• Journal of Communications and Networks
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• v.15 no.2
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• pp.228-239
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• 2013

Peer-to-peer (P2P) systems have proved the most effective and popular file sharing applications in recent years. Previous studies mainly focused on equal service and differentiated service strategies when peers have no initial data before their downloads. For an upload-constrained P2P file sharing system, we model both the equal service process and the differentiated service process when the initial data distribution of peers satisfies some special conditions. Moreover, we show how to minimize the time required to distribute the file to any number of peers. The proposed fluid-based models can reveal the intrinsic relations among the initial data amount, the peer set size, and the minimum last finish time. The closed-form expressions derived from the extended models can closely approximate chunk-based models and systems, especially for relatively large files. As an application of the extended models, we show how to provide differentiated service efficiently to multiple peer sets. Since no limits are imposed on the upload bandwidth of peers or the size of each peer set, we believe that our analytic process and the results achieved can provide not only fundamental insights into bandwidth allocation and data scheduling but also a helpful reference for both improving system performance and building an effective incentive mechanism for P2P file sharing systems.

• ETRI Journal
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• v.33 no.1
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• pp.128-131
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• 2011

This letter describes a file format designed for interactive music service where users are able to recompose music based on their own preferences. The proposed design utilizes the flexible features of the ISO base media file format (ISO/IEC 14496-12, ISO-BMFF). The techniques offered in the proposed file format enable compact storage and efficient preset management, allowing users to recompose music with ease and convenience. Additionally, an implementation scheme for an interactive music player is shown along with its results.

• Proceedings of the Korea Contents Association Conference
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• 2004.11a
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• pp.395-401
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• 2004

In the current high network-centralized computing and enterprising environment, it is getting essential to transmit data reliably at very high rates. Until now previous client/server model based NFS(Network File System) or AFS(Andrew's Files System) have met the various demands but from now couldn't satisfy those of the today's scalable high-performance computing environment. Not only performance but data sharing service redundancy have risen as a serious problem. In case of NFS, the locking issue and cache cause file system to reboot and make problem when it is used simply as ip-take over for H/A service. In case of AFS, it provides file sharing redundancy but it is not possible until the storage supporting redundancy and equipments are prepared. Lustre is an open source based cluster file system developed to meet both demands. Lustre consists of three types of subsystems : MDS(Meta-Data Server) which offers the meta-data services, OST(Objec Storage Targets) which provide file I/O, and Lustre Clients which interact with OST and MDS. These subsystems with message exchanging and pursuing scalable high-performance file system service. In this paper, we compare the transmission speed of gigabytes file between Lustre and NFS on the basis of concurrent users and also present the high availability of the file system by removing more than one OST in operation.

• The KIPS Transactions:PartA
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• v.12A no.6 s.96
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• pp.493-498
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• 2005

P2P service is a method that can share various information through direct connection between computer of a person who have information and a Person who have information without server in the Internet and it is getting a lot of popularity by method for free ex change of file. P2P file sharing systems have become popular as a new paradigm for information exchange. Because all users who use service in P2P file sharing system can use shared files of several users freely by equal access privilege, it is happening the 'free rider' that only download shared file of other users without share own files. Although a user share a malicious file including virus, worm or file that have title differing with actuality contents, can use file sharing service without limitation. In this paper, we propose a method that restrict access of 'free rider' that only download using reputation information that indicate reliability of user. Also, we restrict usage ons hared file of other users about users who share harmful file.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2009.01a
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• pp.364-367
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• 2009

This paper presents a scheme that generates a caption file by extracting a Closed Caption stream from DTV signal. Note that Closed-Captioning service helps to bridge "digital divide" through extending broadcasting accessibility of a neglected class such as hearing-impaired person and foreigner. In Korea, DTV Closed Captioning standard was developed in June 2007, and Closed Captioning service should be supported by an enforcing law in all broadcasting services in 2008. In this paper, we describe the method of extracting a caption data from MPEG-2 Transport Stream of ATSC-based digital TV signal and generating a caption file (SAMI and SRT) using the extracted caption data and time information. Experimental results verify the feasibility of a generated caption file using a PC-based media player which is widely used in multimedia service.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.4 no.5
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• pp.709-735
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• 2010

The reciprocal virtue of peer-to-peer networking has stimulated an explosion of peer population and service capacity, ensuring rapid content distribution in peer-to-peer networks. Critical issues such as peer churn, free riding, and skewed workload significantly affect performance results such as service agility, fairness, and resource utilization. To resolve these problems systematically, this study proposes a peer assignment scheme that supports fair peer-to-peer file sharing applications. The proposed scheme exploits the peer duality of both server-oriented peer capacity and client-oriented peer contribution. Accordingly, the system server can prioritize download requests and appropriately assign server peers to uploading file objects. Several functional extensions, including peer substitution and elimination, bandwidth adjustment, and distributed modification, help cope with subtle situations of service starvation and download blocking, and hence make the system design robust and amenable. Simulation results show this design is examined under both centralized and distributed peer-to-peer environments. Performance results confirm that the proposed mechanisms are simple but effective in maintaining service agility and fairness, without loss of overall service capacity in peer-to-peer files sharing systems.

• Journal of Korea Multimedia Society
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• v.24 no.4
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• pp.558-568
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• 2021

The digital image to be accepted as legal evidence, it is important to verify the authentication of the digital image. This study proposes a method of authenticating digital images through three steps of comparing the file structure of digital images taken with iPhone, analyzing the encoding information as well as media logs of the iPhone storing the digital images. For the experiment, digital image samples were acquired from nine iPhones through a camera application built into the iPhone. And the characteristics of file structure and media log were compared between digital images generated on the iPhone and digital images edited through a variety of image editing tools. As a result of examining those registered during the digital image creation process, it was confirmed that differences from the original characteristics occurred in file structure and media logs when manipulating digital images on the iPhone, and digital images take with the iPhone. In this way, it shows that it can prove its forensic authentication in iPhone.

• Journal of KIISE:Computing Practices and Letters
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• v.13 no.7
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• pp.499-507
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• 2007

In the areas of CAE, CAD and CAO integration & automation technology, the word 'File Wrapping' means a virtualization of TEXT files that supports variables-based I/Os like variable assignments in programming languages. This File Wrapping process is one of the cornerstones of CAE, CAD and GAO integration & automation, and the performance of File Wrapping process, which is depending on the sire of a TEXT file to be accessed and the number of regions and their distribution, has a critical effect on the total performance of the CAE, CAD and CAO integration & automation systems. In this paper, we define TEXT File Region Management which generalizes the main functions of the File Wrapping process, and describe a prototype of TEXT file Region Management which is implemented as a Grid service. After that, the validity of the proposed model and the TEXT File Region Management service are discussed with evaluation results of the prototype.

• ETRI Journal
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• v.29 no.3
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• pp.281-291
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• 2007

Wearable computers consisting of various small devices such as smart phones, digital cameras, MP3 players and specialized I/O devices in personal area networks will play an important role in future ubiquitous computing. In this environment, accessing user data is quite complex due to the dynamic and heterogeneous characteristics of the underlying networks. Moreover, since the amount of user data increases rapidly, automatic data backup management is also critical. To overcome these challenges, several studies have been conducted including our previously proposed file service system, PosCFS, which could be adapted to the requirements with a virtualization technique allowing per-user global namespace for managing and accessing data stored on physical storage spaces detected in PAN. In this paper, we present a smart file service framework, PosCFS+ which is an improved and extended version of our previous work. Performance improvement is made possible by redesigning the metadata management scheme based on database and keywords rather than ontology. In addition, the automatic data replication management is newly designed based on the OSD protocol.

• Journal of Applied Tourism Food and Beverage Management and Research
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• v.10
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• pp.159-186
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• 1999

This study attempted to present the ways of improving relationship marketing activities of tourist hotels. The field survey was carried out at six deluxe hotels in Seoul to find out their relationship marketing activities and analyze the problems of the activities. The problems were analyzed as follow; 1) lack of adequate understanding of the importance of relationship marketing, 2) poor contents of customer file information, 3) insufficient service encounter management, 4) negative inducement of guests' complaints, 5) insufficient survey of guests' satisfaction, 6) insufficient relationship maintenance programs and regaining program of lost guests. This study relationship marketing activities should be improved with customer information file establishment, service encounter mangement, and communication enforcement as follow; 1. Customer Information File Establishment As relationship marketing Is marketing for individual, it needs customer file information. The guest information files should be made in detail in all the market segments. Hotels have to make use of the information strategically for establishing relationship with their guests. 2. Service Encounter Mnagement Because the guest-oriented mind and professionalism of hotel staff are prerequisite for relationship continuity, hotel should make efforts to make its staff keep the mind and cultivate expert service technique of the staff. 3. Communication Enforcement Communication enforcement consists of communication activities and communication programs which are focused on contact intensity and two-way communication.