• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.755-758
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• 2002

The physical phenomena of rectangular open cavity are numerically investigated in this paper Two-dimensional cavity problems with laminar boundary layers in upstream are simulated by using the compressible Wavier-Stokes equations. The high-order and high-resolution numerical schemes are used for the evaluation of spatial derivatives and the time integration. Cross-correlation is used to analyze the characteristics of wave propagation along time and spatial. Sudden phase shifting of 90 degrees is appeared near downstream edge, and this is coincident with the phase lag suggested in original Rossiter's equation. The results give a further understanding of the physical phenomenon of noise generation, and the resonance of flow and acoustic in cavity. Moreover, modified Rossiter's equation, which is more accurate and can be applied in various conditions, is suggested. The distance from the point of vortex generation to the point of vortex collapsing acts as effective distance of cavity resonance, and the phase difference between the point of vortex collapsing and the point of acoustic source acts as phase lag. The mechanism of acoustic generation is fully understood in this paper. The mechanism of acoustic generation is fully understood in this paper.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 춘계학술대회논문집
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• pp.985-990
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• 2004

Leak noise is a good source to identify the exact location of a leak point of underground water pipelines. Water leak generates broadband noise from a leak location and can be propagated to both directions of water pipes. This sound propagation due to leak in water pipelines is not a non-dispersive wave any more because of the surrounding pipes and soil. However, the necessity of long-range detection of this leak location makes to identify low-frequency acoustic waves rather than high frequency ones. Acoustic wave propagation coupled with surrounding boundaries including cast iron pipes is theoretically analyzed and the wave velocity was confirmed with experiment. The leak locations were identified both by the acoustic emission (AE) method and the cross-correlation method. In a short-range distance, both the AE method and cross-correlation method are effective to detect leak position. However, the detection for a long-range distance required a lower frequency range accelerometers only because higher frequency waves were attenuated very quickly with the increase of propagation paths. Two algorithms for the cross-correlation function were suggested, and a long-range detection has been achieved at real underground water pipelines longer than 300m.

• Journal of the Optical Society of Korea
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• 제18권5호
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• pp.605-610
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• 2014

Clouds play an important role in climate change, in the prediction of local weather, and also in aviation safety when instrument assisted flying is unavailable. Presently, various ground-based instruments used for the measurements of the cloud base height or velocity. Lidar techniques are powerful and have many applications in climate studies, including the clouds' temperature measurement, the aerosol particle properties, etc. Otherwise, it is very circumscribed in cloud velocity measurements because there is no Doppler effect if the clouds move in the perpendicular direction to the laser beam path of Doppler lidar. In this paper, we present a method for the measurement of cloud velocity using lidar's range detection and DIC (Digital Image Correlation) system to overcome the disadvantage of Doppler lidar. The lidar system acquires the distance to the cloud, and the cloud images are tracked using the developed fast correlation algorithm of DIC. We acquired the velocities of clouds using the calculated distance and DIC algorithm. The measurement values had a linear distribution.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.798-803
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• 2004

Leak noise is a good source to identify the exact location of a leak point of underground water pipelines. Water leak generates broadband sound from a leak location and this sound propagation due to leak in water pipelines is not a non-dispersive wave any more because of the surrounding pipes and soil. However, the necessity of long-range detection of this leak location makes to identify low-frequency acoustic waves rather than high frequency ones. Acoustic wave propagation coupled with surrounding boundaries including cast iron pipes is theoretically analyzed and the wave velocity was confirmed with experiment. The leak locations were identified both by the acoustic emission (AE) method and the cross-correlation method. In a short-range distance, both the AE method and cross-correlation method are effective to detect leak position. However, the detection for a long-range distance required a lower frequency range accelerometers only because higher frequency waves were attenuated very quickly with the increase of propagation paths. Two algorithms for the cross-correlation function were suggested, and a long-range detection has been achieved at real underground water pipelines longer than 300m.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 추계학술대회논문집
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• pp.327-332
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• 2004

Leak noise is a good source to identify the exact location of a leak point of underground water pipelines. Water leak generates broadband noise from a leak location and can be propagated to both directions of water pipes. This sound propagation due to leak in water pipelines is not a non-dispersive wave any more because of the surrounding pipes and soil. However, the necessity of long-range detection of this leak location makes to identify low-frequency acoustic waves rather than high frequency ones. Acoustic wave propagation coupled with surrounding boundaries including cast iron pipes is theoretically analyzed and the wave velocity was confirmed with experiment. The leak locations were identified both by the acoustic emission (AE) method and the cross-correlation method. In a short-range distance, both the AE method and cross-correlation method are effective to detect leak position. However, the detection for a long-range distance required a lower frequency range accelerometers only because higher frequency waves were attenuated very quickly with the increase of propagation paths. Two algorithms for the cross-correlation function were suggested, and a long-range detection has been achieved at real underground water pipelines longer than loom.

• 한국음향학회지
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• 제29권3호
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• pp.165-172
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• 2010

실제 해양환경에서 수직 배열 트랜스듀서들의 위상 변동 특성과 각 트랜스듀서간의 상관관계를 구하는 것은 수중에서의 통신 기법을 결정하는데 중요하다. 본 논문은 동해시 인근 천해 해역에서 시간에 따라 이동하는 탐침 음원에서 전송하여 수직 배열 트랜스듀서들에 수신된 탐침 신호들을 기반으로 수심에 따라 달라지는 수신 신호의 위상 특성을 분석하였다. 그리고 트랜스듀서간의 거리와 송수신기간의 거리를 바꿔가면서 각 트랜스듀서간의 상관관계를 분석하였고 상관관계 변화에 따르는 이론적인 통신 전송 용량 변화를 구하였다.

• 가족자원경영과 정책
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• 제15권3호
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• pp.83-97
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• 2011

The purpose of this study was to investigate stereotypes, affect and social distance toward people from Southeast Asia among visiting supervisors for multicultural families and to explore the factors that influence social distance. The subjects were 243 visiting supervisors for multicultural families. The data were analyzed with SPSS for Windows 15.0 through means, standard deviations, Cronbach's a, Scheff$\acute{e}$ tests, Pearson's correlation, and stepwise regression. It was found that stereotypes and affect among visiting supervisors toward people from Southeast Asia were somewhat positive, at a little higher than midpoint. Social distance, on the other hand, was found to be a little lower than midpoint. To discover the factors that influenced social distance, a stepwise regression was executed. Stereotype was the factor with the highest magnitude of effect and affect was the second- strongest factor in explaining the social distance found among visiting supervisors. Age was the third significant factor in explaining social distance. These variables accounted for 35.7% of variance in the social distance data.

• 화약ㆍ발파
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• 제39권4호
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• pp.1-11
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• 2021

본 연구에서는 기계식 해체공법을 적용한 슬래브 해체 시 발생하는 진동을 분석하기 위해 진동 자료를 획득하였다. 획득한 진동 자료는 부착장치에 따라 구별하여 파형 및 우세주파수 분석을 수행하였고, 작업위치와 계측위치 사이의 거리를 측정하는 방법을 달리하여 상관관계를 분석하였다. 부착 장치 별 파형분석 결과 장비 작업에 의한 진동 파형의 위상 변화는 거의 없고 진동속도의 크기인 진폭의 변화만 일어났으며, 주파수 분석 결과 압쇄기를 사용한 경우 브레이커를 사용한 경우에 비해 주파수 대역이 낮으며, 해체 대상 건축물의 고유 진동수와 주파수 대역이 근접하였다. 상관관계 분석결과 작업 위치와 계측위치의 이격거리는 상호 간의 직선거리가 아닌 실제 건축물을 따라 진동이 전파하는 경로로 평가해야 높은 상관성을 보임을 확인하였다.

• 한국콘텐츠학회논문지
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• 제18권1호
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• pp.476-486
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• 2018

본 연구에서는 임상에서 재활을 담당하는 물리치료사가 장애인에 대해 갖고 있는 사회적 거리감을 알아보고자 실시하였다. 연구대상자는 경기지역 8곳을 선정하여 146명을 대상으로 하였으며, 성별, 연령, 종교, 근무연수, 주변인 장애유무, 주변인 장애 유형 별로 장애인에 대한 사회적 거리감을 알아보았다. 연구결과는 다음과 같다. 첫째, 장애인에 대한 사회적 거리감 지각 정도는 사회적 거리감(5점만점 평균 3.47점)과 하위요인인 신체적 거리감(5점만점 평균 3.77점), 대인적 거리감(5점만점 평균 3.17점)으로 지각하는 것으로 나타났다. 둘째, 연령이 높을수록(p<.05), 근무연수가 많을수록(p<.05), 남성에게서 사회적 거리감이 더 가깝게 느끼는 것으로 나타났으며(p<.05), 성별에 있어서 남성이 대인적 거리감에서 가깝게 느끼는 것으로 나타났다(p<.05). 셋째, 접촉요인에서 장애인 친구 유무에 따른 신체적 거리감과 사회적 거리감에서 통계적으로 유의한 차이를 나타났다(p<.05). 마지막으로, 치료사의 장애인에 대한 사회적 거리감 간의 상관관계에서 연령은 정적, 성별은 부적으로 유의미한 상관이 나타났으며, 근무연수와 연령의 정적 상관, 성별과 종교와는 부적 상관이 나타났다. 이러한 결과를 볼 때, 장애인과의 접촉 경험의 질과 기회에 따라 장애인에 대한 긍정적인 인식이 형성된다. 이를 통해 치료사를 대상으로 임상 초기부터 장애인 인식의 개선과 장애인과의 직접적인 경험을 통해 긍정적인 장애인에 대한 태도 및 행동의 변화를 유도할 교육을 실시할 필요가 있을 것이다.

• Communications for Statistical Applications and Methods
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• 제10권3호
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• pp.695-705
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• 2003

In this article, we propose a regression and correlation analysis via dynamic graphs and implement them in Java Web Start. For the polynomial relations between dependent and independent variables, dynamic graphics are implemented for both polynomial regression and spline estimates for an instant model selection. The results include basic statistics. They are available both as a web-based service and an application.