• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1997년도 추계학술대회논문집; 한국과학기술회관; 6 Nov. 1997
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• pp.43-49
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• 1997

A rotating rigid disk, attached on a flexible shaft or supported by a torsional spring, experiences precessional whirling due to gyroscopic moment loading. It is well known in rotor dynamics area that, as the rotational speed increases, the precessional mode of the rotating rigid disk starts splitting into two: forward and backward precessional modes. On the other hand, it is also well known in disk vibration area that a rotating flexible disk also shows another kind of mode splitting phenomenon due to the rotation, resulting in forward and backward traveling waves. When rotating multiple flexible disks are coupled in vibration with the supporting Flexible shaft, the associated mode splitting should be compatible with the two seemingly different vibration analysis methods. This paper investigates the possibility of fusing the precessional and traveling wave mode splittings so that the bending coupled disk vibrations in HDD spindle systems can be better understood.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제25권4호
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• pp.224-261
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• 2021

The interest in implicit-explicit (IMEX) integration methods has emerged as an alternative for dealing in a computationally cost-effective way with stiff ordinary differential equations arising from practical modeling problems. In this paper, we introduce implicit-explicit second derivative linear multi-step methods (IMEX SDLMM) with error control. The proposed IMEX SDLMM is based on second derivative backward differentiation formulas (SDBDF) and recursive SDBDF. The IMEX second derivative schemes are constructed with order p ranging from p = 1 to 8. The methods are numerically validated on well-known stiff equations.

• Advances in concrete construction
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• 제10권6호
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• pp.499-507
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• 2020

In current study, utilizing the Kelvin's theory with polynomial, exponential and trigonometric volume fraction laws for functionally graded cylindrical shell vibrations. Effects of different parameters for ratios of length- and height-to-radius and angular speed versus fundamental natural frequencies been determined for two categories of cylindrical shells with clamped-free edge condition. By increasing different value of height-to-radius ratio, the resulting backward and forward frequencies increase and frequencies decrease on increasing length-to-radius ratio. Moreover, on increasing the rotating speed, the backward frequencies increases and forward frequencies decreases. The frequencies are same when the cylinder is stationary. The frequencies increases and decreases on changing the constituent materials. The frequency results are verified with the earlier literature for the applicability of present model.

• Spatial Information Research
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• 제19권1호
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• pp.51-59
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• 2011

라인빙식의 항공디지털 카메라인 ADS 80의 후방(backward)영상으로 정사영성을 제작하고 건물의 기복 변위와 폐색영역을 보정 후, True Ortho Photo을 제작하였다. 또한 제작된 정사영상과 True Ortho-Photo을 검증을 위해 지상검사점, 사진기준점을 이용하여 평면 위치정확도 평가 및 분석한 결과, 프레임방식과 비교하여 상대적으로 소량의 지상기준점을 이용하여 고품질의 정사영상을 제작할 수 있었다. 또한 라인 방식 카메라의 True Ortho Photo 제작 시, 종중복도가 100%이므로 폐색영역 보정시에 효과적임을 검증 할 수 있었다.

• 한국정보통신학회논문지
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• 제7권7호
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• pp.1427-1433
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• 2003

본 논문은 TDM 방식을 적용한 회선 교환 방식의 WDM 네트워크에서 라우팅, 파장 할당 및 시간슬롯할당의 문제로서, 동적으로 광 경로를 설정하기 위한 분산 제어 프로토콜을 제안하였다. 제안한 분산 제어 프로토콜에서는 블록킹 확률을 줄일 수 있도록 후방 예약 방식을 사용하였다. 예약 실패를 최소화하기 위해 여러 채널을 예약하는 진취적 예약 방법과 단지 하나의 채널을 예약하는 보수적 예약 방법을 적용하여 두개의 방법을 시뮬레이션을 통해 비교하였다. 제안한 분산 프로토콜을 성능 평가하여 WDM/TDM 방식이 WDM 방식보다 성능이 우수함을 보이고 진취적 예약 방법이 적절한 채널 수를 사용할 경우 보수적 예약 방법보다 블록킹 확률을 줄일 수 있음을 보인다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1998년도 하계종합학술대회논문집
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• pp.134-137
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• 1998

In this paper, we propose a new consolidation algorithm for point-to-multipoint ABR flow control and compare the performance of the proposed algorithms with that of an existing consolidation algorithm. We first investigate problems of the existing algorithm in consolidating backward RM cells and propose two new consolidation algorithms to resolve these problems. Also, we investigate the performance of the proposed algorithms by simulation. As results, we show that the proposed algorithms exhibit a better performance than the existing algorithm in terms of ACR, queue length, utilization, and fairness.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1999년도 전력전자학술대회 논문집
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• pp.282-286
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• 1999

This paper presents a vector control of parallel drive, a beatless control and a low switching PWM technique for the propulsion system of Electric car as transient state which are included interrupting line voltage, changing line voltage slowly, suddenly, regenerating light load and starting from backward running. Improved performance and a validation of proposed method is shown by the experimental results using a 1.65MVA IGBT VVVF inverter and inertia load equivalent to 160 tons electric cars through a running and transient state test.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2022년도 춘계학술대회
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• pp.249-251
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• 2022

본 연구에서는 뇌파를 이용하여 드론을 제어하기 위한 기계학습을 논의한다. 드론의 이륙과 전진, 후진, 좌측 이동 그리고 우측 이동을 제어대상으로 정의하였고 이를 제어하기 위한 뇌파의 신호를 전두엽을 대상으로 하는 Fp1·Fp2 2채널 건식 전극(NeuroNicle FX2) 뇌파 측정장비를 통하여 5.19초동안 각 제어대상과 연관된 행동의 운동 심상을 눈을 뜬 상태에서 측정(Sampling Rate 250Hz, Cutoff Frequency 6~20Hz) 하였다. 측정된 뇌파신호에 대해 매틀랩의 분류학습기를 이용해서 삼중 계층 신경망, 로지스틱 회귀커널, 비선형 3차 SVM 학습을 실시하였으며 학습결과 로지스틱 회귀 커널 학습에서 드론의 이륙과 전진, 후진, 좌측 이동 그리고 우측 이동을 위한 가장 높은 정확도를 가지고 있음을 클래스 참양성률로 확인할 수 있었다.

• Journal of Mechanical Science and Technology
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• 제18권1호
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• pp.122-131
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• 2004

A constraint equation-based control law design for large angle attitude maneuvers of flexible spacecraft is addressed in this paper The tip displacement of the flexible spacecraft model is prescribed in the form of a constraint equation. The controller design is attempted in the way that the constraint equation is satisfied throughout the maneuver. The constraint equation leads to a two-point boundary value problem which needs backward and forward solution techniques to satisfy terminal constraints. An observer-based tracking control law takes the constraint equation as the input to the dynamic observer. The observer state is used in conjunction with the state feedback control law to have the actual system follow the observer dynamics. The observer-based tracking control law eventually turns into a stabilized system with inherent nature of robustness and disturbance rejection in LQR type control laws.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
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• pp.257-257
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• 2000

The objective of this research is to monitor and control the vehicle motion in order to remove out the existing safety risk based upon the human-machine cooperative vehicle control. A predictive control method is proposed to control the steering wheel of the vehicle to keep the lane. Desired angle of the steering wheel to control the vehicle motion could be calculated based upon vehicle dynamics, current and estimated pose of the vehicle every sample steps. The vehicle pose and the road curvature were calculated by geometrically fusing sensor data from camera image, tachometer and steering wheel encoder though the Perception Net, where not only the state variables, but also the corresponding uncertainties were propagated in forward and backward direction in such a way to satisfy the given constraint condition, maintain consistency, reduce the uncertainties, and guarantee robustness. A series of experiments was conducted to evaluate the control performance, in which a car Like robot was utilized to quit unwanted safety problem. As the results, the robot was keeping very well a given lane with arbitrary shape at moderate speed.