Dissipative Particle Dynamics Simulations of Domain Growth and Phase Separation in Binary Immiscible Fluids

用并行耗散粒子动力学方法研究了二维和三维体系中不同淬火深度下二元不相容流体旋节线分离的相区增长过程. 在二维体系中,在浅度淬火条件下得到了动力学标度指数为1/2的融合机制和2/3的惯性流体动力学机制,在深度淬火情况下发现了有限尺寸效应. 在三维体系中,浅度淬火条件下n=1/3的扩散机制和两种不同淬火深度下n=2/3的惯性流体动力学机制. 由于耗散粒子动力学软相互作用势的本质,所以粘性效应无法被清晰地反映,在该时间区间里,不论是浅度还是深度淬火都表现出n=1/2的指数关系.     

A Short History of Phase Transitions in Ionic Fluids

The paper reviews the development of theory and experiments concerning the nature of the critical point in ionic fluids. Because of the long‐range nature of the Coulomb interactions the possibility of mean‐field critical behaviour was discussed as a possibility. Although some experiments supported mean‐field criticality, simulations on the model fluid of charged hard spheres and later experiments on ionic solutions have shown that phase transition of ionic systems belong to the Ising universality class like phase transitions in non‐ionic fluids. Experiments concerning the crossover from Ising to mean field‐behaviour are discussed as well as systematic differences between the phase behaviour predicted for the model fluid of charged hard spheres and that observed in ionic solutions (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Natural Convection of Temperature-Sensitive Magnetic Fluids in Porous Media

In this article, natural convection of a temperature-sensitive magnetic fluid in a porous media is studied numerically by using lattice Boltzmann method. Results show that the heat transfer decreases when the ball numbers increase. When the magnetic field is increased, the heat transfer is enhanced; however, the average wall Nusselt number increases at small ball numbers but decreases at large ball numbers due to the induced flow being more likely confined near the bottom walls with a high number of obstacles.     

A Higher Dimensional Cosmic Domain Wall in Brans-Dicke Theory of Gravitation

Five dimensional Kaluza-Klein Space-time is considered in the presence of thick domain walls in the scalar-tensor theory formulated by Brans and Dicke (Phys. Rev. 124:925, 1961). Exact cosmological model, in this theory, is presented with the help of special law of variation proposed by Berman (Nuovo Cim. B 74:182, 1983) for Hubble’s parameter. Some physical and kinematical properties of the model are also discussed.     

Five Dimensional Domain Walls in a Scalar-Tensor Theory of Gravitation

Five dimensional Kaluza-Klein space-time is considered in the presence of thick domain walls in the framework of scalar-tensor theory of gravitation proposed by Saez and Ballester (Phys. Lett. A 113:467, [1986]). Exact cosmological model, which represents a stiff domain wall, is presented. Some physical and kinematical properties of the model are also discussed.     

Domain of mixing angles in three flavor neutrino oscillations

We clarify the domain needed for the mixing angles in three flavor neutrino oscillations. By comparing the ranges of the transition probabilities as functions of the domains of the mixing angles, we show that it is necessary and sufficient to let all mixing angles be in . This holds irrespectively of any assumptions on the neutrino mass squared differences.     

Domain wall resistance in perpendicular (Ga,Mn)As: Dependence on pinning

We have investigated the domain wall resistance for two types of domain walls in a (Ga,Mn)As Hall bar with perpendicular magnetization. A sizeable positive intrinsic DWR is inferred for domain walls that are pinned at an etching step, which is quite consistent with earlier observations. However, much lower intrinsic domain wall resistance is obtained when domain walls are formed by pinning lines in unetched material. This indicates that the spin transport across a domain wall is strongly influenced by the nature of the pinning.     

分光光度法测定水基切削液及机械加工废水中亚硝酸盐含量

建立了邻甲氧基苯酚重氮偶联分光光度法测定水基切削液及机械加工废水中亚硝酸盐的方法。对其最佳显色时间、显色体系酸碱加入量、温度、检测波长及主要的基体干扰因素进行了考察。该方法的最佳检测波长为452nm,显色时间为1min—24h。0.1%的Cu2+、0.01%的Fe3+、0.2%的十二烷基苯磺酸钠(DBS)、2%的聚乙二醇(PEG)400对测定无影响。与国标法、高效液相色谱法相比较,方法具有快速、准确、操作简单等优点,适合于基质复杂的水基切削液及机械加工废水的质量监控与检测。对4种实际样品中的亚硝酸盐含量进行了测定,发现样品中均不同程度含有亚硝酸盐,浓度范围为1.50—1.62×104mg/L。     

Monte Carlo Simulation Study on Domain Formation in the Photoinduced Low-Spin High-Spin Transition

The domain formation process of the photo-induced cooperative low-spin (LS) to high-spin (HS) conversion phenomena are studied based on the Monte Carlo simulation method. The existence of the threshold light intensity and the incubation period are demonstrated. It is pointed out that the nucleation barrier of HS domain is surmounted by the fluctuation caused by the repetition of excitation and de-excitation. By defining an effective temperature for this fluctuation, the time scale of incubation period is estimated following the usual domain formation theory. It grossly accounts the Monte Carlo (MC) results in three-dimensional cases. The phase separation of HS and LS domain is reproduced by considering the volume striction effect. The step wise abrupt conversion is ascribed to the de-pinning of the volume striction.     

Cosmic Strings and Domain Walls in a Scale-Covariant Theory of Gravitation

Axially symmetric space-time is considered in the presence of cosmic string source and thick domain walls in the frame work of a scale-covariant theory of gravitation. A relation between metric potential is assumed to get a determinate solution of the field equations of this theory. In this particular case, it is observed that the geometric (Nambu) string p-string (Takabayasi string) and Reddy string do not survive. It is also seen that the stiff (self-gravitating) domain walls do not exist in this theory.     

镧和铈对两种细菌生长的影响及胞内DNA的荧光光谱分析

为了研究镧,铈对细菌生长及核酸的影响,用光电比浊法测定了镧,铈和钙调蛋白抑制剂(氯丙嗪)存在时两种细菌的生长曲线,并用荧光光谱法研究了镧,铈对小牛胸腺DNA和细菌胞内DNA结构的影响。结果显示适当浓度(200 mg·L-1)稀土元素可以促进细菌的生长和繁殖,比对照提前进入对数期,扫描电镜观察也显示镧,铈可以促进枯草芽孢杆菌个体的生长,菌体体积比对照更大,但促进繁殖的作用会被氯丙嗪抑制,表明镧,铈促进细菌生长的机理可能与钙调蛋白的功能有关;荧光光谱分析显示镧,铈会使小牛胸腺DNA荧光增强,镧、铈浓度分别为5和10 mg·L-1时荧光增强作用最大;但镧使细菌胞内DNA荧光猝灭,铈使其荧光增强,结论认为镧,铈对核酸的影响远比想象的要复杂。     

Some recent advances in the understanding of phase-ordering dynamics

We review some of our recent studies of phase ordering dynamics. Specifically, we describe results from numerical simulations of domain growth in systems with quenched disorder. We also present representative results from numerical studies of phase ordering dynamics in anisotropic systems.     

Effect of Deuteration on Phase Transitions in Vanadium Dioxotetrafluoride

Physics of the Solid State - The crystals of (ND4)3VO2F4 with a high degree of deuteration (~87%) have been grown and a significant (~1.5%) increase in the unit cell volume has been detected. The...     

光谱法研究细胞色素c氧化酶CuA结构域蛋白的稳定性

利用荧光光谱和圆二色谱研究了细胞色素c氧化酶CuA结构域蛋白的稳定性.结果表明,随着溶液pH值的升高,CuA结构域蛋白的稳定性降低.随着温度的升高,CuA结构域蛋白的二级结构遭到破坏.脱金属形式蛋白的热稳定性减小,表明双核金属铜中心的存在对CuA结构域蛋白的稳定性起重要作用.     

Domain growth dynamics in multicomponent vesicles composed of BSM/DOPC/cholesterol

We have investigated the domain growth dynamics in vesicles composed of BSM/DOPC/cholesterol using fluorescence microscopy. A ternary mixture of equimolar BSM, DOPC, and cholesterol was employed, and two fluorescent dyes were added for comparison studies. We found that in the early stage the number of the domains on the vesicle surface, N(t), decayed with time as N(t)∼t^−2/3, which confirmed previous theoretical prediction and numerical simulation, while in the late stage N(t) decreased more quickly, as ∼t^−β, with β≈2. We discuss the faster growth dynamics based on the collision-induced collision mechanism.     

Finite Element Analysis of Convection in Growth Cell for Diamond Growth Using Ni-Based Solvent

Thermal-electricaJ-fluid coupled finite element analyses are performed in the model of the growth cell in a high-pressure and high-temperature （HPHT） cubic apparatus in which the large diamond crystal can be grown by using Ni-based solvent with temperature gradient method （TGM）. The convection in the Ni-based solvent with different thicknesses at 1700-1800 K is simulated by finite element method （FEM）. The experiments of diamond crystal growth are also carried out by using Ni-based solvent at 5.7GPa and 1700-1800K in a China-type cubic high pressure apparatus （CHPA）. The simulation results show that the Rayleigh number in the solvent is enhanced obviously with the increasing solvent thickness. Good quality diamond single crystal cannot be grown if the Rayleigh number in the solvent is too high.     

地球外核热对流运动的区域分解多重网格并行数值模拟

旋转球层中热对流运动的数值模拟是地球发电机模型的重要组成部分,对研究地球发电机作用机理具有重要意义.本文设计一个基于国产超级计算平台并行性能良好的地球外核热对流运动并行数值模型.时间积分方案采用与Crank-Nicolson格式和二阶Adams-Bashford公式相结合的近似分解分步法,空间离散基于立方球网格的二阶精度有限体积格式.所得到的两个大规模稀疏线性代数方程组采用带预处理的Krylov子空间迭代法进行求解.为加速迭代求解过程及提高并行性能,迭代过程采用区域分解多重网格的多层限制型加法Schwarz预处理子,减少了求解程序的计算时间,提高了数值模型的并行性能,模型被很好地扩展到上万处理器核数.数值模拟结果与基准模型算例0的参考值吻合得很好.     

Rearrangement of Rare Earth Defects Under Domain Inversion in LiNbO3

Using high resolution excitation-emission spectroscopy we investigated the changes occurring in the optical transition of Er^3? ions in LiNbO₃ during inversion of the ferroelectric axis. In stoichiometric LiNbO₃ we find that a drastic reconfiguration among the different defect sites takes places favoring those centers which have already been dominant in the as-grown sample. The reconfiguration is attributed to changes in the arrangement of the local charge compensators. Furthermore, we find a small shift of the emission transition energy, which is consistent with an increase of the intrinsic electric field. These findings make the Er^3? ions very suitable probes for 3D imaging of domain structures and for in-situ studies of the dynamics of the domain inversion processes and the defect/domain wall interaction.     

基于相干光时域反射计的光纤温度传感测量

  研究了基于相干光时域反射计的光纤传感技术,分析了基于相干光时域反射计的分布式温度传感机理.根据传感系统的组成和原理,建立了仿真模型,利用MATLAB对传感系统的性能进行了仿真与分析,结果表明基于相干光时域反射计的传感系统可以达到温度测量分辨率为0.01 ℃,空间分辨率为1 m的性能指标.     

氢稀释对纳米晶硅薄膜晶化特性的影响及薄膜生长机理

以SiH₄与H₂作为前驱气体,采用射频等离子增强化学气相沉积技术制备了纳米晶硅薄膜.利用Raman散射和红外吸收光谱等技术,对不同氢稀释比条件下薄膜的微观结构和键合特性进行了研究.结果表明,随着氢稀释比增加,薄膜的晶化率明显提高,而氢稀释比过高时,薄膜晶化率呈现减少趋势.红外吸收光谱分析表明,纳米晶硅薄膜中氢的键合模式与薄膜的晶化特性密切相关.随着氢稀释比增加,薄膜中整体氢含量和SiH₂键合密度明显减少,而在高氢稀释比条件下,氢稀释比增加导致薄膜中SiH₂键合密度和整体氢含量增加.