Impact on the magnetic compressor due to CSR

When an electron bunch is compressed in a chicane compressor, the CSR (coherent synchrotron radiation) will induce energy redistribution along the bunch. Such energy redistribution will affect the longitudinal emittance as a direct consequence. It will also excite betatron oscillation due to the chromatic transfer functions, and hence a transverse emittance change. So, it is indispensable for us to find a way to alleviate the CSR-caused emittance dilution and the bad result of chicane compressor in PKU-FEL.     

Centimetre-Long Single Crystalline ZnO Fibres Prepared by Vapour Transportation

Centimetre-long ZnO fibres are synthesized by vapour transportation via thermal evaporation of ZnO powders. The growth process is carried out in a graphite crucible, in which ZnO powder is loaded as the source material, and a silicon wafer is positioned on the top of the crucible as the growth substrate. During the growth process, the source temperature is kept at 800℃ and the substrate temperature is kept at 600℃. Typical growth time to obtain centimetre-long ZnO fibres is 5-10 hours. Scanning electron microscopy （SEM）, x-ray diffraction （XRD）, transmission electron microscopy （TEM）, and selected area electron diffraction （SAED） measurement results show that ZnO fibres are single crystalline with high crystalline quality and very low defects concentration.     

Effects of degree correlation on the controllability of networks

In this paper, we investigate the effects of degree correlation on the controllability of undirected networks with different degree-mixing patterns based on simulation analysis. Considering random pinning, max-degree pinning and mix-degree pinning, some relevance factors on controllability such as the control gain and the number of pinned nodes are discussed in detail. It is found that disassortative mixing enhances the network controllability contrast to assortative mixing, to which the network controllability is sensible. Furthermore, too large or too low value of the feedback gain can reduce the controllability. From the viewpoint of practical application, mix-degree pinning strategy is suggested in assortative network, while in disassortative network, max-degree pinning scheme is better than random pinning.     

Enhanced blue emission from ZnS–ZnO composites confined in SBA-15

A new optical material, the ZnO nanoparticles that are modified with ZnS and confined in SBA-15, has been prepared through the controllable sulfuration at relatively low temperature (40 °C) from the ZnO/SBA-15 composites. The precursor composites can be prepared through a novel path in which the zinc is well dispersed by directly grinding zinc nitrate into the as-synthesized SBA-15 occluded with template followed by calcination, and it is possible to control the conversion of ZnO to ZnS by adjusting the reaction time. The resulting samples are characterized by XRD, nitrogen adsorption–desorption and photoluminescence (PL) spectroscopy. ZnO–ZnS composites, mainly confined in the mesopore of SBA-15, exhibit dramatically enhanced blue emission at the expense of the UV emission.     

Photoactive Polythiophene:Titania Hybrids with Excellent Miscibility for Use in Polymer Photovoltaic Cells

A series of poly{(3‐hexylthiophene)‐co‐[3‐(6‐hydroxyhexyl)thiophene]}:titania (P3HT‐OH:TiO₂) hybrids were synthesized via the in situ polycondensation of titanium (IV) n‐butoxide in the presence of P3HT‐OH. Introducing a hydroxyl moiety onto the side‐chain of poly(3‐hexylthiophene) (P3HT) significantly promotes the polymer‐titania interaction, resulting in the formation of homogeneous hybrid colloids. The UV‐vis spectra of P3HT‐OH:TiO₂ films demonstrate that TiO₂ markedly affects the stacking structure and the chain conformation of P3HT‐OH. The maximum absorption wavelength of these hybrid materials can be tailor‐made by merely varying the weight percentage of TiO₂. Moreover, P3HT‐OH:TiO₂ can be further utilized as an efficient compatibilizer in preparing photoactive P3HT:P3HT‐OH:TiO₂ films with excellent miscibility. The photovoltaic cell based on such a hybrid exhibited a 2.4‐fold higher value of power‐conversion efficiency compared to the cell based on P3HT:TiO₂.

     

Joint density of states and charge density wave in 2H-structured transition metal dichalcogenides

The joint density of states of two different 2H-structured transition metal dichalcogenides (TMDs) with and without charge density wave (CDW), Na_0.05TaS₂ and Cu_0.09NbS₂, respectively, are compared. While there is a clear maximum at the 3×3 charge density wavevector for Na_0.05TaS₂, the joint density of states for Cu_0.09NbS₂ does not show such behavior, consistent with the absence of CDW in the system. Our results illustrate that the joint density of states well represents the charge instability in 2D systems.     

Diffractive micro-optical elements for implementing hollow beam and bi-focus simultaneously

We design diffractive micro-optical elements (DMOEs) with sub-wavelength characteristic size based on a half-π-phase shifting scheme, with the aim of realizing a hollow beam and bi-focus simultaneously. The optical properties of DMOEs, such as the positions of the real focal planes, the aspect ratio of the hollow beam and the diffraction efficiency, are investigated by using the rigorous electromagnetic theory and the boundary element method. The numerical results show that a well-defined hollow beam and bi-focus are achieved simultaneously. Further analysis of the interference between dual-DMOE shows that the interference is much less than that of a conventional dual-microlens. It is indicated that the designed micro-optical element array can not only implement hollow beam and dual focus, but also suppress the interference effect significantly.     

Effects of third-order dispersion on soliton switching in fiber nonlinear directional couplers

The split-step Fourier method is used to study the energy switching characteristics of fiber nonlinear directional couplers with the third-order dispersion. The effects of the third-order dispersion increases with the third-order dispersion coefficient and input power and result in pulse shift and energy decreases. Adding high-order nonlinear can partly overcomes these effects.     

Determination of Methylene Blue and Its Metabolite Residues in Aquatic Products by High-Performance Liquid Chromatography–Tandem Mass Spectrometry

A sensitive and reliable method was developed to determine methylene blue (MB) and its metabolite residues, including azure A (AZA), azure B (AZB), and azure C (AZC) in aquatic products by HPLC–MS/MS. The samples were extracted by acetonitrile and cleaned up by alumina-neutral (ALN) cartridges. The analytes were separated on a Sunfire C18 column (150 mm × 2.1 mm, 5 µm). The method was validated according to the European criteria of Commission Decision 2002/657/CE. Good linearity between 1–500 µg/L was obtained with correlation coefficients (R²) greater than 0.99. The limit of quantification (LOQ) was 1.0 µg/kg. The average recoveries at three levels of each compound (1, 5, and 10 µg/kg) were demonstrated to be in the range of 71.8–97.5%, with relative standard deviations (RSDs) from 1.05% to 8.63%. This method was suitable for the detection of methylene blue and its metabolite residues in aquatic products.     

基于琼斯矩阵的FIR晶体光滤波器设计方法

FIR晶体光滤波器由夹在两个偏振片之间的N个厚度相同的晶片构成,设计过程中需要根据要求的频率响应求出各个晶体波片的光轴方向和输出端偏振片的通光方向.提出了一种基于琼斯矩阵的反向递推设计方法.FIR晶体光滤波器的琼斯矩阵是各个晶片以及偏振片琼斯矩阵的乘积,利用这一关系可以建立简单的反向递推关系,并计算出与输出偏振分量对应的正交偏振分量,通过迭代运算确定所有元件的角度参数.实例设计的结果与使用其它方法得到的结果一致,设计过程简单.