• The Transactions of the Korean Institute of Electrical Engineers A
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• v.55 no.10
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• pp.399-409
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• 2006

This paper presents a novel method for satisfying the thermal comfort of indoor environment and reducing the summer peak demand power by minimizing the power consumption for an Air-conditioner within a space. Korea Electric Power Corporation (KEPCO) use the fixed duty cycle control method regardless of the indoor thermal environment. However, this method has disadvantages that energy saving depends on the set-point value of the Air-Conditioner and direct load control (DLC) has no net effects on Air-conditioners if the appliance has a lower operating cycle than the fixed duty cycle. In this paper, the variable duty cycle control method is proposed in order to compensate the weakness of conventional fixed duty cycle control method and improve the satisfaction of residents and the reduction of peak demand. The proposed method estimates the predict mean vote (PMV) at the next step with predicted temperature and humidity using the back propagation neural network model. It is possible to reduce the energy consumption by maintaining the Air-conditioner's OFF state when the PMV lies in the thermal comfort range. To verify the effectiveness of the proposed variable duty cycle control method, the case study is performed using the historical data on Sep. 7th, 2001 acquired at a classroom in Seoul and the obtained results are compared with the fixed duty cycle control method.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.24 no.1
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• pp.16-24
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• 2016

Despite rapid growing in domestic duty free industry, weight of income from airport duty free area is relatively decreasing because of rapid progress in downtown duty free area. The purpose of this research was investigating the relationship between airport duty free servicescape and its effects on customer satisfaction and image for duty free shop, in order to maintain own competitive advantages. In pursuing above, previous studies related to servicescape, service value, customer satisfaction, and image were examined for literature review. Based on this previous studies, research model were constructed. Hypothesis was verified by effect. Data from 305 samples was employed for final survey. The main results show that functionality, attraction and convenience were meaningful factors to effect perceived servicescape. On the other hand, cleanness and comfort had few or no influence on servicescape. The perceived servicescape affected on service value and customer satisfaction. Service value had positive effects on customer satisfaction which was discovered to affected on image for duty free shop.

• The KIPS Transactions:PartC
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• v.11C no.6 s.95
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• pp.725-730
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• 2004

Separation of Duty(SOD), with delegation, is one of important security principles in access control area. The role-based access control model adopts SOD principle, but it has some problems; SOD concept is inconsistent with role hierarchy, permissions that have no relation with SOD may be restricted, and delegation may violate SOD. We propose permission-based SOD model on role-based access control. We establishes SOD as a set of permissions instead of role level SOD. Furthermore we propose a principle of role activation. It solves SOD problems of RBAC and supports easy implementation of SOD policy.

• Transactions of the Korean hydrogen and new energy society
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• v.32 no.4
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• pp.236-244
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• 2021

Fuel cell systems for medium duty truck require high power demands under driving. Since high power demands results in significant heat generation, thermal management is crucial for the performance and durability of medium duty truck. Therefore, various configurations of dual stacks with cooling systems are investigated to understand appropriate thermal management conditions. The simulation model consists of a dynamic fuel cell stack model, a cooling system model equipped with a controller, and the mounted controller applies a feedback controller to control the operating temperature. Also, In order to minimize parasitic power, the comparison of the cooling systems involved in the arrangement was divided into three case. As a result, this study compares the reaction of fuel cells to the placement of the cooling system under a variety of load conditions to find the best placement method.

• JSTS:Journal of Semiconductor Technology and Science
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• v.13 no.2
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• pp.139-144
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• 2013

Negative bias temperature instability (NBTI) has become a major factor determining circuit reliability. The effect of the NBTI on the circuit performance depends on the duty cycle which represents the stress and recovery conditions of each device in a circuit. In this paper, we propose an analytical model to perform more accurate duty cycle estimation at the gate-level. The proposed model allows accurate (average error rate: 3%) computation of the duty cycle without the need for expensive transistor-level simulations Furthermore, our model estimates the waveforms at each node, allowing various aging effects to be applied for a reliable gate-level circuit aging analysis framework.

• Korea Journal of Hospital Management
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• v.8 no.4
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• pp.76-110
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• 2003

This study analyzed and investigated of positivism to set up a hypothesis with a model of study based on a theoretical consideration to analyze a structural empowerment, a psychological empowerment, an immersion of duty, and a devotion of organization. which made the dental hygienists an object of study of investigation and analyzation in order to understand relation to elements that have an effect on a business result, effect and degree in a dental hygienist's organization. The results of positive analysis in the study are as follows. A psychological empowerment is influenced by a level of satisfaction for their duty, educational level, and types of main duty. A structural empowerment is influenced by a level of satisfaction for their duty, total years of work, a level of salary, type of work place. Organizational devotion is influenced by the structural empowerment, total year of work, type of workplace, and a level of satisfaction for their duty. Devotion for their duty is influenced by the psychological empowerment, total year of work, type of main duty, main duty that they want in the future, and specialization for amin duty.

• Journal of Applied Reliability
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• v.11 no.4
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• pp.433-445
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• 2011

Duty cycle is determined as the ratio of operating time to total time. Duty cycle in reliability prediction is one of the significant factors to be considered. In duty cycle application, non-operating time failure rate has been easily ignored even though the failure rate in non-operating period has not been proved to be small enough. Ignorance of non-operating time failure rate can result in over-estimated system reliability calculation. Furthermore, utilization of duty cycle in reliability prediction has not been evaluated in its effectiveness. In order to address these problems, two reliability models, such as MIL-HDBK-217F and RIAC-HDBK-217Plus, were used to analyze non-operating time failure rate. This research has proved that applying duty cycle in 217F model is not reasonable by the quantitative comparison and analysis.

• Journal of Nutrition and Health
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• v.35 no.6
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• pp.668-680
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• 2002

The purpose of this study was to investigation the importance and categorization of task elements of school food service dietician and to provide the useful data for standard model of the dietician′s tasks of school foodservice. This study was conducted in school food services nationwide in method of written questionnaire. The questionnaires were mailed to the dieticians of 3 type school foodservice system-conventional, commissary, joint management. Of the 660 schools that participated in this study, the responses from 212 conventional system and 212 commissary system and 200 joint management system were selected for analysis. Statistical analysis was performed with SAS/Win 6.12 package program for descriptive analysis, T-test, ANOVA, factor analysis using. The main results of this study can be summarized as follows Importance level was more than 4 score out of 5 scale in most of the task elements. The result was indicative of the appropriateness of definition of the 61 task elements. Of 61 task elements, importance level on ′nutrition education′ and on ′evaluation of foodservice operation management′ indicated the most significant difference between present and ideal situation. Through factor analysis, 61 task elements were regrouped into 7 dimensions; "Duty dimension of cooking and distribution management", "Duty dimension of cost management", "Duty dimension of raw material management", "Duty dimension of education management", "Duty dimension of menu management", "Duty dimension of record keeping of foodservice", "Duty dimension of general management (others)".

• Journal of Distribution Science
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• v.16 no.8
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• pp.39-50
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• 2018

Purpose - The ultimate purpose of this research is to analyze the influence of personal disposition on shopping value and behavioral intention by expanding the theory of planned behavior (TPB). Research design, data, and methodology - An attempt was made to examine the effects of personal disposition (reflecting duty-free shop characteristics) on three selective actions of consumers - compulsive buying, variety seeking, and price sensitivity. We conducted a questionnaire survey with the users of airport duty-free shops, downtown duty-free shops (offline), and online duty-free shops. In total, 410 copies of the questionnaire were analyzed using a structural equation model. Results - According to the results, compulsive buying, variety seeking, and price sensitivity significantly affected shopping value. Shopping value and subjective norms both had significant effects on attitude, the major variable in the TPB, and attitude had the greatest effect on behavioral intention, followed by subjective norms and perceived behavioral control in descending order. Conclusions - This study has academic implications in that it extends the existing theories of planned behavior and applies it to consumer characteristics and shopping value. It has practical implications as well in that it provides basic data that can be used to establish concrete marketing strategies for duty-free shop owners targeting segmented markets by closely examining customer desires.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.2
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• pp.194-201
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• 2006

Roof-fairing and deflector system have been used on heavy-duty trucks to minimize aerodynamic drag force not only for driving stability of the truck but also for energy saving by reducing the required driving power of the vehicle. In this study, a numerical simulation was carried out to see aerodynamic effect of the drag reducing device on the model vehicle. Drag and lift force generated on the five different models of the drag reducing system were calculated and compared them each other to see which type of device is efficient on the reduction of driving power of the vehicles quantitatively. An experiment has been done to see airflow characteristics on the model vehicles. Airflow patterns around the model vehicles were visualized by smoke generation method to compare the complexity of airflow around drag reducing device. From the results, the deflector systems(Model 5,6) were revealed as a better device for reduction of aerodynamic drag than the roof-fairing systems(Model 2,3,4) on the heavy-duty truck and it can be expected that over 10% of brake power of an engine can be saved on a tractor-trailer by the aerodynamic drag reducing device at normal speed range($80km/h{\sim}$).