Ultrasound-assisted extraction of phillyrin from Forsythia suspensa

Forsythia suspensa (Thunb.) Vahl is one of the most widely used traditional Chinese medicines, and possesses important biological activities, such as antibacterial, antiviral, anti-inflammatory and antioxidant activities. Phillyrin is the main bioactive component of Forsythia suspensa. In this paper, ultrasound-assisted extraction of phillyrin from Forsythia suspensa was studied with HPLC-photodiode array detection. Effects of several experimental parameters, such as type and concentration of extracting solvent, ratio of liquid to material, extraction temperature, and time of sonication on extraction efficiencies of phillyrin from Forsythia suspensa were evaluated. The optimal extraction conditions were 1g plant sample with 10 ml of 20% methanol and the extraction for 60 min at 60°C under ultrasonic irradiation. Under the optimum conditions, the yield of phillyrin was 0.713±0.009 mg/g. The results indicated that the ultrasound-assisted extraction is a very useful method for the extraction of important phytochemicals from plant materials.     

Phase transition behavior and piezoelectric properties of low-Li and high-Sb modified KNN based piezoceramics

(Na_0.5K_0.5)_0.975Li_0.025Nb_0.82−xSb_xTa_0.18O₃ lead-free piezoceramics were prepared by the conventional solid-state sintering method. All samples possess a pure perovskite phase, and no secondary phase could be certified. The crystal structure changes from tetragonal to pseudo-cubic with increasing amount of Sb. The ferroelectric Curie temperature (T_c) shifts to lower temperature while the tetragonal to orthorhombic phase transition temperature (T_o-t) shows no obvious change with increasing Sb⁵⁺. Enhanced piezoelectric and electromechanical properties are obtained with x=0.06: d₃₃=352 pC/N, k_p=47% and k_t=38%, showing that they could be promising candidates as lead-free piezoelectric materials.     

Abnormal positive thermal expansion in Mo substituted ZrW2O8

ZrW₂O₈ displays the unusual property of an isotropic bulk contraction in volume as a function of temperature. We report here on the positive thermal expansion (PTE) property caused by substituting Mo for W sites in ZrW₂O₈ at room temperature. The room temperature crystal structure of ZrW_2−xMo_xO₈ compounds, which were synthesized using a low temperature route, could be divided into ordered phase with α-ZrW₂O₈ structure (0≤x≤0.5) and disordered phase with β-ZrW₂O₈ (0.5<x≤1.5) and c-ZrMo₂O₈ structure (1.5<x≤2). ZrW_2−xMo_xO₈ adopting β-ZrW₂O₈ structure shows abnormal PTE property at room temperature due to the existence of water molecules, while ZrW_2−xMo_xO₈ adopting the other two structures (α-ZrW₂O₈ and c-ZrMo₂O₈) shows negative thermal expansion (NTE) property from room temperature until decomposition for α-ZrW₂O₈ structure or trigonal phase transition for c-ZrMo₂O₈ structure. The reason lies in the fact that the oxygen migration caused by the Mo substitution leads to the re-arrangement of W(Mo)O₄ tetrahedra lying along the 3-fold axis, only particular W/Mo ratio (0.5<x≤1.5) produces a special crystal structure, which allows the entrance of water molecules.     

基于自适应主动及滑模控制的分数阶超混沌系统异结构反同步

以超混沌Chen系统和超混沌Lorenz系统为例,研究了慢时变参数超混沌系统的反同步问题.首先利用主动控制的思想,消去超混沌系统中的非线性部分,然后基于Lyapunov稳定性理论,合理地选取参数自适应控制律,很好的解决了时变参数的参数摄动问题,从而实现了两个超混沌系统的反同步.在此基础之上,又进一步研究了分数阶超混沌系统,使用滑模控制方法对其进行控制,理论上分析了该方法的可行性.数值模拟实验进一步验证了所提出方法的有效性. 关键词： 超混沌 分数阶 自适应 滑模     

External cavity diode laser with kilohertz linewidth by a monolithic folded Fabry-Perot cavity optical feedback

We present a extended-cavity diode laser (ECDL) with kilohertz linewidth by optical feedback from a monolithic folded Fabry-Perot cavity (MFC). In our experiments, an MFC replaces the retroreflecting mirror in the traditional ECDL configuration. Beat-note measurements between this MFC-ECDL and a narrow-linewidth reference laser are performed and demonstrate that the linewidth of this MFC-ECDL is about 6.8 kHz. Phase locking of this MFC-ECDL to the reference laser is achieved with a unity gain as small as 10.2 kHz.     

基于物元可拓法的轨道交通PPP项目风险评价研究

风险评价是风险控制的前提,风险控制对项目成功实施至关重要.文章通过文献查阅和专家访谈梳理了PPP(Public-Private-Partnership)项目风险,建立涵盖37条指标的轨道交通PPP项目风险指标体系,构建基于物元可拓法的风险评价模型,以呼和浩特轨道交通PPP项目为例,对其项目风险进行了评价,提供一种PPP项目风险事前事中评价的方法,给项目相关方的项目风险评价和管理提供参考.     

Highly efficient single longitudinal mode-pulsed green laser

A novel design for a highly efficient 1-kHz single-frequency green laser is proposed.An efficient singlefrequency laser pulse output at 532-nm wavelength may be obtained by combining the injection seeding with intracavity frequency doubling in a compact U-shaped cavity formed by two plano dichroic mirrors in an end-pumping arrangement.The laser is capable of producing green pulses with a total energy of 6.3 mJ at a pulse repetition rate of 1 kHz.The pulse width is about 10 ns and the optical-optical efficiency from the 808-nm pump source to the 532-nm green output is around 12.7%.