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김재현,유서윤,정철웅,장동혁,안민기,Kim, Jaehyun,Ryu, Seo-Yoon,Cheong, Cheolung,Jang, Donghyeok,An, Mingi 한국음향학회 2018 韓國音響學會誌 Vol.37 No.6
본 논문에서는 쾌적한 운전 환경을 제공하기 위해 자동차 시트를 냉각시키기 위한 고성능 및 저소음 원심팬을 개발하였다. 먼저 팬 성능 테스터 및 전산유체역학(Computational Fluid Dynamics, CFD) 시뮬레이션을 이용하여 기존 팬 장치의 유동 특성을 분석하였다. 예측한 유동장 분석을 통하여 팬 허브 팁 근처의 와류 및 팬 허브 상단의 정체된 유동 현상이 관측되었다. 이러한 와류 및 정체 유동을 줄이기 위해 두 가지 설계 요소를 고안하였다. 첫째, 팬 날개와 팬 하우징 최소 간극(cut-off)를 증가시켜 난류강도를 줄이고 그 결과로 전체적인 음압 레벨을 줄이고자 하였다. 둘째, 허브 형상은 정체 유동을 줄이기 위해 형상을 변경하였다. 제안된 설계의 타당성을 수치해석을 통해 확인하였다. 수치해석결과를 바탕으로 프로토타입을 제작하고 팬 테스터에서 측정한 성능 곡선(P-Q curve)과 반무향실에서 측정한 음압 레벨의 분석을 통해서 유동과 소음 성능의 향상을 확인하였다. In this paper, a high-performance and low-noise centrifugal fan is developed for cooling automotive seats which provide a driver with pleasant driving environment. First, the flow characteristics of the existing fan unit was analyzed using a fan performance tester and CFD (Computational Fluid Dynamics) simulations. The analysis of the predicted flow field indicated vortex flow near the tip of fan hub and stagnation flow on the top of fan hub. Two design points are devised to reduce the vortex flow and the stagnation flow observed in the existing fan unit. First, the cut-off clearance which is the minimum distance between the fan blade and the fan housing is increased to reduce the vortex strength and, as a result, to reduce the overall sound pressure level. Second, the hub shape is more modified to eliminate the stagnation flow. The validity of proposed design is confirmed through the numerical analysis. Finally, a prototype is manufactured with a basis on the numerical analysis result and its improved flow and noise performances are confirmed through the P-Q curves measured by using the Fan Tester and the SPL (Sound Pressure Level) levels measured in the anechoic chamber.
청년몰 자금, 교육, 컨설팅지원이 창업성과에 미치는 영향 -청년상인 기업가정신 매개효과를 중심으로-
김재현 ( Jaehyun Kim ),임흥순 ( Heungsun Lim ),이종훈 ( Jonghun Lee ) 사단법인 아시아문화학술원 2021 인문사회 21 Vol.12 No.6
본 연구는 청년몰 창업성과를 규명하기 위하며 외부 환경적 변인으로 자금, 교육, 컨설팅 지원을, 매개변인으로 청년상인 기업가정신을 선정하고 구조방정식 모델로 변인 간 인과관계를 검증하는 데 목적이 있다. 청년몰 청년상인 274부 데이터를 AMOS 25.0 프로그램을 이용하여 구조방정식 모델을 분석하였다. 연구결과 첫째, 청년몰 자금지원과 기업가정신은 창업성과에 직접 영향을 미치며 둘째, 청년몰 교육지원은 창업성과에 직접 영향이 없다. 셋째, 자금지원과 교육지원은 창업성과에 미치는 영향에서 기업가정신의 매개효과는 부분매개효과가 나타났다. 본 연구를 통하여 사업초기 모든 자금과 교육이 지원되는 시스템을 지양하고 업종, 청년상인의 개개인의 차이, 내·외부 환경을 고려한 단계적 자금지원과 교육지원의 필요성을 확인하였다. 또한, 향후 코로나19 바이러스 확산 전, 후 비교와 다양한 변인을 적용하여 양적·질적 실증적인 연구가 보완되어야 할 것이다. The purpose of this study is to verify the causal relationship between variables by setting funds, education, and entrepreneurship, which are external environmental variables, as a structural equation model. The structural equation model was analysed using the AMOS 25.0 program for 274 data of youth mall youth merchants. As a result of the study, first, youth mall funding and entrepreneurship directly affect start-up performance, and second, youth mall education support does not directly affect start-up performance. Third, the mediating effect of entrepreneurship was partially mediated in the effect of funding and education support on entrepreneurship performance. Through this study, the necessity of step-by-step funding and education support was confirmed in consideration of the individual differences of industries, business conditions. In addition, quantitative and qualitative empirical studies should be supplemented by applying various variables and comparisons before and after the spread of the COVID-19 virus in the future
선택적 충전방식 전하펌프를 사용한 LED 램프 조광구동 기술
김재현(Jaehyun Kim),윤장희(Janghee Yun),염정덕(Jeongduk Ryeom) 한국조명·전기설비학회 2013 조명·전기설비학회논문지 Vol.27 No.9
A new LED lamp driving technology with a charge pump instead of a conventional DC-DC converter is proposed. The proposed driving technology is used to control the LED lamp with digital dimming. The power loss in the zener diodes is reduced because the charging process of the capacitors is selectively controlled according to the digital control signal. From the experimental results, when dimming four LED lamps simultaneously, the average driving circuit efficiency of 89% is obtained, regardless of the dimming level. White light with color temperature over a range of 2800∼7200K was produced by dimming control of red, green, blue and amber LED lamps with the proposed driving circuit. The characteristics of the driving circuits can be changed depending on the characteristics of the R, G, B, and A LED lamps. The efficiency of the driving circuits up to a maximum 89% can also be obtained depending on the combination of LED lamps. The driving technology with digital dimming control for LED lamps proposed in this paper would be effective for obtaining high efficiency in LED driving circuits and remote control of LED lamps using digital communications.
김재현(Jaehyun Kim),정기석(Gisuk Jung),강연식(Yeonsik Kang) 한국소성가공학회 2010 한국소성가공학회 학술대회 논문집 Vol.2010 No.10
An automotive steel part is required to evaluate its performance and feasibility in the early stage of vehicle development. It is manufactured using prototype die. The hydroforming prototype die for a hydroformed part is expensive as its massive production die. The high cost of the hydro forming prototype die makes engineer to choose a conventional stamping method before hydroforming technology without any evaluations of hydroformed parts. To reduce the cost of hydroforming prototype die plastics are considered. In this paper mono cast nylon for die material is used to evaluate the feasibility of hydro formed parts. The manufacturing time and cost of prototype die can be saved with the die material, mono cast nylon. And the geometry accuracy of the part formed through the mono cast nylon die can be fulfilled with the tolerance ± 1㎜.
광역권 관광개발 정책의 의의와 경제적 파급효과 – 남해안 관광벨트 개발을 중심으로
김재현(Jaehyun Kim),정상철(Sangchul Jung) 한국문화경제학회 2020 문화경제연구 Vol.23 No.3
본 연구는 광역 관광개발 효과를 분석한 연구로 광역 관광개발의 공공투자적 성격을 모형 내에 반영하여 분석을 수행했다. 본 연구는 광역권 관광개발 정책의 효과가 나타나는 경로를 경제 이론에 적합하도록 구성하였다는 점과, 이를 통한 순효과를 정량적으로 분석하였다는 점에서 기존 연구와 차별화된다. 본 연구에서는 정부의 관광개발투자가 반영된 다지역 동태일반균형모형을 구축하고, 실제 국내에서 시행된 남해안 관광개발 정책의 경제적 파급효과를 구축된 모형으로 실증분석했다. 분석 결과 사업 수행 이후 수행 전 대비 연간 약 0.037%(약 6,700억원)의 실질 GDP 파급효과가 나타나는 것으로 분석되었고, 연간 일자리는 0.01%, 총소비는 0.027%, 총자본은 0.011%, 총 투자는 0.01% 증가하는 것으로 나타났다. 또한 광역권 관광개발은 일반재 소비를 줄이고 관광서비스에 대한 소비를 증가시키는 효과가 있는 것으로 분석되었다. This study analyzed the effects of wide-area tourism development, and analyzed the public-invested nature of wide-area tourism development in the model. This study is differentiated from previous studies in that the route through which the effect of the tourism development policy in the metropolitan area appears was organized in accordance with the economic theory and the quantitative analysis results were presented. In this study, a multi-regional dynamic general equilibrium model reflecting the tourism development policy was established, and the economic ripple effect of the South Coast tourism belt development policy implemented in Korea was empirically analyzed with the constructed model. As a result of the analysis, it was analyzed that the real GDP ripple effect of about 0.037% (approximately 670 billion won) per year appeared after the project was executed, compared to before the execution of the project. In addition, it was analyzed that tourism development in the metropolitan area has the effect of reducing the consumption of general goods and increasing the consumption of tourism services.