• 한국지반환경공학회 논문집
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• 제13권9호
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• pp.75-82
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• 2012

본 논문은 2006년 태풍 에위니아와 빌리스의 영향으로 강원 영서지역에서 발생한 집중호우에 의한 산사태 발생 원인과 특성에 대하여 분석한 결과이다. 강원 영서지역은 편마암, 화강암이 풍화된 화강풍화토가 주를 이루는 지역으로 집중호우 시 산사태 및 토석류의 피해에 취약한 것으로 나타났으며 강우특성 분석결과, 산사태 발생은 3일 이내의 누적강우량과 밀접한 관계가 있었고 지역별 발생빈도의 차이는 최대시우량의 영향으로 나타났다. 영서지역에서 발생한 산사태 860개소에 대한 자료의 분석 결과, 파괴 형태는 전이형 슬라이드로 시작되어 유동성 슬라이드로 변화되는 양상을 보였으며, 사면 경사는 $20{\sim}30^{\circ}$ 사면 길이는 11~20m 범위, 사면 폭은 6~10m 범위에서 발생빈도가 높은 것으로 나타났고, 영서지역의 산사태는 사면 폭이 좁은 소규모 형태로 편마암, 화강암 지대의 산사태 전형으로 분석되었다.

• 대한핵의학회지
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• 제19권2호
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• pp.43-50
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• 1985

With the improvement of hemodialysis, the course of the disease in patient with endstage renal disease has been clearly improved. Nevertheless, among several shortcomings to our present mode of renal replacement therapy, cardiovascular complications have been the leading cause of morbidity and mortality. Several factors such as anemia, arteriovenous shunting of blood, intermittent extracorporeal circulation and hypertension may be contributing. But little is known about the quantitative cardiac hemodynamic characteristics occurred during hemodialysis. The purpose of this study is to observe the sequential hemodynamic changes before, during and after the hemodialysis and to investigate reliable parameters in the detection of ventricular dysfunction. In the present study, equilibrium radionuclide cardiac angiography was performed and left and right ventricular volume indices, ejection phase indices of both ventricular, performance were measured in the 16 stable patients with chronic renal failure treated with maintenance hemodialysis sequentially i.e. before, during (early and late phase) and after the hemodialysis. The results obtained were as follows; 1) The indices of the left ventricular function were not changed during the hemodialysis but increased after the hemodialysis. 2) The indices of the right ventricular function(EF, SVI) were significantly decreased in the early phase (15, 30 minutes after starting extracorporeal circulation) but recovered after the hemodialysis. 3) The ratio of right ventricular to left ventricular ejection fraction was significantly decreased in the early phase and the lung volume indices were significantly increased at the same phase. As a conclusion, hemodialysis improves left ventricular function maybe due to increased contractility, and effects on the right ventricular function maybe due to the increased lung volume in the early phase of hemodialysis.

• 한국정보통신학회논문지
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• 제19권8호
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• pp.1973-1980
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• 2015

전투 시스템은 목적에 따라 각기 다른 특성을 가지는데, 주요 목적과 관련된 기능을 하는 부품이 다른 기능과 관련된 부품보다 중요하다. 또한 이러한 부품의 피격 확률은 면적에 비례한다고 볼 수 있다. 따라서 부품의 중요도 및 피격 확률을 모두 고려하여 취약성 분석이 이루어져야 하며, 전투 시스템의 설계 단계에서부터 분석된 결과를 반영하여야 신뢰성을 향상시킬 수 있다. 이를 위해 본 논문에서는 관련 연구를 바탕으로 FMECA 기반의 위험도를 적용하고, 전차의 구성 부품별 위험도를 도출하기 위한 방법과 계산 기준을 정의하며, 통합 위험도를 이용한 부품별 취약성 분석 방법을 제안한다. 추가적으로, 제안한 기법을 자동화해주는 위험도 기반의 취약성 분석 프로그램을 개발하고, 그것을 활용하여 제안한 기법의 유용성을 실험한다.

• Journal of Welding and Joining
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• 제31권5호
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• pp.71-76
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• 2013

The effect of zirconate having - NH functional group on the T-peel and lap shear strength of $CaCO_3$ containing structural epoxy adhesive for car body assembly was investigated. Curing behavior of epoxy adhesive samples were investigated by differential scanning calorimeter (DSC) techniques. The addition of zirconate up to 7.5 phr did not affect the curing mechanism of epoxy adhesive. While the small amount of zirconate addition less than 1.1 phr increased the cross-linking density, the excess addition of zirconate resulted in the increase of uncross-linked impurity. From the increase of T-peel and lap shear strength and the change of fracture mode from the adhesive failure to the mixed one, it was considered that the small addition of zirconate was effective in improving the adhesion strength of epoxy adhesive to the adherend and inorganic filler surfaces. The formation of uncross-linked impurity with the excess addition of zirconate was considered to decrease the joint strength by decreasing the cohesive strength of the cured epoxy.

• Geomechanics and Engineering
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• 제14권2호
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• pp.107-113
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• 2018

Coal samples with different joints morphology were subjected to uniaxial compression experiments, cracks evolution was recorded by Nikon D5300 and acoustic emission (AE) energy signals were collected by AEwin Test for Express-8.0. During loading process, coal samples deformed elastically with no obvious cracks changes, then they expanded gradually along the trace of the original cracks, accompanied by the formation of secondary cracks, and eventually produced a large-scale fracture. It was more interesting that the failure mode of samples were all shear shape, whatever the original cracks morphology was. With cracks and damage evolution, AE energy radiated regularly. At the early loading stage, micro damage and small scale fracture events only induced a few AE events with less energy, while large scale fracture leaded to a number of AE events with more energy at the later stage. Based on the multifractal theory, the multifractal spectrum could explain AE energy signals frequency responses and the causes of AE events with load. Multifractal spectrum width (${\Delta}{\alpha}$), could reflect the differences between the large and small AE energy signals. And another parameter (${\Delta}f$) could reflect the relationship between the frequency of the least and greatest signals in the AE energy time series. This research is helpful for us to understand cracks evolution and AE energy signals causes.

• Structural Engineering and Mechanics
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• 제74권3호
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• pp.351-363
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• 2020

Based on the dynamic tests of recycled aggregate concrete (RAC) short columns confined by the hoop reinforcement, the dynamic failure mechanism and the mechanical parameters related to the constitutive relation of confined recycled aggregate concrete (CRAC) were investigated thoroughly. The fracturing sections were relatively flat and smooth at higher strain rates rather than those at a quasi-static strain rate. With the increasing stirrup volume ratio, the crack mode is transited from splitting crack to slipping crack constrained with large transverse confinement. The compressive peak stress, peak strain, and ultimate strain increase with the increase of stirrup volume ratio, as well as the increasing strain rate. The dynamic confining increase factors of the compressive peak stress, peak strain, and ultimate strain increase by about 33%, 39%, and 103% when the volume ratio of hoop reinforcement is increased from 0 to 2%, but decrease by about 3.7%, 4.2%, and 9.1% when the stirrup spacing is increased from 20mm to 60mm, respectively. This sentence is rephrased as follows: When the stirrup volume ratios are up to 0.675%, and 2%, the contributions of the hoop confinement effect to the dynamic confining increase factors of the compressive peak strain and the compressive peak stress are greater than those of the strain rate effect, respectively. The dynamic confining increase factor (DCIF) models of the compressive peak stress, peak strain, and ultimate strain of CRAC are proposed in the paper. Through the confinement of the hoop reinforcement, the ductility of RAC, which is generally slightly lower than that of NAC, is significantly improved.

• Advances in aircraft and spacecraft science
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• 제3권1호
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• pp.61-75
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• 2016

Climate changes brought on by human interventions have proved to be more devastating than predicted during the recent decades. Recognition of seriousness of the situation has led regulatory organisations to impose strict targets on allowable carbon dioxide emissions from automotive vehicles. As a possible solution, it has been proposed that Fibre Metal Laminate (FML) system is used to reduce the weight of future vehicles. To facilitate this investigation, FML based on steel and self-reinforced polypropylene was stamp formed into dome shapes under different blank holder forces (BHFs) at room temperature and its forming behaviour analysed. An open-die configuration was used in a hydraulic press so that a 3D photogrammetric measurement system (ARAMIS) could capture real-time surface strains. This paper presents findings on strain evolutions at different points along and at $45^{\circ}$ to fibre directions of circular FML blank, through various stages of forming. It was found initiation and rate of deformation varied with distance from the pole, that the mode of deformations range from biaxial stretching at the pole to drawing towards flange region, at decreasing magnitudes away from the pole in general. More uniform strain distribution was observed for the FML compared to that of plain steel and the most significant effects of BHF were its influence on forming depth and level of strain reached before failure.

• The Journal of Advanced Prosthodontics
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• 제11권4호
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• pp.223-231
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• 2019

PURPOSE. The purpose of this study was to evaluate the shear bond strength (SBS) of an indirect resin composite (IRC) to the various resin matrix ceramic (RMC) blocks using different surface treatments. MATERIALS AND METHODS. Ninety-nine cubic RMC specimens consisting of a resin nanoceramic (RNC), a polymer-infiltrated hybrid ceramic (PIHC), and a flexible hybrid ceramic (FHC) were divided randomly into three surface treatment subgroups (n = 11). In the experimental groups, untreated (Cnt), tribochemical silica coating (Tbc), and Neodymium-Doped Yttrium Aluminum Garnet (Nd:YAG) laser irradiation (Lsr) with 3 W (150 mJ/pulse, 20 Hz for 20 sec.) were used as surface treatments. An indirect composite resin (IRC) was layered with a disc-shape mold ($2{\times}3mm$) onto the treated-ceramic surfaces and the specimens submitted to thermal cycling (6000 cycles, $5-55^{\circ}C$). The SBS test of specimens was performed using a universal testing machine and the specimens were examined with a scanning electron microscope to determine the failure mode. Data were statistically analyzed with two-way analysis of variance (ANOVA) and Tukey HSD test (${\alpha}=.05$). RESULTS. According to the two-way ANOVA, only the surface treatment parameter was statistically significant (P<.05) on the SBS of IRC to RMC. The SBS values of Lsr-applied RMC groups were significantly higher than Cnt groups for each RMC material, (P<.05). Significant differences were also determined between Tbc surface treatment applied and untreated (Cnt) PIHC materials (P=.039). CONCLUSION. For promoting a reliable bond strength during characterization of RMC with IRC, Nd:YAG laser or Tbc surface treatment technique should be used, putting in consideration the microstructure and composition of RMC materials and appropriate parameters for each material.

• 한국전산구조공학회논문집
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• 제28권3호
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• pp.267-274
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• 2015

본 논문은 넓은 보의 전단강도를 대상으로 한 실험적 평가에 대해 기술하였다. 본 논문의 실험을 통해 넓은 보에 횡방향 단면에서 GFRP 판의 보강개수와 종방향 전단보강 간격, 그리고 유효깊이가 전단강도에 끼치는 영향에 관하여 연구하였다. 총 7개의 시험체에 유공형 GFRP 판 형태로 전단보강재를 보강하여 전단성능 실험을 실시하였다. 본 논문에 기재된 전단보강재는 유공형 판 형태로 제작되어 타설 시 콘크리트의 유동성을 증가시켜 보강재와 콘크리트의 부착력을 향상시켰다. 7개 시험체의 주 변수로는 전단보강재의 횡방향 단면에 대한 판의 보강개수와 종방향 전단보강 간격, 그리고 유효깊이로 정하였다. 시험체의 균열 및 파괴 양상, 변형률과 전단강도비를 분석하였다. GFRP판으로 전단보강된 넓은 보의 전단강도는 ACI 318-11 기준으로 산정되었다. 실험의 결과를 통해 유공형 GFRP 판이 전단보강재로서 넓은 보에 효과적으로 적용됨을 확인하였다.

• 한국강구조학회 논문집
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• 제25권3호
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• pp.279-287
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• 2013

세장한 부재에 압축력이 작용할 때, 부재는 탄성좌굴이 발생하게 되어 급격히 내하력을 상실하고 파괴에 도달하게 된다. 이러한 현상으로 인한 부재의 파괴는 종국적으로 구조체에 위해를 가하게 되어 붕괴원인이 되기도 한다. 본 연구에서는 세장한 부재에 압축력이 작용할 경우 부재가 탄성좌굴이 발생하기 이전에 항복하도록 유도하는 장치(응력제한장치)를 개발하는 것을 목적으로 하고 있다. 특히, 본 논문에서는 응력제한장치로서 면외저항판 방식을 제안하고 실험과 유한요소 해석을 수행하였다. 실험의 변수는 면외저항판의 두께 및 저항판의 경사도이다. 실험 및 해석결과 면외저항판 실험체는 항복후 소성영역에서 내력의 큰 저하없이 안정적인 거동을 나타내고 있어 응력제한방식으로서 유효성이 확인되었다.