Fast and solvent-free microwave-assisted synthesis of thermoresponsive oligo(glycidyl ether)s

Low-molecular weight linear poly(glycidyl ether)s are typically synthesized via the “classical,” oxy-anionic ring-opening polymerization (ROP) of glycidyl ether monomers at elevated temperatures. To reduce reaction times, a fast process was developed to synthesize oligo(glycidyl ether)s (OGEs) in bulk at a gram-scale utilizing microwave heating. Well-defined thermoresponsive copolymers comprising glycidyl methyl ether and ethyl glycidyl ether with molecular weights of up to 3 kDa were synthesized via microwave-assisted ROP with reaction times of approximately 10 min. The fast reaction kinetics were attributed to the rapid and uniform heating and high temperatures reached during the reaction. Consequently, no significant microwave-specific acceleration of the oxy-anionic ROP was observed. The temperature-triggered phase transition of the OGEs in aqueous solution revealed cloud point temperatures that are highly dependent on the OGE molecular weight, concentration, and comonomer composition, which extends previously reported data. Furthermore, oligo(glycidyl ether) acrylates (OGEAs) with reactive, functional end groups were directly accessible via in situ quenching of the anionic, microwave-assisted ROP with acrylic acid chloride. The obtained thermoresponsive OGEA macromonomers represent a promising material for the functionalization of surfaces via radical grafting methods to obtain functional, thermoresponsive coatings with potential application in cell culture. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 2496–2504     

A matrix-free high-order discontinuous Galerkin compressible Navier-Stokes solver: A performance comparison of compressible and incompressible formulations for turbulent incompressible flows

Both compressible and incompressible Navier-Stokes solvers can be used and are used to solve incompressible turbulent flow problems. In the compressible case, the Mach number is then considered as a solver parameter that is set to a small value, M ≈0.1, in order to mimic incompressible flows. This strategy is widely used for high-order discontinuous Galerkin (DG) discretizations of the compressible Navier-Stokes equations. The present work raises the question regarding the computational efficiency of compressible DG solvers as compared to an incompressible formulation. Our contributions to the state of the art are twofold: Firstly, we present a high-performance DG solver for the compressible Navier-Stokes equations based on a highly efficient matrix-free implementation that targets modern cache-based multicore architectures with Flop/Byte ratios significantly larger than 1. The performance results presented in this work focus on the node-level performance, and our results suggest that there is great potential for further performance improvements for current state-of-the-art DG implementations of the compressible Navier-Stokes equations. Secondly, this compressible Navier-Stokes solver is put into perspective by comparing it to an incompressible DG solver that uses the same matrix-free implementation. We discuss algorithmic differences between both solution strategies and present an in-depth numerical investigation of the performance. The considered benchmark test cases are the three-dimensional Taylor-Green vortex problem as a representative of transitional flows and the turbulent channel flow problem as a representative of wall-bounded turbulent flows. The results indicate a clear performance advantage of the incompressible formulation over the compressible one.     

云计算环境下人脸表情智能识别改进技术研究

随着人脸识别技术的开发,对于如何提高人脸表情智能识别改进技术的研究也越来越多;如何提高人脸识别的准确度和完整度是当前发展的主要需要,而计算机云计算功能在人脸识别中的应用在一定程度上解决了此问题;通过改进细菌觅食算法,再将其应用到主要成分分析算法对图像基本特征进行提取分析;通过以上的算法输入计算机网络云储存当中,实现云计算技术在人脸识别中的应用;文章将通过对于算法部署函数的办法进行图片解析工作,并且利用智能人脸识别软件对图像进行抽丝、分类、匹配等工作进行功能状态进行测试;实验结果表明利用云计算技术通过连接网络云计算系统可以对目前的人脸识别以及分类做到更高的准确性和适应性。     

Impact of subgrid fluid turbulence on inertial particles subject to gravity

Two-phase turbulent flows with the dispersed phase in the form of small, spherical particles are increasingly often computed with the large-eddy simulation (LES) of the carrier fluid phase, coupled to the Lagrangian tracking of particles. To enable further model development for LES with inertial particles subject to gravity, we consider direct numerical simulations of homogeneous isotropic turbulence with a large-scale forcing. Simulation results, both without filtering and in the a priori LES setting, are reported and discussed. A full (i.e. a posteriori) LES is also performed with the spectral eddy viscosity. Effects of gravity on the dispersed phase include changes in the average settling velocity due to preferential sweeping, impact on the radial distribution function and radial relative velocity, as well as direction-dependent modification of the particle velocity variance. The filtering of the fluid velocity, performed in spectral space, is shown to have a non-trivial impact on these quantities.     

计算神经科学

计算神经科学是近三十年来出现的一个新兴交叉学科,它强调采用数学定量的方法,如数学建模、理论分析和数值模拟等来研究和解决神经科学中的重要科学问题,一方面神经科学实验现象为发展新的数学模型、理论和算法提供了基础,另一方面通过数学定量,能反过来揭示神经科学实验现象背后的数理机制、发现新的科学规律.随着欧盟、美国、日本和我国脑...     

LBM伪势MRT三维模型GPU并行计算的性能优化

格子Boltzmann方法伪势模型算法中的格点间计算未完全局部化,因此在并行计算时需要更多次的全局内存读写、使用更多数量的寄存器和线程同步操作,从而导致GPU并行计算效率下降.本文针对伪势模型并行计算的局限性,基于三维十五速格子结构的多松弛时间伪势模型,以气液相分离为算例,通过合并访问的方式提高全局内存的读写效率;并提出一种"定向转移"算法,提高格子边界格点获取邻居格点数据的效率;最后探索不同资源分配中各种因素对计算效率的影响,总结最优资源分配的方法.     

液体薄层中的超声空化*

液体薄层中的超声空化,因其边界及所处空间的特殊性,而呈现出非常独特的空化结构和演化行为,在超声清洗、超声钎焊、表面处理、近场声悬浮、超声化学等领域都有所应用。该文梳理了近几年该课题组在液体薄层中的超声空化研究中的一些成果,力图揭示液体薄层内空泡、空化云、空化场的运动和分布规律,及其产生、发展和演化过程,以期对液体薄层中的超声空化行为有一个相对清晰和完整的认识。     

基于实时公交信息的乘客乘车决策研究

实时交通信息的发布使乘客出行更具灵活性.调查乘客对实时公交系统的应用情况及功能需求,并提取乘客乘车决策规则.考虑乘客决策的"有限理性"特征构建决策模型:将乘车舒适性因素转换为时间成本,运用云模型建立定量时间到定性概念的映射;依据出行参考点确,定出行方案的因素权重,建立期望效用函数;构建不同的出行场景,运用决策模型进行出...     

大气云层分布的偏振激光后向散射研究

 利用大气激光后向散射垂直剖面图与消偏振度相结合的方法,分析CALIPSO卫星偏振激光雷达的后向散射信号。以2008年11月23日和24日的CALIPSO卫星数据为例,研究了北京地区大气中云层在可见光和红外光波段的垂直和水平分布特征。利用交互式数据语言IDL(interactive data language)得到大气后向散射强度的垂直分布及其消偏振度,根据垂直剖面图可以直观地观测大气中各成分（如气溶胶、低空云和卷云等）的空间分布情况,并且能清楚地显示大气边界层的高度,由消偏振度可准确获得云层的分布高度及厚度。观测数据的处理结果表明：在海拔高度3 km~7 km存在厚度为2 km~2.5 km的云,其消偏振度约为0.2。