如何讲授物理化学实验——以燃烧热的测定为例

Based on the conception of "experiment goal-directed" and "result-oriented", we take the experiment of "Measurement of Combustion Heat" as an example to introduce how to teach the physical chemistry laboratory course. By this means, we are aiming to deeply integrate experimental theory lectures with whole experimentation processes, to promote students' coordinated development of knowledge, ability, thinking and quality, and ultimately to cultivate the top and innovative talents.     

苯乙烯阴离子聚合仿真实验软件的研究

烯类单体的阴离子聚合是高分子化学课程中主要理论内容之一,为了使学生更好地掌握和运用理论知识,通常需要配合实验教学加以验证。而传统的烯类单体的阴离子聚合实验由于受各方面条件限制,实验效果欠佳。本文以苯乙烯阴离子聚合实验的开展为背景,介绍了聚合实验软件平台的设计、开发、硬件系统和实验的内容。经过验证,该实验软件平台功能完善,界面简洁,运行稳定,可以结合实际硬件设备以及具体需求进行实验教学。     

Damage simulation of repaired composite laminate with rectangular cut-out

Repaired composite laminate with rectangular cut-out is studied by tensile experiments and FEM simulation in this paper. A user damage subroutine is implemented to ABAQUS to simulate the damage of laminate. Good agreements between experimental data and numerical results are reached. From the experiment and FEM simulation results, the integrality of composite structure is destroyed due to the existence of cut-out. However, the asymmetry of repair gets this effect farther. From damage simulation, the initiation and development of three types of damages are predicted. The matrix cracking occurs at first, fiber–matrix shear and fiber break are subsequent. The effect of matrix cracking to the carrying capacity of structure is very small, but when fiber–matrix shear and fiber break occur, dangerous to structure, the carrying capacity of structure loses rapidly.     

Experiments on a beam-rigid body structure repetitively impacting a rod

This paper investigates the experimental dynamics of a beam structure that supports an attached rigid body and that can impact a comparatively compliant base structure. The problem area is motivated by impact phenomena that are observed in certain structures internal to nuclear reactors. The assembly is subjected to base excitation at specified frequency and acceleration, and the resulting displacement and velocity time histories are recorded and used to obtain spectra, phase diagrams, and Poincaré sections. The measurements validate simulation results obtained by using a constraint and modal mapping method based on the two sets of modes when the structure is in-contact, and when it is not-in-contact. Generalized coordinates are mapped across the impact discontinuities in the modal representation. The forced response simulation predicts the test specimen’s response over a range of excitation frequencies. The specimens are fabricated as single integral structures from acrylnitrile butadene styrene plastic through rapid prototyping technology in order to eliminate the undesirable dissipation and flexibility arising from joints and connections. The experimental system can exhibit complex response characteristics, and the influences on complexity of deadband clearance and of asymmetry in the point of impact are examined in the experiments.     

下坂地坝基深厚覆盖层帷幕灌浆现场试验工艺研究

新疆下坂地水利枢纽工程的坝基为深厚覆盖层,厚度达147.95m,其结构较为复杂,主要由冰碛层、冲洪积砾石层和砂土层透镜体组成,坝基防渗处理难度很大。为此,针对下坂地深厚覆盖层进行了专门的帷幕灌浆现场试验工艺研究,通过对浆液材料、配比、工艺措施和参数经过深入的分析,找出了一套适合于下坂地复杂地层的灌浆施工工艺,为初步设计提供了可靠依据。     

Experiments on the Richtmyer-Meshkov instability of an air/SF6 interface

Results of flow visualization experiments of an impulsively accelerated plane interface between air and SF₆ are reported. The shock tube used for the experiments has a larger test section than in previous experiments. The larger extent of uniform test flow relative to nonuniform boundary-layer flow permits unambiguous interpretation of flow-visualization photographs, and the influence of shock-wave/boundary-layer interactions is no longer dominant. The strong wall vortex observed in previous studies is not observed in these experiments. It is found that the thin membrane, which forms the initially plane interface, has a significant influence on the initial growth rate of the interface thickness. However, the measured growth rates after the first reflected shock are independent of membrane configuration and are in good agreement with analytical predictions.On leave from Stosswellenlabor (Shock Wave Laboratory), RWTH Aachen, Templergraben 55, D-52056 Aachen, Germany.This article was processed by the author using theLAT_EX style filepljour2 from Springer-Verlag.     

Formulation of Visible Light-Curable Glass-Ionomer Cements Containing N-Vinylpyrrolidone

Abstract

The best graft ratio of the light-curable N-vinylpyrrolidone (NVP) modified terpolymers (LC NVPM TPs) with the molar ratio of 8:2:1 (acrylic acid:itaconic acid:NVP) and the optimal formulation for this light-curable glass-ionomer cement, based on the best graft ratio, were determined. Statistical models were utilized to predict the optimal formulations. The terpolymer was prepared using a free-radical polymerization reaction. The LC NVPM TPs were produced by grafting 2-isocyanatoethyl methacrylate (IEM) onto the terpolymer. Cements were formed by both light-curing and the reaction with glass particles. Compressive strength was used as the basic screening property to find the optimal formulation. Diametral tensile and flexural strengths were also used to evaluate the mechanical properties. The strength values were recorded on the specimens conditioned in distilled water at 37&C for 24 hours or 7 days. The best graft ratio for IEM in this system was 15% of the terpolymer by a molar ratio. The optimal formulation was found to be at the weight ratio of 55:15:30 [LC NVPM TP:2-hydroxyethyl methacrylate (HEMA): H₂O]. Stress-strain curves showed that a relatively high amount of water in the formulation led to higher elastic modulus and proportional limit and lower malleability, whereas a relatively high amount of HEMA gave the opposite results. The light-curable NVP modified glass-ionomer cements showed statistically significantly higher values in compressive, diametral tensile, and flexural strengths than the commercial Vitremer^TM.     

Investigation of mini-hydrocyclone performance in removing small-size microplastics

Large amounts of microplastics (MPs) have been found in rivers and oceans, bringing great harm to aquatic animals, plants, even human beings. However, the effective removal method of MPs, especially those with small sizes (5–20 μm) is still lacking. This work presents mini-hydrocyclones to remove 10 μm (average size) diameter MPs. The removal performance of nine mini-hydrocyclones with different diameters of spigot and vortex finder is examined experimentally and numerically. The performance of the designed cyclones is evaluated in terms of recovery, water split, concentration ratio and pressure drop. The results show that mini-hydrocyclones are applicable to removing small-size MPs with the maximum concentration ratio at 2.16 and the particle recovery at 51%. The flow characteristics inside the mini-hydrocyclones are analyzed in detail. It is shown that the distributions of water axial velocity and radial velocity could collectively affect the behaviors of small-size MPs in mini-hydrocyclones. Specifically, a larger amount of water split could entrain more fine particles to underflow. Meanwhile, a less frequent alternation of radial velocity between the positive and negative directions on the same side of the cyclone should benefit the removal of small-size MPs.     

光学实验室网络教学平台的设计

传统的多媒体课件正在受到网络使用环境挑战，取而代之将是基于网而设计的多媒体教学平台。利用FIASH、Cult3D等技术开发的基于网络环境的虚拟实验室案的提出将为大学物理实验开辟一个崭新的多媒体教学方案。     

电子实验类教学的实践与体会

探讨电子实验类教学的目的意义，从几个方面分析方法与效果的关系，小结实施过程中的经验体会。