• The Journal of the Acoustical Society of Korea
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• v.28 no.1E
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• pp.9-15
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• 2009

In this paper, FSTL (Field Sound Transmission Loss) measured in a mock-up simulating ship cabins is studied. A mock-up is built by using 6 mm steel plate, and two identical cabins are made where 25 mm or 50 mm sandwich panel is used to construct wall and ceiling inside the steel structure. Various wall panels and ceilings are tested, where effects of wall and ceiling panel thickness, and presence of a unit toilet on FSTL are investigated. It is found that the effect of unit toilet on FSTL is at most 1 dB. From the comparison of FSTL for panels of the same thickness of 50 mm, it is observed that panel having inside air cavity of 10 mm shows higher STL than that of the panel without air cavity. Comparison of FSTL for panels of 50 mm and 25 mm thickness shows that dependency on surface density predicted by mass law is not observed. The sandwich panels act as a mass-spring system, which shows a resonant mode that cannot be explained by the mass law. It is also found that STL from laboratory test is higher than FSTL by 5- 10 dB, which can be explained by flanking structure-borne noise transmission path such as ceiling, floor and corridor-facing wall.

• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.5
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• pp.410-420
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• 2015

This paper provides a comparison of power converter loss and thermal description for voltage source and current source type 5 MW-class medium-voltage topologies of wind turbines. Neutral-point clamped three-level converter is adopted for a voltage source type topology, whereas a two-level converter is employed for current source type topology, considering the popularity in the industry. To match the required voltage level of 4160 V with the same switching device of IGCT as in the voltage source converter, two active switches are connected in series for the case of current source converter. Transient thermal modeling of a four-layer Foster network for heat transfer is done to better estimate the transient junction and case temperature of power semiconductors during various operating conditions in wind turbines. The loss analysis is confirmed through PLECS simulations. Comparison result shows that the VSC-based wind turbine system has higher efficiency than the CSC under the rated operating conditions.

• Journal of the Korea Society of Computer and Information
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• v.27 no.7
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• pp.65-73
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• 2022

Recently, as the Windows system supports the Windows subsystem for Linux (WSL), various researchers have studied to apply a docker container on various systems such as server systems, workstation system and so on. However, in various existing researchers, there is a lack of performance-related indicators to apply the system to each operating system (linux system and windows system). In this paper, we compared a performance comparison and analysis of container-based host operating systems. We configured experimental environments of operating systems for microsoft windows systems and linux systems based on a docker container support. In experimental results, the containers of linux systems reduced the average data latency of dataset 1-6 by 3.9%, 62.16%, 1552.38%, 7.27%, 60.83%, and 1567.2%, compared to the containers on microsoft windows systems.

• Journal of Ocean Engineering and Technology
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• v.36 no.1
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• pp.1-10
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• 2022

Recently, as the offshore structures are operated in the deep-sea oil fields, interest in the analysis of relative wave elevation around platforms is increased. In this study, it is examined how the analysis results differ depending on the characteristics of the wave probe when interpreting the relative wave elevation in the model test. First, by conducting the wave probe comparison experiment in the two-dimensional wave tank, it is confirmed how the measured values differ according to the type of wave probe for the same physical phenomenon. Two types of wave probe are selected, the resistance type and the capacitance type, and the causes of the difference in measured values is studied. After that, the model test of the semi-submersible platform is conducted to investigate the relative wave elevation. Relative wave elevation is measured with the wave probes used in the wave probe comparison experiment and analyzed to estimate the asymmetric factor and the extreme upwell. The results between the two types of wave probes are compared, and qualitative study for the cause of the difference is conducted by photographing the physical phenomenon using a high-speed camera. Through the above study, it is confirmed that the capacitance type wave probe shows a larger measured value than the resistance type under the breaking-wave condition, and the same results are obtained for the asymmetric factor and the extreme upwell. These results is thought to be due to the difference in the measurement principle between wave probes, which is whether or not they measured water bubbles. This implies that the model test should be conducted using appropriate wave probes by considering the physical phenomenon to be analyzed.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.6 s.97
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• pp.549-555
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• 2005

This paper describes a microwave direction finding technology which is used for RF signal acquisition and monitoring systems. This paper suggests a direction finding method which use a combination of the amplitude-comparison technology and the phase-comparison technology. The amplitude-comparison technology uses the amplitude difference of the RF signals received from the array antennas of direction finding system and removes the ambiguity of wave incident bearing. The phase-comparison technology uses the phase difference of the RF signals received from the same nay antennas and makes a good direction finding accuracy. The suggested direction finding technology is designed to place 8 array antennas in a $45^{\circ}$ distance around the circle for $360^{\circ}$ azimuth angle. Also it is designed to use the phase difference of the received signals ken two nearby antennas to measure the signal incident direction accurately and to use the amplitude difference to remove the ambiguity of wave incident bearing. The simulation and measurement results are under $0.5^{\circ}$ bearing error in $2.0\~6.0$ GHz when SNR is 30 dB.

• 한국초전도학회:학술대회논문집
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• 2008.08a
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• pp.54-54
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• 2008

• Proceedings of the Korean Nuclear Society Conference
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• 2005.10a
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• pp.824-825
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• 2005

• Journal of the Korean Society for information Management
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• v.17 no.2
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• pp.37-66
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• 2000

This study attempts to reorganize the knowledge classification system for the research fields and majors in education by designing a new classification schedule. Content analysis of the majors and curriculums in the universities and major areas of the academic professors in Korea, and the comparison with the various headings in several classification systems for research fields were carried out. Based upon the comparison with library classification systems and reviews and opinions of subject specialists in major disciplines, finally, a knowledge classification system composed of three parts - schedules, tables and a relative index - was presented. The proposed classification scheme was tested for classifying the research projects listed in the 1998 catalog of the academic research funded by Korea Research Foundation. Also, several ways for developing a more useful knowledge classification scheme to organize disciplinary information effectively and to encourage interdisciplinary research were suggested.

• Journal of the Korean Society for Nondestructive Testing
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• v.36 no.2
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• pp.130-137
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• 2016

Non-destructive testing methods for composite materials (e.g., carbon fiber-reinforced and glass fiber-reinforced plastic) have been widely used to detect damage in the overall industry. This study detects defects using optical infrared thermography. The transient heat transport in a solid body is characterized by two dynamic quantities, namely, thermal diffusivity and thermal effusivity. The first quantity describes the speed with thermal energy diffuses through a material, whereas the second one represents a type of thermal inertia. The defect detection rate is increased by utilizing a lock-in method and performing a comparison of the defect detection rates. The comparison is conducted by dividing the irradiation method into reflection and transmission methods and the irradiation time into 50 mHz and 100 mHz. The experimental results show that detecting defects at 50 mHz is easy using the transmission method. This result implies that low-frequency thermal waves penetrate a material deeper than the high-frequency waves.

• Journal of Labour Economics
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• v.20 no.2
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• pp.301-331
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• 1997