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Nonlinear Compensation Using Artificial Neural Network in Radio-over-Fiber System
Najarro, Andres Caceres,Kim, Sung-Man The Korea Institute of Information and Commucation 2018 Journal of information and communication convergen Vol.16 No.1
In radio-over-fiber (RoF) systems, nonlinear compensation is very important to meet the error vector magnitude (EVM) requirement of the mobile network standards. In this study, a nonlinear compensation technique based on an artificial neural network (ANN) is proposed for RoF systems. This technique is based on a backpropagation neural network (BPNN) with one hidden layer and three neuron units in this study. The BPNN obtains the inverse response of the system to compensate for nonlinearities. The EVM of the signal is measured by changing the number of neurons and the hidden layers in a RoF system modeled by a measured data. Based on our simulation results, it is concluded that one hidden layer and three neuron units are adequate for the RoF system. Our results showed that the EVMs were improved from 4.027% to 2.605% by using the proposed ANN compensator.
Predistortion for Frequency-Dependent Nonlinearity of a Laser in RoF Systems
Najarro, Andres C.,Kim, Sung-Man The Korea Institute of Information and Commucation 2016 Journal of information and communication convergen Vol.14 No.3
In radio-over-fiber (RoF) systems, nonlinear compensation is essential to improve performance. Among the several existing nonlinear compensation techniques, we investigate a predistortion technique for a directly modulated laser in an RoF system. First, we obtain the input-to-output response of a directly modulated laser at 160, 820, and 1,540 MHz. The results show that the laser response is dependent on the frequency band. Second, we design an optimal predistortion circuit to compensate for the nonlinear responses of three frequency bands. We design the predistortion circuit with two options: each predistortion circuit for each frequency band and one single predistortion circuit for all the three frequency bands. Finally, we present the simulation results of the predistortion system obtained using a commercial simulator. These results show that the third intermodulation distortion (IMD3) is improved by 0.6-9 dB for the three frequency bands with only a single predistortion circuit.
Differential Evolution with Adaptive Population Size for Target Localization in WSN
Andres Caceres Najarro,Iickho Song,Kiseon Kim 한국통신학회 2022 한국통신학회 학술대회논문집 Vol.2022 No.2
The population size (PS) plays a key role in the performance of any population-based evolutionary algorithm. In this paper, we propose two new techniques for adapting the PS, namely, parabolic and logistic reduction. In contrast to other PS adaptive techniques, the proposed techniques carefully reduce the PS at a higher rate. The proposed techniques together with the differential evolution (DE) are tested when solving the target node localization problem in terms of localization accuracy and computational complexity. Simulation results demonstrate that the DE with the proposed PS adaptive techniques provides better performance over the DE with other adaptive techniques, especially in terms of computational complexity.
LSTM 기반 스태킹 앙상블 기법을 활용한 전력망 내의 전기자동차 충전 전력 수요량 예측 알고리즘
양창석(Changseok Yang),안드레스(Lismer Andres Caceres Najarro),김기선(Kiseon Kim) 한국통신학회 2021 한국통신학회 학술대회논문집 Vol.2021 No.6
최근 여러 기계학습 알고리즘과 딥러닝 신경망을 활용하여 전력망 내의 전기자동차 충전 전력 수요량을 예측하는 연구가 진행되고 있다. 하지만 전기자동차 사용자별 다양한 충전 행동 패턴과 시간대별로 다른 전기자동차 충전 요청 수요의 높은 변동성은 예측 성능을 저하하는 문제를 야기시킨다. 본 연구에서는 기계학습 알고리즘들과 장단기 메모리순환 신경망(Long Short-Term Memory)을 결합한 새로운 스태킹 앙상블 방법을 제안하였다. Caltech 대학 주차장의 EV 충전 사용 데이터 기반 모의 실험 결과, 제안한 방법이 기계학습 알고리즘과 순환 신경망 방법과 비교하여 RMSE과 MAE 두가지 성능 평가 지표에서 충전 전력 수요량 예측 오차를 개선함을 확인하였다.
Rafael Scaf de Molon,Juliana Aparecida Najarro Dearo Morais-Camillo,Celso Eduardo Sakakura,Mauricio Goncalves Ferreira,Leonor Castro Monteiro Loffredo,Gulnara Scaf 대한구강악안면방사선학회 2012 Imaging Science in Dentistry Vol.42 No.4
Purpose: This study was performed to compare the inverted digital images and film-based images of dry pig mandibles to measure the periodontal bone defect depth. Materials and Methods: Forty 2-wall bone defects were made in the proximal region of the premolar in the dry pig mandibles. The digital and conventional radiographs were taken using a Schick sensor and Kodak F-speed intraoral film. Image manipulation (inversion) was performed using Adobe Photoshop 7.0 software. Four trained examiners made all of the radiographic measurements in millimeters a total of three times from the cementoenamel junction to the most apical extension of the bone loss with both types of images: inverted digital and film. The measurements were also made in dry mandibles using a periodontal probe and digital caliper. The Student’s t-test was used to compare the depth measurements obtained from the two types of images and direct visual measurement in the dry mandibles. A significance level of 0.05 for a 95% confidence interval was used for each comparison. Results: There was a significant difference between depth measurements in the inverted digital images and direct visual measurements (p¤|t|=0.0039), with means of 6.29 mm (IC95%:6.04-6.54) and 6.79 mm (IC95%:6.45-7.11), respectively. There was a non-significant difference between the film-based radiographs and direct visual measurements (p¤|t|=0.4950), with means of 6.64mm(IC95%:6.40-6.89) and 6.79mm(IC95%:6.45-7.11), respectively. Conclusion: The periodontal bone defect measurements in the inverted digital images were inferior to film-based radiographs, underestimating the amount of bone loss.
Current outline of regulation of Bt-maize and transgenic insects in Mexico
Mario A. RODRÍGUEZ-PÉREZ,Olga REAL-NAJARRO 한국곤충학회 2010 Entomological Research Vol.40 No.1
This paper discusses the regulation of Bt-maize and transgenic insects in Mexico, pointing out the current state of the use of these biotechnological developments. In addition, as insect biotechnology is new for Mexico, regulatory protocols are still under development. Technical barriers to using Bacillus thuringensis (Bt)-maize for pest control in Mexico have been deployed by regulatory uncertainty which, associated with cultural factors, underplay biological motives. Although the use of Bt-maize is still controversial in Mexico, since 2009, Bt-maize has been cultivated experimentally.