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The Effect of Injector Nozzle Number on Spray and Combustion in a Light-Duty Diesel Engine
( Seungwoo Kang ),( Wonkyu Cho ),( Choongsik Bae ) 한국액체미립화학회 2017 한국액체미립화학회 학술강연회 논문집 Vol.2017 No.-
This paper investigated the number effect of diesel injector nozzle on spray and combustion in a light-duty diesel engine with 250MPa injection. The liquid and vapor spray visualization was conducted in constant-volume combustion chamber. The engine used for the experiment was the 0.4L single-cylinder diesel engine. Three injectors that were compared had identical hydraulic flow rate, and their nozzle numbers were 8 to 10. The orifice diameter decreased from 105 ㎛ to 95 ㎛ as the nozzle number increased. The vapor and liquid spray penetration decreased with larger nozzle number and smaller orifice diameter. However, the total cross-sectional areas of vapor spray from 8 to 10-hole injectors were similar. In the engine, injector with larger nozzle number and smaller orifice diameter showed the shorter ignition delay. The particulate matter(PM) emission was lower with larger nozzle number and smaller orifice diameter. Improved the atomization of the fuel spray from smaller nozzle diameter while the fuel spray area was kept results shorter ignition delay and lower PM emission. However, at higher injection pressure, the NOx-PM trade-offs from three injectors were similar. The effect of injection pressure was dominant for reducing PM emission, and then the effect of nozzle geometry was indistinguishable. The indicated specific fuel consumption was similar because their injection rate and in-cylinder pressure trace was similar. Also, the 8-and 10-hole injectors with same orifice diameter(95 ㎛) was also compared for identify the nozzle effect with constant orifice diameter. The 10-hole injector showed improved PM-NOx emission trade-off and fuel consumption because the increased nozzle number widened the fuel distribution in the cylinder. This research will provide guideline for optimization of the injector nozzle configuration.
Non-invasive Face Registration for Surgical Navigation
Seungwoo Kang,Hyeonjun Kim,Taeyong Park,Jeongjin Lee,Hyunjoo Song 한국정보과학회 2022 Journal of Computing Science and Engineering Vol.16 No.4
This study aims to propose a precise rigid-body face registration method that does not require an invasive marker attachment for surgical navigation devices. The non-invasive face registration involved the following steps: anatomical feature points such as the eyes and nose are found from the computed tomography (CT) image and the location tracking device attached to the patients forehead prior to the procedure; an initial registration is attempted on the two previously extracted feature points; secondary registration was performed using a coherent point drift (CPD) algorithm; and using the Powell method, precise registration was performed to minimize the closest point registration error (CPRE). The CPRE co-registration accuracy was measured for the original and sampled phantom data, and the error was found to be 1.07 mm on average for skin coordinate data. The method introduced in this study enabled precise rigid-body face registration in a non-invasive manner using only skin coordinates.
A Scalable and Energy-Efficient Context Monitoring Framework for Mobile Personal Sensor Networks
Seungwoo Kang,Jinwon Lee,Hyukjae Jang,Youngki Lee,Souneil Park,Junehwa Song IEEE 2010 IEEE transactions on mobile computing Vol.9 No.5
<P>The key feature of many emerging pervasive computing applications is to proactively provide services to mobile individuals. One major challenge in providing users with proactive services lies in continuously monitoring users' context based on numerous sensors in their PAN/BAN environments. The context monitoring in such environments imposes heavy workloads on mobile devices and sensor nodes with limited computing and battery power. We present SeeMon, a scalable and energy-efficient context monitoring framework for sensor-rich, resource-limited mobile environments. Running on a personal mobile device, SeeMon effectively performs context monitoring involving numerous sensors and applications. On top of SeeMon, multiple applications on the mobile device can proactively understand users' contexts and react appropriately. This paper proposes a novel context monitoring approach that provides efficient processing and sensor control mechanisms. We implement and test a prototype system on two mobile devices: a UMPC and a wearable device with a diverse set of sensors. Example applications are also developed based on the implemented system. Experimental results show that SeeMon achieves a high level of scalability and energy efficiency.</P>
Seungwoo Sim,Seungho Kang,Sang-Hee Lee 한국응용곤충학회 2013 한국응용곤충학회 학술대회논문집 Vol.2013 No.04
In the real world, most of biological systems that follow Markov process have internal states which are unobservable, so called hidden states. However, although the states could not be directly observed, events emitted under any hidden states would often be observable. It infers that a lot of biological systems might be simulated by hidden Markov model (HMM). To date, many studies tried to apply the HMM for monitoring and describing of animal behaviors. In this study, we attempted to build a HMM that emulates the traveling behavior of subterranean termites in the artificial tunnels with varying width and curvature, based on the empirical data obtained from our previous study that explored the relationship between subterranean termite's movement efficiency and the geometric pattern of their tunnels.
Trace element analysis of three tissues from Eurasian otters (Lutra lutra) in South Korea.
Kang, Sukmo,Kang, Jung-Hoon,Kim, Soohee,Lee, Seung Heon,Lee, Seungwoo,Yu, Hee Jeong,Oh, Su-Jun,Park, Jung-Duck,Nam, Ki-Hoan,Han, Sung Yong,Lim, Jong-Deock,Ryu, Doug-Young Chapman Hall ; Kluwer Academic Publishers 2015 Ecotoxicology Vol.24 No.5
<P>Eurasian otters (Lutra lutra) are endangered worldwide, but the specific cause of their decline has not been determined. This study analyzed the concentrations of potentially toxic trace elements, including As, Cd, Pb, Hg, Se, Cu, Mn, and Zn, in the liver, kidney, and lung tissues of Eurasian otters in South Korea. There were high individual variations in the tissue concentrations of all the elements analyzed. The kidneys had the highest concentrations of Cd and Se among the three tissue groups, and the livers had the highest concentrations of Cu, Mn, Zn, and Hg. The Pb and As concentrations in the livers were not significantly different from those in the kidneys, and the lungs had the lowest concentrations of all the elements analyzed. The age-related bioaccumulation of Cd and Hg was evident in the three tissue groups, and of Se in the kidneys. The Pb concentration was higher in the livers of juveniles compared with those of adults and the Zn concentration was higher in the lungs of juveniles. There were no apparent gender differences in the concentrations of the elements analyzed among the tissue groups. The Se concentration correlated with the Hg concentration in the livers and kidneys, and with the Cd concentration in the kidneys. The Hg and Cd levels correlated in the three tissue groups. The Cu and Zn levels also correlated in the livers and kidneys. In general, the element concentrations were within the ranges reported by previous studies of this species from European countries, except for Cd and Hg, the levels of which were mostly lower than those reported previously. These findings may provide baseline information to facilitate the conservation of the Eurasian otter. To the best of our knowledge, this is the first available study of trace element concentrations in the tissues of Eurasian otters from South Korea or Asian countries.</P>
결측치 영향에 강인한 특성을 갖는 이미지화 기법 기반의 시계열 예측 모델
강승우(Seungwoo Kang),조오현(Ohyun Jo) 한국통신학회 2021 한국통신학회 학술대회논문집 Vol.2021 No.11
실시간 감염병 전파 예측 문제나 금융현상과 같은 응용 서비스에 시계열 예측 모델들이 적용됨으로써 예측 정확도가 향상되어 활용도가 높아지고 있으며, 최근 ARIMA, DNN, LSTM과 같은 예측 기법을 이용해 데이터를 처리하기 위한 최적 모델연구가 활발해지고 있다. LSTM은 이 중에서도 시계열 예측에 매우 적합하다는 평을 많이 받고 있는 모델이다. 그러나, 연속성이라는 특성을 가진 시계열 데이터에서 결측치가 발생하면 모델 학습에 치명적인 문제가 발생할 수 있다. 본 논문에서는 이러한 문제를 최소화하기 위해 CNN 기반 시계열 예측 모델과 시계열 데이터 이미지화 방법을 제안한다. 제안하는 이미지화 방법은 짧은 시계열 구간의 데이터 셋을 사용하여 결측치에 대한 영향을 감소시키고 관련 데이터를 사용해 정확도를 보강한다. 성능 평가를 위해 LSTM기반 모델과의 비교 실험을 진행하며, 해당 문제를 해결하면서 학습 정확도 뿐만아니라 학습시간 측면에서도 제안 학습 모델이 더 우수함을 보였다.
고고도 장기체공 무인기 적용을 위한 다단 터보차저 가솔린 엔진 시스템 시뮬레이션
강승우(Seungwoo Kang),배충식(Choongsik Bae),임병준(Byeungjun Lim) 한국추진공학회 2018 한국추진공학회 학술대회논문집 Vol.2018 No.5
고고도 장기체공 무인기의 추진 시스템에 적합성을 평가하기 위하여 다단 터보차저 가솔린 왕복기관 시스템의 성능 시뮬레이션을 진행하였다. Ricardo사의 1-D 엔진 시뮬레이션 WAVE를 사용하여 다단터보차저를 포함한 엔진 시스템을 모델링하였다. 엔진 모델은 양산 2.4L 가솔린 4기통 엔진의 제원을 반영하였다. 터보차저 모델에는 상용 터보차저의 성능 맵을 적용하였다. 고도 60,000ft에서 엔진의 적정흡기 압력을 확보하기 위해 3단 터보차저 및 인터쿨러를 구성하였다. 웨이스트 게이트는 하나로 구성하였다. 이를 통해 지상부터 고고도까지의 엔진 시스템 정상 상태 운전성을 평가하였다. This study conducted a simulation for performance of multi-turbocharged gasoline internal combustion engine for high-altitude long endurance unmanned aerial vehicle(HALE UAV) was conducted. The WAVE 1-D engine simulation software from Ricardo was used for engine system modeling and simulation. The specifications of 2.4L 4-cylinder gasoline engine from commercial vehicle and maps of commercial vehicle turbochargers were applied to the multi-stage turbocharged engine system model. Three turbochargers and intercoolers were installed in series for the appropriate intake pressure for gasoline engine at high altitude of 60,000ft. There were one wastegate for the turbochargers. The operability of the engine system were analysed with this simulation model.