Comparative Hydrodynamic Analysis of Narrow and Pilot‐Scale Bubble Columns with Internals

For a stable operation of exothermic processes in bubble column reactors, an appropriate heat control is required, e.g., through dense internal tube bundle heat exchangers. Their impact on hydrodynamic characteristics and scaling approaches is studied for columns of different scales. Two different column dimensions (DN100 and DN400) were equipped with two common tube patterns of triangular and square pitches to study local fluid dynamics. Based on geometrical tube bundle scaling quantities, hydrodynamic similarity as a scale‐up criterion with respect to average holdups, phase distributions, and local gas structures can be reached.     

Characterization of a Modular,Scalable Millistructured Plate Reactor

Micro‐ and millistructured reactors offer significant advantages compared to conventional reactors, e.g., in terms of heat and mass transfer as well as safety. For the substitution of larger batch reactors by continuously operated millireactors a comprehensive reactor characterization is required. The heat transfer and hydrodynamics of the millistructured plate reactor PR37 are studied. The meandering of the process channel and its periodically changing cross‐sectional area increase the heat transfer significantly and lead to a dependency of the heat transfer coefficient on the Reynolds and Prandtl number that is not found in straight channels at Reynolds numbers below 2300.     

数字式称重传感器与8530D称重显示表的应用

由于汽车载重能力的提高，西林钢铁公司2004年新建一台120t汽车衡。它是由先进的数字称重传感器与8530D称重显示表组成的，它克服了传统的模拟称重传感器的多点不足，大大减轻了检斤及维护工作。     

MA-AA-AM三元共聚物的阻垢性能

以马来酸酐(MA)、丙烯酸(AA)和丙烯酰胺(AM)为原料,在水相中聚合制备三元共聚物PMAA,从因素效应方面综合研究其阻垢性能。实验表明,PMAA对温度有较宽的适应范围,在中酸性和弱碱性条件下能较好地发挥阻垢性能,在高浓缩倍数下亦有良好的阻垢效果。在水样pH=7,温度为80℃,阻垢剂PMAA质量浓度为6mg/L时,恒温10 h,对碳酸钙阻垢率为97.38%,对磷酸钙阻垢率为85.69%;PMAA质量浓度为12 mg/L,对碳酸钙阻垢率可达100%,对磷酸钙阻垢率亦能达96.5%以上。     

含膦酰基的MA—AA—AM—SMAS四元共聚物阻垢剂的制备

以马来酸酐(MA)、丙烯酸(AA)、丙烯酰胺(AM)、甲代烯丙基磺酸钠(SMAS)等为原料,以过氧化氢为引发剂,通过水溶液聚合反应和膦酰化反应合成四元共聚物阻垢剂MA-AA-AM-SMAS(PMAAS),并分别探讨了四元共聚物制备和膦酰化反应最佳条件。实验结果表明,四元共聚物最佳制备条件为:n(MA)/n(AA)/n(AM)/n(SMAS)=11∶1.5∶1.0∶1.0,引发剂质量为单体总质量的15%,反应温度为90℃,反应时间为4 h;膦酰化反应的最佳反应条件为:甲醛质量为共聚物总质量的5.0%,亚磷酸质量为共聚物总质量的3.5%,反应温度为90℃,反应时间为2 h。在上述条件下,PMAAS质量浓度为7 mg.L-1时,对CaCO3阻垢率可达99%,对CaSO4阻垢率达88.5%。经红外光谱分析结果表明,四元共聚物阻垢剂PMAAS中含有羧基、膦酰基、磺酸基等官能团。     

浅谈制造业规模化定制要点及解决难题的方案

技术创新、产品特色、市场占比、利润率、资本运作、竞争优势……这些是所有企业家都关心的话题,但是,关于制造企业管理模式转变的话题,尤其值得探讨,这就是"规模化定制(Mass Customization,MC)"。     

指针不平衡对扭簧比较仪示值误差的影响

本文对目前在国内尚存在争议、但在制造和使用中感到困惑而亟待解决的“扭簧比较仪指针不平衡对其在不同安装位置下使用时示值误差的影响”进行了全面的分析与计算.在此基础上对现行国家检定规程对JJG118—86规定的不平衡指标值及检定方法进行了探讨,提出了相应建议.本文提出的分析方法和由此得出的相关结论也适用于其它结构相近的指针式仪表.     

Image enhancement using a human visual system model

In this paper we report the result of a set of computer experiments carried out to enhance digital images. We use a special line weight function (LWF) which is a combination of zero- and second-order Hermite functions. We are motivated by the physiological evidence reported in R. A. Young, Spatial Vision 2(4), 273–293 (1987), that visual receptive fields are shaped like the sum of a Gaussian function and its Laplacian. This function can also be derived mathematically when the contrast sensitivity experiments in psychophysics are posed as an eigenvalue problem (A. L. Stewart and R. Pinkham, Biol. Cybernetics 64, 373–379 (1991). Analyses of the edge location error show that the proposed function has extremely good localization capability (i.e. the points marked by the operator is as close as possible to the center of the true edge). We also show that the LWF does not detect phantom edges which do not correspond to significant image intensity changes.     

Non-linear properties of conditional returns under scale mixtures

This article provides a framework for analyzing multifactor financial returns that violate the Gaussian distributional assumption. Analytical expressions are provided for the non-linear regression equation and its prediction error (heteroscedasticity) by modeling the returns of financial assets as scale mixtures of the multivariate normal distribution. The expressions involve conditional moments of the mixing variable. These conditional moments are explicitly derived when the mixing variable belongs to the generalized inverse Gaussian family, of which gamma, inverse gamma and the inverse Gaussian distributions are distinguished members. The derived expressions are non-linear in the parameters and involve the modified Bessel function of the third kind. The effects of the non-linear model, in terms of both the regression equation and heteroscedasticity against the corresponding values for the standard linear regression model, are captured through simulations for the gamma, inverse gamma and inverse Gaussian distributions. The proposed scale mixture models extend the well-known arbitrage pricing theory (APT) in financial modeling to non-Gaussian cases. The methodology is applied to analyze the intra-day log returns quarterly data for DELL and COKE regressed against S&P 500 for the years 1998-2000.     

基于尺度滤波与小波去噪的PID继电整定

针对PID参数继电整定法存在继电环节对噪声敏感和受噪声污染的输出波形无法提取出特征参数等缺陷,提出一种利用小波技术的解决方法.该方法以尺度函数为低通滤波器在线滤除反馈信号中的高频干扰,并用小波阈值去噪法离线去除输出波形中的噪声,恢复真实波形以提取出精确的特征参数.从理论上证明了尺度滤波与小波去噪的正确性,并给出了实用算法.仿真实例验证了该方法的有效性.