• International Journal of Aeronautical and Space Sciences
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• 제15권2호
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• pp.190-198
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• 2014

The pyramidal reaction wheel arrangement is one of the configurations that can be used in attitude control simulators for evaluation of attitude control performance in satellites. In this arrangement, the wheels are oriented in a pyramidal configuration with a tilt angle. In this paper, a study of pyramidal reaction wheel arrangement is carried out in order to find the optimum tilt angle that minimizes total power consumption of the system. The attitude control system is analyzed and the pyramidal configuration is implemented in numerical simulation. Optimization is carried out by using an iterative process and the optimum tilt angle that provides minimum system power consumption is obtained. Simulation results show that the system requires the least power by using optimum tilt angle in reaction wheels arrangement.

• 동력기계공학회지
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• 제21권4호
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• pp.62-69
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• 2017

Because the moist foods like anchovy were appeared lower quality by hot air that occurred the lipid oxidation, the drying system by using the cold air has been used widely. This study has been carried out on the performance improvement according to arrangement angle of baffle and location of air duct in the cold air dryer. The main parameters in this study are the arrangement angles which are without, $0^{\circ}$, $10^{\circ}$, $20^{\circ}$, $30^{\circ}$ and $40^{\circ}$, and the locations of air duct are without, front, center and back. For this study we have conducted the numerical analysis method using fluent in order to obtain the optimal condition of the drying performance. As the arrangement angle of baffle is increased, the relative humidity is proportionally decreased, the value at $40^{\circ}$ is 42.2% that indicate the reduction of about 4% than without it. After the air duct was installed, the decreased relative humidity is showed within 1%, therefore, the effect of air duct for improving the dry capacity is more large than the arrangement angle of baffle. Finally, we have obtained the optimal conditions that the arrangement angle is $40^{\circ}$ with the air duct for a cold air dryer.

• 한국생산제조학회지
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• 제19권1호
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• pp.15-25
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• 2010

The objective of this study is to investigate the optimal arrangement of cameras used for the robot's vision control scheme. The used robot's vision control scheme involves two estimation models, which are the parameter estimation and robot's joint angle estimation models. In order to perform this study, robot's working region is divided into three work spaces such as left, central and right spaces. Also, cameras are positioned on circular arcs with radius of 1.5m, 2.0m and 2.5m. Seven cameras are placed on each circular arc. For the experiment, nine cases of camera arrangement are selected in each robot's work space, and each case uses three cameras. Six parameters are estimated for each camera using the developed parameter estimation model in order to show the suitability of the vision system model in nine cases of each robot's work space. Finally, the robot's joint angles are estimated using the joint angle estimation model according to the arrangement of cameras for robot's point-position control. Thus, the effect of camera arrangement used for the robot's vision control scheme is shown for robot's point-position control experimentally.

• 항공우주기술
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• 제1권1호
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• pp.147-152
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• 2002

기존의 축소(Ⅰ) 기본형 엔진에 대한 연소 시험을 실시한 결과 분사면의 내열 특성이 불량한 것으로 판명되었다. 이에 기본형 엔진의 설계를 다각도로 수정한 축소(Ⅰ) 수정형 엔진을 제작 하게 되었다. 주요 설계 파라미터는 주분사기의 배열, 주분사기의 충돌각, 내열 코팅이었으며, 이들에 대한 시험적 연구를 수행하고 각 디자인에 따른 엔진 성능 및 내열 성능을 비교하였다. 내열 성능은 직교배열의 경우, 주분사기 충돌각이 작은 경우, 내열 코팅이 있는 경우 증가하는 경향을 보여주었다. 그에 따른 엔진 성능의 변화를 살펴보면 5% 범위 이내에서 성능 차이를 보이며 방사배열의 경우가 직교배열의 경우보다 성능이 높고, 주분사기 충돌각 15°의 경우가 20°의 경우보다 오히려 높게 나타났다. 이러한 현상은 고주파 불안정성과 관련성이 있을 것이며, 향후 시험을 통해 검증할 예정이다.

• Wind and Structures
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• 제32권2호
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• pp.127-142
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• 2021

Wind load acting on a standalone structure is different from that acting on a similar structure which is surrounded by other structures in close proximity. The presence of other structures in the surrounding can change the wind flow regime around the principal structure and thus causing variation in wind loads compared to a standalone case. This variation on wind loads termed as interference effect depends on several factors like terrain category, geometry of the structure, orientation, wind incident angle, interfering distances etc., In the present study, a three building configuration is considered and the mean pressure coefficients on each face of principle building are determined in presence of two interfering buildings. Generally, wind loads on interfering buildings are determined from wind tunnel experiments. Computational fluid dynamic studies are being increasingly used to determine the wind loads recently. Whereas, wind tunnel tests are very expensive, the CFD simulation requires high computational cost and time. In this scenario, Artificial Neural Network (ANN) technique and Support Vector Regression (SVR) can be explored as alternative tools to study wind loads on structures. The present study uses these data-driven approaches to predict mean pressure coefficients on each face of principle building. Three typical arrangements of three building configuration viz. L shape, V shape and mirror of L shape arrangement are considered with varying interfering distances and wind incidence angles. Mean pressure coefficients (Cp mean) are predicted for 45 degrees wind incidence angle through ANN and SVR. Further, the critical faces of principal building, critical interfering distances and building arrangement which are more prone to wind loads are identified through this study. Among three types of building arrangements considered, a maximum of 3.9 times reduction in Cp mean values are noticed under Case B (V shape) building arrangement with 2.5B interfering distance. Effect of interfering distance and building arrangement on suction pressure on building faces has also been studied. Accordingly, Case C (mirror of L shape) building arrangement at a wind angle of 45º shows less suction pressure. Through this study, it was also observed that the increase of interfering distance may increase the suction pressure for all the cases of building configurations considered.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2021년도 봄 학술논문 발표대회
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• pp.317-318
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• 2021

The effect of reinforcing bars embedded in concrete varies depending on the position of the electrode in the electrical resistivity measurement. In this study, the apparent resistivity according to the electrode arrangement is analyzed for each measurement angle. Through this, it is intended to be used to improve the accuracy of measurement in the concrete resistivity.

• Wind and Structures
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• 제34권3호
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• pp.275-290
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• 2022

Mobile sand barriers are a new type sand-retaining structure that can be moved and arranged according to the engineering demands of sand control. When only used for sand trapping, mobile sand barriers could be arranged in single row. For the dual purposes of sand trapping and sand stabilization, four rows of mobile sand barriers can be arranged in a staggered form. To reveal the effect of plane layout, the included angle between sand barrier direction and wind direction on the characteristics of flow fields and the sand control laws of mobile sand barriers, numerical computations and wind tunnel tests were conducted. The results showed that inflows deflected after passing through staggered arrangement sand barriers due to changes in included angle, and the sand barrier combination exerted successive wind resistance and group blocking effects. An analysis of wind resistance efficiency revealed that the effective protection length of staggered arrangement sand barriers approximately ranged from the sand barrier to 10H on the leeward side (H is sand barrier height), and that the effective protection length of single row sand barriers roughly ranged from 1H on the windward side to 20H on the leeward side. The distribution of sand deposit indicated that the sand interception increased with increasing included angle in staggered arrangement. The wind-breaking and sand-trapping effects were optimal when included angle between sand barrier direction and wind direction is 60°-90°.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 춘계학술대회 초록집
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• pp.63.2-63.2
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• 2011

The objective of this study is to investigate the aerodynamic characteristics of a small vertical axis wind turbine with dual blade type. The Wind turbine with dual blade has various angle of attack. so this turbine improve starting characteristics. The various arrangement of the vertical axis wind turbine with dual blade is designed. Among them, it shows superior quality that is arranged in three rows. Among arrangement in three rows, we use general computational fluid dynamics program CFX to find out the optimal arrangement. By comparing the predicted results of the aerodynamic characteristics of the different arrangement of the blades, an appropriate arrangement of the blade is suggested to design the small wind turbine blade.

• 한국해양공학회지
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• 제31권6호
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• pp.419-424
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• 2017

Unlike other leisure boats, a sailing yacht is propelled by wind power using sails that are controlled by the crew. Therefore, the ergonomic design of the equipment that the crew has to operate for sailing might be very important. However, it is difficult to find design rules and regulations for the equipment arrangement of a sailing yacht based on ergonomics. In this study, the arrangement design for the height and side plate angle of a winch for a sailing yacht was examined from an ergonomic design point of view. In a simulation, a Korean male in his 20s was selected as a human model for a grinder. The physical load was analyzed when he was operating a winch using a 3D human simulation. The lower back load showed the highest value when using the grinder at $90^{\circ}$ and $180^{\circ}$. Based on the results for the lower back load when using the grinder with various winch heights, it is suggested that the winch height from the cockpit floor to the top of the winch should be more than 40% of the height of the human operator. In addition, according to the results for the lower back load with various horizontal distances from the body, it is suggested that the side plate angle should be less than $16^{\circ}$.

• 한국해양공학회지
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• 제4권1호
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• pp.110-119
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• 1990

This study is concerned about the stress concentration factor measurement by photoelastic method, for the case of two circular holes arrangement in 3mm semi-infinite plate under tensile load, the ratio of those two circular holes diameter, the ratio of distance apart from circular holes to breadth and the two holes arrangement angle with loading direction were varied. Besides, the measured stress concentration by photoelastic method around one circular hole was compared with that by strain-gage method.