This study was carried out to verify the effect of increasing the ambient temperature around apple trees by directly blowing warm-air under the slender spindle apple training system using an agricultural warm-air blower and ducts used in plastic house cultivation to develop late frost damage reduction technology during the blooming season. The temperature increase effect around apple trees owing to the operating warm-air blowing ducts was most evident at a height of 30 cm from the ground surface. At this height, the branch ducts made of Oxford fabric and Solartex showed a raised ambient temperature of about 2.6oC and 1.1oC, respectively. However, the temperature rising effect at a height of 130 cm and 230 cm from the ground surface owing to the operating warm-air blowing ducts was not distinct compared to that in the control. The effect of raising ambient temperature around apple trees through the operation of warm-air blowing ducts was found to be greater as the ambient temperature did not severely drop below the freezing temperature. Damage to the central flower in the apple inflorescence at the pink stage was significantly reduced in the warm-air blowing ducts made of Oxford fabric (42.8%) compared to that in the control (73.2%). However, the damage to other flowers except the central one was not significant compared to that in the control. The fruiting rate of the central and other flowers in the apple inflorescence depending on the operating warm-air blowing ducts was significantly increased compared to that in the control. The fruiting rates of central and other flowers depending on the ducts materials, such as Oxford fabric, and Solartex, and that of the control were 38.3%/82.7%, 31.4%/82.7%, and 0.5%/61.1%, respectively. In conclusion, in the case of open-field apple orchards, if the warm-air blowing duct is installed close to the laterals where frost damage mainly occurs in the slender- spindle dense cultivation system, the damage caused by late frost in the vicinity of blooming time can be reduced to some extent.

This study was conducted to apply with an air duct for the cooling and a utilizing cultivating method that uses the fruiting node and the defoliation to the high-temperature vertical and hydroponic cultivation of the oriental melon. The lower fruiting node (LF) was to remove all third vines generated from 5 nodes of a secondary vine. The higher fruiting node (HF) was fruiting on the third vine generated from a first node of the third vine. The direction of the stem string; upward (UW), downward (DW). Four treatment conditions were applied with the LF-UW, LF-DW, HF-UW (control), and HF-DW. The leaf age of melon leaves was measured for photosynthesis at 3 days intervals, and the fruit characteristic was conducted on 79 fruits in each treatment. The photosynthesis rate steadily increased after leaf development, reaching 20.8 μmol CO2·m-2·s-1 on the 10 days, gradually increasing to 21.3 μmol CO2·m-2·s-1 on the 19 days, and reaching 23.4 μmol CO2·m-2·s-1 on the 32 days. After that, it lowered to 16.8 μmol CO2·m-2·s-1 on the 38 days and dropped significantly to 7.6 μmol CO2·m-2·s-1 on the 47 days. As a result of the fruit characteristics by fruiting nodes, the treatments of the fruit length was 12.6-13.4 cm, respectively, which was significant, and the fruit width was 7.9- 8.6 cm, respectively, was not significant. The soluble content ranged from 12.9 to 15.7°Brix, and the significance of all treatments, and higher than of LF-DW and HF-UW. The photosynthesis rate of melon leaves was good until 32 days after leaf development, but after that, the rate decreased. As for fruit quality, it was conformed that melons can be cultivated at the LF because the fruit enlargement and soluble content dose not decrease even when set at the LF. Results indicated that those can be used for LF and defoliation in the development of vertical and hydroponic cultivation method in high-temperature season.

This study analyzed the duct characteristics of hubless rim-driven propeller (RDP) used in underwater robots. In the previous study, flow visualization experiments were performed with an advancing ratio of 0.2 to 1. The vortex at the front of the duct increased in strength while maintaining its size as the advancing ratio decreased. Therefore, it is necessary to study the optimization of the duct shape. Conventional propeller thrusters use acceleration/deceleration ducts to increase their efficiency. However, unlike conventional propellers, it is impossible to apply to airfoil acceleration/deceleration ducts due to the RDP structure. In this study, duct wake flow characteristics, thrust force, and efficiency according to the duct shape of RDP were analyzed using numerical analysis techniques. Duct design is limited and six duct shapes were designed. As a result, an optimized duct shape was designed considering duct wake flow characteristics, thrust force, and efficiency. The shape that the outlet width of the RDP was kept constant until the end of the duct showed higher thrust force and efficiency.

To ensure the safety and functionality of a railroad bridge, maintaining the integrity of the bridge via continuous structural health monitoring is important. However, most structural integrity monitoring methods proposed to date are based on modal responses which require the extracting process and have limited availability. In this paper, the applicability of the existing damage identification method based on free-vibration reponses to time-domain deflection shapes due to moving train load is investigated. Since the proposed method directly utilizes the time-domain responses of the structure due to the moving vehicles, the extracting process for modal responses can be avoided, and the applicability of structural health evaluation can be enhanced. The feasibility of the presented method is verified via a numerical example of a simple plate girder bridge.

In this study, a energy recovery ventilation system was applied to the pig model, intake and exhaust duct were installed at a height of top(2.1 m), middle(1.25 m) and bottom(0.4 m). In each of the 9 test sites, one test was performed from 10:00 to 18:00, optimal temperature exchange efficiency and temperature distribution were analyzed. In order to analyze the effect of the energy recovery ventilation system, the temperature of 31 points(4 points of the ventilation system and 27 points in the pig house model) was measured from 10:00 to 18:00. The test that showed the highest heat exchange efficiency was the configuration of middle intake duct and top exhaust duct, which was 75.44%. The test that showed the most uniform distribution was the configuration of middle intake duct and bottom exhaust duct. These results will be utilized to optimally design feeding environment of actual pig houses and to reduce fuel cost.

덕트에 설치되는 오리피스는 압력과 유량 제어용으로 많이 활용되고 있다. 선박의 거주 구역에 통풍 덕트는 환기와 배기를 위해 설치되며 및 선박의 설계 및 건조 후 검사는 공기 유속과 유량 그리고 소음 기준에 대해 수행된다. 이 연구에서는 선박의 선실 별 유량분배에 중요한 요소인 T-분지관을 대상 으로 오리피스를 적용한 경우 난류운동에너지 분포를 고찰하였다.

공조시스템의 소음 예측은 주로 NEBB에서 제안한 경험적인 방법에 의해 수행된다. 그러나, NEBB에서 제안한 방법은 선박에만 있는 대형 덕트의 요소를 반영하지 못하므로 선박에 적용하는데 한계가 있다. 본 논문에서는 선박용 대형 덕트의 소음 예측을 위한 전산해석방법을 연구하였다. 경계요소법을 사용하여 대형 덕트의 단위 길이당 소음 감소량에 대한 추정식을 개발하였고, 경계요소법과 전산유체역학을 사용하여 보강재가 설치된 대형 덕트에서의 유동기인소음을 예측하였다. 유입 유속이 10m/s, 보강재의 종류가 200플랫 바인 경우 100 dB 이상의 큰 소음이 발생하는 것을 알 수 있었다. 또한, 경계요소법과 유한요소법을 사용하여 덕트 투과 소음을 예측하였다. 덕트 내부와 외부의 음압 값 차이는 대략 10~15 dB정도 인 것을 알 수 있었다. 이를 통해 조선소에서는 대형 덕트를 포함한 선박 HVAC 소음 예측을 할 수 있을 것으로 기대한다.

근권부 공기순환 덕트 냉방이 온도 및 생육에 미치는 영향을 구명하고자 고온기 파프리카((Capsicumannum.L. ‘Veyron’)을 코이어배지에서 수경재배하였다. 냉방시간 처리는 24시간 연속 가동한 연속냉방(All-day), 17시부터 다음날 1시까지 8시간 냉방한 야간냉방(Night), 대조구인 냉방 무처리(Control) 등 3 처리하여 온실 상·하부 온도, 근권온도, 엽온, 과실 특성 및 기관 분배율을 측정하였 다. 근권부 덕트 냉방하였을 때, 고온기(6월 ~8월) 온실 하부(바닥으로부터 40cm)와 상부(바닥으로부터 180cm) 온도, 근권온도는 하강되었다. 대조구와 비교하여 온실 하부/상부 온도 차이가 연속냉방에서는 4.4~5.1oC/ 2.1~3.1oC 하강을, 야간냉방 처리에서는 3.4~3.8oC/ 2.2~2.7oC 하강되었다. 근권온도는 온실 하부 온도 결과와 유사했으며, 연속냉방(22.8oC)> 야간 냉방(24.1oC) > 대조구(27.7oC) 순으로 온도가 낮았다. 연속냉방 처리에서 덕트 위치(통로, 베드하단)와 송풍 방향(45o, 90o, 180o)에 따른 온도 변화를 측정한 결과 덕트의 위치가 통로에 위치하고 송풍방향이 상향(45o) 또는 수평(180o) 인 처리는 지상부 100cm까지의 수직 위치에 따른 온도 차이가 크지 않지 않으면서, 근권부위 온도인 지상 50cm 온도가 낮은 특징을 보였고 베드와 베드 공간 사이로 덕트 송풍 방향이 직각(90o)이였을 때는 바닥과 지 상 50cm 부위의 온도가 높고, 지상 100cm 이상 200cm 부위 온도가 상대적으로 낮았다. 연속냉방 또는 야간냉방 처리했을 때 파프리카 엽온은 오후 7시가 오전 9시 보다 엽온 하강이 컸다. 과실 분배율은 대조구(24.4%)에 비해 연속냉방(48.6%)과 야간냉방(45.6%)에서 높았으며, 평균과중, 과수 및 수량도 연속냉방 처리에서 가장 높았다. 한편 야간냉방 처리에서도 고온기 평균 지상부 및 근권온도를 낮추었으나, 누적된 평균온도가 가장 낮은 연속냉방처리에서 과실로의 동화산물 분배율을 높여 파프리카 수량을 증가시킨 것으로 보인다.

This paper analyzed air temperatures at outlet according to condition of absorber plate of the solar air heater. Effects on air temperature at outlet of duct according to absorber plate temperature were analyzed by using numerical analysis technique. And also the effects on air temperatures at outlet were analysed by the height and position of absorber plate. As the results, air temperatures at outlet of duct was small influenced in velocity 5 m/s of inlet according to absorber plate temperature. And the highest outlet average temperature distribution appeared at the height of 2 cm and the bottom absorber plate of duct at the inlet aspect ratio 2.

In this study, the ventilation of duct is simulated by CFD and thermal changes on the seat surface are measured experimentally. These models are the improved duct and the existing one installed at the real seat in order to test the thermal change 1 minute later. The seat with the existing duct has the temperatures of 26℃ and 25℃ on lumber and femoral parts respectively. However, the seat with the improved duct has the temperature of 1℃ lower than the seat with the existing duct. This result contributes to develop the improved duct. Hereafter, the methods used in this study are expected to be useful at checking the flow resistance loss of the ventilation seat duct and assessing the flow channel design

In the paper an efficient numerical algorithm to predict the flow phenomena around the water-jet propulsion system was described. The potential-based flow analysis method was adopted to predict the velocity and the pressure on the inlet duct of the water-jet propulsion system. The method employed normal dipoles and source distributed on the solid surface such as the inlet duct and the tracked vehicle. The inlet duct and outlet open boundary surfaces were introduced where the sources and dipoles were distributed to define a closed boundary surface. The developed numerical algorithm was applied to a tracked vehicle propelled by the water-jet propulsion system with the different IVR(inlet velocity ratio). The results by the numerical analysis were compared with the experimental data in order to verify the feasibility of the proposed numerical algorithm.

Local Nusselt number and temperature field distribution within the compound duct with gap have been measured. Measurement of air and wall temperature span a range of gap width from 2mm to 6mm. Also, the Reynolds number is variated from 20,000 to 40,0000. In order to observe the correlations between gap width and turbulent heat transfer, the present measurement has tried to verify the enhancement effect of heat transfer when a gap exists within the compound channel. From this measurement, we could see that the pulsating flow has generated a strong turbulent flow mixing within the compound channel. And the turbulent flow mixing in the pulsating flow plays an effective role of enhancing the Nusselt number by making the fluid temperature uniformly within the compound channel.

In this paper, numerical investigation of transition characteristics in a square-sectional curved duct flow. Computational fluid dynamic(CFD) simulation was performed using the commercial CFD code FLUENT to investigate the transition characteristics. The flow development is found to depend upon Dean number and curvature ratio. The velocity profiles in center of the duct have lower value than those of the inner and outer walls.

이 연구에서는 정사각 단면을 갖는 덕트 내부에 원심력의 영향을 받는 유동의 천이특성을 실험 및 수치적으로 규명하였다. 실험적 연구로서 레이저도플러 속도계를 이용하여 축방향속도를 측정하였고, 상용소프트웨어인 플루언트를 이용한 전산유체 시뮬레이션으로 천이특성을 고찰하였다. 유동의 발달은 딘수와 굽힘각에 의존한다는 사실을 알 수 있었으며 덕트의 중앙에서의 속도분포는 원심력 때문에 내외벽보다 낮은 값을 나타내었다.

本論文, 旨在要通過考察兩漢時期黃老學代表著作『淮南子』, 探討宇宙生成論的基本含義。宇宙生成論就探討如下幾個問題: 宇宙萬物之根源, 其根源如何發展到具體萬物, 天下萬物之最終根源是如何規定『淮南子』繼承了先秦時期老莊哲學思想、氣論和陰陽五行思想及兩漢時期所發展的自然科學之成果, 而使之適應於自己宇宙論體系之需要。.今爲止, 大多學者從以下方面起規定『淮南子』的宇宙生成論: 有些學者把『淮南子』規定爲‘雜家’而其理論體系最終落到於自相矛盾; .一些學者都從‘道’‘氣’.念的含義和兩者之間的關系問題出發, 建立起了其宇宙生成論的理解方式。從道氣兩個.念之間的關系問題上, 就發生了‘氣一元論’和‘以道爲主的自然觀’而再分爲‘道.氣’或‘道生氣’的觀點。那., 如何解釋『淮南子』所論的宇宙生成論才接近於其.正的含義? 筆者認爲,『淮南子』基本上堅持了宇宙萬物始於整體(‘一氣’)的立場。『淮南子』就把這種整體稱爲‘太昭=虛.=一’, 而從這個狀態起發生了‘陰陽二氣’的分化而最終形成了天地萬物。但在這個過程上, 我們必須解釋宇宙生成的動力是什., 因而『淮南子』提到了 ‘道始于虛.’、‘道始於一’的觀點。.是說, 道沒有直接參與於萬物生成過程, 而道就是所引起各個生成過程的基本動力, 所以『淮南子』把‘道’理解爲宇宙萬物的最終本原。如此, ..淮南子..就把‘道’和 ‘氣’綜合起來, 最終建立了‘以道爲本’的氣化宇宙論。對於向後中國哲學思想裏所發展的宇宙論體系, 『淮南子』的宇宙生成論.生了重大的影響。