• 한국소음진동공학회논문집
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• 제14권12호
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• pp.1354-1359
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• 2004

This paper is concerned with the application of perturbation method to the dynamic analysis of floating flexible body. In dealing with the dynamics of free-floating body, the rigid-body motions and elastic vibrations are analyzed separately. However, the rigid-body motions cause vibrations and elastic vibrations also affect rigid-body motions in turn, which indicates that the rigid-body motions and elastic vibrations are coupled in nature. The resulting equations of motion are hybrid and nonlinear. We can discretize the equations of motion by means of admissible functions but still we have to cope with nonlinear equations. In the previous paper, we proposed the use of perturbation method to the coupled equations of motion and derived zero-order and first-order equations of motion. The derivation process was lengthy and tedious. Hence, in this paper, we propose a new approach to the same problem by applying the perturbation method to the Lagrange's equations, thus providing a systematic approach to the addressed problem. Theoretical derivations show the efficacy of the proposed method.

• 대한조선학회논문집
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• 제45권3호
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• pp.309-314
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• 2008

An experimental method to estimate the added mass of a marine propeller has been developed for the axial rigid body motion in still water, and the experiments have been carried out. The experimental result has been compared to the theoretical result by PRODAS based on the unsteady lifting surface theory. The experimental method developed in this research and the theoretical method by PRODAS have been validated by confirming good agreements between the experimental results and the theoretical ones. Also the comparison to the results by empirical formula has been made and discussed.

• 한국정보통신학회논문지
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• 제18권4호
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• pp.986-991
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• 2014

모바일 헬스케어와 원격진료에서 사용되는 광용적 맥파(PPG) 신호는 환자로부터 발생되는 여러 가지의 동잡음을 포함하고 있다. 이러한 동잡음을 제거하기위해 이동평균필터, 적응필터, 가속도 센서 등을 이용한 기법이 제시되었으나, 아직까지도 그 성능이 만족 스럽지 못하다. 따라서 본 연구에서는 이러한 동잡음 문제를 해결하기 위해 칼만필터와 적응필터를 이용한 새로운 동잡음 제거 기법을 제안하고 그 성능을 평가하기위해 다양한 동잡음을 사용하였다. 이 실험의 결과에서 제안된 방법의 신호대 잡음비는 이동 평균 필터 보다 4.8배인 우수한 성능을 보였다.

• 제어로봇시스템학회논문지
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• 제22권3호
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• pp.192-198
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• 2016

Motion planning problem is still one of the important issues in robotic applications. In many real-time motion planning problems, it is advisable to find a feasible solution quickly and improve the found solution toward the optimal one before the previously-arranged motion plan ends. For such reasons, sampling-based approaches are becoming popular for real-time application. Especially the use of a rapidly exploring random $tree^*$ ($RRT^*$) algorithm is attractive in real-time application, because it is possible to approach an optimal solution by iterating itself. This paper presents a modified version of informed $RRT^*$ which is an extended version of $RRT^*$ to increase the rate of convergence to optimal solution by improving the sampling method of $RRT^*$. In online motion planning, the robot plans a path while simultaneously moving along the planned path. Therefore, the part of the path near the robot is less likely to be sampled extensively. For a better solution in online motion planning, we modified the sampling method of informed $RRT^*$ by combining with the sampling method to improve the path nearby robot. With comparison among basic $RRT^*$, informed $RRT^*$ and the proposed $RRT^*$ in online motion planning, the proposed $RRT^*$ showed the best result by representing the closest solution to optimum.

• 정보통신설비학회논문지
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• 제10권2호
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• pp.53-61
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• 2011

This research presents an adaptive fast motion estimation (ME) computation on the stage of uneven multi-hexagon grid search (UMHGS) algorithm included in an unsymmetrical-cross multi-hexagon-grid search (UMHexagonS) in H.264 standard. The proposed adaptive method is based on statistical analysis and previously obtained motion vectors to reduce the computational complexity of ME. For this purpose, the algorithm is decomposed into three processes: skipping, terminating, and reducing search areas. Skipping and terminating are determined by the statistical analysis of the collected minimum SAD (sum of absolute difference) and the search area is constrained by the slope of previously obtained motion vectors. Simulation results show that 13%-23% of ME time can be reduced compared with UMHexagonS, while still maintaining a reasonable PSNR (peak signal-to-noise ratio) and average bitrates.

• 한국멀티미디어학회논문지
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• 제15권6호
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• pp.827-836
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• 2012

키넥트의 성공적인 등장 이후 이 센서를 이용하여 사용자의 아바타에 해당하는 3차원 캐릭터의 움직임을 제어하는 많은 인터액티브 콘텐츠가 제작되었다. 하지만, 키넥트의 특성 상 사용자는 키넥트를 정면으로 바라보아야 하며, 모션 또한 제자리에서 수행할 수 있는 동작 정도만으로 국한되었다. 이 단점은 게임에서 가장 중요한 요구기능 중 하나인 가상공간 내비게이션을 수행하지 못하게 하는 근본적인 이유가 되었다. 본 논문은 이와 같은 단점을 해결하기 위한 새로운 방법을 제안한다. 두 단계로 이루어진 본 방법은 첫 번째 단계로서 사용자의 내비게이션 의도를 파악하기 위해 제자리 걷기 동작 제스처인식을 수행한다. 내비게이션 의도가 파악되면, 다음 단계에 현재 제자리 걷기동작을 상체와 하체 모션으로 자동으로 분리한 후, 미리 입력 받은 하체모션캡처 데이터를 현재 캐릭터 속도를 반영하여 수정한 뒤 분리된 원래 하체모션과 자연스럽게 교체한다. 본 논문에서 제안된 알고리즘을 이용하면, 키넥트 센서를 통해 사용자의 상체 모션을 그대로 반영함과 동시에 모션캡처 데이터를 이용하여 하체 동작을 실제 걷는 동작으로 바꾸어주기 때문에 사용자가 조정하는 3차원 캐릭터는 가상공간을 자연스럽게 내비게이션할 수 있다.

• Earthquakes and Structures
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• 제10권2호
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• pp.389-408
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• 2016

Recently, seismic hazard analysis has become a very significant issue. New systems and available data have been also developed that could help scientists to explain the earthquakes phenomena and its physics. Scientists have begun to accept the role of uncertainty in earthquake issues and seismic hazard analysis. However, handling the existing uncertainty is still an important problem and lack of data causes difficulties in precisely quantifying uncertainty. Ground Motion Prediction Equation (GMPE) values are usually obtained in a statistical method: regression analysis. Each of these GMPEs uses the preliminary data of the selected earthquake. In this paper, a new fuzzy method was proposed to select suitable GMPE at every intensity (earthquake magnitude) and distance (site distance to fault) according to preliminary data aggregation in their area using ${\alpha}$ cut. The results showed that the use of this method as a GMPE could make a significant difference in probabilistic seismic hazard analysis (PSHA) results instead of selecting one equation or using logic tree. Also, a practical example of this new method was described in Iran as one of the world's earthquake-prone areas.

• 한국통신학회논문지
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• 제30권8C호
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• pp.824-831
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• 2005

LR 영상을 이용하는 HR 영상 재구성에서 추정된 움직임 벡터의 오류는 재구성된 영상의 화질을 저하시킨다. 이를 해결하기 위해 움직임 추정과 HR 영상의 추정을 동시에 하는 방법들이 제안되었으나, 블록 정합법과 같은 간단한 방법을 사용하는 경우 추정된 움직임 벡터에는 여전히 오류가 발생한다. 본 논문에서는 정규화된 움직임 추정과 POCS를 이용한 HR 영상 재구성을 동시에 하는 IBR 재구성 방법을 제안한다. 이 방법에서는 어느 한 화소의 움직임 벡터가 이웃의 움직임 벡터들과 연관성이 있음을 이용하여 블록 정합법에 정규화를 적용하여 움직임 추정이 이루어진다. 제안된 방법을 사용한 실험 결과 종래의 방법에 비하여 움직임 추정이 개선되었으며 이에 따라서 재구성된 고해상도 영상의 화질과 PSNR이 현저히 개선되었다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 하계종합학술대회 논문집(4)
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• pp.54-57
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• 2000

In this paper, we propose a new interpolation method by using the motion between two moving image frames. In the proposed method, the movement is detected by using neighborhood pixels of target pixel in the past frame and the present frame. Then, H-shaped pseudomedian filter (below HPMED) is used for the still part of the image and Delta-shaped interpolation filter (below $\Delta$-shaped) for used in the moving part of the image. We detect the movement by comparing the differences between pixels in 4${\times}$5 window of the past frame and the present frame; the difference has a critical value. We simultaneously accomplish checking PSNR(peak signal noise ratio) and subjective assessment that is placed the focus on edge characteristic for assessment of result in computer simulation. The results show that the proposed adaptive method is better than the conventional methods.

• 제어로봇시스템학회논문지
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• 제18권3호
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• pp.285-294
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• 2012

Using bearing measurement only, target motion state is not directly obtained so that TMA (Target Motion Analysis) is needed for this situation. TMA is a nonlinear estimation technique used in passive SONAR systems. Also it is the one of important techniques for underwater combat management systems. TMA can be divided to two parts: batch estimation and sequential estimation. It is preferable to use sequential estimation for reducing computational load as well as adaptively to target maneuvers, batch estimation is still required to attain target initial state vector for convergence of sequential estimation. Selection of batch time interval which depends on observability is critical in TMA performance. Batch estimation in general utilizes predetermined batch time interval. In this paper, we propose a new method called the BTIS (Batch Time Interval and Initial State Estimation). The proposed BTIS estimates target initial status and determines the batch time interval sequentially by using a bank of GMM-TS (Gaussian Mixture Measurement-Track Splitting) filters. The performance of the proposal method is verified by a Monte Carlo simulation study.