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Evaluation of the Harbor Operation Rate Considering Long Period Waves (장주기파를 고려한 항만 가동율의 평가)

  • 김규한
    • Journal of Ocean Engineering and Technology
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    • v.16 no.2
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    • pp.21-26
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    • 2002
  • In this study, the characteristics of long period waves are analyzed by field observation at Sokcho harbor on the eastern coast of Korea. firstly. the pressure data obtained from field observation are transformed into water surface elevations and the wave by wave analysis is applied to the observed wave data. also, we select long period waves by setting up the range 30-200sec, and suggest the relationship between ordinary waves and long period waves using the concept of the significant wave height. and, we examine the effects oft he long period waves on the rate of the harbor operation. The observation results demonstrate that the long period waves with heights of 1.2-14.6cm and periods of 35.8-162sec exist at Sokcho harbor. also, we found the rates of harbor operation based on long period waves are 61.8%-99.5% lower than the usual rates of 93.8%-100%.

Transition Characteristics of Long Period Waves by Field Observation (현장관측에 의한 장주기파의 천이특성)

  • 김규한;김덕중;류형석
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.14 no.1
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    • pp.34-40
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    • 2002
  • In order to estimate the height of long period wave from character of deep water wave, field observation is carried out three wave gauge are arranged by a straight line from the seashore to offshore direction and the result is analyzed. In addition, the existing theory of the mechanism for long period wave producer is verified by field observation, and the relation between deep water wave and long period wave of shallow area is examined. Observed long period wave is coincided with the existing theory for the most part. In order to add the change of time and space of long period wave, the height of long period wave is calculated by the composition of long period wave in each position. As a result, the relation of long period wave and deep water wave is presented more clear. Estimate formula is drew through them.

Development of Long Period Wave Observation System based on GPS (GPS 신호를 이용한 장주기 파고 관측 시스템 개발)

  • Kim, Tae-Hee;Gang, Yong-Soo;Lee, Won-Boo;Kim, Dae-Hyun
    • Journal of the Korean Society of Marine Engineering
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    • v.35 no.5
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    • pp.682-689
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    • 2011
  • Recently, there are frequent disasters by Swell-like Wave in the coastal area, Korea peninsula. This phenomenon (Swell-like Wave) has long period above 10 seconds compared with wind wave. To prevent these disasters by the long-period wave in advance, it's necessary to observe it in real time. But existing instruments for wave observation can not observe long-period wave because they mainly are aimed to measure the short-period wind wave. Therefore, in this research it is tried to develop the GPS based Long Period Wave Observation System which real time operation can be realzied in the sea.

A Study on Wave Observation System with GPS Arrayed Buoys by using MUSIC Method

  • Yoo, Yun-Ja;Song, Chae-Uk;Kouguchi, Nobuyoshi;Fujii, Hidenobu
    • Journal of Navigation and Port Research
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    • v.27 no.6
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    • pp.677-682
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    • 2003
  • The long-period gravity wave, the wave period from some ten seconds to some minutes, induces not only the big sway of a ship moored and berthed in the harbor due to the horizontal long-distance motion of a water but also strong exfoliated flow and vortices near the harbor entrance. They muse serious problems on the safety navigation of vessels entering and leaving the harbor, but this gravity wave has not been searched sufficiently yet. Then it is quite important to reveal the characteristics of this long-period gravity wave ana to solve various problems induced by this wave. The long-period gravity wave measurement system with arrayed buoys installed the kinematic GPS was already proposed, which provides the precise propagating direction of the long-period gravity wave. In this paper, the observation results of the wave measurement system are shown by the MUSIC method And the propagating wave direction was estimated precisely enough in comparison with other results used other method.

A Modified Standardized Precipitation Index (MSPI) and Its Application (수정 표준강수지수의 제안 및 적용)

  • Ryoo, So-Ra;Yoo, Chul-Sang
    • Journal of Korea Water Resources Association
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    • v.37 no.7
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    • pp.553-567
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    • 2004
  • This study proposes a modified standardized precipitation index (MSPI) which was developed to make up for the weakness of the SPI. Both MSPI and SPI are applied to the monthly rainfall at the Seoul station for the drought analysis. The MSPI proposed is nothing but the SPI for the normalized monthly rainfall, that is, an extra step for normalizing the monthly rainfall is included before driving the SPI. Thus, the MSPI has a structure to transfer the relative amount of rainfall to the next months, but the SPI the absolute amount of rainfall. The monthly rainfall data at the Seoul station used in this study are those collected from 1777 to 1996. The rainfall data collected before and after the long dry period around 1900 were also analyzed separately for the comparison. The results derived are as follows. (1) The MSPI was found to be more practical compared to the SPI. This was assured by comparing the analysis results of the data including and excluding the long dry period around 1900. (2) The MSPI is found to be less sensitive than the SPI to the extreme rainfall events. For the MSPI, the occurrence probabilities of moderate drought before and after the long dry period are similar, but those for the extreme drought becomes slightly decreased after the long dry period (from about 18 years of return period before the long dry period to the 16 years after the long dry period). However, the duration becomes longer after the long dry period (the duration for the extreme drought has been increased from 2 to 2.5 months after the long dry period). This results can also be compared with a rather unreasonable result derived by applying the SPI (for the extreme drought the return period has been decreased to be from 25 to 10 years after the long dry period, on the other hand the duration has been increased from 1.5 months to 3.5 months). So, we man conclude that the MSPI is more practical for the drought analysis that the SPI.

Characteristics of long-period swells measured in the near shore regions of eastern Arabian Sea

  • Glejin, Johnson;Kumar, V. Sanil;Amrutha, M.M.;Singh, Jai
    • International Journal of Naval Architecture and Ocean Engineering
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    • v.8 no.4
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    • pp.312-319
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    • 2016
  • Measured wave data covering two years simultaneously at 3 locations along the eastern Arabian Sea reveals the presence of long-period (peak wave period > 18 s) low-amplitude waves (significant wave height < 1 m) and the characteristics of these waves are described in this article. In a year, 1.4-3.6% of the time, the low-amplitude long-period swells were observed, and these waves were mainly during the nonmonsoon period. The wave spectra during these long-period swells were multi-peaked with peak wave period around 18.2 s, the secondary peak period around 13.3 s and the wind-sea peak period at 5 s. The ratio of the spectral energy of the wind-sea peak and the primary peak (swell) was slightly higher at the northern location (0.2) than that at the southern location (0.15) due to the higher wind speed present at the northern location.

Control of Free Spectral Range of tong Period Fiber Grating by Cladding Mode Waveguide Dispersion

  • Jeong, H.;Oh, K.
    • Journal of the Optical Society of Korea
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    • v.7 no.2
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    • pp.89-96
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    • 2003
  • A new method to control the free spectral range of a long period fiber grating is proposed and theoretically analyzed. As the refractive index decreases radially outward in the silica cladding due to graded doping of fluorine, waveguide dispersion in the cladding modes was modified to result in the effective indices change and subsequently the phase matching conditions for coupling with the core mode in a long period fiber grating. Enlargement of the free spectral range in a long period fiber grating was theoretically confirmed.

A Study on Characteristics and Dynamic Response Spectrum of Near Fault Ground Motions (근거리지진의 특성과 동적응답스펙트럼에 관한 연구)

  • Bang, Myung-Seok;Han, Sung-Ho
    • Journal of the Korean Society of Safety
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    • v.20 no.3
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    • pp.143-151
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    • 2005
  • In this study, it is demonstrated that how the effect of the Near Fault Ground Motion affects the response of the structure. Considering the general characteristic of Near Fault Ground Motion the characteristics of Near Fault Ground Motions is analysed by elastic response spectrums, and the inelastic response spectrum is evaluated with the ductility and the yield strength to consider the inelastic behavior which couldn't be simulated through the elastic response spectrum. The result of this study shows that the effect of Near Fault Ground Motion should be considered in the long period range of long span structures but the domestic seismic design code was developed based on Far Fault Ground Motions, so the effects of Near Fault Ground Motions, which is very serious especially in large structures with a long period, are not considered. Therefore, the effect of the Near Fault Ground Motion has to be examined especially in the seismic performance evaluation of long period structure.

Mechanically Induced Long Period Fiber Grating Array Device and Sensor Application (기계적으로 유도되는 장주기 광섬유 격자 배열 소자 및 센서 응용)

  • Lee, Nam-Kwon;Song, Jae-Won;Park, Jea-Hee
    • Korean Journal of Optics and Photonics
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    • v.18 no.2
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    • pp.142-148
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    • 2007
  • A mechanically induced long-period fiber grating array was fabricated and its transmission characteristics were measured. The grating away consisted of a rubber cover and a 45 cm metal bar with 10 grating groups. Each grating group was composed of 60 gratings. The period of the grating of the grating groups was increased by $10{\mu}m$ increments from $690{\mu}m$ to $780{\mu}m$. The long period fiber grating was induced when the pressure was applied on the long period grating array and the resonant wavelength depended on the position of applied pressure. The experimental results shows that this long period fiber grating away can be used as a various band rejection filter or a fiber optic sensor.

Long-Period Fiber Gratings Based on Periodically Surface-Etched Structure Imprinted by Using a Photoresist Polymer (폴리머 장주기 패턴을 이용한 표면 식각된 격자 구조 기반의 장주기 광섬유 격자)

  • Park, Sang-Oh;Kwon, Oh-Jang;Han, Young-Geun
    • Korean Journal of Optics and Photonics
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    • v.22 no.1
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    • pp.1-4
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    • 2011
  • A new fabrication technique of long-period fiber gratings with periodically surface-etched structures is proposed. Transmission characteristics of the periodically surface-etched long-period fiber gratings are improved by changing strain because of variation of coupling strength between the core and the cladding modes. The sensitivities of the periodically surface-etched long-period fiber gratings to strain, torsion, and ambient refractive index were measured. The strain and the torsion sensitivities were measured to be $-0.033\;dB/\mu\varepsilon$ and -1.30 nm m/rad, respectively. The ambient index sensitivity was measured to be -31.33 nm/RIU from a range from 1.33 to 1.42.