离散化技术在离心泵设计上的应用

论述了采用离散化进行离心泵叶轮轴面投影图设计的两种方法。对轴面投影图设计的正问题－－由前后盖板流线确定轴面投影图的传统的程序设计方法进行了优化;同时着重讨论了由后盖板流线及附加中线方程确定轴面投影的图的一种设计方法－－轴面投影图设计的反问题,采用离散化技术避免了繁琐的内切圆圆心轨迹推导的数学过程,运用高次多项式作为函数,改变多项式的阶数及系数进行优化设计,适用于对汽蚀和效率有不同要求的离心泵设计。     

基于粗集理论的大曲理化指标对白酒质量和产量影响的重要因素分析

运用粗集理论方法对采集到的大曲参数（各理化指标）和用其酿造的白酒质量与产量数据进行了分析,通过对数据进行等间隔离散化处理,得到大曲理化指标与白酒质量和产量的决策表,并用属性重要性方法对决策表进行属性约简,得到了大曲理化指标中影响白酒质量和产量的重要因素。     

Comparison of finite element and finite volume methods for simulation of natural ventilation in greenhouses

This article aims to contribute to the discussion on the efficiency of two different discretization methods used as computational fluid dynamics (CFD) solvers for the simulation of natural ventilation in greenhouses. The focus is not on a general use of CFD, but rather on its specific application to simulate airflow in naturally ventilated greenhouses. After a short review of the basic model and its extensions, we compare the accuracy and computational efficiency of two simulation codes based on the Finite Element Method (FEM) and the Finite Volume Method (FVM) for two-dimensional incompressible turbulent flow in naturally ventilated greenhouses. FVM software (ANSYS/FLUENT v 6.3.) is the most frequently used CFD code in ventilation research, but few papers using FEM software (ANSYS/FLOTRAN v. 11.0) have been published. CFD simulations have been compared to experimental data for 12 cases corresponding to three greenhouse types. The experimental greenhouses were chosen to represent a large range of ventilation situations: buoyancy effect in a mono-span greenhouse with adiabatic walls, buoyancy and wind effect in a multi-span greenhouse and ventilation in an Almería-type greenhouse under conditions of large temperature gradient and high wind speeds. The data from simulations and field experiments were compared using different parameters to analyze the effectiveness of experimental data in the validations of CFD models.The possibility of repeating simulations with different discretization methods and commercial software has been tested, as well as the type of experimental data needed to ensure correct validation of CFD models for use in greenhouse ventilation studies. To this end, temperature distribution measurements are preferable to set-point measurements and the use of visualization techniques (laser sheets) or the measurement of velocity vectors (anemometer) are more indicative than ventilation rates.The computational capacity of these approaches has also been analyzed, comparing their performance in terms of the overall database space necessary to store the numerical models and the necessary CPU time to compute one step of the convergence process. On average, the FEM required twice as much computing time per cell and step as FVM, and the amount of required memory storage was approximately 10 times greater for the FEM.     

多目标优化设计的灰色—混合离散变量寻优算法

根据机械产品对多目标优化设计的更高需求,提出了灰色－混合离散变量多目标寻优算法。此算法把多目标寻优的高维问题简化成低维问题处理,寻优效率高,并且能分析寻优过程的变化态势和利用贫信息作定性分析。此算法不仅注意在启发式搜索技术上有所突破,而且注重跨学科、跨领域新兴寻优技术的最优组合。最后运用工程实例介绍这一算法的应用。