• Journal of Drive and Control
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• v.14 no.4
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• pp.45-50
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• 2017

The gas spring is a hydropneumatic adjusting element, consisting of a pressure tube, a piston rod, a piston and a connection fitting. The gas spring is filled with compressed nitrogen within the cylinder. The filling pressure acts on both sides of the piston and because of area difference it produces an extension force. Therefore, a gas spring is similar in function compare to mechanical coil spring. Conversely, optimization is a process of finding the best set of parameters to reach a goal while not violating certain constraints. The AMESim software provides NLPQL (Nonlinear Programming by Quadratic Lagrangian) and GA (genetic algorithm) for optimization. The NLPQL method builds a quadratic approximation to the Lagrange function and linear approximations to all output constraints at each iteration, starting with the identity matrix for the Hessian of the Lagrangian, and gradually updating it using the BFGS method. On each iteration, a quadratic programming problem is solved to find an improved design until the final convergence to the optimum design. In this study, we conducted optimization design of the gas spring reaction force with NLPQL.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2012.05a
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• pp.92-95
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• 2012

The dual pulse rocket motor is a pressure vessel containing two pulse grains separated by a pulse separation device such as a fragile bulkhead. One of the important things in this systems is case insulation design using the excellent materials in the 1st stage pulse motor. We investigated manufacturing process of fabric/EPDM chamber insulations in order to protect the 1st stage pulse motor case with high intensity gas flow. Simulation motor connected with extension tube having FRP disc was designed to study ablation characteristics of insulation.

• Proceedings of the Korean Nuclear Society Conference
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• 1997.05b
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• pp.201-206
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• 1997

본 연구에서는 Ni-기 합금인 합금 600과 합금 690, Fe-기 합금인 합금 800 및 초내식성 오스테나이트계 스테인리스강인 SR-50A에 대하여 부식 환경의 변화에 따른 특성 평가를 행하였다. 전기화학적 부식 평가는 양극 분극 시험을 통하여 행하였으며 부식 환경은 NaCl, HCI, NaOH(+$Na_2$SO$_4$) 액이었다. 응력 부식 균열 시험으로는 CERT(Constant Extension Rate Test)를 행하였으며 부식환경은 40%NaOH, 40%OH+12%$Na_2$SO$_4$ 용액이었다. CERT시험 후 그 파면을 SEM관찰하여 파괴 양상을 관찰하였다. 각 합금의 양극 분극 특성을 부식 환경에 따라 평가한 결과, 부식 용액의 증류에 따라 서로 다른 분극 거동을 보이고 있는데 산성과 중성 용액에서는 SR-50A가 가장 큰 저항성을 보이는 반면, 강 알카리용액인 NaOH용액에서는 Ni-기 합금의 저항성이 Fe-기 합금의 저항성보다 우수하게 나타났다. 응력 부식 균열 저항성은 전반적으로 Fe-기 합금보다 Ni-기 합금이 우수하게 나타났다. 파단면을 SEM관찰한 결과 합금 800과 SR-50A(tube)는 용액에 관계없이 입내 파괴 모드를 나타내고 있으며, 합금 600과 SR-50A판재는 입계 파괴 양상을 보이고 있다. 또한 가성 용액 중에 $Na_2$SO$_4$를 첨가할 경우, 부식 속도를 가속화시키고 응력 부식 균열 저항성을 감소시키고 있다.

• Journal of Korea Society of Digital Industry and Information Management
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• v.20 no.1
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• pp.133-147
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• 2024

In this study, we examine the components and characteristics of channel brands, the renewal process of channel brands, and the competitiveness of SBS Subusu News and MBC 14F, online channels of Korea's leading terrestrial broadcasting company. We conducted in-depth interviews with staffs YouTube news channels such as Subusu News and 14F. First, examining the brand components and characteristics of SBS's Subusu News and MBC's 14F vertical channel, Subs News maintained its direction through the renewal of the logo type, graphic characterization, emoticon production, and campaign design production. 14F focused on brand renewal of the logo type and modification of thumbnail design to reveal the identity of the channel brand. Subusu News and 14F have achieved success through a spin-off approach that considers content relevance, expanding their brand extension. As a result of analyzing the competitiveness of the channel brand, Subusu News maintained its identity as a combination of B-class sensibility and journalism, while 14F positioned itself as a channel that delivers useful information content.

• Journal of Bio-Environment Control
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• v.19 no.3
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• pp.147-152
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• 2010

Poor fruit set during winter period is one of the biggest problem in plastic tunnel watermelon cultivation. Hand pollination is inevitable to maximize fruit set of the winter watermelon. Productivity and viability of pollen grain and organic solvents for pollen storage were investigated. All cultivars produced more than 10 mg/flower except for 'Kumchun' cultivar. Pollen amount per flower were 13.8 mg in 'Bok' and 12.1 mg in 'Speedkul'. Germination rate of pollen grains incubated at $30^{\circ}C$ right after soaking in pentane solvent were 76% in 'Kumchun' as the lowest and 92% in 'Apollokul' as the highest. The pollen of 'Bok' showed the highest germination rate by 75% after a 15-day storage in pentane. All cultivars showed their pollen germination rate below 25% after a 24-day storage. Among the cuitivars, speed of pollen tube growth in vitro were relatively lower in 'Kumchun' and 'Sambokkul' by below $50\;{\mu}m/hr$. Pollen tube of these cultivars tended to burst during its elongation on the medium. Pollen stored 24 hrs in organic solvents showed 45, 39, 34, 23, and 19% of germination in pentane, ethyl ether, n-hexane, ethyl acetate, and acetone, respectively. Compared with light condition, pollen viability was higher in darkness during pollen storage in organic solvents. Pollen grain was susceptible to the organic solvent. The viability of pollen grains seems to be influenced greatly by duration of soaking pollen in organic solvent and the polarity of solvents. Organic solvent damages surface of pollen grain and extent of damage was varied by the solvents.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.8
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• pp.3792-3799
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• 2012

The dedusting characteristics of pulse air jet type dedusting system which is widely applied in the industries were identified by utilizing the computational fluid dynamics (CFD) and the dedusting performance in modified shape of dedusting unit was compared in this study. The review on the dedusting air volume, air stream distribution and inflow velocity distribution on each shape of dedusting part showed that the case of installing the nozzle on the blow tube (Case-3) and the case of installing the double intaking tube to the venturi (Case-4 and Case-5) were more excellent than the structure (Case-1) which is widely applied in the field in its amplification effect on the air volume and extension of stream width. The specification of venturi was decided to apply the selected Case-5 for the option of the commercial back filter. It is considered that the dedusting air volume will be maintained in maximum in the case of 50 mm and 90 mm for the diameter of internal and external intaking pipe respectively.

• Journal of Space Technology and Applications
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• v.1 no.2
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• pp.217-240
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• 2021

Upon the human exploration era of the Moon, this paper introduces lunar topography and geologic fundamentals to space scientists. The origin of scientific terminology for the lunar topography was briefly summarized, and the extension of the current Korean terminology is suggested. Specifically, we suggest the most representative lunar topography that are useful to laymen as 1 ocean (Oceanus Procellarum), 10 maria (Mare Imbrium, Mare Serenitatis, Mare Tranuillitatis, Mare Nectaris, Mare Fecundatis, Mare Crisium, Mare Vaporium, Mare Cognitum, Mare Humorum, Mare Nubium), 6 great craters (Tyco, Copernicus, Kepler, Aristachus, Stebinus, Langrenus). We also suggest Korean terms for highland, maria, mountains, crater, rille, rima, graben, dome, lava tube, wrinkle ridge, trench, rupes, and regolith. In addition, we introduce the standard model for the lunar interior and typical rocks. According to the standard model on the basis of historical impact events, the lunar geological eras are classified as Pre-Nectarian, Nectarian, Imbrian, Erathostenesian, and Copernican in chronologic order. Finally, we summarize the latest discovery records on the water on the Moon, and introduce the concept of water extraction from the lunar soil, which is to be developed by the Korea Institute of Geoscience and Mineral Resources (KIGAM).

• Korean journal of applied entomology
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• v.61 no.4
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• pp.615-622
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• 2022

In this study, we sought to determine an appropriate LED light source that can be applied for the quality control of Aphidius colemani. Four LED light sources (385, 405, 450, and 660 nm) were evaluated in a Y-tube experiment (choice test) using a 5,000-k white LED as a control. The 385 nm LED light source was found to have attractant effect on A. colemani. In a no-choice test (Y-tube experiment) evaluating the remaining three LED light sources (385, 405, and 450 nm), the attractiveness of these light sources for A. colemani was high in the order 450 nm > 385 nm > 405 nm light, with no statistically significant differences between 450 nm and 385 nm. Given that 385 nm LED illumination may cause skin damage, we selected 450 nm LEDs for application in a device used for the quality control of A. colemani, which we subsequently demonstrated to have an attraction rate of 87.4%. We believe the findings of this study will make a valuable contribution to the quality control of natural enemies.

• Archives of Reconstructive Microsurgery
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• v.24 no.2
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• pp.56-61
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• 2015

Purpose: We report on the clinical result after coverage of a soft tissue defect on the medial foot and ankle with an adipofascial flap based on the perforator from the posterior tibia artery. Materials and Methods: Nine patients with soft tissue defects on the medial foot and ankle area from March 2009 to May 2014 underwent the procedure. Average age was 54 years old (range, 8~82 years). There were five male patients and four female patients. The causes of the defect were trauma (4), tumor (3), and infection (2). The pivot point of transposition of this flap is the lower perforator originating from the posterior tibia artery. The fatty tissue side of this flap could be used to resurface the defect. The donor site was closed primarily with the preserved skin, and a small caliber drain tube was used. The split-thickness skin graft was grafted to the flap and the wound. If the wound was still infected, this skin graft could be performed at a later date. Results: All flaps survived and normal soft tissue coverage was obtained for the medial foot and ankle of all patients after the skin graft. Normal footwear was possible for all cases because of thin coverage. There was an extension contracture on the medial ray of the foot, which was resolved by contracture release and skin graft. Conclusion: For the medial foot and ankle soft tissue defect, the medial crural adipofascial flap based on a perforator branch of the posterior tibia artery could be a good option to cover it.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.7
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• pp.561-568
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• 2013

After we designed Bearingless rotor hub system for 7,000lb class helicopter, flexbeam fatigue analysis was conducted for validation of requirement life time 8,000 hours. sectional structural analysis method applying elastic beam model was used. Fatigue analysis for two sections of flexbeam which were expected to weak to fatigue damage from result of static analysis was conducted. Extension, bending and torsion stiffness of flexbeam section shape was calculated using VABS for structure analysis. S-N curve of two composite material which composed flexbeam was generated using wohler equation. Load analysis of bearingless rotor system was conducted using CAMRAD II and load analysis result was applied HELIX/FELIX standard load spectrum to generate bearingless rotor system load spectrum which was used flexbeam fatigue safe life analysis.