Phase-field study of spinodal decomposition under effect of grain boundary

Grain boundary directed spinodal decomposition has a substantial effect on the microstructure evolution and properties of polycrystalline alloys. The morphological selection mechanism of spinodal decomposition at grain boundaries is a major challenge to reveal, and remains elusive so far. In this work, the effect of grain boundaries on spinodal decomposition is investigated by using the phase-field model. The simulation results indicate that the spinodal morphology at the grain boundary is anisotropic bicontinuous microstructures different from the isotropic continuous microstructures of spinodal decomposition in the bulk phase. Moreover, at grain boundaries with higher energy, the decomposed phases are alternating α/β layers that are parallel to the grain boundary. On the contrary, alternating α/β layers are perpendicular to the grain boundary.     

Static and time-dependent properties of polymer gels around the volume phase transition

Recent progress in the study of the volume phase transition of polymer gels is reviewed. The phenomenological theories of swelling equilibrium and phase transition of gels are summarized, and some basic experimental results on poly-N-isopropylacrylamide (NIPA) gels are compared with the prediction from these theories. Special attention is paid to the elastic properties of the gel network near the volume phase transition. The effect of external stresses on the swelling and the phase transition is analyzed. Some anomalous and unique characteristics revealed in NIPA gels such as shape- and size-dependent swelling and phase transition properties, curious phase coexistence, and domain structure are presented. Experimental results on some time-dependent phenomena such as phase separation, spinodal decomposition, and pattern formation are also presented and discussed. Some problems inherent to gels from biological bodies are briefly discussed.     

A soluble kinetic model for spinodal decomposition

We compare the two-dimensional voter model with approximate theories for spinodal decomposition. The cluster size distribution and the short-time dynamics of the voter model are studied by means of a Monte Carlo simulation. The time-dependent structure factor and the long-time scaling of the voter dynamics are known analytically.This paper is dedicated to Nico van Kampen on the occasion of his 67th birthday.     

Freezing of phase separation in spatiotemporal stripe patterns formed by Ag and Sb co-electrodeposition

Various spatiotemporal patterns of dark and light stripes are formed in the Ag and Sb co-electrodeposition system. In this research, we investigate the time-evolution of the stripe width of a spatiotemporal stripe pattern with a size of ca. 10 μm. The results show that the stripe width increases with time and is eventually saturated. Such a phenomenon is predicted by some theories of spinodal decomposition of materials with chemical reactions in a nonequilibrium system. This suggests that the pattern is formed by the spinodal decomposition of metal alloys, Ag and Sb, with chemical reactions in a nonequilibrium system, which has not yet been reported in a metallic system.     

Phase field simulation of spinodal decomposition under external magnetic field

A computational model was developed to simulate the spinodal decomposition process of ferromagnetic alloys under an external magnetic field. In this model, the temporal evolution of the modulated structure was described by a phase field method, and the magnetic configuration was solved by using a micromagnetic method. The spinodal decomposition and coarsening processes of a single magnetic particle and an A-B hypothetical system under an external magnetic field were simulated using the proposed model. The simulation results show that the precipitated particles were elongated along the direction of the external magnetic field. The dependence of the modulated structure of an A-B hypothetic system on external magnetic field is much more sensitive than that of the single particle structure. The simulation results also demonstrate that the modulation of the external magnetic field is effective even if the spinodal decomposition has been completed and a stable modulated structure was formed.     

Thermodynamic aspects of carbon redistribution during ageing and tempering of Fe–Ni–C alloys

Carbon redistribution is known to occur during martensite ageing. The two associated processes most discussed in the literature are spinodal decomposition and carbon segregation to defects. In order to elucidate the topic, the ageing and tempering of two Fe–Ni–C alloys have been characterised by means of atom probe tomography and synchrotron radiation diffraction. Upon ageing at room temperature, carbon redistribution is clearly observed, where the process of carbon segregation to defects appears to be most likely to occur. Nevertheless, the possibility of spinodal decomposition is not entirely discarded, and the current work presents a series of discussion points that challenge our current understanding of the thermodynamic of ferrite in steels.     

Phase field simulation of microstructure evolution in Fe-Cr-Co alloy during thermal magnetic treatment and step aging

The evolution of modulated structures in Fe-Cr-Co alloys during isothermal aging under an external magnetic field and multiple step aging was simulated based on a phase field method. In this simulation, the magnetic configuration during the decomposition was calculated by a micromagnetic method, and the chemical Gibbs energy function was calculated by the CALPHAD approach based on the experimental equilibrium phase diagram. The calculation results provide a quantitative microstructure change directly linked to the phase diagram and demonstrate obvious microstructure difference between isothermal aging and multiple aging. The ferromagnetic precipitates elongate along the direction of the external magnetic field. The simulated evolution and microstructure are in good agreement with the experimental results.     

Martensitic transformation and related magnetic effects in Ni-Mn-based ferromagnetic shape memory alloys

Ferromagnetic shape memory alloys, which undergo the martensitic transformation, are famous multifunctional materials. They exhibit many interesting magnetic properties around the martensitic transformation temperature due to the strong coupling between magnetism and structure. Tuning magnetic phase transition and optimizing the magnetic effects in these alloys are of great importance. In this paper, the regulation of martensitic transformation and the investigation of some related magnetic effects in Ni-Mn-based alloys are reviewed based on our recent research results.     

Poisson structures on double Lie groups

Lie bialgebra structures are reviewed and investigated in terms of the double Lie algebra, of Manin- and Gauss-decompositions. The standard R-matrix in a Manin decomposition then gives rise to several Poisson structures on the correponding double group, which is investigated in great detail.     

Stochastic theories and scaling relations for early-stage surface growth

Recent theories for the surface growth are reviewed, which describe the nucleation kinetics of binary alloys in the first layer and the nucleation on top of islands in the second layer. In the first part, describing the submonolayer regime, scaling relations for the number density of stable islands in dependence of the growth parameters are derived from an extension of the classical rate equation approach to binary systems. In the second part a general stochastic theory is presented that allows one to predict whether thin films become smooth or rough under non-equilibrium growth conditions.     

Phase space reconstruction of chaotic dynamical system based on wavelet decomposition

In view of the disadvantages of the traditional phase space reconstruction method,this paper presents the method of phase space reconstruction based on the wavelet decomposition and indicates that the wavelet decomposition of chaotic dynamical system is essentially a projection of chaotic attractor on the axes of space opened by the wavelet filter vectors,which corresponds to the time-delayed embedding method of phase space reconstruction proposed by Packard and Takens.The experimental results show that,the structure of dynamical trajectory of chaotic system on the wavelet space is much similar to the original system,and the nonlinear invariants such as correlation dimension,Lyapunov exponent and Kolmogorov entropy are still reserved.It demonstrates that wavelet decomposition is effective for characterizing chaotic dynamical system.     

ICP—AES法测定高温合金中铌,钽,锆,铪——溶样及光谱干扰的进一步探讨

本文在原工作的基础上，继续探讨ＩＣＰ－ＡＥＳ法测定高温合金中Ｎｂ，Ｔａ，Ｚｒ和Ｈｆ能溶样与光谱干扰问题，通过试验研究表明，上述问题的解决在合金样品分析中具有实际意义。     

Separation of magnetic phases in alloys

In this paper we present a study of the separation of phases in multi-phase alloys. The proposed technique is based on the hyperbolic model of magnetization. By using this model it is possible to decompose the magnetic phases of alloys and determine their magnetic properties separately. Experimental verification was carried out on a transformer-like setup, constructed from layered samples representing the various magnetic phases. The samples were constructed from elements of strongly different magnetic properties. The results given by the model are in an excellent agreement with the experimental results, giving justification for the proposed method of decomposition. The proposed method is the first step towards the recognition and the separation of magnetic constituencies of different magnetic properties in an alloy by analytical means.     

石灰石颗粒分解的动力学模型研究

本文应用热重法对石灰石在氮气气氛、不同升温速率下的分解动力学进行了研究,采用普适积分法、微分方程法以及多重速率扫描Kissinger法相结合的方式求解动力学参数,确定反应机理模型。研究结果表明石灰石分解反应符合相边界反应的收缩圆柱体模型,采用三种方式相结合的动力学处理方法可以有效的进行动力学模式函数的选取。     

Adomian decomposition method for solving the telegraph equation in charged particle transport

In this paper, the analysis for the telegraph equation in case of isotropic small angle scattering from the Boltzmann transport equation for charged particle is presented. The Adomian decomposition is used to solve the telegraph equation. By means of MAPLE the Adomian polynomials of obtained series (ADM) solution have been calculated. The behaviour of the distribution function are shown graphically. The results reported in this article provide further evidence of the usefulness of Adomain decomposition for obtaining solution of linear and nonlinear problems.     

一种三维矩阵的奇异值分解算法

提出了一种三维矩阵的奇异值分解算法,该法适合处理具有三维矩阵数据的模式识别和分类模型等领域实际问题,该算法与二维矩阵奇异值分解算法类似,通过求解约束条件极值问题获得,该算法与已有的三线性分解算法比较,相对简单,计算速度快,适合处理数据量大的实际问题,该算法也很容易推广到更高维阵列的光谱数据。     

General Decomposition of Spin Connection and Topological Structure in Gauss-Bonnet-Chern Density

By means of devices of geometric algebra the general decomposition of spin connection on the sphere bundle of a compact n-dimensional Riemannian manifold has been studied in detail. Using this decomposition theory it is shown that the Gauss-Bonnet-Cherniensity of the Euler-PoincarB characterictic can be expressed in terms of a smooth vector field φ and take the form of the 6 function δ(φ). The topological structure in Gauss-Bonnet-Chern theorem is reviewed.     

P-N半导体复合型光电极分解水的原理及应用

利用太阳光分解水制氢是解决能源短缺的重要途径．文章概述了光电极分解水的原理，P—N半导体复合型光电极的两种结构及其近期的科研成果．对开展全氧化物混合光电极的研究进行了简介和展望．     

基于声压梯度参考的部分场分解方法及实验研究

采用扫描测量方式得到的不相干声场需分解成完全相干的部分场后才能用于近场声全息重建. 现有的方法都是将声压作为参考进行部分场分解. 本文提出以声压梯度作为参考, 并建立一种基于声压梯度参考的部分场分解方法. 由于声压梯度比声压的衰减速度更快, 受到其他声源和环境噪声的影响比声压小, 所以以声压梯度为参考在分解完全相干的部分场过程中比以声压为参考更具有优势. 通过数值仿真和实验分析, 一方面验证了基于声压梯度参考的部分场分解方法的正确性和可行性; 同时通过与基于声压参考的部分场分解结果比较, 说明了基于声压梯度参考的部分场分解方法分解更稳健、结果更精确.     

A 3D shape retrieval method for orthogonal fringe projection based on a combination of variational image decomposition and variational mode decomposition

The orthogonal fringe projection technique has as wide as long practical application nowadays. In this paper, we propose a 3D shape retrieval method for orthogonal composite fringe projection based on a combination of variational image decomposition (VID) and variational mode decomposition (VMD). We propose a new image decomposition model to extract the orthogonal fringe. Then we introduce the VMD method to separate the horizontal and vertical fringe from the orthogonal fringe. Lastly, the 3D shape information is obtained by the differential 3D shape retrieval method (D3D). We test the proposed method on a simulated pattern and two actual objects with edges or abrupt changes in height, and compare with the recent, related and advanced differential 3D shape retrieval method (D3D) in terms of both quantitative evaluation and visual quality. The experimental results have demonstrated the validity of the proposed method.