双液滴同时撞击液膜的动力学演变

为了考察液滴的撞击对液膜变形行为的影响规律,利用CLSVOF(coupled level set and volume of fluid)方法模拟双液滴同时撞击平面液膜后的流动过程,获得了不同水平间隔距离、不同撞击速度的两液滴撞击平面液膜后的演变过程特点,通过分析不同时刻压力场分布,探索了两液滴水平间隔距离、韦伯数和撞击速度对双液滴同时撞击液膜后流动过程、形态及对水花高度和中心射流高度的影响。结果表明,碰撞速度较大时的中心液膜射流高度大于碰撞速度较小时的;We数较大时中心射流顶端将产生二次液滴;液滴间距对撞击后初始时(3 ms之前)撞击点两侧的开始水花高度没有明显影响。

柴油机缸内碳烟颗粒生长的动力学演变

以一台缸内直喷柴油机为原型,建立三维仿真模型,耦合详细碳烟模型,研究柴油机在不同负荷下缸内碳烟颗粒的质量分布和数密度变化规律.将计算得到的结果及气流参数作为动力学模拟的初始条件,利用拉格朗日方法建立颗粒动力学模型追踪每个颗粒的运动,计算碳烟颗粒的完整生长过程.结果表明,燃烧结束后,碳烟成核速率逐渐趋近于零,表面生长和凝结速率低于氧化速率,碳烟总质量逐渐降低;气缸顶部、气缸壁及活塞处的碳烟质量分数均较小.利用构建的颗粒动力学模型,可以模拟碳烟基本粒子到团聚体的生长过程,在不同负荷下得到的积聚体形貌主要呈枝状和簇状结构,与实验采样得到的几种主要形貌相似;不同负荷下的分形维数均与实验测量值相近,最大误差约为1.5%.

紫细菌Rb.Sphaeroides601外周捕光天线(LH2) B800吸收带的超快动力学研究

利用从紫细菌Rb.sphaeroides601所提取出的外周捕光天线LH2以及其不同pH值酸化样品(部分和全部去除B800分子LH2)并采用不同波长下的飞秒单色抽运探测技术详细研究了LH2中B800吸收带内的激发态动力学过程。通过对野生型与部分/完全去B800分子LH2的比较研究,分析了B800吸收带激发后所表现出的丰富变化的动力学过程,研究结果表明激发B800带的动力学过程中包含着B850上激子带的直接激发而产生的对激发态动力学的贡献。

单区静电除尘器捕集烟尘过程的数值模拟

通过得到烟尘的颗粒尺度谱(PSD)演变过程的详细信息来定量描述静电除尘器(ESP)对烟尘的捕集过程,此时需要同时考虑静电力、流体对颗粒的水平输运力和颗粒横向湍流和布朗扩散作用等烟尘捕集机制。发展事件驱动常体积法来求解考虑烟尘捕集的通用动力学方程以得到颗粒尺度谱的演变过程。对于典型的火电厂单区ESP进行的数值模拟结果表明:ESP对直径大于10μm的烟尘具有良好的捕集效果,也能有效脱除直径小于0．02μm的烟尘,但是对粒径范围在0．02～10μm的烟尘的除尘效率相对较低;这种“U”型分级除尘效率主要是由于颗粒自身惯性力与静电力之间的相互竞争的结果;布朗扩散机制对任何尺度颗粒的捕集效果影响很小;减小气流输运速度和增加电场强度有利于任何粒径的烟尘颗粒的脱除。

异质性干细胞增殖过程中的熵变化

干细胞在多细胞生物体内广泛存在,其增殖过程在生命体的生长、发育、衰老、组织修复过程中起着重要作用。正常组织中的细胞增殖过程受到严格的控制,干细胞的异常增殖与恶性肿瘤、肥胖症、再生障碍性贫血等疾病有密切关系。生命体内异质性细胞的增殖过程是复杂的动力系统行为,干细胞异常增殖过程伴随细胞的可塑性变化和细胞间相互作用的再平衡过程,如何对这一过程进行定量描述是重要的研究课题。本文构建包含细胞的增殖分化指标和异常增殖性指标异质性的干细胞增殖模型,通过所建立的模型研究由于微环境变化引起的细胞异常增殖过程的熵变化,建立不同增殖条件下的系统熵变化与宏观动力学和系统参数之间的关系。结果表明,在细胞微环境变化引起异常增殖和恢复的过程中,系统的熵与细胞数量之间存在对应关系,而与微环境变化的路径无关。此外,熵对细胞数量的依赖关系在异常增殖和恢复阶段表现出不同的行为,显示了生物过程的微观不可逆性。本文从物理学的角度对细胞异常增殖过程中熵变化与细胞数量变化的动力学给出定量刻画,为定量描述异质性干细胞增殖过程给出新的研究思路。

Effect of TiB_(2) Nanoparticles on Microstructure and Mechanical Properties of Ni_(60)Cr_(21)Fe_(19) Alloy in Rapid Directional Solidification Process:Molecular Dynamics Study

Molecular dynamics(MD)simulations are employed to delve into the multifaceted effects of TiB_(2) nanoparticles on the intricate grain refinement mechanism,microstructural evolution,and tensile performance of Inconel 718 superalloys during the rapid directional solidification.Specifically,the study focuses on elucidating the role of TiB2 nanoparticles in augmenting the nucleation rate during the rapid directional solidification process of Ni_(60)Cr_(21)Fe_(19) alloy system.Furthermore,subsequent tensile simulations are conducted to comprehensively evaluate the anisotropic behavior of tensile properties within the solidified microstructures.The MD results reveal that the incorporation of TiB₂nanoparticles during the rapid directional solidification of the Ni_(60)Cr_(21)Fe_(19) significantly enhances the average nucleation rate,escalating it from 1.27×10^(34)m^(-3)·s^(-1)to 2.55×10^(34)m^(-3)·s^(-1).Notably,within the face centered cube(FCC)structure,Ni atoms exhibit pronounced compositional segregation,and the solidified alloy maintains an exceptionally high dislocation density reaching up to 10^(16)m^(-2).Crucially,the rapid directional solidification process imparts a distinct microstructural anisotropy,leading to a notable disparity in tensile strength.Specifically,the tensile strength along the solidification direction is markedly superior to that perpendicular to it.This disparity arises from different deformation mechanisms under varying loading orientations.Tensile stress perpendicular to the solidification direction encourages the formation of smooth and organized mechanical twins.These twins act as slip planes,enhancing dislocation mobility and thereby improving stress relaxation and dispersion.Moreover,the results underscore the profound strengthening effect of TiB_(2) nanoparticles,particularly in enhancing the tensile strength along the rapid directional solidification direction.

Growth kinetics of interfacial intermetallic compounds formed in SnPbInBiSb high entropy alloy soldered joints on Cu substrates

The growth behavior of the complex intermetallic compounds(IMCs)formed at the interface of Cu/SnPbInBiSb high entropy alloy solder joints was explored.The growth inhibition mechanism of the IMCs at the Cu/SnPbInBiSb solid−liquid reaction interface was revealed.The results showed that the growth rate of the complex IMCs obviously decreased at the Cu/SnPbInBiSb solid−liquid reaction interface.The maximum average thickness of IMCs only reached up to 1.66μm after reflowing at 200℃for 10 min.The mechanism for the slow growth of the complex IMCs was analyzed into three aspects.Firstly,the high entropy of the liquid SnPbInBiSb alloy reduced the growth rate of the complex IMCs.Secondly,the distorted lattice of complex IMCs restrained the diffusion of Cu atoms.Lastly,the higher activation energy(40.9 kJ/mol)of Cu/SnPbInBiSb solid−liquid interfacial reaction essentially impeded the growth of the complex IMCs.

Microstructure evolution in cooling process of Al-Zn-Mg-Cu alloy and kinetics description

The microstructure evolution of Al-Zn-Mg-Cu alloy was studied by differential scanning calorimetry （DSC） and transmission electron microscopy （TEM） during different rate cooling processes. Based on the DSC results, the kinetics analysis was carried out. The results indicate that the precipitation of η phase is the predominant transformation for the alloy during the cooling process after the solution treatment. And the η phase nucleates on dispersoids and at grain boundaries. The amount of η phase decreases with increasing cooling rate, and reduces by 75% as the cooling rate increases from 5 to 50 ℃/min. The kinetics of the precipitation of η phase can be described by the Kamamoto transformation model when the cooling rate is a constant.

Simulation study on non-linear effects of initial melt temperatures on microstructures during solidification process of liquid Mg_7Zn_3 alloy

The non-linear effects of different initial melt temperatures on the microstructure evolution during the solidification process of liquid Mg7Zn3 alloys were investigated by molecular dynamics simulation, The microstructure transformation mechanisms were analyzed by several methods. The system was found to be solidified into amorphous structures from different initial melt temperatures at the same cooling rate of 1×10^12 K/s, and the 1551 bond-type and the icosahedron basic cluster （12 0 12 0 ） played a key role in the microstructure transition. Different initial melt temperatures had significant effects on the final microstructures. These effects only can be clearly observed below the glass transition temperature Tg; and these effects are non-linearly related to the initial melt temperatures, and fluctuated in a certain range. However, the changes of the average atomic energy of the systems are still linearly related with the initial melt temperatures, namely, the higher the initial melt temperature is, the more stable the amorphous structure is and the stronger the glass forming ability will be.

A FVCOM-Based Unstructured Grid Wave, Current,Sediment Transport Model,I.Model Description and Validation

An effort was made to couple FVCOM (a three-dimensional (3D),unstructured grid,Finite Volume Coastal Ocean Model) and FVCOM-SWAVE (an unstructured grid,finite-volume surface wave model) for the study of nearshore ocean processes such as tides,circulation,storm surge,waves,sediment transport,and morphological evolution.The coupling between FVCOM and FVCOM-SWAVE was achieved through incorporating 3D radiation stress,wave-current-sediment-related bottom boundary layer,sea surface stress parameterizations,and morphology process.FVCOM also includes a 3D sediment transport module.With accurate fitting of irregular coastlines,the model provides a unique tool to study sediment dynamics in coastal ocean,estuaries,and wetlands where local geometries are characterized by inlets,islands,and intertidal marsh zones.The model was validated by two standard benchmark tests: 1) spectral waves approaching a mild sloping beach and 2) morphological changes of seabed in an idealized tidal inlet.In Test 1,model results were compared with both analytical solutions and laboratory experiments.A further comparison was also made with the structured grid Regional Ocean Model System (ROMS),which provides an insight into the performance of the two models with the same open boundary forcing.

Simulation on microstructure evolution and mechanical properties of Mg-Y alloys: Effect of trace Y

The influence of trace Y on the microstructure evolution and mechanical properties of Mg_(100−x)Y_(x)(x=0.25,_(0.75),1.5,3,4,5,at.%)alloys during solidification process was investigated via molecular dynamics(MD)simulations.The results show that the Mg_(100−x)Y_(x) alloys are mainly characterized by a face-centered cubic(FCC)crystal structure;this is different from pure metal Mg,which exhibits a hexagonal close packed(HCP)structure at room temperature.Among these alloys,Mg_(99.25)Y_(0.75) has a larger proportion of FCC cluster structures,with the highest fraction reaching 56.65%.As the content of the Y increases up to 5 at.%(Mg95Y5 alloy),the amount of amorphous structures increases.The mechanical properties of the Mg_(100−x)Y_(x) alloys are closely related to their microstructures.The Mg_(99.25)Y_(0.75) and Mg_(97)Y_(3) alloys exhibit the highest yield strengths of 1.86 and 1.90 GPa,respectively.The deformation mechanism of the Mg−Y alloys is described at the atomic level,and it is found that a difference in the FCC proportion caused by different Y contents leads to distinct deformation mechanisms.

Microstructure evolution and recrystallization behavior of cold-rolled Zr-1Sn-0.3Nb-0.3Fe-0.1Cr alloy during annealing

The effects of cold-rolling reduction,annealing temperature,and time on recrystallization behavior and kinetics of cold-rolled Zr-1Sn-0.3Nb-0.3Fe-0.1Cr alloy were investigated using the Vickers hardness test,scanning electronic microscopy(SEM),transmission electron microscopy(TEM)and electron backscatter diffractometry(EBSD).The results show that the rate of the recrystallization increased with increasing annealing temperature and rolling reduction.Recrystallized grains nucleated preferentially at sites with high density dislocation and deformation stored energy and then grew into integral grains.Recrystallization texture changed from-1010-//RD to-1120-//RD.The grain orientation changed from random orientation to the orientation with the maximum misorientation around 30°.Recrystallization kinetics and maps were constructed based on the Johnson-Mehl-Avrami-Kolmogorov(JMAK)equation to derive parameters sensitive to the microstructure.The activation energies for recrystallization of 30%,50%and 70%cold-rolling reductions were determined to be 240,249 and 180 kJ/mol,respectively.

Co-extraction of valuable metals and kinetics analysis in chlorination process of low-grade nickel-copper sulfide ore

To efficiently co-extract Ni and Cu from low-grade nickel-copper sulfide ore,chlorination roasting with NH;Cl followed by a water leaching process was investigated.The results show that 98.4%Ni and 98.5%Cu can be synchronously extracted when the ore particle size is 75-80μm,the roasting time is 2 h,the mass ratio of NH;Cl to ore is 1.6:1 and the roasting temperature is 550°C.The evolution behavior of various minerals was elucidated using X-ray diffraction(XRD)coupled with scanning electron microscopy(SEM).The kinetics of the chlorination process based on the differential thermal and thermogravimetric analysis(DTA-TG)data was analyzed by Kissinger method and Flynn-Wall-Ozawa(FWO)method.The chlorination process of low-grade nickel-copper sulfide ore mainly contains two stages:the decomposition of NH;Cl and the chlorination of ore.The maximum apparent activation energies(Ea)at two stages are determined to be 114.8 and 144.6 kJ/mol,respectively.The condensed product of exhaust gas is determined to be ammonium chloride,which can be recycled as the reactant again,making the process economic and clean.

Microstructural evolution of 2026 aluminum alloy during homogenization

The microstructural evolution of 2026 aluminum alloy during homogenization treatment was investigated by optical microscopy(OM),scanning electron microscopy(SEM),energy dispersive X-ray spectrometry(EDS),differential scanning calorimetry(DSC)and X-ray diffraction(XRD).The results show that severe dendritic segregation exists in the as-cast 2026 alloy and the main secondary phases at grain boundary are S(Al2CuMg)andθ(Al2Cu)phases.Elements Cu,Mg and Mn distribute unevenly from grain boundary to the inside of as-cast alloy.With the increase of homogenization temperature or the prolongation of holding time,the residual phases gradually dissolve into the matrixα(Al)and all the elements become more homogenized.According to the results of microstructural evolution,differential scanning calorimetry and X-ray diffraction,the optimum homogenization parameter is at 490°C for 24 h,which is consistent with the result of homogenization kinetic analysis.

Microstructure evolution and Al_3(Sc_(1-x)Zr_x) precipitates' kinetics in Al-Zn-Mg alloy during homogenization

The microstructure evolutions of two A1-Zn-Mg alloys, one of which was alloyed with Sc and Zr, and the kinetics of A13（SCl-xZrx） precipitates in the A1-Zn-Mg alloy during homogenization were investigated. Both alloys under as-cast condition with supersaturated, non-equilibrium T（Mg32（A1, Zn）49） phase and impurities phase were displayed. When the homogenization temperatures are below 350 ~C, Zn and Mg atoms precipitate from matrix; however, when the temperatures are above 400 ~C, T phase dissolves into matrix, enhancing solid-solution strengthening. Kinetics of A13（Scl.xZrx） precipitates was studied based on Jmat Pro software calculation and the difference values between the hardness of the two alloys in each homogenization condition. The calculations predict that the Sc and Zr solubilities in ct-A1 decline with the presence of Mg and Zn. Investigation of the difference values reveals that when the temperature is between 300 ~C and 350 ~C, the nucleation rate of A13（Sc1-xZrx） precipitates is the highest and the strengthening effect from A13（SCl_xZrx） precipitates is the best. After homogenization at 470℃ for 12 h, non-equilibrium T phase disappears, while impurity phase remains. The mean diameter of A13（Scl_xZrx） precipitates is around 18 urn. Ideas about better fulfilling the potentials of Sc and Zr were proposed at last.

Time Evolution,Dynamical Quantum Fluctuation and High-Order Squeezing Feature in Polariton System——Ⅰ

We have set up a new reduced model Hamiltonian for the polariton system, in which the nonlinear interaction contains the rotating term k l （ a ＋ b ＋ ab＋） and the attractive two-mode squeezed coupling - k2 （ a ＋ b＋ ＋ ab ） . The dynamical evolution of this system has been solved and the nonclassical features relevant to the second-order and high-order squeezing have been obtained in an analytical form. For the first time, in contrast to the existing result, we have confirmed for the phonon field that the attractive two-mode squeezed interaction will not only result in the second-order and high-order squeezing in X-component with the time evolution, but also in time average. Furthermore, the phenomena of collapse and revival of inversion will occur as well in the time evolution of the average number of photon and phonon, as also in the second-order and high-order squeezing of photon field, particularly, in the high-order squeezing of phonon field.

Modeling Evolution of Weighted Clique Networks

We propose a weighted clique network evolution model, which expands continuously by the addition of a new clique （maximal complete sub-graph） at. each time step. And the cliques in the network overlap with each other. The structural expansion of the weighted clique network is combined with the edges＇ weight and vertices＇ strengths dynamical evolution. The model is based on a weight-driven dynamics and a weights＇ enhancement mechanism combining with the network growth. We study the network properties, which include the distribution of vertices＇ strength and the distribution o~ edges＇ weight, and find that both the distributions follow the scale-free distribution. At the same time, we also find that the relationship between strength and degree of a vertex are linear correlation during the growth of the network. On the basis of mean-field theory, we study the weighted network model and prove that both vertices＇ strength and edges＇ weight of this model follow the scale-free distribution. And we exploit an algorithm to forecast the network dynamics, which can be used to reckon the distributions and the corresponding scaling exponents. Furthermore, we observe that mean-field based theoretic results are consistent with the statistical data of the model, which denotes the theoretical result in this paper is effective.

Suspension roasting process of vanadium-bearing stone coal:Characterization,kinetics and thermodynamics

The thermodynamics,kinetics,phase transformation,and microstructure evolution of vanadium-bearing stone coal during suspension roasting were systematically investigated.Thermodynamic calculations showed that the carbon in the stone coal burned and produced CO_(2) in sufficient oxygen during roasting.The mass loss of stone coal mainly occurred within the temperature range from 600 to 840℃,and the thermal decomposition reaction rate increased to the peak at approximately 700℃.Verified by the Flynn−Wall−Ozawa(FWO)and Kissinger−Akahira−Sunose(KAS)methods,the thermal decomposition reaction of stone coal was described by the Ginstling−Brounshtein equation.The apparent activation energy and pre-exponential factors were 136.09 kJ/mol and 12.40 s^(−1),respectively.The illite in stone coal lost hydroxyl groups and produced dehydrated illite at 650℃,and the structure of sericite was gradually destroyed.The surface of stone coal became rough and irregular as the temperature increased.Severe sintering occurred at the roasting temperature of 850℃.

一种简便高效的材料三维组织及其演变的Monte Carlo仿真

建立了一种新的材料三维组织及其演变的 Ｍｏｎｔｅ Ｃａｒｌｏ仿真方法．算法构造简便，使用灵活，不仅能够准确地反映三维正常晶粒长大的动力学过程，而且可以明显提高模拟效率．仿真既能可靠地应用于材料组织及其演变的定量分析，又可方便地用于立体材料水平截面、空间任意角度截面显微组织及其演变过程的观察、三维系统和二维截面组织表征参量及其对应关系的测定等多个方面．

柴油机排气管内碳烟颗粒的形貌计算

以排气管内碳烟颗粒为模拟对象,基于流体-轨道模型,采用拉格朗日方法追踪每个颗粒的运动轨迹,考虑颗粒之间的碰撞、凝并等动力学过程,构建了颗粒动力学演变过程的模型.在柴油机转速为1 800 r/min条件下,计算不同平均有效制动压力(0.38,0.63,0.88,1.13MPa)下排气管内碳烟颗粒的动力学演变过程,获得碳烟颗粒的形貌并统计出分形维数.结果表明:构建的模型可以很好地计算颗粒碰撞后的形貌和分形维数,颗粒最终形貌呈现出枝状和簇状,分形维数与实验结果相符合;随着负荷的增加,分形维数增加.此外,构建的模型可以很好地观察到颗粒的生长过程,有助于更深入地研究碳烟形成.