• Korean Journal of Fisheries and Aquatic Sciences
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• v.55 no.3
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• pp.328-337
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• 2022

This study investigated the removal performance of a foam fractionator under seawater conditions. The foam fractionator was tested using a 3×3×3 factorial design for operating conditions by combining different solids concentrations (SS; 1, 5, and 10 mg·L^-1), surface air velocities (SAV; 1.1, 1.5, and 2.1 cm·sec^-1), and hydraulic residence times (HRT; 1, 3, and 6 min) at 16℃. Performance parameters such as daily solids removal rate and efficiency were measured, and a multi-regression model equation was developed accordingly. The daily solids removal rate and removal efficiency varied with the experimental conditions and ranged from 0.14-2.33 g-solids·m^-3-air·day^-1 and 8.9-96.7 %, respectively. Overall, the daily solids removal rate increased with increasing SS and SAV and decreasing HRT, whereas the removal efficiency increased with increasing SAV and HRT and decreasing SS. The daily solids removal rate (g-solids·m^-3-air·day^-1) of the foam fractionator for SAV (cm·sec^-1), SS (mg·L^-1) and HRT (min) were described by the following multi-regression model: Daily solids removal rate [f(z)]=-0.118+0.422SAV+0.094HRT+0.141SS (r²=0.873).

• Nuclear Engineering and Technology
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• v.53 no.5
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• pp.1416-1428
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• 2021

Pebble flow characteristics can be significantly affected by the configuration of pebble bed, especially for HTGR pebble beds. How to achieve a desired uniform flow pattern without stagnation is the top priority for reactor design. Pebbles flows inside some specially designed pebble bed with arc-shaped contraction configurations at the bottom, including both concave-inward and convex-outward shapes are explored based on discrete element method. Flow characteristics including pebble retention, residence-time frequency density, flow uniformity as well as axial velocity are investigated. The results show that the traditionally designed pebble bed with cone-shape bottom is not the most preferred structure with respect to flow pattern for reactor design. By improving the contraction configuration, the flow performance can be significantly enhanced. The flow in the convex-shape configuration featured by uniformity, consistency and less stagnation, is much more desirable for pebble bed design. In contrast, when the shape is from convex-forward to concave-inward, the flow shows more nonuniformity and stagnation in the corner although the average cross-section axial velocity is the largest due to the dominant middle pebbles.

• Journal of Korean Clinical Nursing Research
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• v.28 no.3
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• pp.270-276
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• 2022

Purpose: The purpose of this study was to validate the Edmonson psychiatric fall risk assessment tool (EPFRAT) for psychiatric inpatients. Methods: Data from retrospective study were collected from 670 adult inpatients in two departments of mental health medicine of a tertiary general hospital by reviewing their electronic medical records. There were 41 patients who experienced falls and 629 patients who did not experience falls during the period from January to December 2019. Data were analyzed by sensitivity, specificity, positive predictive value, negative predictive value, and a receiver-operating characteristic curve (ROC) for validity assessment using the IBM SPSS/WIN 26.0 program. Results: Factors affecting falls were the participant's age, guardian's residence, high-risk determination at the time of admission, and comorbidity. At the 85 points where the point of sum of the sensitivity and specificity was largest, the sensitivity, specificity, positive predictive value, and negative predictive value of EPFRAT were 92.7%, 79.7%, 22.9%, and 99.4%, respectively. The area under the ROC to assess the overall validity of the tool was .92 (95% CI 0.89~0.94). Conclusion: The EPFRAT was proved to be valid and reasonable for predicting falls in psychiatric inpatients. Based on the results of this study, it could be used for the assessment of high-risk patients for falls in psychiatric units.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.16 no.12
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• pp.3836-3854
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• 2022

The student group division is benefit for universities to do the student management based on the group profile. With the widespread use of student smart cards on campus, especially where students living in campus residence halls, students' daily activities on campus are recorded with information such as smart card swiping time and location. Therefore, it is feasible to depict the students with the daily activity data and accordingly group students based on objective measuring from their campus behavior with some regular student attributions collected in the management system. However, it is challenge in feature representation due to diverse forms of the student data. To effectively and comprehensively represent students' behaviors for further student group division, we proposed to adopt activity data from student smart cards and student attributes as input data with taking account of activity and attribution relationship types from different perspective. Specially, we propose a novel student group division method based on a multi-view student attribute heterogeneous information network (MSA-HIN). The network nodes in our proposed MSA-HIN represent students with their multi-dimensional attribute information. Meanwhile, the edges are constructed to characterize student different relationships, such as co-major, co-occurrence, and co-borrowing books. Based on the MSA-HIN, embedded representations of students are learned and a deep graph cluster algorithm is applied to divide students into groups. Comparative experiments have been done on a real-life campus dataset collected from a university. The experimental results demonstrate that our method can effectively reveal the variability of student attributes and relationships and accordingly achieves the best clustering results for group division.

• Journal of The Korea Institute of Healthcare Architecture
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• v.27 no.4
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• pp.41-50
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• 2021

Purpose: This study is aimed at the case of the cognitive health design pilot projects promoted by the Seoul Metropolitan Government since 2014 in terms of design to solve social problems in accordance with the aging population of our society. The purpose of this study is to analyze the maintenance and management of the projects and to suggest implications for the promotion and expansion of sustainable cognitive health design in the future. Method: It set the analysis frame by dividing management into maintenance-damage-demolition for the spatial types and spatial elements suggested in the Seoul Cognitive Health Guidelines. And it analyze the actual conditions of four pilot projects based on the field survey. Results: First, the ratio of damage and demolition was higher than maintenance. Second, designs and techniques with low durability were applied. Most of the cases where floor marks were applied to the external environment were lost or difficult to recognize, and their functions were limited due to storage of goods and parking of vehicles and motorcycles. Third, there was a large variation according to the type of residence. The project contents that can be applied to the low-rise residential area were also limited, and more elements were demolished than in the apartment type. Implications: First, it should limit project contents of space types and space elements that can be maintained even over time. Second, it should seek sustainable design and technical solutions. Third, it should seek alternatives to cognitive health design in low-rise residential areas where a large number of elderly people live.

• Journal of the Korean Society for Library and Information Science
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• v.57 no.1
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• pp.233-261
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• 2023

Drawing on Bronfenbrenner's ecological system, the study explored the effect of the ecological variables affecting library satisfaction for mothers of early school-age children. The study used the eighth wave(2015) of Panel Study on Korean Children and conducted correlation analysis, multiple regression analysis, hierarchical regression analysis, and stepwise regression analysis. Researchers selected ecological variables for each ecological system based on previous studies. Results showed that mothers had moderate satisfaction with libraries, and their satisfaction with libraries was affected by library accessibility, satisfaction with public services, type of residence, children's reading time, and supportiveness of parenting policy. The study showed that external factors such as family, community, and policies could affect library satisfaction along with internal factors in the sociocultural context. The study suggested a possible practical implication for library policy.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.518-518
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• 2023

자연하천에서 오염물질의 혼합 거동은 비균일한 지형학적 요인으로 인해 매우 복잡한 특성을 나타낸다. 일반적으로 오염물질 거동 모델링에서는 수체에서의 혼합을 Fick의 법칙에 따라 유속에 의한 이송과 난류에 의한 확산으로 계산하고, 국부적인 정체현상 등에 의한 non-Fickian 혼합을 야기하는 하천의 특성을 기하학적 지형 형상으로 구현하여 실제 현상에 근접한 혼합 거동을 재현한다. 하지만 계산의 효율성을 위하여 모델링의 차원을 낮추는 경우, 하천의 지형을 경계조건으로 고려할 수 없게 된다. 특히, 1차원 모델링의 경우 하천의 비균일성을 무시하고 1개의 유선으로 간주하며, 이 경우 non-Fickian 물질이동 해석을 위한 추가적인 현상학적 해석이 필요하다. 지난 50년간, non-Fickian 물질이동 해석을 위한 다양한 현상학적 모형이 제시되어 왔다. 하천을 흐름영역과 정체영역으로 구분하고 두 개의 영역 사이의 물질교환 속도를 모델링하거나, Random walk 개념으로 물질이 이동하는 경우와 이동하지 않는 경우를 확률론적으로 모델링하거나, 물질이 정체되었을 때 다시 빠져나오는 시간을 모델링하는 경우가 그 예이다. 본 연구에서는 선행연구에서 제시한 음함수 형태의 현상학적 모형을 기반으로, 수치적 반복계산 없이 상류 경계에서 임의의 형태의 농도곡선(shape-free breakthrough curve)을 갖는 오염물질운(cloud)이 일정 거리를 유하하며 발생하는 변화를 예측할 수 있는 해를 제시한다. 본 연구의 방법론은 추적법(routing procedure)을 활용한 Fickian 혼합 해석, 전달함수(transfer function) 형태의 정체시간분포 해석, 그리고 라플라스 도메인에서의 해석해 유도를 포함한다. 본 연구에서 제시된 해는 2020년 경상북도 김천시에 위치한 감천의 4.5 km 구간에서 수행한 추적자 실험의 현장 자료를 통해 정확도를 검증하여 타당성을 입증하였다.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.200-200
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• 2021

하천은 용수공급, 관개, 친수활동, 산업활동 등 인간의 활동에 중요한 역할을 한다. 이에 따라 수질관리는 필수적이며 유기물, 중금속, 화학물질 등의 용존물질들은 수질문제에 직접적으로 영향을 미친다. 따라서 하천에서의 용존물질의 혼합 거동을 파악하기 위한 연구가 지난 수십년간 이루어지고 있다. 하천 흐름에 따른 오염물질의 이동 및 확산 거동을 예측하기 위하여 1차원 추적모형이 활용되는데, 그 중 하천저장대 모형(Transient Storage Model, TSM)은 자연하천의 복잡하고 불규칙한 수리·지형적인 특성을 단순하게 반영할 수 있다는 장점때문에 가장 많이 사용된다. 하지만 TSM은 매개변수에 대한 의존성과 불확도가 크며, TSM의 저장대에서의 농도분포에 대한 지수함수형태의 모델링이 하상간극수역(Hyporheic zone)에서의 저장대 특성을 반영하기에 구조적으로 부정확하다는 단점이 제기되고 있다. 최근 이러한 TSM의 단점을 보완하고 하천에서의 저장대 메커니즘을 보다 정확하게 구현하고자 체류시간분포(residence time distribution)를 이용한 확률론적 저장대 모델링 프레임워크가 등장하고 있다. 본 연구에서는 본류대와 저장대에서의 오염물질의 체류시간분포를 분리하여 해석하고 이를 전달함수(transfer function)를 이용한 합성곱으로 결합한 형태의 프레임워크를 적용하여 모델링하였다. 상기의 모형을 검증하기 위하여 2019년 감천의 4.85km 구간에서 추적자 실험을 실시하였다. 실험 당시 유량은 12.9 m³/s로 풍수기에 해당되며 평균 유속은 약 0.6 m/s로 측정되었다. 모형의 매개변수는 추적자 실험으로부터 최적화 기법을 통해 역모델링기법으로 결정하였다. 제안된 모형에 의한 모의 결과를 추적자 실험에서의 농도측정자료와 비교한 결과, 평균 0.988의 결정계수를 보여 매우 높은 정확도를 보이고 있음을 알 수 있었다. 저장대특성을 나타내는 농도곡선의 꼬리부에 대하여 같은 조건에서 1차원 이송-분산(ADE) 모형, TSM의 모의결과와도 비교한 결과 본 모형은 추적자 실험 농도측정 결과와 평균 0.195의 오차율을 보이며, 이는 ADE 모형과 TSM의 오차율인 14.03과 1.866에 비해 매우 정확한 것으로 나타났다.

• Transactions of the Korean hydrogen and new energy society
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• v.34 no.3
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• pp.316-326
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• 2023

Development of carbon-neutral fuel production technologies to solve climate change issues is progressing worldwide. Among them, methane can be produced through the synthesis of hydrogen produced by renewable energy and carbon dioxide captured through a CO₂ methanation reaction, and the fuel produced in this way is called synthetic methane or e-methane. The CO₂ methanation reaction can be conducted via biological or thermochemical methods. In this study, a 30 Nm³/h thermochemical CO₂ methanation process consisting of an isothermal reactor and an adiabatic reactor was used. The CO₂ conversion rate and methane concentration according to the temperature measurement results at the center and outside of the adiabatic reactor were analyzed. The gas flow into the adiabatic reactor was found to reach equilibrium after about 1.10 seconds or more by evaluating the residence time. Furthermore, experimental and analysis results were compared to evaluate performance of the reactor.

• Journal of architectural history
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• v.32 no.5
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• pp.69-80
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• 2023

Before the 15th century, the main buildings of the residences of the ruling class in Seoul consisted of Momchae(身梗), Seocheong(西廳), and Naeru(內樓)‧Chimru(寢樓). Based on the equality of the relationship between husband and wife, the couple lived in the main building[Momchae] in the center of the mansion, but based on the individuality of the relationship between husband and wife, each had an area consisting of the same section within the building. Naeru·Chimru was the two floors bedroom building became a common living space for the minister and wife, upstairs in summer, downstairs in winter. In preparation for large gatherings and important receptions, an open-structured West Hall(西廳) was located on the west side of the mansion. Momchae, Seocheong, and Naeru‧Chimru were the common building types and layouts of the residences of the highest ruling class, including high-ranking officials, until the reign of King Sejong. However, from around the time of King Seongjong, Seocheong and Chimru came to be regarded as privileged and luxurious buildings only allowed for the grand prince's residence. The layout of the bedroom, main building (including Wings), Outer Sarang[外舍廊], and Joyangru[朝陽樓] of Prince Bongrim's mansion built in the first half of the 17th century clearly shows the transitional period when the arrangement of chimru, main building, and western office was disrupted and the layout changed to the Inner main building(Anchae for wife) and Outer main building(Sarangchae for husband).