New correlation for liquid hold-up of sodium citrate buffer solution in a Raschig ring packed column

Dynamic liquid hold-up was measured with an air/aqueous sodium citrate buffer solution at 20–40 °C, and an air/water system at 23 °C, in a 0.1 m diameter/1 m high glass column covered by a heat-isolating vacuum jacket and packed with 0.012 m nominal size ceramic Raschig rings. The superficial gas velocity range was extended to 1.2 m s⁻¹. Experimental results of this work were compared with literature data, with different correlations and with a general equation. All expressions were found to be unacceptable for the air/buffer system and useable for the air/water system. In the case of the air/buffer solution a new correlation is recommended on the basis of our measured data and literature values.     

级联RTAC系统动态神经网络辨识与分散镇定控制

针对含不确定关联项的级联RTAC系统的镇定控制问题, 提出了一种基于动态神经网络辨识的分散控制方 案. 应用拉格朗日方程建立起了考虑不确定非线性作用力的级联RTAC系统数学模型, 采用动态神经网络实现级 联RTAC系统中不确定关联项的在线辨识, 通过构造含神经网络权值矩阵迹的Lyapunov函数, 证明了辨识误差的一 致有界性. 通过动态神经网络辨识不确定关联项、补偿系统建模误差, 建立级联RTAC系统分层滑模控制算法, 以实 现级联RTAC系统的高精度分散镇定控制. 数值仿真验证了动态神经网络的引入对级联RTAC系统分散镇定控制系 统瞬态幅值抑制、稳态精度提升的效果.     

Photocatalytic oxidation activity of titanium dioxide film enhanced by Mn non-uniform doping

1 Introduction Heterogeneous photocatalysis is an effective technique for reducing the concentration of pollutants at low concentration. It has been demonstrated that almost all organics can be oxidized to generate carbon dioxide, water and simple mineral…     

稀土Er元素对6063合金时效处理的影响

用硬度测试,金相分析,透射电镜分析等方法研究Er元素对轧制后6063合金时效过程中β″相析出的影响,结果表明Er元素的加入对固溶后的合金再结晶晶粒长大有非常明显的抑制作用,适量的Er元素有助于合金力学性能的改善,与合金生成的Al3Er相对合金β″相的析出有促进作用,加快了β″相的析出。     

基于线结构光的水下目标扫描定位方法

当海底环境噪声及声学散射影响比较严重时,声呐方法无法实现高精度的海底探测．因此,设计了一种基于线结构光的扫测系统．激光中心线条纹提取及系统参数快速标定是影响线结构光测扫精度的2大关键问题．在激光中心条纹处理方面,多阈值算法通过采用不同的阈值可以有效地滤除背景噪声,基于极值法的高斯拟合法则对部分激光条纹采用高斯函数进行拟合,结合多阈值算法和基于极值法的高斯拟合法提出了一个条纹中心线提取算法．该算法在保留多阈值法快速性的同时,又具备高斯拟合法的准确性．而在系统参数标定方面,提出了一种共线点的快速标定法,设计的平面标定靶只需通过确定3个共线的特征点即可快速实现系统参数的标定和高精度的海底快速测扫．最后,在水池中进行了模型实验,验证了该方法的可行性和有效性．     

Conjugate free convection above a cooled finite horizontal flat plate embedded in a porous medium

We investigate conjugate free convection in a semi-infinite porous medium above a cold finite plate. Numerical solutions of the coupled governing equations for the fluid and the plate regions are obtained, and an analytical method is developed to predict the average temperature of the conjugate boundary and the Nusselt number.     

Studies on phytohormones,vitamins and mineral element requirements of Lentinus subnudus (Berk) and schizophyllum commune (Fr. Ex. Fr) from Nigeria

The effects of phytohormones, vitamins and mineral elements on growth of Lentinus subnudus (Berk) and Schizophyllum commune (Fr. ex Fr), two Nigerian edible mushrooms, were studied. Among the phytohormones tested, 1.0 ppm of 2,4 D stimulated the best growth in L. subnudus, followed by 0.1 ppm of GA3. As for S. commune, 10.0 ppm of 2, 4 D enhanced the best growth while 1.0 ppm of GA3 was the second best. The least stimulatory hormone for the two mushrooms was GA3 at 20.0 ppm concentration. Among the vitamins, biotin was the most utilizable for L. subnudus, followed in order by thiamine and folic acid. Pyridoxine promoted best growth for S. commune while the poorest growth was supported by pantothenic acid. In both higher fungi, macroelements (Mg, K and Ca) promoted good mycelial growth but Na was least utilised. Similarly, trace elements (Zn, Fe and Mn) also supported growth to a significant level (P=0.01). The implication of the obtained results are discussed in relation to the cultivation of L. subnudus and S. commune in Nigeria.     

A framework for risk-informed decision support in electricity distribution companies utilizing input from quantitative risk assessment

Electricity distribution companies are to an increasing extent using risk assessment methods in their asset management practices. This paper presents an overall framework for risk-informed decision sup-port where simplified risk analysis methods are used for initial risk assessment, and quantitative risk analysis methods are used to perform more in-depth studies for selected problems. Quantitative risk assessment methods are far more laborious compared to simplified analyses, so it is important that such analyses are performed only to a limited number of risk problems.     

Ship roll damping control

The technical feasibility of roll motion control devices has been amply demonstrated for over 100 years. Performance, however, can still fall short of expectations because of difficulties associated with control system designs, which have proven to be far from trivial due to fundamental performance limitations and large variations of the spectral characteristics of wave-induced roll motion. This tutorial paper presents an account of the development of various ship roll motion control systems together with the challenges associated with their design. It discusses the assessment of performance and the applicability of different mathematical models, and it surveys the control methods that have been implemented and validated with full scale experiments. The paper also presents an outlook on what are believed to be potential areas of research within this topic.     

基于主体参数化分析的潜水器多学科优化

为提高潜水器的综合性能,基于多学科设计优化思想,进行了一型潜水器学科分解,确定了设计参数及总体设计模型的数据传递关系.进行了ABAQUS软件和STAR-CCM+软件的二次开发,设计了结构学科和艇型学科参数化分析流程,实现了主体参数化分析.采用四阶响应面模型建立了艇型学科、结构学科近似模型,对推进器参数进行了拟合,建立了...