칸디다뇨증 환자에 있어서 칸디다혈증 동반과 관련된 위험인자 분석

김창오(Chang Oh Kim),김명환(Myoung Hwan Kim),심대근(Dae Keun Shim),조정호(Jung Ho Cho),김병극(Byoung Keuk Kim),김창년(Chang Nyun Kim),송영구(Young Goo Song),김준명(June Myung Kim) 대한내과학회 2001 대한내과학회지 Vol.60 No.5

N/A Background : The early diagnosis of candidemia is critical for the management. The candidemia is known to be associated with 10% of candiduria. But the risk factors in patients with candiduria who are associated with candidemia are not known. We analyzed the risk factors in patients with candiduria who are associated with candidemia. Methods : We retrospectively reviewed 164 patients with candiduria in Yonsei Medical Center from January 1998 to December 1998. Candiduria patients were divided into two groups. Candiduria patients without candidemia (Group 1 , 147 patients) and candiduria patients with candidemia (Group 2 , 17 patients). Results : 1) The mean age of the patients were 57.5 years in group 1 and 62.5 years in group 2. There were no significant differences in the sex ratio between the two groups. 2) Central venous catheter insertion (53%, 100% in group 1 , 2 ), hypotension (14%, 59% in group 1, 2), other associated infections (64%, 100% in group 1, 2), intensive care (41, 76% in group 1, 2) and fever (46%, 82% in group 1, 2) were the very significant risk factors in patients with candiduria who were associated with candidemia. 3) Urinary tract procedure (11%, 88% in group 1, 2), urinary catheter insertion (63%, 94% in group 1, 2), thrombocytopenia (17%, 41% in group 1, 2) and DM (8%, 24% in group 1, 2) were the significant risk factors of candidemia. 4) Candida colony count (cfu/mL) of urine culture was not a significant risk factor 5 ) Mortality rate (27%, 59% in group 1, 2) was significantly high in patients with candidemia. Conclusion : Central venous catheter insertion , hypotension , other associated infections , intensive care and fever were the very significant risk factors of candidemia in patients with candiduria. (Korean J Med 60:479-484 , 2001)

TMA 농도에 따른 저온축열물질의 과냉각 특성에 대한 연구

김창오(Chang-Oh Kim),김진흥(Jin-Heung Kim),정낙규(Nak-Kyu Chung) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.11

This study is investigated the supercooling characteristics of the TMA-water clathrate compound including TMA (Tri-methyl-amine, (CH3)3N) of 20~25 wt% as a low temperature latent heat storage material at -5℃, cooling source temperature. The results showed that as the concentration of TMA is increased, phase change temperature is increased, the supercooling and retention time of liquid phase are decreased. Especially, low temperature latent heat storage material containing TMA 25 wt% has the average of phase change temperature of 5.8℃, supercooling degree of 8.0℃, retention time of liquid phase for 10 minutes in the cooling process. Phase change temperature higher than that of water and inhibitory effect against superrcooling can be confirmed through experimental study on cooling characteristics of TMA-water clathrate compound. This can lead to shorten refrigerator operation time of low temperature thermal storage system and improve efficiency of refrigerator COP and overall system.

TMA 농도에 따른 저온잠열축열물질의 냉각특성

김창오(Kim Chang-Oh),정현호(Chung Hyoun-Ho),정낙규(Chung Nak-Kyu) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5

The ice storage system uses water for low temperature latent heat storage. However, a refrigerator capacity is increased and COP is decreased due to supercooling of water in the course of phase change from solid to liquid. This study investigates the phase change characteristics of the TMA-water clathrate compound including TMA (Tri-methyl-amine, (CH₃)₃N) of 20~25 wt% as a low temperature latent heat storage material. The results showed that the phase change temperature and the specific heat is increased and the supercooling degree is decreased as the weight concentration of TMA increased. Especially, the clathrate compound containing TMA 25wt% has the average phase change temperature of 5.8℃ and the supercooling degree of 8.0℃ in the cooling process. This can lead to reduction of operation time of refrigerator in low temperature latent heat storage system and efficiency improvement of refrigerator COP and overall system. Therefore, energy saving and improvement of utilization efficiency are expected.

저온잠열저장을 위한 TMA-물계 포접화합물의 과냉각 개선에 대한 연구

김창오(Kim Chang-Oh),김진흥(Kim Jin-Heung),정낙규(Chung Nak-Kyu) 한국태양에너지학회 2007 한국태양에너지학회 학술대회논문집 Vol.- No.-

This study aims to find out cooling characteristics of TMA(Tri-Methyl- Amine, (CH₃)₃N) 25wt%-water clathrate compound with ethanol(CH₃CH₂OH) such as supercooling, phase change temperature and specific heat. For this purpose, ethanol is added as per weight concentration and cooling experiment is performed at -6˜-8℃, cooling heat source temperature, and it leads the following result. (1) Phase change temperature is decreased due to freezing point depression phenomenon. Especially, it is minimized as 3.8℃ according to cooling source temperature in case that 0.5wt% of ethanol is added. (2) If 0.5wt% of ethanol is added, average supercooling degree is 0.9℃ and minimum supercooling is 0.8, 0.7℃ according to cooling heat source temperature. The restraint effect of supercooling is shown. (3) Specific heat shows tendency to decrease if ethanol is added. It is 3.013~3.048 ㎉/㎏℃ according to cooling heat source temperature if 0.5wt% of ethanol is added. Phase change temperature higher than that of water and inhibitory effect against supercooling can be confirmed through experimental study on cooling characteristics of TMA 25wt%-water clathrate compound by adding additive, ethanol. This can lead to shorten refrigerator operation time of low temperature latent heat storage system and improve COP of refrigerator and efficiency of overall system. Therefore energy can be saved and efficiency can be improved much more.

저온잠열저장을 위한 TMA-물계 포접화합물의 과냉각 특성에 대한 연구

김창오(Kim Chang-Oh),김진흥(Kim Jin-Heung),정낙규(Chung Nak-Kyu) 한국태양에너지학회 2006 한국태양에너지학회 학술대회논문집 Vol.- No.-

Ice storage system that water is used as low temperature latent heat storage material, refrigerator capacity is increased and COP is decreased because refrigerator is operated at low temperature due to supercooling of water in the course of phase change from solid to liquid. This study is investigated the cooling characteristics of the TMA-water clathrate compound including TMA(Tri-methyl-amine, (CH₃)₃N) of 20~25 wt% as a low temperature latent heat storage material at -5℃, cooling source temperature. The results showed that the phase change temperature, the specific heat is increased and the supercooling degree is decreased as the weight concentration of TMA became higher. Especially, low temperature latent heat storage material containing TMA 25 wt% has the average of phase change temperature of 5.8℃, supercooling degree of 8.0℃ and specific heat of 4.099kJ/㎏K inthe cooling process. Phase change temperature higher than that of water and inhibitory effect against supercooling can be confirmed through experimental study on cooling characteristics of TMA-water clathrate compound.

저온잠열축열을 위한 TMA-물계 포접화합물의 냉각특성

김창오(Kim Chang-Oh),정현호(Chung Hyoun-Ho),정낙규(Chung Nak-Kyu) 한국태양에너지학회 2009 한국태양에너지학회 학술대회논문집 Vol.- No.-

The ice storage system uses water for low temperature latent heat storage. However, a refrigerator capacity is increased and COP is decreased due to supercooling of water in the course of phase change from solid to liquid. This study investigates the cooling characteristics of the TMA-water clathrate compound including TMA (Tri-methyl-amine, (CH₃)₃N) of 20~25 wt% as a low temperature latent heat storage material. The results showed that the phase change temperature and the specific heat is increased and the supercooling degree is decreased as the weight concentration of TMA increased. Especially, the clathrate compound containing TMA 25wt% has the average phase change temperature of 5.8℃, the supercooling degree of 8.0℃ and the specific heat of 3.499 kJ/㎏K in the cooling process. This can lead to reduction of operation time of refrigerator in low temperature latent heat storage system and efficiency improvement of refrigerator COP and overall system. Therefore, energy saving and improvement of utilization efficiency are expected.

TMA 농도에 따른 저온잠열축열물질의 냉각특성

김창오(Kim Chang-Oh),정현호(Chung Hyun-Ho),정낙규(Chung Nak-Kyu) 대한기계학회 2010 大韓機械學會論文集B Vol.34 No.2

빙축열시스템은 저온잠열저장을 위해 물을 사용한다. 그러나 물은 액체에서 고체로 상변화를 하는 과정에서 물의 과냉각 현상에 의하여 냉동기의 냉동용량 증가와 COP감소의 원인이 되고 있다. 본 연구는 저온잠열축열물질로 적용 가능한 TMA(Tri-methyl-amine, (CH3)3 N) 20~25 wt%를 포함하고 있는 TMA-물계 포접화합물(TMA-water clathrate compound)의 냉각특성에 대한 실험적 연구를 수행하였다. 실험적 연구 결과, TMA 질량농도가 높을수록 상변화온도는 증가하였고, 과냉각도와 비열은 감소하였다. 특히, TMA 25wt%를 포함하고 있는 포접화합물은 냉각과정동안 평균 상변화온도 5.8℃와 과냉각도 8.0℃, 액상유지시간 651sec 및 비열 3.499 kJ/㎏K로서 다른 TMA 농도보다 양호한 냉각특성을 나타내었다. 이와 같이 저온잠열축열물질로서 TMA 25wt%-물계 포접화합물을 적용하는 것이 유리할 것으로 판단된다. The ice storage system uses water for low temperature latent heat storage. However, a refrigerator capacity are increased and COP are decreased due to supercooling of water in the course of phase change from liquid to solid. This study investigates the cooling characteristics of the TMA-water clathrate compound including TMA (Tri-methyl-amine, (CH3)3N) of 20~25 wt% as a low temperature latent heat storage material. The results showed that the phase change temperature are increased and the supercooling degree and the specific heat are decreased according to the weight concentration of TMA increased. Especially, the clathrate compound containing TMA 25wt% has the average phase change temperature of 5.8℃ and the supercooling degree of 8.0℃, retention time of liquid phase for 651sec and specific heat of 3.499 kJ/㎏K in the cooling process. This expressed good than different concentration of TMA cooling characteristic. Like this, to apply TMA 25wt%-water clathrate compound is determined by advantageous as the low temperature latent heat storage material.

P2P 미디어 스트리밍 서비스를 위한 동적 그룹 할당 방식

김창오(Chang-Oh Kim),강경란(Kyungran Kang),조영종(Young-Jong Cho) 한국통신학회 2008 한국통신학회 학술대회논문집 Vol.2008 No.11

트리 구조를 이용한 연관규칙의 효율적 탐색

김창오(Chang-Oh Kim),안광일(Kwang-Il Ahn),김성집(Seong-Jip Kim),김재련(Jae-Yearn Kim) 대한산업공학회 2001 대한산업공학회지 Vol.27 No.1

계층적 네트워크를 위한 분산 멀티캐스트 그룹 키 관리 기법

김창오(Chang Oh Kim),강경란(Kyungran Kang),조영종(Young-Jong Cho) 한국정보과학회 2011 정보과학회논문지 : 정보통신 Vol.38 No.1

본 논문에서는 전술 네트워크 환경과 같이 네트워크 연결이 항상 보장되지 못하며 계층적 구조를 갖는 환경을 지원하기 위한 비중앙화된 멀티캐스트 그룹 키 관리 기법을 제안한다. 연결이 보장되기 어렵고 긴 지연 시간을 초래할 중앙 키 관리자를 사용하지 않고, 네트워크 내 계층 구조를 활용하여 무선 네트워크 내 노드들이 그룹 키 관리자를 담당하도록 함으로써 멀티캐스트 그룹 키의 관리를 분산시킨다. 또한, 팀 단위로 가입 요청과 탈퇴 요청을 묶어서 처리함으로써 멀티캐스트 그룹 키의 갱신 메시지 부담을 줄인다. 시뮬레이션을 통하여 타 비중앙화 기법과의 비교에서도 팀 단위 처리와 인접한 그룹 키 관리자로 인해 그룹 키 갱신을 위한 메시지 부담이 본 기법이 매우 낮게 나타났다. 그리고, 멤버쉽 변화율에 따른 그룹 키 갱신 메시지 부담 측정에서 멤버쉽 변화율에 비해 부담이 증가하는 비율이 낮게 나타나 멤버쉽 변화율에 대해 확장성이 있다는 것을 확인할 수 있었다. 그런데, 수학적 분석과 시뮬레이션에서 팀의 규모가 어느 일정값보다 증가하게 되면 팀 내 처리 비용이 증가하여 전체적으로 그룹 키 갱신 비용이 오히려 증가한다는 것도 관측되었다. In this paper, we propose a decentralized multicast group key management scheme for a hierarchically structured but unstable network like a tactical network. In the tactical network, the connection the infrastructure is not always guaranteed and the unstable connection and long latency would prevent the use of centralized key management scheme. We propose a distributed group key management scheme which distributes the management function to the network nodes by exploiting the hierarchical relationship between the nodes. To reduce the count of key update operations, we propose to aggregate the join and leave requests within a reasonable time bound and process at a time. We build a simulator to evaluate the performance of our proposed scheme and two other decentralized group key management schemes. Our scheme shows less key update cost compared with the other twoschemes thanks to the team-based key management and nearby group key management server. The key update cost of our scheme increases slower than the increase of membership change rate. However, through the numerical analysis and simulation, we discovered that the team size beyond some critical threshold causes the overall key update cost of our scheme to become impractically large.