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하재현(Jae Hyeon Ha),우완식(Wan-Sik Woo),노영화(Young Hwa Roh),이춘만(Choon-Man Lee) Korean Society for Precision Engineering 2017 한국정밀공학회지 Vol.34 No.8
The recent crisis of environmental pollution and resource depletion has become a major global issue, resulting in an increasing interest in remanufacturing in many countries. However, manufacturing for environmental protection is considered an additional cost factor by most companies. Therefore, governments worldwide have actively implemented remanufacturing policies to encourage the participation of numerous companies in the remanufacturing industry. As an eco-friendly technology, remanufacturing has impacted the environmental improvement and resource savings by reducing raw materials and production processes. In particular, the effect of machine tool and automobile part remanufacturing is very remarkable, since most parts are reusable. In this study, the standardization technology for remanufacturing process of machine tools is developed by remanufacturing of used vertical machining center. Based on the work operation sheet for establishing the process, the remanufacturing process chart and program were developed. The performance evaluation of machining centers before and after remanufacturing was also executed, to check the performance improvement of the remanufactured product. The performance evaluation criteria were established to improve reliability.
비대면 시대 고령자의 키오스크 사용자 경험 증대 연구 -맥도날드 키오스크 중심으로-
하재현,김승인,Ha, Jae-Hyeon,Kim, Seung-In 한국디지털정책학회 2021 디지털융복합연구 Vol.19 No.8
본 연구는 비대면 시대 고령자의 키오스크 사용 경험 증대에 관한 연구이다. 선행연구와 문헌 조사를 통해서 키오스크와 고령자에 관하여 고찰하였고. 참여 관찰법과 심층 인터뷰를 통해 개선방안을 제시하였다. 연구 방법으로는 인천 거주 60대 이상 고령자를 대상으로 2021년 4월 4일부터 16일까지 13일간 키오스크 사용 경험이 없는 8명을 대상으로 참여 관찰을 진행하였고, 사용 경험이 있는 3명을 추가하여 총 11명을 심층 인터뷰하였다. 실험 결과 고령자의 사용과정 페인 포인트(pain point)로 인터페이스와 심리적인 요인들이 도출되었고, 이를 종합하여 다섯 가지 개선안을 제시하였다. 본 연구는 고령자 키오스크 사용자 경험과 키오스크 인터페이스 디자인에 관한 연구의 자료로써 활용되기를 기대한다. The purpose of this study is to increase the experience of using kiosks for elderly in the non-face-to-face age. Through prior research and literature research, feature of kiosks and characteristic of elderly user were identified, and improvement were suggested through Ethnography and in-depth interviews. The research method was conducted for 13 days from April 4 to 16, 2021 for 11 senior citizens in their 60s or older living in Incheon. A total of 11 people were interviewed by adding 3 people who had experience in using kiosks. As a result of the experiment, interfaces and psychological factors were derived with paint points in the process of use of the elderly, and the five improvement plan was proposed by combining them. This study is expected to serve as a source for research on the experience of elderly kiosk users or kiosk interface design.
하재현(Jae-hyoun Ha),정석영(Suk Young Jung),이영환(Younghwan Lee),진현(Hyeon Jin) 한국항공우주학회 2021 韓國航空宇宙學會誌 Vol.49 No.3
초음속 비행체에서 발생하는 소닉붐은 일반적인 환경소음과 달리 초저주파 영역을 포함한 충격음으로 전파된다. 본 논문에서는 배열 음향센서를 이용하여 소닉붐의 특징을 왜곡 없이 측정하기 위한 계측방법과 소닉붐의 전파방향을 추정하기 위한 도래각 추정 방법에 대해 연구하였다. 음향센서의 배치에 따른 도래각 추정성능을 이론적인 방법으로 제시하였고 모의실험에서 얻은 통계값을 이용하여 본 연구에서 제안하는 도래각 추정 방법의 성능을 검증하였다. 또한 실제 초음속 비행체에서 발생한 소닉붐을 제안한 방법으로 측정하였고 그 결과를 분석하였다. 본 연구에서 얻은 결과로 소닉붐 측정을 위한 시스템 구성, 도래각 추정 방법과 그 성능에 대한 직관적인 개념을 제공하였다. This paper studies measurement of sonic boom created by supersonic flight and its arrival angle estimation techniques. Since sonic boom propagates as an impulsive noise and includes infrasound frequency, we propose measurement instrumentation acquiring sonic boom signature without distortion. And we suggest the methodology for an arrival angle estimation with its performance analysis in accordance with sensor array configurations. The performance of our estimator is verified by comparing theoretical performance bound with statistics of its Monte-Carlo simulation results. Furthermore, we presents the analysis of the sonic boom measurement from real flight tests. This work provides an intuitive concept for sensor array configurations and measurement instrumentation.
정석영(Suk Young Jung),하재현(Jae-hyoun Ha),이영환(Younghwan Lee),진현(Hyeon Jin) 한국항공우주학회 2020 韓國航空宇宙學會誌 Vol.48 No.7
초음속 비행으로 인해 발생하는 소닉붐을 해석하여 소닉붐의 소음 강도와 대기 전파 특성에 예측할 수 있는 기법을 개발하였다. 소닉붐은 환경 문제를 유발하므로 지상에서 계측되는 소음 강도가 매우 중요한데 본 연구에서는 개략 분석 기법을 이용하여 비행체의 물리량과 비행 정보로부터 계측지 거리에 따른 음압을 산출하였다. 소닉붐의 지상 계측을 위해 비행체에서 발산되는 충격파의 대기 전파 특성을 예측해야하며 이를 위해 시선벡터법과 음선추적기법을 이용하였고, 대기 밀도의 고도별 분포에 따른 굴절을 고려하였다. 개발된 기법을 이용하여 실제 초음속 비행체의 소닉붐을 예측하였고 측정결과와 잘 일치하였다. A technique was developed for analysis on sonic boom created by supersonic flight and for prediction of its sound level and atmospheric propagation characteristics. It is of great importance to anticipate sound level of sonic boom because it causes environmental issue. For that purpose, the simplified sonic-boom prediction method was applied to calculate sound pressure according to physical properties and flight information of the object and distance to measurement site, in this study. Propagation characteristics of shock wave emanated from a flying object was analyzed by using line-of-sight vector and ray tracing method which dealt with refraction of wave due to atmospheric density distribution along altitude. Predicted results agreed well with measured data from real flight.
이춘만(Choon-Man Lee),하재현(Jae-Hyeon Ha),우완식(Wan-Sik Woo),김은중(Eun-Jung Kim) Korean Society for Precision Engineering 2016 한국정밀공학회지 Vol.33 No.12
Recently, the problem of the accumulation of fine sludge from the cutting oil generated during machining processes has become a major threat to the environment. The fine sludge has adverse affects on the human body and the environment, and significantly contributes to marine pollution. However, a microfiltration technique that can process the sludge still needs to be studied and developed on a global scale. Therefore, it is necessary to develop eco-friendly equipment such as an ECO vacuum filter system and eco-friendly technologies for processing cutting oil. In this study, a structural analysis was carried out using a finite element method (FEM). Improved models of the suction chamber for the ECO vacuum filter system were proposed based on the analysis of the displacement and stress of the system. The model with the best result was then optimized using the commercial software, ANSYS. It was confirmed that, in the optimized model, displacement and stress were reduced in comparison with the initial model. Finally, the structural stability of the optimized model was verified through analysis.