• Journal of applied mathematics & informatics
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• 제29권1_2호
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• pp.279-292
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• 2011

In this paper, we consider anti-periodic solutions of the following BAM neural networks with multiple delays on time scales: $$\{{x^\Delta_i(t)=-a_i(t)e_i(x_i(t))+{\sum\limits^m_{j=1}}c_{ji}(t)f_j(y_j(t-{\tau}_{ji}))+I_i(t),\atop y^\Delta_j(t)=-b_j(t)h_j(y_j(t))+{\sum\limits^n_{i=1}}d_{ij}(t)g_i(x_i(t-{\delta}_{ij}))+J_j(t),}\$$ where i = 1, 2, ..., n,j = 1, 2, ..., m. Using some analysis skills and Lyapunov method, some sufficient conditions on the existence and exponential stability of the anti-periodic solution to the above system are established.

• 대한기계학회논문집B
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• 제20권2호
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• pp.616-623
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• 1996

This paper investigates the linear stability of reacting mixing layers with special emphasis on the existence of multiple unstable modes. The governing equations for laminar flows are from two-dimensional compressible boundary-layer equations. The chemistry is a finite rate single step irreversible reaction with Arrhenius kinetics. For the incompressible reacintg mixing layer with variable density. A necessary condition for instability has been derived. The condition requires that the angular momentum, not the vorticity, to have a maximum in the flow domain. New inflectional modes of instability are found to exist in the outer part of the mixing layer. For the compressible reacting mixing layer, supersonic unstable modes may exist in the abscence of a generalized inflection point. The outer modes at high Mach numbers in the reacting mixing layer are continuations of the inflectional modes of low Mach number flows. However, the generalized inflection point is less important at supersonic flows.

• International Journal of Automotive Technology
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• 제8권1호
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• pp.33-38
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• 2007

Since it is difficult to analytically express the Melnikov function when a dynamic system possesses multiple saddle fixed points with homoclinic and/or heteroclinic orbits, this paper investigates a vehicle model with nonlinear suspension spring and hysteretic damping element, which exhibits multiple heteroclinic orbits in the unperturbed system. First, an algorithm for Melnikov integrals is developed based on the Melnikov method. And then the amplitude threshold of road excitation at the onset of chaos is determined. By numerical simulation, the existence of chaos in the present system is verified via time history curves, phase portrait plots and $Poincar{\acute{e}}$ maps. Finally, in order to further identify the chaotic motion of the nonlinear system, the maximal Lyapunov exponent is also adopted. The results indicate that the numerical method of estimating chaotic threshold is an effective one to complicated vehicle systems.

• 소음진동
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• 제10권5호
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• pp.865-872
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• 2000

This paper presents the modeling, theoretical formulation, and stability analysis for a combined system of a spinning disc and a head that contacts the disc. In the analytic model, head interference is considered by a rotating mass-spring-damper system together with a frictional follower force on the damped annular discs. The multiple scale method is utilized to perform the stability system that shows the existence of instability associated with parametric resonances. Using the formulated system , instability regions of optical recording disc are investigated with variation of mass, stiffness and friction force of a head, respectively. The simulation results show that the stiffness of a head is the most sensitive parameter on the instability of the disc.

• 여성건강간호학회지
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• 제22권3호
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• pp.162-169
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• 2016

Purpose: This study was done to investigate the prevalence and factors affecting body shape misperception among Korean adult women. Methods: We analyzed raw data from the fourth Korean Longitudinal Survey of Women and Families, for 7,658 women over 20 years of age. For the multiple logistic regression model, the dependent variable was existence of misperception (yes/no). Results: The prevalence of body shape misperception was 42.6% (overestimation 6.5%, underestimation 36.1%). Multiple logistic regression analysis revealed that age, education level, marital status, economic status and BMI were significantly associated with body shape underestimation. Education level and BMI were significantly associated with body shape overestimation. Conclusion: An effective obesity intervention program for women must reflect and monitor body shape perception as well as BMI.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.34.3-34
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• 2001

The design method of H$\infty$ filter for discrete-time uncertain linear systems with multiple state delays is investigated. The uncertain parameters are assumed to be unknown but belonging to known convex compact set of polytope type less conservative than norm bounded parameter uncertainty. The modified H$\infty$ performance measure is introduced to consider the initial states values which affect the performance of filter. The objective is to design a stable H$\infty$ filter guaranteeing asymptotic stability of filtering error dynamics and minimizing H$\infty$ norm bound. The sufficient condition for the existence of filter and the filter design method are established by LMI (linear matrix inequality) approach.

• 분석과 대안
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• 제2권2호
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• pp.143-162
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• 2018

This paper focuses on the policy framework about "Quantitative and Qualitative Easing (QQE)" of Japan, and analyzes reasons why the policy goal was not reached. The QQE was introduced by the Bank of Japan in 2013 with the purpose of meeting the price stability target of 2% and getting out of deflation that prevents sustained price decline. However, despite the implementation of the bold monetary easing policy unprecedented in the world, the policy goal was not achieved as of June 2018. As a result of analyzing the causes, the following three structural factors were confirmed. 1) The rise in prices by QQE was limited because Japan's consumer price is strongly depending on import price. 2) The effect is high degree of uncertainty and limited because theoretical framework of reflationist which adopted QQE depends on "expectation formation" by "self-fulfilling expectation" and "multiple equilibria". 3) It was confirmed that the expansion of the monetary base did not lead to money stock due to the existence of Japanese liquidity trap, long-term low interest rate policy.

• 대기
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• 제25권4호
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• pp.669-683
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• 2015

In this study, we investigated the prediction skills of four multiple linear regression methods for monthly air temperature over South Korea. We used simulation results from four regional climate models (RegCM4, SNURCM, WRF, and YSURSM) driven by two boundary conditions (NCEP/DOE Reanalysis 2 and ERA-Interim). We selected 15 years (1989~2003) as the training period and the last 5 years (2004~2008) as validation period. The four regression methods used in this study are as follows: 1) Homogeneous Multiple linear Regression (HMR), 2) Homogeneous Multiple linear Regression constraining the regression coefficients to be nonnegative (HMR+), 3) non-homogeneous multiple linear regression (EMOS; Ensemble Model Output Statistics), 4) EMOS with positive coefficients (EMOS+). It is same method as the third method except for constraining the coefficients to be nonnegative. The four regression methods showed similar prediction skills for the monthly air temperature over South Korea. However, the prediction skills of regression methods which don't constrain regression coefficients to be nonnegative are clearly impacted by the existence of outliers. Among the four multiple linear regression methods, HMR+ and EMOS+ methods showed the best skill during the validation period. HMR+ and EMOS+ methods showed a very similar performance in terms of the MAE and RMSE. Therefore, we recommend the HMR+ as the best method because of ease of development and applications.

• 대한전자공학회논문지SP
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• 제41권6호
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• pp.121-126
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• 2004

본 논문에서는 단일 문맥자유 주목 연산자 (context-free attention operator)만을 계층적으로 적용하여 복잡배경의 인물 영상으로부터 여러 얼굴을 효과적으로 동시 검출하는 알고리즘을 제안하였다. 입력 영상을 피라미드 구조로 변환하고, 잡음에 강건한 주목 연산자를 전역적으로 적용하여 먼저 고속으로 얼굴이 존재할 후보영역들을 찾고, 다시 이 영역들에 국한하여 지역적인 주목 연산자를 적용하여 얼굴이 갖는 특징을 확인함으로써 얼굴임을 검증하였다. 복잡 배경 속에 여러 얼굴을 포함하는 여러 가지 인물 영상 데이터베이스에 대해 제안한 알고리즘을 적용한 결과 93.5%의 검출율을 얻을 수 있었다.

• 간호행정학회지
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• 제5권1호
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• pp.77-86
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• 1999

The purpose of this study is to look into nurse's legal duty and to analyze influencing factors, by reading through precedents in nursing-related malpractice cases. 157 clinic nurses and 40 head nurses who were working in 3 university hospitals in the area of Seoul and KyongKi province were surveyed with pre-set questionnaires which were based on 20 cases and to compare precedents with nurses' attitudes. Independent variables were demographic characteristics, job characteristics, experience and education, and personal characteristics. Dependent variables were the extents of understanding in their duty. To analyze the extent of duty understanding t-text. ANOVA, and multiple regression were performed according to the characteristics of each study subject. Main findings are as follows; 1. $X^2$ test was performed for each hospitals and job category. The existence of religion and job-related advisers were significantly different according to hospitals and job categories. The existences of the orientation for nursing, education, and meeting were significantly different according to hospitals. 2. The extent of duty understanding according to the subject characteristics was assessed by means of median. Each case was given the median. 12 cases(46%)out of 26 cases demonstrated the median of more than 6 showing high extent of understanding. 3. When $X^2$ test was performed. the extent of duty understanding was significantly different in the areas of marriage status. the existence of meetings. and the experience of having dispute. When multiple regression(stepwise method) was performed, above variables were not statistically significant. 4.As result of comparative analysis on precedents and nurse's attitudes. it is 4 cases that nurse's attitudes is more active than precedents and it is 9 cases that nurse's attitudes is more passive than precedents and it is 4 cases that nurse's attitudes is parallel with precedents. This study does not present statistical model which can integrate all the cases. The significance of this study is in that it generalized and assessed the nurses' understanding of duty based on nursing -care which was legally disputed and compared nurse's attitude with precedents.