• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.8B
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• pp.1168-1175
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• 2001

H.263부호기에서 정지영상 부호화를 위한 부가 부호기법인 Annex I는 기존의 JPEG, MPEG-1, -2와는 달리 부호화하고자 하는 현재 블록의 DCT 계수를 기부호화된 블록의 DCT 계수들을 이용하여 예측부호화 (Differential Pulse Coded Modulation; DPCM)를 행하고, 이를 통한 부호화 이득의 향상을 얻고 있다. 본 논문에서는 이런 H.263 Annex I의 예측기법을 공간영역에서의 의미를 수학적으로 유도한다. 이를 통해서 H.263 Annex I의 예측기법의 비효율성을 지적하고, 영상신호의 특성에 맞게 예측방식을 수정한다. 제안된 DCT 계수 예측 방식과 기존의 H.263 Annex I 방식의 이론적인 예측성능을 평가하고, H.263 부호기에 적용하여 제안방식의 효율성을 검증한다.

• Proceedings of the KIEE Conference
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• 1988.07a
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• pp.229-231
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• 1988

In this paper, we design adaptive DPCM by the two dimensional linear prediction using the covariance method and propose adaptive algorithm which determines analysis frame size by the compassion of the local standard deviation and the global standard deviation of images.

• Proceedings of the KIEE Conference
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• 1998.07f
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• pp.2172-2174
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• 1998

In this paper, a speed estimation based on the quick torque control is proposed to realize speed sensorless control in a full range of induction motors. The proposed method can be formulated simply from a motor circuit equation and conducted easily by detecting primary motor currents and a voltage command at every sampling time. Since the method need not the differential values of primary currents in an arithmetic of a speed, it can be expected to improve the precision of speed estimation in a very low speed area, especially. Some numerical simulations were conducted with the assumption of using a Pulse Width Modulation voltage source inverter.

• ETRI Journal
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• v.32 no.3
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• pp.464-467
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• 2010

In this letter, we analyze the error performance of a mobile communication system with microdiversity and macrodiversity reception in gamma-shadowed Rician fading channels for a binary differential phase-shift keying modulation scheme. Analytical expressions for the probability density function (PDF) and moment-generating function (MGF) are derived. The average bit error probability can be calculated by averaging the conditional bit error probability over the PDF or using the MGF-based approach. Numerical results are graphically presented to show the effects of macrodiversity, correlation, number of diversity branches, and severity of both fading and shadowing.

• Journal of the Society of Naval Architects of Korea
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• v.40 no.2
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• pp.21-27
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• 2003

The phenomena of vortex shedding around a cylinder oscillating harmonically in a fluid at rest are investigated by a two-dimensional numerical simulation of the Navier-Stokes equations. The simulation is based on a vorticity-velocity integro-differential formulation dealing with vorticity, velocity and pressure variables. Three combinations of Reynolds number(Re) and Keulegan-Carpenter number(KC) were taken to investigate the associated vortex development around the cylinder in the different flow regimes. Drag and lift forces are computed to describe their dominant frequency modulation which is related to the vortex shedding and to the harmonic motion of the cylinder.

• Journal of the Korean Institute of Telematics and Electronics
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• v.24 no.5
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• pp.833-840
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• 1987

A new Block Truncation Coding(BTC) technique reducing the bit-plane and using differential pulse code modulation (DPCM) is proposed and compared with the conventional BTC methods. A new technique decides whether the subblock can be approximated to be uniform or not. If the subblock can be approximated to be uniform(merge mode), we transmit only the gray-level informantion. It not (split mode), we transmity both the bit-plane and the gray-level information. DPCM method is proposed to the encoding of gray-level information when the subblock can be approximated to be uniform. Also modified quantization method is presented to the encoding of gray-level information when the subblock is not uniform. This technique shows the results of coding 256 level images at the average data rate of about 0.75 bits/pel.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.5
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• pp.899-906
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• 1997

It is known that the Differential Phase Shift Keying (DPSK) modulation scheme in the coherent optical communication system is suitable for design of long-distance transmission system because its receiver performance is 3-5dB better than ASK and FSK. In this paper, we descrive a fundamental understanding of the effects of laser phase noise on the performance of coherent lighwave communication systems. Formulas are derived for the bit error rate in homodyne and heterodyne DPSK. Based on detailed mathematical analysis and estimates, we explain the following finding. DPSK can operates at rates only 300 times greater than the laser linewidth.

• Journal of information and communication convergence engineering
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• v.10 no.3
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• pp.225-230
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• 2012

The Korean nationwide differential global positioning system (NDGPS) reference station transmits a global positioning system (GPS) enhancement signal using minimum shift keying modulation with a 200 bps data rate. The ocean-based DGPS covers the service area of 100 NM with 300 W output power; on the other hand, the land-based DGPS transmits the output power of 500 W, which covers the service area of 100 km. The DGPS reference stations with high output power can radiate spurious signals, which may act as interference sources affecting the other DGPS reference stations or the wireless ground stations that utilize the medium frequency band. In this paper, the radiation spectrums of the DGPS reference stations are measured and analyzed in the spurious domain. The DGPS radiation spectrums are evaluated from the perspective of the interference effect.

• Proceedings of the Korean Information Science Society Conference
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• 2001.04a
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• pp.292-294
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• 2001

VoIP(Voice over IP) system은 현재 크게 2가지 형태로 진행되어가고 있다. 첫 번째는 H.323을 이용한 방법이고, 두 번째는 SIP(Session Initiation Protocol)를 이용한 방법이다. H.323은 실제 데이터를 전송하기전 호처리에 많은 signaling이 이루어지는 관계로 SIP보다 많은 RTT(Round Trip Time)를 소모하게 된다. 따라서 매우 복잡하고, LAN환경을 바탕으로 만들어서 확장성면에서도 여러 문제점을 가지고 있다. 그래서 본 논문은 호처리는 SIP를 이용하고, 실제 음성전송은 RTP(Real-Time Transport Protocol)와 RTCP(RTP Control Protocol)를 이용하는 시스템 구현을 제시한다. RTP는 실시간 특성을 가지는 데이터에 대해서 종단간 전송 서비스를 제공해주는 프로토콜로, 어떠한 인코딩에도 적합한 프레임워크를 제공한다. 그런데, RTP는 완전한 하나의 프로토콜이 되기 위해서는 RTP와 페이로드 포맷이 함께 제공되어야 하므로, 구현시스템은 음성신호를 PCM(Pulse Code Modulation), ADPCM(Adaptive Differential PCM)등의 여러 압축기술을 이용하여 파일을 생성하여 실시간으로 RTP와 RTCP를 이용하여 전송하는 방법을 제시한다.

• Food Science and Industry
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• v.55 no.3
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• pp.264-275
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• 2022

The regulation of macrophages is a major target for dietary immune modulation for their involvement in both innate and adoptive immune responses. Studies revealed that macrophages are unique in their plasticity to polarize into either inflammatory M1 subset or anti-inflammatory M2 cells. Recently, cellular energy metabolism including both glycolysis and oxidative phosphorylation is demonstrated to control macrophage dichotomy. In this review, the differential utilization of glucose, lipids, amino acids, and irons by M1 and M2 cells are discussed in detail. In addition, several dietary approaches for the alteration of inflammatory M1 cells to M2 phenotypes are reviewed for development of functional foods for immune regulation.