基于改进粗糙集理论与概率神经网络的变压器故障诊断研究

提出了一种基于改进粗糙集理论与概率神经网络的变压器故障综合诊断方法.利用了粗糙集理论的决策表约简技术,去除冗余信息,并引入可辨识矩阵,更加快速地去除故障冗余属性,减小了约简过程的复杂度.将得到的最小决策表作为改进的概率神经网络的训练样本,提高了PNN的训练速度和诊断的准确率.实例证明,该模型不仅能在信息不完备的情况下进行有效诊断,而且可以提高诊断速率及正判率.     

钻削力数学模型

从最简单的二元直角切削模型出发，根据理论、实验和经验三方面的综合，逐步建立了普通麻花钻钴削灰铸铁的钻削力数学模型，模型包含了钻头几何参数、切削用量、工件材料及钻头磨损各方因素，并经实验验证，证明其理论值与实验值基本吻合。     

Hydrodynamics of gas-solid flow around immersed tubes in bubbling fluidized beds

A numerical study was conducted based on the gas-solid two-fluid model using the body-fitted coordinate system to analyze the behavior of particles and bubbles flow in bubbling fluidized beds without and with immersed tubes. The kinetic theory of granular flow was implemented in the model. The images of simulated instantaneous particle concentration and velocity gave the process of the formation, coalescence and eruption of bubbles. The effects of the tube pitch and superficial gas velocity on the fluidization in a bubbling fluidized bed were investigated. Calculated bubble frequencies without and with immersed tubes were in agreement with previous experimental and simulation findings. The wavelet multi-resolution analysis was used to analyze the simulated data of instantaneous particle concentration. From the random-like particle concentration fluctuations, the fluctuating components due to particle flow and bubble motion can be extracted based on the wavelet multi-resolution analysis over a time-frequency plane.     

喷动床内气固两相流体动力行为的数值模拟

引　言喷动床被广泛应用于不同工业领域中 ,如石油裂解反应 -再生器、煤和农业废弃物气化和燃烧 ,喷动床还被应用于粮食和药品的干燥等[1] .因此 ,喷动床设计应满足不同应用的要求 .喷动床内气相反应物的反应时间和停留时间依赖于床体几何结构和运行参数 .尽管已有许多的实验对喷动床内气固两相流动进行了研究 ,得到了喷射区、环形区和喷泉区内的气固两相流动流体动力特性 ,然而由于喷动床内气固两相流动的复杂性 ,人们对床体几何结构和运行参数对喷动床动力学的影响至今并不清楚 .因此 ,床体几何结构和运行参数等对喷动床动力学的影响成为…     

Effects of different ionic liquids on the electrospinning of a polyacrylonitrile polymer solution

Additives have been proven to be useful in improving electrospinnability and controlling fiber morphology through the modification of solution properties, including the conductivity, viscosity, and surface tension. In this study, the effects of adding small amounts of four different types of ionic liquids [i.e., 1‐butyl‐3‐methylimidazolium chloride (C₄MIMCl), 1‐dodecyl‐3‐methylimidazolium chloride (C₁₂MIMCl), 1‐ethyl‐3‐methylimidazolium bromide (C₂MIMBr), and 1‐ethyl‐3‐methylimidazolium phosphate (C₂MIM)₃PO₄] on the solution properties, electrospinning process, and characteristics of polyacrylonitrile (PAN) were investigated. The results show that the solution conductivities significantly increased with the addition of different ionic liquids with concentrations varying from 0.1 to 1.0 wt %, and the tendency depended on the structures of the ionic liquids. (C₂MIM)₃PO₄ showed the highest conductivity value; this was followed by C₂MIMBr, C₄MIMCl, and C₁₂MIMCl. The ionic liquids formed visible crystals; this made the fiber surfaces rough, and some fiber segments underwent partial aggregation. A regular varying tendency between the minimum mean diameter of the PAN/ionic liquid fibers and the structure of the ionic liquid was found. The PAN/N,N‐dimethylformamide (DMF)/(C₂MIM)₃PO₄ solution showed the highest conductivity among the four systems with different ionic liquids added, and the thinnest minimum diameter of the PAN/(C₂MIM)₃PO₄ fibers appeared with a relatively low ionic liquid concentration of 0.25 wt %, whereas the PAN/DMF/C₁₂MIMCl solution had the lowest conductivity, and the minimum mean diameter of PAN/C₁₂MIMCl fibers appeared at a relatively high ionic liquid concentration of 0.8 wt %. Although the conductivity of the PAN/DMF/C₂MIMBr solution was higher than that of the PAN/DMF/C₄MIMCl solution, the minimum mean diameters of the PAN/C₂MIMBr and PAN/C₄MIMCl fibers appeared at the same ionic liquid concentration of 0.5 wt % because of the similar ionic activities of C₂MIMBr and C₄MIMCl. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2359–2368, 2013     

乙二醇二乙氨基乙基丁基醚存在下的丁二烯负离子聚合

研究了以乙二醇二乙氨基乙基丁基醚(GABE)为调节剂,正丁基锂为引发剂的丁二烯负离子聚合的聚合动力学及聚合物的微观结构。结果表明,随着GABE用量的增加,丁二烯的聚合速率增加,聚丁二烯中1,2-结构质量分数增加,聚合温度升高,聚合速率增加,但聚丁二烯中1,2-结构质量分数有所降低。     

秸秆黄腐酸包膜尿素在水稻上的应用效果

在石灰性土壤上进行田间小区试验，结果表明，秸秆黄腐酸包膜尿素能满足水稻生长最大效率期对营养的要求，有利于有效穗的分化，提高结实率。等氮量试验平均增产9．6％，等重量试验平均增产7．4％。     

二-(4-羟基丁基)四甲基二硅氧烷的合成研究

采用一步法以二甲基二氯硅烷、四氢呋喃和金属镁粉为原料,在碘乙烷和单质碘催化下合成二-(4-羟基丁基)四甲基二硅氧烷。产物温合物减压过滤,以除去镁盐。滤液无需蒸馏提纯,而直接水解,干燥,减压蒸馏,收集71℃/1333Pa馏份。还探讨和优化合成条件:四氢呋喃与二甲基二氯硅烷之摩尔比应大于3.5;Grignard反应停止后应继续加热回流1小时;蒸馏时系统压力为1333Pa。     

Lattice Boltzmann simulation of alumina-water nanofluid in a square cavity

A lattice Boltzmann model is developed by coupling the density (D2Q9) and the temperature distribution functions with 9-speed to simulate the convection heat transfer utilizing Al₂O₃-water nanofluids in a square cavity. This model is validated by comparing numerical simulation and experimental results over a wide range of Rayleigh numbers. Numerical results show a satisfactory agreement between them. The effects of Rayleigh number and nanoparticle volume fraction on natural convection heat transfer of nanofluid are investigated in this study. Numerical results indicate that the flow and heat transfer characteristics of Al₂O₃-water nanofluid in the square cavity are more sensitive to viscosity than to thermal conductivity.     

复合分散体系苯乙烯悬浮聚合的研究

以磷酸三钙(TCP)/羟乙基纤维素(HEC)为复合分散体系、过氧化二苯甲酰(BPO)为引发剂、水为介质进行苯乙烯(St)的悬浮聚合,考察了复合分散剂的用量与配比、引发剂种类与用量及聚合温度、搅拌速率、水油比、杂质等因素对悬浮聚合的影响,并表征了聚合物相对分子质量及其分布.结果表明:复合分散剂总量占St单体质量的0.24...