• Wind and Structures
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• v.38 no.4
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• pp.309-323
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• 2024

The gust factor and turbulence intensity are two crucial parameters that characterize the properties of turbulence. In tropical cyclones (TCs), these parameters exhibit significant variability, yet there is a lack of established formulas to account for their probabilistic characteristics with consideration of their inherent connection. On this condition, a probabilistic analysis of gust factors and turbulence intensities of TCs is conducted based on fourteen sets of wind data collected at the Sutong Cable-stayed Bridge site. Initially, the turbulence intensities and gust factors of recorded data are computed, followed by an analysis of their probability densities across different ranges categorized by mean wind speed. The Gaussian, lognormal, and generalized extreme value (GEV) distributions are employed to fit the measured probability densities, with subsequent evaluation of their effectiveness. The Gumbel distribution, which is a specific instance of the GEV distribution, has been identified as an optimal choice for probabilistic characterizations of turbulence intensity and gust factor in TCs. The corresponding empirical models are then established through curve fitting. By utilizing the Gumbel distribution as a template, the nexus between the probability density functions of turbulence intensity and gust factor is built, leading to the development of a generalized probabilistic model that statistically describe turbulence intensity and gust factor in TCs. Finally, these empirical models are validated using measured data and compared with suggestions recommended by specifications.

• Atmosphere
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• v.18 no.3
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• pp.183-197
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• 2008

The purpose of this study is to summarize tropical cyclone activity in 2007. 24 tropical cyclones of tropical storm (TS) intensity or higher formed in the western North Pacific and the South China Sea in 2007. The total number is less than the thirty-year (1971~2000) average frequency of 26.7. Out of twenty four tropical cyclones, 14 TCs reached typhoon (TY) intensity, while the rest 10 only reached severe tropical storm (STS) and tropical storm (TS) intensity - four STS and six TS storms. The tropical cyclone season in 2007 began in April with the formation of KONG-REY (0701). From April to May, two TCs formed in the western North Pacific in response to enhanced convective activity there. From June to July, convective activity turned inactive over the sea around the Philippines and in the South China Sea, and the subtropical high was weak over the south of Japan. MAN-YI (0704) and USAGI (0705) moved northwestward and hit Japan, bringing serious damage to the country. After August, convective activity became enhanced over the sea east of the Philippines, and the subtropical high turned strong over the sea south of Japan. Many TCs, which formed over the sea east of the Philippines and in the South China Sea, moved westward and hit China and Vietnam. PABUK (0706), WUTIP (0707), SEPAT (0708), WIPHA (0712), LEKIMA (0714) and KROSA (0715) brought serious damage to some countries including China, the Philippines and Vietnam. On the other hand, FITOW (0709) and NARI (0711) moved northward, bringing serious damage to Japan and Korea. After HAIYAN (0716), all four TCs except FAXAI (0720) formed over the sea east of $140^{\circ}E$. Three typhoons among them affected Republic of Korea, MAN-YI (0704), USAGI (0705) and NARI (0711). Particularly, NARI (0711) moved northward and made landfall at Goheng Peninsula ($34.5^{\circ}N$, $127.4^{\circ}E$) in 1815 KST 16 September. Due to $11^{th}$ typhoon NARI, strong wind and record-breaking rainfall amount was observed in Jeju Island. It was reported that the daily precipitation was 420.0 mm at Jeju city, Jeju Island on 16 September the highest daily rainfall since Jeju began keeping records in 1927. This typhoon hit the southern part of the Korean peninsula and Jeju Island. 18 people lost their lives, 14,170 people were evacuated and US$ 1.6 billion property damage was occurred.

• Journal of the Korean association of regional geographers
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• v.17 no.2
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• pp.150-166
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• 2011

This study aims to investigate the differences of synoptic characteristics and frontal structures over East Asia according to the main path types of water vapor flux (WVF) of 850hPa surface in cases of the heavy rainfall in the south coastal region of Korea during the Changma season (June and July), In the cases of type A in which the main path of WVF is running from the South china Sea via the South china to the South Sea of Korea, the North Pacific subtropical anticyclone (NPSA) expands to the South China and strong cyclones appear in the Yellow Sea. In cases of type B and C in those the main paths of WVF are running from the South China Sea via the Western Pacific Ocean near Taiwan to the South Sea and from the Western North Pacific Ocean to the South Sea respectively, tropical cyclones appear frequently near Taiwan and the NPSA shifts northward. In the case of type D in which the main path of WVF appear only near the South Sea, strong cyclones appear near the Yellow Sea. In all cases upper jets are intensified in the northern part of the heavy rainfall region and low-level jets appear near the main paths of WVF. In the view of frontal structure, deep active-type of the Changma front is identified in most cases of all types. In this point the Changma season is different from the Baiu season in Western Japan where many cases of shallow active-type of the Baiu front appear.

• Journal of the Korean earth science society
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• v.31 no.4
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• pp.322-334
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• 2010

Spatiotemporal characteristics of precipitation in Korea, associated with the weakening of Tropical Cyclones (TCs) around the Korean Peninsula ($32-36^{\circ}N$, $122-132^{\circ}E$) over the last 30 years (1979-2008), were investigated. Weakened TCs are classified as WEC (Weakened to Extratropical Cyclone) and WTD (Weakened to Tropical Depression). In WEC, precipitation was evenly distributed all over the Korean Peninsula and the greater precipitation was recorded in the southern coast. In WTD, the most precipitation was recorded in the southern coast but low precipitation was recorded in the central and inland areas of Korea. The difference of precipitation between WEC and WTD was not statistically significant in Region 2 (Jeollanam-do, Gyeongsangnam-do, southeastern part of Gyeongsangbuk-do, Jeju-do); however, the precipitation resulting from WEC was greater than that resulting from WTD in Region 1 (central area of Korea, Jeollabuk-do, inland of Gyeongsangbuk-do). In WEC, the developed upper-level potential vorticity (PV) and low-level temperature trough shifted to the northwest of TCs approaching Korea. In addition, an upper-level jet stream and strong divergence field were observed to the northeast of the TCs. It was assumed that these meteorological factors had induced baroclinic instability and diabatic process, which created a large precipitation area around the TCs. However, the intense PV, temperature trough, jet stream were not observed in WTD, which created a small precipitation area around the TCs.

• Journal of the Korean earth science society
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• v.43 no.1
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• pp.23-29
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• 2022

Although tropical cyclones with wind speeds weaker than 17 ms^-1 (weak tropical cyclones: WTCs) can cause significant damage, particularly over the Seoul metropolitan area, only a few studies have focused on WTC activity over South Korea. In this study, we found that WTC activity is likely associated with the Pacific Decadal Oscillation (PDO). During the negative phases of the PDO, landfall frequency of WTCs increased significantly compared to the positive phases at 95% confidence level. When related to the negative phases of the PDO, a positive relative vorticity anomaly is found in the northern sector of the western North Pacific while a negative relative vorticity anomaly and enhanced vertical wind shear prevail in the southern sector of the WNP. These factors are favorable for the northward shift of the genesis location of tropical cyclones on average, thereby reducing the total lifetime of WTCs. Moreover, a high-pressure anomaly over the Japanese islands would shift a tropical cyclone track westward in addition to the landfall location. Consequently, the effects of the topographical friction and the Yellow Sea Bottom Cold Water on a tropical cyclone may increase. These conditions could result in a weaker lifetime maximum intensity and landfall intensity, ultimately resulting in WTCs becoming more frequent over South Korea during the negative phases of the PDO.

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 1995.10a
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• pp.5-8
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• 1995

Every few years the low-tying coastal plains of Bangladesh are seriously flooded by storm surges, in which fierce cyclones develop in the Bay of Bengal and then move towards the coast, pushing large masses of sea water onto the land. The coastal areas are densely populated and the combination of high winds and deep floods invariably kills thousands of people. (omitted)

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2002.04a
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• pp.338-341
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• 2002

This work is the basis research to apply Hydrocyclone for the separation and the thickening to the reservoir sediment. Chemical analysis result showed that organic contaminants were abundantly found in smaller sediment particles. As a result of the experiment device that higher reduced efficiency was obtained under the high velocity and low concentration with the small cyclones.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2000.11a
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• pp.419-420
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• 2000

The present study introduces and describes the characteristics of the spiral guide and groove body cyclones for the first time. The spiral guide was set inside the cyclone body or the inside of the cyclone body was grooved circumferentially or vertically. Except for the cyclone body, all configurations were the same. The particle collection efficiency for a conventional cyclone (Figure 1) was measured under a series of flow rates ranging from 15 L/min up to 80 L/min, and was compared with that yielded using existing theories. (omitted)

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1999.11a
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• pp.57-60
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• 1999

순환유동층 보일러는 연소로 (상승관: riser)내에 공기를 고속으로 주입하여 비말동반되는 고체입자를 사이클론에서 포집 하여 재주입하는 유동층을 이르는 것으로, 난류유동층(turbulent fluidized bed), 고속유동층(fast fluidized bed) 그리고 희박상 유동(dilute phase flow) 영역에서 조업이 이루어진다. 순환유동층은 비교적 높은 기체 유속에서 조업이 이루어지기 때문에 고체입자의 혼합 및 비산 그리고 재순환이 격렬하게 이루어지고, 기-고체간 접촉효율 및 전열계수가 높아 전체적인 처리량 및 효율이 좋은 장점을 가지고 있다.(중략)

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2003.05b
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• pp.277-278
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• 2003

Cyclone separators are widely used for cleaning gas streams or for catalyst recovery. For many years, the complexity of the gas flow pattern in cyclones has been a matter of many experimental and theoretical work. At present, precise flow measurements have been performed by means of LDA and hot-wire anemometry (Patterson and Munz, 1996; Hoekstra et al., 1999; Peng et al., 2002). In the theoretical work, Computational fluid dynamics (CFD) codes are frequently employed for simulating cyclone gas-particle flows(Hoekstra et al., 1999). (omitted)