• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2003년도 추계학술대회 논문집
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• pp.60-63
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• 2003

Resistance performance of 3 G/T class coastal leisure boat is experimentally investigated at high speed ranges and the effect of a fin attached at hull side is studied together. Wave patterns are observed to make clear the relation between the resistance performances and the wave characteristics.

• 한국항공운항학회지
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• 제17권4호
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• pp.48-54
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• 2009

We implemented the Aural Cueing System(ACS) system of the reconfigurable tactical trainer(RTT) for th rotor aircraft. RTT provides a collective training system to meet aviation training requirements and supports organizational training for aviations units in combined arms collective training and mission rehearsal. ACS handles the volume, pitch and repetition of the digitally stored sounds based on commands it receives from an UDP/IP. In this paper, we explained and implemented the conceptual and detail design the ACS system for the rotor aircraft such as AH-1H(Iroquios), UH-60(Blackhwak), AH-1(Cobra) etc. The conceptual design composed of the sound cueing data analysis, sound modelling which is inner, outer, weapon and warn environment of rotor aircraft, sound synthesis and replay.

• Nuclear Engineering and Technology
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• 제18권4호
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• pp.267-272
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• 1986

핵연료 피복관 제조 및 사용 시에 필요한 자료를 얻기 위하여 지르칼로이-4재료에서 가공과 열처리의 영향을 조사하였다. 지르칼로이-4 재료는 저가공도에서는 경도가 급격히 증가하지만 10% 이상 가공도 에서는 점진적으로 증가하였다. 냉간가공된재료의 재결정은 가공도가 30%, 60%, 80%로 증가함에 따라서 64$0^{\circ}C$, 59$0^{\circ}C$, 555$^{\circ}C$에서 각각 완료되었다. $\beta$구역에서 열처리한후에 노냉, 공냉, 수냉을하였을 때 냉각속도가 증가함에 따라서 경도는 증가하고, 조직은 coarse widmanstatten($\alpha$) $\longrightarrow$ fine parallel plate($\alpha$) $\longrightarrow$ martensite($\alpha$$^{'}$)순으로 변화한다. 변화한다.

• International Journal of Aeronautical and Space Sciences
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• 제18권3호
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• pp.565-573
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• 2017

This paper presents a multistage in-flight alignment (MIFA) method for a strapdown inertial navigation system (SDINS) suitable for moving vehicles with no initial attitude references. A SDINS mounted on a moving vehicle frequently loses attitude information for many reasons, and it makes solving navigation equations impossible because the true motion is coupled with an undefined vehicle attitude. To determine the attitude in such a situation, MIFA consists of three stages: a coarse horizontal attitude, coarse heading, and fine attitude with adaptive Kalman navigation filter (AKNF) in order. In the coarse horizontal alignment, the pitch and roll are coarsely estimated from the second order damping loop with an input of acceleration differences between the SDINS and GPS. To enhance estimation accuracy, the acceleration is smoothed by a scalar filter to reflect the true dynamics of a vehicle, and the effects of the scalar filter gains are analyzed. Then the coarse heading is determined from the GPS tracking angle and yaw increment of the SDINS. The attitude from these two stages is fed back to the initial values of the AKNF. To reduce the estimated bias errors of inertial sensors, special emphasis is given to the timing synchronization effects for the measurement of AKNF. With various real flight tests using an UH60 helicopter, it is proved that MIFA provides a dramatic position error improvement compared to the conventional gyro compass alignment.

• 제어로봇시스템학회논문지
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• 제17권11호
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• pp.1095-1100
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• 2011

In this paper, PHM (Prognostics and Health Management) techniques are briefly outlined. Prognostics, being a central step within the PHM, is explained in more detail, stating that there are three approaches - experience based, data-driven and model based approaches. Representative articles in the field of prognostics are also given in terms of the type of faults. Model based method is illustrated by introducing a case study that was conducted to the crack growth of the gear plate in UH-60A helicopter. The paper also addresses the comparison of the OBM (Overall Bayesian Method), which was developed by the authors with the PF (Particle Filtering) method, which draws great attention recently in prognostics, through the study on a simple crack growth problem. Their performances are examined by evaluating the metrics introduced by PHM society.

• International Journal of Aeronautical and Space Sciences
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• 제12권2호
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• pp.190-199
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• 2011

Unsteady flow simulations of complete helicopter configurations were conducted, and the flow fields and the aerodynamic interferences between the main rotor, fuselage, and tail rotor were investigated. For these simulations, a three-dimensional flow solver based on unstructured meshes was used, coupled with an overset mesh technique to handle relative motion among those components. To validate the flow solver, calculations were made for a UH-60A complete helicopter configuration at high-speed and low-speed forward flight conditions, and the unsteady airloads on the main rotor blade were compared to available flight test data and other calculated results. The results showed that the fuselage changed the rotor inflow distribution in the main rotor blade airloads. Such unsteady vibratory airloads were produced on the fuselage, which were nearly in-phase with the blade passage over the fuselage. The flow solver was then applied to the simulation of a generic complete helicopter configuration at various flight conditions, and the results were compared with those of the CAMRAD-II comprehensive analysis code. It was found that the main rotor blades strongly interact with a pair of disk-vortices at the outer edge of the rotor disk plane, which leads to high pulse airloads on the blade, and these airloads behave differently depending on the specific flight condition.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2011년도 춘계학술대회
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• pp.143-146
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• 2011

본 논문은 1.2Vpp differential 입력 범위를 가지는 50-MS/s 10-hit pipelined ADC를 소개한다. 설계된 pipelined ADC는 8단의 1.5bit/stage, 1단의 2bit/stage와 digital correction 블록, bias circuit 및 reference driver, 그리고 clock generator로 구성된다. 1.5bit/stage는 sub-ADC, DAC, gain stage로 구성된다. 특히, 설계된 pipelined ADC에서는 hardware와 power consumption을 줄이기 위해 SHA를 제거하였으며, 전체 ADC의 dynamic performance를 향상시키기 위해 linearity가 개선된 bootstrapped switch를 사용하였다. Sub-ADC를 위한 reference 전압은 외부에서 인가하지 않고 on-chip reference driver에서 발생시킨다. 제안된 pipelined ADC는 1.8V supply, $0.18{\mu}m$ 1-poly 5-metal CMOS 공정에서 설계되었으며, power decoupling capacitor를 포함하여 $0.95mm^2$의 칩 면적을 가진다. 또한, 60mW의 전력소모를 가진다. 또한, Nyquist sampling rate에서 9.3-bit의 ENOB를 나타내었다.

• 한국가스학회지
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• 제9권4호
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• pp.11-16
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• 2005

스테인리스 강재인 STS444에 있어서 용접조건에 따른 수소취성 거동을 고찰하고자 수소침투실험과 기계적 인장시험을 실시하였다. 즉, $0.5MH_2SO_4+0.001M \;As_2O_3$ 수용액 중에서 $1,400 kg/cm^2$의 하중을 부가하는 동시에 전기화학 부식시험 장치로 $30mA/cm^2$전류를 60분간 인가하여 수소를 침투시킨 후 기계적 인장시험을 통해서 STS444용접부의 수소취성 특성에 관해서 고찰하였다. STS444에 있어서 용접조건이 수소취성에 미치는 특성을 연구한 결과, 용접 전 기름이나 물의 흡착에 의해 인장강도나 연신율은 낮아진다. 또한 기름이나 물이 흡착함으로써 수소취성에 의한 인장응력 및 연신율의 감소율은 더 크게 나타나고, 용접 전 물의 흡착이 기름의 흡착보다 수소취성에 민감하다.

• 수산해양교육연구
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• 제18권1호
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• pp.58-64
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• 2006

In order to examine the effect of humidity on hydrogen embrittlement of STS 444 weld zone for boiler with dry and wet welding conditions, this paper was carried out the accelerated hydrogen osmosis test and the electrochemical Tafel polarization test. In 0.5M $H_2SO_4$ + 0.01M $As_20_3$ solution, this test is added to load of $1400kg/cm^2$ together with hydrogen osmosis by current of $50 {mA/cm^2}$ for 60 min.. The electrochemical Tafel polarization test was carried out in 0.5M $H_2SO_4$ + 0.01M $As_20_3$ solution. Therefore, the effect of humidity on hydrogen embrittlement of STS 444 was considered. The main results are as following: On the basis of hydrogen embrittlement mechanism, that is, integrated electrochemical polarization characteristics with the established mechanism of hydrogen embrittlement, the reduction rate of corrosion current density of weld zone in the wet weld condition is larger than in the dry condition. We can nondestructively predict the degree of hydrogen embrittlement of STS 444 weld zone for boiler through the reduction rate of electrochemical corrosion current density.

• 한국가스학회지
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• 제9권4호
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• pp.30-35
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• 2005

스테인리스 강재 STS444에 있어서 용접조건에 따른 수소취성의 전기화학적 분극특성을 고찰하고자 수소침투 실험과 전기화학적 분극실험을 실시하였다. 즉, $0.5M\; H_2SO_4+0.001M\;As_2O_3$ 수용액 중에서 $1,400kg/cm^2$의 하중을 부가하는 동시에 전기화학적 분극시험 장치로 $30mA/cm^2$전류를 60분간 인가하여 수소를 침투시켰으며 같은 수용액에서 양극분극실험을 하였다. STS444에 있어서 용접조건이 수소취성에 미치는 특성을 연구함에 있어 전보에서는 용접 전 기름이나 물의 흡착 영향으로 인장강도나 연신율이 낮아지는 현상을 규명하였지만, 본보에서는 기존의 보고된 수소취성의 발생 기구를 기초로 하여 전기화학적 부식거동을 접목하여 수소취성의 발생기구를 제안함으로써 부식전류밀도를 알면 수소취성의 민감 정도를 비파괴적으로 예측할 수 있을 것으로 판단된다.