• The Journal of the Korea Contents Association
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• v.14 no.10
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• pp.270-278
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• 2014

The stability and security management of IT data becomes more important because information security threats increases rapidly in Big Data era. The operational policy of the data backup considering information security threats is required because the backup policy is the fundamental method that prevents the damage of security threats. We present an economic approach for a data backup system with information security threats which damage the system. The backup operation consists of the differential backup and the batch backup. We present a stochastic model considering the occurrence of information security threats and their damage. We analyze the stochastic model to derive the performance measures for the cost analysis. Finally we analyze the average cost of the system and give numerical examples.

• IE interfaces
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• v.16 no.spc
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• pp.99-104
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• 2003

While demands for express service are rapidly increasing according to recent progress of electronic commerce, express service companies are struggling to take a larger delivery service market share through ongoing improvement in their service processes. Extension of cut-off time for express service centers can provide the express company with increase of total sales, but it may also cause to increase the possibility not to satisfy customer needs due to work delay in the consolidation terminal. Therefore, compromised decision for cut-off time of each service center should be made by taking operation characteristics of the consolidation terminal into account. This study suggests an approach for determining the cut-off time for express service centers according to operational characteristics of the consolidation terminal with the objective of maximizing expected incremental sales. The problem defined in this study can be represented as two successive models; one is an integer programing model in which the best cut-off time for each sales center are determined, and the other is a single machine scheduling model in which a working schedule in the consolidation terminal is obtained. A genetic algorithm is developed to solve the two models simultaneously. Finally, an example problem is carried out to verify applicability and performance of the algorithm with the data set collected from an express company.

• Smart Structures and Systems
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• v.24 no.5
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• pp.631-639
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• 2019

Finite element analysis is one of the important methods to study the structural performance. Due to the simplification, discretization and error of structural parameters, numerical model errors always exist. Besides, structural characteristics may also change because of material aging, structural damage, etc., making the initial finite element model cannot simulate the operational response of the structure accurately. Based on Bayesian methods, the initial model can be updated to obtain a more accurate numerical model. This paper presents the work on the field test, modal identification and model updating of a Chinese reinforced concrete pagoda. Based on the ambient vibration test, the acceleration response of the structure under operational environment was collected. The first six translational modes of the structure were identified by the enhanced frequency domain decomposition method. The initial finite element model of the pagoda was established, and the elastic modulus of columns, beams and slabs were selected as model parameters to be updated. Assuming the error between the measured mode and the calculated one follows a Gaussian distribution, the posterior probability density function (PDF) of the parameter to be updated is obtained and the uncertainty is quantitatively evaluated based on the Bayesian statistical theory and the Metropolis-Hastings algorithm, and then the optimal values of model parameters can be obtained. The results show that the difference between the calculated frequency of the finite element model and the measured one is reduced, and the modal correlation of the mode shape is improved. The updated numerical model can be used to evaluate the safety of the structure as a benchmark model for structural health monitoring (SHM).

• Knowledge Management Research
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• v.22 no.1
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• pp.139-154
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• 2021

As environmental impacts on business management rapidly rise, the importance of resilience has been emphasized ever. Resilience can be defined as the capability to quickly return to daily operational levels after external shocks. Thus, we suggest and empirically verify a conceptual model using enterprise-level resilience in knowledge management. Based on previous studies, sub-components of resilience have been distinguished into R4(i.e., Robustness, Redundancy, Resourcefulness, and Rapidity) and the internal and external knowledge management activities of companies have been identified as prior factors. Considering resilience as mediating variables, firms' knowledge management activities are assumed to affect a firms' performance. We collected data with the structured survey which had been developed from the stepwise approach to verify the structural model that leads to knowledge management activities, resilience, and performance. In further research, we request exploratory research on independent variables that can increase the firms' resilience and on dependent variables that would be influenced by the enterprise-level resilience.

• Journal of Industrial Convergence
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• v.20 no.7
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• pp.21-30
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• 2022

In this study, This study focuses on exploring the major factors influencing the successful introduction of the cloud-based accounting information system, which is the top priority in the field of corporate digital transformation. Therefore, theories were summarized based on the company's cloud environment and related prior research, and the major performance factors of the company were analyzed by dividing them into organizational factors, business operation factors, and technical system factors. Considering that the cloud-based accounting information system is in the early stages of its introduction, the research analysis method ranks major success factors according to their importance using the Delphi targeting the expert panel, through the AHP method, the major performance variables were finally explored through the mutual importance analysis of each major factor. As a result of the analysis, organizational factors were analyzed as corporate sustainability, business operational factors were the business solutions, and system scalability factors were analyzed. This study will be able to provide additional useful information on the initial introduction strategy and operation for the introduction and operation of the cloud-based accounting information system.

• Journal of Positioning, Navigation, and Timing
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• v.13 no.3
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• pp.355-363
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• 2024

Time synchronization is crucial for ensuring the reliable operation of modern economic and social infrastructures. Techniques such as Global Navigation Satellite System (GNSS)-based methods and Two-Way Satellite Time and Frequency Transfer (TWSTFT) play key roles in precise time comparison and synchronization. TWSTFT, in particular, is recognized for its ability to achieve sub-nanosecond accuracy in time transfer, making it indispensable in fields such as satellite navigation. This paper proposes a comprehensive performance evaluation method for TWSTFT modems, emphasizing pre-validation in controlled environments to mitigate operational challenges. Using the proposed evaluation method, the study presents the standard deviation of RTT according to C/N₀ and compares it with the datasheet of a commercial TWSTFT modem. Through this approach, the aim of this study is to enhance the reliability and accuracy of TWSTFT-based time synchronization across diverse applications.

• Journal of Satellite, Information and Communications
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• v.10 no.2
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• pp.95-101
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• 2015

The backup site operation of the Image Data Acquisition and Control System (IDACS) for Communication Ocean Meteorological Satellite (COMS) is discussed in terms of the ground station configuration, image data processing, and the characteristics of backup activities for both the meteorological image data and the ocean image data. The well-performed backup operation of the COMS IDACS is also confirmed with the first three years normal operation results from April, 2011 to March, 2014. The operation results are analyzed through statistical approach to provide the achieved operational performance of the image data reception, preprocessing, and broadcast.

• ETRI Journal
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• v.39 no.3
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• pp.353-363
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• 2017

Recently, sink mobility has been shown to be highly beneficial in improving network lifetime in wireless sensor networks (WSNs). Numerous studies have exploited mobile sinks (MSs) to collect sensed data in order to improve energy efficiency and reduce WSN operational costs. However, there have been few studies on the effectiveness of MS operation on WSN closed operating cycles. Therefore, it is important to investigate how data is collected and how to plan the trajectory of the MS in order to gather data in time, reduce energy consumption, and improve WSN network lifetime. In this study, we combine two methods, the cluster-head election algorithm and the MS trajectory optimization algorithm, to propose the optimal MS movement strategy. This study aims to provide a closed operating cycle for WSNs, by which the energy consumption and running time of a WSN is minimized during the cluster election and data gathering periods. Furthermore, our flexible MS movement scenarios achieve both a long network lifetime and an optimal MS schedule. The simulation results demonstrate that our proposed algorithm achieves better performance than other well-known algorithms.

• Proceedings of the KOR-KST Conference
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• 1995.02a
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• pp.35-56
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• 1995

A methodology to the operation standards of the service performance of airport terminal fadlities using Perception-Response Model is discussed in this paper. The proposed approach has defined as the graphical presentation of the collective attitudes of a category of passengers towards the range of operational service at a facility of airport terminal. It adopts new concepts to establish service standards through special survey, that can achieve better interpretation of capadty and level of service at each facility. It is expressed in terms of perception of the passenger population of different amounts of the service measure and their response to the respective service conditions classified into distinct levels of satisfaction with service. The methodology can provide a practical service standards of airport terminals and may prove to be a practical and convenient technique to airport planners, designers, consultants, operators, and to airport managers.

• Journal of Korea Association of Health Promotion
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• v.3 no.1
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• pp.97-109
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• 2005

Chronic fatigue syndrome(CFS) is a complex, debilitating disorder characterized by at least 6 months of severe persistent of relapsing fatigue and a group of characteristic but nonspecific symptoms. Many researchers have proposed that CFS has a specific cause. However currently no evidence exists that proves either a specific cause of CFS. And there is no diagnostic test for CFS. The diagnosis of chronic fatigue syndrome is based on the patient's history, excluding other illnesses In the absence of consistent biological markers, the diagnosis of CFS arises from operational criteria that do not afford validity. The prognosis is poor and often disability and impairment of daily function and performance are prolonged. A limited understanding of the CFS has complicated the management of this disorder. Therefore, treatment of CFS may be variable and should be tailored to each patient. Therapy should include exercise, diet, good sleep hygiene, antidepressants, and other medications, depending on the patient's presentation. Regular follow-up is key to continue to exclude other medical problems and provide support for patients. Chronic fatigue syndrome is a challenging illness to manage and requires a team approach of caring providers. For the majority of patients this is a chronic illness with the goals of therapy being to improve functional status and to prevent disability. Further understanding of the etiology and pathogenesis of this illness should lead to better specific therapy.