Sustainable graphene growth and electronics

변선정,한태희,임현섭,오상호,안종현,최희철,이태우 한국고분자학회 2011 한국고분자학회 학술대회 연구논문 초록집 Vol.2011 No.1

정신건강의학과 개방병동 입원 환자의 진단군별 약물 처방 경향 변화 : 경기도 소재 일 대학병원에서의 11년 비교 연구

변선정,김의태,유희정,하태현,윤인영,김기웅,Byun, Seonjeong,Kim, Euitae,Yoo, Hee Jeong,Ha, Tae Hyon,Yoon, In-Young,Kim, Ki Woong 대한생물정신의학회 2015 생물정신의학 Vol.22 No.4

Objectives This study investigated the patterns of psychotropic medications prescribed to patients admitted to an open psychiatric ward. Methods We reviewed 4282 medical records of patients who were discharged from an open psychiatric ward from May 2003 through April 2014. Data were collected on each patient's age, sex, length of hospital stay, number of past admissions, discharge diagnosis, and kinds and dosages of psychotropic medications at discharge. Results Among the 1384 male and 2898 female patients, 3.56 psychotropic medications were prescribed on average, with the number increasing across years, from 3.30 in 2003-2008 to 3.76 in 2009-2014. Prescription rates of antipsychotics, anxiolytics, and hypnotics significantly increased in patients with depressive disorders, bipolar disorders, anxiety disorders, delirium, dementia, and amnestic and other cognitive disorders. Only lithium prescription rates decreased significantly. Prescriptions for two or more anxiolytics and antipsychotics increased during the survey years, while antidepressant polypharmacy rates decreased. Conclusions Recently, there has been a significant increase in the number of psychotropic medications prescribed, including antipsychotics, anxiolytics, and hypnotics. Caution should be exercised when prescribing medications to avoid cost increases and the risk of side effects, with uncertain gains in the quality of care.

부모의 진로관여방식과 진로준비행동 간의 관계에서 진로결정자율성의 매개효과

변선정,김장회 한국상담학회 2020 한국상담학회 학술대회 논문집 Vol.2020 No.8

Acute Variceal Hemorrhage in Patients with Liver Cirrhosis: Weekend versus Weekday Admissions

변선정,안상훈,김승업,박준용,김범경,김도영,한광협,전재윤 연세대학교의과대학 2012 Yonsei medical journal Vol.53 No.2

Purpose: Little is known about the impact of weekend admission on acute variceal hemorrhage (AVH). Thus, we investigated whether day of admission due to AVH influenced in-hospital mortality. Materials and Methods: We retrospectively reviewed the medical records of 294 patients with cirrhosis admitted between January 2005 and February 2009 for the management of AVH. Clinical characteristics were compared between patients with weekend and weekday admission, and independent risk factors for in-hospital mortality were determined by multivariate binary logistic regression analysis. Results: No demographic differences were observed between patients according to admission day or in the clinical course during hospitalization. Seventeen (23.0%) of 74 patients with weekend admission and 48 (21.8%) of 220 with weekday admission died during hospitalization (p=0.872). Univariate and subsequent multivariate analysis showed that initial presentation with hematochezia [p=0.042; hazard ratio (HR), 2.605; 95% confidence interval (CI), 1.038-6.541], in-patient status at the time of bleeding (p=0.003; HR, 4.084; 95% CI, 1.598-10.435), Child-Pugh score (p<0.001; HR, 1.877; 95% CI, 1.516-2.324), and number of endoscopy sessions for complete hemostasis (p=0.001; HR, 3.864; 95% CI, 1.802-8.288) were independent predictors for in-hospital mortality. Conclusion: Weekend admission did not influence in-hospital mortality in patients with cirrhosis who presented AVH.

신장 혈관근지방종의 대량출혈을 일으킨 결절성 경화증 1예

변선정 ( Sun Jeong Byun ),이규백 ( Kyu Beck Lee ),이용수 ( Yong Su Lee ),김향 ( Hang Kim ),홍현표 ( Hyun Pyo Hong ),김승권 ( Seung Kwon Kim ),이영래 ( Young Rae Lee ),채승완 ( Sung Wan Chae ),손진희 ( Jin Hee Son ) 대한신장학회 2007 Kidney Research and Clinical Practice Vol.26 No.4

경안천 용존 산소 예측을 위한 입력 인자 선정 및 기계 학습 모델 비교

김민지,변선정,김경민,안종화 대한환경공학회 2021 대한환경공학회지 Vol.43 No.3

Objectives:In this study, we select input factors for machine learning models to predict dissolved oxygen (DO) in Gyeongan Stream and compare results of performance evaluation indicators to find the optimal model. Methods:The water quality data from the specific points of Gyeongan Stream were collected between January 15, 1998 and December 30, 2019. The pretreatment data were divided into train and test data with the ratio of 7:3. We used random forest (RF), artificial neural network (ANN), convolutional neural network (CNN), and gated recurrent unit (GRU) among machine learning. RF and ANN were tested by both random split and time series data, while CNN and GRU conducted the experiment using only time series data. Performance evaluation indicators such as square of the correlation coefficient (R2), root mean square error (RMSE), and mean absolute error (MAE) were used to compare the optimal results for the models. Results and Discussion:Based on the RF variable importance results and references, water temperature, pH, electrical conductivity, PO4-P, NH4-N, total phosphorus, suspended solids, and NO3-N were used as input factors. Both RF and ANN performed better with time series data than random split. The model performance was good in order of RF > CNN > GRU > ANN. Conclusions:The eight input factors (water temperature, pH, electrical conductivity, PO4-P, NH4-N, total phosphorus, suspended solids, and NO3-N) were selected for machine learning models to predict DO in Gyeongan Stream. The best model for DO prediction was the RF model with time series data. Therefore, we suggest that the RF with the eight input factors could be used to predict the DO in streams. 목적:본 연구에서는 경안천의 용존 산소(dissolved oxygen, DO) 예측을 위해 기계 학습(machine learning) 모델의 최적 입력 인자를 선정하고 성능 평가 지표 결과를 비교하여 최적 모델을 찾고자 한다. 방법:경안천 특정 지점의 수질 자료를 연구대상으로 삼아 1998년 1월 15일부터 2019년 12월 30일까지 자료를 수집하고, 전처리한 데이터를 7:3의 비율에 따라 train과 test 자료로 나누어 실험을 진행하였다. 기계 학습 중 랜덤 포레스트(random forest, RF), 인공신경망(artificial neural network, ANN), 합성곱 신경망(convolutional neural network, CNN), 게이트 순환 유닛(gated recurrent unit, GRU) 등을 이용하였다. RF와 ANN은 무작위 추출(random split)과 시계열 자료(time series)로 구분하여 실험하였으며, CNN과 GRU는 시계열 자료만 이용하여 실험을 진행하였다. 모델별 최적의 결과를 비교하기 위해 성능 평가 지표(결정 계수(square of the correlation coefficient, R2), 평균 제곱근 오차(root mean square error, RMSE), 평균 절대 오차(mean absolute error, MAE))를 사용하였다. 결과 및 토의:RF 기여도 분석 결과와 참고문헌을 통해 최적 입력 인자로 수온, pH, 전기 전도도, PO4-P, NH4-N, 총 인, 부유물질, NO3-N 등으로 선정하였다. RF와 ANN 모두 무작위 추출보다 시계열 자료의 성능이 더 우수하였다. 시계열 자료를 이용하여 모델 성능을 비교해 보면, RF > CNN > GRU > ANN 순으로 나타났다. 결론:본 연구에서 경안천의 DO 예측을 위한 기계 학습 모델의 최적 입력 인자로 8개(수온, pH, 전기 전도도, PO4-P, NH4-N, 총 인, 부유물질, NO3-N)를 선택하였다. DO 예측에 가장 우수한 모델은 시계열 자료를 사용한 RF 모델이었다. 따라서 경안천과 같은 하천의 DO를 예측하는 경우 최적 입력 인자 선정 후 시계열 자료를 바탕으로 RF 모델을 이용할 것을 제안한다.

위장관간질종양으로 오인한 위선암 1예

최성연,변선정,김병권,장승훈,민재훈,김태완,이지애 대한소화기내시경학회 2009 Clinical Endoscopy Vol.39 No.3

Gastric adenocarcinoma is the second most common cause of cancer death worldwide, but there are some geographical differences in its incidence. Gastointestinal stromal tumor (GIST) is an uncommon disease with a wide spectrum of aggressive behavior. These two tumors have a distinct pathogenesis. GIST is frequently identified as an incidental lesion found by routine endoscopy or in resection specimens that are removed for other reasons. We report a case of a gastric adenocarcinoma mimicking GIST in a 79-year-old woman. GIST was suggested by endoscopic ultrasonography and computed tomography scanning, but gastric adenocarcinoma was confirmed by gastroduodenoscopic biopsy. We performed a subtotal gastrectomy with Billroth I, lymph node dissection and transverse colon segmentectomy, and a 15.0×7.5×5.5 cm-sized gastric tumor was confirmed pathologically. Immunohistochemistry was positive for carcinoembryonic antigen and focal weakly positive for cytokeratin7 and cytokeratin20. 위선암과 위장관 간질종양은 상부위장관 내시경에서 흔히 발견된다. 저자들은 복부 불편감을 주소로 내원한 79세 여자 환자에서 복부전산화단층촬영과 내시경 초음파검사에서 위장관 간질종양이 의심되었으나, 조직 생검에서 위선암을 진단하고 수술적으로 절제를 시행했던 1예를 경험하여 문헌 고찰과 함께 보고한다.

거짓동맥류를 동반한 구불결장 Dieulafoy 병변 출혈 1예

김태완,김홍주,민재훈,변선정,이지애,장승훈,최성연 대한소화기내시경학회 2010 Clinical Endoscopy Vol.41 No.5

Dieulafoy’s lesions are characterized by a single large tortuous arteriole in the submucosa, and this arteriole does not undergo normal branching. These lesions are an uncommon cause of massive, sometimes fatal gastrointestinal bleeding; this had been reported to be the cause of 0.3∼1.5% of the cases of major gastrointestinal bleeding. The lesions mainly occur in the proximal stomach, but they may occur in all parts of the gastrointestinal tract, including the small bowel, colon and rectum. Endoscopy is a common method for the diagnosis and treatment of Dieulafoy’s lesions. However, in the case of a high risk lesion, angiography, laparoscopy or laparotomy can be performed instead. We experienced a rare case of bleeding from a Dieulafoy’s lesion with pseudoaneurysm in the sigmoid colon. Angiography with embolization was performed, but the patient expired due to rebleeding. We report on this case along with a review of the relevant literature. Dieulafoy 병변은 작은 점막 결손 부위를 통해 점막하 세동맥이 위장관으로 노출되어 출혈을 유발하는 질환으로, 대량 위장관 출혈의 드문 원인이다. 주로 위장 근위부에서 발생하나 드물게 식도, 소장, 대장과 같이 전 위장관에서도 발생할 수 있다. 내시경이 진단과 치료에 우선적이나 위험군의 경우 혈관조영술이나 수술을 하기도 한다. 이번 증례는 구불결장이라는 드문 위치에 발생한 Dieulafoy 병변에 거짓동맥류가 동반된 경우로 저자들은 혈관조영술로 확인하여 색전술을 시행한 후 초기 치료는 성공적이었으나 3일 후 재출혈로 결국 사망하였다.

기계학습을 이용한 경안천의 용존 산소 예측

김민지(Minji Kim),변선정(Seonjeong Byeon),김경민(Kyungmin Kim),안종화(Johng-Hwa Ahn) 대한환경공학회 2020 대한환경공학회 학술발표논문집 Vol.2020 No.11

성인에서 클라츠킨 종양과 비슷한 양상을 보인 미분화 간육종 1예

이지애 ( Ji Ae Lee ),김태완 ( Tae Wan Kim ),민재훈 ( Jae Hoon Min ),변선정 ( Sun Jung Byon ),장승훈 ( Seung Hoon Jang ),최성연 ( Seung Yeon Choi ),김홍주 ( Hong Joo Kim ) 대한소화기학회 2010 대한소화기학회지 Vol.55 No.2

Undifferentiated sarcoma is an uncommon primary malignant tumor of the liver typically occurring in older children. It is also referred to as malignant mesenchymoma, fibromyxosarcoma, or mesenchymal sarcoma. We experienced a case of undifferentiated sarcoma in 72-year-old male. Contrast enhanced liver CT scan revealed a 3.4 cm heterogeneously enhancing, ill-defined, and low attenuated mass in the left liver and subtle intrahepatic duct dilatation. And, in tubogram, there were segmental stenosis and occlusion from the hilum to the proximal common bile duct. We did ultrasonography guided liver biopsy. The pathologic finding revealed infiltrative growth of atypical cells with rhabdoid features. Some atypical cells showed clear cytoplasm, but no organoid pattern was identified. The stroma around atypical cells was filled with eosinophilic hyaline material. These tumor cells were positive for vimentin only, and the tumor was consistent with undifferentiated sarcoma of the liver. (Korean J Gastroenterol 2010;55:144-148)