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91.
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93.
Robert A. Skutnik Louis Lehmann Sergej Püschel-Schlotthauer George Jackson Martin Schoen 《Molecular physics》2019,117(20):2830-2845
ABSTRACTMonte Carlo simulations in the isothermal-isobaric ensemble are used to investigate the formation of an ordered, biaxial nematic phase in a binary mixture of thermotropic liquid crystals. The orientational dependence of the interaction between molecules of each pure component is the same as in the well-known Maier-Saupe model; each pure component of the mixture is therefore capable of forming a uniaxial nematic phase. For the interaction between molecules of different components, we use the same Maier-Saupe model but change the sign of the coupling constant. As a consequence a T-shaped arrangement of these molecules is energetically favoured. The formation of the biaxial phase occurs in two steps. At higher temperatures T, one of the components forms a uniaxial nematic phase whereas the other is in a quasi two-dimensional restricted isotropic liquid state. We develop a simple theoretical model to understand the high degree of (ostensible) nematic order in the latter. At lower T, the second component becomes nematic and then the entire mixture of the two compounds has biaxial symmetry. The biaxial nematic phase does not demix into domains rich in molecules of one or the other species. 相似文献
94.
由多组分聚合物混合物所形成的多尺度有序结构能够展现出许多新奇的物理化学性质, 从而使其在材料工程领域具有十分重要的潜 在应用价值. 本文通过计算机模拟, 在光敏性不相容三元混合物体系中创建了多尺度有序结构. 通过调节光照区域和掩膜形状, 获得了棋盘形、箭靶状等十分独特的形貌, 并且这些结构可以在实验上通过在适当的时间淬火而稳定较长的时间. 详细探讨了组分比、掩膜宽度、间距以及光照强度对体系的影响, 从而为实现多尺度长程序花样薄膜的制备提供了一个简便的途径, 同时也为纳米器件的制备提供了一定的指导. 相似文献
95.
Rotational viscosity of a liquid crystal mixture: a fully atomistic molecular dynamics study
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Fully atomistic molecular dynamics (MD) simulations at 293, 303 and
313~K have been performed for the four-component liquid crystal
mixture, E7, using the software package Material Studio. Order
parameters and orientational time correlation functions (TCFs) were
calculated from MD trajectories. The rotational viscosity
coefficients (RVCs) of the mixture were calculated using the
Nemtsov--Zakharov and Fialkowski methods based on
statistical-mechanical approaches. Temperature dependences of RVC
and density were discussed in detail. Reasonable agreement between
the simulated and experimental values was found. 相似文献
96.
A new nonlinear three-wave equation of the sixth order for pressure in a polydisperse gas-liquid mixture with bubbles of two
sizes is obtained, and its stationary solutions are analyzed. The equation includes two nonlinear quadratic terms of different
derivative orders. These terms are of fundamental importance for obtaining good correspondence between the solutions to this
equation and the experimentally observed solitary waves in the form of two coupled solitons. 相似文献
97.
Consider the classical nonparametric regression problem yi = f(ti) + ii = 1,...,n where ti = i/n, and i are i.i.d. zero mean normal with variance 2. The aim is to estimate the true function f which is assumed to belong to the smoothness class described by the Besov space B
pq
q
. These are functions belonging to Lp with derivatives up to order s, in Lp sense. The parameter q controls a further finer degree of smoothness. In a Bayesian setting, a prior on B
pq
q
is chosen following Abramovich, Sapatinas and Silverman (1998). We show that the optimal Bayesian estimator of f is then also a.s. in B
pq
q
if the loss function is chosen to be the Besov norm of B
pq
q
. Because it is impossible to compute this optimal Bayesian estimator analytically, we propose a stochastic algorithm based on an approximation of the Bayesian risk and simulated annealing. Some simulations are presented to show that the algorithm performs well and that the new estimator is competitive when compared to the more standard posterior mean. 相似文献
98.
In this work we report theoretical and numerical results on convection in a viscoelastic binary mixture under rotation for realistic rigid-rigid boundary conditions. We focus our analysis in the DNA aqueous suspensions. Instability thresholds for oscillatory convection are calculated. Finally, we analyze the stabilizing effect for the onset of convection. 相似文献
99.
The segmentation of customers on multiple bases is a pervasive problem in marketing research. For example, segmentation service providers partition customers using a variety of demographic and psychographic characteristics, as well as an array of consumption attributes such as brand loyalty, switching behavior, and product/service satisfaction. Unfortunately, the partitions obtained from multiple bases are often not in good agreement with one another, making effective segmentation a difficult managerial task. Therefore, the construction of segments using multiple independent bases often results in a need to establish a partition that represents an amalgamation or consensus of the individual partitions. In this paper, we compare three methods for finding a consensus partition. The first two methods are deterministic, do not use a statistical model in the development of the consensus partition, and are representative of methods used in commercial settings, whereas the third method is based on finite mixture modeling. In a large-scale simulation experiment the finite mixture model yielded better average recovery of holdout (validation) partitions than its non-model-based competitors. This result calls for important changes in the current practice of segmentation service providers that group customers for a variety of managerial goals related to the design and marketing of products and services. 相似文献
100.
We model a call centre as a queueing model with Poisson arrivals having an unknown varying arrival rate. We show how to compute prediction intervals for the arrival rate, and use the Erlang formula for the waiting time to compute the consequences for the occupancy level of the call centre. We compare it to the current practice of using a point estimate of the arrival rate (assumed constant) as forecast. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献