• Journal of Advanced Marine Engineering and Technology
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• v.33 no.2
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• pp.244-251
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• 2009

Porous media have especially large surface area per volume, which contain complex fluid passage. If porous media can be applied to cool a CPU or an electronic device with large heat dissipation, it could result in heat transfer enhancement due to the enlargement of the heat transfer area and the flow disturbance. This study is aimed to identify the heat transfer and pressure drop characteristics of high-porosity metal foams in a horizontal channel. Experiment is performed with the various heat flux, velocity and pore density conditions. Permeabilities, which is deduced from Non-Darcy flow model, become lower with increasing pore density. Nusselt number also decreases with higher pore density. High pore density with same porosity case shows higher pressure loss due to the increase of surface area per unit volume. The fiction factor decreases rapidly with increase of Reynolds number in Darcy flow region. However, it converges to a constant value of the Ergun coefficient in Non-Darcy flow region.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.1159-1165
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• 2009

In the present study, the flow and heat transfer characteristics of a large plate heat exchanger are investigated numerically. The flow passages are very complicated due to the grooved corrugation patterns of the plate surface so that the detailed mesh and the large amount of the computation time have to be required in the numerical simulation for the conjugate heat transfer analysis. In order to accomplish the efficient and fast analysis of the heat transfer characteristics in the plate heat exchanger, a semimicroscopic method using the porous media model has been investigated numerically. The results showed that the characteristics of the heat transfer and pressure drop, which are respectively presented with Colburn j-factor and Fanning f-factor, are in a good agreement between the detailed mesh and the porous media model. The results of the present study could be applicable to the numerical analysis of entire flow passages in the large plate heat exchanger using porous media treatment.

• The Transactions of the Korea Information Processing Society
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• v.7 no.10
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• pp.3195-3200
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• 2000

this paper is a stucy onthe preductionof multi-media traffic flow for the realizationof optimum ATM congestion control. In ATM network it is expected that the characteristic of multi-media traffic flow is varied slowly with a time. Fjor the simulation, time-variable multi-media traffic is penerated using possion distribution(connect calls per process time).\, gamma distribution(transmission rate per a call) and exponential distribution(holding time per a call). And using back-propagation neural netwok and proposed tripple neural network, the simulation to predict generaed traffic is executed. From the result,it's capability is shown that the proposed neural network model can be used in the predictionof ATM traffic flow.

• Journal of Environmental Health Sciences
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• v.35 no.1
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• pp.64-70
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• 2009

The aims of this study is to examine the effects of the changes in HRT(Hydraulic Retention Time) and media charge in a water-mill, among other operation factors, on the nitrogen and phosphorus removal in order to use up-flow anaerobic reactors, anoxic reactors and water-mill aerobic reactors for sewage treatment. The extension of HRT improved the nitrogen removal efficiency, however the removal pattern was constant regardless of HRT. The removal of phosphorus was constant (80%-90%) regardless of the change in HRT. The removal rate with change in influx load varied such that at the OLR (Organic Load Rate) of 1-3 kg/d, the T-N removal efficiency was 80.7%-88.9% and the T-P removal efficiency was 82.9%-89.3% while at the NLR (Nitrogen Loading Rate) of 0.108-0.156 kg/d the removal efficiencies were 80.7-88.9% (T-N) and 82.9-89.3% (T-P). The analyses of the nitrogen and phosphorous removal characteristics with the C/N and C/P ratio showed that the mean T-N removal rate was 88% at the C/N ratio of 1.2-2.6, and that the mean T-P removal rate was 86% at the C/P ratio of 7.2-14.1. Also, the analysis of nitrogen and phosphorous removal characteristics were analyzed in relation to media charge. The comparison between with and without media charge in the water-mill showed that while the nitrogen removal efficiencies were 86-94% and 85-89% respectively, the difference of phosphorous removal efficiencies were between the two conditions was not significant, thus it suggested that the media charge has less effect on the removal efficiency of phosphorous compared to that of nitrogen.

• Journal of Environmental Health Sciences
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• v.13 no.2
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• pp.83-90
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• 1987

The objective of this study is to review the basic theories related substrate removal in wastewater flow variations using submerged biofilm reactor. An aerated biofilm reactor is that in which influent organic substrates are aerobically oxidized by the microorganisms of biofilm grown on the surface of submerged media. No sludge is returned, and oxygen is supplied by diffusers. Three types of aerated biofilm reactor are one stage-central aeration, one stageup flow aeration and two stage-side aeration. The orders of substrate removal capacity in wastewater flow variations showed two stage-side aeration, one stage-upflow aeration and one stage-central aeration. The phenonmenon of nonclosing volid in upflow aeration type was superior to these in central-side aeration type. Attached biofilm masses in case of upflow, side and central aeration reactor were 1.0mg/cm$^2$, 4.1 mg/cm$^2$ and 0.93 mg/cm$^2$, respectively. Yield coefficient for biofilm was 0.31 to 0.48. Especially, removal efficiency can be increased remarkably according to the number of biofilm reactor and the packed condition of media.

• Journal of Energy Engineering
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• v.10 no.3
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• pp.266-271
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• 2001

Buoyancy-driven natural convection is analysed by employing a linear stability theory in hori-zontal porous media with net through flow. Darcy's law is used to model the flow characteristics in porous media. Bated on the results of linear stability analysis, a heat transfer correlation was obtained by employing weakly nonlinear analysis. As the net through flow increases, the system becomes more stable and the effect of the Darcy-Rayleigh number on the Nusselt number decreases.

• Journal of Electrochemical Science and Technology
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• v.5 no.3
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• pp.73-81
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• 2014

This paper describes the continuous flow operation of membraneless sodium perborate fuel cell using acid/alkaline bipolar electrolyte. Here, hydrazine is used as a fuel and sodium perborate is used as an oxidant under Alkaline-acid media configuration. Sodium perborate affords hydrogen peroxide in aqueous medium. In our operation, the laminar flow based microfluidic membranleless fuel cell achieved a maximum power density of $27.2mW\;cm^{-2}$ when using alkaline hydrazine as the anolyte and acidic perborate as the catholyte at room temperature with a fuel mixture flow rate of $0.3mL\;min^{-1}$. The simple planar structured membraneless sodium perborate fuel cell enables high design flexibility and easy integration of the microscale fuel cell into actual microfluidic systems and portable power applications.

• Journal of the Korean Graphic Arts Communication Society
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• v.24 no.2
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• pp.1-10
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• 2006

In the past few years, the printing industry has witness a trend that has become ever more defined: due to the advent of digital technology, the production of short print runs has continued to gain in importance. An important initiative for the support of digital work flow in the manufacturing of printed products is CIP4 consortium. CIP4 stands for "International Cooperation for Integration of Prepress, Press and Post-press, it is an association of around forty international companies, mostly manufacturers of prepress, press and post-press, as well as suppliers and users. In this paper, we studied on the acting application of CIP4 work flow.

• Journal of Information Technology Services
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• v.11 no.1
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• pp.247-272
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• 2012

Social Network Service(SNS) is a kind of advanced Internet service that acts as personal media. This study was intended to find out the structural relationships among factors affecting the usage of social network services by extending the Technology Acceptance Model(TAM). For this purpose, the variable 'Flow' was first integrated into the TAM in order to understand the internal motivations of users. And then the external factors of SNS usage were derived from the perspective of users, contents, and media side of SNS, and finally the dependent variable was set with the intention of sustainable use. Then these factors were carefully integrated into a structural model. We expect the findings of this study will be very helpful for the internet marketing professionals, SNS developers, and the others.

• The Journal of Information Systems
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• v.21 no.1
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• pp.69-91
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• 2012

The study investigates the media distinctiveness between twitter and other social media and describes how product information interpretation and responsiveness by internet users can be affected by the distinctive characteristics of twitter and blog media. The characteristics include relationship formation patterns among users, channel diversity, immediateness of information communication, information flow within media, media credibility, and management cost. Specifically, we statistically tested whether these characteristics are meaningfully differentiated by users. Results also showed that users perceived product information processing level and product evaluation direction differently based on these media characteristics. The current findings can serve as a pioneering work to provide a theoretical framework for examining social media characteristics and their impacts on consumer perception. In addition, this study practically suggests that marketers and network managers need to use differentiated communication strategies for twitters as a marketing strategic option.