• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.4
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• pp.311-317
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• 2015

This paper describes how to apply one-dimensional simulation to predict unsteady state characteristics of the cold-gas pintle thruster. Mass flow rate, chamber pressure, and nozzle exit pressure are key parameters for thrust control. Chamber pressure rose and fell monotonously with the pintle stroke variation, while thrust variation was different from chamber pressure variation. During the forward pintle stroke operation, the thrust value tended to decrease initially and returned to increase when pintle speed and chamber free volume exceed some specified value. Even though one-dimensional simulation has the limitations to predict unsteady state characteristics, it is still useful for initial performance assessment of various thrusters which adopt an altitude compensation nozzle such as a dual-bell nozzle, prior to experiment or numerical analysis.

• 한국방재학회:학술대회논문집
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• 2011.02a
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• pp.75-75
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• 2011

본 논문에서는 진동중인 교량 거더에 작용하는 풍하중을 산정하고 그에 따른 플러터 발생풍속을 예측하기 위하여 분산형 전산환경을 활용한 수치해석 연구를 수행하였다. 분산형 전산환경은 웹 포탈을 기반으로 수치해석 환경을 제공하는 수치풍동 시스템으로서, 전산유체역학(CFD : Computational Fluid Dynamics)에 대한 전문지식이 부족한 사용자들도 격자생성, 수치해석자를 이용한 계산, 가시화 등의 전 과정을 편리하게 수행할 수 있는 차세대 토목분야 연구 환경이다. 본 시스템은 그리드스피어(GfidSphere)를 기반으로 구성되었으며, 기본적으로 사용자 관리, 세션 관리, 그룹 관리, 레이아웃 관리 등을 제공하여 사용자가 포탈을 통해서 다양한 서비스를 쉽게 사용할 수 있는 환경을 구축하도록 도와준다. 수치해석을 위한 유체 지배방정식은 2차원 비정상 비압축성 RANS(Reynolds-Averaged Navier-Stokes) 방정식이며, pseudo compressibility 방법을 적용하였다. 비정상 유동장을 해석하기 위하여 이중시간 전진법(dual time stepping)을 사용하였으며, 수렴가속화를 위해 Multi-grid 기법을 적용하였다. 또한 난류 유동장 해석을 위해서 $k-{\omega}$ SST 난류 모델을 사용하였으며, 난류 천이 과정에서의 유동을 모사하기 위하여 Total stress limitation 방법을 적용하였다. 교량 거더의 연직과 회전방향의 2자유도 움직임을 모사하기 위하여 동적격자 기법을 도입하였다. 교량 거더 주변의 비정상 유동해석 결과를 통해, 거더 표면에서 떨어져나가는 크고 작은 와류의 영향으로 양력 및 모멘트 계수 그래프가 중첩된 진폭과 주기를 갖고 주기적으로 나타나는 것을 확인할 수 있었다. 또한 계산된 비정상 공기력을 적용한 2자유도 플러터 방정식을 통하여 플러터 발생풍속을 산정하였다. 최종적으로 본 연구에서 계산된 결과의 타당성을 검증하기 위하여 수치적으로 구한 플러터 발생풍속과 기존의 실험 및 수치해석 결과를 비교하였으며, 결과는 잘 일치하였다.

• Geotechnical Engineering
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• v.14 no.2
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• pp.67-78
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• 1998

Microtunnelling is a technique applied to install a small-size tunnel in a soft cohesionless ground. In microtunnelling, a series of concrete tubular segments are pushed from a starting pit to power-line tunnel under a runway of JFK international airport at New York. During the microtunneling process, bentonite is jetted with very hyh pressure through a nozzle to advance disturbance in the subgrade caused by the pressurized bentonite in the aspects of subgrade stiffness. SASW measurements were performed on the runway above the center line of the shear wave velocity profiles. Besides the change of subgrade stiffness, the change of subgrade strength was also evaluated by the site-specific relationships between shear wave velocity and N value, which was determined by N values. The estimated N values gave a clue to the understanding of the change of subgrade strength.

• Journal of the Korea Convergence Society
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• v.11 no.1
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• pp.195-200
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• 2020

In this study, the flow analyses by type of shock absorber orifice were carried out. A shock absorber is indispensable for the ride comfort that is important at the standard of a good car. As the analysis procedure, the actual speed of the shock absorber was set as the flow rate when the cylinder was advanced. And the flow analysis results on models A, B and C of shock absorber models were compared with each other. As the examination on the flow orifice in the vicinity of each model through the analysis of flow, the performance of shock absorber were recognized. On the whole, model A had the fastest flow rate and also had the largest flow rate. Model B had the slowest flow rate and the flow rate features of models B and C with the same number of orifices were similar. Through this study, it is possible to see which shock absorber orifice model facilitates the flow inside the cylinder and increases the ride comfort. It is seen that this analysis result on the flow analyses by type of shock absorber orifice can be applied by converging with the field of design.

• Korean Journal of Ichthyology
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• v.8 no.2
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• pp.1-9
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• 1996

Egg and larval stages of the rockfish, Sebastes thompsoni and S. pachycephalus pachycephalus, are described and illustrared. The size of these eggs when released were 1.27~1.33mm in S. thompsoni and 1.39~1.52mm in S. pachycephalus pachycephalus. The size of these hatching larvae when released were 3.02~3.12mm TL (total length) in S. thompsoni and 4.83~5.17mm in S. pachycephalus pachycephalus. Notochord flexion occured 7.56~8.00mm TL (17~20 days after hatching) in S. thompsorzi and 5.43~5.56mm in S. pachycephalus pachycephalus. Preflexion and flexion larvae (averaged 3.97~7.78mm TL) of S. thompsoni were distinguished from related species by pigmentation of the dorsal and ventral midlines of the tail. Larvae of S. pachycephalus pachycephalus were distinguished from related species by pigmentation of the dorsal and ventral midlines of the trunk. Transformation occured 14.22~15.86mm TL in S. pachycephalus pachycephalus.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2005.10a
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• pp.5-10
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• 2005

T.S. HANBADA will navigate to maintain the adequate distance between own ship and other ships safely for about 17 hours on the about 2 kts. On the above situation, M broadcasting station requires to maintain the distance from 100m to 500m between ships. This paper aims to calculate the minimum safe distance between ships, the distance is assessed by using ES Model which is a quantitative model for evaluating the difficulty of shiphandling. After marine traffic flow simulation, minimum safe distance for HANBADA on the 2kts is about 260m based ES value. On this paper, the result was compared about its distance to the actual navigating distance.

• Journal of Korean Society of Archives and Records Management
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• v.3 no.2
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• pp.78-96
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• 2003

Nowadays, mass media innovates and has the great power of revolution of our lives. Marshall MacLuhan says new media is the new method of language and also, it is connecting to the real world possibly. The letters make media world a big different. At the end of voiceless age, the caption not only delivers means of the contents but also provides for the composition of the screen itself. In these kinds of composition elements contain explanations such as aesthetic, entertainment, and revival aspects. The caption as translation that used to use was as changing as new way of exploring method. To deliver means of contents, the letters of inside screen has extremely big changes and meaning as well. The design of lettering is the new aesthetic method of media world. Also, the elements of lettering is approaching as the new way of lives. Therefore, this study is to provide the aspects of the lettering to the mass media respectively.

• Journal of Practical Agriculture & Fisheries Research
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• v.25 no.3
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• pp.14-18
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• 2023

White leg shrimps cultured in an inland private aquaculture farm with low salinity waters showed abnormal swimming behavior and appetite reduction in July 2022. Then, gradual mortality was observed in the aquaculture farm. During the diagnosis, bacterial strain KNUAF-SHP3 was isolated from the hepatopancreas of the dead shrimps. Based on the sequence of 16S rRNA gene, KNUAF-SHP3 was proved to be Shewanella sp., clustering into a group with S. algae MARS 14 and S. chilikensis JC5T. According to the result of experimental infection test, all shrimps challenged with high concentrations, 2.1×108 CFU/ml and 2.1×109 CFU/ml showed apparent disease symptoms and the cumulative mortality rates reached 100% in 7 days post challenge. These results emphasized that Shewanella isolate in this study can be a potential pathogen of white leg shrimp cultured in low salinity water.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.5
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• pp.278-284
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• 2017

In this study, the heat input conditions suitable for the AZ61 magnesium alloy were derived by controlling the welding speed at a constant rotational speed. In addition, from an economic point of view, industry demands higher welding speeds. Therefore,the effects of the welding speed were studied. The rotational speed applied was 800rpm, and the welding speed was varied from 100 to 500mm/min to evaluate the behavior of the welded regions. Tensile and hardness tests were conducted to examine the mechanical properties. Optical microscopy was used to observe the microstructure and soundness of the welded regions. Defects were observed at the welded region when the welding speed was more than400mm/min. As the welding speed increased, the grain size of the stir zone decreased and the hardness tended to increase proportionally. When the rotational speed was 800 rpm and the welding speed was 200mm/min and 300mm/min, there wereno defects in the welded region and excellent mechanical properties were recorded. In addition, the joint efficiencies were 100.5% and 101.2%, respectively, and the ultimate tensile strength was similar to that of the base metal. Fracture of the tensile specimen occurred between the advancing side and stir zone, and the fracture location coincided with the region where the hardness decreased temporarily.

• Korean Journal of Clinical Laboratory Science
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• v.51 no.2
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• pp.221-234
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• 2019

Cancer is genetically, metabolically and infectiously induced life threatening disorder showing aggressive growing pattern with invasive tendency. In order to prevent this global menace from jeopardizing human life, enormous studies on carcinogenesis and treatment for chemotherapy resistance have been intensively researched. Hinokitiol (${\beta}$-thujaplicin) extracted from heart wood of cupressaceous is a well-known bioactive compound demonstrating anti-inflammation, anti-bacteria and anti-cancer effects on several cancer types via apoptosis and autophagy. This study proposed that hinokitiol activates transcription factor EB (TFEB) nuclear translocation for autophagy and lysosomal biogenesis regardless of nutrient condition in cancer cells. Mitophagy and ${\beta}$-catenin translocation into the nucleus under treatment of hinokitiol on non-small cell lung cancer (NSCLC) cells and HeLa cells were investigated. Hinokitiol exerted cytotoxicity on HeLa and HCC827 cells; moreover, artificially induced autophagy by overexpression of TFEB granted imperfect sustainability onto HeLa cells. Taken together, hinokitiol is the prominent autophagy inducer and activator of TFEB nuclear translocation. Alternative cancer therapy via autophagy is pros and cons since the autophagy in cancer cells is related to prevention and survival mechanism depending on nutrition. To avoid paradox of autophagy in cancer therapy, fine-tuned regulation and application of hinokitiol in due course for successful suppressing cancer cells are recommended.