• Journal of the Microelectronics and Packaging Society
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• v.9 no.1
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• pp.29-33
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• 2002

The SrS:Cu, Ag thin film electroluminescient devices were fabricated on $AlTiO_3$/ITO/glass substrates by electron-beam evaporation. The emission spectrum of the device was about 460 nm with $\chi$=0.20, y=0.29 in the CIE color coordinator. It was found that the emission spectrum was saturated to pure blue color when Ag sensitizer was doped in SrS:CuCl phosphors. The luminance of the device was increased by increasing the sulfur pressure. The measured luminance was saturated with 430 cd/$m^2$at the applied voltage of 90 V and the maximum luminance was 580 cd/$m^2$at 110V. The polarization charge and conduction charge of the devices were found to be found to be about $3.5\mu$C/$\textrm{cm}^2$ and $7.4\mu$C/$\textrm{cm}^2$, respectively.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.5
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• pp.186-194
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• 2006

Traffic accident involved with the vulnerable pedestrian is one of the significant concerns, which has higher possibility of fatality than any other accident types. Worldwide significant efforts have been made to establish a vehicle safety regulation, which is internationally agreed, in order to reduce pedestrian casualties in pedestrian-vehicle collisions. One of the key issues in deriving the regulation is how to effectively select the parameter values associated with the regulation. This study firstly develops a method to optimize parameter values. An optimizing problem in terms of maximizing safety benefits, which are life-saving effects by the regulation, is formulated. Extensive actual accident data analysis and simulations are conducted to establish several statistical models to be used in the proposed optimization procedure. A set of parameter values that can produce maximizing life-saving effects is presented as the outcome of this study. It is expected that the proposed method would play a significant role in determining parameters as a decision support tool toward ensuring better pedestrian safety.

• Journal of Power Electronics
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• v.10 no.6
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• pp.647-659
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• 2010

This paper presents a part of North Africa/Europe collaboration results in education to develop project-oriented courses in power electronics and motor drive field. The course aims to teach Permanent Magnet motor drives close to a real world project of significant size and depth so as to be motivational, namely mobile robot project. Particular skills, student will acquire, are those relative to the detailed design and implementation of PM motor controllers in DSP based rapid prototyping environment. Simulation work is completed using graphical modeling tools in Simulink/Plecs, while real-time implementation is achieved by means of eZdspF2812 board and Simulink/TI C2000 Embedded Target tools. This flexible development environment fit the robot traction system very well and provides exactly the functionality necessary for an efficient PM motor drives teaching as demonstrated by a set of simulation and experiments.

• Journal of the Korean Institute of Gas
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• v.20 no.1
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• pp.23-28
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• 2016

"Eco-friendly" automobile has been a symbol of the Low Carbon, Green Growth strategy that Korea government decided to pursue. In line with the recent policy trend, a number of new LPG stations are being constructed. However, communities where mass storage are installed have been suffered from risk of serious accidents. In this work, economic analyses for different installation methods has been performed to prevent accidents in LPG filling station. The review shows that the underground storage is beneficial for the maintenance and the effective land use.

• Journal of Mechanical Science and Technology
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• v.19 no.6
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• pp.1338-1346
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• 2005

Effects of thermal contact resistance between heater and susceptor, susceptor and graphite board in a MOCVD reactor on temperature distribution and film growth rate were analyzed. One-dimensional thermal resistance model considering thermal contact resistance and heat transfer area was made up at first to find the temperature drop at the surface of graphite board. This one-dimensional model predicted the temperature drop of 18K at the board surface. Temperature distribution of a reactor wall from the three-dimensional computational fluid dynamics analysis including the gap at the wafer position showed the temperature drop of 20K. Film growth rates of InP and GaAs were predicted using computational fluid dynamics technique with chemical reaction model. Temperature distribution from the three-dimensional heat transfer calculation was used as a thermal boundary condition to the film growth rate simulations. Temperature drop due to the thermal contact resistance affected to the GaAs film growth a little but not to the InP film growth.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.5 no.5
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• pp.442-446
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• 2004

Computer simulation of a swaging manufacturing process is presented in this paper. Commercially available software has been used to develop the simulation algorithm. Based on the experience gained from trial runs, simulation of a tube swaging process has been carried out. The material parameters "n" (strain hardening exponent) and "K" (plastic modulus) are obtained from actual tensile test measurements of the tube material. Two different geometries for the die and the tube have been used in this work and a comparison made. Numerical simulation of the swaging process has been performed using the commercially available HyperMesh(r) for pre-processing, LS-DYNA(r) for analysis and LS-TAURUS(r) for post-processing. Some of the results obtained from this study are compared with those available in the literature.

• Korean Journal of Materials Research
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• v.29 no.10
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• pp.592-602
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• 2019

Feasibility is investigated for reduction of chromium ore by Si sludge with mixed silicothermic and carbothermic reaction. The reduction behavior of chromium ore using Si sludge is investigated precisely to determine the effects of carbon addition, reaction time, and reaction temperature. The pellets are dropped into the furnace after temperature stabilized. As the amount of C addition increases, the amounts of CO and $CO_2$ gas generation increase. After the dropping of the pellets, the pellets are heated and the reaction starts at about 1,573 K or higher. The pellets maintain their shape until 10 min after the drop, and then melted. As the holding time increased, the size of the reduced metal particles increased. The chromium ore is rapidly reduced by the Si sludge, and the slag penetrated into the chromium ore and reduction progressed inside. As the reduction temperature increased, the reaction initiation time is shortened and the reaction fraction of the reduction reaction increased. As the reaction temperature increased, agglomeration of reduced ferrochrome metal is promoted.

• Journal of the Semiconductor & Display Technology
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• v.8 no.2
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• pp.11-14
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• 2009

The $Sr_{0.7}Bi_{2.3}Nb_2O_9$(SBN) thin films are deposited on Pt-coated electrode(Pt/Ti/$SiO_2$/Si) using RF sputtering method at various $Ar/O_2$ ratio. We investigated the effect of deposition condition(specially $Ar/O_2$ ratio) on the structural properties of SBN thin film. As $Ar/O_2$ ratio was increased, the peaks in the XRD pattern became more sharp. Also, the peaks(008)(115)(220) in 80/20 of $Ar/O_2$ ratio were suddenly appeared. The optimum of the rougness showed about 4.33 nm in 70/30 of $Ar/O_2$ ratio. The crystallinity of SBN thin films were increased with the increase of $Ar/O_2$ ratio. Also, Deposition rate of SBN thin films was about 4.17 nm/min in 70/30 of $Ar/O_2$ ratio. The capacitance of SBN thin films were increased with the increase of $Ar/O_2$ ratio.

• Korean Journal of Optics and Photonics
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• v.32 no.3
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• pp.101-107
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• 2021

In this paper, a study of the design of automotive communication lamps using microlens arrays (MLAs) was conducted. With the development of autonomous driving technology, automobiles need communication lamps to communicate with pedestrians. To reduce the size of the optical system and secure high light intensity, the communication lamp's optical system was designed using an MLA. In addition, to secure a clear image on inclined ground, the design was carried out considering the overlap method. After that, the improved performance was confirmed by comparing it to the MLA optical system before overlapping.

• International Journal of Advanced Culture Technology
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• v.10 no.3
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• pp.339-345
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• 2022

In this paper, the effect of porosity on the acoustic phase velocity of the 3D printed Kelvin closed-cell structure was investigated using the spectral phase analysis. Since Kelvin cells bring about the large amount of scattering, acoustic pulses in ultrasonic measurements undergoes a distortion of waveforms due to the dispersion effect. In order to take account on the dispersion, mathematical expressions for calculating the phase velocity of longitudinal waves propagating normal to the plane of the Kelvin structure are suggested by introducing a complex wave number based on Fourier transform. 3D Kelvin structure composed of identical unit-cells, a polyhedron of 14 faces with 6 quadrilateral and 8 hexagonal faces, was developed and fabricated by 3D CAD and 3D printer to represent the micro-structure of porous materials such as aluminum foam and cancellous bone. Total nine samples of 3D Kelvin structure with different porosity were made by changing the thickness of polyhedron. Ultrasonic pulse of 1MHz center frequency was applied to the Kelvin structures for the measurement of the phase velocity of ultrasound using the TOF(time-of-flight) and the phase spectral method. From the experimental results, it was found that the acoustic phase velocity decreased linearly with the porosity.