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전자상거래의 성공요인과 인터넷서점의 특성이 사용자만족도와 재구매의도에 미치는 영향에 관한 연구
최대우(Daewoo Choi),강문식(Moonsig Kang) 계명대학교 산학연구소 2008 經營經濟 Vol.41 No.1
This study is about the E-Commerce that has brought big changes on the traditional commerce process in terms of rapidity of transition and efficiency. From the moment of continuous soaring growth, the E-Commerce sector of market is becoming bigger than at any time before, especially, in publishing industry. However, researches about the characteristics of the on-line bookstores do not meet the needs. The reason is that the attributes of internet bookstores are included in the concept of E-Commerce and on-line bookstore is considered as one of the E-Commerce practices. This paper is intended to study the effects of E-Commerce success factors and on-line bookstore characteristics on customer satisfaction and re-purchasing process. The result of this study is as follows: First, similar with many preceded studies, the customer satisfaction is revealed to be an important factor of re-purchasing process. Second, the attributes of On-line bookstores and E-Commerce success factors such as price, convenience of searching product, and variety of product have significant impacts on the customer satisfaction.
A Fog Operating System for User-Oriented IoT Services: Challenges and Research Directions
Choi, Nakjung,Kim, Daewoo,Lee, Sung-Ju,Yi, Yung Institute of Electrical and Electronics Engineers 2017 IEEE communications magazine Vol.55 No.8
<P>As the proliferation of mobile devices has ignited cloud computing, it is expected that increasing development and deployment of IoT services will expedite the era of fog computing. Fog computing brings computing, storage, and networking even closer to end users and devices for services with better QoS. We introduce FogOS, a fog computing architecture for IoT services. We take the perspective of designing an operating system, practicing the architectural lessons from the long history of operating systems. We focus on addressing the challenges raised by the diversity and heterogeneity of IoT services and edge devices that are owned by individuals and different owners, and presenting how FogOS is designed to effectively and efficiently provide and manage such IoT services. We provide a city-scale surveillance use case to demonstrate FogOS in action.</P>
( Daewoo Lee ),( Sung Ho Kook ),( Hyeok Ji ),( Seung Ah Lee ),( Ki Choon Choi ),( Kyung Yeol Lee ),( Jeong Chae Lee ) 생화학분자생물학회(구 한국생화학분자생물학회) 2015 BMB Reports Vol.48 No.11
There are controversial findings regarding the roles of nuclear factor (erythroid-derived 2)-like 2 (Nrf2)/heme oxygenase-1 (HO-1) pathway on bone metabolism under oxidative stress. We investigated how Nrf2/HO-1 pathway affects osteoblast differentiation of MC3T3-E1 cells in response to hydrogen peroxide (H2O2), N-acetyl cysteine (NAC), or both. Exposing the cells to H2O2 decreased the alkaline phosphatase activity, calcium accumulation, and expression of osteoblast markers, such as osteocalcin and runt-related transcription factor-2. In contrast, H2O2 treatment increased the expression of Nrf2 and HO-1 in the cells. Treatment with hemin, a chemical HO-1 inducer, mimicked the inhibitory effect of H2O2 on osteoblast differentiation by increasing the HO-1 expression and decreasing the osteogenic marker genes. Pretreatment with NAC restored all changes induced by H2O2 to near normal levels in the cells. Collectively, our findings suggest that H2O2-mediated activation of Nrf2/HO-1 pathway negatively regulates the osteoblast differentiation, which is inhibited by NAC. [BMB Reports 2015; 48(11): 636-641]
입출력 변수 조작에 의한 임베디드 소프트웨어 테스트 방법
김대우 ( Daewoo Kim ),정기현 ( Kihyun Jung ),최경희 ( Kyunghee Choi ) 한국정보처리학회 2005 한국정보처리학회 학술대회논문집 Vol.12 No.1
임베디드 소프트웨어가 날이 갈수록 그 규모가 커지고 복잡해짐에 따라 임베디드 소프트웨어의 품질에 대한 검증 및 테스트는 중요한 문제로 부각하고 있다. 임베디드 소프트웨어의 신뢰성을 확보와 비용절감을 위한 테스트 자동화 시스템의 개발이 필요하다. 이 문서는 테스트 자동화 시스템을 구축하는 과정에서 테스트 대상인 임베디드 시스템의 입출력 변수들의 조작을 통하여 시스템 의존적인 부분을 효과적으로 일반화 시키는 방법을 제시한다. 이 방법을 통하여 테스트 명령을 간소화 할 수 있었으며 테스트 자동화 시스템의 모델을 보다 일반적이고 쉽게 표현할 수 있었다.
Suh, Daewoo,Lee, Sanghoon,Mun, Hyeona,Park, Sung-Hoon,Lee, Kyu Hyoung,Wng Kim, Sung,Choi, Jae-Young,Baik, Seunghyun Elsevier 2015 Nano energy Vol.13 No.-
<P><B>Abstract</B></P> <P>Solution-based synthesis of thermoelectric nanoplates, which provides a low thermal conductivity due to the grain boundary scattering, has received considerable attention as a scalable method. However, the scattering also decreased electrical conductivity leading to a low thermoelectric figure of merit (<I>ZT</I>). Here we employed expanded graphene to enhance thermoelectric performance of p-type Bi<SUB>0.5</SUB>Sb<SUB>1.5</SUB>Te<SUB>3</SUB> composites by simultaneous improvement in electrical conduction and phonon scattering. The addition of expanded graphene (0.1vol%) improved both carrier concentration and electrical conductivity of composites due to the high intrinsic p-type carrier concentration of graphene. Besides, it significantly decreased lattice thermal conductivity due to the phase boundary phonon scattering in spite of the high intrinsic thermal conductivity of graphene. The increased carrier concentration also suppressed the bipolar conduction resulting in a moderate increase in power factor and a slow increase in bipolar thermal conductivity at elevated temperatures. Overall, the maximum <I>ZT</I> increased by 45% (1.13 at 360K) by the addition of expanded graphene. A similar trend with a greater maximum <I>ZT</I> (1.24 at 360K) was observed when ball-milled Bi<SUB>0.5</SUB>Sb<SUB>1.5</SUB>Te<SUB>3</SUB> ingot powders were employed providing reliability of the suggested mechanism.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Thermoelectric properties of graphene-Bi<SUB>0.5</SUB>Sb<SUB>1.5</SUB>Te<SUB>3</SUB> composites prepared by the powder metallurgy were investigated. </LI> <LI> The addition of expanded graphene (0.1vol%) enhanced thermoelectric performance of the p-type Bi<SUB>0.5</SUB>Sb<SUB>1.5</SUB>Te<SUB>3</SUB> composites by simultaneous improvement in electrical conduction and phonon scattering. </LI> <LI> The maximum <I>ZT</I> increased by 45% (1.13 at 360K) by the inclusion of expanded graphene. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
On the Interval Estimation of the Difference between Independent Proportions with Rare Events
im, Yongdai,Choi, Daewoo The Korean Statistical Society 2000 Communications for statistical applications and me Vol.7 No.2
When we construct an interval estimate of two independent proportions with rare events, the standard approach based on the normal approximation behaves badly in many cases. The problem becomes more severe when no success observations are observed on both groups. In this paper, we compare two alternative methods of constructing a confidence interval of the difference of two independent proportions by use of simulation. One is based on the profile likelihood and the other is the Bayesian probability interval. It is shown in this paper that the Bayesian interval estimator is easy to be implemented and performs almost identical to the best frequentist's method -the profile likelihood approach.
단일 프로세스 공간을 제공하는 클러스터 시스템의 설계 및 구현
최민(Min Choi),이대우(DaeWoo Lee),박동근(DongGun Park),유정록(JungLok Yu),맹승렬(SeungRyoul Maeng) 한국정보과학회 2004 한국정보과학회 학술발표논문집 Vol.31 No.1A
Single system image(SSI) have been the mainstay of high-performance computing for many years. SSI requires the integration and aggregation of all types of resources in a cluster to present a single interface to users. In this paper, we describe a cluster computing architecture with the concept of single process space(SPS) where all processes share a uniform process identification scheme. With SPS, a process on any node can create child process on the same or different node or communicate with any other process on a remote node, as if they are on a single node. For this purpose, SPS is built with the support of unique cluster-wide pid, signal forwarding, and remote fork. We propose a novel design of SPS cluster which addresses the scalability and flexibility problem of traditional clusterwidely unique pid implmentation by using blocked pid assignment. We have implemented this new design of SPS cluster, and we demonstrate its performance by comparing it to Beowulf distributed process space. Benchmark performancresults show that our design of SPS cluster realized both scalability and flexibility that are essential to building SPS cluster.