• Proceedings of the KIEE Conference
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• 1988.11a
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• pp.147-150
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• 1988

Since the integration level of VLSI circuits progresses very quickly, a highly reliable thin $SiO_2$ film is required to fabricate a small-geometry MOS device. In the present study we have attempted to eliminate the failure-causing defects that develop in thin oxide films during the oxidation step by performing a long-time preoxidation and postoxidation annealing. The TDDB test and the copper decoration method were used to calculate the oxide defects density of MOS device. The dielectric reliability of high-quality thin oxides have been studied by using the time-zero-dielectric-breakdown (ramp-voltage-stressed I-V) and time-dependent-dielectric -breakdown (Constant-stressed I-V) tests. Failure times against temperature and electric field are examined and acceleration factors are abtained for each parameter. Based on the data obtained, breakdown wearout limitation for thin oxide films is estimated.

• IEMEK Journal of Embedded Systems and Applications
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• v.8 no.3
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• pp.129-136
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• 2013

In this paper, a motion control system based on 2-axis gimbal system is designed and implemented to drive a high speed and precision. The proposed system consists of the RS-422 interface, 2-axis gimbal platform, servo control unit integrated with a high speed DSP chip-set, servo amplifier unit, potentiometer sensor unit, and resolver sensor unit. The servo control unit using the high speed DSP firmware is designed to get a fast response without an overshoot with step input and a RMS error of low probability with ramp input. The servo amplifier unit using a voltage control is designed to resolve the zero-crossing distortion for precise motion. To verify the performance and stability of the implemented system, experiments are performed through a measurement of the time and frequency domain response in a laboratory environment by using a PXI(PCI eXtentions for Instrumentation).

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.6
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• pp.79-85
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• 2013

In this paper, we discussed the traditional methods of generating digital halftoning image and DCT transform. Then we propose a new and simple halftoning algorithm that is based on DCT transformation. We do the feasibility test to verify the proposed algorithm. So we assessed several images generated by adjusting weights of DCT coefficients. As a result, we got the better result for weights of the ramp function type than for weights of the step function type through experiment. As a simple application, we can apply our algorithm to the MPEG video for generating the halftoning video.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.863-866
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• 2003

Multi-walled carbon nanotubes (CNTs) were synthesized on glass substrates in the different ramp-up heating ambient of vacuum, He, Ar, and $N_{2}$ by thermal chemical vapor deposition. CNTs with higher crystallinity were developed in the buffer gases with faster growth rates than in vacuum. Field emission characteristics were strongly related to the relative position of CNT emitters to the cathode electrodes. The areal-spread emission and instability were overcome by locating the emitters far away from the edges of cathode electrodes. The electrical conditioning of emitters improved their emission uniformity over a large area although it decreased the emission current. This study also discussed the long-term stability of CNT emitters.

• Journal of The Korean Astronomical Society
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• v.53 no.3
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• pp.59-67
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• 2020

We propose semi-analytic models for the electron momentum distribution in weak shocks that accounts for both in situ acceleration and re-acceleration through diffusive shock acceleration (DSA). In the former case, a small fraction of incoming electrons is assumed to be reflected at the shock ramp and pre-accelerated to the so-called injection momentum, p_inj, above which particles can diffuse across the shock transition and participate in the DSA process. This leads to the DSA power-law distribution extending from the smallest momentum of reflected electrons, p_ref, all the way to the cutoff momentum, p_eq, constrained by radiative cooling. In the latter case, fossil electrons, specified by a power-law spectrum with a cutoff, are assumed to be re-accelerated from p_ref up to p_eq via DSA. We show that, in the in situ acceleration model, the amplitude of radio synchrotron emission depends strongly on the shock Mach number, whereas it varies rather weakly in the re-acceleration model. Considering the rather turbulent nature of shocks in the intracluster medium, such extreme dependence for the in situ acceleration might not be compatible with the relatively smooth surface brightness of observed radio relics.

• Journal of the Korean Society of Visualization
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• v.15 no.1
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• pp.53-63
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• 2017

Sonic and supersonic jets include many complicated flow physics associated with shock waves, shear layers, vortices as well as strong interactions among them, and have a variety of engineering applications. Much has been learned from the previous researches on the sonic and supersonic jets but quantitative assessment of these jets is still uneasy due to the high velocity of flow, compressibility effects, and sometimes flow unsteadiness. In the present study, the sonic jets issuing from a convergent nozzle were measured by PIV and Schlieren optical techniques. Particle Image Velocimetry (PIV) with Olive oil particles of $1{\mu}m$ was employed to obtain the velocity field of the jets, and the black-white and color Schlieren images were obtained using Xe ramp. A color filter of Blue-Green-Red has been designed for the color Schlieren and obtained from an Ink jet printer. In experiments, two types of sonic nozzles were used at different operating pressure ratios(NPR). The obtained images clearly showed the major features of the jets such as Mach disk, barrel shock waves, jet boundaries, etc.

• Special Issue of the Society of Naval Architects of Korea
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• 2013.12a
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• pp.13-20
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• 2013

In this paper, a collision accident of a container/Ro-Ro ship was numerically analyzed. A container trailer collided with a longitudinal bulkhead of the ship in the accident, which constituted a longitudinal wall of a heavy fuel oil tank. Due to the accident, the bulkhead plate was ruptured and the heavy fuel oil spilled out of the tank. The detailed information regarding the collision velocity and the mass of the trailer was not provided. Therefore, several collision accident scenarios were constructed based upon the arrangement of the ramp way. Each collision accident scenario was analyzed to predict the extents of damage using a commercial numerical package, ABAQUS. Based on the analysis results it is proposed how to minimize the extents of damage. Through the investigations performed in this study it was found that the understandings of various damages due to collision accidents and the developments of structural design guidance against collision are necessary for the betterment of Container/RO-RO ships' performance.

• Journal of the Korean Home Economics Association
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• v.39 no.10
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• pp.39-53
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• 2001

Housing is the most important factor for the elderly and the disabled to live safely and independently. If they want to stay in their familiar community as long as possible, to support their stay in their house must be needed. The purpose of this study was to investigate the housing alterations for the elderly and the disabled. To accomplish the purpose of this study, three cases that had altered housing to fit their needs in three countries, were selected. In Korean case of alterations for the disabled, bathroom and kitchen were the altered spaces in the house. But active alterations were not done, because of the limited expense for the alterations and housing ownership, rented. In one case of housing construction for the elderly in Japan, there was no level difference in the interior. Two bedrooms were provided for the husband and the wife, because of the difference of time to bed. The sunroom for enjoying the outside of the nature was provided. In swedish case, due to the supports of the government and local authority, the house was altered at many spaces such as bathroom, kitchen, ramp at the entrance, elevator and so forth. In conclusion, sufficient supports of government and community services can increase the housing quality of people. The ultimate goal of housing alterations must be done not for the elderly and disabled but for all people.

• Journal of Mechanical Science and Technology
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• v.18 no.10
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• pp.1772-1781
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• 2004

The mechanical as well as tribological characteristics of coating films as thin as a few nm become more crucial as applications in micro-systems grow. Especially, the amorphous carbon film has a potential to be used as a protective layer for micro-systems. In this work, quantitative evaluation of nano-indentation, scratching, and wear tests were performed on the 7nm thick amorphous carbon film using an Atomic Force Microscope (AFM). It was shown that AFM-based nano-indentation using a diamond coated tip can be feasibly utilized for mechanical characterization of ultra-thin films. Also, it was found that the critical load where the failure of the carbon film occurred was about 18${\mu}$N by the ramp load scratch test. Finally, the wear experimental results showed that the quantitative wear rate of the carbon film ranged 10$\^$-9/～10$\^$-8/ ㎣ /N cycle. These experimental methods can be effectively utilized for a better understanding the mechanical and tribological characteristics at the nano-scale.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.5B no.4
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• pp.382-391
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• 2005

Increasing of the nonlinear type power electronics equipment, power conditioning systems (PCS) have been researched and developed for many years in order to compensate for harmonic disturbances and reactive power. PCS's not only improve harmonic current and power factor in the ac grid line but also achieves energy saving used by the renewable energy source (RES). In this paper, the implementation of a current controlled voltage source inverter (CCVSI) using RES for PCS is presented. The basic principle and control algorithm is theoretically analyzed and the design methodology of the system is discussed. The proposed system could achieve power quality control (PQC) to reduce harmonic current and improve power factor, and demand side management (DSM) to supply active power simultaneously, which are both operated by the polarized ramp time (PRT) current control algorithm and the grid-interactive current control algorithm. A 1KVA test model of the CCVSI has been built using IGBT controlled by a digital signal processor (DSP). To verify the proposed system, a comprehensive evaluation with theoretical analysis, simulation and experimental results is presented.