的新途径.     

High-order harmonic generation with a two-color laser pulse

We theoretically investigate the electron dynamics of the high-order harmonics generation process by combining a near-infrared 800 nm driving pulse with a mid-infrared 2000 nm control field.We also investigate the emission time of harmonics using time-frequency analysis to illustrate the physical mechanisms of high-order harmonic generation.We calculate the ionization rate using the Ammosov-Delone-Krainov model and interpret the variations in harmonic intensity for different control field strengths and delays.We find that the width of the harmonic plateau can be extended when the control electric field is added,and a supercontinuum from 198 to 435 eV is generated,from which an isolated 61-as pulse can be directly obtained.