• 한국생물공학회:학술대회논문집
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• 2000.11a
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• pp.457-460
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• 2000

A biofilm airlift reactor filled with biomass-covered carriers (sand) were used to remove ammonium by selective nitrification (ammonium to nitrite). The effects of experimental conditions (ammonium load, pH, dissolved oxygen) on nitrification and nitrite accumulation were investigated. The reactor showed more than 90% nitrification efficiencies at 2.5 kg $NH_4\;^+-N/m^3/d$ and $NO_2\;^--N$ could be accumulated between 75% and 90% in the effluent. It is likely that nitratation (nitrite oxidizer) was inhibited by low dissolved oxygen concentration while nitritation (ammonium oxidizer) was kept stable.

• Journal of the Korean Data and Information Science Society
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• v.21 no.3
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• pp.513-521
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• 2010

Most of universities have carried out course evaluation to apply the performance appraisal for professor. But, course evaluation depends on characteristics of each class such as class size, type of lecture, evaluator's grade and so on. As the results, such characteristics of each class lead to serious bias which makes lecturers distrust the course evaluation results. Hence, we propose a equating method for the course evaluation by regression analysis which use stepwise variable selection. And we compare proposed method with the other method by Cho et al. (2009) with respect to efficiencies. Also we give the example to which the method is applied.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.33B no.1
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• pp.195-200
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• 1996

In this paper, to eliminate some selected harmonics, we implement PWM inverter which can be able to control in real-time. Using walsh function, which is one of the ordered orthogonal functions, we propose a new method to calculate firing angles, and implement logic circuits which can be calculate firing angles in real-time and be applicable to 1- and 3-phase circuits. Finally, using simulation circuits which accept the outputs obtained from the implemented logic circuits as the inputs, we confirmed the characteristics in steady state of the proposed method for PWM inverter.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2015.10a
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• pp.77-78
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• 2015

산업화로 인하여 토지의 사막화, 물부족, 오존층 파괴, 지구 온난화 등 많은 환경문제가 발생되었으며 아직 진행 중에 있다. 이에 UN에서는 환경 규제를 강화하였으며 국제해사기구(IMO:International Maritime Organization)에서는 선박의 배기가스 규제 강화를 위하여 NOx(질소산화물) 및 SOx(황산화물)의 배기량을 줄이도록 하고 있으며 2016년부터는 본격적으로 규제하려 하고 있다. 상기의 규제 물질 중 NOx를 제거하는 선택적환원촉매(SCR:Selectivity Catalytic Reduction) 시스템은 선박의 배기가스가 지나가는 통로에 요소수(Urea)를 분무하여 $260^{\circ}C$ 이상의 높은 온도에서 요소수에 있는 암모니아가 배기가스에 있는 NOx와 반응, 결합함으로서 NOx를 질소와 산소로 분리, 제거하는 방식이다. 하지만 선박의 경우 대부분 엔진이 2행정으로 배기가스 온도가 일반적으로 $180^{\circ}C{\sim}220^{\circ}C$이기 때문에 요소수에 있는 암모니아가 배기가스에 있는 NOx와 반응하지 않아 환원률이 높지 않다. 이에 우리는 초미세기포를 이용하여 낮은 온도에서도 반응할 수 있는 요소수 및 요소수 활성화 기기를 개발하여 상기의 문제점들을 최소화 할 수 있도록 하였다. 또한 SCR 시스템의 점성유동해석을 통하여 보다 효율적인 SCR 시스템의 개발을 할 수 있도록 기여하였다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• fall
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• pp.189-192
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• 2021

three degree of freedom (3DoF), three degree of freedom plus (3DoF+), six degree of freedom(6DoF) 등 몰입형 비디오의 높은 몰입감을 제공하기 위해 다중 비디오 영상을 효율적으로 처리하는 기법이 활발히 연구되고 있다. 이를 위해 원본의 몰입형 비디오가 입력되면 기본 시점 영상과 추가 시점 영상에서의 중복을 제거하고 기본 시점(basic view)에서는 보이지 않지만 추가 시점(additional view)에서는 보이는 영역을 추출하는 프루닝 과정이 이뤄지는 부호기에서의 부호화 모드 결정은 매우 중요하다. 본 논문은 test model for immersive video (TMIV)의 모드 중 하나인 MPEG immersive video (MIV) view mode 를 통해 만들어진 프루닝 (pruning) 그래프에서 선택된 시점들을 활용하여 뷰 간 중복성을 제거할 수 있는 효율적인 부호화 구조로 클러스터를 기반으로 병렬적으로 부호화하는 클러스터 기반 정렬 기법을 제안한다. 선택된 시점들을 인덱스 순서에 따라 부호화하는 기존 방법에 비해 제안하는 방법은 peak signal-to-noise ratio (Y-PSNR)에서 평균 3.9%의 BD-rate 절감을 보여주었다. 본 연구는 또한 더 객관적인 품질 측정을 위해 immersive video peak signal-to-noise ratio (IV-PSNR)에 의한 비교 결과도 함께 제공하며, 참조 순서에 맞게 정렬한 프루닝 기반 정렬 기법과의 비교도 함께 제공한다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.41 no.4
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• pp.399-404
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• 2021

From 1 January 2020, the limit for Sulphur in fuel oil used on board ships operating outside designated emission control areas will be reduced to 0.5 %. This regulation by international maritime organization (IMO) is able to significantly reduce the amount of Sulphur oxides (SOx) discharging from ships and should have environmental advantages and health for all over the world. To meet the regulation, in these days, wet scrubber system is being actively developed. However, this process leads to make washing wastewater. In this study, we evaluated ion exchange resin system in accordance with scrubber wastewater discharge regulation by IMO. Theoretical wastewater used as feed solution of lab scale water treatment systems. The results revealed that nitrate ion was removed selectively in spite of high TDS wash wastewater solution depending on ion exchange resin property. Moreover, it was possible to improve efficiency of the system by optimizing operating conditions.

• Journal of KIISE:Software and Applications
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• v.36 no.3
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• pp.179-186
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• 2009

This paper proposes a target speech extraction which restores speech signal of a target speaker form noisy convolutive mixture of speech and an interference source. We assume that the target speaker is known and his/her utterances are available in the training time. Incorporating the additional information extracted from the training utterances into the separation, we combine convolutive blind source separation(CBSS) and non-negative decomposition techniques, e.g., probabilistic latent variable model. The nonnegative decomposition is used to learn a set of bases from the spectrogram of the training utterances, where the bases represent the spectral information corresponding to the target speaker. Based on the learned spectral bases, our method provides two postprocessing steps for CBSS. Channel selection step finds a desirable output channel from CBSS, which dominantly contains the target speech. Reconstruct step recovers the original spectrogram of the target speech from the selected output channel so that the remained interference source and background noise are suppressed. Experimental results show that our method substantially improves the separation results of CBSS and, as a result, successfully recovers the target speech.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.37 no.3
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• pp.12-26
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• 2000

In this paper, we propose a post-processing algorithm to remove false minutiae which decrease the overall performance of an automatic fingerprint identification system by increasing computational complexity, FAR(False Acceptance Rate), and FRR(False Rejection Rate) in matching process. The proposed algorithm extracts candidate minutiae from thinned fingerprint image. Considering characteristics of the thinned fingerprint image, the algorithm selects the minutiae that may be false and located in recoverable area. If the area where the selected minutiae reside is thinned incorrectly due to noise and loss of information, the algorithm recovers the area and the selected minutiae are removed from the candidate minutiae list. By examining the ridge pattern of the block where the candidate minutiae are found, true minutiae are recovered and in contrast, false minutiae are filtered out. In an experiment, Fingerprint images from NIST special database 14 are tested and the result shows that the proposed algorithm reduces the false minutiae extraction rate remarkably and increases the overall performance of an automatic fingerprint identification system.

• Resources Recycling
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• v.27 no.3
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• pp.30-38
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• 2018

In this study, the behaviors of Fe selective chlorination in ilmenite ore by using PVC or $CO-Cl_2$ gas mixture as reducing agents under the condition of 1173 K, for 60 minutes were investigated. The weight loss ratio was 28% when PVC was applied as the reducing agent. The condensate formed at the outlet of reaction tube was identified as $FeCl_2$ by X-ray diffraction analysis. From these results, it was observed that iron in ilmenite ore reacted with HCl gas and Fe was selectively removed in the form $FeCl_2$. However, when $CO-Cl_2$ gas mixture was used as a reducing agent, the weight reduction ratio was 54%, and the condensate formed at the outlet of reaction tube after the experiment was estimated to be $FeCl_3$. It was observed that the ilmenite ore reacted with the $CO-Cl_2$ gas mixture and was simultaneously removed in the form of $FeCl_3$ and $TiCl_4$. However, the results of X-ray diffraction of ilmenite ore after the reaction showed that Fe was almost removed.

• Journal of the Mineralogical Society of Korea
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• v.21 no.2
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• pp.129-138
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• 2008

The characteristics of beneficiating kaolin mineral by liberation (selective grinding) and air classification have been investigated, comparing the grinding rates of ball mill and impact mill. The ore was ground using a ball mill and a impact mill to evaluate the grindability of the two grinding methods based on the constant production amount of fine particles in size less than 325 mesh. Then, the fine product was further separated into two fractions using an air-classifier and each fraction was chemically analyzed to compare the beneficiation efficiency of the two grinding methods. The chemical grade of kaolin mineral decreased as increasing the grinding rate of both the mills. particularly in the case of ball mill because of overgrinding impurities such as quartz and feldspar. In the case of the ball milling, the fine fraction less than 325 mesh was air-classified at a cutting point of $43\;{\mu}m$. The production rate of the air-classified concentrate was found to be 66.2 wt%, removing 5.3% of $Fe_2O_3$ and 34.6% of CaO. Under the same conditions mentioned above with the impact mill, the production rate of the air-classified concentrate was 64.4 wt%, removing 34.2% of $Fe_2O_3$, 67.6% of CaO and 25.0% of $TiO_2$. Therefore, our results indicate that impact mill is superior to ball mill in terms of impurity removal.