• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.6
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• pp.1599-1606
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• 2008

Recently, new dispersed generation systems such as photovoltaic, wind power, fuel cell etc. are energetically interconnected and operated in the distribution systems, as one of the national projects for alternative energy with the provision against oil crisis. The technical guidelines on the interconnection of dispersed generation systems have been established and conducted positively. However, protection devices (Re-closer) in primary feeder of distribution system interconnected with photovoltaic generation may cause problems with mis-operation, and then many customers could have problems like an interruption. So, this paper presents the optimal method to minimize the impact of interruption, using both the symmetric method and MATLAB/SIMULINK. And, also this paper shows the effectiveness of proposed method by simulating at the real distribution systems.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.1
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• pp.156-162
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• 2015

This paper has analyzed how conduction path and electron concentration for the device parameters such as oxide thickness, channel doping, and top and bottom gate voltage influence on subthreshold swing of asymmetric double gate MOSFET. Compared with symmetric and asymmetric double gate MOSFET, asymmetric double gate MOSFET has the advantage that the factors to be able to control the short channel effects increase since top and bottom gate oxide thickness and voltages can be set differently. Therefore the conduction path and electron concentration for top and bottom gate oxide thickness and voltages are investigated, and it is found the optimum conditions that the degradation of subthreshold swing, severe short channel effects, can reduce. To obtain the analytical subthreshold swing, the analytical potential distribution is derived from Possion's equation. As a result, conduction path and electron concentration are greatly changed for device parameters, and subthreshold swing is influenced by conduction path and electron concentration of top and bottom.

• Journal of Advanced Navigation Technology
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• v.28 no.4
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• pp.552-558
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• 2024

In dispersion management, which involves additionally inserting a dispersion compensation fiber of an appropriate length to eliminate or reduce the chromatic dispersion of a single-mode fiber, determining the form of the dispersion map, which is the cumulative dispersion profile according to the transmission distance, is the most basic and important. In this paper, the various symmetric dispersion map based on trapezoids applied to dispersion-managed links combined with mid-span spectral inversion (MSSI), which compensates for the distortion caused by Kerr nonlinear effects through optical phase conjugation in the middle of the entire transmission link are proposed, and the effect of each dispersion map on distortion compensation of wavelength division multiplexed (WDM) signals is analyzed. Although the degree of compensation varies depending on the factors that determine the detailed shape of the proposed trapezoid-shaped dispersion map and RDPS (residual dispersion per span), overall, it was confirmed that distortion compensation for signals with a small extinction ratio was more effective than distortion compensation for WDM channel signals with a large extinction ratio.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.11 no.1
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• pp.7-22
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• 1981

A morphological and positional classification was undertaken in the transcranial and transorbital views of 174 traceable films which had been selected from those of 274 patients and previous tracing was performed. For the positional analysis, the author adopted the method which is not influenced by TMJ remodelling, and for the morphological classification, made progress the general method by adding indefinite type to four basic types. The aims of this sutudy consists in performing positional and morphological analysis of condylar head and in its morphological and positional variation in symptomatic patients. I want to express my sincere gratitude to Prof. Park, Tae Won in Seoul National University, interesting me in this field researches and for his never failing interests. I would lide to thank Prof. Ahn, Hyung Kyu and Prof. You, Dong Soo for helpful discussion and critical readings. The author is also indebted to Prof. Fuchihate Hajime in Osaka University, Prof. Uemura, Shusaburo and the late Dr. Nishihara, Heihachi for fruitful discussion and encourgements.

• Journal of the Korean Society of Radiology
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• v.13 no.4
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• pp.645-652
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• 2019

Phosphor with phosphorus doped with rare earth ions was investigated by searching Sr and Eu phosphors suitable for substitution of Eu ions with similar ionic radius to polyphosphate host. The $NaSr(PO_3)_3$ phosphor was synthesized by the solid state method and the $NaSr(PO_3)_3:Eu^{2+}$ phosphor was prepared by the carbon thermal reduction method. Both of the phosphors were identified by X - ray diffraction. The excitation and emission spectra of $NaSr(PO_3)_3:Eu^{3+}$ increased fluorescence intensity and intensity quenching with increasing $Eu^{3+}$ concentration. The higher the $Eu^{3+}$ concentration in the emission spectrum, the higher the local symmetry of $Eu^{3+}$ environment. The mechanism of concentration quenching, in which fluorescence decreases due to the energy transfer between $Eu^{2+}$ ions with the closest critical distance between $Eu^{2+}$ ions with increasing $Eu^{2+}$ ion concentration, was confirmed in the emission spectrum of $NaSr(PO_3)_3:Eu^{2+}$ concentration. It is possible to change the fluorescent region through the post-processing of single rare earth ion added phosphors, and it is possible to change the fluorescence by applying the energy transfer and concentration quenching mechanism according to the local symmetry of $Eu^{3+}$ will be used for high phosphor development.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.7C
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• pp.726-734
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• 2005

Traditional watermarking technologies are symmetric method which embedding and detection keys are the same. Although the symmetric watermarking method is easy to detect the watermark, this method has weakness against to malicious attacks remove or modify the watermark information when the symmetric key is disclosure. Recently, the asymmetric watermarking method that has different keys to embed and detect is watched by several researchers as a next generation watermarking technology. In this paper, hybrid asymmetric watermarking algorithm is proposed. This algorithm is composed of correlation detection method and critical criteria method. Each method can be individually used to detect watermark from a watermarked content. Hybrid asymmetric detection is complement between two methods, and more feasible than when each method is used respectively, Private key and public key are generated by secure linear transformation and specific matrix. As a result, we have proved the proposed algorithm is secured than symmetric watermarking algorithms. This algorithm can expand to multi bits embedding watermark system and is robust to JPEG and JPEG2000 compression.

• Convergence Security Journal
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• v.24 no.1
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• pp.51-57
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• 2024

Although industrial control systems (ICSs) recently keep evolving with the introduction of Industrial IoT converging information technology (IT) and operational technology (OT), it also leads to a variety of threats and vulnerabilities, which was not experienced in the past ICS with no connection to the external network. Since various control command messages are sent to field devices of the ICS for the purpose of monitoring and controlling the operational processes, it is required to guarantee the message integrity as well as control center authentication. In case of the conventional message integrity codes and signature schemes based on symmetric keys and public keys, respectively, they are not suitable considering the asymmetry between the control center and field devices. Especially, compromised node attacks can be mounted against the symmetric-key-based schemes. In this paper, we propose message authentication scheme based on double hash chains constructed from cryptographic hash function without introducing other primitives, and then propose extension scheme using Merkle tree for multiple uses of the double hash chains. It is shown that the proposed scheme is much more efficient in computational complexity than other conventional schemes.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.5
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• pp.1-11
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• 2008

This work proposes a 15b 50MS/s CMOS pipeline ADC based on digital code-error calibration. The proposed ADC adopts a four-stage pipeline architecture to minimize power consumption and die area and employs a digital calibration technique in the front-end stage MDAC without any modification of critical analog circuits. The front-end MDAC code errors due to device mismatch are measured by un-calibrated back-end three stages and stored in memory. During normal conversion, the stored code errors are recalled for code-error calibration in the digital domain. The signal insensitive 3-D fully symmetric layout technique in three MDACs is employed to achieve a high matching accuracy and to measure the mismatch error of the front-end stage more exactly. The prototype ADC in a 0.18um CMOS process demonstrates a measured DNL and INL within 0.78LSB and 3.28LSB. The ADC, with an active die area of $4.2mm^2$, shows a maximum SNDR and SFDR of 67.2dB and 79.5dB, respectively, and a power consumption of 225mW at 2.5V and 50MS/s.

• Journal of the Korean Institute of Telematics and Electronics C
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• v.36C no.8
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• pp.10-21
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• 1999

This paper describes a 12bit CMOS current cell matrix D/A converter which shows a conversion rate of 65MHz and a power supply of 3.3V. Designed D/A converter utilizes current cell matrix structure with good monotonicity characteristic and fast settling time, and it is implemented by using the tree structure bias circuit, the symmetrical routing method with ground line and the cascode current switch to reduce the errors of the conventional D/A converter caused by a threshold voltage mismatch of current cells and a voltage drop of the ground line. The designed D/A converter was implemented with a $0.6{\mu}m$ CMOS n-well technology. The measured data shows a settling time of 20ns, a conversion rate of 50 MHz and a power dissipation of 35.6mW with a single power supply of 3.3V. The experimental SNR, DNL, and INL of the D/A converter is measured to be 55dB, ${\pm}0.5LSB$, and ${\pm}2LSB$, respectively.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.38 no.11
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• pp.836-845
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• 2001

A Novel fully-differential bipolar current subtracter(FCS) and its application to current controlled current amplifier(CCCA) for high-accuracy current-mode signal processing were designed. To obtain full-differential current output, the FCS was symmetrically composed of two current follower with low current-input impedance. The CCCA to control output current by the bias current was consisted of the subtracter and a current gain amplifier(CGA) with single-ended current output.. The simulation result shows that the FCS has current-input impedance of 5 Ω and a good linearity. The CCCA has 3-dB cutoff frequency of 20 MHz for the range over bias current 100 $\mu$A to 20 mA. The power dissipation of the FCS and CCCA are 1.8 mW and 3 mW, respectively.