• Journal of Korea Society of Digital Industry and Information Management
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• v.14 no.3
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• pp.1-10
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• 2018

Social network services allow you to share your thoughts and preferences more easily. They share your views with a large number of people who are friends with you without restriction of time or place. In the IoT environment, the amount of data is massively increasing as social network services spread rapidly. This change in the environment is driving the need for research into new retrieval methods that are different from conventional retrieval methods. In this paper, we propose a progressive retrieval method using the intimacy of social network users in the IoT. The first thing is to extract the user with the highest intimacy by using the property that the number of the owner of the information stored in the IoT environment is small. By accessing information in objects owned by these extracted users, the amount of information retrieved is reduced. It also improves retrieval efficiency by gradually retrieving information according to the user's level of interest. We present a new retrieval method and algorithm. The scenario also illustrates the effectiveness of the proposed method.

• International Journal of Contents
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• v.5 no.3
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• pp.8-13
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• 2009

The recent Web service field emerges as the fastest growing IT paradigm as a result of the increasing interest in SOA (Services-Oriented Architecture) and the expansion of B2B market. With an increasing number of Web service that provide similar features, it becomes more important to provide the most appropriate service for the user's request. A service user in general requires the quality information of Web service when selecting a service among a number of similar Web services. Yet, finding a service through UDDI (Universal Description, Discovery and Integration) does not consider the non-functional aspects of users because it is only based on the functional aspects. That is, the quality, non-functional aspect will be an important factor for the mutual success of the user and provider. Using 3 factors in the Qos factors of the existing studies: the execution cost, reliability, and the quality level, the QoS of Web service is saved and the factors for the QoS are recorded in order to consider non-functional factors when selecting a Web service in this study. The Quality Broker determines the rank and shows the desired result of the service for users. The Quality Broker suggested in this thesis can be used to select a Web Service that considers the user-oriented and non-functional factors.

• Journal of Digital Convergence
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• v.7 no.4
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• pp.81-90
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• 2009

SaaS (Software as a Service) provides software in the form of service via internet rather than software package. Thus a large number of users could use the service of new type of software service as long as they connect to internet. SaaS, as a delivery model attracted in the software industry, grows with impelling force. SaaS has been adopted as an information spreading strategy of small and medium corporate so that its effect has been recognized in both academic and practical areas. However, there are not much researches about it because SaaS is still in the introductory stage. This study focused on the success model of SaaS to find out the factors that affect usability and the satisfaction of users. The sample is based on the on-line survey for the 549 government officials who are using SaaS. At last, the number of the employed answers are 157 after unqualified ones are removed. The result shows that Security, Service quality, Price and System Integration significantly affect the usefulness and the satisfactions of users.

• Journal of Web Engineering
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• v.21 no.1
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• pp.27-52
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• 2021

With recent increases in the number of network-connected devices, the number of edge computing services that provide similar functions has increased. Therefore, it is important to recommend an optimal edge computing service, based on quality-of-service (QoS). However, in the real world, there is a cold-start problem in QoS data: highly sparse invocation. Therefore, it is difficult to recommend a suitable service to the user. Deep learning techniques were applied to address this problem, or context information was used to extract deep features between users and services. However, edge computing environment has not been considered in previous studies. Our goal is to predict the QoS values in real edge computing environments with improved accuracy. To this end, we propose a GAIN-QoS technique. It clusters services based on their location information, calculates the distance between services and users in each cluster, and brings the QoS values of users within a certain distance. We apply a Generative Adversarial Imputation Nets (GAIN) model and perform QoS prediction based on this reconstructed user service invocation matrix. When the density is low, GAIN-QoS shows superior performance to other techniques. In addition, the distance between the service and user slightly affects performance. Thus, compared to other methods, the proposed method can significantly improve the accuracy of QoS prediction for edge computing, which suffers from cold-start problem.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.6
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• pp.1107-1113
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• 2015

The number of phishing/pharming attacks occurring has increased and consequently, the number of studies on anti-phishing/pharming has also increased. The target sites of phishing/pharming are financial sites, and these have a low connection rate compared to those of portal sites. In this paper, we propose an anti-phishing/pharming method that uses a portal site as a stopover. The proposed method is based on the reliability of portal sites. This method is intended for general users rather than for professional users or developers. We also analyze the safety of the proposed method by separating the method into sub components of module safety assumption.

• Human Ecology Research
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• v.57 no.2
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• pp.171-183
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• 2019

Convergence between technology and financial services is ubiquitous and widespread. Virtual banks represent an important aspect of financial markets that can generate value added for consumers and enhance the quality of financial services. This study explores the effect of innovation characteristics (relative advantage, compatibility, and perceived risk), consumer characteristics (status quo bias), and social mechanisms (network externality: complementarity, numbers of peers) on consumers' adoption intention and resistance to virtual banks. This study adopted an innovation resistance model with two dependent variables: adoption intention and resistance to virtual banks. An online self-administered survey was conducted and 532 or non-users of virtual banks aged 20 to 69 years old were analyzed. Frequency analysis, descriptive analysis, and hierarchical multiple regression indicated that status quo bias, relative advantage, perceived risk, complementarity, and number of peers insignificantly influence the adoption intention regarding virtual banks. Furthermore, status quo bias, relative advantage, perceived risk, and number of peers insignificantly influence the resistance to virtual banks. Female respondents have a lower adoption intention and higher resistance to virtual banks than male respondents. The findings suggest that the innovation resistance model can be useful in understanding consumers'adoption and resistance behavior as well as reveal that innovation characteristics, consumer characteristics, and social mechanism are important antecedent variables of the innovation adoption decision.

• Journal of Communications and Networks
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• v.11 no.2
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• pp.148-156
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• 2009

The fixed spectrum assignment policy in today's wireless networks leads to inefficient spectrum usage. Cognitive radio network is a new communication paradigm that enables the unlicensed users to opportunistically use the spatio-temporally unoccupied portions of the spectrum, and hence realizing a dynamic spectrum access (DSA) methodology. Interference temperature model proposed by Federal Communications Commission (FCC) permits the unlicensed users to utilize the licensed frequencies simultaneously with the primary users provided that they adhere to the interference temperature constraints. In this paper, we formulate two NP-hard optimal scheduling methods that meet the interference temperature constraints for cognitive radio networks. The first one maximizes the network throughput, whereas the second one minimizes the scheduling delay. Furthermore, we also propose suboptimal schedulers with linear complexity, referred to as maximum frequency selection (MFS) and probabilistic frequency selection (PFS). We simulate the throughput and delay performance of the optimal as well as the suboptimal schedulers for varying number of cognitive nodes, number of primary neighbors for each cognitive node, and interference temperature limits for the frequencies. We also evaluate the performance of our proposed schedulers under both additive white gaussian noise (AWGN) channels and Gilbert-Elliot fading channels.

• Journal of Family Resource Management and Policy Review
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• v.16 no.4
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• pp.213-233
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• 2012

This descriptive study about a community center for elderly users identifies factors influencing economic dependency. The objective of this study is to find factors that contribute to increased economic dependency and to provide basic data for preventing conflict between caregivers and elderly dependents. The subjects are 204 elderly persons who are community-center users in SongPa-Gu. Thirteen dongs (administrative areas) were chosen randomly in a cluster sample from among 26 dongs in Soungpagu containing a total of 158 community centers for the elderly. I obtained informed consents for my research from all subjects, and collected data by conducting interviews from June 28th, 2011 to August 7th, 2011. The data was analyzed by descriptive statistics, t-test, one-way ANOVA, Duncan test and multi regression analysis. The mean economic dependency score was 3.23, meaning that subjects with this score are dependent at a level that is "over intermediate". The level of formal education, homeownership, financial assistance from family and the number of families, financial assistance to the family and the number of families, economic life satisfaction, self efficacy and social support.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.8
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• pp.2607-2625
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• 2014

Previous studies on multiuser multiple-input multiple-output (MIMO) mostly assume a homogeneous signal-to-noise ratio (SNR), where each user has the same average SNR. However, real networks are more likely to feature heterogeneous SNRs (a random-valued average SNR). Motivated by this fact, we analyze a multiuser MIMO downlink with a zero-forcing (ZF) receiver in a heterogeneous SNR environment. A transmitter with Mantennas constructs M orthonormal beams and performs the SNR-based proportional fairness (S-PF) scheduling where data are transmitted to users each with the highest ratio of the SNR to the average SNR per beam. We develop a new analytical expression for the sum throughput of the multiuser MIMO system. Furthermore, simply modifying the expression provides the sum throughput for important special cases such as homogeneous SNR, max-rate scheduling, or high SNR. From the analysis, we obtain new insights (lemmas): i) S-PF scheduling maximizes the sum throughput in the homogeneous SNR and ii) under high SNR and a large number of users, S-PF scheduling yields the same multiuser diversity for both heterogeneous SNRs and homogeneous SNRs. Numerical simulation shows the interesting result that the sum throughput is not always proportional to M for a small number of users.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.5
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• pp.1693-1701
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• 2010

In this paper, requirements of efficient group key creation in multiple hierarchy structure environment with clear distinction of hierarchical roles within organizations are explained and the method of creating a group key that satisfies such requirements is proposed. The proposed method creates the group key through logical sum operation of hierarchy identifier created using uni-directional hash chain and group identifier randomly created according to the access right. The problem of excessive possession of key information by upper group users in the existing static group key creation technique was resolved. At the same time, lower group users were prevented from deducing key information of upper group users. In addition, as a result of comparative analysis performed with an experiment on existing super group key creation technique and multiple hierarchy group key method, the proposed method was found to be equivalent or superior to existing method in terms of various items including the total number of keys created, the number of keys possessed by users, the number of keys used for encoding and decoding of information, and expandability of keys.