• Ocean and Polar Research
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• v.31 no.3
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• pp.231-238
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• 2009

A study was carried out to investigate the effect of water temperature on daily pattern and rate of total ammonia nitrogen (TAN) excretion in juvenile dark-banded rockfish Sebastes inermis (mean body weight: $14.8{\pm}0.3g$) under fasting and feeding conditions. Fish were acclimated over 10 days under three different water temperatures (15, 20 and $25^{\circ}C$). After 72 hours of starvation, fasting TAN excretion was measured at each temperature. To investigate post-prandial TAN excretion, fish were hand-fed with a commercial diet containing 47.7% crude protein for 7 days, two times daily at 09:00 and 17:00 hr. Water was sampled from both the inlet and outlet of each chamber every 2 hrs over a 24 hr period. Both fasting and post-prandial TAN excretion increased with increase in water temperature (P<0.05). Mean fasting TAN excretion rates at 15, 20 and $25^{\circ}C$ were 8.1, 9.0 and 9.2 mg TAN kg $fish^{-1}h^{-1}$, respectively. The value of $15^{\circ}C$ was lower than those of 20 and $25^{\circ}C$ (P<0.05), but there was no significant difference between $20^{\circ}C$ and $25^{\circ}C$ (P>0.05). Mean post-prandial TAN excretion rates at 15, 20 and $25^{\circ}C$ were 20.1, 22.9 and 23.4 mg TAN kg $fish^{-1}h^{-1}$, respectively. A peak post-prandial TAN excretion rate occurred after 12 hrs from the first feeding at $15^{\circ}C$ (mean 28.7 mg TAN kg $fish^{-1}h^{-1}$), $20^{\circ}C$ (33.7 mg TAN kg $fish^{-1}h{-1}$) and $25^{\circ}C$ (36.8 mg TAN kg $fish^{-1}h{-1}$), respectively. The TAN loss for ingested nitrogen at $15^{\circ}C$ (36.2%) was lower than that of $20^{\circ}C$ (40.8%) and $25^{\circ}C$ (41.7%). Based on overall results, water temperature exerts a profound influence on the nitrogen metabolism of juvenile dark-banded rockfish.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.27 no.5
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• pp.281-294
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• 2015

In order to quantitatively estimate the nonlinear destructive interaction of wave load with wind load, which is very vital for the optimal design of offshore wind energy converter, we carried out a hydraulic model test and wind tunnel test. As a substructure of offshore wind energy converter, we would deploy the monopile, which is popular due to its easiness in construction. Based on the simulation using Monte Carlo simulation using Kaimal spectrum and cross spectrum, the instantaneous maximum wind velocity is adjusted to 10 m/s. And, considering the wave conditions of the Western Sea where a pilot wind farm is planned to be constructed, $H_s=0.1m$, 0.15 m, 0.2 m is carefully chosen. It turns out that the nonlinear destructive interaction between the wind and wave loads acting on the offshore wind energy converter is more clearly visible at rough seas rather than at mild seas, which strongly support our deduction that a Large eddy, a swirling vortex developed near the bumpy water surface in the opposite direction of the wind, is the driving mechanism underlying nonlinear destructive interaction between the wind and wave loads.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.24 no.3
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• pp.189-202
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• 2012

An Oscillating Water Column (OWC) wave generation system uses the air flow induced by the vertical motion of water column in the air chamber as a driving force of turbine. It is well known that OWC is one of the most efficient devices to harness wave power. This study estimated the air flow velocity from the time variation of the water level fluctuation in the air chamber under regular wave conditions using 3-dimensional numerical irregular wave tank (3D-NIT) model that can simulate the 3-dimensional irregular wave field. The applicability of the 3D-NIT model was validated by comparing numerically predicted air flow velocities with hydraulic experimental results. In addition, the characteristics of air flow frequency spectrum variation due to the incident frequency spectrum change, and the variations of frequency spectrum and wave reflection due to the existence of converter inside the air chamber were discussed. It is found that the phase difference exists in between the air flow velocity and the water level fluctuation inside the air chamber, and the peak frequency of the spectrum in water level fluctuation is amplified by the resonance in the air chamber.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.20 no.4
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• pp.328-340
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• 1987

In order to clarify major reasons of a poor harvest, the Porphyra-cultivation ground was investigated in Kwangyang Bay in terms of the laver production per unit area, diseases, and fouling organisms from January to April in 1986. The laver production per unit area of the control station was more than that of the study area at 'Soppal' cultivation ground, while the difference at the cultivation groud using 'nets' seemed to be insignificant. The vertical attachment range of laver was directly associated with the production per unit area at 'Soppal' cultivation ground. The number of young thalli of 1-3 mm length was almost similar between control and study sites at 'nets' cultivation ground. Two kinds of diseases in cultured laver, the crape and shot hole, were prevalent during the study period. However, the affected thalli were gradually decreased at the end of the study period. Major fouling organisms attached to 'Soppal' were Balanus albicostatus, Enteromorpha prolifera, Capsosiphon fulvescens, and Scytosiphon lomentaria. In conclusion, the poor harvest of laver in 1986 may result from such following problems as the decrease in vertical attachment range of laver and fouling problems as the decrease in vertical attachment range of laver and fouling organisms at 'Soppal' cultivation ground, prevalence of certain diseases, changes in environmental conditions, arrangement and maintenance of facilities for laver cultivation.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.29 no.3
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• pp.200-213
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• 1993

A model experiment on a midwater rope trawl net which is used in the North Pacific to catch alaska pollack is carried out in the circulating tank to examine the basic efficiency of the net. The prototype is the net used by M/S Hanil(1, 179GT, 2, 700PS), a Korean trawler. The model net was made according to the Tauti's Similarity Law of Fishing Gear in 1/100 scale by considering the condition of the tank. To measure the basic efficiency of the standard model net, the vertical opening and width between some points marked on the net were measured, and the hydrodynamic resistance were determined. Then the constructive conditions of the net were varied as follows and the factors were measured again to compare the efficiency of those nets with that of the standard net(A-1 type) front weight multiplied 1.5 times: A-2 type. buoyancy and depressing force multiplied 1.7 times: A-3 type. front weight multiplied 1.5 times on A-3 type: A-4 type. depressors rigged at ground rope: B type. cod-end stuffed with cashmylon wad: C type. The results obtained can be summarized as follows: 1. The vertical opening at the center of head rope was steeply decreased with the flow velocity increasing and the vertical opening H(m) can be expressed in H=1.2v super(-1.2)(v : flow velocity in m/sec). The width of the net varied a little when the flow velocity was over 0.4m/sec, and the width of net mouth showed about 37% of the distance between the fore tips of net pendant. The shape of net mouth was almost a circle at 0.2m/sec and then steeply flatted elliptically with the flow velocity increasing and the area of mouth S(m super(2)) can be expressed in S=(1.65-2.3v)$\times$10 super(-2). The hydrodynamic resistance of the net increased almost linearly with the flow velocity increasing and the resistance R(kg) can be expressed in R=3.2$\times$d/l$\times$abv. where d/l denotes the mean of d(diameter of netting twine) and l(length of a leg in a mesh) from wing tip to the end of bag-net except cod-end on the side pannel, and a denotes the strectched circumference of the net at the fore end of a meshed part and b the stretched length of the whole net from wing tip to the end of cod-end. 2. In the condition-varied nets, the vertical opening of head rope showed some increase in every type net except the C type, and the increase showed the greatest in the B type by 30~54%, whereas it showed decrease in the C type by 5~10%. Variation of the area of net mouth showed almost the same tendency as the vertical opening and the increase showed the greatest in the B type by 20%, whereas it showed decrease in the C type by 12%. Hydrodynamic resistance showed some increase in every type compared with the standard net, and the rate of increase indicated 5~10% in the A-2, A-3 and A-4 type, 22% in the B type and 3% in the C type.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.26 no.1
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• pp.65-75
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• 1990

There have been many methods for measuring the injection rate of diesel engines, but the results of them are not always identical and the reason for the discordance is not clear. Besides, a single shot injection equipment has been used for the fuel spray and the combustion research of diesel engines, but the results of experiment using the equipment don't apply to a volleyed shot injection of real engines. This paper investigates the merits and faults of the Bosch's method and the Zeuch's method, at the same, this paper also compares the injection rates of single shot inject rates of single shot injection and a volleyed shot injected by the Bosch's method. the results are summarized as follows: (1) The measurement error of the Bosch's method is about $\pm$1%, therefore, its accuracy is reliable. (2) By the Bosch's method, as the speed and the load of fuel pump increase, the injection rate becomes higher, on the contrary, the injection period(ms) shortens as the speed increases and the load decreases. (3) In this experiment, the injection rate of a single shot injection is lower than that of a volleyed shot injection under the same conditions. (4) The bulk modulus of elasticity using the Zeuch's method increases in proportion to the back pressure. (5) The Zeuch's method is less accurate than the Bosch's method.

• Korean Journal of Remote Sensing
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• v.32 no.5
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• pp.435-452
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• 2016

Land Surface Temperature (LST) has been operationally retrieved from the Communication, Ocean, and Meteorological Satellite (COMS) data by the spilt-window method (CSW_v2.0) developed by Cho et al. (2015). Although the CSW_v2.0 retrieved the LST with a reasonable quality compared to the Moderate Resolution Imaging Spectroradiometer (MODIS) LST data, it showed a relatively poor performance for the strong inversion and lapse rate conditions. To solve this problem, the LST retrieval algorithm (CSW_v2.0) was updated using the simulation results of radiative transfer model (MODTRAN 4.0) by considering the diurnal variations of air temperature. In general, the upgraded version, CSW_v3.0 showed a similar correlation coefficient between the prescribed LSTs and retrieved LSTs (0.99), the relatively smaller bias (from -0.03 K to-0.012 K) and the Root Mean Square Error (RMSE) (from 1.39 K to 1.138 K). Particularly, CSW_v3.0 improved the systematic problems of CSW_v2.0 that were encountered when temperature differences between LST and air temperature are very large and/or small (inversion layers and superadiabatic lapse rates), and when the brightness temperature differences and surface emissivity differences were large. The bias and RMSE of CSW_v2.0 were reduced by 10-30% in CSW_v3.0. The indirect validation results using the MODIS LST data showed that CSW_3.0 improved the retrieval accuracy of LST in terms of bias (from -0.629 K to -0.049 K) and RMSE (from 2.537 K to 2.502 K) compared to the CSW_v2.0.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.28 no.6
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• pp.408-415
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• 2016

Small fishing ports and coastal structures installed in a relatively low sea water depth disturb the wave induced current and cause the collapse of equilibrium state of sediment transport. These structures creates diffracted waves and matter the concentration of waves to cause the beach erosion. In order to mitigate these eroding problems on the beach, many counter measurements were proposed such as detached breakwater, groin or headland; however, these methods interrupt the aesthetic view of sandy beach due to the exposed structures above the sea level and have difficulty of applying to those beaches with the good scenery. Furthermore, some of these methods create secondary environmental problems after the installations. To eliminate these problems, one of the countermeasures, artificial reefs have been selected and used worldwide to minimize the disturbance of the scenery and secondary effects on the environment. Meanwhile, it is important to set the design elements for installing the artificial reefs such as that of length, opening width, clearing distances from the shoreline and more. Nevertheless, there are no construction manuals or standards for designing the artificial reefs with these important design elements yet. In this study, different conditions of artificial reefs were used with various cases throughout hydraulic model test to precisely analyze the changes of waves and currents to propose the standards of design elements to install the artificial reefs.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.17 no.4
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• pp.294-306
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• 2005

Most immersed tunnels investigated have been investigated based on the engineer's experience with design and construction. From engineering point of view, it is very important to understand the wave interaction with the seabed and immersed tunnel, since the stability of an immersed tunnel depends largely on the behavior of the seabed foundation. In this study, for the first stage research to find out the mechanism of the wave interaction with the seabed and immersed tunnel, the benchmarking method called as direct numerical simulation (DNS) was employed to analyze comprehensively the wave-induced pore water pressures, vorticity and flows in seabed or inside rubble stone around the immersed tunnel. The immersed tunnel is modeled based on Busan-Geoje fixed link project in Korea, which is now on the stage of planning. Moreover, the nonlinear water wave interaction with an immersed tunnel/its seabed foundation was thoroughly examined with regard to the stabilities of the immersed tunnel subjected to various water wave conditions, median grain size and so forth.

• Applied Microscopy
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• v.40 no.2
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• pp.117-123
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• 2010

This study has examined experimentally the Beer's law which is a precondition for quantitative electron tomography. We used carbon support film and latex spheres, which have similar absorption coefficients with biological samples, as the test samples to take a tilt-series of images for electron tomography. First, the 3D information of carbon film and latex spheres was obtained by electron tomography. Then, the regression analysis on the relationship between the intensities of the incident and the transmitted beams in a tilt series was carried out to examine the Beer's law. The regression results with RMS error of 0.976 show the linear intensity variations of the transmitted beam as the tilt angles were increased. In addition, the relative absorption coefficients of carbon support film and latex spheres calculated experimentally through the Beer's law were 1.71 (5) and 2.67 (6)/${\mu}m$, respectively. The absorption coefficients remained constant within a full tilt range. Therefore, it is expected that quantitative electron tomography could be performed for biological samples by applying Beer's law provided the exact intensity of incident beam can be obtained under the thoroughly controlled experimental conditions.