• Proceedings of the KSME Conference
• /
• 2003.11a
• /
• pp.670-675
• /
• 2003

With the increase in recording density and higher rotation speeds, the aerodynamic aspect of hard disk drives (HDDs) is now quite significant. To achieve high TPI (tracks per inch) for hard disk drives, the actuator must induce less air turbulence. Also, alternative cross sections for the actuator arms are proposed for the reduction of air turbulence. In this study, off-track vibration of actuator arms used in of 3.5" hard disk drives with different cross sections have been measured by using Laser Doppler Vibrometer (LDV). It has been found that the vibration of the actuator arms with modified cross sections is lower than the conventional one.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
• /
• 2008.04a
• /
• pp.255-258
• /
• 2008

본 연구에서는 이전의 연구를 통해 계단형 공동주택 화재 시 재실자 피난특성 및 연기거동에 관한 연구를 실물실험을 통해 수행한 바 있으나 이때 야기된 문제점들을 적절한 방재설비를 도입함으로써 일부 해소하고자 하였다. 따라서 본 연구에서는 이전의 연구와 동일한 대상 건물과 조건에서 수치해석을 수행하며 특히 계단실에 방재설비(배연팬 등) 설치 유 무에 따른 독성가스의 전파 특성 및 최상층까지의 도달시간등을 비교 검토하였다. 계단형 공동주택에서 층간에 배연팬이 설치되어 작동되는 경우가 배연팬이 없는 경우보다 약 45%의 CO 방출량을 줄일 수 있을 것으로 판단되지만 1층 출입구를 통해 유입되는 공기량은 배연팬이 없는 경우가 배연팬이 설치되어 작동되는 경우보다 약 23% 크기 때문에 이로 인해 제연풍속의 증가를 가져올 수도 있을 것이다.

• Proceedings of the KAIS Fall Conference
• /
• 2009.05a
• /
• pp.821-824
• /
• 2009

고속도로를 주행 중인 차량에 강풍이 작용할 경우 차량의 주행안정성 저하와 운전자의 상황에 따른 치명적인 교통사고로 이어질 수 있다. 특히, 최근에 건설되거나 추진 중인 고속도로는 교량과 터널의 연속적인 조합으로 강풍발생위험에 노출되어 있어 적극적인 강풍저감 대책이 필요하다. 효과적인 방풍 시설 설치나 사전예고 시스템의 도입을 위해서는 차량의 동역학적 거동 분석, 주행 중인 차량의 위험도 판단기준 연구, 강풍위험지역의 정확한 풍속 추정기법 연구, 지능화된 방풍벽 개발, 방풍시설 설치판단 기준 제시, 합리적인 차량 속도 규제정책 등의 연구 개발이 수행되어야 한다. 본 연구에서는 강풍 발생 구간을 주행하는 차량의 동역학적 거동모델을 제시하고, 이를 기반으로 기존에 제안된 위험도 판단기준의 합리성을 제고하였으며, 운전자의 상황을 고려한 현실적인 차량주행위험도 판단기준 제시를 목표로 하였다.

• Proceedings of the Korean Society of Disaster Information Conference
• /
• 2016.11a
• /
• pp.302-303
• /
• 2016

최근 화학사고는 '10년 15건에서 '15년 111건으로 급속히 증가되고 있다. 이는 기존 산업시설의 노후화와 더불어 사용량 증가에 기인한 것으로 판단된다. 화학사고를 관리하기 위해서는 예방, 대비, 대응, 복구 단계별 대책 마련이 필요하다. 특히, 재난사고의 피해를 저감시키기 위해서는 현장중심의 위험물질에 대한 모니터링을 통해 신속히 위험을 감지하는 기술이 필요하다. 본 연구에서는 화학단지 모니터링체계 구축을 위해 공간정보 기반의 위험물질 정보를 구축하였다. 또한 실시간 기상정보의 취득 및 처리를 위한 기반을 마련하였다. 실시간 기상정보를 활용하여 화학단지 내 바람장 분석을 통해 지점별로 풍향, 풍속을 산정하고 이를 기반으로 지형, 지물을 고려한 화학사고 발생시 그에 따르는 영향범위에 대한 분석을 실시하였다.

• Journal of Korean Society of Steel Construction
• /
• v.17 no.3 s.76
• /
• pp.263-270
• /
• 2005

This paper presents a program for protecting vehicles against side winds on highways. The present study consists of three processes. The first one involves giving a guideline for evaluating driving safety in high winds. The second one involves making a guideline for determining the necessity of wind protection system for a certain road area. A reasonable procedure is suggested based on the probability model of wind data on weather stations and the correction of local topographical conditions. The third one involves design of wind barriers. Both CFD analyses and wind tunnel tests were performed to find the proper type of wind barrier considering vehicle controllability, structural safety, economical efficiency as well as driver's visibility. Performance of the designed wind fences was verified from field tests. The performance of the four different types of wind barrier installed at the elevated bridge were tested and some of the results were provided.

• Journal of Biosystems Engineering
• /
• v.36 no.5
• /
• pp.355-360
• /
• 2011

This study was carried out to analyze the installation effect of an anti-wind net on reducing wind velocity which was used to protect orchards as well as single-span plastichouses. The pressure drop through three types of anti-wind net was measured in a subsonic wind tunnel. The wind reduction through the anti-wind facility for several sets in respect to three types of the net and heights of the facility ranging from 3 to 11 m was analyzed by using computational fluid dynamics (CFD). The measured data showed that the pressure drop increased as an equation of the second degree of the inlet wind velocity. Numerical computations exhibited that the effect of wind reduction definitely augmented as the net size became smaller and increased with the height of the facility being heightened to some extent. For the typical and widely used anti-wind facility with a height of 5 m and a net size of 4mm, the amount of wind reduction came up to 5.1 m/s for the inlet wind velocity of 20 m/s, and also 7.6 and 10.1 m/s for the inlet wind velocities of 30 and 40 m/s, respectively. In case for the orchard's longitudinal length to be within about 200 m, the appropriately effective height of the facility was predicted to be 5 m. Finally, the negative total pressure on the top face of the single-span plastichouse certainly reduced for all the cases with the anti-wind facility being installed. In particular, the reduction of the negative total pressure was more considerable as the inlet wind velocity increased.

• Journal of Korean Association for Spatial Structures
• /
• v.6 no.1 s.19
• /
• pp.111-115
• /
• 2006

The effects of porous wind fence on the pressure characteristics around low-rise building model were investigated experimentally. Flow characteristics of velocities and turbulences behind wind fence were measured using hot-wire anemometer The wind fence characterize by varying the porosity of 0%, 20% and the distances from the wind fence from 1H to 9H with maintaining the uniform flow velocity of 6 m/s. we investigated the overall characterization of the low-rise building by measuring pressure seventy four on model. The effects of porosity fences varied with the porosity of the fence and measurement locations(1H-9H). The 20% porosity proved to be effective for the protection area of 1H to 3H, but the 40% porosity proved to be effective for the protection area of 4H to 6H.

• Journal of the Korean Society of Environmental Restoration Technology
• /
• v.12 no.3
• /
• pp.98-105
• /
• 2009

The objective of this study is to develop numerical simulation model for analysing the wind speed reduction effect by coastal forest belts. The horizontally homogeneous turbulent flow equations, which are derived from the Reynolds-averaged Navier-Stokes method, both above the tree canopy and within the canopy were first formulated, and a first-order closure scheme with the capability of accounting the bulk momentum transport term within the canopy was employed. The averaged equations were solved numerically by finite difference method, FTCS (forward time centered space) scheme. The proposed model was also used to numerically investigate the effects of structural characteristic of forest belt on the wind speed. The effects of maximum leaf area density were evaluated, with the leaf area density of $1.0m^2/m^3$, $2.0m^2/m^3$, $3.0m^2/m^3$, and $4.0m^2/m^3$. Vertical distributions of leaf area, both uniform and varied distribution with a height, were also considered. A comparison of wind profile indicated that there was in good agreements between simulated and measured wind speed. Also, the results showed horizontal wind speed decreased under a height of the tree with increasing maximum leaf area density. In conclusion, in applications where computational efficiency and simplicity are desirable, the proposed numerical model has of great capability to determine the vertical turbulent momentum transport and wind profile in the costal forest belt.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2018.05a
• /
• pp.321-321
• /
• 2018

태풍은 단시간동안 인류활동에 막대한 영향력을 미치는 저기압 시스템 중 하나로 인류에 중요한 수자원을 공급하여 물 부족 현상을 해소하거나, 열대해역에 축적된 과잉 에너지를 수송하여 에너지 균형을 유지하고, 해양 및 대기 정화로 인한 생태계를 활성화하는 긍정적인 면과 육지에 상륙함에 따라 심한 강풍과 폭우를 동반하여 인적 경제적 피해를 주는 부정적인 면을 동시에 지니고 있는 중요한 대기현상이다(Lee, 2006; Wang, 2010; Xu, 2013; Delphine et al., 2013). 2002년 루사, 2003년 매미, 2012년 볼라벤, 2013년 하이옌 그리고 2016년 차바와 같이 세력이 강한 태풍으로 인해 동아시아 지역은 매년 막대한 인명 및 재산피해가 야기되고 있는 실정임에 따라, 태풍으로 인한 재해를 최소화하고 태풍이 가지는 긍정적인 혜택을 적극 활용하기 위해서는 태풍의 활동 및 호우 예측 및 경향성에 대해 보다 정량적인 연구가 필요하다(Oh et al., 2011; Kim and Jain, 2011; Li and Zhou, 2012; Son et al., 2013). 따라서, 본 연구에서는 Son et al.(2014)이 제시한 태풍의 경로 및 규모를 고려한 태풍 추출기법을 적용하여 한반도에 영향을 미친 태풍 및 태풍강우를 추출하였으며, 이를 과거 1977-1994년(Period 1)과 1995-2012년(Period 2) 두 기간으로 분류하였다. 또한, 태풍의 최대풍속을 기준으로 3단계(35-64kt, 65-94kt, 95kt이상)로 구분하여 과거 시기별 태풍 활동(최대풍속, 최소중심기압, 발생빈도, 발생지점, 전향점, 경로) 특성을 분석하고, 과거 시기별 태풍강우(시간 최대 태풍강우량, 총 태풍 강우량)의 변화 분석을 수행하였다. 본 연구의 결과는 향후, 태풍과 관련하여 수질개선 및 수자원확보 등과 같은 태풍 활용방안과 태풍 피해저감을 위한 치수대책 수립 등에 대한 기초자료로 활용가능하며, 기후변화로 인해 야기될 수 있는 태풍의 활동 및 강우 특성 변화를 파악하는 데 이용가능 할 것으로 판단된다.

• Journal of the Korean Institute of Landscape Architecture
• /
• v.45 no.5
• /
• pp.105-112
• /
• 2017

In order to analyze the effect of street trees on human thermal sensation(thermal comfort) in summer, microclimatic data were measured and analyzed at sunny and shaded locations of two deciduous broadleaf and three broadleaf evergreen species of street trees. As a result, the mean differences by species in air temperature, relative humidity and wind speed were small: $0.2{\sim}1.5^{\circ}C$, 0.9~5.3% and $0.1{\sim}0.5 ms^{-1}$, respectively, but the mean difference in the mean radiant temperature was great, $27.1^{\circ}C$. In the results of physiological equivalent temperature(PET) and universal thermal climate index(UTCI), which are human thermal sensation(thermal comfort) indexes, the shaded locations by the trees showed mean reduction rates of 21.2~31.3% in the PET compared with the sunny location, which are equivalent to 1.5~2.5 levels of thermal perception. Also, 12.7~20.0% in the UTCI was reduced by the trees' shadows, which is equivalent to 1~1.5 levels of heat stress. In addition, although the broadleaf evergreen trees had 5% greater mean reduction in PET than that of the deciduous broadleaf trees, the Zelkova serrata that belonged to the deciduous broadleaf trees showed the equivalent thermal reduction effect as the broadleaf evergreen trees because of the high density of branches and leaves. Therefore, the mean radiant temperature and the density of the crown(branches and leaves) were the main influences in thermal modification by these street trees in summer.