• Earthquakes and Structures
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• v.6 no.5
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• pp.539-560
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• 2014

Shaking tables are devices for testing structures or structural components models with a wide range of synthetic ground motions or real recorded earthquakes. They are essential tools in earthquake engineering research since they simulate the effects of the true inertial forces on the test specimens. The destructive earthquakes that occurred at the north part of Algeria during the period of 1954-2003 resulted in an initiative from the Algerian authorities for the construction of a shaking simulator at the National Earthquake Engineering Research Center, CGS. The acceleration tracking performance and specifically the inability of the earthquake simulator to accurately replicate the input signal can be considered as the main challenge during shaking table test. The objective of this study is to validate the uni-axial sinusoidal performances curves and to assess the accuracy and fidelity in signal reproduction using the advanced adaptive control techniques incorporated into the MTS Digital controller and software of the CGS shaking table. A set of shake table tests using harmonic and earthquake acceleration records as reference/commanded signals were performed for four test configurations: bare table, 60 t rigid mass and two 20 t elastic specimens with natural frequencies of 5 Hz and 10 Hz.

• Korean Journal of Computational Design and Engineering
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• v.22 no.2
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• pp.202-214
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• 2017

The augmented visualization of analysis results can play an import role as a post-processing tool for the modeling & simulation (M&S) technology. In particular, it is essential to develop such an M&S tool which can run on various multi-devices. This paper presents an augmented reality (AR) approach to visualizing and interacting with M&S post-processing results through mobile devices. The proposed approach imports M&S data, extracts analysis information, and converts the extracted information into the one used for AR-based visualization. Finally, the result can be displayed on the mobile device through an AR marker tracking and a shader-based realistic rendering. In particular, the proposed method can superimpose AR-based realistic scenes onto physical objects such as 3D printing-based physical prototypes in a seamless manner, which can provide more immersive visualization and natural interaction of M&S results than conventional VR or AR-based approaches. A user study has been performed to analyze the qualitative usability. Implementation results will also be given to show the advantage and effectiveness of the proposed approach.

• Journal of the Korean Society of Safety
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• v.25 no.2
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• pp.65-70
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• 2010

Interest to the RTLS is increasing recently, and the RTLS is used in various fields. It is one of applications for locating and tracking using RFID tags which are attached to something like container, pallet, or all thing. In this study, a RTLS system was developed for efficient safe management in chemical industry. This system could manage dangerous substance and a personal history regarding entry. Detailed results of this study are as follows: (1) Through RTLS entry management system which is developed this study, the events along a movement of dangerous substances and the person in charge could be grasped and recorded. (2) A user, goods and a warehouse could be managed and monitored efficiently as using the developed RTLS history system. (3) RTLS system will contribute to efficient safety management of the chemical industry. Besides, RTLS system might be applied to the other industries like shipbuilding and car industry.

• Journal of the Korea Institute of Military Science and Technology
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• v.5 no.2
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• pp.169-184
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• 2002

In order to extract bearing information from the directional sensors of DIFAR(directional frequency analysis and recording) that is a kind of passive sonobuoy, the cardioid beamforming algorithm applicable to DIFAR system was studied in the frequency domain. the algorithm uses narrow-band signals propagated though the media from the acoustic sources such as ship machineries. The proposed algorithm is expected to give signal to noise ratio of 6dB when it uses the maximum response axis(MRA) among the Cardioid beams. The estimated bearings agree very well with those from GPS data. Assuming the bearings from GPS data to be real values, the estimation errors are analyzed statistically. The histogram of estimation errors in each frequency have Gaussian shape, the mean and standard deviation dropping in the ranges -1.1~$6.7^{\circ}$ and 13.3~$43.6^{\circ}$, respectively. Estimation errors are caused by SMR degradation due to propagation loss between the source and receiver, daily fluctuating geo-magnetic fields, and non-stationary background noises. If multiple DIFAR systems are employed, in addition to bearing, range information could be estimated and finally localization or tracking of a target is possible.

• Journal of Communications and Networks
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• v.9 no.3
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• pp.219-228
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• 2007

In this paper, we present a novel blind adaptive multiuser detector structure and three robust recursive filters to improve the performance in CDMA environments: Sigma point kalman filter (SPKF), particle filter (PF), and Gaussian mixture sigma point particle filter (GMSPPF). Our proposed robust recursive filters have superior performance over a conventional extended Kalman filter (EKF). The proposed multiuser detector algorithms initially use Kalman prediction form to estimated channel parameters, and unknown data symbol be predicted. Second, based on this predicted data symbol, the robust recursive filters (e.g., GMSPPF) is a refined estimation of joint multipaths and time delays. With these estimated multipaths and time delays, data symbol detection is carried out (Kalman correction form). Computer simulations show that the proposed algorithms outperform the conventional blind multiuser detector with the EKF. Also we can see it provides a more viable means for tracking time-varying amplitudes and time delays in CDMA communication systems, compared to that of the EKF for near-far ratio of 20 dB. For this reason, it is believed that the proposed channel estimators can replace well-known filter such as the EKF.

• Annual Conference of KIPS
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• 2018.10a
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• pp.478-479
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• 2018

수부는 일상생활동작(ADL, activities of daily living)을 위한 중요 부위로 손상이나 장애가 있는 경우 재활치료를 통해 과제수행능력을 향상시킨다. 그러나 치료 과정은 주관적으로 진행되어 정확한 치료 성과를 위한 객관적 지표가 필요하다. 본 논문에서는 실제 수부 움직임을 추적할 수 있는 동작인식 장비인 립모션 컨트롤러와 Unity3D로 가상공간 상에서 구현된 Box&Block Test를 이용하여 수부 움직임에 대한 객관적인 데이터를 얻었다. 기존 Box&Block Test와 제안한 모션인식과 추적에 의한 수지손상 환자용 진단 및 치료시스템의 성능을 T검정 수행한 결과 통계적으로 유의미한 차이가 없음을 보였으며 수부 움직임의 정량적인 데이터를 통해 정확한 치료성과 판단의 가능성을 확인하였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.7
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• pp.3599-3619
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• 2019

In human activity recognition system both static and motion information play crucial role for efficient and competitive results. Most of the existing methods are insufficient to extract video features and unable to investigate the level of contribution of both (Static and Motion) components. Our work highlights this problem and proposes Static-Motion fused features descriptor (SMFD), which intelligently leverages both static and motion features in the form of descriptor. First, static features are learned by two-stream 3D convolutional neural network. Second, trajectories are extracted by tracking key points and only those trajectories have been selected which are located in central region of the original video frame in order to to reduce irrelevant background trajectories as well computational complexity. Then, shape and motion descriptors are obtained along with key points by using SIFT flow. Next, cholesky transformation is introduced to fuse static and motion feature vectors to guarantee the equal contribution of all descriptors. Finally, Long Short-Term Memory (LSTM) network is utilized to discover long-term temporal dependencies and final prediction. To confirm the effectiveness of the proposed approach, extensive experiments have been conducted on three well-known datasets i.e. UCF101, HMDB51 and YouTube. Findings shows that the resulting recognition system is on par with state-of-the-art methods.

• The Journal of Korea Robotics Society
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• v.14 no.1
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• pp.74-79
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• 2019

In this paper, we develop a virtual experimental environment to investigate users' eye gaze in human-robot social interaction, and verify it's potential for further studies. The system consists of a 3D robot character capable of hosting simple interactions with a user, and a gaze processing module recording which body part of the robot character, such as eyes, mouth or arms, the user is looking at, regardless of whether the robot is stationary or moving. To verify that the results acquired on this virtual environment are aligned with those of physically existing robots, we performed robot-guided quiz sessions with 120 participants and compared the participants' gaze patterns with those in previous works. The results included the followings. First, when interacting with the robot character, the user's gaze pattern showed similar statistics as the conversations between humans. Second, an animated mouth of the robot character received longer attention compared to the stationary one. Third, nonverbal interactions such as leakage cues were also effective in the interaction with the robot character, and the correct answer ratios of the cued groups were higher. Finally, gender differences in the users' gaze were observed, especially in the frequency of the mutual gaze.

• Physical Therapy Korea
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• v.29 no.2
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• pp.87-93
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• 2022

To solve the pathological problems of the musculoskeletal system based on evidence, a sophisticated analysis of human motion is required. Traditional optical motion capture systems with high validity and reliability have been utilized in clinical practice for a long time. However, expensive equipment and professional technicians are required to construct optical motion capture systems, hence they are used at a limited capacity in clinical settings despite their advantages. The development of information technology has overcome the existing limit and paved the way for constructing a motion capture system that can be operated at a low cost. Recently, with the development of computer vision-based technology and optical markerless tracking technology, webcam-based 3D human motion analysis has become possible, in which the intuitive interface increases the user-friendliness to non-specialists. In addition, unlike conventional optical motion capture, with this approach, it is possible to analyze motions of multiple people at simultaneously. In a non-optical motion capture system, an inertial measurement unit is typically used, which is not significantly different from a conventional optical motion capture system in terms of its validity and reliability. With the development of markerless technology and advent of non-optical motion capture systems, it is a great advantage that human motion analysis is no longer limited to laboratories.

• Nuclear Engineering and Technology
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• v.56 no.9
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• pp.3933-3941
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• 2024

The paper concerns a room-temperature cross-bar H-mode (CH) drift tube linac (DTL) with KONUS (Kombinierte Null Grad Struktur) [1,2] beam dynamics. To make the acceleration in DTL cell more efficient, we studied the correlation between transit time factor (TTF) and structural coefficients, first. Furthermore, we developed a new code with Python to demonstrate the longitudinal dynamics more clearly. The code computationally generates clusters, bunch centers, and emittance growth in a single figure. Thus, the stabilization region and cluster evolution at various negative phases can be studied. Based on the above studies, we designed a 162.5 MHz CH-DTL to accelerate 10 mA D⁺ from 2.11 MeV to 3.25 MeV in continuous-wave (CW) mode. The proposed CH-DTL is a part of the Middle Energy Neutron Source (MENS). The dynamics and RF design were iterated to make the gap voltage error lower than 1 %. The initial beam is assumed to come from a Radio Frequency Quadrupole accelerator (RFQ). The geometries of the CH-DTL are optimized by using CST. Multiparticle tracking from LEBT to RFQ is performed with TraceWin and the transmission efficiency in the CH-DTL is 100 %.