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Electromagnetic Field Interference on Transmission Lines due to On-Board Antenna
Lee, Heekwon,Ryu, Soojung,Lee, Seungbae,Kim, SoYoung,Nah, Wansoo Hindawi Limited 2015 International journal of antennas and propagation Vol.2015 No.-
<P>As the available space in the board of a mobile device becomes smaller and more compact, circuit elements and transmission lines are arranged in very close proximity, especially from the antennas which are usually installed on the same board. Due to the various on-board antennas which are designed in small space, the transmission lines on the board are electromagnetically interfered, resulting in the performance degradation of the circuit. So the engineers and circuit designers should find the least interfered place for the transmission lines and components to minimize the electromagnetic interferences. This paper discusses and presents a methodology to find the least sensitive position in the induced current distribution as well as in the noise power delivered from the antenna. For this purpose some vertical, horizontal, and bent transmission lines with antenna on the same board are designed and fabricated with and without common ground, and the transferred powers to the transmission lines were measured and were also simulated using a full-wave simulator. The results predicted by the EM simulation model were successfully confirmed through the measurement of<I>S</I>-parameters in the experimental setup, which shows the validness of the suggested analysis method.</P>
A study on the ergonomic aspects of the proper luminance level of displays
Lee, Eunjung,Kim, Sangho,Park, HyeRyoung,Bae, Jaewoo,Lee, Seungbae,Kim, Haksun The Korean Infomation Display Society 2012 Journal of information display Vol.13 No.4
In this paper, a display's emotional image quality can be primarily determined by designing the proper luminance level. Though displays with high luminance are preferred, too much light emission from a display may cause glare or visual fatigue to viewers. To find out the proper luminance level based on various video contents, this study was conducted with an OLED display with a real-black level and a wide color gamut, and with an LCD display with a high luminance level, to set the glare threshold under various conditions. The optimum luminance levels according to the display's loading ratio were found, and the maximum luminance that did not cause a glare in the test is proposed.
Cavitation Mode Analysis of Pump Inducer
Lee, Seungbae,Jung, Keun-Hwa,Kim, Jin-Hwa,Kang, Shin-Hyoung The Korean Society of Mechanical Engineers 2002 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.16 No.11
The onset of cavitation causes head and efficiency of a main pump to be reduced significantly and generates vibration and noise. In order to avoid these phenomena, the inlet of the pump is fitted with a special rotor called an inducer, which can operate satisfactorily with extensive cavitation. The motivation of this study is to find out cavitation modes from the inducer inlet pressure signals and event characteristics from outlet ones at various operating conditions. The cavitation modes are analyzed by using a cross-spectral density of fluctuating pressures at the inducer inlet. The time-frequency characteristics of wall pressures downstream of the inducer are presented in terms of event frequency, its duration time, and number of events by using the Choi-Williams distribution.
Computation of Turbulent Flows and Radiated Sound From Axial Compressor Cascade
Seungbae Lee,Hooi-Joong Kim,Jin-Hwa Kim,Seung Jin Song 대한기계학회 2004 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.18 No.2
The losses at off-design points from a compressor cascade occur due to the deviation from a design incidence angle at the inlet of the cascade. The self-noise from the blade cascade at off-design points comes from a separated boundary layer and vortex sheddings. If the incidence angle to the cascade increases, stalling in blades may occur and the noise level increases significantly. This study applied Large-Eddy Simulations (LES) using deductive and deductive dynamic SGS models to low Mach-number, turbulent flow with each incidence angle to the cascade ranging from -40° to +20°, and compared numerical predictions with measured data. It was observed that the oscillating separation bubbles attached to the suction surface do not modify wake flows dynamically for cases of negative incidence angles. However, an incidence angle greater than 8° caused a separated vortex near the leading edge to be shed downstream and created stalling. The computed performance parameters such as drag coefficient and total pressure loss coefficient showed good agreement with experimental results. Noise from the cascade of the compressor is summarized as sound generated by a structure interacting with unsteady, turbulent flows. The hybrid method using acoustic analogy was observed to closely predict the measured overall sound powers and directivity patterns at design and off-design points of blade cascade.<br/>
Computation of Turbulent Flows and Radiated Sound From Axial Compressor Cascade
Lee, Seungbae,Kim, Hooi-Joong,Kim, Jin-Hwa,Song, Seung-Jin The Korean Society of Mechanical Engineers 2004 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.18 No.2
The losses at off-design points from a compressor cascade occur due to the deviation from a design incidence angle at the inlet of the cascade. The self-noise from the blade cascade at off-design points comes from a separated boundary layer and vortex sheddings. If the incidence angle to the cascade increases, stalling in blades may occur and the noise level increases significantly. This study applied Large-Eddy Simulations (LES) using deductive and deductive dynamic SGS models to low Mach-number, turbulent flow with each incidence angle to the cascade ranging from -40$^{\circ}$ to +20$^{\circ}$ and compared numerical predictions with measured data. It was observed that the oscillating separation bubbles attached to the suction surface do not modify wake flows dynamically for cases of negative incidence angles. However, an incidence angle greater than 8$^{\circ}$ caused a separated vortex near the leading edge to be shed downstream and created stalling. The computed performance parameters such as drag coefficient and total pressure loss coefficient showed good agreement with experimental results. Noise from the cascade of the compressor is summarized as sound generated by a structure interacting with unsteady, turbulent flows. The hybrid method using acoustic analogy was observed to closely predict the measured overall sound powers and directivity patterns at design and off-design points of blade cascade.
Cavitation Mode Analysis of Pump Inducer
Seungbae Lee,Keun-Hwa Jung,Jin-Hwa Kim,Shin-Hyoung Kang 대한기계학회 2002 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.16 No.11
The onset of cavitation causes head and efficiency of a main pump to be reduced significantly and generates vibration and noise. In order to avoid these phenomena, the inlet of the pump is fitted with a special rotor called an inducer, which can operate satisfactorily with extensive cavitation. The motivation of this study is to find out cavitation modes from the inducer inlet pressure signals and event characteristics from outlet ones at various operating conditions. The cavitation modes are analyzed by using a cross-spectral density of fluctuating pressures at the inducer inlet. The time-frequency characteristics of wall pressures downstream of the inducer are presented in terms of event frequency, its duration time, and number of events by using the Choi-Williams distribution.<br/>
송풍기ㆍ압축기의 소음레벨 측정방법 KS B 6361의 개정
이승배(Seungbae Lee),김경호(Kyoung-Ho Kim) 한국유체기계학회 1999 유체기계 연구개발 발표회 논문집 Vol.- No.-
The revision was proposed for methods A-weighted sound pressure measurement for fans, blowers and compressors in order to apply newly developed measurement techniques to KS B 6361 established in 1987. This proposal includes modification of terminologies, revision of sound power methods for radiated sound from the body, inclusion of In-duct measurement method, and correction method for flow noise upon microphon.
이승배(Seungbae Lee),김회룡(H.-R. Kim),김광용(Kwang-Yong Kim),정근화(Keun-Hwa Jung) 한국유체기계학회 2000 유체기계 연구개발 발표회 논문집 Vol.- No.-
The revision was proposed for forward curved bladed fans in order to make the KS B 6326 established in 1987 in agreements with newly revised KS standards. This proposal includes modification of Application range, numbering system, classification based on performance, and allowing dimensions for specified sizes.