• Journal of the Korea Society for Simulation
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• v.7 no.2
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• pp.63-78
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• 1998

The hierarchical cell structure consists of the macrocell and microcells to increase the system capacity and to achieve broad coverage. The hierarchical cell structure provides services for users in different mobility. In this paper, an analytical queueing model in mobile networks is proposed for the performance evaluation of the hierarchical cell structure. The model for networks with the multiple levels can simplify multi-dimensional ones into one-dimensional queueing model. The computational advantage will be growing as the layers are constructed in multiple levels. The computer simulation is provided for validating the proposed analytical model.

• Journal of Korean Library and Information Science Society
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• v.32 no.4
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• pp.45-75
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• 2001

University library is more than just a collection. In other words, it is an access point and gateway to a world-wide information. Therefore, the evaluation of hybrid library and information services should be recognized an essential management activity. The goal of this study is to develope a new evaluation model for Korean university libraries, based on the analysis of existing models and perception level of the shakeholder groups. As result of statistical analysis, the study suggested six evaluation domains, thirty-seven indicators, and the relative importance (weight) and measure criterion.

• Convergence Security Journal
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• v.11 no.6
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• pp.67-72
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• 2011

A system that provides a ubiquitous service is a networked system that has to overcome their circumstances that the service survivability is weak. the survivability of a networked system is defined as an ability of the system that can offer their services without interruption, regardless of whether components comprising the system are under failures, crashes, or physical attacks. This paper presents an approach that end users can obtain a quantitative evaluation of U-service survivability to reflect intended cyber attacks causing the networked system to fall into byzantine failures in addition to the definition of the survivability. In this paper, a Jini system based on wireless local area networks is used as an example for quantitative evaluation of U-service survivability. This paper also presents an continuous time markov chain (CTMC) Model for evaluation of survivability of U-service that a Jini system provides, and an approach to evaluate the survivability of the U-service as a blocking probability that end users can not access U-services.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.32 no.2
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• pp.112-119
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• 2009

Telecare, one of the e-healthcare services with lCT, is a promising technology which aims to monitor the state of patients and then provide the medical services appropriately in remote sites. Virtual telecare team based on the concept of virtual collaborative teams which consist of a patient, a doctor, and a telecare team, operates on a temporary basis in need. Reputation, which means the degree of a patient's belief to a doctor in consideration, is the most important factor to make the virtual telecare team trustable. In this paper, we propose the fuzzy reputation model of a virtual telecare team, which is a reputation-based trust model based on fuzzy set theory. An illustrative example is also given in order to show the applicability of the model to the concept of a virtual telecare team.

• Journal of Information Technology Services
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• v.15 no.3
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• pp.97-114
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• 2016

One of the key success factors for the intelligent IT service which is characterized by personalization and automation, is to obtain relevant data from either sensors or data storage for reasoning, analyzing and forecasting. The availability of the open data sources such as public portal sites remarkably increases the efficiency and quality of the intelligent IT service. However, with the condition that not all data in the existing public or private sites are opened or have various types of openness, it prohibits the value of utilization. For these reasons, it is highly required to evaluate the extent of openness of data storage. However, there are only a few studies which explore the factors which affect the degree of data openness with respect to intelligent IT services. Hence, this study aims to propose an evaluation model including the indices to evaluate a process of opening data for the intelligent IT service from a viewpoint of data utilization process. The indices are applied to evaluate the actual multinational websites, which provide public data for verification. We also discuss the implications of the evaluation according to the results.

• Journal of the Korea Convergence Society
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• v.9 no.10
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• pp.75-80
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• 2018

In this paper, we propose heterogeneous lifelog mining model in health big-data platform. It is an ontology-based mining model for collecting user's lifelog in real-time and providing healthcare services. The proposed method distributes heterogeneous lifelog data and processes it in real time in a cloud computing environment. The knowledge base is reconstructed by an upper ontology method suitable for the environment constructed based on the heterogeneous ontology. The restructured knowledge base generates inference rules using Jena 4.0 inference engines, and provides real-time healthcare services by rule-based inference methods. Lifelog mining constructs an analysis of hidden relationships and a predictive model for time-series bio-signal. This enables real-time healthcare services that realize preventive health services to detect changes in the users' bio-signal by exploring negative or positive correlations that are not included in the relationships or inference rules. The performance evaluation shows that the proposed heterogeneous lifelog mining model method is superior to other models with an accuracy of 0.734, a precision of 0.752.

• Journal of Information Technology Services
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• v.13 no.3
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• pp.323-331
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• 2014

This research is based on real-time service model that uses lock screen of smart devices which is mostly exposed to device users. The potential for lock screen space is immense due to their exposing time for user. The effect can be maximized by offering useful information contents on lock screen. This service model offers real-time keyword with abridged sentence. They match real-time keyword with news by using text matching algorithm and extracts kernel sentence from news to provide short sentence to user. News from the lock screen to match real-time query sentence, and then only to the original core of the ability to move a user evaluation was conducted after adding. The report provided a key statement users feel the lack of original Not if you go to an average of 5.71%. Most algorithms allow only real-time zoom key sentence extracted keywords can accurately determine the reason for that was confirmed.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.9 no.2
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• pp.50-57
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• 1995

In this paper the model was analyzed on performance evaluation for IN facility and we carried out evaluation on it's service performance using this model as an example. We used simulation method and operation analysis method as evaluation technology. As the evaluation results, the case of simulation method was nearly consistent with the case of the operation analysis method and the user-network interaction time had more effect on service performance than delay time of IN facility. We expects that the performance models proposed in this paper is useful when operating, managing and designing IN services in considering service performance.

• Journal of Information Technology Services
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• v.8 no.1
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• pp.59-71
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• 2009

Korean government has operated EA by the act on efficient introduction of information system and operation. etc. But the utilization and the evaluation system for EA don't prepare well. In this study. we analyzed characteristics and advantages of EA maturity models that is developed by some domestic and foreign government departments in logical view. and then we derive evaluation scopes and factors of the models. Also. we applied the models to EA maturity for the B organization and measured maturity levels. We identify similarity and difference between the models. We propose evaluation scopes, levels and factors between the models and solutions for evaluation ambiguity by evaluators and maturity improvement through the identified results.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.5
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• pp.2396-2413
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• 2018

Trust management is one of the most challenging issues for the highly heterogeneous Internet of Things (IoT). In the context of the IoT, it is difficult to evaluate the node's trustworthiness in the same trust model when a node provides different services. Guaranteeing the availability of the trust management service is another significant challenge because of the dynamic nature of IoT environments. With these issues in mind, this paper propose a robust and adaptive trust management system for the IoT that is able to measure the trustworthiness of nodes based on feedbacks collected from participants in a specific context and ensure the availability of trust management services. The main contributions of our system are: 1) Proposing a partly decentralized trust management framework, which improves the resiliency of the trust mechanism; 2) Proposing an adaptive trust evaluation scheme and a three-dimensional context representation makes trust evaluation more accurate and specific; 3) Enhancing the adaptive trust evaluation scheme by incorporating a bad behavior factor in trust estimation, which efficiently distinguishes misleading feedbacks from On-Off attacks. Simulation results show the good performance of the proposed system and especially show effectiveness against On-Off attacks compared to other trust mechanisms.