• Title/Summary/Keyword: WATER DEPTH

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Numerical Study on Floating-Body Motions in Finite Depth

  • Kim, Tae-Young;Kim, Yong-Hwan
    • International Journal of Ocean System Engineering
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    • v.2 no.3
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    • pp.176-184
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    • 2012
  • Installing floating structures in a coastal area requires careful observation of the finite-depth effect. In this paper, a Rankine panel method that includes the finite-depth effect is developed in the time domain. The bottom boundary condition is satisfied by directly distributing Rankine panels on the bottom surface. A stepwise analysis is performed for the radiation diffraction problems and consequently freely-floating motion responses over different water depths. The hydrodynamic properties of two test hulls, a Series 60 and a floating barge, are compared to the results from another computation program for validation purposes. The results for both hulls change remarkably as the water depth becomes shallower. The important features of the results are addressed and the effects of a finite depth are discussed.

Effect of Carbonation Threshold Depth on the Initiation Time of Corrosion at the Concrete Durability Design (콘크리트의 내구성 설계시 탄산화 임계깊이가 철근부식 개시시기에 미치는 영향에 관한 연구)

  • Yang, Jae-Won;Lee, Sang-Hyun;Song, Hun;Lee, Han-Seung
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2010.05a
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    • pp.229-230
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    • 2010
  • The Carbonation, one of the main deterioration factors of concrete, reduces capacity of members with providing rebar corrosion environment. Consequently it suggested standards of all countries of world, carbonation depth prediction equation of respective researchers and time to rebar corrosion initiation. As a result of carbonation depth prediction equation calculation, difference of time to rebar corrosion initiation is 149 years and difference of carbonation depth prediction equation is 162 years when water cement ratio is 50%. So a study on rebar corrosion with carbonation depth will need existing reliable data and verifications by experiment.

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Shallow Water Effect on Resistance Performance of Large Container Ship Based on CFD Analysis (천수 효과가 대형 컨테이너선의 저항 성능에 미치는 영향에 관한 전산유체역학 해석 연구)

  • Sun-kyu, Lee;Youngjun, You;Jinhae, Kim
    • Journal of the Society of Naval Architects of Korea
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    • v.59 no.6
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    • pp.345-354
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    • 2022
  • It is easy for a ship passing through confined waters to be exposed in dangers of collisions and grounding due to different hydrodynamic responses. Since marine accidents can cause significant impacts on environments, global economy, and human lives, it is necessary to study the effect of shallow water on hydrodynamic performance of a ship. In this paper, the effect of water depth on resistance performance was investigated using CFD analysis as an initial study for improving navigational safety of a large container ship under confined waters. After a CFD set-up for deep water condition was validated and verified by comparing CFD analysis with model test results, CFD calculations according to ship speed and water depth were conducted. The features were investigated in terms of tendency and physical knowledge related to resistance performance. The increase of resistance due to shallow water effect was reviewed with empirical formula suggested from SWABE JIP. Speed loss due to shallow water effect was additionally reviewed from estimated delivered power according to ship speed and water depth.

Seedling Emergence and Initial Growth between Water and Dry Seeding in Forage Millet (사료용 피의 건답과 무논 파종 시 입모 및 초기생육특성)

  • Ahn, Seok-Hyeon;Chung, Nam-Jin
    • KOREAN JOURNAL OF CROP SCIENCE
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    • v.59 no.1
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    • pp.83-88
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    • 2014
  • This research was carried out to determine the characteristics of germination in relation to temperature, and seedling emergence and growth affected by soil moisture in forage millet. The seeds of forage millet could germinate at more than $15^{\circ}C$ at the rate of 0, 90.5, 97.3 and 96.8% respectively 10 days after seeding at 10, 15, 20 and $25^{\circ}C$. The result showed that the temperature needs to be $15^{\circ}C$ or more for the seeds to germinate. The effects of seeding depth on the growth characteristics and emergence of millet seed were investigated in waters and direct seeding methods by thoroughly mixing the seed and soil. In water treatment, the emergence rates were 3.7% at $15^{\circ}C$, 7.6% at $20^{\circ}C$, 6.3% at $25^{\circ}C$, while direct seeding treatment showed the emergence rates of 65.6, 75 and 71% at 15, 20 and $25^{\circ}C$, respectively. At 15, 20, and $25^{\circ}C$, seeds in water seeding could germinate at 0.5, 1.8, 1.5 cm of soil depth, while in direct seeding, they could germinate at the depth of 9.5, 10.0, 9.9 cm. When the initial growth characteristics of the seeds were investigated, there was positive correlation between seeding depth and mesocotyl length in both water and direct seed methods. Growth and development in terms of leaf age, root length, coleoptiles and mesocotyl length, and plant height were found maximum at 0.5 cm soil depth for water seeding, and 3-5 cm soil depth for direct seeding. Results showed that there were close relationship among temperature, soil depth and moisture acquiring methods, and the combination of these factors greatly affected the initial growth characteristics and development of millet seeds. It can be concluded that, to get good seedling stand and germination of millet seed, millet should grown in field condition at the depth of 0.5 cm or less for water seeding, and 3-5 cm for direct seeding method.

Effects of Silica Fume Content and Polymer-Binder Ratio on Properties of Ultrarapid-Hardening Polymer-Modified Mortars

  • Choi, Jong Yun;Joo, Myung-Ki;Lho, Byeong Cheol
    • International Journal of Concrete Structures and Materials
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    • v.10 no.2
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    • pp.249-256
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    • 2016
  • This paper deals with the effects of silica fume content and polymer-binder ratio on the properties of ultrarapid-hardening polymer-modified mortar using silica fume and ethylene-vinyl acetate redispersible polymer powder instead of styrene-butadiene rubber latex to shorten the hardening time. The ultrarapid-hardening polymer-modified mortar was prepared with various silica fume contents and polymer-binder ratios, and tested flexural strength, compressive strength, water absorption, carbonation depth and chloride ion penetration depth. As results, the flexural, compressive and adhesion strengths of the ultrarapid-hardening polymer-modified mortar tended to increase as increasing polymer-binder ratio, and reached the maximums at 4 % of silica fume content. The water absorption, carbonation and chloride ion penetration resistance were improved according to silica fume content and polymer-binder ratio.

GIS를 이용한 영산강 유역의 지하수의 산출특성

  • Seo Gu-Won;Park Bae-Yong;Jeong Chan-Deok
    • Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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    • 2005.04a
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    • pp.61-64
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    • 2005
  • The calculated characteristics of groundwater within the Youngsan river basin are : casing depth-17.1m, well depth-74.8m, natural water-2.6m, pumping water-43.9m, yields-391$m^3/D$, transmissivity-16.3$m^3/D/m$, storativity-0.068. As far as hydrogeological units are concerned, in casing depth, weathered granites are deepest followed by gneiss, volcanics, and sediments. In major aquifer development areas, sediments are deepest followed by volcanics, granites and gneiss in more shallow areas, Altogether, the major aquifar development depth of the Youngsan river basin is within the $35{\sim}60m$ range.

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Numerical Method for Calculating Fourier Coefficients and Properties of Water Waves with Shear Current and Vorticity in Finite Depth

  • JangRyong Shin
    • Journal of Ocean Engineering and Technology
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    • v.37 no.6
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    • pp.256-265
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    • 2023
  • Many numerical methods have been developed since 1961, but unresolved issues remain. This study developed a numerical method to address these issues and determine the coefficients and properties of rotational waves with a shear current in a finite water depth. The number of unknown constants was reduced significantly by introducing a wavelength-independent coordinate system. The reference depth was calculated independently using the shooting method. Therefore, there was no need for partial derivatives with respect to the wavelength and the reference depth, which simplified the numerical formulation. This method had less than half of the unknown constants of the other method because Newton's method only determines the coefficients. The breaking limit was calculated for verification, and the result agreed with the Miche formula. The water particle velocities were calculated, and the results were consistent with the experimental data. Dispersion relations were calculated, and the results are consistent with other numerical findings. The convergence of this method was examined. Although the required series order was reduced significantly, the total error was smaller, with a faster convergence speed.

Correlation Analysis between GPS Precipitable Water Vapor and Heavy Snowfall on Gangwon Province in Early 2011 (2011년 강원 폭설과 GPS 가강수량의 상관성 분석)

  • Song, Dong-Seob
    • Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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    • v.30 no.1
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    • pp.97-104
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    • 2012
  • In this paper, the GPS precipitable water vapor was retrieved by estimating of GPS signal delay in the troposphere during the progress of heavy snowfall on the Gangwon Province, 2011. For this period, the time series analysis between GPS precipitable water vapor and fresh snow depth was accomplished. The time series and the comparison with the GPS precipitable water vapor and the fresh snow depth indicates that the temporal change of two variations is closely related to the progress of the heavy snowfall. Also, the periodicity of GPS precipitable water vapor using the wavelet transform method was showed a similar cycle of saturated water vapor pressure as the limitation of this study span. The result shows that the decrement of GPS precipitable water vapor was conflicted with the increment of fresh snow depth at two sites, Gangneung and Uljin. The correlation between the GPS precipitable water vapor and the saturated water vapor pressure for the event was showed a positive correlation, compare with the non-heavy snowfall periods.

Effect of Irrigation Water Depth on Greenhouse Gas Emission in Paddy Field (논물 담수심이 온난화 가스 배출에 미치는 영향)

  • Lee, Kyeong-Bo;Kim, Jong-Gu;Park, Chan-Won;Shin, Yong-Kwang;Lee, Deog-Bae;Kim, Jae-Duk
    • Korean Journal of Soil Science and Fertilizer
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    • v.38 no.3
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    • pp.150-156
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    • 2005
  • The increasing emission of greenhouse gases may change agricultural environment. The agronomic productivity will depend upon change of temperature, precipitation, solar radiation and fertilization. This study was conducted to investigate greenhouse gas emission with irrigation water depth in paddy field. Area of each experiment plot is $70m^2$, Three treatments with three replications were carried out in this experiment, which was laid out as randomized complete block design. The treatments of irrigation water were maximum field water capacity and 4 and 8 cm depth. The application rate of fresh rice straw was $8,000kg\;ha^{-1}$ in combination with chemical fertilizers ($110kg\;N\;ha^{-1}$, $45kg\;P_2O_5\;ha^{-1}$ and $57kg\;K_2O\;ha^{-1}$). The $CH_4$ emission was highest at 32 days after rice transplanting with rice straw treatment. The $CH_4$ emission in the plot of maximum field water capacity was lower compared with 4 and 8 cm of irrigation depth. $CH_4$ and $N_2O$ emission under different water depth in the paddy field were 30 and $1.52kg\;ha^{-1}$ at 8 cm depth, 281 and $1.71kg\;ha^{-1}$ at 4 cm depth, and 219 and $2.01kg\;ha^{-1}$ at water saturated condition. The total emission of greenhouse gases equivalent to $CO_2$ emission with rice straw application were $6,939kg\;CO_2\;ha^{-1}$ at 8 cm depth plot, $6,431kg\;CO_2\;ha^{-1}$ at 4 cm depth plot and $5,222kg\;CO_2\;ha^{-1}$ at water saturated condition. The GWPs without rice straw application were $4,449kg\;CO_2\;ha^{-1}$ at 8 cm depth plot, $3,702kg\;CO_2\;ha^{-1}$ at 4 cm depth plot and $4,579kg\;CO_2\;ha^{-1}$ at water saturated condition.

Inorganic Nutrient Distributions in Association with Thermocline at KOMO Station in the Northeast Equatorial Pacific Ocean during 1995-2002 (북동태평양 KOMO 정점에서 수온약층에 따른 무기영양염 분포 특성(1995-2002))

  • Son, Seung-Kyu;Son, Ju-Won;Kim, Kyeong-Hong;Kang, Jung-Hoon;Chi, Sang-Bum;Yoo, Chan-Min;Park, Cheong-Kee;Kim, Woong-Seo
    • Ocean and Polar Research
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    • v.26 no.2
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    • pp.377-384
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    • 2004
  • Annual variations of inorganic nutrients such as nitrate(+nitrite), phosphate and silicate in association with thermocline were investigated in the upper 200 m of the water column at KODES Long-term Monitoring (KOMO) station in the northeast equatorial Pacific from 1995 to 2002. Global climatic disturbances such as El Nino and La Nina, should have affected KODES area during the study period. In 1995-97 and 2000-2002, a thermocline where temperatures rapidly decrease with depth, was formed at 50-70 m water depth. Nutrient depletion, specially for nitrate and phosphate, was extended down to approximately 50 m depth, which coincided with the surface mixed layer depth. In 1998 and 1999, however a very fluctuating thermocline was observed at 20-100 m water depth. In the photic zone (up to 100 m depth), depth integration of nitrate, phosphate and silicate ranged from 2.02 to $23.14\;gN/m^2$, from 0.87 to $4.05\;gP/m^2$ and from 35.67 to $176.21\;gSi/m^2$, respectively. As a result of changes in the water column structures, nutrient concentrations also showed fluctuation parallel to the changes of thermocline in the study area.