• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2006년도 하계종합학술대회
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• pp.159-160
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• 2006

We present a multiuser synchronization scheme for OFDMA uplink systems. First a new preamble structure is proposed by which timing and frequency offsets estimation is developed. Based on proposed structure a new joint synchronization scheme is presented and the simulation results show that the performance of this scheme don't suffer from the number of users.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2005년도 전력전자학술대회 논문집
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• pp.96-98
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• 2005

Proposed Multi-level PDP sustain Driver make use of element which has a low voltage rating instead of suggested method by the existing Webber and it passes through a second phase both rising and falling at sustaining voltage waveform In accordance with the change of timing phase(Tr1, Ti1, Tr2) performance comparison of a electric discharge characteristics in a PDP module has been carried out. At the conclusion of experimentation, the feature is extended by alteration of Ti1 and it has little to do with alteration of Tr1.

• 한국통신학회논문지
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• 제21권7호
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• pp.1777-1786
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• 1996

This paper describes theories and implementation techniques of a digital high-definition television(HDTV) modem based on 32-QAM for terrestrial broadcasting. We proposed a digital demodulation scheme and a symbol timing recovery structure based on the band edge component maximization(BECM) method. The adaptive equalizer has 256 complex taps to remove the multipath of delays ranging from -2.mu.s~+24.mu.s with a new T/2-spaced blind equalization algorithm. computer simulation results reveal that the proposed algorithm outperforms other conventional blind equalization algorithm a digital HDTV modem with 4.91MHz symobol rate is implemented by utilizing the proposed algorithms. All processings for modem operations such as demodulation, estimation of symbol timing phase error, adaptive equalization, and carrier recovery except IF signal processing and sampling phase control part of the AD converter are done in digital domain. Especially, the carrier recovery loop can track a carrier offset of upto .+-.350KHz.

• Journal of Power Electronics
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• 제2권4호
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• pp.297-304
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• 2002

The paper identifies a severe form of core saturation instability in a DC/AC interaction system. It then seeks solutions to the problem by HVDC control means. This is achieved by a proper design of the Voltage Dependent Current Order Limiter (VDCOL), the Current Regulate. and Timing Pulse generator. Supplementary control loops have also been introduced to result in a satisfactory performance as compared to that obtained one with the use of uncharacteristic harmonic filter on the AC side. All the options have been demonstrated through recovery performance of the DC link in response to both 1-phase and 3-phase 5 cycle faults on both rectifier and inverter commutating buses.

• 대한교통학회지
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• 제20권7호
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• pp.23-29
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• 2002

일반적으로 4지 또는 3지의 교차로가 설계·운영되고 있으나 적지 않게 5지 또는 그 이상 의 원형 신호교차로가 실질적으로 이용되고 있다. 접근로 수에 따른 교차로 형태별 분류에 의하면 5지 이상의 교차로에서의 상충지 점의 수는 4지 교차로의 그것보다 월등히 높아 설계지침에서도 4지 이하의 교차로를 설계할 것을 권하고 있으며 마찬가지로 5지 원형 신호교차로에서도 그 상충지점 수가 많다. 이러한 이유로 5지 신호 교차로의 신호 설계는 교통소통이 아닌 교통안전측면에서 신호현시 순서 및 길이가 결정되어야 할 필요가 있으며 또 그러한 현시순서는 교차로 내 원활한 교통의 흐름을 심각한 수준으로 방해하지 않을 필요가 있다. 본 연구에서는 5지 신호교차로의 안전을 고려한 현시순서설계 방안을 제시한다. 울산광역시에서 운영중인 공업탑 5지 신호교차로를 대상으로 현장자료를 수집하였으며, 신호시간 설계모형은 TRANSYT-7F를 적용했다. TRANSYT-7F에서의 최적 신호현시의 길이를 토대로 기본적으로 "한 현시에 2개 교통류의 이동" 원칙에 따라 재배열하였다. 제안된 방법으로 보정된 신호현시 순서 및 길이를 사용하여 모의실험한 결과 TRANSYT-7F에서 제시한 최적 신호현시 순서 및 길이를 적용한 것에 비하여 평균 6.2%지체도 증가가 있었으나 교차로 내 상충수를 61.5% 줄이는 결과를 도출하였다.

• 대한기계학회논문집B
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• 제35권10호
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• pp.981-987
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• 2011

단기통 직접분사 가솔린엔진의 성층연소 조건에서 연소실험을 수행하였다. 각 분사압조건마다 실화가 발생하지 않는 성층연소가능 분사시기영역이 존재하였으며 이는 혼합기 형성과정의 분위기압에 따른 영향으로 판단하였다. 연소효율은 분사시기를 지각할수록 증가하며 32~28 CAD BTDC에서 최대값을 갖고 이후 감소하는 경향을 보였고 분사압이 높을수록 높은 연소효율이 나타났다. 이러한 연소효율의 경향은 IMEP와 다른 경향을 보였으며 그 이유는 높은 연소효율 조건에서 연소상이 진각되어 음의 일이 증가하였기 때문으로 판단된다. Smoke의 배출은 분사시기가 지각됨에 따라 증가하였으며 높은 분위기 압에서 국부적으로 농후한 영역이 증가하였기 때문으로 생각된다. NOx 배출도 분사시기를 지각함에 따라 감소하였으며 연소상의 지각으로 최대 연소실압력과 온도가 감소하였기 때문으로 생각된다.

• 한국정보통신설비학회:학술대회논문집
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• 한국정보통신설비학회 2007년도 학술대회
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• pp.136-141
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• 2007

The frequency accuracy and phase alignment is necessary for ensuring the quality of service (QoS) for applications such as voice, real-time video, wireless hand-off, and data over a converged access medium at the telecom network. As telecom networks evolve from circuit to packet switching, proper synchronization algorithm should be meditated for IP networks to achieve performance quality comparable to that of legacy circuit-switched networks. The Time of Packet (ToP) specified in IEEE 1588 is able to synchronize distributed clocks with an accuracy of less than one microsecond in packet networks. But, The ToP can be affected by impairments of a network such as packet delay variation. This paper proposes the efficient method to minimize the expectable delay variation when ToP synchronizes the distributed clocks. The simulation results are presented to demonstrate the improved performance case when the efficient ToP transmit algorithm is applied.

• 한국자동차공학회논문집
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• 제11권1호
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• pp.166-171
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• 2003

This paper presents the algorithms and Matlab Toolbox for co-simulation of distributed real-time control system based on OSEK-OS and CAN protocol. This toolbox enables the developers to analyze the timing uncertainty, which is caused by resource sharing including shared memories and networks, and to take the timing uncertainty into consideration in the early design phase. Furthermore, this toolbox helps the developers to model the behaviors of a control system by providing graphical user interface for objects of OSEK-OS and CAN. To prove the feasibility of this toolbox, a vehicle body network system is modeled with this toolbox, and the timing uncertainties are analyzed.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1999년도 하계종합학술대회 논문집
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• pp.857-860
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• 1999

It is made possible a removal of the preamble for carrier recovery and symbol-timing recovery by storing a burst in memory with low overhead QPSK demodulation and this demodulation method also effects frame efficiency improved by processed synchronization performance. In this paper, we have proposed that new algorithm for arc-tangent look-up table which transform the input I, Q data by phase. This I, Q data plays an important role in demodulation and makes demodulator with low-overhead by storing a burst in memory. To evaluate proposed new algorithm and symbol-timing recovery method, function simulation and timing verification have been done by using synopsys VHDL tool.

• 대한기계학회논문집B
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• 제26권4호
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• pp.614-621
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• 2002

This study was performed to investigate the behavior of vapor phase of fuel mixtures with different piston bowl shapes(F, B and R-type) in a optically accessible engine. The images of liquid and vapor phases were captured in the motoring engine using exciplex fluorescence method. Fuel was injected into atmospheric nitrogen to prevent quenching phenomenon by oxygen. Injection pressure was 5.1MPa. Two dimensional spray fluorescence image of vapor phase was acquired to analyze spray behaviors and fuel distribution inside of cylinder. Four injection timings were set at BTDC 90$^{\circ}$, 80$^{\circ}$, 70$^{\circ}$, and 60$^{\circ}$. With a fuel injection timing of BTDC 90$^{\circ}$, fuel-rich mixture level in the center region was highest in a B-type piston. With a fuel injection timing of BTDC 60$^{\circ}$, R-type piston was best. R-type piston shape was suitable under enhanced swirl ratio and late injection condition and B-type piston shape was right in a weak swirl ratio. It was found that the piston bowl shape affected the mixture stratification inside of cylinder.