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장서원,변용익,신민수,이한,김명진,문홍규,최영준,Sang-Mok Cha,이용석 한국천문학회 2018 Journal of The Korean Astronomical Society Vol.51 No.5
The DEEP-South (the Deep Ecliptic Patrol of the Southern Sky) photometric census of small Solar System bodies produces massive time-series data of variable, transient or moving objects as a by-product. To fully investigate unexplored variable phenomena, we present an application of multi-aperture photometry and FastBit indexing techniques for faster access to a portion of the DEEP-South year-one data. Our new pipeline is designed to perform automated point source detection, robust high-precision photometry and calibration of non-crowded fields which have overlap with previously surveyed areas. In this paper, we show some examples of catalog-based variability searches to find new variable stars and to recover targeted asteroids. We discover 21 new periodic variables with period ranging between 0.1 and 31 days, including four eclipsing binary systems (detached, over-contact, and ellipsoidal variables), one white dwarf/M dwarf pair candidate, and rotating variable stars. We also recover astrometry ($<\pm$1--2 arcsec level accuracy) and photometry of two targeted near-earth asteroids, 2006 DZ169 and 1996 SK, along with the small- ($\sim$0.12 mag) and relatively large-amplitude ($\sim$0.5 mag) variations of their dominant rotational signals in $R$-band.
와인소비자의 유형에 따른 와인 선택속성과 재구매의도에 미치는 영향: 음용횟수의 조절효과
장서원,서정희,이종호 (사)한국조리학회 2019 한국조리학회지 Vol.25 No.5
본 연구는 와인 소비자의 유형에 따른 와인 선택속성이 재구매의도에 미치는 영향관계를 실증 분석하고자 한다. 연구의 목적을 달성하기 위하여 SPSS 21.0 통계패키지 프로그램을 이용하여, 와인 소비자의 유형, 와인 선택속성, 재구매의도와의 영향관계를 검증하기 위해 다중회귀분석(multiple regression), 위계적회귀분석(hierarchical regression analysis)을 실시하였다. 연구결과 와인소비자유형 모두 와인선택속성의 하위요인인 외적속성, 내적속성요인에서 p<0.001에서 유의한 차이가 있는 것으로 나타났다. 와인선택속성의 하위요인인 외적속성(β=0.102, p=.048), 내적속성(β=0.625, p=.000)에서 통계적으로 유의하게 분석되었다. 이는 와인을 재 구매하는데 있어 내적속성이 영향력이 외적속성보다 크다는 것을 알 수 있다. 즉, 와인의 품질(질감, 맛, 색, 향)이 좋은 재품을 재구매한다는 것이다. 와인선택속성과 재 구매의도와의 관계에서 음용회수의 조절효과의 검정결과 음용횟수는 조절효과가 있는 것으로 분석되었다. 이는 와인을 자주마시는 그룹과 그렇지 않는 그룹에 따라서 와인선택속성이 재구매에 미치는 영향관계의 강도에 차이가 있다는 결과를 의미하고 있다. 본연구의 한계점으로는 표본을 추출하는 데 있어서 부산ㆍ울산지역의 와인 구매경험이 있는 집단과 와인전문가 집단을 표본을 선택하였다는 것과 선택속성과 재구매의도 와의 관계만 검정하였다는데 한계점을 가지고 있다. 향후 와인소비자 유형에 따른 선택속성과 재구매의도와의 관계의 연구에서 본연구의 한계점을 보완하여 보다 완성도 높은 후속연가가 있기를 기대한다.
8 MW급 대용량 풍력발전기용 피치감속기 안전성 평가에 관한 연구
장서원,박세호,이형우 한국풍력에너지학회 2022 풍력에너지저널 Vol.13 No.4
In this paper, a study was conducted to evaluate the safety of pitch reducers for 8 MW class wind turbines. The housing and carrier of the pitch reducer were subjected to structural analysis for the ultimate load by load duration distribution (LDD). As a result of the finite element analysis of the housing parts, the part with the highest stress was the output housing, and the equivalent stress was 522.4 MPa and the safety factor was 1.14. As a result of finite analysis of the carrier, the highest stress occurred at 80.5 MPa in the first carrier, and the safety factor was 10.3. In addition, extreme strength and life analysis by LDD load were performed for gears and bearings included in each stage. The strength analysis of the planetary gear train was conducted based on ISO 6336, and the stability evaluation of the bearings through life analysis based on ISO 281 found all to be safe.
8 MW급 대용량 풍력발전기용 피치 감속기 진동특성에 관한 연구
장서원,박세호,이형우 한국풍력에너지학회 2022 풍력에너지저널 Vol.13 No.4
In this paper, a study on the vibration characteristics of the pitch gearbox of 8 MW large capacity wind turbines was conducted. The vibration analysis method of the pitch gearbox was proposed by combining the planetary gear train vibration model with the housing and carrier finite element model using the substructural synthesis method. We modeled the vibration excitation source for mass unbalance, gear mesh frequency, and bearing defect error action on the pitch gearbox, and performed a critical speed analysis. As a result of analyzing the critical speed of the pitch gearbox, the critical speed for the excitation source did not occur within the operation speed (84.87 rpm). In addition, as a result of applying 10 %, 20 %, …, 100 % of the largest load duration distribution (LDD) load, it was found that the bearing stiffness and the primary natural frequency were larger as the LDD load was larger. The primary natural frequency was 81.47 Hz for the lowest load among LDD data, which exceeded an operating speed of 84.87 rpm (5.09 Hz), so it was found that vibration caused by the change of LDD load did not occur in the operating speed range.