• Design & Manufacturing
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• v.13 no.2
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• pp.37-43
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• 2019

This study conducted a research as to condensation heat transfer friction loss headby using three types of flat micro multi-channel tubes with different processing of micro-fin and number of channels inside the pipes and different sizes of appearances. In addition, identical studies were conducted by using smoothing circular tubes with 5mm external diameter to study heat enhancement factor and pressure drop penalty factor. 1) The friction head loss showed an increase as the vapor quality and mass flux increased. In case of saturation temperature, it shows an increase as it gets lower. These factors are the reason occurring as the lower the saturation temperature is, the higher the density of refrigerant vapor gets. The influence of heat flux is similar as the dryness is low, but as it gets higher, it lowers in heat flux, and as the high temperature of high heat flux, it is a factor that occurs as the density gets lower. 2) RMS error of the in case of friction head loss, it showed to be predicted as 0.45~0.67 by Chisholm, Friedel, Lockhart and Martinelli. 3) As forfriction head loss penalty factor, the smaller the aspect ratio is, the larger the penalty factor gets, and as for the effect of micro-fin, the penalty factor increased because it decreases to the gas fluid the way groove for the refrigerant's flow.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.21 no.7
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• pp.417-423
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• 2009

Air curtains are widely used for gates of shopping mall, warehouse, cold stores and refrigerated display cabinets. The purpose of the air curtain is to reduce the infiltration of outdoor air and heat loss from the air conditioning space to ambient air. Design data for the air curtain given by previous researchers do not mention the influence of wind speed. Thus, this paper presents a performance of single jet air curtain in heating space when the wind blows toward the opening space of the building. A numerical simulation is used to study the influence of various parameters on the efficiency of the downward-blowing air curtain device which is installed inside of the wall above the door. The performance of the air curtain is evaluated by sealing efficiency which provides the assessment of the energy savings. A new safety factor is also proposed for determination of air curtain jet velocity under the various wind conditions.

• Journal of Distribution Science
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• v.22 no.5
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• pp.117-129
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• 2024

Purpose: This research aims to explore the ramifications of job stress on cabin crews within the air service distribution sector, specifically examining its impact on service quality through mediating variables such as job satisfaction and engagement during the pandemic era. Research design, data and methodology: The study is based on a sample size of 312 individuals, exclusively comprising cabin crews employed in the airline industry. Methodologically, Confirmatory Factor Analysis (CFA) and Structural Equation Modeling (SEM) were employed for statistical analysis. Results: The findings reveal that both performance evaluation and job responsibility exerted a significant impact on both job satisfaction and job engagement. Furthermore, job engagement demonstrated a substantial influence on service quality. However, in contrast, factors like unstable employment and the working environment showed no significant impact on either job satisfaction or engagement. Additionally, job satisfaction did not exert a significant influence on service quality. Conclusions: These insights will offer the valuable guidance to the airline industry in preparing for unforeseen external environments that may affect the industry. As the aviation sector navigates the challenges posed by the pandemic, understanding and addressing the intricate relationships among job stress, satisfaction, engagement, and service quality will be crucial for effective industry resilience and adaptation.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.19 no.4
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• pp.29-40
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• 2024

This study analyzed the impact of venture companies' innovation capabilities on business performance by growth stage. Innovation capability, which is an independent variable, is composed of entrepreneur characteristics, technology development capabilities, marketing capabilities, and external cooperation. And the dependent variables were set as sales and long-term growth prospects. This study utilized data from the '2022 Precise Survey on Venture Companies'and conducted descriptive statistics analysis, correlation analysis, and multiple regression analysis as research methodology. As a result of the analysis, the negative influence of the educational background of entrepreneurs' characteristics was found to decrease as the growth stage increased, and the long-term growth prospects of entrepreneurs with abundant industrial practical experience were perceived positively. Research and development personnel was a negative factor during the start-up period, but as the growth stage increased and technology accumulation occurred, it changed into a positive factor. Marketing competency level was found to be an important factor in all growth stages. For external collaboration activities, all hypotheses regarding sales were rejected, but hypotheses regarding the start-up and growth periods regarding long-term growth prospects were accepted. it is interpreted that external collaboration activities are necessary to overcome the limitations of internal resources.

• International Journal of Precision Engineering and Manufacturing
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• v.8 no.1
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• pp.46-51
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• 2007

Environmental contamination creates shortages of potable water. In such situations, the leakage of water due to breakage or aging of rubber valve seats is a serious problem. Rubber is apt to break when it is placed between two materials that contact each other. One way to avoid water leakage due to rubber damage and breakdown is to replace the rubber with metal, which is currently taking place in water distribution systems. In tribology, a severe form of wear is characterized by local macroscopic material transfer or removal, or by problems with sliding protrusions when two solid surfaces experience relative sliding under load. One of the major problems when metal slides is the occurrence of galling. Experimentally, various conditions influence incipient galling, such as hardness, surface roughness, temperature, load, velocity, and the external environment. This study sought to verify the galling tendencies of metal according to its hardness, surface roughness, load, and sliding velocity, and determine the quantitative effect of each factor on the galling tendencies.

• Proceedings of the Korean Reliability Society Conference
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• 2011.06a
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• pp.281-288
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• 2011

Hydraulic hose assemblies deliver a fluid power in various oil pressure equipments such as construction machinery, automobile, aircraft, industrial machinery, machine tools, and machinery for ships, or they are used as pipes in oil pressure circuit. However, as the traditional measure for estimating life under the influence of various external factors incurs hardship in terms of time and expenses, it is essential to take accelerated life test by choosing the factor that suits the usage condition of the test object. The objective of the this study is to propose a acceleration model that takes both temperature and pressure without flexing condition into consideration. The life that is calculated by the equation for evaluating life and the test data show similar slopes as a result of comparing and analyzing the equation for evaluating life that is obtained in this research and the test data, which illustrates that they estimate life similarly, and the proposed equation is proved to be an accelerated life equation that presents the test results.

• Journal of Korea Society of Digital Industry and Information Management
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• v.7 no.1
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• pp.127-141
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• 2011

This paper provides a method to evaluate the competitiveness based on IT innovativeness considering the adoption phase and shows how to apply the method with a case of foreign market in the early-adoptive phase. The proposed method considers a variety of corporate and market characteristics concerned with the technology adoption, and it consists of several internal and external impacting factors that can influence the level of IT diffusion. Main advantage of this method is the ease of its applicability that allows evaluating the innovativeness, regardless of corporate size, industry type, or level of technology adoption. Therefore, it is possible for this method to evaluate the technology competitiveness easily and repeatedly, in terms of IT innovativeness by inter-organizations and inter-nations. For the case analysis, the Mongolian IT market with several Korean IT joint firms is introduced, and final data resulted from an early-adoptive phase case are analyzed.

• Proceedings of the Korea Database Society Conference
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• 2002.10a
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• pp.3-21
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• 2002

The purpose of this study is to demonstrate individual's mobile Internet acceptance by extending the technology acceptance model (TAM) to the field of the mobile Internet. This research utilized the structural equation model to examine the research model on the mobile Internet use. System quality and information quality as external variables were examined, and playfulness as an intrinsic factor was tested. The research model was successfully validated in the environment of extension model for the mobile internet.

• Journal of the Korea Society of Computer and Information
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• v.23 no.12
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• pp.195-201
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• 2018

This study is attempted to demonstrate the structure of the influencing factors on the performance of services of knowledge based service firms. In the model presented, the structure is that service performance in knowledge-based services are affected by the strategic utilization of knowledge resources and service orientation factors of the service organization. And the service performance are also affected in which the systemization of service processes and customer satisfaction play a mediating role. As an analysis result of examining 148 practitioners engaged in the knowledge service industry, it is necessary to increase the satisfaction of external customers in order to improve service performance in a knowledge-based service organizations. This can be achieved by increasing the satisfaction of internal customers. In addition, for this structure to be successful, the service production process to be provided to the customer must be enhanced. The service production process has been found to be an important factor influencing the internal customer satisfaction and service delivery process, especially in the use of knowledge resource, and customer oriented service among service orientation factors.

• Kyungpook Mathematical Journal
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• v.60 no.4
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• pp.853-867
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• 2020

The aim of this study was to analyze the momentum and heat transfer of a rotating nanofluid with conducting spherical dust particles. The fluid flows over a stretching surface under the influence of an external magnetic field. By applying similarity transformations, the governing partial differential equations were trans-formed into nonlinear coupled ordinary differential equations. These equations were solved with the built-in function bvp4c in MATLAB. Moreover, the effects of the rotation parameter ω, magnetic field parameter M, mass concentration of the dust particles α, and volume fraction of the nano particles 𝜙, on the velocity and temperature profiles of the fluid and dust particles were considered. The results agree well with those in published papers. According to the result the hikes in the rotation parameter ω decrease the local Nusselt number, and the increasing volume fraction of the nano particles 𝜙 increases the local Nusselt number. Moreover the friction factor along the x and y axes increases with increasing volume fraction of the nano particles 𝜙.