• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.4
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• pp.17-22
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• 2011

The underwater environments are quite different from the terrestrial ones in terms of the communication channel and constrains. In underwater wireless sensor network, the probability of node failure is high because sensor nodes are deployed in more harsh environments than the ground based networks and moved by waves and currents. There are researches considering the communication environments of underwater to improve the data transmission throughput. In this paper, we present a checkpointing scheme of the cluster heads that recoveries from a cluster head failure quickly. Experimental results show that the proposed scheme enhances the reliability of the networks and more efficient in terms of the energy consumption and the recovery latency than without checkpointing.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.12
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• pp.4725-4747
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• 2020

Software defined networking (SDN) is considered to be one of the most promising paradigms in the future. To solve the scalability and performance problem that a single and centralized controller suffers from, the distributed multi-controller architecture is adopted, thus forms multi-domain SDN. In a multi-domain SDN network, it is of great importance to ensure a reliable control plane. In this paper, we focus on the reliability problem of multi-domain SDN against controller failure from perspectives of backup controller deployment and controller replication. We firstly propose a placement algorithm for backup controllers, which considers both the reliability and the cost factors. Then a controller replication mechanism based on shared data storage is proposed to solve the inconsistency between the active and standby controllers. We also propose a shared data storage layout method that considers both reliability and performance. Besides, a fault recovery and repair process is designed based on the controller backup and shared data storage mechanism. Simulations show that our approach can recover and repair controller failure. Evaluation results also show that the proposed backup controller placement approach is more effective than other methods.

• Nuclear Engineering and Technology
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• v.53 no.10
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• pp.3236-3246
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• 2021

Lessons learned from the Fukushima Daiichi nuclear power plant accident directed that multiple failures should be considered more seriously rather than single failure in the licensing bases and safety cases because attempts to take accident management measures could be unsuccessful under the high radiation environment aggravated by multiple failures, such as complete loss of electric power, uncontrollable loss of coolant inventory, failure of essential safety function recovery. In the case of the complete loss of electric power called station blackout (SBO), if there is no mitigation action for recovering safety functions, the reactor core would be overheated, and severe fuel damage could be anticipated due to the failure of the active heat sink. In such a transient condition at CANDU-6 plants, the seal failure of the primary heat transport (PHT) pumps can facilitate a consequent increase in the fuel sheath temperature and eventually lead to degradation of the fuel integrity. Therefore, it is necessary to specify the regulatory guidelines for multiple failures on a licensing basis so that licensees should prepare the accident management measures to prevent or mitigate accident conditions. In order to explore the efficiency of implementing accident management strategies for CANDU-6 plants, this study proposed a realistic accident analysis approach on the SBO transient with multiple-failure sequences such as seal failure of PHT pumps without operator's recovery actions. In this regard, a comparative study for two PHT pump seal failure modes with and without coolant seal leakage was conducted using a best-estimate code to precisely investigate the behaviors of thermal-hydraulic parameters during transient conditions. Moreover, a sensitivity analysis for different PHT pump seal leakage rates was also carried out to examine the effect of leakage rate on the system responses. This study is expected to provide the technical bases to the accident management strategy for unmitigated transient conditions with multiple failures.

• Journal of the Korean Operations Research and Management Science Society
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• v.35 no.3
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• pp.1-24
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• 2010

As the Internet is explosively growing and the market is rapidly globalized, many entrepreneurs have been given an impetus to take on the function of the intermediation between providers and customers. Organizations performing the mediating roles in the cyberspace are termed 'cybermediary' and often called 'Openmarket' as a kind of transactional cybermediary in Korea. Despite sustainable growth of Openmarket, customer complaints and damages are increasing because of absence of recovery standards after a service failure. Therefore, it is important that a service provider converts dissatisfied customers to advocates for the growth of the Openmarket. This study aims to examine the role of recovery of the service failures for the Openmarket by proposing a relationship between complaint handling and continuance based on the equity theory. From the empirical results, we found that interactional equity had significant effects on both overall service satisfaction and recovery satisfaction, while procedural equity significantly influenced only recovery satisfaction. Recovery satisfaction also had an impact on overall service satisfaction and each satisfaction factor was positively related to continuance intention.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.9B
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• pp.793-805
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• 2003

In OBS (Optical Burst Switching) networks which decouple the burst from its header, the fault of a fiber link can lead to the failure of all the light-path that traverses the fiber. Because each light-path is expected to operate at a rate of a few Gbps by using WDM (Wavelength Division Multiplexing) technology, any failure may lead to large data loss. Therefore, an efficient recovery scheme must be provided. In this paper, we analyze network utilization and BCP (Burst Control Packet) loss rate according to each link failure by applying the conventional restoration schemes in OBS networks. And through these simulation results, an ASPR scheme is proposed improve the fault management scheme in terms of recovery time and throughput. Finally, We compare the performance of our proposed scheme with that of the conventional one with respect to burst loss rate, resource utilization and throughput by OPNET simulations.

• Journal of Communications and Networks
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• v.16 no.5
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• pp.534-547
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• 2014

Large-scale failures resulting from natural disasters or intentional attacks are now causing serious concerns for communication network infrastructure, as the impact of large-scale network connection disruptions may cause significant costs for service providers and subscribers. In this paper, we propose a new framework for the analysis and prevention of network service disruptions in large-scale failure scenarios. We build dynamic deterministic and probabilistic models to capture the impact of regional failures as they evolve with time. A probabilistic failure model is proposed based on wave energy behaviour. Then, we develop a novel approach for preventive protection of the network in such probabilistic large-scale failure scenarios. We show that our method significantly improves uninterrupted delivery of data in the network and reduces service disruption times in large-scale regional failure scenarios.

• Knowledge Management Research
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• v.11 no.3
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• pp.59-76
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• 2010

The knowledge of customer in healthcare service industry is widely accepted as one of the key information for the customers' satisfaction. Previous studies on the customer knowledge about service recovery showed that service providers are having difficulties with standardizing interaction with customer, This study investigated the attribution according to the failure in providing medical services and customer's participation as preceding variable of attribution. A survey was carried out targeting an obesity clinic having high participating rate from May 10 to May 28, 2010. The research results revealed that from whom the responsibility of the service failure originated between the patients and the medical institutions depending on the extent of the patients involvement in service process.

• Journal of Service Research and Studies
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• v.9 no.4
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• pp.97-114
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• 2019

The relationship quality and recovery of service failures perceived by consumers play an essential role in affecting the service provider's image and sales in terms of the highly involved service industry. In particular, implementation of successful relationship marketing strategies and effective recovery of service failures provide greater satisfaction for customers expecting customized services and reinforce the relationships between the companies and consumers. Based on these previous studies, this research conducted to find out the causal relationship between the variables influencing service recovery expectations and word of mouth(WOM) by approaching the severity of service failures from the perspective of relationship marketing and attribution theory. For the empirical analysis of this research, we conducted a questionnaire surveys of 360 service users of beauty salons, who have experienced in high-involvement services, and utilized 333 questionnaires for the final analysis. The hypothesis was experimented using the Structural Equation Model(SEM), and the results are as follows. First, we identified that the higher the customer perceived the severity of the service failure, the lower the quality of the relationship. Second, we verified that service users observed service failure as a temporary and uncontrollable factor as they distinguished service quality as higher. Third, the hypothesis that customers recognize service failures as a temporary one has a positive impact on service recovery expectation level is determined through empirical analysis. Forth, it was figured out that the higher the perceived quality of the relationship with the service provider, the higher the service recovery level expected by the consumers. At the same time, the hypothesis that optimism for service recovery expectation affects positive word of mouth has been verified. The results of this study help develop the customer-oriented business model of the service companies. Furthermore, the academic significance in that it suggested a new direction for the research of high-involvement service marketing.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2002.03a
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• pp.187-194
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• 2002

Bridge dynamic behaviors and the failure of the foundation are examined in this study under seismic excitations including the local scour effect. The simplified mechanical model, which can consider the effect of various influence elements, is proposed to simulate the bridge motions. The scour depths around the foundations are estimated by the CSU equation recommended by the HEC-18 and the local scour effect upon global bridge motions is then considered by applying various foundation stiffness based upon the reduced embedded depths. From the simulation results, it is found that seismic responses of a bridge with the same scour depth for both foundations increase due to the local scour effect. The bridge scour is found to be significant under weak and moderate seismic intensity. The recovery durations of the foundation stiffness after local scour are found to be critical in the estimation of the probability of foundation failure under earthquakes. Therefore, the safety of the whole bridge system should be conducted with the consideration of the scour effect upon the foundations and the recovery duration of stiffness should be determined rationally.

• Journal of Embryo Transfer
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• v.17 no.3
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• pp.235-238
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• 2002

The present study was undertaken to find out possibilities for superovulation and recovery of freezable/transferable embryo from repeat breeding crossbred cows. For this study a total of 10 Holstein crossbred cows having history of failure of conception even after more than 4~5inseminations were taken and superovulated using Folltropin-V at 100 to 140% dose schedule. The results indicated that out of 10 donors, 8 responded to superovulatory treatment and yielding a total of 94 embryos, out of which 45 were of transferable/freezable quality. The mean ovulations and mean transferable embryos were 11.5$\pm$2.91 and 4.5$\pm$1.66, respectively. These observations suggests that the repeat breeding cows having conception failure after several artificial inseminations can be used as donors for production of embryos and calves through embryo transfer technology.