• Earthquakes and Structures
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• 제17권1호
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• pp.49-61
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• 2019

A novel asymmetrical resistance friction damper (ARFD) was proposed in this study to be applied on a rocking column base. The damper comprises multiple steel plates and was fastened using high-strength bolts. The sliding surfaces can be switched into one another and can cause strength to be higher in the loading direction than in the unloading direction. By combining the asymmetrical resistance with the restoring resistance that is generated due to an axial load on the column, the rocking column base can develop a self-centering behavior and achieve high connection strength. Cyclic tests on the ARFD proved that the damper performs a stable asymmetrical hysteretic loop. The desired hysteretic behavior was achieved by tuning the bolt pretension force and the diameter of the round bolt hole. In this study, full-scale, flexural tests were conducted to evaluate the performance of the column base and to verify the analytical model. The results indicated that the column base exhibits a stable self-centering behavior up to a drift angle of 4%. The decompression moment and maximum strength reached 42% and 88% of the full plastic moment of the section, respectively, under a column axial force ratio of approximately 0.2. The strengths and self-centering capacity can be obtained by determining the bolt pretension force. The analytical model results revealed good agreement with the experimental results.

• Structural Engineering and Mechanics
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• 제88권5호
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• pp.463-480
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• 2023

The buckling-restrained braced frames with eccentric configurations (BRBF-Es) exhibit stable cyclic behavior and possess a high energy absorption capacity. Additionally, they offer architectural advantages for incorporating openings, much like Eccentrically Braced Frames (EBFs). However, studies have indicated that significant residual drifts occur in this system when subjected to earthquakes at the Maximum Considered Earthquake (MCE) hazard level. Consequently, in order to mitigate these residual drifts, it is recommended to employ self-centering systems alongside the BRBF-E system. In our current research, we propose the utilization of the Direct Displacement-Based Seismic Design method to determine the design base shear for a hybrid system that combines BRBF with an eccentric configuration and a self-centering frame. Furthermore, we present a methodology for designing the individual components of this composite system. To assess the effectiveness of this design approach, we designed 3-, 6-, and 9-story buildings equipped with the BRBF-E-SCF system and developed finite element models. These models were subjected to two sets of ground motions representing the Maximum Considered Earthquake (MCE) and Design Basis Earthquake (DBE) seismic hazard levels. The results of our study reveal that although the combined system requires a higher amount of steel material compared to the BRBF-E system, it substantially reduces residual drift. Furthermore, the combined system demonstrates satisfactory performance in terms of story drift and ductility demand.

• Steel and Composite Structures
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• 제51권3호
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• pp.289-304
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• 2024

The seismic performance of traditional steel frame-shear wall structures was significantly improved by the application of self-centering steel-reinforced concrete (SRC) wall-panel structures in the steel frames. This novel resilience functionality can rapidly restore the structure after an earthquake. The presented steel frame with steel-reinforced concrete self-centering wall-panel structures (SF-SCW) was validated, indicating its excellent seismic performance. The seismic design method based on bear capacity cannot correctly predict the elastic-plastic performance of the structure, especially certain weak floors that might be caused by a major fracture. A four-level seismic performance index, including intact function, continued utilization, life safety, and near-collapse, was established to achieve the ideal failure mode. The seismic design method, based on structural displacement, was proposed by considering performance objectives of the different seismic action levels. The pushover analysis of a six-floor SF-SCW structure was carried out under the proposed design method and the results showed that this six-floor structure could achieve the predicted failure mode.

• 대한치과보철학회지
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• 제29권3호
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• pp.121-140
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• 1991

Fifteen dental college students of Chosun University without the abnormal occlusion, the history and symptom of temporomandibular dysfunction(TMD), and who had all permanent teeth except third molar and the fifteen moderate group and the fifteen severe group classified according to Helkimo's dysfunction index among patients on the basis of the symptom of TMD were selected. The occlusal contact, occlusal force and occlusal interference in eccentric movement was studied and analyzed using T-Scan system. The result were as follows : 1. The TLR centering around midsagittal axis was located at $1.42{\pm}0.82mm$ in control group, $3.36{\pm}1.45mm$ in severe group, and as TMD was heavier, occlusal contact was located at the farther point from midsagittal axis. 2. The PLR from the first contact to the fifth contact centering around midsagittal axis was located at $1.73{\pm}1.78mm$ in control group, $3.36{\pm}1.41mm$ in moderate group, and $5.39{\pm}4.32mm$ in severe group, and as TMD was heavier, occlusal contact was located at the farther point from midsgittal axis. 3. The TFB, PFB, RFB and LFB of occlusal contact centering around incisal axis had no significant difference statistically among control group, moderate group, and severe group, and it was located at first molar. 4.The LF and RF was smaller in TMD group than in control group. 5. The LR moment of occlusal force centering around midsagittal axis was located at $178.51{\pm}139.81N.mm$ in control group, $466.25{\pm}296.47N.mm$ in moderate group, and $749.18{\pm}588.18N.mm$ in severe group. And as TMD was heavier, it was located at the farther point from midsagittal axis. 6. The RL and LL of occlusal force centering around incisal axis had not-significance statistically among control group, moderate group, and severe group, and it was at the first molar. 7. The number of occlusal interference of the eccentric movement was increased in the patients of TMD.

• 한국강구조학회 논문집
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• 제29권1호
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• pp.73-80
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• 2017

잔류변형이 효과적으로 제어되어 곧은 상태를 유지시켜주는 셀프센터링 접합부에 대하여 반복가력 해석을 시행했으며 초기 긴장력과 긴장재의 개수에 따른 구조적 거동을 분석하였다. 셀프센터링 효과를 발휘하기 위해서 초기 긴장력은 ㄱ형강의 항복모멘트보다 커야하며 주요부재의 손상을 최소화 하기 위해서 압축상쇄모멘트는 보의 전소성모멘트의 0.35이하로 하는 것이 타당하다고 판단된다. 또한 긴장재 개수가 증가할수록 단일 긴장재에 작용하는 초기 긴장력이 감소하여 셀프센터링 성능을 확보할 수 있으므로 긴장재의 초기 긴장응력은 항복응력의 75% 이하로 하는 것을 제안하였다.

• 한국화재소방학회:학술대회논문집
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• 한국화재소방학회 2009년도 춘계학술논문발표회 논문집
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• pp.23-32
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• 2009

국내 전국대학 실험실을 비롯한 위험물 관련 사고사례를 조사하였으며, 중앙소방학교를 비롯한 서울, 경기, 부산, 광주, 경북, 충청소방학교의 위험물에 대한 교과운영이 어떻게 이루어지고 있는지 조사하고, 각 대학 소방관련학과에서 운영하고 있는 위험물질론 교과 운영이 어떻게 진행되고 있는지에 대해서도 조사하였다. 또한 중앙 119 구조대를 비롯한 각 지방소방학교에서 교육을 받고 있는 현직 소방공무원을 대상으로 위험물관련 교육에 대한 설문조사를 실시하였다. 본 연구에서는 이와 같은 설문결과를 분석하여 현행 위험물 교육의 문제점을 찾고 새로운 실험중심의 위험물 교과운영방안으로 효율적인 학습방안을 제시함으로서 위험물관련 사고사례를 사전에 예방할 수 있는 교육 안에 대해 제시코자 하였다.

• Structural Engineering and Mechanics
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• 제72권3호
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• pp.355-366
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• 2019

Self-centering wall (SCW) is a resilient and sustainable structural system which incorporates unbonded posttensioning (PT) tendons to provide self-centering (SC) capacity along with supplementary dissipators to dissipate seismic energy. Hysteretic energy dissipators are usually placed at two sides of SCWs to facilitate ease of postearthquake examination and convenient replacement. To achieve a good prediction for the skeleton curve of the wall, this paper firstly developed an analytical investigation on lateral load responses of self-centering walls with distributed vertical dampers (VD-SCWs) using the concept of elastic theory. A simplified method for the calculation of limit state points is developed and validated by experimental results and can be used in the design of the system. Based on the analytical results, parametric analysis is conducted to investigate the influence of damper and tendon parameters on the performance of VD-SCWs. The results show that the proposed approach has a better prediction accuracy with less computational effects than the Perez method. As compared with previous experimental results, the proposed method achieves up to 60.1% additional accuracy at the effective linear limit (DLL) of SCWs. The base shear at point DLL is increased by 62.5% when the damper force is increased from 0kN to 80kN. The wall stiffness after point ELL is reduced by 69.5% when the tendon stiffness is reduced by 75.0%. The roof deformation at point LLP is reduced by 74.1% when the initial tendon stress is increased from $0.45f_{pu}$ to $0.65f_{pu}$.

• Computers and Concrete
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• 제5권6호
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• pp.525-544
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• 2008

In this research, the self-centering effect in precast and prestressed reinforced concrete structures was investigated experimentally. The reinforced concrete beams and columns were precast and connected by post-tensioning tendons passing through the center of the beams as well as the panel zone of the connections. Three beam-to-interior-column connections were constructed to investigate parameters such as beam to column interfaces (steel on steel or plastic on plastic), energy dissipating devices (unbonded buckling restrained steel bars or steel angles) and the spacing of hoops in the panel zone. In addition to the self-centering effect, the shear strength in the panel zone of interior column connections was experimentally and theoretically evaluated, since the panel zone designed by current code provisions may not be conservative enough to resist the panel shear increased by the post-tensioning force.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2002년도 ICCAS
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• pp.96.5-96
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• 2002

This paper describes extraction procedures for the center coordinates of steam generator tubes of Youngkwang nuclear power plant No. 6 unit. The centering coordinates of tubes are needed for monitoring whether ECT probe is exactly inserted into tube or not. However, The tube image tends to have poor contrast because steam generator bowl is sealed. The centering coordinates extraction procedure consists of two steps. The first step is to process the region with high contrast in entire image of steam generator tubes. Using the center points extracted in the first step and the geometry of tubes lined up in regular triangle patterns the centering coordinates of the rest region with low contrast...

• 한국언어정보학회지:언어와정보
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• 제17권1호
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• pp.17-32
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• 2013

Birner (1998) analyzes the construction of inversion within the centering theory, claiming that the preposed constituent in the inversion structure represents the backward-looking center that connects the current utterance to the previous discourse. However, this paper refutes such a strong claim, pointing out various problems of her work. Instead, this paper argues that the preposed element in the inversion construction is merely the preferred center under the condition that the ranking of the forward-looking centers is determined by the surface word order, rather than by grammatical relations. Thus, this paper claims that the discourse function of the construction of inversion is not text development but merely prominence-giving, in the sense of Ili$\acute{c}$ (1998).