• Journal of Wetlands Research
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• v.16 no.2
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• pp.193-204
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• 2014

The distribution of animals is affected by habitat selection, and habitat type and prey resource are important factors affecting their survival. This study was conducted to investigate the distribution pattern of the Red-tongue viper snake (Gloydius ussuriensis) with respect to altitude, habitat type and distribution of potential prey resource in Cheon-ma mountain, Korea. The study area of Cheon-ma mountain was separated into three altitude categories (low, middle, and high altitude) and the habitat types were categorized according to presence or absence of aquatic ecosystem and the preferred habitat in relation to altitude was determined. The distribution pattern of Red-tongue viper snakes was significantly different according to altitude and habitat type: they were mainly distributed at low altitude and in the water valleys. The distribution pattern of the Red-tongue viper snake correlated with that of amphibians. The analyses of microhabitat use of the Red-tongue viper snake and amphibians showed that their microhabitat types were not different significantly in water valleys. In conclusion, Red-tongue viper snakes were mainly distributed in the water valleys at low altitude and this is because amphibians are important as potential prey of the Red-tongue viper snake in Cheon-ma mountain.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.403-406
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• 2009

This research is based on the altitude temperature, pressure and humidity, as defined by MIL-HDBK-310 standard and modifies this conditions to conform to the new standard MIL-STD-810F and test procedure given in AIAA-2466 from this fundamental guideline optimal design and sizing of test section, inlet, exhauster duct, temperature and humidity control was performed.

• Proceedings of the KAIS Fall Conference
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• 2012.05b
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• pp.649-652
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• 2012

회전익항공기의 연료셀 내부는 연료보관 및 연료를 엔진으로 공급하기 위한 배관과 구성품들이 배치되어 있다. 특히, 기동헬기는 전장에서 사용되는 헬기로써, 수 km 고도에서 비행하는 고정익기보다 비행고도가 낮기 때문에 피탄될 가능성이 높다. 따라서, 항공기의 생존성을 극대화하기 위해서는 피탄시 유체내부 상승압력에 의한 내부 LRU 가 받는 영향성을 검토하여 설계되어야 함은 주지의 사실이다. 그러나, 내탄시험은 연료셀 자체의 제작비용 및 준비기간이 상당히 소요되고, 실탄사용에 따른 시험수행의 제약 때문에 수치모사를 통한 관련 데이터의 확보가 필요하다. 이를 위해 본 연구에서는 유체-구조 수치모사 프로그램인 Autodyn을 이용하여 회전익항공기 연료셀의 내탄 수치모사를 수행하여, 피탄 후 연료셀 내부에서의 탄 거동을 분석하고 유체내부의 압력과 연료 셀 자체의 등가응력을 평가하였다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1998.04a
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• pp.6-6
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• 1998

중형항공기용 터보팬 엔진의 정상상태 및 천이상태 성능을 해석하고 제어기 설계를 위한 선형모델을 구하였다. 정상상태 성능해석은 설계점으로 선정한 지상정지조건과 최대상승조건(Mach=0.78, 고도=36000ft) 및 순항조건(Mach=0.78, 고도=39000ft)을 고려하였으며, 저압압축기의 공회전 상태에서 최대 회전속도까지의 부분부하성능해석을 수행하였다. 부분부하 성능해석 결과 90% RPM 조건에서 가장 연료소모율이 적어 경제적임을 알 수 있다. 동적 성능모사는 각각의 대기조건에서 연료가 Step 증가, Ramp 증가 및 감소, Step 증가 후 Ramp 감소하는 경우에 대해 수행하였다. 모사결과 고려된 모든 조건에서 연료의 Step 증가시 고압압축기의 터빈입구온도가 제한온도를 초과하여, 보다 빠른 가속과 최적의 성능을 위해서는 적절한 제어가 필요함을 알 수 있었다. 또한 최대상승조건에서 연료를 Step 증가시킬 경우 고압압축기에서 실속이 발생하여 이에 대한 대책도 필요함을 알 수 있었다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.9
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• pp.703-711
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• 2018

A preliminary design tool of a hypersonic Ludwieg tube facility which simulates real-flight environment was developed and its performance was verified by CFD(Computation Fluid Dynamics) calculations. The operating theory of Ludwieg tube was studied to develop the preliminary design tool. Using the preliminary design tool, Ludwieg tube specifications were determined to satisfy target performance. The Ludwieg tube which produces high speed flows(the Mach number ranging 4 to 10) was designed. Especially altitude simulation at Mach 4 flow could be performed.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.11a
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• pp.411-415
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• 2008

This paper presents on design factor considered in an altitude test cell facility to determine the best sizing to optimize exhaust diffuser pressure recovery and the exact cooling load required to be supplied under transient operation. Engine simulation was performed to analyse the exhaust gas temperature, exit mass flow rate, specific fuel consumption and exhaust velocity helpful in determining secondary mass air flow and the mixed air temperature entering the ejector. based on this, the amount of cooling load was deduced. It was found that improved pressure recovery reduces operational cost(air supply facility, cooling water).

• Proceedings of the KAIS Fall Conference
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• 2010.05a
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• pp.156-159
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• 2010

본 논문은 전파의 다중경로에 의한 추적레이더의 추적 오차에 대한 분석과 모사 알고리즘 개발에 관한 것이다. 일반적으로 알려진 저고도 추적 레이더의 연구내용을 분석 하였고 이를 바탕으로 Matlab을 이용한 추적오차 계산용 수치해석 프로그램을 개발하였다. 본 연구에서는 고도 오차의 요인들을 분석하고 안테나 빔 폭, 확산계수, 지면의 반사계수 등을 고려한 오차 계산방법을 제시 하였다. 시뮬레이션 결과들이 이론적인 예측 결과와 잘 일치함을 볼 수 있다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.11a
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• pp.153-156
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• 2008

Ignition and combustion performance of a gas-turbine engine were changed by various high-altitude condition. A goal of this study is to make the small test facility to simulate high-altitude condition. To perform the low pressure condition, a diffuser was used in various diffuser front of primary nozzle pressure. To perform the low temperature, heat exchanger was used in various mixture ratio of cryogenic air and ambient temperature air. The experimental result shows that high-altitude conditions can be controled by diffuser front of primary nozzle pressure and mixture ratio of cryogenic air and ambient temperature air.

• Journal of the Korean Society of Propulsion Engineers
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• v.10 no.1
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• pp.54-63
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• 2006

Ejector system are used to transport a low momentum flow to the higher pressure flow by the momentum change between high and low momentum flows. This system is used to simulate the high altitude and Mach number condition over altitude 20 km and Mach 4 of the supersonic test facility. We applied the design and the performance analysis technique(EISIMP code) of the Ramjet Test Facility(RJTF) air system in JAXA to the ejector system of the ramjet test facility in KARI. After preliminary design of the ejector system, we performed a computational study using FLUENT and investigated shock structures and flow characteristics of the ejector system.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.346-351
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• 2017

A numerical study has been conducted to investigate flow characteristics of STED with ram structure shape. By increasing the attack angle of shock cone, vacuum pressure is increased because of oblique shock at ram structure and separation point moved to the downstream of the second throat. By increasing blockage ratio, expansion wave angle is increased at ram structure while vacuum pressure is constant.