• 대한기계학회논문집A
• /
• 제24권6호
• /
• pp.1419-1426
• /
• 2000

A dynamic analysis of rectangular Reissner-Mindlin plate was carried out using pseudospectral method. The pseudospectral method is superior to the finite element method because of more rapid conver gence speed of approximate solutions. Especially, the improvement in accuracy of the pseudospectral method is remarkable. Numerical examples demonstrate the excellent performance and robustness of the pseudospectral method with respect to thickness ratio of rectangular Reissner-Mindlin plate. The natural frequencies of rectangular Reissner-Mindlin plate calculated with the pseudospectral method are more reliable than those calculated with other numerical methods.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2000년도 춘계학술대회논문집
• /
• pp.501-507
• /
• 2000

This paper presents a very simple procedure for determining the sensitivities of the eigenpairs of damped vibratory system with distinct eigenvalues. The eigenpairs derivatives can be obtained by solving algebraic equation with a symmetric coefficient matrix whose order is (n+1) ${\times}$ (n+1), where n is the number of degree of freedom the mothod is an improvement of recent work by I. W. Lee, D. O. Kim and G. H. Jung; the key idea is that the eigenvalue derivatives and the eigenvector derivatives are obtained at once via only one algebraic equation, instead of using two equations separately as like in Lee and Jung's method. Of course, the method preserves the advantages of Lee and Jung's method.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 1999년도 추계 학술대회논문집
• /
• pp.48-58
• /
• 1999

The Characteristic Flux Difference Splitting (CFDS) scheme designed to adapt the characteristic boundary conditions at the wall and inflow/outflow boundary planes satisfies Roe's property U, although the CFDS Jacobian matrix is decomposed by a product of elaborate transformation matrices and explicit eigenvalue matrix. When the CFDS algorithm, thus a variant of Roe's scheme, is applied straightforwardly to hypersonic flows over a blunt body, the strong bow shock gradually breaks down near the stagnation point. This numerical instability is widely observed by many researchers employing flux-difference method, known in the literature as the carbuncle phenomenon. Many remedies have been proposed and resulted in partial cures. When the idea of Sanders et al. which identifies the minimum eigenvalues near the discontinuity present is applied to CFDS method, it is shown that the instability problem can be controlled successfully. A few flux splitting methods have also been tested and results are compared against the Nakamori's Mach 8 blunt body flow.

• 대한기계학회논문집A
• /
• 제27권4호
• /
• pp.585-592
• /
• 2003

Among various sensitivity evaluation techniques, semi-analytical method(SAM) is quite popular since this method is more advantageous than analytical method(AM) and global finite difference method(FDM). However, SAM reveals severe inaccuracy problem when relatively large rigid body motions are identified fur individual elements. Such errors result from the numerical differentiation of the pseudo load vector calculated by the finite difference scheme. In the present study, an iterative method combined with mode decomposition technique is proposed to compute reliable semi-analytical design sensitivities. The improvement of design sensitivities corresponding to the rigid body mode is evaluated by exact differentiation of the rigid body modes and the error of SAM caused by numerical difference scheme is alleviated by using a Von Neumann series approximation considering the higher order terms for the sensitivity derivatives.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1996년도 하계학술대회 논문집 B
• /
• pp.1327-1329
• /
• 1996

This paper presents an active noise control (ANC) algorithm using orthogonalization property of Walsh transform. Conventional ANC algorithm known as filtered-x LMS(FXL) algorithm has a problem of decreasing convergence speed in FIR adaptive filters operating in colored noise environments. Walsh transform decompose an input signal into a set of N uncorrelated components and reduce eigenvalue spread of autocorrelation matrix of input sequences. Computer simulations show that proposed (FXW) algorithm is superier to FXL in convergence speed.

• 한국정보기술학회 영문논문지
• /
• 제10권1호
• /
• pp.1-14
• /
• 2020

Antenna selection is a method to enhance the performance of spatial multiplexing multiple-input multiple-output (MIMO) systems, which can achieve the diversity order of the full MIMO systems. Although various selection criteria have been studied in the literature, they should be adjusted to the detection operation implemented at the receiver. In this paper, antenna selection methods that optimize the post-processing signal-to-noise ratio (SNR) and eigenvalue are considered for the lattice reduction (LR)-based receiver. To develop a complexity-efficient antenna selection algorithm, the incremental selection strategy is adopted. Moreover, for improvement of performance, an additional iterative selection method is presented in combination with an incremental strategy.

• 한국의료질향상학회지
• /
• 제3권1호
• /
• pp.104-124
• /
• 1996

Background : In these days, the health care organizations have concerned about customer-centered care in order to empower the competitiveness on the health care markets. The departments working for quality management of the hospitals have used health care quality indicators in terms of medical areas as well as service areas of the hospitals. However, there were insufficient efforts to develop the credible measurement to seek the customers' needs, their expectations and their satisfaction levels related to health care services because various kinds of challenges were in the process of scale development to measure customers' satisfaction in health care. The purpose of this study was to develop the satisfaction scale to health care services in a Korea health care organization and to test its tool with validity and reliability. Method : The concept of this tool was acceptability that one of the components of health care quality defined by Donabedian. Acceptability has the five dimensions of concept: Accessibility; Patient-Practitioner Relations; Amenities; Patient Preferences as to the effects of care; and Patient Preferences as to the costs of care. The Satisfaction Tool to Health Care Services was reviewed by expert panel with five researchers, including hospital managers and a professor related to quality management of the hospitals. As a result, the content validity index was .84 in the outpatient satisfaction tool. The inpatient satisfaction tool had .87 of the content validity index. The Satisfaction Tools to Health Care Services finally consisted of 44 items for outpatients/their families and of 60 items for inpatients/their families. Study subjects of the construct validity test were 479 outpatients/their families and 561 inpatients/their families who visited or admitted at a University hospital from July 1, 1996 through August 10, 1996. The data were examined by Factor Analysis with SPSS. Result : The items of Satisfaction tools for outpatients/their families were categorized by eleven factors with eigenvalue greater than 1.0 accounting for 64.2 percent of the variation in item scores. Also, the items of inpatient tool had eleven factors with eigenvalue greater than 1.0 accounting for 60.3 percent of the variation in item scores. The reliability of overall scale were .95 and .96 for the outpatients/their families satisfaction scores and inpatient/their families satisfaction scores. The internal consistency reliability with eleven factors was ranged from .30 to .94 for inpatients/their families. The Satisfaction Tool with eleven factors for inpatients/their families had internal consistency reliability ranged from .53 to .89. Conclusion : The Satisfaction Tools to Health Care Services focused on outpatients/their families and inpatients/their families developed in this study had a high reliability and the strong evidence of content validity and construct validity based on quality concept. Therefore, this tool would be utilized as a credible quality indicator of health care services to assess the quality problems and to monitor the quality improvement activities in Korean Health Care Organizations.

• 한국지진공학회논문집
• /
• 제22권3호
• /
• pp.201-210
• /
• 2018

The improvement in computing systems and sensor technologies devotes to conduct data-driven structural health monitoring algorithms for existing civil infrastructures. Despite of the development of techniques, the uncertainty oriented from the measurement results in the discrepancy to the actual structural parameters and let engineers or decision makers hesitate to adopt such techniques. Many studies have shown that the modal identification results can be affected by the uncertainties due to the applied methods and the types of loading. This paper aims to compare the performance of modal identification methods using Structural Modal Identification Toolsuite (SMIT) which has been developed to facilitate multiple identification methods with a user-friendly designed platform. The data fed into SMIT processes three stages for the comprehensive identification including preprocessing, eigenvalue estimation, and post-processing. The seismic and white noise response for shear frame model was obtained from numerical simulation. The identified modal parameters is compared to the actual modal parameters. In order to improve the quality of coherence in identified modal parameters, several hurdles including modal phase collinearity and extended modal amplitude coherence were introduced. Numerical simulation conducted on the 5 dof shear frame model were used to validate the effectiveness of using these parameters.

• 한국정보전자통신기술학회논문지
• /
• 제6권2호
• /
• pp.88-94
• /
• 2013

본 논문은 LMS 알고리즘의 수렴 속도를 향상시키기 위한 효율적인 신호간섭 제어기법을 제안한다. 수신 데이터를 재활용하여 심볼 시간 주기에 계수들을 곱함으로써 적응되는 제안된 알고리즘의 수렴특성이 수렴 속도의 향상을 이론적으로 증명하기 위해 분석한다. 스텝-크기 매개변수 ${\mu}$가 증가 됨에 따라 알고리즘의 수렴 속도가 제어된다. 고유치 확산을 증가시킴에 따라 적응 등화기의 수렴속 도를 천천히 제어하고 평균 자승 에러의 안정-상태 값을 증가시키는 효과를 나타내며 데이터-재사 용 LMS 기술이 수렴속도를 (B+1)배만큼 증가시켜 적응 등화기에서 신호간섭제어의 우수성을 입증 한다.

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