• Composites Research
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• v.34 no.6
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• pp.380-386
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• 2021

This paper aims to improve the critical speed of power-take-off (PTO) shafts by using carbon fiber reinforced plastics (CFRPs). The PTO shaft was designed with titanium-CFRPs hybrid structure in order to compensate the low shear strength of CFRPs. Based on the requirements for PTO shafts, the dimensions of PTO shafts were determined through a parametric study. To evaluate the performance of the PTO shaft, a vibration test, a static torsion test, and a torsion durability test were performed. In the vibration test, the critical speed of PTO shafts was 20570 rpm, which was 7.5% higher than that of titanium shafts. Additionally, it was confirmed that the maximum allowable torque of the PTO shaft was 2300 N·m. Finally, under repeated load in the range of 11.3 to 113 N·m, the fatigue failure in the PTO shaft did not occur up to 10⁶ cycles.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.4
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• pp.588-592
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• 2012

This study concentrates the effect of hybridisation on the collapse mode and energy absorption for composite cylinders. The static collapse behavior of laminated(Al/CFRP/GFRP) circular-cylindrical composite shell under quasi-static axial compressive load has been investigated experimentally. Eight different hybrids of laminated(Al/CFRP/GFRP) circular-cylindrical composite shell were fabricated by autoclave. Eight types of composites were tested, namely, Al/carbon fiber/epoxy, Al/glass fiber/epoxy, Al/carbon-carbon-glass/epoxy, Al/carbon-glass-carbon/epoxy, Al/carbon-glass-glass/epoxy, Al/glass-glass-carbon/epoxy, Al/glass-carbon-glass/epoxy and Al/glass-carbon-carbon/epoxy. Collpase modes were highly dominated by the effect of hybridisation. The results also showed that the hybrid member with material sequence of Al-glass-carbon-carbon/epoxy exhibited good energy absorption capability.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.05a
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• pp.116-116
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• 2004

편마비 환자의 보행운동 개선을 위한 보조기구로 족부보장구(Ankle Foot Orthosis, A.F.O.)가 활용되고 있다 족부보장구는 Fig. 1에 제시한 바와 같이 보행특성상 무수히 반복되는 충격과 굽힘하중을 받는다. 따라서 족부보장구용 재료는 피로특성이 우수한 탄소섬유 강화재(Carbon Fiber Reinforced Plastic, 이하 CFRP)를 주로 사용한다. 그러나 CFRP의 상용재인 프리프레그(prepreg)는 강한 이방성의 단방향 섬유이므로 섬유방향과 하중작용방향의 관계에 매우 민감하다.(중략)

• Proceedings of the Korean Society of Computer Information Conference
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• 2018.07a
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• pp.23-24
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• 2018

스마트 팩토리의 핵심 요소 중 하나인 AGV를 운용하기 위해서 스케줄링은 간과할 수 없는 문제이다. 기존의 정적인 휴리스틱 방식은 실시간으로 운용되는 스마트 팩토리에 다소 부적합한 면이 있다. 본 논문에서는 이러한 스케줄링에 관한 문제를 해결하고자 SLAM 기반의 자율주행 AGV를 운용 할 수 있는 3D 가상 환경을 설계하고 해당 환경에서 강화학습을 기반으로 한 스케줄링을 구현해 실시간으로 변화하는 공장에 적합한 동적인 스케줄링을 설계하였다.

• Proceedings of the Korea Information Processing Society Conference
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• 2024.05a
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• pp.839-842
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• 2024

서비스 메시 환경에서의 트래픽 분산은 시스템의 성능과 안정성, 그리고 보안에 필수적인 기능을 담당한다. 현재의 트래픽 분산 방식들은 대부분 정적 설정을 기반으로 하기 때문에 시스템 환경의 변화에 신속하게 대응하기 어렵고 최적화된 성능을 보장하기 힘들다. 본 논문에서는 강화학습을 활용해 서비스 메시 환경 내에서의 트래픽 분산을 자동화하고 최적화할 수 있는 새로운 시스템을 제안한다. 특히, 텔레메트리 기술을 활용해 트래픽의 분산을 실시간으로 추적하며, 강화학습 알고리즘을 이용해 트래픽 가중치를 조정함으로써 기존의 로드 밸런싱 방법들에 비해 더 빠른 처리 시간과 보다 효율적인 로드 밸런싱을 달성할 수 있을 것으로 기대한다.

• The Journal of the Korea Contents Association
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• v.19 no.3
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• pp.72-79
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• 2019

Autonomous locomotion has two essential functionalities: mapping builds and updates maps by uncertain position information and measured sensor inputs, and localization is to find the positional information with the inaccurate map and the sensor information. In addition, obstacle detection, avoidance, and path designs are necessarily required for autonomous locomotion by combining the probabilistic methods based on uncertain locations. The sensory inputs, which are measured by a metric-based scanner, have difficulties of distinguishing moving obstacles like humans from static objects like walls in given environments. This paper proposes the low resolution grid map combined with reinforcement learning, which is compared with the conventional recognition method for detecting static and moving objects to generate obstacle avoiding path. Finally, the proposed method is verified with experimental results.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.10
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• pp.368-376
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• 2018

The purpose of this research is to investigate the relationship of flow experience on self-esteem and exercise adherence through intention in youth sports club so that youths can continue to exercise. A non-probabilistic sampling method was used as a convenience sampling method with 257 questionnaires being analyzed by frequency, factor analysis, correlation analysis, and multiple regression analysis using the SPSS 21.0 version statistical program for Windows. The results of this study are as follows. First, cognitive flow showed a negative relationship with negative self-esteem, a positive relationship with positive self-esteem, and a positive relationship with tendency and possibility in interrelation. Behavioral flow showed a positive relationship with tendency, possibility, and reinforcement. Second, positive and negative self-esteem showed positive relationships with behavioral flow and did not show any relation. Third, reinforcement showed a positive relationship and tendency and possibility did not affect behavioral flow. It is possible to enhance self-esteem and improve physical fitness through continuous physical activities and to live a lively school life by understanding the immersion experiences of the adolescents' participation in sports clubs and by providing more appropriate physical activity information to adolescents.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.8
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• pp.881-887
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• 2012

CFRP composite materials have been widely used in various fields of engineering because of their excellent properties. They show high specific stiffness and specific strength compared with metallic materiasl. Woven CFRP composite materials are fabricated from carbon fibers with two orientation angles ($0^{\circ}/90^{\circ}$), which influences the mechanical properties. Therefore, woven CFRP composite materials show different types of fracture behavior according to the load direction. Therefore, the fracture behavior of these materials needs to be evaluated according to the load direction when designing structures using these materials. In this study, we evaluate the fracture strength of plain-woven CFRP composite materials according to the load direction. We performed tests for six different angles (load direction: $0^{\circ}/90^{\circ}$, $30^{\circ}/-60^{\circ}$, $+45^{\circ}/-45^{\circ}$) and estimated the fracture strength for an arbitrary fiber angle by using the modified Tan's theory and harmonic function.

• Composites Research
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• v.22 no.1
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• pp.15-21
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• 2009

In this paper, static compressive test and compression-compression fatigue test of carbon/epoxy composites which have different micro-structures were carried out with respect to the bias angle. In order to find out the effect of the micro-structure of the fabric composite on compressive characteristics the specimens made of UD carbon/epoxy composite comprising the same fiber and matrix system as the fabric composite were also prepared. The compressive strength and modulus were measured and these values were used to develop a semi-empirical formula for predicting compressive strength of the fabric composite with bias angles. The fatigue behavior of the fabric composite with respect to the bias angle variation was also investigated.

• Journal of the Korean Applied Science and Technology
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• v.37 no.4
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• pp.755-761
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• 2020

The purpose of this study was to investigate the effects of balance board and whole-body vibration stimulator application on body muscle activities during static squat motion. Twenty adult males(age, 21.90±0.36 years; height, 174.30±1.09 cm; body mass, 66.50±1.00 kg; and BMI, 21.90±0.31 kg/㎡) were participated in this study as subjects. Three types' static squat motions were performed(basic static squat motion, BSSM; static squat motion with balance board, SSBB; static squat motion with whole-body vibration stimulator, SSVS). We measured the right side's body muscle activities of the rectus abdominis(RA), internal oblique(IO), external oblique(EO), rectus femoris(RF), vastus lateralis(VL), and vastus medialis(VM). The research findings were as follows. There was a significant higher RA, IO, and EO muscle activity of SSBB and SSVS(p=.001, p=.004, p=.000). And RF, VL, and VM muscle activities were greatest during SSVS(p=.000). These findings are expected to serve as references for static squat motion applications in training programs for body muscle strengthening.