• 제어로봇시스템학회논문지
• /
• 제4권5호
• /
• pp.574-578
• /
• 1998

This paper considers the robust positive real problem for linear systems with linear fractional-type norm-bounded repeated scalar block parameter uncertainty. It is shown that the robust positive real problem can be converted into the standard positive real problem without uncertainty that can be used for the analysis of the given uncertain linear system and the synthesis of a controller that robustly stabilizes and achieves the extended strict positive realness property of the closed-loop transfer function. These results can be also applied to the linear system with general structured uncertainty containing repeated scalar block parameters and are extensions of the previous works that consider only norm-boundedness of the affine unstructured uncertainty.

• 제어로봇시스템학회논문지
• /
• 제5권6호
• /
• pp.641-646
• /
• 1999

This paper deals with the robust stability of discrete-time linear systems with time- varying delays and norm-bounded uncertainties. In this paper, the magnitude of time-varying delays is assumed to be upper-bounded. The sufficient condition is presented in terms of linear matrix inequality. It is also shown that the robust stability of uncertain discrete-time linear systems with time-varying delays is related with the quadratic stability of uncertain discrete-time linear systems with constant time delay.

• Journal of applied mathematics & informatics
• /
• 제9권1호
• /
• pp.61-76
• /
• 2002

The robust non-fragile guaranteed cost control problem is studied in this paper for class of uncertain linear large-scale systems with time-varying delays in subsystem interconnections and given quadratic cost functions. The uncertainty in the system is assumed to be norm-hounded arid time-varying. Also, the state-feedback gains for subsystems of the large-scale system are assumed to have norm-bounded controller gain variations. The problem is to design state feedback control laws such that the closed-loop system is asymptotically stable and the closed-loop cost function value is not more than a specified upper bound far all admissible uncertainties. Sufficient conditions for the existence of such controllers are derived based on the linear matrix inequality (LMI) approach combined with the Lyapunov method. A parameterized characterization of the robust non-fragile guaranteed cost contrellers is 7iven in terms of the feasible solution to a certain LMI. Finally, in order to show the application of the proposed method, a numerical example is included.

• 한국방송∙미디어공학회:학술대회논문집
• /
• 한국방송∙미디어공학회 2018년도 하계학술대회
• /
• pp.20-21
• /
• 2018

행렬의 rank 최소화 기법은 영상 잡음 제거, 행렬 완성(completion), low rank 행렬 복원 등 다양한 영상처리 분야에서 효과적으로 이용되어 왔다. 특히 nuclear norm 을 이용한 low rank 최소화 기법은 convex optimization 을 통하여 대상 행렬의 특이값(singular value)을 thresholding 함으로써 간단하게 low rank 행렬을 얻을 수 있다. 하지만, nuclear norm 을 이용한 low rank 최소화 방법은 행렬의 rank 값을 정확하게 근사하지 못하기 때문에 잡음 제거가 효과적으로 이루어지지 못한다. 본 논문에서는 영상의 잡음을 제거 하기 위해 다중 잡음 제거 영상을 이용하여 유사도가 높은 유사 패치 행렬을 구성하고, 유사 패치 행렬의 rank 를 non-convex function 을 이용하여 최소화시키는 방법을 통해 잡음을 제거하는 방법을 제안한다.

• 대한수학회지
• /
• 제61권1호
• /
• pp.183-205
• /
• 2024

In this paper, for an m-dimensional (m ≥ 5) complete non-compact submanifold M immersed in an n-dimensional (n ≥ 6) simply connected Riemannian manifold N with negative sectional curvature, under suitable constraints on the squared norm of the second fundamental form of M, the norm of its weighted mean curvature vector |H_f| and the weighted real-valued function f, we can obtain: • several one-end theorems for M; • two Liouville theorems for harmonic maps from M to complete Riemannian manifolds with nonpositive sectional curvature.

• Communications for Statistical Applications and Methods
• /
• 제31권2호
• /
• pp.203-212
• /
• 2024

The area under the ROC curve (AUC) is one of the most common criteria used to measure the overall performance of binary classifiers for a wide range of machine learning problems. In this article, we propose a L₁-penalized AUC-optimization classifier that directly maximizes the AUC for high-dimensional data. Toward this, we employ the AUC-consistent surrogate loss function and combine the L₁-norm penalty which enables us to estimate coefficients and select informative variables simultaneously. In addition, we develop an efficient optimization algorithm by adopting k-means clustering and proximal gradient descent which enjoys computational advantages to obtain solutions for the proposed method. Numerical simulation studies demonstrate that the proposed method shows promising performance in terms of prediction accuracy, variable selectivity, and computational costs.

• 대한한방부인과학회지
• /
• 제20권4호
• /
• pp.101-110
• /
• 2007

Purpose: Oligomenorrhea is clinically important because it can be progressed to amenorrhea. The purpose of this study is to analyse Autonomic Nerve Function of some oligomenorrheic patients by using HRV(Heart Rate Variability). Methods: We studied 35 patients visiting OO Oriental Hospital from 1st November 2006 to 31th May 2007. One woman who takes antidepressant is excluded. 17 oligomenorrheic group and 17 normal menstrual cycle group were compared with HRV. The SPSS 12.0 for windows was used to analyze the data and Mann Whitney U-test were used to verify the results. Results: Mean PR, LF norm, LF/HF ratio of oligimenorrheic group are higher than normal menstrual cycle group. But there is no statistically significance. SDNN, RMS-SD, ln TP, ln VLF, ln LF, ln HF, HF norm of oligimenorrheic group are lower than normal menstrual cycle group. But there is no statistically significance. Conclusion: It can be suggested that oligomenorrhea can be related to increased activities of sympathetic nerve and decreased activities of general autonomic nerve function. But, we need study with more subjects for settling this.

• 방송공학회논문지
• /
• 제8권1호
• /
• pp.37-44
• /
• 2003

신호를 원하는 해상도의 신호로 다시 샘플링하기 위해 일반적으로 쓰이는 방법은 원래의 영상을 연속된 모델로 나타낸 후 이를 원하는 해상도의 신호로 다시 샘플링하는 것이다. 이산 신호를 연속 신호로 바꿀 때 이용하게 될 B-spline 함수는 다른 기저함수에 비해 진동하는 성향이 적고 적은 계수로 표현이 가능하다. 디지털 신호를 B-spline 모델로 표현하고 이 spline 신호를 새로운 해상도로 다시 샘플링하게 되면 B- spline에 기반한 비정규 리사이징이 된다. 이때 해상도는 공간에 따라 변하는 변환함수에 의해 결정하게 된다. 이 방법은 구현하기 좋지만 정보를 손실하는 약점이 있으므로 이를 극복한 최적 비정규 알고리즘을 제안한다. 최적의 비정규적인 수식 유도를 위해, 다시 샘플링된 신호는 변환 함수로 결정된 shift varying spline의 조합으로 나타내게 된다. 원래의 영상에 가장 가까운 함수를 선택함으로써 이 함수는 일반화될 수 있다.

• Journal of the Optical Society of Korea
• /
• 제10권4호
• /
• pp.169-173
• /
• 2006

This paper describes an efficient optimal design method for an arrayed waveguide grating (AWG) having MMI coupler with flattened transfer function. The objective function is the norm of the difference between calculated and target spectra. To analyze the AWG transfer function, the Fresnel-Kirchhof diffraction formula was employed and the design variable was optical path difference of each array waveguide. The (1+1) Evolution Strategy was applied to an eight-channel coarse wavelength division multiplexing (CWDM) AWG as the optimization tool. For obtaining a broadened spectrum, we use a MMI coupler and the variation in optical path difference at each array waveguide changes the shape of the transfer function to obtain the optimal spectrum shape.

• Journal of the Optical Society of Korea
• /
• 제10권1호
• /
• pp.33-36
• /
• 2006

This paper describes an efficient optimal design method for an arrayed waveguide grating (AWG) with flattened transfer function. The objective function is the norm of the difference between calculated and target spectra. To analyze the AWG transfer function, the Fresnel-Kirchhof diffraction formula was employed and the design variable was optical path difference of each array waveguide. The (1+1) Evolution Strategy was applied to an eight-channel coarse wavelength division multiplexing (CWDM) AWG as the optimization tool. The optimized transfer function will considerably improve the system performance.