• Journal of Energy Engineering
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• v.8 no.2
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• pp.333-340
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• 1999

A numerical study of turbulent condensing vapor jet submerged in subcooled liquids has been conducted. A physical model of the process is presented employing the locally homogeneous flow approximation of two phase flow in conjunction with a $\kappa$-$\varepsilon$-g model of turbulence properties. In this model the turbulence is represented by differential equations for its kinetic energy and dissipation. A differential equation for the concentration fluctuations is solved and a clipped normal probability distribution function is proposed for the mixture fraction. Effects of steam mass flux, pool temperature and nozzle internal diameter on the condensing vapor jet are also analyzed. The model is evaluated using existing data for turbulent condensing vapor jets. The agreement between the predictions and the available experimental data is good.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.24 no.2
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• pp.31-46
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• 2016

The purpose of this study is to examine the effects of human touch on turnover intention of ground handling employees at airport. Additionally, this study examines a comprehensive mediating effect of the work schedule and workload between human touch and turnover intention. To examine them, over 700 ground handling employees from six international airports of South Korea were surveyed using the simple random sampling method. The instrument for data collection was a questionnaire, and it was developed based on previous research results. The methodology adopted in this study is the structural equation modeling (SEM). According to SEM analysis, it was proven that both psychological and physical human touch have a significant effect on turnover intention of the employees. Work schedule played a mediating role among all three factors of human touch and turnover intention. However, workload has a mediating effect only between communication human touch and turnover intention. Based on the above findings, theoretical and practical implications are also discussed.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.20 no.4
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• pp.91-105
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• 2012

This study, the cause of an aviation security employees' job satisfaction and dissatisfaction will be understood and the data can be used as evidence to explain the position of the employees. Moreover, the results of this study shall be conducted to increase the level of service delivery and also to remove unsatisfactory factors. Thus, according to this research survey shows the understanding of the job satisfaction and service delivery influences on the overall job satisfaction of a secure enterprise's security screeners. As a results, by improving the job satisfaction of aviation security screeners, the world's most safe, convenient service and quick airport service delivery could be achieved. Therefore, in order to improve the level of Korea and the international competitiveness of airlines, the promotion of job satisfaction of employees would be very important. Moreover based on the results of this study, the advanced research on the recognition differences for service evaluation between the customers and security screeners are needed.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.22 no.1
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• pp.85-94
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• 2014

Incheon international airport has been successful, that is, the winner of Airport Service Quality (ASQ) evaluation performed by ACI(Airport Council International) for nine consecutive years. It goes without saying that such an outstanding performance was made not only by airport authority itself but by the collaboration among subcontractors at Incheon international airport. Since Incheon airport is showing more than 80% of outsourcing rate, it is important to mention and study the roles and functions of subcontractors who has made a major contribution to ASQ performance. According to empirical research in this paper, it was found out service attitude, communication skill and interdependence between airport authority and subcontractors were important factors affecting the ASQ score. It is also analyzed that those independent factors have an impact on ASQ performance through the intermediate factor of trust. As a result, service attitude and interdependence between airport authority and subcontractors have statistically a significant effect to the relational satisfaction and ASQ performance. It could be concluded that trust is significant factor determining the causal relationship among service attitude, communication skill, relational satisfaction and ASQ score.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.28 no.3
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• pp.61-73
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• 2020

This study is an empirical analysis of the cultural competencies of college students majoring in aviation services on their major satisfaction and professionalism. In order to focus on the cultural competencies of aviation service college students, who are rarely addressed in the preceding study and to see how cultural competencies have significant effects on their major satisfaction and professionalism, we divid them into six sub factors: willingness to participate, cognitive openness/flexibility, emotional control, patience with uncertainty, self-efficacy, and cultural empathy. And the mediated effects of major satisfaction on cultural competency and professionalism are analyzed to provide educational implications for cultural competency. Based on the results of this study, it is expected to apply to the education of aviation service-related departments, it will be a basic data to promote students' adaptation to the department and satisfaction of the department and to train global professional service personnel who can improve their post-employment work adaptability, job satisfaction, and service productivity.

• Progress in Superconductivity
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• v.11 no.1
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• pp.78-82
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• 2009

We have fabricated a helmet type magnetoencephalogrphy(MEG) with a $1^{st}$ order gradiometer in vacuum to improve the signal-to-noise ratio(SNR) and the boil-off rate of liquid helium(LHe). The axial type first-order gradiometer was fabricated with a double relaxation oscillation SQUID(DROS) sensor which was directly connected with a pickup coil. The neck space of LHe dewar was made to be smaller than that of a conventional dewar, but the LHe boil-off ratio appeared to increase. To reduce the temperature of low Tc SQUID sensor and pickup coil to 9 K, a metal shield made of, such as copper, brass or aluminum, have been usually used for thermal transmission. But the metal shield exhibited high thermal noise and eddy current fluctuation. We quantified the thermal noise and the eddy current fluctuation of metal. In this experiment, we used the bobbin which was made of an alumina to wind Nb superconductive wire for pickup coil and the average noise of coil-in-vacuum type MEG system was $3.5fT/Hz^{1/2}$. Finally, we measured the auditory evoked signal to prove the reliability of coil-in-vacuum type MEG system.

• Progress in Superconductivity
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• v.11 no.1
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• pp.30-35
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• 2009

We have investigated the characteristics of a superconductive Pb shield for hemispherical shape and plate to improving signal-to-noise ratio(SNR) of biomagnetism. We measured the shielding factor for the position of helmet shape Pb and for changing the distance from Pb surface. To make a uniform magnetic field, a $1.5m{\times}1.5m$ set of the helmholtz coils activated at several frequencies. The shielding factor of hemispherical shape Pb was from 20 to 57 dB and of Pb plate was about $6{\sim}26dB$ as a function of distance from the lead surface. The shielding factor was rapidly reduced as increasing the distance from Pb surface. The white noise of superconductive quantum interference device(SQUID) with a superconductive shield was about $12fT/Hz^{1/2}$ at 1 Hz, $7fT/Hz^{1/2}$ at 100 Hz. The white noise was more increased about two times than conventional SQUID system without Pb shielding. An auditory signal was measured by first order gradiometer and magnetometer with Pb superconductive shield and compared the SNR. The SQUID system with Pb shield had better performance at low frequency noise level.

• Archives of Plastic Surgery
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• v.36 no.3
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• pp.344-347
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• 2009

Purpose: Malignant soft tissue tumors, known as sarcomas, are well known to be locally aggressive, frequently metastatic, and highly recurrent. In other hands, intermediate soft tissue tumors often recur locally with adjacent tissue infiltration so the clinical management is difficult as sarcoma. In the present study, we evaluate the clinical course of the intermediate soft tissue tumors and consider the management plan for those. Methods: From March, 1998 to April 2008, total 3 patients of intermediate soft tissue tumors underwent operations. A patient with fibrohistiocytic neoplasm, a free flap reconstruction was performed, and he underwent several more operations because of recurrences. Other patients with desmoids - type fibromatosis showed local invasion and adhesion, and one of them underwent reoperation due to local recurrence. Results: 2 of 3 patients underwent recurrences of tumors and reoperations were performed. In another patient with no recurrence, follow-up period was just 5 months, so there may be recurrence of tumor in long term follow-up. Conclusion: The clinical course of intermediate soft tissue tumors shows high recurrence rate. So clinically, intermediate soft tissue tumors should be considered as sarcomas. The successful management requires wide resection, carefully planned reconstruction, and close follow up with radiologic evaluation.

• Progress in Superconductivity
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• v.5 no.1
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• pp.31-37
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• 2003

Wide-bandwidth SQUID current amplifier and its control electronics have been constructed for detecting pulse outputs of a superconducting microcalorimeter. The current amplifier made of a double relaxation oscillation SQUID (DROS) has a bandwidth of 1.2 MHz and typical white noise level of about 6 pA/(equation omitted) Hz. To increase the dynamic range of the current amplifier, the flux-locked loop (FLL) has additional circuits to reset the integrator and to count reset numbers which present the number of passed flux quanta. In this system, dynamic range covers from -65 mA to +65 mA. SQUID electronics are controlled by software to get the optimum FLL condition, and to control the current to bias the transition edge sensor (TES). The electronics are shielded from the outside electromagnetic noises by using an aluminum case of 66 mm ${\times}$ 25 mm ${\times}$ 100 mm, and consist of 2 separate printed-circuit-boards for the current amplifier and the control electronics, respectively. The SQUID current amplifier and its control electronics will be used in TESs for detecting photons such as UV and X-ray with high energy resolution.

• Progress in Superconductivity
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• v.5 no.1
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• pp.38-44
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• 2003

The aim of this study is to confirm clinical usefulness of magnetocardiogram (MCG) by analyzing MCG data of health subjects and patients with Wolff-Parkinson-White (WPW) syndrome and dilated cardiomyopathy (DCM). Measurement of MCG signals was done with a home-made 40-channel SQUID system. MCG signals of 30 healthy subjects were measured as the reference of MCG signals. Among the DCM patients, 7 patients showed abnormal the direction of T wave vector. For a WPW syndrome patient, we measured the MCG signals before and after the surgery. and compared the difference. From the measured magnetic field distribution, current vector map was obtained to show the myocardium current activity. By comparing the MCG signals and current maps, we showed the differences in the analysis results between the healthy subjects and patients with heart diseases.