• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.269-275
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• 2005

This article describes the development on a new style active hybrid bearing system including both merits of an aerostatic bearing system and a magnetic bearing system. The developed active hybrid bearing system has several advantages: exact rotation, robust controller against the variation of a disturbance, improvement of stiffness and a damper of the system at a high-speed operation, and constraints of the heat generated by a bias current. In order to measure a rotating error due to the change of a cutting force and the variation of a system parameter, a CCS (Cylindrical Capacity displacement Sensor) was used.

• 대한전자공학회논문지
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• 제9권5호
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• pp.6-11
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• 1972

임의의 안정한 전달함수를 실현하는 일반적인 능동 RC회로합성방법에 대하여 논의하였다. 회로요소는 R, C, 및 연산증폭기 뿐이며, 회로구성은 박막 RC전로와 IC연산증폭기를 적용하는데 적합하다. 극과 전송령은 서로 독립식으로 조정될 수 있으며, 이들은 회로요소들의 변화에 민감하지 않다.

• 한국정보과학회:학술대회논문집
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• 한국정보과학회 2001년도 가을 학술발표논문집 Vol.28 No.2 (1)
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• pp.619-621
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• 2001

현재 대부분의 액티브 네트워크에서 액티브 노드로 전송된 패킷은 프로그램 코드와 데이터를 동시에 가지고 있으며, 기존 네트웍 방식에서의 저장(store)-전송(forward) 형태와는 달리 저장(store)-연산(compute)-전송(forward) 방식으로 패킷 처리를 한다 이 과정에서 패킷에 악성 코드가 추가되거나 실제 데이터가 변경되는 경우에는 데이터의 무결성을 보장할 수 없다. 따라서 이 논문에서는 액티브 노드에 들어오는 패킷과 그 노드에서 처리가 이루어진 후 나가는 패킷을 비교하여 악의적이거나 악의 적이지는 않지만 실수로 인한 패킷의 오류를 방어함으로서 액티브 노드의 QoS를 향상시켜주는 방식을 제안한다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.135-136
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• 2006

A precise linear motion stage supported by magnetically preloaded air bearings is introduced where preloading magnetic actuators are combined with permanent magnets and coils to adjust air bearing clearance by controlling magnetic force actively. Each of the magnetic actuators has a permanent magnet generating nominal magnetic flux for required preload and a coil to perturb the magnetic force resulting adjustment of air-bearing clearance. The characteristics of porous aerostatic bearing are analyzed by numerical analysis, and analytic magnetic circuit model is driven for magnetic actuator to calculate nominal preload and variation of force due to current. A 1-axis linear stage motorized with a coreless linear motor and a linear encoder is built for verifying this design concept. With the active magnetic preloading actuators controlled with DSP board and PWM power amplifiers, the active on-line adjusting tests about the vertical, pitching and rolling motion were performed, and the result shows very good linearity.

• 전자공학회논문지B
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• 제33B권4호
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• pp.52-62
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• 1996

In this paper, a new continuous-time current-mode integrator as basic building block of the low-voltage analog current-mode active filters was proposed. Compared to the current-mode integrator which was proposed by Zele, the proposed current-mode integrator had higher unity gain frequency and output impedance in addition to lower power dissipation. And also, a current-mode third-order lowpass active filter was designed with the proposed current-mode integrator. The designed circuits were fabricated using the ORBIT's 1.2.mu.m double-poly double-metal CMOS n-well process. The experimental resutls of the active filter designed and fabricated for this research have shown that it has the performance of 44.5MHz cutoff frequency, 3.3mW power dissipation and the third-order active filter area was 0.12mm$^{2}$.

• Structural Engineering and Mechanics
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• 제49권3호
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• pp.329-353
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• 2014

Increasing usage of tank cars and their intrinsic instability due to sloshing of contents have caused growing maintenance costs as well as more frequent hazards and defects like derailment and fatigue of bogies and axels. Therefore, varieties of passive solutions have been represented to improve dynamical parameters. In this task, assuming 22 degrees of freedom, dynamic analysis of partially filled tank car traveling on a curved track is investigated. In order to consider stochastic geometry of track; irregularities have been derived randomly by Mont Carlo method. More over the fluid tank model with 1 degree of freedom is also presented by equivalent mechanical approach in terms of pendulum. An active suspension system for described car is designed by using linear quadratic optimal control theory to decrease destructive effects of fluid sloshing. Eventually, the performance of the active suspension system has been compared with that of the passive one and a study is carried out on how active suspension may affect the dynamical parameters such as displacements and Nadal's derailment index.

• 한국자동차공학회논문집
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• 제5권2호
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• pp.205-212
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• 1997

In this study, active vibration control for a flexible cantilever beam was performed by using the intelligent control technique. The intelligent control method which integrating the back propagation algorithm and the fuzzy inference technique was proposed and its performance was examined. The proposed control algorithm for the flexible cantilever beam was verified via computer simulation of active vibration control. Furthermore, the control system and its efficiency were investigated via experiments on active vibration control by the intelligent control technique without a digital signal processing device.

• 전기학회논문지
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• 제64권1호
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• pp.143-148
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• 2015

In this paper a new method is proposed for realizing active floating inductors from voltage differencing transconductance amplifier(VDTA) which is being studied nowadays. This proposed method employs only one VDTA and one transconductance for designing an active inductor from a passive floating inductor and implementing it to integrated circuits. The number of CMOS transistors can be considerably reduced from 6~18 as 1~3 gm circuits can be eliminated and even without R the design can be made, which can help in reducing the size of the circuit and power consumption. The proposed VDTA floating inductor was successfully used in constructing 1 MHz second order biquad active bandpass filter and bandwidth could be adjusted from 77kHz~1.59MHz by the changes made in gm from 6uS~20uS.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 추계학술대회논문집
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• pp.857-861
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• 2004

An active method that improves low frequency characteristics of a reverberation chamber has been proposed. Spatial uniformity of sound pressure at low frequency has been increased by applying active noise control system. The system acts as frequency selective damping materials, which decreases resonance at low frequency and leave high frequency sound field as it is. Linearity of the chamber, which is essential for sound power measurement in the chamber, is guaranteed since fixed control logic has been adopted. Simple application and tests have been done in a small sized rectangular reverberation chamber which has 400Hz cutoff, Loud speakers were used to simulate a noise source and to construct an active noise control system. The spatial distribution of a sound field at 250Hz, 315Hz and 400Hz bands has been measured before and after control. The standard deviation of sound field has been decreased from 3.4dB to 2.5dB. The results show the possibility of active control system as a sound diffuser.

• Structural Engineering and Mechanics
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• 제83권2호
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• pp.167-178
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• 2022

Surrogate models aim to approximate the performance function with an active-learning design of experiments (DoE) to obtain a sufficiently accurate prediction of the performance function's sign for an inexpensive computational demand in reliability analysis. Nevertheless, many existing active-learning methods are limited to the Kriging model, while the uncertainties of the Kriging itself affect the reliability analysis results. Moreover, the existing general active-learning methods may not achieve a fully satisfactory balance between accuracy and efficiency. Therefore, a novel active-learning method GLM-CM is constructed to yield the issues, which conciliates several merits of existing methods. To demonstrate the performance of the proposed method, four examples, concerning both mathematical and engineering problems, were selected. By benchmarking obtained results with literature findings, various surrogate models combined with the proposed method not only provide an accurate reliability evaluation while highly alleviating the computational burden, but also provides a satisfactory balance between accuracy and efficiency compared to the other reliability methods.