• 디지털콘텐츠학회 논문지
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• 제15권3호
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• pp.319-326
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• 2014

IEEE 802.11 무선랜은 CSMA/CA(Carrier Sense Multiple Access/Collision Avoidance) 방식의 MAC(Media Access Control) 프로토콜을 사용하며, 데이터 충돌을 회피하기 위하여 데이터 전송 시 다른 사용자가 채널을 사용하고 있는지를 캐리어 감지를 통해 확인하게 된다. 현재 IEEE 802.11 표준에서는 캐리어 감지 범위에 영향을 주는 임계값을 일정한 고정 값으로 운용을 하고 있는데, 모바일 Ad-hoc 네트워크와 같이 이동성으로 인해 가변성이 큰 경우에는 고정 특정 캐리어 감지 임계값으로는 효율적인 네트워크 운영이 어렵다. 본 논문에서는 신호대간섭잡음비를 고려하여 캐리어 감지 임계값과 전송속도를 적절히 선택하는 제안된 SINR 기반 동적 캐리어 감지 임계값 방법을 모바일 Ad-hoc 네트워크 환경에 맞게 운영을 함으로써 더 좋은 네트워크 처리율을 얻을 수 있음을 보여준다.

• 한국빅데이터학회지
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• 제8권2호
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• pp.177-187
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• 2023

준지도 학습(Semi-supervised learning)은 소량의 라벨이 있는 데이터와 다량의 라벨이 없는 데이터를 사용하여 모델을 훈련하는 효과적인 방법이다. 그러나 많은 논문에서 준지도 학습시 하나의 고정된 임계값을 사용하여 각 클래스별 서로 다른 이미지들의 특징별 차이를 고려하지 않고 임의 라벨을 만든다. 본 논문에서는 합성개구 레이더(SAR) 이미지 분류 준지도 학습시 모든 클래스가 하나의 고정된 임계값을 사용하는 대신 각 클래스에 대해 서로 다른 임계값을 적용한다. 모델에 임계값 학습 모듈을 추가하여 임계값을 학습하여 클래스별로 학습되는 차이를 고려하여 클래스별로 서로 다른 임계값을 얻는다. 서로 다른 임계값을 사용한 준지도 학습기반의 SAR 이미지 분류 방법을 적용유무를 비교하여 클래스별 임계값을 사용하는 이점에 대해 고찰하였다.

• Current Optics and Photonics
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• 제7권4호
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• pp.345-353
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• 2023

We propose a turbulence-tolerant Manchester on-off keying (M-OOK) transmission for free-space optical (FSO) communication. At the transmitter end, a M-OOK signal featuring a spectrum with low-frequency components absent is modulated and transmitted into a turbulent channel. At the receiver end, a low-pass filter (LPF) -based adaptive-threshold decision (ATD) with LPF-extracted channel-state information (CSI) and a high-pass filter (HPF)-based fixed-threshold decision (FTD) are employed to compensate for the effects of turbulence, owing to the low-frequency spectral characteristics of the turbulent channel. The performance of LPF-based ATD and HPF-based FTD are evaluated for various cutoff frequencies for the LPF and HPF. Besides, the proposed M-OOK transmission is compared to conventional non-return-to-zero OOK (NRZ-OOK) for different data rates. The proposed technique is verified in simulation. The simulation results show that the proposed M-OOK detection with optimized cutoff frequencies of LPF and HPF has better bit-error-rate (BER) performance compared to NRZ-OOK, and it is close to the theoretical ATD with the knowledge of precise CSI under various degrees of turbulence effects.

• 한국군사과학기술학회지
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• 제27권3호
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• pp.319-328
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• 2024

Semi-supervised learning is a good way to train a classification model using a small number of labeled and large number of unlabeled data. We applied semi-supervised learning to a synthetic aperture radar(SAR) image classification model with a limited number of datasets that are difficult to create. To address the previous difficulties, semi-supervised learning uses a model trained with a small amount of labeled data to generate and learn pseudo labels. Besides, a lot of number of papers use a single fixed threshold to create pseudo labels. In this paper, we present a semi-supervised synthetic aperture radar(SAR) image classification method that applies different thresholds for each class instead of all classes sharing a fixed threshold to improve SAR classification performance with a small number of labeled datasets.

• 제어로봇시스템학회논문지
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• 제12권3호
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• pp.277-283
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• 2006

A recently proposed method for stabilizing haptic interfaces and teleoperation systems was tested with a 'PHANToM' commercial haptic device. The 'Passivity Observer' (PO) and 'Passivity Control1er' (PC) stabilization method was applied to stabilize the system but also excited a high frequency mode in the device. To solve this problem, we propose a method to use a timevarying desired energy threshold instead of fixed zero energy threshold for the PO, and make the actual energy input follow the timevarying energy threshold. With the time-varying energy threshold, we make the PC control action smooth without sudden impulsive behavior by distributing the dissipation. The proposed new PO/PC approach is applied to PHANToM with high stiffness (K = 5000N/m), and stable and smooth contact is guaranteed. Resetting and active environment display problems also can be solved with the reference energy following idea.

• Journal of the Korean Statistical Society
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• 제31권2호
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• pp.177-198
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• 2002

The estimation of variance components or variance ratios in linear model is an important issue in plant or animal breeding fields, and various estimation methods have been devised to estimate variance components or variance ratios. However, many traits of economic importance in those fields are observed as dichotomous or polychotomous outcomes. The usual estimation methods might not be appropriate for these cases. Recently threshold linear model is considered as an important tool to analyze discrete traits specially in animal breeding field. In this note, we consider a hierarchical Bayesian method for the threshold animal model. Gibbs sampler for making full Bayesian inferences about random effects as well as fixed effects is described to analyze jointly discrete traits and continuous traits. Numerical example of the model with two discrete ordered categorical traits, calving ease of calves from born by heifer and calving ease of calf from born by cow, and one normally distributed trait, birth weight, is provided.

• 한국화재소방학회논문지
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• 제17권3호
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• pp.26-30
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• 2003

본 논문은 화재발생시 열감지기가 오동작하는 특성을 열방출률(Heat Release Rate : HRR)을 이용하여 경계값을 정량적으로 나타내고 그 경계값을 기준으로 감지기의 오동작 영역을 분석하였다. Crib 형태의 목재를 가지고 small-scale의 화재실험을 통하여 화재감지기의 동작시간 등을 측정하였고 이를 이용하여 화재감지기가 동작하는 순간의 HRR을 계산하였다. 화재실험으로부터 얻은 변수를 가지고 화재감지기가 오동작하는 HRR의 경계값을 계산한 결과 정온식 감지기는 20.24 kW 차동식 감지기는 13.59 kW로 나타났다.

• 반도체디스플레이기술학회지
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• 제18권4호
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• pp.110-115
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• 2019

Blur detection and segmentation play vital role in many computer vision applications. Among various methods, local binary pattern based methods provide reasonable blur detection results. However, in conventional local binary pattern based methods, the blur map is computed by using a fixed threshold irrespective of the type and level of blur. It may not be suitable for images with variations in imaging conditions and blur. In this paper we propose an effective method based on local binary pattern with adaptive threshold for blur detection. The adaptive threshold is computed based on the model learned through the multinomial logistic regression. The performance of the proposed method is evaluated using different datasets. The comparative analysis not only demonstrates the effectiveness of the proposed method but also exhibits it superiority over the existing methods.

• ETRI Journal
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• 제26권3호
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• pp.269-272
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• 2004

We propose an efficient scheme for camera motion characterization in MPEG-compressed video. The proposed scheme detects six types of basic camera motions through threshold-based qualitative interpretation, in which fixed thresholds are applied to motion model parameters estimated from MPEG motion vectors (MVs). The efficiency and robustness of the scheme are validated by the experiment with real compressed video sequences.

• 대한전기학회논문지
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• 제35권7호
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• pp.278-284
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• 1986

Double-diffused metal oxide power semiconductor field effect transistors are used extensively in recent years in various circuit applications. The temperature variation of the drain current at a fixed bias shows both positive and negative resistance characteristics depending on the gate threshold voltage and gate-to source bias votage. In this paper, the decision method of the gate crossover voltage by the temperature variation and a new method to determine the gate threshold voltage graphecally are presented.