• Proceedings of the Korean Radioactive Waste Society Conference
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• 2004.06a
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• pp.333-333
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• 2004

고온의 용융염 매질에서 전해 정련 또는 전해제련에 의해 원하는 물질을 회수하기 위한 공정에 있어서 정확한 산화/환원 전위 측정 및 안정된 전위를 인가하기 위해서는 재현성과 내구성이 확보된 기준 전극이 필요하다. 용융염 매질에서 많이 사용되는 기준 전극은 Ag/AgCl 전극으로서 온도 사이클에 대한 전위의 히스테리시스가 작고 고온에서도 전위가 안정하다. Ag/AgCl 기준전극으로 pyrex 봉 하단부를 수 마이크론 두께의 pyrex 박막으로 제작된 것은 고온 용융염에 접촉시 열 충격, 전극류와 충돌에 의한 물리적 취약성 및 고온의 용융염에 의한 부식과 같은 단점이 있다.(중략)

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.436-439
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• 2005

Dynamic contact of a cantilever beam with Sap at the end is discussed. The gap in a structure induces dynamic contact, and the contact problem is always accompanied by inequality constraints which mean that the solution of the structure with contact condition should satisfy variational inequality. Inequality, but, can be reduced to equality condition considering convex penalty function. In this paper, formulation of a beam with contact is derived using quasi convex penalty function. General coordinate solution which is needed to increase computational efficiency is applied. Nonlinear behavior of a beam with rigid and elastic contact condition was discussed.

• Journal of the Korea Institute of Military Science and Technology
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• v.11 no.6
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• pp.164-171
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• 2008

A modified generalized particle algorithm, MGPA, was suggested to improve the computational efficiency of standard SPH method in numerical analysis of high speed impact behavior. This method uses a numerical failure mechanism than material failure models to describe the target penetration. MGPA algorithm was more effective to describe the impact phenomena and new boundaries produced during the calculation process were well recognized and treated in the target penetration problem of a bullet. When bullet perforation problems were analyzed by this method, MGPA algorithm calculation gives the stable numerical solution and stress oscillation or particle penetration phenomena were not shown. The error range in ballistic velocity limit is less than $2{\sim}13%$ for various target thickness.

• Journal of the Korea Institute of Military Science and Technology
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• v.6 no.3
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• pp.62-73
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• 2003

The characteristics of constitutive equations, for hydrocodes, were Investigated by the comparison between the smoothed particle hydrodynamcis simulation and the experiment of rod impact test which resulted in a deformation history of impacting front where high strain and high strain rate dominate. The constitutive equations used in the simulation Is J-C(Johnson-Cook) model, Z-A(Zerilli-Armstrong) model, and S-C-G(Steinberg-Cochran-Guinan) model. The modification of Z-A model, based on the increased effect of strain-rate hardening, showed better correlation with expriment.

• Proceedings of the KIEE Conference
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• 2007.10a
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• pp.493-494
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• 2007

RFID (Radio Frequency IDentification) 시스템에서 수동 태그의 낮은 전송 파워 때문에 리더는 태그와의 통신시 많은 에러를 경험하게 된다. 이것은 리더가 태그의 정보를 빠르고 정확하게 인식하는 것을 어렵게 만든다. 따라서, 이러한 문제를 해결하기 위해 에러에 강한 알고리즘을 개발하고 적용할 필요가 있다. 리더가 태그의 정보를 인식하기 위해 사용하는 대표적인 프로토콜에는 ALOHA 기반의 DFSA (Dynamic Framed-Slotted ALOHA) 프로토콜과 트리 기반의 이진트리 프로토콜이 있다. 기존의 두 프로토콜 중 DFSA는 에러가 없을 때 이진트리 보다 성능이 우수하나, 에러가 존재할 때, 이진트리 보다 약 35% 정도 에러의 영향을 많이 받는 성질을 보인다. 본 논문에서는 에러가 있는 환경과 없는 환경에서의 DFSA와 이진트리 프로토콜의 성능을 분석하고, 시뮬레이션을 이용하여 이 논문에서의 성능 분석 방법이 타당함을 증명한다. 그리고 에러가 많은 환경에서는, 빠른 RFID 태그 인식을 위해 DFSA 프로토콜보다 이진트리 프로토콜을 사용할 것을 제안한다.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.11 s.104
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• pp.1255-1261
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• 2005

The dynamic contact model of a beam that contacts to a rigid wall in a reactor core was studied. The gap between the beam and contact wall results in dynamic contact accompanying inequality constraints. The inequality constraints can be relieved to an equality constraint problem by introducing a convex Penalty function. In this work, a beam with contact condition is formulated using quasi-convex penalty function and numerically solved. General coordinate solution is adopted to raise computational efficiency. Also nonlinearity is examined In the beam contacting to a rigid wall.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.4
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• pp.108-112
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• 2007

This study analyzes the dynamic fracture phenomenon that aluminum rod impacts aluminum plate or rigid plate and deforms. The value of von-Mises stress in the instance that aluminum rod deforms on rigid plate after contact becomes 1.3 times as large as that in the instance of contact. On the contrary, the value of von-Mises stress in the instance that aluminum rod goes through aluminum plate after contact becomes 0.7 times as small as that in the instance of contact. The value of internal energy in the instance that aluminum rod contacts aluminum plate becomes 2.3 times as large as that in the instance that aluminum rod contacts rigid plate. But the value of kinetic energy in the instance that aluminum rod contacts aluminum plate becomes 0.9 times as small as that in the instance that aluminum rod contacts rigid plate. The value of internal energy in the instance that aluminum rod goes through aluminum plate after contact becomes 0.7 times as small as that in the instance that aluminum rod impacts rigid plate and deforms. And the value of sliding energy in the instance that aluminum rod contacts aluminum plate becomes 0.2 times as small as that in the instance that aluminum rod contacts rigid plate. The value of total energy in case that aluminum rod impacts aluminum plate becomes 0.9 times as small as that in the case that aluminum rod impacts rigid plate.

• Journal of Advanced Navigation Technology
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• v.25 no.6
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• pp.485-492
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• 2021

Vision-based autonomous precision landing technology for UAVs requires precise position estimation and landing guidance technology. Also, for safe landing, it must be designed to determine the safety of the landing point against ground obstacles and to guide the landing only when the safety is ensured. In this paper, we proposes vision-based navigation, and algorithms for determining the safety of landing point to perform autonomous precision landings. To perform vision-based navigation, CNN technology is used to detect landing pad and the detection information is used to derive an integrated navigation solution. In addition, design and apply Kalman filters to improve position estimation performance. In order to determine the safety of the landing point, we perform the obstacle detection and position estimation in the same manner, and estimate the speed of the obstacle using LSM. The collision or not with the obstacle is determined based on the CPA calculated by using the estimated state of the obstacle. Finally, we perform flight test to verify the proposed algorithm.

• Journal of the Korea Institute of Military Science and Technology
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• v.20 no.5
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• pp.654-664
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• 2017

The temperature profiles upon high speed impact of reactive structural materials were analyzed. A two color pyrometer, which included high-speed camera, spectral splitter, and band pass filters, was utilized to measure transient temperature profiles during and after reactive metal samples impacted into steel plate with velocities of 1600~1700 m/s. The spatial temperature distribution was analyzed from the ratio of spectral radiances at two different wavelength in infrared zone, i.e. 700 and 900 nm. The measured temperatures were calibrated with black body source. Two different types of metal samples, namely aluminum and nickel, were employed to understand reaction behavior upon the impact of samples in ambient condition. According to our experiments, the Ni sample appeared to barely react with ambient air producing an instant small fireball, while Al sample reacts violently with air generating a relatively prolong fireball.

• The Transactions of the Korea Information Processing Society
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• v.2 no.3
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• pp.364-373
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• 1995

We propose a probabilistic design method and performance analysis in the area of dynamic data structures. We assign two stacks to a block which consists of m contiguous memory cells. Frequencies of delete and insert operations are not fixed, but depend on stack heights. We present various probabilistic schema and a rigorous performance analysis for a random memory allocation. Especially, stack coillision problem is studied and exponential increase of the mean of collision time as mlongrightarrow$\infty$is showed. We also present general mathematical schema which can be applied to the performance problems of finite automata and other computer information systems.