• 한국소음진동공학회논문집
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• 제25권3호
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• pp.207-215
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• 2015

This paper deals with a theoretical method to calculate natural frequencies of a fixed-free rectangular tank partially in contact with an outer water gap. Orthogonal polynomials satisfying the boundary conditions of the tank are used as admissible functions in the Rayleigh-Ritz method. A quarter model of the liquid-coupled system is constructed and it is simplified to a line supported flat plate in contact with the liquid. The liquid displacement potential functions satisfying the Laplace equation and water boundary conditions are derived, and the finite Fourier transform is accomplished in conjunction with the compatibility requirement along the contacting interfaces between the tank and water. An eigenvalue problem is derived so that the natural frequencies of the wet rectangular tank can be extracted. The predictions from the proposed analytical method show good agreement with the finite element analysis results.

• Smart Structures and Systems
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• 제22권1호
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• pp.121-132
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• 2018

This research investigates the free vibration analysis of advanced composite plates such as functionally graded plates (FGPs) resting on a two-parameter elastic foundations using a hybrid quasi-3D (trigonometric as well as polynomial) higher-order shear deformation theory (HSDT). This present theory, which does not require shear correction factor, accounts for shear deformation and thickness stretching effects by a sinusoidal and parabolic variation of all displacements across the thickness. Governing equations of motion for FGM plates are derived from Hamilton's principle. The closed form solutions are obtained by using Navier technique, and natural frequencies are found, for simply supported plates, by solving the results of eigenvalue problems. The accuracy of the present method is verified by comparing the obtained results with First-order shear deformation theory, and other predicted by quasi-3D higher-order shear deformation theories. It can be concluded that the proposed theory is efficient and simple in predicting the natural frequencies of functionally graded plates on elastic foundations.

• Advances in aircraft and spacecraft science
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• 제7권4호
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• pp.353-369
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• 2020

This paper presents the flutter analysis and optimum design of axially functionally graded box beam cantilever wing section by considering various geometric and material parameters. The coupled dynamic equations of the continuous model of wing system in terms of material and cross-sectional properties are formulated based on extended Hamilton's principle. By expressing the lift and pitching moment in terms of plunge and pitch displacements, the resultant two continuous equations are simplified using Galerkin's reduced order model. The flutter velocity is predicted from the solution of resultant damped eigenvalue problem. Parametric studies are conducted to know the effects of geometric factors such as taper ratio, thickness, sweep angle as well as material volume fractions and functional grading index on the flutter velocity. A generalized surrogate model is constructed by training the radial basis function network with the parametric data. The optimized material and geometric parameters of the section are predicted by solving the constrained optimal problem using firefly metaheuristics algorithm that employs the developed surrogate model for the function evaluations. The trapezoidal hollow box beam section design with axial functional grading concept is illustrated with combination of aluminium alloy and aluminium with silicon carbide particulates. A good improvement in flutter velocity is noticed by the optimization.

• 한국통신학회논문지
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• 제22권10호
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• pp.2310-2316
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• 1997

본 논문에서는 고차통계에 의한 적응알고리즘 가운데 오차의 평균절대값삼승 (LMAT)을 최소화하는 알고리즘과 이미 널리 사용되고 있는 경쟁 알고리즘의 성능을 서로 비교 평가하였다. 사용된 입력선호가 Gaussian 분포를 갖는다는 가정하에, LMAT 알고리즘의 정상상태 추청오차에 대한 평균자승특성 근사식을 유도하였다. 유도된 근사식은 컴퓨터 모의실험을 통하여 그 타당성을 검증하였다. LMAT 알고리즘 및 경쟁 알고리즘들이 정상상태에서 같은 값의 평균자승추정오차를 갖는 경우에 대하여 각 알고리즘의 수렴속도를 비교하였고, LMAT 알고리즘의 우수한 수렴 성능을 알 수 있었다 특히, 입력신호의 eigenvalue spread ratio 및 measurement noise power 등 환경이 변화함에도 불구하고 LMAT 알고리즘이 여전히 나은 특성을 보임을 알 수 있었다.

• 지역사회간호학회지
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• 제31권2호
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• pp.130-142
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• 2020

Purpose: The purpose of this study was to verify the validity and reliability of the Korean version of the Pain in Older Adults Knowledge Survey (K-POAKS) to assess knowledge of pain in older adults including people with dementia for use in long-term care hospital nurses. Methods: Survey data were collected from a convenience sample of 179 nurses who have worked in long-term care hospitals in B, D and U cities. The Kuder-Richardson Formula 20 for internal consistency for test reliability was conducted. The content, criterion-related and construct validity were evaluated using SPSS/WIN 22.0. Results: The KR 20 was .75 and Content Validity Ratio (CVR) was a range of 0.84~1.00. The criterion-related validity was positively correlated with attitudes (r=.28, p<.001) and performance (r=.21, p=.004). The construct validity of K-POAKS was analyzed by conducting the principal component method using the exploratory factor analysis varimax rotation, and seven factors were derived above the eigenvalue of 1.0. The seven factors explained 58.5% of the total variation. Conclusion: The Korean version of the POAKS showed satisfactory internal reliability, content validity, criterion-related validity and construct validity. These results suggest that the K-POAKS could be used as a suitable tool to measure the knowledge of the aged people's pain, including that of dementia patients for long-term care hospital nurses.

• 한국지구과학회지
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• 제38권3호
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• pp.173-181
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• 2017

The stability of the steady Rossby-Haurwitz wave (R-H wave) in the nondivergent barotropic model (NBM) on the sphere was investigated with the normal mode method. The linearized NBM equation with respect to the R-H wave was formulated into the eigenvalue-eigenvector problem consisting of the huge sparse matrix by expanding the variables with the spherical harmonic functions. It was shown that the definite threshold R-H wave amplitude for instability could be obtained by the normal mode method. It was revealed that some unstable modes were stationary, which tend to amplify without the time change of the spatial structure. The maximum growth rate of the most unstable mode turned out to be in almost linear proportion to the R-H wave amplitude. As a whole, the growth rate of the unstable mode was found to increase with the zonal- and total-wavenumber. The most unstable mode turned out to consist of more-than-one zonal wavenumber, and in some cases, the mode exhibited a discontinuity over the local domain of weak or vanishing flow. The normal mode method developed here could be readily extended to the basic state comprised of multiple zonalwavenumber components as far as the same total wavenumber is given.

• Journal of Korean Biological Nursing Science
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• 제7권1호
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• pp.57-68
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• 2005

Purpose : The purpose of this study was to develop a tool to assess the need for hospice care in families of patients with cancer. Method : Research design was a methodological study. The tool was developed in 3 stages : first, preliminary items were developed based on a questionnaire about the needs for hospice care that was given to 8 families of patients with cancer; second, a panel of specialists reduced the number of preliminary items using 2 validity tests on the contents. Finally, reliability and validity were tested by a sample of 98 families who have a patient with cancer from April 2003 to July 2004. Result: Cronbach's alpha coefficient for internal consistency was .94 for the final total 22 items. Using the factor analysis, 4 factors with eigenvalue of more than 1.0 were extracted and these factors explained 65% of the total variance. The four factors were labeled as 'control of terminal physical problems', 'emotional care', 'spiritual care for preparing for death', and 'family support'. The final items of the tool developed on the need of hospice care consisted of 22 items. Conclusion : The instrument, for accessing the need for hospice care in families of patients with cancer, developed in this study was identified as a tool with a high degree of reliability and validity. In this sense, this tool can be effectively utilized for implementing and improving hospice care for patients with terminal cancer.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2004년도 추계학술발표대회 논문집
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• pp.69-72
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• 2004

A new three-node triangular shell element based on higher order zig-zag theory is developed for laminated composite shells with multiple delaminations. The present higher order zig-zag shell theory is described in a general curvilinear coordinate system and in general tensor notation. All the complicated curvatures of surface including twisting curvatures can be described in an exact manner in the present shell element because this element is based on geometrically exact surface representation. The displacement field of the proposed finite element includes slope of deflection, which requires continuity between element interfaces. Thus the nonconforming shape function of Specht's three-node triangular plate bending element is employed to interpolate out-of-plane displacement. The present element passes the bending and twisting patch tests in flat surface configurations. The developed element is evaluated through the eigenvalue problems of composite cylindrical shells with multiple delaminations. Through the numerical examples it is demonstrated that the proposed shell element is efficient because it has minimal degrees of freedom per node. The present shell element should serve as a powerful tool in the prediction of natural frequency and modes of multi-layered thick laminated shell structures with arbitrary-shaped multiple delaminations.

• 대한기계학회논문집
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• 제14권2호
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• pp.310-323
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• 1990

A three-noded, with three degree-of-freedom at each node, in-plane curved beam element is formulated and employed in eigen-analysis of constant curvature beam. The conventional quadratic shape functions used in a three noded C .deg. type curved beam element produce such an undesirable large stiffness that a significant error is introduced in displacements and stresses. These phenomena are called 'Stiffness Locking Phenomena', which result from spurious strain energy due to inappropriate assumptions on independent isoparametric quadratic interpolation functions. Stiffness locking phenomena can be alleviated by using modified interpolation functions which get rid of spurious constraints of conventional interpolation functions. Eigenvalues and their modes as well as displacements and stresses may be locked because they are related to stiffness. Using modified curved beam element in eigenvalue problem of cantilever and arch, the property and performance of modified curved beam element are examined by numerical experimentations. In these eigen-analyses, mass matrices are calculated by using both modified and unmodified curved beam element, are compared with theoretical solutions. These comparisons show that the performance of the modified curved beam element is better than that of the unmodified curved beam element.

• Journal of Mechanical Science and Technology
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• 제17권1호
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• pp.57-63
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• 2003

An eigenvalue design sensitivity formulation of a general nonsymmetric-matrix rotor-bearing system is devised. using the DDM (direct differential method). Then, investigations on the design sensitivities of critical speeds are carried out for an APU turbogenerator with a spline shaft connection. Results show that the dependence of the rate of change of the critical speed on the stiffness changes of bearing models of spline shaft connection points is negligible, and thereby their modeling uncertainty does not present any problem. And the passing critical speeds up to the 4th critical speed are not sensitive to the design stiffness coefficients of four main bearings. Further, the dependence of the rate of change of the critical speed on the shaft-element length changes shows quantitatively that the spline shaft has some limited influence on the 4th critical speed but no influence on the 1st to 3rd critical speeds. With no adverse effect from the spline shaft, the APU system achieves a critical speed separation margin of more than 40% at a rated speed of 60,000 rpm.