Growth of NaBi（WO4）2 Dendrite and Mechanism

The solid-liquid interface motion of NaBi（WO4）2 （NBWO） melt crystal growth is observed in an in situ system, in which the whole processes of interface transition from fiat interface and cellular to dendrite are visualized. The spacing of the dendrite under smaller temperature gradient turns out to be larger than that under larger temperature gradient, which is found to be sensitive to the temperature distribution. The mechanism of dendrite growth of NBWO is studied based on the model of the growth units of anion coordination polyhedra. The { 001} face has two apex links, so it shows higher stability and has high growth rate and forms the arm of dendrite, whereas the {010} face has only one apex link, and thus shows relative slower growth rate and firstly forms the branches.     

In Situ Observation of Skeletal Shape Transition during BaB2O4 Crystal Growth in High-Temperature Solution

The transition from a fiat solid-liquid interface to a skeletal shape during BaB2O4 （BBO） single crystal growth in Li2B4O7 flux is observed in real time by an optical high-temperature in-situ observation system. The movement of crystal step is also investigated. The observation results demonstrate that the steps propagate along and parallel to the fiat interface when the crystal size is small. Nevertheless, they will ‘bend＇ close to the face centre if the crystal size becomes greater. Atomic force microscopy reveals that more deposition places near the face centre give rise to the bending of advancing steps and thus the formation of a vicinal interface structure. Measurements of step velocity show that the velocity keeps nearly constant at different moments for one specific step, whereas the step on a newly formed layer advanced faster than that on a previously formed one when the crystal size is larger than 210μm or so. Thus interracial morphological instability occurs and a skeletal interface is obtained.     

Effects of interface kinetics and anisotropy on the stability of the growing crystal face and dissolution face during crystallization from solution under microgravity

The stability of the shapes of the growing crystal face and dissolution face in a two-dimensional mathematical model of crystal growth from solution under microgravity is studied. Effects of the interface kinetics and anisotropy of crystallization and dissolution on the stability are also studied. It is proved that the stable shapes of crystal growth face and dissolution face do exist, which are of suitably shaped curves with their upper parts inclined backward properly no matter whether the interface kinetics and the anisotropy are taken into account or not. The stable shapes of the growing crystal faces and dissolution faces are calculated for various cases. The interface kinetics will make the inclination degree of stable crystal growth face reduce and that of stable dissolution face reduce slightly. The anisotropy of crystallization and dissolution may make the inclination degree of stable-growing crystal face smaller or larger, and that of the stable dissolution face varies very slightly.     

非齐次核的Hilbert型重积分不等式适配参数的等价条件及应用

利用权函数方法和实分析技巧，讨论了一类非齐次核■(λ₁λ₂>0)的Hilbert型重积分不等式的搭配参数，得到最佳搭配参数的充分必要条件及最佳常数因子的表达式。利用所得结果，讨论了相应的重积分算子的有界性及算子范数。     

Optical and atomic force microscopic study on step bunching in BaB2O4 crystal growth

The formation of macrostep during high-temperature phase of barium meta-borate (α-BaB 2 O 4) single crystal growth has been investigated by both optical in-situ observation system and atomic force microscopy (AFM).The insitu observation results demonstrate that the critical linear size of growing facet exceeding the size that the macrostep generates is significantly anisotropic.The critical linear sizes are around 280 μm and 620 μm for {1010} and {1010} planes,respectively.AFM study illustrates that macrostep train with a height of 150 nm～200 nm is one typical morphological feature of the as-grown crystal surface.The riser of each macrostep consists of several straight and parallel sub-steps,indicating the occurrence of step bunching.Additionally,triangular sub-steps with heights of several nanometers on the treads of the macrosteps are found to be another typical feature of surface morphology,which implies a microscopically competitive bunching of sub-steps between various crystallographic orientations.     

一类具有准齐次核的Hilbert型奇异重积分算子的范数及应用

引入准齐次函数的概念,研究了具有准齐次核的一类Hilbert型奇异重积分算子的范数问题,并讨论其应用.     

微重力条件下晶体生长过程的实时观察

从材料科学的微重力效应和晶体生长基本过程等两个方面出发，阐明了一种新的生长技术（晶体生长过程的光学实时观察法）的必要性，并介绍了空间高温实时观察装置的基本特性．在我国的科学技术探测卫星上，该装置进行了搭载实验，并首次清楚地观察到了空间溶质扩散效应和高温溶液的表面张力对流图像．     

一类带齐次核的奇异重积分算子的范数及其应用

设核函数K(u,v)具有对称性和齐次性,对如下定义的奇异重积分算子T:(Tf)(y)=∫R_+~n K(‖x‖α,‖y‖α)f(x)dx,y∈R_+~n,其中‖x‖α=(x_1~α+…+x_n~α)~1/α(α>0),研究了T的范数及其应用.     

核为G(nλ1xλ2)(λ1λ2 > 0)的半离散Hilbert型不等式成立的等价参数条件及应用*

利用权函数方法和实分析技巧, 在λ₁λ₂ > 0 的条件下,讨论具有非齐次核K(n,x)=G(n^λ₁x^λ₂)的半离散Hilbert型不等式成立的等价参数条件及最佳常数因子问题, 最后讨论其在算子理论中的应用.     

轴向振动对圆柱形液体自由表面流的影响

通过光学实时观察法研究了轴向振动对恒温圆柱形容器内液体自由表面流动行为的影响。该地面实验是在一个频率为100赫兹的电磁振动台上进行的，水－甘油的混合溶液作为模型体系。结果发现，小于100mm的振动振幅能够使自由表面产生稳定的流动。这种流动主要是由沿自由表面传播的毛细波与斯托克斯边界层效应的共同作用驱动的。随着振动振幅的变化，稳态流会呈现不同的流动花样。高振幅作用下，稳态流动趋向于周期性流甚至成为湍流，这个过程可以通过临界无量纲雷诺数(Nre)c来表征，实验中得到的(Nre)c值在10-2 ～ 10-1范围内。此外，利用示踪粒子散射技术对自由表面的流动速度进行了测量，结果显示流速随粘度的增大而减小，并且随振幅的增加呈抛物线形增长。