• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2000년도 제14회 학술강연논문집
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• pp.14-14
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• 2000

One of the most important aerodynamic performance characteristics for projectiles is the total drag which can be typically divided into three components, pressure drag (excluding the base), viscous skin friction drag, and base drag. In a range of supersonic flight speeds the base drag is a major contributor to the total drag and can be as much as 50%∼70% of the total drag, depending on the afterbody configuration of projectiles. It is of especial importance to minimize this part of. the drag.

• 한국압력기기공학회 논문집
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• 제16권2호
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• pp.58-67
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• 2020

This study presents cyclic stress-strain and tensile test results at room temperature (RT) and 316℃ using cold-worked TP304 stainless steel base and weld metals. By comparing the cyclic hardening/softening behavior and failure cycle of cold-worked materials with those of irradiated austenitic stainless steels, the feasibility of simulating the irradiation effect on cyclic deformation and failure behaviors of TP304 stainless steel base and weld metals was investigated. It was found that, in the absence of strain-induced martensite trasformation, cold-working could properly simulate the change in cyclic hardening/softening behavior of TP304 stainless steel base and weld metals due to neutron irradiation. It was also recognized that cold-working could adequately simulate the reduction in failure cycles of TP304 stainless steel base and weld metals due to neutron irradition in the low-cycle fatigue region.

• 한국추진공학회지
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• 제16권1호
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• pp.72-78
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• 2012

IBcode를 사용하여 강내 차압감소를 위한 추진제 위치 연구를 수행하였다. 보통 화포의 추진제는 금속재질의 탄피나 소진탄피에 장전된다. 따라서 약실이 탄피보다 크다면 탄피(추진제)의 위치가 강내탄도 성능의 주요 인자가 된다. 본 연구에서는 약실 내 빈 공간이 발생하였을 경우를 고려하여 연구를 수행하였다. 약실 내 추진제 위치를 3가지로 변형하여 연구를 수행하였고, 추진제가 포미(Breech)나 탄저(Base)에 위치하였을 경우 마이너스 차압이 발생하였으며 포미 압력과 탄저 압력의 차가 추진제를 약실 가운데에 위치하였을 경우에 비해 증가함을 확인했다. 따라서 약실 가운데에 추진제를 위치시키는 것이 강내탄도 성능 향상에 유리하다는 결론을 내릴 수 있었다.

• PNF and Movement
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• 제15권3호
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• pp.343-351
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• 2017

Purpose: This study aimed to suggest effective lunge exercise methods for various purposes by comparing differences in the muscle activity of thigh and plantar pressure according to changes in base of support during lunge exercises. Methods: The subjects were 20 college students who agreed to participate in the experiment. They performed three types of lunges-a basic lunge (BL), wide lunge (WL), and narrow lunge (NL). In a static position during each lunge, the muscle activity of the thigh and plantar pressure were measured. Each movement was maintained for 7 seconds, and the muscle activity for the 3 seconds in the middle was measured and analyzed. The plantar pressure was divided into six areas for analysis. The subjects randomly performed the lunges to prevent the influence of an experimental sequence. Each movement was performed three times, and the mean value of the three measurements was analyzed. Results: The analysis of muscle activities in the thigh during the three lunge movements showed statistically significantly higher muscle activity of biceps femoris in WL and NL than BL. Moreover, the analysis of plantar force showed statistically significant differences between BL and WL and WL and NL on the medial-forefoot and medial-midfoot, as well as between BL and WL and BL and NL on the lateral-midfoot. The analysis of plantar contact pressure exhibited statistically significant differences between BL and NL and WL and NL on the medial-forefoot, as well as a statistically significant difference between WL and NL on the medial-midfoot and lateral-hindfoot. Conclusion: This study suggests that changing the base of support during lunges can be useful to suit the purposes of various rehabilitation programs.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2011년도 제36회 춘계학술대회논문집
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• pp.236-241
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• 2011

IBcode를 강내 차압감소를 위한 추진제 위치 연구를 수행하였다. 보통 화포의 추진제는 금속재질이나 소진탄피에 장전된다. 따라서 약실이 탄피보다 크다면 추진제(탄피)의 위치가 강내탄도 성능의 주요인자가 된다. 본 연구에서는 약실 내 빈 공간이 발생하였을 경우를 고려하여 연구를 수행하였다. 3가지 경우에 대해 연구를 수행하였고, 추진제가 약실 가운데에 위치하였을 경우 Breech나 Base에 위치하였을 때의 강내 차압이 감소함을 확인할 수 있었다. 따라서 약실 가운데에 추진제를 위치시키는 것이 강내탄도 성능 향상에 유리하다는 결론을 내릴 수 있었다.

• 한국추진공학회지
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• 제12권5호
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• pp.60-66
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• 2008

각종 무기체계에서 포구속도는 보다 정확한 사격제원을 산출하기 위한 자동사격통제시스템의 기초 데이터로 활용될 수 있다. 그러나 전장환경의 여러 변수들을 고려한다 해도 동일한 탄약(추진제)에서 발생하는 불규칙적인 성능특성은 정확한 포구속도 데이터를 얻는 것을 곤란하게 한다. 본 논문에서는 강내 압력을 측정하고 약실압력과 탄저압력의 실험적 관계식을 구하여 포구속도를 산출하는 방법에 대하여 연구하였다. 이러한 방법을 통해 추진제의 불규칙적인 성능특성을 보정한 포구속도를 얻음으로써 보다 정확한 데이터를 제공할 수 있으리라 생각한다.

• 한국가시화정보학회지
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• 제10권1호
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• pp.47-54
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• 2012

Single Stage To Orbit (SSTO) missions which require its engines to be operated at varying back pressure conditions, use engines operate at high combustion chamber pressures (more than 100bar) with moderate area ratios (AR 70~80). This ensures that the exhaust jet flows full during most part of the operational regimes by optimal expansion at each altitude. Aero-spike nozzle is a kind of altitude adaptation nozzle where requirement of high combustion chamber pressures can be avoided as the flow is adapted to the outside conditions by the virtue of the nozzle configuration. However, the thrust prediction using the conventional thrust equations remains to be a challenge as the nozzle plume shapes vary with the back pressure conditions. In the present work, the performance evaluation of a new aero-spike nozzle is being carried out. Computational studies are carried out to predict the thrust generated by the aero-spike nozzle in varying back pressure conditions which requires the unsteady pressure boundary conditions in the computational domain. Schlieren pictures are taken to validate the computational results. It is found that the flow in the aero-spike nozzle is mainly affected by the base wall pressure variation. The aerospike nozzle exhibits maximum performance in the properly expanded flow regime due to the open wake formation.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2012년도 추계학술대회 논문집
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• pp.546-552
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• 2012

This paper is a study on squeal noise simulation under the consideration of temperature and pressure dependent material properties of friction material. For this, data of pressure and temperature dependent material properties of lining is achieved by using lining data base and exponential curve fit. Complex eigenvalue analysis is performed for predicting squeal noise frequency and instability and chassis dynamo test is performed for achieving squeal noise frequency, sound pressure level, occurrence temperature & pressure. Initial multi models are composed for considering complex interface conditions such as pad ear-clip, piston-housing and guide pin-torque member. The simulation result of base models is compared with the test result. Squeal noise simulation under the consideration of temperature and pressure dependent material properties of friction material is performed and analyzed using multi models. And additional condition is disc material property variation. Entire simulation conditions are combined and analyzed. Finally, this paper proposes direction of the warm squeal noise model.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2002년도 추계 학술발표회 논문집
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• pp.98-105
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• 2002

The effects of the base-isolation system and elastic soil foundation on the behavior of a liquid storage tank are studied. To evaluate the seismic response of liquid storage tank accurately, the coupled dynamic system considering base isolation and soil interaction problem is formulated in time domain. Results show that the base isolation system reduces effectively the radial displacements, base shears, overturning moments, axial resultant stresses and the hydrodynamic pressure by providing flexibility and energy dissipation capability. Base Isolation may, however, increase the relative liquid sloshing amplitude due to the effect of liquid-structure interaction and cause excessive large relative displacements between structure and foundation. In addition to base-isolator, the dynamic behavior of liquid storage tank is related to the flexibility of base foundation, so the analysis of soil-structure interaction s achieved.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1589-1594
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• 2004

A numerical analysis has been performed to give an understanding of the physics of a compressible base flow with mass bleed in a Mach 2.47 freestream. Axisymmetric, compressible mass-averaged Navier-Stokes equations are computed using a two-equation turbulence model, standard ${\kappa}-{\omega}$, and a fully implicit finite volume scheme. The mass bleed is characterized by the change in the mass flow rate of the bleed jet non-dimensionalized by the product of the base area and freestream mass flux. The result showing that there is an optimum bleed condition with maximum base pressure, leading to a minimum base drag, is clearly predicted and the validation with experimental data shows reasonable agreement.