• Journal of KIISE:Computing Practices and Letters
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• v.8 no.4
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• pp.399-410
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• 2002

Group communication is one of key components supporting object replication. CORBA provides little support for fault tolerance and high availability that can be supported by means of object replication. The existing approaches do not allow transparent plug-in of group communication protocols into CORBA with which CORBA application programmers are able to directly exploit group communication protocols. They either require modification of CORBA or OS, or provide no room for incorporating group communication transport protocols into CORBA. In this paper, we propose a generic group communication framework that allows transparent plug-in of various group communication protocols with no modification of standard CORBA. For this, we extend the Open Communications Interface(OCI) to support interoperability, reusability of existing group communication, and independency on ORB and OS. The proposed approach can also be applied to various group communication protocols.

• The KIPS Transactions:PartA
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• v.12A no.6 s.96
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• pp.507-514
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• 2005

This paper presents a partially decentralized passive replication algorithm for deterministic servers in message-passing distributed systems. The algorithm allows any backup server, not necessarily the primary server, to take responsibility for processing its received client request and coordinating with the other replica servers after obtaining the delivery sequence number of the request from the primary. Thanks to thus desirable feature, the algorithm with conventional load balancing techniques can efficiently avoid extreme load conditions on the primary. Therefore, it can provide better scalability of deterministic and replicated sewer systems than traditional passive replication algorithms. Simulation results indicate that the proposed algorithm can reduce $16.5\%{\~}52.3\%$ of the average response time of a client request compared with the traditional ones.

• The KIPS Transactions:PartC
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• v.10C no.6
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• pp.779-786
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• 2003

We propose a correction security framework as next generation security technology to provide secure and reliable Internet services. The framework guarantees durability of the services in spite of external attack, intrusion, vulnerability for fault tolerance, and network management technology that covers the set of techniques aimed at providing rapid service recovery. The improvement technology includes system itself improvement and synamic improvement preventing faults from being re-activated, in cooperation with other systems such as vulnerability anaysis system, NMS, ESM. It is expected that our framework will be applied to global networks as well as system alone, and be able to guarantee the network survivability and reliable Internet services.

• Smart Media Journal
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• v.6 no.3
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• pp.68-74
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• 2017

Big data processing processes various types of data such as files, images, and video to solve problems and provide insightful useful information. Currently, various platforms are used for big data processing, but many organizations and enterprises are using Hadoop for big data processing due to the simplicity, productivity, scalability, and fault tolerance of Hadoop. In addition, Hadoop can build clusters on various hardware platforms and handle big data by dividing into a name node (master) and a data node (slave). In this paper, we use a fully distributed mode used by actual institutions and companies as an operation mode. We have constructed a Hadoop cluster using a low-power and low-cost single board for smooth experiment. The performance analysis of Name node is compared through the same data processing using single board and laptop as name nodes. Analysis of influence by number of data nodes increases the number of data nodes by two times from the number of existing clusters. The effect of the above experiment was analyzed.

• The KIPS Transactions:PartA
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• v.13A no.4 s.101
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• pp.289-294
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• 2006

Checkpointing is an effective mechanism that allows a process to resume its execution that was discontinued by a system failure without having to restart from the beginning. Especially, page-level incremental checkpointing saves only the modified pages of a process to minimize the checkpointing overhead. This means that in incremental checkpointing, the time consumed for checkpointing varies according to the amount of modified pages. Thus, the efficient interval of checkpointing must be determined on run-time of the process. In this paper, we present an efficient and adaptive page-level incremental checkpointing facility that is based on the cost analysis of process execution time. In our simulation, results show that the proposed mechanism significantly reduced the average process execution time compared with existing fixed-interval-based page-level incremental checkpointing.

• The KIPS Transactions:PartA
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• v.8A no.4
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• pp.287-292
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• 2001

Multimedia service systems should have efficient capacity to serve the growing clients and new data. In the general streaming services, users can endure the small amount of time delay at the beginning of service. But they want to have good quality of service. A streaming server tries to transfer video files to clients from a repository of files in real time. The server must guarantee concurrent and uninterrupted delivery of each video stream requested from clients. To achieve its purpose, many stream servers adopt multi-processors, sufficient memory, and RAID or SAN in their systems. In this paper, we propose a Linux-based parallel media streaming server. It is superior to the other systems in the storing structure, fault-tolerance, and service capacity. Since this system supports the web interlace, users can operate easily through the www. This system uses unique striping policy to distribute multimedia files into the parallel storage nodes. If a service request occurs, each storage node transmits striped files concurrently to the client. Its performance is better than the single media streaming service because of the parallel architecture.

• Journal of the Korea Society of Computer and Information
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• v.25 no.4
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• pp.47-53
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• 2020

Blockchain is a distributed shared ledger that transparently manages information through verification and agreement between nodes connected to a distributed network. Recently, cases of data management among authorized agencies based on private blockchain are increasing. In this paper, we investigated the application cases and technical processes of PBFT, the representative consensus algorithm of private blockchain, and proposed a modified PBFT algorithm that enables efficient consensus by simplifying duplicate verification and consensus processes that occur during PBFT processing. The algorithm proposed in this paper goes through the process of selecting a delegation node through an authoritative node and can increase the safety of the delegation node selection process by considering an efficient re-election algorithm for candidate nodes. By utilizing this research, it is possible to reduce the burden on the network communication cost of the consensus process and effectively process the final consensus process between nodes.

• Journal of the Korea Institute of Military Science and Technology
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• v.24 no.3
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• pp.328-338
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• 2021

A study on common modular design based on open standards to reduce the life cycle cost of ground weapon system is underway. Since the ground weapon system includes major mission equipment such as fire control system, it is essential to apply the concept of fault tolerance through automatic reconfiguration and blocking unspecified equipment through connectivity control. However, it is difficult to generalize due to the difference in operating characteristics for each system. In this paper, we propose a plug-and-play framework, which includes plug-and-play architecture and mechanism. The proposed method can be used in common by the application of each component as it is divided into a common service layer. In addition, the proposed connectivity control and autonomous reconfiguration method facilitates reflection of operating characteristics for each system. We constructed a verification environment that can simulate ground weapon systems and components, and verified that the proposed framework works through scenario-based functional tests.

• Journal of Advanced Navigation Technology
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• v.25 no.4
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• pp.273-279
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• 2021

A flight control computer(FLCC) applied to an unmanned aerial vehicle(UAV) is a safety-critical item, and which is designed in a multiple structure to increase the reliability of operation by securing fault tolerance. These FLCC of multiple structure should be designed so that each independent processing/control components can perform the same operation at the same time. And for this reason, a synchronization algorithm for synchronizing the operation between FLCCs should be included in an operational flight program. In this paper, we propose a software design method for synchronization between dual FLCCs applied to UAVs. The proposed synchronization method is designed to synchronize using only the minimum hardware resources to reduce a failure rate. In addition, the proposed synchronization method is designed to minimized synchronization errors due to a timer operation by designing in consideration of operation characteristics of the hardware timer used for the synchronization.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.1
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• pp.146-152
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• 2022

Information collected from temperature, humidity, inclination, and pressure sensors using Raspberry Pi or Arduino is used in automatic constant temperature and constant humidity systems. In addition, by using it in the agricultural and livestock industry to remotely control the system with only a smartphone, workers in the agricultural and livestock industry can use it conveniently. In general, temperature and humidity are expressed in a line graph, etc., and the change is monitored in real time. The technology to visually express the temperature has recently been used intuitively by using an infrared device to test the fever of Corona 19. In this paper, the information collected from the Raspberry Pi and the DHT11 sensor is used to predict the temperature change in space through intuitive visualization and to make a immediate response. To this end, an algorithm was created to effectively visualize temperature and humidity, and data representation is possible even if some sensors are defective.