热力学第零定律的教学思考

有些教材对热力学第零定律这一重要内容的处理不科学,不严谨,也不完整。针对这一问题,经研究分析提出了对第零定律的合适表述,以及相应的实验设计和实验证明。     

Numerical study of the melting of nano-enhanced phase change material in a square cavity

A comprehensive numerical study was conducted to investigate heat transfer enhancement during the melting process in a 2D square cavity through dispersion of nanoparticles. A paraffin-based nanofluid containing various volume fractions of Cu was applied. The governing equations were solved on a non-uniform mesh using a pressure-based finite volume method with an enthalpy porosity technique to trace the solid-liquid interface. The effects of nanoparticle dispersion in a pure fluid and of some significant parameters, namely nanoparticle volume fraction, cavity size and hot wall temperature, on the fluid flow, heat transfer features and melting time were studied. The results are presented in terms of temperature and velocity profiles, streamlines, isotherms, moving interface position, solid fraction and dimensionless heat flux. The suspended nanoparticles caused an increase in thermal conductivity of nano-enhanced phase change material (NEPCM) compared to conventional PCM, resulting in heat transfer enhancement and a higher melting rate. In addition, the nanofluid heat transfer rate increased and the melting time decreased as the volume fraction of nanoparticles increased. The higher temperature difference between the melting temperature and the hot wall temperature expedited the melting process of NEPCM.     

阶跃光激励的光热光偏转技术测量材料的热扩散率

基于光热光偏转技术的基本原理,通过分析阶跃光激励的光热光偏转信号的上升快慢与材料热扩散率的关系,提出了测量材料热扩散率的新方法.结果表明,该方法与传统的光热光偏转技术测量材料热扩散率方法相比,具有实验装置简单、测量方便快捷等优点.     

Thermal conductivity of soils with heavy metals concentration from the Niger Delta region of Nigeria

INTRODUCTION Knowledge of soil thermal properties is an im- portant factor in understanding mass and energy ex- change processes in the soil-atmosphere system. The chemical composition of the soils will therefore in- directly relate to their thermal conductivities. Ac- cording to Usowicz (1993), this knowledge can also help in controlling the thermal-moisture regime of soils. Soil properties often correlated with metal ad- sorption include soil pH (Christensen, 1984; Harter, 1983), soil …     

2×5×5纯态量子体系完全纠缠态的分类

基于"随机局域操作和经典通讯"对2×5×5纯态量子系统的完全纠缠态进行了分类,共得到34个不等价类.其中有3个类对应的纠缠态含有连续参数.对含参数类的参数进行了详细研究,发现其中有2个类只含1个独立参数;另外1个含有2个独立参数.而且这些独立参数并不完全任意,它们有确定的对称性.对于1个独立参数情形,得到该参数具有D3群对称性.     

Predicting the shrinkage of thermal insulation mortar by probabilistic neural networks

This study explored the potential of using probabilistic neural networks （PNN） to predict shrinkage of thermal insulation mortar.Probabilistic results were obtained from the PNN model with the aid of Parzen non-parametric estimator of the probability density functions （PDF）.Five variables,water-cementitious materials ratio,content of cement,fly ash,aggregate and plasticizer,were employed for input variables,while a category of 56-d shrinkage of mortar was used for the output variable.A total of 192 groups of experimental data from 64 mixtures designed using JMP7.0 software were collected,of which 120 groups of data were used for training the model and the other 72 groups of data for testing.The simulation results showed that the PNN model with an optimal smoothing parameter determined by the curves of the mean square error （MSE） and the number of unrecognized probability densities （UPDs） exhibited a promising capability of predicting shrinkage of mortar.     

Bayesian networks modeling for thermal error of numerical control machine tools

The interaction between the heat source location, its intensity, thermal expansion coefficient, the machine system configuration and the running environment creates complex thermal behavior of a machine tool, and also makes thermal error prediction difficult. To address this issue, a novel prediction method for machine tool thermal error based on Bayesian networks （BNs） was presented. The method described causal relationships of factors inducing thermal deformation by graph theory and. estimated the thermal error by Bayesian statistical techniques. Due to the effective combination of domain knowledge and sampled data, the BN method could adapt to the change of running state of machine, and obtain satisfactory prediction accuracy. Experiments on spindle thermal deformation were conducted to evaluate the modeling performance. Experimental results indicate that the BN method performs far better than the least squares （LS） analysis in terms of modeling estimation accuracy.     

量子微腔中不同原子合作效应之研究

处于量子微腔真空辐射场中的两个不同原予呈现合作效应，其关联程度随两原予各自跃迁频率、腔场频率接近而加强。此种性质非常类似经典宏观力学系统中的共振现象。     

厚壁圆筒热冲击作用下的温度场

针对冲击的瞬时特性，在热冲击问题的边界条件中引入6函数，运用Laplace变换的方法求解了厚壁圆筒内部受热冲击作用时的温度场．探讨了温度场随时间和圆筒内外径比的变化．为研究管式反应器热冲击应力场奠定基础．     

实现纠缠交换的基本方案

阐述了量子隐形传态及量子纠缠交换的基本理论,通过单光子的量子纠缠交换、连续变量纠缠交换实证说明纠缠交换的机制,纠缠交换可使得从未直接发生相互作用的量子系统产生纠缠,利用纠缠交换可达到实现信息传递的目的,纠缠交换是目前信息学中实现信息交换非常重要的途径之一。