• Journal of the Korean association of regional geographers
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• v.7 no.2
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• pp.71-81
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• 2001

According to the change of stream power/resisting power relationship due to the crustal movement or the climatic change, most channel landforms which reflect the equilibrium state of fluvial system are eroded and a part of them is remained as a river terrace. In many rivers in Korea are extensively distributed the relatively younger low river terraces. But their accurate formation mechanism is not known. In this paper, the formation processes and the dating of low river terraces distributed in Nakdong River basin will be investigated. Stream power of the downward erosion was revived because the sea level fell down. So stream power was superior to the resisting power under the cool-wet climatic condition during the last glacial period. Thus the river bed was excavated deeply, so that low river terraces were built up. And many incised meander loops were cut during this period. But, when fluvial system did not have equilibrium over all reaches, the last glacial period ended and the sea level initiated to rise rapidly. The headward erosion from the fall of sea level during the last glacial period had kept up to Hagye Fall because of the cutting of incised meander loops. Deeply excavated valleys and abandoned channel of cut-meander in lower reaches of a stream were filled with sediments. Thus the longitudinal profile of the uppermost reaches reflect the last interglacial, the upper reaches the last glacial, and the middle/1ower reaches recent fluvial system. Therefore low river terraces have been formed since the last glacial period.

• Journal of the Korean earth science society
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• v.29 no.6
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• pp.454-465
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• 2008

Benthic foraminiferal assemblage and AMS radiocarbon dating of core sediments from the northern shelf of the East China Sea were analyzed in order to understand the paleoenvironment and sedimentary environmental changes around the Korean marginal seas since the last glacial maximum (LGM). The core sediments, containing continuous records of the last 16,000 years, reveal a series of well-defined vertical changes in number of species (S), P/T ratio and species diversity (H) as well as foraminiferal assemblage. Such down-core variations display a sharp change at a core depth of approximately 240 cm, which corresponds to ca. 10,000 year B.P. The sediments of the lower part of the core (240${\sim}$560 cm, Zone I), including the well-developed tide-influenced sedimentary structures, are characterized by high abundances of Ammonia beccarii and Elphidium clavatum (s.l.) and low values in number of species, P/T ratio and diversity. These tide-influenced signatures and foraminiferal assemblage characters suggest that the sediments of Zone I were deposited in a coastal environment (water depths of 20${\sim}$30 m) such as tidal estuary with an influence of the paleo-rivers (e.g., old-Huanghe and Yangtze rivers) during the early phase of the sea-level rise (ca. 16,000 to 10,000 years) since the LGM. In contrast, the upper core sediments (0${\sim}$240 cm, Zone II) are characterized by abundant Eilohedra nipponica and Bolivina robusta with a minor contribution of A. ketienziensis angulata and B. marginata. and high values in number of species, P/T ratio and diversity. Based on relative abundance of these assemblage, Zone II can be divided into two subzones (IIa and IIb). Zone IIa is interpreted to be deposited under the inner-to-middle shelf environment during the marine transgression in the early Holocene (after ca. 9,000 yr B.P.) when sea level rapidly increased. The sediments of zone IIb most likely deposited after 6,000 yr B.P. under the outer shelf environment (80${\sim}$100 m water depth), which is similar to modem depositional environments. The muddy sediments of zone IIb were probably transported from the old-Huanghe and Yangtze Rivers during the late Holocene. We suggest that the present-day oceanographic conditions over the Yellow and the East China Seas have been established after ca. 7,000${\sim}$6,000 yr B.P. when the Kuroshio Current began to influence this area.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.14 no.1
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• pp.10-21
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• 2009

Muan Bay has extensively undertaken artificial influences through a series of construction of dams and dykes nearby resulting in a substantial increase in highest high water level. To unravel sedimentary responses to the water level rise, we collected a number of surface sediment samples and hydrodynamic data from in-situ observations of tidal currents in Muan Bay in 1998 and 2007. Comparison of the data between 1998 and 2007 shows that the relative content of coarse fractions, sand and gravel, in the sediment samples has increased with a decreased mean size, on average, from 6.2 to 5.8${\phi}$ at the expense of silt contents. Such a coarsening trend, which is more evident around high water level, particularly on the tidal flats of Dongam-ri, Guro-ri and Aphae-do, is most likely attributable to rising water level. On the other hand, an increase of fine fractions locally in the western entrance of the bay can be explained with changes in characteristics of tidal currents imposed by construction of bridges therein, such as decreased velocities and varied direction and phase of the tidal currents.

• Journal of Korean Society on Water Environment
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• v.35 no.6
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• pp.580-588
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• 2019

The flow of the middle and downstream of the Yeongsan River is stagnant by two weirs of Seungchon and Juksan and the estuary dam and maintained in freshwater. In this study, the Environmental Fluid Dynamics Code-National Institute of Environment Research(EFDC-NIER) model was applied to the Yeongsan River to simulate water flow, temperature, and salinity stratification. The EFDC-NIER model is an improved model which can simulate multi-functional weirs operation, multiple algal species, and the vertical movement mechanism of algal based on the EFDC model. The simulation results for the water level, water temperature, velocity, and salinity reproduced the observed values well. The mean absolute error(MAE) of the model calibration in the annual variations of the water level was 0.1-0.3 m, water temperature was 0.8-1.7 ℃, velocity was 4.5-7.1 cm/sec, and salinity was 1.5 psu, respectively. In the case of scenario simulation for the full opening of the estuary dam, the water level of the estuary dam was directly impacted by the tide so it was predicted to rise - 1.35 m to 0.2 m on average sea level. The velocity was also predicted to increase from 2.7 cm/sec to 50.8 cm/sec, and the flow rate to increase from 53 ㎥/sec to 5,322 ㎥/sec.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.1B
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• pp.99-106
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• 2006

Due to both global warming and constructions of seadike/seawalls, continuously or abruptly rising tendencies of extreme high water levels have been detected at Kunsan and Mokpo harbors. This paper deals firstly with the separation of each effect, namely global warming effect and construction effect, on increases of water level quantitatively by a linear regression method. And then, it can be explained why and how the extreme high water levels had been risen just after constructions at both harbors. A numerical simulation of $M_2$ tidal constituent at Mokpo coastal zone shows that the tidal amplification by constructions is mainly due to the extinguishment of TCE at Mokpogu. The tidal flat effect makes the amplification more deepen at spring tide or extreme high tide, which results in the increase of inundation risk at Mokpo harbor. A frequency analysis method is applied, which is shown to be effective at such a site of having non-homogeneous tidal data due to constructions as Mokpo harbor.

• Atmosphere
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• v.20 no.3
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• pp.379-386
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• 2010

Impact of global warming on the ocean environment is reviewed based on most recently published publications. The most significant impact of global warming on marine environment is due to the melting of mountain and continental glaciers. Ice melting causes slow down and/or shut down of thermohaline circulation, and makes hypoxic environment for the first time, then makes anoxic with time. This can cause decreasing biodiversity, and finally makes global extinction of animals and plants. Furthermore, global warming causes sea-level rise, soil erosion and changes in calcium carbonate compensation depth (CCD). These changes also can make marine ecosystem unstable. If we emit carbon dioxide at a current rate, the global mean temperature will rise at least $6^{\circ}C$ at the end of this century, as predicted by IPCC (Intergovernmental Panel on Climate Change). In this case, the ocean waters become acidic and anoxic, and the thermohaline circulation will be halted, and marine ecosystems collapsed.

• Journal of Marine Bioscience and Biotechnology
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• v.3 no.1
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• pp.54-60
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• 2008

Compared to other North African countries, Tunisia has reached a significant level of fish consumption. The only relevant historical dimension of aquaculture in Tunisia are traditional lagoon management (80,000 ha of lagoon and coastal lakes) and culture of shellfish. Semi-intensive and intensive cultures are relatively new concepts in Tunisia and only recently also the public sector is involved. The Tunisian fishing industry has expanded over the last 20 years and annual catches at present are more than four times those registered in mid-fifties. Production of the year 2007 reached 105 thousand tons against 111 thousand tons during the same period of 2006 thus recording a fall of 5%. Unfavorable weather conditions mainly during the last quarter year had the effect to reduce the number of days out at sea. Exports reached 24.3 thousand tons for one value 240.5 MD against respectively 22.2 thousand tons and 234.1 thus recording MD at the end of the past year a rise of 9% in volume and from 3% in value. Commercial value such as shellfish - consequence of one regression of the production - with in parallel raises blue fish exports. The imports were stabilized in volume of 39.1 thousand tons and increased from 6% in value with respectively 67.4 MD in 2007 against 63.7 MD at the end of 2006. The importation in larger quantities of intended fish to the fattening of tuna in floating cages explains partly this rise. Nevertheless, the pay of balance import/export of produced fishing remains positive with a surplus of 173.1 MD against 170.4 MD in 2006.

• Journal of Appropriate Technology
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• v.5 no.2
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• pp.118-125
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• 2019

Climate change is one part of 17 Sustainable Development Goals (SDGs). According to the Fifth Assessment Report by the Inter- governmental Panel on Climate Change(IPCC) published in 2014, global warming is caused by greenhouse gas (GHG) emissions. The most important GHG is carbon dioxide (CO₂), which is released by the burning of fossil fuels and, to a lesser extent, by land use practices, followed by nitrous oxide and methane. IPCC predicts that global temperatures will rise 3.7℃ and sea level will rise 0.63 m by 2099 in the case of no strong restraint. According to the report, we can expect a massive species extinctions, changes in storm and drought cycles, altered ocean circulation, and redistribution of vegetation by global warming. However, climate changes, especially global warming, are the largest potential threat to human health and the source of a number of diseases globally. If climate changes are continued uncontrolled, human health will be adversely affected by the accelerating climate change and the natural disaster induced by climate change. It means we will face more serious conditions of injury, disease, and death related to natural disasters such as flood, drought, heat waves, malnutrition, more allergy, air pollution and climate change related infections related to morbidity and mortality. This review emphasizes on the relationship between global climate changes and human health and provides some suggestions for improvement.

• Journal of the Korean Society of Marine Environment & Safety
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• v.26 no.5
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• pp.506-513
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• 2020

Due to climate change, there is an increasing risk of complex (hybrid) disasters, comprising rising sea-levels, typhoons, and torrential rains. This study focuses on Marine City, Busan, a new residential city built on a former landfill site in Suyeong Bay, which recently suffered massive flood damage following a combination of typhoons, storm surges, and wave overtopping and run-up. Preparations for similar complex disasters in future will depend on risk impact assessment and prioritization to establish appropriate countermeasures. A framework was first developed for this study, followed by the collection of data on flood prediction and socioeconomic risk factors. Five socioeconomic risk factors were identified: (1) population density, (2) basement accommodation, (3) building density and design, (4) design of sidewalks, and (5) design of roads. For each factor, absolute criteria were determined with which to assess their level of risk, while expert surveys were consulted to weight each factor. The results were classified into four levels and the risk level was calculated according to the sea-level rise predictions for the year 2100 and a 100-year return period for storm surge and rainfall: Attention 43 %, Caution 24 %, Alert 21 %, and Danger 11 %. Finally, each level, indicated by a different color, was depicted on a complex disaster risk map.

• Journal of Advanced Navigation Technology
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• v.20 no.1
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• pp.29-36
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• 2016

Accuracy of GPS (global positioning system) deteriorates dramatically or positioning is impossible in urban area occasionally since high-rise buildings and elevated roads make the reception of navigation signal very difficult so that number of visible satellites decreases. In these cases, vertical error usually becomes much larger than the horizontal error due to the intrinsic geometry of GPS satellites. To obtain more accurate and reliable height information, this paper proposes a hybrid method that combines GPS and a low-cost barometric altimeter. In the proposed method, the sea-level pressure and the sea-surface temperature are applied to the output of the altimeter. Next, the difference between the ellipsoid and the geoid is compensated. Finally, a simple Kalman filter combines the compensated barometric altitude and the GPS height. By static and car experiments, performance of the proposed method is evaluated. By the experiment results, it can be seen that the proposed method improves the altitude accuracy considerably.