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1/3-옥타브 대역통과필터를 이용한 음상정위기법 성능 향상
황신,양진우,정완섭,김순협,Hwang, Shin,Yang, Jin-Woo,Cheung, Wan-Sup,Kim, Soon-Hyob 한국음향학회 2001 韓國音響學會誌 Vol.20 No.3
인간의 청각기관은 소리의 방향과 거리인지에 있어서 여러 가지의 정보들을 복합적으로 이용한다. 이러한 양 귀에 들어오는 소리세기의 차이, 위상의 차이, 그리고 주파수 스펙트럼의 차이 등의 정보들을 종합적으로 포함하고 있는 것이 머리전달함수이다. 본 논문에서는 이 머리전달함수를 이용한 3차원 음상정위를 위해 사람의 청각기관에 알맞은 1/3-옥타브 대역통과필터를 이용한 알고리즘을 제안한다. 먼저 측정된 머리전달함수의 음색왜곡 및 음질저하를 최소화하기 위해 1/3-옥타브 대역통과필터를 이용해 간략화시켰으며, 간략화된 데이터베이스를 크기와 시간의 부분으로 나누어 모듈을 구성하였다. 이의 성능평가를 위해 객관평가와 주관평가를 실시하였으며, 실험결과 85.7%정도의 음상정위의 성능 개선을 가져왔다. The binaural auditory system of human has the capability of differentiating the direction and distance of sound sources. This feature is well characterised in terms of the inter-aural intensity difference (IID), the inter-aural time difference (ITD) and/or the spectral shape difference (SSD) arising from the acoustic transfer of a sound source to the outer ears. This paper proposes an effective way of extracting the three sound perception factors (IID, ITD, SSD) from the head-related transfer functions (HRTF's) that depends on the direction and distance of the acoustic source from the listener. It includes the estimation method of the equivalent ITD and 1/3-octave band-based IID factors and their usage to locate a sound source in space. Subjective and objective tests were carried out to examine the effectiveness of the proposed methodology and its applicability to real sound systems. Those experimental results are illustrated in this paper.
Shin Hwang(황신),Sung-Gyu Lee(이승규),Dong-Hwan Jung(정동환),Ki-Hum Kim(김기훈),Tae-Yong Ha(하태용),Gi-Won Song(송기원) 한국간담췌외과학회 2009 한국간담췌외과학회지 Vol.13 No.1
Hepatitis B virus (HBV)-induced FHF fulminant hepatic failure (FHF) has been a main indication for urgent liver transplantation (LT), and these patients with hepatitis B virus (HBV)-induced FHF have a UNOS status of I. However, HBV-associated FHF has been downgraded to status IIa since late 2007 to eliminate the possibility of confusion between FHF and subacute / acute-orchronic liver failure. This current study evaluated the influence of this change of the UNOS status on organ allocation by using 4 sets of data (a single-institution study without LT cases, a singleinstitution study that included LT cases, a single-institution LT study and the nation-wide LT data). During the 12-year experience at Severance Hospital, HBV infection made up 30% of the 60 FHF patients. For the FHF patients, only 28.3% survived without LT. During the 6-year experience at Asan Medical Center, HBV infection made up 15.8% of the 114 FHF patients. Fifteen percent survived without LT, but 86% survived after LT. Only 1 out of the 14 cases of LT was deceased-donor LT. During the 2-year study on urgent LT at Asan Medical Center, there were 578 LT cases, including 520 living-donor LT and 58 deceased-donor LT. Of them, 120 patients (21.7%) had a UNOS status of I or IIa. The patients with HBV made up 17.8% of the status I patients and 80.3% of the status IIa patients. The one-year patient survival was 83.2% following living-donor LT and this was 71.1% following deceased-donor LT. For the nation-wide data for 8 years, 245 patients were allocated for a deceased-donor liver graft as status I (n=85) or IIa (n=160). Of them, 231 grafts were actually implanted. It was estimated that there is a 2.9- times difference in the probability for organ allocation between UNOS status I and IIa. In conclusion, down-grading of HBV-associated FHF from UNOS status I to status IIa would result in a significantly decreased probability to receive deceased-donor liver grafts. Therefore, it is concluded that such down-grading seems to involve unreasonable discrimination, leading to a disadvantage for patients with HBV-associated FHF. To avoid such dilemma for deceased organ allocation, Korea should consider adopting the model for end-stage liver disease (MELD).