• Steel and Composite Structures
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• 제49권5호
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• pp.473-486
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• 2023

A through-railway bridge with an inclined girder has recently been applied to optimize the cross-section of a slender bridge structure in railway bridges. To achieve the additional cross-section optimization effect by the bolted end-plate connection, it is necessary to investigate the application of the bolted end-plate tension connection between the inclined girder and the crossbeam. This basic study was conducted on the application of the bolted end-plate moment connection of crossbeams to half-through girders with inclined webs. The combined behavior of vertical deflection and rotational behavior was observed due to the effect of the web inclination in the inclined girder where the steel crossbeam was connected to the girder by the bolted end-plate moment connection. Therefore, in the experiment, the deflection of the inclined girder was 1.77-2.93 times greater than that of the vertical girder but the lateral deflection of the inclined girder was 0.4 times less than that of the vertical girder. Moreover, the tensile stress of the upper bolts in the inclined girder with low crossbeams was clearly 0.81 times lower than that of the vertical girder. According to the results, the design formula for vertical girders does not reflect the influence of the web inclination. Therefore, this study proposed the design procedures for the inclined girder to apply the bolted end-plate moment connection of the crossbeam to the inclined girder by reflecting the design change factors according to the effect of the web inclination.

• Steel and Composite Structures
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• 제49권2호
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• pp.231-244
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• 2023

Many of the recent investigations in the field of geotechnical engineering focused on the bearing capacity theories of multilayered soil. A number of factors affect the bearing capacity of the soil, such as soil properties, applied overburden stress, soil layer thickness beneath the footing, and type of design analysis. An extensive number of finite element model (FEM) simulation was performed on a prototype slope with various abovementioned terms. Furthermore, several non-linear artificial intelligence (AI) models are developed, and the best possible neural network system is presented. The data set is from 3443 measured full-scale finite element modeling (FEM) results of a circular shallow footing analysis placed on layered cohesionless soil. The result is used for both training (75% selected randomly) and testing (25% selected randomly) the models. The results from the predicted models are evaluated and compared using different statistical indices (R² and RMSE) and the most accurate model BBO (R²=0.9481, RMSE=4.71878 for training and R²=0.94355, RMSE=5.1338 for testing) and TLBO (R²=0.948, RMSE=4.70822 for training and R²=0.94341, RMSE=5.13991 for testing) are presented as a simple, applicable formula.

• Geomechanics and Engineering
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• 제35권6호
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• pp.637-646
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• 2023

At present, the research on wave propagation in graphene platelet reinforced composite plates focuses on the propagation behavior of bulk waves, in which the effect of boundary condition is ignored, there is no literature report on propagation behaviors of guided waves in graphene platelet reinforced metal foams (GPLRMF) plates. In fact, wave propagation is affected by boundary conditions, so it is necessary to study the propagation characteristics of guided waves. The aim of this paper is to solve this problem. The effective performance of the material was calculated using the mixing law. Equations of motion of GPLRMF plate is derived by using Hamilton's principle. Then, the eigenvalue method is used to obtain the expressions of bending wave, shear wave and longitudinal wave, and the degradation verification is carried out. Finally, the effects of graphene platelets (GPLs) volume fraction, elastic foundation, porosity coefficient, GPLs distribution types and porosity distribution types on the dispersion relations are studied. We find that these factors play an important role in the propagation characteristics and phase velocity of guided waves.

• Steel and Composite Structures
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• 제50권1호
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• pp.15-24
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• 2024

This research presents dynamical reaction investigation of pore-dependent and nano-thickness beams having functional gradation (FG) constituents exposed to a movable particle. The nano-thickness beam formulation has been appointed with the benefits of refined high orders beam paradigm and nonlocal strain gradient theory (NSGT) comprising two scale moduli entitled nonlocality and strains gradient modulus. The graded pore-dependent constituents have been designed through pore factor based power-law relations comprising pore volumes pursuant to even or uneven pore scattering. Therewith, variable scale modulus has been thought-out until process a more accurate designing of scale effects on graded nano-thickness beams. The motion equations have been appointed to be solved via Ritz method with the benefits of Chebyshev polynomials in cosine form. Also, Laplace transform techniques help Ritz-Chebyshev method to obtain the dynamical response in time domain. All factors such as particle speed, pores and variable scale modulus affect the dynamical response.

• 한국식품저장유통학회지
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• 제30권6호
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• pp.905-917
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• 2023

The optimal fermentation conditions for producing fermented black soybeans rich in sulfur-containing amino acids were investigated. Response surface methodology monitored fermentation conditions. A central composite design examined the effect of independent variables: enzyme concentration (X₁) and fermentation time (X₂) on yield and methionine content. Both factors significantly influenced these dependent variables. Enzyme concentration more profoundly affected amino nitrogen content than fermentation time. β-Glucan content and cystine level were primarily affected by fermentation time. We elicited each variable's regression formula and identified optimal fermentation conditions for functional compounds. The predicted optimum conditions were an enzyme concentration of 0.28-0.32% and a fermentation time of 58.0-62.0 min. Under these optimal conditions, each black soybean variety's sulfur amino acid content ranged from 818.62 to 922.62 mg/100 g, demonstrating significant variety differences.

• Steel and Composite Structures
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• 제50권2호
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• pp.237-247
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• 2024

Research on interfacial crack formation in orthotropic bi-materials has experienced a notable increase in recent years, driven by growing concerns about structural integrity and reliability. The existence of a crack at the interface of bi-materials has a substantial impact on mechanical strength and can ultimately lead to fracture. The primary objective of this article is to introduce a comprehensive analytical model and establish stress relationships for investigating interfacial crack between two non-identical orthotropic materials with desired crack-fiber angles. In this paper, we present the application of the Interfacial Maximum Tangential Stress (IMTS) criterion, in combination with the Reinforcement Isotropic Solid (RIS) model, to investigate the behavior of interfacial cracks in orthotropic bi-materials under mixed-mode I/II loading conditions. We analytically characterize the stress state at the interfacial crack tip using both Stress Intensity Factors (SIFs) and the T-stress term. Orthotropic materials, due to their anisotropic nature, can exhibit complex crack tip stress fields, making it challenging to predict crack initiation behavior. The secondary objective of this study is to employ the IMTS criterion to predict the crack initiation angle and explore the notable impact of the T-stress term on fracture behavior. Furthermore, we validate the effectiveness of our approach in evaluating Fracture Limit Curves (FLCs) for interfacial cracks in orthotropic bi-materials by comparing our FLCs with relevant experimental data from existing literature.

• Steel and Composite Structures
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• 제50권4호
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• pp.403-418
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• 2024

In this paper, vibration and energy absorption characteristics of a nanostructure which is composed of two embedded porous annular/circular nanoplates coupled by a viscoelastic substrate are investigated. The modified couple stress theory (MCST) and the Gurtin-Murdoch theory are applied to take into account the size and the surface effects, respectively. Furthermore, the structural damping effect is probed by the Kelvin-Voigt model and the mathematical model of the problem is developed by a new hyperbolic higher order shear deformation theory. The differential quadrature method (DQM) is employed to obtain the out-of-phase and in-phase frequencies of the structure in order to predict the dynamic response of it. The acquired results reveal that the vibration and energy absorption of the system depends on some factors such as porosity, surface stress effects, material length scale parameter, damping and spring constants of the viscoelastic foundation as well as geometrical parameters of annular/circular nanoplates. A bird's-eye view of the findings in the research paper offers a comprehensive understanding of the vibrational behavior and energy absorption capabilities of annular/circular porous nanoplates. The multidisciplinary approach and the inclusion of porosity make this study valuable for the development of innovative materials and applications in the field of nanoscience and engineering.

• Steel and Composite Structures
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• 제51권6호
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• pp.601-617
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• 2024

This work aims to explore the static behaviour of a tapered functionally graded porous plate (FGPP) with even and uneven porosity distributions resting on two parametric elastic foundations. The plate under investigation is subjected to bi-sinusoidal loading and the edges of the plate are exposed to different combinations of edge restrictions. In order to examin the static behaviour, bending factors (BF) related to bending and normal stresses have been evaluated using classical plate theory. To achieve this, the governing equations have been derived employing the energy concept. And to solve it, the Rayleigh-Ritz method with an algebraic function has been utilised; it is simple, precise, and computationally intensive. After convergence and validation analyses, new findings are made available. The BF of the plate have been exhaustively examined to explain the influence of aspect ratios, material property index, porosity factor, taper factor, and Winkler and Pasternak stiffness. It is observed that the BF of an elastically supported FGPP are influenced by the index of material propery and the aspect ratio. Findings also indicate that the impact of porosity is more when it is spread evenly, as opposed to when it is unevenly distributed. Further, the deformed plate's structure is significantly influenced by the different thickness variations. Examination of bending characteristics of FGPP having different new cases of thickness variations with different types of porosity distribution under fifteen different mixed edge constraints is the prime novality of this work. Results presented are reliable enough to be taken into account for future studies.

• 대한소아치과학회지
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• 제34권2호
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• pp.273-284
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• 2007

본 연구는 광중합형 복합레진 Composan LCM Flow(Promedica, Germany), Clearfil ST(Kuraray medical, Japan) Durafil VS(Heraeus Kulzer, U.S.A), Point 4(Kerr, U.S.A)를 사용하여 각 제품의 물리적, 화학적 평가를 하고자 하였다. 마모시험 후 마모된 면의 깊이를 측정하였고 0.1N NaOH에 보관 후. 각 제품의 분해저항성을 무게손실, 표면하 분해층 깊이, 용출된 Si 농도를 기준으로 평가하였으며 주사전자현미경과 공촛점 레이저 현미경으로 분해 층을 관찰하여 다음과 같은 결과를 얻었다. 1. 무게 손실량은 $1.02{\sim}6.04%$까지 다양하였으며 Durafil VS에서 가장 높았다$(6.04{\pm}0.29%)$. 2. 분해층 깊이는 Durafil VS이 가장 깊었고 Clearfil ST, Point 4, Composan LCM Flow순이었고 Point 4와 Composan LCM Flow는 다른 제품과 유의한 차이를 보였다(p<0.001). 3. Si 용출량은 Clearfil ST가 가장 많았으며 Durafil VS, Composan LCM Flow, Point 4 사이에 유의한 차이를 보였다(p<0.001). 4. 주사전자현미경 관찰시 표면 양상 및 분해층 깊이를 관찰할 수 있었고 공촛점 레이저 현미경 관찰시 NaOH 용액에 보관한 후 수복재의 기질과 충전제 사이의 결합의 파괴 양상을 관찰할 수 있었다. 5. 최대마모깊이는 Durafil VS, Composan LCM Flow, Point 4, Clearfil ST 순으로 낮았으며 유의한 차이를 보이지 않았다(p>0.001). 6. 각 제품의 Si 용출량과 분해층 깊이 사이(r=0.892, p<0.01), Si 용출량과 무게손실 사이(r=0.736, p<0.01)에는 유의한 상관관계를 보였다.

• 대한소아치과학회지
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• 제31권4호
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• pp.685-695
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• 2004

복합레진은 치질과 우수한 결합력을 가지며 심미적인 이유로 치과의 대표적 수복재로 자리잡고 있다. 그러나 저작력에 따른 마모와 구강내 환경에서의 수분흡수에 따른 가수분해가 복합레진의 강도약화를 야기하고 있다. 실험에 사용된 복합레진은 현재 임상에서 많이 사용되고 있는 Point4, Tetric flow, Heliomolar flow, Filtek supreme 이다. 각 제품의 화학적 분해와 마모도를 평가하기 위해 각각 10개의 시편을 제작하여 그 중 5개는 $37^{\circ}C$의 수중하에 1Kg의 하중을 가하여 10,000 cycle동안의 마모도를 측정하였다. 나머지 5개 시편은 무게 측정을 한 후 0.1N NaOH용액, 3ml에 저장하여 $60^{\circ}C$에서 보관한 후 2주 후 제거하여 1.23% HCl로 2시간 동안 중화하고 증류수로 세척한 후 $60^{\circ}C$에서 건조하였다. 무게 손실, 분해층 깊이 및 시편내의 Si의 농도 변화. 최대 마모 깊이를 근거로 평가하여 다음과 같은 결과를 얻었다. 1. 각 제품의 무게 손실량은 Heliomolar flow, Filtek supreme, Point4, Tetric flow 순이었으며 Heliomolar flow, Filtek supreme을 제외한 다른 제품간에는 유의한 차이를 보였다(P<0.05). 2. 각 제품의 표면하 분해층 깊이는 Filtek supreme, Heliomolar flow, Tetric flow, Point4 순이었으며 Heliomolar flow, Tetric flow을 제외한 다른 제품간에는 유의 한 차이를 보였다(P<0.05). 3. 각 제품으로부터 용출된 Si은 Filtek supreme, Heliomolar flow, Point4. Tetric flow 순이었으며 Point4, Tetric flow을 제외 한 다른 제품간에는 유의한 차이를 보였다(P<0.05). 4. 최대마모깊이 측정시 Heliomolar flow, Point4, Filtek supreme, Tetric flow 순이며 0.1N NaOH 용액에 보관한 레진의 마모깊이가 물에 보관한 레진에 비해 증가한 양상을 보였다. 5. 주사전자현미경 관찰시 NaOH 용액에 보관한 후 레진 기질과 충전제 사이의 결합의 파괴를 관찰할 수 있었으며, 공촛점 레이저 현미경 관찰시 NaOH 용액에 보관한 후 수복재의 기질과 충전제 사이의 파괴양상인 분해층 깊이를 관찰할 수 있었다.