• 한국정보통신설비학회:학술대회논문집
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• 2004.08a
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• pp.273-277
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• 2004

서울대학교와 KT는 연구 환경 조성과 U-Campus 시범 구축을 위해서 산학협력 협약을 하고, 서울대학교에 NESPOT 시설을 구축하였다. 본 논문은 서울대학교 내의 NESPOT 이용자들의 NESPOT 서비스 이용 패턴 및 무선랜의 트래픽 특성을 분석하기 위한 시스템의 설계와 구현에 대한 내용을 다룬다. NESPOT 트래픽 특성을 분석하기 위한 시스템은 TCPDUMP를 이용하여 백본 라우터로부터 네트워크 전체에 대한 정보를 획득하고, SNMP (Simple Network management Protocol)을 통해 AP로부터 무선랜 관련 정보를 얻는다. 그리고, NESPOT 사용자의 단말에 관련된 보다 구체적인 정보를 얻기 위해서 TIS (Terminal Information System)을 개발하였다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.10a
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• pp.616-617
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• 2010

This paper presents a model of e-learning based on ubiquitous computing configuration. The proposed e-learning model as following. we propose the e-learning system's hardware and software configurations which are server and networking systems. Also, we construct the proposed e-learning systems's services. There are attendance and absence service, class management service, common knowledge service, score processing service, facilities management service, personal management service, personal authorization issue management service, campus guide service, lecture-hall management service. Also, we propose the laboratory equipment management service, experimental materials management service etc.

• International Journal of Reliability and Applications
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• v.8 no.2
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• pp.183-197
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• 2007

There is a growing trend for asset intensive industries to outsource maintenance services of their complex assets since outsourcing through service contract reduces upfront investments in infrastructure, expertise and specialised maintenance facilities. Estimation of costs for such contracts is complex and it is important to the user and the service providers for economic variability. The service provider's profit is influenced by many factors such as the terms of the contract, reliability of asset, and the servicing strategies, costs of resources needed to carryout maintenance. There is a need to develop mathematical models for understanding future costs to build it into the contract price. Three policies for service contracts are proposed in this paper considering the concepts of outsourcing maintenance service of assets to the service providers. Conceptual models are developed for estimating servicing costs of outsourcing through service contracts by considering time dependent failure mode.

• Journal of the Korean Society of Food Science and Nutrition
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• v.41 no.8
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• pp.1182-1189
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• 2012

The purpose of this study was to analyze university student' perception of the price of coffee shops using price sensitivity measurements. The questionnaires were distributed to 640 university students in Changwon, Korea from March 13 to April 8, 2011. A total 571 were used for the final analysis, which excluded improperly-completed questionnaires. The results of this study were as follows. Indifference prices (IDPs) were \2,200 for on-campus coffee shops and \2,850 for off-campus coffee shops. The optimum price points (OPP) were \2,300 for on-campus coffee shops and \2,850 for off-campus coffee shops. The price stress range (PSR) was \100 (\2,200~2,300) for on-campus coffee shops and \0 (\2,850~2,850) for off-campus coffee shops. The point of marginal cheapness (PMC) was \1,100 for on-campus coffee shops and \1,500 for off-campus coffee shops, whereas the point of marginal expensiveness (PME) was \3,600 for on-campus coffee shops and \4,100 for off-campus coffee shops. The ranges of acceptable prices (RAP) were \2,500 (\1,100~3,600) for on-campus coffee shops and \2,600 (\1,500~4,100) for off-campus coffee shops. On the basis of IDP percentage, university students were more sensitive to off-campus coffee shops than on-campus coffee shops. In contrast, on the basis of PSR and RAP, university students were more sensitive to on-campus coffee shops than off-campus coffee shops. Therefore, the price increase for an americano should be recommended to be from \1,100 to \3,600 for on-campus coffee shops and from \1,500 to \4,100 for off-campus coffee shops. The manager of on-campus coffee shops should be careful when increasing the prices, and the manager of off-campus coffee shops should make it possible for customers to perceive service quality.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.16
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• pp.6805-6810
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• 2014

Background: Previous studies have suggested a link between obesity and breast cancer (BC). However, there is no universal consensus, especially in population based studies. Because only few studies have been conducted on African women, we aimed here to assess the relationship between BMI at time of diagnosis and the BC histopathological features among Tunisian patients according to menopausal status using a hospital-based prospective cohort study. Materials and Methods: Clinical and pathological data were collected from 262 patients stratified on four groups according to their BMI. The relationship between BMI and histopathological features at diagnosis was analysed using univariate and multivariate analysis. Receiver-operating characteristic (ROC) curves were used to evaluate the performance of BMI in predicting of high tumor grade, in comparison to ki-67 index of proliferation. Results: Obesity was correlated with larger tumors, advanced grade and with ER-PR-Her2+ BC subtype. An association of BMI with tumor size and tumor grade was observed in both premenopausal and postmenopausal women. Additionally, a significant association between BMI and ER+, ER+PR+Her2+ and ER-PR-Her2+ status was revealed for premenopausal patients, while only ER+PR+Her2+ was associated with BMI for postmenopausal women. Finally, our results showed that compared to Ki67 proliferation index, BMI is a useful prognostic marker of high grade BC tumors. Conclusions: These data are the first to show that in Tunisia obese women suffering from BC have significantly larger tumors and advanced tumor grade and that higher BMI might influence tumor characteristics and behavior.

• Journal of the Korea Society of Computer and Information
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• v.19 no.9
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• pp.11-19
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• 2014

In this paper, we propose a real-time video transcoding scheme for N-Screen service based on cloud computing. This scheme creates an intro-block and several playback blocks by splitting the original video. And there is the first service request, after transmitting the intro-block, transmits the playback blocks that converting the blocks on real-time. In order to completing trans-coding within playback time of each block, we split and allocate the block to node according to performance of each node. Also, in order to provide real-time video playback service, the previous scheme convert original video into all format and resolution. However we show that the proposed scheme can reduce storage usage by converting original video into format with proper resolution suitable to device and platform of client. Through simulation, we show that it is more effective to real-time video playback for N-screen service than the previous method. We also show that the proposed scheme uses less storage usage than previous method.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.3
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• pp.838-856
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• 2014

Enhanced network speed and the appearance of various applications have recently resulted in the rapid increase of Internet users and the explosive growth of network traffic. Under this circumstance, Internet users are eager to receive reliable and Quality of Service (QoS)-guaranteed services. To provide reliable network services, network managers need to perform control measures involving dropping or blocking each traffic type. To manage a traffic type, it is necessary to rapidly measure and correctly analyze Internet traffic as well as classify network traffic according to applications. Such traffic classification result provides basic information for ensuring service-specific QoS. Several traffic classification methodologies have been introduced; however, there has been no favorable method in achieving optimal performance in terms of accuracy, completeness, and applicability in a real network environment. In this paper, we propose a method to classify Internet traffic as the first step to provide stable network services. We integrate the existing methodologies to compensate their weaknesses and to improve the overall accuracy and completeness of the classification. We prioritize the existing methodologies, which complement each other, in our integrated classification system.

• Smart Structures and Systems
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• v.22 no.4
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• pp.441-457
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• 2018

Characteristic parameter values of seismic isolators deviate from their nominal design values due to uncertainties and/or errors in their material properties and element dimensions, etc. Deviations may increase over service life due to environmental effects and service conditions. For accurate evaluation of the seismic safety level, all such effects, which would result in deviations in the structural response, need to be taken into account. In this study, the sensitivity of the probability of failure of the structures equipped with nonlinear base isolation systems to the uncertainties in various isolation system characteristic parameters is investigated in terms of various isolation system and superstructure response parameters in the context of a realistic three-dimensional base-isolated building model via Monte Carlo Simulations. The inherent record-to-record variability nature of the earthquake ground motions is also taken into account by carrying out analyses for a large number of ground motion records which are classified as those with and without forward-directivity effects. Two levels of nominal isolation periods each with three different levels of uncertainty are considered. Comparative plots of cumulative distribution functions and related statistical evaluation presented here portray the potential extent of the deviation of the structural response parameters resulting from the uncertainties and the uncertainty levels considered, which is expected to be useful for practicing engineers in evaluating isolator test results for their projects.

• Journal of Information Processing Systems
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• v.10 no.4
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• pp.618-627
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• 2014

Nowadays mobile users are using a popular service called Location-Based Services (LBS). LBS is very helpful for a mobile user in finding various Point of Interests (POIs) in their vicinity. To get these services, users must provide their personal information, such as user identity or current location, which severely risks the location privacy of the user. Many researchers are developing schemes that enable a user to use these LBS services anonymously, but these approaches have some limitations (i.e., either the privacy prevention mechanism is weak or the cost of the solution is too much). As such, we are presenting a robust scheme for mobile users that allows them to use LBS anonymously. Our scheme involves a client side application that interacts with an untrusted LBS server to find the nearest POI for a service required by a user. The scheme is not only efficient in its approach, but is also very practical with respect to the computations that are done on a client's resource constrained device. With our scheme, not only can a client anonymously use LBS without any use of a trusted third party, but also a server's database is completely secure from the client. We performed experiments by developing and testing an Android-based client side smartphone application to support our argument.

• ETRI Journal
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• v.43 no.5
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• pp.799-811
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• 2021

This paper considers a challenging problem: to simultaneously optimize the cost and the quality of service in opaque wavelength division multiplexing (WDM) networks. An optimization problem is proposed that takes the information including network topology, traffic between end nodes, and the target level of congestion at each link/ node in WDM networks. The outputs of this problem include routing, link channel capacities, and the optimum number of switch ports locally added/dropped at all switch nodes. The total network cost is reduced to maintain a minimum congestion level on all links, which provides an efficient trade-off solution for the network design problem. The optimal information is utilized for dynamic traffic in WDM networks, which is shown to achieve the desired performance with the guaranteed quality of service in different networks. It was found that for an average link blocking probability equal to 0.015, the proposed model achieves a net channel gain in terms of wavelength channels (𝛾_w) equal to 35.72 %, 39.09 %, and 36.93 % compared to shortest path first routing and 𝛾_w equal to 29.41 %, 37.35 %, and 27.47 % compared to alternate routing in three different networks.