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K-SVD 기반 사전 훈련과 비음수 행렬 분해 기법을 이용한 중첩음향이벤트 검출
최현식,금민석,고한석,Choi, Hyeonsik,Keum, Minseok,Ko, Hanseok 한국음향학회 2015 韓國音響學會誌 Vol.34 No.3
비음수 행렬 분해(Nonnegative Matrix Factorization, NMF) 기법은 사전행렬과 크기성분을 번갈아 가며 업데이트 하면서 구하는 방법이며 직관적 해석 및 구현의 용이성으로 인해 중첩음향이벤트 분리 및 검출방법으로 널리 활용되었다. 하지만 비음수 행렬 분해의 고유한 특성인 부분기반표현(part-based representation)으로 인해 하나의 음향 이벤트를 구성 하는 사전(dictionary)의 파편화 현상이 발생하고, 다른 음향이벤트와 중복되는 사전이 생성되어 결과적으로 분리, 검출 성능의 저하 문제가 발생한다. 본 논문에서는 사전 획득 단계의 부분기반표현에 의한 문제를 해소하기 위해 K-Singular Value Decomposition(K-SVD)을 사용하여 사전을 획득하고, 음향이벤트 검출 단계 에서는 기존 비음수 행렬 분해 기법을 이용하여 크기를 획득 한다. 제안하는 방식을 통해 비음수 행렬 분해 기반의 사전을 사용하는 경우보다 중첩음향이벤트 검출 성능이 개선되는 것을 확인하였다. Non-Negative Matrix Factorization (NMF) is a method for updating dictionary and gain in alternating manner. Due to ease of implementation and intuitive interpretation, NMF is widely used to detect and separate overlapping sound events. However, NMF that utilizes non-negativity constraints generates parts-based representation and this distinct property leads to a dictionary containing fragmented acoustic events. As a result, the presence of shared basis results in performance degradation in both separation and detection tasks of overlapping sound events. In this paper, we propose a new method that utilizes K-Singular Value Decomposition (K-SVD) based dictionary to address and mitigate the part-based representation issue during the dictionary learning step. Subsequently, we calculate the gain using NMF in sound event detection step. We evaluate and confirm that overlapping sound event detection performance of the proposed method is better than the conventional method that utilizes NMF based dictionary.
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높은 수율의 임계값 스위칭 특성을 위한 CMOS 호환 전극을 갖는 NbO<SUB>x</SUB> 층에서 산화물 장벽의 역할
최현식(Hyeonsik Choi),김윤서(Yunsur Kim),박형진(Hyoungjin Park),정지애(Jiae Jeong),우지용(Jiyong Woo) 대한전자공학회 2023 대한전자공학회 학술대회 Vol.2023 No.11
This study shows how the threshold switching (TS) characteristics of a NbOx layer with noninert W electrodes can be improved by introducing an oxide barrier. The ~10-nm-thick NbOx layer exhibits TS, which is known to originate from NbO₂, after electroforming. However, through X-ray photoelectron spectroscopy, a Nb₂O<SUB>5</SUB> layer, which is known to cause resistive memory switching, is formed mainly at the top interface as well. This results in a worsening TS yield. Therefore, thin oxides were introduced to improve the TS behavior and systematically investigate the role of the oxide barrier by considering their location and material properties. The barrier inserted at the bottom interface makes the formation of NbO₂ difficult, preventing TS. When the barrier was introduced at the top interface, the unwanted Nb₂O<SUB>5</SUB> created through reaction with the W electrode can be mitigated, promoting the occurrence of TS. Note that when an AL₂O₃ (or HfO₂) barrier is used, which prefers to scavenge (or provide) oxygen from (or to) the NbOx, a dielectric (or weak TS) behavior is shown. As a result, excellent cell-to-cell uniformity of the TS is achieved in the ZrO₂/NbOx stack, which not only prevents the formation of Nb₂O<SUB>5</SUB> but also stabilizes the NbO₂ in the NbOx layer. Through examining the temperature dependence of the TS obtained from the W/NbOx/W and W/ZrO₂/NbOx/W stacks, it was found that the suppression of the Nb₂O<SUB>5</SUB> at the top interface is indirectly shown as a strengthened Schottky barrier from an electrical measurement perspective.
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