• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.11 no.3
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• pp.321-331
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• 1999

A numerical study is carried out for increasing heat removal using indirect cooling system. Computation is performed for nine cases as variation of flow condition in the lower channel. As the result of this study, water is more effective than air at the same pressure loss in spite of the lower inlet velocity. In channel configuration, the vertical channel is more effective than horizontal channel because of the buoyancy effect. Under the condition that heat generation is the same, counter flow effectively decreases the temperature difference among blocks. Parallel flow is more effective than counter flow when average temperature of all blocks is considered. In the case of installing obstacles in the lower channel, it is desirable to install obstacles in the bottom of lower channel. Heat transfer rate increases as the height of obstacles increases.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.743-748
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• 2006

Ren et al. analyzed the performance of the indirect evaporative cooler according to the direction of the flow considering evaporation water flow and wetness. However the effect of NTU of each channel on the performance of the indirect evaporative cooler according to the direction of the flow was not analyzed exactly. In this study the effect of the direction of the flow on the Indirect evaporative cooling performance changing NTU of each channel are investigated theoretically. The cooling process of the indirect evaporative cooler by flow direction is modeled into a set of linear differential equations and solved to obtain the exact solutions to the temperatures of the hot fluid, the moist air, and evaporation water. Based on the exact solution in the case of different NTU of each channel, we study the change of the distribution of the temperature according to each flow direction and at the same time analyze the effect of the flow direction on the cooling performance.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.12
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• pp.8165-8175
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• 2015

In Korea, summer is hot and humid, and air-conditioners consume lots of electricity. In such case, simultaneous usage of indirect evaporative cooler may reduce the sensible heat and save the electricity. In this study, heat transfer and pressure drop characteristics of indirect evaporative cooler made of aluminum, plastic, plastic/paper are investigated both under dry or wet condition. Results show that indirect evaporation efficiencies of the plastic/paper sample (38.5% ~ 51.4%) are approximately the same as those of the aluminum sample (41.9% ~ 47.5%), and are larger than those of the plastic sample (29.0% ~ 37.4%). This suggests that the plastic/paper sample could be a good substitute to the aluminum sample. However, the pressure drops across the paper channel are 92% ~ 106% larger than those across the aluminum channel. The heat transfer coefficients of the paper channel under dry condition are 15% ~ 44% larger than those of the plastic channel. The increases are 185% ~ 203% for the aluminum channel. The pressure drops of the paper channel are 34% ~ 48% larger than those of the plastic channel and 93% ~ 106% larger than those of the aluminum channel. Rigorous heat transfer analysis reveals that, for the plastic sample, 30% ~ 37% of the wet channels remain dry, whereas all the channels are wet for plastic/paper sample. For aluminum sample, the ratio is 17% ~ 23%.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.1
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• pp.21-28
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• 2017

Indirect evaporative cooling, which utilizes a cooling effect obtained by the evaporation of water, is energy-effective compared to the conventional vapor compression method. It is also eco-friendly, due to the non-usage of CFC refrigerant. In this study, three indirect evaporative cooler samples of the cross flow type(size: $300mm{\times}300mm{\times}300mm$, channel pitch: $5mm{\times}5mm$, $5mm{\times}7mm$, $7mm{\times}7mm$) were made using plastic/paper composites. Tests were conducted to measure indirect evaporative efficiencies and pressure drops. Results showed that the efficiency was the highest for the $5mm{\times}5mm$ sample, owing to the largest surface area. The saved electrical energy was also the greatest for that sample. The pressure drop of the wet channel was larger than that of the dry channel as expected. A theoretical model was proposed, which underestimated both the indirect evaporation efficiency and the pressure drop.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38C no.8
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• pp.706-712
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• 2013

In this paper, channel modeling of VLC(Visible Light Communication) was investigated under indirect lightning circumstance which was the way that all phontons started from LED(Light Emitting Diode) were reached on the floor with NLOS paths. I supposed width(6m), depth(4m), height(2.2m) cube room circumstance for VLC communication channel and supposed that 4 LEDs were located at 2m height, which emitted photons at the direction of wall and ceiling. Channel characteristics, which were power attenuation and delayed receiving of light signal, were abstracted from receivers(PDs) which were located at 0.5m above from floor. The availability of channel was verified via BPSK based communication simulation.

• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.127-130
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• 2009

The uniform gas distribution between anode channels of the indirect internal reforming type molten carbonate fuel cell (MCFC) is crucial design parameter because of the electric performance and the durability problems. A three-dimensional computational fluid dynamics (CFD) analysis is performed to investigate flow characteristics in the anode channels and manifold under different pressure drop and channel temperature conditions. The combined meshes consists of hexadral meshes in the channels and polyhedral meshes in the manifold are adopted and chemical reactions inside the MCFC system are not included because of computational difficulties associated with the size and geometric complexity of the system. Results indicate that the uniformity in flow-rate is in the range of $\pm$ 0.048 % between the anode channels when the pressure drop of anode channel is about 150 Pa. A gas flow-rate uniformity decreases as the pressure drop of anode channels decreases and as the temperature difference between indirect internal reforming (IIR) channels and anode channels increases.

• Journal of Korean Society of Transportation
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• v.28 no.1
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• pp.77-86
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• 2010

The study developed physical distribution channel choice models reflecting decision making of the firms and studied how choice decision factors influence selection of distribution channel. The distribution channel survey data in Korea was used to do empirical study. As a choice set, distribution channels were classified into two main choice channels: direct and indirect channels. In addition, indirect channels were classified into other three channels according to the type of intermediate point: distribution center, wholesale store, and agency. This study developed choice models by applying both binary and multinomial logit model with various set of factors. The results showed that the developed logit models seemingly reflect distribution channel choice behaviors. The hypothesis tests on how each factor influences choice of distribution channel were performed and discussed as well.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.1
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• pp.88-98
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• 2016

The Korean summer is hot and humid, and air-conditioners consume considerable amounts of electricity. In such cases, the simultaneous use of indirect evaporative coolers may help reduce the sensible heat and save electricity. In this study, heat transfer and pressure drop characteristics of indirect or regenerative evaporative coolers made from plastic/paper are investigated. The results showed that heat and mass transfer model based on the ${\epsilon}-NTU$ method predicted the indirect evaporation efficiencies, cooling capacities and pressure drops adequately. Both for indirect or regenerative evaporative cooler, the indirect evaporation efficiency increased with increasing dry channel inlet temperature or relative humidity. The indirect evaporation efficiency of the regenerative evaporative cooler was larger than that of the indirect evaporative cooler.

• Journal of Distribution Science
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• v.19 no.11
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• pp.27-36
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• 2021

Purpose: COVID-19, government regulation and social media have changed many aspects of life including consumption behavior. The influence of social media by spreading massive news about COVID-19 also have the impact toward emotions threat, perceived risk, and perceived value of consumption behavior in Bengkulu Province, Indonesia. This research aims to analyze the extent to which changes in the consumption behavior, mainly for purchasing of corona prevention products through indirect distribution channels. Research design, data and methodology: This research was descriptive quantitative using the IPA method with sample of people in Bengkulu Province. This study obtained 208 respondent data from questionnaires and tested the validity and reliability with corrected-item total correlation method. Results: The study found that COVID-19 pandemic and government regulation variable were in quadrant II, in quadrant III there were social media variable, emotions threat and perceived risk. Meanwhile, in quadrant IV there were perceived value variable. Conclusions: The findings indicated that COVID-19 and government regulation are the most variable that influence people to buy corona prevention product, meanwhile perceived value is the less influence variable. Therefore, government and marketers have to prepare strategic plan in order to raise people awareness to avoid corona by buying corona prevention product.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.6
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• pp.71-78
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• 2013

Recently, the opportunistic incremental relaying systems have been studied to improve the system performance effectively in wireless fading channel. Most of the performance analysis of the system includes a source-destination direct link. And there are few analysis which consider source-relay-destination indirect paths only. Therefore this paper proposes a transmission protocol which relays the source information using the selected relay from the partial channel information at the first stage in an opportunistic incremental relaying system. If the transmission fails, the selected best relay from the full channel information retransmits the information to the destination incrementally. The performance of the proposed system is derived analytically and verified from Monte Carlo simulation. The derived results can be applied to the system design and the performance estimation of the mobile systems and the bidirectional TV broadcasting systems which adapt an opportunistic incremental relaying system.