Reliability study of super-ellipsoid DEM in representing the packing structure of blast furnace

In industrial blast furnaces (BFs), the investigations involving the flow behaviors of particles and the resultant burden structure are essential to optimize its operation stability and energy consumption. With the advance of computing capability and mathematical model, the discrete element method (DEM) specialized in characterizing particle behavior has manifested its power in the investigation of BFs. In the framework of DEM, many particle models have been developed, but which model is more suitable for simulating the particle behaviors of BFs remains a question because real particles in BFs have large shape and size dispersity. Among these particle models, the super-ellipsoid model possesses the ability to change shape flexibly. Therefore, the focus of this study is to investigate whether the super-ellipsoid model can meet the requirement of authenticity and accuracy in simulating the behaviors of particles with large shape and size dispersity. To answer this question, a simplified BF charging system composed of a hopper and a storage bin is established. The charging process and the final packing structure are analyzed and compared between experiments and simulations with different shape indexes. The results show that super-ellipsoid particles have prominent advantages over spherical particles in terms of representing the real BF particles, and it can more reasonably reproduce the flow behaviors and packing structure of experimental particles. The computation cost of super-ellipsoid particles is also acceptable for engineering applications. Finally, the micro-scale characteristics of packing structure is analyzed and the single-ring charging process in industry-scale BF using super-ellipsoid particles is conducted.     

Steric effects upon transition states of radical addition polymerizations

Transition states (TSs) of radical addition homopolymerization reactions of methyl acrylate, methyl methacrylate, dimethyl itaconate, and N-methyl itaconimide were examined with two-unit radical models using MOPAC (PM3 UHF) semiempirical method. Calculated activation energies (E_as) show good correlations with experimental values. Calculated activation entropies (−ΔS^‡s) are found to be well proportional to E_as. The entropy terms play an important role as well as E_a in radical additions. E_a depends on the angle (θ_rs) between reaction points of radical and of monomer at TS. The bond length between reaction points at TS is constant regardless of monomers studied. The geometries and thermodynamical properties calculated here for TS indicate the importance of steric effects caused by substituted group(s) rather than electronic perturbation energies reported previously. © 1996 John Wiley & Sons, Inc.     

AN EXPLICIT FINITE VOLUME SPATIAL MARCHING METHOD FOR REDUCED NAVIER–STOKES EQUATIONS

This paper develops a spatial marching method for high-speed flows based on a finite volume approach. The method employs the reduced Navier– Stokes equations and a pressure splitting in the streamwise direction based on the Vigneron strategy. For marching from an upstream station to one downstream the modified five-level Runge–Kutta integration scheme due to Jameson and Schmidt is used. In addition, for shock handling and for good convergence properties the method employs a matrix form of the artificial dissipation terms, which has been shown to improve the accuracy of predictions. To achieve a fast rate of convergence, a local time-stepping concept is used. The method retains the time derivative in the governing equations and the solution at every spatial station is obtained in an iterative manner. The developed method is validated against two test cases: (a) supersonic flow past a flat plate; and (b) hypersonic flow past a compression corner involving a strong viscous–inviscid interaction. The computed wall pressure and wall heat transfer coefficients exhibit good general agreement with previous computations by other investigators and with experiments.     

METHOD–OF–LINES SOLUTION OF TIME–DEPENDENT TWO–DIMENSIONAL NAVIER–STOKES EQUATIONS

A novel approach to the development of a code for the solution of the time-dependent two-dimensional Navier–Stokes equations is described. The code involves coupling between the method of lines (MOL) for the solution of partial differential equations and a parabolic algorithm which removes the necessity of iterative solution on pressure and solution of a Poisson-type equation for the pressure. The code is applied to a test problem involving the solution of transient laminar flow in a short pipe for an incompressible Newtonian fluid. Comparisons show that the MOL solutions are in good agreement with the previously reported values. The proposed method described in this paper demonstrates the ease with which the Navier–Stokes equations can be solved in an accurate manner using sophisticated numerical algorithms for the solution of ordinary differential equations (ODEs).     

关于图的同构判定方法的探讨

对于两图的同构的判定方法进行较深入的探讨,给出判定两图同构和判定两图不同构的几种方法,并对其判定方法的优劣进行比较.     

Boussinesq方程行波解的存在性

利用平面动力系统方法的分支理论,研究了Boussinesq方程,通过对Boussinesq方程进行行波变换,得到了相应行波系统的首次积分和平衡点,给出了不同参数条件下的相图,证实了Boussinesq方程存在孤立波解和周期波解。     

基于PI法的门源MS6.4地震前震中附近地震热点图像异常变化研究

基于1980年以来青海省和甘肃省区域地震台网的定位地震目录,分析了研究区最小完备震级,选取空间网格尺度为0.2°×0.2°、地震活动异常学习时间段和预测时间段均为3 a,应用图像信息（PI）法,分析了门源M_S6.4地震发生前震中附近地震热点图像的异常变化过程。结果表明,在2013年1月1日至2016年1月1日的预测时间窗内,冷龙岭断裂和祁连山北缘断裂附近存在明显的地震热点,且地震热点图像颜色偏深,发震概率较高,向前滑动至2014年1月1日至2017年1月1日,2015年1月1日至2018年1月1日和2016年1月1日至2019年1月1日3个预测时间窗,此两断裂附近仍存在地震热点,地震热点图像颜色逐渐由深变浅,而门源M_S6.4地震就落在PI法得到的地震热点内。门源M_S6.4地震前存在明显的地震热点,且地震热点相对集中,地震热点图像颜色由深变浅,震后消失;在祁连山北缘断裂附近,地震热点持续存在,分布较集中,地震热点图像颜色也呈由深变浅的过程。未来需关注祁连山北缘断裂,附近有发生强震的可能。     

转移矩阵法在负折射率介质材料平板波导中的应用研究

利用严格电磁理论,推导出了适用于负折射率介质材料光波导的转移矩阵,分析讨论了转移矩阵的性质和应用.利用转移矩阵方法,推导出导波层为负折射率介质材料、覆盖层和衬底为右手材料的三层对称介质光波导的本征色散方程.用图解法研究了负折射率介质波导中TE波的异常色散特性.在负折射材料介质波导中没有零阶模,最低阶为1阶模,并且有截止频率,只有波导参量满足一定条件的时候才会存在,导模的横向波数可以为实数和纯虚数,而正折射率介质波导导模的横向波数只能为实数.     

基于模糊综合评判的大学数学考核方式改革

独立高校数学课程的开设旨在让学生掌握数学知识的基础上,提高数学应用能力.然而现行的考核方式存在重考试结果,轻学习过程等问题.从传统考核方式入手,指出其不足之处,基于模糊综合评判法建立新型评价体系和数学模型,通过试点运行验证了新的考核方式的可行性、客观性、合理性和科学性.