• Journal of Korean Society of Steel Construction
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• v.16 no.1 s.68
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• pp.81-89
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• 2004

The vibration analysis of the circular arch as a member of a structure has been an important subject of mechanics due to its various applications to many industrial fields. In particular, circular arches with variable cross section are widely used to optimize the distribution of weight and strength and to satisfy special architectural and functional requirements. The Generalized Differential Quadrature Method (GDQM) and Differential Transformation Method (DTM) were recently proposed by Shu and Zou, respectively. In this study, GDQM and DTM were applied to the vibration analysis of circular arches with variable cross section. The governing equations of motion for circular arches with variable cross section were derived. The concepts of Differential Transformation and Generalized Differential Quadrature were briefly introduced. The non-dimensionless natural frequencies of circular arches with variable cross section were obtained for various boundary conditions. The results obtained using these methods were compared with those of previous works. GDQM and DTM showed fast convergence, accuracy, efficiency, and validity in solving the vibration problem of circular arches with variable cross section.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.5
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• pp.502-510
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• 2009

Laser Inertial Navigation System(LINS) consists of Ring Laser Gyroscopes(RLG) and accelerometers. RLG has a lock-in region in which there is zero output for input angular rates less than 0.1deg/sec. The lock-in region is generated by the imperfect mirrors in RLG. To avoid the lock-in region, sinusoidal motion which is called dither motion is applied on RLG. Therefore without the fault in LINS, the dither motion must be measured by RLG/accelerometer. In this paper, we propose the method to detect the fault of LINS through checking out whether or not the dither motion is always measured by RLG/accelerometer using the Fast Fourier Transformation(FFT) on the real time. The feasibility of the fault detection method proposed in this paper is verified through the stationary and van test.

• Proceedings of the Korea Contents Association Conference
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• 2009.05a
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• pp.921-926
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• 2009

After the scientific development of human history, numerous images have been developed and expanded in digital media as a communication tools. Image digital media make communication closer between sender and receptor. The image digital media which has been developed with the change of technology and media transformation have shortened visual information transportation and the time as well by combining the sense of visual and audio. Motion graphic field has been emerged as the type of image digital media development. The development of motion graphic make possible for the expressive effect and dynamic image technique which is impossible by the existing media type. Especially, it is applied to various field such as the title of movie, TV program, and advertise or music video etc. These image expression techniques are stimulating acceptor's emotion to take a role of emotion communication function also. This study aims to find the characteristics motion graphic of which how influence as an effective communication tool as important role to the receptors, and the examine the effect and application of motion graphic to the receptors as a emotion communication tool by case study.

• Korean Journal of Applied Biomechanics
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• v.16 no.4
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• pp.115-124
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• 2006

This study was conducted to investigate the running motion in the max-velocity phase(150-160m) and the fatigue phase(350-360m) during 400m sprint by performed elementary school athletes. Eighteen elementary school male athletes who achieved at least the 3rd place in the sprint at the Korea Gangwon-Do elementary school track and field meetings during 2004 and 2005 were selected as subjects. The running motions performed by the subjects were recorded using two 8mm high speed cameras at the nominal speed of 100 frames per second. The Direct Linear Transformation technique was adopted from the beginning of filming to the final stage of data extraction. KWON 3D motion analysis package program was used to compute the 3 Dimensional coordinates, smoothing factor in which lowpass filtering method was used and cutoff frequency was 6.0 Hz. The movement patterns during foot touchdown and takeoff for the running stride were related with the biomechanical consideration. Within the limitations of this study it is concluded: In order to increase running velocity, several conditions must be fullfilled at the instant of leg touchdown and takeoff during the fatigue phase(350-360m). First, the body C.O.G(Center of Gravity) height should be raised at the instant of leg touchdown and takeoff during the fatigue phase. Second, the foot contact time should be shortened and the takeoff distance should be increased at the foot takeoff during the fatigue phase. Third, the shank angular velocity with respect to a transverse axis through the center of gravity should be increased during the leg touchdown and takeoff in the fatigue phase. Forth, the active landing style described as clawing the ground with the sole of the foot should be performed during the leg touchdown and takeoff in the fatigue phase) phase. Fifth, In order to increase running velocity in the fatigue phase while taking a slightly greater leg knee angle and body lean angle within the range of the subject's running motion during the fatigue phase would result in greater flight distance.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.7
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• pp.656-665
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• 2015

In this paper, we improved the clarity and quality of the radar imaging by applying motion compensation for time-frequency transform in B-ISAR imaging. The proposed motion compensation algorithm using UWB radar is verified. B-ISAR algorithm procedure and time-frequency transform for improved motion compensation are provided for theoretical ground. The image was created by a UWB Radar B-ISAR imaging algorithm method. Also, creating a B-ISAR imaging algorithm for motion compensation of time-frequency transformation method was used. The B-ISAR Imaging algorithm is implemented using STFT(Short-Time Fourier Transform), GWT(Gabor Wavelet Transform), and WVD(Wigner-Ville Distribution) approaches. The performance of STFT is compared with the GWT and WVD algorithms. It is found that the WVD image shows more clarity and decreased spread phenomenon than other methods.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.6
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• pp.549-559
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• 2015

In this paper, an efficient dynamic reactive motion planning method for an autonomous vehicle in a dynamic environment is proposed. The purpose of the proposed method is to improve the robustness of autonomous robot motion planning capabilities within dynamic, uncertain environments by integrating a virtual plane-based reactive motion planning technique with a sensor fusion-based obstacle detection approach. The dynamic reactive motion planning method assumes a local observer in the virtual plane, which allows the effective transformation of complex dynamic planning problems into simple stationary ones proving the speed and orientation information between the robot and obstacles. In addition, the sensor fusion-based obstacle detection technique allows the pose estimation of moving obstacles using a Kinect sensor and sonar sensors, thus improving the accuracy and robustness of the reactive motion planning approach. The performance of the proposed method was demonstrated through not only simulation studies but also field experiments using multiple moving obstacles in hostile dynamic environments.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.47 no.6
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• pp.19-27
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• 2010

This paper proposes a method for enhancing detection performance and reducing computational cost when detecting a human face by applying B-spline active contour to the frame difference of consecutive images. Firstly, the method estimates amount of user's motion using kurtosis. If the kurtosis is smaller than a pre-defined threshold, it is considered that the amount of user's motion is insufficient and thus the contour fitting is not applied. Otherwise, the contour fitting is applied by exploiting the fact that the amount of motion is sufficient. Secondly, for the contour fitting, difference edges are detected by combining the distance transformation of the binarized frame difference and the edges of current frame. Lastly, the face is located by assigning the contour fitting process to the detected difference edges. Kurtosis-based motion amount estimation can reduce a computational cost and stabilize the results of the contour fitting. In addition, distance transformation-based difference edge detection can enhance the problems of contour lag and discontinuous difference edges. Experimental results confirm that the proposed method can reduce the face localization error caused by the contour lag and discontinuity of edges, and decrease the computational cost by omitting approximately 39% of the contour fitting.

• Geophysics and Geophysical Exploration
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• v.13 no.3
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• pp.219-226
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• 2010

Current earthquake alert notification for immediate post-earthquake procedures for the critical facilities is exclusively dependent on the ground-motion intensity measures observed at the seismic station located within the site. This practice is prune to false notification due to a noise and problems of missing and poor quality records of the seismic station. The credibility of the earthquake alert notification can be enhanced by utilizing the multiple transformed records of the nearby seismic stations at other sites interconnected to the same earthquake monitoring system by a network. The time-domain transformation of the site-response between the seismic stations is implemented by convoluting the nearby records with a pair of forward and inverse FIR filters designed for the site response relative to a seismic basement. The transformed records from the nearby seismic stations can be used to estimate the ground-motion intensity measures missing at the site or to evaluate the data quality along with other various possible applications in the area of geoscience and earthquake engineering.

• Journal of the Korea Society of Computer and Information
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• v.14 no.6
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• pp.41-49
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• 2009

In this paper, the multi-camera calibration algorithm for optical motion capture system is proposed. This algorithm performs 1st camera calibration using DLT(Direct linear transformation} method and 3-axis calibration frame with 7 optical markers. And 2nd calibration is performed by waving with a wand of known length(so called wand dance} throughout desired calibration volume. In the 1st camera calibration, it is obtained not only camera parameter but also radial lens distortion parameters. These parameters are used initial solution for optimization in the 2nd camera calibration. In the 2nd camera calibration, the optimization is performed. The objective function is to minimize the difference of distance between real markers and reconstructed markers. For verification of the proposed algorithm, re-projection errors are calculated and the distance among markers in the 3-axis frame and in the wand calculated. And then it compares the proposed algorithm with commercial motion capture system. In the 3D reconstruction error of 3-axis frame, average error presents 1.7042mm(commercial system) and 0.8765mm(proposed algorithm). Average error reduces to 51.4 percent in commercial system. In the distance between markers in the wand, the average error shows 1.8897mm in the commercial system and 2.0183mm in the proposed algorithm.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.12
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• pp.2039-2046
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• 2003

Storage tank filled with fluid has unique dynamic characteristics compared to general structures, due to the interaction between fluid and structure. The oscillation of the fluid surface caused by external forces is called sloshing, which occurs in moving vehicles with contained liquid masses, such as trucks, railroad cars, aircrafts, and liquid missles. In this study, the evaluation method for the reduction of sloshing, the optimized size and location of wing and diaphragm baffles are suggested based on the experimental results. The experimental device can simulate the translation motion. A rectangular tank and various baffles are fabricated to study on the sloshing characteristics. The forces measured using the load cell at tank wall and those are compared with each other through the Fourier transformation for various conditions. The study of the sloshing of the rectangular tank equipped with baffles is conducted under the same conditions with non-baffled rectangular tank experiment. From the experimental results, the sloshing reduction effect by the baffles is observed. In conclusion in case of diaphragm baffles, the optimized size ratio of the width of baffle to the water height is 0.44 and the installation location has no effect to the damping of sloshing. In case of wing baffles, the optimized size ratio of the width of baffle to the length of a rectangular tank is 0.1 and the optimized location ratio of the baffle to the water height is 0.9.