Laser absorption density direct measurements with limitation of temperature variation field in shock-induced gaseous mixing

We describe a laser absorption technique to obtain reasonably accurate density profiles within a shock-induced Richtmyer-Meshkov mixing zone. Assuming a small temperature variation through the probed region, a single wavelength absorption experiment only is needed. When this criterium is satisfied, the technique described represents a considerable simplification over the more generally required dual wavelength experiments. Received 4 May 1996 / Accepted 7 October 1996     

Grain Boundary Migration in Fe-3wt.%Si Alloys

The studies of three different laboratories on grain boundary migration in Fe-3wt.%Si alloys are presented. In all cases bicrystal techniques employing capillarity as driving force were used. [100] tilt boundaries were studied in the temperature range from 1223 K to 1373 K, and [110] tilt boundaries in the range from 1220 K to 1625 K. Proportionality between grain boundary velocity and driving force was confirmed. All data fulfil a linear relation between activation enthalpies and logarithms of the pre-exponential factors, corresponding to a compensation temperature of 1386 K where all boundaries theoretically should possess the same mobility. A considerably lower activation enthalpy was found in one case for an asymmetrical grain boundary compared to the symmetrical boundary of the same misorientation. High values of activation enthalpy of migration were found for special [100] boundaries compared to general ones although an opposite tendency was also observed for [100] boundaries.     

Composite Grid Finite Element Method: Implementation and Iterative Solution with Inexact Subproblems

This paper concerns the composite grid finite element (FE) method for solving boundary value problems in the cases which require local grid refinement for enhancing the approximating properties of the corresponding FE space. A special interest is given to iterative methods based on natural decomposition of the space of unknowns and to the implementation of both the composite grid FEM and the iterative procedures for its solution. The implementation is important for gaining all benefits of the described methods. We also discuss the case of inexact subproblems, which can frequently arise in the course of hierarchical modelling.     

An experimental study of the drag force on a sphere exposed to an argon thermal plasma flow

Experimental data are presented concerning the drag force on a stationary phere exposed to an argon plasma flow with temperatures about 10⁴ K and velocities about 10² m/s. A novel probe construction has been employed in the drag measurements in order to exclude the effect of the supporting wire on the sphere drag data. By using the new probe construction with a compensating wire, drag forces on an individual steel sphere in the plasma flow have been measured and compared with those obtained by using the probe construction ernployed by a few previous authors. Experimental results show that the measured drag forces are always less than their counterparts obtained from the standard sphere-drag curve under isothermal flow conditions with the same Reynolds numbers based on the oncoming plasma properties. The drag force on a sphere increases only slightly with the increasing surface temperature of the sphere before it melts. Appreciable diference was found between the experimental data and the predicted results of the available expressions for drag on a sphere exposed to a thermal plasma flow. Further research effort is required to build a more suitable drag correlation.     

Piston-driven ultra rapid pressure swing adsorption

The piston-driven ultra rapid pressure swing adsorption (URPSA) equipment was developed and oxygen enrichment from air was examined as an example. The adsorbent bed is directly connected to the cylinder where a piston moves at high frequency. Thus pressurization and depressurization in the bed are driven by mechanical piston motion, which can achieve far more rapid cycles compared with the conventional pressure swing operation using valves. The cycle time is usually on the order of seconds or sub seconds. Oxygen enrichment from air up to about 60% or higher of oxygen concentration was achieved by small-scale equipment using zeolite 5A with a oxygen production capacity of 100 Nm³-product gas/m³-zeolite/hr, which is about ten times larger than those of commercialized PSAs for this purpose.A simplified numerical model describing the mass transfer taking place in URPSA was developed. The model could simulate fairly well the air separation characteristics in terms of oxygen concentration, oxygen production capacity and oxygen yield. The proposed model helps in the understanding of the basic nature of URPSA and possible applications. This novel PSA is promising as a compact yet high-capacity PSA to be utilized in a wide variety of applications.     

Bounds to the difference between the predictions of stochastic and quantum optics in the optical test of bell inequalities

We summarize the main ideas and problems of stochastic optics, a theory recently proposed by T.W. Marshall and E. Santos, which explains in a local realist way some experiments thought to be non-local, generalizing previous results in order to make it possible to calculate the difference between the quantum mechanical and the stochastic optical predictions for the optical test of Bell's inequalities.     

基于PROTEUS的李萨如图形观绘实验

针对在传统示波器的使用实验教学过程中学时相对较短、实验操作不规范及实验仪器存在系统误差导致实物实验教学效果不佳的问题,与实物实验相结合,通过Proteus VSM提供的虚拟示波器进行多种频率比与不同相位差情况下的李萨如图形观察实验,可更加直观方便地学习测量正弦振动频率的方法,加深理解互相垂直振动合成理论。这种将实物实验与虚拟仪器实验相结合的实验教学方法,显著改善了示波器的实验教学效果。     

扫描电子显微镜在本科生创新实验中的应用教学探索

介绍扫描电子显微镜的样品制备方法;阐述了扫描电子显微镜在本科生创新实验中的应用价值。     

拓展物理实验教学需求调研报告

作者设计调查问卷,并对本校电信学院505名学生的调查问卷进行分析,了解学生对拓展物理实验的需求．根据学生感兴趣的知识点,发掘出与通信专业相关的新的物理实验项目,并请部分学生进行试做,希望达到深化大学物理实验教学改革,提高人才培养质量的目标．