• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2017년도 학술발표회
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• pp.265-269
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• 2017

Because of abrupt changes for velocity in water, transient flow is occurred in practical life. To reduce and avoid the high or low pressure of pipe network system, various surge protection facilities are used to prevent the risk in pipe network system. Especially, we focused on study not only preventing positive and negative pressure but also selecting adequate equipment for high pressurized pipelines. Several critical cases were considered by undertaking a steady state hydraulic study and transient dynamic simulation and we suggested that the surge vessel of various surge protection system was recommended to control high and low pressures on pipeline system in perspective.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.9-10
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• 2002

Human circulatory system between heart and tissue is not directly connected in normal condition but mandatory to go through the capillary system in order to fulfill its physiologic aim to deliver oxygen and nutrients, etc. to the tissue and retrieve used blood together with waste products from the tissue properly. When abnormal connection between arterial and venous system (AV fistula), these two circulatory systems respond differently to the hemodynamic impact of this abnormal connection between high pressure (artery) and low pressure (vein) system. Depending upon the location and/or degree (e.g. size and flow) of fistulous condition, each circulatory system exerts different compensatory hemodynamic response to this newly developed abnormal inter-relationship between two systems in order to minimize its hemodynamic impact to own system of different hemodynamic characteristics. Pump action of the heart can assist the failing arterial system directly to maintain arterial circulation against newly established low peripheral resistance by the AV fistula during the compensation period, while it affects venous system in negative way with increased venous loading. However, the negative impact of increased heart action to the venous system is partly compensated by the lymphatic system which is the third circulatory system to assist venous system independently with different hemodynamics. The lymphatic system with own unique Iymphodynamics based on peristaltic circulation from low resistance to high resistance condition, also increases its circulation to assist the compensation of overloaded venous system. Once these compensation mechanisms should fail to fight to newly established hemodynamic condition due to this abnormal AV connection, each system start to show different physiologic ${\underline{de}compensation}$ including heart and lymphatic system. The vicious cycle of decompensation between arterial and vein, two circulatory system affecting each other by mutually negative way steadily progresses to show series of hemodynamic change throughout entire circulation system altogether including heart. Clinical outcome of AV fistula from the compensated status to decompensated status is closely affected by various biological and mechanical factors to make the hemodynmic status more complicated. Proper understanding of these crucial biomechanical factors iii particular on hemodyanmic point of view is mandatory for the advanced assessment of biomechanical impact of AV fistula, since this new advanced concept of AY fistula based on blomechanical information will be able to improve clinical control of the complicated AV fistula, either congenital or acquired.

• 한국프랜차이즈경영연구
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• 제13권4호
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• pp.39-48
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• 2022

Purpose: COVID-19 has negatively influenced the financial performance of restaurant firms. Previous literature suggests that the franchising strategy effectively helps restaurant firms recover from difficult business conditions through various methods for expanding business size and enhancing business efficiency. According to risk-sharing theory, restaurant franchisors may minimize operational risks by sharing the risks with their franchisees. For instance, restaurant franchisors could generate more stable cash flow using franchise fees from their franchisees. However, research on the effect of franchise's risk reduction factor on business performance during pandemic is scarce. Thus, this study aims to examine the positive moderating effect of franchising between COVID-19 and restaurants' financial performance. Research design, data, and methodology: Panel data including financial information and franchising status of restaurant firms were collected for analysis. In order to control for unobserved firm-specific factors, generalized least squared estimation in fixed effects model was conducted. Huber-White robust standard errors were used to deal with heteroscedasticity issues. Results: It was found that COVID-19 pandemic has a negative effect on the restaurants' financial performance such as ROA (return on assets), ROE (return on equity), and PM (profit margins), which confirms the findings from existing literature. More importantly, results show that the degree of franchising has a positive moderating effect on the relationship between COVID-19 and financial performance of restaurant firms. This suggests that more active engagement in franchising may decrease negative impacts of COVID-19 on the restaurants' financial performance. Conclusions: The study supports existing literature related to risk-sharing theory, by confirming that pandemics, such as COVID-19, negatively affect financial performance of the restaurants. Furthermore, it was found that franchising strategy can help lessen negative impacts of pandemics on the firm performance. These findings can contribute to the franchise and restaurant management literature by suggesting the role of franchising in reducing business risks, thereby positively affecting financial performance. Moreover, this study offers business managers of franchisors and franchisees insights for utilizing franchising in restaurant risk management. Policymakers may also gain information on aiding restaurant firms during global crisis, such as COVID-19.

• Nuclear Engineering and Technology
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• 제45권6호
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• pp.721-730
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• 2013

Within the framework of the ASTRID project, core design studies are being conducted by the CEA with support from AREVA and EDF. The pre-conceptual design studies are being conducted in accordance with the GEN IV reactor objectives, particularly in terms of improving safety. This involves limiting the consequences of 1) a hypothetical control rod withdrawal accident (by minimizing the core reactivity loss during the irradiation cycle), and 2) an hypothetical loss-of-flow accident (by reducing the sodium void worth). Two types of cores are being studied for the ASTRID project. The first is based on a 'large pin/small spacing wire' concept derived from the SFR V2b, while the other is based on an innovative CFV design. A distinctive feature of the CFV core is its negative sodium void worth. In 2011, the evaluation of a preliminary version (v1) of this CFV core for ASTRID underlined its potential capacity to improve the prevention of severe accidents. An improved version of the ASTRID CFV core (v2) was proposed in 2012 to comply with all the control rod withdrawal criteria, while increasing safety margins for all unprotected-loss-of-flow (ULOF) transients and improving the general design. This paper describes the CFV v2 design options and reports on the progress of the studies at the end of pre-conceptual design phase 1 concerning: - Core performance, - Intrinsic behavior during unprotected transients, - Simulation of severe accident scenarios, - Qualification requirements. The paper also specifies the open options for the materials, sub-assemblies, absorbers, and core monitoring that will continue to be studied during the conceptual design phase.

• 전력전자학회논문지
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• 제26권2호
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• pp.90-95
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• 2021

In contrast to AC grounding systems, the ground electrode in DC systems continuously maintains positive or negative polarity. Ground electrodes with (+) polarity proceeds by oxidation reaction. Thus, the DC current should flow opposite to the polarity of the leakage current flowing through the (+) ground electrode by using a compensation electrode, and the current flowing through the (+) ground electrode can be 0A. However, according to protecting the (+) ground electrode, the compensation electrode corrodes and gets damaged. Thus, the (+) ground electrode must be protected from corrosion, and the service life of the compensation electrode must be extended. As an alternative, the average value of the current flowing through the compensation electrode should be equal with the value of the leakage current flowing through the (+) ground electrode by using the square waveform. Throughout the experiment, the degree of corrosion on the compensation electrode is analyzed by the frequency of the compensation electrode for a certain time. In the experiment, the frequencies of the square waveform are considered for 0.1, 1, 10, 20, 50, 100 Hz, and 1 kHz. Through experiments and analysis, the optimal frequency for reducing the electrolytic damage of the (+) electrode and compensation electrode in an LVDC grounding environment is determined.

• Asia pacific journal of information systems
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• 제19권3호
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• pp.69-98
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• 2009

We investigated what factors motivate gamers to participate in a guild and why they continue to be engaged as members of the guild. We find that, based on the result of focus group interviews with MMORPG gamers, social support and self-esteem factors play important roles. Considering both prior research and the focus group interviews we have conducted, we define social support and character control as independent variables. Character identity, guild identity, and self-esteem are proposed as mediating variables while guild flow and game loyalty as dependent variables. Accordingly, we develop the research model and hypotheses, and verify them empirically. Based on our experiences of playing the WoW game, we proposed a research model and conducted focus-group interviews (FGIs). FGIs involve formulating a hypothesis and then collecting some relevant data. FGIs were conducted face-to-face with students of C University in Korea. We formulated structured interview schedules, and the questions were based on our research variables and personal experiences. The questions for the interviews encompassed the following areas: (a) the demographic characteristics of the focus group; (b) the number of years for which respondents had played online games; (c) the motive for starting a game; (d) the number of game-characters assumed by each gamer; (e) the type of game played; and (f) other issues such as the reasons for involvement in the play, the willingness to reuse the game in case new versions were released, etc. On average, it took two hours to interview each of three groups. A primary set of FGIs was conducted with three groups on the premise that there would be some differences caused by character race (Horde vs. Alliance) or by playable server (Normal vs. Combat). With respect to the manner of playing, we found that guild members shared information, felt a sense of belonging, and played computer games for quite a long time through the guild; however, they did not undergo these experiences when playing alone. Gamers who belonged to a specific guild helped other players without expecting compensation for that, freely shared information about the game, gave away items for free, and more generous with other members who made mistakes. The guild members were aware of the existence other members and experienced a sense of belonging through interactions with, and evaluations from, other players. It was clear that social support was shown within the guild and that it played an important role as a major research variable. Based on the results of the first FGIs, a second set of in-depth FGIs was carried out with a focus on the psychology of the individual within the guild and the social community of the guild. The second set of FGIs also focused on the guild's offline meetings. Gamers, over all, recognize the necessity of joining a community, not only off-line but also online world of the guild. They admit that the guild is important for them to easily and conveniently enjoy playing online computer games. The active behavior and positive attitudes of existing guild members can motivate new members of the guild to adapt themselves to the guild environment. They then adopt the same behaviors and attitudes of established guild members. In this manner, the new members of the guild strengthen the bonds with other gamers while feeling a sense of belonging, and developing social identity, thereby. It was discovered that the interaction among guild members and the social support encouraged new gamers to quickly develop a sense of social identity and increase their self-esteem. The guild seemed to play the role of socializing gamers. Sometimes, even in the real world, the guild members helped one another; therefore, the features of the guild also spilled over to the offline environment. We intend to use self-esteem, which was found through the second set of FGIs, as an important research variable. To collect data, an online survey was designed with a questionnaire to be completed by WoW gamers, who belong to a guild. The survey was registered on the best three domestic game-sites: 'WoW playforum,' 'WoW gamemeca,' and 'Wow invent.' The selected items to be measured in the questionnaire were decided based on prior research and data from FGIs. To verify the content of the questionnaire, we carried out a pilot test with the same participants to point out ambiguous questions as a way to ensure maximum accuracy of the survey result. A total of 244 responses were analyzed from the 250 completed questionnaires. The SEM analysis was used to test goodness-of-fit of the model. As a result, we found important results as follows: First, according to the statistics, social support had statistically significant impacts on character control, character identity, guild identity and self-esteem. Second, character control had significant effects on character identity, guild identity and self-esteem. Third, character identity shows its clear impact on self-esteem and game loyalty. Fourth, guild identity affected self-esteem, guild flow and game loyalty. Fifth, self-esteem had a positive influence on the guild flow. These days, the number of virtual community is rising along with its significance largely because of the nature of the online games. Accordingly, this study is designed to clarify the psychological relationship between gamers within the guild that has been generally established by gamers to play online games together. This study focuses on the relationships in which social support influences guild flow or game loyalty through character control, character identity, guild identity, and self-esteem, which are present within a guild in the MMORPG game environment. The study results are as follows. First, the effects of social support on character control, character identity, guild identity and self-esteem are proven to be statistically significant. It was found that character control improves character identity, guild identity and self-esteem. Among the seven variables, social support, which is derived from FGIs, plays an important role in this study. With the active support of other guild members, gamers can improve their ability to develop good characters and to control them. Second, character identity has a positive effect on self-esteem and game loyalty, while guild identity has a significant effect on self-esteem, guild flow and game loyalty. Self-esteem affects guild flow. It was found that the higher the character and guild identities become, the greater the self-esteem is established. Contrary to the findings of prior research, our study results indicate that the relationship between character identity and guild flow is not significant. Rather, it was found that character identity directly affects game players' loyalty. Even though the character identity had no direct effect on increasing guild flow, it has indirectly affected guild flow through self-esteem. The significant relationship between self-esteem and guild flow indicates that gamers achieve flow, i.e., a feeling of pleasure and excitement through social support. Several important implications of this study should be noted. First, both qualitative and quantitative methods were used to conduct this study. Through FGIs, it was observed that both social support and self-esteem are important variables. Second, because guilds had been rarely studied, this research is expected to play an important role in the online community. Third, according to the result, six hypotheses (H1, H5, H6, H7, H8, and H11) setup based on FGIs, were statistically significant; thus, we can suggest the corresponding relationships among the variables as a guideline for follow-up research. Our research is significant as it has following implications: first, the social support of the guild members is important when establishing character control, character identity, guildidentity and self-esteem. It is also a major variable that affects guild flow and game loyalty. Second, character control when improved by social support shows notable influence on the development of character identity, guild identity and self-esteem. Third, character identity and guild identity are major factors to help establish gamers' own self-esteem. Fourth, character identity affects guild flow through self-esteem and game loyalty. The gamers usually express themselves through characters; the higher character identity is, the more loyalty a gamer has. Fifth, guild identity, established within the guild, has clear effects on self-esteem, guild flow and game loyalty. Sixth, qualitative and quantitative methods are employed to conduct this study. Based on the results of focus group interviews and SEM analysis, we find that the social support by guild members and psychological factors are significant in strengthening the flow of guild and loyalty to the game. As such, game developers should provide some extra functions for guild community, through which gamers can play online games in collaboration with one another. Also, we suggest that positive self-esteem which is built up through social support can help gamers achieve higher level of flow and satisfaction, which will consequently contribute to minimizing the possibility for the players to develop negative attitude toward the guild they belong to.

• 경영과정보연구
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• 제37권4호
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• pp.21-39
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• 2018

오늘날 스마트폰 기술의 향상과 함께 모바일인스턴트메신저(MIM)는 많은 사람들이 일상적으로 이용하는 커뮤니케이션 수단이 되었다. 그 중 카카오톡은 현재 국내에서 가장 높은 점유율을 차지하고 있으며 카카오게임은 대표적인 SNG 플랫폼으로 지속적인 수익을 창출하고 있다. 그러나 카카오게임의 대중적 인기와 수익창출 기여도가 증가함에도 불구하고, SNG이용자의 특성과 지속적인 게임 이용간의 관계를 다룬 연구는 부족한 실정이다. SNG이용자가 지인들 간의 관계를 통해 형성하는 사회자본과 모바일 게임 이용 시 제공하는 개인정보에 대한 우려는 모두 개인적 특성이며 커뮤니티 몰입도에 영향을 미치는 요인이다. 이에 본 연구는 개인이 타인과 관계를 형성하는 양상과 개인정보제공과 관련된 우려가 게임의 플로우 경험에 미치는 영향을 살펴보고자 하였다. 또한 플로우가 SNG재이용의도와 추천의도에 미치는 영향을 실증 분석하였다. 검증 결과, 응답자의 연결적 사회자본은 SNG에 대한 플로우에 긍정적인 영향을 미쳤으며, 결속적 사회자본은 SNG에 대한 플로우에 부정적인 영향을 미치는 것으로 나타났다. 또한 개인정보제공에 대한 인지성은 SNG에 대한 플로우에 부정적 영향을 미치나, 통제성은 긍정적인 영향을 미치는 것으로 나타났다. 마지막으로 SNG에 대한 플로우는 SNG재이용의도와 추천의도에 긍정적인 영향을 미쳤으며 SNG 재이용의도 또한 추천의도에 긍정적인 영향을 미치는 것으로 나타났다. 본 연구는 SNS의 폐쇄적 특성과 개방형 특성을 모두 갖춘 카카오 플랫폼을 중 카카오게임을 대상으로, SNG이용자의 사회자본이 플로우 경험을 통해 소비자행동에 영향을 미치는 요인이 될 수 있다는 점을 밝혔다. 또한, 아직 연구가 활발하게 진행되지 않은 SNG이용자의 개인정보제공에 대한 우려와 플로우 간의 관계를 실증적으로 검증했다는 점에서 의의가 있다. 마지막으로 본 연구의 결과를 토대로 SNG에 대한 게임몰입을 촉진시키기 위하여 이용자의 특성을 기반으로 보다 유용한 마케팅전략을 고안할 수 있을 것이다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 C
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• pp.1536-1538
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• 2002

Effects at thermal treatment on the structural and electrical properties at DLC films have been studied. The DLC films were deposited by using a modified FCVA system as a function at negative substrate bias voltage, deposition time, and nitrogen flow rate. The thermal treatment on DLC films could be achieved by performing the RTA process at $600^{\circ}C$, 2min. Structural investigation on the thermal treatment effect was evaluated by inspecting the Raman spectroscopy, XPS, AFM, and internal compressive stress. In addition, the electrical properties of DLC films were evaluated by using the high current source and Lab-View data acquisition system. As the result at RTA treatment, $sp^3/sp^2$ ratio and internal compressive stress of the DLC films were decreased tram 5% to 22% and from 1GPa to 3GPa, and the $I_D/I_G$ intensity ratios was increased from 0.19 to 0.35. It was also found that the variation of internal stress of DLC films strongly agree with the variation of $sp^3/sp^2$ fraction and $I_D/I_G$ intensity ratio.

• 한국치위생학회지
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• 제8권1호
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• pp.119-131
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• 2008

This study was peformed in order to find out the relationship between the causing factors and the production of each gas 01 oral malodor, to contribute the oral malodor control at dental clinic as well as to establish the effective application of malodor control project for public oral health program 127 patients from 20 to 40 years old who had been visited for preventive dental cares were participated for the study. Such items as caries status, periodontal status, salivary flow, viscosity, pH. Snyder test, plaque deposit and tongue plaque were checked through the oral examination in order to find out the contributing factors Hydrogen sulfide, Methyl mercaptan, Di-methyl sulfide and Ammonia gas components were checked with Oral-Chroma and Attain, the oral malodor check units. Not only the corelation coefficiencies but also the multi-way variance analysis were calculated between each causing factor and each component of oral malodor gases to estimate the contributing factors of the oral malodor. 1. There was no relationship between the caries status and each component pf the oral malodor such as sulfur compound or Ammonia, both in laboratory test and VAS test (pF0.05). It revealed negative relationship between Hydrogen sulfide and FT(rM-0.1904. pE0.05) as well as the VAS and FT (rM-0.210. pE0.05). S0, it was estimated that the less oral malador was recognized when caries state changed to filled state in Hydrogen sulfide laboratory test or VAS test 2. High relationship was showed between salivary flow and Hydrogen sulfide (rM-0.183, pM0.039), Methyl mercaptan(rM-0.234, p-0.008). Dimethyl sulfide(rM-0.234, pM0.008) and Ammonia(-0.361. pM0.001) gas(pE0.05). 3. There was a high relationship between M-PHP(Modified-Patient Hygiene Performance Index) and tong plaque all kinds of sulfide(rM0.249. pM0.005). Ammonia gas component(rM0.232, pM0.009). 4. It was found that considerable relationship was appeared between the periodontal status and Ammonia gas (rM0.274, pM0.002), so, it should be needed to control Ammonia. Such dental Cares as the prevention or early treatment of periodontal disease and the accelerating the salivary flow as well as reducing the amounts and activities of filament or spiral typed oral micro-organism were recommended for adults, not only for dental care program at the dental clinics but also for public health programs, in order to promote the oral health and quality of file for individual and community peoples.

• Journal of Astronomy and Space Sciences
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• 제25권4호
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• pp.405-414
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• 2008

이 연구에서는 고위도 하부 열권 역학을 좌우하는 물리적 과정을 이해하기 위하여, 상이한 행성간 자기장(Interplanetary Magnetic Field, IMF)에 따른 남반구 고위도 하부 열권에서의 소용돌이도(vorticity)와 발산(divergence)을 분석하였다. 이 연구를 위하여 미국립대기연구소(National Center for Atmospheric Research, NCAR)의 열권-이온권 전기역학적 대순환 모델(Thermo sphere-Ionosphere Electrodynamic General Circulation Model, TIEGCM)을 이용하였다. 소용돌이도와 발산 분석은 전체 수평 바람장을 최종적으로 결정하는 운동량원(momentum source)을 밝히는데 도움을 주는 근원적인 흐름을 파악할 수 있게 해주며, 운동량원들의 상대적인 강도를 분석해내는데 좋은 도구가 된다. 고위도 하부 열권의 평균 바람장은 태양 복사와 쥴가열에 의해 유발되는 발산운동 보다는 이온대류에 의해 유발되는 회전운동에 의해 주로 지배된다는 것이 확인되었다. $IMF{\neq}0$와 IMF=0인 경우의 고위도 열권 하부에서의 소용돌이도 차이(difference vorticity)가 모든 IMF 조건에서 발산장 차이(difference divergence)에 비해 훨씬 더 크게 나타났다. 이는 IMF가 발산적인 흐름보다 회전적인 흐름에 더 강하게 영향을 끼치며, 나아가 IMF가 발산운동을 유발하는 에너지 유입보다는 회전운동을 유발하는 운동량 유입에 더 강하게 영향을 끼침을 의미한다. IMF의 방향에 따라 고위도 하부 열권에서의 소용돌이도 차이의 양상이 매우 달랐다 $B_y$가 음일 때는 지자기 위도 $-70^{\circ}$ 이상의 고위도에서 극을 중심으로 양의 소용돌이도 차이가 나타나고 $B_y$가 양일 때는 음의 소용돌이도 차이가 나타났다. $B_z$가 음인 경우 소용돌이도 차이가 저녁 영역에는 양이고 새벽 영역에는 음이며, $B_z$가 양인 경우에는 반대의 분포를 보였다. $B_z$가 음일 때가 양일 때보다 소용돌이도 차이가 더 큰 것으로 확인되었는데, 이는 IMF $B_z$가 남쪽으로 향할 때가 북쪽으로 향할 때보다 고위도 이온권의 이온대류를 더 강화시켜 열권 중성대기의 회전적인 흐름을 더 강하게 유발시킴을 의미한다.