• 한국지능시스템학회논문지
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• 제24권3호
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• pp.330-336
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• 2014

연속교반탱크반응기, 담수화 플랜트, 증류탑, pH 중화 프로세스 등을 포함한 많은 산업용 프로세스들은 높은 비선형성과 시변 특성으로 인해 제어가 까다로워 보다 정밀하고 안정된 성능을 가지는 제어기를 설계하려는 많은 노력들이 있어 왔다. 본 논문에서는 기존 연구의 단점을 개선한 CSTR 프로세스의 농도제어용 PID 제어기를 동조하는 문제를 다룬다. 액추에이터 포화 문제를 극복하기 위해 PID 제어기에는 적분기 안티와인드업 피드백 루프가 구성되며, PID 제어기의 파라미터는 전체 제어 프로세스가 만족스러운 설정치 추종 성능을 가지도록 진화연산(EA)에 의해 동조된다. 제안하는 방법은 시뮬레이션을 통해 설정치 추종 성능, 외란 억제 성능과 파라미터 변동에 대한 강인성을 확인한다.

• 한국추진공학회지
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• 제11권2호
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• pp.1-8
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• 2007

연소 안정화를 위해 로켓엔진 연소기에 장착될 수 있는 반파장 음향 공명기의 비선형 음향 감쇠 특성을 비선형 해석을 통해 조사하였다. 먼저, 공명기가 장착되지 않은 기본 연소실에 대해 넓은 범위의 진폭($80{\sim}150$ dB)을 갖는 음향 가진에 대한 연소실의 감쇠 거동을 조사한 결과, 진폭에 따라 연소실의 감쇠인자가 증가하며 125 dB 이상의 진폭에 대해서는 비선형 거동이 뚜렷이 나타남을 알았다. 반파장 공명기가 장착된 연소기에서의 계산 결과, 해당 공명기의 최적 동조조건은 진폭에 무관하였고, 높은 진폭의 압력파를 감쇠하는 기능은 유지되지만, 상대적으로 음향 공명기로서의 역할은 약화됨을 알 수 있었다.

• 제어로봇시스템학회논문지
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• 제15권3호
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• pp.258-264
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• 2009

This paper presents two control algorithms for the frequency and amplitude of the resonator of a micro sensor. One algorithm excites the resonator at its a priori unknown resonant frequency, and the other algorithm alters the resonator dynamics to place the resonant frequency at a fixed frequency, chosen by the designer. Both algorithms maintain a specified amplitude of oscillations. The control system behavior is analyzed using an averaging method, and a quantitative criterion is provided for the selecting the control gain to achieve stability. Tracking and estimation accuracy of the natural frequency under the presence of measurement noise is also analyzed. The proposed control algorithms are applied to the MEMS dual-mass gyroscope without mechanical connecting beam between two proof-masses. Simulation results show the effectiveness of the proposed control algorithms which guarantee the proof-masses of the gyroscope to move in opposite directions with the same resonant frequency and oscillation amplitude.

• Journal of Welding and Joining
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• 제16권6호
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• pp.104-112
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• 1998

In the previous study, the countermeasure for welding deformation of bracket tilt is through up through experimental inspection for total process including welding process. For completeness of systematic examination of parts having sensitivity on welding deformation, the comparison and feedback between the result through simulation of welding process and experimental data is needed. In other words, it is necessary to control welding deformation that construct the prediction system for welding deformation through comparison and tuning with experimental data. In the present study, the application of FEA on welding process of bracket tilt with susceptibility to deformation is made and deformation behavior through change of welding sequence is focused on. It is used to improve the exactness of deformation analysis that three dimensional analysis for moving heat source, activated and deactivated bead element, and volume heat flux etc.

• International Journal of Naval Architecture and Ocean Engineering
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• 제8권1호
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• pp.38-52
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• 2016

This paper describes the nonlinear dynamic motion behavior of a ship equipped with a portable dynamic positioning (DP) control system, under external forces. The waves, current, wind, and drifting forces were considered in the calculations. A self-tuning controller based on a neuro-fuzzy algorithm was used to control the rotation speed of the outboard thrusters for the optimal adjustment of the ship position and heading and for path tracking. Time-domain simulations for ship motion with six degrees of freedom with the DP system were performed using the fourth-order RungeeKutta method. The results showed that the path and heading deviations were within acceptable ranges for the control method used. The portable DP system is a practical alternative for ships lacking professional DP facilities.

• 마이크로전자및패키징학회지
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• 제11권2호
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• pp.49-52
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• 2004

세라믹 모듈 내부에 내장되는 인덕터와 캐패시터와 같은 수동소자들은 주변 소자 및 패턴의 영향으로 모듈 내부에서는 변형된 특성을 갖게 된다. 이 때문에 수동소자들의 특성을 모듈내부에 내장된 상태로 추출하는 것이 가장 정확하다. 본 연구에서는 세라믹 VCO를 개발함에 있어서 전체 회로를 공진부와 발진부로 나누어서 각 block의 특성을 측정하였고 이를 통해 VCO의 고주파수 거동을 예측하여 개발에 활용할 수 있도록 하였다.

• 한국공작기계학회논문집
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• 제11권1호
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• pp.70-76
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• 2002

Unmanned vehicles have to decide their velocities suitable for the paths which should be generated by the vehicles themselves, based on the kinematic and dynamic aspects of vehicles. For this purpose, this paper is to propose a mathematical modeling of tuning trace for the cornering of an unmanned vehicle by using normal-tangent coordinates as well as extracting the characteristics of behavior for car drivers in cornering. In the proposed modeling, the limitations of velocity can be determined based on the knowledge that the handling of drivers means the control of radius of curvature. The proposed modeling can reduce computational load and generate turning angles and velocities suitable for the cornering of unmanned vehicles.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 춘계학술대회논문집
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• pp.115-120
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• 2001

A gyroscope is a rotating body possessing one axis of symmetry and whose rotation about the symmetry axis is relatively large compared with the rotation about any other axis. Tuning fork is this type of structure that various modem gyro-sensors are based on. In this paper, dynamic behavior of a cantilevered beam subjected ta a base rotation with respect to the eccentric axis that is parallel to the beam axis is analyzed. The final equations of motion in terms of generalized coordinates can be solved with numerical scheme with various values of angular velocities and angular accelerations of the rotating axis. In contrast to the case of rotating cantilever beam like helicopter blade, the rotational motion with respect to the beam axis has effect to decrease the stiffness of the beam and has unstable region depending on the magnitude of the rotational angular velocity and angular acceleration.

• Animal cells and systems
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• 제4권3호
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• pp.215-221
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• 2000

Our anatomical and behavioral studies of embryonic rats that developed in microgravity suggest that the vestibular sensory system, like the visual system, has genetically mediated precesses of development that establish crude connections between the periphery and the brain. Environmental stimuli also regulate connection formation including terminal branch formation and fine-tuning of synaptic contacts. Axons of vestibular sensory neurons from grabistatic as well as linear acceleration receptors reach their targets in both microgravity and norm81 gravity, suggesting that this is a genetically regulated component of development. However, microgravity exposure delays the development of terminal branches and synapses in gravistatic but not linear acceleration-sensitive neurons and also produces behavioral changes. These latter changes reflect environmentally controlled processes of development.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1999년도 춘계학술대회 논문집
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• pp.126-129
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• 1999

Dielectric and piezoelectric properties of perovskite materials such as La modified $Pb(Zr,Ti)O_3$ ceramics and $Pb(Zn_{1/3}Nb_{2/3})O_3-PbTiO_3$ single crystals were investigated for cryogenic capacitor and actuator applications. Enhanced extrinsic contributions resulted in piezoelectric coefficient (d33) as high as 250 pC/N at 30 K, superior to that of PZT ($d_{33}$ ~ 100 pC/N). This cryogenic property enhancement was associated with retuning the MPB (or cryogenic temperatures. PZN-PT single crystals exhibited dramatic property improvements such as $d_{33}$ > 500 pC/N at 30 K as a result of an engineered domain state.