Modeling of bubble coalescence and disintegration in confined upward two-phase flow

This paper presents the modeling of bubble interaction mechanisms in the two-group interfacial area transport equation (IATE) for confined gas–liquid two-phase flow. The transport equation is applicable to bubbly, cap-turbulent, and churn-turbulent flow regimes. In the two-group IATE, bubbles are categorized into two groups: spherical/distorted bubbles as Group 1 and cap/slug/churn-turbulent bubbles as Group 2. Thus, two sets of equations are used to describe the generation and destruction rates of bubble number density, void fraction, and interfacial area concentration for the two groups of bubbles due to bubble expansion and compression, coalescence and disintegration, and phase change. Five major bubble interaction mechanisms are identified for the gas–liquid two-phase flow of interest, and are analytically modeled as the source/sink terms for the transport equation in the confined flow. These models include both intra-group and inter-group bubble interactions.     

Model evaluation of two-group interfacial area transport equation for confined upward flow

The bubble interaction mechanisms have been analytically modeled in the first paper of this series to provide mechanistic constitutive relations for the two-group interfacial area transport equation (IATE), which was proposed to dynamically solve the interfacial area concentration in the two-fluid model. This paper presents the evaluation approach and results of the two-group IATE based on available experimental data obtained in confined upward flow, namely, 11 data sets in or near bubbly flow and 13 sets in cap-turbulent and churn-turbulent flows. The two-group IATE is evaluated in steady-state, one-dimensional (1D) form. To account for the inter-group bubble transport, the void fraction transport equation for Group-2 bubbles is also used to predict the void fraction for Group-2 bubbles. Agreement between the data and the model predictions is reasonably good and the average relative difference for the total interfacial area concentration between the 24 data sets and predictions is within 7%. The model evaluation demonstrates the capability of the two-group IATE focused on the current confined flow to predict the interfacial area concentration over a wide range of flow regimes.     

MEMS麦克风促进声学设计

现在,消费类电子设备(如:电话、PDA、MP3、DSC、笔记本电脑等)的设计人员不断地为这些产品加入新的功能.这就不断地推动电子设计向以下两个方向发展:器件的高集成度和器件尺寸的减小.在一些设计中,电路板的空间是非常珍贵的,设计人员千方百计地将所有器件的管脚最小化.还有一些设计,超薄是产品的主要特点,因此器件的高度就更为重要.无论是何种情况,设计人员都希望采用自由灵活和使用方便的器件.     

On-line recognition of hand-printed Korean characters

The Korean alphabet is a set of phonetic symbols which are combined to form characters, somewhat in the Chinese style. The phonetic quality of the symbols naturally limits the combinations that are useful, and character formation constraints further limit these combinations. Advantage of this is made in an on-line computer recognition system. Korean characters are entered by means of a graphic tablet, using the standard stroke sequences taught in schools. Recognition is perfect for carefully drawn characters and nearly so for characters written at an unhurried rate, provided the system is tuned to the writer's style.     

Safety climate and injuries: An examination of theoretical and empirical relationships.

Our purpose in this study was to meta-analytically address several theoretical and empirical issues regarding the relationships between safety climate and injuries. First, we distinguished between extant safety climate→injury and injury→safety climate relationships for both organizational and psychological safety climates. Second, we examined several potential moderators of these relationships. Meta-analyses revealed that injuries were more predictive of organizational safety climate than safety climate was predictive of injuries. Additionally, the injury→safety climate relationship was stronger for organizational climate than for psychological climate. Moderator analyses revealed that the degree of content contamination in safety climate measures inflated effects, whereas measurement deficiency attenuated effects. Additionally, moderator analyses showed that as the time period over which injuries were assessed lengthened, the safety climate→injury relationship was attenuated. Supplemental meta-analyses of specific safety climate dimensions also revealed that perceived management commitment to safety is the most robust predictor of occupational injuries. Contrary to expectations, the operationalization of injuries did not meaningfully moderate safety climate–injury relationships. Implications and recommendations for future research and practice are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A gastric acid secretion model

A theory of gastric acid production and self-protection is formulated mathematically and examined for clinical and experimental correlations, implications, and predictions using analytic and numerical techniques. In our model, gastric acid secretion in the stomach, as represented by an archetypal gastron, consists of two chambers, circulatory and luminal, connected by two different regions of ion exchange. The capillary circulation of the gastric mucosa is arranged in arterial-venous arcades which pass from the gastric glands up to the surface epithelial lining of the lumen; therefore the upstream region of the capillary chamber communicates with oxyntic cells, while the downstream region communicates with epithelial cells. Both cell types abut the gastric lumen. Ion currents across the upstream region are calculated from a steady-state oxyntic cell model with active ion transport, while the downstream ion fluxes are (facilitated) diffusion driven or secondarily active. Water transport is considered iso-osmotic. The steady-state model is solved in closed form for low gastric lumen pH. A wide variety of previously performed static and dynamic experiments on ion and CO2 transport in the gastric lumen and gastric blood supply are for the first time correlated with each other for an (at least) semiquantitative test of current concepts of gastric acid secretion and for the purpose of model verification. Agreement with the data is reported with a few outstanding and instructive exceptions. Model predictions and implications are also discussed.     

Interfacial area transport and evaluation of source and sink terms for confined air–water bubbly flow

The interfacial area transport equation applicable to the bubbly flow is presented. The model is evaluated against data acquired by a state-of-the-art miniaturized double-sensor conductivity probe in an adiabatic air–water co-current vertical test loop under atmospheric pressure condition. In general, a good agreement, within the measurement error of ±10%, is observed for a wide range in the bubbly flow regime. The evaluation of the individual particle interaction mechanisms demonstrates the active interactions between the bubbles and highlights the mechanisms playing the dominant role in interfacial area transport. The analysis employing the drift flux model is also performed for the data acquired. Under the given flow conditions, the distribution parameter of 1.076 yields the best fit to the data.     

An epidemic of hemorrhagic fever with renal syndrome in Croatia in 1995

In the spring of 1995, the largest outbreak of hemorrhagic fever with renal syndrome (HFRS) so far was recorded in Croatia. There were 125 patients reported to the National Croatian Institute of Public Health, Department of Epidemiology. The disease occurred simultaneously in several localities, some of them close to the previously known natural foci (Mala Kapela, western Slavonia); the focus on Dinara was newly discovered. War circumstances in Croatia were closely related to this outbreak. There were 50 patients hospitalized in the University Hospital of Infectious Diseases in Zagreb; 5 of them were civilians from Zagreb area and 45 soldiers (Mala Kapela 33, Dinara 7, western Slavonia 5). In all patients the disease was serologically proven (in 6 by indirect immunofluorescence method and in 44 by ELISA-test). Both previously known types of viruses--Hantaan and Puumala were diagnosed in each locality. In general, the illness was more severe in patients with Hantaan virus infection. Two patients died, the illness was severe in 25, moderately severe in 11 and mild in 12 patients. For the first time inflammatory lung changes were recorded in 13 out of 37 (35.1%) patients who were examined by X-ray in the early stage of the disease.     

Superoxide dismutase enhances tolerance of freezing stress in transgenic alfalfa (Medicago sativa L.)

Activated oxygen or oxygen free radicals have been implicated in a number of physiological disorders in plants including freezing injury. Superoxide dismutase (SOD) catalyzes the dismutation of superoxide into O2 and H2O2 and thereby reduces the titer of activated oxygen molecules in the cell. To further examine the relationship between oxidative and freezing stresses, the expression of SOD was modified in transgenic alfalfa (Medicago sativa L.). The Mn-SOD cDNA from Nicotiana plumbaginifolia under the control of the cauliflower mosaic virus 35S promoter was introduced into alfalfa using Agrobacterium tumefaciens-mediated transformation. Two plasmid vectors, pMitSOD and pChlSOD, contained a chimeric Mn-SOD construct with a transit peptide for targeting to the mitochondria or one for targeting to the chloroplast, respectively. The putatively transgenic plants were selected for resistance to kanamycin and screened for neomycin phosphotransferase activity and the presence of an additional Mn-SOD isozyme. Detailed analysis of a set of four selected transformants indicated that some had enhanced SOD activity, increased tolerance to the diphenyl ether herbicide, acifluorfen, and increased regrowth after freezing stress. The F1 progeny of one line, RA3-ChlSOD-30, were analyzed by SOD isozyme activity, by polymerase chain reaction for the Mn-SOD gene, and by polymerase chain reaction for the neo gene. RA3-ChlSOD-30 had three sites of insertion of pChlSOD, but only one gave a functional Mn-SOD isozyme; the other two were apparently partial insertions. The progeny with a functional Mn-SOD transgene had more rapid regrowth following freezing stress than those progeny lacking the functional Mn-SOD transgene, suggesting that Mn-SOD serves a protective role by minimizing oxygen free radical production after freezing stress.     

提升VoIP品质的一种语音处理系统

简介 VoIP(IP电话)是一种使用IP协议为基本架构的语音传输系统.语音信号由此系统进行一连串的取样、压缩、打包,利用IP协议传输到另一个有相同IP协议的系统做反向的动作.VoIP软件提供使用者一个类似传统电话拨号的模式,但是实际上语音的传输完全不经由任何传统式电话的回路架构.除此之外,VoIP还提供所有一切网际网络所能提供的应用,例如:传递档案、程序计算、多方通信与会议、多媒体应用等.