• Ocean and Polar Research
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• 제31권4호
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• pp.389-399
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• 2009

Subsurface pressure gauge has many advantages in measuring a wide range of wave spectra in coastal waters from wind waves to long waves. However, a shortcoming of the gauge is related to the difficulties in recovering surface wave spectra from subsurface pressure records. In this study, the effect of current on the pressure transfer function of the pressure gauge, and hence on the surface wave energy spectrum, was investigated by analyzing the subsurface pressure data based on the linear wave theory. For this purpose, laboratory experiments were carried out in a wave-current flume. Subsurface pressure records, as well as the surface elevation data, were obtained simultaneously under different wave and current conditions. Pressure transfer functions were obtained and compared with those estimated from the linear wave theory, both with and without inclusion of the current-effect. It was established that wave spectra obtained from subsurface pressure gauge were in closer agreement with those from surface wave gauge when current-effect on the pressure transfer function was taken into consideration for analysis.

• Restorative Dentistry and Endodontics
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• 제46권1호
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• pp.14.1-14.7
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• 2021

Objectives: The aim of this study was to evaluate the apical pressure generated by 2 endodontic irrigation needles and the GentleWave system in mandibular molars. Materials and Methods: The mesial and distal root canals of 12 mandibular molars were irrigated with a 30-gauge close-end needle or with a 30-gauge open-end needle. Procedures were performed in the mesial and distal canals. The GentleWave procedure and irrigation at 1 mm from the apex in the distal roots using an open-end needle were used, respectively, as negative and positive controls. The apical pressure was measured using a data acquisition pressure setup. Apical pressure exerted by the different needles in the 2 different canal types was statistically compared using 2-way analysis of variance. Results: Significant differences were found in the apical pressure for both needles and the canal type. The lowest values were obtained with close-end needles and in mesial canals. Negative apical pressure values were obtained using GentleWave. Conclusions: The needle and the canal type influenced the apical pressure. The GentleWave procedure produced negative apical pressure.

• 설비공학논문집
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• 제9권4호
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• pp.561-571
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• 1997

In this paper, the fundamental equations are developed for the pulsatile laminar flow generated by changing the oscillatory flow with $0{\leq}f{\leq}48Hz$ into a steady one with $0{\leq}Re{\leq}2500$ in a rigid circular pipe. Analytical solutions for the wave propagation factor k, the axial distributions of cross-sectional mean velocity $u_m$ and pressure p are schematically derived and confirmed experimentally. The axial distributions of centerline velocity and pressure were measured by using Pitot-static tubes and strain gauge type pressure transducers, respectively. The cross-sectional mean velocity was calculated from the centerline velocity by applying the parabolic distribution of the laminar flow and it was confirmed by using the ultrasonic flowmeter. It was found that the axial distributions of cross-sectional mean velocity and pressure agree well with theoretical ones and depend only on the Reynolds number Re and angular velocity $\omega$.

• 한국해안·해양공학회논문집
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• 제25권6호
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• pp.422-432
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• 2013

해수면과 해저파압을 연계하는 모수 모형을 개발하기 위한 시스템 식별법을 제시하였다. 비선형 고정변수를 포함한 선형 시불변 모형 구조를 가정하고 추가적인 입력자료를 갖는 자기회귀모형 (ARX)을 이용하여 해저파압 시계열자료로부터 해수면 시계열자료를 또는 해수면 시계열자료로부터 해저파압 시계열자료를 추출하는 방법을 제시하였다. 임의로 선정된 해수면과 해저 파압 자료를 이용하여 모형을 검증하였으며, 유사한 해저수심의 파압자료와 다른 해상 기상조건으로 생성된 해수면 스펙트럼 자료를 통해 재검증하였다. 시스템 식별법을 이용한 방법이 전통적인 선형파 이론을 이용한 선형전송함수(LTF) 방법보다 전반적으로 더 정확하게 수행됨을 확인하였다. 또한 본 논문에서 제시된 방법으로 추정된 해저 파압 시계열모의는 수정 선형전송함수(corrected LTF)에 의한 결과와 유사함을 확인하였다.

• 한국해안·해양공학회논문집
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• 제34권4호
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• pp.119-127
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• 2022

본 연구에서는 테트라포드로 피복된 경사식 마운드 위의 직립벽에 작용하는 충격쇄파압을 쇄파 형태에 따라 구분하기 위해 규칙파를 생성하고 충돌 직전의 유속장과 기포분율을 측정하였다. 유속장 측정을 위해 쇄파 중 발생하는 기포의 움직임을 추적하는 기포영상유속계를 사용하고 기포분율 측정을 위해 복합파고계 기법(Na and Son, 2021)을 활용하였다. 측정된 입사파의 주기가 짧을수록 최대평균유속은 사면에서 파속에 비해 적은 감소율을 보였지만 파랑이 사면을 따라 진행하며 쇄파가 더 빨리 발생하여 기포분율이 증가하였고 결과적으로 중복파압형태의 파압이 작용하였다. 주기가 큰 실험파의 경우 충돌 전 유입되는 공기가 적어 flip-through 형태(Cooker and Peregrine, 1991)의 흐름양상을 보였고, 파압이 급격하게 증가함을 확인할 수 있었다.

• 센서학회지
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• 제20권5호
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• pp.322-328
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• 2011

There are many ways to detect the heart rate non-invasively such as ECG, PPG, strain gauge, and pressure sensor. In this paper, the pulse wave measurement system using bipolar biased head on mode of the Hall sensor is proposed for measuring the radial artery pulse. TMS320F2812 was used to implement the proposed system and a portable wireless network(zig-bee) was used to show the experimental result. It was confirmed from experiment that the performance of the implemented system was more stable and faster than PPG sensor or piezoelectric film pressure sensor.

• 한국산학기술학회논문지
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• 제19권1호
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• pp.654-659
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• 2018

본 연구에서는 연안 환경에 대한 대표적인 지상 원격 관측 기기인 Ocean Radar를 이용하여 장기파랑관측을 수행하였다. 지상에 설치한 기기로부터 이루어지는 원격 관측은 소수의 현장 기기 개수로는 관측할 수 없는 넓은 범위의 해역을 통시에 관측할 수 있고 또한 높은 빈도의 지속적인 관측이 가능한 장점이 있다. 장기관측을 위한 Ocean Radar는 과거 지진해일에 의한 피해가 발생하고, 원자력 발전소가 위치한 한국 동해안의 삼척지역에 대해 장기관측을 수행하였으며, 원격관측의 적용성을 검토하기 위해 수압식 파고계를 설치하여 각각의 조사자료를 비교하였다. 원격파랑관측은 연구대상해역 전면에 독일 Helzel사에서 개발된 Array type의 HF-RADAR인 WERA (WavE RAdar)를 2개소에 설치하여 자료를 취득하였으며, 장기간 연속된 관측된 자료의 취득률을 분석해본 결과, Ocean Radar 가 설치된 두 Site의 중심에서 약 24km이며, 약 27km의 범위 내에서는 Wave 자료가 90% 이상 취득되었으며, 시계열로 분석한 결과, 결측된 시간이 전체 계측기간의 1% 미만이다. 직접관측방식인 수압식 파고계와 관측자료를 비교한 결과, RMS 편차는 20cm 이내이며, 상관계수가 0.84 ~ 0.87로 높은 상관관계를 가지는 것으로 분석되었다. 따라서, 금회적용한 Ocean Radar는 기존의 파랑 계측 장비를 대체하여 장기간 면적 파랑관측이 가능할 것으로 생각된다.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2006년도 Proceedings of ISRS 2006 PORSEC Volume I
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• pp.52-55
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• 2006

It's used to be said that tsunami is a rare event. The recurrence time of tsunami in Sumatra area is approximately 230 years as CalTech Research Group‘s study from paleocoral. However, the tsunami occurred in Indian Ocean on 26 December 2004, 28 March 2005 and 17 July 2006, because the earthquakes still release the energy. To cope with the tsunami disaster, we have to put the much effort on better disaster preparedness. The Tsunami Reduction Of Impacts through three Key Actions (TROIKA) was suggested by Eddie N. Bernard, the director of NOAA/PMEL (Pacific Marine Environmental Laboratory). They are Hazard Assessment, Mitigation and Warning Guidance. The satellite remote sensing has potential on these actions. The medium and high resolution satellite data were used to assess the degree of damage at the six-damaged provinces on the Andaman seacoast of Thailand. Fast and reliable interpretation of the damage by remote sensing method can be used for inundation mapping, rehabilitation and housing plans for the victims. For tsunami mitigation, the satellite data can be used with GIS to construct the evacuation map (evacuation route and refuge site) and coastal zone management. It is also helpful for educational program for local residents and school systems. Tsunami is a kind of ocean wave, therefore any satellite sensors such as SAR, Altimeter, MODIS, Landsat, SPOT, IKONOS can detect the tsunami wave in 2004. The satellite images have shown the characteristics of tsunami wave approaching the coast. For warning, satellite data has potential for early warning to detect the tsunami wave in deep ocean, if there are enough satellite constellation to monitor and detect the first tsunami wave like the pressure gauge, seismograph and tide gauge with the DART buoy can do. Moreover, the new methods should be developed to analyse the satellite data more faster for early warning procedure.

• 한국해안·해양공학회논문집
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• 제32권6호
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• pp.465-480
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• 2020

2012년 남해안에 내습한 태풍 산바에 의해 발생한 폭풍해일과 파랑을 JMA-MSM 예보기상자료, NCEP-CFSR 재분석 기상자료, ECMWF-ERA5 재분석 기상자료, JTWC의 최적경로를 이용한 기상자료를 이용하여 수치모의하고, 계산된 해일고를 전국 해안의 항만에서 관측된 폭풍해일 시계열 자료와 비교하였으며, 파랑에 대해서는 계산된 유의파고를 해상 부이 및 수압식 파고 관측 자료와 비교하였다. 이 비교를 통해 태풍 산바에 대한 각종 기상장의 신뢰도를 평가하였다. 그 결과 JMA-MSM 기상자료와 NCEP-CFSR 기상자료가 가장 신뢰도가 높았고, ECMWF-ERA5 기상자료는 전반적으로 해일고나 파고의 크기가 작게 나타났으나, 태풍 전면부의 수렴대는 가장 잘 재현하는 것으로 나타났다. JTWC의 최적경로를 이용한 기상자료는 신뢰도가 가장 낮게 나타났다.

• Journal of Mechanical Science and Technology
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• 제15권12호
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• pp.1822-1828
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• 2001

The experiment for the sympathetic detonation (Sudo et al., 1951) (Fukuyama et al., 1958) in water was conducted. Composition B (RDX: 64%, TNT: 36%, Detonation velocity: 7900m/s) was used for both donor (the thickness was 50mm, and the diameter was 31mm) and receptor charges. The distance between the donor and the receptor, and the thickness (5, 7.5, 10mm) of the receptor were varied in the experiments. In order to investigate the basic characteristics of the underwater sympathetic detonation of high explosive, the sympathetic detonation phenomena were visualized by a high-speed camera (HADLAND PHOTONICS, IMACON790) in forms of streak and framing photographs. The 200ns/mm streak velocity was 2㎲. Manganin gauges (KYOWA Electronic INSTRUMENTS CO. SKF-21725) were used for the pressure measurements. The gauges were set under the receptor. The pressures during the complete and incomplete explosions were measured.