• 한국전자통신학회논문지
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• 제6권1호
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• pp.20-26
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• 2011

본 논문에서는 NM(node monitoring) 알고리듬과 NP(Piecewise Linear Function Approximation)를 사용해서 LDPC 코드 복호의 복잡도를 감소시키기 위한 효율적인 알고리듬을 제안한다. 이 NM 알고리듬은 새로운 node-threshold 방법과 message passing 알고리듬에 근거해서 제안되었는데, 이에 NP 방법을 사용해서 알고리듬의 복잡도를 더 줄일 수 있었다. 이 알고리듬의 효율성을 입증하기 위해서 모의 실험을 하였다. 모의실험결과, 기존에 잘 알려진 방법에 비해서 20% 정도 더 효율적이었다.

• 한국전자통신학회논문지
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• 제10권11호
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• pp.1231-1238
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• 2015

본 논문에서는 노드 모니터링(NM)과 Piecewise Linear Function Approximation(: NP)을 사용하여 LDPC 디코딩 알고리듬의 계산복잡도를 감소시키는 알고리듬을 제안한다. 이 알고리듬은 기존의 알고리듬보다도 더 효율적이다. 제안된 알고리즘이 기존의 방법보다도 개선되었다는 것을 확인하기 위해서 모의실험을 하였다. 실험결과, 제안된 알고리즘의 계산은 기존의 방법에 비해 약 20 % 향상되었음을 확인하였다.

• 방송공학회논문지
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• 제2권2호
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• pp.194-205
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• 1997

동영상 압축 표준인 MPEG이나 저속 통신용 비디오 부호화 표준인 H.263등과 같은 DPCM/DCT 복합 부호화기에서 비트율 제어는 매우 중요한 요소이다. 본 논문에서는 전송매체에서의 실시간 비디오 부호화나 저장 미디어 응용을 위하여 부분 선형 근사 모델을 이용한 간단한 적응적 비트율 제어 방법을 제안한다. 선형 모델에 기반한 기존의 버퍼 제어 기법은 버퍼 충만도에 따라서 선형적으로 양자화매개변수를 제어하지만 제안된 방법은 영상 부호화에서 logarithmic관계라고 알려진 양자화 매개변수와 비트량의 비선형적인 관계를 부분적으로 선형 근사화 시킨 모델을 이용한다. 또한 보다 좋은 화질을 얻기 위하여 I 화면마다 공간영역에서 영상의 복잡도를 해석하여 적응적으로 제어한다. 실험적으로 기존의 선형 모델 방법과 비교하여 제안된 방법이 화질의 변화가 심하지 않으면 전체적으로 안정된 복원 영상을 얻었다.

• Journal of Power Electronics
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• 제11권3호
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• pp.327-334
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• 2011

Single-phase power factor correction (PFC) converter circuits are non-linear systems due to the contribution of their multiplier. This non-linearity causes difficulties in analysis and design. Models that reduce the system to a linear system involve considerable approximation, and produce results that are susceptible to instability problems. In this paper a piecewise affine (PWA) system is introduced for describing the nonlinear averaged model. Then robust output feedback controllers are established in terms of the linear matrix inequality (LMI). Simulation and experiments results show the effectiveness of the proposed control method.

• 한국경영과학회:학술대회논문집
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• 한국경영과학회/대한산업공학회 2003년도 춘계공동학술대회
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• pp.1122-1127
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• 2003

Typical application of detecting piecewise-linear curves includes vectorizing of scanned drawings whirh is a vital step in installing any geographic information system. This paper considers the problem of optimally approximating a piecewise linear curve to a set of digital points while satisfying given intersection angles between each pair of neighboring lines. The criterion for optimality is to minimize the sum of squared deviations. The problem is formulated as an unconstrained nonlinear programming model. An algorithm which guarantees an optimal solution is then proposed and its validity is tested with both a synthetically generated image and a real image. The test results illustrate the excellent performance of the proposed algorithm.

• 산업경영시스템학회지
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• 제44권1호
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• pp.26-36
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• 2021

The topic of this study is the field of humanitarian logistics for disaster response. Many existing studies have revealed that compliance with the golden time in response to a disaster determines the success or failure of relief activities, and logistics costs account for 80% of the disaster response cost. Besides, the agility, responsiveness, and effectiveness of the humanitarian logistics system are emphasized in consideration of the disaster situation's characteristics, such as the urgency of life-saving and rapid environmental changes. In other words, they emphasize the importance of logistics activities in disaster response, which includes the effective and efficient distribution of relief supplies. This study proposes a mathematical model for establishing a transport plan to distribute relief supplies in a disaster situation. To determine vehicles' route and the amount of relief for cities suffering a disaster, it mainly considers the urgency, effectiveness (restoration rate), and uncertainty in the logistics system. The model is initially developed as a mixed-integer nonlinear programming (MINLP) model containing some nonlinear functions and transform into a Mixed-integer linear programming (MILP) model using a logarithmic transformation and piecewise linear approximation method. Furthermore, a minimax problem is suggested to search for breakpoints and slopes to define a piecewise linear function that minimizes the linear approximation error. A numerical experiment is performed to verify the MILP model, and linear approximation error is also analyzed in the experiment.

• 대한전자공학회논문지
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• 제20권1호
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• pp.7-14
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• 1983

직선 및 곡선과 같은 선형 특징은 영상 처리에 있어 중요한 특징중의 하나이다. 본 논문에서는 의미있는 선형 특징의 새로운 기법이 제안된다. 이 기법은 그래프 이론의 미니멀 스패닝 트리를 이용하여 경계점들을 연결하고 그 다음, 헤어(의미없는 잔가지)와 불합리한 선분을 제거한다. 이와 같이 추적된 선형 특징을 근사화 묘사하기 위하여 부분 선형 근사화를 수행한다. 본 논문에서 제안된 기법으로 실험을 수행하여 그 결과를 보여 주었다.

• ETRI Journal
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• 제15권2호
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• pp.35-51
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• 1993

This paper presents function approximation based on nonparametric estimation. As an estimation model of function approximation, a three layered network composed of input, hidden and output layers is considered. The input and output layers have linear activation units while the hidden layer has nonlinear activation units or kernel functions which have the characteristics of bounds and locality. Using this type of network, a many-to-one function is synthesized over the domain of the input space by a number of kernel functions. In this network, we have to estimate the necessary number of kernel functions as well as the parameters associated with kernel functions. For this purpose, a new method of parameter estimation in which linear learning rule is applied between hidden and output layers while nonlinear (piecewise-linear) learning rule is applied between input and hidden layers, is considered. The linear learning rule updates the output weights between hidden and output layers based on the Linear Minimization of Mean Square Error (LMMSE) sense in the space of kernel functions while the nonlinear learning rule updates the parameters of kernel functions based on the gradient of the actual output of network with respect to the parameters (especially, the shape) of kernel functions. This approach of parameter adaptation provides near optimal values of the parameters associated with kernel functions in the sense of minimizing mean square error. As a result, the suggested nonparametric estimation provides an efficient way of function approximation from the view point of the number of kernel functions as well as learning speed.

• Korean Journal of Mathematics
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• 제22권4호
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• pp.599-609
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• 2014

We refer to the saturation assumptions on the finite element approximation for a one dimensional convection-diffusion model. By examining piecewise linear finite elements with refined mesh by half and hierarchical bases, we verify the saturation results, respectively.

• ETRI Journal
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• 제30권1호
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• pp.170-172
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• 2008

A substitution box (S-box) plays a central role in cryptographic algorithms. In this paper, an efficient method for designing S-boxes based on chaotic maps is proposed. The proposed method is based on the mixing property of piecewise linear chaotic maps. The S-box so constructed has very low differential and linear approximation probabilities. The proposed S-box is more secure against differential and linear cryptanalysis compared to recently proposed chaotic S-boxes.