Analysis of supersaturation and nucleation in a moving solution droplet with flowing supercritical carbon dioxide

A supercritical antisolvent (SAS) process is employed for production of solid nanoparticles from atomized droplets of dilute solution in a flowing supercritical carbon dioxide (SC CO₂) stream by attaining extremely high, very rapid, and uniform supersaturation. This is facilitated by a two‐way mass transfer of CO₂ and solvent, to and from the droplet respectively, rendering rapid reduction in equilibrium solubility of the solid solute in the ternary solution. The present work analyses the degree of supersaturation and nucleation kinetics in a single droplet of cholesterol solution in acetone during its flight in a flowing SC CO₂ stream. Both temperature and composition are assumed to be uniform within the droplet, and their variations with time are calculated by balancing the heat and mass transfer fluxes to and from the droplet. The equilibrium solubility of cholesterol with CO₂ dissolution has been predicted as being directly proportional to the Partial Molar Volume Fraction (PMVF) of acetone in the binary (CO₂–acetone) system. The degree of supersaturation has been simulated up to the time required to attain almost zero cholesterol solubility in the droplet for evaluating the rate of nucleation and the size of the stable critical nuclei formed. The effects of process parameters have been analysed in the pressure range of 7.1–35.0 MPa, temperature range of 313–333 K, SC CO₂ flow rate of 0.1136–1.136 mol s^?1, the ratio of the volumetric flow rates of CO₂‐to‐solution in the range of 100–1000, and the initial mole fraction of cholesterol in acetone solution in the range of 0.0025–0.010. The results confirm an extremely high and rapid increase in degree of supersaturation, very high nucleation rates and stable critical nucleus diameter of the order of a nanometre. Copyright © 2005 Society of Chemical Industry     

SAS数据挖掘在冷轧酸洗卷质量缺陷分析中的应用

数据挖掘作为一种发现大量数据中潜在信息的数据分析技术,受到各界的密切关注。SAS数据挖掘技术是众多数据挖掘方法中的佼佼者,它在大型企业中得到很好的应用。本文介绍数据挖掘的背景知识,并利用SAS/EM工具,对该技术在冷轧酸洗卷质量缺陷原因分析作了初步尝试。     

变电站自动化系统时间同步协同攻击的检测与防护方法

为了使攻击的后果最大化,受国家支持的攻击者可以使用时间同步的协同机制发起高度隐蔽的网络攻击,而无须进行通信。这可能会使多个变电站内的所有断路器同时跳闸,从而引发大停电。提出了一种基于时间加速的方法来检测时间同步的协同攻击。在变电站自动化系统年度检修期间,通过逐步加速系统时间来触发时间逻辑,以识别是否存在潜在的恶意软件。此外,还提出了一种基于变电站自动化系统的异步化时间同步管理方法。将根据结构脆弱性指数识别的几个关键变电站的时间保持异步。因此,这些关键变电站将不会与其他变电站一起遭受时间同步的协同攻击,并且可以大大降低相关后果。基于IEEE 39节点系统的数值模拟表明,通过使2个关键变电站保持时间异步,可以显著减少2到3个变电站的协同攻击的负荷损失,并且电网可以具备应对时间同步协同攻击的韧性。     

方位向时变非均匀采样的合成孔径声纳成像

采用多接收阵技术能够使合成孔径声纳的测绘速率和测绘带同时得到提高,但带来了方位向非均匀采样以及不满足停走停假设的问题.本文建立了高测绘速率、宽测绘带条件下不做停走停近似的多接收阵合成孔径声纳信号模型,采用频域方法对合成孔径声纳时变的非均匀方位向信号进行了重构,并导出了重构方法的快速算法.重构方法解决了高测绘速率、宽测绘带条件下的偏移及散焦问题.仿真和实验验证了该方法的可行性.     

SAS判别分析在商业银行信用风险评估中的应用

针对我国商业银行传统客户风险评级体系现有的缺陷,介绍了如何把SAS判别分析方法应用于商业银行的客户信用风险评估,并进行验证分析,结果表明,SAS判别分析方法是一种高效,高准确度的评估方法.     

基于整合模式的EMS/SAS监控系统研究与设计

针对IEC61970EMS系统与IEC61850变电站模型的差异,介绍了将两个标准整合集成,以实现通信和信息交互方案。根据CORBA和Web Services各自存在的优缺点,阐述了将CORBA与Web Services整合的设计思想,从而实现监控系统更大范围的应用集成。     

A SAS macro for target dose estimation by reinforced urn processes in phase I clinical trials

The reinforced urn processes (RUPs) approach can estimate the target dose on the basis of the prior distribution function precisely and conveniently without the requirements about the explicit-estimated dose-response curve and the posterior complicated inference. The application of the RUPs approach was not discussed from the perspective of phase I clinical trial in the previous studies which just focused on the theory and methodology. And the modification of the traditional RUPs design should be considered for the purposes of ethnics and efficiency. A SAS macro was designed to explore the appropriate parameter settings according to the simulation outcomes in different situations and apply the RUPs approach for two state processes in phase I clinical trail with the modified RUPs design. The posterior estimation can be obtained precisely and efficiently with application of SAS program following the appropriate workflow and determination rule which were described in the example.     

A SAS(®) macro implementation of a multiple comparison post hoc test for a Kruskal-Wallis analysis

The Kruskal-Wallis (KW) nonparametric analysis of variance is often used instead of a standard one-way ANOVA when data are from a suspected non-normal population. The KW omnibus procedure tests for some differences between groups, but provides no specific post hoc pair wise comparisons. This paper provides a SAS^® macro implementation of a multiple comparison test based on significant Kruskal-Wallis results from the SAS NPAR1WAY procedure. The implementation is designed for up to 20 groups at a user-specified alpha significance level. A Monte-Carlo simulation compared this nonparametric procedure to commonly used parametric multiple comparison tests.     

TPOs研究中的多赫勒均匀网法案例分析

西班牙研究者M．A．Lopez-Manchado和M．Arroyo在聚烯烃热塑性弹性体(佻)研究中应用多赫勒均匀网法(an uniform net of Doehlert)。这种TPOs是一种以共混物PP／(乙烯-辛烯共聚物)为基质、用PET短纤维补强的三元复合物。多赫勒均匀网法是一种国内未见应用的试验设计方法。他们应用多赫勒均匀网法设计试验方案，求得复合物的拉伸模量等4项力学性能与组分变量PP和PET纤维用量之间关系的响应方程式。笔者从研究者的论文提取一个二变量的多赫勒均匀网法在TPOs研究中应用的案例，并说明和评议多赫勒均匀网法和试验设计的全过程；特别是利用原著提供的基本试验数据进行逐步回归分析。讨论应用回归方程式应注意的几个基本问题和指出原著响应方程式存在的问题。     

Numerical investigation of drag force on flow through circular array of cylinders

A 2-D model for flow through a circular patch with an array of vertical circular cylinders in a channel is established using the Navier-Stokes equations with a hybrid RANS/LES turbulence model–the Scale Adaptive Simulation (SAS) model. The applicability of the model is first validated by test cases where experimental data are available for comparison with the computed results. It is verified that the present model can predict well the average velocity and turbulence structure. The drag force and drag coefficient are then calculated using the present model for a number of cases with different solid volume fractions, cylinder Reynolds numbers and patch diameters. It is shown that the drag coefficient increases with increasing solid volume fraction, but decreases with increasing Reynolds number. However, the drag coefficient is independent of the diameter of circular batch when the solid volume fraction and Reynolds number are kept constant.