• Advances in Computational Design
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• v.5 no.3
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• pp.261-276
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• 2020

The reasonable layout of vacuum cleaner can effectively improve the collection efficiency of iron filings generated in the process of steel production. Therefore, in this study, the CFD-DEM coupling model and two-fluid model are used to calculate the iron filings collection efficiency of vacuum cleaner with different inclination/cross-sectional area, pressure drop and inlet angle. The results are as follows: The CFD-DEM coupling method can truly reflect the motion mode of iron filings in pneumatic conveying. Considering the instability and the decline of the growth rate of iron filings collection efficiency caused by high pressure drop, the layout of 75° inclination is suggested, and the optimal pressure drop is 100Pa. The optimal simulation results based on two-fluid model show that when the inlet angle and pressure drop are in the range of 45°~65° and 70Pa~100Pa, larger mass flow rate of iron filings can be obtained. It is hoped that the simulation results can offer some suggestion to the layout of vacuum cleaner in the rolling mill.

• Current Optics and Photonics
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• v.1 no.2
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• pp.101-106
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• 2017

Optical structures of a tapered ultra-thin light guide film (LGF) were optimized by optical simulation for increasing coupling efficiency between light sources and the LGF. A serration pattern on the entrance side surface could provide a comparable coupling efficiency to that of the conventional LGF where a linear, asymmetric prism array was formed on the taper surface. Several micro-patterns were applied to the top and/or bottom surface of the LGF for achieving better luminance property, and it was found that an optimized micro-pyramid pattern exhibited the highest average luminance together with satisfactory luminance uniformity.

• Korean Institute of Interior Design Journal
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• v.21 no.5
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• pp.106-113
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• 2012

A study on techniques to evaluate auditorium assignment visible efficiency using three-dimensional simulation. The most important thing to be considered is to ensure the visibility to the podium upon assigning auditorium of venues, classrooms or seminar rooms. However, since there are so many variables to be considered such as the form of the stage, the area and height of the stage, size of screen, and the distance and angle of the auditorium from the podium, the methods to assign auditorium are staying at the level of basic for a long time. Thus, in this study, we proposed simulation methodology to quantitatively evaluate the three-dimensional visible efficiency based on Visual Graph Analysis (VGA) theory. After analytical methodology manufactures application, it sets examples of visibility depending on location of screen, visibility depending on degree of height difference and visibility about three-dimensional Mass Zoning like a stage and verifies the efficacy. In addition, based on results, visibility expectation curve is drawn and the method to calculate the stepped height depending on necessary visibility is proposed.

• KIEAE Journal
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• v.15 no.4
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• pp.5-11
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• 2015

Purpose: Recently, renewable energy system has been widely used to reduce the energy consumption and CO2 emission of building. A photovoltaic/thermal(PVT) system is a kind of efficient energy uses, which is combined with photovoltaic module and solar thermal collector. PVT system removes heat from PV module by through thermal fluid to raise the performance efficiency of the PV system. However, though PVT system has the merit of the improved efficiency in theoretical approach, there have been few performance analysis for PVT system using the dynamic energy simulation. In this study, in order to establish the optimum design method of this system, simulation was conducted by using individual system modules. Method: For the dynamic simulation, TRNSYS17 was used and local weather data was utilized. Furthermore, the system performance in various installation condition was calculated by case studies. Result: As a result, the amount of electric generation and heat production in each case was found by the simulation. The gap of system performance was also evident according to the installation condition.

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.2
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• pp.94-110
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• 1997

In the present study, a mean torque predictive model has been proposed and experimentally validated. It includes induction air mass model, fuel delivery model and mean production mode. Air induction and fuel delivery model considering dynamic behaviors of air induction and fuel delivery were proposed to predict the air-fuel ratio excursions under transient condition. Torque function model reflects thermal efficiency, volumetric efficiency, friction and effect of spark timing. In the spark timing model, knock limit and acceleration retard are included. Experiments were carried out to validate the simulation model for the step changes of throttle at constant engine speed. The results show reasonable agreements between simulation and experiment at fully warmed condition. Using this model, fueling strategies are varied with fast throttle open and it can predict air-fuel ratio excursion and IMEP.

• Journal of the Korea Society for Simulation
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• v.14 no.3
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• pp.129-136
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• 2005

We develop a variance reduction technique applicable in one simulation experiment whose purpose is to estimate the parameters of a first order linear model. This method utilizes the control variates obtained during the course of simulation run under Schruben and Margolin's method (S-M method). The performance of this method is shown to be similar in estimating the main effects, and to be superior to S-M method in estimating the overall mean response in a given model. We consider that a proposed method may yield a better result than S-M method if selected control variates are highly correlated with the response at each design point.

• Journal of Electrical Engineering and Technology
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• v.12 no.5
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• pp.1891-1901
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• 2017

In this paper, optimal control of the fuel cell and design of a high-efficiency power converter is implemented to build a high-priced fuel cell system with minimum capacity. Conventional power converter devices use a non-isolated boost converter for high efficiency while the battery is charged, and reduce its conduction loss by using MOSFETs instead of diodes. However, the efficiency of the boost converter decreases, since overshoot occurs because there is a moment when the body diode of the MOSFET is conducted during the dead time and huge loss occurs when the dead time for the maximum-power-flowing state is used in the low-power-flowing state. The method proposed in this paper is to adjust the dead time of boost and rectifier switches by predicting the power flow to meet the maximum efficiency in every load condition. After analyzing parasite components, the stability and efficiency of the high-efficiency boost converter is improved by predictive compensation of the delay component of each part, and it is proven by simulation and experience. The variation in switching delay times of each switch of the full-bridge converter is compensated by falling time compensation, a control method of PWM, and it is also proven by simulation and experience.

• Journal of Drive and Control
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• v.17 no.2
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• pp.19-27
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• 2020

The purpose of this study was to suggest design criteria for the HMT (hydro-mechanical transmission) of a 55 kW-class agricultural tractor, develop a simulation model, and evaluate its performance such as axle rotational speed, tractor speed, and power transmission efficiency. In this study, the HMT comprised a compound planetary gear and a HSU (hydro-static unit), and the compound planetary gear comprised two planetary gear sets. The HMT has three gear stages, and the maximum tractor speed was selected as 40 km/h. The simulation time was set at 2736 hours considering the lifetime of the tractor, and the simulation was performed for each gear stage at the engine-rated power conditions. As a result of the simulation, the axle rotational speeds for each gear stage were 39, 77, and 158 rpm, respectively. The range of tractor speed for each gear stage were 1.05-10.22 km/h, 10.74-20.17 km/h, and 20.70-41.40 km/h, respectively. The APE (absolute percentage gear) for the tractor's maximum speed between target value and simulation results were 2.20%, 0.85%, and 3.50%, respectively. Also, the power transmission efficiency for each gear stage were 0-75%, 72-81%, and 69-81%, respectively. The simulation results for the power transmission efficiency of the HMT were similar with the results of the previous research. This was a basic study on the development of the HMT for an agricultural tractor. In future studies, it is necessary to develop a tractor platform and evaluate the performance. The comparison between the simulation model and the HMT tractor should be performed.

• Journal of Biosystems Engineering
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• v.38 no.1
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• pp.33-40
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• 2013

Purpose: The goal of this study was to build an accurate digital factory that evaluates the performance of a factory using computer simulation. To achieve this goal, we evaluated the effect of worker-related variables on production in a simulation model using comparative analysis of two cases. Methods: The overall work process and worker-related variables were determined and used to build a simulation model. Siemens PLM Software's Plant Simulation was used to build a simulation model. Also, two simulation models were built, where the only difference was the use of the worker-related variable, and the total daily production analyzed and compared in terms of the individual process. Additionally, worker efficiency was evaluated based on worker analysis. Results: When the daily production of the two models were compared, a 0.16% error rate was observed for the model where the worker-related variables were applied and error rate was approximately 5.35% for the model where the worker-related variables were not applied. In addition, the production in the individual processes showed lower error rate in the model that included the worker-related variables than the model where the worker-related variables were not used. Also, among the total of 22 workers, only three workers satisfied the IFRS (International Financial Reporting Standards) suggested worker capacity rate (90%). Conclusions: In the daily total production and individual process production, the model that included the worker-related variables produced results that were closer to the real production values. This result indicates the importance of worker elements as input variables, in regards to building accurate simulation models. Also, as suggested in this study, the model that included the worker-related variables can be utilized to analyze in more detail actual production. The results from this study are expected to be utilized to improve the work process and worker efficiency.

• Land and Housing Review
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• v.15 no.2
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• pp.73-87
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• 2024

To evaluate the efficiency of commuting patterns, various commuting indicators such as excess commute and commuting potential utilized have been developed and used. It is crucial to calculate these indicators reasonably to reveal the differences in commuting patterns among metropolitan areas and to consider these in the process of formulating commuting policies. However, commuting indicators are generally calculated at the administrative district level, and thus, they are not free from the problem of the modifiable areal unit problem (MAUP). This issue can undermine the rationality of comparing commuting efficiency between metropolitan areas, making it necessary to handle the calculation of commuting indicators carefully. Therefore, this study utilises Monte Carlo Simulation to calculate optimal, actual, and maximum commuting distances, and thereby presents the excess commute and the commuting potential utilized. To apply Monte Carlo Simulation to the context of South Korea, a constrained Monte Carlo Simulation is conducted, where residential and workplace locations used in the simulation are selected based on the actual locations of buildings. The analysis is conducted on 13 metropolitan areas with established metropolitan plans using the 2016 Household Travel Survey data. The commuting indicators calculated through the simulation showed minimal differences compared to the results obtained through conventional methods. The comparison of commuting efficiency among metropolitan areas revealed that even if the degree of spafial balance between residential and workplace locations is similar, the actual commuting patterns can differ significantly. It is suggested that further research considering characteristics such as the area of each metropolitan region will be necessary in the future.