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텍스트 마이닝을 활용한 항공 화물 운임에 영향을 미치는 요인 분석: L.A. 및 프랑크푸르트 노선을 중심으로
최동현,박다현 한국산업정보학회 2023 한국산업정보학회논문지 Vol.28 No.3
본 연구는 2015년 1월부터 2021년 9월까지의 뉴스 기사를 분기별로 수집하여 토픽 모델링 분석 후 인천 출발 LA와 프랑크푸르트 노선의 항공 화물 운임과 회귀분석을 하여 항공 화물 운임 변동 예측에 영향을 미치는 요인을 분석하였다. 그 결과, 국내 물류 대비 LA 노선은 ‘Oil Price’, ‘Shipping’ 토픽이 영향 있다는 점을 예측하였고, 프랑크푸르트 노선은 ‘Oil Price’ 토픽이 영향을 미친다는 점을 결과로 제시하였다. 본 연구는 온라인 뉴스 기사 텍스트로부터 수집한 비정형 데이터를 활용하여 시장 참여자의 ‘보이지 않는 심리’에 영향을 주는 특정 키워드의 빈도 분석을 하고, 항공 화물 운임 사이의 동태적 관계를 파악하고자 하였다. 항공 화물 운임 예측은 항공사와 항공 산업 관련 다양한 분야에서 의사결정에 기초자료로 활용할 수 있을 것이다.
최동현,장윤석 한국압력기기공학회 2023 한국압력기기공학회 논문집 Vol.19 No.1
Lots of researches have been conducted on in-vessel retention (IVR) to prevent or mitigate severe accident in nuclear power plants. Various methodologies were proposed and the external reactor vessel cooling was selected as a part of promising IVR strategy. In this study, the strategy is strengthened by enhancing the natural circulation performance through the adoption of insulation in the reactor cavity. A thermal analysis was carried out based on an assumed accident scenario and its results were used as boundary conditions for subsequent seven flow analysis cases. By comparing the natural circulation performance, effects of annular gaps and insulation shapes on the mass flow rate and flow velocity were quantified. The improvement in cooling performance can be reflected in actual design via detailed assessment.
최동현,홍원표,송경준,김태한,신상도,홍기정,박정호,정주 연세대학교의과대학 2021 Yonsei medical journal Vol.62 No.12
Purpose: The objective of this study was to modify and validate an emergency department (ED) triage system with improved prediction performance on hospital outcomes by modifying the Korean Triage and Acuity Scale (KTAS). Materials and Methods: We performed a retrospective observational study at three academic universities in South Korea. The KTAS code, determined by the chief complaint and the selected modifier of a patient, was used to derive the Modified KTAS (MKTAS). We calculated the area under the receiver operating characteristics curve (AUC) and the test characteristics to evaluate the performance of MKTAS to predict hospital mortality, critical outcome, and admission. Results: A total of 272402 and 128831 ED visits were used for the derivation and validation of MKTAS, respectively. Compared to KTAS, MKTAS had significantly higher AUC values for the prediction of hospital mortality [MKTAS 0.826 (0.818–0.835) vs. KTAS 0.794 (0.784–0.803)], critical outcome [MKTAS 0.836 (0.830–0.841) vs. 0.798 (0.792–0.804)], and admission [MKTAS 0.725 (0.723–0.728) vs. KTAS 0.685 (0.682–0.688)]. The sensitivity for predicting hospital mortality and critical outcome, as well as the specificity for predicting admission, were significantly improved. Conclusion: MKTAS was derived by modifying the KTAS, and then validated. Compared with KTAS, MKTAS showed better discriminating ability to predict hospital outcomes. Continuous efforts to evaluate and modify widely used triage systems are required to improve their performance.
동해 천해환경에서 수중 통신 프레임 설계를 위한 상관 대역폭과 상관 시간의 산출
최동현,김현수,김남리,김성일,정재학,Choi, Dong-Hyun,Kim, Hyeon-Su,Kim, Nam-Ri,Kim, Seong-Il,Chung, Jae-Hak 한국음향학회 2010 韓國音響學會誌 Vol.29 No.6
원활한 수중 디지털 통신을 위해 데이터 신호는 물리계층 단위의 프레임으로 전송되고, 채널 추정을 위한 프레임 내의 파일릿 간격은 수중 통신 환경에 맞게 설계되어야 한다. 본 논문은 주파수와 시간에 따른 수중 채널 변화에 관련된 상관 대역폭과 상관 시간에 대하여 기술하고 실제 동해 천해환경에서의 실험을 통해 상관 대역폭과 상관 시간 값들을 산출하였다. 그리고 파일럿 간격의 변화에 따른 실제 수중 통신의 비트 오류율 변화를 구함으로써 산출한 결과가 적절함을 보였다. For effective underwater digital communications, a frame structure is used, which includes pilots in time and frequency domains for channel estimation at a receiver. To estimate channel precisely, the each pilot should be located less than coherence time and coherence bandwidth. This paper measured underwater communication environments to provide coherence time and coherence bandwidth. Based on the measurement, the paper exhibits the calculated coherence time and coherent bandwidth is adequate by computer simulations.
캡부착 내시경이 대장내시경의 질을 향상시키는데 도움을 주는가?
최동현,신현근,이영찬,임청호,정승규,이석환,양형규 대한대장항문학회 2010 Annals of Coloproctolgy Vol.26 No.2
Purpose: Recently, the use of a transparent cap attached to the tip of the colonoscope has been revealed to be helpful in both detecting colorectal polyps and shortening the intubation time to the cecum. The aim of this study was to examine the usefulness of transparent cap-attached colonoscopy (CAC) as compared with conventional colonoscopy (CC) in terms of the technical ease and efficiency. Methods: Colonoscopies from a total of 228 patients between May and October 2008 were prospectively collected. All colonoscopies were performed by single colorectal surgeon whose experience exceeded 3,000 colonoscopies. Patients were assigned to the CAC group (n=114) or to the CC group (n=114). The cecal intubation rate and time, the polyp detection rate, the adenoma detection rate, the withdrawal time, and the visual analogue scale (VAS) of the patient’s pain were compared. Results: There were no significant differences in the age, sex, body mass index, previous history of abdominal operation,diverticulosis, and the degree of bowel preparation between the two groups. The cecal intubation rate was 100% in both groups. The cecal intubation time was significantly shorter in the CAC group than in the CC group overall (5.3±4.0 min vs. 7.6±4.3 min, P<0.001), as well as for female (6.1±2.8 min vs. 9.1±4.7 min, P<0.001) patients. There were no statistically significant differences in the total colonoscopy time (13.1±6.3 min vs. 14.5±5.2 min, P=0.066), the polyp detection rate (38.6% vs. 33.3%, P=0.408), the adenoma detection rate (28.1% vs. 25.4%, P=0.654), and the VAS scale of pain (2.48 vs. 2.74, P=0.353) between the CAC and the CC groups. Conclusion: The transparent cap is effective in shortening the cecal intubation time, especially in female patients.