• Journal of Internet Computing and Services
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• v.2 no.5
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• pp.71-79
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• 2001

Replication in distributed databases is to improve efficiency, availability, and autonomy, But applying the strict consistency in real systems is very difficult. In this paper, I introduce a hybrid protocol permitting group update through eager update propagation and weakening consistency through lazy update, This protocol manages replica version number for the group update consistency and generates partially ordered replica spanning tree for the serializability of lazy update transactions. It preserves weak consistency by combining synchronous and asynchronous update mechanism. Study of performance analysis for the efficiency of the protocol be included in next paper.

• Proceedings of the Korea Multimedia Society Conference
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• 2002.05d
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• pp.752-757
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• 2002

IP 멀티캐스트는 다자간 통신을 위한 효과적인 방법이지만 신뢰성 보장과 FTP나 Telnet등 TCP제공하는 다양한 전송프로토콜을 지원하지 않는다. 본 논문에서는 멀티캐스트의 UDP와 TCP계층의 전송 프로토콜을 동시에 사용할 수 있는 신뢰성 있는 멀티캐스트 서버라우터를 제안한다. 신뢰성 있는 멀티캐스트가 반드시 고려해야 할 확장성과 오류회복, 흐름제어를 위해, 그룹의 확장성과 오류회복에 적합한 기존의 SRM방식을 이용하였다. SRM방식은 신뢰성 있는 다-대-다 멀티캐스트 패킷을 전달한다. 각 참여자는 동시에 수신자와 송신자 역할을 할 수 있다. 모든 그룹 멤버는 낮은 주파수의 세션 메시지를 교환하고 그룹내의 주변 가입자에 대한 정보를 얻게 되며 패킷 손실 판단에 필요한 지연시간을 측정하고 복구하는 방식이다. UDP의 트래픽 기반은 멀티캐스트에 적합한 CBR과 SRM을 사용하였다. 본 연구에서는 멀티캐스트의 UDP 패킷과 TCP 패킷을 동시에 보낸 수신율과 멀티캐스트의 UDP만 보낸 수신율을 지연이 가장 큰 멀티캐스트 수신자측에서 패킷 번호와 수신율을 측정하고, 시뮬레이션을 통해서 검증을 통하여 기존의 멀티캐스트 전송방법과 비교하였다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.6
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• pp.1256-1264
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• 2011

MBS (Multicast Broadcast Service) is defined in WiBro networks for implementing multicast-based services. However, most of the WiBro networks currently used in Korea do not have the MBS functionality and it causes some difficulty in implementing multicast-based services. This paper evaluates the performance of VoIP-based group communication services when implementing using the following two cases: unicast-based and multicast-based group communication systems. The performance evaluation is done using QualNet for each case in terms of the amount of network resource for the service, the delay and delay jitter of packets, and the difference of the delay of members in a group. The simulation result shows that the number of groups and members in a group in a WiBro network is limited because the amount of network resource for the service is increased according to the number of members in a group, and so, the MBS service is required in a WiBro network for a fully-fledged service of VoIP-based group communications. The simulation result also shows that, when a packet bundling is used, the number of groups and members in a group that can be supported in a WiBro network can be increased due to the decrease of the amount of network resource for the service.

• The Journal of Korean Academy of Sensory Integration
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• v.7 no.2
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• pp.13-22
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• 2009

Objective : The aim of this study is to verify the effects of group sensory integrative intervention for sensory motor ability, behaviors in children with developmental delay. Method : The subjects were five children with developmental delays aged between 3 and 5. All Children participated in 26 sessions of group sensory integrative intervention. Children' behavior during testing was observed to assess the sensory motor ability, behaviors, the clinical observation. One group pretest- posttest design was used to verify the effect of group sensory integrative intervention. The observed children' behavior during testing were tested by the Wilcoxon matched-pair signed rank test. Results : There is no significant difference in the clinical observation between pre and post intervention. However, subjects showed the significant difference in Social interaction(Z=-2.121, p=.034), Attention(Z=-2.032, p=.042), total score in Behavior during testing(Z=-2.032, p=.042). Conclusions : The result in this study suggested that the sensory integrative intervention is effective in facilitating the social skills and improving the attention and behaviors. On the other hand, there is no effect in sensory motor ability. It is difficult to generalize the conclusion because the number of the subject was limited and the environmental confounding factors has not been controlled. Therefore, it is needed to supplement these limitations in the future study.

• Journal of Korea Multimedia Society
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• v.7 no.10
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• pp.1436-1442
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• 2004

A shared-based tree established by the Core Based Tree multicast routing protocol (CBT), the Protocol Independent Multicast Sparse-Mode(PIM-SM), or the Core-Manager based Multicast Routing(CMMR) is rooted at a center node called core or Rendezvous Point(RP). The routes from the core (or RP) to the members of the multicast group are shortest paths. The costs of the trees constructed based on the core and the packet delays are dependent on the location of the core. The location of the core may affect the cost and performance of the shared-based tree. In this paper, we propose three methods for selecting the set of candidate cores. The three proposed methods, namely, k-minimum average cost, k-maximum degree, k-maximum weight are compared with a method which select the candidate cores randomly. Three performance measures, namely, tree cost, mean packet delay, and maximum packet delay are considered. Our simulation results show that the three proposed methods produce lower tree cost, significantly lower mean packet delay and maximum packet delay than the method which selects the candidate cores randomly.

• Journal of the Korean Society of Radiology
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• v.15 no.5
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• pp.575-584
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• 2021

The aim of this study was to achieve optimal portal phase while reducing contrast medium by applying weight-based dose protocol compared to standard fixed dose protocol to performing of pediatric abdominal CT examination. Discovery 750HD (General Electric Medical Systems, Milwaukee, USA) was used, and a total of 167 children consisting of 85 men and 82 women under the age of 18 were studied. The group in which the 300 mgI/ml(Xenetix, Guerbet, France) contrast medium was fixedly injected at twice body weight and the group injected with physiological saline while gradually decreasing the injection amount by 10% while applying the weight-based protocol were distinguished. Also, the CT number and SNR of abdominal organs were compared and evaluated while changing the scan delay time. Subjective image quality of enhancement and beam-hardening artifacts of around the heart was assessed with five-point criterion. The group adapted weight-based protocol with 20% reduction in contrast medium was most similar in contrast enhancement in the group with fixed injection at twice body weight. Furthermore, the group with a delay time of 20% had the highest contrast enhancement effect, and the difference in CT attenuation coefficient from the group scanned immediately after injection of the contrast media. Therefore, the appropriate delay time after injection of the contrast agent increased the contrast enhancement of the parenchymal organ. In addition, the weight-based injection protocol with normal saline reduced artifacts around the heart, and the effect of contrast enhancement could be maintained. In conclusion, it is possible to reduce dosage of contrast media through the application of weight-based injection protocols and appropriate latency, and to characterize optimal portal phase imaging on pediatric abdominal CT.

• Journal of the Korean Society of Radiology
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• v.13 no.2
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• pp.305-311
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• 2019

In this study, present the most useful delay scan time by statistical analysis of SUVm data for 30 suspected pancreatic cancer patients. Two statistical analysis and a mathematical model was applied to the theoretical formula by glucose and insulin mechanics, and a mathematical model was created. Statistical analysis was performed via Metlab p/g. Optimal delay scan time was suggested by Metlab p/g for the change of SUV value over time.In this study, for diagnosis pancreatic cancer by dual time point PET/CT, propose optimal delay scan time 131.5 minuts. The proposed delay scan time showed statistical reliability applicable to the diagnosis of pancreatic cancer (p<0.05). Delayed scanning with the suggested delay scan time of 131.5 minutes is considered to be useful for the diagnosis of pancreatic cancer compared to general PET / CT scan.hen the delayed test is performed with the proposed delay scan time 131.5 minuts, Compared with general PET/CT scans.

• The Journal of the Korea Contents Association
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• v.3 no.3
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• pp.63-73
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• 2003

Today, in exponential growth of internet, the importance of file caching which could reduce the sun load, the volume of network traffic, and the latency of response has emerged. Actually, in one network, the traffic has reduced by using the cache and this means that file caching can improve the internet environment by cost a fraction of link upgrades. In this paper, we address a dynamic cache group configuration policy, to solve the scalable problem. The simulation result shows that the cache group using our proposal policy reduces the latency of response time and it means that out cache group configuration is more scalable than the static cache configuration.

• Proceedings of the Korean Information Science Society Conference
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• 1998.10a
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• pp.181-183
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• 1998

방대한 분산 응용들은 예측할 수 없는 통신 지연이나, 부분적인 오류, 네트워크 결합등을 처리해야한다. 또한, 화상회의, VOD(vido-on-demend),병행소프트웨어 공학과 같은 정교한 응용들은 추상적 그룹 통신을 필요로 하지만, 현재의 CORBA 버전들은 이러한 패러다임을 적절히 수용하지 못한다[7][8]. CORBA 는 주로 Point-to-Point 통신을 하는데 분산 시스템에서 예측 행위를 하는 신뢰성있는 응용기술에 대한 구현은 지원하지 않는다. 따라서 존 논문에서는 머지 복제 기법을 이용한 에이전트를 통해 신뢰성있는 그룹통신을 지원하는 확장된 CORBA를 제시한다.

• The Optical Journal
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• s.97
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• pp.43-45
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• 2005

첨단산업을 일컬을 때 빼놓을 수 없는 말이‘나노’라고 할때 연구실 명칭에서도 알 수 있듯이 한국표준 과학연구원 나노광계측그룹에서는 첨단산업을 리드해가는 연구개발을 수행하고 있다. 즉, 빛을 이용한 계측기술을 통해 나노미터 수준의 부품이나 시스템에서 일 미터 이상 되는 대형 광학계까지 포괄하는 다양한 측정기술을 개발하고 있다. 단순 연구를 위한 연구에서 머무는 것이 아니라 우리나라 산업전반의 흐름을 이끌어갈 최첨단 산업기술을 개발하여 실질적으로 산업체에 지원하고 있다는 점에서 나노광계측그룹의 팀원들은 자부심을 갖기에 충분하다.