• Journal of the Institute of Electronics Engineers of Korea SD
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• v.39 no.3
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• pp.34-40
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• 2002

In this paper, a new encryption method for a binary image using Phase modulation and Fourier transform is proposed. For decryption we use the characteristics of square law detector. In encryption process, a key image is obtained by phase modulation of 256 level random pattern and its Fourier transformation, and input image is encrypted by Fourier transforming the multiplication of the phase modulated random pattern and phase modulated input image. The encrypted image and key image have only phase information, so they can not be copied or counterfeited and the original image can not be decrypted without the key image. To reconstruct the original image, each phase mask of the key image and the encrypted image must be placed on each path of the Mach-Zehnder interferometry with Fourier transform lens and the output image is obtained in the form of intensity in the CCD(Charge Coupled Device) camera. The real-time decryption is possible in the proposed system by use of a LCD as a phase modulator and a CCD camera as an intensity detector. The proposed method shows a good performance in the computer simulation and optical experiment as an encryption scheme.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.3
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• pp.707-714
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• 2010

Since an LFSR(linear feedback shift register) as a pattern generator has solely linear dependency in itself, it generates sequences by moving the bit positions for pattern generation. So the correlation between the generated patterns is high and thus reduces the possibility of fault detection. To overcome these problems many researchers studied to have goodness of randomness between the output test patterns. In this paper, we propose the new and effective method to construct phase shifter as PRPG(pseudo random pattern generator).

• The Transactions of the Korean Institute of Power Electronics
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• v.9 no.5
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• pp.430-437
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• 2004

This thesis proposes novel SRP-PWM(Separately Random Pulse Position PWM) techniques and novel two-phase switching pattern applied to four-switch inverter, having various advantages such as operation time decrease that is required for decrease of switching damage, easy of implementation and inverter control at high frequency switching. In this thesis, we wish to confirm that SRP-PWM techniques disperse harmonic spectrum of inverter output current evenly into wide frequency area, that is, side-band of specification frequency. And we confirm the harmonic reduction effect of proposed techniques. Therefore, we will achieve an experiment by IGBT inverter using DSP and will verify the validity of proposed techniques compared with simulation results that use MATLAB/SIMULINK.

• Journal of Korean Institute of Industrial Engineers
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• v.24 no.3
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• pp.381-386
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• 1998

We frequently encounter stopped random sums when modelling queueing systems. We also notice occasional mishandling of stopped random sums in the literature. The purpose of this note is to prevent further mistakes by identifying and correcting typical mistakes about stopped random sums. As an example model, we use the two-phase M/G/1 queue with multiple vacations.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2000.04a
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• pp.59-62
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• 2000

In this study, the distribution of the effective modulus was investigated statistically Plain weave structures were modeled with random stacking phase shift angles and the effective modulus was calculated by the unit cell analysis. The analysis results indicated that the effect of random phase shift angles was significant on the modulus distribution. As the number of layers increased, the coefficient of variation decreased and higher degree of homogeneity was attained.

• Proceedings of the Optical Society of Korea Conference
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• 2001.02a
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• pp.72-73
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• 2001

대용량 정보의 보안이 매우 중요해짐에 따라 활발히 진행 중인 광정보의 보안에 대한 연구 중에서 광학적 위상암호화는 많은 양의 정보를 한린에 암호화하고 해독할 수 있다(·：). 특히 Javidi 등이 제안한 Fresnal 영역 임의 위상판(random phase mask; RPM)을 이용한 암호화 방법은 3차원 위치 정보를 암호화 키로 사용한다. 이와 같은 암호화 방법에 회전에 의한 위상변화를 추가하면 암호화 수준을 높일 수 있다. (중략)

• Journal of Sensor Science and Technology
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• v.14 no.1
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• pp.42-46
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• 2005

It has been known that 1/f noise of MOSFET is generated by superposition of random telelgraph signals (RTS). In this study, jitters and phase noise caused by 1/f noise of MOSFET are analysed with RTS supplied to all of the nodes of the CMOS ring oscillator under investigation. Through the analysis of jitters and jitter ratios with varying values of the amplitude of RTS, it is found that the jitters and the jitter ratios are proportional to the amplitude of RTS. And the analysis of FFT of the output of the ring oscillator reveals that the jitters are closely related to the phase noise of the high order harmonics of the ring oscillator outputs.

• Journal of the Korean Institute of Telematics and Electronics
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• v.8 no.6
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• pp.33-41
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• 1971

This paper presents a theoretical calculation and measurements for the RCS(Radar Cross Scetion) value of a moving complex target, a small metal aircraft. The front view of aircraft on the drawing is divided in to several simple models to calculate its RCS value by the relative phase nlethod and the random phase method at the given frequency. The aircraft, cessna 305, inbounded from 170$^{\circ}$ to X international airport, is searched by radar with the wave length of 11cm to measure its miximum range which is necessary to determine the RCS value. The measured data are found to be similar to the theoretical values.

• Proceedings of the KIEE Conference
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• 2002.04a
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• pp.82-89
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• 2002

In this paper, a new two-phase space vector RPWM(Random PWM) is proposed. In the proposed RPWM, each of two-phase PWM pulses is located randomly in each switching interval. Based on the space vector modulation technique, the duty ratio of the pulses is calculated. Along with the randomization of the PWM pulses, we can obtain the effects of spread spectra of inverter output voltage, d.c link current and audible switching acoustic noise as in the case of randomly changed switching frequency. To verify the validity of the proposed two-phase RPWM scheme, the experiment based on the C167 micro-controller was executed. The performance of the proposed scheme was compared with traditional PWM schemes experimentally.

• Proceedings of the KIEE Conference
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• 2007.11a
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• pp.106-107
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• 2007

A detailed investigation of cell structure and electrical characteristic in chalcogenide-based phase-change random access memory(PRAM) devices is presented. We used compound of Ge-Se-Te material for phase-change cell. Actually, the performance properties have been improved surprisingly then conventional Ge-Sb-Te. However, crystallization time was as long as ever for amorphization time. We conducted this experiment in order to solve that problem by doping-Sb with annealing.