• Journal of the Korean Society for Precision Engineering
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• v.19 no.11
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• pp.89-95
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• 2002

A shadow mask inside the Braun tube of a TV is sustained by springs attached to the glass panel, its vibration cause the picture image to discolor, which is called the microphonic phenomenon. It is found that it results from resonance when the natural frequency of the shadow mask coincides with that of built-in speaker sound. This paper describes experimental and analytical investigations by using FEM on the vibration problem of the shadow mask assembly. The simulation scheme may be efficiently used to develop a new design for a large-screen flat TV.

• Journal of the Korean Institute of Educational Facilities
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• v.5 no.2
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• pp.16-29
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• 1998

Bell Laboratory introduced the sound and visual system for the first time in 1927. Since then, the development of telecommunication technology made it possible for people located far away to communicate each other watching through the TV screen. Over the period different types of telelecturing systems have prospered in line with the development of telecommunication technology. Therefore, it is quite natural that telelecturing/conferending system attracts the attention of many people as a new way of educating people located in a long distance. In the industrial sector, telelecturing systems already come into wide use to save time and training and travelling expense. In this study, I examine the concept and characteristics of telelecturing/conferencing system and introduce different types telelecturing system developed in parallel with the development of communication technology. Then, I analyze how those merits of the telelecturing system can be applied to educational purpose. Finally, I propose and design ideal telelectuirng/conference facilities consisting of telelecturing rooms, bilateral movie system, seats, ceilings, color, TV screen, lighting, acoustics, humidities and temperature control, security system, projection system to maximize the educational purpose and effectiveness.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.9
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• pp.952-960
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• 2008

Fan noise prediction method is presented for air conditioning, automobile and electronic cooling system applications where fan acts as an internal equipment having very complicated flow interaction with other various system components. The internal flow paths and distribution in the fan-applied systems such as computer or air conditioner are analyzed by using the FNM(flow network modeling). Fan noise prediction method comprises two models for the discrete frequency noise due to rotating steady aerodynamic lift and blade interaction and for the broadband noise due to turbulent boundary layer and wake vortex shedding. Based on the fan operation point predicted from the FNM analysis results and fan design parameters, the present far noise model predicts overall sound pressure level and spectrum. The predictions for the flow distribution, the fan operation and the noise level in air cooling system by the present method are well agreed with 3-D CFD and actual noise test results.

• Proceedings of the Acoustical Society of Korea Conference
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• 1998.06c
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• pp.265-268
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• 1998

본 논문에서는 1채널(mono)이나 2채널(stereo)의 오디오 입력을 5채널(center, left, right, left side, right side)로 출력시키는 음장 시스템을 설계하고 그 성능을 분석하였다. 가정의 리스닝 룸 같이 작은 공간에서 콘서트 홀 같은 커다란 공간의 음장을 재현하기 위한 멀티 채널 음장 시스템은 지연기, 초기 반사음처리기, 잔향기를 이용해 설계하였다. 초기 반사음 처리기의 지연과 이득은 실제 공간에서 측정한 암펄스 응답을 이용하여 결정하였으며, 구현된 초기 반사음을 전방 30$^{\circ}$방향에서 재생함으로써 확장감을 증가시킬 수 있도록 하였다. 잔향기는 자연스러운 주파수 및 감쇠 특성을 갖도록 설계되었으며, 후방 60$^{\circ}$방향에서 재생되는 잔향의 상관 계수를 작게 함으로써 청취시 공간감을 느끼게 하였다. 설계된 음장 시스템은 무향실 데이터를 입력으로 시뮬레이션되었고, 그 결과로 얻어진 5개의 PCM 출력은 멀티 트랙 재생 장치에 의해 일반 리스닝 룸에서 재생된다.

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.283-286
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• 2004

Due to advances in electronics very high quality audio reproduction is today possible. But the listening environment causes deviation of the audio system from the expected behavior. Firstly the listening Room significantly changes the audio signal frequencies and their phase. Secondly the position of the user in the room affects the perceived sound. With existing DSP technology it is possible to adequately correct these effects. In our work we developed a room correction system, correcting up to 7.1 channels using dual Motorola 56367 fixed point DSP's, implementing position dependent room effects measurement, real time compensation filter design and equalization filtering procedures.

• 유체기계공업학회:학술대회논문집
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• 1998.12a
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• pp.105-114
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• 1998

Flow field and near-field noise of a centrifugal fan has been studied with an efrcient compressible method and STAR-CD. The flow field of the centrifugal fan is assumed two-dimensional. Most of the compressible studies has been done by inviscid solver because viscous simulation shows little difference. The near field noise is estimated in term s of sound pressure level in frequency domain transformed from the computed pressure fluctuations using FFT. The simulation has been done on various design elements such as impeller blade shapes, the number of blades and cut-off clearance. The comparison shows that the number of blades has a significant effect on near-field noise without losing aerodynamic performance.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2002.05a
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• pp.110-116
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• 2002

In this paper, various kinds of A-Frame are surveyed and classified according to their functional ability and sizes. Based on the study, a A-Frame that is suitable for ROV/AUV operation is designed. Basic theoretical structural requirements are applied and relevant Finite Element Analysis are carried out for the verification of the sound workability of the proposed A-Frame. Final configuration and the specification are proposed for the usage of ROV/AUV operation.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.11
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• pp.1988-1993
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• 2008

Photovoltaic (PV) modules operate over a large range of conditions but manufacturer's information is not sufficient to determine their overall performance. Designers need a reliable tool to predict energy production from a photovoltaic module under all conditions in order to make a sound decision. The modeling method of photovoltaic (PV) module are useful to perform detailed analysis of PV system performance for changing meteorological conditions, verify actual rated power of PV system sizing and determine the optimal design of PV system and components. This paper indicates a modeling approach of PV module performance in terms of meteorological conditions and identifies validity of PV modules modeling by comparing measured with simulated value.

• Journal of Korean Institute of Industrial Engineers
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• v.16 no.2
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• pp.11-21
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• 1990

With a general trend toward larger and more complex systems with centralized control, an operator's role of supervisory decision making in the control room becomes more important. Identification of potential man-machine interface (MMI) problems with CRT-based process control systems was attempted using a structured questionnaire survey. Based on the survey results, a laboratory experiment was carried out to investigate the performance of alarm detection on a process control CRT display. The user performance was measured in terms of reaction time from the onset of an alarm sound until the completion of predefined response procedures. The results revealed that for a highly complex tasks, mean reaction time ($\bar{RT}$) with a color consistent display was 10.5% faster than that with the original display, and $\bar{RT}$ with a grouped display was reduced by 8.2% in comparison with the color consistent display.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.486-491
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• 2002

Auditory experiments based on subjective responses were undertaken for the standard heavy and light weight impact noise. Relations between noise levels and subjective evaluations were also investigated. As a result, it was shown that the noise class was rated with the range of sensible satisfaction by investigating the various social responses for the floor impact noise. The rate classification for the heavy weight impact noise is suggested as a design guide for concrete slabs which satisfy the residents' requirements in various sound insulation capacities of multistory residential buildings.