Application of a very high internal pressure on the thick-walled pressure vessel induces beneficial compressive tangential residual stresses near the bore of the pressure vessel after unloading the internal pressure. However, a reverse yielding due to the Bauschinger effect during the unloading process causes the reduction of the compressive residual stress near the bore. In order to evaluate the autofrettage residual stress distributions of the thick-walled pressure vessel, the Bauschinger effects were considered. Magnitudes of the compressive residual stresses at the bore determined by considering the Bauschinger effects decreased by about 25 percent, compared to the case of linear elastic unloading, i.e., without Bauschinger effects. Measured residual stress distributions agreed fairly well with the calculated distributions considering the Bauschinger effects.

The fluctuating wind pressure of the low rise ratio(f/D=0.1) for the elliptical dome roof was analyzed to compare it with the previous studies of circular dome roofs. Wind tunnel test were conducted on a total of 10 wind directions from 0° to 90° while changing wall height-span ratios(H/D=0.1-0.5). For this, meanCP, rmsCP and wind pressure spectrum were analyzed. The analysis result leads to find differences in the shape of the spectra in the spanwise direction and leeward of the elliptical dome according to the wind direction variations of the elliptical dome roof.

In this paper, the mean and fluctuating pressure coefficients derived from the results of wind tunnel tests on closed and open dome roofs were analyzed. The distribution characteristics of the fluctuating pressure according to the opening ratio and the height change were discussed. The analysis results showed that when the roof is open, the overall wind pressure decreases due to the open space, but more fluctuation occurred than the closed dome roof.

인삼은 반음지성 식물로 해가림을 위해 지붕 및 벽에 해가림막 시설이 필요하다. 하지만 해마다 강해지는 강풍이나 태풍으로 인해 많은 농가시설물이 피해를 입고 있으며, 특히 인삼재배시설의 경우 시설물이 길게 하나로 연결되어 있어 피해가 크다. 이러한 피해를 방지하기 위해서는 인삼재배시설에 가해지는 풍하중을 평가하여 그것에 견딜 수 있도록 내풍설계를 해야 한다. 이 연구에서는 관행식과 후주연결식 인삼재배시설의 구조골조에 대한 풍하중을 산정하기 위해 필요한 지붕 및 벽 해가림막의 순압력계수를 풍동실험을 통해 정량적으로 평가하였다. 이 연구결과는 인삼재배시설에 대한 내풍설계의 기초자료가 될 것이다.

인삼은 반음지성 식물로 해가림을 위한 해가림막 시설이 필요하다. 하지만 해마다 강해지는 강풍이나 태풍으로 인해 많은 시설물이 피해를 입고 있으며, 특히 인삼재배시설의 경우 시설물이 연결되어 하나의 단지를 이루고 있어 피해가 크다. 해가림막은 차광을 위한 것이지만 바람이 투과하는 재질로 이루어진 것도 있어 강풍에 의해 바람이 투과 하는지 아닌지를 판단할 필요가 있다. 따라서 본 연구에서는 인삼재배시설의 대표적인 두 가지의 설치유형(관행식, 후 주연결식)을 고려하여 모형을 재현하였다. 그리고 먼저 열선풍속계를 이용하여 투과실험을 선행한 후 다점풍압계를 이용하여 본 실험을 수행하여 인삼재배시설의 골조용 풍압분포 특성을 규명하였다. 실험 결과는 인삼재배시설의 설치유형에 따라 하방향 순압력계수와 상방향 순압력계수로 나누어 그래프로 정리하였다.

Dispersion conditions of exhaust gas emitted from the ship stack are varied due to the state of sea surface, ship velocity and external environment condition etc. In the certain circumstances, the exhaust gas flowing backward phenomena is appeared due to the shape of vessel structure. The negative pressure layers can appear at the rear part of deck house and cause the exhaust gas flowing backward phenomena. In this study, 1:100 scale model ship was manufactured and tested in the large wind tunnel test center to ensure the exhaust gas flow patterns. Measurement results showed that the greatest pressure point was x/H=1.55 at zone 6 and Case 2 was a relatively high wind pressure distribution.

This paper attempted to bridge this gap by identifying the number of flat-plate solar collectors. The characteristics of wind pressure coefficients acting on flat-plate solar collectors which are most widely used were investigated for various wind direction. Findings from this study found that the location where the maximum wind pressure coefficient occurred in the solar collector was the edge of the collector. Regarding the characteristics according to the number of collectors, the paper found that downward wind pressure coefficient of the lower edge of the collector was higher than the upward wind pressure coefficient of the upper edge of the collector in the basic module (1 piece). However, as the number of collectors increases, the upward wind pressure coefficient of the upper edge become higher than the downward wind pressure coefficient of the lower edge. Finally yet important, it was found that the location of the maximum wind pressure coefficient was changed according to the number of solar collectors.

To improve the properties of fine metal powder, such as particle size distribution and geometric standard deviation, this work was done at various atomizing conditions. The new atomization mechanism and the correlation equation were proposed to estimate the mean particle diameter.

부표시스템 침수체의 주요형상인 실린더에 원형 제어봉을 부착하여 2차원 단면의 유동특성에 대해서 수치해석을 수행하였다. 유속을 0.1m/s에서 0.5m/s로 변화시키면서 부표시스템 주위의 유동현상을 파악하고, 부표시스템의 효과적인 유동제어를 위해 실린더 (D=50mm)에 제어봉의 직경을 0.1D 에서 0.5D까지 부착하여 조류에 의한 압력분포를 조사하였다. 유동장내의 속도분포는 PIV 계측기법 중 2프레림 입자추적 법을 사용하여 수치해석의 정도를 높이고자 0.3m/s에서 비교 평가하였다. 실린더 주위의 압력분포는 0.2D의 제어봉을 부착하였을 경우, 유속의 변화에 관계없이 가장 양호한 경향을 보이는 것을 알 수 있었다.