• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.216-224
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• 2014

층간소음의 대부분의 원인이 아이들 뛰거나 발걸음으로 나타나고 있어 층간소음 저감을 위한 선행 연구로 층간소음의 주요 충격원인 보행 행위에 대한 정밀한 연구가 필요하다. 성인 보행 충격력과 그에 따른 바닥충격음을 계측하여 보행하중이 바닥충격음에 영향을 주는 요소를 분석하였다. 보행하중 중 발 뒤꿈치 충격력은 전체 충격하중을 주파수 특성을 대변할 수 있는 임펄스 형태의 하중으로 충격력은 뱅머신 또는 고무공보다 낮지만 1 차 영점(First zero)이 80Hz 정도로 높아 유효 가진 주파수 대역이 표준 중량충격원 보다 높았다. 구조물과 수음실의 고유모드 특성으로 인해 외부 충격에 대한 구조체 진동 및 음압의 공진 현상이 발생되기 때문에 공진 성분이 포함되는 바닥충격음 레벨은 순수 충격력 특성인 보행 또는 표준 중량충격원의 옥타브 밴드 충격력 폭로레벨과는 전혀 다른 주파수 특성을 나타내었다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.8
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• pp.853-860
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• 2012

In this paper, We shed light on radio spectrum policy and strategic planning of the United States of America and draw some conclusions. First of all, as the radio technology evolves with time, paradigm shift from command & control to market-based approach and spectrum commons is reviewed. Strategic spectrum planning of USA is also analyzed and some suggestions are drawn. In particular, USA plan for developing dynamic spectrum access(DSA) technologies and implementation of the test-bed for the DSA spectrum sharing is discussed, which improves the spectral utilization. Finally We deal with spectrum re-farming issue for mobile broadband and implicative points based on the National Broadband Plan.

• 정보화사회
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• s.151
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• pp.62-67
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• 2001

정부는 오는 2005년까지 현재 40GHz대역까지 실용화된 전파자원을 80GHz대역까지 개발해 초고속 구내무선통신, 차량 충돌방지서비스 등 신규 광대역 서비스에 활용토록 할 계획이다.또 민.관 합동으로 450억원을 투자, 무궁화위성에 탑재할 중계기.안테나 등 통신방송 위성 탑재체를 산.학.연 공동으로 독자 개발키로 했다.정보통신부는 지난 7월11일 귀중한 국가자원인 주파수를 효율적으로 관리하고 관련 산업을 육성하기 위해 이 길은 내용의 전파산업진흥 기본계획을 확정, 발표했다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1993.04a
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• pp.115-122
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• 1993

본 연구의 목적은 다공관 소음기의 설계변수인 공동과 다공관의 치수 및 구 멍배열의 변화에 따른 휘파람소리의 발생특성을 실험에 의하여 체계적으로 구하는데 있다. 소음기의 각 설계변수마다 유속변화에 따른 휘파람소리가 발 생하는가를 확인하고 발생하게 되면 스펙트럼 분석을 통하여 휘파람 소리의 주파수특성을 구한다.

• Electric Engineers Magazine
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• v.252 no.8
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• pp.27-29
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• 2003

최근 송전선로 및 변전소 인근 주민들이 전자계 때문에 각종 질병에 시달리고 있다고 주장하고 있고 환경단체에서도 전력설비에서 발생하는 전자계가 임신장해나 백혈병, 뇌종양 등 癌유발에 영향을 미친다는 주장에 따라 사회적으로 이에 대한 염려가 미친다는 주장에 따라 사회적으로 이에 대한 염려가 커지고 있는 상황에서 송전, 환경팀에서는 전기의 생산, 공급, 사용할 때 발생되는 주파수 60Hz에서의 전자계 영향을 객관적으로 파악하기 위하여 한국전기연구원 및 화학연구소와 공동으로 송전선로의 전자계 영향연구를 수행하였다.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10b
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• pp.1279-1284
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• 2000

This study introduces a simulation model of radar responses with frequencies on subsurface voids in concrete. In this model, the resolution and the attenuation according to radar frequencies in each interface which has different electromagnetic property are analyzed. This model aims to select the best frequency of radar which can analyze the thickness of voids in concrete from radar response. It also can be applied to estimate the limitation of propagation depth of radar on subsurface voids in concrete. The computed results show the radar images based on radar signal processing using convolution technique.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.6
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• pp.477-483
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• 2015

Investigations into cavity flows have been conducted for noise and vibration problems that arise in cavity systems. Cavity systems have been applied in engineering devices and have undergone rapid development in the aerospace industry. Meanwhile, to the author's best knowledge, the cavity on a curved wall has been seldom studied. The present work is conducted to study the flow physics of a cavity mounted on a curved wall. Numerical analysis is performed to investigate the cavity flow. Two variables of sub- and supersonic cavity flows were considered: the radius of curvature of the curved wall (L/R) and the inlet Mach number. The results show that the uniform vortex generated by the cavity flow on the curved wall stabilize the pressure fluctuation as time passes. As the inlet Mach number increases, the pressure fluctuation amplitude increases. The results obtained from the curved wall are compared with those from a straight wall using Rossiter's formula. The Strouhal number of the curved wall is lower than that of the straight wall. Lower Strouhal numbers have been obtained in the present computational fluid dynamics (CFD) results than in the theoretical results using Rossiter's formula.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.5 s.120
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• pp.496-502
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• 2007

In this paper, a slotted waveguide feeder for the electric field uniformity in multi-mode cavity is designed and fabricated. In case of the conventional feeder, a mode stirrer or a turntable is used for improving electric field uniformity in the multi-mode cavity. The proposed feeder has four slots, which have uniform radiation characteristic, on broad wall and shorted terminations at both ends. The electric field uniformity is simulated by CST's MWS(Microwave Studio) for the conventional and proposed feeders, respectively. The fabricated feeder shows the return loss of less than -20 dB at 2.45 GHz. To verify the validity of our proposal, the temperature distribution of the water samples in the multi- mode cavity is observed after a few minutes' heating. The proposed feeder is confirmed to have much better field uniformity in the multi-mode cavity than the conventional feeder.

• Geophysics and Geophysical Exploration
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• v.3 no.1
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• pp.19-24
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• 2000

Seismic reflection data was obtained by using 28 and 100 Hz geophones at the ground subsidence sites in an old coal mine area. Frequency spectrum of the geophone analyzed with offset revealed that 1) In the near offset ($1\~10m$), the signals in the 100 Hz geophone data contains higher frequency components (up to 300 Hz) than that of the 28 Hz (<200 Hz), 2) In the intermediate offset ($11\~39m$), although the 28 Hz geophone data showed very similar frequency characteristics as the near offset data, the 100Hz geophone data seemed to be contaminated by noise at high frequency zone (>200 Hz). In the far offset ($\geq40\;m$), the signals in both the 28 and 100 Hz geophone data are attenuated to noise level at high frequency Bone more than 150 Hz.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.9
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• pp.944-950
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• 2013

This paper is a study of a rain sensor using an open-ended coaxial cavity resonator which senses the amount of rain drops linearly. It shows that it will be used as a sensor to sense the amount of rain dropped on the windshield of an automobile based on the principle of varied resonant frequency and the loss according to the amount and characteristics of an dielectric lied on the open side of a resonator. The input and output ports are built in the both sides of the resonator and the input and output coupling probes are formed like 'ㄱ' shape. The response of rain drops were simulated by the radius of inner conductor of 2 mm, 5 mm, and 10 mm respectively and it showed that the raindrop was sensed most linearly and sensitively when the radius of inner conductor is 5 mm, We have measured that the resonant frequency have varied from 3.55 GHz to 3 GHz and the Q value have varied from 42.38 to 24.3 according to the variation of rain drop amount on the fabricated resonator. Therefore, it shows that the designed resonator can be applied as a rain sensor that measures the amount of rain drops linearly by using the resonant frequency as a measurement parameter.