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디지털 보청기 사용자를 위한 압신 알고리즘의 성능 연구
황윤수,한종희,지윤상,홍성화,이상민,김동욱,김인영,김선일,Hwang, Y.S.,Han, J.H.,Ji, Y.S.,Hong, S.H.,Lee, S.M.,Kim, D.W.,Kim, In-Young,Kim, Sun-I. 대한의용생체공학회 2011 의공학회지 Vol.32 No.3
Companding algorithms have been used to enhance speech recognition in noise for cochlea implant users. The efficiency of using companding for digital hearing aid users is not yet validated. The purpose of this study is to evaluate the performance of the companding for digital hearing aid users in the various hearing loss cases. Using HeLPS, a hearing loss simulator, two different sensorinerual hearing loss conditions were simulated; mild gently sloping hearing loss(HL1) and moderate to steeply sloping hearing loss(HL2). In addition, a non-linear compression was simulated to compensate for hearing loss using national acoustic laboratories-non-linear version 1(NAL-NL1) in HeLPS. In companding, the following four different companding strategies were used changing Q values(q1, q2) of pre-filter(F filter) and post filter(G filter). Firstly, five IEEE sentences which were presented with speech-shaped noise at different SNRs(0, 5, 10, 15 dB) were processed by the companding. Secondly, the processed signals were applied to HeLPS. For comparison, signals which were not processed by companding were also applied to HeLPS. For the processed signals, log-likelihood ratio(LLR) and cepstral distance(CEP) were measured for evaluation of speech quality. Also, fourteen normal hearing listeners performed speech reception threshold(SRT) test for evaluation of speech intelligibility. As a result of this study, the processed signals with the companding and NAL-NL1 have performed better than that with only NAL-NL1 in the sensorineural hearing loss conditions. Moreover, the higher ratio of Q values showed better scores in LLR and CEP. In the SRT test, the processed signals with companding(SRT = -13.33 dB SPL) showed significantly better speech perception in noise than those processed using only NAL-NL1(SRT = -11.56 dB SPL).
용융탄산염 연료전지용 in-situ 소결된 Ni-Al 합금 연료극 개발
천현아,윤성필,한종희,남석우,임태훈,Chun, H.A.,Yoon, S.P.,Han, J.,Nam, S.W.,Lim, T.H. 한국전기화학회 2006 한국전기화학회지 Vol.9 No.3
기존의 용융탄산염 연료전지용 연료극인 Ni-Cr전극은 제조과정이 복잡하며, 운전조건에서 전극의 소결과 creep현상으로 인하여 전극의 기공률과 두께가 감소하는 문제점이 있어 상용화에 걸림돌이 되고 있다. 이에 본 연구에서는 Ni-Cr계 전극보다 creep저항성이 우수하다고 알려져 있는 Ni-Al계 합금을 사용하였다. 또한 공정의 단순화로 비용을 절감시키기 위해, 소성과정을 제외하고 tape casting과 건조과정을 거친 green sheet를 단위전지에 장착하여 전처리 과정 중에 소결시키는 in-situ 소결법에 대해 연구하였다. 그러나 기존의 전처리 방법을 이용한 단위전지 평가에서 Ni-Al 합금의 상분리 현상으로 인해 기대하였던 creep저항성 향상을 확인하지 못했고, 운전중 Ni-Al합금 연료극에 단위전지의 구성요소인 matrix 기공크기보다 작은 기공(${\leq}0.4{\mu}m$)이 다량 생성되어 전해질 재분배를 일으켜 성능이 하락하는 문제점이 나타났다. 따라서 이러한 문제점을 해결하고자 전처리 조건을 변화시키며 실험을 수행하였다. 그 결과, 비활성 기체인 질소를 일정한 구간에 사용함으로써 기존 전처리에서 발생하였던 Ni-Al 합금의 상분리 현상을 억제할 수 있었으며 이로 인해 creep저항성 또한 향상시킬 수 있었다. 그러나 운전 중 생성되는 matrix기공크기보다 작은 기공(${\leq}0.4{\mu}m$) 형성비율은 억제할 수 없었다. 위의 전처리 조건을 가지고 단위전지 운전실험을 하였고, 전해질 함침비율을 조절함에 따라 성능을 향상시킬 수 있었으며 2000시간 동안 일정하게 유지함을 확인하였다. 이로부터 기존의 소성전극과 비교하여 많은 장점을 가지고 있는 in-situ 소결법의 가능성을 확인할 수 있었다. For commercialization of molten carbonate fuel cell (MCFC), it has some problems to be overcome such as decrease of porosity and thickness of the anode under the operating condition (at $650^{\circ}C$ and working pressure of more than 2 $kg_f/cm^2$). Recently, Ni-Al alloy anode has been proposed to replace the conventional Ni-Cr anode as an alternative material to resist a creep and inhibit the sintering. The objective of this research is to sinter the green sheet of Ni-Al alloy anode during single cell pre-treatment process, which has several advantages like cost down and simplification of manufacturing process. However, the Ni-Al alloy anode prepared with a conventional pre-treatment process showed the phase separation of Ni-Al alloy and formation of micropore(${\leqq}0.4{\mu}m$), resulting in low creep resistance and high electrolyte re-distribution. In order to prevent the Ni-Al alloy anode from phase-separating, nitrogen gas was used in the process of pre-treatment. Introducing the nitrogen, the phase separation from Ni-Al alloy into nickel and alumina was minimized and increased creep resistance. However, there was some micropore formation on the surface of Ni-Al alloy anode during the cell operation due to creation of lithium aluminate. Addition of more amount of electrolyte into a cell, especially at cathode, made the cell performance stable for 2,000 hrs. Consequently, it was possible to make the Ni-Al alloy anode with good creep resistance by the modified in-situ sintering technique.