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현장실험을 통한 강연선과 폴리머 모르타르에 의해 보수 · 보강된 교량의 거동 특성
황정호 ( Hwang¸ Jeong-ho ),양동석 ( Yang¸ Dong-suk ),박선규 ( Park¸ Sun-kyu ),윤주현 ( Yun¸ Ju-hyoun ) 한국구조물진단유지관리공학회 2003 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.7 No.2
As many researchers have been interested in the repair and reinforcement of structure, recently, the importances of those are increasing. In this papers, it was inspected to applicate repair and reinforcement by strand and polymer mortar to the construction field among many method. A static loading test and a dynamic loading test was tested in the field. In result, deflection of reinforced structure decreased between 14 and 30 % and load carrying capacity increased 22%.
Theoretical Study of Various Unit Models for Biomedical Application
( Jeongho Choi ) 한국산업융합학회 2019 한국산업융합학회 논문집 Vol.22 No.4
This paper presents an analytical study on the strength and stiffness of various types of truss structures. The applied models are triangular-like opened truss-wall triangular model (OTT), closed truss-wall triangular model (CTT), opened solid-wall triangular model (OST), and hypercube models defined as core-filled or core-spaced cube. The models are analyzed by numerical model analysis using DEFORM 2D/3D tool with AISI 304 stainless steel. Then, the ideal solutions for stiffness and strength are defined. Finally, the relative elastic modulus of the core-spaced model is obtained as 0.0009, which is correlated with the cancellous bone for the relative density range of 0.029- 0.03, and the relative elastic modulus for the core-filled model is obtained as 0.0015, which is correlated with cancellous bone for the relative density range of 0.035-0.036. For the relative compressive yield strength, the OTT reasonably agrees with the cancellous bone for the relative density of 0.042 and the relative compressive strength of 0.05. The CTT and OST are in good agreement at the relative density of 0.013 and the relative compressive yield strength of 0.002. The hypercube models can be used for the cancellous bone for stiffness, and the triangular models can be used for the cancellous bone for strength. However, none of the models can be used to replace the compact bone because it requires much higher stiffness and strength. In the near future, compact bone replacement must be further studied. In addition, previously mentioned models should be developed further.
Parametric Study on Geogrid-Reinforced Track Substructure
Jeongho Oh 한국철도학회 2013 International Journal of Railway Vol.6 No.2
The purpose of this paper was to evaluate the effectiveness of geogrid for conventional ballasted track and asphalt concrete underlayment track using PLAXIS finite element program. Geogrid element was modeled at various locations that include subballast/subgrade, subballast/ballast interfaces, middle of the ballast, and one-third depth of the ballast. The results revealed that the effectiveness of geogrid reinforcement appeared to be larger for ballasted track structure compared to asphalt concrete underlayment track. Particularly, in case of installing geogrid at one-third depth of ballast layer in a conventional ballasted track, the most effectiveness of geogrid reinforcement was achieved. The influence of geogrid axial stiffness on track substructure response was not clear to conclude. Further validations using a discrete element method along with experimental investigation are considered as a future study. The effect of asphalt concrete layer modulus was evaluated. The results exhibited that higher layer modulus seems to be effective in controlling displacement and strain of track substructure. However it also yields slightly higher stresses within track substructure. It infers that further validations are required to come up with optimum asphalt concrete mixture design to meet economical and functional criteria.
Jeongho Yeo,Joon Ho Cho IEEE 2014 IEEE transactions on information theory Vol.60 No.7
<P>In this paper, the block processing of a discrete-time (DT) improper-complex second-order cyclostationary (SOCS) random process is considered. In particular, it is of interest to find a preprocessing operation that enables the adoption of conventional signal processing techniques and algorithms developed for the filtering of proper-complex signals and that leads to computationally efficient near-optimal postprocessing. An invertible linear-conjugate linear (LCL) operator named the DT frequency shift (FRESH) properizer is first proposed. It is shown that the DT FRESH properizer converts a DT improper-complex SOCS random process input to an equivalent DT proper-complex SOCS random process output by utilizing the information only about the cycle period of the input. An invertible LCL block processing operator named the asymptotic FRESH properizer is then proposed that mimics the operation of the DT FRESH properizer but processes a finite number of consecutive samples of a DT improper-complex SOCS random process. It is shown that the output of the asymptotic FRESH properizer is not proper but asymptotically proper and that its frequency-domain covariance matrix converges to a highly structured block matrix with diagonal blocks as the block size tends to infinity. Two representative estimation and detection problems are presented to demonstrate that asymptotically optimal low-complexity postprocessors can be easily designed by exploiting these asymptotic second-order properties of the output of the asymptotic FRESH properizer.</P>
Feedback Reduction for Multiuser OFDM Systems
Jeongho Jeon,Kyuho Son,Hyang-Won Lee,Song Chong IEEE 2010 IEEE Transactions on Vehicular Technology VT Vol.59 No.1
<P>Feedback reduction in multiuser orthogonal frequency-division multiplexing (OFDM) systems has become an important issue due to the excessive amount of feedback required to use opportunistic scheduling, particularly when the number of users and carriers is large. In this paper, we propose a novel feedback-reduction scheme for efficient downlink scheduling. In the proposed scheme, each user determines the amount of feedback based on the so-called <I>feedback efficiency</I> in a distributed manner. The key idea is to give more of an opportunity for feedback to users who are more often scheduled. Simulation results demonstrate that the proposed scheme can substantially decrease the feedback load while achieving almost the same scheduling performance as in the case of full feedback. In addition, the proposed scheme offers unique advantages over existing ones. First, it is not tailored to a specific scheduling policy; thus, it has adaptability to the change of the underlying scheduling policy. Second, the total feedback load can be maintained below a target level, regardless of the number of users in the system.</P>
Jeongho Han,Jinwon Lee,Jeongsam Yang 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.6
The quality of a braid preform generated by the braiding process is affected by the movement path and speed. Previous studies have obtained an optimal movement path and an efficient speed profile of the mandrel, but no studies have considered robot kinematics for the mandrel’s motion, thereby causing errors occur during the braiding process. This study developed an off-line programming system that generates an optimal mandrel movement path to produce a high-quality preform based on the 3D curvature shape of the mandrel. This movement path is then converted into a robot command. The via-points for the robot path generation were extracted from the mandrel surface geometry. Afterwards, the process of generating a continuous motion and rearranging the via-points for radial braiding was performed. Continuous motion was created by separating the straight and curved paths, and the via-point rearrangement was applied depending on the change in speed.