• Journal of the Korean Institute of Gas
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• v.19 no.4
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• pp.22-28
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• 2015

In order to keep the competitiveness of LPG fuel for transportation fuel, the difference in fuel consumption with gasoline and cost for an aftertreatment system should be reduced with continuous development of technology for LPG engine. In the present study, spray-guided type direct injection combustion system, whose configuration is composed of direct injector in the vicinity of spark plug, was employed to realize stable lean combustion. A certain level of nitrogen oxides($NO_x$) emits due to a locally rich mixture regions in the stratified mixture. With the application of EGR system for the reduction of $NO_x$, 15% of $NO_x$ reduction was achieved whereas fuel consumption and hydrocarbon emission increased. By the application of EGR, the combustion speed reduced especially appeared at initial flame development period and peak heat release rates and increasing rates for heat release rate decreased as EGR rate increased due to the dilution effect of intake air.

• Journal of Energy Engineering
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• v.13 no.2
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• pp.144-151
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• 2004

Stabilization and reduction of combustion noise and NOx emission from dry low NOx combustor of GE MS7001F gas turbine were achieved. Dry low NOx gas turbines that adopt the lean premixed combustion technology frequently generate the flame instability and high NOx emissions if not adequately tuned. Dynamic pressure oscillation during the combustion mode transfer increased as ambient temperature decreased with frequency of 80㎐ and magnitude of 4-9 psi. Effects of both combustor tuning for uniform fuel flow with burner nozzles and fuel pre-filling into transfer fuel valves on stabilisation of the dry low NOx combustor were very significant. Dynamic pressure oscillation during the combustion mode change was decreased up to 2.5 psi. Also, NOx emission from GE7F DLN-1 combustor can be maintained as low as 35-43ppm (15% O$_2$) in base load operation of 150 MW.

• Journal of Intelligence and Information Systems
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• v.13 no.4
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• pp.65-78
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• 2007

This paper proposes a new method of weighted template matching for machine-printed numeral recognition. The proposed weighted template matching, which emphasizes the feature of a pattern using adaptive Hamming distance on local feature areas, improves the recognition rate while template matching processes an input image as one global feature. Template matching is vulnerable to random noises that generate ragged outlines of a pattern when it is binarized. This paper offers a method of chain code trimming in order to remove ragged outlines. The method corrects specific chain codes within the chain codes of the inner and the outer contour of a pattern. The experiment compares confusion matrices of both the template matching and the proposed weighted template matching with chain code trimming. The result shows that the proposed method improves fairly the recognition rate of the machine-printed numerals.

• Database Research
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• v.34 no.3
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• pp.86-98
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• 2018

Point-of-Interest(POI) recommendation systems suggest the most interesting POIs to users considering the current location and time. With the rapid development of smartphones, internet-of-things, and location-based social networks, it has become feasible to accumulate huge amounts of user POI visits. Therefore, instant recommendation of interesting POIs at a given time is being widely recognized as important. To increase the performance of POI recommendation systems, several studies extracting users' POI sequential preference from POI check-in data, which is intended for implicit feedback, have been suggested. However, when constructing a model utilizing sequential preference, the model encounters possibility of data distortion because of a low number of observed check-ins which is attributed to intensified data sparsity. This paper suggests refinement of temporal intervals based on data confidence. When building a POI recommendation system using temporal intervals to model the POI sequential preference of users, our methodology reduces potential data distortion in the dataset and thus increases the performance of the recommendation system. We verify our model's effectiveness through the evaluation with the Foursquare and Gowalla dataset.

• Journal of the korean Society of Automotive Engineers
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• v.14 no.3
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• pp.80-89
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• 1992

An experimental study of in-cylinder of flow and combustion characteristics in two gasoline engines of different intake ports which are denoted as original port and masked shroud head (MSH) ports is presented. The flows generated by the MSH and the original port are invest- igated by laser Doppler velocimeter(LDV) under steady flow and motoring (non-firing) condit -ions. Combustion characteristics with different swirl levels produced by two intake ports are analyzed by combustion pressure measurement and statistical calculation. The swirl inside the cylinder of the MSH port engine is found to be much higher than the original port, and the MSH has a large eddy motion of cylinder diameter size. Using ensemble average method to valuate engine turbulence under motoring condition, the MSH port engine is shown to have h -igher turbulence intensity than the original port, so that the effect of the MSH port on fast burn is shown. Also the cyclic variations of peak pressure and the reaching time in the MSH port are apparently reduced.

• Journal of Power System Engineering
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• v.11 no.3
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• pp.16-21
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• 2007

Three dimensional numerical study was carried out to investigate the effect of aspect ratio on microchannel flow. We considered five straight rectangular channels with aspect ratios (height/width) 0.2, 0.4, 0.6, 0.8 and 1.0. Nitrogen gas flow was investigated for both slip and noslip wall boundary conditions. Isothermal wall condition was assumed. We used control volume method for this simulation. The slip velocity increases with the increase of aspect ratio. Friction coefficient decreases with the increase of aspect ratio. Slip friction coefficient is lower than noslip friction coefficient. Mass flow rate of slip model is higher than that of noslip model. We compared our results with the experimental result reported in the literature. The agreement was good.

• TTA Journal
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• s.37
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• pp.60-70
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• 1995

미래육상이동통신시스템(FPLMTS-Future Public Land Mobile Telecommunication Systems)은 2000년대초 서비스를 목표로 ITU-R에서 권고(안)을 작성하고 있는 제3세대 이동통신시스템(TGMS-Third Generation Mobile System)이다. FPLMTS의 기본목적중의 하나는 이동전화, 코드리스폰, 이동데이터, 위성 등 다양한 시스템을 통합하여 제한된 무선접속을 통해 일체화된 이동통신 서비스를 제공하는 것이다. 또한 FPLMTS는 사용자들로 하여금 어느 나라에서나 통화할 수 있도록 함으로써 이용자들에게 국제로밍을 제공하고, 넓은 지역을 관할하면서 인구가 희박한 지역에도 효과적으로 서비스를 제공할 수 있도록 지상망과 위성망을 연동한다. 본 보고서는 FPLMTS의 권고(안) 작성을 담당하고 있는 ITU-R TG8/1의 국제표준화동향 및 기술동향에 관한 정보를 수집/분석한 내용을 담고 있다. 이 보고서가 국내 이동통신분야, 특히 개인통신서비스 개발의 정확한 방향정립과 연구개발에 도움이 되었으면 한다.

• Proceedings of the Korea Information Processing Society Conference
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• 2005.05a
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• pp.1019-1022
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• 2005

멀티미디어 콘텐츠에 대한 처리기술과 사용자 인터페이스의 발전으로 인해, 교육 현장에서 광범위하게 사용되는 교육 도구로 e-러닝이 자리 잡고 있다. 현재까지 연구되어온 교육 콘텐츠는 단순한 상호작용만을 허용하고, 실습형 인터페이스를 제공하기에는 제약이 따르며, 기존의 콘텐츠를 재구성하여 개발하기에는 많은 비용과 시간이 소요된다. 그리고 학습효과 측정에 대한 의식이 희박하고, 콘텐츠 평가의 명확한 기준이 없어 품질 향상에 많은 어려움이 뒤따른다. 이를 개선하기 위해 본 논문에서는 멀티미디어를 이용한 자기주도적 학습 콘텐츠를 제작한다. 이렇게 제작된 교육 콘텐츠를 비전 기반의 증강현실을 이용하여 더욱더 직관적이고, 인터랙티브한 교육 콘텐츠를 제공한다.

• Journal of the Korean Society of Combustion
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• v.18 no.3
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• pp.68-74
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• 2013

가스터빈용 희박 예혼합 연소기 내부에 와류 발생기(vortex generator)를 장착하여 그에 따른 연료/공기혼합 및 NOx 배출 특성 변화를 조사하였다. 이를 위해 수치해석적 방법을 채택하여 연소기내 유동특성, 연료/공기 혼합도, 배기가스(NOx), 화염형상을 분석하였다. 와류 발생기를 장착한 경우, 연소기 내부에서 와류 발생기에 의한 나사산 형상으로 인해 와류가 형성되며 이는 연소기 전면부까지 유지되었다. 또한 연소기 내부 면적 차로 인해 압력섭동이 발생하였다. 이와 더불어 연소기 전면부 기준 상류지역의 연료와 공기의 혼합도가 증가됨으로서 연료 과농지역이 감소하게 되며 이로 인해 전반적인 NOx 발생량의 감소 효과를 볼 수 있었다. 화염 형상의 변화로부터 와류 발생기의 영향으로 선회수는 다소 감소할 것으로 예상되며, 이는 와류 발생기로 인한 유속의 반복적 증감에 의한 결과라고 판단된다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.6
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• pp.1633-1639
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• 1993

In spark ignition engine, EGR of lean mixture operation has advantage in emission, but disadvantages in power output and combustion flame propagation. Fast burn system is known to be a useful method to solve these disadvantages. This paper presents the characteristics of in-cylinder flow for different combustion chamber geometries, and the correlation between the in-cylinder flow and the combustion flame speed using an ion current method.