Computer simulation of morphology and packing behaviour of irregular particles, for predicting apparent powder densities

This paper describes a methodology for prediction of powder packing densities which employs a new approach, designated as random sphere construction (RSC), for modelling the shape of irregular particles such as those produced by water atomization of iron. The approach involves modelling an irregular particle as a sphere which incorporates smaller corner spheres located randomly at its surface. The RSC modelling technique has been combined with a previously developed particle packing algorithm (the random build algorithm), to provide a computer simulation of irregular particle packings. Analysis of the simulation output data has allowed relationships to be established between the particle modelling parameters employed by the RSC algorithm, and the density of the simulated packings. One such parameter is η, which is the number of corner spheres per particle. A relationship was established between η (which was found to have a profound influence on packing density), and the fractional density of the packing, fd. Vision system techniques were used to measure the irregularity of the simulated particles, and this was also related to η. These two relationships were then combined to provide a plot of fractional density for a simulated packing against irregularity of the simulated particles. A comparison was made of these simulated packing densities and observed particle packing densities for irregular particles, and a correlation coefficient of 0.96 was obtained. This relatively good correlation indicates that the models developed are able to realistically simulate packing densities for irregular particles. There are a considerable number of potential applications for such a model in powder metallurgy (PM), process control. In combination with on-line particle image analysis, the model could be used to automatically predict powder densities from particle morphology.     

有约束随动系统控制策略研究

提出了一种新的有约束的复杂随动系统--小碗摆球系统,并针对该系统利用达朗伯静力学的方法进行了建模。在讨论了系统能控和能观性的基础上分别采用状态反馈的极点配置法和基于遗传算法的LQR最优控制2种方法进行了实际系统控制效果的实验对比,通过对比可知极点配置的状态反馈控制器具有更好的鲁棒性和瞬态特性,而遗传算法优化的LQR控制具有更好的稳态特性,以及更短的调节时间。同时在参数选择方面相比于极点配置试特征值的方法,遗传算法优化LQR控制控制器更有针对性,便于实际的应用操作。     

采用遗传算法直接获取模糊控制器的查询表

在实际应用中,模糊控制器常常被转化为一个查询表,以减小实时运行中的计算量。这样的查询表仍然能够保留原模糊控制器的性能特征,但另一方面这个查询表是如何获得的对控制器来说并不是本质的,控制器的性能只取决于查询表本身。这样,在模糊控制器的结构下采用其他方法直接生成这种查询表,或许能够比采用模糊逻辑的方法更为有效。本文给出了采用遗传算法直接搜索查询表的方法,以获取性能优良的控制器,给出了查询表式下二队控制     

Solution of a Groundwater Control Problem with Implicit Filtering

In this paper we describe the application of a parallel implementation of the implicit filtering algorithm to a control problem from hydrology. We seek to control the temperature at a group of drinking water wells by placing barrier wells between the drinking water wells and a well that injects heated water from an industrial site.     

洁净系统中激光诱导颗粒污染物的分析与评估

高功率激光系统要求在洁净环境中运行,若光学元件表面在工作过程中附着污染物,将导致光学元件的损伤及整个系统负载能力的下降。针对洁净系统中激光与材料作用而产生的颗粒物,分析其作用机制,探讨用于评估的理论依据,讨论测量的需求和方法,并对系统表面存在的颗粒污染物进行了实际测量分析,提出了深入开展高功率激光系统中颗粒污染物测量与评估的技术途径。     

Developments in the tools for the investigation of mixing in particulate systems – A review

Mixing of powders and granular materials of different functions and/or properties is frequently encountered by engineers and scientists. Nevertheless, the guidelines for the selections of particle mixers are still not fully developed and predictions of the mixture quality after mixing operations are still not possible. These are largely due to the fact that the tools for particle mixing studies are far from well developed. In the last decades, advances in experimental and computational methods have brought lights to better particle mixer design and operation. This paper reviews the tools for the investigation of mixing in particulate systems.     

含反馈时滞的非线性动力系统参数辨识

以方程残差作为目标函数,运用基因遗传算法同时辨识受控系统的反馈时滞和物理参数。由于遗传算法具备良好的全局特性,且不要求目标函数光滑,该方法既适于线性系统的辨识也适于非线性系统的时滞辨识,方法中引入几种交叉和变异算子同时操作,大大提高了辨识效率和辨识精度,当需辨识参数过多时,可先用开环实验辨识部分系统参数,再用闭环实验辨识时滞和剩余的系统参数。     

Theoretical Explanation of Observed Decreasing Failure Rate

Pooled data on the times of successive failures of the air conditioning system of a fleet of jet airplanes seemed to indicate that the life distribution had a decreasing failure rate. More refined analysis showed that the failure distribution for each airplane separately was exponential, but with a different failure rate. Using the theorem that a mixture of distributions each having a non-increasing failure rate (e.g., a mixture of exponential distributions) itself has a non-increasing failure rate, the apparent decreasing failure rate of the pooled air-conditioning life distribution was satisfactorily explained. The present study has implications in other areas where an observed decreasing failure rate may well be the result of mixing exponential distributions having different parameters.     

碱性条件下二氧化硅介孔颗粒的形态控制

在碱性条件下,以十六烷基三甲基溴化铵为模板剂,制备出二氧化硅介孔颗粒材料.本文应用TEM和XRD等测试手段研究了pH值、反应温度、前驱体及共溶剂浓度等因素对SiO₂介孔颗粒形态的影响.结果证明,在适当的温度下,通过适当降低前驱体的浓度可以制备出粒径为30-50nm,孔道分布均匀,结构稳定的介孔材料.     

A model for simulating the grinding and classification cyclic system of waste PCBs recycling production line

Crushing and separating technology is widely used in waste printed circuit boards (PCBs) recycling process. A set of automatic line without negative impact to environment for recycling waste PCBs was applied in industry scale. Crushed waste PCBs particles grinding and classification cyclic system is the most important part of the automatic production line, and it decides the efficiency of the whole production line. In this paper, a model for computing the process of the system was established, and matrix analysis method was adopted. The result showed that good agreement can be achieved between the simulation model and the actual production line, and the system is anti-jamming. This model possibly provides a basis for the automatic process control of waste PCBs production line. With this model, many engineering problems can be reduced, such as metals and nonmetals insufficient dissociation, particles over-pulverizing, incomplete comminuting, material plugging and equipment fever.     

Hybridizing a genetic algorithm with an artificial immune system for global optimization

This paper proposes an algorithm based on a model of the immune system to handle constraints of all types (linear, nonlinear, equality, and inequality) in a genetic algorithm used for global optimization. The approach is implemented both in serial and parallel forms, and it is validated using several test functions taken from the specialized literature. Our results indicate that the proposed approach is highly competitive with respect to penalty-based techniques and with respect to other constraint-handling techniques which are considerably more complex to implement.     

Investigating the optimal passive and active vibration controls of adjacent buildings based on performance indices using genetic algorithms

This study proposes the optimal passive and active damper parameters for achieving the best results in seismic response mitigation of coupled buildings connected to each other by dampers. The optimization to minimize the H₂ and H_∞ norms in the performance indices is carried out by genetic algorithms (GAs). The final passive and active damper parameters are checked for adjacent buildings connected to each other under El Centro NS 1940 and Kobe NS 1995 excitations. Using real coded GA in H_∞ norm, the optimal controller gain is obtained by different combinations of the measurement as the feedback for designing the control force between the buildings. The proposed method is more effective than other metaheuristic methods and more feasible, although the control force increased. The results in the active control system show that the response of adjacent buildings is reduced in an efficient manner.     

重庆万达广场商业中心暖通空调设计

介绍了重庆万达广场商业中心的概况、空调冷热源的选择和空调水系统、通风和防排烟及自动控制系统的设计,在满足相关规范和使用要求的前提下,力求节能。     

遗传算法在结构振动主动控制中的应用研究

基于遗传算法，对简支梁振动主动控制的传感器/作动器位置优化问题，提出了一种以结构总储能量小为优化目标的数学模型，并编制了遗传算法软件包Ga205对此模型进行优化计算，结果表明，较之穷举法，用遗传算法解决感器/作动器进行位置优化问题是高效的，同时也是全局收敛的。     

基于GA-ANFIS在石灰矿技术经济系统中的参数优化研究与应用实践

为掌握水泥原料矿山系统中的技术经济参数对矿石成本影响的关联规律性，首先运用自适应模糊神经网络对矿山技术经济系统建模，再用并行遗传算法对模型求解，得到了确保矿石成本最小的各项最优技术经济指标，为提高矿山生产管理与经济效益提供了重要的参考价值。     

一种适用于配料控制的累积量PID算法

配料是材料生产过程的重要环节 ,在一些连续称量配料工艺过程中 ,以往大多通过控制每种物料的瞬时流量来满足工艺要求 ,但往往误差较大 ,给生产带来不良影响。为提高控制精度 ,本文提出了一种累积量控制PID算法 ,并在水泥生料配料控制中进行了实施 ,取得了理想的效果 ,并有很好的推广前景     

二元冰蓄冷系统中的测控系统

随着科学技术飞速的发展,越来越多的领域开始使用自动化控制技术,本文主要介绍了二元冰蓄冷系统的计算机测控系统的开发目的,测控系统界面的特点以及此测控系统的主要功能:即对图形对象进行直观操作,包括系统流程的显示、各测点参数以及数据动态趋势曲线的显示、实验数据的自动采集分析、数据库的管理等.