• Journal of Ocean Engineering and Technology
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• v.34 no.5
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• pp.294-303
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• 2020

This study discusses data collection, calculation of wind and wave-induced resistance, and speed-power analysis of an 8,600 TEU container ship. Data acquisition system of the ship operator was improved to obtain the data necessary for the analysis, which was accomplished using SPA (Ship Performance Analysis, Park et al., 2019) in conformation with ISO15016:2015. From a previous operation profile of the container, the standard operating conditions of mean draft were 12.5 m and 13.6 m, which were defined with the mean stowage configuration of each condition. Model tests, including the load-variation test, were conducted to validate new ship performance and for the speed-power analysis. The major part of the added resistance of container ship is due to the wind. To check the reliability of wind-resistance calculation results, the resistance coefficients, added resistance, and speed-power analysis results using the Fujiwara regression formula (ISO15016:2015) and Computational fluid dynamics (Ryu et al., 2016; Jeon et al., 2017) analysis were compared. Wind speed and direction measured using an anemometer were used for wind-resistance calculation and the wave resistance was calculated using the wave-height and direction-data from weather information. Also, measured water temperature was used to calculate the increase in resistance owing to the deviation in water density. As a result, the SPA analysis using measured data and weather information was proved to be valid and able to identify the ship's resistance propulsion performance. Even with little difference in the air-resistance coefficient value, both methods provide sufficient accuracy for speed-power analysis. The differences were unnoticeable when the speed-power analysis results using each method were compared. Also, speed-power analysis results of the 8,600 TEU container ship in two draft conditions show acceptable trends when compared with the model test results and are also able to show power increase owing to hull fouling and aging. Thus, results of speed-power analysis of the existing 8,600 TEU container ship using the SPA program appropriately exhibit the characteristics of speed-power performance in deal conditions.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.35 no.2
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• pp.131-140
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• 2022

Installing Continuous Welded Rail (CWR) is one of the economical ways to resolve the challenges of noise, vibration, and the open-deck steel railway bridge impact, and the SSF method using the interlocking sleeper fastener has recently been developed. In this study, the method employed for determining the optimum vertical stiffness of the sleeper pad installed under the bridge sleeper, which is utilized to adjust the rail height and absorb shock when the train passes when the interlocking sleeper fastener is applied, is presented. To determine the optimal vertical stiffness of the sleeper pad, related existing design codes are reviewed, and, running safety, ride comfort, track safety, and bridge vibration according to the change in the vertical stiffness of the sleeper pad are estimated via flexible multi-body dynamic analysis,. The flexible multi-body dynamic analysis is performed using commercial programs ABAQUS and VI-Rail. The numerical analysis is conducted using the bridge model for a 30m-long plate girder bridge, and the response is calculated when passing ITX Saemaeul and KTX vehicles and freight wagon when the vertical stiffness of the sleeper pad is altered from 7.5 kN/mm to 240 kN/mm. The optimum stiffness of the sleeper pad is calculated as 200 kN/mm under the conditions of the track components applied to the numerical analysis.

• Korean Journal of Ecology and Environment
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• v.35 no.4 s.100
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• pp.273-284
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• 2002

During January 1998-October 1999, the impact of free-floating plants (FFP) on limnology of the wetland ecosystem was evaluated through the investigation of physicochemical characteristics of the Woopo Wetland along with in situ manipulation experiments of aquatic plants. Flooding events occurred in the wetland during the summer period (Jun.-Aug.) and water levels rose to 2-3 m due to precipitation from the catchment and inflow from the main channel of the Nakdong River. Physicochemical parameters and plankton dynamics in the wetland during the summer were greatly influenced by floods and growth of free-floating plants. Dissolved oxygen (Jun.-Sept., 4.5${\pm}$2.5 mg/1; Oct.-May, 8,1 ${\pm}$4.0 mg/1) and pH (Jun.-Sept., 6.9${\pm}$0.4; Oct.-May,7.4${\pm}$0.8) levels were significantly lower during the summer than any other seasons. Three types of enclosure experiments (100 L, treatments with floating plants, screened and opened) were conducted under the presence and absence of sediment for 15 days in the 1999 summer. The treatments with sediment had higher levels of nutrient concentrations than those of the others. Among the treatments with sediment, nutrient concentrations in the treatments with free-floating plants were higher than the others. Zooplankton communities in each treatment showed a similar variation, although the scale of zooplankton densities differed. Rotifer community dominated the zooplankton at the initial phase of the experiment, but decreased drastically along with an increase of cladoceran and copepod communities. In conclusion, low levels of dissolved oxygen and pH in the Woopo Wetland during the summer seemed to be caused by a proliferation of free-floating plants and active decomposition process at the bottom of the sediment.

• Economic and Environmental Geology
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• v.47 no.1
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• pp.39-48
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• 2014

In coastal region, estuaries have complex environments where dissolved and particulate matters are mixed with marine water and substances. Suspended sediment (SS) dynamics in coastal water, in particular, plays a major role in erosion/deposition processes, biomass primary production and the transport of nutrients, micropollutants, heavy metals, etc. Temporal variation in suspended sediment concentration (SSC) can be used to explain erosion/sedimentation patterns within coastal zones. Remotely sensed data can be an efficient tool for mapping SS in coastal waters. In this study, we analyzed the variation in SSC in coastal water using the Geostationary Ocean Color Imager (GOCI) and Landsat Enhanced Thematic Mapper Plus (ETM+) in Gyeonggi-bay. Daily variations in GOCI-derived SSC showed low values during ebb time. Current velocity and water level at 9 and 10 am is 37.6, 28.65 $cm{\cdot}s^{-1}$ and -1.23, -0.61 m respectively. Water level has increased to 1.18 m at flood time. In other words, strong current velocity and increased water level affected high SSC value before flood time but SSC decreased after flood time. Also, we compared seasonal SSC with the river discharge from the Han River and the Imjin River. In summer season, river discharge showed high amount, when SSC had high value near the inland. At this time SSC in open sea had low value. In contrast, river discharge amount from inland showed low value in winter season and, consequently, SSC in the open sea had high value because of northwest monsoon.

• Journal of the Korean Society for Marine Environment & Energy
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• v.15 no.2
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• pp.133-141
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• 2012

Effects of temperature and salinity on the growth of the toxic dinoflagellate $Alexandrium$ $tamarense$ and $A.$ $catenella$ isolated from the southern coast of Korea were examined in the laboratory. Growth experiment was conducted under the following combinations of temperature and salinity; 10, 15, 20, 25 and $30^{\circ}C$, 10, 15, 20, 25, 30 and 35 psu at a constant irradiance of 300 ${\mu}mol$ photons $m^{-2}s^{-1}$. Temperature and salinity conditions for maximum growth rate were indicated as follows: temperature $15^{\circ}C$ and salinity 30 psu (0.31 $d^{-1}$) in $A.$ $tamarense$, temperature $25^{\circ}C$ and salinity 30 psu (0.36 $d^{-1}$) in A. catenella. Temperature and salinity ranges for optimum growth condition of two species were $10{\sim}20^{\circ}C$, 25~35 psu and $120{\sim}30^{\circ}C$, 25~35 psu, respectively. The result of two-factor ANOVA indicated significant effects (P<0.001) of temperature and salinity on the growth rate, and two species were more effected by a temperature than a salinity on the growth. In addition, prediction equations were obtained through the multiple regressions of the specific growth rates as ${\mu}=0.04+0.0193T-0.0339S- 0.0005T^2+0.0021S^2+0.00073TS-0.000022T^3-0.000038S^3+0.00000086TS^2-0.0000255T^2S$ in $A.$ $tamarense$ and ${\mu}=1.01-0.1288T-0.0778S+0.0067T^2+0.0038S^2+0.00204TS-0.0001T^3-0.000059S^3-0.0000131TS^2-0.0000392T^2S$ in $A.$ $catenella$. Correlation coefficient between experimental values and simulated values was highly indicated. These results seem to provide information for understanding the spreading mechanism of $A.$ $tamarense$ and $A.$ $catenella$.

• Asian-Australasian Journal of Animal Sciences
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• v.11 no.5
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• pp.480-485
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• 1998

Application of trans rectal ultrasonography to buffaloes (n=6) to follow the growth of large antral follicles individually, on each day of one interovulatory interval revealed that follicular turnover during oestrous cycle occured in waves. There was a predominance of a two-wave pattern (5/6 animals) compared to that of a three-wave pattern (1/6 animals). For two-wave pattern, the first wave emerged at Day $0.20{\pm}0.19$ (Day 0 = day of ovulation) and was marked by development of a dominant anovulatory follicle which grew in size from $5.40{\pm}0.24mm$ at the day of detection to a maximum diameter of $12.40{\pm}0.81mm$ on Day $8.60{\pm}1.57$, with a growth rate of $0.88{\pm}0.17mm/day$ and then regressed, with a mean persistence of $19.40{\pm}1.54$ days. The second wave emerged at Day $9.20{\pm}1.06$ and was marked by development of a dominant ovulatory follicle which grew in size from $4.20{\pm}0.37mm$ at the day of detection to a maximum diameter of $13.80{\pm}0.37mm$ on Day $21.00{\pm}1.38$, with a growth rate of $0.66{\pm}0.12mm/day$ and then ovulated on Day $21.60{\pm}1.25$, with a mean persistence of $11.80{\pm}1.39$ days. The maximum diameters attained and the growth rates of dominant anovulatory and dominant ovulatory follicles, and the mean number of follicles ${\geq}3mm$ diameter detected at the time of emergence of first and second waves ($11.80{\pm}1.74$ and $9.00{\pm}2.81$, respectively) were not significantly different. In the animal which showed a three-wave pattern, the first, second and third waves emerged on Days 1, 10 and 19, respectively. All animals, except one had at least one subordinate follicle in the first or second or both waves. The subordinate follicles increased in diameter over a few days and then regressed. The results indicate that in buffaloes, the follicular turnover during oestrous cycle occurs predominantly in a two-wave pattern.

• Journal of The Korean Society of Agricultural Engineers
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• v.59 no.6
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• pp.61-71
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• 2017

The tracer gas method has an advantage that can estimate total and local ventilation rate by tracing air flow. However, the field measurement using tracer gas has disadvantages such as danger, inefficiency, and high cost. Therefore, the aim of this study was to evaluate ventilation rate in pig house by using the thermal distribution data rather than tracer gas. Especially, LMA (Local Mean Age), which is an index based on the age of air theory, was used to evaluate the ventilation rate in pig house. Firstly, the field experiment was conducted to measure micro-climate inside pig house, such as the air temperature, $CO_2$ concentration and wind velocity. And then, LMA was calculated based on the decay of $CO_2$ concentration and air temperature, respectively. This study compared between LMA determined by $CO_2$ concentration and air temperature; the average error and root mean square error were 3.76 s and 5.34 s. From these results, it was determined that thermal distribution data could be used for estimation of LMA. Finally, CFD (Computational fluid dynamic) model was validated using LMA and wind velocity. The mesh size was designed to be 0.1 m based on the grid independence test, and the Standard $k-{\omega}$ model was eventually chosen as the proper turbulence model. The developed CFD model was highly appropriate for evaluating the ventilation rate in pig house.

• Journal of the Society of Naval Architects of Korea
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• v.61 no.1
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• pp.51-60
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• 2024

Hi Air Korea and Hanwha ocean are currently developing an Onboard Carbon dioxide Capture System (OCCS) to absorb CO₂ emitted from ship's engine using a sodium hydroxide(NaOH) solution, and converting the resulting salt into a solid form through a chemical reaction with calcium oxide (CaO). The system process involves the following steps; 1)The reaction of CO₂ gas absorption in water, 2)The reaction between carbonic acid (H₂CO₃) and NaOH solution to produce carbonate or bicarbonate, and 3)The reaction between carbonate or bicarbonate and CaO to form calcium carbonate (CaCO₃). And ultimately, the solid material, CaCO₃, is separated and discharged using a separator. The OCCS has been installed on an ship and the test results have confirmed significant reduction effects of CO₂ in the ship's exhaust gas. A portion of the exhaust gas emitted from the engine was transferred to the OCCS using a blower. The flow rate of the transferred gas ranged from 800 to 1384 m³/hr, and the CO₂ concentration in the exhaust gas was 5.1 vol% for VLSFO, 3.7 vol% for LNG and a 12 wt% NaOH solution was used. The results showed a CO₂ capture efficiency of approximately 42.5 to 64.1 vol% and the CO₂ capture rate approximately 48.4 to 52.2kg/hr. Additionally, to assess the impact of the discharged CaCO₃on the marine ecosystem, we conducted "marine ecotoxicity test" and performed Computational Fluid Dynamics (CFD) analysis to evaluate the dispersion and dilution of the discharged effluent.

• Journal of Food Hygiene and Safety
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• v.14 no.4
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• pp.372-379
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• 1999

A bacteriological study of sea water and oyster in Tongyeong coastal area was conducted to evaluate sanitary conditions of the bay and compliance of waters with the recommended bacteriological criteria fur the designated area of shellfish cultivation. The Samples were collected at 5 zone, 34 sampling stations(Fig. 1) established once a month from September 1997 to August 1998. During the study period, temperature ranged from 6.9 to 23.6$^{\circ}C$, transparency ranged from 2.6 to 6.2 m, chemical oxygen demand ranged from 1.35 to 1.82 mg/ι, dissolved oxy-gen ranged from 5.0 to 9.9 mg/ι, dissolved nitrogen ranged from 1.60 to 8.17 $\mu\textrm{g}$-at/ι, phosphate ranged from 0.14 to 1.21 $\mu\textrm{g}$-at/ι, Chlorophyll-a ranged from 2.03 to 69.9 mg/㎥, respectively. The coliform group and fecal coliform MPN's of sea water were ranged from <3.0~1,600 and <3.0~540, respectively. The coliform group and fecal coliform MPN's of oysters were ranged from <18~16,000 and <18~2,200, respectively. The viable cell counts in oyster ranged from $1.5\times$10$^2$to 8.2$\times$10$^3$. The coliform stoup, fecal coliform, classification of coliform group with IMViC reactions and pathogenic vibrios were analyzed. 437 strains that were obtained from Tongyeoung coastal area seawater samples represented E. coli group 47.5%, C. freundii group 14.8%, K. aerogenes 10.9%, unknown 26.8%, respectively. During the study period, infectious bacteria such as Vibrio ohoEerae, Salmonella sp. and Shigella sp. were not detected from the samples, but detection ratios of Vibrio parahaemolyticus and Vibrio vulnificus were 12~21% in summer months.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.7 no.3
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• pp.140-147
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• 2002

We investigated the temporal variations in the heterotrophic dinoflagellates (hereafter HTD), tintinnid ciliates(TC), and naked ciliates(NC) from August to November 1999 in the coastal waters off the southern Saemankeum areas where a huge red tide dominated by Cochlodinium polykrikoides/Gymnodinium impudicum was first observed in 1998. We took water samples from 2-5 depths of 4 stations in each of the 5 cruises and then measured the species composition and abundances of HTD, TC, and NC The maximum species numbers and densities of HTD, TC, and NC(11, 12, and 10 cells $m\ell$$^{-1}$ , respectively) were observed when the density of diatoms was highest (August 10), while the lowest values (1.0, 0.5, and 2.4 cells $m\ell$$^{-1}$ , respectively) were found when the red tide dominated by C. polykrikoides/G. impudicum took placed (October 18). On August 10 and November 11 when diatoms dominated the abundance of phytoplankton, the correlation coefficients between TC, NC and diatoms were relatively high. However, On September 16 and October 18 when autotrophic+mixotrophic dinoflagellates(ATD+MTD) were abundant, the correlation coefficients between HTD and ATD+MTD were relatively high. The large HTD Noctiluca scintillans was the most dominant heterotrophic protists during the C. polykrikoides/G. impudicum red tide on October 18. N. scintillans has been known to feed on the prey cells when the swimming speeds of C. polykrikikoides/G. impudicum markedly reduced at the decline stage of the red tide. Therefore, N. scintillans could be effective grazers on C. polykrikoides/G. impudicum. The maximum densities of HTD, TC, and NC in the study area were fairly lower than those obtained in the waters off Kohung-Yeosu areas in the summer-fall, 1997. The results of the present study provide the basis of understanding predator-prey relationships between dominant phytoplankton and heterotrophic protists and the roles of the protist grazers in bloom dynamics in the waters off the western Korea.