Shear buckling modes of cylindrical sandwich shells under external pressure, tension-compression of bearing layers with unequal forces, and inhomogeneous across-the-thickness temperature

Equations are set up for describing, in a correct statement and with an accuracy sufficient in actual practice, the shear buckling modes (BMs) of cylindrical sandwich shells with a transversely soft core of arbitrary thickness. Based on them, solutions are obtained to a number of problems on the buckling instability according to shear modes under some force and thermal loadings. It is found that the BMs occur in the shell along the circumferential and axial directions if, in the precritical state, a normal compressive stress arises in the transverse direction. It is shown that this condition is fulfilled in the following cases: in axial tension of the shell with unequal forces applied to the end faces of bearing layers (the parameter of critical load is maximum if the tensile forces are equal); under external (internal) pressure; on cooling the outer and heating the inner layers. The results obtained are presented in the form of simple analytical formulas for determining the corresponding critical parameters of the force and thermal actions.Translated from Mekhanika Kompozitnykh Materialov, Vol. 41, No. 1, pp. 37–48, January–February, 2005.     

Phase morphology and mechanical properties of the electrospun polyoxymethylene/polyurethane blend fiber mats

Polyoxymethylene/thermoplastic polyurethane (POM/TPU) blends containing 10–30 wt % of TPU were electrospun using hexafluoroisopropanol as the solvent. The average fiber diameter increases with the increase in TPU content from 0.68 μm for neat POM fibers to 0.92 μm for POM/TPU 7:3 blend fibers due to the increase in solution viscosity. Core/sheath structure with the major component POM as the core and the minor component TPU as the sheath was observed by transmission electron microscopy and further confirmed by surface N contents of the blend fiber mats. The crystalline melting point and the degree of crystallinity of POM have no obvious change by coelectrospinning with TPU due to lack of interaction between POM and TPU as revealed by Fourier transform infrared spectroscopy. Tensile tests showed that the unusual high ductility of POM fiber mat could be further increased by coelectrospinning with 10 or 20 wt % TPU without significantly decreasing the stiffness and strength. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1853–1859, 2009     

基于学科素养论证分析2020年高考全国卷Ⅰ物理压轴题

2020年高考物理试题依托高考评价体系,结合物理学科特点,考试内容以学科素养考查为导向,即以物理观念、科学思维、科学探究、科学态度与责任的物理学科素养为导向,注重对核心物理概念和规律的考查,引导学生夯实学习发展的基础,促进中学重视培养学生的基础知识、基本技能以及提升学生的基本素养.基于物理学科素养,论证分析2020年高考全国理综卷Ⅰ物理压轴计算题,助力培养学生科学思维.     

Creep life evaluation of aluminum conductor composite core utilized in high voltage electric transmission

The creep life of aluminum conductor composite core (ACCC) utilized in high voltage electric transmission was investigated using an experimental method based on the equivalence relationship. First, the time-temperature-stress equivalence relationship was developed using the time-temperature and the time-stress equivalence relationships. Then, tensile creep experiments were conducted under different temperatures and different stress levels to obtain the strain-time curves of the ACCC. Finally, the creep strain master curve was obtained using the experimental data based on the time-temperature-stress equivalence relationship, allowing prediction of ACCC creep life. The results will play an important role in evaluation of the long-term characteristics of the ACCC for engineering applications.     

Forced Nonstationary Vibrations of a Sandwich Cylindrical Shell with Cross-Ribbed Core

The equations of nonaxisymmetric vibrations of sandwich cylindrical shells with discrete core under nonstationary loading are presented. The components of the elastic structure are analyzed using a refined Timoshenko theory of shells and rods. The numerical method used to solve the dynamic equations is based on the integro-interpolation method of constructing finite-difference schemes for equations with discontinuous coefficients. The dynamic problem for a sandwich cylindrical shell under distributed nonstationary loading is solved with regard for the discreteness of the core__________Translated from Prikladnaya Mekhanika, Vol. 41, No. 2, pp. 60–67, February 2005.     

CdTe/ZnSe核壳量子点免疫层析试纸条检测克伦特罗的研究

采用巯基丁二酸作为表面修饰剂,水相法合成水溶性的CdTe/ZnSe核壳量子点,然后在N-羟基琥珀酰亚胺(NHS)的作用下,将CdTe/ZnSe核壳量子点与抗克伦特罗多克隆抗体(Anti-CLE pAb)连接。通过凝胶电泳和斑点杂交实验,验证CdTe/ZnSe核壳量子点与Anti-CLE pAb连接成功,并且CdTe/ZnSe-Anti-CLE pAb偶联物能识别克伦特罗-BSA抗原(CLE-BSA)。光谱分析表明,量子点与抗体连接后荧光增强,荧光峰位从628nm红移至635nm。将合成的CdTe/ZnSe-Anti-CLE pAb偶联物作为指示克伦特罗(CLE)分子的荧光标记物,制备出一种用于检测CLE的免疫层析试纸条,其最低检测量可达1μg/L。与ELISA法的对比实验表明,此试纸条能应用于CLE残留的快速检测。     

有机液芯光纤拉曼谱测量的研究

我们选用CCl4和CS2混合溶液作为芯液制作了有机液芯光纤,采用后向泵浦的方式测量了光纤的拉曼光谱.实验中发现,随着溶质浓度和光纤长度的变化,拉曼谱强度也随之变化,并存在溶质最佳浓度和最佳光纤长度,这与理论分析值相符,并发现随着溶质浓度的降低,拉曼光谱线宽变窄.     

基于双芯光纤耦合器的梳状滤波器及其CO2激光调节

基于光纤耦合器的波长特性,分析了光纤耦合器作为梳状滤波器的光谱特性;将长度不同的双芯光纤(twin-core fiber,TCF)熔接在两根单模光纤(single mode fibors,SMF)之间,实验制得具有不同峰值波长间隔的基于双芯光纤耦合器的全光纤型梳状滤波器,其消光比可达25 dB. 首次使用CO₂激光对其进行光谱调节,调节导致光谱向长波方向漂移和消光比的变化. 这种调节是基于CO₂与光纤相互作用时的残余应力释放和熔融变形机理,使用氢载TCF可以在相同实验参数下得到更大的波长调节激光. 关键词： 双芯光纤耦合器 梳状滤波器 2激光')" href="#">CO₂激光 残余应力     

Hadron interactions in lattice QCD

Progress on the potential method, recently proposed to investigate hadron interactions in lattice QCD, is reviewed. The strategy to extract the potential in lattice QCD is explained in detail. The method is applied to extract NN potentials, hyperon potentials and the meson–baryon potentials. A theoretical investigation is made to understand the origin of the repulsive core using the operator product expansion. Some recent extensions of the method are also discussed.