• Structural Engineering and Mechanics
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• 제32권2호
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• pp.251-267
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• 2009

Reinforced concrete (RC) structures consist of two different materials: concrete and steel bar. The stress transfer behaviour between the two materials through bond plays an important role in the load-carrying capacity of RC structures, especially when they subject to lateral load such as blast and seismic load. Therefore, bond and slip between concrete and reinforcement bar will affect the response of RC structures under such loads. However, in most numerical analyses of blast-induced structural responses, the perfect bond between concrete and steel bar is often assumed. The main reason is that it is very difficult to model bond slip in the commercial finite element software, especially in hydrodynamic codes. In the present study, a one-dimensional slide line contact model in LS-DYNA for modeling sliding of rebar along a string of concrete nodes is creatively used to model the bond slip between concrete and steel bars in RC structures. In order to model the bond slip accurately, a new approach to define the parameters of the one-dimensional slide line model from common pullout test data is proposed. Reliability and accuracy of the proposed approach and the one-dimensional slide line in modelling the bond slip between concrete and steel bar are demonstrated through comparison of numerical results and experimental data. A case study is then carried out to investigate the bond slip effect on numerical analysis of blast-induced responses of a RC column. Parametric studies are also conducted to investigate the effect of bond shear modulus, maximum elastic slip strain, and damage curve exponential coefficient on blast-induced response of RC columns. Finally, recommendations are given for modelling the bond slip in numerical analysis of blast-induced responses of RC columns.

• 천문학논총
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• 제30권2호
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• pp.495-497
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• 2015

Galaxies can be "pre-processed" in the low-density outskirts by ambient medium in the filaments or tidal interactions with other galaxies while falling into the cluster. In order to probe how early on and by which mechanisms galaxies can be affected before they enter high-density cluster environments, we are carrying out an atomic hydrogen ($H\small{I}$) imaging study of a sample of galaxies selected from three filamentary structures around the Virgo cluster. Our sample consists of 14 late-type galaxies, which are potentially interacting with their surroundings. The $H\small{I}$ observations have been done using the Westerbork Synthesis Radio Telescope, the Giant Metrewave Radio Telescope, and the Jansky Very Large Array with column density sensitivity of ${\approx}3-5{\times}10^{19}cm^{-2}$ in $3{\sigma}$ per channel, which is low enough to detect faint $H\small{I}$ features in the outer disks of galaxies. In this work, we present the Hi data of two galaxies that were observed with GMRT. We examine the $H\small{I}$ morphology and kinematics to find the evidence for gas-gas and/or tidal interactions, and discuss which mechanism(s) could be responsible for pre-processing in these cases.

• International Journal of Naval Architecture and Ocean Engineering
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• 제9권2호
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• pp.160-176
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• 2017

The interaction of focused wave groups with a vertical wall is investigated based on the second order potential theory. The NewWave theory, which represents the most probable surface elevation under a large crest, is adopted. The analytical solutions of the surface elevation, velocity potential and wave force exerted on the vertical wall are derived, up to the second order. Then, a parametric study is made on the interaction between nonlinear focused wave groups and a vertical wall by considering the effects of angles of incidence, wave steepness, focal positions, water depth, frequency bandwidth and the peak lifting factor. Results show that the wave force on the vertical wall for obliquely-incident wave groups is larger than that for normally-incident waves. The normalized peak crest of wave forces reduces with the increase of wave steepness. With the increase of the distance of focal positions from the vertical wall, the peak crest of surface elevation, although fluctuates, decreases gradually. Both the normalized peak crest and adjacent crest and trough of wave forces become larger for shallower water depth. For focused wave groups reflected by a vertical wall, the frequency bandwidth has little effects on the peak crest of wave elevation or forces, but the adjacent crest and trough become smaller for larger frequency bandwidth. There is no significant change of the peak crest and adjacent trough of surface elevation and wave forces for variation of the peak lifting factor. However, the adjacent crest increases with the increase of the peak lifting factor.

• Restorative Dentistry and Endodontics
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• 제40권2호
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• pp.155-160
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• 2015

Objectives: Achieving adequate anesthesia with inferior alveolar nerve blocks (IANB) is of great importance during dental procedures. The aim of the present study was to assess the success rate of two anesthetic agents (bupivacaine and lidocaine) for IANB when treating teeth with irreversible pulpitis. Materials and Methods: Sixty volunteer male and female patients who required root canal treatment of a mandibular molar due to caries participated in the present study. The inclusion criteria included prolonged pain to thermal stimulus but no spontaneous pain. The patients were randomly allocated to receive either 2% lidocaine with 1:80,000 epinephrine or 0.5% bupivacaine with 1:200,000 epinephrine as an IANB injection. The sensitivity of the teeth to a cold test as well as the amount of pain during access cavity preparation and root canal instrumentation were recorded. Results were statistically analyzed with the Chi-Square and Fischer's exact tests. Results: At the final step, fifty-nine patients were included in the study. The success rate for bupivacaine and lidocaine groups were 20.0% and 24.1%, respectively. There was no significant difference between the two groups at any stage of the treatment procedure. Conclusions: There was no difference in success rates of anesthesia when bupivacaine and lidocaine were used for IANB injections to treat mandibular molar teeth with irreversible pulpitis. Neither agent was able to completely anesthetize the teeth effectively. Therefore, practitioners should be prepared to administer supplemental anesthesia to overcome pain during root canal treatment.

• 생명과학회지
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• 제17권12호
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• pp.1605-1609
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• 2007

미생물 제제의 실내 pot 실험을 통한 효능 실험에서 선발된 Monacrosporium thaumasium을 이용한 KBC3017 제제의 실외 포장 실험을 통해 최적의 구성과 효능 조건을 찾았다. 선발된 균주의 미생물제제 제조를 위해 첨가한 첨가제 중 무기증량제로 Diatomite와 유기증량제로 생옥분이 효과적이었으며, 처리량별 선충 밀도 억제효과는 처리량이 많을수록 효과가 높았으나, 적정 처리량은 2%의 diatomite와 옥가루가 포함된 KBC3017 제제를 이용하여 방제하였을 때 71%의 선충 방제 효과가 나타났다. 이 방제가는 대조구와 비교하였을 때 뿌리와 줄기에서 보다 좋은 효과가 있었다.

• 한국방재학회 논문집
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• 제9권1호
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• pp.145-150
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• 2009

댐과 같은 대규모 수리구조물의 신설이 점차 어려워짐에 따라, 이에 대한 대안으로 천변저류지의 설치가 검토되고 있다. 천변저류지는 규모가 작은 시설물로 홍수량, 유입수문곡선, 천변저류지 용량 및 월류위어의 월류고 등에 따라 홍수저감효과가 민감하게 반응한다. 따라서 최대의 홍수저감효과를 얻기 위해서는 홍수저감효과를 기대하는 홍수사상에 적합한 월류고를 적용하여야 하며, 본 연구에서는 월류고 값의 변화가 천변저류지군의 홍수저감효과에 미치는 영향을 분석해보았다. 이를 위해 천변저류지의 최적위치를 결정하기 위해 개발된 기존의 의사결정모형을 사용하였다. 천변저류지의 위치를 결정변수로 사용하고 홍수저감목표 지점에서의 홍수저감효과를 최대화하는 과정을 통해 천변저류지의 최적위치를 결정하는 의사결정모형에 월류고의 높이를 결정 변수로 추가하여 수정하였다. 제안된 모형을 안성천 유역에 적용하여 기존의 연구결과와 비교하였으며, 모형의 적용결과 대상 홍수사상에 대해 보다 효율적인 홍수저감이 가능토록 하는 월류고 및 위치를 결정 할 수 있었다.

• 기록학연구
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• 제54호
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• pp.45-79
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• 2017

본고에서는 최근의 전자기록 환경을 맞아 새롭게 조명 받고 있는 기록이 지닌 지식 정보 자원으로서의 의미를 기존의 연구성과 및 사례들을 기반으로 고찰하였다. 기록의 생산모태라 할 수 있는 조직의 운영방식 및 업무패턴의 변모에 따라 종래 비현용단계에서의 역사문화적 가치를 우선시하는 경향을 탈피하고, 조직 경영과 업무 수행에 실질적 이익을 주는 지식 정보 자원으로서의 가치 역시 중시되고 있음을 파악하고자 하였다. 이를 위해 2장에서는 최근의 업무환경 변화상을 살펴본 후, 기록이 지닌 증거로서의 속성뿐만 아니라 정보로서의 속성 역시 강조되고 있음을 고찰하였다. 이러한 논의를 기반으로 3장에서는 1980년대부터 서구 기록학계에서 논의되어 온 기록과 정보의 관계를 고찰한 후, 이어 최근의 업무환경에서 정보를 대체하는 개념인 지식과 기록의 상관관계와 함께 기록관리와 지식관리의 연계 필요성을 논의하였다. 그리고 4장에서는 호주 및 영국, 미국 사례를 통해 기록관리와 지식관리를 연계시키기 위한 최근의 기록학계 동향을 살펴본 후, 우리나라 공공기록관리 영역의 현황과 함께 지식 정보 자원으로서의 기록관리를 진작시키기 위한 제도적 개선방향을 세 가지 측면에서 제시하였다.

• 한국과 국제사회
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• 제3권1호
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• pp.221-244
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• 2019

본 논문은 나이지리아 보코하람 소요사태를 다루는 과정에서 나이지리아 현 대통령 소령(rtd) 마하무두 부하리(mahamudu buhari)와 직계전 대통령 굿럭 조나단(jonathan)의 역할을 분석하고자 한다. 나이지리아는 공정한 분쟁 분담이 없는 적이 없었다. 사실, 독립 후 10년 동안 어떤 나이지리아도 분쟁이 없었던 적이 없었다. 몇몇 쿠데타와 총파업 그리고 내전으로 나이지리아 사람들은 의견과 불신의 차이에서 비롯되는 가장 비참한 비극들 중 일부를 경험해야 했다. 나이지리아에서의 갈등이 지금처럼 필요한 관심을 받지 못했다는 얘기가 흥미롭다. 굿럭 조나단 지도부는 2015년 5월 취임한 무함마두 부하리 전 총리와 비교할 때 같은 노력과 협조를 받지 못했다. 본 논문은 두 나이지리아 지도자가 협력하는 것을 돕거나 방해하는 중요한 역할을 한다고 주장한다. 굿럭 조나단은 약하고 우유부단한 지도자로 인식되어 보코하람의 폭동을 효과적으로 다루지 못했다. 무하마두 부하리는 나이지리아 국민과 국제 사회가 보코하람 반란을 타개할 큰 희망과 기대를 안고 취임했다.

• Steel and Composite Structures
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• 제29권6호
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• pp.717-734
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• 2018

This paper presents the flexural performance of steel beam-to-column joints composed of hollow structural section beams and columns. A finite element (FE) model was developed incorporating geometrical and material nonlinearities to evaluate the behaviour of joints subjected to bending moments. The numerical outcomes were validated with experimental results and compared with EN1993-1-8. The demountability of the structure was discussed based on the tested specimen. A parametric analysis was carried out to investigate the effects of steel yield strength, end-plate thickness, beam thickness, column wall thickness, bolt diameter, number of bolts and location. Consequently, an analytical model was derived based on the component method to predict the moment-rotation relationships for the sub-assemblies with extended end-plates. The accuracy of the proposed model was calibrated by the experimental and numerical results. It is found that the FE model is fairly reliable to predict the initial stiffness and moment capacity of the joints, while EN1993-1-8 overestimates the initial stiffness extensively. The beam-to-column joints are shown to be demountable and reusable with a moment up to 53% of the ultimate moment capacity. The end-plate thickness and column wall thickness have a significant influence on the joint behaviour, and the layout of double bolt-rows in tension is recommended for joints with extended end-plates. The derived analytical model is capable of predicting the moment-rotation relationship of the structure.

• 천문학회보
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• 제44권1호
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• pp.35.4-35.4
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• 2019

We have conducted a 22 GHz very long baseline interferometry (VLBI) survey of 281 local (z < 0.05) active galactic nuclei (AGNs) selected from the Swift Burst Alert Telescope (BAT) 70-month ultra hard X-ray (14-195 keV) catalog. The main goal is to investigate the relation between the strengths of black hole accretion and the parsec-scale nuclear jet, which is expected to tightly correlate but has not been observationally confirmed yet. The BAT AGN Spectroscopic Survey (BASS) provides the least biased AGN sample against obscuration including both Seyfert types, hence it makes an ideal parent sample for studying the nuclear jet properties of an overall AGN population. Using the Korean VLBI Network (KVN), the KVN and VERA Array (KaVA), and the Very Long Baseline Array (VLBA), we observed 281 objects with a 22 GHz flux > 30 mJy, detecting 11 targets (~4% of VLBI detection rate). This implies that the fraction of X-ray AGNs which are currently ejecting a strong nuclear jet is very small. Although our 11 sources span a wide range of pc-scale morphological types, from compact to complex, they lie on a tight linear relation between accretion luminosity and nuclear jet luminosity. Our finding may indicate that the power of nuclear jet is directly responsible for the amount of black hole accretion. We also have probed the fundamental plane of black hole activity in VLBI scale (e.g., few milli-arcsecond). The results from our high-frequency VLBI radio study support that the change of jet luminosity and size follows what is predicted by the AGN evolution scenario based on the Eddington ratio (ƛ$_{Edd}$) - column density ($N_H$) plane, proposed by a previous study.