A Calphad-compatible method to calculate liquid/liquid interfacial energies in immiscible metallic systems

For the calculation of liquid/liquid interfacial energies in monotectic metallic alloys only simplified models are known, which suppose the validity of the regular solution model for the liquid solution. In the present paper a Calphad-compatible method is developed to calculate the liquid/liquid interfacial energies in binary, ternary and multicomponent liquid monotectic alloys. The method can be considered as the extension of the Butler equation to the liquid/liquid interfaces. The first order interfacial phase transition has been predicted at a certain critical temperature, which is about 18% of the bulk critical temperature. Below this critical temperature the compositions of the two sides of the liquid/liquid interface are different, while above this critical temperature the compositions at the two sides of the interface are identical. The latter case is valid for the majority of liquid metallic systems above their monotectic temperatures. The method has been validated against the experimentally measured liquid/liquid interfacial energies in the Ga–Pb and Al–Bi systems. The method is found to be very sensitive to the correctness of the Calphad-assessment of the partial excess Gibbs energies of the components in the liquid solution. The excess Gibbs energy function of the liquid Al–Bi solution was reassessed using our recent exponential temperature dependence of the interaction energies.     

Capillary and electrostatic limitations to the contact angle in electrowetting-on-dielectric

The shape of a conducting liquid droplet placed on a hydrophobic dielectric surface is simulated numerically by solving the Laplace–Young capillary equation. The electric force, acting on the conducting surface, distorts the droplet shape leading to a change in the apparent contact angle; its variation is compared with a theoretical Young–Lippman prediction. At sufficiently large values of voltage, applied to the droplet, the numerical algorithm fails to converge, which is interpreted as the break-up of the droplet surface with small droplets being ejected from the surface. These highly charged droplets, as well as any other electric charges near the triple contact line, generated for example by the electric corona discharge, cause a change of the distribution of the electric forces. This effect can be helpful in explaining saturation of the apparent contact angle: an appropriately selected surface charge near the contact line can completely stop droplet distortion, and the contact angle variation, despite the increased droplet voltage. Furthermore, the simulation results show the effect of the permittivity of the medium surrounding the droplet, on the contact angle variation.     

Numerical study of droplet impact and coalescence in a microline patterning process

The droplet impact and coalescence on a substrate, which is applicable to the manufacture of microlines, is studied numerically by solving the equations governing the conservation of mass and momentum. The liquid–gas interface or droplet shape is tracked by a sharp-interface level-set method which is modified to account for the change between advancing and receding contact angles at the liquid–gas–solid interline. The numerical results show that the droplet impact and merging pattern depends significantly on the advancing and receding contact angles. Also, the effect of droplet spacing on the droplet motion is investigated to find the optimal conditions in manufacturing microlines.     

Monitoring of droplet growth with nano-litre resolution for liquid flow rate, level or surface tension measurement

The determination of small liquid volumes and their changes over a period of time is a measuring problem with increasing importance considering the growing market of micro-systems. In this paper, experimental investigations are described which aim to observe the growth of droplets at the end of a micro-channel, such as a cannula or capillary. The main focus of the work lies on the calculation of flow rates below 1 ml/h. Furthermore, the potential of the measuring equipment for liquid level and surface tension measurement is described.     

A general model to calculate coherent solid/solid and immiscible liquid/liquid interfacial energies

Interfacial energy plays a significant role in the microstructure evolution of materials. A general model for predicting both coherent solid/solid and immiscible liquid/liquid interfacial energies is derived from a thermodynamic point of view. In this model, the interfacial energy can be calculated only using the data about molar area and Gibbs energies of two bulk phases and interface phase. The present model is applied to the coherent solid/solid interfacial energies in the Al–Ni, Ni–Ge, Ni–Ga, Ni–Si, Ni–Ti, Au–Ni and Ni–Cr–Al systems. The model-predicted interfacial energies show a reasonable agreement with the literature data. The presently developed model can calculate the interfacial energies between the disordered γ (fcc_A1) and ordered γ’ (fcc_L12) phases, where the Gibbs energies of both γ and γ’ phases are given by the same expression. The previous model in the literature cannot capture some disordered/ordered interfacial energies, like the Al–Ni system. The present model can also be used to calculate the immiscible liquid/liquid interfacial energies in the Al–Pb, Al–In and Al–Bi systems, showing a good agreement with the literature data. These applications validate the reliability of present model in the calculation of coherent solid/solid and immiscible liquid/liquid interfacial energies in the binary and multi-component systems.     

多种结构框架在拉压试验机中的应用研究

现代工业的发展对拉压试验机的应用范围和实验性能提出了越来越高的要求。文中介绍了拉压试验机常见的立式和卧式框架结构,分析了其结构形式、应用场合及基本应用方法,并将拓扑优化设计方法引入到拉压试验机的设计中,最终减轻了结构重量,改进了结构的强度、刚度等特性。     

可逆冷带轧机速度张力系统的分散重叠控制

针对可逆冷带轧机速度张力系统的耦合和协调控制问题,提出了速度张力分散重叠控制方法.该方法首先利用包含原理和重叠结构分解,扩展原系统的状态空间,得到多个解耦的重叠子系统,并应用线性二次型(LQ)最优控制和顺序设计方法,设计各子系统的控制律.其次,将所设计的控制律收缩至原系统的状态空间,得到原系统的控制器.最后对某1422mm可逆冷带轧机的速度张力控制系统进行了仿真研究.结果表明,本文所提出的速度张力分散重叠控制方法能有效弱化速度与张力间的耦合,实现主轧机与左、右卷取机间的协调控制,同时改善了张力控制系统的动态性能,保证了轧机升降速时的张力控制精度.     

连续退火机组张紧辊带钢张力的建模及解耦控制

在带钢连续退火机组中,张紧辊区域的带钢张力直接影响着机组的运行速度以及带钢质量,因此,张紧辊区域的带钢张力是连续退火机组中的关键被控变量.本文首先建立了张紧辊区域带钢张力的动态机理模型和状态空间模型,并针对张紧辊带钢张力系统的多变量、强耦合等特性,采用极点配置和动态解耦算法,提出了带钢张力的多变量解耦控制器.仿真实验结果表明,所提出的解耦控制器实现了多个带钢张力控制回路之间的动态解耦,并可获得良好的控制效果.     

差动式磁弹型索力传感器的磁路设计与分析

磁弹效应索力传感器的磁路结构及其参数和磁路的磁动势是通过磁路设计和磁路分析来确定的。结合差动式索力传感器的结构,讨论了磁路结构设计及其参数确定,磁场强度选取及其磁通的确定,以及通过磁路分析确定磁路的总磁动势等关键问题,搭建了试验系统,进行拉力试验。试验表明:提出的磁路设计和磁路分析方法是合理的,为磁弹效应法监测索力的磁路设计开拓了一条新路。     

Looper and tension control in hot rolling mills: A survey

Looper and tension control is important in hot strip mills because they affect the strip quality as well as strip threading. Moreover, the most difficult challenge in controller design and control performance arises from the interaction between looper angle and strip tension. Disturbances from several sources cause a deterioration in control performance, and thus a major role of the control algorithm is effective disturbance rejection. Many authors have proposed and applied a variety of control schemes to this control problem, but nevertheless, the increasingly strict market demand for strip quality requires further improvements in this control area. Hence, this paper critically surveys the strengths and weaknesses of several existing academic and industrial approaches and explores the potential for development in this area.     

Neural network modelling on temperature coefficient of surface tension and its usage in melting point prediction of nanosized metal particles

Temperature coefficient of surface tension is a very important parameter to calculate phase diagrams of nanoparticle metal systems. In this paper, neural network calculation was for the first time used to evaluate the temperature coefficient. It shows that the constructed neural network can predict the temperature coefficient values for 37 metals, with the deviation from the averaged experimental measurements smaller than 25%. Furthermore, the neural network predictions were compared with the calculated values by using an empirical equation and it shows a better performance.     

基于共轭梯度法的反馈差分进化混合算法及其在弹簧设计中的应用

分析了差分进化算法多种变异方式的特点以及每种变异方式所适应的搜索状态,建立了一条能够让种群根据自身的搜索环境来动态选择变异方式的反馈回路,使个体能够自学习、自调节地高效搜索。在每一代的最优个体邻域内,采用共轭梯度法确定最佳的共轭搜索方向,向量能够在最优解邻域内进行细致的局部搜索。根据混合算法的子代更新形式,从理论上证明了种群能够以概率1的方式收敛到全局最优解。与其它进化算法的对比实验结果表明,本文的差分进化算法有效提高了benchmark函数的最优值精度,加快了收敛速度。在弹簧设计问题中,利用改进的差分进化混合算法得到了较好的结构参数。     

Statistical and computational intelligence tools for the analyses of warp tension in different back-rest oscillations

In this paper, experimental, computational intelligence based and statistical investigations of warp tensions in different back-rest oscillations are presented. Firstly, in the experimental stage, springs having different stiffnesses are used to obtain different back-rest oscillations. For each spring, fabrics are woven in different weft densities and the warp tensions are measured and saved during weaving process. Secondly, in the statistical investigation, the experimental data are analyzed by using linear multiple and quadratic multiple-regression models. Later, in the computational intelligence based investigation, the data obtained from the experimental study are analyzed by using artificial neural networks that are universal approximators which provide a massively parallel processing and decentralized computing. Specially, radial basis function neural network structure is chosen. In this structure, cross-validation technique is used in order to determine the number of radial basis functions. Finally, the results of regression analysis, the computational intelligence based analysis and experimental measurements are compared by using the coefficient of determination. From the results, it is shown that the computational intelligence based analysis indicates a better agreement with the experimental measurement than the statistical analysis.     

Extended Jones matrix method and its application in the analysis of compensators for liquid crystal displays

We describe an extended Jones matrix method which is a powerful tool to treat the transmission of light through birefringent networks, where the incident angle of light and the optical axis of the birefringent media are arbitrary. The method is generalized to cover all dielectric media including uniaxial and biaxial crystals and gyrotropic materials that exhibit optical rotatory power and Faraday rotation. We then apply this method to investigate various birefringent optical thin films that can be used to improve the viewing angle characteristics and gray scale stability of conventional twisted nematic liquid crystal displays (TN-LCDs). The birefringent phase retardation films include negative uniaxial, positive uniaxial and biaxial films of various orientations. The results are presented and discussed.