• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.22 no.3
• /
• pp.74-79
• /
• 2021

This study examined the mixing efficiency of exhaust gas and urea according to the mixer shape in the SCR system. For the experiment, an SCR simulation system was manufactured, and a uniformity detector was attached to the catalyst location to measure the uniformity. The experiment was conducted by setting the exhaust-gas flow rate, temperature, mixer type, and catalyst distance as variables. The experimental results confirmed the swirl angle analysis, urea number distribution, and uniformity. The swirl angle experiment of Models A and B confirmed that the swirl angle of Model A was formed approximately 7 to 8 degrees higher over the entire RPM range. When there was no mixer in the SCR system, the urea and water were concentrated to one side. Mixer Model A showed an even distribution overall, and Model B showed a slightly concentrated tendency at the beginning but then showed a stable distribution of urea. The mixing efficiency of 90%, which was the uniformity target, could be satisfied in Model A and Model B. In particular, Model A showed excellent results that satisfied 90% efficiency at 10 cm of the catalyst position.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.19 no.4
• /
• pp.954-964
• /
• 2015

In this research, an overlapped illumination model was newly proposed for designing a freeform LED lens with a uniform illuminance distribution on its illuminating plane. Based on the proposed model and conventional illumination models, freeform lenses were designed and their performances and tolerances were compared. As a result of the tolerance analysis about thickness change in lens, position, size change, central direction change of light emission and characteristic change in LED source. This proposed model and divergent illumination model are similar to the performance about central direction change of light emission in LED source. but the uniformity illumination value in this proposed model is more remarkably value than it in divergent illumination model about characteristic change in LED source.

• Proceeding of EDISON Challenge
• /
• 2014.03a
• /
• pp.625-630
• /
• 2014

연료전지의 성능을 결정짓는 가장 중요한 변수 중의 하나는 각 스택의 채널에 얼마나 균일하게 연료를 공급할 수 있느냐이다. 본 연구에서는 네 가지의 모델을 사용하여 연료전지 매니폴드 형상에 따른 최적 설계를 수행하였다. 위 네 가지 모델은 각기 다른 기하학적 형상을 가지며 Edison CFD를 이용하여 형상 내의 유동을 비교하였다. 초기 모델에서는, 입구부에서 매니폴드로 유입되는 유동의 확산이 잘 일어나지 않아 각 채널의 질량유량이 불균일한 분포를 보였으며 특히 속도가 빠른 중심 영역의 채널에 많은 연료가 유입되었다. 이를 위한 디퓨져 모델링이 제안되었으며 실속이 최소한도로 발생할 때 채널당 질량유량이 가장 균일하다고 가정하였다. 이를 위해 다양한 디퓨져 각을 가진 모델을 사용했고, 이론상으로 실속이 발생하지 않는 형상에서 가장 균일한 분포를 보임을 확인하였다.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.21 no.1
• /
• pp.157-164
• /
• 2017

In this research, the overlapped illumination model was used for designing a freeform LED lens with a uniform illuminance distribution on its illuminating plane, and their performances and tolerances were compared. And, the illuminations on a illumination plane was measures for change with average illuminance and illuminance uniformity. As a result of the tolerance analysis about z-axis direction change, thickness change in lens and tilt change of light emission and characteristic change in LED source, overlapped model and divergent illumination model are similar to the performance about Z-axis direction change of light emission in LED source. but the uniformity illumination value in this overlapped model is more remarkably value than it in divergent illumination model about thickness change in LED lens. Also, even though the lens based on a divergent illumination model showed good performance compare to the lens based on an overlapped illumination model, the latter was less the deviation to variation of LED beam radiation ability.

• Journal of the Korea Society for Simulation
• /
• v.20 no.1
• /
• pp.97-105
• /
• 2011

In rivers and streams, biofilms are thin layers of greenish-brown slime attached to rocks, plants, and other surfaces. Biofilms play key roles in primary production and cycling of nutrients, water quality remediation, suspended sediment removal, and energy flow to higher trophic levels. In the present study, we developed a two-dimensional cellular automata model to simulate mixed biofilms of toxin-sensitive and toxin-producing species in hydrodynamic flow. The flow was generated by a stochastic process for uniform flow and by using the Navier-Stokes equation for non-uniform flow. Minimized local rules governing reproduction and mortality of the species were executed in the self-organizing processes to elucidate interactions between toxin-producing and toxin-sensitive species in competition over nutrients. We briefly discuss the morphology of the simulated biofilm under different flow conditions.

• Proceedings of the Korean Nuclear Society Conference
• /
• 1998.05b
• /
• pp.711-714
• /
• 1998

H$_2$$^{15}$ O PET을 이용하여 심근혈류를 측정할 때 물의 분포가 조직마다 불균일한 특성을 나타내고자 관류 가능한 조직분획(perfusable tissue index; PTI)$^{1)}$ 개념을 도입한 연구가 보고된 바 있으나 PTI로는 비균일성을 정량적으로 다루지 못하였다$^{2)}$ . 반면에 단일 구획 모델에서 분배계수(partition coefficient: λ)를 변수로 추정하여 혈류분포의 비 균일성을 나타낼 수 있음을 컴퓨터 모의실험으로 보인 연구가 있다$^{3)}$ . 이 연구에서는 이미 앞서 발표한 연구의 혈류측정 모델을 정상인 실험용 개에 적용하였으며 그 결과 혈류와 분배계수 모두가 정상 범위 안에 들어옴을 확인하였다. 또한 컴퓨터 모의실험을 통해 얻은 분배계수와 비균일성 지표인 구성비균일성(constitution heterogeneity; CH) 와의 관계를 이용하여 동물실험에서 측정한 분배계수로부터 CH를 유추해 보았다.

• Journal of Internet Computing and Services
• /
• v.5 no.4
• /
• pp.35-42
• /
• 2004

In this paper the more accurate models than any other ones so far have been proposed for the performance evaluation of single-buffered banyan-type Multistage Interconnection Networks(MINs)'s under nonuniform traffic condition is obtained. Small clock cycle instead of big clock cycle is used. The accuracy of proposed models are conformed by comparing with the results from simulation.

• Journal of Internet Computing and Services
• /
• v.5 no.5
• /
• pp.61-68
• /
• 2004

In this paper, a more accurate model than any other ones so far have been proposed for the performance evaluation of muntibuffered banyan-type Multistage Interconnection Networks(MINs)'s under nonuniform traffic condition is obtained. Small clock cycle instead of big clock cycle is used to improve the performance. The accuracy of the proposed model is conformed by comparing with the results from simulation.

• Proceedings of the KIEE Conference
• /
• 2007.10a
• /
• pp.403-404
• /
• 2007

소자 수율을 향상시키기 위해서는 웨이퍼 전체에 걸쳐 플라즈마 공정특성이 균일하게 분포되어야 한다. 본 연구에서는 Actinomeric 광 반사분광기 (Otical Emission Spectroscopy) 정보를 이용하여 식각률 비균일도에 대한 모델을 개발하였다. 제안된 기법은 Oxide 식각공정에서 수집한 데이터에 적용하였으며, 체계적인 모델링을 위해 공정데이터는 통계적 실험계획 법을 적용하여 수집되었다. 신경망의 예측성능은 유전자 알고리즘을 이용해서 증진시켰다. OES의 차수를 줄이기 위해 주인자 분석을 세 종류의 분산(100, 99, 98%)에 대해서 적용하였다. 개발된 모델은 발표된 이전의 모델에 비해 17% 증진된 예측성능을 보였다.

• The Korean Journal of Nuclear Medicine
• /
• v.32 no.1
• /
• pp.32-49
• /
• 1998

For estimation of regional myocardial blood flow with O-15 water PET, a few modifications considering partial volume effect based on single compartment model have been proposed. In this study, we attempted to quantify the degree of heterogeneity and to show the effect of tissue flow heterogeneity on partition coefficient(${\lambda}$) and to find the relation between perfusable tissue index(PTI) and ${\lambda}$ by computer simulation using two modified models. We simulated tissue curves for the regions with homogeneous and heterogeneous blood flow over a various flow range(0.2-4.0ml/g/min). Simulated heterogeneous tissue composed of 4 subregions of the same or different size of block which have different homogeneous flow and different degree of slope of distribution of blood flow. We measured the index representing heterogeneity of distribution of blood flow for each heterogeneous tissue by the constitution heterogeneity(CH). For model I, we assumed that tissue recovery coefficient ($F_{MME}$) was the product of partial volume effect($F_{MMF}$) and PTI. Using model I, PTI, flow, and $F_{MM}$ were estimated. For model II, we assumed that partition coefficient was another variable which could represent tissue characteristics of heterogeneity of flow distribution. Using model II, PTI, flow and ${\lambda}$ were estimated. For the simulated tissue with homogeneous flow, both models gave exactly the same estimates, of three parameters. For the simulated tissue with heterogeneous flow distribution, in model I, flow and $F_{MM}$ were correctly estimated as CH was increased moderately. In model II, flow and ${\lambda}$ were decreased curvi-linearly as CH was increased. The degree of underestimation of ${\lambda}$ obtained using model II, was correlated with CH. The degree of underestimation of flow was dependent on the degree of underestimation of ${\lambda}$. PTI was somewhat overestimated and did not change according to CH. We conclude that estimated ${\lambda}$ reflect the degree of tissue heterogeneity of flow distribution. We could use the degree of underestimation of ${\lambda}$ to find the characteristic heterogeneity of tissue flow and use ${\lambda}$ to recover the underestimated flow.