• Proceedings of the KIPE Conference
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• 2008.10a
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• pp.100-102
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• 2008

As Utility interactive fuel cell systems are widely used, it is required for each power conditioning system(PCS) to have higher generating performance and more stable connecting characteristics. This study is focused to minimization of power losses and hence higher efficiency related to the new half bridge type 3-stage utility interactive PCS topology. The loss factor of half-bridge converter becomes only 1.2[%] under the rated load, and hence total efficiency is maintained to be higher as 91[%].

• Journal of The Institute of Information and Telecommunication Facilities Engineering
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• v.4 no.2
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• pp.37-43
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• 2005

A simple scheduler satisfying the proportional fairness (PF) was introduced in wireless access networks and revealed that it can achieve a good compromise between total throughput and user fairness. Though it has received much attention for some time, its application was mainly restricted to the single channel systems. In this paper, we study how to implement the PF scheduler in the multi-channel environments such as OFDMA/TDMA. Besides the traditional PF-SC scheme, we propose a new PF-OPT scheme that is the genuine PF scheduler in a sense of maximizing the total log-utility of users. The simulation results show that PF-OPT gives large throughput under the heterogeneous subchannel statistics.

• Journal of Energy Engineering
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• v.7 no.1
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• pp.81-88
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• 1998

This paper describes the method decide to optimal sizing and operation scheduling of total cogeneration system which is interconnected with cogeneration unit of utility and auxiliary thermal devices of heating company. Optimal sizing and operation scheduling is established in order to minimize the fuel cost under national viewpoint. Simulations are carried out to show the reliability of method suggested by seasons and kinds. The simulated results can be effectively used as the guideline of operation scheduling between the utility and the heating company.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.518-522
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• 2001

In recent years, natural energy has attracted growing interest because of environmental concerns. Many studies have been focused on photovoltaic power generation systems because of the ease of use in urban areas. On the conventional system, many photovoltaic modules (PV modules) are connected in series in order to obtain the sufficient DC-bus voltage for generating AC output voltage at the inverter circuit. However, the total generation power on the PV modules sometimes decreases remarkably because of the shadows that partially cover the PV modules. In order to overcome this drawback, an AC module strategy is proposed. On this system, a small power DC-AC utility interactive inverter is mounted on each PV module individually and the inverter operates so as to generate the maximum power from the corresponding PV module. This paper presents a novel flyback-type utility interactive inverter circuit suitable for AC module systems. The feature of the proposed system are, (1) small in volume and light in weight, (2) stable AC current injection, (3) enabling a small DC capacitor. The effectiveness of the proposed system is clarified through the simulation and the experiments.

• Journal of the Korean Society of Clothing and Textiles
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• v.40 no.1
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• pp.12-25
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• 2016

Based on the self-congruity theory, this study investigated how congruity between multi-brand store image and consumers' self-image affect store attributes and consumer responses. A total of 331 questionnaires were used to analyze data. The results of research were: 1) 'Sophistication' as the congruity factor between store image and consumers' self-image affected 'utility', 'atmosphere', and 'design' among store attribute factors. Also, 'sincerity' influenced 'utility' as the store attribute factor. 2) 'Atmosphere' as the store attribute factor positively influenced consumers' emotional responses, and 'utility' and 'design' factors positively influenced consumers' cognitive responses. 3) Consumers' emotional responses had a positive impact on consumers' cognitive responses; in addition, consumers' emotional and cognitive responses had positive impacts on consumers' behavioral responses. 4) A-Land indicated higher scores on 'sophistication', 'atmosphere', and 'design' factors than ABC Mart. ABC Mart had shown higher scores on 'ruggedness' and 'utility' factors than A-Land. This study provides practical implications to develop effective marketing strategies to manage multi-brand stores.

• Korean journal of food and cookery science
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• v.19 no.5
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• pp.581-590
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• 2003

The purpose of this study was to identify the combinations of factors combinations conferring the highest utility of family restaurants to university students, and establish the relative importance of these factors in terms of their contribution to total utility. 196 of 200 questionnaires were utilized for the analysis. (Eds note: to whom were the questionnaires administered) Frequencies, crosstabs, and the conjoint, max. utility, BTL and Logit models, K-means cluster and one-way ANOVA analysesis, and the Friedman test were the statistical methods used for this study. The findings from this study were as follows: 1) the Pearson's R and Kendall's tau statistics (Eds note: these were not mentioned earlier) show that the model (Eds note: which model is this) fits the data well. 2) it was found that of all the respondents, especially the first and third clusters, regarded both the type of food and the price as very important factors. 3) it was found that all the respondents, especially the third cluster, most preferred a family restaurant (design and simulation) that provided less than 6 fusion and traditional foods. The first cluster most preferred family restaurant (design) that provided over 10 traditional and less than 6 ethnic foods. The second cluster most preferred a family restaurant (design and simulation) that provided over 10 traditional foods. 4) the results of the study have provided some insights into the effective types of family restaurant designs that can be successfully developed by those who manage menu variety, quality and type of food, price, and quality of service to university students dining at family restaurants.

• Journal of Information Processing Systems
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• v.5 no.3
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• pp.151-158
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• 2009

This paper proposes a utility-based data rate allocation algorithm to provide high-quality mobile video streaming over femtocell networks. We first derive a utility function to calculate the optimal data rates for maximizing the aggregate utilities of all mobile users in the femtocell. The total sum of optimal data rates is limited by the link capacity of the backhaul connections. Furthermore, electromagnetic cross-talk poses a serious problem for the backhaul connections, and its influence passes on to mobile users, as well as causing data rate degradation in the femtocell networks. We also have studied a fixed margin iterative water-filling algorithm to achieve the target data rate of each backhaul connection as a counter-measure to the cross-talk problem. The results of our simulation show that the algorithm is capable of minimizing the transmission power of backhaul connections while guaranteeing a high overall quality of service for all users of the same binder. In particular, it can provide the target data rate required to maximize user satisfaction with the mobile video streaming service over the femtocell networks.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.3
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• pp.156-162
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• 2004

In this paper, a technique that estimate the optimal capacity of the solar-wind hybrid power system for minimizing the total monthly electric power expenses is presented. The hybrid power system is assumed to be operated in connection with the utility power system and electric bill be paid for the power not covered by the hybrid system generation. Monthly generation cost is estimated based on total life-cycle cost analysis. The monthly utility power bill is assumed to be increased quadratically in proportion with the net utility power consumption which is the difference between the total monthly load minus the hybrid system generations. Test results demonstrate applications potential of the proposed technique.

• Journal of the Korean Society of Safety
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• v.31 no.3
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• pp.143-155
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• 2016

Recently, a massive loss of life and property is occurring in Korea due to traffic accidents, with the rapid increase in cars. For improvement of traffic safety, the Korea Transportation Safety Authority intensively analyzes accident data in local governments with low traffic safety index, performs a field investigation to extract problems and offers local governments improvements for problems, by conducting the 'Special Survey of Actual Conditions of Traffic Safety' each year, starting 2008. But local governments cannot strongly push forward the improvement projects due to the limited budget and the uncertainty of the improvement plan effects. Therefore, this study suggested a model which applied the Utility concept to the AHP theory, in order to efficiently decide a priority of the improvement plans in accident black spots in consideration of the limited budget of local governments. The number of accidents in each spot for improvement and accident severity, traffic volume, pedestrian volume, the improvement project cost and the accident reduction effect were chosen as evaluation factors for deciding a priority, and data about the improvement plan costs and the accident reduction effects, traffic accidents and traffic volume in the spots to undergo the special research on the real condition of traffic accident in the past were collected from the existing studies. Then, regression analysis was carried out and the Utility Curve of each evaluation factor was computed. Based on the AHP analysis findings, this study devised a priority decision method which calculated the weight and the utility function of each evaluation factor and compared the total utility values. The AHP analysis findings showed that among the evaluation factors, accident severity had the biggest importance and it was followed by the improvement plan cost, the number of accidents, the improvement effect, traffic volume and pedestrian volume. The calculated utility function shows a rise in utility, as the variables of the 5 evaluation factors; the number of accidents, accident severity, the improvement plan effect, traffic volume and pedestrian volume increase and a fall in utility, as the variables of the improvement plan cost increase, since the improvement plan cost is included in the budget spent by a local government.

• The Journal of Society for e-Business Studies
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• v.26 no.2
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• pp.1-17
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• 2021

This paper elucidates the effect of characteristics of service quality on continuance usage intention of digital healthcare service using mediating factors of user expectation and user utility. First, we classified independent factors into three types such as service system characteristics, user characteristics, and healthcare service characteristics from the previous studies, and investigated the effect of three independent factors on continuance usage intention of digital healthcare service. Second, we analyzed the impact of two mediating factors, user expectation and user utility, on the continuance usage intention. We developed a research model that includes three types of independent factors, mediated factors of user expectation and user utility, and a dependent factor of continuance usage intention. We surveyed a total of 357 samples from digital healthcare service users and analyzed the research model. The research results significantly show that Characteristics of Users is essential factor impacting a dependent factor of Continuance Usage Intention. The results indicate the followings: (1) Characteristics of Users including the variables of Innovation impacts User Expectation, and User Expectation affects Users Utility, and Users Utility also affects Continuance Usage Intention. (2) Characteristics of Service Systems including the variables of Functionality, Compatibility, and Convenience and Characteristics of users of Innovation variable impact the mediating factor of User Expectation, and User Expectation also affects the factor of Continuance Usage Intention. (3) Characteristics of Healthcare Services including the variables of Reliability, Ease of Operation, Safety, and Accuracy impact User Utility, and User Utility also affects Continuance Usage Intention.