• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.7
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• pp.1001-1012
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• 1998

This paper reports the analysis of dynamic characteristics of air-cooled condenser. At first, there is an assumption that the superheated vapor flows into the condenser inlet. And in order to consider the effect of pressure change in the dynamic characteristics of the condenser the combined system of condenser and compressor was used. By using the equation of energy balance and the equation of mass balance, the basic equation for describing the dynamic characteristics of condenser can be derived. The transfer function for describing dynamic response of the condenser to flow rate change outlet can be obtained from using linearizations and Laplace transformations of the equation. From this transfer function, analytical investigation which affects the frequency responses of condenser has been made. Through this study, it became possible that the information about the dynamic characteristics of air-cooled condenser is offered. While the average heat transfer coefficient of the refrigerant side necessary for the theoretical calculation of the dynamic characteristics is given by calculation method for the tube length and pressure drop of air-cooled condenser.

• Transactions of Materials Processing
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• v.22 no.2
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• pp.67-73
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• 2013

The deformation characteristics and microstructure changes in a round copper pipe under biaxial compression was studied using a horizontal compression die. The change of material properties, punch load and deformation behavior were monitored using various compressive deformation rates in the range of 0.5mm/min.~450mm/min. The strains, either tensile or compressive, were estimated from Vickers microhardness test results. The punch load and deformation characteristics of the round copper pipes were found to change greatly at a deformation rate of about 200mm/min. The punch load decreased with increasing compressive deformation rate. The results of numerical simulations agreed well with what was expected from the final microstructure and the hardness profile estimated from the final deformation strains.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.34 no.5
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• pp.51-58
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• 2018

The purpose of this study was to analyze the effect of seasonal change in characteristics of hygiene activity on domestic hot water energy consumption. With 16 residents of 4 households, the data about frequency of hygiene activity and water temperature was collected from February to August, 2017. The results of collected data discovered that the frequency of hygiene activity was higher especially in summer, whereas the consumption of warm water they used was higher in winter. The seasonal change in characteristics of hygiene activity was analyzed to be changed and strongly influenced by outdoor temperature. The influence of characteristics of hygiene activity on hot water consumption was analyzed. There was 13% of difference between consumption that was calculated taking characteristics of hygiene activity into account and consumption that was not. Therefore, this study suggested hygiene activity schedule, hot water profile and hot water consumption pattern, which can be utilized for improving simulation as well.

• Korean Linguistics
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• v.77
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• pp.95-124
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• 2017

The purpose of this study is to examine aspects and causes of the change and disappearance in the Gangneung dialect vocabulary about costume. A typical example of linguistic factors that influence the change of costume vocabulary is competition with the standard language. However, costume as culture has a more powerful effect than linguistic factor. For example, the following factors lead to the disappearance: the disappearance of the referent, the inherent characteristics of the costume, the introduction of the new culture, and the change in values about costume.

• Journal of Fisheries and Marine Sciences Education
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• v.26 no.3
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• pp.611-626
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• 2014

Based on adolescents' perspectives, this study attempts to explore the distinguishing characteristics of teachers that influence students to positively change in areas such as psychological adaptation and development of their potential. Essays focusing on memories of twenty seven significant teachers written by eighteen adolescents in middle schools and high schools in Daegu, Korea in 2011 were used for analyzing the factors that have influenced them to positively change. Subsequently, five critical factors were identified: warmness and acceptance; encouragement and support; communication and understanding; respect and care; modeling and expectation. The adolescents perceived that those factors not only contributed to their psychological wellbeing but also enabled them to positively change and achieve more in life. Moreover, the educational implications focusing on teachers' productive function and healing power were discussed. The role of teachers in reinforcing and building the character students in order to facilitate their holistic development was dealt with. Finally, the reference for promotion of further studies of the research field was made.

• Journal of ILASS-Korea
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• v.27 no.1
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• pp.36-41
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• 2022

In this study, the combustion instability characteristics according to the change in the hydrogen ratio in the fuel in the single nozzle system of the hydrogen-natural gas mixed gas turbine for power generation was analyzed using a three-dimensional finite element analysis-based Helmholtz solver. This combustor shows the instability characteristics in which mode transition occurs from a mode having a low amplitude near 70 Hz to a mode having a high amplitude of 250 Hz or higher as the hydrogen fraction in the fuel increases. The current modeling results are found to reasonably predict the main characteristics of the change in measured instability frequency and growth rate with the change in fuel composition.

• Journal of Power System Engineering
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• v.17 no.2
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• pp.121-127
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• 2013

The air spring is used widely because of the easy change of spring constant, and, a superior vibration and shock insulation performance. Among the apparatus using the merits of that, the air spring connected an auxiliary chamber has been developed and used as a component of suspension system for an automobile and a railroad car. The purpose of this study is to suggest a design method reflecting heat transfer effect for an air spring system connected auxiliary chamber. In order to do so, this study investigates change of reaction force along with variations in heat transfer coefficient, and, analyzes an effectiveness of a heat transfer characteristics of an auxiliary chamber for external force attenuation characteristics and impedance characteristics of an air spring connected an auxiliary chamber.

• Journal of the Korean Society of Industry Convergence
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• v.13 no.2
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• pp.113-124
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• 2010

Since the 1970s the increased economy allowed population to concentrate on larger cities which facilitated the lack of apartment complex in the cities. In order to have the solution to the problem, apartment complex were expected to consider the efficiency of using its land. Therefore, The purpose of this study is to clarify the change of the Apartment Complex especially in the Forms and Compositions of outdoor planning of Apartment complex. As a result, the analysis of this researching process of them has shown us the following important characteristics in the change of the Apartment Complex.

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.8
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• pp.1225-1238
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• 2004

The present study has been performed for obtaining the melting heat transfer enhancement characteristics of water mixture slurries of plural microcapsules having different diameters encapsulated with solid-liquid phase change material(PCM) flowing in a pipe heated under a constant wall heat flux condition. In the turbulent flow region, the friction factor of the present PCM slurry was to be lower than that of only water flow due to the drag reducing effect of the PCM slurry. The heat transfer coefficient of the PCM slurry flow in the pipe was increased by both effects of latent heat involved in phase change process and microconvection around plural microcapsules with different diameters. The experimental results revealed that the average heat transfer coefficient of the PCM slurry flow was about 2～2.8 times greater than that of a single phase of water.

• Transactions of Materials Processing
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• v.19 no.4
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• pp.236-241
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• 2010

The frictional behavior of bare steel sheet highly depends on surface roughness. It was investigated that the change of surface roughness of bare steel sheet due to deformation for each forming mode. The flat type friction test was done to check the effect of surface roughness change on frictional characteristics of bare steel sheet. As increasing the deformation, the Ra value was increased at stretching forming mode and drawing forming mode, however the change of Pc showed different trends. The Pc was decreased as increasing stretch deformation but increased at compression deformation. At drawing forming mode, the friction coefficient was increased as deformation was increased after initial big drop with drawing oil. As deformation was increased, the friction coefficient was decreased with drawing oil at stretching forming mode. The results show that the deformation changes the surface roughness and frictional characteristics of steel sheet but the effect depends on the forming mode.