• Journal of the Korea Society of Computer and Information
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• v.13 no.4
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• pp.11-18
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• 2008

Document clustering is an important method for document analysis and is used in many different information retrieval applications. This paper proposes a new document clustering model using the re-weighted term based NMF(non-negative matrix factorization) to cluster documents relevant to a user's requirement. The proposed model uses the re-weighted term by using user feedback to reduce the gap between the user's requirement for document classification and the document clusters by means of machine. The Proposed method can improve the quality of document clustering because the re-weighted terms. the semantic feature matrix and the semantic variable matrix, which is used in document clustering, can represent an inherent structure of document set more well. The experimental results demonstrate appling the proposed method to document clustering methods achieves better performance than documents clustering methods.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.1A
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• pp.76-83
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• 2009

In this paper, we provide opportunistic scheduling schemes for elastic services in OFDMA systems with fairness constraints for each user. We adopt the network utility maximization framework in which a utility function is defined for each user to represent its level of satisfaction to the service. Since we consider elastic services whose degree of satisfaction depends on its average data rate, we define the utility function of each user as a function of its average data rate. In addition, for fair resource allocation among users, we define fairness requirements of each user by using utility functions. We first formulate an optimization problem for each fairness requirement that aim at maximizing network utility, which is defined as the sum of utilities of users. We then develop an opportunistic scheduling scheme for each fairness requirement by solving the problem using a dual approach and a stochastic sub-gradient algorithm.

• Journal of the Korea Society of Computer and Information
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• v.6 no.3
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• pp.1-10
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• 2001

Recently, way of Electronic Commerce is changing with increment of Internet users. In the previous way of commerce, users used to search for information by themselves. However, for user's convience, it can be done for users from one site. Mobile in order to provide users with such service. By the mobile agent-based Electronic Commerce system, users can get information from one site, and service companies can provide various and useful information to users. This is very important for construction of reliable Electronic Commerce environment, However, in generally used mobile agent-based platforms, the user should know URL information. and it is based on search engines. And as user's requirement levels become higher, they want to be provided with integrated and summarized service. In this paper, we implement product-trading system by applying mobile agent concept in order to satisfy user's requirement of getting required information from one site with minimal mouse click. For implementing the product trading system, E-speak, which is a platform for E-Service, is used And contents are saved as XML documents and data are shared based on these documents.

• Journal of KIISE:Software and Applications
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• v.31 no.1
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• pp.29-42
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• 2004

According to rapid growth of a web environment, usage-centered design is being highlighted. This paper suggests the development step and algorithm to generate a user interface prototype automatically on the basis of usage-centered design. For this purpose, The transition object of the user interface is modeled from requirement analysis, and an modeling rule as well as algorithms of business events are made for the creation of the user interface. Through these processes, visual cohesions of business events become strong and unskilled designers can develop the qualified user interface prototypes. A user's understanding of business tasks can also be improved and prototype iterations reduced.

• Proceedings of the Korean Nuclear Society Conference
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• 2005.10a
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• pp.1021-1022
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• 2005

• ETRI Journal
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• v.29 no.2
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• pp.153-161
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• 2007

In this paper, we analyze the algorithm of the methodology developed by ITU for the calculation of spectrum requirements of IMT-Advanced. We propose an approach to estimate user density using traffic statistics, and to estimate spectrum efficiencies using carrier-to-interference ratio distribution and capacity theory as well as experimental data under Korean mobile communication environments. We calculate the IMT-Advanced spectrum requirements based on the user density and spectral efficiencies acquired from the new method. In the case of spectral efficiency using higher modulation and coding schemes, the spectrum requirement of IMT-Advanced is approximately 2700 MHz. When applying a $2{\times}2$ multiple-input multiple-output (MIMO) antenna system, it is approximately 1500 MHz; when applying a $4{\times}4$ MIMO antenna system, it is approximately 1050 MHz. Considering that the development of new technology will increase spectrum efficiency in the future, the spectrum requirement of IMT-Advanced in the Korean mobile communication environment is expected to be approximately 1 GHz bandwidth.

• The KIPS Transactions:PartC
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• v.18C no.5
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• pp.293-302
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• 2011

The various information services can be delivered by smartphone through advanced high-speed mobile communication. A smartphone is a mobile device that offers more powerful computing capacity than feature phone. Therefore this device can provide such as web surfing, editing documents, playing video, and playing games. A lot of personal information stored on smartphone. Because it has High usability. Personal information Leaks if the smart phone is lost or stolen may become a big problem. In this paper we have analyzed existing method for providing secure storage and user authentication on mobile platform and derived security requirement. Therefore we propose the following scheme that satisfy security requirement. Proposed scheme providing secure storage with preventing authentication bypass, and availability from damaged data to access secure area.

• International Journal of Computer Science & Network Security
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• v.21 no.9
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• pp.303-316
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• 2021

Digital content protection has recently become an important requirement in biometrics-based authentication systems due to the challenges involved in designing a feasible and effective user authentication method. Biometric approaches are more effective than traditional methods, and simultaneously, they cannot be considered entirely reliable. This study develops a reliable and trustworthy method for verifying that the owner of the biometric traits is the actual user and not an impostor. Watermarking-based approaches are developed using a combination of a color face image of the user and a mobile equipment identifier (MEID). Employing watermark techniques that cannot be easily removed or destroyed, a blind image watermarking scheme based on fast discrete curvelet transform (FDCuT) and discrete cosine transform (DCT) is proposed. FDCuT is applied to the color face image to obtain various frequency coefficients of the image curvelet decomposition, and for high frequency curvelet coefficients DCT is applied to obtain various frequency coefficients. Furthermore, mid-band frequency coefficients are modified using two uncorrelated noise sequences with the MEID watermark bits to obtain a watermarked image. An analysis is carried out to verify the performance of the proposed schema using conventional performance metrics. Compared with an existing approach, the proposed approach is better able to protect multimedia data from unauthorized access and will effectively prevent anyone other than the actual user from using the identity or images.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.12 no.3
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• pp.119-128
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• 2002

In case certification between user and service provider is achieved, problem that user's identity is revealed is occurring by social issue, so it was presented identity escrow scheme to solve these problem. In identity escrow scheme, the issuer who have correct user's identity transmits securely anonymity authentication information to user, and user achieves authentication phase with service provider keeping oneself anonymity using this. In this paper, we present requirement for security and trusty of identity escrow scheme and propose new mechanism that can security this. Also, propose method that service provider can deliver securely contents to user and propose mechanism that improve that support ky recovery at encryption communication that using secret key that it was generated by key agreement between users.

• Proceedings of the Korea Institutes of Information Security and Cryptology Conference
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• 2002.11a
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• pp.266-269
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• 2002

As a simulation or replacement of analog money in cyber space, the e-cash was introduced by using cryptographic primitives. Since a perfect anonymity system causes some illegal activities, such as money laundering, blackmailing, and illegal purchase, a revocable electronic system was paid a great attention to control the anonymity. In general, Trust Third Party(TTP) is introduced to detect any dubious user and coin, namely user tracing and coin tracing. In this paper we propose a new revocable anonymity e-cash system, and verify the security requirement as well. In our scheme a user first withdraws the e-coin from bank by using blind signature, and then TTP verifies the bank's signature and records the tracing information.