A weakly compressible MPS method for modeling of open‐boundary free‐surface flow

A mesh‐free particle method, based on the moving particle semi‐implicit (MPS) interaction model, has been developed for the simulation of two‐dimensional open‐boundary free‐surface flows. The incompressibility model in the original MPS has been replaced with a weakly incompressible model. The effect of this replacement on the efficiency and accuracy of the model has been investigated. The new inflow–outflow boundary conditions along with the particle recycling strategy proposed in this study extend the application of the model to open‐boundary problems. The final model is able to simulate open‐boundary free surface flow in cases of large deformation and fragmentation of free surface. The models and proposed algorithms have been validated and applied to sample problems. The results confirm the model's efficiency and accuracy. Copyright © 2009 John Wiley & Sons, Ltd.     

糖基亚苄基NaBH_3 CN-HCl选择性开环过程中乙酰基迁移现象的研究

用NaBH3CN HCl/Et2 O对 3 O 乙酰基 4,6 O 亚苄基 β D 吡喃半乳糖乙硫苷 (2 )进行还原开环 ,发现有乙酰基迁移至 2 位的产物生成 ;进一步的实验表明 ,室温条件下 ,NaBH3CN与 2的作用导致乙酰基的迁移     

Weighted averaged equations for modeling velocity profiles of 1D steady open channel flows

A new mathematical algorithm is proposed to address the essential details of vertical distributions of horizontal velocity for one‐dimensional steady open‐channel flow. This new algorithm comprises a system of weighted averaged equations developed from corresponding Reynolds equations by performing weighted average operations instead of conventional depth average operations. It is the system of weighted averaged equations, instead of the vertical grids, that allows for more hydraulic coefficients identifiable. It can be thought of as an extension of the St. Venant equations to address the vertical distributions of horizontal velocities, as well as the water surface profiles. To avoid the difficult expansion of governing partial differential equations in high order, an indirect scheme is proposed to solve hydraulic variables through their weighted average values. The governing partial differential equations are generated by using a variety of weight functions, and the weighted averages of relevant hydraulic variables are taken as the unknown independent variables to be solved first. Then, on the basis of the values and polynomial expansions of these weighted averaged velocities, a system of linear algebraic equations is generated and the unknown hydraulic variables or their coefficients are easily solved. Note that the new model is not proposed to compete with any three‐dimensional models in modeling accuracy or accommodation ability to all conditions. It just provides a valuable option to study the vertical structure of flow in open channels where only essential detail and reasonable accuracy of vertical distributions are required, and the data availability and other conditions limit the application of fully three‐dimensional models. The performance of the model is evaluated with experimental data of flows in two different flumes. It is shown that the model well predicted the velocity profiles of sections along the centerlines of these flumes with reasonable accuracy and essential details of vertical distributions of horizontal velocity. Copyright © 2013 John Wiley & Sons, Ltd.     

Comparison of non‐reflective boundary conditions for a free‐rising turbulent axisymmetric plume

The stability and accuracy of radiation type non‐reflective outflow boundary conditions, as well as the standard Neumann boundary condition with zero normal derivative, have been compared for the numerical simulation of a turbulent axisymmetric plume with Reynolds number of 7700 and Prandtl number of 0.71. Comparison of the performance of the boundary conditions with respect to each other, and to the results obtained for an extended domain, shows that a one‐dimensional scheme in which advection and diffusion terms are included in the radiation equation is the optimum approach for the plume simulation. Copyright © 2013 John Wiley & Sons, Ltd.     

开源教学平台的可用性研究——以Sakai为例

越来越多的国内外高校开始考虑使用基于开源软件的网络教学平台,在投入使用之前,开源教学平台一般需要进行二次开发过程,其中需要重点解决平台的可用性问题,因为网络教学平台的可用性是影响学习效果的重要因素.发现并解决网络教学环境中的可用性问题,是促进人机交互、提高学习效率的重要途径.开源教学平台的可用性指的是系统的有效性、效率和满意度,分析了网络教学平台的可用性诉求,并以浙江大学Sakai开放学习平台为例,进行个案研究.使用了ThinkAloud、观察法和访谈法等可用性测试方法,研究结果发现,浙江大学Sakai开放学习平台主要功能人机交互设计合理,但是由于文化差异和用户使用习惯问题,部分功能存在一定的可用性问题,值得学习平台设计者借鉴.     

Tuning the frontier molecular orbital energy levels of n‐type conjugated copolymers by using angular‐shaped naphthalene tetracarboxylic diimides,and their use in all‐polymer solar cells with high open‐circuit voltages

An angular‐shaped naphthalene tetracarboxylic diimide (NDI) was designed and synthesized as a new building block for n‐type conjugated polymers to tune their energy levels. Three n‐type copolymers incorporating this angular‐shaped NDI as the acceptor moiety were obtained by Stille coupling reactions and had number average molecular weights of 18.7–73.0 kDa. All‐polymer bulk‐heterojunction solar cells made from blends of these polymers with poly(3‐hexylthiophene) gave a power conversion efficiency up to 0.32% and exhibited an open‐circuit voltage (V_oc) up to 0.94 V due to their relative high‐lying lowest unoccupied molecular orbital energy levels. The high V_oc of 0.94 V is higher than that of solar cells based on linear‐shaped NDI‐containing polymers (<0.6 V). The results indicate that the angular‐shaped NDI is a promising building block for constructing nonfullerene polymer acceptors for solar cells with high open‐circuit voltages. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

人民币汇率变动对我国开放经济中外资流人影响的研究

就人民币汇率变动对我国开放经济外资流入的传导机制进行理论分析,并以高开放地区和行业为代表,结合实际数据利用面板模型进行实证研究,结果表明:人民币汇率与我国开放经济中外资流入呈现反向变动.由于外资对我国开放经济稳定健康发展具有重大意义和影响.因此,我国需保持人民币汇率在中长期稳定,从而避免对外资流入产生大的冲击.