• Journal of Mechanical Science and Technology
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• 제20권7호
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• pp.1059-1067
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• 2006

In order to develop a compact evaporator, experiments that show characteristics of evaporating heat transfer and pressure drop in the helically coiled minichannel were performed in our previous research. This study was focused on the performance analysis of helically coiled heat exchangers with circular minichannels with an inner diameter=1.0 mm. The working fluid was R-22, and the properties of R-22 were estimated using the REFPROP program. Numerical simulation was performed to compare results with the experimental results of the helically coiled heat exchanger. As the heat transfer rate and pressure drop were calculated at the micro segment of the branch channels, the performance of the evaporator was evaluated. The following conclusions were obtained through the numerical simulations of the helically coiled heat exchanger. It showed good performance when the flow rate of each branch channels was suitable to heat load of air-side. The numerical simulation value agreed with experimental results within ${\pm}15%$. In this study, a numerical simulation program was developed to estimate the performance of a helically coiled evaporator. And, an optimum helically coiled minichannels evaporator was designed.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권2호
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• pp.684-702
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• 2016

The changes new technologies have brought to banking over the past decade are enormous in their impact on the ways of doing business and providing customer services, most notably in the areas of customer service channels. Banks have been trying to move away from the traditional, branch-based and costly staff-assisted channels toward self-assisted channels, i.e. internet banking and mobile banking, to drive down costs and improve customer loyalty. How internet and mobile have reshaped the user experience of banking service channel? To provide valuable insights for this question, this research investigates and compares customer's channel choice behavior and profit changes from bank's branch closure. Applying the propensity scoring matching method, the results of analysis demonstrates that the mobile channel can be a realistic alternative to conventional branches. Also, the reserch result shows banks can reduce conventional branches while experiencing a positive implications on their profits from the customers. Another significant implication from the research is, to accelerate the shift to digital channels, banks need to put more efforts on developing functions in the mobile channel that will allow friendly interaction with customers and consultation, such as video consultation, interactive chat, and location-based product recommendation.

• 문화기술의 융합
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• 제5권4호
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• pp.283-288
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• 2019

수강생들의 정보와 경험 부족을 극복하기 위해, 의사 결정 트리를 활용한 콘텐츠 기획 트리를 개발하였다. 콘텐츠 기획 트리는 수강생들이 개발할 주제와 스토리를 선택하는 나무 몸통 생성단계, 해당 스토리를 바탕으로 개발 가능한 형태 '범주'를 선택하는 부모 가지 생성단계, 해당 콘텐츠를 효과적으로 제작하는 흥미 '효과'를 선택하는 자식가지 생성단계 그리고 시각화할 멀티미디어 표현 '요소'를 선택하는 잎사귀 생성단계로 구성된다. 교육 모델은 게임기획 디자인과 정보시각화 강의에 적용되었고, 각 강의에서 사용된 범주, 효과 그리고 요소의 예를 사례로 제시한다. 교육 모델은 145개 팀 프로젝트에 사용되었고, 단계별 학습 프로세스로 효율성을 확인하였다.

• Structural Engineering and Mechanics
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• 제73권2호
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• pp.191-207
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• 2020

This study aims at investigating the size-dependent free vibration of porous nanoplates when exposed to hygrothermal environment and rested on Kerr foundation. Based on the modified power-law model, material properties of porous functionally graded (FG) nanoplates are supposed to change continuously along the thickness direction. The generalized nonlocal strain gradient elasticity theory incorporating three scale factors (i.e. lower- and higher-order nonlocal parameters, strain gradient length scale parameter), is employed to expand the assumption of second shear deformation theory (SSDT) for considering the small size effect on plates. The governing equations are obtained based on Hamilton's principle and then the equations are solved using an analytical method. The elastic Kerr foundation, as a highly effected foundation type, is adopted to capture the foundation effects. Three different patterns of porosity (namely, even, uneven and logarithmic-uneven porosities) are also considered to fill some gaps of porosity impact. A comparative study is given by using various structural models to show the effect of material composition, porosity distribution, temperature and moisture differences, size dependency and elastic Kerr foundation on the size-dependent free vibration of porous nanoplates. Results show a significant change in higher-order frequencies due to small scale parameters, which could be due to the size effect mechanisms. Furthermore, Porosities inside of the material properties often present a stiffness softening effect on the vibration frequency of FG nanoplates.

• Journal of Korean Neurosurgical Society
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• 제48권2호
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• pp.105-108
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• 2010

Objective : Some neurosurgeons intentionally ligate the branches of the superficial temporal artery (STA) that are not used in standard STA-to-middle cerebral artery (MCA) anastomosis for the purpose of improving the flow rate in the bypass graft. We investigated changes in bypass flow during temporary occlusion of such unused branches of the STA. Methods : Bypass blood flow was measured by a quantitative microvascular ultrasonic flow probe before and after temporary occlusion of branches of the STA that were not used for anastomosis. We performed measurements on twelve subjects and statistically assessed changes in flow. We also examined all the patients with digital subtraction angiography in order to observe any post-operative changes in STA diameter. Results : Initial STA flow ranged from 15 mL/min to 85 mL/min, and the flow did not change significantly during occlusion as compared with preocclusion flow. The occlusion time was extended by 30 minutes in all cases, but this did not contribute to any significant flow change. Conclusion : The amount of bypass flow in the STA seems to be influenced not by donor vessel status but by recipient vessel demand. Ligation of the unused STA branch after completion of anastomosis does not contribute to improvement in bypass flow immediately after surgery, and furthermore, carries some risk of skin necrosis. It is better to leave the unused branch of the STA intact for use in secondary operation and to prevent donor vessel occlusion.

• Ocean and Polar Research
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• 제31권2호
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• pp.177-187
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• 2009

This study examined the multi-scale variabilities of sea surface temperature (SST) and salinity in the Japan/East Sea (JES) based on statistical analyses of observational data, with a focus on the northwestern part of the sea. The regionality of JES SST variability was estimated for different frequency ranges on semimonthly (11-17 days), monthly to seasonal (30-90 days), quasi-semiannual (157-220 days), and quasi-biennial (1.5-3 years) time scales using cluster analyses of daily gridded SST data for 1996 to 2007 from the Japan Meteorological Agency (JMA). Several significant peaks and regional cores were found in each frequency range of the SST anomaly (SSTA) oscillations. Quasi-semiannual SSTA oscillations with high amplitude were found in the south-southwestern part of the Japan Basin ($41-43^{\circ}N$) and were amplified in the area adjacent to Peter the Great Bay. Oscillations with periods of 79 and 55 days also prevailed over the southwest Japan Basin between the Yamato Rise and the continental slope. A similar method was applied to classify SST and the annual cycle of surface salinity using Generalized Digital Environmental Model (GDEM) gridded data. The Tatarskii Strait and adjacent area showed the most specific annual cycles and variability in salinity on interannual to interdecadal time scales. The most significant inverse relationship between surface salinity in the Tatarskii Strait and southern JES areas was found on the interdecadal time scale. Linkages of sea water salinity in the Tatarskii Strait with Amur River discharge and wind velocity over Amurskii Liman were also revealed.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제51권5호
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• pp.213-221
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• 2002

In order to improve the reliability of XLPE cables, it is necessary to find the useful diagnostic parameter according to long term aging. This paper described the change of partial discharge(PD) phase Properties of XLPE cable insulation with branch type electrical tree degradation. for long term aging. To understand the PD Properties with $\phi$ -q-n distributed shape of XLPE insulation, specimens were prepared by 22.9㎸ distribution cable and made in a type of block(16${\times}$16${\times}$3[mm]). Ogura needles having tip radius of l0${\mu}{\textrm}{m}$ were inserted into each block pieces. The measuring system was consisted of PD detector, digitizer for digital conversion, VXI system for signal processing. The PD properties of the specimens were measured from initiation of tree to breakdown and their characteristics were analyzed. We analyzed the relationship between electrical properties(PD Quantity, PD initiation angle, PD extinction angle, PD occurrence angle : (PD extinction angle - PD initiation angle)) and the normalized aging rate. We found PD parameter, PD initiation angle and occurrence angle, which are a useful diagnostic parameter in estimating the branch type electrical tree for XLPE insulation condition.

• 한국의학물리학회:학술대회논문집
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• 한국의학물리학회 2002년도 Proceedings
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• pp.385-388
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• 2002

We measured and evaluated digital, pre-sampling and overall imaging properties (characteristic curves, Modulation Transfer Function (MTF), Wiener spectra (WS), Noise Equivalent Quanta (NEQ) and Detective Quantum Efficiency (DQE)) for the direct type and indirect type of Flat-Panel Detector (FPD). First, the digital and overall characteristic curves of the both types of FPD had more wide dynamic range than that of the S/F system. Second, the pre-sampling and overall MTF of the direct-type FPD were superior to those of the indirect-type FPD. Third, for identical exposures, the digital and overall WS of the direct-type FPD were similar or worse than those of the indirect-type FPD, and for larger exposure, the digital WS of the both types of FPD were smaller, but overall WS of the both types of FPD were larger. Fourth, the digital and overall NEQ and DQE of the direct-type FPD were worse than both NEQ and DQE of the indirect-type FPD at lower spatial frequencies, but were better at higher spatial frequencies.

• 한국콘텐츠학회논문지
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• 제13권12호
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• pp.48-61
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• 2013

디지털 시대가 도래함에 따라 e스포츠와 같은 디지털 레저문화가 등장하면서 국민들의 레저 문화 양상이 변화하고 있다. 그 중에서도, 상호작용적인 미디어를 대표하는 디지털 게임은 그 고유한 특성으로 인해 국민들이 선호하는 디지털 레저 활동으로 성장하고 있다. 레저란 참여자들의 주관적 인식에 따라 정신적 수준을 포함할 수 있기 때문에 정서적이며 인지적인 기능을 포함하는 디지털 게임은 유의미한 디지털 레저 활동이 될 수 있는 것이다. 본 연구에서는 디지털 게임에 창조적 생산성과 목적성 콘텐츠를 가미한 시리어스 게임이 의미 있는 디지털 레저 활동이 될 수 있다는 주장을 전제로, 학제적 연구에 기반하여 디지털 게임의 개념과 기능적 특성에 대해 알아보았다. 그리고 그 특성들과 목적지향성에 근간하여 시리어스 게임이 디지털 레저 문화가 될 수 있다는 새로운 개념을 제안하였으며 시리어스 게임의 개념과 활용범위에 대한 이론적 고찰을 바탕으로 기존 유형별 범위에 레저/관광 부분을 추가로 제안하였다. 이어서, 디지털 레저 문화로써 그 기능적 요구를 충족시킬 수 있는 게임 사례들인 의미추구 레저형, 건강지식교육 레저형, 사회인식변화 레저형 시리어스 게임과 관광 레저형 시리어스 게임을 분석하여 제시한 뒤 시리어스 게임의 효과성 연구를 통해 디지털 레저 문화로써 시리어스 게임의 활용력 부분에 대한 근거를 제시하였다. 연구 결과, 현재 디지털 레저문화는 창의적으로 진화 하고 있으며 그 창조적 산물인 시리어스 게임은 디지털 레저문화로써 즐거움과 동시에 사회문화적 가치를 지닐 수 있는 유용한 도구가 될 수 있다고 나타났다.

• 디지털콘텐츠학회 논문지
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• 제18권6호
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• pp.1151-1156
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• 2017

일반적으로 GPU 기반 트리 탐색을 수행할 경우 병렬 처리 속도가 생각보다 크게 향상되지 않는 경우가 대부분이다. 본 논문에서는 이러한 원인을 분석하고 그 분석 결과로 GPU 병렬 처리 하드웨어 아키텍처 내 최소 물리적 스레드 실행 단위인 warp 내에서 분기문(if문)으로 인한 warp divergence가 일어나기 때문임을 제시한다. 또한 이러한 warp divergence를 최소화할 수 있는 병렬 shifted sort 알고리즘과의 비교를 통해 shifted sort 알고리즘이 일반적인 GPU 내 트리 탐색에 비해 우수한 성능을 보이는 구조임을 제시하였다. 분석 결과 GPU 기반 kd-tree 탐색에 비해 warp divergence가 발생하지 않은 shifted sort 탐색은 3차원 공간에서 데이터나 쿼리의 수가 $2^{23}$개 일 때 16배 이상의 빠른 처리 속도를 보였으며 이 성능 차이는 데이터나 쿼리의 개수가 증가함에 따라 더 커지는 경향을 보였다.