• Journal of the Korean Society for Aviation and Aeronautics
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• v.23 no.2
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• pp.51-56
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• 2015

This paper presents the procedure of drag prediction for EAV-1, based on a numerical analysis correlated to an in-flight test. EAV-1, developed by Korea Aerospace Research Institute, is a small-sized UAV to test a hydrogen-fuel cell power system. The long-endurance test flight of 4.5 hours provides numerous in-flight data. The thrust and drag of EAV-1 during the flight test are estimated based on the wind-tunnel test results for EAV-1's propeller performance. In addition, the CFD analysis using a commercial Navier-Stokes code is carried out for the full-scale EAV-1. The computational result suggests that the initial CFD analysis substantially under-predicts the in-flight drag in that the discrepancy is up to 27.6%. Therefore, additional investigation for more accurate drag prediction is performed; the effect of propeller slipstream is included in the CFD analysis through "fan disk" modelling. Also, the additional drag from airplane trim and load factor that actually exists during the flight test in a circular path is considered. These supplemental analyses for drag prediction turn out to be effective since the drag discrepancy reduces to 2.3%.

• Journal of the Korea Society of Computer and Information
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• v.12 no.6
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• pp.251-259
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• 2007

A Bluetooth ad hoc network can be formed by interconnecting piconets into scatternet. Many algorithms of scatternet formation have been proposed so far. However, these have a problem that takes a long time to reform scatternet, especially for the case of master moving out. In this paper we propose a Fast-Recovery algorithm. which aims at reducing the time of scatternet reformation owing to master moving out. In the algorithm, we select a slave with the weigh similar to its master as Sub-Master from a piconet device table created by the master When a master leaves its piconet is detected by its slaves, the Sub-Master becomes the new master of the piconet instead of the old and directly connect to other slaves and bridge(s) through piconet device table in page state.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.26 no.3
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• pp.219-225
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• 1981

Strong wind of 6.5m/s from electric fan was applied to rice at heading stage to find out the nature of wind damage to panicle. Damaged panicles caused by typhoon were sampled out of field to measure the yield and milling components. Wind-treated glumes were developed into two forms, fertile and sterile, and each of them showed all degree of glume discoloration. The number of fertile grains were higher than sterile grains in a damaged panicle. Averagesdegree of glume discoloration was higher in not flowered glume than in flowered glume. The more recently flowered glumes resulted the higher degree of discoloration among flowered glume. The percent of sterile grain to total number of grains was the highest at stage of just flowering. The glume discoloration representing wind damage at heading state advanced in degree in ten days after treatment compared to that just after treatment. Grain length and grain width were decreased with the increased degree of glume discoloration, while grain thickness was not changed greatly. Chalkiness was a little higher in damaged grain than in normal grain without definite trends by degree of discoloration. Ripening ratio, 1000 grain weight and yield decreased with increased degree of glume discoloration in damaged panicle by typhoon. Decreasing order in yield was white rice, rough rice and brown rice. Ratio of brown rice to rough rice increased, white rice to brown rice decreased, and milling recovery was not changed greatly with increased degree of 히ume discoloration.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.30 no.2
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• pp.71-77
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• 1994

A serious of study is carried out to practical use of the three-slot cambered otter board improved by the authors. As the first step, we designed main plates, slots and accessories, such as holding plate, fan-shaped towing plate, normans, center ring, etc. Standing on this design, we made the simple cambered and three-slot cambered model otter board with accessories in a linear scale 6:1. and carried out model test to examine the efficiency of these boards. The obtained results can be summarized as follows: 1. On the simple cambered board with accessories, the values of the maximum shear coefficient($C _{LX}$ ). drag coefficient(($C _{D}$) and hydrodynamic efficiency($C _{L}$/$C _{D}$ ) are 1.39, 0.56, 2.48 at $22^{\circ}$ of the angle of stall respectively. 2. On the three-slot cambered board with accessories, $C _{LX}$/$C _{D}$ and $C _{I}$/$C _{D}$ are 1.67, 0.92, 1.82 at $32^{\circ}$ of the angle of stall respectively. 3.$C _{LX}$ of board with accessories is smaller 10~12% than that of only the main plate, and the angle of stall is almost same. 4. $C _{LX}$ and the angle of stall of the three-slot cambered board with accessories are greater 20% and $10^{\circ}$ than that of the simple cambered board respectively.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.21 no.1
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• pp.49-54
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• 2009

Ventilation requirement of apartment was mandated according to building equipment standards in 2006. When ventilation unit was considering for indoor air quality maintenance, we needed energy saving and efficiency ventilation control methods. This study carried out experiment of ventilation rate 0.7 adequacy. When we lived in apartment, we assumed that sleeping time was long stayed time in unconsciousness. Experiments carried out ventilation rate 0, 0.1, 0.4 and 0.7 in environment chamber from 22 o'clock to 06 o'clock, the concentration of $CO_2$, temperature and humidity rate measured. Analyzing the results, conclusions are as follows. 1) When we sleep in bedroom, ventilation rate 0.4 meet the requirements of domestic legal standards. Conform fan of similarity law, ventilation rate 0.4 reduced power cost about 80% than 0.7. 2) In generally sleeping time 8 hours, peak point control reduced running time of ventilation unit about 43% than normal control.

• The KSFM Journal of Fluid Machinery
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• v.5 no.3 s.16
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• pp.54-59
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• 2002

A commercial CFD code is used to compute the 3-D viscous flow field within the inlet flow concentrator of the newly developed AHU (Air Handling Unit). To improve the performance of the AHU, the inlet air needs to be gradually accelerated to the fan's annular velocity without causing turbulence or flow separation. Three major geometric parameters were selected to specify the inlet shape of the AHU. The performance of the AHU could be measured by the inlet and outlet flow uniformity and the total pressure loss through the inlet flow concentrator. Several numerical calculations were carried out to determine the influence of the geometric parameters on the performance of the AHU. The best geometric values were decided to have efficient inlet shape with analyzing CFD calculation results.

• Journal of Korea Spatial Information System Society
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• v.11 no.2
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• pp.39-44
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• 2009

In order to make the effect of the navigation system more direct, the paper proposes a thought of vehicle navigation system based on Video-GIS. A semantic framework has been defined whose core is focused on the integration and interaction of video and spatial information, which supports full content retrieval based on multimodal metadata extraction and fusion, and supports kinds of wireless access mode. Furthermore, requirements of prototype system are discussed. Then the design and implementation of framework are discussed. Next, describe the key ideas and technologies involved. Finally, we point out its future research trend.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.71-74
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• 2005

More than five pulleys are used in an automobile, such as crankshaft, water pump, air-con compressor, fan and power steering pump pulley. These pulleys are parts that need durability until retiring a car. But there is no design criterion for durability, so pulleys are designed by the experience of designer and trial and error. So, in this study, we carried out stress analysis at durability test condition and compared analysis results to durability test results. It is found that the design criterion for durability is defined as a safety factor and a safety factor is different according to the distance between the center line of v-grooves and the mating surface.

• Journal of Advanced Marine Engineering and Technology
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• v.27 no.6
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• pp.776-782
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• 2003

This paper describes a newly developed double squirrel cage induction motor in which the rotor is located outside the stator. The outside rotor type brushless dc motor has been used for VTR's head drum and PC's cooling fan, but this kind of induction motor has not been developed yet. The parameters of outside rotor type induction motor were measured from the locked rotor test and no load test. It is possible to determine the parameters which are presented in the steady-state equivalent-circuit of the outside rotor type induction motor. Load test of induction motor was carried out using a dynamometer. For the characteristics of torque, efficiency, power factor and output. the developed double squirrel cage induction motor is compared with the ordinary induction motor It is believed that the results of this paper can be used for the development of the outside rotor type induction motor.

• Journal of Mechanical Science and Technology
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• v.18 no.4
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• pp.535-549
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• 2004

This paper proposes a sliding mode controller with fuzzy adaptive perturbation compensator(FAPC) to get a good control performance and reduce the chatter, The proposed algorithm can reduce the chattering because the proposed fuzzy adaptive perturbation compensator compensates the perturbation terms. The compensator computes the control input for compensating unmodeled dynamic terms and disturbance by using the observer-based fuzzy adaptive network(FAN) The weighting parameters of the compensate. are updated by on-line adaptive scheme in order to minimize the estimation error and the estimation velocity error of each actuator. Therefore, the combination of sliding mode control and fuzzy adaptive network gives the robust and intelligent routine to get a good control performance. To evaluate the control performance of the proposed approach, tracking control is experimentally carried out for the hydraulic motion platform which consists of a 6-DOF parallel manipulator.