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권승민,유홍희 대한기계학회 2011 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.25 No.11
A multi-packet blade system consists of several blades which are attached to a disk and connected through shrouds. The blades of a multi-packet blade system are usually assumed to be identical. However, there always exists small, random mistuning among the blades due to manufacturing tolerance, in-operation wear and environmental changes. Such mistuning may cause significant increase in the forced vibration responses of some blades in the multi-packet blade system. Critical fatigue problems often occur in mistuned systems since the forced vibration response of a mistuned system is often significantly larger than that of a tuned system. Therefore, it is very important to predict the maximum blade response. In this study, blades are idealized as cantilever beams and the flexibilities of the disk and shrouds are idealized as discrete springs. Equations of motion are derived using the hybrid deformation variable method. To realize vibration localization with random mistuning, transient analysis is carried out for a multi-packet blade system excited by multiple nozzle jet forces.
권승민,손영부,하종훈,유홍희,Kwon, Seungmin,Son, Youngboo,Ha, Jonghun,Yoo, Hong Hee 대한기계학회 2015 대한기계학회 논문집 C. 기술과 교육 Vol.3 No.2
최근 생활수준의 향상으로 인해 가정용 에어컨의 보급률이 꾸준히 증가함에 따라 품질에 대한 소비자의 눈높이 또한 점점 높아지고 있다. 과거에 소비자의 요구는 제품의 효율성에 집중되었지만 점차 저진동/저소음에 대한 부분으로 확장되고 있다. 에어컨의 압축기는 제품의 효율을 결정하는 주요한 부분이면서 동시에 진동/소음의 주된 원인을 제공하고 있다. 압축기에서 발생한 진동/소음은 압축기 케이스와 배관을 통해 주위 구조물로 전달되고 이들은 다시 구조기인 소음이나 2 차적인 진동을 유발하게 된다. 본 연구에서는 RecurDyn 을 이용해 압축기의 진동/소음에 영향을 미치는 모터의 가진력이 고려된 MFBD(Multi Flexible Body Dynamics) 해석 모델을 개발하였다. 개발된 모델을 이용하여 압축기의 진동/소음 특성을 조사하고 압축기에서 발생하는 진동을 계산하여 실험 결과와 비교하였다. Recently, noise reduction in room air conditioner has been one of the most important issues as well as cooling efficiency. A rotary compressor is widely used in room air conditioners. But, the rotary compressor is the dominant vibration/noise source in an air conditioner. A number of studies have been conducted on reducing rotary compressor vibration/noise through improving muffler and resonator design. However, a noise delivering path between compressor and pipe is not fully taken into consideration. In this paper, the vibration analysis model of rotary compressor is modeled using RecurDyn and experimental validation is presented.
Structural Method 을 이용한 Superimposition : Part1:Facial Superimposition
권승민,이영미,오용덕,양희상,박금석,박관수,김중한,윤영주,김광원 朝鮮大學校 口腔生物學硏究所 1997 口腔生物學硏究 Vol.21 No.1
When evaluating the dentofacial changes that occur as a result of growth or treatment, orthodontists are interested in observing specific areas of alterations. As a result, cephalometric superimposition involve the evaluation of change in the overall face, in the maxilla and its dentition, in the mandible and its dentition, amount and direction of condylar growth and mandibular rotation. The method of superimposition vary according to structures used as references within the skull. Cephalograms were superimposed according to the four methods : ⑴ structural method, ⑵ superimposition on SN line, registerd at S point, ⑶ superimposition on registration - point R with Bolton - nasion planes parallel, and ⑷ superimposition on basion - nasion, registered at point CC. The superimposition methode differ according to reference structures used within the skull. To evaluate facial changes, such structures must be relatively stable over time and located outside the face itself. Unlike the facial skeleton, the cranial base grows rapidly in early postnatal life, reaching 90% of its full size by 4 to 5 years of age. For this reason, the cranial base is considered a satisfactory reference four cephalmetric superimpositions. But, the cranial base is consisted of frontal bone, sphenoidal bone, occipital bone and symphysis, and growth of its structures are difference. Therefore, structural method, which is used fast full growth and most stable structure, may be considered more exact and reliable superimposition method.
권승민,황재욱 한국체육학회 2022 한국체육학회지 Vol.61 No.5
본 연구의 목적은 경쟁불안에 대한 개념적 구조를 파악한 후 관련 내용을 토대로 타당성과 신뢰성이 있는 야구선수용 경쟁불안 측정 도구를 개발하는 것이다. 본 연구에서는 질적 분석 단계 102명, 본 조사 단계 330명, 외적 타당도 확보 단계 206명, 총 야구선수 638명이 참여하였다. 질적 자료는 개방형 질문과 면담을 통해 자료를 수집했으며, 양적 자료는 자기평가 기입법으로 자료를 수집하고 SPSS 20.0 Version과 AMOS 20.0 Version을 통해 분석되었다. 첫째, 경쟁불안은 인지 불안, 수행 불안, 환경 불안, 신체 불안으로 4개의 일반영역으로 범주화되었다. 둘째, 문항 분석, 신뢰도 분석, 탐색적 요인분석을 통해 19문항을 제거한 후 야구선수들의 경쟁불안 4요인 25문항을 추출하였고 확인적 요인분석을 통해 측정 도구의 적합도를 확인하였다. 셋째, 개발된 야구선수 경쟁불안 측정 도구는 수렴 타당도, 구인 동등성 검증, 잠재평균 분석을 통해 외적 타당성을 확보하였다. 야구선수용 경쟁불안 측정 도구의 활용은 불안의 정도를 확인하는 것에 국한하지 않고 야구선수들이 불안에 대처하는 능력과 경기력 향상에 도움을 줄 수 있을 것으로 기대한다.
안면 비대칭을 동반한 골격성 3급 부정교합 환자에서 악교정 수술을 이용한 치험례
권승민,김광수,임신영,김정호,박미숙,윤영주,김광원 朝鮮大學校 口腔生物學硏究所 1998 口腔生物學硏究 Vol.22 No.2
In recent years, facial asymmetric patients are increasing with increasing patient's desire, development of surgical technique, increased of growth amount. The etiology of asymmetry includes : a) Genetic and congenital malformation e. g. hemifacial microsomia and unilateral cleft the lip and palate ; b) Environmental factor, e. g. habit and trauma ; c) Functional deviation, e. g. mandibular shift as a result of tooth interference. For the evaluation of asymmetric patients, skull A-P, submentovertex radiographs are usually needed. With these X-rays, we can assess 3-dimensional location of maxilla and mandible. Patient's complain and desire to be addressed since they are vary from unrealistic expections to lack of concern even in the presence of large deviation. In mild dental, skeletal and soft tissue deviations cases, the advisability of treatment should be carefully considered.
리그 시험기를 활용한 서스펜션 시스템 진동 특성 분석 기반의 승차감 성능 육성 프로세스
권승민,김성훈 한국자동차공학회 2024 한국 자동차공학회논문집 Vol.32 No.1
The era of future mobility is emerging, and ride comfort will be a telling factor as customer demand increases. Ride comfort performance should be rapidly developed in future mobility systems, so predicting ride comfort by using only the suspension system of the vehicle would be very helpful. In this paper, test rigs for ride comfort testing(suspension module test rig, dynamic comfort roadway, and roller bench) were used to determine the effect of the vibration characteristics of suspension systems on ride comfort performance. Tests on vibration characteristics and ride comfort were carried out by using only the suspension test rig, and the correlation between performance and vibration characteristics was analyzed. Ride comfort development at the system level, based on the analysis of suspension vibration characteristics, was proposed. Likewise, the vibration characteristics target for the suspension system, which can help improve ride comfort and design component specifications, was suggested.
한 개의 크랙을 가진 회전하는 패킷 블레이드 시스템의 진동해석
권승민(Kwon, Seung-Min),유홍희(Yoo, Hong-Hee) 한국소음진동공학회 2009 한국소음진동공학회 논문집 Vol.19 No.12
In this paper the vibrational behavior of a multi-packet blade system having a cracked blade is investigated. Each blade is assumed as a slender cantilever beam. The coupling stiffness effect that originates from either disc flexibility or shroud is considered in the modeling. Hybrid deformation variables are employed to derive the equations of motion. The flexibility due to crack, which is assumed to be open during the vibration, is calculated basing on a fracture mechanics theory. In the paper, the results of the change in modal parameters due to crack appearance are presented. The influence of the crack parameters, especially of the changing location of the crack is examined.