본 연구에서는 낮은 막 저항과 높은 수산화 이온 전도성을 가지는 세공 충진 이온교환막 제조법으로 연구하였다. 알칼리 내구성을 향상하기 위해 폴리 테트라 플로오 에틸렌 소재인 다공성 지지체를 사용하였고 세공에는 단량체 2-(dimethylamino)ethyl methacrylate (DMAEMA), vinylbenzyl chloride (VBC)를 이용하여 copolymer를 제조했다. 가교제는 divinylbenzene (DVB)를 사용하였고 가교제 함량별로 이온교환막을 제조하여 DMAEMA-DVB와 VBC-DMAEMA-DVB copolymer에서 가교제 함량이 미치는 영향에 관해 연구하였다. 그 결과, PTFE 소재 지지체를 이용하여 화학적 안정성이 향상 했고 저압 UV 램프를 사용하여 낮은 온도에서 빠른 광중합이 가능하여 생산성을 높일 수 있는 장점이 있다. 음이온교환 막 연료전지에 요구되는 이온교환막의 물리적 및 화학적 안정성을 확인하기 위해서 인장강도와 내알칼리성 테스트를 진행하였 다. 그 결과, 가교도가 증가할수록 인장강도 대략 40 MPa가 증가하였고, 최종적으로 이온전도도와 내알칼리성 테스트를 통해 가교제 함량이 증가할수록 알칼리 안정성이 증가하는 것을 확인하였다.

PURPOSES : Traffic congestion on freeway generally occurs when the traffic volume exceeds the road capacity. Most traffic manuals *such as the Korean Highway Capacity Manual) present the highway capacity as approximately 2,000 units/hour. However, in the real world, freeway congestion occurs for various reasons, including unusual driver behaviors, physical road limitations, and large traffic volumes. Thus, the flow rate at a traffic breakdown can have a wide range of volumes. Therefore, using 5-min volume and speed data from the field, this study explores the stochastic features of traffic breakdowns on major urban freeways in Seoul. METHODS : First, a breakdown point is defined by applying a wavelet transform to identify the sharp drop in the speed data near freeway bottlenecks. Second, based on the flow rate at and before a breakpoint, a survival analysis is performed to construct the probability distributions of the traffic breakdown. Log-rank tests are also conducted to verify the similarities of the distributions between freeways. RESULTS : The analysis results confirm the stochastic features of the urban freeways in Seoul. Specifically, the freeways have typical S-shaped distributions of breakdown probabilities. However, the distributions rise steeply (exceeding a 50% of breakdown probability) at flow rates of 1,150 vphpl to 1,700 vphpl; this is lower than the general expectation. CONCLUSIONS : The statistical differences in the probability distributions for freeways indicates that applying a general standard to every urban highway could raise problems. This study has a limitation in identifying the specific causes of traffic congestion owing to the by physical relationships between individual vehicles. An investigation if vehicle trajectory data should be conducted to examine these aspects in further detail.

급격한 산업화와 도시화로 인해 해양 오염이 심각해지고 있으며, 이러한 해양 오염을 실효적으로 관리하기 위해 수질평가 지수(Water Quality Index, WQI)를 마련하여 활용하고 있다. 하지만 수질평가지수는 다소 복잡한 계산과정으로 인한 정보의 손실, 기준값 변동, 실무자의 계산오류, 통계적 오류 등의 불확실성(uncertainty)을 내포하고 있다. 이에 따라 국내ㆍ외에서 인공지능 기법을 활용하여 수질평가지수를 예측하기 위한 연구가 활발히 이루어지고 있다. 본 연구에서는 해양환경측정망 자료(2000 ~ 2020년)를 활용하여 우리나 라 전 해역 즉, 5개의 생태구에 대한 WQI를 추정할 수 있는 가장 적합한 인공지능기법을 도출하기 위해 총 6가지의 기법(RF, XGBoost, KNN, Ext, SVM, LR)을 실험하였다. 그 결과, Random Forest 기법이 다른 기법에 비해 가장 우수한 성능을 보였다. Random Forest 기법의 WQI 점수 예측값과 실제값의 잔차 분석 결과, 모든 생태구에서 시간적 및 공간적 예측 성능이 우수한 것으로 나타났다. 이를 통해 본 연구에서 개발한 Random Forest 기법은 높은 정확도를 바탕으로 우리나라 전해역에 대한 WQI를 예측 가능할 것으로 사료된다.

Despite the consumption of disinfectants have been increased by COVID-19 pandemic, the fate of the chemicals in aquatic food webs are still unclear. In order to understand the trophic transfer of the chemicals, the concentration of disinfectants including six benzalkonium chloride (BACs) and five didecyldimethylammonium chlorides (DDACs) were measured at the Geum (2020), Han (2021), and Yeongsan River (2021), before and after rainfall. The highest concentration of ΣBACs (mainly C12 and C14) and ΣDDACs (mainly C10 and C14) were observed in the Han River, followed by Yeongsan River, Geum River Estuary, and Gapcheon. After rainfalls, both concentration and detection frequency were decreased in all sites. Although the BAC and DDAC seems to be accumulated in organisms, they were bio-diluted rather than magnified in the aquatic food web with the biomagnification factor (BMF) of less than 1, trophic magnification slope (TMS) from - 0.236 to 0.001, and trophic magnification factor (TMF) from 0.85 to 1.01.

Purpose: This study reviews trends in the development of nursing simulation evaluation instruments and their characteristics in South Korea. Methods: Published and unpublished studies were analyzed using Korean electronic databases, such as the Research Information Sharing Service, the National Library of Korea, and the Korea Institute of Science and Technology Information. The keywords for the search included “nursing,” “simulation,” “instrument development,” “evaluation,” “validity,” and “reliability.” Results: A total of 16 studies and 17 evaluation instruments from between 2012 and 2022 were included and categorized. The participants included junior or senior undergraduate nursing students. The evaluation was conducted through observation and self-report and classified into cognitive, psychomotor, and affective domains. Only one instrument used for observation was measured for intra-rater reliability. Overall, 35.3% of the instruments integrally evaluated the cognitive, psychomotor, and affective domains, and 23.5% only reported one type of validity. Conclusion: The results indicate that the instruments insufficiently reflect the various learning outcomes of simulation education. Therefore, future research should be conducted to develop simulation evaluation instruments to evaluate integral learning areas according to the learning goals and examine their validity.

In this work, the ablation behavior of monolith ZrB2-30 vol%SiC (Z30S) composites were studied under various oxy-acetylene flame angles. Typical oxidized microstructures (SiO2/SiC-depleted/ZrB2-SiC) were observed when the flame to Z30S was arranged vertically. However, formation of the outmost glassy SiO2 layer was hindered when the Z30S was tilted. The SiC-depleted region was fully exposed to air with reduced thickness when highly tilted. Traces of the ablated and island type SiO2 were observed at intermediate flame angles, which clearly verified the effect of flame angle on the ablation of the SiO2 layer. Furthermore, the observed maximum surface temperature of the Z30S gradually increased up to 2,200 °C proving that surface amorphous silica was continuously removed while monoclinic ZrO2 phase began to be exposed. A proposed ablation mechanism with respect to flame angles is discussed. This observation is expected to contribute to the design of complex-shaped UHTC applications for hypersonic vehicles and re-entry projectiles.