• 오토저널
• /
• 제10권4호
• /
• pp.39-56
• /
• 1988

In this study, the computer program was developed to predict the engine performances and exhaust emissions of a 4-cylinder 4-stroke cycle ignition engine including intake and exhaust system. The simulation models applied to each process were as follows. For the combustion process, two zone model which requires only one empirical constant was applied, and for the gas exchange process, the method of characteristics that allows the calculations of the time variation and spatial variation of properties along the pipes was used. Constant pressure perfect mixing model was applied to take into account of the interaction at manifold branches. To predict exhaust emissions, twelve chemical species were considered to be present in combustion products. These species were calculated through equilibrium thermodynamics and kinetic theory. The empirical constants reduced to least number as possible were determined through the comparison with the experimental indicator diagram of one particular operating condition and these constants were applied to other operating conditions. The predicted performances and emissions were compared with the experimental results over the wide range of operating conditions.

• International Journal of Automotive Technology
• /
• 제7권2호
• /
• pp.129-137
• /
• 2006

The representative interactive flamelet(RIF) concept has been applied to numerically simulate the combustion processes and pollutant formation in the HSDI diesel engine. In order to account for the spatial inhomogeneity of the scalar dissipation rate, the eulerian particle flamelet model using the multiple flamelets has been employed. The vaporization effects on turbulence-chemistry interaction are included in the present RIF procedure. the results of numerical modeling using the rif concept are compared with experimental data and with numerical results of the widely-used ad-hoc combustion model. Numerical results indicate that the rif approach including the vaporization effect on turbulent spray combustion process successfully predicts the ignition delay characteristics as well as the pollutant formation in the HSDI diesel engines.

• Structural Engineering and Mechanics
• /
• 제35권3호
• /
• pp.365-377
• /
• 2010

In the present article, effect of non-uniform excitation due to spatially variation of seismic input on nonlinear response of concrete gravity dams is considered. The reservoir is assumed compressible. Isotropic damage mechanics approach is used to model static and dynamic nonlinear behavior of mass concrete in 2D space. The validity of utilized nonlinear model is considered using available theoretical results under static and dynamic conditions. The tallest monolith of Pine Flat dam is selected as a case study. Two cases are analyzed for considering the effect of limited wave propagation velocity on seismic behavior of the dam-reservoir system in which travelling velocities are chosen as 2000 m/s and infinity. It is found that tensile damage in neck and toe regions and also, in the vicinity of the base increase when the system is excited non-uniformly.

• Journal of Mechanical Science and Technology
• /
• 제20권9호
• /
• pp.1459-1474
• /
• 2006

The present study is focused on the development of the RIF (Representative Interactive Flamelet) model which can overcome the shortcomings of conventional approach based on the steady flamelet library. Due to the ability for interactively describing the transient behaviors of local flame structures with CFD solver, the RIF model can effectively account for the detailed mechanisms of $NO_x$ formation including thermal NO path, prompt and nitrous $NO_x$ formation, and reburning process by hydrocarbon radical without any ad-hoc procedure. The flamelet time of RIFs within a stationary turbulent flame may be thought to be Lagrangian flight time. In context with the RIF approach, this study adopts the Eulerian Particle Flamelet Model (EPFM) with mutiple flamelets which can realistically account for the spatial inhomogeneity of scalar dissipation rate. In order to systematically evaluate the capability of Eulerian particle flamelet model to predict the precise flame structure and NO formation in the multi-dimensional elliptic flames, two methanol bluffbody flames with two different injection velocities are chosen as the validation cases. Numerical results suggest that the present EPFM model has the predicative capability to realistically capture the essential features of flame structure and $NO_x$ formation in the bluff-body stabilized flames.

• ETRI Journal
• /
• 제46권1호
• /
• pp.22-34
• /
• 2024

Exposure to varied noisy environments impairs the recognition performance of artificial intelligence-based speech recognition technologies. Degraded-performance services can be utilized as limited systems that assure good performance in certain environments, but impair the general quality of speech recognition services. This study introduces an audiovisual speech recognition (AVSR) model robust to various noise settings, mimicking human dialogue recognition elements. The model converts word embeddings and log-Mel spectrograms into feature vectors for audio recognition. A dense spatial-temporal convolutional neural network model extracts features from log-Mel spectrograms, transformed for visual-based recognition. This approach exhibits improved aural and visual recognition capabilities. We assess the signal-to-noise ratio in nine synthesized noise environments, with the proposed model exhibiting lower average error rates. The error rate for the AVSR model using a three-feature multi-fusion method is 1.711%, compared to the general 3.939% rate. This model is applicable in noise-affected environments owing to its enhanced stability and recognition rate.

• 대한지리학회지
• /
• 제47권4호
• /
• pp.606-624
• /
• 2012

이 논문의 연구 목적은 한국 지리학계에서 이루어진 지리공간분석 및 모델링 분야의 연구를 개관하는 것이다. 여기에서 지리공간분석과 모델링이라는 분야는 공간데이터분석 및 공간통계학, 공간최적화, 지오시뮬레이션 관련 연구를 의미하는 것으로 한정한다. 한국의 지리공간분석과 모델링 분야는 컴퓨터 혹은 분석 지도학과 GIS가 도입된 1990년대의 초기 단계를 거쳐, 관련 연구 논문이 쏟아진 2000년대의 성장 단계로 이행했으며, 현재 성숙 단계를 향해 진화하고 있다. 공간데이터분석과 공간통계학 분야에서는 공간적 포인트 패턴 데이터, 에이리어 데이터, 지구통계학적 데이터, 공간적 상호작용 데이터에 대한 다양한 연구가 이루어져 왔다. 공간최적화 분야에서는 시설물 입지문제, 구획문제, 경로설정 문제 등에 대한 모델의 개발 및 적용과 관련된 연구가 활발하게 진행되어 왔다. 지오시뮬레이션 분야에서는 셀룰라 오토마타와 관련된 연구가 대부분을 차지하고 있는 것에 비하여, 에이전트 기반 모델링은 이제 시작단계에 있다. 이 모든 연구 성과들 중 몇몇은 표준 기법의 단순한 적용을 넘어 방법론적 진보를 이끌어 낸 것으로 평가된다.

• 한국실내디자인학회논문집
• /
• 제27권3호
• /
• pp.14-23
• /
• 2018

The spatial planning of the elderly care facility plans is analyzed using space syntax in terms of encouraging the social interaction of the residents in this study. First, through the visibility graph analysis, openness and accessibility of space is analysed. Second, the walking behavior of residents through agent analysis model is simulated. Third, the space planning methods for the elderly care facilities are proposed based on the results. The results are as follows. According to the visibility graph analysis, the main corridor has high visual openness and high accessibility. The visual openness and accessibility of the unit living room, where social interaction among residents is possible in each unit, is low. Space planning is needed to increase direct protection and observation of employees to the unit living room. The location of the nurse station that manages the entire floor needs to be located where the openness and accessibility is most high. The nursing station should have a high degree of connectivity to the entire space, so that any accidents can be managed and contact is accessible. Through the agent simulation the flow from the center to each unit space is highest in the corridor space and the inflow to the private rooms and the living room are similar. Therefore, it is necessary to plan the accessibility of the unit living room more for the natural inflow of residents.

• 대한교통학회지
• /
• 제32권4호
• /
• pp.357-368
• /
• 2014

지금까지 토지이용-교통모형은 전적으로 수치해석적 분석도구로만 이용되어 왔는데, 최근 이론개발 노력의 결과 정책변수에 대한 후생함수의 1계 도함수 간편식을 구할 수 있게 되었다. 본 논문은 혼잡통행료가 소득세 경감을 통해 재순환될 때 혼잡통행료의 변화에 대한 후생함수의 도함수를 어떻게 유도할 수 있는지 보여준다. 분석결과 혼잡통행료의 부과가 가져오는 후생변화분을 (1)혼잡의 완화로 인한 후생증가분과 (2)노동공급과의 상호작용에서 발생하는 후생손실로 분해할 수 있다. 이 결과는 기존의 연구결과와 일치한다.

• Ecology and Resilient Infrastructure
• /
• 제1권1호
• /
• pp.1-7
• /
• 2014

본 연구에서는 파랑과 흐름이 공존하고 있는 해안지역에 이용이 가능한 물에 용해된 물질의 정확한 이동을 예측하기 위한 수심적분형 수치모의 기법을 제시한다. 대상 영역에 일반적으로 발생하는 파랑의 전파와 변형 과정 및 쇄파와 흐름의 발달 과정에 대한 모의가 가능한 boussinesq equation 흐름모형과 동일한 과정을 거쳐 유도된 수심적분형 물질수송모형을 지배방정식으로 이용한다. 지배방정식은 approximate riemann solver를 이용하는 유한체적법을 이용하여 해석한다. 제시된 수치모형을 이용하여 해일발생에 의한 흐름양상을 계측한 실험을 재현하였으며, 해당 수역에 가상의 물질의 이송과 확산에 대한 수치모의를 수행하고 그 결과를 분석하였다.

• Nuclear Engineering and Technology
• /
• 제53권1호
• /
• pp.244-252
• /
• 2021

Wind plays an important role in cases of unexpected radioactive pollutant dispersion, deciding distribution and concentration of the leaked substance. The accurate prediction of wind has been challenging in numerical weather prediction models, especially near the surface because of the complex interaction between turbulent flow and topographic effect. In this study, we investigated the characteristics of atmospheric dispersion of radioactive material (i.e. ¹³⁷Cs) according to the simulated boundary layer around the HANARO research nuclear reactor in Korea using the Weather Research and Forecasting (WRF)-Mesoscale Model Interface (MMIF)-California Puff (CALPUFF) model system. We examined the impacts of orographic drag on wind field, stability calculation methods, and planetary boundary layer parameterizations on the dispersion of radioactive material under a radioactive leaking scenario. We found that inclusion of the orographic drag effect in the WRF model improved the wind prediction most significantly over the complex terrain area, leading the model system to estimate the radioactive concentration near the reactor more conservatively. We also emphasized the importance of the stability calculation method and employing the skillful boundary layer parameterization to ensure more accurate low atmospheric conditions, in order to simulate more feasible spatial distribution of the radioactive dispersion in leaking scenarios.