• Earthquakes and Structures
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• 제23권6호
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• pp.549-580
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• 2022

This paper assesses the influences of modeling assumptions and uncertainties on the performance of the non-linear finite element (FE) model updating procedure and model clustering method. The results of a shaking table test on a four-story steel moment-resisting frame are employed for both calibrations and clustering of the FE models. In the first part, simple to detailed non-linear FE models of the test frame is calibrated to minimize the difference between the various data features of the models and the structure. To investigate the effect of the specified data feature, four of which include the acceleration, displacement, hysteretic energy, and instantaneous features of responses, have been considered. In the last part of the work, a model-based clustering approach to group models of a four-story frame with similar behavior is introduced to detect abnormal ones. The approach is a composition of property derivation, outlier removal based on k-Nearest neighbors, and a K-means clustering approach using specified data features. The clustering results showed correlations among similar models. Moreover, it also helped to detect the best strategy for modeling different structural components.

• Steel and Composite Structures
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• 제43권1호
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• pp.55-66
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• 2022

To develop high-efficiency lateral force resistance components for high-rise buildings, a novel energy dissipation shear wall with concrete-filled steel tubular (CFST) column elements was proposed. An energy dissipation shear wall specimen with CFST column elements (GZSW) and an ordinary reinforced concrete shear wall (SW) were constructed, and experimented by low-cycle reversed loading. The mechanical characteristics of these two specimens, including the bearing capacity, ductility, energy dissipation, and stiffness degradation process, were analyzed. The finite-element model of the GZSW was established by ABAQUS. Based on this finite-element model, the effect of the placement of steel-plate energy dissipation connectors on the seismic performance of the shear wall was analyzed, and optimization was performed. The experiment results prove that, the GZSW exhibited a superior seismic performance in terms of bearing capacity, ductility, energy dissipation, and stiffness degradation, in comparison with the SW. The results calculated by the ABAQUS finite-elements model of GZSW corresponded well with the results of experiment, and it proved the rationality of the established finite-elements model. In addition, the optimal placement of the steel-plate energy dissipation connectors was obtained by ABAQUS.

• 한국조경학회지
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• 제45권4호
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• pp.81-91
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• 2017

본 연구는 효과적인 치유정원 계획에 필요한 치유정원 계획요소의 체계를 세우기 위해 선행 연구문헌을 종합 분석하여 치유정원 계획분야와 계획요소를 도출하고, 전문가 설문을 통하여 치유정원 계획요소의 중요도를 평가하였다. 연구결과는 다음과 같다. 첫째, 5개 계획분야와 19개 계획요소를 도출하였으며, 그 내용은 다음과 같다. $\LARGE{\cdot}$ 계획분야: 물리적 환경, 사회적 환경, 인지적 환경, 기능적 환경, 심리적 환경 $\LARGE{\cdot}$ 계획요소: 식물식재, 정원경관, 수경공간, 그늘공간, 작업공간, 레크레이션공간, 커뮤니티공간, 운동공간, 랜드마크요소, 사인시스템, 안전한 시설물과 재료, 재해안전시설, 유니버설디자인, 접근이 쉬운 동선, 경제적 유지관리, 시각적 개방성, 프라이버시 보장, 휴식공간의 다양성, 예술적 요소 둘째, 계획요소의 중요도 순위 분석 결과, 상위요소로 1순위는 식물식재, 2순위는 재해안전시설, 3순위로는 휴식공간의 다양성이 차지하였고, 하위요소로 예술적 요소와 랜드마크 요소가 각각 18위와 19위로 나타났다. 셋째, 계획요소의 중요도 수준을 평가하여 3개의 그룹으로 분류하였으며, 가장 중요한 A그룹은 식물식재, 재해안전시설이 포함되었고, 다음으로 중요한 B그룹은 휴식공간의 다양성, 커뮤니티공간, 수경공간, 유니버설 디자인, 안전한 시설물과 재료, 경제적 유지관리, 접근이 쉬운 동선, 프라이버시 보장, 정원경관, 작업공간, 시각적 개방성이 포함되었으며, 상대적으로 덜 중요한 C그룹은 그늘공간, 운동공간, 레크레이션공간, 사인시스템, 예술적 요소, 랜드마크 요소가 포함되었다. 그룹의 중요도 1순위의 2개 요소는 치유정원 계획 시에 필수적으로 적용되어야할 요소로 판단되며, 2순위의 11개 요소는 중요하게 고려되어야 하는 요소로 해석된다. 또한, 3순위의 6개 요소는 상대적으로 낮은 중요도 수준을 보여 치유정원 계획 시 설계자가 임의적으로 선택할 수 있는 요소로 판단된다.

• 대한치과보철학회지
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• 제27권2호
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• pp.79-100
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• 1989

The Purpose of this study was to investigate material differences in stress transmission among various artificial teeth and denture base materials. For this study, a two-dimensional finite element model and a two-dimensional photoelastic model of a mandible with complete denture were made. A resin tooth and a porcelain tooth were used as artificial teeth, and a resin base, a metal lined base, and a soft-liner lined base were used as denture bases. An occlusal load was applied and principal stresses generated in the supporting tissues were compared. To test the impact stress transmission, strain gauge attached to the denture base specimens made of the different materials were made in thick and thin groups. Voltage outputs from hitting the specimen with a steel ball were compared. The results were as follows : 1. In FEM, increasing the mucosal thickness reduced the maximum principal stresses in the supporting tissues, but altering the tooth materials and the base materials induced no difference in the stresses. 2. In photoelastic model study, no difference in fringe order among the specimens were observed, but the thick mucosa group and the soft-liner lined group revealed a more uniform distribution of the load. 3. In strain measuring, the impact force transmission was highest in the soft-liner lined group, and was the lowest in the metal lined group(p<0.01). 4. In the thin group using the resin base, the porcelain tooth showed higher impact stress transmission than the resin tooth(p<0.01), but no difference was observed between them in the thick group. In the soft-liner lined group, the porcelain tooth showed higher impact stress transmission than the resin tooth(p<0.01), but no difference was observed between them in the metal lined group. 5. The thick group showed lower impact stress transmission than the thin group(p<0.01).

• Nutrition Research and Practice
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• 제11권1호
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• pp.17-24
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• 2017

BACKGROUND/OBJECTIVES: In this study, we investigated whether Gelidium amansii extract (GAE) ameliorates obesity in diet-induced obese (DIO) mice. MATERIALS/METHODS: The mice were maintained on a high-fat diet (HD) for 5 weeks to generate the DIO mouse model. And then mice fed HD plus 0.5% (GAE1), 1% (GAE2) or 2% (GAE3) for 8 weeks. RESULTS: After the experimental period, GAE-supplemented groups were significantly lower than the HD group in body weight gain and liver weight. GAE supplemented groups were significantly lower than the HD group in both epididymal and mesenteric adipose tissue mass. The plasma leptin level was significantly higher in the HD group than in GAE-supplemented groups. The leptin level of HD+GAE3 group was significantly lower than that of the HD+conjugated linoleic acid (CLA) group. In contrast, plasma adiponectin level of the HD group was significantly lower than those of HD+GAE2 and HD+GAE3 groups. The expression levels of adipogenic proteins such as fatty acid synthase, sterol regulatory element-binding protein-1c, peroxisome proliferator-activated receptor ${\gamma}$, and CCAAT/enhancer binding protein ${\alpha}$ in the GAE supplemented groups were significantly decreased than those in HD group, respectively. In addition, the expression levels of HD+GAE2 and HD+GAE3 groups are significantly decreased compared to those of HD+CLA group. On the contrary, the expression levels of hormone-sensitive lipase and phospho-AMP-activated protein kinase, proteins associated with lipolysis, were significantly increased in the GAE supplemented groups compared to those in the HD group. HD+GAE3 group showed the highest level among the GAE supplemented groups. CONCLUSIONS: These results suggested that GAE supplementation stimulated the expressions of lipid metabolic factors and reduced weight gain in HD-fed C57BL/6J obese mice.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제5B권3호
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• pp.253-257
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• 2005

By using a coupled circuit, time-stepping, two-dimensional finite element method (2-D FEM), the performance of a stand-alone permanent-magnet synchronous generator (PMSG) with inset rotor can be computed without involving the classical two-axis model. The effects of interpolar air gap length and armature resistance on the load characteristics are investigated. It is shown that the interpolar flux density, and hence the amount of voltage compensation, is affected by magnetic saturation. Validity of the coupled circuit and field analysis is confirmed by experiments on a prototype generator. The machine exhibits an approximately level load characteristic when it is supplying an isolated unity-power-factor load.

• Interaction and multiscale mechanics
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• 제4권4호
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• pp.321-336
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• 2011

This paper presents the results of static vertical load tests carried out on a model building frame supported by pile groups embedded in cohesionless soil (sand). The effect of soil interaction on displacements and rotation at the column base and also the shears and bending moments in the columns of the building frame were investigated. The experimental results have been compared with those obtained from the finite element analysis and conventional method of analysis. Soil nonlinearity in the lateral direction is characterized by the p-y curves and in the axial direction by nonlinear vertical springs along the length of the piles (${\tau}-z$ curves) at their tips (Q-z curves). The results reveal that the conventional method gives the shear force in the column by about 40-60%, the bending moment at the column top about 20-30% and at the column base about 75-100% more than those from the experimental results. The response of the frame from the experimental results is in good agreement with that obtained by the nonlinear finite element analysis.

• Structural Engineering and Mechanics
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• 제11권2호
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• pp.221-236
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• 2001

A local point interpolation method (LPIM) is presented for the stress analysis of two-dimensional solids. A local weak form is developed using the weighted residual method locally in two-dimensional solids. The polynomial interpolation, which is based only on a group of arbitrarily distributed nodes, is used to obtain shape functions. The LPIM equations are derived, based on the local weak form and point interpolation. Since the shape functions possess the Kronecker delta function property, the essential boundary condition can be implemented with ease as in the conventional finite element method (FEM). The presented LPIM method is a truly meshless method, as it does not need any element or mesh for both field interpolation and background integration. The implementation procedure is as simple as strong form formulation methods. The LPIM has been coded in FORTRAN. The validity and efficiency of the present LPIM formulation are demonstrated through example problems. It is found that the present LPIM is very easy to implement, and very robust for obtaining displacements and stresses of desired accuracy in solids.

• Structural Engineering and Mechanics
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• 제24권4호
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• pp.411-427
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• 2006

The Discrete Element Method, DEM, is increasingly used in fracture studies of non-homogeneous continuous media, such as rock and concrete. A 2D circular rigid DEM formulation, developed to model concrete, has been adopted. A procedure developed to generate aggregate particles with a given aspect ratio and shape is presented. The aggregate particles are modelled with macroparticles formed by a group of circular particles that behave as a rigid body. Uniaxial tensile and compression tests performed with circular and non-circular aggregates, with a given aspect ratio, have shown similar values of fracture toughness when adopting uniform strength and elastic properties for all the contacts. Non-circular aggregate assemblies are shown to have higher fracture toughness when different strength and elastic properties are set for the matrix and for the aggregate/matrix contacts.

• 동력기계공학회지
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• 제15권3호
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• pp.18-24
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• 2011

In this study, the reflection of the L(0,2), axially symmetric guided elastic wave from defects in pipes above ground is examined using finite element method. Phase and group velocity dispersion curves for the pipe were presented for the selection of the excitation mode. Some simple signal processing was applied to determine the amplitude of each of the reflected waves and to calculate the reflection coefficient. The results show the reflection coefficient of this mode is very close to a linear function of the circumferential extent of the defect. The motivation for the work was the development of a technique for inspecting chemical plant pipelines, but the study addresses the nature of the reflection function and its general applicability.