• Tunnel and Underground Space
• /
• v.28 no.4
• /
• pp.293-303
• /
• 2018

Monitoring is the act of collecting and analyzing accurate engineering information using various methods and instruments. The purposes of the monitoring are design verification, construction management, quality control, safety management, and diagnose of structure etc.. The diagnose evaluation of the geotechnical structures corresponds to the confirmation of the structural performance. It is aimed to judge the soundness of geotechnical structures considering the degree of damage due to the environmental change and elapsed time. Recently, microseismicity, which is widely known in Korea, can be used for safety management and diagnoses of structure as it detects the micro-damage without disturbance of the structure. This report provides guideline on the procedure for assessing an underground oil storage cavern using microseismic monitoring techniques. Guidelines cover the selection of monitoring systems, sensor array, sensor installation and operation of systems, and interpretation.

• Annual Conference of KIPS
• /
• 2023.11a
• /
• pp.662-664
• /
• 2023

해양 식물플랑크톤의 성장은 유해적인 적조를 유발할 수 있으며, 이는 여러 국가의 생태계에 피해를 주는 상황이다. 적조를 모니터링하는 것은 식물플랑크톤 미생물의 증가를 예방하고 통제하기 위해 중요하다. 그러나 현재의 적조 모니터링 기술은 날씨, 시간 제약 및 실시간 모니터링에 대한 어려움으로 인해 측정 정확도에 영향을 미치는 한계가 있다. 본 연구는 특히 적조 발생을 감지하기 위한 목적으로 개발된 자동 실시간 모니터링 시스템의 성공적인 개발을 보여준다. 개발한 시스템은 음향 반사파 데이터 처리를 통해 합성곱 신경망(Convolutional neural networks, CNN)을 활용하여 식물플랑크톤 농도를 정확하게 구별할 수 있다. 특히, 이 CNN 모델은 음향 신호의 변환된 주파수 스펙트럼과 Cochlodinium polykrikoides (C. polykrikoides)의 농도 간의 상관 관계를 수립하는 데 뛰어난 효과를 나타냈다. 이 CNN 은 C. polykrikoides 를 감지하는 데 0.90 의 정확도를 보여준다. 이러한 모니터링과 CNN 분류의 활용은 실시간 측정의 중요한 잠재력을 보여주며, 추가적인 절차가 필요 없는 자동 모니터링 시스템을 구축할 수 있을 것으로 예상된다.

• Proceedings of the Korean Society of Computer Information Conference
• /
• 2018.07a
• /
• pp.67-68
• /
• 2018

본 논문에서는 다수의 음향방출 센서로부터 취득한 원 데이터를 관리하고 보일러 튜브에 대한 상태를 실시간으로 진단하고 모니터링을 할 수 있는 네트워크 기반의 보일러 튜브 모니터링 시스템을 제안한다. 본 시스템을 화력발전소 보일러 튜브에 설치한다면 보일러의 불시정지를 예방하는데 효과적일 것으로 기대된다.

• Journal of the Korean Society for Precision Engineering
• /
• v.22 no.4
• /
• pp.37-43
• /
• 2005

Real time monitoring of exit burr formation is critical in manufacturing automation. In this paper, acoustic emission (AE) was used to detect the burr formation during drilling. By using wavelet transform (WT), AE data were compressed without unnecessary details. Then the transformed data were used as selected features (inputs) of a back-propagation artificial neural net (ANN). In order to validate the in process AE monitoring system, both WT-based ANN and cutting condition (cutting speed, feed, drill diameter, etc.) based ANN outputs were compared with experimental data.

• Proceedings of the KWS Conference
• /
• 2009.11a
• /
• pp.109-109
• /
• 2009

최근 유럽의 완성차 업체에서 조립라인에 적용을 시작하고 있는 레이저 원격 용접기술은 저항 점용접에서의 문제점들을 동시에 해결하고 작업 시간을 획기적으로 감소시켜 생산성을 향상시킬 수 있는 용접공정으로 떠오르고 있다. 레이저 원격 용접기술은 레이저 빔을 용접부의 원거리에서 조사하여 용접하는 기술로서 레이저의 초점거리와 갈바노미터의 고속 이송를 이용한 최첨단 용접공정이다. 높은 생산성을 유지 하기 위하여 정확한 용접 컨트롤이 필요하지만, 레이저 용접의 경우 용접시 안전 문제로 육안으로 관찰하기가 힘들다. 이러한 문제를 해결하기 위하여 모니터링이 필수적이다. 기존의 레이저 모니터링으로는 음향 센서를 이용하여 음향을 측정하는 방법이나 UV 센서, IR 센서 등의 빛을 이용한 방법이 많이 사용되어왔다. 하지만 이 방법들은 간접적인 방법들로 노이즈에 민감하고 또 설치가 까다로운 단점이 있었다. 본 연구에서는 CCD 카메라를 이용하여 시스템의 복잡함을 줄이고 더 정확하고 빠르게 용접 현상을 관찰하기 위하여 동축 모니터링 시스템을 이용하였으며, 이를 통해 Keyhole을 관찰하고 센서를 이용한 용접 변수(레이저 출력, 용접 속도 등)의 변화에 따른 용접 현상을 규명하였다.

• The Journal of the Acoustical Society of Korea
• /
• v.26 no.1
• /
• pp.32-41
• /
• 2007

The control room has been usually designed by the consideration of only one listening position for the sound engineer. By this study. many listening positions with the very similar acoustical condition were located in the specific region, so-called 'the reflection free zone', where the several engineer could evaluate the quality of sound at the same time. For constructing the reflection free zone, the control room has been designed by the concept of the $LEDE^{TM}$, and the initial time delay gap has been controled by the structure of control room and the properties of sound-absorbing materials. diffuser, Helmholtz resonator and image source of sound. The occurrence of any harmful phenomena like the standing wave, acoustic focusing. coloring. Hass effect and flutter echo, has greatly reduced in the reflection free zone.

• Korean Journal of Environment and Ecology
• /
• v.38 no.4
• /
• pp.405-415
• /
• 2024

The bioacoustics generated in urban parks contribute to the overall sound diversity of a city, creating a harmonious acoustic environment and maintaining the balance of the soundscape. However, due to the rapid urbanization process, the acoustic environment in urban parks is continuously deteriorating due to increased noise. In this study, we present an approach to monitoring the acoustic environment of urban parks by analyzing the soundscape of Namsan Urban Natural Park in Seoul. Acoustic data were collected continuously for one month from August 2021 in four facility districts of the study site using autonomous recording units, and a total of 2,784 hours of sound material were obtained. We also compared soundscape characteristics over time in each district using acoustic indices (ACI, ADI, BI, NDSI) representing soundscape complexity, acoustic diversity, degree of bioacoustics, and anthropogenic disturbance. The results showed that acoustic indices related to bioacoustics varied between districts, but most indices showed similar variation patterns due to the influence of anthropogenic sounds. In particular, regional differences closed during periods of high bird activity but not during periods of high human activity. We suggest that considering both acoustic characteristics and multiple acoustic indices is necessary for managing the soundscape of urban parks. The results of this study are expected to provide essential data for assessing the health of urban ecosystems based on soundscapes and to be used for monitoring the acoustic environment of urban parks.

• Annual Conference of KIPS
• /
• 2023.11a
• /
• pp.665-666
• /
• 2023

미세 물질을 포함하고 있는 광산 폐기물의 디워터링 과정(dewatering process)은 작은 입자들의 침전속도가 낮기 때문에 시간이 오래 걸리고 어려운 과정이다. 따라서 광산 폐기물이 안정적으로 침전되었는지 확인하기 위해서 디워터링 과정을 연속적으로 모니터링하는 기술이 필요하다. 이 연구에서는 kaolinite, illite, bentonite 3 종류의 점토를 3 가지 농도(0.1g/L, 1g/L, 5g/L)로 나눠서 초음파 음향 감지를 이용해 후방산란 신호를 측정했다. 그리고 측정된 신호를 활용하여 합성곱 신경망(CNN) 모델을 개발하여 점토의 분류 모델을 만드는 연구를 수행했다. 본 연구에서 보여준 CNN 의 높은 정확도는 광산 폐기물의 디워터링 과정에서 미세 광물과 미세 농도 분류 모니터링에 적합한 저렴하고 측정하기 쉬운 음향 감지의 사용 가능성을 입증했다.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.38 no.8
• /
• pp.863-867
• /
• 2014

In this study, an acoustic emission (AE) sensor was used for measuring the abrasive and molecular-scale phenomena in chemical mechanical polishing (CMP). An AE sensor is a transducer that converts a mechanical wave into an electrical signal, and is capable of acquiring high-level frequencies from materials. Therefore, an AE sensor was installed in the CMP equipment and the signals were measured simultaneously during the polishing process. In this study, an AE monitoring system was developed for investigating the sensitivity of the AE signal to (a) the variations in the material properties of the pad, slurry, and wafer and (b) the change in conditions during the CMP process. This system was adapted to Oxide and Cu CMP processes. AE signal parameters including AE raw frequency, FFT, and amplitude were analyzed for understanding the abrasive and molecular-level phenomena in the CMP process. Finally, we verified that AE sensors with different bandwidths could function in complementary ways during CMP process monitoring.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.22 no.4
• /
• pp.121-125
• /
• 2018

This paper presents the assessment of 7-wire strand monitoring using acoustic emission technique for bridges. 7-wire strand is widely used construction materials to provide additional tensile force to bridges. PSC (PreStressed Concrete) bridge and cable-stayed bridge are representatives for such cases. However, as the bridge aging progresses recently, corrosion problems of strand are emerging. For this reason, various NDT (Non-Destructive Test) methods for cable inspection are being studied and applied to the field. One of the NDT methods, acoustic emission technique, is known as an effective technique to detect cable damage and breakage. In this study, to evaluate the applicability of acoustic emission technique to bridges, acoustic emission signals according to damage of the strand were acquired and analyzed by tensile test. Moreover, The optimal AE sensor type was selected for field application. As a result, it is considered that the acoustic emission technique will be able to detect corrosion breakage and signs of rupture.