CD++: a toolkit to develop DEVS models

The features of a toolkit for modeling and simulation based on the DEVS formalism are presented. The tool is built as a set of independent software pieces running on different platforms. Not only are the main characteristics of the environment presented, a focus on its use is also considered by inclusion of application examples for a variety of problems. Many models can be defined in an automated fashion, simplifying the construction of new models and easing their verification. The use of this formal approach has allowed the development of safe and cost‐effective simulations, significantly reducing development time. Copyright © 2002 John Wiley & Sons, Ltd.     

Comparison of Lactic Acid Productivities at High Substrate Conversions in a Continuous Two-stage Fermenter With Cell Recycle Using Different Kinetic Models

The steady-state performance of a two-stage recycle fermenter with two different types (I and II) of configurations for staging was investigated numerically for the continuous production of lactic acid. In Type I the bleed broth withdrawn from the first stage is supplied to the second fermenter, and in Type II both filtrate and bleed broth from the first stage are introduced to the second stage. Using four different kinetic models taken from the literature, the effects of operating parameters on the overall lactic acid productivities and the overall substrate conversions are examined. At moderate conversions, productivities for Type I operation are found to be higher than those for Type II and for the single-stage system. In the case of high conversions close to complete consumption, Type II operation is more efficient than the Type I and single-stage systems. For 99% conversion and 40 kg m^-3 substrate feed concentration, productivities for Type II are predicted to be 14-74% higher compared to those for the single-stage system at the same bleed ratios.     

Separating n-alkane mixtures by exploiting differences in the adsorption capacity within cages of CHA, AFX and ERI zeolites

The saturation capacity of n-alkanes in CHA, AFX and ERI zeolites, that consist of cages separated by windows, decreases with increasing carbon number. The major aim of the present communication is to demonstrate the possibility of separating n-alkane mixtures relying on differences in saturation capacities. To investigate this possibility, Configurational-Bias Monte Carlo simulations for adsorption of C3–nC6, nC4–nC6, and nC5–nC6 mixtures in CHA, AFX and ERI were carried out for equimolar bulk fluid phase. These mixture simulations show that for operation at fluid phase fugacities below about 1 MPa, the adsorbed phase in equilibrium with the bulk vapor phase is predominantly the alkane with the longer chain length, i.e. nC6. However, for operation at pressures in excess of 1 MPa, the adsorbed phase in equilibrium with the bulk liquid phase is richer in the component with the smaller chain length. In some cases, the nC6 is practically excluded from the zeolite.     

Vital-Fluorochromization of Microorganisms Using 3′,6′-Diacetylfluorescein to Determine Damages of Cell Membranes and Loss of Metabolic Activity by Ozonation

Cell suspensions of Escherichia coli as a model for bacterial populations in wastewaters were treated with ozone as a disinfectant in a continuously operated pilot plant with a plug flow reactor. Suspensions with an initial number of CFU (colony forming units) of 10⁸ mL^?1 were ozonized with ozone concentrations up to 12 mg/L. Metabolic activities and membrane functions break down with increasing ozone concentrations. The fluorochromization using 3′,6′-diacetylfluorescein (FDA) proved to be a suitable method for the detection of an alteration in permeability of the cell membranes and an inactivation of metabolic activity. By fluorescence microscopic and photometric investigations it could be clearly demonstrated that, in the case of disinfection with ozone, inactivation of the cells includes first of all a damage of the cell membranes. In contrast to the determination of the number of CFU, fluorochromization allows the detection of alteration in metabolic activities.     

人支气管上皮靶细胞形态学参数的测量

支气管上皮靶细胞形态学参数对计算受氡子体照射的支气管的剂量是很重要的。本文介绍利用奥尔新兰-PAS 染色的外科切除人肺组织切片,测量基底细胞粘液细胞和的胞核深度与数目。结果表明,叶、段和小支气管的粘液细胞核深度分别为相应节段基底细胞的61%、69%和73%;此三节段粘液细胞的数目分别为基底细胞的53%、29%和28%,平均为37%。     

Excel的常用函数在单元格中的粘贴要素

以十种函数为例,讨论了在EXCEL电子表格软件中的单元格里粘贴函数的应用要素,即参数的数量、参数的种类、参数之间的关系、函数的书写及粘贴过程等。例举少许易懂函数样例,有助于人们理解、发挥函数功能的强大作用,提高工作效率。     

吸入短寿命氡子体动物肺组织剂量与体重关系的探讨

本文介绍吸入短寿命氡子体的不同种动物肺组织吸收剂量与体重的关系。实验结果表明,吸收剂量随体重的增加而减小。     

Pulse-Width Dependence in Current-Driven Magnetization Reversal Using GaMnAs-Based Double-Barrier Magnetic Tunnel Junction

We have investigated the current pulse width dependence on current-driven magnetization reversal in double-barrier structures using GaMnAs-based magnetic tunneling junctions (MTJ) in order to clarify the origin of low threshold current density for current-driven magnetization reversal. Comparing with the case of single-barrier MTJ, the pulse-width dependence reveals that threshold current density is reduced by double-barrier MTJ. We confirmed that the threshold current density in the order of 10⁴ A/cm² is estimated considering the effect of current pulse width.     

ATM交换机的硬件体系结构探讨

本文首先对ＡＴＭ的背景作了一个简单的介绍，接着阐述了ＡＴＭ和ＡＴＭ交换机的主要原理和技术，然后从硬件系结构的角度具体地分析了一种实验ＡＴＭ交换机是怎样ＡＴＭ技术的详细方法。     

ATM技术浅析

网络通信技术正在迅猛地发展，各种各样的高速通信技术如雨后春笋，其中ＡＴＭ作为一种信元换技术，具有以兆或千兆级速率传送话音、数据和图象的能力，它在网络通信技术中占有特别重要的地位。本文介绍了ＡＴＭ技术的产生、基本特点、体系结构、在ＢＩＳＤＮ中的作用、存在的问题以及发展前景。