• 농촌계획
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• 제25권3호
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• pp.129-139
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• 2019

The purpose of this study is to monitor the long-term vegetation change of the village complementary forest after restoration. Based on the monitoring in 2010, six years after the restoration project in 2004, the monitoring of the complementary forest in Dubang village in 2019 after 9 years was conducted. This study identifies the change of species diversity and structure, growth, vegetation coverage, structural quality etc. and succession through long-term monitoring. For this, field survey was conducted in 2003 and 2010, 2019. The results demonstrate significant increase of species diversity and multi-layer structure and progress of natural succession. Overall, Part I is considered to be a quasi-natural complementary village forest, which has a natural balance between natural vegetation that have remained in nature for a long time and anthropogenic vegetation, revealing the coexistence of nature and humanity. It means ecological structure and function have improved. Part II should be restored to the lost part and adaptive management rather than excessive management should be carried out to leave natural succession.

• Journal of Computing Science and Engineering
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• 제9권2호
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• pp.39-50
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• 2015

Genetic algorithm (GA) and particle swarm optimization (PSO) are two excellent approaches to multimodal optimization problems. However, slow convergence or premature convergence readily occurs because of inappropriate and inflexible evolution. In this paper, a novel optimization algorithm with a flexible grid optimization (FGO) is suggested to provide adaptive trade-off between exploration and exploitation according to the specific objective function. Meanwhile, a uniform agents array with adaptive scale is distributed on the gird to speed up the calculation. In addition, a dominance centroid and a fitness center are proposed to efficiently determine the potential guides when the population size varies dynamically. Two types of subregion division strategies are designed to enhance evolutionary diversity and convergence, respectively. By examining the performance on four benchmark functions, FGO is found to be competitive with or even superior to several other popular algorithms in terms of both effectiveness and efficiency, tending to reach the global optimum earlier. Moreover, FGO is evaluated by applying it to a parameter decision in a least squares support vector machine (LS-SVM) to verify its practical competence.

• 한국통신학회논문지
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• 제33권11A호
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• pp.1095-1104
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• 2008

다중 사용자 OFDM 시스템에서 제한된 자원을 효율적으로 사용하기 위해서는 부반송파와 비트의 할당은 중요한 역할을 한다. 하지만 부반송파와 비트의 할당문제는 비선형적 문제로 모든 경우의 수를 계산하여 최적의 값을 얻기에는 사실상 불가능하다. 본 논문에서는 비선형적 문제의 효율적인 자원 활용을 위해서 새로운 유전자 알고리즘을 사용하였다. 논문에서 제안된 알고리즘은 기존의 정형화된 유전자 알고리즘보다 다양한 조합을 참고하여 해를 찾게 된다. 따라서 수치적 시뮬레이션 결과들을 통해서 기존의 알고리즘들과 제안된 알고리즘을 비교해 볼 때, 제안한 알고리즘이 기존의 알고리즘들보다 뛰어난 성능을 보임을 확인하였다.

• 한국정보통신학회논문지
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• 제18권4호
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• pp.790-796
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• 2014

통신채널의 인식문제는 현재 이론적 부분과 실제 관점 부분의 문제점을 가지고 있다. 최근에 이 문제를 해결키 위해 제안된 기법들은 안테나 구조와 시간 오버샘플링에 의해 유도된 다이버시티를 이용하고 있다. 이 방법은 선형 제한조건을 가진 적응필터를 이용하고 있다. 본 논문에서는 값 분할에 근거한 기법이 제안되었다. 수신신호 상관행렬의 최소 단일값에 의한 단일벡터는 채널 임펄스 응답을 포함하며 상기 문제를 해결키 위한 적응 알고리즘을 보인다. 제안된 기법은 기존 기법의 성능보다 우수함을 알 수 있다.

• 센서학회지
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• 제22권5호
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• pp.338-345
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• 2013

Premature ventricular contractions are the most common of all arrhythmias and may cause more serious situation like ventricular fibrillation and ventricular tachycardia in some patients. Therefore, the detection of this arrhythmia becomes crucial in the early diagnosis and the prevention of possible life threatening cardiac diseases. Most methods for detecting arrhythmia require pp interval, or the diversity of P wave morphology, but they are difficult to detect the p wave signal because of various noise types. Thus, it is necessary to use noise-free R wave. So, the new approach for the detection of PVC is presented based on the rhythm analysis and the beat matching in this paper. For this purpose, we removed baseline wandering of low frequency band and made summed signals that are composed of two high frequency bands including the frequency component of QRS complex using the wavelet filter. And then we designed R wave detection algorithm using the adaptive threshold and window through RR interval. Also, we developed algorithm to classify PVC using RR interval. The performance of R wave and PVC detection is evaluated by using MIT-BIH arrhythmia database. The achieved scores indicate average detection rate of 99.76%, sensitivity of 99.30% and specificity of 98.66%; accuracy respectively for R wave and PVC detection.

• 한국정보통신학회논문지
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• 제12권2호
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• pp.336-342
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• 2008

Amplify and forward(AF)와 decode and forward(DF)의 두 가지 모드에 대하여 네트워크의 네트워크 수명을 극대화할 수 있는 단순한 구조의 전력할당 방식을 제안한다. 네트워크 수명을 극대화하기 위해서는 전송전력을 최소화하는 것뿐만 아니라 전력을 네트워크의 모든 노드에게 균등하게 할당하는 것이 중요하다. 제안된 전력할당기법에서 송신전력은 노드의 잔여전력에 비례하고 목적지 노드에서 요구되는 수신 SNR을 만족하도록 할당된다. 본 논문에서는 AF와 DF의 두 가지 모드에 대하여 할당전력을 계산하였고 시뮬레이션을 통하여 그 성능을 분석하였다. 시뮬레이션 결과 제안된 전력할당 방식은 균등할당방식에 비하여 네트워크 수명을 크게 증가시킬 수 있었다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제13권1호
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• pp.617-627
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• 2021

Underwater Acoustic Channels (UAC) have inherent sparse characteristics. The traditional adaptive equalization techniques do not utilize this feature to improve the performance. In this paper we consider the Variable Adaptive Subgradient Projection (V-ASPM) method to derive a new sparse equalization algorithm based on the Minimum Symbol Error Rate (MSER) criterion. Compared with the original MSER algorithm, our proposed scheme adds sparse matrix to the iterative formula, which can assign independent step-sizes to the equalizer taps. How to obtain such proper sparse matrix is also analyzed. On this basis, the selection scheme of the sparse matrix is obtained by combining the variable step-sizes and equalizer sparsity measure. We call the new algorithm Sparse-Control Proportional-MSER (SC-PMSER) equalizer. Finally, the proposed SC-PMSER equalizer is embedded into a turbo receiver, which perform turbo decoding, Digital Phase-Locked Loop (DPLL), time-reversal receiving and multi-reception diversity. Simulation and real-field experimental results show that the proposed algorithm has better performance in convergence speed and Bit Error Rate (BER).

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권4호
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• pp.632-650
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• 2013

The paper considers a spectrum sharing cognitive radio (CR) network coexisting with a primary network under the average interference power constraint. In particular, the secondary user (SU) is assumed to carry delay-sensitive services and thus shall satisfy a given delay quality-of-service (QoS) constraint. The secondary receiver is also assumed to be equipped with multiple antennas to perform maximal ratio combining (MRC) to enhance SU performance. We investigate the effective capacity of the SU with MRC diversity under aforementioned constraints in Nakagami fading environments. Particularly, we derive the optimal power allocation to achieve the maximum effective capacity of the SU, and further derive the effective capacity in closed-form. In addition, we further obtain the closed-form expressions for the effective capacities under three widely used power and rate adaptive transmission schemes, namely, optimal simultaneous power and rate adaptation (opra), truncated channel inversion with fixed rate (tifr) and channel inversion with fixed rate without truncation (cifr). Numerical results supported by simulations are presented to consolidate our studies. The impacts on the effective capacity of various system parameters such as the number of antennas, the average interference power constraint and the delay QoS constraint are investigated in detail. It is shown that MRC diversity can significantly improve the effective capacity of the SU especially for cifr transmission scheme.

• 한국위성정보통신학회논문지
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• 제12권4호
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• pp.141-145
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• 2017

스펙트럼 센싱은 인지무선 (cognitive radio) 시스템을 동작시키기 위한 주요한 기법이며 인지무선 시스템을 통해 최근 주목받고 있는 무선에너지하비스팅 시스템에 에너지 하비스팅 효율을 개선할 수 있다. 최근 스펙트럼 센싱을 위한 다양한 기술이 연구되었는데, 그 중에서 가장 널리 쓰이고 있는 에너지 검출 (energy detection) 기술이 있다. 그러나 2차 유저 (secondary user; SU) 가 주파수 페이딩 (frequency fading) 및 쉐도잉 (shadowing)에 의해 영향을 받을 수 있기 때문에, 에너지 검출은 실제 무선 통신에서 숨겨진 단말기 문제 (hidden terminal problem)를 갖는다. 협력 스펙트럼 센싱 (cooperative spectrum sensing)은 SU의 공간적 다양성을 이용하여 이 문제를 해결할 수 있습니다. 그러나 다중 보조를 처리하여 데이터를 증가시키는 문제가 있기 때문에 우리는 적응형 스펙트럼 센싱 알고리즘을 사용하는 시스템 모델을 제안하고 성능을 시뮬레이션 한다. 이 알고리즘은 기본 사용자 (primary user; PU)의 수신 신호의 신호 대 잡음비 (signal to Noise Ratio; SNR)에 따라 단일 에너지 검출과 협동 에너지 사이의 감지 방법을 선택하는 방법을 이용한다. 시뮬레이션 결과를 통해 적응형 스펙트럼 센싱이 인지무선 시스템에서 더 효율적이라는 것을 확인한다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권10호
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• pp.3490-3507
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• 2014

License plate detection (LPD) is one of the most important aspects of an automatic license plate recognition system. Although there have been some successful license plate recognition (LPR) methods in past decades, it is still a challenging problem because of the diversity of plate formats and outdoor illumination conditions in image acquisition. Because the accurate detection of license plates under different conditions directly affects overall recognition system accuracy, different methods have been developed for LPD systems. In this paper, we propose a license plate detection method that is rapid and robust against variation, especially variations in illumination conditions. Taking the aspects of accuracy and speed into consideration, the proposed system consists of two stages. For each stage, Haar-like features are used to compute and select features from license plate images and a cascade classifier based on the concatenation of classifiers where each classifier is trained by an AdaBoost algorithm is used to classify parts of an image within a search window as either license plate or non-license plate. And it is followed by connected component analysis (CCA) for eliminating false positives. The two stages use different image preprocessing blocks: image preprocessing without adaptive thresholding for the first stage and image preprocessing with adaptive thresholding for the second stage. The method is faster and more accurate than most existing methods used in LPD. Experimental results demonstrate that the LPD rate is 98.38% and the average computational time is 54.64 ms.