• 설비공학논문집
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• 제3권3호
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• pp.161-167
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• 1991

This paper presents the results of some measurement of the fluctuating velocity field in the turbulent boundary layer disturbed by a triangular prism and discusses the discovery of the disturbed boundary layer. A prism of height 8mm was used for experiments. The streamwise location of the prism was fixed at 1200mm downstream from the leading edge and the space between the prism center and the wall was set at three different values, 6, 15 and 33.5mm. The results show that the near-wall region of the disturbed boundary layer recovers original state much more quickly than the outer region. In the case h=6mm the recovery is faster than the other cases. Moreover, it was found that peak of fluctuating velocities moves outwards somewhat rapidly with increasing ${\times}$ mainly due to the turbulent diffusion of the fluctuating velocity.

• 한국환경과학회지
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• 제23권3호
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• pp.335-357
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• 2014

This study aims at classifying and interpreting on the vegetation structure and the vegetation transition over 25 years (between 1986 and 2010), and the correlation with the change of some conditions (the vegetation height and coverage on each layer and the climate factors as WI, CI, mean annual temperature, mean annual total precipitation etc.) in the Evergreen Broad-Leaved Forest,, Hong-Do island. The EBLF is classified into five units of vegetation (Hedera rhombea-Machilus thunbergii community (M-M comm.), Castanopsis sieboldii forest (Machilus japonica-Castanopsis sieboldii community; Raphiolepis indica var. umbellata-C. sieboldii community), community (Qa comm.), Carpinus turczaninovii community (Ct comm.), Camellia japonica stand (Cj stand)). The vegetation transition by CCA had high correlation with the height and coverage on each layer and the climate factors, and it did the succession (transition) that the M-M comm. (2010) from Mallotus japonicus community Machilus thunbergii community Carpinus coreana community (Cc comm.) Aucuba japonica community (Aj comm.) Trachelos permum asiaticum var. intermedium-Quercus acuta community (TQ comm.) (1986), the communities of C. sieboldii forest (2010) from Aj comm. TQ comm. Raphiolepis umbellata-Camellia japonica community (RC comm.) (1986), the Qa comm. (2010) from Ardisia japonica-Castanopsis sieboldii community (AC comm.) and TQ comm. (1986), the Ct comm. (2010) from Cc comm. RC comm. Aj comm. Quercus serrata community and the Cj stand (2010) from AC comm. (1986). the height and coverage on each layer are also changed.

• 한국환경과학회지
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• 제16권9호
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• pp.1011-1018
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• 2007

This study was conducted to analysis the ecological characteristics of "Wando HolIy"$(llex{\times}wandoensis)$ which is expecting as a possible ornamental tree with its beautiful leaves, flowers and fruits, and to find special breeding material which have particular characteristics and also provide correct environmental information which are required for commercial cultivation. The hill of Galmoon-Ri, Gunoei-Myon, Jeonnam Province, Korea, were reported as a original habitat of native $llex{\times}wandoensis$. The investigation shows that soil pH of native habitat was 6.18, hardness was 2.39, humidity was 38.6%, direction of slope is SSW, and average inclination was $15^{\circ}. The vegetation around $I.{\times}wandoensis$ is occupied by trees like an Quercus variabilis, Q. serrata, Q. acuta and so on. These are mixed forest of deciduous trees. Tree height reached up to about 12m and its coverage is about 30%. Q. salicina, Camellia japonica, I. integra, Cryptomeria japonica account for sub-tree layer. Tree height is around 8m and coverage is about 20%. Shrub layer was taken by Viburnum furcatum, Callicarpa japonica, Styrax japonica, Eurya japonica, Lindera obtusiloba, Ligustrum japonicum, Smilax china, Cornus walteri etc. Tree height reaches around l.2m and coverage is around 20%. Herb layer includes Trachelospermum asiaticum var. intermedium, Cymbidium goeringii, Dryopteris bissetiana, Disporum viridescens, Disporum smilacinum, Sasa borealis var. gracilis etc. Trachelospermum asiaticum var. intermedium, which are observed in southern evergreen zone, are dominant and its coverage is around 20%. The native habitat was in spoiled condition because of artificial thin out.

• The Korean Journal of Ecology
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• 제25권1호
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• pp.33-39
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• 2002

Objectives of this study are to make clear the vegetation structure of Hovenia dulcis community in the Korean Peninsula over ten mountains including 17 plots. The results were summarized as follows. Habitat of the community indicated that elevation ranged from 115 meter to 720 meter at the sea level, slope aspect in nearly all directions, bare rock from 0 to 90 percent, slope degree from 10$^{\circ}$ to 40$^{\circ}$, topography from valley to middle slope, the height of tree layer from 8m to 22m, the diameter at breast height from 12cm to 59cm and coverage from 65% to 95$\%$$\%$

• 한국환경과학회지
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• 제21권9호
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• pp.1097-1113
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• 2012

Ozone is the secondary photochemical pollutant formed from ozone precursor such as nitrogen dioxide and non-methane volatile organic compounds(VOCs). The ambient concentration of ozone depends on several factors: sunshine intensity, atmospheric convection, the height of the thermal inversion layer, concentrations of nitrogen oxides and VOCs. Busan is located in the southeast coastal area of Korea so the ozone concentration of Busan is mainly affected from the meteorological variables related to the sea such as sea breeze. In this study the ozone concentrations of Busan in 2008~2010 were used to analyse the cause of the regional ozone difference in eastern area of Busan. The average ozone concentration of Youngsuri was highest in Busan however the average ozone concentration of Gijang was equal to the average ozone concentration of Busan in 2008~2010. The two sites are located in eastern area of Busan but the distance of two sites is only 9km. To find the reason for the difference of ozone concentration between Youngsuri and Gijang, the meteorological variables in two sites were analyzed. For the analysis of meteorological variables the atmospheric numerical model WRF(Weather Research and Forecasting) was used at the day of the maximum and minimum difference in the ozone concentration at the two sites. As a result of analysis, when the boundary layer height was lower and the sea breeze was weaker in Youngsuri, the ozone concentration of Youngsuri was high. Furthermore when the sea breeze blew from the south in the eastern area of Busan, the sea breeze at Youngsuri turned into the southeast and the intensity of sea breeze was weaker because of the mountain in the southern region of Youngsuri. In that case, the difference of ozone concentration between Youngsuri and Gijang was considerable.

• 한국화재소방학회논문지
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• 제17권3호
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• pp.1-6
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• 2003

본 연구에서는 특정의 업무용 건축물에 대해서 화재 및 피난 시나리오를 선정하여 FAST 3.1.7(전실화재 예측), SIMULEX 32-bit(피난시간의 예측), JASMINE 3.25d(특정시간까지의 연기 유동성 평가)등의 S/W를 이용하여 이를 평가했으며 그 결과는 다음과 같다. Scenario #1 결과, 화재실에서 전실화재가 발생하지 않았고, 층 피난시간은 25.2 sec로 나타났으며 이때까지의 FAST 3.1.7결과에서 연기층은 2.4m를 기록, 연기유동성 평가에서도 재실자들은 연기의 피해(가시거리, 독성)없이 피난이 완료될 것으로 나타났다. Scenario #2 결과, 화재실에서 6 min 33.2 sec에 전실화재가 발생했으며, 수계산에 의한 피난시간은 5 min 23sec로 나타났다. 본 대상건물에 대해서 선정한 Scenario #1, #2 모두 인명안전설계는 적정하게 설계되었다고 판단된다.

• Composites Research
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• 제24권6호
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• pp.31-36
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• 2011

성형조건에 따른 GMT-Sheet를 관찰하여, 성형품 표면의 섬유돌출을 조사했다. 섬유돌출은 모재의 수축에 의해서 성형품 표면에 생성되는 불량현상의 하나이다. 즉, 섬유돌출은 성형온도에서 상온까지 성형품이 냉각될 때 모재와 유리섬유의 수축차에 의해 발생하는 표면불량 현상이다. 성형품 표면의 섬유돌출 높이는 보압 냉각과정에서 성형압력이 클수록 작게 나타남을 알 수 있다. 성형품 표면의 섬유돌출 높이는 성형압력의 영향이 지배적임을 알 수 있다. 성형압력을 고려하여, 성형품의 표면요철 생성과정과 섬유돌출 높이 변화를 규명했다. 그리고 피복층은 표면불량 현상을 억제하는 효과가 있고, 표면으로부터 섬유돌출이나 크랙이 보이지 않았다. 피복층은 표면거칠기를 단일재료인 폴리프로필렌 정도까지 개선하였다.

• Wind and Structures
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• 제36권3호
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• pp.161-174
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• 2023

The analytical model of tornado vortices plays an essential role in tornado wind description and tornado-resistant design of civil structures. However, there is still a lack of guidance for the selection and application of tornado analytical models since they are different from each other. For single-cell tornado vortices, this study conducts a comparative study on the velocity characteristics of the analytical models based on numerically simulated tornado-like vortices (TLV). The single-cell stage TLV is first generated by Large-eddy simulations (LES). The spatial distribution of the three-dimensional mean velocity of the typical analytical tornado models is then investigated by comparison to the TLV with different swirl ratios. Finally, key parameters are given as functions of swirl ratio for the direct application of analytical tornado models to generate full-scale tornado wind field. Results show that the height of the maximum radial mean velocity is more appropriate to be defined as the boundary layer thickness of the TLV than the height of the maximum tangential mean velocity. The TLV velocity within the boundary layer can be well estimated by the analytical model. Simple fitted results show that the full-scale maximum radial and tangential mean velocity increase linearly with the swirl ratio, while the radius and height corresponding to the position of these two velocities decrease non-linearly with the swirl ratio.

• 한국어류학회지
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• 제17권3호
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• pp.167-172
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• 2005

조간대와 강하구에 출현하는 미끈망둑 Luciogobius guttatus은 썰물 동안에 건조하기 쉬운 자갈 바닥 아래에서 서식하는 특징을 보인다. 이러한 서식처를 선호하는 미끈망둑의 호흡체계를 조사하기 위해 지느러미 및 흡반을 포함하는 5개의 부속지의 표피구조를 관찰하였다. 표피는 모두 맨바깥층(outermost layer), 중간층(middle layer), 기저층(stratum germinativum)으로 구성된다. 맨바깥층은 다형세포 또는 편평세포, 그리고 점액세포로 구성되었으며, 특히 단일세포성의 점액세포는 $11.1{\sim}16.1{\mu}m$의 크기로 1~2층으로 배열되어 있으며, 산성다당류로 확인되었다. 중간층은 이웃한 표피세포로 팽대해진 팽대세포 (swollen cell)로 구성되어 있으며, $12.3{\sim}15.2{\mu}m$의 크기로 1~11층으로 배열되어 마치 거미망구조를 보인다. 이러한 팽대세포로 인해 상피 두께의 대부분을 차지한다. 많은 모세혈관이 기저막 아래에 분포하고 있으며, 미뢰 (taste bud)가 표피에 존재한다. 이러한 표피의 특징은 미끈망둑이 이중호흡체계인 피부호흡 (cutaneous respiration)과 밀접한 관계가 있는 것으로 생각된다.

• 대한기계학회논문집B
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• 제20권8호
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• pp.2637-2649
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• 1996

Flow characteristics and aerodynamic forces acting on an elliptic cylinder placed in a plane boundary layer were investigated experimentally. Four cylinder models with axis ratio(major axis to minor axis, AR=A/B) of 1, 2, 3, and 4 having the same equivalent diameter were used in this experiment. The Reynolds number based on the equivalent diameter $D_e$(=20mm) was 13,000. In the case of circular cylinder, regular vortex shedding occurs for the cylinder gaps larger than G/B=0.3 and is not almost related to the boundary layer thickness. But, for the elliptic cylinders, the vortex shedding frequency is increased with increasing the gap ratio (G/B) and the axis ratio (AR) of elliptic cylinders. The maximum drag coefficient acting on a circular cylinder is mainly affected by the boundary layer thickness. But, the elliptic cylinders(AR$\geq$2), except for the smaller gap G/B<0.2, show a nearly constant drag coefficient which is much smaller than that of a circular cylinder. The base pressure on the flat plate decreases with increasing the axis ratio(AR) of the elliptic cylinder. In the case of a circular cylinder, the base pressure has the minimum value at the gap ratio G/B=0.4, but it occurs at G/D=2 for elliptic cylinders. The mean velocity of the cylinder wake is quickly recovered at a small cylinder height ratio(H/$\delta$), but the turbulent intensity is rapidly recovered at a large cylinder height ratio(H/$\delta$). The effective wake region in the plane boundary layer is shrinkaged with increasing the axis ratio(AR) of elliptic cylinder. And the drag coefficient and streamwise turbulent intensity of the elliptic cylinder with AR=4 are less than half of those for the circular cylinder(AR=1).