• 상하수도학회지
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• 제20권6호
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• pp.875-883
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• 2006

The carbon and nitrogen removal process using PVA-gel (Polyvinyl Alcohol) immobilized microorganisms was studied. The process has been operated under diverse process conditions for 12 months. The process consists of denitrification with internal recycle of 300%, nitrification, aerobic digestion reactors and settling tank. Nitrificatoin and nitrogen removal efficiency according to gel packing ratio and temperature were studied. Yield for Heterotrophs ($Y_H$), decay coefficient for Heterotrophs($b_H$) in aerobic digestion reactor were determined to seize sludge reduction mechanism and compared with typical data of activated sludge process. Then SRT in aerobic digestion reactor was determined on an experimental basis and sludge reduction efficiency was calculated. The process was implemented successfully with sludge reduction efficiency of 92.0~98.5% on a basis of biomass.

• Composites Research
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• 제32권2호
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• pp.85-89
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• 2019

나노입자에 기반한 화학 촉매 반응 효율성에는 크기, 형태 및 조성이 중요한 영향을 미치는 것으로 알려져 있다. 이에 대한 체계적인 비교를 위해 갈바닉 치환 반응을 통해 100 nm 직경의 요철형 표면 구조를 갖는 금, 백금, 팔라듐 나노플레이트에 대한 정량적인 분석 조건 형성이 가능하였으며, 4-나이트로페놀과 4-나이트로아닐린을 대상으로한 촉매 반응 진행을 분광분석법을 통해 확인할 수 있었다. 이로부터 동일 형태 및 형태에서 구성 원소에 따라 확연히 다른 Pd > Au > Pt의 촉매성 환원 반응 효율을 보임을 관찰할 수 있었으며, 기질의 형태에 따라 추가적인 영향을 받음을 관찰 가능하였다.

• 대한금속재료학회지
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• 제47권5호
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• pp.304-310
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• 2009

Recently, manganese nodule has been focused on alternative resources because of its high grade of noble metallic elements such as Co, Ni, and Cu etc. From the viewpoint of an optimization the operating variables for energy efficiency of smelting reduction process, thermodynamic model for smelting reduction process of Manganese nodule was developed by using energy and material balance concept. This model provided that specific consumption of pure oxygen and coke was strongly depended on post combustion ratio (PCR) and heat transfer efficiency (HTE). The dressing and dehydrating process of low grade manganese can be proposed an essential process to minimize the specific energy consumption with decreasing slag volume. The effect of electricity coal base smelting reduction process was also discussed from the energy optimizing point of view.

• Current Optics and Photonics
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• 제2권5호
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• pp.468-473
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• 2018

We investigate the temperature dependence of efficiency droop in InGaN/GaN multiple-quantum-well (MQW) blue light-emitting diodes (LEDs) in the temperature range from 20 to $80^{\circ}C$. When the external quantum efficiency (EQE) and the wall-plug efficiency (WPE) of the LED sample were measured as injection current and temperature varied, the droop of EQE and WPE was found to be reduced with increasing temperature. As the temperature increased from 20 to $80^{\circ}C$, the droop ratio of EQE was decreased from 16% to 14%. This reduction in efficiency droop with temperature can be interpreted by a temperature-dependent carrier distribution in the MQWs. When the carrier distribution and radiative recombination rate in MQWs were simulated and compared for different temperatures, the carrier distribution was found to become increasingly homogeneous as the temperature increased, which is believed to partly contribute to the reduction in efficiency droop with increasing temperature.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제15권2호
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• pp.522-539
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• 2021

In order to solve the problems of the existing audio fingerprint method when extracting audio fingerprints from long speech segments, such as too large fingerprint dimension, poor robustness, and low retrieval accuracy and efficiency, a robust audio fingerprint retrieval method based on feature dimension reduction and feature combination is proposed. Firstly, the Mel-frequency cepstral coefficient (MFCC) and linear prediction cepstrum coefficient (LPCC) of the original speech are extracted respectively, and the MFCC feature matrix and LPCC feature matrix are combined. Secondly, the feature dimension reduction method based on information entropy is used for column dimension reduction, and the feature matrix after dimension reduction is used for row dimension reduction based on energy feature dimension reduction method. Finally, the audio fingerprint is constructed by using the feature combination matrix after dimension reduction. When speech's user retrieval, the normalized Hamming distance algorithm is used for matching retrieval. Experiment results show that the proposed method has smaller audio fingerprint dimension and better robustness for long speech segments, and has higher retrieval efficiency while maintaining a higher recall rate and precision rate.

• KIEAE Journal
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• 제12권3호
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• pp.89-94
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• 2012

The international community is paying close attention to the climatic changes caused by the meteorological anomalies. In response to such phenomena, after the adoption of the United Nations Framework Convention on Climate Change in 1992, efforts to actively respond to the meteorological changes are proliferating all over the world; even in the Republic of Korea, the issue to tackle the meteorological changes has emerged as a top-priority national agenda. In the year of 2008, after the declaration of the low-carbon, green-growth paradigm by the government, the UNFCCC COP15 has announced a 30% reduction target of the emission of the greenhouse gases by 2020 as compared to the "Business As Usual, BAU" and has also confirmed, as a commitment plan to achieve reduction in the emission of greenhouse gases, the reduction target of greenhouse gases for all sectors, industries and years. (26.9% for buildings) Since the construction of the new apartment houses in the year of 2001, the "Building Energy Efficiency Rating", has been applied to newly constructed building complexes, built in 2010; the accumulated emission reduction has been evaluated at around 450,000toe and the accumulated carbon dioxide emission reduction is at $826,000tCO_2$ And through the prediction of these values under various scenarios (New construction, new construction / expansion of existing uses, when transferred to 1stgrade), the effects on the degree of reduction of greenhouse gases by the increased certification of the Building Energy Efficiency Rating are an alyzed and it is our aim to express the importance of the certification system capable of carrying out a quantitative evaluation of the building energy in order to establish the strategy to reduce the emission of carbon dioxide.

• 한국자동차공학회논문집
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• 제21권6호
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• pp.117-122
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• 2013

This study is aimed to develop LNT(Lean NOx Trap) aftertreatment system for DME engine. Modified DME engine, which was changed from diesel to current DME engine, is used for this research and is equipped with common rail type injector and fuel supplying system. LNT system has reductant injector. DME is also used as reduction agent. For this research, reduction agent injection time width and interval were varied. And also, swirler was used to improve homogeneity of reducing agent in exhaust pipe. The reduction rate of NOx by LNT was increased by longer injection width, short interval and swirler. The maximum diminution of NOx by LNT was over 85%.

• 자원ㆍ환경경제연구
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• 제25권2호
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• pp.299-320
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• 2016

본 연구는 자료포락분석의 target-setting approach를 기초로 우리나라 16개 지자체의 에너지 효율성을 추정하고, 에너지 효율향상을 통해 저감할 수 있는 에너지 소비수준을 계측한다. 나아가 에너지 믹스변화에 의한 지역별 환경성과를 분석하고 그에 따른 이산화탄소 감축효과를 평가한다. 분석결과, 표본기간 2004년~2013년 동안 평균적으로 14.0%의 에너지 비효율이 존재하며, 특히 석유연료의 비효율적 사용이 주요 광역시를 중심으로 크게 나타났다. 또한 에너지 소비구조의 변화를 통해 에너지 효율향상과 추가적인 이산화탄소 저감가능성이 발생하며, 적극적인 에너지 믹스전략의 필요성을 확인할 수 있었다.

• 한국멀티미디어학회논문지
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• 제25권10호
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• pp.1448-1456
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• 2022

This paper studies a model to diagnose efficiency reduction of inverter using Multilayer Perceptron(MLP). In this study, two inverter data which started operation at different day was used. A Multilayer Perceptron model was made to predict photovoltaic power data of the latest inverter. As a result of the model's performance test, the Mean Absolute Percentage Error(MAPE) was 4.1034. The verified model was applied to one-year-old and two-year-old data after old inverter starting operation. The predictive power of one-year-old inverter was larger than the observed power by 724.9243 on average. And two-year-old inverter's predictive value was larger than the observed power by 836.4616 on average. The prediction error of two-year-old inverter rose 111.5572 on a year. This error is 0.4% of the total capacity. It was proved that the error is meaningful difference by t-test. The error is predicted value minus actual value. Which means that PV system actually generated less than prediction. Therefore, increasing error is decreasing conversion efficiency of inverter. Finally, conversion efficiency of the inverter decreased by 0.4% over a year using this model.

• 한국자동차공학회논문집
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• 제21권6호
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• pp.64-71
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• 2013

In this study we designed a lean $NO_x$ trap (LNT) model with $GT-POWER^{TM}$ program and then the LNT model was compared to the bench flow reactor test results. This model consists of 9 kinetic reactions to represent the main steps of NO oxidation, $NO_x$ adsorption, $NO_x$ release and then its reduction. The comparison was performed on the operating conditions at the space velocity of 50,000 1/hr and 80,000 1/hr with the temperature range of $200^{\circ}C{\sim}500^{\circ}C$ with the even spaced temperature step of $50^{\circ}C$. The experimental results show that the $NO_x$ conversion efficiency was enhanced by the temperature up to $350^{\circ}C$ and then decayed at higher temperatures. The LNT model predicts the similar trend of the $NO_x$ conversion efficiency to the experimental results below $350^{\circ}C$, but overestimates above $350^{\circ}C$. This overestimation comes from the higher reduction efficiency which was obtained by the different reduction gas composition such as $C_3H_6$ in the model to replace $CH_4$, $C_2H_4$ in the bench test.