Clay-cellulose nanocomposites inspired by the complex structures of nacre

장다슬,심봉섭 한국공업화학회 2014 한국공업화학회 연구논문 초록집 Vol.2014 No.1

Nacre (or mother-of-pearl) is well known for its superior mechanical properties such as high fracture toughness and tensile strength. Unlike artificial nanocomposites, nacre exhibits extremely high contents of mineral and unique molecular level structures; a brick-and-mortar structure with 95% aragonite nanocrystals (CaCO₃) and 5% biopolymers. Thus, following the nature’s wonderful design, we fabricated clay - cellulose composites, particularly with high montmorillonite (MMT) and minimal carboxymethylcellulose (CMC) contents. In this study, MMT-CMC composites were prepared by scalable solvent casting, varying MMT/CMC ratio. Mechanical properties of the fabricated films were assessed by direct tensile testing. Their molecular level structures were observed by field-emission scanning electron microscopy (FE-SEM).

다발골수종 환자의 정맥혈전색전증 위험 계층화 및 항혈전제 사용 현황

장다슬,고종희,손은선,유윤미 한국병원약사회 2023 병원약사회지 Vol.40 No.2

Background : The risk of venous thromboembolism (VTE) increases in multiple myeloma (MM), and the National Comprehensive Cancer Network (NCCN) guidelines recommend VTE prevention using the IMPEDE VTE score. Although there have been studies analyzing the correlation between score increase and VTE incidence, there is a lack of validation on Asian ethnicity. This study applies the IMPEDE VTE score to MM patients to stratify the risk of VTE and analyze VTE incidences and the use of antithrombotics. Methods : We conducted a retrospective analysis of electronic medical records of patients newly diagnosed with MM who visited the Hematology Department of a single-center from January 2018 to December 2021. The occurrence of VTE was followed up for 6 months after treatment initiation. The IMPEDE VTE score was calculated at the start of treatment, and the incidence of VTE and the use of anti-thrombotic drugs were analyzed according to risk. Results : Among 239 patients, 139 (58.2%), 98 (41.0%), and 2 (0.8%) were classified in the low-risk (≤3 points), intermediate-risk (4-7 points), and high-risk group (≥8 points) respectively. Age was significantly higher in the low-risk group than intermediate-risk group. Two cases of VTE occurred within 6 months of treatment initiation, both of which were in the low-risk group. Fifty-one patients (21.3%) received antithrombotics that according to the guideline, and all of them were in the low-risk group. There were 14 cases of bleeding associated with the use of antithrombotics. Conclusion : This study highlights the potential association between age and VTE risk in MM patients. While the current guideline does not consider patients’ age as a risk factor, the higher incidence of VTE in the low-risk group of older patients suggests that old age may need to be taken into account when predicting VTE in MM. Further large-cohort studies are needed to investigate this association and to develop guidelines for VTE risk prediction and prevention in MM patients in Korea.

과거시차를 고려한 지지벡터 회귀모형에 기반한 서울지역 가뭄예측

장다슬,차경준 한국자료분석학회 2017 Journal of the Korean Data Analysis Society Vol.19 No.2

The purpose of this study overcomes the limitation in time series data analysis using the support vector regression (SVR) model, which is one of the machine learning methods. We apply the SVR model to the nonstationary monthly SPI (standardized precipitation index) time series data which is one of the measures of drought. We consider two different data types to build SVR model. First, we do not consider the past time-lag. Second, we consider the reasonable amount of past time-lags. The data of considering past time-lags are 4 type, these are 3, 6, 9 and 12 months as the independent variable. Totally, we define 5 types of data sets. Therefore, in this study, SVR model according to 5 types of data was applied, and also SVR model with seasonality was applied after identify the seasonal factors of precipitation. In conclusion, it is more accurate to consider the past time-lag in all SVR models. Among the data considering the past time-lag, the data considering the past 6 months shows the best performance. However, the difference between the SVR model without seasonality and with seasonality is not significant. Therefore, we conclude that seasonal factors is not significant for prediction SPI. 본 연구에서는 가뭄의 척도를 나타내는 표준강수지수(SPI)를 이용하여 기계학습 기법 중 하나인 지지 벡터 회귀(support vector regression; SVR) 모형과 더불어 과거시차를 고려함으로서 시계열 분석방법의 단점을 보완하고자 한다. 본 논문에서는 SVR모형 적용시 자료의 형태를 크게 두 가 지로 구분한 후, 그 중 하나를 다시 4가지로 구분하여 총 5가지의 자료형태를 정의하였다. 첫째로 과거시차를 고려하지 않은 자료의 형태로 현재시점의 독립변수로 현재시점의 종속변수를 예측하는 자료형태이다. 둘째로 과거시차를 고려한 자료형태이다. 과거시차를 고려한 자료형태는 4가지로 과거 3개월, 6개월, 9개월, 12개월의 자료를 독립변수로 고려하고 현재시점의 종속변수를 예측하는 자료형태이다. 가뭄현상이란 오랫동안 계속해 비가 내리지 않아 메마른 날씨로 강수량의 영향을 받는다. 따라서 본 연구에서는 5가지의 자료형태에 따른 SVR모형을 적용하고, 강수량의 계절적 요인을 파악한 후 계절적 요인을 고려한 SVR을 적용한 후 비교평가 하였다. 결론적으로 과거시차를 고려한 자료형태가 고려하지 않은 자료형태보다 SVR모형의 예측정확도가 높았다. 그 중 과거 6개월을 독립변수로 고려한 SVR모형의 예측정확도가 가장 우수했다. 이를 통해 본 연구의 본래목적에 부합한 자료의 형태는 과거시차를 고려한 자료 중 과거 6개월을 독립변수로 고려한 자료임을 확인하였다. 하지만 본 연구에서는 계절성을 고려하지 않은 SVR모형과 계절성을 고려한 SVR모형의 예측정확도의 값의 차는 크지 않았다. 따라서 본 연구에서는 과거시차를 고려한 자료를 통해 SPI를 예측하는데 계절적 요소가 유의하지 않다고 판단하였다.

Nacre mimetic cellulose-based nanocomposites

우경배,장다슬,배은실,허재은,심봉섭 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.1

Although nacre (mother of pearl) is composed of mostly brittle aragonite (CaCO3) nanoplatelets and little amount of biopolymers, it shows superior mechanical properties because of its hierarchical brick-andmortar structures from molecular to macro levels. In this research, we fabricated montmorillonite (MMT)-cellulose nanofiber (CNF) nanocomposites by a simple filtration process to mimic nacre structure for enhancing its mechanical performances. We compared the properties of MMT/ CNF composites by varying MMT/CNF ratio, which was characterized by a scanning electron microscope (SEM), an X-ray diffraction (XRD), and a Fourier transform infrared spectroscopy (FT-IR). The opacity of the composites was decreased compared to pure MMT films, and selfextinguish property was also observed. Furthermore, relatively high toughness and strength were obtained by measuring in a tensile tester. These results suggest that our MMT-CNF composites have a potential replacement of commercial polymers.

Bioinspired binary system for mechanical properties in cellulose-based nanocomposites

허경아,장다슬,심봉섭 한국공업화학회 2018 한국공업화학회 연구논문 초록집 Vol.2018 No.1

High performance PVA-MMT freeze casting film inspired bybrick-and-mortar nacre structures

황홍섭,장다슬,심봉섭 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.0

Natural nacre, which has delicate hierarchical brick-and-mortar structures with ordinary constituents, exhibits exceptional mechanical strength and toughness. The goal of our research is to mimic the hierarchically arranged nacre structure in order to reproduce its high mechanical performances using our directed assembly techniques. We fabricated biomimetic nanocomposite films between poly(vinyl alcohol) (PVA) and exfoliated nanoclay with locally layered structures by freeze gelation techniques. We also measured the mechanical performances of the film including Young’s modulus, toughness, and ultimate strength. And we analyzed the hierarchical structures by using x-ray diffraction analysis (XRD) and scanning electron microscope (SEM) image.

Improving mechanical properties of bioinspired Clay-Cellulose Nanofibers composites

허재은,장다슬,배은실,심봉섭 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.1

In nature, nacre has the hierarchical brick-and-mortar structures and precise inorganic-organic interfaces, which enable it to achieve remarkably high fracture toughness and tensile strength. Because of these properties, nacre-mimetics hold great potential as mechanical high-performance and functional materials. Previously, we have fabricated nacre-like nanocomposites via vacuum filtration of montmorillonite (MMT) and cellulose nanofibers(CNFs) mixtures. Although the composites exhibited higher strength and toughness than pure MMT and CNFs, we tried to improve the mechanical properties further y by additional post treatmentsive work. In this study, adding polymers and cross-linking were introduced to improve the mechanical propertiesy of the composites. The resulting materials were analyzed by a Scanning electron microscopy(SEM), an X-ray diffraction(XRD), and a tensile tester. We compare the resulting mechanical properties with the previous results.

Nano- and Micro-structured Materials for Soft Neural Interfaces

김현,엄태식,장다슬,심봉섭 한국고분자학회 2014 한국고분자학회 학술대회 연구논문 초록집 Vol.2014 No.4

영흥 풍력발전단지의 풍력발전량 예측을 위한 입력변수 선정 및 인공신경망과 1차원 합성곱 신경망 비교

박태희(Tae-Hui Park),장다슬(Da-Seul Jang),배경민(Gyeong-Min Bae),김경민(Kyung-Min Kim),안종화(Johng-Hwa Ahn) 대한환경공학회 2021 대한환경공학회지 Vol.43 No.4

목적 : 본 연구에선 비선형적 풍력발전량 예측 모델 개발을 목적으로 총 설치 용량 46 MW의 풍력발전단지가 설치된 영흥 풍력발전 단지의 자료를 이용하여 인공신경망(artificial neural network, ANN)과 1차원 합성곱신경망(1-dimension convolutional neural network, 1D-CNN)의 성능을 비교하고자 하였다. 방법 : 자료는 46 MW 발전능력을 가진 영흥 풍력발전단지의 2018년 1월부터 12월의 1시간 단위 풍력발전량 자료와 기상청에서 얻은 기상자료를 이용하였다. 최적 입력변수를 선정을 위하여 문헌연구를 바탕으로 시행착오를 거쳐 인자를 선정하였다. 전처리 과정을 거친 17,306개의 자료의 80%를 학습(training), 20%를 테스트(test)으로 사용하였으며, 학습 자료의 20%를 검증(validation)자료로 구성하였다. 모델 내 활성화 함수로는 rectified linear unit를 사용하였으며, 시행착오법을 통해 하이퍼파라미터(hyperparameter)의 최적값을 도출하였다. 모든 모델은 Python의 Keras 라이브러리를 이용하여 설계하였으며, 성능지표인 결정계수(coefficient of determination, R²), 평균제곱근오차(root mean square error, RMSE), 평균절대오차(mean absolute error, MAE) 등은 Scikit-learn 라이브러리에서 이용하였다. 결과 및 토의 : 최적 입력변수는 풍속, 풍향, 온도, 습도 등이었다. ANN의 최적점으로는 은닉층 8층, 은닉층별 노드수는 모두 100으로 나왔다. 최적 ANN 모델에서 성능지표는 R²=0.848, MAE=1.054, RMSE=1.616이었다. 1D-CNN 의 최적점으로는 합성곱층 4층, 층별 필터 수는 1층부터 64, 128, 64, 32개, 전결합층 1층에 노드 100개이다. 최적 1D-CNN 모델의 성능지표는 R²=0.875, MAE=0.982, RMSE=1.583였다. 1D-CNN이 ANN보다 R²는 높고, MAE와 RMSE는 낮았다. ANN, 1D-CNN의 결정계수가 모두 0.8 이상으로 예측 성능이 우수하나, 1D-CNN이 ANN보다 모든 성능지표에서 높았다. 결론 : 최적화된 모델의 성능지표 비교 결과 1D-CNN이 ANN보다 높은 성능을 보여 영흥 풍력 발전소 발전량 예측에 적합할 것으로 보인다. 최적 입력변수는 풍속, 풍향, 온도, 습도였다. Objectives : In this study, deep learning models of artificial neural network (ANN) and one-dimension convolutional neural networks (1D-CNN) were compared to predict nonlinear wind power generation at Yeongheung wind power plant. Methods : The study site was Yeongheung-do, which has a 46 MW wind power plant. Hourly wind power and meteorological data from January to December 2018 were collected. After pre-processing with standardscaler, the training data were 64%, the validation data were 16%, and the test data were 20%. The optimum input variables of the model were selected using literature, and trial and error method. Rectified linear unit was used as the activation function. Hyperparameters were adjusted by trial and error method to optimized models. To compare the optimized models, the coefficient of determination (R²), mean absolute error (MAE), and root mean square error (RMSE) were used as the performance efficiency. Both ANN, and 1D-CNN were imported from the Keras library, and all of the performance efficiency was imported from the Scikit-learn library. Results and Discussion : The optimized input variables in this study were wind speed, wind direction, temperature, and humidity. The optimized ANN performance was R²=0.848, MAE=1.054, and RMSE=1.616, and the hyperparameters were 8 hidden layers with 100 nodes in each layer. The optimized 1D-CNN (R²=0.875, MAE=0.982, and RMSE=1.583) had 4 convolutional layers and the number of filters were 64, 128, 64, and 32 in order from the first layer, and one hidden fully connected layer had 100 nodes. The 1D-CNN had higher R², and lower MAE and RMSE than the ANN. Therefore, the 1D-CNN was selected as the optimized model to predict wind generation of the Yeongheung wind power plant. Conclusions : The optimized 1D-CNN model in this study was more effective in predicting the Yeongheung wind power plant than the ANN. The optimal input variables were wind speed, wind direction, temperature, and humidity.

국내 코로나19 대유행에 대한 예방접종 및 사회적 거리두기 정책

김정아,이희언,김지원,장다슬,최남경 한국에프디시규제과학회 2023 FDC법제연구 Vol.18 No.2

2019년 12월 중국 우한시에서 최초 보고된 코로나바이러스감염증-19(코로나19)는 전 세계적으로 대유행을 일 으켰다. 한국은 코로나19 백신이 개발되지 않았던 초반에 사회적 거리두기 정책을 실시하며 코로나19 확산을 억제하 려고 노력하였다. 하지만 다양한 방역 정책을 추진함에도 불구하고 코로나19 확진자가 지속적으로 증가하였고, 이에 코로나19 바이러스의 감염 및 전파를 예방하는 효과적인 수단인 코로나19 예방접종의 중요성이 강조되었다. 2020년 하반기에 코로나19 백신이 개발 및 생산되면서 2021년 2월 26일에 국내에서 첫 코로나19 예방접종이 시작되었다. 국 내 코로나19 대응 과정과 예방접종 전략은 미래의 신종감염병을 대비하는 중요한 수단으로써 주요 사항들을 파악하 는 것이 필요하다. 이에 본 연구는 국내에 도입된 코로나19 백신 종류, 예방접종기관, 예방접종 일정, 코로나19 대유 행 및 사회적 거리두기 정책에 대해 살펴보고자 한다. 한국은 바이러스벡터 백신 2종(아스트라제네카, 얀센), mRNA 백신 2종(화이자, 모더나), 유전자재조합 백신 2종(노바백스, 스카이코비원) 등 총 6종의 코로나19 백신을 도입하여 사 용하였다. 예방접종은 예방접종센터, 위탁의료기관, 보건소, 자격을 갖춘 인력이 직접 찾아가는 방문접종 서비스를 통 해 이루어졌다. 또한, 국내에 여러 종류의 코로나19 백신이 순차 공급됨에 따라, 예방접종은 코로나19 감염 시 중증 진행 위험, 코로나19 전파특성 및 의료 방역체계 등을 고려하여 순차적으로 시행되었다. 사회적 거리두기 정책은 코 로나19 환자가 한국에서 최초로 발생한 2020년 1월 20일부터 여러 번의 대유행을 거치며 기준 및 수행 규칙이 지속 적으로 변경되며 시행되었다. 본 연구는 추후 신종감염병 출현 시, 감염병 대응 정책을 계획하고 필요한 보건 및 의 료자원의 우선순위와 범위를 결정하는 데 기초자료로 활용되고자 한다. 또한, 예방접종전략 수립을 위해 백신 안전성 과 효과에 대한 지속적인 모니터링과 새로운 변이 유행에 대한 해외 동향을 지속적으로 감시해야 함을 제안한다. The COVID-19 outbreak, first reported in Wuhan, China, in December 2019 led to a global pandemic. In the absence of a COVID-19 vaccine, South Korea implemented social distancing policies as a measure to mitigate its spread. Despite various quarantine policies, a sustained increase in cases emphasized the importance of vaccination as an effective tool against the COVID-19 infection and transmission. The first COVID-19 vaccination in South Korea began on February 26, 2021, following the development and production of vaccines in the latter half of 2020. Understanding Korea's approach to COVID-19 response and vaccination is vital for preparing for future outbreaks of emerging infectious diseases. This review examines the types of COVID-19 vaccines introduced in South Korea, vaccination institutions, vaccination schedules, and social distancing strategies. South Korea introduced a total of six COVID-19 vaccine types, including two viral vector vaccines (AstraZeneca, Janssen), two messenger ribonucleic acid (mRNA) vaccines (Pfizer, Moderna), and two recombinant protein vaccines (Novavax, SKYCovione). COVID-19 vaccines were administered through vaccination centers, entrusted medical institutions, public health centers, and door-to-door services by qualified personnel. The vaccinations were initiated sequentially, considering the severe progression of COVID-19 infection, the maintenance of medical systems, and the characteristics of COVID-19 transmission. Social distancing policies evolved continuously since the first COVID-19 case in South Korea on January 20, 2020, adapting standards and implementation guidelines through multiple waves of the pandemic. This study contributes foundational information for shaping policies for emerging infectious diseases, establishing priorities, and aiding in the allocation of crucial healthcare resources. Furthermore, it suggests continuous monitoring of vaccine safety and effectiveness, as well as global surveillance of new variant trends, to formulate vaccination strategies and respond to emerging infectious threats