IEEE 802.11n 무선 랜에서 재전송 프레임 수를 줄이기 위한 향상된 Block ACK 방법

이현웅,김선명,Lee, Hyun-Woong,Kim, Sunmyeng 한국시뮬레이션학회 2014 한국시뮬레이션학회 논문지 Vol.23 No.4

IEEE 802.11n 표준은 네트워크 성능을 향상시키기 위해 MAC과 물리 계층에서 새로운 방법들을 제안하였다. MAC 계층에서 성능 향상을 위해 제안된 주요 방법은 프레임 집적(Frame Aggregation)과 Block ACK이다. IEEE 802.11n 표준에도 여전히 문제점은 존재한다. Block ACK 요청 프레임이나 Block ACK 응답 프레임이 손실되거나 에러가 포함되어 수신되면, 전송 단말은 집적된 큰 프레임에 포함된 작은 프레임들의 성공적인 전송 여부를 알지 못하기 때문에 모든 작은 프레임을 재전송한다. 이는 성공적으로 전송된 프레임도 재전송될 수 있기 때문에 네트워크의 성능 저하를 초래할 수 있다. 이 문제를 해결하기 위해 본 논문에서는 RRM(Reduced Retransmissions of MPDUs) 방법을 제안한다. 제안된 방법에서 송신 단말이 Block ACK 응답을 못 받으면 모든 프레임을 재전송하는 대신에 다음 데이터 프레임 하나를 전송하고 다시 Block ACK를 요청한다. 응답을 받은 후에 에러가 발생한 프레임에 대해서만 재전송을 수행한다. 제안된 방법의 성능을 시뮬레이션을 통해 분석한다. 시뮬레이션 결과, 제안된 방법이 다양한 패킷 에러 환경에서 효과적이고 네트워크 성능을 향상 시키는 것을 보여주었다. IEEE 802.11n standard has introduced the new schemes in MAC and PHY layers to improve network throughput. Frame aggregation and Block ACK are mainly defined to increase the efficiency of the MAC layer. There exists still problem in IEEE 802.11n. When block ACK request and/or response frames are missing or received in error, the sender does not know the status (success/failure) of each frame in the aggregated large frame and retransmits all the frames. This can cause a lower network performance. To solve this problem, we propose a new effective scheme, called reduced retransmission of MPDUs (RRM) scheme. In the proposed scheme, when a sender does not receive a block ACK response frame, it just transmits a next data frame and requests a block ACK. Therefore, it can retransmits the erroneous frames. Performance of the proposed scheme is investigated by simulation. Our results show that the proposed scheme is very effective and improves the performance under a wide range of channel error conditions.

Protection Circuit Module에 최적화된 60 V급 TDMOSFET 최적화 설계에 관한 연구

이현웅,정은식,오름,성만영,Lee, Hyun-Woong,Jung, Eun-Sik,Oh, Reum,Sung, Man-Young 한국전기전자재료학회 2012 전기전자재료학회논문지 Vol.25 No.5

Protected Circuit Module protects battery from over-charge and over-discharge, also prevents accidental explosion. Therefore, power MOSFET is essential to operate as a switch within the module. To reduce power loss of MOSFET, the on state voltage drop should be lowered and the switching time should be shorted. However there is trade-off between the breakdown voltage and the on state voltage drop. The TDMOS can reduce the on state voltage drop. In this paper, effect of design parameter variation on electrical properties of TDMOS, were analyzed by computer simulation. According to the analyzed results, the optimization was performed to get 65% higher breakdown voltage and 17.4% on resistance enhancement.

이온성 액체로켓 연료용 테트라졸리윰 유도체의 합성 및 점화지연시간 및 점도에 대한 연구

이현웅,최성호,Lee, Hyun-Woong,Choi, Seong-Ho 한국군사과학기술학회 2022 한국군사과학기술학회지 Vol.25 No.3

In order to use the liquid rocket fuel, 1,5-diamino-4-methyltetrazolium azide, [DMT]⁺[N₃]^- and 1,5-diamino-4-methyltetrazolium cyanide, [DMT]⁺[CN]^- were synthesized and prepared the ionic liquid rocket fuel after dissolving the synthesized solid-type energetic chemicals in hydrazine, respectively. The thermal decomposition temperatures(T_d) and densities(d) of the prepared ionic liquid rocket fuels were about 200 ℃ and above 1.0 g/cm³ respectively. The ignition delay times(I_dt) of the ionic liqud rock fuels with [DMT]⁺[N₃]^- and [DMT]⁺[CN]^- were in a range of 26.6 - 82.5 ms and the 44.0 - 98.5 ms, respectively. These results mean that the synthesized tetrazolium salts could be used as an ionic liquid rocket fuels. The viscosities of the ionic liqud rock fuels with [DMT]⁺[N₃]^- and [DMT]⁺[CN]^-, which were dissolved in mixture solution of hydrazine/2-hydroxyethylhydrazine were to be 1.34 - 101 cP, and 1.29 - 80.5 cP, respectively. The synthesized ionic liquid rocket fuels in this study could be used as rocket fuel because the [I_dt(100 ms or less), T_d(150 ℃ or more), d(1.00 g/cm³ or more), and η(40.0~ 100 cP)] were achieved to satisfy the range of the used liquid rocket fuels.

간세포암종의 근치적 치료 : 어떤 방법을 선택할 것인가?

이현웅 ( Hyun Woong Lee ) 대한간학회 2021 간질환 연수강좌 Vol.2021 No.1

K-BEMS 기반 섹터 커플링 사업화 모델 제시

이현웅(Hyun-Woong LEE),하영진(Young-Jin Ha) 대한전기학회 2021 대한전기학회 학술대회 논문집 Vol.2021 No.7

Disaster Management and Role of Local Government: Lesson from Hull's Experience

Hyun Woong Lee(李賢雄),Hyun Jae Choi(李賢雄),Jong Eop Kim(金鍾業) 위기관리 이론과 실천 2013 Crisisonomy Vol.9 No.7

최근 들어 글로벌 기후변화와 그 영향으로 이전과는 비교하기 어려운 규모의 자연적 재난이 빈번하게 발생하고 있다. 이러한 자연적 재난의 발생에 효과적으로 대응하기 위해 정부의 계획과 대응이 필요하게 되었다. 2007년 영국은 이전에 보기 어려운 폭우로 인해 홍수 피해를 입었는데, 헐 시티(Hull City)는 그 피해가 가장 극심한 곳 중의 하나였다. 홍수 피해를 입으면서 헐 시티는 새로운 형태와 규모의 이전에 볼 수 없었던 홍수로 인한 자연적 재난에 대비하기 위한 방안을 마련하기 시작했다. 2011년 서울시도 기록적인 폭우로 인해 도시의 일부가 물에 잠기고, 산사태로 큰 피해를 입었다. 본 연구는 헐 시티와 서울시의 폭우로 인한 홍수 피해를 중심으로 지방정부의 재난관리 방안, 특히 홍수 재난 관리에 대한 방안을 도출하였다. 본 연구의 결과는 기후변화로 인해 예측하기 힘든 자연적 재난에 대한 지방정부의 역할과 대응방안에 도움을 줄 수 있을 것이다. In these times of escalating concern over global warming and its effects on weather patterns, as well as the size and frequency of natural disasters, it seems fitting to analyse and discuss how effectively governments are planning for disasters and whether they are responding to them appropriately. During the summerof 2007 the United Kingdom experienced some of the worst flooding in its history, with the city of Hull amongst the worst affected. An examination of the government handling of mitigation measures and disaster response in this instance raises comparisons to the 2011 heavy rain related flooding in Seoul, South Korea. These events are especially appropriate for comparison given the vulnerability of each city and general feeling of dissatisfaction among residents. This paper examines each event individually and presents a comparison of the actions and inactions of each local government. The result is a call for stronger and more decisive measures to combat climate change and protect vulnerable populations more efficiently against natural disasters.

Tenofovir alafenamide and besifovir

이현웅 ( Hyun Woong Lee ) 대한간학회 2017 간학회 싱글토픽 심포지움 Vol.2017 No.1

Besifovir는 국내에서 만들어진 acyclic nucleotide phosphonate로서 간세포내에서 triphosphate로 인산화를 거친 후 바이러스 DNA와 결합하여 바이러스 복제를 억제한다. 임상 시험에서 보여준 besifovir의 효과와 미미한 부작용은 기대가 되는 약제임에는 틀림없다. 그러나, L-carnitine의 보충이 반드시 요구된다는 점과, 내성변이종에 대한 분석이 없으며, 치료기간이 짧은 점은 향후 보완이 필요하다. 또한, TAF는 acyclic nucleoside phosphonate 로서 간세포내로 수송되어 diphosphate로 인산화를 거치는데 이때 생성된 TFV-diphosphate가 바이러스 DNA와 결합하여 바이러스 복제를 억제한다. 비록 치료기간이 짧기는 하지만, 임상 시험에서 보여준 TAF의 효과는 TDF와 유사하며 부작용을 효과적으로 낮추어 향후 TDF를 대체할 약제로 기대를 모으고 있다. Current antiviral therapies have dramatically improved the long-term outcomes of patients with chronic hepatitis B virus (HBV) infection. However, persistent covalently closed circular DNA can result in a viral relapse after discontinuation of antiviral treatment. While effective therapies exist, all have specific limitations, including emergence of drug resistance and certain safety concerns associated with long-term use. Furthermore, lifelong antiviral treatment is necessary for most patients, as few experience seroclearance of hepatitis B surface antigen indicative of cure. Thus, there remains a need for new antiviral therapies that are safe and effective with a high genetic barrier to resistance. Besifovir (LB80380) is a novel and potent acyclic nucleotide phosphonate with a similar chemical structure to adefovir and tenofovir (TDF). In a multicenter-randomized trial, there were no differences in the proportions of patients achieving undetectable HBV DNA, normalization of ALT or HBeAg seroconversion between besifovir and entecavir therapy. Tenofovir alafenamide (TAF) is a prodrug of tenofovir. In an in vitro study, TAF resulted in high levels of the pharmacologically active metabolite tenofovir diphosphate than TDF. In a recent study, whatever the TAF dose, the mean change in serum HBV DNA in patients receiving TAF treatment were similar to those receiving TDF. In addition, TAF has no renal transporter-dependent cytotoxicity, which may result in an improved renal safety profile. Thus, both TAF and besifovir provide effective and safer treatment for CHB patients. we hope to reach the ultimate goal of a cure to HBV in the near future.

말초담관암과 병발한 간의 염증가성종양 1예

이현웅 ( Hyun Woong Lee ),장병국 ( Byoung Kuk Jang ),정우진 ( Woo Jin Chung ),박경식 ( Kyung Sik Park ),조광범 ( Kwang Bum Cho ),황재석 ( Jae Seok Hwang ),강유나 ( Yu Na Kang ),강구정 ( Koo Jeong Kang ),권중혁 ( Jung Hyeok Kwon 대한소화기학회 2006 대한소화기학회지 Vol.48 No.3

Inflammatory pseudotumor is an uncommon mass which develops most frequently in the lung of young adults. It is characterized by localized fibrous proliferations with chronic inflammatory cell infiltration. Due to its rarity and similarity in radiologic appearance with malignant hepatic tumors, hepatic inflammatory pseudotumor (HIPT) is often misdiagnosed and resected accidentally. We report a case of HIPT which was unnecessarily resected due to synchronous small peripheral cholangiocarcinoma located on the other segment of liver. (Korean J Gastroenterol 2006;48:200-204)

간의 국소 염증성 병변

이현웅 ( Hyun Woong Lee ) 대한내과학회 2013 대한내과학회지 Vol.84 No.3

Focal inflammatory lesions are benign lesions of various etiology reported in numerous anatomic sites. Because of the development of imaging study, most of focal inflammatory lesions were noted incidentally without symptom and sign. Among them, eosinophilic liver disease and inflammatory pseudotumor are relatively important diseases and are associated with a variety of other disease such as parasitic infestations, bacterial and viral infection, allergic conditions, autoimmune disease, and internal malignancies. These are largely self-limiting entities and have favorable prognosis. The terminology of eosinophilic liver disease is not strictly defined and a variety of terms, including focal eosinophilic infiltration, eosinophilic abscess, and eosinophilic granuloma exist histologically. Inflammatory pseudotumor was composed of diffuse infiltration of spindle-shaped cells, myofibroblasts, and mixed inflammatory cells (plasma cells, lymphocytes, and histiocytes), microscopically. Focal inflammatory lesions are difficult to differentiate clinically from malignant tumors, because these show variable imaging findings. Thus, it is important to preoperatively distinguish these lesions from malignancy. Meticulous liver biopsy is frequently needed to make differential diagnosis from malignant tumors and to avoid unnecessary resection.(Korean J Med 2013;84:333-340)

2009년 미국간학회 하이라이트 : C형간염 치료 관련 분야

이현웅 ( Hyun Woong Lee ) 대한간학회 2009 Clinical and Molecular Hepatology(대한간학회지) Vol.15 No.4