• Journal of Communications and Networks
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• 제18권3호
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• pp.299-310
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• 2016

In practical wireless relay communication systems, non-destination nodes are assumed to be idle not receiving signals while the relay sends messages to a particular destination node, which results in reduced bandwidth efficiency. To improve the bandwidth efficiency, we relax the idle assumption of non-destination nodes and assume that non-destination nodes may receive signals from sources. We note that the message relayed to a particular node in such a system gives rise to interference to other nodes. To study such a more general relay system, we consider, in this paper, a relay system in which the relay first listens to the source, then routes the source message to the destination, and finally produces interference to the destination in sending messages for other systems. We obtain capacity upper and lower bounds and study the optimal method to deal with the interference as well as the optimal routing schemes. From analytic results obtained, we find the conditions on which the direct transmission provides higher transmission rate. Next, we find the conditions, by numerical evaluation of the theoretical results, on which it is better for the destination to cancel and decode the interference. Also we find the optimal source power allocation scheme that achieves the lower bound depending on various channel conditions. We believe that the results provided in this paper will provide useful insights to system designers in strategically choosing the optimal routing algorithms depending on the channel conditions.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2016년도 추계학술대회
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• pp.382-383
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• 2016

영상의 캐니 에지 검출은 영상의 가우시안 필터, 기울기(gradient)의 계산, 비최대억제법(Non-maximum suppression), 그리고 이력 임계값(Hypothesis Thresholding)의 4가지로 구성된다. 특징은 에지 영상에서 얻어진 차체, 창문들, 그리고 바퀴들 사이의 비율이 된다. 차량의 이러한 특징이 되는 비율들은 차종마다 각기 다르다. 우리는 여기서 소형 차량에만 본 알고리즘을 적용하여 식별하였다.

• Structural Engineering and Mechanics
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• 제77권3호
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• pp.355-368
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• 2021

The time-varying mean (TVM) component of non-stationary wind speeds is commonly extracted utilizing empirical mode decomposition (EMD) in practice, whereas the accuracy of the extracted TVM is difficult to be quantified. To deal with this problem, this paper proposes an approach to identify and extract the optimal TVM from several TVM results obtained by the EMD. It is suggested that the optimal TVM of a 10-min time history of wind speeds should meet both the following conditions: (1) the probability density function (PDF) of fluctuating wind component agrees well with the modified Gaussian function (MGF). At this stage, a coefficient p is newly defined as an evaluation index to quantify the correlation between PDF and MGF. The smaller the p is, the better the derived TVM is; (2) the number of local maxima of obtained optimal TVM within a 10-min time interval is less than 6. The proposed approach is validated by a numerical example, and it is also adopted to extract the optimal TVM from the field measurement records of wind speeds collected during a sandstorm event.

• 한국통신학회논문지
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• 제31권3C
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• pp.237-244
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• 2006

본 논문에서는 2차원 결합 가우시안 Q-함수(Two-dimensional joint Gaussian Q-function)를 이용하여 AWGN(Additive White Gaussian Noise) 환경에서 M-PSK(M-ary Phase Shift Keying) 신호의 I/Q 위상 불균형(Phase unbalance) 존재 시 수치 적분이 필요 없는 정확하고 일반화된 closed-form 형태의 비트 오류율(Bit Error Rate) 표현을 유도한다. 새롭게 유도된 표현은 평균 BER 뿐만 아니라 k-번째 비트의 BER에 대하여도 일반화된 식으로 되어 있어 다양한 환경으로의 적용이 용이하여 M-PSK를 적용하는 많은 디지털 통신 시스템에서 복조 시 발생할 수 있는 I/Q 위상 불균형에 의한 시스템 성능 변화에 대하여 정확한 이론적 성능 기준을 제공할 것으로 기대된다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제12권1호
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• pp.755-767
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• 2020

A significant development has been made on a new fatigue damage model applicable to Gaussian wide band stress response spectra using numerical approximation methods such as data processing, time simulation, and regression analysis. So far, most of the alternative approximate models provide slightly underestimated or overestimated damage results compared with the rain-flow counting distribution. A more reliable approximate model that can minimize the damage differences between exact and approximate solutions is required for the practical design of ships and offshore structures. The present paper provides a detailed description of the development process of a new fatigue damage model. Based on the principle of the Gaussian wide band model, this study aims to develop the best approximate fatigue damage model. To obtain highly accurate damage distributions, this study deals with some prominent research findings, i.e., the moment of rain-flow range distribution MRR(n), the special bandwidth parameter μk, the empirical closed form model consisting of four probability density functions, and the correction factor QC. Sequential prerequisite data processes, such as creation of various stress spectra, extraction of stress time history, and the rain-flow counting stress process, are conducted so that these research findings provide much better results. Through comparison studies, the proposed model shows more reliable and accurate damage distributions, very close to those of the rain-flow counting solution. Several significant achievements and findings obtained from this study are suggested. Further work is needed to apply the new developed model to crack growth prediction under a random stress process in view of the engineering critical assessment of offshore structures. The present developed formulation and procedure also need to be extended to non-Gaussian wide band processes.

• Wind and Structures
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• 제9권6호
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• pp.457-471
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• 2006

This paper is devoted to the non linear quasi-steady aerodynamic loading. A linear approximation is often used to compute the response of structures to buffeting forces. Some researchers have however shown that it is possible to account for the non linearity of this loading. This non linearity can come (i) from the squared velocity or (ii) from the shape of the aerodynamic coefficients (as functions of the wind angle of attack). In this paper, it is shown that this second origin can have significant implications on the design of the structure, particularly when the non linearity of the aerodynamic coefficient is important or when the transverse turbulence is important.

• Journal of the Korean Statistical Society
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• 제29권1호
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• pp.9-16
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• 2000

This article addresses the problem of maximum likelihood estimation in ARCH regression with lagged dependent variables. Some topics in asymptotics of the model such as uniform expansion of likelihood function and construction of a class of MLE are discussed, and the regularity property of MLE is obtained. The error process here is possibly non-Gaussian.

• 한국통신학회:학술대회논문집
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• 한국통신학회 2006년도 하계종합학술발표회 논문 초록집
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• pp.587-587
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• 2006

• 대한자기공명의과학회:학술대회논문집
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• 대한자기공명의과학회 2003년도 제8차 학술대회 초록집
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• pp.75-75
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• 2003

목적： MR 영상에 나타나는 bias field, 즉 영상의 특정 부분이 주위보다 어둡거나 밝게 나타나는 현상을 보다 균일하게 보정시키는 방법으로 제시된 N3 방법에서 Gaussian kernel을 사용한 smoothing 방법 대신에 Wavelet(Daubechies, D4)함수를 smoothing기법으로 사용했을 때 어느 정도 균일함에 향상이 일어나는지를 알아보는 것이다.

• 방송공학회논문지
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• 제19권2호
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• pp.195-204
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• 2014

이 논문에서는 순환정상 프로세스의 고차 통계 특성을 바탕으로 2-FSK, 4-FSK, 8-FSK, MSK, BPSK, QPSK, 8-PSK, 16-QAM, 32-QAM, 64-QAM 등 10개의 기저대역 디지털 변조신호를 자동으로 인식하는 방법을 제안하였다. 변조신호의 고유한 성질을 나타내는 특징변수로는 1차 순환 모멘트와 고차 순환 큐뮬런트를 이용하였다. 제안한 변조인식기는 크게 두 단계로 구성되며, 첫 번째 단계에서는 1차 순환 모멘트가 나타내는 첨두치를 이용하여 M-FSK와 비FSK로 변조신호를 분류한다. 두 번째 단계에서는 비FSK를 분류하기 위해 고차 순환 큐뮬런트 값을 이용하는 Gaussian 혼합 모델 기반의 분류기를 적용하였다. 제안한 방법의 성능을 검증하기 위해서 모의실험을 실시하였다. 모의실험 결과 제안한 분류기는 주파수와 위상 옵셋이 존재하는 환경에서도 우수한 분류확률을 나타내었다.