• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.5
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• pp.711-718
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• 1999

Some of modern communication systems make use of broadband digital modulation with 5 MHz and 10 MHz. In the broadband communication systems, the nonlinear properties of power amplifier have a great effect on all systems. This paper analyzed the ACPR characteristics of WLL reverse link power amplifier with the varying AM and PM nonlinearities and suggests the required backoff from 1 dB compression point to satisfy the ACPR specifications. Also the comparions between the measured and the simulated characteristics are presrnted.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.497-502
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• 2005

In mobile phones of multimedia era, microspeakers of high quality sound are essential parts to generate human voice in speaker phone and MP3 song player. In this paper, two types of microspeakers, outer permanent magnet (PM) and combined PM type, are analyzed using electromagnetic, mechanical, acoustical and their coupling analysis. For performance comparison, voice coil diameter is chosen as a design parameter to change excitation position and magnet volume for both types. For combined PM type, sound pressure level (SPL) is improved due to increased PM volume compared to outer PM type. Also, with the decreased voice coil diameter for combined PM type, the 1st resonant mode of the diaphragm is more efficiently excited due to concentrative excitation, resulting in lower and broader frequency range. Therefore, it can be said that the combined PM type microspeakers are more advantageous for high performance microspeaker which are essential for multimedia era.

• The Journal of the Acoustical Society of Korea
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• v.38 no.2
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• pp.145-153
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• 2019

Adaptive beamforming methods are known to suppress sidelobes and improve detection performance of weak signal by constructing weight vectors depending on the received signal itself. A standard adaptive beamforming like the MVDR (Minimum Variance Distortionless Response) is very sensitive to mismatches between weight vectors and actual signal steering vectors. Also, a large computational complexity for estimating a stable covariance matrix is required when wideband beamforming for a large-scale array is used. In this paper, we exploit the WBRCB (Wideband Robust Capon Beamforming) method for stable and robust wideband adaptive beamforming of a passive large uniform line array sonar. To improve robustness of adaptive beamforming performance in the presence of mismatches, we extract a optimum mismatch parameter. WBRCB with extracted mismatch parameter shows performance improvement in beamforming using synthetic and experimental passive sonar signals.

• The Korean Journal of Coaching Psychology
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• v.7 no.3
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• pp.27-55
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• 2023

Employee well-being, along with its associated barriers and improvement strategies, has become an escalating concern for researchers and organizations worldwide. This study examined the mechanism behind workplace bullying and depression, exploring the role of psychological safety as a mediating factor. Additionally, we investigated the potential impact of organizational compassion, distinguishing between supervisor and co-worker compassion, as a means of supporting employees subjected to workplace bullying. Based on an analysis of 392 online survey responses from full-time employees in South Korea, our findings demonstrate that workplace bullying undermines psychological safety, resulting in increased depression rates among employees. As anticipated, supervisor compassion mitigated the adverse effect of workplace bullying, whereas co-worker compassion did not exhibit the same moderating effect. These results emphasize the importance of fostering a supportive and compassionate work environment led by supervisors to lessen the strain on employee well-being. Theoretical and practical implications, along with directions for future research, are discussed.