• 대한교통학회지
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• 제30권6호
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• pp.71-80
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• 2012

본 연구에서는 개별차량의 구간통행시간 정보를 이용한 독립교차로의 실시간 신호제어 알고리즘을 개발하였다. DSRC와 같이 개별차량의 ID와 검지시각 정보를 수집할 수 있는 검지체계를 적용하였으며, 개별차량의 통행시간 정보로 부터 도착교통류율, 지체, 적색시간 변화에 따른 지체 변화량을 산정하기 위한 모형을 정립하였다. 통행시간기반 신호제어 알고리즘은 교차로 지체를 최소화 시키기 위한 현시별 적색시간 변화량을 결정하며, 선형계획모형을 적용하여 신호시간의 최적화 과정을 수행한다. 알고리즘의 효과평가를 위해 CORSIM과 RUN TIME EXTENSION을 적용한 미시적 시뮬레이션 분석을 시행하였으며, 이동류의 포화상태를 확인하여 지체 최소화를 위한 신호시간이 산정됨을 확인하였다. 또한 Probe 차량의 비율에 따라 이동류의 지체추정 성능을 확인하였으며, 특정 시나리오에 한정된 결과이나 40% 이상 Probe 차량 비율이 확보되는 경우 효과적 신호제어가 가능함을 확인하였다. 최근 국내 교통관리분야에서는 하이패스, 첨단교통관리시스템(ATMS), 광역교통정보사업(UTIS) 등 개별차량의 구간정보를 수집할 수 있는 검지체계가 급격히 확산되고 있으며, 본 연구는 실시간 신호운영 분야에서 검지체계의 변화를 수용하기 위한 방안으로서 새로운 형태의 신호제어 방법론을 제시하였다는데 의의가 있겠다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 하계종합학술대회 논문집(5)
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• pp.21-24
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• 2002

There has been a growing need for interaction between human operator and a remote system to perform a complex task in an unpredictable environment and to operate an important work at a remote distance. The interaction becomes an important parameter in the teleautonomous operation because it permits the operator to control the system at remote distance. As the environmental uncertainties to be applied are getting increased, so is the difference between the plan of the operator and the execution of the system increased. Since the operator may be difficult to know the latest information from frequently changing environment due to time-varying delays, remote system may be hard to control in accordance with the operators command. Interactive Teleautonomous Control System (ITCS) is an approach based on interactions at these environments. The ITCS can be regarded as a control system using the transmitted a system's intnetion. The interactive teleautonomous control does not mean the interaction from operators point of view only considering feedback environmental information and forward simulation but an interaction between the operator and the system that transmits or receives intentions. The proposed ITCS is based on the intention communication that transmits their intentions to each other. The ITCS can correctly control the system in accordance with the operator's intention. Using the intention communication, a system intention is helpful to the operator. In the interactive teleautonomous control, the intention communication has to be provided by the interaction between the operator and the system.

• Journal of Communications and Networks
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• 제18권3호
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• pp.387-396
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• 2016

Multiuser communication has been an important research area of underwater acoustic communications and networking. This paper studies the use of adaptive orthogonal frequency-division multiple access (OFDMA) in a downlink scenario, where a central node sends data to multiple distributed nodes simultaneously. In practical implementations, the instantaneous channel state information (CSI) cannot be perfectly known by the central node in time-varying underwater acoustic (UWA) channels, due to the long propagation delays resulting from the low sound speed. In this paper, we explore the CSI feedback for resource allocation. An adaptive power-bit loading algorithm is presented, which assigns subcarriers to different users and allocates power and bits to each subcarrier, aiming to minimize the bit error rate (BER) under power and throughput constraints. Simulation results show considerable performance gains due to adaptive subcarrier allocation and further improvement through power and bit loading, as compared to the non-adaptive interleave subcarrier allocation scheme. In a lake experiment, channel feedback reduction is implemented through subcarrier clustering and uniform quantization. Although the performance gains are not as large as expected, experiment results confirm that adaptive subcarrier allocation schemes based on delayed channel feedback or long term statistics outperform the interleave subcarrier allocation scheme.

• Nuclear Engineering and Technology
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• 제51권6호
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• pp.1514-1524
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• 2019

Hydrogen-steam gas mixture may be injected into containment with flow regime varying both spatially and transiently due to wall effect and pressure difference between primary loop and containment in severe accidents induced by loss of coolant accident. Preliminary CFD analysis is conducted to gain information about the helium flow regime transition process from jet to buoyancy plume for forthcoming experimental study. Physical models of impinging jet and wall condensation are validated using separated effect experimental data, firstly. Then helium transportation is analyzed with the effect of jet momentum, buoyancy and wall cooling discussed. Result shows that helium distribution is totally dominated by impinging jet in the beginning, high concentration appears near gas source and wall where jet momentum is strong. With the jet weakening, stable light gas layer without recirculating eddy is established by buoyancy. Transient reversed helium distribution appears due to natural convection resulted from wall cooling, which delays the stratification. It is necessary to concern about hydrogen accumulation in lower space under the containment external cooling strategy. From the perspective of experiment design, measurement point should be set at the height of connecting pipe and near the wall for stratification stability criterion and impinging jet modelling validation.

• 한국농공학회지
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• 제28권3호
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• pp.79-88
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• 1986

Drought occurs most frequently and severely around transplanting season of the rice plants in Korea. Shortage of water due to drought for the paddy fields often delays transplanting, and less often the rice plants are subjected to water stress after delayed transplanting. The present study aimed at quantification of the rice crop loss due to delayed transplanting, different inten3ity of water stress, and the combined effect of delay in transplanting followed by water stress for better use of limited water for irrigation under drought. The rice variety Chucheong, a japonica, and Nampung, an indica x japonica, were grown, transplanted to 1/200 a plastic pots, and subjected to different timing of transplanting and degree of water stress under a rainfall autosersing, sliding clear plastic roof facility with completely randomized arrangement of 5 replications. The results obtained are summarized as follows: 1.Twelve days or 22 days delay in transplanting without water stress reduced rice yield by 25% and 43% in the japonica variety, and by 15% and 60% in the indica x japonica variety. 2.The 10 days or 20 days water stress developed without irrigation after drainage in the rice plants transplanted at proper time lowered the water potential at the paddy soil 10cm deep to -4 bar, and -12 bar and caused rice yield reduction by 14%, and 45% in the japonica variety and by 8%, and 50% in the indica X japonica variety. 3.The 12 days delay in transplanting and 10 days or 20 days water stress reduced rice yield by 39% and 59% in the japonica variety, and by 38% and 52% in the indica x japonica variety. The 22 days delay in transplanting plus 10 days water stress caused yield reduction by 76%, i.e. meaningless yield, in both varieties. 4.The intermittent irrigation just to wet the soil body for 10 days after 10 days water stress without irrigation increased rece yield by 12 to 16% compared to the rice plants water stessed without irrigation continuously for 20 days in both varieties respectively. 5.The above results suggest strongly 1) to transplant the rice plants at proper .time even with some water stress rather than delay for sufficient water from later rainfall, and 2) to distribute insufficient irrigation water to broader area of transplanted rice with limited irrigation for better use of limited irrigation water. A greater sensitivity of japonica variety to a moderate water stress than the indica X japonica variety during initial rooting and tillering stage was noticed. To cope with frequent drought in rice culture, firstly the lasting time of transplanting without yield reduction should be clarified by region and variety, and secondly a scheme of rational distribution of limited water should be developed by region with better knowledge on the varietal distribution of limited water should be developed by region with better knowledge on the varietal responses to varying intensity of water stress.