• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.6
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• pp.1120-1125
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• 2010

In the speech system, for example hearing aid as well as speech communication, speech quality is degraded by environmental noise. In this study, to enhance the speech quality which is degraded by environmental speech, we proposed an algorithm to reduce the noise and reinforce the speech. The minima controlled recursive averaging (MCRA) algorithm is used to estimate the noise spectrum and spectral weighting factor is used to reduce the noise. And partial masking effect which is one of the human hearing properties is introduced to reinforce the speech. Then we compared the waveform, spectrogram, Perceptual Evaluation of Speech Quality (PESQ) and segmental Signal to Noise Ratio (segSNR) between original speech, noisy speech, noise reduced speech and enhanced speech by proposed method. As a result, enhanced speech by proposed method is reinforced in high frequency which is degraded by noise, and PESQ, segSNR is enhanced. It means that the speech quality is enhanced.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.13 no.4
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• pp.11-28
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• 2005

The research purpose of A Study on the Effect of Aviation Safety over the Air Passenger's Behavior for enhancement of aviation safety management lies at the judgement that passenger's airlines choice criteria has much changed after several serious aviation accidents as before when we used to overlook "aviation safety" variable through surveying to Korean aviation passengers and foreigners visit or travel Korea on various purposes. This study will be regarded significant in terms that empirical analysis was used to prove "Aviation Safety", a variable which had not been regarded as a airline choice factor within Korea air transport market so far, and has an effect on the air passengers' airline preference change and choice after recent frequent aviation accidents. I wish, it can be another opportunity for Korean two national flag airlines to reappraise and reinforce the significance of "aviation safety" and set forth immediate vigorous efforts to support the government's aviation safety improvement countermeasures.

• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.3
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• pp.98-104
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• 2013

The effect of the tool-sheet interaction on formability enhancement in electromagnetic forming is investigated using FEM. A free bulging and a conical forming die with 0.7mm AL1050 sheet are used to evaluate damage evolution based on Gurson-Tvergaard-Needleman plasticity material model. The impact between the tool and sheet results in complex stress states including compressive hydrostatic stresses, which leads to a suppression of void growth and restrain ascending void volume fraction of the sheet. Therefore, the damage suppression due to the tool-sheet interaction can be the main factor contributing to the increased formability in the electromagnetic forming process.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.54 no.2
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• pp.51-60
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• 2005

In this paper, we design the GA-fuzzy precompensator of a Power System Stabilizer for Thyristor Controlled Series Capacitor(TCSC-PSS) for enhancement of power system stability. Here a fuzzy precompensator is designed as a fuzzy logic-based precompensation approach for TCSC-PSS. This scheme is easily implemented by adding a fuzzy precompensator to an existing TCSC-PSS. And we optimize the fuzzy precompensator with a genetic algorithm for complements the demerit such as the difficulty of the component selection of fuzzy controller, namely, scaling factor, membership function and control rules. Nonlinear simulation results show that the proposed control technique is superior to conventional TCSC-PSS in dynamic responses over the wide range of operating conditions and in convinced robust and reliable in view of structure.

• KSBB Journal
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• v.13 no.1
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• pp.26-30
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• 1998

The suspension cultures of Mentha piperita produce menthol which has very low solubility in water due to its hydrophobicity. This can be considered as a factor for its low production in the suspension suspension cultures. Cyclodextrin has the hydrophobic cavity inside the molecule in which menthol can be captured and allow to form a stable complex. The suspension culture of Mentha piperita showed 70% higher production enhancement in the medium containing 1.5%(w/v) $\beta$-cyclodextrin than the control. $\beta$-cyclodextrin had no adverse effect on the cell growth and showed the best result among $\alpha$-, $\beta$- and $\gamma$-cyclodextrins tested in terms of menthol production. We demonstrated that $\beta$-cyclodextrin can be used to enhance the production of menthol in the suspension cultures by capturing hydrophobic menthol into the cavity of cyclodextrin molecules.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.55 no.6
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• pp.236-241
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• 2006

This paper presents a transfer capability enhancement process using VSC HVDC system which can control active power as well as reactive power. The transfer capability is constrained by stability like voltage stability as well as thermal rating of power system components. Transfer capability of the power system limited by these constraints may be enhanced by reactive power control ability and active power flow control ability of the VSC HVDC system. To enhance the transfer capability of the system using VSC HVDC, selection of the HVDC installation site is performed. In this work, power zones which consist of major power plants and their sinks are identified using power tracing and distribution factor. Alternative route of major AC transmission line in the power zone is identified as VSC HVDC system.

• Current Optics and Photonics
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• v.1 no.6
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• pp.626-630
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• 2017

GaN-based green light-emitting diode (LED) structures suffer from low internal quantum efficiency (IQE), known as the "green gap" problem. The IQE of LED structures is expected to be improved to some extent by exploiting the Purcell effect. In this study, the Purcell effect on the IQE of green LED structures is investigated numerically using a finite-difference time-domain simulation. The Purcell factor of flip-chip LED structures is found to be more than three times as high as that of epi-up LED structures, which is attributed to the high-reflectance mirror near the active region in the flip-chip LED structures. When the unmodified IQE is 20%, the relative enhancement of IQE can be greater than 50%, without utilizing the surface-plasmon coupling effect. Based on the simulation results, the "green gap" problem of GaN-based green LEDs is expected to be mitigated significantly by optimizing flip-chip LED structures to maximize the Purcell effect.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.51 no.2
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• pp.83-92
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• 2002

In this paper, we design a GA-fuzzy precompensator for enhancement of power system stability. Here, a fuzzy prerompensator is designed as a fuzzy logic-based precompensation approach for Power System Stabilizer(PSS). This scheme is easily implemented simply by adding a fuzzy precompensator to an existing PSS. And we optimize the fuzzy precompensator with a genetic algorithm for complements the demerit such as the difficulty of the component selection of fuzzy controller, namely, scaling factor, membership function and control rules. Simulation results show that the proposed control technique is superior to a conventional PSS in dynamic responses over the wide range of operating conditions and is convinced robustness and reliableness in view of structure.

• Proceedings of the KIEE Conference
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• 2001.07a
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• pp.137-139
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• 2001

In this paper, we design a GA-fuzzy precompensator for enhancement of power system stability. Here, a fuzzy precompensator is designed as a fuzzy logic-based precompensation approach for Power System Stabilizer(PSS). This scheme is easily implemented simply by adding a fuzzy precompensator to an existing PSS. And we optimize the fuzzy precompensator with a genetic algorithm for complements the demerit such as the difficulty of the component selection of fuzzy controller, name1y, scaling factor, membership function and control rules. Simulation results show that the proposed control technique is superior to a conventional PSS in dynamic responses over the wide range of operating conditions and is convinced robustness and reliableness in view of structure.

• Proceedings of the Korean Nuclear Society Conference
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• 1995.05a
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• pp.937-942
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• 1995

Great interest has prompted Boron Neutron Capture Therapy (BNCT) as a new treatment for brain tumors. The use of $^{252}$Cf as a neutron source for BNn makes the in-hospital treatments of tumors to be possible. Newly proposed subcritical multiplying assemblies (SMA) are explored to improve relatively tow neutron fluxes of the source and construct the feasibilities of $^{252}$Cf as a neutron source. The MCNP code has been used to evaluate the effective multiplication factor of the entire system and the intensities and percentages of epithermal neutron flux at the patient-end surface of the system. The neutron beam using SMA shows the epithermal neutron flux enhancement of about 13 times as large as the beam without using SMA. It is expected that the neutron beam proposed in this research will be more effective for treatment of tumors due to the increased therapeutic neutron fluxes.