• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.3
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• pp.1373-1392
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• 2017

WiFi Direct (WD) is a state of the art technology for a Device-to-Device (D2D) communication in 802.11 networks. The performance of the WD system can be significantly affected by some key factors such as the type of application, specifications of MAC and PHY layer parameters, and surrounding environment etc. It is, therefore, important to develop a system model that takes these factors into account. In this paper, we focus on investigating the design parameters of the PHY layer that could maximize the efficiency of the WD 802.11 system. For this purpose, a basic theoretical model is formulated for a WD network under a 2x2 Multiple In Multiple Out (MIMO) TGn channel B model. The design level parameters such as input symbol rate and antenna spacing, as well as the effects of the environment, are thoroughly examined in terms of path gain, spectral density, outage probability and Packet Error Rate (PER). Thereafter, a novel adaptive algorithm is proposed to choose optimal parameters in accordance with the Quality of Experience (QoE) for a targeted application. The simulation results show that the proposed method outperforms the standard method thereby achieving an optimal performance in an adaptive manner.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.3
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• pp.1406-1424
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• 2017

Recent advancements in network infrastructures provide increased opportunities to support data delivery over multiple paths. Compared with multi-homing scenario, overlay network is regarded as an effective way to construct multiple paths between end devices without any change on the underlying network. Exploiting multipath characteristics has been explored for TCP with multi-homing device, but the corresponding exploration with overlay network has not been studied in detail yet. Motivated by improving quality of experience (QoE) for reliable data delivery, we propose a multipath message transport protocol based on application level relay (MPMTP-AR). MPMTP-AR proposes mechanisms and algorithms to support basic operations of multipath transmission. Dynamic feedback provides a foundation to distribute reasonable load to each path. Common source decrease (CSD) takes the load weight of the path with congestion into consideration to adjust congestion window. MPMTP-AR uses two-level sending buffer to ensure independence between paths and utilizes two-level receiving buffer to improve queuing performance. Finally, the MPMTP-AR is implemented on the Linux platform and evaluated by comprehensive experiments.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.10 no.5
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• pp.173-178
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• 2010

In this paper, we analyze the performance of multilink Bluetooth service and design the multilink application between various Bluetooth devices. There are many restrictions for the Bluetooth based multilink services. Especially, these restrictions occur due to SCO and ACL which construct logical links. In forming ake a scatternet, only one SCO link can be utilized. Also, the number of ACL link depends on the number of RFCOMM channels. High quality audio data streaming cannot be supported by using SCO link. In that case, ACL link should be used for the audio streaming and the data rate of other data links decreases. We implemented the multilink services to verify the considerations for the multilink service.

• Women's Health Nursing
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• v.23 no.3
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• pp.155-165
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• 2017

Purpose: The aim of this study was to understand the hand-on breast massage techniques used by well-known experts in breastfeeding clinics. Methods: A qualitative multiple-case design was applied that involved a feasibility test. Four experts sampling qualitative data collected by observing participants and in individual interviews were analyzed by content analysis, linking data to the propositions, and cross-case pattern matching. This study explored differences within and between cases, and the possibilities of replicating findings across cases. Thirty-nine postpartum women participated voluntarily in the feasibility test, which investigated the usability of four massage techniques. Results: The four techniques showed considerable similarities in terms of the application of stimulation to the breast base and increased flexibility of the wired flexible body, which was the core mechanism underlying the techniques. The breast management strategies were consistent with existing practice guidelines with the exception of using cold cabbage to control engorgement pain. There was insufficient scientific evidence for supporting the massage techniques used by the experts. All of the techniques showed 100% education completeness, but application rates were higher for self-control-oriented techniques. Conclusion: The massage techniques applied by experts in breastfeeding were based on hypotheses and self-control techniques are feasible to apply in practice.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.3
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• pp.1205-1223
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• 2018

Image enhancement is an emerging method for analyzing the images clearer for interpretation and analysis in the spatial domain. The goal of image enhancement is to serve an input image so that the resultant image is more suited to the particular application. In this paper, a novel method is proposed based on Mamdani fuzzy inference system (FIS) using multiple fuzzy membership functions. It is observed that the shape of membership function while converting the input image into the fuzzy domain is the essential important selection. Then, a set of fuzzy If-Then rule base in fuzzy domain gives the best result in image contrast enhancement. Based on a different combination of membership function shapes, a best predictive solution can be determined which can be suitable for different types of the input image as per application requirements. Our result analysis shows that the quality attributes such as PSNR, Index of Fuzziness (IOF) parameters give different performances with a selection of numbers and different sized membership function in the fuzzy domain. To get more insight, an optimization algorithm is proposed to identify the best combination of the fuzzy membership function for best image contrast enhancement.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.7
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• pp.2977-2997
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• 2018

In big data era, fresh data grows rapidly every day. More than 30,000 gigabytes of data are created every second and the rate is accelerating. Many organizations rely heavily on real time streaming, while big data stream computing helps them spot opportunities and risks from real time big data. Storm, one of the most common online stream computing platforms, has been used for big data stream computing, with response time ranging from milliseconds to sub-seconds. The performance of Storm plays a crucial role in different application scenarios, however, few studies were conducted to evaluate the performance of Storm. In this paper, we investigate the performance of Storm under different application scenarios. Our experimental results show that throughput and latency of Storm are greatly affected by the number of instances of each vertex in task topology, and the number of available resources in data center. The fault-tolerant mechanism of Storm works well in most big data stream computing environments. As a result, it is suggested that a dynamic topology, an elastic scheduling framework, and a memory based fault-tolerant mechanism are necessary for providing high throughput and low latency services on Storm platform.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.9
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• pp.7-10
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• 2010

Recently, roll-to-roll printers are being developed actively by various research teams such as research institutes, universities and companies for the application of printed electronics. The printing methods that are widely used in the roll-to-roll printing equipments are gravure, gravure and flexo, which depend on the inks used and electronic devices produced. In general, a single printing unit of roll-to-roll printing equipment adopts only one printing method and this method is not changeable, which limits the application fields of the developed printing equipments. In this paper, the roll-to-roll printer, in which the printing unit has the novel design concept, is described.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.55 no.3
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• pp.91-97
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• 2006

A major difficulty with the practical application of the multiple observer based IFDI schemes is the computational burden of the residual generation. In this paper, a new residual generator that employs function observers is proposed to reduce the computational burden, and the design methods of the IFDIS, equipped with the residual generator, are presented. The function observers employed in the residual generator can be considered as a dual of the unknown input (function) observer And it can be designed to estimate the measurement errors that are due to sensor faults. The error estimates are further processed to generate the residuals by which reliable fault detection/isolation result car be obtained. The proposed scheme is more useful, in real-time application, than any other multiple state observer based IFDISs. It can be effectively applied to fault tolerant control because the failure effects can be compensated by the use of the estimates of measurement errors. The proposed IFDI scheme is applied to an inverted pendulum control system for the IFDI of failed sensor and fault compensation.

• Journal of Convergence Society for SMB
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• v.3 no.1
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• pp.1-6
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• 2013

As the important of software quality has being emphasized, the studies on software architecture also have being performed actively. On the other hand, due to the diversification of Smartphone platforms, the effort was increased to develop the application for supporting those multiple platforms. However several solutions are suggested to reduce the effort, and a representative solution is FireMonkey framework. In this paper, we represent the FireMonkey framework using ACME which is a language to describe software architecture. Such representation can provide the guideline to develop the application for the multiple platforms. Also it supports the information of that which perspectives are critical to develop such applications.

• International Commerce and Information Review
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• v.9 no.3
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• pp.33-57
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• 2007

This study tests e-business performance difference of the inter group by strategy type through the cluster analysis, after confirming the linear relationship between the e-business strategy type and its performance. According to the result of the study the effect on the e-business performance reveals to differ by the e-business strategy type. That is to say, while the firm's information system performance, e-business realization and the inter group competition dominance are affected positively by the e-process strategy, web application strategy and customer attracting strategy. This confirms that the information system performance, the realization performance and the competition dominance are affected by e - business strategy type. The key factor leading to the success of e-business is the commitment of e-process strategy and web application strategy. For the case of the customer attracting strategy the result shows the importance of the strategy. In the cluster group analysis, the additional analysis, the effect is seen to be more powerful in the firm's information system performance, e - business realization and securing the competition advantage for the case of the multiple strategy than that of single one. Accordingly, the firm needs to adopt the multiple strategy suited for the characteristic of the firm rather than the single strategy.