• Journal of the Korean Geosynthetics Society
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• 제13권1호
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• pp.71-83
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• 2014

Busan is located at the mouth of Nakdong River and if an earthquake occurs, it is very likely that the damage by the earthquake will be worse as liquefaction can happen in the sand layer, builtup soil, and landfill ground due to amplification in the lower sedimentary layer that is well developed in the river mouth. Therefore, this study first examined the possibility of liquefaction in the replaced sand layer under breakwater using 14 earthquakes in 5.6-7.9 scale and artificial earthquakes including the seismic wave suggested in the standard specifications for seismic design of ports and fishing port facilities to evaluate the stability of breakwater which is the primary protective structure for port facilities against earthquakes. Second, analysis on characteristics of the seismic energy and acceleration response spectrum by size of earthquake was performed to suggest the most appropriate size of seismic wave for the condition in Korea. Third, finite element analysis was performed using the suggested seismic wave to study the characteristics of earthquake by finding the dynamic lateral displacement of breakwater and verifying the stability of structure and the displacement and forces occurring at geotextile. Results of the study showed that the possibility of liquefaction in the landfill and replaced sand layer, the dynamic lateral displacement of breakwater, and changes of geotextile are greatly affected by the subsurface ground (replaced sand layer).

• Journal of the Korean Society for Marine Environment & Energy
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• 제10권2호
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• pp.112-117
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• 2007

This study aims to develop an alternative energy like oil made from marine organic waste by marine products waste, spent fishing nets. There are already many commercial examples and case studies based on the petroleum industry-refuse plastic or refuse tire, however, it is rare that a research developing alternative energy from food waste and organic waste. Therefore, this study investigated the oil made from thermal decomposition under the high temperature and high pressure condition, and examined the possibility for commercial use by testing its own characteristics. A bio-oil from thermal decomposition at $250^{\circ}C$ and 40 atm was hard to remove impurities because of its high viscosity, showed lower caloric value than heavy oil, and generated various gases which were not appropriate for the use of fuel. It is noticeable that thermal decomposition was occurred at $250{\pm}5^{\circ}C$ using steam pressure, which much lower compared to the existing method of thermal decomposition, more than $500^{\circ}C$. Since the high viscosity of bio-oil, it is necessary a further study to use as liquid fuel.

• Journal of the Korean Society for Marine Environment & Energy
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• 제4권2호
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• pp.43-51
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• 2001

Now our ocean environment pollution is very serious. Its harm hinders in marine breeding and the safe navigation of ships at the coast. We have used an assembly system for a measure taken against environment pollution like this. But, here are some problems awaiting solution. First, most of combustible materials among ocean waste are high polymer, so it is necessary some special equipment to incinerate them. In the process we can't overlook air pollution by exhaust gas. Also, when we reclaim these wastes, we remember that they can't be decomposed naturally and leaking water may pollute soil. Thus now a days new treatment method has been developed, it recycles and doesn't product secondary pollution materials by recovering oil from pyrolysis. For it, this study investigated chemicalㆍphysical properties of wastes. And it found condition of recovering the most oil. Also it probed that the variation of temperature raising speed affects the weight reduction characteristics of wastes. Also, while studying recovered oil by waste pyrolysis and the rate of non-condensing gas in accordance with the variation of temperature raising speed. Finally we had confidence the development of pyrolysis oil recovery would succeed because we carried out evaluation at an economic point of view about it.

• Korean Journal of Fisheries and Aquatic Sciences
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• 제14권2호
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• pp.59-65
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• 1981

The purpose of the present study is to find the light intensity which induces maximum gathering rate and to observe the variation of the gathering rate both in daytime and at night by rising two species of commercial fishes: gray rock cod. Sebastes inermis (Cuvier et Valenciennes) and cat shark, Scyliorhinus torazame (Tanaka). An experimental tank $(360L\;{\times}\;50W\;{\times}\;55H\;cm)$ was set up in a dark room. An illumination system was attached to one end of the tank to control horizontal light intensity. Six artificial light sources were prepared by combination of two light bulbs (5W, 150W) and seven filters. During the experiment water depth was maintained 50 cm level in the tank. The tank was marked into six longitudinal sections each being 60 cm long to observe the distribution of fish. The fish were acclimatized in dark condition for 40 minutes prior to the main experiment. Upon turning on the light, the number of fish in each section was counted 40 times every 30 seconds, and the gathering rates were obtain from the average number of fish in each section. The light intensity inducing maximum gathering rate is as follows: gray rock cod: 16.6 lux (10.6-24.5 lux) (day), 0.7 lux (0.5-1.1 lux) (night), cat shark: 1.9 lux (1.2-2.9 lux) (day), 16.6 lux(10.6-24.5lux) (night). Trend of the gathering rate in illumination time revealed different results in two fish species. Gathering rate of gray rock cod did not show any definite pattern but fluctuated irregularly. The gathering rate was some fluctuating at night. However, that of cat shark was almost constant and did not show any distinctive difference between day and night.

• The Journal of Art Theory & Practice
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• 제13호
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• pp.35-71
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• 2012

The purpose of this essay is to examine the responses of artists on nuclear experiences through an analysis of the nuclear images represented in contemporary Japanese art. Japan has previously as twice experienced nuclear disaster in 20th century. The first atomic bombs were dropped in 1945 as well as the 5th Fukuryumaru, Japanese pelagic fishing boat, exposed by hydrogen bomb test operated by the US in 1954 nearby Bikini atoll. Due to Tsunami taken place by the great earthquake that caused the meltdown of Fukushima Nuclear Power Plant in March 2010, Japan is being experienced a nuclear disaster again. Despite practical experiences, comtemporary Japanese art has avoided the subject of nuclear disasters since the end of the Asia-Pacific War for a variety of reasons. Firstly, GHQ prohibited to record or depict the terrible effect of atomic bomb until 1946. Secondly, Japanese government has tried to sweep the affair under the carpet quite a while a fact of nuclear damage to their people. Because Japan has produced numerous war record paintings during the Second World War, in the aftermath of the defeated war, most of Japanese artists thought that dealing with politics, economics, and social subject was irrelevant to art as well as style of amateur in order to erase their melancholic memory on it. In addition, silence that was intended to inhibit victims of nuclear disasters from being provoked psychologically has continued the oblivion on nuclear disasters. For these reasons, to speak on nuclear bombs has been a kind of taboo in Japan. However, shortly after the atomic bomb dropped on Hiroshima, the artist couple Iri and Toshi Maruki visited to ruin site as a volunteer for Victim Relief. They portrayed the horrible scenes of the legacy of nuclear bomb since 1950 based on their observation. Under the condition of rapid economical growth in 1960s and 1970s, Japanese subculture such as comics, TV animations, plastic model, and games produced a variety of post apocalyptic images recalling the war between the USA and Japanese militarism, and battle simulation based on nuclear energy. While having grown up watching subculture emerged as Japan Neo-Pop in 1990s, New generation appreciate atomic images such as mushroom cloud which symbolizes atomic bomb of Hiroshima. Takashi Murakami and other Neo-Pop artists appropriate mushroom cloud image in their work. Murakami curated three exhibitions including and persists in superflat and infantilism as an evidence in order to analyze contemporary Japanese society. However, his concept, which is based on atomic bomb radiation exposure experience only claimed on damage and sacrifice, does not reflect Japan as the harmer. Japan has been constructing nuclear power plants since 1954 in the same year when the 5th Fukuryumaru has exposed until the meltdown of Fukushima Nuclear Plant although took place of nuclear radiation exposures of Three Mile and Chernobyl. Due to the exploding of Fukushima Nuclear Power Plant, Japan reconsiders the danger of nuclear disaster. In conclusion, the purpose of this paper may be found that the sense of victim which flowed in contemporary art is able to inquire into the response of artist on the subject of nuclear as well as the relationship between society, politics, culture, and modern history of Japan and international political situation.

• Korean Journal of Fisheries and Aquatic Sciences
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• 제12권4호
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• pp.201-207
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• 1979

The stow net now used in the Yellow Sea, are traditional bag net with the opening held by a lighter upper and a weighted lower beams standing against the current. Such bag net anchored at the bottom are known in many countries, particularly in the estuaries of large rivers, but more rarely in sea fisheries, because they are too much affected by the weather, moreover a permanent strong current is necessary. Some scientists intended to improve this fishing gear, using the shearing devices instead of a lighter upper and a weighted lower beams in order to widen mouth of the stow net however they are unsuccessful. One-fortieth scale model net of the stow net was tested in a circular water tank with an effective volume of $5.67m\times1.76m\times1.00m$ of observing the configuration and tension of the net. Experiments were carried out under the various combination including water velocity, spherical floats and elevating floats with the shearing hoods instead of the upper beam. We found those devices offered a very low resistance per net area to current compared with the spherical floats or upper beam, and had a fairly good shearing power at any velocity and direction of the current. The total resistance (R) of the model net to which shearing hoods and floats are attached can be induced by the following formula under the condition of 0.25m/sec to 0.5m/sec, $$R(kg)=3.11V^{1.54}$$ The height (h) of the improved model net (m-B) is higher than traditional model net(m-A) with upper and lower beams, m-A: h(cm)=89.22-2.42(V-15). $V\geqq15,\;cm/sec$ m-B: h(cm)=89.20-0.78V (V:cm/sec) The catch efficiency of improved model net is 1.5 times traditional model net.

• Korean Journal of Ecology and Environment
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• 제46권3호
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• pp.395-408
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• 2013

Environmental condition can induce changes in early life-history traits in order to maximise the ecological fitness. Here I investigated how temperature change and variation in human aquatic activity/behaviour affect early life-history consequences in fish using a dynamic-state-dependent model. In this study, I developed a general fish's life-history model including three life-history states depend-ing on foraging activity, such as body mass, mass of reproductive tissue (i.e., gonadal development) and accumulated stress (i.e., cellular or physiological damage). I assumed the level of foraging activity maximises reproductive success-ultimately, fitness. The model predicts that growth rate, development of reproductive tissues and damage accumulation are greater in higher temperature whereas higher human aquatic activity rapidly reduced the growth rate and development of reproductive tissue and increased damage accumulation. While higher foraging activity in higher temperature is less affected by human aquatic activity, the foraging activity in lower temperature rapidly declined with human aquatic activity. Moreover, lower survival rate in higher temperature or human aquatic activity was independent on mortality rate due to human aquatic activity or mortality rate when foraging activity, respectively. However, the survival rate in lower temperature or human aquatic activity was dependent on these mortality rates. My findings suggest that including of early life-history traits in relation to climate-change and human aquatic activity on the analysis may improve conservation plan and health assessment in aquatic ecosystem.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• 제53권4호
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• pp.471-475
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• 2017

This study aims to suggest the methodology to improve to estimate back-calculated fish growth parameters using weighted average. It is to contribute to correct errors in the calculation of back-calculated growth equation with unequal numbers of sample by age. If the numbers of sample were evenly collected by age, each back-calculated length at age was equal between arithmetic and weighted averages. However, most samples cannot be evenly collected by age in reality because of different catchability by fishing gear and limitation of environment condition. Therefore, the estimation of back-calculated length by weighted average method is essential to calculate growth parameters. There were some published growth equations from back-calculated length using a simple arithmetic average with different numbers of samples by age when searching for back-calculated growth equations from 91 relevant papers. In this study, the process of deriving growth equation was investigated and two different average calculations were applied to a fish growth equation, for example of Acheilognathus signifer. Growth parameters, such as $L_{\infty}$, k and $t_0$, were estimated from two different back-calculated averages and the growth equations were compared with growth performance index. Based on the correction of back-calculated length using weighted average by age, the changes by female and male were -14.19% and -5.23% for $L_{\infty}$, and 59.28% and 18.91% for k, respectively. The corrected growth performance index by weighted average improved at 7.05% and 2.46% by female and male, respectively, compared to the arithmetic averages.

• Korean Journal of Ichthyology
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• 제32권3호
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• pp.148-159
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• 2020

This study investigated the seasonal and inter-annual changes in vertical distribution and size spectrum of walleye pollock, Gadus chalcogrammus inhabiting middle eastern coast of Korea (hear after pollock). Pollock was distributed between 50 m and 600 m depth range, and body size (total length) ranged from 16.6 cm to 81.5 cm. The trends of population body size were increased in autumn and winter and decreased in spring and summer. Vertical distribution of pollock showned depth-dependent patterns with distributing smaller individuals mainly in the upper layer (shallower depth), while larger fish in deeper habitats. Those patterns in vertical distribution of pollock population is probably due to be the results of energy-saving strategy, metabolic effects, and changes in prey selections according to pollock growth, derived from spatial and temporal changes in oceanic condition in habitat grounds. When water temperature in upper layer were increased and that of below thermocline depth became decreased in 2017, the ratio of smaller (<35 cm) and larger (≥35 cm) individuals was biased toward larger fishes, extending their distribution into shallow depth, and consequently main fishing ground was formed in far from coastal area. In addition, the ratio of smaller individual distributing between 100~300 m was increased with decreasing temperature gradient between below thermocline and bottom layer. Changes in spatial and temporal distributions of pollock population likely be related with vertical and horizontal changes in oceanic conditions and, consequently food supplies.

• Korean Journal of Ichthyology
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• 제29권2호
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• pp.146-150
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• 2017

Length and weight relationship (LWR) for dominant Antarctic fishes was determined in two species of the family Nototheniidae; black rockcod (Notothenia coriiceps) and marbled rockcod (Notothenia rossii). Samples were caught in the offshore sea around King Sejong station located on King George Island, Antarctica in January, 2017. A total of 30 N. coriiceps and 7 N. rossii were caught by fishing rod and hook. Average total length was 266.0 mm for N. coriiceps and 275.4 mm for N. rossii. Average total weight was 283.1g for N. coriiceps and 290 g for N. rossii. In terms of LWR and b value, the results showed that both two species had positive allometries (b>3) in good health. This size information of two dominant Antarctic fishes would be useful for future physiological studies to understand of adaptation mechanism and biological pathway of Antarctic marine organisms.