• Bulletin of the Korean Mathematical Society
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• v.55 no.2
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• pp.431-448
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• 2018

This paper is concerned with the positive definite solutions of the nonlinear matrix equation $X-A^*{\bar{X}}^{-1}A=Q$, where A, Q are given complex matrices with Q positive definite. We show that such a matrix equation always has a unique positive definite solution and if A is nonsingular, it also has a unique negative definite solution. Moreover, based on Sherman-Morrison-Woodbury formula, we derive elegant relationships between solutions of $X-A^*{\bar{X}}^{-1}A=I$ and the well-studied standard nonlinear matrix equation $Y+B^*Y^{-1}B=Q$, where B, Q are uniquely determined by A. Then several effective numerical algorithms for the unique positive definite solution of $X-A^*{\bar{X}}^{-1}A=Q$ with linear or quadratic convergence rate such as inverse-free fixed-point iteration, structure-preserving doubling algorithm, Newton algorithm are proposed. Numerical examples are presented to illustrate the effectiveness of all the theoretical results and the behavior of the considered algorithms.

• Journal of the Earthquake Engineering Society of Korea
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• v.22 no.4
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• pp.245-251
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• 2018

In this paper, we address some issues in existing seismic hazard closed-form equations and present a novel seismic hazard equation form to overcome these issues. The presented equation form is based on higher-order polynomials, which can well describe the seismic hazard information with relatively high non-linearity. The accuracy of the proposed form is illustrated not only in the seismic hazard data itself but also in estimating the annual probability of failure (APF) of the structural systems. For this purpose, the information on seismic hazard is used in representative areas of the United States (West : Los Angeles, Central : Memphis and Kansas, East : Charleston). Examples regarding the APF estimation are the analyses of existing platform structure and nuclear power plant problems. As a result of the numerical example analyses, it is confirmed that the higher-order-polynomial-based hazard form presented in this paper could predict the APF values of the two example structure systems as well as the given seismic hazard data relatively accurately compared with the existing closed-form hazard equations. Therefore, in the future, it is expected that we can derive a new improved APF function by combining the proposed hazard formula with the existing fragility equation.

• Computational Structural Engineering
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• v.8 no.4
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• pp.57-64
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• 1995

This paper introduced a simple numerical analysis algorithm for the calculation of the dynamic responses of the beam structure with a moving mass. The dynamic equation of motion of the Bernoulli-Euler beam is derived by considering the moving mass as a moving particle, and the dynamic equation of motion is transformed into an integro-differential equation by use of the structural influence function. The numerical solutions of the integro-differential equation are obtained by the modal analysis approach, and compared with those cited from well-known references. The proves that the numerical analysis algorithm proposed herein provide very reliable results, and thus it can be utilized in the design analysis of the beamlike structures exited by a mass which is traveling on it.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.13 no.3
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• pp.77-82
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• 2014

In this study, we carried out the interrupted cutting of carbon steel for a machine structure (SM45C) with a CVD-coated tool and conducted an ANOVA test and a confidence interval analysis to find factors influence the surface roughness and to obtain a regression equation. We found that factor which mostly affects the surface roughness during interrupted cutting was the feed rate. The cutting speed and depth of the cut only had small effect on the surface roughness. From the result of a multi-regression analysis during an interrupted cutting experiment, we obtained regression equation. Its coefficient of determination was 0.918, indicating that the regression equation was predictable. Compared to continuous cutting, if the feed rate increases, the surface roughness will also increase during interrupted cutting.

• Korean Journal of Crystallography
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• v.13 no.2
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• pp.96-100
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• 2002

The title compound, (H/sub 3/NCH/sub 2/CH/sub 2/NH/sub 3/)HPO/sub 4/ (Ⅰ), has been synthesized by hydrothermal technique for the first time and its novel structure analyzed by X-ray single crystallography. The compound (Ⅰ) crystallizes in the monoclinic system, P2/sub 1//c space group with a＝10.209(1), b＝7.891(1), c＝ 8.039(1) (equation omitted), β＝ 92.138(9)°, V＝: 647.2(2) (equation omitted), Z＝4, R/sub 1/＝0.0295 and ωR/sub 2/＝0.0811 for 1141 independent reflections. The compound (Ⅰ) is interconnected to give a three-dimensional network through hydrogen-bonding interactions.

• Journal of Advanced Marine Engineering and Technology
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• v.29 no.4
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• pp.391-398
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• 2005

In this investigation, turbulent premixed combustion and flame front propagation in a gas turbine combustion chamber is studied. Direct numerical simulation of turbulent reacting flows demands extremely high computational resources, especially in more complicated geometry. The alternative choice may be left for Large Eddy Simulation (LES) by which only large scales are solved directly. In combustion problems, capturing the large scales' behavior without solving the details of small scales is a difficult task. Using a transport equation for description of the flame front propagation and therefore avoiding the calculation of inner flame structure is the basic idea of this study. For this purpose. the so-called G-equation has been used by which any iso-level of the G variable provides the flame location. A comparison with the experiment indicates that the present method can predict a turbulent velocity field and also capture a instantaneous 3-dimensional flame structure.

• Structural Engineering and Mechanics
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• v.85 no.5
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• pp.607-620
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• 2023

The classical optimal control (COC) method has been widely used for linear quadratic regulator (LQR) problems of structural control. However, the equation of motion of the structure is incorporated into the optimization model as the constraint condition for the LQR problem, which needs to be solved through the Riccati equation under certain assumptions. In this study, an explicit optimal control (EOC) method is proposed based on the explicit time-domain method (ETDM). By use of the explicit formulation of structural responses, the LQR problem with the constraint of equation of motion can be transformed into an unconstrained optimization problem, and therefore the control law can be derived directly without solving the Riccati equation. To further optimize the weighting parameters adopted in the control law using the gradient-based optimization algorithm, the sensitivities of structural responses and control forces with respect to the weighting parameters are derived analytically based on the explicit expressions of dynamic responses of the controlled structure. Two numerical examples are investigated to demonstrate the feasibility of the EOC method and the optimization scheme for weighting parameters involved in the control law.

• Journal of Communications and Networks
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• v.16 no.1
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• pp.92-97
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• 2014

A novel method for extracting frequency slippage signal from radar full pulse sequence is presented. For the radar full pulse sequence received by radar interception receiver, radio frequency (RF) and time of arrival (TOA) of all pulses constitute a two-dimensional information sequence. In a complex and intensive electromagnetic environment, the TOA of pulses is distributed unevenly, randomly, and in a nonstationary manner, preventing existing methods from directly analyzing such time series and effectively extracting certain signal features. This work applies Gaussian noise insertion and structure function to the TOA-RF information sequence respectively such that the equalization of time intervals and correlation processing are accomplished. The components with different frequencies in structure function series are separated using empirical mode decomposition. Additionally, a chaos detection model based on the Duffing equation is introduced to determine the useful component and extract the changing features of RF. Experimental results indicate that the proposed methodology can successfully extract the slippage signal effectively in the case that multiple radar pulse sequences overlap.

• Agribusiness and Information Management
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• v.5 no.1
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• pp.42-54
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• 2013

Information System (IS) Success Model proposed by DeLone and McLean is applied as a successful operation tool of information system, with its basic assumption of symmetric relationship between independent variables and dependent variables of the structural equation modeling. However, because previous studies have proved asymmetry of quality factors' influence structure on dependent variable by applying three-factor analysis, this study examined asymmetry of impact structure of quality factors introduced in IS Success Model on user satisfaction. Also the study applies structure equation modeling (SEM), three-factor analysis and importance and performance analysis (IPA) to develop resource allocation strategy for IS success. The study is able to provide IS practitioners with strategic implications for allocating and managing limited resources more effectively.

• Journal of KSNVE
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• v.7 no.4
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• pp.589-596
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• 1997

A energy equation for a thin plate and surrounding fluid is derived. The equation essentially determines the relation between internal loss of thin plate, energy of acoustic radiation, and structure intensity. We attempted to use this relation to measure internal loss of thin plate. The significance of this approach is that internal loss at any point of a thin plate can be measured. The quality of this measure is dicated by the accuracy of associated measurement systems such as structure and acoustic intensity measurements. A strain gauge bridge system has been developed to measure structure intensity of thin plate. Its performance is tested by experiments.