• Proceedings of the KSR Conference
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• 2000.05a
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• pp.352-359
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• 2000

In this paper, the method is used that each system isolates the part in which faults are occurred in case of fault occurrence since total system is designed in the type of hot standby sparing system construction and self-checking circuit in each system is attached to the memory being of the high failure rate in common communication system. Thus reliability and availability in system are improved. In this thesis, self-checking circuit was designed using 2 out of 6 code and didn't have any effect to the system operation. For the purpose of verification, each system attached with self-checking circuit was simulated through fault injection arid the continuity of each system in hot standby sparing system was tested in case that the system was switched when faults in the system were occurred.

• The KIPS Transactions:PartD
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• v.10D no.6
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• pp.949-960
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• 2003

Main memory database systems use the different implementation techniques to sturucture and organize the user dta and system catalogs, since traditional database systems are optimized for the characteristics of disk storage environment. We present, in this paper, the design considerations for our main memory database system $ALTIBASE^{TM}$ that is currently applied to the time-critical applications. We focus on the design issues of storage manager in $ALTIBASE^{TM}$. The major components are introduced, and features and characteristics of transaction management and recovery method are described. We also present the database replication mechanism and its conflict resolution mechanism for high availability and performance. In order to evaluate our transaction performance, we show various experimental reports as measured by the TPS.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.11
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• pp.1628-1632
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• 2013

HEP(Head Electric Power) system, supplying 3-phase service power to the coach vehicles, is a kind of special auxiliary power equipment which is boarded on 8200 series electric locomotives in KORAIL. This equipment shares high voltage DC link with a main propulsion converter/inverter systems. It was difficult to use high frequency PWM technique so that GTO has been used as a power device same like the main power system. Due to low PWM frequency(300Hz) of HEP inverter, the output voltage has less power quality comparing to normal SIV(Static Inverter) system. In this paper, an optimal PWM strategy is presented for new IGBT type HEP inverter system. Several PWM techniques were investigated to improve output voltage quality under fixed lower filter inductance and not high PWM frequency. Finally PC simulations have been done to clarify its availability.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.44 no.6
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• pp.10-18
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• 2007

In consideration of increment and importance for data, an efficient and large storage backup system requires. Existing backup system solutions show some limitations in speed and technical. In order to solve these deficiencies, backup and recovery system of high efficiency and large storage capacity was designed and implemented by using high speed, compression technique and backup accelerator etc. Backup and recovery system applies to multi-threading, multi-processing and multi-streaming technology. And already established systems based on tape, but proposed backup operating model designed on disk. Therefore, the implemented of system leads to these backup media problems as well as solutions to aforementioned issues with existing backup system.

• The KIPS Transactions:PartA
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• v.12A no.2 s.92
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• pp.171-180
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• 2005

In distributed systems data are replicated and stored at several nodes to increase the availability and overall performance. Here Quorum protocol doffing a certain set of replicas required for read/write operation exists for global concurrency control. One of the representative replication Protocols - the Tree Quorum protocol - has a drawback of rapidly growing number of replicas as the level increases, while the Grid protocol requires the same operation cost even without any failure. In this paper, thus, we propose a new replication protocol called hybrid protocol which capitalizes the merits of the existing protocols and solves the problems of them at the same time. The proposed hybrid protocol has very low operation cost in the absence of failure like the tree quorum protocol, and has relatively lower operation cost and higher availability than existing protocols when failure occurs by employing tree architecture as the overall organization while each level of the tree is organized as a row of a grid architecture. It is thus effective to be applied to survival storage system. We conduct cost and availability analysis of the proposed protocol through mathematical modeling, and response time and throughput are compared with those of the Tree Quorum protocol through computer simulation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.2
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• pp.447-454
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• 2009

This study investigates to information medium and small enterprises and analyzed how enterprise's integration information system affects to business users. Many medium and small enterprises are introducing and operate new integrated system for latest several years, but it is suffering difficulty in substantial business analysis as unstable system, maintenance and insufficiency of management controls. Therefore, in this study, tried to analyze common problem and solution to enterprise which is operating integration information system stably. Designed study model and research hypothesis to variable of information level, system availability, information availability, information creation level, service availabilities for this analysis. This studγ got conclusion as following. First, If system usefulness, information usefulness, information creation level, service usefulness are high, Analysis result about user business performance appeared very positive effect. Second, Analyzed to which lack a little user realization about information level in details measured variable. This study will be able to become data that is useful in stable system introduction in various field of industry of medium and small enterprises hereafter.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.45 no.4
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• pp.41-52
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• 2008

Ubiquitous service environment is poor in reliability of connection and has a high probability that the intrusion and the system failure may occur. Therefore, in the environment, the capability of a system to collectively accomplish its mission in spite of active intrusions and various failure scenarios, that is, the survivability of services are needed. In this paper, we analyze the Jgroup/ARM framework that was developed in order to help the development of fault- tolerant Jini services. More importantly, we propose an intrusion-tolerant Jini service architecture to satisfy the security availability and quality of services on the basis of the analysis. The proposed architecture is able to protect a Jini system not only from faults such as network partitioning or server crash, but also from attacks exploiting flaws. It is designed to provides performance enough to show a low response latency so as to support seamless service usage. Through the experiment on a test-bed, we have confirmed that the architecture is able to provide high security and availability at the level that degraded services quality is ignorable.

• Journal of Korean Institute of Industrial Engineers
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• v.42 no.1
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• pp.20-29
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• 2016

This paper considers one-shot systems such as missiles, air bags of automobiles that are stored for a long time and are used at most once. One shot systems are inspected periodically to detect system failures and repair the system because we do not know whether the system will work or not on demand. Thus, we can keep high availability of the system by periodic inspection. Martinez (1984) obtained the system reliability approximately. In this paper, we obtain the exact system reliability under periodic inspection. Finally, we compare the system reliability from our formula with one of Martinez (1984) by numerical examples.

• Journal of the Korean Vacuum Society
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• v.5 no.4
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• pp.269-277
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• 1996

The vacuum systems of PLS linac provides average pressure of $2.6\times 10^{-6}$Pa under high power microwave of 54 MW peak with 4.1 $\mu \textrm s$ pulse width and 10 Hz repetition rates. The base pressure of system is$2.4\times 10^{-6}$Pa with 45$^{\circ}C$ cooling water. The outgassing rate of the system is decreased from $3.0\times 10^{-11}Torr-l/sec-\textrm{cm}^2$ at the initial stage after installation to $1\times 10^{-12}Torr-l/sec-\textrm{cm}^2$ at present. Total accumulated microwave energy dose is about 140 GJ per module. All ion pumps are working under saturated regime and effective pumping speeds of 60 I/s, 230 I/s ion pumps are 45 I/s, 65 I/s, 140 I/s under the operating range. Main problems occurred in recent year are troubles of ion pump controller and vacuum gauge controller, vacuum leak of energy doubler window and electron gun ceramic, and water leak in the dummy load of acceleraing columns. Total of 41 troubles with 140. 8 hours down time give good system availability of 98%. Down time can be reduced by high power waveguide valves and water dummy loads under development, and then availability is expected to be increased up to 99.5%.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.10A
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• pp.1113-1122
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• 2004

This paper is basically to achieve the high-availability and high-reliability of the control system from the implementation of the fault-tolerant system using the hot-standby sparing technique. To meet the objective, we design and implement a board with fault tolerance I/O bus to detect the fault. Warm-standby sparing technique is the fault tolerance technique usually used for switching control system in present. This technique can be easily implemented, but can not detect the fault quickly and can malfunction because of the hardware fault. The hot-standby sparing fault tolerant technique implemented in this paper is consists of dual processor modules and a I/O processor using fault tolerant I/O bus. The proposed method can find the faults as soon as possible, so it can prevent from wrong operation. Also it is possible to normal re-service due to the short recovering time. To implement the fault-tolerant dual system with fault detection be, two daughter, called FTMA and FTIA, boards designed and implemented are applied to the system. And we also simulated the proposed method to verify the high-availability and high-reliability of the control system using Markov process.