• KSCE Journal of Civil and Environmental Engineering Research
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• v.42 no.4
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• pp.537-548
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• 2022

It is important to design the pavement thickness considering heavy-duty traffic loads, which can cause excessive stress and strain in the pavement. Port-rear roads and industrial roads have many problems due to early stress in pavement because these have a higher ratio of heavy loads than general roads such as national roads and expressways. Internationally, composite pavement has been widely applied in pavement designs in heavy-duty areas. Composite pavement is established as an economic pavement type that can increase the design life by nearly double compared to that of existing pavement while also decreasing maintenance and user costs. This study suggests a thickness design method for composite pavement using roller-compacted concrete as a base material to ensure long-term serviceability in heavy-duty areas such as port-rear roads and industrial roads. A three-dimensional finite element analysis was conducted to investigate the mechanical behavior and the long-term pavement performance ultimately to suggest a thickness design method that considers changes in the material properties of the roller-compacted concrete (RCC) base layer. In addition, this study presents a user-friendly catalog design method for RCC-base composite pavement considering the concept of linear damage accumulation for each container trailer depending on the season.

• Transactions of Materials Processing
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• v.19 no.8
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• pp.447-451
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• 2010

In this paper, a useful die system for warm plate forging of a large axle housing of heavy-duty trucks is presented. A die system composed of material flow guide pin as well as upper die and lower die is proposed to reduce the inherent thickness reduction along the bent corner of the product which deteriorates structural strength and fatigue life in its service. The role of the pin assembled in the upper die is to prevent formation of sharp corner in early forming stage and to supply material in the lower die cavity sufficient enough to thicken the bent corner at the final stroke. The mechanism of the die system is given and its effect on corner thickness of the product is revealed by two-dimensional finite element analysis under plain strain assumption. Three-dimensional finite element solutions are also given to verify validity of the two dimensional approach and to show the mechanics of the die system in detail. The die system has been successfully applied to manufacturing the axle housing of heavy-duty trucks.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.19 no.1
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• pp.74-87
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• 2011

This paper tried to research the relationship among the passenger's satisfaction and expectation of in-flight service quality, overall satisfaction and passenger's Loyalty by emphasizing on two groups of passengers and cabin crews from K-airline to find out which service quality area should be focused on for pursuing premium in-flight service. Such six service quality areas as in-flight equipment, food&beverage, duty-free sales, service ability, service image and specialized service were conceived and survey questions were made based on relevant previous researches. The analysis has used the data of 281 passengers and 336 cabin crews from K-airline. According to the analysis, in physical service factors, passengers perceive satisfaction from duty-free sales contributes to overall service satisfaction. However, cabin crews believed in-flight equipment and food&beverage are important to overall service satisfaction. In human service factors, both groups seemed to agree service ability and service image have a positive impact on overall service satisfaction. Among service satisfaction factors, the customer's satisfaction from cabin crew's service ability(service response, professional knowledge and foreign language skill) is also proven to be directly connected to customer loyalty.

• Journal of Korean Society for Atmospheric Environment
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• v.22 no.3
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• pp.383-391
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• 2006

In Korea, the major source of serious air pollution is motor vehicles. Air pollution from vehicles has been annually increased. Then the government will try to control the vehicle emission by applying the effective emission management policy for the manufactured and in-used car. It is necessary to correctly calculate the emission factor for successful propulsion of the vehicle emission control policy. In this study, correlation analysis of exhaust emissions from vehicles between CVS-75 mode and Korea mode was conducted. A total of 25 light-duty buses were tested on the chassis dynamometer system in order to measure CO, HC, NOx PM and fuel efficiency (F.E.). For the test modes, 10 different Korea modes and CVS-75 mode were used. As the result of correlation analysis between those modes, most of the correlation coefficients were higher than 0.90. On the basis of high correlation between those modes, correction factors by driving conditions were estimated. Through the results of this study, we obtained essential basic data to correct difference from those modes.

• Korea Journal of Hospital Management
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• v.19 no.1
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• pp.54-67
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• 2014

Purpose: The aim of this study was to explore the relationship between nursing work environment and nursing outcome of clinical nurses. Also, the purpose of this study was to identify the nurses' workload. Method: The participants in this study were 246 nurses working at one hospital in a province. Data was collected using a structured questionnaire from October 2011 to November 2011. Open questions were subject to content analysis; closed questions were subject to descriptive statistics and Pearson correlation coefficient with SPSS 18.0 program were used. Result: The number of patients per nurse in day-duty and overtime work had a positive correlation. Nursing performance and the overtime work in night duty nurses had a negative correlation. The results of this study, with a much higher number of patients per nurse, showed an increase in overtime hours. In the nursing delivery system experience of nurses, 13 themes were identified and they were divided into five categories. Conclusion: Therefore, in order to improve nursing performance and increase job satisfaction, efforts must be made to reduce overtime, and nursing personnel placement to secure a substantial nursing staff.

• Journal of IKEEE
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• v.23 no.3
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• pp.1054-1060
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• 2019

A extension of the high boost voltage-lift DC-DC converter with large conversion ratio has been proposed in this paper. The proposed extension is combined the switched-inductor cell (SL-cell) and modular voltage cell (MV-cell). The proposed structure can achieve the large voltage conversion without high duty-cycle and the low voltage of the components. Moreover, the PID controller for novel SL-MV voltage-lift DC-DC converter also introduces. This technique a good-performance output voltage can kept constant with an good transient performance when the output load is suddenly changed. In order to prove the theoretical analysis, the experimental setup has been built for the DC load of $150[{\Omega}]$ and $300[{\Omega}]$. In addition, the transient of output voltage has been tested to determine the controller. Experimental results validate the effectiveness of the theoretical analysis proving the satisfactory converter performance.

• The Transactions of the Korean Institute of Power Electronics
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• v.25 no.6
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• pp.442-450
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• 2020

A small-signal modeling approach for a three-level boost (TLB) converter and a design methodology for a double-loop controller are proposed in this study. Conventional modeling of TLB converters involves three state variables. Moreover, TLB converters have two operation modes depending on the duty ratio. Consequently, complex mathematical calculations are required for controller design. This study proposes a simple system modeling method that uses two state variables, unlike previous methods that require three state variables. Analysis shows that the transfer functions of the two operation modes can be expressed as identical equations. This condition means that the linear feedback controller can be applied to all operational ranges, that is, for full duty ratios. The design method for a double-loop controller using a PI controller is presented in step-by-step sequences. Simulation and experimental verifications are conducted to verify the effectiveness of the small-signal analysis and control system design.

• Journal of East-West Nursing Research
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• v.15 no.2
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• pp.71-81
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• 2009

Purpose: This study was conducted to find out interrelation of health behavior and related variables to provide basic data for an effective health promotion for the taxi-divers. Methods: 293 male taxi-drivers from 2 cities in Korea participated in this study. The data were collected using questionnaires from April 17th to Jun 3rd, 2006, and analyzed by descriptive statistics, t-test, ANOVA, Pearson correlation, and multiple regression. Results: There were statistically significant differences according to monthly income, past illness or surgery, current disease or medication, frequency of fright on daily driving (FFDD), driving fatigue, working style, social support in health status; current disease or medication, FFDD, driving fatigue, duty shift, social support in health perception; body mass index (BMI), FFDD, driving fatigue, intention of changing job, social support in health behavior. Social support, health status, health perception, and health behavior were significantly correlated with one another. The multiple regression analysis showed that health perception (17.8%), BMI (6.8%), intention of changing job (5.7%), and driving fatigue (4.2%) explained the 34.5% variance of health behavior. And the 22.6% of variance of health perception was explained by social support (12.2%), health status (6.9%), and duty shift (3.2%). Conclusions: To promote the taxi-drivers' health, nursing intervention strategies unique for them should consider health behavior and affecting factors.

• 대한공업교육학회지
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• v.31 no.1
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• pp.63-85
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• 2006

This study was performed to deduce the constituents of competence for the practical duty in technical high school's heat treatment and tensile test practice. In order to accomplish this purpose 1) the constituents of competence for the practical duty were deduced through the job analysis and the skill hierarchy analysis of heat treatment and tensile test, 2) the deduced constituents of competence for the practical skill performance were correspond to the Mager's five performance type, that is, discrimination (knowing when to do it, knowing when it's done), problem solving (how to decide what to do it), recall (knowing what to do, knowing why to do it), manipulation (how to do it) and speech (how to say it). The results of this study will be helped to the selection of learning objective, learning content, instruction and evaluation method.

• Proceedings of the IEEK Conference
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• 1999.11a
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• pp.743-746
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• 1999

In this paper, Flyback type DC/DC Switching Converter was designed, analyzed and fabricated. Worst Case Analysis(WCA) was peformed with Mathcad program and presents circuit simulation results for the in-rush current limit circuit. The value of the maximum OFF voltage stress is 131.84V, it is less than device specification(200V). The switching frequency(nominal case) and duty cycle at the wont case analysis are 75KHz and 34.62%, respectively. The maximum in-rush current presents 0.5A Those results show a possibility for use in space