基于能量法的矿柱稳定性分析

能量法因可以避免研究采场结构失稳破坏的中间复杂受力过程,所以受到研究者的青睐. 人工矿柱是地下矿山一种重要的采场结构,由于其失稳破坏过程的应力、应变较复杂,因此从能量守恒的角度对其承载上覆岩体的稳定性进行综合评判和研究. 通过对人工矿柱的受力特性和破坏模式进行分析,建立其力学模型,根据能量守恒原理得出考虑外载荷做功、自重势能和应变能条件下的人工矿柱总能量方程,推导出了人工矿柱势能函数表达式. 基于突变理论知识,构建了在考虑弹性模量、高宽比等参数条件下的人工矿柱能量极限状态方程,根据势函数的稳定判据得出外载荷的临界应力函数关系式,系统讨论和分析了外载荷变化过程对人工矿柱稳定性的影响,定量评判了人工矿柱受外界载荷的影响程度. 最后将所建立的临界应力函数关系式对焦冲金矿人工矿柱尺寸进行优化设计,经现场实测人工矿柱承受载荷约为其理论设计临界载荷的十分之一,达到安全支护规范要求;经过多年的金属矿山现场生产实践,人工矿柱及覆岩都较稳定,能够满足矿山安全生产的需要. 研究结果表明所建立的人工矿柱能量极限状态方程,可为地下金属矿山人工矿柱的合理设计提供理论依据.      

基于规则学习的传统纹样统一生成模式研究

传统纹样的生成是图案生成领域最具代表性的研究方向之一，从传统纹样的构图规则出发生成纹样是最常用的方法之一。以传统纹样为研究对象，针对现有传统纹样生成方法泛化能力差的问题，通过对不同传统纹样进行特征分析，找出其生成规则的异同，提出了一种传统纹样统一生成模式：寓意嵌入的层次迭代生成模式。选取几何纹、动物纹、植物纹中的典型纹样，利用统一生成模式进行重构，验证了模式的有效性。实验结果表明，统一生成模式适合多种传统纹样的重构，一定程度上是对传统纹样重构的创新应用。     

Pattern formation in particle systems driven by color field

The structural evolution of systems with two kinds of particles driven in opposite directions, i.e., driven by a color field, is investigated by molecular dynamics simulations. Gaussian thermostat, a common treatment to restrict the thermal velocity of the particles in the systems, has been used so as to account for the dissipation of heat and allow the system to reach a steady state. It has been found that with the increase of the strength of driving force （F）, the system undergoes an obvious structural transition from an initially random mixing state to a state characterized by separate lanes and in each lane only one kind of particles exists. The analysis shows that the reason for the formation of lane structure is not only the increase of F but also the variation of particle friction coefficient. While using Gaussian thermostat the particle friction coefficient becomes a function of F. Increasing F leads to high particle friction coefficient and inevitably results in lane formation for strong enough driving force. When lifting the effect of F on friction coefficient and choosing a constant friction coefficient, our results show that for a given F there always exists a critical value of friction coefficient higher than which the system will develop into lane structure.     

颗粒物质混合行为的离散单元法研究

颗粒物质的混合是化学工业生产的重要单元操作,由于颗粒物质运动行为的复杂性,工业混合器中的颗粒运动规律及物理机制至今仍未被全面认识。作为一种精细的数值方法,离散单元法(discrete element method,DEM)在单颗粒尺度上描述颗粒物质的受力与运动行为,因此在研究混合机理方面具有独特优势。随着DEM模型与计算技术的快速发展,DEM已被广泛应用于各种混合过程的研究。通过DEM可以全面考察不同的颗粒性质、混合器类型以及操作条件等因素对混合机理的影响,从而对于指导粉体工业的生产操作及设备优化改进具有重要意义。本文重点阐述了DEM在无黏颗粒、黏结性颗粒、非球形颗粒混合过程模拟以及大规模计算等方面的最新进展,并对未来发展进行了展望。     

Singularity analysis of response bifurcation for a coupled pitch–roll ship model with quadratic and cubic nonlinearity

Nonlinear Dynamics - Based on the coupling of roll and pitch motion of ships, a mathematical model with quadratic and cubic nonlinear terms is presented. Primary resonance is discussed by the...     

基于规则学习的传统纹样统一生成模式研究

传统纹样的生成是图案生成领域最具代表性的研究方向之一，从传统纹样的构图规则出发生成纹样是最常用的方法之一。以传统纹样为研究对象，针对现有传统纹样生成方法泛化能力差的问题，通过对不同传统纹样进行特征分析，找出其生成规则的异同，提出了一种传统纹样统一生成模式：寓意嵌入的层次迭代生成模式。选取几何纹、动物纹、植物纹中的典型纹样，利用统一生成模式进行重构，验证了模式的有效性。实验结果表明，统一生成模式适合多种传统纹样的重构，一定程度上是对传统纹样重构的创新应用。     

浅谈质心分数坐标在确定等径圆球密堆积空隙中的应用

理解等径圆球密堆积的性质和特点是学习金属晶体结构和性质的基础,密堆积中的空隙问题对学习和理解离子晶体的结构和性质非常重要。但晶体结构的多样性和复杂性,导致这部分内容成为结构化学课程中讲解和学习的一个难点问题。本文将以A1,A2,A3这三种最常见的密堆积结构为例,详细介绍一种利用质心分数坐标计算推导密堆积结构中四面体和八面体空隙中心的方法,以及如何通过坐标计算求解中心到顶点的距离和中心到堆积球面的最短距离。与立体几何方法相比较,质心分数坐标法不仅更加简洁易学,而且更有助于理解空隙在晶胞中的位置和分布问题。     

Quasi-real-time simulation of rotating drum using discrete element method with parallel GPU computing

Real-time simulation of industrial equipment is a huge challenge nowadays. The high performance and fine-grained parallel computing provided by graphics processing units (GPUs) bring us closer to our goals. In this article, an industrial-scale rotating drum is simulated using simplified discrete element method (DEM) without consideration of the tangential components of contact force and particle rotation. A single GPU is used first to simulate a small model system with about 8000 particles in real-time, and the simulation is then scaled up to industrial scale using more than 200 GPUs in a 1D domain-decomposition parallelization mode. The overall speed is about 1/11 of the real-time. Optimization of the communication part of the parallel GPU codes can speed up the simulation further, indicating that such real-time simulations have not only methodological but also industrial implications in the near future.     

Simultaneous Determination of Levoglucosan,Mannosan and Galactosan at Trace Levels in Snow Samples by GC/MS

A method for the simultaneous determination of levoglucosan, mannosan and galactosan at trace levels in snow samples is reported by using GC/MS. This method is an improvement on previous aerosol studies. The required sample volume for this method is a mere 5.00 mL of melt water. Discrimination of three isomers is analyzed on the basis of different retention time and fragmentation patterns. The limit of detection is 0.070, 0.058 and 0.046 ng mL^?1 ice melt water for three isomers. This method has the advantage of simultaneous determination of three monosaccharide anhydrides at trace concentration levels in small sample volumes. The relatively high extraction efficiency and low limit of detection will facilitate further studies on biomass burning recorded in snow and ice samples.