• Current Optics and Photonics
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• 제6권6호
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• pp.521-549
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• 2022

Fiber lasers have made remarkable progress over the past three decades, and they now serve far-reaching applications and have even become indispensable in many technology sectors. As there is an insatiable appetite for improved performance, whether relating to enhanced spatio-temporal stability, spectral and noise characteristics, or ever-higher power and brightness, thermal management in these systems becomes increasingly critical. Active convective cooling, such as through flowing water, while highly effective, has its own set of drawbacks and limitations. To overcome them, other synergistic approaches are being adopted that mitigate the sources of heating at their roots, including the quantum defect, concentration quenching, and impurity absorption. Here, these optical methods for thermal management are briefly reviewed and discussed. Their main philosophy is to carefully select both the lasing and pumping wavelengths to moderate, and sometimes reverse, the amount of heat that is generated inside the laser gain medium. First, the sources of heating in fiber lasers are discussed and placed in the context of modern fiber fabrication methods. Next, common methods to measure the temperature of active fibers during laser operation are outlined. Approaches to reduce the quantum defect, including tandem-pumped and short-wavelength lasers, are then reviewed. Finally, newer approaches that annihilate phonons and actually cool the fiber laser below ambient, including radiation-balanced and excitation-balanced fiber lasers, are examined. These solutions, and others yet undetermined, especially the latter, may prove to be a driving force behind a next generation of ultra-high-power and/or ultra-stable laser systems.

• 한국환경보건학회지
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• 제46권6호
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• pp.676-684
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• 2020

Objectives: In this study, the extent of environmental exposure reduction behavior among the elderly living in Gongju City was identified according to demographic and sociological characteristics of individual health behavior and environmental factors. In addition, the relationship between subjective health knowledge and environmental exposure reduction behavior among the elderly was investigated. Methods: Demographic and sociological factors, subjective health status, environmental factors, and environmental exposure reduction behavior were investigated among 120 elderly people in Gongju City. Through multiple regression analysis, variables with significant relationships with environmental exposure reduction behavior were identified (SPSS ver. 22, IBM, Armonk, NY, USA). The survey (IRB-2018-0096) was conducted over about two weeks (from Dec. 3 to 14, 2018). Results: The extent of practicing environmental exposure reduction behavior by the elderly in Gongju City was high in terms of cleaning, ventilation when cooking food, periodic outdoor activities, and ventilation when smoking. Significant variables were gender, past smoking and current non-smoking, subjective health knowledge, and subjective health status. The most influential variable was subjective health knowledge (β= .411). Conclusion: There was a significant relationship between the level of subjective health knowledge and the level of objective education for health behavior related to the reduction of environmental exposure among the elderly.

• Journal of Information Processing Systems
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• 제16권6호
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• pp.1424-1436
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• 2020

Although huge progress has been made in current image segmentation work, there are still no efficient segmentation strategies for tree image which is taken from natural environment and contains complex background. To improve those problems, we propose a method for tree image segmentation combining adaptive mean shifting with image abstraction. Our approach perform better than others because it focuses mainly on the background of image and characteristics of the tree itself. First, we abstract the original tree image using bilateral filtering and image pyramid from multiple perspectives, which can reduce the influence of the background and tree canopy gaps on clustering. Spatial location and gray scale features are obtained by step detection and the insertion rule method, respectively. Bandwidths calculated by spatial location and gray scale features are then used to determine the size of the Gaussian kernel function and in the mean shift clustering. Furthermore, the flood fill method is employed to fill the results of clustering and highlight the region of interest. To prove the effectiveness of tree image abstractions on image clustering, we compared different abstraction levels and achieved the optimal clustering results. For our algorithm, the average segmentation accuracy (SA), over-segmentation rate (OR), and under-segmentation rate (UR) of the crown are 91.21%, 3.54%, and 9.85%, respectively. The average values of the trunk are 92.78%, 8.16%, and 7.93%, respectively. Comparing the results of our method experimentally with other popular tree image segmentation methods, our segmentation method get rid of human interaction and shows higher SA. Meanwhile, this work shows a promising application prospect on visual reconstruction and factors measurement of tree.

• 한국농림기상학회지
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• 제23권4호
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• pp.356-365
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• 2021

농업기상재해 조기경보 서비스를 전국으로 확대하기 위해서는 각 지역별로 고유한 지리적, 농업환경적 특성에 대한 연구가 필요하다. 그리고 그에 적합한 전산 환경을 개발하는 것은 연구 대상 지역의 많은 농가에게 다양한 작물과 품종에 대한 서비스를 가능하게 하는 중요한 요소이다. 특히 확장성 있는 전산 환경의 설계는 서비스 영역이 확대되면서 전산 환경의 규모가 증가하게 되므로 농업 기상 서비스 품질에 상당한 영향을 미칠 수 있다. 이 연구의 목적은 각 지역별로 분산되어 서비스를 제공하고 있는 현재의 전산 구성에 대한 문제를 도출하고 그 해결책을 모색하는 것이다. 약 1년간 실험 운영을 통해 자체 평가한 결과 지역별로 분산된 조기경보서비스 시스템을 통합하면 중복 연산을 줄이고, 데이터의 효율적 저장과 종합적인 관리가 가능할 것으로 확인되었다. 이는 서비스 지역이 전국 규모로 확대되는 상황에서도 보다 안정적인 조기경보 서비스가 가능함을 의미한다. 이 연구를 통해 개별 농가에 대해 보다 향상된 품질의 서비스가 가능할 것으로 기대한다.

• 인간식물환경학회지
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• 제23권2호
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• pp.159-170
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• 2020

The purpose of this study was to understand the current status of education and programs and to identify the items that urban residents need most for garden management. First of all, there were 45 sites (40.5%) with gardens operated by city and county local governments nationwide, and 41(91.1%) of them had dedicated staff (1.8 persons on average). The average area of gardens was 18,623 m², garden area per person was 20.27m², the average number of participants was 683, and the average period of use was 8.69 months. In addition to gardening activities, 14 (31.1%) out of 45 sites were operating small group meetings, with an average of 2.29 meetings and 67 participants. In the satisfaction survey after gardening activities, 88.9% of 18 sites were satisfied. According to the questionnaire about education and programs related to garden users, an average of four sessions were conducted per education. In terms of education, the contents were in the following order: basic education on garden cultivation (33.9%) > prior education on garden operation (28.9%) > pest control (14.0%) > eco-friendly management (11.6%) > pesticides and Positive List System (9.9%) > others (1.7%). Over 95% of the respondents were generally satisfied. Regarding the perception survey on which items are needed to develop garden management guidelines, the most necessary items were in the order of crop management (38.7%) > public garden etiquettes among users (27.9%) > pest control (14.4%) > weed management (13.5%) > activities using harvest (5.4%). The contents that are to be included in the guidelines were in the order of garden planning and crop selection (17.2%) > cultivation techniques and schedule (16.5%) > pest and soil management (15.7%) > introduction of garden crops and gardening models (12.7%) > garden etiquettes (10.7%). In establishing urban garden management plans by region, the results will have high utility value as the basic data for continuous garden operation by setting a direction that meets the regional characteristics as well as the needs of urban residents.

• 한국산업보건학회지
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• 제31권4호
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• pp.396-416
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• 2021

Objectives: This study was conducted to analyze the trends of government R&D (R&D) projects related to laboratory safety over the past 20 years. Methods: We collected publications from various databases(DBs) with words such as laboratory(ies), lab(s), researcher(s), laboratory worker(s), safety, environment, hazard(s), risk(s), and so on. Selected publications were analyzed by the research funds and the number of projects according to the investment subject and research characteristics. Results: About 93% of the total R&D budget went to government policy projects, not scientific research. Second, from the perspective of 'safety management activities', most of the research is related to management and inspection at the organizational level. Issues that need to be discussed at the national level like policy governance are not included. Third, focusing on the 'safety management cycle', there were few studies related to 'prediction' or 'post-response'. Fourth, when an analysis framework combining the perspectives of 'safety management activities' and 'safety management cycle' is applied, most of the budget is spent on infrastructure such as digital management systems, whereas basic knowledge for prevention and production of evidence was very few. Conclusions: In order to prevent policy planning without policy evaluation, implementation without strategy, and evaluation without evidence, it is necessary to expand investment in empirical research on risks, research on the effectiveness of current application methods, and research on theory development. The government budget for laboratory safety-related projects should be managed separately from the R&D budget for scientific research. Although less than 5% of the budget allocated to scientific research is the total budget, an optical illusion occurs because both the project budget and the scientific research budget are counted as R&D budgets.

• Nuclear Engineering and Technology
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• 제54권3호
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• pp.860-866
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• 2022

An accurate prediction of the pressure drop along the flow paths is crucial in the design of advanced passive systems cooled by heavy liquid metal coolants. To date, a generic pressure drop correlation over spacer grids by Rehme has been applied extensively, which was obtained from substantial experimental data with multiple types of components. However, a few experimental studies have reported that the correlation may give large discrepancies. To provide a more reliable correlation for ring-type spacer grids, the current numerical study aims at figuring out the most critical factor among four hypothetical parameters, namely the flow area blockage ratio, number of fuel rods, type of fluid, and thickness of the spacer grid in the flow direction. Through a set of computational fluid dynamics simulations, we observed that the flow area blockage ratio dominantly influences the pressure loss characteristics, and thus its dependence should be more emphasized, whereas the other parameters have little impact. Hence, we suggest a new correlation for the drag coefficient as C_B = C_ν,m/ε^2.7, where C_ν,m is formulated by a nonlinear fit of simulation data such that C_ν,m = -11.33 ln(0.02 ln(Re_b)).

• 문화기술의 융합
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• 제9권1호
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• pp.443-448
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• 2023

지난 5년간 수면질환자 수는 2017년 84만명에서 2021년 109만명으로 약 25만명이 증가하는 등 수면장애인구에 관한 정부의 수면다원검사 급여화이후 그 관리비용은 지속적으로 증가하고 있다. 또한 수면장애가 치매 위험인자를 유발하는 요인이며, 나아가 초고령화 추세에서 전국민 건강관리라는 측면에서 수면장애인구는 향후 안정적인 건강보험 재정관리 측면에서도 매우 중요한 정책이슈이다. 따라서 본 연구는 최근들어 증가하는 수면장애인구에 관한 수면다원검사현황 및 효과적인 급여정책화가 실제 이를 담당하는 의료기관에서 효율적인 진료환경을 구축하고 있으며, 그 올바른 시행을 통해 향후 수면장애에 관한 적정한 수면관리정책으로 기능하고 있는지 관련기관 및 전문가 인터뷰를 통해 그 실태와 개선방안을 모색하고자 한다.

• Journal of Ceramic Processing Research
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• 제13권spc2호
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• pp.260-264
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• 2012

We have investigated the effect of ambient gases on the structural, electrical, and optical characteristics of IZO thin films intended for use as anode contacts in the organic light emitting diodes (OLED) devices. These IZO thin films were deposited on the PES film by radio frequency (RF) magnetron sputtering under different ambient gases (Ar, Ar + O2, and Ar + H2) at room temperature. In order to investigate the influences of the ambient gases, the flow rate of oxygen and hydrogen in argon has been changed from 0.1 sccm to 0.5 sccm, respectively. All the IZO thin film has an (222) preferential orientation regardless of ambient gases. The electrical resistivity of the IZO film increased with increasing O2 flow rate, whereas the electrical resistivity decreased sharply under an Ar + H2 atmosphere and was nearly similar regardless of the H2 flow rate. The change of electrical resistivity with changes in the ambient gas composition was mainly interpreted in terms of the charge carrier concentration rather than the charge carrier mobility. All the films showed the average transmittance over 85% in the visible range. The OLED device was fabricated with different IZO substrates made with the configuration of IZO/α-NPD/DPVB/Alq3/LiF/Al in order to elucidate the performance of the IZO substrate. The current density and the luminance of OLED devices with IZO thin films deposited in 0.5 sccm H2 ambient gas are the highest amongst all other films.

• 한국프랜차이즈경영연구
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• 제4권1호
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• pp.25-53
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• 2013

국내 커피전문점 시장은 지난 1999년 스타벅스가 매장을 개설한 시점으로부터 10여년 이상의 시간이 경과하면서 양적으로도 급격한 성장을 지속하여 왔다. 최근에는 각 커피전문점 브랜드별로 경쟁이 가속화되면서 맛이나 서비스의 차이가 줄어드는 경향을 보이는 등 성숙기 시장의 특성을 보이고 있다. 경쟁이 매우 치열해지는 성숙기 시장에서는 제품 및 서비스 차별화와 가격 프리미엄의 확보를 위해서는 차별적인 브랜드 이미지를 구축하는 것이 필요하다. 본 연구는 성숙기에 진입한 국내 커피전문점 시장의 주요 5개 브랜드에 대해 점포개성 척도를 사용하여 현재의 포지셔닝을 실증적으로 분석하였다. 그 결과를 바탕으로 실무적인 시사점을 제시하였다는 점에서 본 연구의 의의가 있다. 연구 결과, 소비자들은 커피전문점 브랜드를 국내 중소기업 전문브랜드와 외국 전문브랜드로 나누거나, 매장의 규모가 큰 매장이 다수인 브랜드와 소규모 매장이 많은 브랜드로 구분하여 인식하고 있다는 점, 그리고 소비자들이 이상적으로 생각하는 브랜드의 점포개성은 신뢰, 세련, 매력이라는 점을 발견하였다. 이와 같은 연구 결과를 바탕으로 파악된 각 커피전문점의 점포개성 이미지 강약점을 토대로 강점은 강화하고 약점을 보완하기 위한 마케팅 전략을 수립하고 실행해야 할 것이다.