• 한국정보과학회논문지:시스템및이론
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• 제29권6호
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• pp.354-360
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• 2002

지연시간 계산은 지연시간을 고려한 배치 단계에서 백만 번 이상도 수행되므로 효과적이면서 간단해야 한다. 본 논문에서는 계산은 매우 빠르고 간단하지만 수 백%의 오차를 가질 수 있는 Elmore delay를 개선하기 위해 Elmore delay와 SPICE 결과의 비율을 보상값으로 이용하는 방법을 제안한다. 제안한 새로운 방법은 resistance shielding effects를 고려하여 실험적으로 지연시간을 보상하여 그 오차를 크게 줄이며, 계산 복잡도는 Elmore delay와 같은 정도로 간단하다. Elmore delay가 31.6 ~ 145.2% 오차를 갖는 RC 트리에 대하여 실험한 결과, 보상된 delay의 오차는 2.5 ~ 22.7%로 크게 줄었다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2008년도 하계종합학술대회
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• pp.439-440
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• 2008

A high-speed DCO is proposed that uses the negative-skewed delay scheme. The DCO consists of a ring of inverters with each PMOS transistor driven from the output of 3 earlier stage through a set of minimum-sized pass-transistors. The digitization of negative-skewed delay is achieved by selecting pass-transistors turned on and digitizing the gate voltages of the selected pass-transistors. The proposed 7-stage DCO has been simulated using 1.8V, $0.18\;{\mu}m$ TSMC CMOS process to obtain a resolution of 3ps and an operation range of 2.88-5.03GHz.

• 전자공학회논문지A
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• 제31A권3호
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• pp.68-76
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• 1994

In the automatic transistor sizing with computer for optimizing delay and the chip area of CMOS digital circuits, conventionally either a mathematical method or a heuristic method has been used. In this paper, we present a new method of transistor sizing, a sort of combination of the above two methods, in which the mathematical method is used for sizing of critical paths and the heuristic method is used for desizing of non-critical paths. In order to reduce the overall problem dimension, a basic block called an extended stage is introduced which includes a basic stage, parallel transistors and complementary part. Optimization for multiple critical paths is formulated as a problem of area minimization subject to delay constraints and is solved by the augmented Lagrange multiplier method. The transistor sizes along non-critical paths are decreased successively without affecting the critical path delay times. The proposed scheme was successfully applied to several test circuits.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제48권9호
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• pp.517-522
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• 1999

This paper addresses the issue of current sampling in a high performance AC drive system fed by a discontinuous PWM inverter. The effect of the sampling error due to the measurement delay produced by an input stage low pass filter and an A/D converter is described in the case of discontinuous PWM. To compensate for the sampling error, a method to estimate the delay time of the whole measurement system based on the measured current is proposed and its effectiveness is verified by experimental results. The proposed algorithm can automatically estimate the system delay introduced by the low pass filter and the A/D converter at the commissioning stage. By delaying the current sampling by the estimated value, experimental results indicate that more than 50% reduction of current ripple can be achieved.

• 정보처리학회논문지B
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• 제10B권6호
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• pp.695-704
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• 2003

본 논문은 멀티미디어 데이터 스트림들을 이동단말기에서 연출(play)하기 위해 스트림의 특성을 파악한 후 변환 시킬 스트림을 선정하여 트랜스코딩하는 스케줄링 기법을 제시하였다. 이것은 연출될 모든 스트림들을 트랜스코딩하는 것보다 선정정책에 의해 특정 스트림을 선택하여 트랜스코딩하는 것이 최초 재생 지연 시간을 줄일 수 있는 장점이 있다. 따라서 본 논문은 멀티미디어 데이터 스트림들의 요구 대역폭을 네트워크 대역폭 보다 낮추면서, 이동 단말기에서 멀티미디어 데이터 스트림들이 재생되기까지의 최초 재생 지연시간을 최소화시킬 수 있는 방법으로 EPOB(End Point of Over Bandwidth) 기반의 트랜스코딩 스트림 선정 정책을 제안하였다.

• Journal of Information Processing Systems
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• 제10권2호
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• pp.176-192
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• 2014

The realization of Wireless Multimedia Sensor Networks (WMSNs) has been fostered by the availability of low cost and low power CMOS devices. However, the transmission of bulk video data requires adequate bandwidth, which cannot be promised by single path communication on an intrinsically low resourced sensor network. Moreover, the distortion or artifacts in the video data and the adherence to delay threshold adds to the challenge. In this paper, we propose a two stage Quality of Service (QoS) guaranteeing scheme called Prioritized Multipath WMSN (PMW) for transmitting H.264 encoded video. Multipath selection based on QoS metrics is done in the first stage, while the second stage further prioritizes the paths for sending H.264 encoded video frames on the best available path. PMW uses two composite metrics that are comprised of hop-count, path energy, BER, and end-to-end delay. A color-coded assisted network maintenance and failure recovery scheme has also been proposed using (a) smart greedy mode, (b) walking back mode, and (c) path switchover. Moreover, feedback controlled adaptive video encoding can smartly tune the encoding parameters based on the perceived video quality. Computer simulation using OPNET validates that the proposed scheme significantly outperforms the conventional approaches on human eye perception and delay.

• 한국콘텐츠학회논문지
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• 제14권7호
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• pp.407-426
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• 2014

본 연구는 인터넷 소비자의 구매지연행동에 영향을 미치는 요인을 규명하고자 하였고, 인터넷 소비자의 상황적 요인과 지각된 불확실성이 구매지연행동에 미치는 영향을 분석하였다. 서울 수도권 지역의 인터넷 소비자를 대상으로 설문조사를 하여 394부의 자료를 분석에 사용하였다. 본 연구의 결과를 요약하면 첫째, 전반적 구매지연에는 부정적 경험과 후회회피가 정(+)의 영향요인으로 나타났다. 결제단계 지연에는 시간압박성, 구매변경 가능성, 부정적 경험 및 후회회피가, 장바구니 포기에는 시간압박성과 부정적 경험, 후회회피가 정(+)의 영향을 미치고 있었다. 둘째, 전반적인 구매지연과 결제단계 지연에는 정보, 선호 및 심리불확실성이, 장바구니 포기에는 정보 및 심리 불확실성이 정(+)의 영향을 미치고 있었다. 본 연구는 인터넷 소비자의 구매지연행동의 상황적 요인과 지각된 불확실성을 분석함으로써 인터넷 분야 연구의 이론 확장 및 다양화에 기여하였고, 인터넷 쇼핑몰의 고객관리와 마케팅 전략에 유용한 자료를 제공한 의의가 있다.

• 한국연소학회지
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• 제18권4호
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• pp.21-28
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• 2013

HCCI engines have mainly focused on achieving low temperature combustion in order to obtain higher efficiency and lower emission. One of practical difficulties in HCCI combustion is to control the start of combustion and subsequent combustion phasing. The choice of primary reference fuels in HCCI strategy is one of various promising solutions to make HCCI combustion ignition-controlled. The behavior of ignition delay to the frequency variation of sinusoidal velocity oscillation is computationally investigated under HCCI conditions of PRF75 using a reduced chemistry in a counterflow configuration. The second-stage ignition is more delayed as the higher frequency is imposed on nozzle velocity fluctuation whereas the first-stage ignition is not much influenced.

• 한국연소학회:학술대회논문집
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• 한국연소학회 제26회 KOSCO SYMPOSIUM 논문집
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• pp.13-19
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• 2003

As the environmental pollution becomes serious global problem, the regulation of emission exhausted from automobiles is strengthen. Therefore, it is very important to know how to reduce the NOx and PM simultaneously in diesel engines, which has lot of merits such as high thermal efficiency, low fuel consumption and durability. By this reason, the new concept called as Homogeneous Charge Compression Ignition(HCCI) engines are spotlighted because this concept reduced NOx and P.M. simultaneously. However, it is well known that HCCI engines increased HC and CO. Thus, the investigation of combustion characteristics which consists cool and hot flames for HCCI engines were needed to obtain the optimal combustion condition. In this study, combustion characteristics for direct inject type HCCI engine such as quantity of cool flame and hot flame, ignition timing and ignition delay were investigated to clarify the effects of these parameters on performance. The results revealed that diesel combustion showed the two-stage ignition of cool flame and hot flame, the rate of cool flame increase and hot flame decrease with increasing intake air temperature. On the other hand, the gasoline combustion is the single-stage ignition and ignition timing is near the TDC. In addition mixed fuel combustion showed different phenomenon, which depends on the ratio of gasoline component. Ignition timing of mixed fuel is retarded near the TDC and the ignition delay is increased according to ratio of gasoline.

• 한국자동차공학회논문집
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• 제12권1호
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• pp.17-24
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• 2004

As the environmental pollution becomes serious global problem, the regulation of emission exhausted from automobiles is strengthened. Therefore, it is very important to know how to reduce the NOx and PM simultaneously in diesel engines, which has lot of merits such as high thermal efficiency, low fuel consumption and durability. By this reason, the new concept called as Homogeneous Charge Compression Ignition(HCCI) engines are spotlighted because this concept reduced NOx and P.M. simultaneously. However, it is well known that HCCI engines increased HC and CO. Thus, the investigation of combustion characteristics which consists cool and hot flames for HCCI engines were needed to obtain the optimal combustion condition. In this study, combustion characteristics for direct injection type HCCI engine such as quantity of cool flame and hot flame, ignition timing and ignition delay were investigated to clarify the effects of these parameters on performance. The results revealed that diesel combustion showed the two-stage ignition of cool flame and hot flame, the rate of cool flame increase and hot flame decrease with increasing intake air temperature. On the other hand, the gasoline combustion is the single-stage ignition and ignition timing is near the TDC. In addition mixed fuel combustion showed different phenomenon, which depends on the ratio of gasoline component. Ignition timing of mixed fuel is retarded near the TDC and the ignition delay is increased according to ratio of gasoline.