• Steel and Composite Structures
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• 제47권2호
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• pp.297-313
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• 2023

This study aims to extend the application of the spectral element method (SEM) to wave propagation and free vibration analysis of functionally graded (FG) plates integrated with thin piezoelectric layers, plates with tapered thickness and structure on elastic foundations. Also, the dynamic response of the smart FG plate under impact and moving loads is presented. In this paper, the dynamic stiffness matrix of the smart rectangular FG plate is determined by using the exact dynamic shape functions based on Mindlin plate assumptions. The low computational time and results' independence with the number of elements are two significant features of the SEM. Also, to prove the accuracy and efficiency of the SEM, results are compared with Abaqus simulations and those reported in references. Furthermore, the effects of boundary conditions, power-law index, piezoelectric layers thickness, and type of loading on the results are studied.

• Earthquakes and Structures
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• 제26권2호
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• pp.163-174
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• 2024

Dynamic equilibrium equations for finite element analysis were derived for the free field one-dimensional shear wave propagation through the horizontally layered soil deposits with the elastic half-space. We expressed Rayleigh's viscous damping consisting of mass and stiffness proportional terms. We considered two cases where damping matrices are defined in the total and relative displacement fields. Two forms of equilibrium equations are presented; one in terms of total motions and the other in terms of relative motions. To evaluate the performance of new equilibrium equations, we conducted two sets of site response analyses and directly compared them with the exact closed-form frequency domain solution. Results show that the base shear force as earthquake load represents the simpler form of equilibrium equation to be used for the finite element method. Conventional finite element procedure using base acceleration as earthquake load predicts exact solution reasonably well even in soil deposits with unrealistically high damping.

• Journal of Oral Medicine and Pain
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• 제49권1호
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• pp.5-11
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• 2024

Halitosis is defined as a nasty odor emanating through the mouth and is primarily related to the enhanced concentration of volatile sulfur compounds (VSCs). VSC measurements have been commonly used for experimental comparison and clinical diagnosis. As quantitative methods for comparative analyses of oral malodor, gas chromatography devices have been most commonly used to quickly and easily determine the concentration of several gas components of VSCs, which are agents primarily responsible for halitosis. The concentrations of VSCs fluctuate dynamically depending on contributing factors, including various oral/systemic conditions, intake of medicine and food/drink, oral hygiene, and even routine daily activities. Therefore, the exact analysis of VSCs requires the appropriate standardization of not only exact measurement techniques but also participant conditioning with scientific considerations. Thus, this paper describes the experimental standardizations commonly recommended in previous literature and their scientific background.

• 한국전산유체공학회지
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• 제12권3호
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• pp.47-54
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• 2007

A periodic CFD approach for the performance analysis of compact high temperature heat exchangers is introduced and applied to selected benchmark problems, which are a fully developed 2D laminar heat transfer, a conjugate heat transfer between parallel plates which have exact solutions, and a heat transfer in a real high temperature heat exchanger module. The results for the 2D laminar heat transfer and the 2D conjugate heat transfer showed a very good agreement with the exact solutions. For the high temperature heat exchanger module, the pressure drops were predicted well but some difference was observed in the temperature parameters when compared to the full channel CFD analysis due to assumptions introduced into the periodic approach. Considering its assumptions and simplicities, however, the results showed that the periodic approach provides physically reasonable results and it is sufficient to predict the performance of a heat exchanger within an engineering margin and with much less CPU time than the case of a full channel analysis.

• 대한교통학회지
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• 제27권1호
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• pp.107-114
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• 2009

보행은 인간의 기본적이면서 중요한 교통수단이다. 최근 들어 보행자 사고와 관련하여 보행안전이 중요시되고 있다. 이에 본 연구에서는 보행환경요소가 보행안전에 영향을 미치는지 살펴보았다. 선행연구에서 15개의 보행환경요소를 추출하여 설문조사를 실시하였고, 요인분석을 통해 4개의 요인을 추출하였다. 다중회귀분석 결과 F-value는 9.211, P-value는 0.000으로 귀무가설이 기각되어 보행환경요인은 보행안전에 영향력을 미치는 것으로 나타났다. 영향력은 보도특성, 경관성, 상업성, 보행특성의 순으로, 특히 경관성과 보도특성은 유의미한 것으로 분석되었다.

• 한국정보시스템학회지:정보시스템연구
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• 제21권3호
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• pp.137-161
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• 2012

The increasing interest in big data analysis using various data mining techniques indicates that many commercial data mining tools now need to be equipped with fundamental text analysis modules. The most essential prerequisite for accurate analysis of text documents is an understanding of the exact semantics of each term in a document. The main difficulties in understanding the exact semantics of terms are mainly attributable to homonym and synonym problems, which is a traditional problem in the natural language processing field. Some major text mining tools provide a thesaurus to solve these problems, but a thesaurus cannot be used to resolve complex synonym problems. Furthermore, the use of a thesaurus is irrelevant to the issue of homonym problems and hence cannot solve them. In this paper, we propose a semantic text mining methodology that uses ontologies to improve the quality of text mining results by resolving the semantic ambiguity caused by homonym and synonym problems. We evaluate the practical applicability of the proposed methodology by performing a classification analysis to predict customer churn using real transactional data and Q&A articles from the "S" online shopping mall in Korea. The experiments revealed that the prediction model produced by our proposed semantic text mining method outperformed the model produced by traditional text mining in terms of prediction accuracy such as the response, captured response, and lift.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.366-371
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• 2007

In many CAD systems, NURBS has been employed to construct exact geometries. Recently, NURBS finite element analysis methods were proposed by some authors for convenient connection between CAD and finite element analysis. Additional advantages of NURBS FEA, such as exact geometry and no mesh generation, are obtained. However, NURBS is inefficient in local refinement and merging patches. For refinement of local region in interest, additional control points should be inserted into the entire row or column which contains the local region. There is another inefficiency of NURBS during merging patches into a large structure due to propagation of control points. In order to overcome these inefficiencies of NURBS, T-spline was proposed by Sederberg. In this work, T-spline based finite element method is proposed for efficient local refinement and merging patches. At first, accuracy and efficiency of NURBS FEA is verified and efficiency of T-spline FEA is verified by comparing with NURBS FEA.

• Structural Engineering and Mechanics
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• 제58권6호
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• pp.949-966
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• 2016

The second order analysis taking place due to non-linear behavior of the structures under the mechanical and geometric factors through implementing exact and approximate methods is an indispensible issue in the analysis of such structures. Among the exact methods is the slope-deflection method that due to its simplicity and efficiency of its relationships has always been in consideration. By solving the differential equations of the modified slope-deflection method in which the effect of axial compressive force is considered, the stiffness matrix including trigonometric entries would be obtained. The complexity of computations with trigonometric functions causes replacement with their Maclaurin expansion. In most cases only the first two terms of this expansion are used but to obtain more accurate results, more elements are needed. In this paper, the effect of utilizing higher order terms of Maclaurin expansion on reducing the number of required elements and attaining more rapid convergence with less error is investigated for the Bernoulli beam with various boundary conditions. The results indicate that when using only one element along the beam length, utilizing higher order terms in Maclaurin expansion would reduce the relative error in determining the critical buckling load and kinematic parameters in the second order analysis.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 추계학술대회 논문집
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• pp.1077-1092
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• 2007

The structural analysis model for estimate of load carrying capacity of railway bridge on service line is important to determine safety of bridges in service, we need to take response of bridge exactly, applying analysis model similar to the real railway bridge most. Track structure which is to distribute loads and decrease vibrations occurred from running train is constructed on the railway bridges. And it is important factor which should be considered to understand exact dynamic and static responses of bridge. But track structure is currently classified as a none structural members in the structural analysis model for estimating load carrying capacity of railway bridge and not considered in analysis model. That's the reason it is difficult to understand exact behavior of bridges. Therefore, the major objective of this study is to develop an analytical track-bridge model which is similar to real railway bridges considering track structure for safety assessment of railway bridge on service line to be effectively done.

• 한국응급구조학회지
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• 제27권1호
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• pp.127-137
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• 2023

Purpose: This study aimed to analyze the treatment outcomes according to the socioeconomic factor of patients who visited the emergency room. Methods: This study conducted frequency analysis, percentage analysis, and Fisher's exact test analysis method, using the R 4.1.2 program based on the 2019 data from the Korea Health Panel. Results: Among the treatment results of 1,648 patients, 392 patients were hospitalized or transferred to other hospitals, 845 were discharged after treatment, 224 were discharged, and 7 died. The Fisher's exact test of treatment outcomes and socioeconomic factors was not statistically significant for status of the worker and employment relationship, but was significant for the housing, household, economic activity, and insurance types, and marital status and education. Conclusion: The results of this study indicate that it is necessary to conduct follow up studies on socioeconomic factors to provide basic data that can contribute to fairness and equity in the health care field.