• Journal of KIISE:Information Networking
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• v.30 no.3
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• pp.343-354
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• 2003

This paper describes algorithm that minimizes recovery time of packet loss resulting from handoff in multicast environments and guarantees reliability through interaction of FN(Foreign Network) with PMTP(Predictable Multicast Tree Protocol). To solve the problems that inefficient routing and handoff delay taking plate when using hi-directional tunneling and remote subscription independently in multicast environments, proposed algorithm uses tunneling and rejoining multicast group according to the status of an arriving FA in a foreign network. Furthermore, proposed algorithm sends packet loss information and register message to previous FA or current FA at the same time. so, MH is able to recovery packet loss in handoff delay as soon as possible. As a result of performance analysis, proposed algorithm is more efficient than previous researches and is applicable to existing handoff method without requiring additional procedures.

• Journal of the Korean Academy of Child and Adolescent Psychiatry
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• v.16 no.2
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• pp.219-230
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• 2005

Objectives : This study was designed to compare the demographic data, clinical characteristics, developmental delay, and psychological tests between childhood-onset and adolescent-onset schizophrenic in-patients. Methods Medical records of the 17 childhood-onset (very early onset) Schizophrenia and 16 adolescent-onset (early onset) Schizophrenia in-patients were reviewed. Sex, age, psychiatric past history, prodromal symptoms and period, subtype, co-morbid disease, developmental delay, prescribed drug and dosage, treatment response, intelligence quotient (IQ), and Rorschach test were evaluated. Results : The mean admission age of childhood-onset (very early onset) group and adolescent-onset (early onset) group were 12.69$({\pm}2.34)$ and 15.13$({\pm}1.04)$ years. The mean onset age of childhood-onset(very early onset) group and adolescent-onset (early onset) group were 10.79$({\pm}1.95)$ and 14.46$({\pm}0.82)$ years. The mean prodromal period of childhood-onset (very early onset) group and adolescent-onset (early onset) group were 15.94$({\pm}12.33)$ and 8.06$({\pm}6.10)$ month. The time to remission period of childhood-onset (very early onset) group and adolescent-onset (early onset) group were 50.58$({\pm}24.67)$ and 30.06$({\pm}18.04)$ days. Longer time to remission period in childhood-osnet (very early onset) group was associated with earlier age of onset. The mean of total IQ, performance IQ, verbal IQ were at an average level. Discussion : Childhood-onset (very early onset) group and adolescent-onset (early onset) group Schizophrenia had different clinical and psychological features including prodromal period, and IQ subtests.

• Journal of Chest Surgery
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• v.37 no.5
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• pp.391-400
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• 2004

Xenotransplantation in discordant species results in immediate and irreversible hyperacute rejection due to natural antibodies, IgM. With this, antibody depletion is one option to reduce hyperacute rejection, we investigated the effect of PCPP (postcentrifugal plasmapheresis) on the depletion of natural antibodies and the effect of antibody titer on xenograft survival. Material and Method: Outbred swines (n=4) weighing 10∼20 kg were used as donors and mongrel dogs (n=4) weighing 25∼30 kg were used as recipients. Recipient canines underwent plasmapheresis (COBE TPE Laboratories, Lakewood. CO, USA). Pre-transplantation PCPP was peformed on day －2 and day 0. There were three groups (Group 0: no PCPP, Group 1: 1 pla sma-volume (PV) at day －2 and 2 PV at day 0, Group 2: 2 PV at day －2 and 2 PV at day 0). A swine heart was heterotopically transplanted into a recipient's abdominal infrarenal aorta and inferior vena cava. Mean percent depletion of total IgM and IgG in plasma of the recipients was calculated. Serum albumin, electrolyte, complement activity and coagulation factors were measured. Histopathologic examination of heart specimens was performed. Result: Mean percent depletion of IgM and IgG were 95.7$\pm$1.2%, 80.5$\pm$2.4% in the group 2 at the end of PCPP. The percent depletion of serum albumin concentration was decreased from 2.8 to 1.4 g/㎗ in the group 1 and 3.0 to 1.5 g/㎗ in the group 2. Complement hemolytic activity was decreased in group 1 and 2, but returned to normal level within 24 hours. Complement hemolytic activity was reduced to 10% of pre-PCPP level in group 2. Serum fibrinogen decreased to 20% or less and was recovered within 24 hours in group 2. Antithrombin III decreased but less than fibrinogen. PT and aPTT were sometimes but not always prolonged during plasmapheresis. After plasmapheresis, PT and aPTT were prolonged beyond the measurable level. D-dimer was not found during PCPP, but appeared and maintained from 10 minutes after trasplantation. Graft Survival time was 5 min in group 0, and it was 90$\pm$0 min in the group 2. Histopathologic changes were more typically characterized by edema, hemorrhages, thrombosis in all groups at the end of experiment. Conclusion: PCPP effectively removed immuoglobulins and reduced the titer of natural antibodies, as a result, significantly prololonged swine heart xenograft survival.

• The Transactions of the Korea Information Processing Society
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• v.5 no.4
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• pp.1033-1043
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• 1998

In this paper, we present an improved multicasting path assignment algorithm based on the minimum cost spanning tree. In the method presented in this paper, a multicasting path is assigned preferentially when a node to be received is found among the next degree nodes of the searching node in the multicasting path assignment of the constrained steiner tree (CST). If nodes of the legacy group exist between nodes of the new group, a new path among the nodes of new group is assigned as long as the nodes may be excluded from the new multicasting path assignment taking into consideration characteristics of nodes in the legacy group. In assigning the multicasting path additionally, where the source and destination nodes which can be set for the new multicasting path exist in the domain of identical network (local area network) and conditions for degree constraint are satisfied, a method of producing and assigning a new multicasting path is used. The results of comparison of CST with MCSTOP, MCSTOp algorithm enhanced performance capabilities about the communication cost, the propagation delay, and the computation time for the multicasting assignment paths more than CST algorithm. Further to this, research activities need study for the application of the international standard protocol(multicasting path assignment technology in the multipoint communication service (MCS) of the ITU-T T.120).

• Journal of Korea Multimedia Society
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• v.14 no.9
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• pp.1165-1174
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• 2011

In data broadcasting systems, servers continuously disseminate data items through broadcast channels, and mobile client only needs to wait for the data of interest to present on a broadcast channel. However, because broadcast channels are shared by a large set of data items, the expected delay of receiving a desired data item may increase. This paper explores the issue of designing proper data allocation on multiple broadcast channels to minimize the average expected delay time of all data items, and proposes a new data allocation scheme named two level bin-packing(TLBP). This paper first introduces the theoretical lower-bound of the average expected delay, and determines the bin capacity based on this value. TLBP partitions all data items into a number of groups using bin-packing algorithm and allocates each group of data items on an individual channel. By employing bin-packing algorithm in two step, TLBP can reflect a variation of access probabilities among data items allocated on the same channel to the broadcast schedule, and thus enhance the performance. Simulation is performed to compare the performance of TLBP with three existing approaches. The simulation results show that TLBP outperforms others in terms of the average expected delay time at a reasonable execution overhead.

• Journal of Korea Multimedia Society
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• v.6 no.7
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• pp.1256-1265
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• 2003

Content Delivery Network(CDN) is a mechanism to deliver multimedia content to end users on behalf of web content providers. Provider's content is distributed from content server to a set of delivery platforms located at Internet Service Providers(ISPs) through the CDN in order to realize better performance and availability than the system of centralized provider's servers. Existing work on CDN has primarily focused on techniques for efficiently multicasting the content from content server to the delivery platforms or to end users. Multimedia contents usually require broader bandwidth and accordingly WDM broadcast network has been highly recommended for the infrastructure network of CDN. In this paper, we propose methods for partitioning a multicast group into smaller subgroups using the previous status of receivers. Through the computer simulation, we show that proposed algorithm are useful to reduce the average receiver's waiting time and the number of transmissions.

• Journal of Internet Computing and Services
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• v.6 no.3
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• pp.55-70
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• 2005

In order to provide mobile hosts with multicast service in mobile communication environment, we proposed a multicast mechanism named HXcast++ which is an extended version of the existing Xcast++ with hierarchical architecture, We assured that mobile hosts could get multicast service through an optimal path regardless of their location by making DR(Designated Router) join a group on behalf of the mobile hosts, In this present research we introduced hierarchical architecture in order to reduce the maintenance cost resulting from frequent handoff. We also proposed a GMA (Group Management Agent) based group management mechanism which enables the mobile hosts to join the group without waiting for a new IGMP Membership Query. A fast handoff method with L2 Mobile Trigger was, in this work, employed in order to reduce the amount of the packet loss which occurs as a result of the handoff, We also managed to curtail the packet loss caused by the latency of the group join by using a buffering and forward mechanism.

• Journal of Digital Contents Society
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• v.18 no.1
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• pp.133-139
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• 2017

To address the problems caused by such high installation and maintenance cost in the conventional server-based cloud systems, researches on P2P cloud storages have been conducted recently. In this paper, we propose a hierachical overlay structure that can improve the playback quality in P2P cloud storage systems for video transmission. In this structure, after we make groups by clustering the participating peers based on their similarities, we construct subgroups by geographically dividing the peers belonging to a specific group considering the physical proximities among them. Therefore, when a request for video playback is issued, we can minimize the transmission delay by selecting the source peers depending on their locality. By simulations, we show that our proposed hierarchical overlay structure considering the peers' locality outperforms the structure where source peers are selected randomly.

• The KIPS Transactions:PartC
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• v.9C no.3
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• pp.323-330
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• 2002

Multicast services are gradually diversified and used widely. Proportionately, they become the center of attackers' attention and there are growing possibilities of an intelligence leak. Therefore, research related to secure multicast should be required to provide multicast service efficiently. This paper presents the architecture for secure multicast which provides efficient group management mechanism in group consists using member's dynamic join and leave. This architecture can provide secure multicast services to many users with regard to security aspects in one-to-many communication. The simulation results show that the proposed architecture achieves an efficient group management and a secure data transmission with low latency compared with the other existing secure multicast architecture.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.12
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• pp.81-88
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• 2012

As the performance of the next-generation broadband wireless networks is dramatically enhanced, various services (i.e., education, Live video streaming, Live video conferencing, online games, etc.) have been provided to users through a smart mobile platform. Those services are usually provided by using the centralized communication server. However, since all multimedia traffic is exchanged through a communication server, it often has the scalability problem with regard to traffic management. Our main purpose is for group smart users to provide scalable live multimedia streaming service based on P2P network. To do this, we have designed an architecture of P2P-based service management for mobile group communication management and service management protocol. In order to verify the performance of the proposed scheme, we have mathematically analyzed the performance in terms of the average transmission delay and bandwid th utilization.