• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2007.12a
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• pp.11-13
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• 2007

본 연구에서 개발한 운항환경 모니터링 시스템은 5개의 가속도계와 자이로, 데이터 취득장치를 포함한 계측 및 통신부, 중앙에서 데이터를 관리하고, 운항지수를 계산하는 전산기로 구성된다. 계측된 가속도와 각속도를 이용하여 운항환경을 나타내는 정량적 지수인 뱃멀미 지수(Motion Sickness Incidence, MSI), 분당 작업방해회수(Motion Induced Interrupt, MII)를 실시간으로 계산한다. 개발된 시스템은 한국해양대학교 실습선인 한나라호의 부산 목포 연안항해시 실선시험을 통하여 유효성을 확인하였다.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.17 no.3
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• pp.202-212
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• 2005

In the design of an of offshore structure located near an underwater shoal, the same amount of attention given to the wave height may have to be put to the wave induced current as well since some of the wave energy translates to the current. In the present study, two numerical models each based on the nonlinear Boussinesq equation and the linear mild slope equation are applied to calculate the wave deformation and secondly induced current around a shoal. The underwater shoal in Vincent and briggs' experiment (1989) is used here, and all non-breaking wave conditions of the experiment with various monochromatic and unidirectional or multidirectional spectral wave incidences are concerned. Both numerical models clearly showed wave induced currents symmetrically farmed along the centerline over the shoal. The calculated wave heights along a preset line also generally showed very nice agreements with the experimental values.

• Journal of the Korean Geotechnical Society
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• v.28 no.8
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• pp.55-63
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• 2012

The evaluation of shear modulus (or shear wave velocity) profile of the site is very important in various fields of geotechnical engineering and various surface wave methods have applied to determine the shear wave velocity profiles and showed good performance. Surface wave methods evaluate the dispersion curve in the field and determine the shear wave velocity profile through the inversion process. In this paper, the automated inversion process using the genetic algorithm is developed for HWAW method which is one of surface wave methods recently developed. The proposed method uses the error function based on the wavelength domain dispersion curve and can determine the reliable shear wave velocity profile not only in shallow depth but also in deep depth. To estimate the validity of the proposed method, numerical simulations and field test were performed and the proposed method was applied to determine the shear wave velocity profiles. Through the numerical simulations and field applications, the promising potential of the proposed method was verified.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.20 no.4
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• pp.413-420
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• 2008

Wave force is an important factor which gives a direct affect to stability of the rubble mound breakwater. Particularly wave force has been considered as the main cause of displacement for replaced rubble mound breakwater which permits a little displacement to some degree. But the effect on displacement by wave force has not been considered and reflected in design. Therefore in this study, we compared numerical analysis displacement with field measured displacement so that the effect of wave force on displacement can be reflected in design. Result of the numerical analysis displacement was well consistent with field measured displacement data.

• Journal of the Korean Society for Marine Environment & Energy
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• v.7 no.1
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• pp.47-55
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• 2004

In this paper, The statistical properties of ocean waves in the sea area of Hong-do, Korea are examined based on 1998-2002's wave data from a directional wave buoy. Wave data aquisition rate, mean wave heights, frequency of wave direction are summarized. Wave height and period scatter diagrams and n-year return period wave heights are estimated. Wave periods of maximum wave heights are also estimated. Large amplitude wave characteristics during the typhoon Prapiroon in 2000, Rusa in 2002 are also examined.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.440-444
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• 2017

Two-dimensional hydrodynamic analysis was performed to analyze the attenuating characteristics of shock waves generated by the detonation of the bulkhead initiator. Through the interlocking analysis between HNS and HMX stacking initiator and STS bulkhead, we have precisely simulated detonation growth and pressure wave attenuation phenomena. The free surface velocity at the surface of the bulkhead was measured for quantitative comparison with the test data by VISAR. As a result, it was confirmed that the pressure attenuating pattern of the shock wave exponentially decreased according to the bulkhead thickness. The observed inflection point at the particle velocity measured over time is due to the subsequent propagation of the shock wave due to the rapid spallation of the interface between the detonator and the bulkhead.

• Journal of the Korean Society for Nondestructive Testing
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• v.30 no.2
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• pp.139-145
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• 2010

Bending fatigue of aluminium alloy was characterized by acoustic nonlinearity of narrow band laser-generated surface wave. The higher harmonic components generated intrinsically by arrayed line laser beam were analyzed theoretically and acoustic nonlinearity was measured successfully on the surface of fatigue damaged aluminium 6061 alloy. The acoustic nonlinearity increased as a function of fatigue cycles and has close relation with damage level. Consequently, the nonlinear acoustic technique of laser-generated surface wave could be potential to characterize surface damages subjected to fatigue.

• Bulletin of the Korean Space Science Society
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• 1993.04a
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• pp.17-17
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• 1993

태양의 전자파 복사와 입자의 방출은 지구자기구에 변화를 주어 여러 종류의 플라즈마를 발생시킨다. 관측되는 플라즈마파중에서 주파수가 가장 낮은 영역의 파를 극초저주파수 파동(Ultra Low Frequency pulsation)이라 부르며 주기는 수 초에서 수십 분에 이른다. 본 연구에서는 자기권 내부에 존재하는 플라즈마구 영역(L <5)에서 발생되는 주기가 10 \ulcorner45초인 Pc 3파를 다룬다. 210˚ 자기자오선상에 위치한 Kagoshima(KAG. L=1.22), Chichihima(CBI, L=1.44), Birdsvile(BSV, L=1.57) Adelaide(ADE, L=2.13)관측소에서 1990년 7월27일 잡음정도가 0.1nT rms인 fluxgate 자기계측기를 사용하여 측정하였으며 이 자료를 이용하여 Pc 3파의 Power Spectrurn을 구하고 자기위도 변화에 따른 Pc 3파간의 상관성을 알아본다.

• Explosives and Blasting
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• v.19 no.1
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• pp.85-92
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• 2001

본 논문에서는 암굴착시 발파에 의한 암반사면의 균열방지 및 사면안정 재고를 위하여 대 구-포항간 고속도로 건설현장에서 시험발파를 실시하고 그 결과를 분석하여 천공깊이별 안전 발파패턴을 제시하였다. 또한 현지 탄성파 속도를 측정하여 발파에 의해 암반에 미치는 균열상태를 조사한 결과 탄성파속도의 감소가 40 ∼ 53%로서 암반 중에 균열을 발생시킨 것으로 나타났다. 발파진동 계측결과를 분석하여 암반에 균열을 일으킬 수 있는 진동속도 기준을 설정하여 균열권 범위를 추정하였으며 사면의 기하학적 형상을 고려하여 손상대를 최소화 할 수 있는 적정 안전설계 패턴을 제시하였다.

• Journal of Advanced Marine Engineering and Technology
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• v.36 no.4
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• pp.527-532
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• 2012

Recently, in power system, even though the needs of protective IED(Intelligent Electronic Device) is highly increased, there are some problems in the field when use the IED. When the IED is in the fluctuated overload condition, because of the existing algorithm calculate the trip time only with the measured current of just previous measuring stage, the calculated trip time is not a proper value for the overload protection at this kind of condition, and when the load current fluctuate between overload and normal condition, because of the instantaneous reset characteristic of existing algorithm the IED dose not trip. And the non linear loads using power electronic elements seem to be increased. These non linear loads require a counterplan about various harmonics incoming to electric power systems. So we will give solutions about these problems.