化学学案的设计和运用

现代教育学认为：要优化课堂教学结构,教师不但要注重自己的教法,更应研究学生的学法。只有这样,才能帮助学生掌握知识,发展能力,形成科学的学习方法。     

Design of europium doped SiO2–TiO2 hybrids as novel luminescent photocatalyst

SiO₂/TiO₂:Eu³⁺ composite materials were facially prepared by the sol–gel technique and all the as-derived powders exhibited europium characteristic red emissions under multiple excitation wavelengths extended to visible range (395 and 465 nm). The influence factors such as Si/Ti ratio, orders of hydrolysis, annealing temperature and doping concentration were systematically studied. The novel photocatalytic behavior for removing phenol was thoroughly investigated.     

Novel lanthanide pH fluorescent probes based on multiple emissions and its visible-light-sensitized feature

A new type of Eu(III) ofloxacin complex as the fluorescent pH indicator has been presented. Compared to pure ligand, the complex offers more distinguished color changes (green–red–blue) derived from both lanthanide line emissions and the secondary ionization steps of ofloxacin. During the concentration dependence experiments, the photoluminescence studies on the complex showed that the excitation of this pH probe can occur at a very long wavelength which extends to visible range (Ex = 427 nm). Furthermore, the functional complex was successfully incorporated into soft networks and two novel luminescent hydrogels (rod and film) were fabricated. The soft materials also exhibited specific responses towards the pH variation. Finally, the onion cell-stain experiments were carried out to further confirm the validity of pH dependence and the results support the idea that the material will be suitable for monitoring biological samples in the future.     

Dynamic analysis of an axially moving finite-length beam with intermediate spring supports

This paper presents the analysis for the transverse vibration of an axially moving finite-length beam inside which two points are supported by rotating rollers. In this study, the rollers are modeled as uniaxial springs in the transverse direction. Hamilton?s principle is applied to derive the equations of motion and boundary conditions of the system. The equations of motion include translational and rotational motions as well as flexible motion. These equations are discretized using Galerkin?s method, and then the dynamic characteristics of a flexible beam with spring supports are studied by solving an eigenvalue problem. The veering phenomenon of natural frequency loci and mode exchanges are investigated for different positions of the springs and various values of the spring stiffness. In addition, the mode localization is also analyzed using the peak amplitude ratio. It is found in this study that the first mode is localized in one of the beam spans if an appropriate value of the spring constant is selected. Furthermore, it is shown that mode localization can be used to reduce the vibration transferred from one span to the other span while a beam moves axially.     

Dynamic analysis of a tethered satellite system with a moving mass

This paper presents a dynamic analysis of a tethered satellite system with a moving mass. A dynamic model with four degrees of freedom, i.e., a two-piece dumbbell model, is established for tethered satellites conveying a mass between them along the tether length. This model includes two satellites and a moving mass, treated as particles in a single orbital plane, which are connected by massless, straight tethers. The equations of motion are derived by using Lagrange’s equations. From the equations of motion, the dynamic response of the system when the moving mass travels along the tether connecting the two satellites is computed and analyzed. We investigate the global tendencies of the libration angle difference (between the two sections of tether) with respect to the changes in the system parameters, such as the initial libration angle, size (i.e. mass) of the moving mass, velocity of the moving mass, and tether length. We also present an elliptic orbit case and show that the libration angles and their difference increase as orbital eccentricity increases. Finally, our results show that a one-piece dumbbell model is qualitatively valid for studying the system under certain conditions, such as when the initial libration angles, moving mass velocity, and moving mass size are small, the tether length is large, and the mass ratio of the two satellites is large.     

从上林苑到《上林赋》：汉帝国的博物空间及其笔端营造

《上林赋》是描绘上林苑的赋作,在景观转化为文本的过程中,文学创作与现实世界呈现出既相互依存、又彼此独立的微妙互动。上林苑因陈列多元物种而表现出博物空间性质,《上林赋》则可视为这一博物空间的文本化形态。以此为视点,《上林赋》中夸张描写并非完全凭虚,而是匹配了现实上林苑“再现天下”和“通天见神”的空间布局意图。上林苑的某些建筑理念受制于客观环境而无法完整付诸实践,故借助《上林赋》文本得以延展实现。上林苑因帝国苑囿性质而呈现出权力意义,《上林赋》修饰了这一权力并借助文本流通突破了现实时空束缚,从而使权力以一种理想化形态被永久及广泛地展演。由此可见,历史景观的权力意义主要是通过对其进行修饰性描绘的文本得以再现的。     

Dynamic analysis of a BLDC motor with mechanical and electromagnetic interaction due to air gap variation

In this study, the dynamic behaviors of a BLDC motor are analyzed, when the motor undergoes mechanical and electromagnetic interaction due to an air gap variation between the stator and rotor. When considering the air gap variation caused by the translational motion of the rotor relative to the stator, the kinetic and potential energies, Rayleigh dissipation function, and the magnetic coenergy are expressed in terms of the rotor displacements and stator currents. With these energies and function, new equations of motion are derived using Lagrange’s equation. The equations for the proposed model are nonlinear equations in which the displacements and currents are coupled. The time responses for the displacements and currents are computed for the proposed and previous models. Furthermore, the effects of rotor eccentricity are also investigated. It is found that, when the air gap varies with time, the time responses for the proposed and previous models have small differences in the stator currents, electromagnetic torques, and rotating speeds. However, the time responses have large differences in the rotor displacements. Therefore, this paper claims that the proposed model describes the dynamic behaviors of the motor more accurately than the previous model. It is also shown that rotor eccentricity increases the stator current period and the electromagnetic torque, while it decreases the rotating speed of the rotor.     

Dynamic contact analysis of a tensioned beam with a moving mass–spring system

The dynamic contact problem of a tensioned beam with clamped-pinned ends is analyzed when the beam contacts a moving mass–spring system. The contact and contact loss conditions are expressed in terms of constraint equations after considering the dynamic contact between the beam and the moving mass. Using these constraints and equations of motion for the beam and moving mass, dynamic contact equations are derived and then discretized using the finite element method, which is based on the Lagrange multiplier method. The time responses for the contact forces are computed from these discretized equations. The contact force variations and contact loss are investigated for the variations of the moving mass velocity, the beam tension, the moving mass, and the stiffness of the moving mass–spring system. In addition, the possibility of contact loss and safe contact conditions between the moving mass and the tensioned beam are also studied.     

A Remark on the FRTS Realization and Drinfeld Realization of Quantum Affine Superalgebra U q (o $${\hat s} $$ sp(1,2))

In this Letter, we present the hidden symmetry behind the Faddeev–Reshetikhin–Takhtajan–Semenov–Tian–Shansky (FRTS) realization of quantum affine superalgebras U(o sp(1,2)) and add the q-Serre relation to the Drinfeld realization of U(o sp(1,2)), derived from the FRTS realization.