• Structural Engineering and Mechanics
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• 제14권2호
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• pp.119-133
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• 2002

A beam-column fiber element for the large displacement, nonlinear inelastic analysis of Concrete-Filled Steel Tubes (CFT) is implemented. The method of description is Total Lagrangian formulation. An 8 degree of freedom (DOF) element with three nodes, which has 3 DOF per end node and 2 DOF on the middle node, has been chosen. The quadratic Lagrangian shape functions for axial deformation and the quartic Hermitian shape function for the transverse deformation are used. It is assumed that the perfect bond is maintained between steel shell and concrete core. The constitutive models employed for concrete and steel are based on the results of a recent study and include the confinement and biaxial effects. The model is implemented to analyze several CFT columns under constant and non-proportional fluctuating concentric axial load and cyclic lateral load. Good agreement has been found between experimental results and theoretical analysis.

• Advances in materials Research
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• 제12권2호
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• pp.83-100
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• 2023

In this paper, sandwich plate, constructed with orthotropic and isotropic composite materials, is analyzed to obtain the static and harmonic behavior. The analysis is done by using ANSYS APDL FEM tool. A solid-shell 190 and an 8-node solid 185 elements are employed for face and core material respectively to analyze the plate. Results was attained by using Reissner-Mindlin theory. Effect of increasing thickness ratio of face sheet to depth of the plate is presented on static, vibration and harmonic response on the sheet and the results are discussed briefly. Published work in open domain was used to validate the results and observed excellent agreement. It can be stated that proposed model presents results with remarkable accuracy. Results are obtained to reduce the weight of the plate and minimizing the vibration amplitudes.

• Steel and Composite Structures
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• 제33권1호
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• pp.111-122
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• 2019

This paper presents an experimental work on the post-fire behavior of two kinds of innovative composite stub columns under eccentric compression. The partially precast steel reinforced concrete (PPSRC) column is composed of a precast outer-part cast using steel fiber reinforced reactive powder concrete (RPC) and a cast-in-place inner-part cast using conventional concrete. Based on the PPSRC column, the hollow precast steel reinforced concrete (HPSRC) column has a hollow column core. With the aim to investigate the post-fire performance of these composite columns, six stub column specimens, including three HPSRC stub columns and three PPSRC stub columns, were exposed to the ISO834 standard fire. Then, the cooling specimens and a control specimen unexposed to fire were eccentrically loaded to explore the residual capacity. The test parameters include the section shape, concrete strength of inner-part, eccentricity ratio and heating time. The test results indicated that the precast RPC shell could effectively confine the steel shape and longitudinal reinforcements after fire, and the PPSRC stub columns experienced lower core temperature in fire and exhibited higher post-fire residual strength as compared with the HPSRC stub columns due to the insulating effect of core concrete. The residual capacity increased with the increasing of inner concrete strength and with the decreasing of heating time and load eccentricity. Based on the test results, a FEA model was established to simulate the temperature field of test specimens, and the predicted results agreed well with the test results.

• 스마트미디어저널
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• 제9권4호
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• pp.109-117
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• 2020

최근 디지털 트윈은 제4차 산업혁명의 도래와 더불어 물리적 시스템과 사이버 시스템을 연계하고 통합하는 중요한 기술로 부각되고 있다. 본 논문에서는 에너지 분야의 전력기자재 디지털 트윈화를 위하여 필요한 디지털 트윈화의 절차에 따른 요구사항을 분석하고, 또한 이러한 디지털 트윈을 구축하기 위한 핵심 구성요소라 할 수 있는 인더스트리 4.0 기반의 AAS(Asset Administration Shell)의 개념과 기능 및 특성 분석을 기반으로 구체적인 설계를 하였다. 하지만, 아직까지는 국내·외 적으로 디지털 트윈구현을 위한 공통된 플랫폼이나 실증 모델에 관해서는 많은 연구가 이루어 지지 못하고 있는 상황이므로, 본 논문에서는 에너지 분야의 전력기자재 디지털 트윈화를 염두에 두고 디지털 트윈 플랫폼 구축하는데 필요한 핵심 요구사항을 분석하고, 실제 디지털 트윈을 구축함에 있어서 핵심적 역할을 수행하게 될 AAS의 기능과 특성을 기반으로 실제로 전력기자재를 대상으로한 AAS의 설계를 함으로써 향후 스마트 에너지 디지털 트윈을 구축 및 실증을 위한 절차와 구체적 기능들을 제시하고자 하였다.

• 한국지반신소재학회논문집
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• 제20권1호
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• pp.45-55
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• 2021

본 연구에서는 수치해석모형을 통하여 수위변동시 필댐의 거동 특성을 분석하고 저수지의 안전관리 방안을 고찰하였다. 수치해석 프로그램(GTS NX 및 LIQCA)을 이용하여 필댐의 상·하류측 Shell 및 Core에서 수위승강에 따른 소성전단변형률, 수평변위, 응력경로, 간극수압 등을 분석하였다. 제체의 거동을 분석한 결과, 제체 내의 수위가 빠른 속도로 상승하면 간극수압 및 변위 또한 급격하게 증가하는데, 수위의 상승은 제체 내의 간극수압 증가와 제체의 포화도 증가를 유발하며, 제체의 유효응력을 감소시키는 것으로 나타났다. 이러한 수위승강 시 필댐의 거동 특성은 제체의 강도 및 강성이 저하되는 원인이 되고, 침투로 인해 발생하는 제체의 변형에 의해 소성전단변형률이 축적되어 변위 증가를 유발하는 것으로 판단된다. 본 연구를 통해 저수지의 정밀안전진단 상태평가 기준 개선안을 제안하였으며, 향후 저수지 안전진단지침 개정안 마련 시 기초자료로 활용될 수 있을 것으로 판단된다.

• Molecular & Cellular Toxicology
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• 제3권1호
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• pp.1-10
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• 2007

The persistent and ubiquitous environmental contaminant, tributyltin chloride (TBT), induces not only imposex in gastropods but also the differentiation of adipocytes in vitro and increases adipose mass in vivo in vertebrates. TBT is a nanomolar affinity ligand for retinoid X receptor (RXR) in the rock shell(Thais clavigera) and for both the RXR and the peroxisome proliferator activated receptor $\gamma(PPAR\gamma)$ in the amphibian (Xenopus laevis), mouse, and human. The molecular mechanisms underlying induction of imposex by TBT have not been clarified, though several hypotheses are proposed. TBT promotes adipogenesis in the murine 3T3-L1 cell model and perturbs key regulators of adipogenesis and lipogenic pathways in vivo primarily through activation of RXR and $PPAR\gamma$. Moreover, in utero exposure to TBT leads to strikingly elevated lipid accumulation in adipose depots, liver, and testis of neonate mice and results in increased adipose mass in adults. In X. laevis, ectopic adipocytes form in and around gonadal tissues following organotin, RXR or $PPAR\gamma$ ligand exposure. TBT represents the first example of an environmental endocrine disrupter that promotes adverse effects from gastropods to mammals.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2010년도 제39회 하계학술대회 초록집
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• pp.304-304
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• 2010

The study on the catalytic oxidation of carbon monoxide (CO) to carbon dioxide ($CO_2$) using the noble metals has long been the interest subject and the recent progress in nanoscience provides the opportunity to develop new model systems of catalysts in this field. Of the noble metal catalysts, we selected ruthenium (Ru) as metal catalyst due to its unusual catalytic behavior. The size of colloid Ru NPs was controlled by the concentration of Ru precursor and the final reduction temperatures. For catalytic activity of CO oxidation, it was found that the trend is dependent on the size of Ru NPs. In order to explain this trend, the surface oxide layer surrounding the metal core has been suggested as the catalytically active species through several studies. In this poster, we show the influence of surface oxide on Ru NPs on the catalytic activity of CO oxidation using chemical treatments including oxidation, reduction and UV-Ozone surface treatment. The changes occurring to UV-Ozone surface treatment will be characterized with XPS and SEM. The catalytic activity before and after the chemical modification were measured. We discuss the trend of catalytic activity in light of the formation of core-shell type oxide on nanoparticles surfaces.

• 천문학회보
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• 제37권1호
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• pp.73.1-73.1
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• 2012

We present the results of dust scattering simulations carried out for the Orion Eridanus Superbubble region by comparing them with observations made in the far-ultraviolet. The albedo and the phase function asymmetry factor (g-factor) of interstellar grains were estimated as well as the distance and thickness of the dust layers. The results are: 0.39-0.45 for the albedo and 0.25-0.65 for the g-factor, in good agreement with previous determinations and theoretical predictions. The distance of the assumed single dust layer, modeled for the Orion Molecular Cloud Complex, was estimated to be -110 pc and the thickness ranged from -130 at the core to -50 pc at the boundary for the region of the present interest, implying that the dust cloud is located in front of the Superbubble. The simulation result also indicates that a thin (-10 pc) dust shell surrounds the inner X-ray cavities of hot gas at a distance of -70-90 pc.

• 한국세라믹학회지
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• 제48권6호
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• pp.493-498
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• 2011

Optimal atomic configurations in a nanoparticle were predicted by genetic algorithm. A truncated octahedron with a fixed composition of 1 : 1 was investigated as a model system. A Python code for genetic algorithm linked with a molecular dynamics method was developed. Various operators were implemented to accelerate the optimization of atomic configuration for a given composition and a given morphology of a nanoparticle. The combination of random mix as a crossover operator and total_inversion as a mutation operator showed the most stable structure within the shortest calculation time. Pt-Ag core-shell structure was predicted as the most stable structure for a nanoparticle of approximately 4 nm in diameter. The calculation results in this study led to successful prediction of the atomic configuration of nanoparticle, the size of which is comparable to that of practical nanoparticls for the application to the nanocatalyst.

• Smart Structures and Systems
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• 제13권4호
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• pp.501-515
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• 2014

This paper presents a linear computational homogenization framework to evaluate the effective (or generalized) electromechanical coupling coefficient (EMCC) of adaptive structures with piezoelectric structural fiber (PSF) composite elements. The PSF consists of a silicon carbide (SiC) or carbon core fiber as reinforcement to a fragile piezo-ceramic shell. For the micro-scale analysis, a micromechanics model based on the variational asymptotic method for unit cell homogenization (VAMUCH) is used to evaluate the overall electromechanical properties of the PSF composites. At the macro-scale, a finite element (FE) analysis with the commercial FE code ABAQUS is performed to evaluate the effective EMCC for structures with the PSF composite patches. The EMCC is postprocessed from free-vibrations analysis under short-circuit (SC) and open-circuit (OC) electrodes of the patches. This linear two-scale computational framework may be useful for the optimal design of active structure multi-functional composites which can be used for multi-functional applications such as structural health monitoring, power harvest, vibration sensing and control, damping, and shape control through anisotropic actuation.