• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.5
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• pp.640-651
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• 2000

For the heat and fluid flow analyses of a parallel flow heat exchanger, an improved model considering the effect of flat tube with micro-channels is proposed. The effect of flow distribution on the thermal performance of a heat exchanger is numerically investigated. The flow distribution is examined by varying geometrical parameters, i.e., the position of the separators and the inlet/outlet, and the aspect ratio of micro-channels of the heat exchanger. The flow nonuniformities along the paths of the heat exchanger are proposed and observed to evaluate the thermal performance of the heat exchanger. The optimization using ALM method has been accomplished by minimizing the flow nonuniformity. It is found that the heat transfer rate of the optimized model is increased by 6.0% of that of the reference heat exchanger model, and the pressure drop by 0.4%

• Journal of Advanced Marine Engineering and Technology
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• v.22 no.4
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• pp.505-514
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• 1998

Flow pattern of air-water two phase flow depends on the conditions of pressure void fraction and channel geometry. We classify the flow pattern by measuring the output signal of the conductivity probe. under the classified flow pattern we mount a visualization equipment on the test section and take pictures. We vary the concentration of pure solvent and polymer to measure local void fraction. We know that the maximum point position of local void fraction distribution move from the center of the pipe to the wall of the pipe as JSL increase when JSA is constant in two phase flow. But we find that the maximum point position of local void friction move from the wal of the pipe to the center of the pipe when polymer concentration increase.

• Bulletin of the Korean Chemical Society
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• v.21 no.5
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• pp.487-492
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• 2000

The combustion characteristics of a mixture of acetaldehyde, oxygen and argon behind a reflected shock wave at temperatures ranging from 1320 to 1897 K at 100 torr were studied. The emission from the OH radical at 306.4 nm and the pressure profile behind the reflected shock were measured to monitor ignition delay time. The ignition delay times were computed from a proposed mechanism of 110 elementary reactions involving 34 species. The simulation and sensitivity analysis confirm that the main channel for oxidation of acetaldehyde at high temperature consists of the Rice-herzfeld mechanism, the decomposition and oxidation of HCO, and the reaction of H with $O_2$.

• Proceedings of the Korea Information Processing Society Conference
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• 2004.05a
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• pp.797-800
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• 2004

FED(Field Emission Display)는 CRT(Cathode Ray Tube)의 화질과 LCD(Liquid Crystal Display)와 같은 FPD(Flat Panel Display)의 경량, 박형의 장점을 만족시키는 차세대 Display 소자로서 주목을 받고 있다. 본 논문은 저항열을 이용하여 256 Gray-Scale Level을 출력하는 8 비트 FED Data Driver IC 설계에 관한 것이다. 즉, 저항열과 D/A 변환기를 통하여 디지털 입력 데이터에 따른 아날로그 출력 데이터를 갖는 FED 용 Data Driver IC이다. 본 논문에서 설계된 Driver IC는 집적도를 높여 Output Channel 수를 증가시키는 것을 목표로, 하이닉스 0.6um High Voltage 공정을 사용하였으며, 8 비트 RGB 데이터 입력과 40V 구동전압에서 동작하도록 설계하였다.

• Current Optics and Photonics
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• v.6 no.3
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• pp.297-303
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• 2022

Multiple fiber Bragg gratings (FBGs) have been proposed and demonstrated for gas-flow measurements in a flow channel, using the temperature-difference method. This sensor consists of two FBG temperature sensors and two coil heaters. Coil heaters are used to heat the FBGs. The flow rate of the gas can be obtained by monitoring the difference in the Bragg-wavelength shifts of the two FBGs, which has features that exclude the effect of temperature fluctuations. In this study, experiments are conducted to measure the wavelength shift based on the flow rate, and to evaluate the gas-flow rate in a gas tube. Experimental results show that the sensor has a linear characteristic over a flow-rate range from 0 to 25 ℓ/min. The measured sensitivity of the sensor is 3.2 pm/(ℓ/min) at a coil current of 120 mA.

• The Journal of the Korea Contents Association
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• v.20 no.2
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• pp.150-161
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• 2020

Generation Z(Gen Z), which is referred to people in their late teens to early 20s, becomes one of new major consumer groups in the society. More than 80 percent Gen Z use YouTube content as a main information channel. In this study, we investigate what kind of factors make Gen Z immersed when watching YouTube content. In the background study, we examined immersion and set the cognitive conditions of immersion as reality, fascination, control, and driving as a framework for analysis of case study. In the case study, we analyzed the most popular YouTube channels of each category among the Gen Z with the established framework and then identified 3 main factors: reality, 5 senses, and unpretentiousness and 8 characteristics of them. By conducting survey with Gen Z, we wanted to verify the validity of the characteristics and find out the difference among categories. Subjects answered on a five-point scale how the characteristics of each immersion factor corresponded to their favorite channels. As a result, seven characteristics: 1) familiarity of background, 2) reality of acting, 3)familiarity of material, 4)YouTubers' appearance and 5) voice, 6)multi-sensory, and 7)YouTuber's ability to resemble viewers influenced more than 50% of users' immersion. Although there was no significant difference among categories, the familiarity of the material and the five senses stimulus (YouTube's appearance, voice, audiovisual and surrogate taste) were the most important factors in the entertainment category.

• The Journal of the Korea Contents Association
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• v.15 no.6
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• pp.24-32
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• 2015

The global success of PSY's Gangnam Style was mediated through combination of YouTube and SNS. PSY's success led into some communication scholars' consideration of new international circulation of Korean pop culture (Korean Trend 2.0). In terms of global circulation of pop culture, it is noticeable how users appropriate YouTube channel beyond mere watching music videos and mere international circulation of Korean pop culture. The mode of fan's activity and appropriation contributes to the expansion of the width and amplification of the volume of Korean popular culture as well. The circulation of pop culture was considered in the level of exchange of tangible commodities such as CD, DVD, and so on until the adoption of digital media and Internet. YouTube has brought new mode in which the international circulation of pop culture is mediated without exchange of tangible commodities but was amplified with the diffusion of network. This study grasps how the mode of users' appropriation contributes to international circulation of pop culture through case studies of some K-pop music videos and international K-pop fans' tribute activities. In terms of theoretical perspective, fandom studies will be examined. In terms of research method, the researcher adopts netnography, a participatory observation on network, to find the feature of fandom and its contribution to the international circulation of pop cultures.

• Journal of the Korean Graphic Arts Communication Society
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• v.29 no.1
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• pp.23-33
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• 2011

This experimental focus to characterize luminescence properties related to CNT (Carbon Nano Tube) element dispersedly implanted in ZnS-based phosphor thin film panel fabricated by a screen printing method. More specifically FE-SEM measurements, L-V(Luminescence vs. Voltage) and photo luminescence were carried out to determine an optimum value of CNT concentration and film thickness for the thin film structure of CNT-ZnS:(Cu, Al) by the screen printing method. We confirmed that an optimum value of CNT concentration in the ZnS:(Cu, Al) film panel is about 0.75 wt% resulting that the electric conductivity is 1.6 times higher than that of pure CNT sample and showing that the luminescence intensity is increasing until the optimum concentration. Clearly, CNT is presenting in the luminescence process providing a pathway for the creation of hot electron and a channel for the electron-hole recombination but overly inserted CNT may hinder to produce the hot electron for making an avalanching process. In case of the overly doped CNT 1.0 wt% in the ZnS-based phosphor, the luminescence intensity is decreasing although the electric conductivity is exponentially increasing. Based on these results, we realized that hot electron occurred by the external electric field or exciton arose by the external photon source are reduced dramatically over the critical value of CNT concentration because CNT element provide various isolated residues in the composites of ZnS based phosphor rather than pathway or channel for the D-A(Donnor to Acceptor) pair transition or the radiative recombination of electron-hole.

• Journal of Astronomy and Space Sciences
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• v.19 no.4
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• pp.305-318
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• 2002

We have constructed two flight models of airglow photometer system (AGP) to be onboard Korea Sounding Rocket-III (KSR-III) for detection of MUV dayglow above the Korean peninsular. The AGP system is designed to detect dayglow emissions of OI 2972${\AA}$, $N_2$ VK(0,6) 2780${\AA}$, $N_2$ 2PG 3150${\AA}$ and background 3070${\AA}$ toward the horizon at altitudes between 100 km and 300 km. The AGP system consists of a photometer body, a baffle an electronic control unit and a battery unit. The MUV dayglow emissions enter through a narrow band interference filter and focusing lens of the photometer, which contains an ultraviolet sensitive photomultiplier tube. The photometer is equipped with an in-flight calibration light source on a circular plane that will rotate at the rocket's apogee. A bane tube is installed at the entry of the photometer in order to block strong scattering lights from the lower atmosphere. We have carried out laboratory measurements of sensitivity and in-flight calibration light source for the AGP flight models. Although absolute sensitivities of the AGP flight models could not be determined in the country, relative sensitivities among channels are well measured so that observation data during rocket flight in the future can be analyzed with confidence.

• Journal of Korean Society of Steel Construction
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• v.21 no.5
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• pp.515-526
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• 2009

There are three main production processes in the manufacture of concrete-filled square steel columns. The first process is known as the 'box-type process' or 'four-seam method,' wherein four beams are welded together at the seams. The second is the 'cold-forming process' or 'two-seam method,' wherein the seams of two channel beams are welded together. The third is the 'pressing process' or 'one-seam method,' wherein a circular column is pressed until it becomes a square column. In calculating the production cost for the making of a steel tube, it is very important to consider the welding process to be used and the desiredthickness of the steel tube, such as a square column that was developed under a new method, formed through the four-seam flare welding method at the center of the steel column width, following the L-shape formation. Certain tests were suggested in this study to evaluate the welding amount of concrete-filled square steel columns. With the parameters of the production method of a square steel column, the thickness of the steel square columns, and the welding amount, six specimens were produced. A structural test and finite-element analysis were conducted to assess the behavior of the steel column according to the water pressure inside the steel columns.