Analysing chaos in fractional-order systems with the harmonic balance method

In this paper, the fractional-order Genesio--Tesi system showing chaotic behaviours is introduced, and the corresponding one in an integer-order form is studied intensively. Based on the harmonic balance principle, which is widely used in the frequency analysis of nonlinear control systems, a theoretical approach is used to investigate the conditions of system parameters under which this fractional-order system can give rise to a chaotic attractor. Finally, the numerical simulation is used to verify the validity of the theoretical results.     

Effect of the mutation of carotenoids on the dynamics of energy transfer in light-harvesting complexes （LH2） from Rhodobacter sphaeroides 601 at room temperature

Energy transfers in two kinds of peripheral light-harvesting complexes (LH2) of {Rhodobacter sphaeroides} (RS) 601 are studied by using femtosecond pump--probe spectroscopy with tunable laser wavelength at room temperature. These two complexes are native LH2 (RS601) and green carotenoid mutated LH2 (GM309). The obtained results demonstrate that, compared with spheroidenes with ten conjugated double bonds in native RS601, carotenoid in GM309 containing neurosporenes with nine conjugated double bonds can lead to a reduction in energy transfer rate in the B800-to-B850 band and the disturbance in the energy relaxation processes within the excitonic B850 band.     

Scanning tunnelling microscope studies of growth of RuO2（110） thin layer on Ru（0001）

This paper reports that the growth of RuO_x(110) thin layer growth on Ru(0001) has been investigated by means of scanning tunnelling microscope (STM). The STM images showed a domain structure with three rotational domains of RuO_x(110) rotated by an angle of 120℃. The as-grown RuO_x(110) thin layer is expanded from the bulk-truncated RuO_x(110) due to the large mismatch between RuO_x(110) and the Ru(0001) substrate. The results also indicate that growth of RuO_x(110) thin layer on the Ru(0001) substrate by oxidation tends first to formation of the Ru-O (oxygen) chains in the [001] direction of RuO_x(110).     

Relative entropy as a measure of entanglement for Gaussian states

In this paper, we derive an explicit analytic expression of the relative entropy between two general Gaussian states. In the restriction of the set for Gaussian states and with the help of relative entropy formula and Peres--Simon separability criterion, one can conveniently obtain the relative entropy entanglement for Gaussian states. As an example, the relative entanglement for a two-mode squeezed thermal state has been obtained.     

Preparation and tribological properties of DLC/Ti filmby pulsed laser arc deposition

This paper reports that DLC (diamond like carbon)/Ti and DLC films were prepared by using pulsed laser arc deposition. R-ray diffraction, Auger electron spectroscopy, Raman spectroscopy, atomic force microscopy, nanoindenter, spectroscopic ellipsometer, surface profiler and micro-tribometer were employed to study the structure and tribological properties of DLC/Ti and DLC films. The results show that DLC/Ti film, with $I(D)/I(G)$ 0.28 and corresponding to 76{\%} sp$^{3}$ content calculated by Raman spectroscopy, uniform chemical composition along depth direction, 98 at{\%} content of carbon, hardness 8.2 GPa and Young's modulus 110.5 GPa, compressive stress 6.579 GPa, thickness 46~nm, coefficient of friction 0.08, and critical load 95mN, exhibits excellent mechanical and tribological properties.     

基于光导微探针的近场/远场可扫描太赫兹光谱技术

太赫兹技术已经成为涉及公共安全、军事国防和国民经济等国家核心利益的前沿研究领域.以往太赫兹测量技术中通常以远场测量为主,如常用的太赫兹时域光谱仪.近年来太赫兹近场技术得到了迅猛的发展,特别是基于光导天线的探针技术的发展,为可扫描的太赫兹近场测量提供了可能.本文详细报道了我们近期在可扫描太赫兹近场光谱仪研究中的进展.采用光纤耦合的光导微探针实现了方便灵活的太赫兹近场/远场三维扫描,并同时获得振幅和相位信息.该系统将有可能广泛应用于人工微结构、石墨烯、表面等离子激元、波导传输、近场成像、生物样品检测、芯片检测等研究领域.     

计算电容中Fabry-Perot干涉仪测量位移的相位修正方法

计算电容是复现电学阻抗单位的基准装置, 利用计算电容值和量子霍尔电阻值可以准确计算出精细结构常数α. 计算电容的本质是通过高准确度地测量屏蔽电极的位移, 实现对电容量值的测量. 因此, 基于Fabry-Perot干涉仪的精密电极位移测量系统是计算电容装置中最为核心和关键的部分. 在Fabry-Perot干涉仪测位移过程中, 由于高斯激光束存在轴向Gouy相位, 该附加相位将会引起相邻干涉条纹对应位移的变化(大于或者小于λ/2), 导致位移的测量值与实际值存在偏差. 本文阐述了高斯激光场的传播特性, 利用高斯激光束在自由空间和透过薄透镜复振幅的变换关系, 建立了计算电容装置中Fabry-Perot干涉仪透射光束的传输模型; 通过对不同腔长的Fabry-Perot干涉仪透射光场相位的分析, 获得了高斯激光束轴向Gouy相位修正与传输距离的关系. 结果表明, 当腔长从111.3 mm移动至316.3 mm时, 在接收距离为560 mm的情况下, 高斯光束轴向Gouy 相位引起的位移修正的绝对值最小为0.7 nm, 其相对相位修正量|δL|/|ΔL| = 3.4×10^-9.     

高温条件下Ga3PO7晶体热学及声表面波性质的理论研究

高温压电晶体是许多机电器件必需的一种多功能材料, Ga₃PO₇晶体的居里温度高达1364 ℃, 可应用于高温极限条件. 但是预测高温极限条件下晶体的结构以及物理性质的问题采用实验研究的手段非常困难, 而理论上的预测未见研究. 本文采用密度泛函-准谐振近似理论计算了温度在0-1200 ℃范围内Ga₃PO₇ 晶体的结构常数和热学性质, 结果表明Ga₃PO₇晶体的晶格常数a和c随温度的升高呈线性增大, 且c方向受温度影响更为显著; 晶体的密度随温度的升高而减小, 计算的a 和c方向平均热膨胀系数分别为1.67×10^-6 K^-1和3.58×10^-6 K^-1, 高温区定压热容为2.067 J/g·K, 与实验值一致. 计算了从常温到高温下该晶体的弹性常数以及体弹性模量的变化, 研究了高温条件下的声表面波特性, 发现随着温度的升高, 声表面波速度浮动较小, 而机电耦合系数略有增大; 在传播角为151° 时该晶体具有较好的温度稳定性且机电耦合系数达到最大值, 这表明Ga₃PO₇ 晶体是一种有望应用于高温环境下的压电晶体.     

Widely tunable dual-pump parametric amplifiers with photonic crystal fibres

This paper theoretically studies the double-pumped fibre-optical parametric amplifiers （FOPAs） in photonic crystal fibres. Two distinct working regimes of FOPAs are researched, which depend on the dispersion at the central wavelength of the two pumps. Extremely broad tuning range can be obtained when the central pump wavelength is in the normal dispersion regime and is insensitive to the wavelength separation between the two pumps, while the tuning range is narrow in the anomalous dispersion regime and can be significantly enhanced by increasing the wavelength separation. Impacts of higher-order dispersions and temporal walk-off on the gain spectra are also discussed.     

氧化石墨烯猝灭罗丹明6G荧光的机理研究

The fluorescence quenching of Rhodamine 6G (R6G) by graphene oxide (GO) was interrogated by R6G fluorescence measurements using a set of controlled GO samples with varied C/O ratios as the quencher.The carbonyl groups on the GO nanosheet turned to play a dominant role in quenching the R6G fluorescence.The quenching in the static regime can be described by the "sphere of action" model.The significant absorption of the R6G fluorescence by the ground-state complex formed between R6G and GO was identified to be responsible for the static quenching.This work offers helpful insights into the fluorescence quenching mechanisms in the R6G/GO system.