• Steel and Composite Structures
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• 제46권1호
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• pp.133-141
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• 2023

Based on the third-order shear deformation theory, the wave propagations in doubly curved spherical- and cylindrical- panels reinforced by carbon nanotubes (CNTs) are firstly investigated in present work. The coupled equations of wave propagation for the carbon nanotubes reinforced composite (CNTRC) doubly curved panels are established. Then, combined with the harmonic balance method, the eigenvalue technique is adopted to simulate the velocity-wave number curves of the CNTRC doubly curved panels. In the end, numerical results are showed to discuss the effects of the impact of key parameters including the volume fraction, different shell types (including spherical (R₁=R₂=R) and cylindrical (R₁=R, R₂=→∞)), wave number as well as modal number on the sensitivity of elastic waves propagating in CNTRC doubly curved shells.

• 센서학회지
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• 제27권2호
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• pp.76-81
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• 2018

Au@ZnO core-shell nanoparticles (NPs) were prepared by a simple method followed by heat-treatment for gas sensor applications. The advantage of the core-shell morphology was investigated by comparing the gas sensing performances of Au@ZnO core-shell NPs with pure ZnO NPs and different wt% of Au-loaded ZnO NPs. The crystal structures, shapes, sizes, and morphologies of all sensing materials were characterized by XRD, TEM, and HAADF-STEM. Au@ZnO core-shell NPs were nearly spherical in shape and Au NPs were encapsulated in the center with a 40-45 nm ZnO shell outside. The gas sensing operating temperature for Au@ZnO core-shell NPs was $300^{\circ}C$, whereas it was $350^{\circ}C$ for pure ZnO NPs and Au-loaded ZnO NPs. The maximum response of Au@ZnO core-shell NPs to 1000 ppm CO at $300^{\circ}C$ was 77.3, which was three-fold higher than that of 2 wt% Au-loaded ZnO NPs. Electronic and chemical effects were the primary reasons for the improved sensitivity of Au@ZnO core-shell NPs. It was confirmed that Au@ZnO core-shell NPs had better sensitivity and stability than Au-loaded ZnO NPs.

• Korean Chemical Engineering Research
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• 제48권1호
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• pp.98-102
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• 2010

목련잎 추출액을 이용하여 Au core-Ag shell 합금 나노입자를 합성하였다. 환원제인 식물잎 추출액을 먼저 $HAuCl_4$ 용액과 반응시키고 다음에 $AgNO_3$ 용액과 반응시켜 금 seed와 은 shell을 형성시켰다. 반응시간에 따른 UV-visible spectroscopy의 변화를 모니터링하여 합금 나노입자의 형성을 관찰하였다. 합성된 합금 나노입자를 transmission electron microscopy(TEM), energy dispersive X-ray spectroscopy(EDS), X-ray photoelectron spectroscopy(XPS) 등으로 특성화 하였다. TEM image로부터 관찰된 합금 나노입자는 삼각형, 오각형, 육각형 등의 평판과 구 구조의 혼합물이었다. EDS와 XPS 분석으로부터 결정된 금/은 합금 나노입자의 원자 은 함량은 각각 34와 65 wt%로 Au core-Ag shell 나노구조가 형성되었음을 알 수 있었다. 이러한 core-shell 형태의 나노구조는 표면 강화 라만 분광 및 생물분자의 고감도 검출 등에 잠재적인 응용이 기대된다.

• Structural Engineering and Mechanics
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• 제19권3호
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• pp.321-336
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• 2005

The structural feasibility of a variety of non-conventional sludge digesters, in the form of thin shells of revolution constructed in concrete, has formed the subject of investigation of a recent programme of research at the University of Cape Town. Such forms are usually known in the literature as "egg-shaped", and the advantages of these over conventional digesters of the wide-cylindrical type are now well-recognised: superior mixing efficiency, less accumulation of deposits at the bottom, easier removal of bottom deposits and surface crust, reduced heat losses, and so forth. With the aim of exploring the structural feasibility of various non-conventional forms for concrete sludge digesters, and making available usable analytical data and practical guidelines for the design of such thin shell structures, a number of theoretical studies have recently been undertaken, and these have covered conical assemblies, spherical assemblies and parabolic ogival configurations. The purpose of the present paper is to bring together the different analytical approaches employed in each of these studies, summarise the main findings in each case, draw comparisons among the various studied configurations with regard to structural efficiency and functional suitability, and make appropriate conclusions and recommendations.

• Advances in materials Research
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• 제5권4호
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• pp.205-221
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• 2016

In this article, the buckling responses of functionally graded curved (spherical, cylindrical, hyperbolic and elliptical) shell panels under elevated temperature load are investigated numerically using finite element steps. The effective material properties of the functionally graded shell panel are evaluated using Voigt's micromechanical model through the power-law distribution with and without temperature dependent properties. The mathematical model is developed using the higher-order shear deformation theory in conjunction with Green-Lagrange type nonlinear strain to consider large geometrical distortion under thermal load. The efficacy of the proposed model has been checked and the effects of various geometrical and material parameters on the buckling load are analysed in details.

• Earthquakes and Structures
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• 제13권5호
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• pp.455-464
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• 2017

This paper develops a new method for analyzing the structural seismic behavior of single-layer reticulated shells based on exponential strain energy density (ESED). The ESED method reveals a characteristic point from a relationship between ESED sum and peak seismic acceleration. Then, the characteristic point leads to an updated concept of structural failure and an ESED-based criterion for predicting structural failure load. Subsequently, the ESED-based criterion and the characteristic point are verified through numerical analysis of typical single-layer reticulated shells with different configurations and a shaking table test of the scale shell model. Finally, discussions further verify the rationality and application of the ESED-based criterion. The ESED method might open a new way of structural analysis and the ESED-based criterion might indicate a prospect for a unified criterion for predicting seismic failure loads of various structures.

• 폴리머
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• 제26권2호
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• pp.227-236
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• 2002

열가역적인 polyvinylidene fluoride (PVDF)/propylene carbonate (PC) 의 매우 묽은 농도에서의 pregel 상태의 구조를 레이저 광산란법으로 조사한 결과 겔형성농도의 100배 이상 묽은 농도 조건에서도 PVDF 사슬은 낱개로 용해되어 있는 것이 아니라 많은 PVDF 사슬들이 응집된 거대한 구형 상태로 존재하며 이때의 응집체의 분산도는 상당히 낮으며 용액온도 $40^{\circ}C$에서 회전반경$R_G$ 는 232 nm, 동력학적 반경 $R_H$는 407 nm로 측정되었다. $R_H/R_G$=1.75의 커다란 비 값, 극소점을 갖는 정적 광산란 패턴 등으로부터 예측하건대 이 응집체의 구조는 core-shell 형태의 구형이며, 이때 내부 core의 반지름은 대략 215 nm, 외부 shell의 두께는 192 nm가 되며, shell 부분에서의 PVDF의 단량체 밀도는 core 부분의 단량체 밀도의 약 75% 수준에 머무르는 것으로 판명되었다.

• 대한조선학회 특별논문집
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• 대한조선학회 2005년도 특별논문집
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• pp.22-30
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• 2005

Sloshing loads, produced by the violent liquid free-surface motions inside the cargo tank have become an important design parameter in ship building industry since there have been demands for the increased sizes of the cargo containment system of LNG carriers. In this study, sloshing impact pressure acting on the shell of the spherical cargo tank of an LNG carrier as well as dynamic pressure and flow behavior around the pump tower located at the center of the tank have been calculated. Comparative numerical sloshing simulations for a spherical LNG tank using 2-D LR.FLUIDS which is based on the finite difference method and 3-D MSC.DYTRAN which is capable of calculating nonlinear fluid-structure interaction have been carried out. A method of calculating sloshing-induced dynamic loads and the subsequent structural strength analysis for pump tower of a spherical LNG carrier using MSC. DYTRAN and MSC.NASTRAN have been presented.

• Structural Engineering and Mechanics
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• 제74권2호
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• pp.297-311
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• 2020

The main purpose of this study is to analyze the effects of external pressure on the vibration and buckling of functionally graded (FG) spherical panels resting of elastic medium. The material characteristics of the FG sphere continuously vary through the thickness direction based on the power-law rule. In accordance with first-order shear deformation shell theory and by the use of Ritz formulation the governing equations are presented. In this regard, the beam functions are applied in two-dimensions for different sets of boundary supports. The Winkler and Pasternak models of elastic foundations are also taken into account. In order to show the validity and applicability of the presented formulation, various comparison studies are given. Furthermore, a diverse range of numerical results is reported to check the impacts of geometrical and material parameters along with external pressure on the vibration and buckling analysis of FG spherical panels.

• 한국결정성장학회지
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• 제6권4호
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• pp.521-531
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• 1996

분무건조법을 이용하여 무기질막 microcapsule과 무기질/유기질막 microcapsule을 제조하였다. 무기질막 microcapsule은 core 물질로 $K_{4}SO$와 clay shell 물질로 colloidal silica를 사용하였고, 무기질/유기질막 microcapsule은 core 물질로 상기 제조된 무기질막 microcapsule을 shell 물질로는 ethyl cellulose를 사용하여 각각의 microcapsule를 제조하였다. 제조된 microcapsule이 기능성을 갖기 위하여는 구형의 균일한 표면과 세공용적이 매우 중요하다. 무기질막 microcapsule인 경우 core/shell의 체적비가 0.3/0.7인 경우 구형의 균일한 표면의 microcapsule이 제조되었으며, 무기질/유기질막 microcapsule인 경우, 무게비가 0.76/0.24일 때 균일한 표면을 갖는 microcapsule이 제조되었다. 무기질/유기질막 microcapsule인 경우, 무기질막 microcapsule보다 세공용적이 감소하였고, shell물질(ethyl cellulose)의 양이 증가할수록 피복이 균일하게 되며, 세공용적도 감소하였다.