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201.
The partition-enabled analysis of cluster histograms (PEACH) method is used to calculate the free energy surface of NaCl aggregation using cluster statistics from MD simulations of small systems (40–90 ions plus solvent) in four solvents. In all cases (pure methanol, pure water, and two methanol/water mixtures) NaCl clusters show a transition from amorphous to rocksalt structure with increasing cluster size. The crossover sizes, and the apparent kinetic barrier to ordering, increase with increasing water content. Implications for the proposed two-step mechanism of NaCl crystal nucleation (in which the ordered structure emerges from a large disordered cluster), and how this mechanism might depend on solvent and on degree of supersaturation, are discussed. In pure water, nonideal crowding effects that promote clustering are identified from systematic concentration-dependent deviations between simulation results and the PEACH model fit. In contrast, the ability of PEACH to fit aggregation statistics in mixed solvents is consistent with negligible interactions between ions in different clusters. © 2018 Wiley Periodicals, Inc. 相似文献
202.
二次阳极氧化技术在多孔阳极氧化铝和氧化钛纳米管的制备过程中得到广泛应用,但其理论依据还不清楚。本文详细综述了二次阳极氧化和预压印技术的由来及其理论依据,阐明了二次阳极氧化过程中传统“场致助溶”理论无法解释的实验事实,分析了二次阳极氧化和预压印技术在多孔阳极氧化铝制备中的局限性和前提条件,并用氧气气泡模型对文献中报道的一些特殊孔道的形成机制进行了诠释,揭示了气泡模具和氧化物的黏性流动对圆柱形、规则有序孔道的形成的重要影响,展望了电子电流和氧气气泡模具对多孔氧化铝、氧化钛纳米管的制备和结构调控的指导作用。本综述对阳极氧化钛纳米管的制备和机理的深入研究,促进其在光催化和太阳能电池领域的应用有重要的意义。 相似文献
203.
A two-step deterministic secure quantum communication (DSQC) scheme using blocks of three-qubit W state is proposed. In this scheme, the secret messages can be encoded by employing four two-particle unitary operations and directly decoded by utilizing the corresponding measurements in Bell basis or single-particle basis. Comparing with most previous DSQC protocols, the present scheme has a high total efficiency, which comes up to 50%. Apartfrom this, it has still the advantages of high capacity as each W state can carry two bits of secret information, and high intrinsic efficiency because almost all the instances are useful. Furthermore, the security of this communication can be ensured by the decoy particle checking technique and the two-step transmitting idea. 相似文献
204.
On the basis of an implicit iterative method for ill-posed operator equations,we introduce a relaxation factor and a weighted factor , and obtain a stationarytwo-step implicit iterative method. The range of the factors which guarantee theconvergence of iteration is explored.We also study the convergence properties and ratesfor both non-perturbed andperturbed equations.An implementable algorithm is presented by using Morozov discrepancy principle.The theoretical results show that the convergence rates of the new methods always lead to optimal convergentrates which are superior to those of the original one after choosing suitable relaxation and weightedfactors. Numerical examplesare also given, which coincide well with the theoretical results. 相似文献
205.
206.
两步共振光电离中的动力学过程分析 总被引:2,自引:1,他引:1
利用密度矩阵方程和麦克斯韦方程耦合,探讨了光学厚样品中两步共振光电离的物理机制,利用数值求解分析了有关原子及脉冲参量对分离效率的影响,给出了优化实验方案的一些限制条件,并对多脉冲相干类孤立子(Simulton)现象进行了初步讨论。 相似文献
207.
本文阐述了全息、散斑、云纹干涉法与Moiré几何理论的相似规律,用Moiré几何理论统一解释,比拟全息、散斑、云纹干涉法并给出相应的表达式。一、引言全息、 相似文献
208.
对于两个相依线性回归方程组成的系统(1.1),本文提出了β1的待定系数估计β^*1(k,c)=(x′1x1 k1)^-1(x′1y1-cσ12/σ22x′1N2y2),其中岭参数k≥0.c是待定系数.与β^*1(k,c)对应的非限定两步估计记为β^41(T,k,c).当c=1时β^*1(k,1)=β1(k)和β^*1(T,k,1)=β1(T,k)等干[6]引入的一双有偏估计,结果表明总可以选取适当的c值和k值使β^*1(k,c)和β^*1(T,k,c)在均方误差阵准则下分别优于β1和β1(T),并讨论了c值的最佳选择问题. 相似文献
209.
In Ref. 1, Nocedal and Overton proposed a two-sided projected Hessian updating technique for equality constrained optimization problems. Although local two-step Q-superlinear rate was proved, its global convergence is not assured. In this paper, we suggest a trust-region-type, two-sided, projected quasi-Newton method, which preserves the local two-step superlinear convergence of the original algorithm and also ensures global convergence. The subproblem that we propose is as simple as the one often used when solving unconstrained optimization problems by trust-region strategies and therefore is easy to implement.This research was supported in part by the National Natural Science Foundation of China. 相似文献
210.