• The Journal of Information Technology and Database
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• v.2 no.2
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• pp.25-34
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• 1995

In this paper, we present design philosophy and implementation issues of a functionality testing tool for object-oriented database systems. A testing tool has been developed to validate UniSQL/X functionalities with C++ interface. A testing tool is designed under consideration of scaleability, simplicity and extendibility. The schema is deliberately constructed to verify the object-oriented functionalities such as abstraction, inheritance and aggregation. Each test item has been derived under various black box techniques such as equivalent partitioning and boundary-value analysis. The testing tool consists of six phases, namely, database creation, database population, construction of testindex, compilation and link, execution and result reporting, and final cleanup. The prototype provides more than 140 test items at 90 programs.

• Journal of Korean Society for Quality Management
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• v.46 no.2
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• pp.283-300
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• 2018

Purpose: Since the servant leadership of project managers is seemingly related to the project performance by influencing project team members' positive attitude and behavior, this study attempts to provide empirical evidence for a link between servant leadership and project performance. In addition, the present study investigates the mediating effects of customer satisfaction on the servant leadership-project performance relations. Methods: The data of servant leadership and project performance were collected from 185 project team members of a company providing IT service, and customer satisfaction data were collected from 100 project clients served by the company. Before testing the hypotheses, we calculated aggregation statistics(e.g., $r_{wg}$, ICC(1), and ICC(2)) to ensure appropriate aggregation of servant leadership scores. The statistics confirmed the use of 67 team level servant leadership scores with project performance and customer satisfaction. Results: The results show that servant leadership is significantly related to three project performance measures(perceptions of performance contribution and sales contribution, and actual project profits) in the current team-level sample. Results also indicate that the clients' perception of customer satisfaction shows a mediating effect in the process of servant leadership affecting sales contribution of project performance. Conclusion: The present study empirically confirms that servant leadership plays a major role in enhancing project performance on team level analysis. The results suggest that servant leadership increases customer satisfaction since the project managers serve and care for their team members which translate into effective customer service. Theoretical and practical implications are reviewed, and limitations of the study and suggestions for future research are addressed.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.11
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• pp.2187-2192
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• 2016

A data-centric routing protocol considering a data aggregation technique at relay nodes is required to increase the lifetime of wireless sensor networks. An energy-efficient data-centric routing algorithm is proposed by considering a tradeoff between acquisition time and energy consumption in the wireless sensor network. First, the proposed routing scheme decides the sink node among all sensor nodes in order to minimize the maximum distance between them. Then, the proposed routing extends its tree structure in a way to minimize the link cost between the connected nodes for reducing energy consumption while minimizing the maximum distance between sensor nodes and a sink node for rapid information gathering. Simulation results show that the proposed data-centric routing algorithm has short information acquisition time and low energy consumption; thus, it achieves high energy efficiency in the wireless sensor network compared to conventional routing algorithms.

• Journal of Digital Convergence
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• v.12 no.12
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• pp.323-328
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• 2014

D-MAC protocol is used convergence network, which is designed to connect wireless link between things. This protocol is supported to local data exchange and aggregation among neighbor nodes, and distributed control packet from sink to sensor node. In this paper, we analysis about efficiency of power consumption according to whether or not security authentication of D-MAC in convergence network. If authentication scheme is applied to MAC communication, it is related to power consumption of preamble whether or not with and without authentication process. It is reduced to energy consumption against denial attack of service, when it is applied to authentication. Future work will take the effort to deal with security authentication scheme.

• Journal of Electrical Engineering and Technology
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• v.10 no.3
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• pp.1319-1327
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• 2015

As wind power farm (WPF) installations continue to grow, monitoring and controlling large-scale WPFs presents new challenges. In this paper, a hierarchical network architecture is proposed in order to provide remote monitoring and control of large-scale WPFs. The network architecture consists of three levels, including the WPF comprised of wind turbines and meteorological towers, local control center (LCC) responsible for remote monitoring and control of wind turbines, and a central control center (CCC) that offers data collection and aggregation of many WPFs. Different scenarios are considered in order to evaluate the performance of the WPF communications network with its hierarchical architecture. The communications network within the WPF is regarded as the local area network (LAN) while the communication among the LCCs and the CCC happens through a wide area network (WAN). We develop a communications network model based on an OPNET modeler, and the network performance is evaluated with respect to the link bandwidth and the end-to-end delay measured for various applications. As a result, this work contributes to the design of communications networks for large-scale WPFs.

• Proceedings of the Korean Society of Applied Pharmacology
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• 2008.04a
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• pp.89-99
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• 2008

GPCRs are large families of cell surface receptors that transmit signals through conformational changes upon ligand activation and an interaction with the heterotrimeric G-proteins. GPCRs regulate the cell-signaling pathways and participate in the regulation of physiological processes through the G-proteins defined by their ${\alpha}$ subunits. A family of 20 G protein-coupled receptors (GPCRs) that provide a large class of tractable drug targets for new anti-inflammatory drugs and, in certain instances, for the treatment of the inflammatory indications such as atherosclerosis, rhinitis, asthma, pulmonary disease and arthritis. In view of the important findings showing that $G{\alpha}_{12}/G{\alpha}_{13}$ regulate the various cellular processes such as actin-stress fiber formation, neurite retraction, platelet aggregation, gene induction, and apoptosis, we became interested in whether, after coupling to the activated GPCRs, the G-proteins and their downstream molecules might be involved in the pathologic processes of chronic inflammatory diseases (e.g., liver fibrosis). In this symposium, the possible link of the G-proteins with the pathophysiology will be discussed with the aim of finding potential new drug targets.

• Journal of Communications and Networks
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• v.13 no.1
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• pp.17-25
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• 2011

A convergecast is a popular routing scheme in wireless sensor networks (WSNs) in which every sensor node periodically forwards measured data along configured routing paths to a base station (BS). Prolonging lifetimes in energy-limited WSNs is an important issue because the lifetime of a WSN influences on its quality and price. Low-energy adaptive clustering hierarchy (LEACH) was the first attempt at solving this lifetime problem in convergecast WSNs, and it was followed by other solutions including power efficient gathering in sensor information systems (PEGASIS) and power efficient data gathering and aggregation protocol (PEDAP). Our solution-chain routing with even energy consumption (CREEC)-solves this problem by achieving longer average lifetimes using two strategies: i) Maximizing the fairness of energy distribution at every sensor node and ii) running a feedback mechanism that utilizes a preliminary simulation of energy consumption to save energy for depleted Sensor nodes. Simulation results confirm that CREEC outperforms all previous solutions such as LEACH, PEGASIS, PEDAP, and PEDAP-power aware (PA) with respect to the first node death and the average lifetime. CREEC performs very well at all WSN sizes, BS distances and battery capacities with an increased convergecast delay.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.5
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• pp.1973-1991
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• 2018

Multimedia applications over wireless networks have been evolving to augmented reality or virtual reality services. However, a rich data size compared to conventional multimedia services causes bandwidth bottlenecks over wireless networks, which is one of the main reasons why those applications are not used widely. To overcome this limitation, bandwidth aggregation techniques, which exploit a multi-path transmission, have been considered to maximize link utilization. Currently, most of the conventional researches have been focusing on the user end problems to improve the quality of service (QoS) through optimal load distribution. In this paper, we address the joint pricing and load distribution problem for multi-homing in heterogeneous wireless access networks (ANs), considering the interests of both the users and the service providers. Specifically, we consider profit from resource allocation and cost of power consumption expenditure for operation as an utility of each service provider. Here, users decide how much to request the resource and how to split the resource over heterogeneous wireless ANs to minimize their cost while supporting the required QoS. Then, service providers compete with each other by setting the price to maximize their utilities over user reactions. We study the behaviors of users and service providers by analyzing their hierarchical decision-making process as a multileader-, multifollower Stackelberg game. We show that both the user and service provider strategies are closed form solutions. Finally, we discuss how the proposed scheme is well converged to equilibrium points.

• Nuclear Engineering and Technology
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• v.53 no.6
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• pp.1979-1990
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• 2021

Evacuation Time Estimate (ETE) can provide decision-makers with a likelihood to implement evacuation of a population with radiation exposure risk by a nuclear power plant. Thus, the ETE is essential for developing an emergency response preparedness. However, studies on ETE have not been conducted adequately in Korea to date. In this study, different cohorts were selected based on assumptions. Existing local data were collected to construct a multi-model network by TSIS-CORSIM code. Furthermore, several links were aggregated to make simple calculations, and post-processing was conducted for dealing with the stochastic property of TSIS-CORSIM. The average speed of each cohort was calculated by the link aggregation and post-processing, and the evacuation time was estimated. As a result, the average cohort-based evacuation time was estimated as 2.4-6.8 h, and the average clearance time from ten simulations in 26 km was calculated as 27.3 h. Through this study, uncertainty factors to ETE results, such as classifying cohorts, degree of model complexity, traffic volume outside of the network, were identified. Various studies related to these factors will be needed to improve ETE's methodology and obtain the reliability of ETE results.

• Journal of Korean Society of Transportation
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• v.34 no.6
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• pp.570-579
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• 2016

This study proposes a concept of Stepwise Transfer Coefficient(STC) which implies greater transfer cost with increasing the number of transfers. Thus, the public transport information system provides the choice sets of travel routes by the consideration of not only transportation time but also the optimum number of transfers. However, path choice problems that involve STC are found to include non additive cost, which requires additional route enumeration works. Discussions on route enumeration in actual transportation networks is very complicated, thereby warranting a theoretical examination of route search considering STC. From these points of view, this study results in a probability based transit trip assignment model including STC. This research also uses incoming link based entire route deletion method. The entire route deletion method proposed herein simplifies construction of an aggregation of possible routes by theoretically supporting the process of enumeration of the different routes from origin to destination. Conclusively, the STC reflected route based logit model is proposed as a public transportation transit trip assignment model.