• Ocean and Polar Research
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• 제33권3호
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• pp.309-319
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• 2011

This is a preliminary study of the feasibility of obtaining reliable tidal current harmonic constants, using one month of current observations, to verify the accuracy of a tidal model. An inference method is commonly used to separate out the tidal harmonic constituents when the available data spans less than a synodic period. In contrast to tidal constituents, studies of the separation of tidal-current harmonics are rare, basically due to a dearth of the long-term observation data needed for such experiments. We conducted concurrent and monthly harmonic analyses for tidal current velocities and heights, using 2 years (2006 and 2007) of current and sea-level records obtained from the Tidal Current Signal Station located in the narrow waterway in front of Incheon Lock, Korea. Firstly, the l-year harmonic analyses showed that, with the exception of $M_2$ and $S_2$ semidiurnal constituents, the major constituents were different for the tidal currents and heights. $K_1$, for instance, was found to be the 4th major tidal constituent but not an important tidal current constituent. Secondly, we examined monthly variation in the amplitudes and phase-lags of the $S_2$ and $K_1$ current-velocity and tide constituents over a 23-month period. The resultant patterns of variation in the amplitudes and phase-lags of the $S_2$ tidal currents and tides were similar, exhibiting a sine curve form with a 6-month period. Similarly, variation in the $K_1$ tidal constant and tidal current-velocity phase lags showed a sine curve pattern with a 6-month period. However, that of the $K_1$ tidal current-velocity amplitude showed a somewhat irregular sine curve pattern. Lastly, we investigated and tested the inference methods available for separating the $K_2$ and $S_2$ current-velocity constituents via monthly harmonic analysis. We compared the effects of reduction in monthly variability in tidal harmonic constants of the $S_2$ current-velocity constituent using three different inference methods and that of Schureman (1976). Specifically, to separate out the two constituents ($S_2$ and $K_2$), we used three different inference parameter (i.e. amplitude ratio and phase-lag diggerence) values derived from the 1-year harmonic analyses of current-velocities and tidal heights at (near) the short-term observation station and from tidal potential (TP), together with Schureman's (1976) inference (SI). Results from these four different methods reveal that TP and SI are satisfactorily applicable where results of long-term harmonic analysis are not available. We also discussed how to further reduce the monthly variability in $S_2$ tidal current-velocity constants.

• 한국환경과학회지
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• 제23권4호
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• pp.661-672
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• 2014

Due to tidal force, it is very difficult to estimate the hydraulic parameters of high permeable aquifer near coastal area in Jeju Island. Therefore, to eliminate the impact of tidal force from groundwater level and estimate the hydraulic properties, tidal response technique has been mainly studied. In this study we have extracted 38 tidal constituents from groundwater level and harmonic constants including frequency, amplitude, and phase of each constituent using T_TIDE subroutine which is used to estimate oceanic tidal constituents, and then we have estimated hydraulic diffusivity associated with amplitude attenuation factor(that is the ratio of groundwater level amplitude to sea level amplitude for each tidal constituent) and phase lag(that is phase difference between groundwater level and sea level for each constituent). Also using harmonic constants for each constituent, we made the sinusoidal wave and then we constructed the synthesized wave which linearly combined sinusoidal wave. Finally, we could get residuals(net groundwater level) which was excluded most of tidal influences by eliminating synthesized wave from raw groundwater level. As a result of comparing statistics for synthesized level and net groundwater level, we found that the statistics for net groundwater level was more insignificant than those of synthesized wave. Moreover, in case of coastal aquifer which the impact of tidal force is even more than those of other environmental factors such as rainfall and groundwater yield, it is possible to predict groundwater level using synthesized wave and regression analysis of residuals.

• Bulletin of the Korean Chemical Society
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• 제3권2호
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• pp.44-49
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• 1982

Dynamic and equilibrium structures of a polymer chain immersed in solvent molecules have been investigated by a molecular dynamic method. The calculation employs the Lennard-Jones potential function to represent the interactions between two solvent molecules (SS) and between a constituent particle (monomer unit) of the polymer chain and a solvent molecule (CS) as well as between two non-nearest neighbor constituent particles of the polymer chain (CC), while the chemical bond for nearest neighbor constituent particles was chosen to follow a harmonic oscillator potential law. The correlation function for the SS, CS and CC pairs, the end-to-end distance square and the radius of gyration square were calculated by varying the chain length (= 5, 10, 15, 20). The computed end-to-end distance square and the radius of gyration square were found to be in a fairly good agreement with the corresponding results from the random-flight model. Unlike earlier works, the present simulation rsesult shows that the autocorrelation function of radius of gyration square decays slower than that of the end-to-end distance square.

• 해양환경안전학회:학술대회논문집
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• 해양환경안전학회 2017년도 추계학술발표회
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• pp.191-191
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• 2017

• 한국소음진동공학회논문집
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• 제20권6호
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• pp.583-592
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• 2010

Equations of motion of thin-walled composite H-type cross-section beams exposed to concentrated harmonic and non-harmonic time-dependent external excitations, incorporating a number of nonclassical effects of transverse shear, primary and secondary warping, and anisotropy of constituent materials are derived. The forced vibration response characteristics of a composite H-type cross-section beam exhibiting the circumferentially asymmetric stiffness(CAS) configuration are exploited in connection with the structural bending-torsion coupling resulting from directional properties of fiber reinforced composite materials.

• 한국해양공학회지
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• 제16권2호
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• pp.6-9
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• 2002

The long-term monthly variations of tide with tidal harmonic analysis in Pusan Harbour are investigated. The present spring tidal range decreased 1.4 cm and the variation of phase lag increased than 1974. The high and low water level of yearly mean sea level is show during the February to March and August to September, respectively. It is important to note that the larger lunar elliptic N2 is large in comparison with lunisolar diurnal K1 and principal lunar diurnal O1. The ratios (Correction Factors) of monthly mean sea level and the main 4 tidal constituents are evaluated to correct the shortly (monthly) observed tide for the design of harbour facilities.

• 물과 미래
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• 제24권2호
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• pp.81-95
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• 1991

본 연구는 조석과 하천류의 상호작용을 살펴보기 위해 지배방정식을 섭동근사댑을 이용하여 해석 해를 구하였다. 또한 여기에 이류항과 비선형 마찰항을 포함 하였다. 하천류와 조석분조들과의 복잡한 상호작용을 각각의 분조와의 상호작용으로 단순화 시키기 위해 조화분석을 실시하였다 조석의 무차원 매개변수, 특히 감쇄율을 각각의 해에 대하여 구하였다. 평가결과 해석해로부터 구한 감쇄율은 조화분석으로부터 구한 측정치보다 낮게 평가되어 그들의 상관관계를 설정하여 보정 하였다. 해석해를 금강의 감조구간에 적용하여 관측치와 비교한 결과 잘 일치하였다.

• 한국해안·해양공학회논문집
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• 제20권1호
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• pp.14-24
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• 2008

목포와 제주를 위시한 서남해안에서 최근 예측 고조위가 증가하는 경향을 보이고 있다. 조화분석을 통한 자료분석 결과 서남해안 전반에 걸쳐 평균해수면이 뚜렷하게 증가하는 반면 반일주조의 진폭은 감소하는 것으로 나타나고 있다. 또한 태양연주조(Sa분조)의 진폭이 증가한 것으로 나타나고 있으며 이에 따라 하절기의 고조위가 더욱 상승한 것으로 확인되었다. 21세기 들어 RUSA와 MAEMI등 대형 태풍의 발생이 잦아지고 있어 1990년대에 비해 서남해안에서의 최대해일고가 크게 증가하였다. 또한 이들은 7월${\sim}$9월에 집중되고 있어 하절기 고조위 상승과 함께 이상고조위 발생 가능성을 더욱 우려스럽게 하고 있다. 특히 목포해역은 하구언과 방조제 건설이후 이상고조 발생 가능성이 현격히 높아진 해역이므로 더욱 그러한 실정이며, 평균해수면 상승경향이 매우 뚜렷한 제주해역 역시 향후 이상고조 발생 가능성이 매우 높을 것으로 판단된다.

• 한국지구과학회:학술대회논문집
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• 한국지구과학회 2010년도 춘계학술발표회 논문집
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• pp.59-62
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• 2010

우리나라 주변 해역별 조석특성을 쉽게 보기 위해 정의된 비조화상수를 고찰하였다. 국립해양조사원의 표준항 가운데 20개 조위관측소의 자료로부터 계산한 조화상수 값을 기반으로 비조화 상수를 계산하였다. 이 가운데 표준항의 관측 및 예보조위자료를 이용하여 임의지점의 조위를 개략적으로 추산하기 위해 사용되는 개정수(조시차 및 조고비)는 천해분조가 강하게 발달하는 해역에서는 적용하는데 한계가 있음을 알 수 있었다. 또한 기존의 조화분해 소프트웨어로부터 구한 표준시 자오선기준 지각(phase lag, 또는 epoch)에서 로컬 지각(local phase lag)을 구하는데 사용하고 있는 p 값을 관습적으로 통용되고 있는 정수(integer)형의 첨가수(suffix)대신 a/15(a=각 분조의 각속도)를 사용하는 방안을 제시하였다.

• Journal of international Conference on Electrical Machines and Systems
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• 제1권2호
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• pp.85-90
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• 2012

This paper presents a topology structure and control method for an input-parallel-output-series(IPOS) inverter system which is suitable for high input current, high output voltage, and high power applications. In order to ensure the normal operation of the IPOS inverter system, the control method should achieve input current sharing(ICS) and output voltage sharing(OVS) among constituent modules. Through the analysis in this paper, ICS is automatically achieved as long as OVS is controlled. The IPOS inverter system is controlled by a three-loop control system which is composed of an outer common-output voltage loop, inner current loops and voltage sharing loops. Simulation results show that this control strategy can achieve low total harmonic distortion(THD) in the system output voltage, fast dynamic response, and good output voltage sharing performance.