인터넷 캐쉬를 위한 멀티미디어 데이터의 재배치 정책

홍현옥,임은지,박성호 동의공업대학 2000 論文集 Vol.26 No.1

Through the dramatic growth of Internet, it becomes easy for people to access geographically distributed vast amounts of information. But, currently Internet is suffering from problems such as server overload, network congestion and client response time. In addition, currently the number of continuous media data such as audio and video is growing rapidly. In this paper, we propose SCU(Smallest Caching Utility) proxy caching scheme that stores a portion of continuous media stream or entire stream on the Internet. The proposed scheme reduces client latency and maximizes the amount of data served directly from cache without accessing the central server. By caching the initial fraction of stream data, service startup latency can be reduced. And, by varying the size of the fraction of stream to be cached according to variation of stream popularity, we can utilize the cache space efficiently and maximize the amounts of data served directly from cache. We use the caching utility formula of each stream for the measurement of cache replacement. The way to measure popularity of continuous media stream should be different from that of traditional data such as text and image. We propose the method of measuring popularity of stream using the amounts of data played by clients. We have performed simulations to evaluate our caching policy, Simulation results show that our caching policy outperforms other caching algorithms such as LRU, LFU and SIZE in aspects of BHR(byte hit ratio), initial latency and replacement overhead.

주폐자충 폐렴으로 발현된 Felty 증후군 1예

김성호,남대근,문재현,김지홍,김보석,안진광,문태건,안병재,김성일 全南大醫大 2001 전남의대학술지 Vol.37 No.3

노인 입원 환자의 질병 양상과 의료이용 실태

김현주,홍성철,이상이,김명주,황승욱 대한노인병학회 2003 대한노인병학회지 Vol.7 No.4

제주도 고등학교 학생들의 비만 유병률과 심혈과 위험인자

황승욱,김현주,홍성철,이상이 제주대학교 생명과학연구소 2002 제주생명과학연구 Vol.5 No.6

연구배경 : 최근 청소년 연령층의 비만이 급격히 증가하고 있으며, 비만 청소년들에 있어서 고혈압, 당뇨, 고지혈증이 조기에 발현될 뿐 아니라 성인비만과 성인병 발생의 주 원인이 되고 있다. 본 연구는 제주도내 고등학생들의 비만 유병률과 청소년 비만과 심혈간 위험인자인 혈압, 총콜레스테롤, 공복시혈당의 관련성을 알아보고 소아비만과 청소년 비만의 관련성을 조사하였다. 방법 : 연구대상은 제주도내 22개 고등학생 1학년 6,064명을 대상으로 하였고. 체격조사는1999년도 학교 신체검사 자료와 병원 건강검진 자료를 이용하였다. 비만에 대한 평가는 대한소아과학회에서 발행한 1998년도 한국소아표준치와 체질량 지수 두가지를 이용하였다 심혈관 위험인자로는 총콜레스테롤 수축기 혈압, 이완기혈압 공복시 혈당으로 하였으며, 배상자중 646명에 대해 과거 건강기록부를 열람하여 초등학생 때의 비만실태를 조사하였다. 결과 : 제주도 고등학생의 비만 유병률은 표준체중에 의한 비만 산출법으로는 남, 여학생 각각 12.6%, 13.3%이었고 체질량 지수에 의한 비만 위험군 및 비만 학생이 남, 녀 각각 12.7%, 13.4%로 나타났다. 지역에 따른 비만 유병률은 남학생의 경우 시 지역 12.9%, 군 지역 10.3%로 시 시역에서 비만 유병률이 유의하게 높았으며, 여학생의 경우 시·군지역 각각 12.9%, 14.2%이었으나 통계적 유의성은 없었다. 고등하교 계열에 따른 비만 유병률은 남학생의 경우 인문계 13.9%, 실업계 10.1%로 인문계가 유의하게 높았으나, 여학생의 경우는 통계적 유의성은 없었다. 비만 정도에 따른 심혈관 위험인자와의 관련성에서 남학생의 경우 수축기와 이완기혈압, 공복시혈당, 총콜레스테롤 수치가 비만 정도에 따라 유의한 차이를 보였으며(P<0.05), 여학생의 경우 공복시혈당을 제외한 나머지 변수에서 유의한 차이를 보였다. 체질량지수와 심혈간 위험인자간의 상관관계에서 남학생은 혈압, 공복시혈당 총콜레스테롤이 유의한 양의 상관관계를 보였으며, 여학생의 경우 공복시혈당 외에 다른 수치에서 유의한 양의 상관관계를 보였다. 연구대상자 중 646명에 대해 초등학교 1학넌 때의 비만실태를 추적한 결과 초등학생 비만이 고등학생 비만에 미치는 비교위험도가 남녀 각각 3.77, 2.16으로 유의하게 나타났다(P<0.05). 결론 : 제주도지역 고등학생들의 비만 유병률이 상당히 높게 나타났고, 청소년 비만과 심혈관 위험인자간의 관련성을 알 수 있었다. 또한 소아비만이 청소년 비만으로 상당수 이행되었으므로 소아 및 청소년기에 적절한 비만관리 프로그램이 요구된다. Background: Recently, adolescent obesity was increased and tended to become obese adults, facing increased risk for diabetes, cardiovascular disease. Even vefore reaching adulthood, adolescent, obesity already was experiencing hypertension, dyslipidemia, and diabetes mellitus. The purpose of this study was to find prevalence of obesity of high school students in Jeju island and association between obesity and cardiovascular risk factors and association between childhood obesity and adolescent obesity. Method: The study subjects were 6,064 students of twenty-two high school in Jeju island and health survey data was gathered from high school health examination data and hospital health examination data from Aug. 1999 to Dec. 1999. Adolescent obesity was evaluated by ideal body weight method in 1998 and body mass index. Cardiovascular risk factors were checked total cholesterol, systolic and diastolic blood pressure, fasting blood sugar. In 646 students, obesity at primary school is checked by primary school health record. Results: Prevalence of obesity in Jeju island high school students was 12.6% in male students, 13.3% in female students by ideal body weight method and Prevalence of obesity risk and obesity was 12.7% in male students, 13.4% in female student by body mass index. Prevalence of obesity of male students in city area and district area of Jeju island were each 12.9%, 10.3% and that of male students in city area was significantly higher. Prevalence of obesity of female students in city area and district area of Jeju island were each 12.9%, 10.3% and that of male students in city area was significantly higher. Prevalence of obesity of female students in city area and district area of Jeju island were each 12.9%, 14.2% and not significantly different. Prevalence of obesity of male students in general and commercial school group were each 13.9%, 10.1% and that of general school group was significantly higher. In female students, Prevalence of obesity general and commercial school group was not significantly different. Total cholesterol, systolic and diastolic blood pressure were significantly associated with degree of obesity in male and female students(P<0.05) and fasting blood sugar was only significantly associated with degree of obesity in male students (P<0.05). In 646students, Relative risk of obesity at primary school and that at high school in male and female students were 3.77, 2.66 and was significantly associated. Conclusion: Prevalence of obesity of high school students in Jeju island is very high and adolescent obesity was significantly associated with cardiovascular risk factors. Mostly childhood obesity tended to become adolescent obesity and program of control of obesity at childhood and adolescence is required.

Paraquat 투여 백서에서 Cyclophosphamide와 Dexamethasone의 치료 효과

신정철,신양수,유병전,임현성,정태흥,박찬국,오금탁,이병래 朝鮮大學校 附設 醫學硏究所 1991 The Medical Journal of Chosun University Vol.16 No.1

Paraquat (N,N'-dimethy 1-4,4'bipyrydinium : Gramoxone^(R), a widely used herbicide, is extremely toxic to all green plants and many eukaryotic organisms. In human, paraquat intoxication leads to multiple organ failure, it preferentially damages the lung, kidney and liver and may result in death. The participation of superoxide in initiating tissue damage by administration of paraquat is well known in which one electron reduction of paraquat leads to the formation of radical species which react with molecular oxygen to give superoxide. This process initiates immunological changes with the activation of neutrophilic leukocytes, which is related to further production of superoxide. In this experiment, therapeutic effects of cyclophosphamide and dexamethasone on blood cell count, malondialdehyde as a indicator of lipid peroxidation, and antioxidant enzymes levels in the lung, liver and kidney of paraquat intoxicated rats were inbestigated. The WBC count were significantly decreased by combined treatment of cyclophosphamide and dexamethasone in paraquat intoxicated rats at 3 and 5 days but RBC count were not changed. The contents of malondialdehyde were significantly decreased in the lung and Kidney by combined treatment at 10 days after paraquat intoxication. The catalase acitvities were markedly increased in the lung and liver of rats at 10 days after paraquat intoxication, and superoxide dismutase activities showed minimal changes in the lung, liver and kidney of rats by combined treatment. These results suggest that paraquat induced tissue damage in rats can be redeced by combined administration of cyclophosphamide and dexamethasone.

Preparation of Mg-MgH2 Flakes by Planetary Ball Milling With Stearic Acid and Their Hydrogen Storage Properties

Seong-Hyeon Hong,Myoung Youp Song 대한금속·재료학회 2016 METALS AND MATERIALS International Vol.22 No.3

Many studies preparing magnesium hydride using catalyst addition were performed, resulting in the preparation of additive-containing magnesium hydride. Preparation of a sample with a MgH2 phase without additives requires high pressure and high temperature and is time-demanding. In order to prepare an additive-free sample with a MgH2 phase, 90 wt% Mg+10 wt% MgH2 (named 90Mg+10MgH2) was milled under a hydrogen atmosphere with 6 wt% stearic acid as a process-controlling agent, which led to a formation of Mg-MgH2 flakes. The hydrogen storing and releasing properties of the prepared flakes were investigated and compared with those of purchased MgH2. A sample with a majority fraction of MgH2 phase was prepared by planetary ball milling of 90 Mg+10 MgH2 with 6 wt% stearic acid. The resultant particles of 90 Mg+10 MgH2 obtained after hydridingdehydriding cycling were much smaller and had significantly more cracks and defects than those of MgH2 after hydriding-dehydriding cycling. 90 Mg+10 MgH2 released 0.12 wt% hydrogen for 4 min, 3.70 wt% for 20 min, and 5.30 wt% for 60 min at 648 K at the first cycle.

Hydrogen Storage Characteristics of Melt Spun Mg-23.5Ni-xCu Alloys and Mg-23.5Ni-2.5Cu Alloy Mixed with Nb2O5 and NbF5

( Seong Hyeon Hong ),( Sung Nam Kwon ),( Myoung Youp Song ) 대한금속재료학회(구 대한금속학회) 2011 대한금속·재료학회지 Vol.49 No.4

Mg-23.5 wt%Ni-xwt%Cu (x=2.5, 5 and 7.5) samples for hydrogen storage were prepared by melt spinning and crystallization heat treatment from a Mg-23.5 wt%Ni-5 wt%Cu alloy synthesized by the gravity casting method. They were then ground under H2 to obtain a fine powder. Among these samples the Mg- 23.5Ni-2.5Cu sample had the highest hydriding and dehydriding rates after activation. The Mg-23.5Ni-2.5Cu sample absorbed 3.59 and 4.01 wt%H for 10 and 60 min, respectively, at 573K under 12 bar H2. The activated 88(87.5Mg-10Ni-2.5Cu)-5Nb2O5-7NbF5 sample absorbed 2.93 wt%H for 10 min, and 3.14 wt%H for 60 min at 573K under 12 bar H2.

Synthesis and consolidation of nanostructured W–10–40wt.% Cu powders

Hong, Seong-Hyeon,Kim, Byoung-Kee,Munir, Zuhair A. Elsevier 2005 Materials science & engineering. properties, micro Vol.405 No.1

<P><B>Abstract</B></P><P>Nanostructured W–(10–40)% Cu composite powders were prepared by calcinations of a spray dried W–Cu salt and a subsequent reduction treatment. The sintering of these powders was investigated as a function of copper content and temperature. W–Cu composites with 20–40wt.% Cu could be consolidated to high densities (>98%) when sintered at 1250°C for 1h. However, the sintering of samples with lower copper content (10wt.%) did not result in high densities (a maximum of 92% at 1450°C for 2h). The addition of WO<SUB>3</SUB> prior to the reduction step was found to markedly enhance the sinterability of these composites. Samples can be densified to >98% by sintering at 1400°C with zero hold time. A proposed role played by the added oxide is given. The electrical conductivity of the composites was measured and the values were consistent with theoretical calculations for composites with Cu content between 10 and 40wt.%.</P>

Hydrogen storage characteristics of melt spun Mg–23.5Ni–5Cu alloys mixed with LaNi5 and/or Nb2O5

Seong-Hyeon Hong,권성남,Jong-Soo Bae,송명엽 한국공업화학회 2012 Journal of Industrial and Engineering Chemistry Vol.18 No.1

Mg-based materials have a high potential for commercialization due to the large hydrogen storage capacity, low cost and abundance in the Earth’s crust. Despite these advantages, reaction kinetics of Mg with hydrogen is slow. Various investigations to increase the hydriding kinetics of Mg were performed. Although LaNi5 has a low hydrogen storage capacity, it can store hydrogen at a low temperature. In this study, a Mg–23.5Ni–5Cu alloy was prepared by gravity casting method in a large quantity (approximately 7.5 kg), and then melt-spun and heat-treated. LaNi5, Nb2O5 or LaNi5 + Nb2O5 were added to the Mg–23.5Ni–5Cu alloy by reactive mechanical grinding in a planetary mill. The hydrogen storage capacity and hydriding behavior of the Mg–23.5Ni–5Cu alloys with LaNi5, Nb2O5 or LaNi5 + Nb2O5 added were then investigated.

Study on the Reactivity with Hydrogen of Planetary Ball Milled 90 wt% Mg+10 wt% MgH2: Analyses of Reaction Rates with Hydrogen and Microstructure

( Seong Hyeon Hong ),( Myoung Youp Song ) 대한금속재료학회(구 대한금속학회) 2016 대한금속·재료학회지 Vol.54 No.5

Much research has been performed on the synthesis of magnesium hydride with added catalysts, leading to the preparation of magnesium hydride with additives. High pressure, high temperature, and long periods are required to prepare a sample with an MgH2 phase without additives. In order to synthesize an additive(s)-free sample with a single MgH2 phase, 90 wt% Mg+10 wt% MgH2 (named 90Mg+10MgH2) was milled in a hydrogen atmosphere of 15 bar for 10 h. Hydrogen absorption and release properties of the prepared samples were investigated, and compared with those of a purchased MgH2. A sample whose large fraction is the MgH2 phase was prepared. Particles of 90Mg+10MgH2 after hydriding-dehydriding cycling have a form of agglomerates consisting of fine particles and have more defects than are present in MgH2 after hydriding-dehydriding cycling. 90Mg+10MgH2 released 0.06 wt% H for 8 min, 0.40 wt% H for 10 min, 4.66 wt% H for 20 min, 5.54 wt% H for 25 min, 5.62 wt% H for 30 min, 5.64 wt% H for 50 min, and 5.65 wt% H for 60 min at 648 K in the first cycle. (Received September 2, 2015)