• 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.

• 설비공학논문집
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• 제13권7호
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• pp.653-665
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• 2001

The characteristics of the pulsating flow in a hydraulic pipe have been investigated. It is necessary to study the power control of the power transmission system in the landing gear system of aircraft and the design of robots. In this system, the power transmission pipeline is composed of a hydraulic system, and the operating flow is unsteady flow. The wave equation varying with frequency is analyzed in order to investigate the characteristics of unsteady flow in such a pipe. This wave equation involves the propagation coefficient in terns of frequency and viscosity. The theoretical result of this wave equation are compared with experimental result. Each wave equation, varying with the propagation coefficient, is analyzed theoretically. then, a sinusoidal wave generator is built in order to make better sinusoidal waves, and a rectifier is built to eliminate the noise from the hydraulic pump. The theoretical results of the wave equation in the flow of viscous fluid agree well with experimental results.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 춘계학술대회논문집
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• pp.121-126
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• 2001

This paper presents the experimental study for the reduction of transmitted shock waves in smart structures incorporating MR insert. MR fluid is filled within the two aluminum layers and two piezoceramic disks are embedded on the host plate as a transmitter and a receiver of the shock wave. Pulse wave generated by the transmitter is transmitted to the receiver through the MR insert and the plate. By applying magnetic field to the MR insert, the amplitude of the transmitted shock wave is reduced remarkably. The attenuation performance is tested by changing the applied magnetic field on MR inserts in two ways: by changing angle of permanent rubber magnet from 90 to 5 with 5 decrements, by using electromagnet in which magnetic field is controllable. The propagating wave speed of MR insert is also investigated.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 춘계학술대회논문집
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• pp.629-633
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• 2006

We investigated a new longitudinal acceleration wave decomposition method in time domain. The proposed method separates up- and down-stream waves with an axial strain and axial acceleration measured at a single point on the transmission path. The advantages such as low computation load and easy implementation would be possible by developing time domain under the following assumptions; low frequency range, uniform cross sectional area and elastic wave propagation. We confirmed the feasibility and performance of the method through experiment using Split Hopkinson Pressure Bar (SHPB). The method can be effective in several applications, including active vibration control with wave view point, where real time wave decomposition is necessary.

• International Journal of Reliability and Applications
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• 제5권1호
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• pp.37-46
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• 2004

Coil spring of automobile suspension system is very important to safety and dynamics of passenger car and requires a highly advanced quality control during manufacturing processes. Surface cracks on the coil spring rod produced by mechanical machining and heat treatment may cause a severe accident and large cost to the manufacturer. In order to detect surface cracks of the rod, guided wave technique is applied for a fast total volumetric inspection. Pochhammer equation is studied to investigate the dispersion characteristics of the guided wave in the spring rod and optimal wave modes sensitive to the surface crack are selected experimentally to design the experimental arrangement for the generation of guided wave. Rod samples with different size of artificial axial EDM notch on the surface ranging from 50${\mu}{\textrm}{m}$ to 1 mm are examined by guided wave and inspection results discussed.

• Journal of information and communication convergence engineering
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• 제13권1호
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• pp.36-41
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• 2015

With the rapidly increasing and widespread use of electronic and controlling equipment, the control of the electromagnetic (EM) wave environment becomes an important social issue. To solve the electromagnetic compatibility (EMC, both electromagnetic interface and electromagnetic susceptibility) problems, in this paper, we introduce the countermeasure techniques focused on EM wave absorbers for EMC problems in our laboratory at the Korea Maritime and Ocean University. The current technologies related to EM wave absorbers to solve EMC problems will first be described. The prospects of and a design for EM wave absorbers including a smart absorber with a heat radiating function will then be suggested.

• 한국항만학회지
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• 제10권1호
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• pp.53-61
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• 1996

This paper describes the effect of wave control using submerged flat plate by the numerical calculation and the hydraulic model test. The boundary element method is used to develop a numerical solution for the flow field caused by monochromatic oblique waves incident upon an infinitely long, sumerged flat plate situated in arbitrary water depth. The effect of wave blocking is examined according to the change of length, submerged depth of flat plate and incident angles. Numerical results show that longer length, shallower submergence of flat plate and larger incident angles enhance the effect of wave blocking. To validate numerical analysis method, hydraulic model test was conducted in 2-D wave flume with 60 cm metal sheet. Reflected waves are extracted from water surface elevation in front of the location of a submerged plate by least square method with 3 wave gages. From comparing experimental results with numerical results, efficiency of numerical analysis method by this study could be confirmed well within wide ranges of wave frequencies.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.634-639
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• 2001

The current study addresses experimental and computational work of impulse wave discharged from the exit of two kinds of right-angle pipe bends, which are attached to the open end of a simple shock tube. The weak normal shock wave with its magnitude of Mach number from 1.02 to 1.20 is employed to obtain the impulse wave propagating outside the exit of the pipe bends. A Schlieren optical system visualizes the impulse wave discharged from the exit of the pipe bends at an instant. The experimental data of the magnitude of the impulse wave and its propagating directivity are analyzed to characterize the impulse waves discharged from the exit of the pipe bends and compared with those discharged from a straight pipe. Computational results well predict the experimented dynamic behaviors of the impulse wave. The results obtained show that a right-angle miter bend considerably reduces the magnitude of the impulse wave and its directivity toward to the pipe axis, compared with the straight pipe and right-angle smooth bend. It is believed that the right-angle miter bend pipe can playa role of a passive control against the impulse wave.

• 한국멀티미디어학회논문지
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• 제19권8호
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• pp.1377-1385
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• 2016

Conventional X-band marine radar has been used as one of the effective tools for collecting and retrieving ocean surface information parameters for three decades. Several wave information extracting algorithms have been designed in such a way that they can be utilized for efficiently estimating sea surface wave parameters such as current velocities, wave direction, significant wave heights in VTS (Vessel Traffic Service). However, their performances are still restricted. For the purpose of overcoming the performance limits, in this paper, first the conventional algorithms are analyzed and their performances are compared, and then a new control algorithm is proposed. Furthermore, we try to improve the estimation performances of typical wave parameters including wave directions and significant wave heights by introducing linear regression model in the process of computing wave information extraction. Through several simulations with the X-band radar images, it is shown that the proposed method is very effective in estimating the wave information compared to the real measured buoy data.

• 한국항공우주학회지
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• 제30권8호
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• pp.21-29
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• 2002

본 연구는 다공벽과 공동을 사용한 피동제어법을 천음속 습공기 유동에서 발생하는 충격파와 경계층 간섭에 적응하였다. 지배방정식은 액적성장 방정식과 완전히 결합된 2차원, 비정상, 압축성 Navier-Stokes 방정식이며, 3차 오더 MUSCL 타입의 TVD 기법을 사용하였다. 또 난류모델로는 Baldwin-Lomax 모델을 적용하였다. 본 연구에서 적용한 제어법의 유용성을 조사하기 위해 유동의 전압손실과 충격파 변위의 시간의존성 거동을 해석하였다. 수치계산 결과로부터 본 연구의 피동제어기법을 통해 천음속 습공기 유동에서 발생하는 충격파/경계층 간섭으로 인한 전압손실이 상당히 감소하였고, 익에서 충격파 운동을 억제하는 것으로 나타났다. 또 다공영역의 위치가 본 연구의 제어법의 효과에 상당한 영향을 준다는 것이 발견하였다.