• The Journal of the Korea Contents Association
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• v.20 no.12
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• pp.266-277
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• 2020

As users' convenience increases, the issue of personal information leakage about smartphones is also becoming serious. Since all of the user's personal information needed to provide functions such as electronic banking services and personal file storage is stored in the smartphone, the user's important personal information may be exposed if the smartphone is lost or stolen. In order to protect this privacy, governments and telecommunications companies offer smartphone locking or initialization services, but there are many loopholes and problems. In this paper, we design and implement applications that prevent malicious use of a user's personal information stored on a smartphone when a smartphone is lost or stolen, and that automatically initializes the smartphone used after removing or altering the USIM chip and destroys the user's personal information stored within the phone. The proposed application prevents users from maliciously using their personal information when a smartphone is lost or stolen.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.5
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• pp.2275-2293
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• 2020

This paper focuses on the simplified receiver design for multi-user circular block oversampled filter bank (CB-OSFB) uplink systems. Through application of discrete Fourier transform (DFT), the special banded structure and circular properties of the modulation matrix in the frequency domain of each user are derived. By exploiting the newly derived properties, a simplified zero-forcing (ZF) receiver is proposed for multi-user CB-OSFB uplink systems in the multipath channels. In the proposed receiver, the matrix inversion operation of the large dimension multi-user equivalent channel matrix is transformed into DFTs and smaller size matrix inversion operations. Simulation is given to show that the proposed ZF receiver can dramatically reduce the computational complexity while with almost the same symbol error rate as that of the traditional ZF receiver.

• Journal of Information Processing Systems
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• v.17 no.3
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• pp.462-472
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• 2021

With an increase in the scale of recommender systems, users' rating data tend to be extremely sparse. Some methods have been utilized to alleviate this problem; nevertheless, it has not been satisfactorily solved yet. Therefore, we propose an effective pre-rating method based on users' dichotomous preferences and average ratings fusion. First, based on a user-item ratings matrix, a new user-item preference matrix was constructed to analyze and model user preferences. The items were then divided into two categories based on a parameterized dynamic threshold. The missing ratings for items that the user was not interested in were directly filled with the lowest user rating; otherwise, fusion ratings were utilized to fill the missing ratings. Further, an optimized parameter λ was introduced to adjust their weights. Finally, we verified our method on a standard dataset. The experimental results show that our method can effectively reduce the prediction error and improve the recommendation quality. As for its application, our method is effective, but not complicated.

• The Journal of the Korea Contents Association
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• v.18 no.9
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• pp.141-148
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• 2018

Currently, the user authentication technology used by users to access multiple applications within an organization is being applied with ID/PW-based SSO technology. These user authentication methods have the fundamental disadvantages of ID/PW and SSO. This means that security vulnerabilities in ID/PW can lead to periodic changes in PWs and limits on the number of incorrect PW inputs, and SSO adds high cost of the SSO server, which centrally stores the authentication information, etc. There is also a fundamental vulnerability that allows others to freely use other people's applications when they leave the portal application screen with SSO. In this paper, we proposed an app-based 2-channel authentication scheme to fundamentally eliminate problems with existing ID/PW-based SSO user authentication technologies. To this end, it distributed centralized user authentication information that is stored on SSO server to each individual's smartphone. In addition, when users access a particular application, they are required to be authenticated through their own smartphone apps.

• Journal of KIISE
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• v.42 no.1
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• pp.23-32
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• 2015

In the Android market, a large portion of the market share consists of third party applications, but not much research has been performed in this respect. Of these applications, mobile Voice Over IP (VoIP) applications are one of the types of applications that are used the most. In this paper, we focus on user authentication methods for three representative applications of the Google Voice service, which is a famous mobile VoIP application. Then, with respect to the Android file system, we developed a method to store and to send user information for authentication. Finally, we demonstrate a vulnerability in the mechanism and propose an improved mechanism for user authentication by using hash chaining and an elliptic curve Diffie-Hellman key exchange.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.12 no.3
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• pp.231-241
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• 2019

Web Usage Mining (WUM) is one part of Web mining and also the application of data mining technique. Web mining technology is used to identify and analyze user's access patterns by using web server log data generated by web users when users access web site. So first of all, it is important that the data should be acquired in a reasonable way before applying data mining techniques to discover user access patterns from web log. The main task of data acquisition is to efficiently obtain users' detailed click behavior in the process of users' visiting Web site. This paper mainly focuses on data acquisition stage before the first stage of web usage mining data process with activities like data acquisition strategy and field extraction algorithm. Field extraction algorithm performs the process of separating fields from the single line of the log files, and they are also well used in practical application for a large amount of user data.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2016.10a
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• pp.887-888
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• 2016

Internet data for IoT(Internet of Things) period was changed in such a way that the data is done by sharing information for the user. However, in the existing system IoT environment for the user to utilize the system it has a problem does not take into account the individual characteristics. And there must be an intermediate vectors are capable of controlling problems such as Dongle. In this paper, through the flow sensor control applications as a way to solve this problem to control the flow of the sensor according to the characteristics desired by the user. Due to this makes it possible to easily manage the sensor compared to conventional IoT environment. Accordingly, the user must manage the sensor through the application regardless of time and place. So it is believed to reduce the unnecessary power consumption is possible effective control sensor.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.2
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• pp.817-828
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• 2018

Modern software, especially web-based software, is broadly used in various fields. Most web applications employ design patterns, such as a model-view-controller (MVC) pattern and a factory pattern as development technology, so the application can have a good architecture to facilitate maintenance and productivity. A web application, however, may have defects and developers must fix the defects when a user submits bug reports. In this paper, we propose a novel approach to improving fault traceability in web application by using software revision information and software behavior model to reduce costs and effectively handle the software defect. We also provide a case study to show effectiveness of our approach.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.9
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• pp.44-52
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• 1994

When a constructed multimedia application system transfers a various media of which quality of service is different, a previously constituted synchronization at source site generates the synchronization anomaly that the synchronization relation is broken by a delay or a data loss at destination. To solve the synchronization anomaly, we propose the “Multimedia synchronization scenario method : MSSM” which defines as one(1) event all objects generated at multimedia application and creates the optimal scenario of multimedia presentation under temporal constraints. The characteristics of MSSM can minimize the delay effect, guarantee the media stream continuity for preventing the media stretch, and provide the synchronization information to a user and/or a system. After deciding a synchronization possibility. MSSM confirm user its information. If there is a synchronization possibility. MSSM products optimal multimedia presentation scenario, and can present multimedia adaptively.

• Knowledge Management Research
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• v.15 no.3
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• pp.13-36
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• 2014

Recently, with the increasing popularity of smartphones, mobile applications have been being used in various sectors. In these environments, some mobile applications are being made for special purposes. The mobile campus application is one exemplary type of such special-purpose mobile applications, which have unique characteristics that allow only designated users, belonging to a specific group, to access and use relevant knowledge. The aim of this study is to identify and investigate critical success factors of mobile campus applications based on the DeLone & McLean's information systems (IS) success model and to find unique characteristics of mobile campus applications, compared to general-purpose mobile applications. In order to empirically test our research model, 199 samples were collected from students who actually had experience of using the mobile campus application of A university at least once. The findings of the structural equation modeling using SmartPLS 2.0 confirmed the DeLone & McLean's IS success model, with the exception for relationships between service quality and user satisfaction/intention to use. Moreover, the moderating role of sense of belonging to school on the relationships between quality-related factors (i.e., information, system, and service qualities) and success-related factors (i.e., user satisfaction and intention to use) was examined.