基于RBF神经网络的磨矿粒度软测量模型及实现

磨矿分级作业是选矿生产中的重要环节,磨矿粒度的好坏直接影响浮选的精矿品位和尾矿回收率;在实际生产中粒度的测量有在线粒度分析仪,但存在成本高、维修率高,离线实验室化验又有时间延迟大的问题;对实际磨矿分级作业过程进行了分析,提出用径向基函数(RBF)神经网络建立磨矿粒度软测量模型,采用正交最小二乘法(OLS)算法对网络进行训练学习,泛化校验;仿真结果表明,在较少训练数据下该网络非线性处理能力和逼近能力依然很强,学习时间短,模型基本符合要求;通过OPC技术将Matlab与PKS控制系统相结合,实现实时软测量磨矿粒度。     

铝粉度对自蔓延高温合成AlB2-Al2O3复合粉体的影响

以金属Al粉和B2O3粉为原料,采用自蔓延高温合成法(SHS)制备AlB2-Al2O3复合粉体.采用X射线衍射仪、扫描电镜和能谱仪分析手段,对所制得的复合粉体进行了表征.研究了Al粉粒度(100目、300目和600目)对自蔓延高温合成方法制备AlB2-Al2O3复合粉体的燃烧学、相组成及微观结构的影响.结果表明:铝粉粒度越小,燃烧温度越高、燃烧波速度越快,复合粉体中AlB2相含量增加,实验测得600目铝粉反应的燃烧温度为2060K,燃烧波速度为2.08 mm/s.复合粉体以AlB2和Al2O3为主晶相,显微结构为数量较少、粒径约5μm的AlB2粉弥散分布于粒径约2 μm的Al2O3和Al的混合粉中.     

材料颗粒度对粉末药型罩特性的影响

为研究粉末材料的颗粒尺寸及其分布对粉末药型罩特性的影响,以W、Cu粉末为药型罩的主体材料,添加少量Bi粉以增加其流动性,在配比一定的条件下,通过改变各组分的颗粒尺寸,制备了3种药型罩。利用扫描电子显微镜,观察了W、Cu粉末的颗粒形貌,发现W粉的颗粒形状为规则的结晶体,而Cu粉颗粒的形状不规则。对3种药型罩进行了微观结构观察、密度测定、维氏硬度测定以及破甲威力实验。结果表明:在粉末材料特性和配比一定的条件下,减小颗粒尺寸可有效提高粉末药型罩的致密性、密度和破甲威力,但对维氏硬度的影响不明显。     

初始模型对含噪动态光散射数据正则化反演结果的影响

分别采用最小模型矩阵、最平坦模型矩阵、最光滑模型矩阵作为初始化模型,对加入5种不同水平随机噪声的90nm窄单峰、90nm宽单峰和250nm窄单峰、250nm宽单峰颗粒体系的模拟分布进行了正则化反演,并对反演结果进行比较。结果表明:当噪声水平为0时,正则化初始模型的选择对反演结果没有明显影响。随着噪声水平的增加,采用三种初始化模型反演得到的峰值误差和粒度分布误差都随之变大,但采用最平坦模型和最光滑模型反演得到的峰值和粒度分布误差明显小于采用最小初始模型的反演误差。当噪声水平大于0.01时,选择最平坦初始模型获得的粒度分布结果优于采用最光滑初始模型和最小初始模型获得的结果,而采用最光滑初始模型反演得到的峰值优于最平坦初始模型和最小初始模型的反演峰值。因此,采用正则化算法处理含噪动态光散射数据时,为得到最优的粒度分布信息,宜采用最平坦初始模型,若需要获取最准确的峰值信息,则应选择最光滑初始模型。     

Effect of system parameters on the size distributions of hollow nickel microspheres produced by an ultrasound-aided electrical discharge machining process

Ultrasound-aided electric discharge machining（EDM） is an emerging technology for producing hollow nickel microspheres.This technology combines traditional EDM with the cavitation and vibration effects of ultrasound to produce hollow microspheres.In this paper,ultrasound-aided EDM was carried out in a kerosene medium（the working solution）.The effects of various parameters on the sizes of microspheres were investigated using scanning electronic microscopy（SEM）.Smileview software was used to measure the sizes of the microspheres.Originpro software was used for statistical analysis to determine the size distributions of the microspheres.To study the effects of the system parameters on the sizes of the microspheres,we first investigated the necessity of using an ultrasonic wave with EDM.After comparing the experimental results with and without the ultrasonic field,we found that ultrasound-induced cavitation and vibration effects reduced the diameters of the microspheres.We then studied the effects of several electrical parameters,including the arc current,pulse width,and gap voltage,on the sizes of the microspheres at an ultrasound frequency of 40 kHz.Smaller microspheres could be obtained by lowering the arc current,pulse width,and gap voltage.     

Accelerating CFD–DEM simulation of processes with wide particle size distributions

Size-reduction systems have been extensively used in industry for many years. Nevertheless, reliable engineering tools to be used to predict the comminution of particles are scarce. Computational fluid dynamics(CFD)–discrete element model(DEM) numerical simulation may be used to predict such a complex phenomenon and therefore establish a proper design and optimization model for comminution systems.They may also be used to predict attrition in systems where particle attrition is significant. Therefore,empirical comminution functions(which are applicable for any attrition/comminution process), such as:strength distribution, selection, equivalence, breakage, and fatigue, have been integrated into the threedimensional CFD–DEM simulation tool. The main drawback of such a design tool is the long computational time required owing to the large number of particles and the minute time-step required to maintain a steady solution while simulating the flow of particulate materials with very fine particles.The present study developed several methods to accelerate CFD–DEM simulations: reducing the number of operations carried out at the single-particle level, constructing a DEM grid detached from the CFD grid enabling a no binary search, generating a sub-grid within the DEM grid to enable a no binary search for fine particles, and increasing the computational time-step and eliminating the finest particles in the simulation while still tracking their contribution to the process.The total speedup of the simulation process without the elimination of the finest particles was a factor of about 17. The elimination of the finest particles gave additional speedup of a factor of at least 18.Therefore, the simulation of a grinding process can run at least 300 times faster than the conventional method in which a standard no binary search is employed and the smallest particles are tracked.     

粒度分析及粒度标准物质研究进展

综述了当前粒度分析测试方法的研究进展,并简单介绍了各种测试方法的基本原理以及包括美国、欧洲、中国在内的国家和地区在粒度标准物质方面的研究概况。     

一种冲击分离式颗粒浓度测量装置的设计

为测量大气中颗粒物的粒度浓度,本文在传统的冲击采样原理的基础上设计出冲击式分级装置,并对其进行严格定标;运用消光法原理对分级后的样品进行测量,利用反射镜增大光程提高装置测量灵敏度,实现了对大气中0～5μm、5～20μm、15～40μm三个粒径区间的数量密度和质量浓度的准确测量.     

褐煤颗粒表面官能团的分布特征

采用原位傅里叶红外光谱漫反射测试了北皂褐煤在粒度为40—60目、60—80目、80—100目、100—160目和160目—0.1mm的官能团分布特征,对比分析了不同粒度范围内的红外测试谱图。结果表明,粒度在40—60目以后,官能团区域可识别的特征吸收峰基本一致,可识别的官能团主要是醇羟基、多元醇及缔合羟基,甲基亚甲基,不饱和醛、脂肪烃链式饱和羧酸盐、烯烃,以及苯环取代;在160目—0.1mm的粒度范围内,指纹区验证更加准确,谱图峰型峰位以及峰面积更加准确,能够满足定量分析的要求。研究成果对研究煤不同粒度的宏观特性以及红外特征的定性分析具有重要的指导作用。     

Size-dependent coalescence kernel in fertilizer granulation-A comparative study

Granulation is a key process in several industries like pharmaceutical, food, fertilizer, agrochemicals, etc. Population balance modeling has been used extensively for modeling agglomeration in many systems such as crystallization, aerosols, pelletisation, etc. The key parameter is the coalescence kernel, β（ij） which dictates the overall rate of coalescence as well as the effect of granule size on coalescence rate. Adetayo, Litster, Pratsinis, and Ennis （1995） studied fertilizer granulation with a broad size distribution and modeled it with a two-stage kernel. A constant kernel can be applied to those granules which coalesce successfully. The coalescence model gives conditions for two types of coalescence, Type I and II. A twostage kernel, which is necessary to model granule size distribution over a wide size distribution, is applied in the present fluidized bed spray granulation process. The first stage is size-independent and non-inertial regime, and is followed by a size-dependent stage in which collisions between particles are non-random, i.e. inertial regime. The present work is focused on the second stage kernel where the feed particles of volume i and j collide and form final granule ij instead of i ＋j （Adetayo et al., 1995） which gives a wider particle size distribution of granules than proposed earlier.