• The Journal of the Korea Contents Association
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• v.5 no.2
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• pp.257-266
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• 2005

As developing of the internet and computer technology, more interests are gathered to the conference service which provides capability of multi-party real-time visual conference. In this paper, we have designed and implemented a SIP-based visual conference system which includes Presence service. The elements of this conference system are user system, which has conference UA(User Agent) capability, presence seuer and conference server. For the presence service, we have adapted publication method which uses SIP PUBLISH message, and with this service various status informations of users are easily acquired. Also invitations and involvements to the conference are easily made through this service. For the conference server which controls establishment and management of multi-party connections, we have included conference event package. This package provides dynamically changing conference informations and users informations through SIP subscription and notification functions.

• Communications for Statistical Applications and Methods
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• v.17 no.3
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• pp.391-411
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• 2010

For estimating the mean of a finite population, three classes of estimators using multi-auxiliary information with unknown means using two phase sampling in presence of non-response have been proposed with their properties. Asymptotically optimum estimator(AOE) in each class has been identified along with their mean squared error formulae. An empirical study is also given.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.9B
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• pp.867-875
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• 2009

The reliability of wireless body area networks is an important research issue since it may jeopardize the vital human life, unless managed properly. In this article, a new modeling and analysis of node misbehaviors in wireless body area networks is presented, in the presence of multi-type failures. First, the nodes are classified into types in accordance with routing capability. Then, the node behavior in the presence of failures such as energy exhaustion and/or malicious attacks has been modeled using a novel Semi-Markov process. The proposed model is very useful in analyzing reliability of WBANs in the presence of multi-type failures.

• The Journal of the Acoustical Society of Korea
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• v.39 no.5
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• pp.490-496
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• 2020

We present a method to improve the performance of the multi-channel Wiener filter in noisy environment. To build subspace-based multi-channel Wiener filter, in the case of single target source, the target speech component can be effectively estimated in the principal subspace of speech correlation matrix. The speech correlation matrix can be estimated by subtracting noise correlation matrix from signal correlation matrix based on the assumption that the cross-correlation between speech and interfering noise is negligible compared with speech correlation. However, this assumption is not valid in the presence of strong interfering noise and significant error can be induced in the principal subspace accordingly. In this paper, we propose to adjust the principal subspace vector using speech presence probability and the steering vector for the desired speech source. The multi-channel speech presence probability is derived in the principal subspace and applied to adjust the principal subspace vector. Simulation results show that the proposed method improves the performance of multi-channel Wiener filter in noisy environment.

• Communications for Statistical Applications and Methods
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• v.17 no.5
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• pp.625-637
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• 2010

In this paper we propose generalized multi-phase multivariate ratio estimators in the presence of multiauxiliary variables for estimating population mean vector of variables of interest. Some special cases have been deduced from the suggested estimator in the form of remarks. The expressions for mean square errors of proposed estimators have also been derived. The suggested estimators are theoretically compared and an empirical study has also been conducted.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.24 no.1
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• pp.103-109
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• 2015

This paper introduces a multi-purpose smart fusion sensor. Normally, this type of sensor can contribute to energy savings specifically related to lighting and heating/air conditioning systems by detecting individuals in an office building. If a fire occurs, the sensor can provide information regarding the presence and location of residents in the building to a management center. The system consists of four sensors: a thermopile sensor for detecting heat energy, an ultrasonic sensor for measuring the distance of objects from the sensor, a fire detection sensor, and a passive infrared sensor for detecting temperature change. The system has a wireless communication module to provide the management center with control information for lighting and heating/air conditioning systems. We have also demonstrated the usefulness of the proposed system by applying it to a real environment.

• Journal of the Korean housing association
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• v.19 no.1
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• pp.39-48
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• 2008

The purpose of this study was to examine the characteristics of service facilities, and needs for service facilities using for leisure in multi-family housing properties. The multi-family housing complexes in Seoul were selected in this study. Site visits, analysis of drawing of complex and questionnaire survey were conducted. The statistical techniques used for data analysis included frequencies. The research results were as follows; The studied apartment complexes provided the appropriate and adequate service facilities in accordance to the regulations of multi-family housing. Playground for children, senior center, resting place were found in all the complexes, but the presence of exercise facilities, shared spaces, green spaces, and community parks was somewhat different across the studied complexes. Satisfaction with leisure facilities were different with the apartment complexes. The respondents who had lived older apartment complexes were more likely to increase dissatisfaction, and the reason was attributed to no presence of the leisure facilities they wanted to use. The respondents said that such service facilities using for leisure facilities as playground for children, senior center, community parks, walkways, reading room, and fitness center were highly needed.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2003.05a
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• pp.729-733
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• 2003

The presence of local features within clusters incurred by multi-modal nature of data prohibits many conventional clustering techniques from working properly. Especially, the clustering of datasets with non-Gaussian distributions within a cluster can be problematic when the technique with implicit assumption of Gaussian distribution is used. Current study proposes a simple tandem clustering method composed of k-means type algorithm and hierarchical method to solve such problems. The multi-modal dataset is first divided into many small pre-clusters by k-means or fuzzy k-means algorithm. The pre-clusters found from the first step are to be clustered again using agglomerative hierarchical clustering method with Kullback- Leibler divergence as the measure of dissimilarity. This method is not only effective at extracting the multi-modal clusters but also fast and easy in terms of computation complexity and relatively robust at the presence of outliers. The performance of the proposed method was evaluated on three generated datasets and six sets of publicly known real world data.

• Journal of the Korea Computer Graphics Society
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• v.24 no.3
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• pp.11-20
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• 2018

This study proposes collaboration based multi-user interaction to provide improved presence and satisfying experience to multiple HMD users in immersive virtual reality. The core of the proposed multi-user interaction is to present the direction in which HMD users in virtual reality environment can interact through communication and collaboration with each other based on their separate roles and behaviors. Each user in the virtual collaborative environment uses a hand to interact with a virtual environment or virtual objects. Based on the basic structure, this study designs methods (synchronization and communication) that can be achieved a common goal together through communication and collaboration. Then, this study creates a virtual reality application of arcade genre that considers communication and collaboration in order to verify whether the proposed multi-user interaction provides improved presence and satisfaction experience. And, the survey experiments are conducted for participants. Through these processes, it is confirmed that the interaction in the proposed immersive virtual collaborative environments provide the presence and experience that is satisfactory to all users.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2006.07a
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• pp.516-516
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• 2006