• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.1271-1272
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• 2006

The vacuum infiltration method is one of the composite producing methods. There are several parameters in composite production by vacuum infiltration. One of them is particle size of reinforcement in particulate reinforced composites. In this study, MgO powder and Al were used as reinforcement and matrix respectively. MgO powders with different size and amount to give same height were filled in quartz tubes and liquid metal was vacuum infiltrated into the MgO powder under same vacuum condition and for same time. Infiltration height was measured and microstructure and fracture behavior of composite were investigated. It has been found that infiltration height and fracture strength were increased with particulate reinforcement sizes. It has also been determined that molten metal temperature facilitates infiltration.

• 한국구조물진단유지관리공학회 논문집
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• 제2권3호
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• pp.205-211
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• 1998

The purpose of this study is to evaluate shear strengthening effects of R/C beams with carbon fiber sheets. The major variables are shear reinforcement ratios, CFS strengthening ratios and strengthening methods of CFS. Following conclusions can be extracted. The shear capacity of beam strengthened with CFS is about 32~87% higher than that of beams without shear reinforcement. The strengthening effects of patch type is larger than those of strip type. The strain distribution in CFS intersected with shear crack is similar to that in stirrup and larger strain is observed in the middle of the shear span. It can be estimated that shear strength reduction factor ${\alpha}$=0.3 is appropriate for peeling effect of CFS.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1996년도 가을 학술발표회 논문집
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• pp.213-217
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• 1996

The electrochemical methods of early detection and analysis of corrosion related deterioration in concrete reinforcement structures are very useful techniques. The generally using procedure for corrosion monitoring of reinforced structures employs a method of half-cell potential measurement. Whilst the technique has provided a useful means of delineating areas of high or low corrosion risk, there are difficulties in its use and interpretation, particularly when assessing corrosion rates of reinforcement. The aim of this study is to describe the AC-impedance method being employed to monitor and assess corrosion rates, to estimate corrosion mechanism of reinfrocement in laboratory conditions. The AC-impedance monitoring technique applies a small amplitude(20mV) AC signal to embedded steel in concrete and reference electrode (Cu/$CuSo_4$). We obtained over a wide frequency range(10MHz~1mHz) to produce a complex plane plot or Nyquist plot.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(II)
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• pp.197-200
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• 2005

In this study, for the establishment of the performance evaluation methods and the quality control standards of durability recovery method, the quantitative exposure data by long term exposure test under the coast is accumulated and analyzed Investigating and evaluating the result of exposure test at 30 month of exposure age under the coastal environment, carbonation and salt damage are not happened at all but the difference in electric potential are found. Therefore, it is considered that the reinforcement corrosion at replacement with repair material are caused by active-passive corrosion macrocells.

• 콘크리트학회논문집
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• 제26권1호
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• pp.47-55
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• 2014

최근 빈번하게 발생하는 대규모의 지진으로 구조물의 내진보강에 관심이 높아지고 있다. 내진설계가 반영되지 않은 기둥의 취성파괴는 구조물 전체 붕괴를 유발하기 때문에 내진보강이 필수적이다. 기존에는 단면증설법, 강판보강법, 섬유보강법이 내진보강법으로 주로 이용되었다. 하지만 이 보강법들은 구조물의 물리적 손상과 넓은 작업공간, 오랜 시간이 소요되는 단점이 있다. 이에 이 연구에서는 기존에 개발된 FRP 보강재의 보강 성능을 평가하였다. 대상 시험체는 학교건물을 실험실 여건에 맞춰 80% 축소하여 제작하였다. 보강재의 재료를 유리섬유와 알루미늄 다공판을 사용하여 보강재를 제작하였다. 평가 결과 두 종류의 보강재를 사용한 모두에서 시험체의 내진성능이 증가하였다.

• 로봇학회논문지
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• 제12권3호
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• pp.297-305
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• 2017

As the development of autonomous vehicles becomes realistic, many automobile manufacturers and components producers aim to develop 'completely autonomous driving'. ADAS (Advanced Driver Assistance Systems) which has been applied in automobile recently, supports the driver in controlling lane maintenance, speed and direction in a single lane based on limited road environment. Although technologies of obstacles avoidance on the obstacle environment have been developed, they concentrates on simple obstacle avoidances, not considering the control of the actual vehicle in the real situation which makes drivers feel unsafe from the sudden change of the wheel and the speed of the vehicle. In order to develop the 'completely autonomous driving' automobile which perceives the surrounding environment by itself and operates, ability of the vehicle should be enhanced in a way human driver does. In this sense, this paper intends to establish a strategy with which autonomous vehicles behave human-friendly based on vehicle dynamics through the reinforcement learning that is based on Q-learning, a type of machine learning. The obstacle avoidance reinforcement learning proceeded in 5 simulations. The reward rule has been set in the experiment so that the car can learn by itself with recurring events, allowing the experiment to have the similar environment to the one when humans drive. Driving Simulator has been used to verify results of the reinforcement learning. The ultimate goal of this study is to enable autonomous vehicles avoid obstacles in a human-friendly way when obstacles appear in their sight, using controlling methods that have previously been learned in various conditions through the reinforcement learning.

• Journal of Acupuncture Research
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• 제20권6호
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• pp.190-200
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• 2003

Objective: The purpose of this study is to examine influences by the order, Reduction and Reinforcement in Acupuncture on cerebral hemodynamics [regional cerebral blood flow(rCBF) and mean arterial blood pressure(MABP)] in normal rats. Methods: This experiments was to to investigate eath other changes of rCBF and MABP at Xingjian(LR2)(1st) Shaofu(HT8)(2nd) Reduction, Xingjian(LR2)(1st) Shaofu(HT8)(2nd) Reinforcement, Shaofu(HT8)(1st) Xingjian(LR2)(2st) Reduction and Shaofu(HT8)(1st) Xingjian(LR2)(2st) Reduction in Acupuncture. Results: 1. LR2(1st) HT8(2nd) Reduction in Acupuncture was decreased rCBF and MABP in compared with normal condition. 2. LR2(1st) HT8(2nd) Reinforcement in Acupuncture was significantly decreased rCBF, and was decreased MABP in compared with normal condition. 3. HT8(1st) LR2(2st) Reduction in Acupuncture was decreased rCBF during acupuncture but was recovered rCBF after with-drawing of the neddle. 4. HT8(1st) LR2(2st) Reduction in Acupuncture was decreased MABP during acupuncture and after withdrawing of the neddle. 5. HT8(1st) LR2(2st) Reinforcement in Acupuncture was significantly increased rCBF during acupuncture and 30min after withdrawing of the neddle. 6. HT8(1st) LR2(2st) Reinforcement in Acupuncture was decreased MABP during acupuncture, but was recovered MABP after withdrawing of the neddle. Conclusions: I suggested that LR2 HT8 Reduction in Acupuncture and LR2 HT8 Reinforcement in Acupuncture cause a diverse response of cerebral hemodynas.

• Computers and Concrete
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• 제14권3호
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• pp.211-231
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• 2014

Prestressed hollow-core slabs (HCS) are widely used for modern lightweight precast floor structures because they are cost-efficient by reducing materials, and have excellent flexural strength and stiffness by using prestressing tendons, compared to reinforced concrete (RC) floor system. According to the recently revised ACI318-08, the web-shear capacity of HCS members exceeding 315 mm in depth without the minimum shear reinforcement should be reduced by half. It is, however, difficult to provide shear reinforcement in HCS members produced by the extrusion method due to their unique concrete casting methods, and thus, their shear design is significantly affected by the minimum shear reinforcement provision in ACI318-08. In this study, a large number of shear test data on HCS members has been collected and analyzed to examine their web-shear capacity with consideration on the minimum shear reinforcement requirement in ACI318-08. The analysis results indicates that the minimum shear reinforcement requirement for deep HCS members are too severe, and that the web-shear strength equation in ACI318-08 does not provide good estimation of shear strengths for HCS members. Thus, in this paper, a rational web-shear strength equation for HCS members was derived in a simple manner, which provides a consistent margin of safety on shear strength for the HCS members up to 500 mm deep. More shear test data would be required to apply the proposed shear strength equation for the HCS members over 500 mm in depth though.

• Computers and Concrete
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• 제20권4호
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• pp.391-407
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• 2017

Fiber reinforced polymer (FRP) bars have been recently used to reinforce concrete members in flexure due to their high tensile strength and especially in corrosive environments to improve the durability of concrete structures. However, FRPs have a low modulus of elasticity and a linear elastic behavior up to rupture, thus reinforced concrete (RC) components with such materials would exhibit a less ductility in comparison with steel reinforcement at the similar members. There were several studies showed the behavior of concrete beams with the hybrid combination of steel and FRP longitudinal reinforcement by adopting the experimental and numerical programs. The current study presents a numerical and analytical investigation based on the data of previous researches. Three-dimensional (3D) finite element (FE) models of beams by using ANSYS are built and investigated. In addition, this study also discusses on the design methods for hybrid FRP-steel beams in terms of ultimate moment capacity, load-deflection response, crack width, and ductility. The effects of the reinforcement ratio, concrete compressive strength, arrangement of reinforcement, and the length of FRP bars on the mechanical performance of hybrid beams are considered as a parametric study by means of FE method. The results obtained from this study are compared and verified with the experimental and numerical data of the literature. This study provides insight into the mechanical performances of hybrid FRP-steel RC beams, builds the reliable FE models which can be used to predict the structural behavior of hybrid RC beams, offers a rational design method together with an useful database to evaluate the ductility for concrete beams with the combination of FRP and steel reinforcement, and motivates the further development in the future research by applying parametric study.

• 예술인문사회 융합 멀티미디어 논문지
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• 제8권2호
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• pp.351-358
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• 2018

강화 학습은 변화하는 환경에서의 최적의 보상을 얻을 수 있는 행동을 결정하기 위한 정책을 얻는 기계 학습 기법이다. 하지만 기존에 연구되어 온 강화 학습은 불확실하고 연속적인 실제 환경에서 최적의 행동을 얻기 위해 발생되는 높은 계산 복잡도 문제와 학습된 결과를 얻기 위해서는 많은 시간이 소요 된다는 문제점을 가지고 있다. 앞에서 언급한 문제를 해결하기 위해, 높은 계산 복잡도 문제를 해결을 위해서는 강화 학습을 구성하는 가치 함수와 정책을 독립적으로 구성하는 AC(actor-critic) 기법이 제안되었다. 그리고 빠른 학습 결과를 얻기 위해 기 학습된 지식을 새로운 환경에서 이용하여 기존 학습보다 빠르게 학습 결과를 얻을 수 있는 전이 학습(transfer learning) 기법이 제안되었다. 본 논문에서는 기존에 연구되어 왔던 기계 학습 기법의 향상 기법인 AC 기법과 전이 학습 기법에 대해 소개하고, 이를 무선 액세스 네트워크 환경에서 기지국 상태 조정을 위해 적용되고 있는 사례를 소개한다.