• 화약ㆍ발파
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• 제40권2호
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• pp.15-24
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• 2022

최근 노후화로 불용되는 산업구조물의 해체 수요가 증가하면서 산업구조물 해체에 대한 관심이 부각되고 있으며, 해체된 산업부지를 원래 자연의 모습으로 복원하는 공사가 주요 이슈로 부상하고 있다. 본 시공사례는 구조적 노후화와 기능적 요건을 만족하지 못하는 산업용 연돌 해체에 발파해체공법 중 전도공법을 적용하였다. 해당 연돌은 높이 150.0m이고, 연돌 외벽이 철근콘크리트 셸 구조물이며, 내부 연통은 스틸 셸 구조물인 복합구조물이다. 발파해체결과, 연돌은 예측된 방향으로 정확히 전도하였고, 주변 시설물에 피해 없이 발파해체를 완료하였다.

• Journal of Electrochemical Science and Technology
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• 제12권1호
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• pp.74-81
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• 2021

Silicon (Si) is recognized as a promising anode material for high-energy-density lithium-ion batteries. However, under a condition of electrode comparable to commercial graphite anodes with low binder content and a high electrode density, the practical use of Si is limited due to the huge volume change associated with Si-Li alloying/de-alloying. Here, we report a novel core-shell composite, having a reversible capacity of ~ 500 mAh g-1, by forming a shell composed of a mixture of nano-Si, graphite nanosheets and a pitch carbon on a spherical natural graphite particle. The electrochemical measurements are performed using electrodes with 2 wt % styrene butadiene rubber (SBR) and 2 wt.% carboxymethyl cellulose (CMC) binder in an electrode density of ~ 1.6 g cm-3. The core-shell composites having the reversible capacity of 478 mAh g-1 shows the outstanding capacity retention of 99% after 100 cycles with the initial coulombic efficiency of 90%. The heterostructure of core-shell composites appears to be very effective in buffering the volume change of Si during cycling.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.804-809
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• 2008

In this study, the cooling performance of a C/C composite material structure with metallic cooling tubes fixed by elastic force without chemical bonding was evaluated experimentally using combustion gas in a rocket combustor. The C/C composite chamber was covered by a stainless steel outer shell to maintain its airtightness. Gaseous hydrogen as a fuel and gaseous oxygen as an oxidizer were used for the heating test. The surface of these C/C composites was maintained below 1500 K when the combustion gas temperature was about 2900 K and heat flux to the combustion chamber wall was about 9 $MW/m^2$. No thermal damage was observed on the stainless steel tubes which were in contact with the C/C composite materials. Results of the heating test showed that such a metallic-tube-cooled C/C composite structure is able to control the surface temperature as a cooling structure(also as a heat exchanger), as well as indicating the possibility of reducing the amount of the coolant even if the thermal load to the engine is high. Thus, application of the metallic-tube-cooled C/C composite structure to reusable engines such as a rocket-ramjet combined cycle engine is expected.

• Steel and Composite Structures
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• 제42권6호
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• pp.747-764
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• 2022

The design codes and calculation methods related to soil-steel composite bridges and culverts only specify the minimum soil cover depth. This value is connected with the bridge span and shell height. In the case of static and dynamic loads (like passing vehicles), such approach seems to be quite reasonable. However, it is important to know how the soil cover depth affects the behaviour of soil-steel composite bridges under seismic excitation. This paper presents the results of a numerical study of soil-steel bridges with different soil cover depths (1.00, 2.00, 2.40, 3.00, 4.00, 5.00, 6.00 and 7.00 m) under seismic excitation. In addition, the same soil cover depths with different boundary conditions of the soil-steel bridge were analysed. The analysed bridge has two closed pipe-arches in its cross section. The load-carrying structure was constructed as two shells assembled from corrugated steel plate sheets, designed with a depth of 0.05 m, pitch of 0.15 m, and plate thickness of 0.003 m. The shell span is 4.40 m, and the shell height is 2.80 m. Numerical analysis was conducted using the DIANA programme based on the finite element method. A nonlinear model with El Centro records and the time history method was used to analyse the problem.

• Advances in nano research
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• 제17권1호
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• pp.1-8
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• 2024

In this paper, stability analysis of sandwich toroidal shell segments (TSSs) with carbon nanotube (CNT)-reinforced face sheets featuring various types of auxetic cores, surrounded by elastic foundations under radial pressure is presented. Two distinct types of auxetic structures are considered for the core, including re-entrant auxetic structure and graphene origami (GOri)-enabled auxetic structure. The nonlinear stability equilibrium equations of the longitudinally shallow shells are formulated using the von Karman shell theory, in conjunction with Stein and McElman approximation while considering Winkler-Pasternak's elastic foundation to simulate the interaction between the shell and elastic foundation. The Galerkin method is employed to derive the nonlinear stability responses of the shells. The numerical investigations show the influences of various types of auxetic-core layers, CNT-reinforced face sheets, as well as elastic foundation on the stability of sandwich shells.

• Korean Journal of Chemical Engineering
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• 제35권12호
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• pp.2379-2383
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• 2018

We report a facile one-pot aqueous-phase synthesis of PdAu bimetallic nanoparticles with different Pd/Au ratio. The synthesis was conducted by co-reduction of Pd and Au precursor using ascorbic acid as a reducing agent and in the presence of polyallylamine hydrochloride (PAH). By high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) and energy-dispersive X-ray spectrometry (EDS) analyses, we found that the synthesized nanoparticles had an onion-like core/shell/shell/shell structure with Au-rich core, Pd-rich shell, Au-rich shell, and Pd shell, respectively. We also investigated the catalytic performance of the synthesized PdAu nanoparticles toward hydrogen peroxide generation reaction.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2004년도 춘계학술발표대회 논문집
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• pp.288-291
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• 2004

The characteristics of the buckling analysis module for stiffened composite structures were studied in this paper. Composite stiffened structures have geometrical asymmetry and material properties asymmetry. Due to these reason, postbuckling analysis was essential and the characteristics of postbuckling analysis modules for ABAQUS were researched. Static analysis module was considered. By considering the material nonlinearity, progressive failure mechanism was applied and buckling strength was estimated

• 한국철도학회:학술대회논문집
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• 한국철도학회 2004년도 추계학술대회 논문집
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• pp.616-621
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• 2004

In this paper, the crush characteristics of a tilting train express (TTX) M-car design are evaluated with a head-on collision scenario. Its body shell is divided into three parts - front end, middle section, and rear end. For each part, crush-force relation is evaluated numerically through 3-dimensional shell element analysis with LS-DYNA. TTX's embody structure is a hybrid type structure made of steel and composite materials. Composite sandwich panels are modeled as layered shells whose layers have different material properties. And a damage material model is used to consider the effect of stiffness degradation during deformation. The crush characteristics obtained from these calculations will be used as material modeling data of full-rake collision analyses.

• Structural Engineering and Mechanics
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• 제71권6호
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• pp.657-668
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• 2019

The numerical thermal frequency responses of the skew sandwich shell panels structure are investigated via a higher-order polynomial shear deformation theory including the thickness stretching effect. A customized MATLAB code is developed using the current mathematical model for the computational purpose. The finite element solution accuracy and consistency have been checked via solving different kinds of numerical benchmark examples taken from the literature. After confirming the standardization of the model, it is further extended to show the effect of different important geometrical parameters such as span-to-thickness ratios, aspect ratios, curvature ratios, core-to-face thickness ratios, skew angles, and support conditions on the frequencies of the sandwich composite flat/curved panel structure under elevated temperature environment.

• 청정기술
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• 제28권2호
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• pp.154-162
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• 2022

알루미늄 (Al) 금속을 전구체 및 구조체로 이용, 수열 반응을 통하여 Al@Al₂O₃와 Al@Ni-Al LDH (LDH = layered double hydroxide) 코어-쉘 복합 구조체를 합성하였다. 제조된 구조체의 형상, 조성, 결정 구조는 수용액에 존재하는 이온들에 의하여 크게 영향을 받았으며, 이를 활용하여 다양한 특성의 촉매 구조체 유도가 가능하였다. Al@Ni-Al LDH 코어-쉘 구조체의 환원을 통하여 Ni 나노 입자가 고정화된 Ni/Al@Al₂O₃ 촉매를 제조하였고, CO₂ 메탄화 반응에 적용하여 촉매의 특성을 평가하였다. Ni/Al@Al₂O₃ 촉매는 전통적 incipient wetness impregnation 방법에 의하여 제조된 Ni/Al₂O₃ 촉매에 비교하여 Ni 입자의 분산도와 균일성이 매우 높았으며 약 2 배 이상의 CO₂ 전환율로 높은 촉매적 활성과 더불어 구조의 안정성을 보여 주었다. 이러한 Ni/Al@Al₂O₃ 구조체 촉매의 우수한 특성은 Al 금속을 기반으로 한 새로운 개념의 촉매 구조체 설계와 합성 방법의 타당성을 보여준다.