• Journal of information and communication convergence engineering
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• 제2권4호
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• pp.214-218
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• 2004

In this paper, we have analyzed TCP performance over wireless correlated fading links with and without Snoop protocol. For a given value of the packet error rate, TCP performance without Snoop protocol is degraded as the fading is getting fast (i.e. the user moves fast). When Snoop protocol is introduced in the base station, TCP performance is enhanced in most wireless environments. Especially the performance enhancement derived from using Snoop protocol is large in fast fading channel. This is because packet errors become random and sporadic in fast fading channel and these random packet errors (mostly single packet errors) can be compensated efficiently by Snoop protocol's local packet retransmissions. But Snoop protocol can't give a large performance improvement in slow fading environments where long bursts of packet errors occur. Concerning to packet error rate, Snoop protocol results in the highest performance enhancement in the channel with mid-high values of packet error rate. This means Snoop protocol cannot fully fulfill its ability under too low or too high packet error rate environments.

• Journal of Advanced Marine Engineering and Technology
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• 제37권5호
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• pp.453-460
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• 2013

평판형 태양열 집열기의 효율을 높이기 위한 방법으로 열전달 향상 장치의 삽입, 표면 거칠기의 변화 등 다양한 방법들이 알려져 있다. 본 연구는 실험을 통해 다양한 열전달 향상 장치를 제작하고 이를 덕트에 삽입해 실험을 수행하였다. 실험은 기본적으로 덕트 윗 평판에 일정한 열유속을 가하였고, 삽입된 모델은 매끈한 덕트 형상(Base case)과 Chamfered rib $10^{\circ}$, Chamfered rib $20^{\circ}$, Rib & Groove, Rib & Dimple 모델이다. 실험은 Reynolds 수가 2,300~22,000의 범위에서 이루어졌으며 이는 난류영역에 해당한다. 열전달 향상 장치를 삽입하면 면적의 증가와 2차 유동으로 인하여 열전달이 향상되고, Reynolds 수가 증가할수록 열전달이 향상되었으며 압력강하도 증가하였다. 열전달 측면에서는 Rib & Dimple 모델이 열전달 향상 효과가 가장 좋았으며, 압력강하는 Chamfered rib $10^{\circ}$ 모델이 가장 낮았으며, 성능계수 측면에서도 Chamfered rib $10^{\circ}$ 모델이 가장 높은 것으로 나타났다.

• 플랜트 저널
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• 제15권4호
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• pp.30-35
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• 2019

미세먼지 감축에 대한 사회적 요구 증가와 강화되는 대기오염물질 배출허용기준을 충족시키기 위해 구조적 제약조건을 갖는 500 MW급 석탄화력발전소 탈황설비의 성능개선 방안을 제시하였다. 탈황설비 흡수탑을 통과하는 배기가스가 선회하도록 내부 설비를 개조하여 난류를 형성시켜 물질전달효율을 증가시키고 반응 면적 및 시간을 증가시킴으로써 황산화물 저감 및 먼지 포집 능력을 향상시킬 수 있었다. 개선결과 황산화물 제거효율은 91.61%에서 98.43%로 향상되었고 먼지 제거성능은 77.4%에서 87.08%로 향상되었다. 배출농도는 황산화물 7.85 ppm, 먼지 4.67 mg/㎥이 배출되어 2023년의 대기오염물질 배출허용기준인 황산화물 25 ppm, 먼지 5 mg/㎥을 만족하는 수준이다. 본 연구의 성능 개선 방식은 유사한 제약조건을 갖는 다른 석탄화력발전소에도 효과적으로 적용될 수 있으리라 기대된다.

• 동의신경정신과학회지
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• 제30권1호
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• pp.13-21
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• 2019

Objectives: To investigate the research trends of qigong interventions to make influence on performance enhancement. Methods: Korean databases were searched for papers related to studies of qigong interventions to assist subjects perform better. Results: Twelve articles published in Korean Journals from 2000 to 2017 were reviewed. Among the retrieved papers, eight were applied with breathing exercises, including Dan-jeon breathing training, one applied with brain breathing meditation with DoIn exercise, one applied with qigong meditation, one applied with qi-training, and one applied with brain breathing training. RoBANS was used for assessment. The quality of selected articles was generally low. 10 of the 12 articles on qigong reported that experimental group showed statistically significant increase of performance enhancement both directly and indirectly. Conclusions: Reviewing 12 articles, this study established that qigong interventions might be beneficial for enhancing performance especially in sports. However, more scientifically designed study on qigong therapy are needed to prove the efficacy and effectiveness.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2003년도 하계종합학술대회 논문집 Ⅳ
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• pp.2004-2007
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• 2003

This paper describes a method of performance enhancement using Flatness Mesure(FM) for the Gaussian Mixture Model(GMM) face recognition systems. Using this measure we discard the frames having low information before training and test. As the result, the performance increases about 9％ in the lower mixtures and calculation burden is decreased. As well, the recognition error rate is decreased under the illumination change surroundings. We use the 2D DCT coefficients lot face feature vectors and experiments are carried out on the Olivetti Research Laboratory (ORL) face database.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 ITC-CSCC -2
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• pp.865-868
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• 2000

In this paper we derive a new VAD algorithm, which combines the preprocessing algorithm and the optimum decision rule. To improve the performance of the VAD algorithm we employ the speech enhancement algorithm and then apply the maximal ratio combining technique in the preprocessing procedure, which leads to maximized output SNR. Moreover, we also perform extensive computer simulations to demonstrate the performance improvement of the proposed algorithm under various background noise environments.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권2호
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• pp.837-856
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• 2016

Underwater image enhancement has received considerable attention in last decades, due to the nature of poor visibility and low contrast of underwater images. In this paper, we propose a new automatic underwater image enhancement algorithm, which combines nonsubsampled contourlet transform (NSCT) domain enhancement techniques with the mechanism of the human visual system (HVS). We apply the multiscale retinex algorithm based on the HVS into NSCT domain in order to eliminate the non-uniform illumination, and adopt the threshold denoising technique to suppress underwater noise. Our proposed algorithm incorporates the luminance masking and contrast masking characteristics of the HVS into NSCT domain to yield the new HVS-based NSCT. Moreover, we define two nonlinear mapping functions. The first one is used to manipulate the HVS-based NSCT contrast coefficients to enhance the edges. The second one is a gain function which modifies the lowpass subband coefficients to adjust the global dynamic range. As a result, our algorithm can achieve contrast enhancement, image denoising and edge sharpening automatically and simultaneously. Experimental results illustrate that our proposed algorithm has better enhancement performance than state-of-the-art algorithms both in subjective evaluation and quantitative assessment. In addition, our algorithm can automatically achieve underwater image enhancement without any parameter tuning.

• 한국통신학회논문지
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• 제37권3A호
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• pp.135-140
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• 2012

이 논문은 순환 지연 다이버시티 OFDM 시스템의 성능을 향상시키기 위하여 주파수 다이버시티를 적용하는 알고리즘을 제안한다. OFDM 시스템에서 주파수 다이버시티 적용은 동일한 심볼을 상관관계가 없는 부반송파로 반복 전송하는 것으로 수행되며, 반복 전송 회수에 비례하여 변조 레벨을 증가시켜서 종래의 전송 시스템의 성능과 비교한다. 이 방법은 순환 지연 다이버시티 알고리즘과 같이 송신기 개수가 많아짐에 따라 수신기에서 부가적인 특별한 하드웨어가 필요하지 않다는 동일한 장점이 있게 되며, 성능 시험을 위해서 다중 송수신 안테나 환경하에서 모의 실험을 수행하였다. 제안하는 알고리즘은 종래의 순환 지연 다이버시티를 활용한 OFDM 시스템과 비교하여 저밀도 변조 레벨에서 성능 향상이 현저함을 보여준다.

• 멤브레인
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• 제13권4호
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• pp.283-290
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• 2003

BSA 용액을 대상으로 한 dead-end 및 cross-flow 한외여과에서 막모듈에의 초음파 조사가 막성능 향상에 미치는 효과를 연구하였다. 이 결과 막모듈에의 간헐적 또는 연속적 초음파 조사는 막오염의 형성 억제 및 막오염 층의 제거에 상당한 효과가 있음이 확인되었다. 초음파 조사에 의한 막성능 향상 효과는 막오염을 크게 유발시키는 운전조건(도입액 농도와 TMP가 높고, 유량이 낮은 운전조건)일수록 더 컸으며, 막모듈에 초음파를 조사시키면 조사시키지 않은 경우와 비교할 때 dead-end 한외여과에서는 최대 약 1.9배, cross-flow 한외여과에서는 최대 약 1.5배의 투과플럭스 향상을 얻을 수 있었다.

• 전기학회논문지P
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• 제67권2호
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• pp.75-81
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• 2018

In this paper for developing and implementing the car driver's front lane attention enhancement developed system using the car camera. The developed system automatically alarm the car driver when front cars make the dangerous situation. We use Raspberry Pi camera module V2 as car camera module, Raspberry Pi 3 board as hardware main board of implementing embedded system and develop the application library module which can be operated on the Raspberry situation. The application library module widely consist of two part, front car recognition part and dangerous situation distinguish part. Our developed system satisfy the performance test of the target system at the software test certification laboratory of TTA(Telecommunication Technology Association). We test four items as attentive car recognition ability at day and night, system performance, response time. We get the performance of developed system based on the four goal. The car driver's front lane attention enhancement system in this paper will be widely used at the ADAS(Advanced Driving Assistance System) because of the better performance and function.