http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
동축 와류형 분사기의 연소안정성에 대한 분사기 리세스 및 연소실 길이의 영향
박수진(Sujin Bak),황동현(Donghyun Hwang),안규복(Kyubok Ahn),윤영빈(Youngbin Yoon) 한국추진공학회 2020 한국추진공학회지 Vol.24 No.1
In this study, model combustion tests were conducted to investigate the combustion instability characteristics of swirl coaxial injectors for a liquid rocket engine. To examine the effects of the combustion chamber resonant frequency and the injector mixing conditions, pressure fluctuations in the combustion chamber were measured by changing the combustion chamber length, injector recess length, and propellant mixture ratio. From the test results, the variation in the pressure fluctuations for each experimental condition was confirmed and the combustion stability was evaluated by stability mapping. It was found that the longitudinal mode and Kelvin-Helmholtz instabilities occurred due to the change in the combustion chamber and recess lengths.
라벨 주석이 없는 국내 공공기관의 비지도 학습 기반 ESG 평가 프로세스 개발
유도혁(Do Hyeok Yoo),박수진(SuJin Bak) 한국컴퓨터정보학회 2024 韓國컴퓨터情報學會論文誌 Vol.29 No.5
본 연구는 ESG 등급이 제공되지 않는 국내 공공기관의 ESG 등급을 추정하는 비지도 학습 기반 군집모형을 제안한다. 이를 위해, 스펙트럼 군집과 k-means 군집에서 최적의 클러스터 수를 비교했고, 그 결과의 신뢰성을 보장하기 위해 성능지표인 Davies-Bouldin Index (DBI)를 계산했다. 결과적으로, 스펙트럼 군집과 k-means 군집에서 각각 0.734 및 1.715의 DBI 값을 산출했는데, 이는 값이 작을수록 우수한 성능을 의미하므로 스펙트럼 군집의 우수성을 확인하였다. 게다가, T-검정 및 ANOVA를 이용하여 ESG 비재무 데이터 간 통계적으로 유의미한 차이를 밝혀내고, 상관계수를 이용하여 ESG 항목 간 상관관계를 확인했다. 본 연구는 이러한 결과를 바탕으로 기존 ESG 등급 없이 공공기관별 ESG 성과 순위를 추정할 가능성을 제시한다. 이는 최적의 클러스터 수를 계산한 다음, 각 클러스터 내 ESG 데이터의 평균 총합을 결정함으로써 달성된다. 따라서, 제안된 모델은 다양한 국내 공공기관의 ESG 등급을 평가하는 근거로 활용될 수 있고, 국내 지속가능경영 실천과 성과관리에 유용할 것으로 기대된다. This study proposes an unsupervised learning-based clustering model to estimate the ESG ratings of domestic public institutions. To achieve this, the optimal number of clusters was determined by comparing spectral clustering and k-means clustering. These results are guaranteed by calculating the Davies-Bouldin Index (DBI), a model performance index. The DBI values were 0.734 for spectral clustering and 1.715 for k-means clustering, indicating lower values showed better performance. Thus, the superiority of spectral clustering was confirmed. Furthermore, T-test and ANOVA were used to reveal statistically significant differences between ESG non-financial data, and correlation coefficients were used to confirm the relationships between ESG indicators. Based on these results, this study suggests the possibility of estimating the ESG performance ranking of each public institution without existing ESG ratings. This is achieved by calculating the optimal number of clusters, and then determining the sum of averages of the ESG data within each cluster. Therefore, the proposed model can be employed to evaluate the ESG ratings of various domestic public institutions, and it is expected to be useful in domestic sustainable management practice and performance management.
황동현(Donghyun Hwang),박수진(Sujin Bak),안규복(Kyubok Ahn) 한국연소학회 2019 KOSCOSYMPOSIUM논문집 Vol.2019 No.11
An experimental study was conducted to investigate the effects of swirler geometry and flow condition on self-excited thermo-acoustic instability and bifurcation of flame structure. The combustion chamber length was manufactured in two types to simulate acoustically coupled/uncoupled conditions. Dynamic pressure, heat release, inlet velocity fluctuation, and CH* chemiluminescence image were measured to analyze the mechanism for combustion instability. Bifurcation of the flame structure was not necessarily coincide with the onset of thermo-acoustic instability, but occurred at nearly same condition regardless of the combustor length. The results showed that the combustion instability occurred based on the principle of the limit cycle in the case of coupled long combustor. In the uncoupled short combustor, however, only stable combustion was observed under the same flow conditions.