• International Journal of Precision Engineering and Manufacturing
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• v.1 no.2
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• pp.105-114
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• 2000

An output feedback control (OFC) is presented for a linear stochastic system with known disturbance and applied to a flexible spacecraft for the reduction of residual vibration while allowing the natural deflection during operation. By converting the tracking problem into regulator problem, the OFC minimizes the expected value of a guadratic objective function composing of error stats which always remain on the intersection of sliding hypersurfaces. For the numerical evaluation with a flexible spacecraft, a large slewing maneuver strategy is devised with a tracking model for nominal trajectory and start-cost-stop strategy for economical maneuver in conjunction with the input shaping technique. The performance and efficacy of the proposed control scheme are illustrated with the comparison of different maneuver strategies.

• Tribology and Lubricants
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• v.23 no.2
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• pp.43-48
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• 2007

Leakage reduction through annular type labyrinth seals of steam turbine is necessary for enhancing their efficiency. In this study, modified geometry of the original combination-type-staggered-labyrinth seal has been suggested and numerical analysis for leakage prediction has been carried out for the modified-combination-type-staggered-labyrinth seal both based on bulk-flow model and using the CFD code FLUENT. The theoretical analysis based on bulk-flow model yields leakage reduction of the modified combination type staggered labyrinth seal by about 11%. Comparing with the result of Bulk-flow model analysis, the leakage result of CFD analysis shows reasonable agreement within 9.8% error.

• Journal of the Korean Institute of Telematics and Electronics
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• v.24 no.4
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• pp.667-674
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• 1987

In this paper an effective block matching algorithm is proposed to find the motion vector. There are two approaches to the estimation of the motion vector in MCC (motion compensated coding), i.e., pel(pixel element) recursive algorithm and block matching algorithm. The search algorithm in this paper is based on the block matching method. The advantage of a proposed algorithm using integral projections is the reduction of the computation time. While the conventional block matching methods have to be computed in 2-dimensional arrays, the proposed algorithm using integral projections can be computed in 1-dimensional arrays. In comparison with conventional block matching methods, a computer simulation shows that though the prediction error increases 0.23 db, it is not detectable for human eyes and the average reduction ratio of computation time obtained from the proposed algorithm is about 3-4.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.7 s.238
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• pp.1035-1041
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• 2005

Dynamic characteristics of CD/DVD deck fur vehicle are analyzed in this paper. Generally CD/DVD deck for vehicle is used from inferior environment with the vibration of the vehicle, shock of outside and so on. Therefore it must have the structure which is stabilized from the vibration to prevent read error. For this purpose, vibration characteristic of the deck for vehicle should be identified. To analyze characteristic of the deck system, we perform the signal analysis and modal testing using the EFT analyzer. Also we change the design factor degrading the performance of the deck system and verify the efficiency improvement using the acceleration measurement occurring to the sound discontinuation.

• International Journal of Automotive Technology
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• v.8 no.1
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• pp.75-82
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• 2007

This paper presents practical work on the reduction of gear whine noise. In order to identify the source of the gear whine noise, transfer paths are searched and analyzed by operational deflection shape analysis and experimental modal analysis. It was found that gear whine noise has an air-borne noise path instead of structure-borne noise path. The main sources of air-borne noise were the two global modes caused by the resonance of an axle system. These modes created a vibro-acoustic noise problem. Vibro-acoustic noise can be reduced by controlling the vibration of the noise source. The vibration of noise source is controlled by the modification of structure to avoid the resonance or to reduce the excitation force. In the study, the excitation force of the axle system is attenuated by changing the tooth profile of the hypoid gear. The modification of the tooth profile yields a reduction of transmission error, which is correlated to the gear whine noise. Finally, whine noise is reduced by 10 dBA.

• Journal of Institute of Control, Robotics and Systems
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• v.4 no.1
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• pp.19-25
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• 1998

발란싱 축소모델의 상태변수는 플랜트의 상태변수에 대한 정보를 주지 못한다. 발란싱 축소모델을 좌표 변환하여 얻은 상태유지 축소모델은 그 축소오차가 발란싱 축소모델의 축소오차와 같음을 증명하였다. 상태축소오차를 정의하였고, 이 오차를 구하는 방법을 제시하였는데, 이 오차는 축소모델의 차수가 정해지면 불변임을 증명하였다. 상태유지 축소모델의 상태변수는 그 상태축소오차가 작은 경우 원 시스템의 상태변수를 근사하는 장점이 있다. 상태유지 축소모델을 저차원제어기 설계에 적용하여 저차원 상태변수가 플랜트의 상태변수를 근사하는 예를 보여주었다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.7
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• pp.3117-3130
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• 2016

High peak-to-average power ratio (PAPR) of transmitted signals is a major drawback in Multicarrier modulation (MCM) systems. Companding transform is a well-known method to reduce the PAPR without restrictions on system parameters such as the number of subcarriers, frame format and constellation type. In this paper, a novel adaptive companding scheme, mainly focuses on compressing the large signals into the desirable distribution, is proposed to reduce the PAPR with low implementation complexity. In addition, formulas to calculate its PAPR and bit error rate (BER) performance are also derived. Simulation results confirm that the proposed scheme can achieve an effective tradeoff between PAPR reduction and BER performance by carefully choosing the companding parameter.

• Journal of the Korea Society of Computer and Information
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• v.4 no.4
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• pp.25-33
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• 1999

Exchanging parametric curves and surfaces between different geometric modeling systems often require degree reductions to approximate the curves and surfaces to the degree of supporting systems within the given tolerance. This paper is a research for approximate conversion of a degree reduction methods for Bezier curves in the data exchange between the different systems. Our approximate conversion is implemented that shows the experimental results with the others to reduce the degree from the given degree n to n-1 for the Bezier curves about the different degree reductions.

• Journal of Biomedical Engineering Research
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• v.41 no.1
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• pp.28-34
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• 2020

In this paper, we introduce motion artifact reduction algorithm for interleaved MRI using an advanced 3D approximation algorithm. The motion artifact framework of this paper is data corrected by post-processing with a new 3-D approximation algorithm which uses data structure for each voxel. In this study, we simulate and evaluate our algorithm using Shepp-Logan phantom and T1-MRI template for both scattered dataset and uniform dataset. We generated motion artifact using random generated motion parameters for the interleaved MRI. In simulation, we use image coregistration by SPM12 (https://www.fil.ion.ucl.ac.uk/spm/) to estimate the motion parameters. The motion artifact correction is done with using full dataset with estimated motion parameters, as well as use only one half of the full data which is the case when the half volume is corrupted by severe movement. We evaluate using numerical metrics and visualize error images.

• Bulletin of the Korean Space Science Society
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• 2004.10b
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• pp.332-336
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• 2004

This paper describes the remote tracking algorithm using measurements (azimuth, elevation, and slant range) of the radar ground station. Kalman filter model for noise reduction of the measured information is first derived by linearizing with respect to angle, angular rate, range, and range rate. And then a tracking algorithm is introduced to calculate the position of the vehicle during in-flight. The simulation results show that the algorithm is practical and effective enough tracking position of the vehicle in considerably less error.