查询词典 nucleation

One undercooling criterion of equi-nucleation is derived from analysis of Gaussian distribution model of heterogeneous nucleation.

通过对高斯异质形核公式的研究，给出了等轴晶开始形核的过冷度判据，更为准确的描述柱状晶向等轴晶的转变过程。

This project studies the scale-dependent deformation behavior of the metal matrix composite, the void nucleation and void growth mechanisms at the micron/submicron scale. The main results are:(1) In prophase, growth and coalescence of the void embedded in the graded matrix are analyzed in detailed;(2) Based on the infinite solid model containing a micro-void, coupling effects of the void shape and the void size on the void growth are studied carefully, the results show that it seems to exist a critical equivalent void radius, which is associated with the material length. When radius of a microvoid is close to or smaller than the critical void radius, the micro-void growth rate is essentially eliminated;(3) The coupling effects of the particle shape and size on the mesoscopic stress fields within the particle and matrix are also investigated by introducing the conception of inclusion/matrix interfacial energy. The results show that the stress concentration factors within the particle and on the matrix/particle interface are also strongly size-dependent,so the void nucleation mechanism is size-dependent.(4) By employing a specific orthogonal curve coordinate frame and a 'kernel function' conception, a 'unified method'solving the spheriodal and spherical void problems is suggested; by this unified method, size-dependent plastic potentials of the porous materials containing the spheriodal or spherical voids are obtained, which extend the traditional Gurson model for the spherical void and GLD model for the spheriodal voids to the micron scale.(5) Based on the RVE model containing the spheriodal or spherical particles, the influences of the particle shape and size on the size-dependent mechanical behavior of metal matrix composite are studied.

中文摘要：本项目对金属基复合材料在微细观尺度下的尺度相关变形行为、孔洞形核及长大的机理和模型进行了研究，取得了如下主要结果：1）在前期研究中，探讨了基体的梯度分布对孔洞长大和聚合的影响；2）基于含孔洞的无限大体模型，探讨了孔洞形状和孔洞尺寸对其长大的耦合作用，结果表明：可能存在一个与材料特征长度相关的临界孔洞尺寸，当椭球孔洞的等效半径小于临界孔洞半径时，孔洞的长大受到明显抑制；3）通过引入基体/夹杂界面能的概念，分析了夹杂尺寸、夹杂形状对材料细观应力场的耦合影响，结果表明：颗粒内部和界面上的应力集中因子强烈地依赖于夹杂的尺寸和形状，因此，孔洞的形核机理是尺寸相关的；4）采用一种特殊的正交曲线坐标系和引入"核函数"的概念，"统一"地得到了含椭球和球形孔洞的材料的尺寸相关塑性势，它将传统的Gurson球形孔洞模型和GLD椭球孔洞模型推广到微尺度范围；5）基于含椭球和球形夹杂的体胞模型，初步研究了夹杂形状、夹杂尺寸对金属基复合材料尺寸相关力学行为的影响。

A continuous nucleation model was used to deal with the heterogeneous nucleation of a liquid metal.

采用连续形核的方法处理液态金属的异质形核现象。

Through the addition ofβnucleator, the crystallization process of iPP is transferred from homogeneous nucleation to heterogeneous nucleation.

随着α成核剂质量分数的增加，iPP的拉伸性能和弯曲性能得到了一定程度的提高。

Presently, the nucleation and growth mechanism of diamond hasnt been known completely. Thermodynamically, the nucleation and growth of diamond at low temperature and low pressure is still considered as a paralogism.

目前金刚石的热力学成核及生长机理尚不完全清楚，金刚石在低温低压下的成核和生长，仍被认为是一种热力学的"悖论"。

Through the experiments on hydration of AH in the following sulphate（Li_2SO_4、MgSO_4 、 Al_2(SO_4)_3 、MnSO_4 、CuSO_4 、CoSO4 、CdSO_4 、ZnSO_4 、NiSO_4 、FeSO_4）, dissoluble sulfate hydrate origining from hydration process of AH affects it's hydrous rate, hydrous rate of AH does not connect with Z/R of cation in stimulation, theory that Z/R affect hydrous rate of AH does not exist. Third, hydration of AH in dissoluble sulfate complies with dissolve-nucleate -grow theory, concentration of Ca~2+ from dissolving of CaSO_4 is higher than one of CaSO_4·2H_2O, calcium sulphate dihydrite gets a motivity of crystallization. dissoluble sulfate takes the following function: double-salt or dissoluble sulfate hydrate from hydration of AH in it becomes heterogeneous particle and a kind of nucleation catalyzer, and reduces surface barrier when DH becomes crystal because the crystal of DH precedently appears in uneven place. Results indicate hydration of AH does not conform with double-salt theory, but it conform with this mechanism: dissolve-nucleate-grow, formation of DH is an uneven nucleation and crystalizaion process.

通过对CaSO_4在Na_2SO_4 、K_2SO_4 、Rb_2SO_4 、Cs_2SO_4 、(NH_4)_2SO_4溶液中水化过程，以及CaSO_4·2H_2O、CaSO_4与以上硫酸盐反应速度、产物的研究，说明复盐理论不正确；CaSO_4在（Li_2SO_4、MgSO_4 、 Al_2(SO_4)_3 、MnSO_4 、CuSO_4 、CoSO_4 、CdSO_4 、ZnSO_4 、NiSO_4 、FeSO_4）溶液中水化，水化过程中硫酸盐水合物的析晶影响着无水硫酸钙水化，与激发剂阳离子Z/R值大小无关，阳离子的Z/R参数影响水化率的规律并不存在； 3、无水硫酸钙在可溶性硫酸盐中的水化按照溶解-成核-生长理论进行，CaSO_4达到溶解平衡时Ca~2+的浓度大于CaSO_4·2H_2O溶解平衡的Ca~2+的浓度，CaSO_4·2H_2O获得结晶的驱动力，可溶性硫酸盐起到形成晶核的作用：水化过程与CaSO_4生成复盐或析出水合物所形成的细小物相，作为异质微粒使母相中存在不均匀性，这些不均匀性有效地降低成核时的表面能位垒，使CaSO_4·2H_2O晶核优先地在这些具不均匀性的地方形成，因此这些物质起成核催化剂作用。

Its rapidsolidification behaviour during recalescence was studied by means of high speed cinematography andrapid infrared pyrometry,It is found that interface heterogeneous nucleation takes place in preferenceto homogeneous nucleation even at an undercooling above the previously accepted critical undercool-ing 0.2T_mfor homogeneous nucleatio...

采用高速摄影及快速红外测温技术研究了深过冷熔体的快速凝固行为。发现尽管过冷度超过了以往认为的均质形核临界过冷度0.2T_m，但是 Ni-32.5%Sn 共晶合金仍然优先发生界面异质形核，再辉过程中瞬时凝固速度最大可达784mm/s。

The content of the irregular bigger drop phase approached to pyrope. It showed that the crystallization and phase separation mechanics of the glass was the nucleation-and-growth transformation and the crystallization is bulk crystallization. The activation energies of phase separation and crystallization were calculated by the modified Kissinger method, about 310.445 KJ/mol and 249.26 KJ/mol respectively. Using the aluminum hydroxide as the reference, we calibrated the phase separation exothermal enthalpy of the quenched and nucleation treated glass, ca

钠镁侣硅系统徽晶玻瑞快速徽晶化机理的研究利用上式求得混合系统中两相的单位体积相变自由能、两相间的表面能和相互作用参数，分别为刁。6753xlo3了zcm3·、3ss.gozzem3、5.316xlo一JzcmZ和一442 xlol，进而求得球形核的临界半径为nnm，以及一个临界核的成核自由能变化为2石89 x10一14/cm3；成核半径16.5纳米时，球形核稳定存在，实测 1752个球形核中最小核半径为20纳米，与计算结果基本吻合。

For single phase solid solution Cu—Ni alloy, an apparent nucleation stage exists during its supercooling solidification, which is different from the traditional view combining nucleation into recalescence crystal growth.

3对单相固熔体Cu—Ni合金而言，其深过冷凝固过程中存在着明显的形核阶段，区别于传统观点将形核过程并入再辉阶段晶粒长大过程的看法。

According to classical nucleation theory, it was possible to distinguish the homogeneous and heterogeneous nucleation from the influence of temperature and supersaturation on induction period.

本文根据经典均匀成核理论，分别研究了硝酸酸沉和盐酸酸沉制备的四钼酸铵过饱和溶液的成核过程，并讨论了过饱和比和温度对成核速率及成核机制的影响。

Diabetes is a social disease that affects several million people worldwide.

糖尿病是一个社会性疾病，全世界有数百万人罹患此病。

I'll call you on Friday to see if we can reschedule our luncheon meeting at your convenience.

我星期五会给您打电话在您方便的时候我们重新安排我们的午餐约会。