多普勒效应验证实验仪器的改进

原多普勒效应验证实验仪器在使用过程中出现数据不稳定、重复性差、维修率高等问题.为了解决上述问题,提高实验的精度与准确度,对原实验装置的相关部分进行了改进.通过比较原实验装置和改进后的实验装置,分析了原实验装置的缺点与不足,并总结改进后装置的优点.     

对电动向心力定量分析演示仪的改进

针对现有"向心力演示仪"实验的不足,对电动向心力定量分析演示仪进行改进,新仪器保留了电动向心力演示仪的部分元件,改进了转动半径测量和向心力测量装置.通过改变电动机转速、圆周运动半径、金属球质量等参量,该装置可定性演示向心力和定量研究向心力表达式.     

CGZ型机械振动实验系统的研究和应用

CGZ型机械系统是专为工科物理实验专门设计的机械振动类仪器。该实验系统包括振动实验装置、振动测试系统、计算机分析处理系统三大部分,本文将重点介绍实验装置和实验结果分析。     

极化效应对Bohr速度能区O5+离子在低密度氢等离子体中的能损影响

基于HIRFL加速器装置的低能束实验平台,实验测量了1.07 MeV(～66.9 keV/u)高电荷态O⁵⁺离子穿过中性氢气和部分电离的低密度氢等离子体靶后的能量损失,观测到等离子体中离子能损减小的新实验现象.分别考虑部分电离等离子体对炮弹离子的电荷屏蔽效应以及靶区原子的极化效应(Barkas修正),重新计算了离子能损,讨论了离子能损减小的可能物理机制.研究结果表明:在部分电离的低密度等离子体中,靶区的原子极化效应将显著影响Bohr速度能区离子的能量损失过程.     

综合性大学物理实验教学仪器评奖工作试行办法

多年来,许多高等学校的教师,实验技术人员为教学需要设计、制作和改进了许多物理实验教学仪器、装置,使物理实验课教学取得了较好的效果,受到广大教师和学生的欢迎。有些仪器、装置在设计制作上还有所创新,具有一定特色。这些工作是提高实验课教学质量而必不可少的重要组织部分,也是一项艰苦的工作。为了鼓励更多的教师、实验技术人员积极从事这项工作,促进实验教学工作的发展,教育部理科物理教材编审委员会物理实验编审小组、中国物理学会教学研究委员会决定将新仪器的设计、创造和仪器装置改进的评奖活动作为实验教学讨论会的一项内容。对…     

ICP-AES法快速测定金属铬中微量铜

本文是以ICP-AES法测定金属铬中微量的铜。描述了以2%HCl介质的铜标准溶液及1克/升铬(Ⅲ)溶液引入ICP焰中,以WPG-100型光栅摄谱仪分光,EMI9789QB型光电倍增管接收,采用TI-59可编程序计算器数一、实验部分1.仪器装置及工作条件实验仪器装置及工作条件见表1。     

液体表面张力系数测量装置的改进

对用力敏传感器测量液体表面张力系数仪器进行研究,重新设计了吊环,便于吊环的水平调节,对待侧液体表面均匀下降的方法和实验装置做了重新设计,减小了实验误差,同时增加了待测液体的变温控制,能够精确测量液体表面张力系数与温度的关系,扩充了实验内容.     

倒挂式弹性模量测量仪

设计了倒挂式弹性模量测量仪,消除了传统悬挂式仪器的诸多弊病,简化了仪器的调节并减小了测量误差.     

冰的熔解热实验装置的改进

将保温杯引入到测定冰熔解热的实验中,提高了实验装置的保温性能;利用马达和风扇自制了搅拌装置,保证了搅拌均匀性;利用单片机、传感器模块和液晶屏实现了温度数显功能,提高了实验精度.通过对比改进前后的实验装置的实验数据可知,改进后的实验装置有效地减小了实验误差.     

改进型向心力探究仪

针对传统“ D I S向心力实验器”的不足, 设计了改进型向心力探究仪. 新仪器保留了传统向心力实验器 的部分元件, 改进了转动半径测量和向心力测量装置. 通过改变电动机转速、 圆周半径和砝码质量等参量, 可定量 研究向心力表达式     

Specific heat studies on Ru substituted FeSi Kondo Insulator

The temperature dependent specific heat studies of a Ru substituted Fe_1−xRu_xSi Kondo Insulating system has been carried out in the 77 to 300 K range. The specific heat has been analyzed based on contributions from an electronic part and a lattice part. For the electronic part a Gaussian density of states model, which incorporates the effect of correlation, band structure and disorder in its defining parameters is used. The lattice part of specific heat is described in the Debye model. Parameters that define the electronic density of states and the Debye temperature are extracted from fits of the temperature dependent specific heat data and are compared with earlier resistivity measurements that employed a similar analysis.     

Effect of control modes and turbine cooling on the part load performance in the gas turbine cogeneration system

This work aims to analyse the part load performance in a cogeneration system which consists of a single shaft gas turbine and a heat recovery steam generator. Two distinct part load control modes are considered: the constant air flow and the variable air flow. Meanwhile, the effect of variation in the coolant fraction is evaluated, whose purpose is to maintain the blade temperature as high as possible and thus minimise the coolant consumption. The design point parameters of the heat recovery steam generator are determined by the limiting factors on the part load operation, which are represented by the pinch point temperature difference and the approach temperature difference. It turns out that for both air flow control modes, the variable control of coolant fraction leads to improvement of the gas turbine efficiency, while it reduces the heat recovery potential. On the whole, the variable control of coolant fraction has a favourable effect on the overall fuel economy in the cogeneration system.     

等离子弧焊接熔池演变过程的模拟和验证

本文建立了描述等离子弧焊接熔池相变传热与流动的三维数理模型,考虑表面张力、电磁力和浮升力的作用,并针对等离子弧焊接特点,改进组合式体积热源模型,上部采用双椭球热源,下部采用圆锥体热源。重点分析了焊接熔池形状和温度场的演变过程,熔合线的模拟形状与实验焊缝吻合,较好地呈现了焊缝的凸起和熔池宽度,验证了数学模型和热源模型的正确性。本文还进一步开展了焊接功率和焊接速度的影响分析。研究结果表明,流动对焊缝形状的影响不容忽略,而表面张力在三个流动驱动力中占主导地位;焊接功率越大,焊接速度越小,越有利于焊件焊透,数值模拟得到优化的焊接功率和速度有益于实际焊接生产质量及效率。     

煤颗粒热解的传热传质分析

采用分布活化能模型及能量守恒方程对煤颗粒热解的传热传质过程建立数学模型,模型考虑煤热解的吸热效应及挥发分逸出时对流换热的影响.与有关煤粉和大颗粒煤热解的实验数据对比,对模型进行验证.针对煤颗粒的温度变化过程和煤热解过程进行数值分析,研究煤热解的吸热效应、挥发分气体逸出的对流效应、颗粒尺寸等参数的影响.     

热采耦合数学模型定量化研究及数值模拟

针对稠油油藏开发过程的薄弱环节,提出了油藏热质传递过程的黑箱分析法和白箱分析法,建立了包含蒸汽相的稠油热采耦合黑箱模型和白箱模型,使得储层温度场模型得以完整化和系统化。应用CMG软件进行数值模拟,验证了所建数学模型的合理性,并得到了孔隙度对油藏温度的影响关系。最后,对油藏热流体的指进现象进行了机理分析,并总结了热流体指进现象的产生范围。     

Heat source reconstruction from noisy temperature fields using a gradient anisotropic diffusion filter

This paper presents a post-processing technique for noisy temperature maps based on a gradient anisotropic diffusion (GAD) filter in the context of heat source reconstruction. The aim is to reconstruct heat source maps from temperature maps measured using infrared (IR) thermography. Synthetic temperature fields corrupted by added noise are first considered. The GAD filter, which relies on a diffusion process, is optimized to retrieve as well as possible a heat source concentration in a two-dimensional plate. The influence of the dimensions and the intensity of the heat source concentration are discussed. The results obtained are also compared with two other types of filters: averaging filter and Gaussian derivative filter. The second part of this study presents an application for experimental temperature maps measured with an IR camera. The results demonstrate the relevancy of the GAD filter in extracting heat sources from noisy temperature fields.     

Heat transfer performance of a toluene loaded two-phase thermosyphon

Large dimension thermosyphons are efficient heat transfer components in heat recovery systems. Their performance limits depend on the following parameters: geometrical (length, diameter, inclination angle), physical (fluid, fill charge), thermal (temperature, heat flux).An experimental investigation was carried out with a large dimension, closed, two-phase thermosyphon which correspond to a device used in industrial recuperators. A vertical or inclinded steel thermosyphon, 3 m long and 27 mm inner diameter, was tested at temperatures varying from 100°C to 300°C with toluene as the working fluid. The lower part of the pipe was electrically heated along a variable length and the upper zone was cooled with an air stream whose flow rate and temperature were controlled. The maximum heat flux was measured as a function of temperature for different liquid fill charges and inclination angles. From these experimental data, boiling and condensation heat transfer coefficients were deduced. It was observed that the critical heat flux depends little on the fill ratio unless the charge is less than 20% for which a local dry-out occurs. The optimal fill charge was found to be between 20% and 50%. Experimental data have been compared with existing theories. The inclination effects have been taken into account with an empirical formula.     

Anomalous Hall effect in the phonon thermal conductivity of paramagnetic dielectrics

A theory of the phonon Hall effect during heat transfer in a paramagnetic dielectric discovered by Strohm et al. [Phys. Rev. 95, 155901 (2005)] is developed. The heat flux emerging in the direction perpendicular to the magnetic field and to the temperature gradient is associated with the interaction of magnetic ions with the oscillating crystal field. In crystals with an arbitrary phonon spectrum, this interaction induces elliptic polarization of phonons. On the other hand, for any type of scattering, the temperature gradient forms part of the phonon density matrix, which is nondiagonal in modes. The combined action of these factors leads to the anomalous Hall effect.     

Efficiency of energy separation at compressible gas flow in a planar duct

The method of energy separation in a high-speed flow proposed by A.I. Leontyev is investigated numerically. The adiabatic compressible gas flow (of a helium-xenon mixture) with a low Prandtl number in a planar narrow duct and a flow with heat exchange in a duct partitioned by a heat-conducting wall are analysed. The temperature recovery factor on the adiabatic wall, degree of cooling the low-speed flow part, temperature efficiency, and the adiabatic efficiency in a duct with heat exchange are estimated. The data are obtained for the first time, which make it possible to compare the efficiency of energy separation in a high-speed flow with the efficiency of similar processes in vortex tubes and other setups of gas-dynamic energy separation.     

A stochastic model for solidification

A 3-dimensional (2-space, 1-time) model relating the diffusion of heat and mass to the kinetic processes at the solid-liquid interface, using a stochastic approach is presented in this paper. This paper is divided in two parts. In the first part the basic set of equations describing solidification alongwith their analysis and solution are given. The process of solidification has a stochastic character and depends on the net probability of transfer of atoms from liquid to the solid phase. This has been modeled by a Markov process in which knowledge of the parameters at the initial time only is needed to evaluate the time evolution of the system. Solidification process is expressed in terms of four coupled equations, namely, the diffusion equations for heat and mass, the equations for concentration of the solid phase and for rate of growth of the solid-liquid interface. The position of the solid-liquid interface is represented with the help of a delta function and it is defined as the surface at which latent heat is evolved. A numerical method is used to solve the equations appearing in the model. In the second part the results i.e. the time evolution of the solid-liquid interface shape and its concentration, rate of growth and temperature are given.