• Journal of the Optical Society of Korea
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• 제19권3호
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• pp.237-240
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• 2015

We derived the average bit error rate (BER) of coherent free-space optical (FSO) systems with digital binary phase shift keying (BPSK) modulations over atmospheric turbulence channels with a gamma-gamma distribution. To obtain a generalized derivation in a closed-form expression, we used special integrals and transformations of the Meijer G function. Furthermore, we numerically analyzed and simulated the average BER behavior according to the average SNR for different turbulence strengths. Simulation results are demonstrated to confirm the analytical results.

• 한국통신학회논문지
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• 제41권10호
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• pp.1240-1243
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• 2016

In this paper, we analyze the queueing performance of cumulative distribution function (CDF)-based opportunistic scheduling over Nakagami-m Markov fading channels. We derive the formula for the average queueing delay and the queue length distribution by constructing a two-dimensional Markov chain. Using our formula, we investigate the queueing performance for various fading parameters.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 추계학술대회 초록집
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• pp.82.2-82.2
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• 2011

A channel design which is closely related with the mass transport overpotential is one of the most important procedures to optimize the whole fuel cell performance. In this study, three dimensional results of a numerical study for gas distribution in channels of a molten carbonate fuel cell (MCFC) unit cell for a 1kW class stack was presented. The relationship between the fuel and air distribution in the anode and cathode channels of the unit cell and the electric performance was observed. A charge balance model in the electrodes and the electrolyte coupled with a heat transfer model and a fluid flow model in the porous electrodes and the channels was solved for the mass, momentum, energy, species and charge conservation. The electronic and ionic charge balance in the anode and cathode current feeders, the electrolyte and GDEs were solved for using Ohm's law, while Butler-Volmer charge transfer kinetics described the charge transfer current density. The material transport was described by the diffusion and convection equations and Navier-Stokes equations govern the flow in the open channel. It was assumed that heat is produced by the electrochemical reactions and joule heating due to the electrical currents.

• 유통과학연구
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• 제22권1호
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• pp.115-125
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• 2024

Purpose: This study is to analyze the purchasing process and distribution management requirements for teaching materials that have important meaning in the practical field of preschool education. Research design, data and methodology: A structured questionnaire was used to survey 103 childcare staffs regarding the purchasing process and distribution managements. The collected data underwent Likert's 5-point scale analysis and keyword grouping. Additionally, ANOVA was conducted to examine the distribution management demands based on demographic characteristics. Results: The purchasing of teaching materials involved more offline channels than online, and the purchase decisions were predominantly made by principals rather than teachers. Although the purchasing process is similar to that of general businesses, there are difficulties in purchasing due to the disorganized distribution channels and limited accessibility to product information. Additionally, the management of inventory for teaching materials is challenging due to limited personnel and storage. Childcare staffs have requirements for classification systems, evaluation criteria, environments and policies related to teaching materials distribution. The need to introduce a teaching material evaluation and certification system to ensure quality was not high. Conclusions: Most of the respondents recognized that strict management and measures should be taken for the distribution of teaching materials. There were differences in the demand of teaching material distribution depending on the respondents' status, age, education, and experience.

• 유통과학연구
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• 제19권12호
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• pp.103-114
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• 2021

Purpose: This study was conducted with the goal of increasing research interest in H&B stores as a new distribution channel to identify factors influencing the revitalization of the H&B stores in Korea in distribution channels, in detail, the relationships among perceived values, satisfaction, trust, and loyalty. Research design, data and methodology: With 499 respondents, this study used exploratory factor analysis and reliability analysis to verify the reliability and validity of measured variables. Multiple regression was employed as a statistical method for the hypotheses of the study. Results: According to the results of the analysis, H&B stores are targeted by female customers in their 20s and 30s. The findings showed that four perceived values affect store satisfaction and trust. Store satisfaction and trust have positive effects on loyalty. Comparing the two variables, store satisfaction had a slightly stronger effect on loyalty than on trust. Conclusions: This study identified the store’s diverse values for the revitalization of the H&B stores need to provide to customers. The stores need to form facilities that can enhance the value of shops perceived by customers, and to establish distribution strategies that can further increase store satisfaction, trust, and loyalty to expand trading areas as multi-brand shops.

• 한국유통학회지:유통연구
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• 제4권1호
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• pp.123-140
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• 1999

For more than a decade, trust and commitment have received much attention in marketing channels literature. This study investigates the effects of these two core relational dimensions on the performance of EDI-supported marketing channels. A survey of the 92 suppliers of large department stores in Korea indicates that commitment to EDI increases significantly the organizational and economic performance of EDI-supported marketing channels. Trust was found to increase EDI performance indirectly by enhancing commitment to EDI. Based on the Social Information Processing(SIP) theory the present study also explored the effects of time on trust and commitment to EDI and their impacts on EDI performance. Analyses supported the hypothesized time effects that trust and commitment to EDI develop positively as EDI moves from initial stage to application stage. However, the impacts of these two dimensions on EDI performance did not change significantly over time.

• Journal of Mechanical Science and Technology
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• 제20권6호
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• pp.840-848
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• 2006

We carried out numerical studies to investigate the single- and two-phase flow characteristics in the single- and multi-channels. We used the finite volume method to solve the mass and momentum conservation equations. The volume of fluid model is used to predict the two-phase flow in the channel. We obtained the distribution of velocity fields, pressure drop and air volume fraction for different water mass flow rates. We also calculated the distribution of mass flow rates in the multi-channels to understand how the flow is distributed in the channels. The calculated results for the single- and two-phase flow are partly compared with the present experimental data both qualitatively and quantitatively, showing relatively good agreement between them. The numerical scheme used in this study predicts well the characteristics of single-and two-phase flow in a multi-channel.

• 전자공학회논문지A
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• 제31A권9호
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• pp.26-33
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• 1994

In this paper, the performance of the trellis coded CPFSK with the coherent detection over mobile communication channels is calculated. The characteristics of channels, including phase jitter effects and fading effects, are examined and modeled. The phase jitter channel is modeled to have a nonzero mean and a gaussian distribution. The fading channel has a Rayleigh distribution in the multipath. For the optimal decoding method(MLSE), the Viterbi algorithm is used for the trellis structure of trellis coded CPFSK. The results indicate that the trellis coded CPFSK with a small moulation indes gets more sensitive, as the index gets smaller, to the phase noise under the phase jitter channel. Using the interleaving method. It gives considerable improvements in the error rate under the fading channel.

• 대한교통학회지
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• 제26권6호
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• pp.17-27
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• 2008

기업의 물류활동은 화물의 기종점 정보와 더불어 출발지와 도착지간 수배송특성, 업종간 거래관계, 가격흐름, 경로 등 다양한 공급사슬관점에서 설명되어야 한다. 그동안 공공부문의 물류관련 연구들은 물류현황조사 자료로부터 지역간 기종점 통행량에 기초하여 물류시설을 포함한 국가의 사회간접자본 투자정책에 주로 활용된 경향이 있었다. 또한, 민간부문의 유통경로 관련 연구는 주로 상적인 유통경로에 한정되어 보다 종합적인 공급사슬관리 측면에서 기업의 물적 유통경로선택에 대한 이해가 부족하였다. 본 연구에서는 2001년 전국물류현황조사중 기업의 물류실태조사에서 수행된 600개의 표본자료에 기초하여 기업들의 유통경로 선택의 특성을 분석하였다. 사용된 자료들의 설문조사방식은 다양한 유통노드들이 제시되고, 기업들이 상위 매출액이 높은 품목들이 다양한 유통경로 상에서 어떻게 노드들을 이용하는지 조사되었고, 이를 공장순회형, 물류센터 중심형, 도매자 중심형, 소비자 중심형 등 4개로 유형화 하였다. 본 연구는 이들 4개의 유통경로들의 선택에 미치는 영향을 사업체 현황, 수배송현황, 취급화물 품목 등의 다양한 변수을 고려하여 미치는 영향을 분석하였다. 본 연구는 우리나라에서 물적유통경로연구의 시발점으로서 유통경로조사가 가지는 의의와 2001년 조사자료를 이용함에 따른 발견점보다는 한계점과 개선방향위주로 진행하였다.

• 유통과학연구
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• 제21권2호
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• pp.7-20
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• 2023

Purpose: With the unique feature of O2O, consumers are now able to check the profile of the services and products online and then consume them in offline venues or vice versa. This study provides motivation and practical implications about online-to-offline (O2O) distribution channels and investigates the relationship between economic values, service consistency and brand identity attractiveness in the O2O distribution channel. Then identify the impact of brand identity attractiveness on the performance (reputation and reuse intention). Research design, data, and methodology: Structural equation modeling (SEM) has been used to investigate the relationship between economic value and brand identity attractiveness, which affects the reputation and reuse intention of services in O2O. Results: Empirical results show the positive and significant impact of economic value and service consistency on brand identity attractiveness which results the positive and significant impact on performance (reputation and reuse intention) in O2O. Conclusion: In the O2O distribution channel, economic value is an important aspect for the attractive image and brand identity. On the other side, brand identity attractiveness is important for the bright future of O2O services, continuous growth, achieving the distinct goal, keeping good promises with customers, and a better reputation of O2O services in distribution channels.