Partitioning of Selected Anisole and Veratrole Derivatives between Water and Anionic Surfactant Micelles

The UV absorption spectra of six structurally related derivatives of anisole and veratrole, i.e., anisaldehyde, (E)-anethole, estragole, veratraldehyde, methyleugenol and (E)-methylisoeugenol, were recorded at various concentrations of the anionic surfactants, either sodium lauryl sulfate (SLS) or sodium lauryl ether sulfate (SLES) at T = 298 K. In addition, conductivity and density measurements were made for the SLS and SLES solutions to determine the volumetric properties of the studied surfactants. Next, using the W. Al-Soufi, L. Pińeiro and M. Novo model (APN model) including the pseudo-phase model for micellar solubilization, the values of micelle-water partition coefficients for each perfume-surfactant system were determined. In addition, the relations between the molecular structures of the solute and the head group of the surfactant and the value of the micelle-water partition coefficient as well as the octanol-water one were discussed.     

Generalized Hirshfeld Partitioning with Oriented and Promoted ProatomsSCI北大核心CSCD

In this study, we show how to generalize Hirshfeld partitioning methods to possibly include non-spherical proatom densities. While this generalization is numerically challenging(requiring global optimization of a large number of parameters), it is conceptually appealing because it allows the proatoms to be pre-polarized, or even promoted, to a state that more closely resembles the atom in a molecule. This method is based on first characterizing the convex set of proatom densities associated with the degenerate ground states of isolated atoms and atomic ions. The preferred orientation of the proatoms' densities are then obtained by minimizing the information–theoretic distance between the promolecular and molecular densities. If contributions from excited states(and not just degenerate ground states) are included in the convex set, this method can describe promoted atoms. While the procedure is intractable in general, if one includes only atomic states that have differing electron-numbers and/or spins, the variational principle becomes a simple convex optimization with a single unique solution.     

Analytical Solutions for Partitioned Diffusion in Laminates: II. Harmonic Forcing Conditions

The migration of organic compounds in stratified media is of fundamental concern in environmental and chemical engineering research. The diffusive transport of volatile organic compounds through laminate systems is characterized by partitioning, i.e., the development of concentration discontinuities at the interfaces between the individual laminae. If the transport is governed by cyclic transients, the relevant equations can be written in terms of coupled systems of diffusion equations subject to sinusoidal boundary conditions. This paper solves these systems of equations to present new algebraic solutions for propagation of the sinusoidal modes through arbitrary (finite) numbers of contiguous one-dimensional laminae. Both Cartesian and radial coordinate systems are considered. Two independent formulations of the lamina interface matching conditions are considered, corresponding to (1) an instantaneous partitioning model and to (2) a mass-limited partitioning model. It is shown that sinusoidal components of the concentration solutions propagate dispersively throughout the laminates. This is manifested, for example, in changes in shape of concentration pulses as measured at different points in the laminate system. Algorithms for generating exact dispersion relations for partitioning laminates are given, and an experimental technique for studying interfacial dynamics via frequency domain measurements is proposed.     

Dispersion polymerization of styrene in ethanol–water media: Monomer partitioning behavior and locus of polymerization

A simulation model has been developed to predict the partitioning behavior of styrene in dispersion polymerization in ethanol–water mixtures. The composition of both the continuous phase and the dispersed phase are quantitatively estimated throughout the polymerization process. The presence of water in the system causes a considerable increase of the styrene partitioning in favor of the particles. Thus, at 70°C and for an initial composition of ethanol/water/styrene = 63.3/26.9/9.8, the concentration of styrene in the particles is about 4.8 times higher than that in the serum instead of about one in pure ethanol. The higher the polymerization temperature, the lower the styrene concentration in the particles; the higher the initial styrene concentration, the higher the styrene concentration in the particles, whereas the partition coefficient is not largely effected. In contrast, neither the interfacial tension nor the final particle size do significantly alter the simulation results. The predicted data from this model have been successfully applied to clarify the mechanisms involved in dispersion polymerization, in terms of stabilization and of kinetic events. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36 : 325–335, 1998     

Residual Monomer Reduction in Polymer Latex Products by Extraction with Supercritical Carbon Dioxide

Summary: Extraction of residual monomer from a latex product with supercritical carbon dioxide ((sc)CO₂) in a column was studied. Operating conditions were chosen at 35 °C and 100 bar. For reducing the residual styrene level in a polystyrene latex from 10⁴ ppm to 100 ppm and from 10⁴ ppm to 10 ppm, a countercurrent bubble column with latex as continuous and (sc)CO₂ as dispersed phase is suggested. Monomer partitioning was demonstrated to be a key parameter in the equipment design. Monomer transport was found to be governed by the shuttle effect, caused by Brownian motion of the latex to and from the H₂O/CO₂ interface. The drift-flux approach was followed to determine the column flooding conditions. Small column volumes are obtained. (sc)CO₂ is a promising extraction medium for residual monomer reduction in latex products. Performance towards steam stripping is better as the final residual monomer level becomes lower.     

A unified exact method for solving different classes of vehicle routing problems

This paper presents a unified exact method for solving an extended model of the well-known Capacitated Vehicle Routing Problem (CVRP), called the Heterogenous Vehicle Routing Problem (HVRP), where a mixed fleet of vehicles having different capacities, routing and fixed costs is used to supply a set of customers. The HVRP model considered in this paper contains as special cases: the Single Depot CVRP, all variants of the HVRP presented in the literature, the Site-Dependent Vehicle Routing Problem (SDVRP) and the Multi-Depot Vehicle Routing Problem (MDVRP). This paper presents an exact algorithm for the HVRP based on the set partitioning formulation. The exact algorithm uses three types of bounding procedures based on the LP-relaxation and on the Lagrangean relaxation of the mathematical formulation. The bounding procedures allow to reduce the number of variables of the formulation so that the resulting problem can be solved by an integer linear programming solver. Extensive computational results over the main instances from the literature of the different variants of HVRPs, SDVRP and MDVRP show that the proposed lower bound is superior to the ones presented in the literature and that the exact algorithm can solve, for the first time ever, several test instances of all problem types considered.      

一种复杂多边形最大内圆的快速查找算法

任意多边形的最大内圆的快速查找在多个领域有着重要的应用。首先给出了任意多边形的Voronoi图的生成方法,以及基于Voronoi图实现该多边形的最大内圆的寻找算法,在此基础上分别采用中线简化及并行化处理对算法进行了效率方面的改进,并重点研究了矢量数据并行化过程中的数据分配策略,给出了其最优数据划分策略——算法复杂度均衡法。最后对北美阿拉斯加地区的多个湖泊进行了最大内圆的查找实验,相应的实验结果表明,改进的方法能够很大程度地提高最大内圆的查找效率。     

Angle-resolved desorption and removal of surface nitrogen in deNOx

This paper reports on recent progress on angle-resolved desorption leading to structure-sensitive desorption dynamics. The sensitivity is exemplified in NO and N₂O reduction on Pd and Rh surfaces. The energy partitioning in the repulsive desorption of hyper-thermal products into their rotational and translational modes is an indispensable concept to examine the structure of a reaction site from desorbing molecules because it connects the structure of a transition state with each energy of desorbed products. The extent of the energy partitioning will be derived from the desorption-angle dependences of both the rotational and translational energies at each vibrational state. Such energy analysis has never been completed for any thermal reactive desorption. A new type of measurement is thus proposed. Additionally, we discuss the inadequate use of the detailed balance principle in desorption dynamics, which has prevented desorption dynamics from being sensitive to surface structures.     

基于改进图划分的异构并行计算模型设计

为了实现大规模计算机集群上的高效分布式并行计算,设计了一种基于改进图划分和量子遗传算法的异构节点并行计算模型;首先,介绍了传统图划分模型并分析了其不足,然后从图的有向性、通信开销计算和负载均衡度等方面对传统的图划分模型进行了改进,从而得到一个改进的图划分模型;最后,以最小化通信开销和优化资源负载均衡为目标,通过设计编码方案,在改进的图划分模型上提出了采用量子遗传算法获取最优任务划分方案的最优解;仿真实验表明:文中方法能有效实现任务的并行计算,与其它方法相比,具有较小的通信开销和较好的负载均衡度,具有很强的可行性。