• Korean Journal of Applied Biomechanics
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• v.34 no.2
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• pp.71-80
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• 2024

Objective: This study aimed to explore the brain connectivity between brain and biomechanical variables by exploring motion recognition through FFT (fast fourier transform) analysis and AI (artificial intelligence) focusing on quiet standing movement patterns. Method: Participants included 12 young adult males, comprising university students (n=6) and elite gymnasts (n=6). The first experiment involved FFT of biomechanical signals (f_CoP, f_AJtorque and f_EEG), and the second experiment explored the optimization of AI-based GRU (gated recurrent unit) using f_EEG data. Results: Significant differences (p<.05) were observed in frequency bands and maximum power based on group and posture types in the first experiment. The second study improved motion prediction accuracy through GRU performance metrics derived from brain signals. Conclusion: This study delved into the movement pattern of upright standing posture through the analysis of bio-signals linking the cerebral cortex to motor performance, culminating in the attainment of motion recognition prediction performance.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.1054-1059
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• 2005

The artificial potential method uses a potential field to guide a robot from a start to a goal configuration respectively. The potential field consists of attractive potential used to pull a robot toward a goal and repulsive potential to keep it away from obstacles. However, there are two problems concerning local minimum and computational cost to be resolved in conventional artificial potential methods. This study proposes a method utilizing a spline surface that interpolates arbitrary boundaries and a domain reduction method that reduces the unnecessary area. The proposed spline surface interpolates arbitrary shaped boundaries and is used as an artificial potential to guide a robot for global motion planning of a mobile robot. A reduced domain process reduces the unnecessary domain. We apply a distance-weighted function as such a function, which blends distances from each boundary with a reduction in computational time compared with other analytical methods. As a result, this paper shows that an arbitrary boundary spline surface provides global planning and a domain reduction method reduces local minimum with quick operation.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1998.10a
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• pp.497-504
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• 1998

In the nonlinear dynamic structural analysis, the given ground excitation as an input should be well defined. Because of the lack of recorded accelerograms in Korea, it is required to generate an artificial earthquake by a stochastic model of ground excitation with various dynamic properties rather than recorded accelerograms. It is well own that earthquake motions are generally non-stationary with time-varying intensity and frequency content. Many researchers have proposed non-stationary random process models. Yeh and Wen (1990) proposed a non-stationary stochastic process model which can be modeled as components with an intensity function, a frequency modulation function and a power spectral density function to describe such non-stationary characteristics. This model is based on the simulation for the strong-motion earthquakes with magnitude greater than approximately 5.0~6.0, because it will be not only expected to cause structural damage but also involved the characteristics of earthquake motions. Also, the recorded earthquake motion within this range are still very scarce in Korea. Thus, it is necessary to verify the model by the application of it to the mid-magnitude (approximately 4.0~6.0) earthquakes actually recorded in domestic or foreign area. The purpose of the paper is to generate an artificial earthquake using the model of Yeh and Wen in the area with low seismicity.

• Structural Engineering and Mechanics
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• v.71 no.4
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• pp.377-390
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• 2019

A method for estimating the floor response spectra (FRS) of elastic structures under earthquake excitations is proposed. The method is established based on a previously proposed direct estimation method for single degree of freedom systems, which generally overestimates the FRS of a structure, particularly in the resonance period range. A modification factor is introduced to modify the original method; the modification factor is expressed as a function of the period ratio and is determined through regression analysis on time history analysis results. Both real and artificial ground motions are considered in the analysis, and it is found that the modification factors obtained from the real and artificial ground motions are significantly different. This suggests that the effect of ground motion should be considered in the estimation of FRS. The modified FRS estimation method is further applied to a 10-story building structure, and it is verified that the proposed method can lead to a good estimation of FRS of multi-story buildings.

• Korean Journal of Artificial Intelligence
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• v.4 no.1
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• pp.1-3
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• 2016

These days, citizens are interested in the energy. IT technology needs to develop and to make use of energy effectively and to save energy. In this study, motion recognition LED lamp was used to have good energy efficiency and to be made of environment friendly material. The purpose of development of the lamp was to add motion recognition to LED lamp. In this study, infrared ray sensor's distance measurement was used to develop LED lamp. Most of the lamps were used under dark environment, so that infrared ray sensor was used to perceive movement under dark environment. And, LED lamp with good efficiency and less power consumption was used to increase efficiency. Citizens were interested in perception of the movement to distinguish from conventional type of the lamps.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.1134-1139
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• 2005

Seismic motion amplification owing to the input motion level at bedrock is one of the important topics to understand various geomaterials behavior. The extremely valuable borehole records at Port Island were obtained during the 1995 Hyogoken Nanbu Earthquake and also before and after the main event. In this study, the seismic motion amplification at the soft reclaimed ground was discussed. Comparison of measured records with numerical simulation results were made with focus on seismic motion amplification characteristics at the soft reclaimed ground.

• The Transactions of the Korea Information Processing Society
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• v.6 no.3
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• pp.773-780
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• 1999

In this paper, we explore a behavioral animation of artificial birds that have lived by doing an aggregate motion. We first model individual birds and then propose a behavioral model for an aggregate motion of a flock of birds. In order to represent realistically collision avoidance and flock centering among birds, which are necessary properties in a flock of birds, we consider motive of a flock of birds, and role, velocity, momentum, banking and internal characteristics of each bird. The paper presents the simulation result of the proposed model for a flock of 100 birds.

• Journal of Biomedical Engineering Research
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• v.24 no.6 s.81
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• pp.543-548
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• 2003

Injuries of wrist in upper extremity is common onset in industrialized world. The development of joint arthroplasty and mechanical joint is area of research for biomechanical engineer and surgeon for a decade. Therefore. the knowledge of characteristic of joint motion is essential to develop the artificial wrist joint. In this study. the joint motions of wrist required for activities of daily living (ADLs). including personal hygiene and care. and general home activity were measured using flexible electrogoniometer. Total of 25 different daily activities were separated into four groups and tested on 15 subjects who did not show any abnormality of their joint functions. The maximum functional range of motion required for ADLs were obtained and standardized for analysis and comparison. Also. a least functional range of motion for ADLs were investigated. Results revealed that any significant differences were not found in least functional range of motion between left and right wrist to perform ADLs. However. a significant difference was found in different ADLs. Therefore. least range of motion obtained in this study can be used as basic data to design artificial joint and set a goal for surgeon to achieve appropriate treatment from patients.

• Journal of the Earthquake Engineering Society of Korea
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• v.11 no.2 s.54
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• pp.1-9
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• 2007

The method of generating the artificial acceleration time histories for seismic analysis based on genetic algorithms is presented. For applying to the genetic algorithms, the frequencies are selected as the decision variables eventually to be genes. An arithmetic average crossover operator and an arithmetic ratio mutation operator are suggested in this study. These operators as well as the typical simple crossover operator are utilized in generating the artificial acceleration time histories corresponding to the specified design response spectrum. Also these generated artificial time histories are checked whether their outward features are to be coincident with the recorded earthquake motion or not. The features include envelope shape, correlation condition between 2 horizontal components of motion, and the relationship of max. acceleration, max. velocity and max. displacement of ground.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.244-247
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• 2005

Although several artificial disc designs have been developed for the treatment of discogenic low back pain and used clinically, biomechanical change with its implantation seldom studied. To evaluate the effect of artificial disc implantation on the biomechanics of lumbar spinal unit, nonlinear three-dimensional finite element model of L1-L5, S1 was developed and strain and stress of vertebral body and surrounding spinal ligaments were predicted. Intact osteoligamentous L1-L5, S1 model was created with 1-mm CT scan of a volunteer and known material property of each element were applied. This model also includes the effect of local muscles which was modeled with pre-strained spring elements. The intact model was validated with reported biomechanical data. Two models implanted with artificial discs, SB Charite or Prodisc, at L4/5 via anterior approach were also developed. The implanted model predictions were compared with that of intact model. Angular motion of vertebral body, force on spinal ligaments, facet joint contact force with $2\sim12$ Nm flexion-extension moment.