• Wind and Structures
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• 제35권3호
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• pp.177-191
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• 2022

Trains emerging on a streamlined bridge-girder may have salient interference effects on the aerodynamic properties of the bridge. The present paper aims at investigating these interferences by wind tunnel measurements, covering surface pressure distributions, near wake profiles, and flow visualizations. Experimental results show that the above interferences can be categorized into two primary effects, i.e., an additional angle of attack (AoA) and an enhancement in flow separation. The additional AoA effect is demonstrated by the upward-moved stagnation point of the oncoming flow, the up-shifted global symmetrical axis of flow around the bridge-girder, and the clockwise-deflected orientation of flow approaching the bridge-girder. Due to this additional AoA effect, the two critical AoAs, where flow around the bridge-girder transits from trailing-edge vortex shedding (TEVS) to impinging leading-edge vortices (ILEV) and from ILEV to leading-edge vortex shedding (LEVS) of the bridge-girder are increased by 4° with respect to the same bridge-girder without trains. On the other hand, the underlying flow physics of the enhancement in flow separation is the large-scale vortices shedding from trains instead of TEVS, ILEV, and LEVS governed the upper half bridge-girder without trains in different ranges of AoA. Because of this enhancement, the mean lift and moment force coefficients, all the three fluctuating force coefficients (drag, lift, and moment), and the aerodynamic span-wise correlation of the bridge-girder are more significant than those without trains.

• 센서학회지
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• 제31권5호
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• pp.318-323
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• 2022

Barium titanate (BaTiO₃) is considered to be a beneficial ceramic material for multilayer ceramic capacitor (MLCC) applications because of its high dielectric constant and low dielectric loss. Numerous attempts have been made to improve the physical properties of BaTiO₃ in response to recent market trends by employing multicomponent alloying strategies. However, owing to its significant number of atomic combinations and unpredictable physical properties, finding a traditional experimental approach to develop multicomponent systems is difficult; the development of such systems is also time-consuming. In this study, 168 new structures were fabricated using special quasi-random structures (SQSs) of Ba_1-xCa_xTi_1-yZryO₃, and 1680 physical properties were extracted from first-principles calculations. In addition, we built an integrated database to manage the computational results, and will provide big data solutions by performing data analysis combined with AI modeling. We believe that our research will enable the global materials market to realize digital transformation through datalization and intelligence of the material development process.

• 한국해양공학회지
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• 제36권5호
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• pp.340-352
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• 2022

This article presents a modeling method for the uncorrelated measurement error of the ultra-short baseline (USBL) acoustic positioning system for aiding navigation of underwater vehicles. The Mahalanobis distance (MD) and principal component analysis are applied to decorrelate the errors of USBL measurements, which are correlated in the x- and y-directions and vary according to the relative direction and distance between a reference station and the underwater vehicles. The proposed method can decouple the radial-direction error and angular direction error from each USBL measurement, where the former and latter are independent and dependent, respectively, of the distance between the reference station and the vehicle. With the decorrelation of the USBL errors along the trajectory of the vehicles in every time step, the proposed method can reduce the threshold of the outlier decision level. To demonstrate the effectiveness of the proposed method, simulation studies were performed with motion data obtained from a field experiment involving an autonomous underwater vehicle and USBL signals generated numerically by matching the specifications of a specific USBL with the data of a global positioning system. The simulations indicated that the navigation system is more robust in rejecting outliers of the USBL measurements than conventional ones. In addition, it was shown that the erroneous estimation of the navigation system after a long USBL blackout can converge to the true states using the MD of the USBL measurements. The navigation systems using the uncorrelated error model of the USBL, therefore, can effectively eliminate USBL outliers without loss of uncontaminated signals.

• 산업융합연구
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• 제21권1호
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• pp.43-53
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• 2023

중국에서 기업 내부의 창의적인 아이디어와 건설적인 제안은 새로운 글로벌 기회와 도전을 더 잘 맞이할 수 있다. 따라서 본 연구는 실증분석을 통해 채택된 발언행동이 중국 직원들의 업무성과에 미치는 영향을 검증하고, 매개변수로 조직지원 인식을 선정하고자 한다. 본 연구는 이론적 연구를 바탕으로 6가지 연구 가설을 제안하고 연구모형을 설정한다. 조사 방법으로 중국의 직원들로부터 데이터를 수집했고 구조 방정식 모델(SEM)을 사용하여 가설을 검증하였다. 분석결과는 채택된 발언행동과 직무만족, 직무몰입, 직무성과의 관계에서 조직지원 인식이 매개역할을 하는 것으로 나타났다. 그러나 본 연구는 자료수집의 편의성 때문에 연구결과의 일반화에 한계가 있고 향후 연구는 이 방법론 문제를 개선해야 한다.

• 한국환경과학회지
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• 제32권8호
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• pp.595-611
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• 2023

The purpose of this study is to improve the daily prediction results of PM2.5 from the air quality diagnosis and evaluation system operated by the Busan Institute of Health and Environment in real time. The air quality diagnosis and evaluation system is based on the photochemical numerical model, CMAQ (Community multiscale air quality modeling system), and includes a 3-day forecast at the end of the model's calculation. The photochemical numerical model basically has limitations because of the uncertainty of input data and simplification of physical and chemical processes. To overcome these limitations, this study applied DNN (Deep Neural Network), a deep learning technique, to the results of the numerical model. As a result of applying DNN, the r of the model was significantly improved. The r value for GFS (Global forecast system) and UM (Unified model) increased from 0.77 to 0.87 and 0.70 to 0.83, respectively. The RMSE (Root mean square error), which indicates the model's error rate, was also significantly improved (GFS: 5.01 to 6.52 ug/m³ , UM: 5.76 to 7.44 ug/m³ ). The prediction results for each concentration grade performed in the field also improved significantly (GFS: 74.4 to 80.1%, UM: 70.0 to 77.9%). In particular, it was confirmed that the improvement effect at the high concentration grade was excellent.

• 지능정보연구
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• 제29권3호
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• pp.341-359
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• 2023

메타버스는 다양한 기술 수단을 활용하여 몰입형 관광 서비스 경험을 제공할 수 있어 문화관광 산업에 큰 혁신을 가져올 것으로 예상되나 관련 연구는 아직 미미한 실정이다. 이에 본 연구는 S-O-R 모델을 기반으로 메타버스 플랫폼에서의 문화관광 활동 참여 의도에 영향을 미치는 요인을 분석하는 것을 목표로 하였다. 본 연구 결과는 문화관광 참여자의 학습 및 오락에 대한 내적 동기와 메타버스가 제공하는 다양한 감각 자극 및 사회적 상호작용과 같은 기능이 몰입 경험과 인지된 즐거움을 매개로 참여 의도에 유의미한 영향을 미치는 것을 보여주었다. 본 연구는 이를 통해 문화관광 산업의 메타버스 플랫폼 구축에 활용될 수 있는 다양한 실무적 시사점을 제시한다.

• 대한간호학회지
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• 제53권4호
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• pp.426-438
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• 2023

Purpose: Walking practice is a representative indicator of the level of physical activity of local residents. Although the world health organization addressed reduction in prevalence of insufficient physical activity as a global target, the rate of walking practice in Korea has not improved and there are large regional disparities. Therefore, this study aimed to explore the spatial variations of walking practice and its associated factors in Korea. Methods: A secondary analysis was conducted using Community Health Outcome and Health Determinants Database 1.3 from Korea Centers for Disease Control and Prevention. A total of 229 districts was included in the analysis. We compared the ordinary least squares (OLS) and the geographically weighted regression (GWR) to explore the associated factors of walking practice. MGWR 2.2.1 software was used to explore the spatial distribution of walking practice and modeling the GWR. Results: Walking practice had spatial variations across the country. The results showed that the GWR model had better accommodation of spatial autocorrelation than the OLS model. The GWR results indicated that different predictors of walking practice across regions of Korea. Conclusion: The findings of this study may provide insight to nursing researchers, health professionals, and policy makers in planning health programs to promote walking practices in their respective communities.

• 한국정책학회보
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• 제23권4호
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• pp.179-209
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• 2014

사회-기술 시스템의 근본적 변화를 다루는 전환연구가, 지속가능한 발전에 대한 논의 확대를 배경으로 정책적 활용의 폭을 넓혀가고 있다. 본 논문의 목적은 대표적인 전환이론인 다층적 관점, 전환관리, 전략적 니치관리 및 기술혁신시스템 이론의 특징과 정책적 함의를 고찰하고, 이를 전환정책 설계와 운영과정에 활용하기 위한 통합적 분석틀을 제시하는 것이다. 각 전환이론은 서로 다른 연구적 입장을 견지하고 있으나, 사회-기술 시스템의 근본적 변화를 동태적으로 분석하고 있다는 점에서 상호보완적이다. 따라서 전환현상이 복잡해지고 전환에 영향을 미치는 변수가 확대될수록, 각 이론의 연계 및 통합적 활용에 대한 필요성이 높아지고 있다. 최근 국내에서도 전환이론을 혁신정책 및 과학기술정책에 접목하기 위한 연구가 진행되고 있으며, 전환적 사고가 반영된 정책도 등장하고 있다. 기후변화, 에너지 자원의 활용 등 우리 사회와 정부가 대응해야 할 지속가능성 이슈가 증가할수록, 효과적인 전환정책의 설계와 운영에 대한 필요성은 증가하게 된다. 본 논문은 개별 전환이론에 대한 비판적 고찰을 토대로 통합적 전환정책 분석틀을 도출하고, 우리나라의 스마트그리드 정책사례에 예시적으로 적용하여 분석한 결과를 제시한다.

• 대기
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• 제32권1호
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• pp.27-37
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• 2022

The Korean Integrated Model (KIM) forecast system was extended to assimilate Horizontal Line-Of-Sight (HLOS) wind observations from the Atmospheric Laser Doppler Instrument (ALADIN) on board the Atmospheric Dynamic Mission (ADM)-Aeolus satellite. Quality control procedures were developed to assess the HLOS wind data quality, and observation operators added to the KIM three-dimensional variational data assimilation system to support the new observed variables. In a global cycling experiment, assimilation of ALADIN observations led to reductions in average root-mean-square error of 2.1% and 1.3% for the zonal and meridional wind analyses when compared against European Centre for Medium-Range Weather Forecasts (ECMWF) Integrated Forecast System (IFS) analyses. Even though the observable variable is wind, the assimilation of ALADIN observation had an overall positive impact on the analyses of other variables, such as temperature and specific humidity. As a result, the KIM 72-hour wind forecast fields were improved in the Southern Hemisphere poleward of 30 degrees.

• 해양환경안전학회지
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• 제29권2호
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• pp.215-222
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• 2023

세계적 선박 배출가스 저감에 대한 규제로 인해 항만 및 부두에서 육상전원공급장치(AMP, Alternative Marine Power)가 지속적으로 사용되고 있다. 국내 또한 항만 대기질 개선 특별법에 따라 AMP의 사용이 의무화되고 있고, 다양한 친환경선박과 연계하여 활용하도록 지속적인 시도를 하고 있다. 본 논문에서는 AMP를 통해 선내 전력을 공급하는 상황을 모델링 하여 AC Load Flow Analysis를 수행하였다. 이를 통해 선박에 전력이 공급될 때의 전기적 파라미터와 손실 등에 대해서 분석할 수 있다. 아울러 Transient Stability Analysis를 통해 계통의 사고 발생 시 선내 발전기를 통한 무정전전환에 대한 HSGT(High Speed Generation Transfer)의 한계값을 도출하고 이를 적용하였을 경우 결과에 대해 검토하였다.