• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.613-617
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• 2008

One of the important parts on multimedia era is acoustic ones. With increased demand of smallest multimedia products such as personal digital assistant (PDA) and mobile phones, it is necessary to develop acoustic devices which have higher performance and smaller size. Acoustic parts with various function for hearing impaired persons. This paper introduces a bone conduction vibrator (BCV) for hearing impaired persons to use portable acoustic device without additional devices. For vibration analysis of the BCV, electromagnetic, mechanical and their coupling effects are considered for the analysis. This paper shows that the development of design and analysis technique by finite element method (FEM) of BCV.

• Journal of Korea Multimedia Society
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• v.17 no.12
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• pp.1494-1502
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• 2014

Since smartphones are utilized in the ranges from personal usages to governmental data exchanges, known but not patched vulnerabilities in smartphone operating systems are considered as major threats to the public. To minimize potential security breaches on smartphones, it is necessary to estimate possible security threats. So far, there have been numerous studies conducted to evaluate the security risks caused by mobile devices qualitatively, but there are few quantitative manners. For a large scale risk evaluation, a qualitative assessment is a never ending task. In this paper, we try to calculate relative risk levels triggered by software vulnerabilities from unsecured smartphone operating systems (Android and iOS) among 51 Asian countries. The proposed method combines widely accepted risk representation in both theory and industrial fields. When policy makers need to make a strategic decision on mobile security related agendas, they might find the presented approach useful.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.2 no.2
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• pp.103-119
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• 2008

Traditional web-based services that require users to browse via documents and fill out forms, are difficult to use with mobile devices. Moreover, as the web paradigm assumes active clients, further complications are introduced in cases where the server is the active entity, instead of the client. This paper presents a Server-Centric Interaction Architecture (SCIA) for wireless applications. The architecture enables servers to initiate communication with clients as well as push secure targeted data to them, in a piecemeal fashion. It further enables the development of highly collaborative wireless services with interactive user interfaces.

• Journal of Korea Multimedia Society
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• v.19 no.8
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• pp.1466-1470
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• 2016

As individuals create many contents anytime and anywhere together with the widespread dissemination of smart devices as well as various social networking services (SNS), content centric networking (CCN) has regarded as a new networking technology. However, CCN is exposed to malicious attacks on the mobility management of mobile content sources during handover and high volume of control messages. Therefore, this paper presents a secure duplicate name detection (SecureDND) mechanism without additional control messages by signed information and secure token. It is shown from the performance evaluation that the proposed scheme can provide low control overhead, which results in the network scalability.

• Journal of Korea Multimedia Society
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• v.24 no.3
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• pp.440-447
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• 2021

Smartphones are currently being produced with similar functions, shapes, and software. The foldable smartphone is a product that dramatically changed the shape of the existing smartphone. Therefore, it affects the functions and software. In this paper, we analyze the potential security vulnerability of current mobile authentication methods by dividing them into two parts, security vulnerabilities of non-foldable smartphones, and security vulnerability that appears with the changed smartphone structure. According to the analysis result, the classic and current mobile user authentication methods appears to be easily affected by the smartphone display structure. Finally, we propose an appropriate authentication method as well as the concept of security measures for smartphones with foldable screen. Our method shows that it is more secure than the conventional authentication methods in foldable display smartphone.

• Journal of Korea Society of Digital Industry and Information Management
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• v.10 no.1
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• pp.139-146
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• 2014

Through numerous mobile device technology advances, various multimedia contents is moving towards mobile devices from existing personal computer (PC). These paradigm has emerged taking into account these idea, the so-called N-Screen, N-Screen is user-centric service to provide running and sharing on everywhere via advanced smart system in C-P-N-T (Content, Platform, Network, Terminal). Therefore we must provide securing of various contents, openended platform, and user-centric service for efficient N-Screen service. For These characteristic of N-Screen, this paper propose design and implementation of user location-based N-Screen service system. The proposed system realize user location through user's smart phone and offer automatic streaming service to user. And also, we provide web service-based extended N-Screen service. Thus, user can access various device, such as laptop, tablet, and mobile device.

• Journal of Korea Multimedia Society
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• v.20 no.1
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• pp.1-9
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• 2017

Explosive deployment of smart mobile devices such as smart phones, and tablets along with expansion of wireless internet bandwidth have enabled the deployment of mobile video streaming such that video traffic becomes the most important service in wireless networks. Recently, for more efficient video streaming services, the ISO MPEG group standardized a protocol called DASH (Dynamic Adaptive Streaming over HTTP) and the standard has been quickly adopted by many service providers such as YouTube and Netflix. Despite of the convenience of mobile streaming services, users also suffer from low QoE(Quality of Experience) due to dynamic channel fluctuations and unnecessary downloading due to high churning rates. This paper proposes a noble efficient video rate selection algorithm considering user buffer level, channel condition and churning rate. Computer simulation based performance study showed that the proposed algorithm improved the QoE significantly compared to a method that determines the video rate based on current channel conditions. Especially, the proposed method reduced the rebuffering rate, one of the most important performance factors of the QoE, to a nonnegligible level.

• The Journal of the Korea Contents Association
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• v.10 no.8
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• pp.130-137
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• 2010

An advancement and wide use of portable multimedia devices make it easy to spread digital sound source, enabling users to use portable multimedia devices and search and enjoy digital sound sources and related contents. In opposition the off-line musical service market with CD stagnates gradually and in the crisis where the off-line musical service market vanishes away. In this paper, we propose the mobile music album information retrieval system which combines the barcode and a cellular phone musical service. To get digital sound sources and related information from music albums, the proposed retrieval system uses one-dimensional barcodes attached to music albums and obtains information on related albums from the sound source servers. Also, to reflect user preferences in search results, the system uses search frequency by music album, and searches albums in music genres selected by users in the order of the recent preference. The proposed mobile music album retrieval system is implemented on the basis of WIPI, and is now providing pilot services.

• Journal of Korea Multimedia Society
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• v.11 no.1
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• pp.106-116
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• 2008

It is difficult to provide Web services on a mobile environment because of the intermittent disconnection of a wireless network and the frequent change of context information. To resolve this, Web services must be migrate to devices, which can provide services to users seamlessly. However, researches on hosting, migrating, and replicating Web services on mobile devices are still in an early stage. This paper presents a lightweight Web service framework and an efficient method for establishing a policy of migrating Web services. Based on the WS-Policy standard, the proposed method defines a policy schema, which provides constructs for describing various kinds of contextual information. Specifically, the schema is designed to be extensible enough for different service providers to use different vocabularies to describe their policies. To show the validity, the proposed method for establishing a migration policy has been applied to our mobile Web services framework, resulting in a seamless provisioning of services.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.14 no.4
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• pp.51-56
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• 2014

Thesedays, there are many smart device applications developed, especially on the using various sensors included in the smart device. Smart devices have several sensors which are camera, GPS, mike, and communication module for collecting ubiquitous environment, and many applications are developed by using such sensors. In this paper, we developed the multimedia stream architecture and examined the smart device applications based on open source with front and back-end server clouds for developing the conceptual architecture. Also, we examined the back-end distributed servers, realtime multimedia stream transferring, multi-media store, and media relay for other server and smart devices. We test the examined architecture on the real target environment to collect the SIP initial setup time, media stream delay, and end-to-end play time. The test results show that there have good network operation environment to provide realtime multimedia services, and we need to improve the end-to-end play time by minimizing the initial setup time.