• Annals of Clinical Neurophysiology
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• 제4권2호
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• pp.108-113
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• 2002

Background and Objective : Carpal tunnel syndrome (CTS) is the most common mononeuropathy encountered in clinical practice. No single procedure or group of procedures has demonstrated adequate sensitivity. F-wave study in CTS is very rarely reported. To determine the diagnostic usefulness of new parameters of F-wave and comparative study of F-wave parameters of median and ulnar nerves in patients with CTS. Methods : F-wave responses of median and ulnar nerves were analyzed from 27 patients with clinically diagnosed CTS and 22 age and gender-matched normal control. Conventional F-wave parameters were studied. Also, the usefulness of new parameters such as mean and maximal ulnar-median F-wave latency differences, ulnar-median F-wave persistence and chronodispersion differences, median/ulnar F-wave amplitude ratio, and F-wave conduction velocity (FCV) using mean and maximal latency were assessed. Results : Compared with controls, median F-wave minimal, maximal and mean latencies, mean F-wave amplitude/M-wave amplitude, minimal, mean and maximal ulnar-median F-wave latency differences, and FCVs using minimal, maximal and mean latency were significant (P<0.05~0.001). Median F-wave minimal, maximal and mean latencies, mean ulnar-median F-wave latency difference, and FCVs using minimal, maximal and mean latency showed high sensitivity and specificity. Mean ulnar-median F-wave latency difference and FCVs using maximal and mean latency were new parameters. Conclusion : New F-wave parameter including mean ulnar- median F-wave latency difference and FCVs using maximal and mean latency may be a useful to assess the CTS. Also, median F-wave minimal, maximal and mean latencies, and FCV using minimal latency may be included in routine diagnostic tests in CTS.

• 한국연안방재학회지
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• 제4권4호
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• pp.189-196
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• 2017

Ocean Research Stations (ORSs) is the ocean platform type observation towers and measured oceanic, atmospheric and environmental data. These station located on the offshore area far from the coast, so they can produce the data without land effect. This study focused to improve the wave data quality of ORS station. The wave observations at ORSs are used by the C-band (5.8 GHz, 5.17 cm) MIROS Wave and Current Radar (MWR). MWR is convenient to maintenance and produce reliability wave data under bad weather conditions. MWR measured significant wave height, peak wave period, peak wave direction and 2D wave spectrum, so it's can provide wave information for researchers and engineers. In order to improve the reliability of MWR wave data, Datawell Waverider Buoy was installed near the one ORS (Socheoncho station) during 7 months and validate the wave data of MWR. This study found that the wave radar tend to be overestimate the low wave height under wind condition. Firstly, this study carried out the wave Quality Control (QC) using wind data, however the quality of wave data was limited. So, this study applied the four filters (Correlation Check, Direction Filter, Reduce White Noise and Phillips Check) of MWR operating software and find that the filters effectively improve the wave data quality. After applying 3 effective filters in combination, the RMSE of significant wave height decreased from 0.81m to 0.23m, by 0.58m and Correlation increased from 0.66 to 0.96, by 0.32, so the reliability of MWR significant wave height was significantly improved.

• International Journal of Fluid Machinery and Systems
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• 제2권2호
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• pp.156-164
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• 2009

This paper aims to describe the importance of data, data collection methods, parameters to estimate the potential of wave energy and environmental impacts. The technical and economical status in wave energy conversion is outlined. Power and energy efficiency relationships are discussed. Many different types of wave-energy converters have been detailed. The progress in wave energy conversion in Malaysia is reviewed.

• 한국해안·해양공학회논문집
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• 제29권1호
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• pp.36-45
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• 2017

본 연구에서는 파랑 후측모의 실험을 통해 2016년 4월 대한해협에서 발생한 폭풍 파랑을 재현하고, 당시 폭풍 파랑의 특성을 조사하였다. 파랑 후측모의 실험에 앞서 파랑관측자료를 분석하고, 이를 바탕으로 계산 영역을 설정하였다. 본 연구의 분석에 따르면, 대한해협 지역은 NE 계열의 파랑이 지배적으로 나타나며 이는 동해 지역의 파랑 특성과 일치하고 있다. 이에 따라 본 연구에서는 Ahn et al.(2016)과 동일한 계산 조건을 적용하여 파랑 계산을 수행하였다. 본 연구의 계산 결과, 최대 유의파고 및 해당되는 유의파 주기는 각각 5.06 m, 9.2 s로, 이의 오차는 4 cm, 0.8 s 정도 되며 관측결과와 잘 일치하고 있었다. 이 후, 파랑계산 결과 얻은 유의파고 및 첨두주기를 JONSWAP 관계식과 비교하였는데, 이에 따르면 2016년 4월의 폭풍 파랑은 너울성 파랑보다는 풍파 성향이 더욱 강한 것으로 분석되었다.

• 한국해양공학회지
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• 제33권6호
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• pp.504-509
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• 2019

The wave-generation performance of a piston-type wave maker was analyzed using the numerical wave tank technique, and the numerical results were compared with theoretical solutions. A two-dimensional frequency domain analysis was conducted based on the Rankine panel method. Various parameters were used to examine the wave-generation performance, such as the width and gap of the wave board. The effects of the thickness of the wave board and of the gap from the bottom of the tank were evaluated. The difference in the amplitude of the generated wave between the analytical solution and the numerical result was examined, and its causes were addressed due to the gap flow between the bottom of the tank and the wave board. This parametric analysis can be utilized to design an optimum wave make parametric analysis to design an optimum wave maker that can generate waves with amplitudes that can be predicted accurately.

• 대한토목학회논문집
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• 제36권4호
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• pp.645-650
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• 2016

본 연구에서는 기존의 수리모형실험에서 나타나는 파랑-흐름 상호작용에 의한 파고감쇠현상을 분석하기 위하여 Navier-Stokes Solver를 이용한 수치시뮬레이션을 수행하였다. 파랑과 흐름이 만날 경우, 유속의 난류성분이 증가하여 난류강도가 커지는 것을 확인하였다. 이것으로부터 파랑이 전파될수록 난류의 영향으로 파랑에너지가 감소하고, 파고가 줄어드는 현상을 이해할 수 있었다. 그리고 흐름의 유속이 증가할수록 난류강도가 증가함으로 파고감쇠효과가 크게 나타났다. 또한 파랑이 동일한 거리를 전파할 때에 파고가 작을수록, 주기가 짧을수록 파고감쇠현상이 심화되는 것을 확인할 수 있었다.

• 한국해양공학회지
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• 제19권6호통권67호
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• pp.8-15
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• 2005

Wave energy has been considered to be one of the most promising energy resources for the future, as it is pollution-free and an abundant natural resource. However, since it has drawbacks of non-stationary energy density, it is necessary to change the wave energy into a simple concentrated energy. Progressive waves in a coastal area can be amplified, swashed, and overtopped by a wave overtopping control structure. By conserving the quantity of overflow in a reservoir, the kinetic energy of the waves can be converted to the potential energy with a hydraulic head above the mean sea level. The potential energy in the form of a hydraulic head can be utilized to produce electric power, similar to hydro-electric power generation. This study aims to find the most optimal shape of wave overtopping structure for maximum overtopping volume of sea water; for this purpose, we carried out the wave overtopping experiment in a wave tank, under both regular and irregular wave conditions.

• 한국해안·해양공학회논문집
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• 제22권2호
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• pp.73-78
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• 2010

파에너지는 쇄파되기 이전까지 주로 해저면과의 마찰력에 의하여 감소한다. 파마찰력을 산정하기 위한 연구는 여러 연구자들에 의해 진행되어 왔으며 어느 특정지점에서의 파마찰력 또는 파마찰손실률은 선형파이론으로 주어지는 해저면 입자유속과 연관된 파마찰계수의 도입으로 상당히 정확하게 간단하게 산정할 수 있다. 그러나 장구간에 걸쳐 파마찰력에 의하여 점차적으로 감소되는 파고변이는 상당한 반복 과정을 거쳐야 산정할 수 있었다. 본 연구에서는 기존 경험식을 이용해 전난류, 완난류 경우에 대해 일정경사면에서 천수효과와 마찰손실에 의한 파고 변화를 비교적 간단한 방법으로 추정하는 방법을 제시하였다. 해빈경사가 일정할 때 파고 변이률은 천수계수와 파고 마찰손실계수의 곱으로 간단히 구할 수 있다. 실제 해안과 비슷한 조건의 경우에 대하여 반복시산 과정으로 구한 수치와 간편 산정식으로 간단히 계산한 결과를 비교하여 제시하였다.

• Journal of the Korean Wood Science and Technology
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• 제24권3호
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• pp.18-27
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• 1996

The feasibility of using stress-wave technique in the transverse direction for the assessment of early stages of decay was investigated using compression test specimens having different annual ring orientations subjected to decay by Tyromyces palustris for various time intervals. Decay detection, quantitative assessment of decay, and the prediction of residual strength of decayed wood with less than five percent weight loss can be feasible using stress-wave parameters (wave velocity, wave impedance, and stress-wave elasticity) and their percent reduction due to decay, measured by stress-wave technique in the transverse direction. The use of stress-wave technique in the transverse direction for the application of this technique to structural members in service is desirable, when considering the easiness of attachment of accelerometers of stress-wave measuring device on the surface of members and also accurate detection of localized decayed areas. In stress-wave technique in the transverse direction, stress-wave parameters measured were different according to the angles between wave propagation path and annual ring, due to the anisotropy of wood structure. Therefore, it is recommended to use percent reduction in stress-wave parameters instead of stress-wave parameters. This evaluation method using percent reduction in stress-wave parameters is ideal when it is impossible to observe annual ring orientation on the transverse surface of wood.

• 한국해양공학회지
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• 제3권2호
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• pp.517-517
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• 1989