• 한국태양에너지학회 논문집
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• 제25권2호
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• pp.45-51
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• 2005

The solar shading height for the cultivation of plants is a very important factor because it has an effect on the variations of the solar energy. In this study, the solar shadings were built in Daegu region to investigate the optimum thermal conditions for the cultivation of plants and to provide the basic data. The thermal environment factors (dry bulb temperature, relative humidity, air velocity) were then measured and analyzed. It is found that the heights of the solar shadings have an uniform effect on the thermal environment for the cultivation of plants: the higher the heights of the solar shadings the higher temperature was obtained. But surprisingly this trend was not found for the relative humidity and the air velocity.

• 국제초고층학회논문집
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• 제2권4호
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• pp.323-330
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• 2013

The ASHRAE Technical Committee for Tall Buildings, TC 9.12, has defined a tall building as one whose height is greater than 300 feet (91m). Since the publication of the HVAC Design Guide for Tall Commercial Buildings in 2004, there were only about 300 buildings taller than 200 meters; this number has risen to 600 in 2010 and the prediction 765 buildings taller than 200 meters in 2012. There has also been an introduction of two new classes of tall buildings: ${\bullet}$ Mega tall, which are buildings taller than 300 m, and ${\bullet}$ Super tall, which are buildings taller than 600 m. The effect of ambient air temperature over the height of buildings, especially Mega tall and Super tall buildings. The ambient climatic conditions vary with altitude and these changes in ambient conditions can seriously affect load calculations and performance of super and mega tall buildings. This paper presents revised calculations for stack effect for Tall, Mega Tall and Super tall Buildings.

• 국제초고층학회논문집
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• 제1권2호
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• pp.73-80
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• 2012

In order to use sea breezes to counter the heat island phenomena, i.e. to promote urban ventilation, it is necessary to clarify the effect of building morphology and height on large-scale wind fields. In this study, the sea breeze in the vicinity of the Kanto Plain in Japan is simulated using a mesoscale meteorological model incorporating an urban canopy model, and the inland penetration of sea breezes is accurately reproduced. Additionally, a mean kinetic energy balance within a domain (Control Volume; CV) moving along the sea breeze is analysed. From the results, it is clarified that the sea breeze is interrupted by the resistance and turbulence caused by buildings at the centre of Tokyo. The interruption effect is increased in accordance with the height of these buildings. On the other hand, adverse pressure gradients interrupt in the internal region.

• Wind and Structures
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• 제15권5호
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• pp.355-367
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• 2012

Atmospheric boundary layer winds experience two types of effects due to friction at the ground surface. One effect is the increase of the wind speeds with height above the surface. The second effect, called the Ekman layer effect, entails veering - the change of the wind speed direction as a function of height above the surface. In this study a practical procedure is developed within a database-assisted design (DAD) framework that accounts approximately for veering effects on tall building design. The procedure was applied in a case study of a 60-story reinforced concrete building, which also considered the dependence of veering effects on the orientation of the building. Comparisons are presented between response estimates that do not account for veering, and account for veering conservatively. For the case studied in this paper veering effects were found to be small.

• 설비공학논문집
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• 제18권7호
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• pp.578-586
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• 2006

The present study has been conducted to examine the effect of obstacles around a cooling tower and an air-guide to prevent recirculation. In order to analyze the interaction between external flow and cooling tower exit flow, the external region as well as the cooling, tower are included in computational domain. Two dimensional analysis is performed using the finite volume method with non-orthogonal and unstructured grid system. The standard ${\kappa}-{\varepsilon}$ turbulence model is used. To investigate the recirculation phenomena, flow and temperature fields are calculated with three approaches such as, the distance between cooling tower and obstacle, the allocated geometrical type, and the effect of height of obstacle. In addition, the air-guide is considered in the current computation. The mean recirculation rate increases with the height of obstacle. The effect of air-guide to reduce the mean recirculation rate is obviously observed.

• 한국정밀공학회지
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• 제16권3호통권96호
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• pp.47-52
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• 1999

Theoretical and experimental studies on burr formation and deburring in many manufacturing processes have been actively pursued. Though micro-drilling has become more important in the production of precision parts such as PCB, air bearing, camera and nozzle, most studies on drilling burr formation have focused on the conventional drilling process. This paper describes burr formation process and the effect of cutting conditions such as spindle speed, feedrate and drilling depth per one step on burr formation in drilling A6061 with drills of diameter 1.0mm and 0.6mm. Experimental results showed that burr with cap were formed at relatively low feedrates, while petal burrs with several large burr fragments were formed at high feedrates. Burr height appeared to increase at the hight feedrates and lower spindle speeds. The effect of final cutting depth on burr height was negligible.

• International Journal of Naval Architecture and Ocean Engineering
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• 제12권1호
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• pp.799-809
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• 2020

In this study, the supercavitating flow of a high-velocity moving body near air-water surface is calculated and analyzed based on a commercial CFD software ANSYS Fluent. The effect of regular wave parameters including both wave height and wavelength on the cavitating flow and force characteristics of a body at different velocities is investigated. It is found that the cavity shape, lift coefficient and drag coefficient of the body vary periodically with wave fluctuation, and the variation period is basically consistent with wave period. When the wavelength is much greater than the cavity length, the effect of wave on supercavitation is the alternating effect of axial compression and radial compression. However, when the wavelength varies around the cavity length, the cavity often crosses two adjacent troughs and is compressed periodically by the two wave troughs. With the variation of wavelength, the average area of cavity shows a different trend with the change of wave height.

• 한국자원식물학회지
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• 제22권4호
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• pp.299-303
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• 2009

넓은잎큰조롱의 두둑높이에 따른 생산성 및 품질향상을 위하여 재배법 확립의 기초자료로 제공하고자 두둑높이를 달리하여 2005년부터 3년간 시험한 결과, 만장, 엽장, 엽폭, 엽수, 엽록소함량, 경엽 건물중은 두둑높이가 높을수록 양적인 증가를 가져왔으나, 경태와 분지수는 두둑높이가 낮을수록 굵거나, 많은 경향이었다. 근수와 근장은 두둑높이 20 cm까지는 두둑높이가 높을수록 많거나, 길었으나, 20 cm 이상의 두둑높이에서는 생육량이 감소하였으며, 근태는 두둑높이가 낮을수록 굵어지는 경향이었다. 비상품근 중 세근은 두둑높이 20 cm에서 다소 많았으며, 부패근은 두둑높이가 낮을수록 많은 경향이었고, 근수량은 두둑높이 20 cm내지 30 cm 까지는 두둑높이가 높을수록 증수되어 두둑높이 10 cm의 515 kg/10a 대비 3%, 11% 증수되었다.

• Spatial Information Research
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• 제9권1호
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• pp.1-13
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• 2001

위성영상을 이용하여 지형도를 제작하는 새로운 방법으로 레이다 간섭기법에 관한 연구가 활발히 진행되고 있다. 레이다 간섭기법은 동일한 지역을 촬영한 두 장의 SAR 영상의 위상정보를 이용하여 표고값을 추출하는 기법으로, 기존의 SPOT과 같은 광학영상에 비하여 날씨나 시간의 제약을 받지 않고 지형정보를 얻을 수 있다는 장점을 가지고 있다. 즉, 영상취득의 유연성이 뛰어나며 광범위한 면적에 대하여 저렴한 표고데이터 추출이 가능하여 GIS에서의 활용 가능성 또한 밝다고 할 수 있다. 그러나 레이다 간섭기법은 SAR 시스템에 따라 발생하는 기하학적 왜곡으로 인해 일부지역에 대해서는 위상불구속화 알고리즘에 따라 표고값이 잘못 추정되거나 아예 그값을 얻지 못하는 단점을 가지고 있다. 본 연구에서 사용한 ERS 텐덤자료의 경우에는 산악지형에서의 수직위치 정확도가 가장 부정확했으며, 기하학적 왜곡으로는 ERS 위성의 짧은 입사각으로 인한 layover 현상이 주로 발행하였다. 위상불고속화 기법별로는 경로추적방식 알고리즘을 사용했을 경우, 산출된 표고값의 정확도는 최소제곱방식을 수행했을 경우보다 2∼5m 가량 우수하였으나 기하학적 왜곡이 발생한 지역에서의 데이터를 얻지 못하는 결과를 보였다. 이 지역에 대하여 고도민감도를 이용하여 표고값을 추정한 결과 경로추적방식의 정확도를 유지하면서 전체 영상에 대하여 표고값을 갖는 DEM을 제작할 수 있었다.

• 한국초지조사료학회지
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• 제21권2호
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• pp.89-96
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• 2001

Carbohydrate and soluble protein reserves and regrowth characteristics in response to cutting height were investigated over four regrowth cycles of turf-type perennial ryegrass(Lolium perenne L. cv. preludeII). When the plants were at the full-vegetative stage (twelve weeks-old), three sequential defoliations at 3, 6 and 9 cm above the root base were imposed at 2-week intervals. Shoot dry weight in all three treatments continuously decreased with progressing regrowth cycle and the decreasing rate was higher as cutting height was lowered. TNC (total non-structural carbohydrate) in stubble at the end of the fourth regrowth cycle in 3, 6 and 9 cm cutting height decreased by 98%, 82% and 27%, respectively, comparing the initial content. TNC in roots also largely decreased with similar pattern in response to cutting height, whereas the absolute amount was much less compared to stubble. Soluble protein in stubble in 3, 6 and 9 cm cutting height decreased by 98%, 82% and 57%, respectively, at the end of fourth regrowth. A significant correlations between TNC (r=0.906) or protein (r=0.879) at the fourth defoliation and dry weight of regrowing shoots at the end of fourth regrowth were observed. these results indicated that cutting height closely influences the levels of organic reserves available for new growth, and that the levels of reserves might provide a useful tool as a determinant for regrowth dynamics.