• IEMEK Journal of Embedded Systems and Applications
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• v.12 no.2
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• pp.105-112
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• 2017

To control the depth of an underwater glider, a control method by using Lyapunov's direct method is proposed. The underwater glider has a torpedo-shape hull, a movable mass in the hull, and an inflatable buoyancy bag in the hull, but doesn't have large wings that increase the lift force for the conventional underwater glider. The control laws to adjust the position of the movable mass and the mass of the inflatable buoyancy bag are derived. For a selected speed and an angle of attack, we simulated the operation of the underwater glider using Matlab/Simulink. The efficiency of the proposed controller is shown in the fact that the control effort is active during only a short period of time when the zigzag trajectory is changed from downward to upward or vice versa.

• Animal Systematics, Evolution and Diversity
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• v.33 no.3
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• pp.200-202
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• 2017

The fly genus Orchisia Rondani belonging to the tribe Coenosiini of the family Muscidae, known to be distributed throughout old world, is newly recorded in Korean fauna, along with the type species O. costata (Meigen, 1826). This genus has been known to include only two species, O. costata and O. subcostata Cui, Xue et Liu, 1995. These flies can be readily distinguished by the other related taxa of the tribe Coenosiini in having prominent color pattern on wings. The Korean population has been observed on the grass vegetation at marsh area. Photographs of external features and male genitalic characters are provide.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.6
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• pp.17-22
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• 2020

This study investigates the flow efficiency based on valve shape. Three models are designed for the throttle, ball, and butterfly valves. Results show that Flow Model B, representing the ball valve, demonstrates the fastest flow rate among the three models. Although pressure contours are present on the side surfaces of the valve wings for all models, Flow Model C, representing the butterfly valve, demonstrates to be under the least amount of applied pressure among the three models. The results of this study can be utilized to efficiently control the air flow through various types of valves.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.16 no.3
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• pp.1-6
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• 2008

The stalling speed flight test of light airplane, ChangGong-91, was performed to acquire the certification. With power-off engine condition, the wings level stall flight tests were conducted at the aircraft configuration of various flap angle - clean, 20degree, and full flap, respectively. They were performed considering with the combination of the maximum and minimum test weight, and forward and afterward center of gravity. The stalling speeds and the minimum speeds of light airplane were determined from the results of flight test. Also, the appropriateness of stall warning speeds are evaluated through the flight test measures. The airplane is recoverable only with pitch control and engine throttle from stall state without exceptional operation.

• Korean journal of applied entomology
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• v.22 no.3 s.56
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• pp.213-227
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• 1983

Thirteen species distributed over 3 genera of the subfamily Lithocolletinae are reported from Korea. Of them 8 species are new to the Korean fauna. Two genera, Hyloconis and Chrysaster, are recorded from the Asian continent for the first time. Fore wings of all the species and male and female genitalia of some ones are illustrated. Besides these Korean species, one North American species, Argyromiges ostensackenella Fitcher, 1859, is newly transferred to the genus Chrysoster.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.2
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• pp.87.1-87.1
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• 2013

Ellerman bombs(EB) are small-scale bright features observed best in the wings of H alpha line. We used the Fast Imaging Solar Spectrograph(FISS) with the 1.6m New Solar Telescope at Big Bear Solar Observatory, in order to investigate characteristics of each EB. We analyzed H alpha line profiles of EBs, and classified EBs by their contrast profiles. To analyse characteristics of EBs, we applied power-law fitting ($C={\alpha}{\Delta}{\lambda}^{-n}$) to the EB contrast profiles. The amplitude ${\alpha}$ is a measure of the strength of an EB event (or the amount of released energy), and the power-law index n is a measure of spatial concentration of energy in the higher layers of the solar atmosphere. With the two parameters, we classified EBs into a few groups. We try to understand the physical properties of each group.

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.1
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• pp.125-133
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• 2006

It is important to understand flow characteristics and performances of sails for both sailors and designers who want to have efficient thrust of yacht In this Paper the viscous flows around sail-like rigid wings, which are similar to main and jib sails of a 30 feet sloop, are calculated using a CFD tool. Lift, drag and thrust forces are estimated for various conditions of gap distance between the two sails and the center of effort of the sail system is obtained. Wind tunnel experiments are also carried out to measure aerodynamic forces acting on the sails system and to validate the computation. It is found that the combination of two sails produces the lift force larger than the sum of that produced separately by each sail and the gap distance between the two sails is an important factor to determine total lift and thrust.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.504-509
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• 2004

Chemical machining(CHM) is a special process which material removed by contact of strong etchant. The application as industrial process was started from aircraft industry after 2nd world war. Chemical milling, one of the CHM process, initially became commercial bussiness and it was called chem-mill. Even today, this process widely used to remove the material from aircraft wings and fuselage panel in aircraft industry. In this study, it is attempted to design the cylinder pattern which minimize the weight within the allowable stress using chemical milling.

• International Journal of Aeronautical and Space Sciences
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• v.10 no.1
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• pp.20-29
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• 2009

There are concerns about the influence of the gust wind caused by helicopters affecting the moving vehicles while hovering over the road during rescue activities. For the understanding of such complicated flow. numerical simulation of a rotor hovering above the ground has been carried out, changing the rotor/ground clearances. The rotor thrust is kept constant. and the rotor control is determined by trim adjustments incorporated into the CFD algorithm. Collective pitch angle and the required power decreases with the rotor/ground clearance which agrees with experience. Changes of the flowfield near the rotor with regard to the rotor height are investigated based on the calculated results.

• Korean Journal of Veterinary Research
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• v.32 no.2
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• pp.235-238
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• 1992

The diseased Chuckar partridges that were raised at the wild bird-raising farms located in Ockchun, Chungbuk province, were submitted for diagnosis in the laboratory in July. 1990. The diseased partridges aged 3~4 weeks old were shown clinical signs such as anorexia, depression, white-colored or transparent-watery diarrhea and dropping of the head and wings. At necropsy, major gross lesions were found in the livers, ceca and lungs. Histopathologically, numerous histomonads were observed in the necrotic tissues of the livers and ceca. In the cecal specimens, it was found that the ameboid histomonads have flagellum and the size of 10~20 micrometer. The case was confirmed as histomoniasis due to the infection of Histomonas meleagridis.