• Aerospace Engineering and Technology
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• v.11 no.2
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• pp.65-72
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• 2012

Numerical simulations were performed to study the stall characteristics of turboprop aircraft. Stall characteristics were qualitatively investigated using the computational results of various configurations based on the combinations of propeller and high lift device. For the analysis of stall characteristics, three-dimensional Navier-Stokes solver with Spalart-Allmaras turbulence model was used and the relative motion between propeller and wing was simulated using sliding mesh technique. For the cruise configurations, major flow separation was occurred at the fuselage/wing fairing and the separation was reduced under propeller slipstream condition. For the high lift device configuration without propeller, major flow separation was occurred at the outboard side of nacelle. With rotating propeller, early stall onset due to low relative velocity and high effective angle of attack was observed on the outboard wing section. Regarding rotating direction of propeller, inboard-down direction was preferred due to the stall delay effect of propeller slipstream.

• Korean journal of applied entomology
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• v.39 no.1
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• pp.13-19
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• 2000

This studies was carried out to investigate the natural enemies of citrus red mite, pononychus citri and seasonal occurrence of its major beneficial insects in Yuzu groves (Chonnam province) from 1996 to 1998. Natural enemies against citrus red mite were 9 species including Oligota kashmirica benifica, 0. yasumatsui, Stethorus punctillum, Chrysopa pallens, Propylea japonica, Orius sauteri, Scolothrips takahashii, Amblyseius womersleyi and one unidentified species of thrips (Family: Phlaeothripidae). Among them, Oligota kashmirica benzficu and Stethorus punctillum were found to be dominant species. 0 . kushmirica henifica had 4-5 generations from middle May to middle November with peak in early September. S. punctillum had 3 generations from late May to late October with peak of late June to middle July. Population dynamics between predator ( 0 . kushmiricu benifica and S. punctillum) and prey (Panonychus citri) were quite well synchronized until September but predator density was decreased abruptly after October.

• Journal of the Society of Naval Architects of Korea
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• v.34 no.1
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• pp.60-67
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• 1997

This paper presents the results of 3rd wind tunnel test for the wings of WIG R/C test models, 'Hanjin-1' & 'Hanjin-2'. We made 'Hanjin-1' in last May 1995 and had a success in test flight. And in order to grasp the aerodynamic characteristics of wings in ground effect, the measurements of lift and drag were carried out for the various kinds of wing. It was shown that lift and lift-drag ratio increase with decrease of the clearance, but the feature was considerably depended on the shape of wing section. In this case we select the three kind of wing. section, and then compare their characteristics especially for a stability in longitudinal motion. They are NACA6409 for 'Hanjin-1' and the two kinds of DHMTU for ekranoplans of Russia. Experimental results show that the pitching moments of DHMTU wing sections are smaller than NACA6409.

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 1999.06a
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• pp.19-24
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• 1999

Ti-6A1-4V재는 1950년대에 개발된 이후, 전체 Ti-합금 수요의 50% 이상을 차지하고 있으며 주로 항공기 터빈 엔진 날개나 자동차의 엔진 밸브 등 각종 열기관의 부품으로 사용되어 왔으나 최근에는 인체의 인공관절로도 수요가 증가하고 있다. (중략)

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.10a
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• pp.57-58
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• 2011

• Korean journal of applied entomology
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• v.55 no.3
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• pp.223-233
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• 2016

In order to identify a new control measure for a sporadic insect pest, Pochazia shantungensis, 23 types of essential oils were screened for their repellent effects, with an olfactory test using a Y-tube olfactometer. Results indicated that 21 essential oils, except lemongrass oil and peppermint oil, did not show repellent activity against P. shantungensis. The repellent effect of peppermint oil was over 80%. When 0.1, 0.5, and $1{\mu}l$ of peppermint oil were used, the rate of repelling of P. shantungensis gradually increased, and was as high as 76.5% when $10{\mu}l$ was used. The main components of peppermint oil were 1,8-cineole, iso-menthyl acetate, menthone, and menthol, at 4.7, 8.0, 23.8 and 53.7%, respectively. When the three main components were mixed using a Y-tube olfactometer, a strong repellent effect (76.2%) was observed when $5{\mu}l$ was used. Peppermint oil showed a repellent and ovipositional repellent effect against P. shantungensis in the field. However, this activity persists only for a short period, and high concentrations can lead to phytotoxicity. Therefore, it is necessary to develop ideal formulations.

• Korean journal of applied entomology
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• v.41 no.4
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• pp.233-238
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• 2002

The seasonal occurrence trends of the brown-winged green bug, Plautia stali, and the brown malmorated stink bug, Halyomorpha halys, were monitored in sweet persimmon orchards in southern region of Korea using light traps (in 2000 and 2001), and aggregation pheromone traps (methyl (E, E, Z)-2 ,4, 6-decatrienoate)) of P. stali (in 2001). Light trap data showed that H. halys started to occur from the end of June, and reached its peak in early or mid August, while P. stali was mostly attracted to the traps from mid July to late August without any distinct attraction peak. Both species did not occur after September in the persimmon orchards studied. The attraction patterns of both species to aggregation pheromone traps were different from those observed in light traps. Both species were attracted to the pheromone traps from mid May to late August. The peak occurrence of H. halys could not be detected due to low catches. However, the period of peak attraction for P. stali was from late June to late August depending on the geographical locations. The aggregation pheromone traps of P. stali attracted more number of P stali than H. hails, but the light traps showed a reverse pattern. In both species, more females were attracted to the aggregation pheromone traps than males. The difference of attraction patterns between 2 types of traps was discussed in relation to content of soluble tannin in persimmon fruits.

• Korean journal of applied entomology
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• v.54 no.3
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• pp.179-189
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• 2015

In 2014, surveys were conducted in Korea to study the geographical distribution, host plants, and potential habitats of Pochazia shantungensis. The occurrence of P. shantungensis was confirmed in 43 cities and counties nationwide, and identified for the first time in Gyeongsangbuk-do. P. shantungensis has a wide range of diverse host plants comprising 113 species in 53 families, including crops, fruits, and forest trees. Since the hemipteran was first reported in Korea, 138 species from 62 families have been identified as P. shantungensis host plants. This insect feeds on the following major host plants: Malus pumila, Aralia elata, Styrax japonicus, Salix gracilistyla, Broussonetia kazinoki, Albizia julibrissin, Ailanthus altissima, Castanea crenata, Robinia pseudoacacia, and Cornus officinalis. Potential habitat was analyzed in the present study using the Maxent model with 12 variables (8 climate, 1 land cover, 1 forest type, 1 ecological zoning, and 1 distance). The model ROC AUC was 0.884, indicating a high accuracy. In the present study, precipitation of warmest quater, mean temperature of warmest quarter, forest type, and land cover were the most significant factors affecting P. shantungensis distribution, and habitat.

• Aerospace Engineering and Technology
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• v.12 no.2
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• pp.180-185
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• 2013

In this study, preliminary design of human powered aircraft was performed by considering the aerodynamic performance. For this, overall weight including the aircraft and pilot was determined. Then, the main wing and horizontal/vertical tail were designed with appropriate selection of the airfoils and planform shapes. Based on these, three dimensional flow was calculated to obtain lift and drag coefficients and the position of center of gravity (CG). Consequently, it was shown that the lift and power of the aircraft satisfied the constraints of the minimum required lift and the pilot's available power. Also, the CG of the aircraft was located at aerodynamic center (AC) of the main wing, which guaranteed 26% of the static margin.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.3
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• pp.167-174
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• 2021

Computational Fluid Dynamics (CFD) was performed under low-speed wind tunnel test conditions using a 29.7% scale model of the NASA common research model. A wind tunnel test was conducted to measure the aerodynamic coefficient of the CRM with Belly sting model support configuration at a low Reynolds number of 0.3×106 and it was compared with the aerodynamic coefficient of CFD analysis. In order to verify the validation of the analysis, a computational analysis under the conditions of the advance research was performed and compared. The interference effect of the Belly sting model support affected not only the fuselage but also the main and tail wings.