• 대한치과보철학회지
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• 제44권4호
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• pp.383-393
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• 2006

Statement of problem : Limited research on flowable resin has been undertaken on its application directly on dentin associated with the adhesive systems. Purpose : This study was to evaluate the shear bond strengh and fracture aspect of flowable resin on human dentin with various types of dentin bonding adhesives with thermo cycling effect. Materials and methods: Filtek-Flow(3M ESPE, USA) was used as flowable resin and Eighty human molars were randomly divided into 4 groups : three dentin bonding adhesives (Scotchbond-Multipurpose : 3-step contentional system, One-Step : One-bottle system. Prompt L-Pop : All-in-one, self-etching primer) and 32% etching treatment without bonding adhesive as a control group. For evaluating their durability of bonding, each group was subdivided : storaging in the water at 37$^{\circ}C$(24 hours) and thermocycling (0$^{\circ}C$-55$^{\circ}C$, 30 seconds intervals, 1000 cycle). Shear bond strength tests were performed and resin-dentin interface and fracture mode were observed. Results were analysed by one-way ANOVA and Scheffe's multiple range test. Results and Conclusion : 1. At 0 cycle, the mean shear bond strength of One-Step exhibited the highest value of all groups(p<0.05), and there were no significant differences between Prompt L-Pop and Scotchbond-Multipurpose, Scotchbond-Multipurpose and control(p>0.05). After 1000 thermocycling, One-Step exhibited higher value than other groups(p<0.05), and there were no significant differences among other groups (p>0.05). 2. The shear bond strength of each group was significantly decreased after thermocycling except Scotchbond-Multipurpose (p>0.05). 3. The most common failure mode was adhesive type and mixed type, next in order.

• Smart Structures and Systems
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• 제23권2호
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• pp.107-122
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• 2019

As one of the most important parameters in structural health monitoring, structural frequency has many advantages, such as convenient to be measured, high precision, and insensitive to noise. In addition, frequency-change-ratio based method had been validated to have the ability to identify the damage occurrence and location. However, building a precise enough finite elemental model (FEM) for the test structure is still a huge challenge for this frequency-change-ratio based damage detection technique. In order to overcome this disadvantage and extend the application for frequencies in structural health monitoring area, a novel method was developed in this paper by combining the cross-model cross-mode (CMCM) model updating algorithm with the frequency-change-ratio based method. At first, assuming the physical parameters, including the element mass and stiffness, of the test structure had been known with a certain value, then an initial to-be-updated model with these assumed parameters was constructed according to the typical mass and stiffness distribution characteristic of shear buildings. After that, this to-be-updated model was updated using CMCM algorithm by combining with the measured frequencies of the actual structure when no damage was introduced. Thus, this updated model was regarded as a representation of the FEM model of actual structure, because their modal information were almost the same. Finally, based on this updated model, the frequency-change-ratio based method can be further proceed to realize the damage detection and localization. In order to verify the effectiveness of the developed method, a four-level shear building was numerically simulated and two actual shear structures, including a three-level shear model and an eight-story frame, were experimentally test in laboratory, and all the test results demonstrate that the developed method can identify the structural damage occurrence and location effectively, even only very limited modal frequencies of the test structure were provided.

• The Journal of Advanced Prosthodontics
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• 제14권4호
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• pp.262-272
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• 2022

PURPOSE. This study aimed to analyze the shear bond strength between the 3D-printed denture base and the chairside relining material, according to the surface treatment. MATERIALS AND METHODS. Cylindrical specimens were prepared using DENTCA Denture Base II. The experimental groups were divided into 6 (n = 10): no surface treatment (C), Tokuyama Rebase II Normal adhesive (A), sandblasting (P), sandblasting and adhesive (PA), sandblasting and silane (PS), and the Rocatec system (PPS). After bonding the chairside relining material to the center of the specimens in a cylindrical shape, they were stored in distilled water for 24 hours. Shear bond strength was measured using a universal testing machine, and failure mode was analyzed with a scanning electron microscope. Shear bond strength values were analyzed using one-way analysis of variance, and Tukey's honest significant difference test was used for post-hoc analysis (P < .05). RESULTS. Group PPS exhibited significantly higher shear bond strength than all other groups. Groups P and PA displayed significantly higher bond strengths than the control group. There were no significant differences between groups PS and A compared to the control group. Regarding the failure mode, adhesive failure occurred primarily in groups C and A, and mixed failure mainly in groups P, PA, PS, and PPS. CONCLUSION. The shear bond strength between the 3D-printed denture base and the chairside relining material exhibited significant differences according to the surface treatment methods. It is believed that excellent adhesive strength will be obtained when the Rocatec system is applied to 3D-printed dentures in clinical practice.

• Structural Engineering and Mechanics
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• 제51권6호
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• pp.893-907
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• 2014

Meshless local collocation method produces much better conditioned matrices than meshless global collocation methods. In this paper, the meshless local collocation method based on thin plate spline radial basis function and first-order shear deformation theory are used to calculate the natural frequencies and mode shapes of laminated composite shells. Through numerical experiments, the accuracy and efficiency of present method are demonstrated.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1995년도 추계학술대회 논문집
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• pp.34-39
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• 1995

Particle displacement distributions of the fundamental mode and overtone modes in an energy-frapped single resonator and an energy-trapped double acoustically coupled filter using the thickness shear vibration were calculated. And the effects of the width of a pair of partial electrodes, the width of the gap between two pairs of partial electrodes and the magnitude of the plate back on the displacement distributions of the symmetric vibration mode and anti-symmetric vibration mode of the resonators and the filters were investigated.

• 한국환경과학회지
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• 제16권12호
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• pp.1401-1409
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• 2007

The formation mechanism of the snow cells of the Yellow Sea associated with snowfall over the southwestern part of Korea on 4 February, 2004 has been investigated using special upper-air sounding and radar data obtained for the KEOP(Korea Enhanced Observing Period) Intensive Observing Period(IOP). Results show that the types of snow cells for the selected period are classified into L(Longitudinal)-mode, Low-level convergence, and T(Transverse)-mode with their evolution from L-mode to T-mode. In particular, the existence of low-level warm and humid layer associated with temporally southwesterly inflow for about 4 hours provides a favorable condition in forming the T-mode snow cells. The vertical depth of the T-mode snow cells is deeper than that of L-mode ones due to the southeastward penetration of cold and dry air into relatively warm and humid air. In addition, it is found that wind shear vector between 1000 hPa and 600 hPa is one of the factors which control the orientation of snow cells in formation embedded into the snowbands for the both modes.

• Geomechanics and Engineering
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• 제19권5호
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• pp.463-472
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• 2019

The mode perturbation method (MPM) is suitable and efficient for solving the eigenvalue problem of a nonuniform soil deposit whose property varies with depth. However, results of the MPM do not always converge to the exact solution, when the variation of soil deposit property is discontinuous. This discontinuity is typical because soil is usually made up of sedimentary layers of different geologic materials. Based on the energy integral of the variational principle, a new mode perturbation method, the energy-based mode perturbation method (EMPM), is proposed to address the convergence of the perturbation solution on the natural frequencies and the corresponding mode shapes and is able to find solution whether the soil properties are continuous or not. First, the variational principle is used to transform the variable coefficient differential equation into an equivalent energy integral equation. Then, the natural mode shapes of the uniform shear beam with same height and boundary conditions are used as Ritz function. The EMPM transforms the energy integral equation into a set of nonlinear algebraic equations which significantly simplifies the eigenvalue solution of the soil layer with variable properties. Finally, the accuracy and convergence of this new method are illustrated with two case study examples. Numerical results show that the EMPM is more accurate and convergent than the MPM. As for the mode shapes of the uniform shear beam included in the EMPM, the additional 8 modes of vibration are sufficient in engineering applications.

• 대한기계학회논문집A
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• 제38권2호
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• pp.121-127
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• 2014

단층 그래핀 시트(Single layer graphene sheet, SLGS)의 찢어짐 모드(모드 III) 파괴 예측을 위한 원자 기반 미세결합요소모델이 개발되었다. 이 모델은 그래핀 시트의 최대 변형률 관계를 예측하기 위해 수정된 모스포텐셜을 사용한다. 면외 전단하중 조건에서 그래핀의 모드 III 파괴를 광범위한 분자역학(Molecular mechanics, MM) 시뮬레이션으로 조사하였다. 분자역학은 원자의 균열선단 근처 원자의 변위를 설명하기 위해 사용되었고, 선형탄성파괴역학은 이 영역 바깥의 영역을 설명하기 위해 사용되었다. 해석 결과 분자역학 방법이 SLGS의 전단 물성 계산뿐만 아니라 armchair 및 zigzag 방향 모드 III 파괴인성 연구에도 단순하면서도 신뢰할만하다는 것을 보여준다. SLGS 의 모드 III 파괴인성은 zigzag 방향에 대해 $0.86MPa{\sqrt{m}}$, armchair 방향에 대해 $0.93MPa{\sqrt{m}}$로 예측되었다.

• 한국지진공학회논문집
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• 제3권2호
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• pp.87-96
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• 1999

시간영역에서의 구조물의 해석은 직접적분법과 모드중첩법에 의하여 구해질 수 있다 그 중에서도 모드중첩법에 의한 해석방법은 몇가지 저차 진동모드를 사용하여 비교적 정확한 해를 구할 수 있기 때문에 동적해석에 널리 사용되고 있다, 그러나 비선형해석에서는 각 부재들의 상태에 따라 강성이 달라지므로 고유 진동모드를 정의할수 없거나 변화되는 강성에 따라 고유진동 모드를 지속적으로 다시 구하여야 하는 불편 있으므로 모드 중첩법을 이용한 비선형해석은 완전탄소성모델 등 극히 제한된 조건에서만 실행이 가능하였다 본논문에서는 강성행렬을 각 부재별로 분리시키고 비선형복원력과 초기선형복언력과 초기선형복원력의 차이를 하중항에 반영시킴으로써 모드중첩법을 이용하여 비선형 해석은완전탄소성모델 등 극히 제한된 조건에서만 실행이 가능하였다 본 논문에서는 강성행렬을 각 부재별로 분리시키고 비선형 복원력과 초기선형복원력의 차이를 하중항에 반영시킴으로써 모드중첩법을 이용하여 비선형해석이 가능한 방법을 제시하고자 한다. 특히 각 부재 강성을 각 부재의 상대변위의 함수로 나타냄으로써 연속적인 계산이 가능하게 하였다 본 논문에서 제시된 방법은 전단보모델에 적용하였으며 모드 개수를 변화시켜 지진하중에 의한 최대변위를 계산하여 이를 직접적분버에 의한 결과와 비교하였다.

• Computational Structural Engineering : An International Journal
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• 제1권2호
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• pp.117-130
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• 2001

Investigations of low-rice unbounded reinforced concrete shear walls with or without openings are performed with comparison of analytical and experimental results. Theoretical analysis is based on nonlinear finite element algorithm, which incorporates concrete failure criterion and nonlinear constitutive relationships. Studios focus on the effects of height-to-length ratio of shear walls, opening ratio, horizontal and vertical reinforcement radios, and diagonal reinforcement. Analytical solutions conform well with experimental results. Equations for cracking, yielding and ultimate loads with corresponding lateral displacements are derived by regression using analytical results and experimental data. Also, failure modes of low-rise unbounded shear walls are theoretically investigated. An explanation of change in failure mode is ascertained by comparing analytical results and ACI code equations. Shear-flexural failure can be obtained with additional flexural reinforcement to increase a wall's capacity. This concept leads to a design method of reducing flexural reinforcement in low-rise bounded solid shear wall's. Avoidance of shear failure as well as less reinforcement congestion leer these walls is expected.