• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.21 no.4
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• pp.75-80
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• 2021

This paper relates with the Hybrid-DSE-MMA (Hybrid-Dithered Signed Error-MMA) that is possible to improving the equalization performance by using the adaptive modulus and adaptive stepsize in DSE-MMA adaptive equalizer. The DSE-MMA possible to improve the robustness performance to external noise of SE-MMA by using the sign after adding the dither signal for get the error signal in order to update the tap coefficient. But it has a drawback of performance degradation in convergence speed and residual isi by using the fixed modulus and fixed stepsize. In this paper, it was confirmed that this equalization performance degradation was improved by applying the adaptive modulus and stepsize in DSE-MMA propotional to the output power of equalizer by computer simulation. In order to compare the improved equalization performance to currently DSE-MMA, the recovered signal constellation that is the output of the equalizer, residual isi, Maximum Distortion, MSE and the SER were used as a performance index. As a result of computer simulation, the Hybrid-DSE-MMA improve the equalization performance in every index, but gives slower convergence speed compared to DSE-MMA.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.260-263
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• 2008

공항에 인접한 주거지역에서 항공기 소음문제로 인하여 거주자들에게 소음피해가 발생하고 있다. 이러한 항공기소음을 저감하기 위한 방법 중 건물외피를 차음성능이 높은 구조로 변경하여 건축물의 차음량을 개선시키는 수음원 대책이 일반적으로 사용되고 있다. 특히 건축물 방음시설 설치는 건물외피 중 외부소음에 가장 취약한 창호의 차음량을 증가시키는 것이 효과적인데, 본 연구에서는 기존 창호에 비하여 차음성능이 높은 창호를 교체 설치하여 건축물의 차음량 개선치를 $L_{max}$, SEL, $L_{eq}$로 각각 검토 비교함과 동시에 창호의 기밀성능을 위한 기밀재 및 추가 모헤어의 설치조건에 따른 차음성능을 검토해 보았다. 측정결과 방음시설 설치 후 항공기소음을 $L_{max}$, SEL, $L_{eq}$로 차음량 개선치를 각각 평가한 결과 1.8dB 이내의 편차를 갖는 것으로 나타났으며, 창의 차음성능 개선치는 기밀재 설치 후 $R'45^{\circ}$,w가 5dB, 기밀재 및 추가 모헤어 설치 후 8dB로 나타났다.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.40 no.4
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• pp.304-310
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• 2004

Resistance performance of small size fishing vessel is experimentally investigated to find out the effect of fore-body shape and trim for the better hull from development. The tests are performed for five different cases in the high speed circulating water channel(CWC). Wave patterns are observed to investigate the relation between the resistance performance and the wave characteristics.

• Proceedings of the Materials Research Society of Korea Conference
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• 2010.05a
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• pp.17.1-17.1
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• 2010

2000년대 들어 소재기술의 진보와 함께 혁신적인 성능개선이 이뤄지고 있는 유기박막 태양전지는 가장 신형의 3세대 태양전지로서, 유기 재료의 손쉬운 가공성과 다양성, 낮은 재료비, 그리고 프린팅, 코팅 공정과 같은 값싼 소자 제작공정으로 인해 차세대 저가 태양전지로서 큰 기대를 모으고 있다. 현재 유기박막 태양전지는 단위소자 기준으로 7%대의 광전변환 효율을 달성하고 있는데, 다양한 반도체성 고분자나 단분자 도너 물질에 특히 전자 수용성이 좋은 fullerene(C60)계 억셉터 물질을 채택함으로써 급격히 성능 개선이 이뤄지고 있다. 그러나 상용화를 위해서는 궁극적으로 대면적에서 10% 이상의 성능 수준이 요구되는 바, 유기재료의 낮은 전하 이동도와 짧은 수명을 극복하고 성능을 극대화하기 위해서는 고성능 신규소재의 개발이 필수이다. 태양광 스펙트럼의 장파장 까지 빛흡수가 가능하면서도 광흡수계수가 높은 저밴드갭 도너 물질, 전하 이동도가 획기적으로 개선되고 광 안정성도 높은 신규 소재 개발이 일차적으로 요구되며, 박막 특성 개선과 소자구조의 최적화 등에서도 보다 광범위한 연구개발이 요구되고 있다. 특히 저가의 용액공정에 의한 소자 제작시 박막의 나노-모폴로지 제어는 소자의 성능에 지대한 영향을 미치므로 공정별 한계와 최적조건을 구축하는 것도 매우 긴요하다. 본 발표에서는 당 연구팀을 포함한 국내외 연구그룹들의 최근 유기박막 태양전지 신소재 개발 및 용액공정 기술 현황에 대하여 간략히 살펴보고자 한다.

• The Journal of the Acoustical Society of Korea
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• v.16 no.1
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• pp.10-15
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• 1997

In this paper, an efficient LSF quantizer, named improved PSVQ(IPSVQ), is proposed to apply in the 8 kbps QCELP speech coder. By using 27 bits IPSVQ instead of 40 bits DPCM quantizer per frame, we can save 13 bits/frame and allocate those bits to the codebook gain and the pitch gain parameters. Hence we improve the overall performance of the QCELP codec. The enhanced QCELP shows the performance improvement of 0.9 dB SNR and 0.4 dB SEGSNR. Informal listening tests also confirm the improvement in the speech quality.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.10C
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• pp.1378-1386
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• 2004

In this paper, we propose an OFDM scheme to increase the BER performance. The proposed OFDM scheme makes the baseband OFDM signal by using the oversampled OFDM signal values which are obtained by inserting N(=2$\^$k/) zeros and carrying out 2N point IFFT. In the demodulation part, the sampling operation for A/D conversion is carried out with the 2 times high sampling speed. 2 N point FFT is carried out for the data demodulation. In this paper, we show, with the mathematical method and the computer simulation, that the SNR of the proposed OFDM scheme is 3 dB higher than that of the conventional OFDM in the same AWGN channel conditions given.

• Journal of Korea Multimedia Society
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• v.11 no.11
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• pp.1536-1546
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• 2008

RSVP-capable router supporting guaranteed services on the internet generally uses a packet scheduler based on the Weighted Fair Queuing (WFQ) algorithm to secure required qualities of traffic flows. A RSVP-capable router based on the LOFQ (Latency optimized fair queuing) algorithm had been proposed to improve the performance of the WFQ-based RSVP-router, but it required not only the RESV message to be expanded but also its performance could be evaluated only through simulation. This paper proposed a LOFQ based RSVP-capable router using the conventional RESV message and developed an algorithm to analyze the performance of the LOFQ based RSVP-capable routers. The performance evaluation using the developed algorithm showed that in terms of performance improvement the proposed router is inferior to the one using the expanded RESV message under a small packet size, but on the range of a large packet size both routers provide the same improvement.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.1
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• pp.329-332
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• 2012

LEDs are using widely in a field of illumination, LCD LED backlight, mobile signals because they have several merits, such as low power consumption, long lifetime, high brightness, fast response, environment friendly. To achieve high performance LEDs, one needs to enhance output power, reduce operation voltage, and improve device reliability. In this paper, we have proposed that the optimum design and specialized process could improve the performance of LED chip. It was showed an output power of 7cd and input supplied voltage of 3.2V by the insertion technique of current blocking layer. In this paper, GaN-based LED chip which is built on the sapphire epi-wafer by selective MOCVD were designed and developed. After that, their performances were measured. It showed the output power of 7cd more than conventional GaN-based chip. It will be used the lighting source of a medical equipment and LCD LED TV with GaN-based LED chip.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1998.04a
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• pp.753-758
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• 1998

이 글에서 살펴본 바의 내용에 의하면 철도차량 습식 바닥구조의 차음성능은 기존의 35 mm를 47 mm로 하는 경우 약 4dB 정도의 차음개선 효과를 기대할 수 있으며, 제진층을 추가로 도입하는 경우 1~2dB의 추가적인 차음개선을 기대할 수 있다고 결론된다. 바닥충격음에 대한 차단성능은 경량충격음의 경우 두께 증가 및 제진층 적용에 의하여 각각 3dB 및 7dB의 차음개선이 예상된다. 그러나 중량충격음의 경우에는 차음개선 효과가 거의 없으며 오히려 감소하는 경우도 있으므로 보다 구체적인 검토 연구의 필요성이 있다.산업계에서는 현재의 진동소음저감기술을 좀더 단시간에 차량개발 프로그램에 적용하는데 더욱 큰 노력을 할 필요가 있을 것이다. 따라서 여기에서는 현재 자동차업체에서 수행하는 진동, 소음및 충격시험평가에 대해서만 국한하여 기술하고자한다.urce)을 찾아 직접 그 원인을 차단 및 치유하는 적극적이고 공격적인 방법을 이용하고있다. 본 글에서는 이러한 진동소음 문제를 차량의 개발 단계에서 해결하기 위한 일련의 과정 및 여러가지 개선기법에 대해서 살펴보고 그를 통한 진동소음 문제 해결방법을 제시하고자 한다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.2
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• pp.51-60
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• 2011

In this study, structural safety capacity analysis of the overpass railway bridge between Konkuk Univ. and Guui station railroad has been performed. The overpass is expected to have suffered durability reduction by deterioration. The weight reduction of the overpass has been implemented to prevent further durability reduction and to improve performance capacity. To reduce the weight, 3 procedures of replacing concrete soundproofing wall to light-weight soundproofing wall, replacing gravel ballast to concrete ballast, and reducing the weight of trough have been performed. The analysis of static/dynamic behaviors and improved capacity of the light-weighted overpass bridge has been performed. The structural safety verification of the improved structure has been implemented by using rating factors of load carrying capacity of PSC I girder. The results have shown that the deflection has been reduced by 2.6mm and tensile strength has been improved by 1.07MPa, which indicate that the structural capacity has effectively been improved. Also, the natural frequency has improved by approximately 30% where vibration reduction and dynamic behavior improvement have been achieved. Moreover, in the rating factor evaluation based on analysis and test results, an improvement from 1.82 to 1.93 has been observed. Therefore, weight reduction method for the overpass is effective considering overall results.