• Journal of the Korean Geographical Society
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• v.51 no.1
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• pp.23-40
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• 2016

In this study, long-term changes in means and extreme events of precipitation during summer rainy period called Changma (late June~early September) are examined based on rainfall data observed by Chukwooki during Joseon Dynasty (1777~1907) and by modern rain-gauge onward (1908~2015) in Seoul, Korea. Also, characterizations of the relevant changes in synoptic climate fields in East Asia are made by the examination of the NCEP-NCAR reanalysis I data. Analyses of 239-year time series of precipitation data demonstrate that the total precipitation as well as their inter-annual variability during the entire Changma period (late June~early September) has increased in the late 20th century and onward. Notably, since the early 1990s the means and extreme events during the summer Changma period (late June~mid-July) and Changma break period (late July~early August) has significantly increased, resulting in less clear demarcations of sub-Changma periods. In this regard, comparisons of synoptic climate fields before and after the early 1990s reveal that in recent decades the subtropical high pressure has expanded in the warmer Pacific as the advection of high-latitude air masses toward East Asia was enhanced due to more active northerly wind vector around the high pressure departure core over Mongolia. Consequently, it is suggested that the enhancement of rising motions due to more active confluence of the two different air masses along the northwestern borders of the Pacific might lead to the increases of the means and extreme events of Changma precipitation in Seoul in recent decades.

• Korean Journal of Remote Sensing
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• v.37 no.6_2
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• pp.1837-1847
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• 2021

This study investigated wind corridors for the entire Suwon-city area using a geographic information system and a computational fluid dynamics model. We conducted numerical simulations for 16 inflow wind directions using the average wind speeds measured at the Suwon automated synoptic observation system (ASOS) for recent ten years. We analyzed the westerly (dominant wind direction) and easterly cases (not dominant but strong wind speed) in detail and investigated the characteristics of a wind speed distribution averaged using the frequencies of 16 wind directions as weighting factors. The characteristics of the wind corridors in Suwon city can be summarized as; (1) In the northern part of Suwon, complicated flows were formed by the high mountainous terrain, and strong (weak) winds and updrafts (downdrafts) were simulated on the windward (leeward) mountain slope. (2) On the leeward mountain slope, a wind corridor was formed along a valley, and relatively strong airflow flowed into the residential area. (3) The strong winds were simulated in a wide and flat area in the west and south part of Suwon city. (4) Due to the friction and flow blocking by buildings, wind speeds decreased, and airflows became complicated in the downtown area. (5) Wind corridors in residential areas were formed along wide roads and areas with few obstacles, such as rivers, lakes, and reservoirs.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.2
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• pp.373-380
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• 1988

The effect of sound on the heat transfer from an isothermal cylinder in cross flow is investigated by numerical analysis. The modeling is made for the laminar incompressible flow fluctuating in the range of the Reynolds number, 5.leq.Re.leq.35, by the sinusoidal acoustic field. The instantaneous response of the flow and heat transfer is simulated for various frequencies. It is shown that the heat transfer amplitude decreases and the phase lags behind the flow velocity with increase in the frequency. The time-mean effects of the acoustic field on the flow field and heat transfer, known as the acoustic and thermoacoustic streaming, are analyzed. The time-mean heat transfer coefficients are decreased around the forward stagnation point but increased in the wake region. Such a local difference in heat transfer coefficients is a function of the frequency and becomes greatest at some frequency. However, with balance between the local increase and decrease, the overall heat transfer coefficient is almost unaffected by sound.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2003.05b
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• pp.245-246
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• 2003

아시아 지역 SO$_2$와 NOx 배출량의 2/3을 차지하는 중국이 1996년에 최대배출량을 기록한 후 석탄사용량 감소 등으로 점차 감소경향을 나타내고 있을지라도 한국을 포함한 동아시아 지역은 여전히 전세계적으로 이들 대기오염물질에 대한 주요 배출원 지역으로 알려져 있다. 대기중으로 배출된 이들 오염물질은 여러가지 반응기구를 통하여 2차 오염물질로 전환되고 기류의 흐름에 따라 풍하지역으로 이동하면서 습성 또는 건성강하물의 형태로 지표면에 침착하는 것으로 알려져 있다. 이러한 이유로 중국의 풍하지역에 위치한 우리나라와 일본에서는 대기오염물질의 장거리 이동에 대한 연구가 활발히 진행되고 있는 실정이다. (중략)

• Proceedings of the Korean Environmental Sciences Society Conference
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• 2006.11a
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• pp.47-51
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• 2006

전주시의 도심 내에 고층건물의 건설전과 후의 풍속변화를 알아보기 위한 풍동실험을 통하여 다음과 같은 결론을 얻을 수 있었다. 고층건물의 건설은 도심주변의 풍속변화에 절대적 영향을 끼치는 요소인 것으로 파악되었다. 특히 건설 후에 최소 50% ${\sim}$ 최대 90%까지 풍속이 감소하는 부분이 발생하고 있다는 점은 고층건물과 같은 인공구조물의 건축과 입지가 주변의 기류변화가 급격한 영향을 주는 요소인 것이다. 이는 해당입지를 중심으로 바람의 원활한 소통이 발생하지 않아 국지적으로 도시기온이 신선한 바람의 흐름에 영향을 받지 않아 온실효과와 같은 현상을 발생시키게 되며, 이는 결과적으로 국지기온의 상승과 같은 문제를 발생시키게 됨을 의미하는 것이다.

• Journal of Korean Society of societal Security
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• v.4 no.1
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• pp.29-37
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• 2011

Recently, Inhabitants nearby the high embankment road have requested a civil complaint on the environmental deteriorations and economic harms. This study was carried out numerical simulation using the 3-D microclimate model 'Envi-met' in order to investigate the variations of a flow field and a temperature field at the road sections with a high embankment and a bridge. About the simulation of flow field, the wind field has changed due to the disturbance of airflow by a high embankment road considerably. And the wind velocity decreased in the whole of simulation space widely. But, the wind velocity and wind direction sited loose to the section of a bridge, relatively. In the results of a temperature field, the slight variations of temperature field were discovered by the disturb of the mixing flow from a high embankment road. These results indicate that the numerical simulation can provide useful information to minimize the disasters, such as traffic accidents and various microclimatic environments in the transportation projects.

• Journal of the Korean earth science society
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• v.27 no.2
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• pp.177-187
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• 2006

Due to a lack of reproducibility and visibility of the conventional equipment for westerly wave simulation, it is difficult to have indoor experiments at high school that show the stream of Hadley cell. A modified improvement of the old one improves the problem. The side wall and bottom of the new equipment is made by copper and acrylic resin, respectively, in order to clarify the difference between the water temperature inside and outside of the water tank. The equipment also has a high quality digital record for generating exact analysis of the results. And we also carried out several experiments that relate theoretical and experimental aspection of westerly wave. Temperature Detected Sheet (TDS) in flow visualization unit provides not only visual information of liquid flow, but also clear understanding of the relation between upper and lower wind flow structure. And the liquid stream simulated in indoor experiment using proposed equipment is commensurate with westerly wave in real atmosphere. The efficiency of educational properties of the proposed equipment is verified indirectly by Likert Scales survey of high school teachers.

• Proceedings of the KAIS Fall Conference
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• 2012.05a
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• pp.367-370
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• 2012

본 연구는 하나의 장치 내에서 "싸이클론-관성충돌-여과포 집진"이라는 다단 제진 단계가 동시에 이루어져 입경 분포별로 순차적인 제진이 가능한 멀티 집진기의 처리가스 제어 효율을 극대화시킬 수 있는 기류 흐름을 얻기 위한 최적화 설계 조건을 검토하는 것이다. 우선 1단계 제진 과정인 원심력을 이용하여 조대입자의 유선 이탈을 촉진시킬 수 있는 사이클론 유동을 최적화시키기 위한 집진기 입구 형상 설계 검토를 위해 수치 해석적 연구를 수행하였다. 그 결과, 멀티집진기 입구 형상을 일반적인 설계 방식인 접선 유입식으로만 설계한 것에 비해 선회류를 한번 더 가속화시킬 수 있는 가이드 베인을 추가로 설계한 경우 선회류의 pitch가 짧고 강하게 형성되어 사이클론부에서 조대입자의 유선 이탈을 촉진시키는데 매우 효과적인 것으로 예측되었다. 단, 사이클론부 하단 벤츄리 형상으로 인해 약 4~5 m/s의 강한 하향 흐름이 호퍼 하단까지 형성되고 있어 탈리 분진의 재비산 문제가 발생할 가능성이 크므로 벤츄리 형상 설치 유무에 대한 영향도 추가적으로 연구가 필요할 것으로 판단된다.

• The Journal of the Convergence on Culture Technology
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• v.8 no.3
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• pp.493-499
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• 2022

This paper reports the results of the eruption of a volcano on Jeju Island at a certain rate, and the tumulus formed after the eruption and the basalt that erupted from the middle of Mt. Halla washed up to the sea. We analyzed the speed when basalt underground magma breaks through the neutral zone on the ground with an absolute temperature of about 1000K and explodes at an absolute temperature of 1200K at an altitude of 1950m. The density of combustion gas becomes smaller than the surrounding air due to the plume volcanic eruption, which is the heat flow of the flame column due to buoyancy, and buoyancy is generated and an updraft is formed. Flame pillars are classified as continuous, intermittent, and buoyant flame zones. As the speed of the flame pillar of Mt. Halla (1950m) falls from the highest point it has risen, potential energy is converted into kinetic energy and is caused by the flow of fluid, solving these two equations equal, the volcanic eruption velocity is 87.5 m/s. At this time, the density of magma is inversely proportional to the temperature. Geomunoreum (456m) had an explosion speed of 42.6m/s.

• The korean journal of orthodontics
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• v.27 no.1
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• pp.91-103
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• 1997

This paper aimed to study what the influences of orthodontic treatment of pronunciation are. We compared the duration and the acoustic wave patterns of Korean consonants pronounced by a control group with those of a patient who had his four premolars extracted and had been given orthodontic treatment The results were as follows : 1. Compared to the control group, the treatment group had a longer duration time of consonant pronunciation for all consonants but "ㅅ(s)" and "ㅌ($(t^h)$" in CV(consonant-vowel) pairs. Especially in the case of "ㅈ(dz)", "ㅆ$({\varphi}^h)$" for CV-pairs, and "ㄷ(d)" in VCV(vowel-consonant-vowel) clusters, the duration of consonant sound showed a sharp contrast between the control group and the treatment group. 2. There were clear differences in the acoustic wave patterns of "ㅉ(ts)", "ㅆ$({\varphi}^h)$" and "ㅊ$(c^h)$", all of which were in VCV-clusters. The acoustic wave pattern of "ㅉ(ts)", when pronounced by the treatment group, was stronger than the control group's. This phenomenon was most remarkable in the transitive section where the "ㅉ(ts)" sound flowed into the following vowel. When a preceding vowel shifted to the consonant "ㅆ$({\varphi}^h)$", the attack property of the appeared clearly in the acoustic waves of the treament group, while in the control group the starting point of consonart was indistinctive. Consonant duration for the treatment group was longer, and the appearance of a zero crossing point in the acoustic wave was more frequent. In the case of "ㅊ$(c^h)$", the treatment group produced a strong acoustic wave, and the property of aspiration was obvious in it. 3. When the treatment group pronounced "ㄷ(d)" and "ㅈ(dz)" in CV-pairs, the acoustic-wave was similar to that of aspirated "ㅌ$(t^h)$" and "ㅊ$(c^h)$". 4. The aspirated "ㅌ$(t^h)$" and "ㅊ$(c^h)$" pronounced by the treatment group showed the stronger airstream and acoustic wave form.