• Journal of the Ergonomics Society of Korea
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• v.13 no.1
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• pp.3-14
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• 1994

In this study, the human gait trajectories during normal walking were synthesized using the inverse kinematics and optimization techniques. The synthesis is based on a gait model consisting of a torso and two legs. Each let has three segments: thigh, shank, foot, and has six degrees-of-freedom. In order to synthesize trajectories of this redundant system, the sum of angular displacements of articulating joints was selected as an objective function to be minimized. The proposed algorithm in this study is very useful for the analysis of human gait. For the gait analysis, the trajectories of four points in each leg should be measured. Hpwever, by using the algorithm, measuring the trajectories of two points is sufficient, and thus the experimental set-up can be simplified.

• Advances in aircraft and spacecraft science
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• v.3 no.4
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• pp.399-425
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• 2016

The dynamical requirements are obtained for airplanes to travel on inclined circular trajectories. Formulas are provided for determining the load factor, the bank angle, the lift coefficient and the thrust or power required for the motion. The dynamical properties of the airplane are taken into account, for both, airplanes with internal combustion engines and propellers, and airplanes with jet engines. A procedure is presented for the construction of tables from which the flyability of trajectories at a given angle of inclination can be read, together with the corresponding minimum and maximum radii allowed. Sample calculations are shown for the Cessna 182, a Silver Fox like unmanned aerial vehicle, and a F-16 jet airplane.

• Korean Journal of Child Studies
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• v.30 no.2
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• pp.43-55
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• 2009

This study investigated trajectories of change in the career maturity of elementary school students and of attachment to parents and academic achievement as predictors of change. The 2844 participants were 1524 boys and 1320 girls in the Korea Youth Panel Survey. They were fourth graders in 2004 and became seventh graders in 2007. Latent growth curve modeling indicated that : (1) Trajectories of change in career maturity from fourth grade to seventh grade modeled quadratic growth. (2) Variance of career maturity in initial levels, linear slope and quadratic slope indicated individual differences intrajectories of change in career maturity. (3) Attachment to parents influenced initial levels of career maturity academic achievement influenced both initial levels and linear slope of career maturity.

• Korean Journal of Child Studies
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• v.33 no.4
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• pp.1-17
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• 2012

This study examined the developmental trajectories of perceived level of stress and depression in Korean youth using longitudinal data from the Korean Youth Panel Study (KYPS) of 2,844youth (1,524 boys) across $4^{th}$ grade through $8^{th}$ grade. Latent growth modeling indicated the presence of age-related, significant increases in stress and depression for both boys and girls. Girls experienced greater in stress and depression than did boys. Multiple group analysis indicated that there was no significant sex difference in effects of stress on depression. Overall, increases in stress were associated with increases in depression levels for both boys and girls. Conceptual and clinical implications of the findings were discussed.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1770-1771
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• 2011

In mission planning of UAV applications, especially for the missions requiring height transitions, it is required to generate reference flight trajectories considering the performances of the engine installed in the UAV. Even though the vertical line following guidance based height transition trajectory generation method has been developed to build reference height transition trajectories easily, it is not adequate for considering engine performances effectively since many engine characteristics and performances have conventionally been described in the V-H(speed-height) plane which is not the very space where the UAVs are actually flying. In this paper, we derive the trajectories in V-H plane for the vertical line following flights. And based on the results, a new algorithm to design the reference height transition trajectories for UAV applicaions. Simulation results demonstrate that the proposed algorithm is very effective and easily applicable.

• Journal of the Korean Society for Precision Engineering
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• v.10 no.3
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• pp.133-140
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• 1993

In this paper, we prpose a method for tracking optimally a spatial trajectory of the end-effector of flexible robot arms with multiple joints. The proposed method finds joint trajectories and joint torques necessary to produce the desired end-effector motion of flexible manipulator. In inverse kinematics, optimized joint trajectories are computed from elastic equations. In inverse dynamics, joint torques are obtained from the joint euqations by using the optimized joint trajectories. The equations of motion using finite element method and virtual work principle are employed. Optimal control is applied to optimize joint trajectories which are computed in inverse kinematics. The simulation result of a flexible planar manipulator is presented.

• Journal of Institute of Control, Robotics and Systems
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• v.5 no.8
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• pp.969-976
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• 1999

This paper is concerned with the generation of a balancing trajectory for improving the walking performance. The balancing motion has been determined by solving a second -order differential equation. However, this method caused some difficulties in linearizing and approximating the equation and had restrictions on using various balancing trajectories. The proposed difficulties in linearizing and approximating the equation and had restrictions on using various balancing trajectories. The proposed method i this paper is based on the genetic algorithm for minimizing the motins of balancing joints, whose trajectories are generated by the fifth-order polynomial interpolation after planning leg trajectories. The real walking experiments are made on the biped robot IWR-III, developed by our Automatic Control Laboratory. The system has 8 degrees of freedom and the structure of three pitches in each leg, and one roll and one prismatic joint in the balancing joints. The experimental result shows the validity and applicability of the new proposed algorithm.

• Journal of Korea Multimedia Society
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• v.21 no.4
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• pp.478-484
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• 2018

The choice of the motion features influences the result of the human action recognition method directly. Many factors often influence the single feature differently, such as appearance of the human body, environment and video camera. So the accuracy of action recognition is restricted. On the bases of studying the representation and recognition of human actions, and giving fully consideration to the advantages and disadvantages of different features, the Dense Trajectories(DT) algorithm is a very classic algorithm in the field of behavior recognition feature extraction, but there are some defects in the use of optical flow images. In this paper, we will use the improved Dense Trajectories(iDT) algorithm to optimize and extract the optical flow features in the movement of human action, then we will combined with Support Vector Machine methods to identify human behavior, and use the image in the KTH database for training and testing.

• Korean Journal of Applied Biomechanics
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• v.16 no.1
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• pp.129-138
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• 2006

The motion of a spinning table-tennis ball is investigated in both theory and experiment. The equation of motion of spinning table-tennis ball is made using aerodynamics and calculated by C++ program In theoretical part, gravity, drag force and lift force are regarded as main force. Velocity, angular velocity, mass and Drag and lift coefficients are considered as a independent variable. Experiments are made by a digital stroboscope, a digital camera and a mirror, and snap multi-exposed images were took as a dependent result In experimental part, both magnitude and direction of velocity and angular velocity are changed in each situation. The predicted three-dimensional trajectories of spinning balls are compared with experimental trajectories. As a result the theoretical trajectories were predicted within 10% of experimental trajectories.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.6
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• pp.217-222
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• 2007

This paper describes a static gait generation process and a mechanical design process of leg mechanisms for quadruped robots. Actually robot walking is realized with the joint motion of leg mechanisms. In order to calculate the time-angle trajectories for each joint of leg mechanisms, we generate end-tip trajectories with time for each leg in the global inertial coordinate system intuitively, followed by coordinate transformations of the trajectories into the local coordinates system fixed in each leg, finally the angle-time trajectories of each joint of leg mechanisms are obtained with inverse kinematics. The stability of the gait generated in this paper was verified by a multi-body dynamic analysis using the commercial software $ADAMS^{(R)}$. Additionally the mechanical specifications such as gear reduction ratio, electrical specifications of motor and electrical power consumption during walking have been confirmed by the multi-body dynamic analysis. Finally we constructed a small quadruped robot and confirmed the gait.