• Journal of the korean Society of Automotive Engineers
• /
• v.10 no.4
• /
• 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
• /
• v.7 no.2
• /
• 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
• /
• v.35 no.3
• /
• 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
• /
• v.20 no.9
• /
• 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
• /
• v.46 no.1
• /
• 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.

• Journal of the Korean Geographical Society
• /
• v.47 no.4
• /
• pp.606-624
• /
• 2012

The main objective of this paper is to provide an adequate and comprehensive review of what has been done in South Korea in the field of geospatial analysis and modeling. This review focuses on spatial data analysis and spatial statistics, spatial optimization, and geosimulation among various aspects of the field. It is recognized that geospatial analysis and modeling in South Korea got through the initial stage during the 1990s when computer and analytical cartography and GIS were introduced, moved to the growth stage during the first decade of the $21^{st}$ century when there was a surge of relevant researches, and now is heading for its maturity stage. In spatial data analysis and spatial statistics, various topics have been addressed for spatial point pattern data, areal data, geostatistical data, and spatial interaction data. In spatial optimization, modeling and applications related to facility location problems, districting problems, and routing problems have been mostly researched. Finally, in geosimulation, while most of research has focused on cellular automata, studies on agent-based model and simulation are in beginning stage. Among all these works, some have fostered methodological advances beyond simple applications of the standard techniques.

• Korean Institute of Interior Design Journal
• /
• v.27 no.3
• /
• 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.

• The Journal of the Korea Contents Association
• /
• v.10 no.10
• /
• pp.120-127
• /
• 2010

Today we always can take a picture and enjoy it anywhere and anytime with a propagation of digital camera and camera phone. Even though the amount of digital picture content produced in every day life has been increasing, the way of enjoying it was just with phones or PC monitors. A small size screen of a cell phone and a desktop monitor are not suitable environment for enjoying digital picture, so the new market for digital photo frame has been opened. Until now, various kind of digital photo frames of many manufactures have been released for several years, but they have similar interaction way each other due to the limitation of their hardware specification so don't fill the intuitive mental model that users have about the product called a photo frame. Thus, this research aims to suggest an interaction way of digital photo frame providing with better usability and emotional satisfaction according to the spatial environment that it's located and users' behaviors.

• Journal of Korean Society of Transportation
• /
• v.32 no.4
• /
• pp.357-368
• /
• 2014

So far, land use-transportation models have been used exclusively for numerical analysis. A recent theoretical endeavor now enables us to derive the first-order derivative of the model's welfare function with respect to policy variables. I extend this methodology into the institutional setting where toll revenues are recycled through labor income tax. In this setting, the first-order derivative is composed of (1) the increase in welfare due to reduced congestion, and (2) the decrease in welfare due to interaction with the existing labor income tax. This result coincides with existing theory in the non-spatial model.

• Ecology and Resilient Infrastructure
• /
• v.1 no.1
• /
• pp.1-7
• /
• 2014

In this study, a numerical simulation technique for coastal area where wave and current interactions are observed is proposed. Considering the spatial scale of coastal area and the coastal processes such as wave, current, shoaling, wave breaking, and inundation processes, boussinesq equation model is used. A depth-integrated transport model based on the consistent assumption with the boussinesq equation model is used for the prediction of solute transport. To solve the equations, finite volume method with an approximate riemann solver is used. The proposed model is applied to a coastal area and reasonable computational results are obtained.