Model for oxygen transfer in rotating biological contactor

Rotating biological contactor is being widely used for wastewater treatment but there is an apparent lack of knowledge about the rate at which oxygen transfer occurs, in physical and biological system. In this study the transfer of oxygen from air to water by a rotating disc air-liquid contactor in physical system is investigated. The oxygen transfer model suggested by Kim and Molof, Water Sci. Technol. 14 (1982) 569, was modified and the developed model is termed as modified Kim and Molof model. The model was calibrated by using available data in literature and validated by experiments conducted in this study. The effect of significant physical parameters was integrated into a single term and is termed as volume renewal number. The modified Kim and Molof model was compared with the other available models. The coefficient of determination (R(2)) for the modified Kim and Molof model obtained is 0.95 which is much higher than in the other available models. Thereby the model is expected to estimate oxygen transfer more accurately. Further, a simplified linear model between K(L)a and the volume renewal number is proposed. Both modified Kim and Molof and linear model estimate the overall oxygen transfer coefficient (K(L)a) accurately.     

考虑毛管数和非达西效应的凝析气液两相流入动态

近期的大量理论和实验研究发现,高速流动导致的毛管数和非达西效应对近井油气相对渗透率有显著影响,而目前仅仅考虑非达西效应无法准确描述油气真实渗流状态。如何准确理解并考虑这两种效应的影响对于凝析气藏渗流动态分析以及生产动态预测有很重要的意义。本文建立了油气两相渗流的定解问题,得到了拟稳态形式的流入动态方程。在三区渗流机理上,首次综合考虑了毛管数和非达西效应对相对渗透率的影响。实例分析揭示了高速流动下油气相对渗透率变化及油气分布状态新特征。对不同流入动态模型的对比分析表明,本文方法较之现有方法更有助于正确预测生产动态,评估气井产能。     

Fuzzy normal regression model and related neural networks

A fuzzy normal regression model that takes normal fuzzy numbers as its elements for fuzzy sampling points is presented in this paper. This is a continuation of the authors work in the paper [1]. The related fuzzy regression NN system makes the model more flexible in order to accommodate the renewing or refining of the sampling process. The essential ideas of fuzzy regression model and the related neural networks will be explained in a clear manner in this work using an application problem.     

Estimation of particle volume fraction, mass fraction and number density in thermophoretic deposition systems

A method is presented to predict the soot volume fraction in soot-laden gas streams in systems where thermophoresis is the dominant mechanism of particle deposition onto adjoining surfaces. In particular, we considered deposition of silica particles on a circular cylinder in cross-flow to a premix CH₄/O₂ flame, a setup similar to the one used in the outside vapor deposition process used for making optical fibers. Silica particles were produced by introducing SiCl₄ along with the premix gases to the burner and were collected on a cylinder. Heat flux and mass deposition rate measurements on the cylinder were performed and recorded as a function of time. Considering thermophoresis to be the dominant mechanism of particle deposition, a simple theory was developed to establish the relationship between the measured quantities. The theory predicted that the thickness at any given time t was expected to increase linearly with the integral of (integrated from t=0 to t=t), where q^′′(t) is the heat flux. Such a linear relationship was observed for five different reactant flow rates confirming thermophoresis to be the dominant mechanism of particle deposition. Soot volume fraction and soot mass fraction were calculated from the slope of these linear fits and were seen to be in good agreement with the estimates of the soot fraction from light scattering measurements. Based on the light scattering estimates of particle diameter, particle number densities were also estimated.     

HT-6M托卡马克杂质输运行为研究

以HT -6M托卡马克在欧姆加热条件下的氧、碳杂质空间分布的实际测量结果及该装置背景等离子体的具体特征为基础 ,建立起杂质输运分析程序 ,并由此展开模拟分析 .结果表明 ,该装置氧、碳杂质的浓度分别为 5 %ne和 3 %ne(ne为电子密度 ) ,杂质输运行为是反常的 ;扩散系数为 2 0m2 ·s- 1,有效电荷数Zeff接近 4     

In vitro iontophoretic release of lithium chloride and lidocaine hydrochloride from polymer electrolytes

Ionically conducting polymers, frequently known as polymer electrolytes, are potential candidates as hosts for drugs to be delivered iontophoretically. The iontophoretic delivery of lithium or lidocaine from polymer electrolyte films through a cellophane membrane was examined using different delivery current regimes. Thin, mechanically strong, polymer electrolyte films were fabricated from poly(ethylene oxide) (PEO) with lithium chloride or lidocaine hydrochloride. Experiments showed that iontophoretic transport of both lithium chloride and lidocaine hydrochloride might be achieved from these PEO-based films. Cation transport number determinations give values for PEO-based films of about 0.4 for lithium chloride systems and 0.12 for lidocaine hydrochloride systems. The mechanism of transport from these PEO-based polymer electrolyte films allows the delivery of ionic salts such as lithium chloride and lidocaine hydrochloride to be controlled solely by current, thus providing a system that can deliver precise amounts of drug.     

基于LM3914的电平切割细分电路

常规电平切割细分电路的细分数越高,细分电路所需的比较器也越多,会造成电睡结构烦杂,装调困难,这是限制细分数的实际原因。以点／线显示驱动器ＬＭ３９１４替代常规电平切割细分电路中的比较器阵列,可以减少比较器芯片的使用数量,提高电路的集成度,增强系统的可靠性。对ＬＭ３９１４采用级联,还可有效地提高细分电路的细分数。     

任意概率分布的伪随机数研究和实现

非均匀随机数在计算机仿真、信息安全、自动控制等领域有重要应用,但计算机系统中一般只提供均匀分布的随机数。介绍如何通过均匀分布的伪随机数来产生任意概率分布的伪随机数分理论和方法,包括反函数法、变换法和舍选法,并给出了舍选法的具体实现,最后通过实验结果进行检验。     

Summarization of text-based documents with a determination of latent topical sections and information-rich sentences

A method is proposed for use in summarization of text-based documents. By means of the method it is possible to discover latent topical sections and information-rich sentences. The underlying basis of the method — clustering of sentences — is formulated mathematically in the form of a problem of quadratic-type integer programming. An algorithm that makes it possible to determine with specified precision the optimal number of clusters is developed. The synthesis of a neural network is described for the purpose of solving a problem of integer quadratic programming.