• International journal of advanced smart convergence
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• 제11권3호
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• pp.17-22
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• 2022

As the sixth generation (6G) promising technique, intelligent reflecting surface (IRS) has recently attracted much attention. The IRS based wireless communication is expected to deploy the upcoming 6G mobile networks, to increase energy and spectrum efficiency in the fifth generation (5G) wireless networks. In this paper, we compare the bit-error rate (BER) performances for phase-shift schemes of IRS non-orthogonal multiple access (NOMA). First, we derive a BER expression for the equalizing phase-shift scheme in IRS-NOMA networks. Then we compare the BER of the equalizing phase-shift scheme to that of the identical phase-shift scheme in IRS-NOMA networks, and show the BER improvement of the equalizing phase-shift scheme IRS NOMA over the identical phase-shift scheme IRS NOMA. Furthermore, we also validate the proposed analytical BER for the equalizing phase-shift scheme in IRS-NOMA by Monte Carlo simulations, and demonstrate that they well match each other.

• 한국광학회:학술대회논문집
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• 한국광학회 2003년도 제14회 정기총회 및 03년 동계학술발표회
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• pp.62-63
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• 2003

We propose an improved image encryption and the shift-tolerance method in the Fourier space using a virtual phase image. The encrypted image is obtained by the Fourier transform of the product of a phase-encoded virtual image, not an original image, and a random phase image. We demonstrate the robustness to noise, to data loss and shift of the encrypted image or the Fourier decryption key in the proposed technique.

• Journal of Mechanical Science and Technology
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• 제17권7호
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• pp.1083-1094
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• 2003

This study represents an assessment of the phase-Doppler technique to the measurements of dense droplet laden jet. High-pressure injection fuel sprays have been investigated to evaluate the use of the Phase-Doppler anemometry (PDA) technique. The critical issue is the stability of the phase-Doppler anemometry technique for dense droplet laden jet such as Diesel fuel spray in order to insure the results from the drop size and velocity measurements are repeatable, consistent, and physically realistic because the validation rate of experimental data is very low due to the thick optical density. The effect of shift frequency is minor, however, the photomultiplier tube (PMT) voltage setting is very sensitive to the data acquisition and noise in dense droplet laden jet. The optimum PMT voltage and shift frequency should be chosen so that the data such as volume flux and drop diameter do not change rapidly.

• 한국통신학회논문지
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• 제17권10호
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• pp.1147-1156
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• 1992

본 논문에서는 $\pi/4$ shift QPSK에 Trellis 부호화된 변조 기법(Trellis-Coded Modulation. TCM)을 적용시키기위하여 $\pi/8$ shift 8PSK를 제안하고 위상차에 의한 신호 집합 확장과 신호 집합 분할을 수행하는 trellis 부호화된 π/8 shift 8PSK를 제안한다. 또한 BER(Bit Error Rate) 성능을 향상시키기위하여 제1차 위상차뿐만아니라 제L차 이상차의 자승 유클리드 거리를 매트릭(Branch Metric)으로 갖는 비터비 디코더(Viterbi decoder)를 설계한다. 그리고 $\pi/4$ shift QPSK, trellis 부호화된 $\pi/8$ shift 8PSK와 제L차 위상차의 자승 유클리드 거리를 메트릭(Branch Metric)으로 갖는 trellis 부호화된 $\pi/8$ shift 8PSK 의 BER 특성을 AWGN에서 Monte Carlo 시뮬레이션을 통해 알아본다. 제안된 알고리즘은 MDPSK에도 적용될 수 있다.

• 한국정밀공학회지
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• 제19권9호
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• pp.172-178
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• 2002

One of the ever-increasing demands on the performances of heterodyne interferometers is to improve the measurement resolution, of which current state -of-the-art reaches the region of sub-nanometers. So far, the demand has been met by increasing the clock speed that drives the electronics involved fur the phase measurement of the Doppler shift, but its further advance is being hampered by the technological limit of modem electronics. To cope with the problem, in this investigation, we propose a new scheme of phase -measuring electronics that reduces the measurement resolution without further increase in clock speed. Our scheme adopts a super-heterodyne technique that lowers the original beat frequency to a level of 1 MHz by mixing it with a stable reference signal generated from a special phase- locked-loop. The technique enables us to measure the phase of Doppler shift with a resolution of 1.58 nanometer at a sampling rate of 1 MHz. To avoid the undesirable decrease in the maximum measurable speed caused by the lowered beat frequency, a special form of frequency up-down counting technique is combined with the super-heterodyning. This allows performing required phase unwrapping simply by using programmable digital gates without 2n ambiguities up to the maximum velocity guaranteed by the original beat frequency.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 하계종합학술대회 논문집(1)
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• pp.233-236
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• 2001

Orthogonal freqency division multiplexing (OFDM) is an attractive technique for achieving high-bit-rate wireless data transmission. However, the potentially large peak-to-average power ratio (PAPR) has limited its application; An OFDM signal with the large PAPR can cause power degradation (In-band distortion) and spectral spreading (Out-of-band distortion) by being clipped passing through a power amplifier. Thus, we propose the combining algorithm of Hadamard transform and phase shift, which is ascribed to the relation between the correlation of the IFFT input sequence function and PAPR. Extensive computer simulations show that the combining algorithm is an effective technique to reduce PAPR.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2005년도 전력전자학술대회 논문집
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• pp.286-288
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• 2005

Conventional phase shift full bridge (PSFB) converter has serious voltage oscillation problem across the secondary rectifier diodes, which would require the dissipate snubber circuit, thus degrades the overall efficiency. To overcome this problem, a new voltage oscillation reduction technique (VORT) which effectively reduce the voltage oscillation of the secondary rectifier diodes for phase shift 1011 bridge converter is proposed. Therefore, no dissipate snubber for rectifier diodes is needed. In addition, since it has wide zero voltage switching (ZVS) range, high efficiency can be achieved. Operational principle, analysis of voltage oscillation, and design consideration are presented compare with that of the conventional PSFB converter. To confirm the validity of the proposed VORT, experimental results from a 420W, 385Vdc/210Vdc prototype are presented.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2007년도 Proceedings of ISRS 2007
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• pp.625-628
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• 2007

We present an efficient and robust technique to estimate the velocity of moving targets from a single SAR image. In SAR images, azimuth image shift is a well known phenomenon, which is observed in moving targets having slant-range velocity. Most methods estimated the velocity of moving targets from the distance difference between the road and moving targets or between ship and the ship wake. However, the methods could not be always applied to moving targets because it is difficult to find the road and the ship wake. We adopted a method estimating the velocity of moving targets from azimuth differentials of range-compressed image. This method is based on an assumption that Doppler center frequency shift of moving target causes a phase difference in azimuth differential values. The phase difference is linearly distorted by Doppler rate due to the geometry of SAR image. The linear distortion is eliminated from phase removal procedure, and the constant phase difference is estimated. Finally, range velocity estimates for moving targets are retrieved. This technique is tested using an ENVISAT ASAR image in which several unknown ships are presented. The theoretical accuracy of this technique is discussed by SAR simulation. The advantages and disadvantages of this method over the conventional method are also discussed.

• 전력전자학회논문지
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• 제10권6호
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• pp.598-609
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• 2005

기존의 위상 천이 풀-브릿지 컨버터는 변압기 2차측 다이오드의 전압 스트레스를 증가시키는 심각한 전압 진동 문제를 가지고 있으며, 이를 해결하기 위한 부가적인 스너버의 사용은 전체 시스템 효율의 저하를 초래한다. 본 논문에서는 부가적인 스너버의 사용없이 효과적으로 전압 진동 문제를 해결하는 위상 천이 풀-브릿지 컨버터의 새로운 동작 방식을 제안한다. 또한 제안된 방법은 동작 특성 상 넓은 영전압 스위칭 범위를 보장하므로 향상된 효율을 기대할 수 있다. 기존의 동작 방식과 비교하여 제안된 전압 진동 제거 기술의 동작 원리, 전압 진동 분석 및 설계 고려 사항을 나타내었으며, 420W사양의 시험모델을 제작하여 제안된 전압 진동 제거 기술의 타당성을 입증하였다.

• 대한전자공학회논문지SD
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• 제40권9호
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• pp.658-665
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• 2003

본 논문에서는 위상 변조된 가상 영상을 이용하여 암호화 수준을 향상시키고 퓨리에 영역에서 잡음이나 변이에 강한 복호화 방법을 제안하였다. 암호화된 영상은 원 영상이 아닌 위상 변조된 가상 영상과 무작위 위상 영상을 곱하여 퓨리에 변환하여 만든다. 따라서 허가되지 않은 사용자가 암호화된 영상을 분석함으로써 있을 수 있는 복제 가능성을 원 영상의 어떤 정보도 포함하지 않은 가상 영상을 사용함으로써 배제할 수 있다. 복호화 과정은 암호화된 영상과 제안한 위상 대응 규칙으로 만들어진 퓨리에 복호화 키를 간섭시킨 후 퓨리에 역변환하여 간단히 원 영상을 재생하고 컴퓨터 모의 실험을 통하여 제안한 방법의 암호화된 영상과 복호화 키 영상에 잡음이나 영상의 절단, 변이가 발생하더라도 원 영상의 복원이 가능함을 확인하였다.