• Atmosphere
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• v.21 no.1
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• pp.69-83
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• 2011

The synoptic condition of clear-air turbulence (CAT) events occurred over South Korea is investigated, using the Regional Data Assimilation and Prediction System (RDAPS) data obtained from the Korea Meteorological Agency (KMA) and pilot reports (PIREPs) collected by Korea Aviation Meteorological Agency (KAMA) from 1 Dec. 2003 to 30 Nov. 2008. Throughout the years, strong subtropical jet stream exists over the South Korea, and the CAT events frequently occur in the upper-level frontal zone and subtropical jet stream regions where strong vertical wind shears locate. The probability of the moderate or greater (MOG)-level turbulence occurrence is higher in wintertime than in summertime, and high probability region is shifted northward across the jet stream in wintertime. We categorize the CAT events into three types according to their generation mechanisms: i) upper-level front and jet stream, ii) anticyclonically sheared and curved flows, and iii) breaking of mountain waves. Among 240 MOG-level CAT events reported during 2003-2008, 103 cases are related to jet stream while 73 cases and 25 cases are related to the anticyclonic shear flow and breaking of mountain wave, respectively.

• International Journal of High-Rise Buildings
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• v.7 no.4
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• pp.363-374
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• 2018

The façade is an important, complex, and costly part of a building, performing multiple objectives of value to the occupants, like protecting from wind, rain, sunlight, heat, cold, and sound. But the frequency of façade fires in large buildings is alarming, and has multiplied by seven times worldwide over the last three decades, to a current rate of 4.8 fires per year. High-performing polymer based materials allow for a significant improvement across several objectives of a facade (e.g., thermal insulation, weight, and construction time) thereby increasing the quality of a building. However, all polymers are flammable to some degree. If this safety problem is to be tackled effectively, then it is essential to understand how different materials, and the façade as a whole, perform in the event of a fire. This paper discusses the drivers for flammability in facades, the interaction of facade materials, and current gaps in knowledge. In doing so, it aims to provide an introduction to the field of façade fires, and to show that because of the drive for thermal efficiency and sustainability, façade systems have become more complex over time, and they have also become more flammable. We discuss the importance of quantifying the flammability of different façade systems, but highlight that it is currently impossible to do so, which hinders research progress. We finish by putting forward an integral framework of design that uses multi-objective optimization to ensure that flammability is minimized while considering other objectives, such as maximizing thermal performance or minimizing weight.

• Wind and Structures
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• v.34 no.3
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• pp.313-319
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• 2022

The resiliency of electricity transmission and distribution lines towards natural and man-made hazards is critical to the operation of cities and businesses. The extension of these lines throughout the country increases their risk of extreme loading conditions. This paper investigates a unique extreme loading condition of a 100-year old distribution line segment that passes across a river and got entangled with a boom of a ship. The study adopts the Applied Elements Method (AEM) for simulating 54 cases of the highly deformable structural behaviour of the tower. The most significant effects on the tower's structural integrity were found to occur when applying the load with components in all three of the cartesian directions (i.e., X, Y and Z) with the full capacities of the four cables. The studied extreme loading condition was determined to be within the tower's structural capacity, attributed to the shear failure of the anchor bolts, which acted as a sacrificing element that fails to protect the transfer of tensioning load to the supporting tower.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.25 no.1
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• pp.15-28
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• 1992

Temporal variations of the path of the East Korea Warm Current(EKWC) which flows northward along the east coast of Korea were analysed to investigate whether the EKWC directly influences the existence of the so-called Warm Core in the Ulreung basin. From the 13 years(1975-1987) data of the Fisheries Research and Development Agency(FRDA), the $10^{\circ}C$ isotherm at the 100m depth and the depth of $2^{\circ}C$ isotherm and the temperature field at the 200m depth were used for identification of the path and the central position of the Warm Core. Sea surface winds computed from the surface pressure charts gave the monthly-averaged wind stress curl over the East Sea which was used for determination of the Sverdrup transport. And the mass transport stream functions were computed by use of the Sverdrup balance. The variations of the path show that the EKWC does not always have a fixed path and fluctuates with time. And the existence of the Warm Core is independent upon the presence of the EKWC even when the EKWC doesn't flow northward along the east coast of Korea. In view of the mass transport stream functions, the influences of the sea surface winds on the branching of the Tsushima Warm Currents and the presence of the EKWC were investigated. The presence of the EKWC may be hindered by the southward flow driven by the sea surface winds when the Tsushima currents are rather weak. A very weak correlation exists between the north-south component of the Sverdrup transport and the position of the Warm Core. However, a small but significant part of the southward transport across the latitudinal line of $38^{\circ}N$ indicates that cold water from the northern part of the East Sea may be driven and be forced to flow beneath the permanent thermocline in such a way that the thermal structure of the Warm Core and its position might be changed.

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.6
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• pp.738-749
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• 2016

To understand the characteristics of the spatio-temporal distribution of phytoplankton after barrage construction in the Nakdong River Estuary, this study investigated relevant environmental parameters and phytoplankton status based on bi-monthly samples collected from the Nakdong River Estuary itself from February 2013 to December 2015. Environmental parameters did not differ significantly across these years but did vary between zones and seasons. The results suggested that the upper zone was dominated by fresh-water diatoms, green algae, and blue-green algae, whereas the lower zone was mostly dominated by dinoflagellates. The presence of Stephanodiscus spp., Asterionellopsis formosa, and Microcystis spp. in the upper zone was related to the inflow of freshwater discharge by artificial control of dyke gates. The dominant phytoplankton species in this zone were dependent on temperature, wind speed, DIP, and DIN, while those in the lower zone were mostly dependent on nutrients and wind speed. In addition, at the lower zone, there were negative correlations between Prorocentrum donghaiense, DIN, and wind speed, with its abundance being higher during the summer than other seasons. Analysis of temporal variations did not indicate any significant differences in the upper zone but did reveal variations among seasons at the lower zone. Except in 2014, the lower zone could be divided into periods dominated by diatoms (October-April) and dinoflagellates (June-August). These results suggest that the characteristics of the phytoplankton community were influenced by changes in the inflow of freshwater species and nutrients given the difference in the range affected by freshwater discharge.

• Wind and Structures
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• v.7 no.5
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• pp.317-332
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• 2004

Wind tunnel experiments were conducted under highly turbulent and disturbed flow conditions over a solid/perforated plate with a long splitter plate in its plane of symmetry. The effect of varied level of perforation of the normal plate on fluctuating velocities and fluctuating pressures measured across and along the separation bubble was studied. The different perforation levels of the normal plate; that is 0%, 10%, 20%, 30%, 40% and 50% are studied. The Reynolds number based on step height was varied from $4{\times}10^3$ to $1.2{\times}10^4$. The shape and size of the bubble vary with different perforation level of the normal plate that is to say the bubble is reduced both in height and length up to 30% perforation level. For higher perforation of the normal plate, bubble is completely swept out. The peak turbulence value occurs around 0.7 to 0.8 times the reattachment length. The turbulence intensity values are highest for the case of solid normal plate (bleed air is absent) and are lowest for the case of 50% perforation of the normal plate (bleed air is maximum in the present study). From the analysis of data it is observed that $\sqrt{\overline{u^{{\prime}2}}}/(\sqrt{\overline{u^{{\prime}2}}})_{max}$, (the ratio of RMS velocity fluctuation to maximum RMS velocity fluctuation), is uniquely related with dimensionless distance y/Y', (the ratio of distance normal to splitter plate to the distance where RMS velocity fluctuation is half its maximum value) for all the perforated normal plates. It is interesting to note that for 50% perforation of the normal plate, the RMS pressure fluctuation in the flow field gets reduced to around 60% as compared to that for solid normal plate. Analysis of the results show that the ratio [$C^{\prime}_p$ max/$-C_{pb}(1-{\eta})$], where $C^{\prime}_p$ max is the maximum coefficient of fluctuating pressure, $C_{pb}$ is the coefficient of base pressure and ${\eta}$ is the perforation level (ratio of open to total area), for surface RMS pressure fluctuation levels seems to be constant and has value of about 0.22. Similar analysis show that the ratio $[C^{\prime}_p$ max/$-C_{pb}(1-{\eta})]$ for flow field RMS pressure fluctuation levels seems to be constant and has a value of about 0.32.

• Journal of the Korean earth science society
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• v.26 no.7
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• pp.652-660
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• 2005

The distribution of PM10 was investigated using its measurement data collected from a total of 152 AQM stations located across South Korea from 1998 to 2003. It was found that PM10 concentration reaches its peak in the springtime due to massive wind-blown dusts during the Asian Dust (AD) period. Then the concentration level decreases in the summertime, after the rain shower season. When the PM10 data sets were compared across different cities, their patterns contrasted sharply. The highest PM10 concentration was measured in Seoul $(68.2{\mu}g/m^3)$, while the lowest PM10 concentration was measured in Jeju $(39.2{\mu}g/m^3)$. The results of our analysis indicate that PM10 concentrations exhibit a strong proportional relationship with respect to the size of the city. With respect to the correlation analysis of our results, it was evident that PM10 concentrations of nearby cities were found to affect each other.

• Korean Journal of Environmental Biology
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• v.34 no.1
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• pp.30-36
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• 2016

We investigated the diversity pattern of spring moths across two regions of South Korea, Yongin city (middle part) and Muan gun (southern part) and the effects of climatic variables on moth species richness and abundance. Moths were weekly collected using UV light trap in April from 2013 to 2015. Climatic factors included growth degree day with base temperature 8 (GDD8), average temperature, precipitation, duration of sunshine, wind speed, and snow cover. The climatic effects on moth species richness and abundance were analyzed by short (0~3 weeks before collecting) and long (4~12 weeks before collecting) time periods, respectively. The diversity of spring moths showed the similar pattern of species composition at family level. However the dominant family differed depending on the region: Geometridae at middle part and Noctuidae at southern part. In addition the dominant species of Noctuidae occurred early in April and that of Geometridae moths occurred later in April. Three short-term climatic factors, GDD8, duration of sunshine, and precipitation one week before collecting were significant on moth species richness and abundance, while only one long-term climatic factor, temperature four weeks before collecting was significantly affected on moth species richness. We found that both Geometridae and Noctuidae were dominant in spring moth fauna across South Korea and they were different in the dominance and flying time in April. The occurrences of spring moths were largely affected by warmness and precipitation. The current global warming could affect the occurrence of spring moths and this should be monitored consistently.

• Journal of Environmental Science International
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• v.3 no.2
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• pp.111-128
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• 1994

The distributions of sea surface temperature across the Cheju Strait and the Korea Strait have been measured by using a thermometer installed on board No.1 Cheju, a ferry that operates regularly between Pusan and Seogwipo. The data from 14 October 1991 to 15 August 1992 were analyzed in this paper. A clear temperature front is wormed at the adjacent sea of Geomundo, and its position is not fixed and moves north and south. The slow northward movement of the front can easily be traced, but the southward movement from March to October is obscure. The temperature contrast in the Cheju Soait and the Korea Strait is very we in this period. Some periodical fluctuations with a period of several tens of days are observed in the region of the temperature front from November to February. This fluctuation seems to be caused by winter heat flux exchange and the strong southeastward wind force. The result shows that continous observation of the sea surface temperature distribution across the Cheju Strait and the Korea Strait yields a good method for monitoring the presence of Tsushima Warm Current and the fluctuations of South Korea Coastal Water. The formation and structure of shelf front in the Cheju Strait and the Korea Strait was analysed based on the detailed oceanographic data observed during the period of 1990-1992. The analysis shows that well-defined fronts were formed through yearly around the Chuja Island, particularly, in summer. In nature, its structure and formation position can be changed easily from year % year and by season. But, in region of the Korea Strait this front is relatively weak.

• Ocean Science Journal
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• v.40 no.1
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• pp.25-44
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• 2005

Long-term, continuous, and real-time ocean monitoring has been undertaken in order to evaluate various oceanographic phenomena and processes in the East/Japan Sea. Recent technical advances combined with our concerted efforts have allowed us to establish a real-time monitoring system and to accumulate considerable knowledge on what has been taking place in water properties, current systems, and circulation in the East Sea. We have obtained information on volume transport across the Korea Strait through cable voltage measurements and continuous temperature and salinity profile data from ARGO floats placed throughout entire East Sea since 1997. These ARGO float data have been utilized to estimate deep current, inertial kinetic energy, and changes in water mass, especially in the northern East Sea. We have also developed the East Sea Real-time Ocean Buoy (ESROB) in coastal regions and made continual improvements till it has evolved into the most up-to-date and effective monitoring system as a result of remarkable technical progress in data communication systems. Atmospheric and oceanic measurements by ESROB have contributed to the recognition of coastal wind variability, current fluctuations, and internal waves near and off the eastern coast of Korea. Long-tenn current meter moorings have been in operation since 1996 between Ulleungdo and Dokdo to monitor the interbasin deep water exchanges between the Japanese and Ulleung Basins. In addition, remotely sensed satellite data could facilitate the investigation of atmospheric and oceanic surface conditions such as sea surface temperature (SST), sea surface height, near-surface winds, oceanic color, surface roughness, and so on. These satellite data revealed surface frontal structures with a fairly good spatial resolution, seasonal cycle of SST, atmospheric wind forcing, geostrophic current anomalies, and biogeochemical processes associated with physical forcing and processes. Since the East Sea has been recognized as a natural laboratory for global oceanic changes and a clue to abrupt climate change, we aim at constructing a 4-D continuous real-time monitoring system, over a decade at least, using the most advanced techniques to understand a variety of oceanic processes in the East Sea.