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H.264의 인트라 프레임을 위한 하이브리드 에러 은닉 알고리즘
임창훈,김원정,임혜숙,Yim Chang-Hoon,Kim Won-Jung,Lim Hye-Sook 한국통신학회 2006 韓國通信學會論文誌 Vol.31 No.8C
H.264는 향상된 압축 성능과 에러 복구 기술, 네트워크로의 적응력을 포함하고 있는 비디오 압축 표준으로, 실시간 비디오 스트리밍, 디지털 멀티미디어 방송 등의 여러 분야에서 적용되고 있다. 인터넷 상으로 비디오를 전송할 경우 압축된 비디오 스트림은 패킷 손실에 약하므로 에러 복구 기술과 에러 은닉 기술은 필수적인 요소이다. 본 논문은 먼저 움직임이 상대적으로 적을 경우 H.264의 인트라 프레임을 위한 에러 은닉 성능을 향상시킬 수 있는 간단한 시간방향 에러 은닉 방법을 제안한다. 그리고 제안된 시간방향 에러 은닉 방식과 H.264의 인트라 프레임을 위해서 사용하고 있는 공간방향 에러 은닉 방식을 적응적으로 결합한, H.264의 인트라 프레임을 위한 하이브리드 에러 은닉 방법을 제안한다. 패킷이 손실되는 환경에서 시뮬레이션을 했을 때, 제안된 하이브리드 에러은닉 방법은 H.264의 인트라 프레임에 사용되는 기존의 공간방향 에러 은닉 방법에 비하여, 약 0.5-4dB 정도의 PSNR 성능 향상을 보인다. H.264 is the prominent video coding standard in various applications such as real-time video streaming and digital multimedia broadcasting, since it provides enhanced compression performance, error resilience tools, and network adaptation. Since compressed video stream is vulnerable to packet loss, error resilience and error concealment(EC) tools are essential for the transmission of video over the Internet. In this paper, we first propose a simple temporal EC method that improves the EC performance for intra-frame in H.264 when the amount of motion is relatively small. Then we propose a new hybrid EC method for intra-frame in H.264, which combines the spatial EC and temporal EC adaptively. The simulations are performed in packet-lossy environments, and the proposed hybrid EC method shows about 0.5-4dB PSNR improvement compared to the conventional spatial EC method that is used for intra-frame in H.264.
초내열합금분말에 의한 PTA 오버레이부의 연삭 마모 특성 연구
김영식,최영국,임창훈,김종도,Kim, Young-Sik,Choi, Young-Gook,Lim, Chang-Hoon,Kim, Jong-Do 대한용접접합학회 2009 대한용접·접합학회지 Vol.27 No.3
The Plasma Transferred Arc (PTA) overlay welding method is lately introduced as one of the most useful surface overlay method of the engine component. In this paper, the overlay welding on the SNCrW heat resisting alloy was conducted by the PTA overlay welding process using the super alloy powder. The characteristics of the overlay layers were investigated through the metallurgical and abrasive test. Experimental results showed that the overlay on the SNCrW heat resisting alloy surface was successfully made without hot cracking. The friction wear characteristics of the Co-base Stellite 6 overlayer were most superior. However the abrasive wear characteristics were most inferior in the Co-base Stellite 6 overlayer.
패킷 손실이 발생하는 네트워크 환경에서의 H.264의 FMO 성능분석과 비교에 관한 연구
김원정,임혜숙,임창훈,Kim Won-Jung,Lim Hye-Sook,Yim Chang-Hoon 한국통신학회 2006 韓國通信學會論文誌 Vol.31 No.5C
H.264 is the most recent video coding standard, containing improved error resilience tools than previous video compression schemes. This paper shows an analysis of the dependency of error concealment (EC) performance on the expected number of correctly received neighboring macroblock(MB)s for a lost MB, applying error concealment schemes to the raster scan mode that is used in the previous video coding standard and the flexible macroblock ordering (FMO) which is one of error-resilience tools in H.264. We also present simulation results and performance evaluation with various packet loss rates. Simulation results show that the FMO mode provides better EC performances of $1{\sim}9dB$ PSNR improvements compared to the raster scan mode because of larger expected number of correctly received neighboring MBs. The PSNR improvement by FMO mode becomes higher as the intra-frame period is larger and the packet loss rate is higher. H.264는 현재 IP를 기반으로 하는 유무선 네트워크분야에서 많은 관심을 받고 있는 표준으로서 기존에 제정된 비디오 표준들보다 향상된 에러 복구 기술들을 포함하고 있다. 본 논문에서는 기존의 비디오 표준에서 사용되어 오던 raster scan 방식과 H.264의 에러 복구 기술들 중 하나인 FMO (flexible macroblock ordering) 방식에 에러 은닉 기술을 적용하여 에러 은닉의 성능이 정확히 온 인접한 매크로블락 수에 따라 좌우됨을 분석하고, 다양한 패킷 손실율에서의 성능을 보인다. 시뮬레이션 결과, FMO 방식이 raster scan 방식에 비해 손실없이 오는 인접한 매크로블락 수가 많아 에러 은닉에 의한 PSNR 성능이 $1{\sim}9dB$ 정도 향상되고, 특히 인트라 프레임 간격이 길고 패킷 손실율이 높은 경우에 FMO 방식에 의한 PSNR 성능 향상이 더 크다.
박철홍 ( Cheol Hong Park ),임창훈 ( Chang Hoon Lim ),장형진 ( Hyoung Jin Chang ),손상원 ( Sang Won Son ),정성진 ( Sung Jin Jung ),박철휘 ( Cheol Whee Park ),장윤식 ( Yoon Sik Chang ) 대한신장학회 2008 Kidney Research and Clinical Practice Vol.27 No.2
A 46-year-old woman with chronic renal failure due to polyarteritis nodosa was referred to the hospital for evaluation of abdominal pain. She had been treated with cathartics (magnesium oxidate 2.0 g/day) for constipation for several days. One day before the admission, the patient had been taken magnesium enema twice at another hospital. On admission, she was comatose, suffering from lethargy and respiratory failure. Her serum magnesium and amylase concentrations were markedly elevated (8.2 mg/dL and 1,698 IU/L respectively), and plain abdominal image and abdominal computed tomography revealed acute pancreatitis and non-obstuctive ileus. Thereafter, aggressive cardiopulomonary support with mechanical ventilation and continuous renal replacement therapy using continuous veno-venous hemofiltration (CVVH) applied due to cardio-respiratory failure and hypermagnesemia. After 3 days of CVVH treatment, the concentration of serum magnesium was normalized to 3.2 mg/dL, and respiratory failure and abdominal ileus were markedly improved. Four days after aggressive treatment, her hemodynamic and gastroenteric symptoms stabilized. Therefore, we report the case of hypermagnesemia with acute pancreatitis, severe hypotension and respiratory failure after cathartic ingestion and enema containing magnesium oxidate treated with CVVH.
소아 천식 환자에서 호기산화질소 농도와 노력성중간호기유량과의 관계
임현욱 ( Hyun Wook Lim ),김은지 ( Eun Ji Kim ),임창훈 ( Chang Hoon Lim ),박상희 ( Sang Hee Park ),정지태 ( Ji Tae Choung ),유영 ( Young Yoo ) 대한천식알레르기학회 2016 Allergy Asthma & Respiratory Disease Vol.4 No.1
Purpose: Fractional exhaled nitric oxide (FeNO) is considered an indirect marker of airway inflammation, and forced expiratory flow between 25% and 75% of vital capacity (FEF_(25%?75%)) is widely used as a sensitive indicator of small airway obstruction in asthma. The aim of this study was to investigate relationships between FeNO and FEF_(25%?75%) in children with asthma. Methods: A total of 118 children with asthma underwent spirometry and measurement of eosinophil markers. FeNO levels were measured, and skin prick tests to 13 common allergens were done. Study subjects were divided into 2 groups according to FEF_(25%?75%) values (group 1, normal FEF_(25%?75%)≥65%pred, n=90; group 2, impaired FEF_(25%?75%)<65%pred, n=28). Results: The mean (±standard deviation, SD) age was not significantly different between groups 1 and 2 (10.3±2.8 years vs. 11.1±3.4 years), and the sex ratio was also not significantly different between 2 groups. The geometric mean (range of 1 SD) concentration of FeNO was significantly higher in group 2 than in group 1 (25.8 ppb [14.2?46.9 ppb] vs. 37.2 ppb [24.2?57.2 ppb], P=0.008). A significant inverse correlation between FeNO and FEF_(25%?75%) was observed in group 2 (r=?0.493, P=0.038), but not in group 1 (r=?0.037, P=0.749) after adjustment for confounders, such as atopy, age, sex, weight, and height. Conclusion: FeNO levels were higher in group of asthmatic children with impaired FEF_(25%?75%) level. FeNO levels were inversely correlated with FEF_(25%?75%) only in impaired small-airway obstruction group after adjustment for atopy. These results suggest that small-airway obstruction may relate more closely to airway inflammation in asthmatic children with impaired small-airway function.
Rituximab으로 치료한 불응성 특발성혈소판감소성자반증
서석민 ( Suk Min Seo ),임창훈 ( Chang Hoon Lim ),최선욱 ( Son Ook Choi ),김희제 ( Hee Je Kim ),이종욱 ( Jong Wook Lee ),민우성 ( Woo Sung Min ),김춘추 ( Chun Choo Kim ) 대한내과학회 2005 대한내과학회지 Vol.69 No.-
Idiopathic thrombocytopenic purpura (ITP) is an immune disorder in which platelets are opsonized by autoantibodies and prematurely destroyed by the reticuloendothelial system. Among adult patients, approximately 25~30% develop a chronic disease that will become refractory to corticosteroids and splenectomy, as well as other available agents. Rituximab is a human-murine chimeric monoclonal antibody specific for the CD20 antigen, found on the surface of B lymphocytes. It acts via complement-dependent cytotoxicity, antibody-dependent cellular cytotoxicity, and induction of apoptosis. We report a case of 32-year-old female with severe, refractory ITP, who presented with generalized petechiae, intractable vaginal bleeding, and pulmonary hemorrhage. After multiple conventional therapeutic trials, the patient was finally placed on weekly infusion of rituximab that resulted in a favorable response. (Korean J Med 69:S934-S938, 2005)