• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.11a
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• pp.367-370
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• 2006

The ballistic range has long been employed in a variety of engineering fields such as high-velocity impact engineering, projectile aerodynamics, creation of new materials, etc, since it can create an extremely high-pressure state in very short time. Two-stage light gas gun is being employed most extensively. The present experimental study has been conducted to develop a new type of ballistic range which can easily perform a projectile simulation. The ballistic range consists of a high-pressure tube, piston, pump tube, shock tube and launch tube. The experiment is conducted to find out the dependence of various parameters on the projectile velocity. The pressure in high-pressure tube, pressure of diaphragm rupture and projectile mass are varied to obtain various projectile velocities. This study also addresses the effect of the presence of a shock tube located between the pump tube and launch tube on system study. The experimental results are compared with those obtained through an author's theoretical study.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.9 no.3
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• pp.20-29
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• 2010

The variable message sign(VMS) is a representative traffic information service medium which has the largest users and is provided and operated by a governmental agency. In this paper, we focused on psychological responses of individuals who use VMS traffic information in the light of the need for VMS to provide user-oriented service. A total of t재 scenarios were plotted to conduct our experiment on a virtual test track. A stress index analysis on VMS location, the first scenario, showed the lowest stress value at the point of 1.5 kilometers before the exit. A stress index analysis on the contents of VMS information (communication, time, and speed), the second scenario, showed the lowest stress value at time information.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.11 no.1
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• pp.13-27
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• 2012

According to the development of Intelligent Transportation System technology, VMS(Variable Message Signs) are operating on highway. But, VMS display information which don't reflect traffic condition and driver's human factor. So driver can't read VMS message during limited time, it makes to reduce VMS's reliability. This paper presents a model for VMS message reading time and distance considering traffic condition and human factor. We built driving simulator by Winroad package which is able to copy real driving condition. Subjects were comprised of 20 people who reflect domestic driver's condition such as sex. We did regression analysis with experiment results and draw the model. The model could be possible to develop message- set considering traffic condition and human factor.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.6 s.336
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• pp.53-60
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• 2005

Considerable efforts has been recently devoted to the determination of accurate channel models for the power line environment, both for the indoor and outdoor cases. The common limitation of the known and previously published models is the particular type of approach followed. This paper is concerned with a power line channel characteristic measurement for the more fast and efficiently power line communication experiment. The need arises from the fact that indoor power cables consist of conductors and inductors. A capacitive load simulator is a essential equipment in the power line modem development for indoor power line network. We accomplished a channel data base by the frequency response method about the total 224 capacitor load cases. On the basis of this measurement modeling it is here revealed that the power line communication channel is a more deterministic media.

• Journal of the Korean Solar Energy Society
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• v.34 no.4
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• pp.123-129
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• 2014

Photovoltaic and fuel cell systems can be used as power source in mobile robots. At this time the photovoltaic system generally generate power in daytime. The starting time of fuel cell is slower than the lithium battery. To compensate for these disadvantages, a battery charge-discharge system is used. Especially the bi-directional converter is used mainly in the charge-discharge method. The controller in a buck converter controls the input voltage of the converter to meet the maximum power point tracking(MPPT) performance. First of all, the simulations of hybrid system for battery charge-discharge system in each step simulated using solar and fuel cell modeling as input source in PSIM. Experiment of the buck and bi-directional converter system is conducted through using photovoltaic/fuel cel simulator(pCube) instead of solar and fuel cell. This hybrid system for battery charge discharge using photovoltaic/fuel cell generates emergency power for the communication system in mobile robot.

• Journal of the Korean Geotechnical Society
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• v.30 no.9
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• pp.67-75
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• 2014

Methane gas hydrate which is considered energy source for the next generation has an urgent need to develop reliable numerical simulator for coupled THM phenomena in the porous media, to minimize problems arising during the production and optimize production procedures. International collaborations to improve previous numerical codes are in progress, but they still have mismatch in the predicted value and unstable convergence. In this paper, FEM code for fully coupled THM phenomena is developed to analyze methane hydrate dissociation in the porous media. Coupled partial differential equations are derived from four mass balance equations (methane hydrate, soil, water, and hydrate gas), energy balance equation, and force equilibrium equation. Five main variables (displacement, gas saturation, fluid pressure, temperature, and hydrate saturation) are chosen to give higher numerical convergence through trial combinations of variables, and they can analyze the whole region of a phase change in hydrate bearing porous media. The kinetic model is used to predict dissociation of methane hydrate. Developed THM FEM code is applied to the comparative study on a Masuda's laboratory experiment for the hydrate production, and verified for the stability and convergence.

• Journal of Hydrogen and New Energy
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• v.18 no.2
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• pp.109-115
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• 2007

Solar energy conversion to hydrogen was carried out via a two-step thermochemical water splitting using metal oxide redox pair. To simulate the solar radiation, a 7 kW short arc Xe-lamp was used. Partially reduced iron oxide and cerium oxide have the water splitting ability, respectively. So, $Fe_3O_4$ supported on $CeO_2$ was selected as the active material. $Fe_3O_4/CeO_2$(20 wt/80 wt%) was prepared by impregnation method, then the active material was washcoated on the ceramic honeycomb monolith made of mullite and cordierite. Oxygen was released at the reduction step($1673{\sim}1823\;K$) and hydrogen was produced from water at lower temperature($873{\sim}1273\;K$). The result demonstrate the possibility of the 2-step thermochemical water splitting hydrogen production by the active material washcoated monolith. And hydrogen and oxygen was produced separately without any separation process in a monolith installed reactor. But the SEM and EDX analysis results revealed that the support used in this experiment is not suitable due to the thermal instability and coating material migration.

• The Journal of the Korea institute of electronic communication sciences
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• v.12 no.6
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• pp.1049-1056
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• 2017

In this paper, a microstrip-fed dual-band monopole antenna with two arc-shaped lines for WLAN(: Wireless Local Area Networks) applications was designed, fabricated and measured. The proposed antenna is based on a microstrip-fed structure, and composed of two arc-shaped lines and then designed in order to get dual band characteristics. We used the simulator, Ansoft's High Frequency Structure Simulator(: HFSS) and carried out simulation about parameters L2, L5, and with/without slit to get the optimized parameters. The proposed antenna is made of $13.0{\times}34.0{\times}1.0 mm^3$ and is fabricated on the permittivity 4.4 FR-4 substrate($12.0{\times}34.0{\times}1.0mm^3$). The experiment results are shown that the proposed antenna obtained the -10 dB impedance bandwidth 360 MHz (2.29~2.65 GHz) and 1,245 MHz (4.705~5.95 GHz) covering the WLAN bands. Also, the measured gain and radiation patterns characteristics of the proposed antenna are presented at required dual-band(2.4 GHz band/5.0 GHz band), respectively.

• Journal of the Ergonomics Society of Korea
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• v.34 no.1
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• pp.75-83
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• 2015

Objective: The aim of this study is to suggest the standard of the direction sign on the pendant switch of overhead cranes which can reduce human errors in control. Background: A great number of crane accidents occur in industries. One of the major causes of the accidents is the mistake in the control of cranes by confusing the orientation of crane movements. Nevertheless, three different direction sign styles, 'East, West, South, North (EWSN)', 'Forward, Backward, Left, Right (FBLR)', and arrows for four directions are used without standardization. Method: An overhead crane simulator was installed for a laboratory experiment. It could move along six directions by the control of a pendant switch. 90 participants were evenly assigned to the three different conditions of direction sign styles. The participants were asked to control the pendant switch according to the continuously appearing 16 direction signs on a monitor ahead. The participants were allowed to refer an orientation sign board on the ceiling representing correct movement directions of the overhead crane simulator. Results: The direction sign style, 'EWSN', showed statistically significant better performance in task completion time and number of errors than the other sign styles. The direction sign style, 'EWSN', adopting the cardinal direction system, made the participants clear in direction controls after customizing to the crane movements. However, the direction sign styles, 'FBLR' and the arrows adopting the relative direction system made conflicts in direction controls due to the egocentric view of human. Conclusion: The direction sign style, 'EWSN', is the most appropriate for the standardization of the direction sign on the pendant switch of overhead cranes. Application: The results of this study can be applied to the standardization of direction sign in the legal notification on the safety certifications of crane manufacturing.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.2
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• pp.268-275
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• 2014

In this paper, a dual-band circular ring monopole antenna with stub and ground slot for WLAN(Wireless Local Area Networks)/WiMAX(World interoperability for Microwave Access) applications. The proposed antenna is based on a planar monopole design, and composed of one circular ring of radiating patch, cross strip in circular ring, modified feed line, and two rectangular slot in the ground plane for triple-band operation. To obtain the optimized parameters, we used the simulator, Ansoft's High Frequency Structure Simulator(HFSS) and found the parameters that greatly effect antenna characteristics. Using the obtained parameters, the antenna is fabricated. The numerical and experiment results demonstrated that the proposed antenna satisfied the -10 dB impedance bandwidth requirement while simultaneously covering the WLAN and WiMAX bands. And characteristics of gain and radiation patterns are determined for WLAN/WiMAX application.