Analytic solutions for the generalized complex Ginzburg–Landau equation in fiber lasers

Nonlinear Dynamics - This paper presents a study on the energy exchange taking place on articulated helicopter main rotor blades. The blades are hinged, and the flap/lag modes are highly coupled....     

Aerothermal dynamic failure of infrared window in high-speed aircraft

红外罩材料包括红外罩增透保护膜和基底材料, 是高速导弹结构--功能一体化的关键部件, 应用极为广泛. 但是, 红外罩材料通常工作于恶劣的外界环境下, 处于复杂的热力混合作用状态, 可能导致窗口失效, 因此对红外罩材料热力响应和失效的研究具有重要的科学研究价值和工程实际意义.本文针对高速飞行器环境下红外罩材料的气动热力失效机制, 从典型材料的特性及制备、气动热力响应机理及分析、红外罩材料的结构性和功能性失效等方面总结相关学者的研究成果, 并对今后的发展趋势进行展望.     

The ringing of quantum corrected Schwarzschild black hole with GUP

Schwarzschild black holes with quantum corrections are studied under scalar field perturbations and electromagnetic field perturbations to analyze the effect of the correction term on the potential function and quasinormal mode (QNM). In classical general relativity, spacetime is continuous and there is no existence of the so-called minimal length. The introduction of the correction items of the generalized uncertainty principle, the parameter β, can change the singularity structure of the black hole gauge and may lead to discretization in time and space. We apply the sixth-order WKB method to approximate the QNM of Schwarzschild black holes with quantum corrections and perform numerical analysis to derive the results of the method. Also, we find that the effective potential and QNM in scalar fields are larger than those in electromagnetic fields.     

双波长数字全息相位解包裹方法研究

使用两个不同的波长分别记录数字全息图,分别由数值再现得到每个波长对应的包裹相位图,再求得两者的相位差得到等效波长的相位图,通过此双波长相位解包裹方法得到连续的相位分布以消除相位包裹。通过数值模拟研究了双波长相位解包裹方法,搭建了双波长数字全息实验系统,并利用660nm和671nm两个波长的激光对标准石英平片和平凹透镜进行了相衬成像。通过双波长相位解包裹方法得到了连续的相位分布,实验结果与数值模拟结果具有较好的一致性,证明了双波长相位解包裹方法的有效性。     

Ce促进Ni/SAPO-11催化剂上正庚烷的临氢异构化

通过浸渍法制备了Ni/SAPO-11催化剂, 并进一步通过分步浸渍法制备了Ni-Ce /SAPO-11双金属催化剂, 对其晶相结构和表面酸性进行了表征. 实验结果表明, Ce的引入导致比表面积和孔容增大, 总酸量升高而酸强度降低, 金属Ni在载体SAPO-11表面的分散度提高. 通过对正庚烷的临氢异构化反应研究发现, 引入Ce可以显著提高异庚烷的选择性. 在n(H₂)/n(n-C₇H₁₆)=12, MHSV=3.52 h^-1, 催化剂量0.3 g, 反应温度300 ℃条件下, Ni-2%Ce/SAPO-11催化剂的正庚烷转化率可达25.4%, 异庚烷的选择性可达90.4%.     

Interfacial and mechanical properties of carbon fibers modified by electrochemical oxidation in (NH4HCO3)/(NH4)2C2O4·H2O aqueous compound solution

Polyacrylonitrile-based carbon fibers were electrochemical oxidized in (NH₄HCO₃)/(NH₄)₂C₂O₄·H₂O aqueous compound solution to improve its tensile strength and interfacial bounding strength with resin matrix simultaneously. AFM, XPS, XRD and Raman spectra were employed to characterize morphology, chemical states, crystallites size and ordered degree of CFs surface. The results indicated that the optimal modified condition in this paper could increase the tensile strength of CFs by 17.1%, meantime improve the interlaminar shear strength (ILSS) by 14.5%. The improvement of interlaminar shear strength not only causes by increase of surface roughness, but also causes by interaction effects of oxygen-containing and nitrogen-containing functional groups on carbon fibers. Among oxygen-containing functional groups, –COOH functional group plays an important role in enhancing the ILSS. Furthermore, after electrochemical oxidation the crystallites size decreased by 23–27%; ordered degree on CFs surface has an increase with suitable etching which did not peel off the ordered region on CFs surface and create new cracks; both above increase the tensile strength of CFs.     

Simultaneous determination of 17 bisphenols in polycarbonate by ultra‐high performance supercritical fluid chromatography with tandem mass spectrometry

A novel method was developed for the first time for the determination of 17 bisphenols by ultra‐high performance supercritical fluid chromatography with tandem mass spectrometry. Under the optimal conditions, 17 bisphenols were separated successfully on a high density diol column in 9 min using methanol and carbon dioxide as mobile phase. 0.02% ammonium hydroxide/methanol v/v was used as the post‐column compensation solvent to improve response of mass spectrometry. Linear relations of matrix‐matched calibration curve were favorable over the selected concentration range of 1–100 μg/kg with correlation coefficients greater than 0.9981. The method limit of detection and limit of quantitation were 0.1–0.5 μg/kg and 0.5–2.5 μg/kg, respectively. The average recoveries at three spiked levels in polycarbonate were in the range of 81.8–114.5%. Intra‐day and inter‐day precisions for six replicates were below 15.0%. This method was successfully applied to determine bisphenols in polycarbonate.     

Stereoselective β‐Mannosylation with 2,6‐Lactone‐bridged Thiomannosyl Donor by Remote Acyl Group Participation

Stereoselective β‐mannosylation has been recognized as one of the greatest challenges of carbohydrate chemistry. Herein, we described a practical method for stereoselective construction of β‐mannosides by using a 2,6‐lactone‐bridged thiomannosyl donor through the remote acyl‐group participation as well as the steric effect of O‐4 substituent. The two effects are enabled through the conversion of a regular mannopyranosyl ⁴C₁ conformation into a 2,6‐lactone bridged conformation. The lactone donor could be readily prepared in three steps on a gram scale and the β‐mannosylation proceeded smoothly with high stereoselectivity for primary, secondary and tertiary alcohol acceptors. In addition, this strategy was successfully applied to the synthesis of a naturally occurring trisaccharide.     

Round‐the‐Clock Photocatalytic Hydrogen Production with High Efficiency by a Long‐Afterglow Material

Long afterglow materials can store and release light energy after illumination. A brick‐like, micrometer‐sized Sr₂MgSi₂O₇:Eu²⁺,Dy³⁺ long‐afterglow material is used for hydrogen production by the photocatalytic reforming of methanol under round‐the‐clock conditions for the first time, achieving a solar‐to‐hydrogen (STH) conversion efficiency of 5.18 %. This material is one of the most efficient photocatalysts and provides the possibility of practical use on a large scale. Its remarkable photocatalytic activity is attributed to its unique carrier migration path and large number of lattice defects. These findings expand the application scope of long afterglow materials and provide a new strategy to design efficient photocatalysts by constructing trap levels that can prolong carrier lifetimes.     

食品及环境样品中双酚类物质的前处理及检测方法研究进展

双酚类物质作为一种环境内分泌干扰物,广泛存在于食品包装材料及环境介质中,对生态环境造成污染,也对人体健康产生一定危害。双酚残留是目前重要的食品安全问题,检测食品和环境样品中的双酚类物质的含量对人体健康具有重要的意义。由于残留目标物浓度通常较低,且实际样品存在基质干扰,因此需经一定的样品前处理,并结合仪器分析方法,提高检测效率,增强分析灵敏度与可靠性。常用的前处理分析方法主要有液液萃取、微波辅助萃取、固相萃取、固相微萃取、基质分散固相萃取、QuEChERS等,常用仪器分析方法包括液相色谱法、气相色谱法、毛细管电泳法、酶联免疫吸附测定法、生物传感器法等。该文综述了食品及环境样品中双酚类物质的样品前处理及仪器分析方法,为双酚类化合物的残留监测提供了参考依据。