• 대한교통학회지
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• 제11권1호
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• pp.87-103
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• 1993

The subject this paper is the signal control strategy under oversaturated conditions. The nature of traffic control for oversaturation is essentially different from the standard control modes. While under non-saturated situation traffic control is needed for the sake of safety and efficiency, the throughput is essential under oversaturated conditions. Therefore berth objective and strategies differ. For an oversaturated stream the cycle time and the signal offset are thought to be of rather secondary importance. For this case the green split may well be the most important control variable to serve the excessive demand. Up to now, however, most efforts have concentrated on the strategy with the concept which lies just on the extension of Webster's. "Green-split Coordination Strategy for Over-Saturated Networks", presents newly contrived three types of strategies named Forward-coordination, Backward-coordination and Network-coordination respectively and describes the algorithms with the evaluations. The forward coordination strategy treats the forward wave of flow between two signals. The aim is to prevent the outbreak of queue due to the accumulation of temporary excess of demand in near-saturation or saturation flow. The backward coordination strategy treats the backward rave of flow between two signals. The goal is to prevent the waste of green time caused by the exit block at the upstream signal. for this purpose a feedback regulation is provided of the upstream green-split so that the inflow-outflow balance is kept zero. The resultant surplus of green time is alloted to other signal stages. Also here the examination is made of the appropriate value of the feedback control parameter. The network coordination strategy is operated to maximize the network throughput in a specific direction applying a bang-bang control at the bottleneck intersection. This is a type of intervenient control for policy reasons. For this strategy the green-split coordinations, particuarly the backward coordination, are essential as the tactical elements. In order to evaluate the preposed strategies those are compared with the latest existing strategy called saturation-degree-ratio control by the simulation experiments in an assumed 4$\times$4 grid network. The results are satisfactory showing a 10-15% reduction in delays and a 15% increase in network capacity.

• 대한교통학회지
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• 제26권5호
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• pp.63-72
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• 2008

현재 우리나라 신호교차로는 긴급차량에 대한 우선신호(Preemption) 제어전략을 적용하지 않고, 긴급차량의 교차로 진입 및 통과여부와 관계없이 일반적인 신호로 운영되고 있다. 본 연구에서는 국내외 긴급차량 Preemption 제어 전략을 검토하고. 이를 국내 교통상황을 대상으로 시뮬레이션을 통해 평가하여 교통상황에 따른 효과의 변동성을 분석하였다. 그리고 실제 현장자료를 기반으로 평가하여 국내 적용성 평가를 실시하였다. 분석결과 긴급차량 preemption 제어가 긴급차량의 운영에 긍정적인 영향을 주나 v/c가 증가 할 수록 이와 같은 효과는 감소하는 것으로 나타났다. 그리고 일반차량의 경우는 preemption 제어로 인하여 지체가 증가하고 통행속도가 감소하였으나 네트워크 전체적으로는 큰 차이가 없는 것으로 분석되었다. 그러므로 교통상황에 따라 개선효과의 차이는 존재하지만, preemption 제어 알고리즘을 국내에 도입한다면 사회적으로 긍정적인 효과가 있을 것으로 기대된다.

• 한국ITS학회 논문지
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• 제12권4호
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• pp.11-21
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• 2013

교차로 과포화 시 대응할 수 있는 실시간 신호제어전략은 전방향 및 대기행렬 검지를 위해 많은 검지기가 필요하며, 높은 설치비용이 요구된다. 또한, 기존 앞막힘 예방제어는 해당 접근로의 현시시간을 축소하는 단편적인 전략으로 대응하기 때문에 그 효과가 일시적으로 제한된다. 본 연구에서는 현장에 설치된 ITS영상정보를 활용한 과포화 신호제어전략을 개발하였다. 교차로 과포화 시 발생되는 대기행렬을 영상분석으로 추출하여 이를 기반으로 포화도 비를 산출하여 포화도 비에 따른 신호제어전략을 수립하였다. 신호제어전략은 과포화를 2단계로 나누어 과포화 1단계는 대기행렬 기반 주방향 신호개선, 과포화 2단계는 과포화 시 발생되는 꼬리물기 현상에 대응할 수 있는 신호제어기법을 개발하였다. 신호제어전략의 현장 적용성을 높이기 위해 기존 현시순서, 옵셋, 주기 등을 고정시키고 운영변수의 미세조정전략을 채택하였고, 주도로 위주의 검지 체계를 구축하였다. 신호제어전략별 모의실험 결과, 과포화 상황에서 지체감소 효과가 뚜렷하였고 실시간신호제어인 COSMOS와 비교하여 비용 대비 효율이 더 높은 것으로 확인하였다.

• 센서학회지
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• 제29권3호
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• pp.141-148
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• 2020

To find food, homes, and mates, some animals have adapted special sensing capabilities. Rather than using a passive method, they discharge a signal and then extract the necessary information from the response. More importantly, they use the slope of the detected signal to find the destination of an object. In this paper, similar strategy is mathematically formulated. A perturbation and correlation-based gradient estimation method is developed and used as a sensing strategy. This method allows us to adaptively sense an object in a given environment effectively. The proposed strategy is based on the use of gradient values; rather than instantaneous measurements. Considering the gradient value, the sampling frequency is planned adaptively, i.e., sparse sampling is performed in slowly varying regions, while dense sampling is conducted in rapidly changing regions. Using a temperature sensor, the proposed strategy is verified and its effectiveness is demonstrated.

• Management Science and Financial Engineering
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• 제21권2호
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• pp.13-23
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• 2015

This study addresses the question as to whether the option prices have useful predictive information on the direction of stock markets by investigating a forecasting power of volatility curvatures and skewness premiums implicit in S&P 500 index option prices traded in Chicago Board Options Exchange. We begin by estimating implied volatility functions and risk neutral price densities every minute based on non-parametric method and then calculate volatility curvature and skewness premium using them. The rationale is that high volatility curvature or high skewness premium often leads to strong bullish sentiment among market participants. We found that the rate of return on the signal following trading strategy was significantly higher than that on the intraday buy-and-hold strategy, which indicates that the S&P500 index option prices have a strong forecasting power on the direction of stock index market. Another major finding is that the information contents of S&P 500 index option prices disappear within one minute, and so one minute-delayed signal following trading strategy would not lead to any excess return compared to a simple buy-and-hold strategy.

• Smart Structures and Systems
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• 제1권2호
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• pp.121-140
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• 2005

This paper presents a systematic investigation of the effect of sensor location on the data quality and subsequently, on the effectiveness of machine health monitoring. Based on an analysis of the signal propagation process from the defect location to the sensor, numerical simulations using finite element modeling were conducted on a bearing test bed to determine the signal strength at several representative sensor locations. The results showed that placing sensors closely to the machine component being monitored is critical to achieving high signal-to-noise ratio, thus improving the data quality. Using millimeter-sized piezoceramic plates, the obtained results were evaluated experimentally. A comparison with a set of commercial vibration sensors verified the developed structural dynamics-based sensor placement strategy. It further demonstrated that the proposed shock wave-based sensing technique provided an effective alternative to vibration measurement, while requiring less space for sensor installation.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제15권2호
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• pp.461-484
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• 2021

Compressed sensing in image reconstruction has attracted attention and many studies are proposed. As we know, adding prior knowledge about the distribution of the support on the original signal to CS can improve the quality of reconstruction. However, it is still difficult for a recovery framework adjusts its strategy for exploiting the prior knowledge efficiently according to the current estimated signals in serial iterations. With the theory of information geometry, we propose an adaptive strategy based on the current estimated signal in each iteration of the recovery. We also improve the performance of existing algorithms through the adaptive strategy for exploiting the prior knowledge according to the current estimated signal. Simulations are presented to validate the results. In the end, we also show the application of the model in the image.

• 전기학회논문지
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• 제64권10호
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• pp.1493-1500
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• 2015

For efficient and economical train operation in low-density railway line, on-board oriented train control system, which reduces expensive wayside equipment, is being developed. In this paper, we discuss a tram signal priority strategy which enables efficient and safe train operation when the developing system is applied to train-tram railway environment. Based on the well-known transit signal priority strategies, we develop a tram signal priority algorithm and conduct simulations by using model-based systems engineering (MBSE) tool. Various considerations such as operation procedure, linkage to existing road traffic system, applicability with respect to crossroad types, and so on, are also dealt with.

• Journal of Electrical Engineering and Technology
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• 제9권1호
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• pp.60-70
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• 2014

This paper discusses the impacts of large scale grid-connected wind farm equipped with permanent magnet synchronous generator (PMSG) on power system small signal stability (SSS) incorporating wind generation uncertainty and volatility. Firstly, a practical simplified PMSG model with rotor-flux-oriented control strategy applied is derived. In modeling PMSG generator side converter, the generator-voltage-oriented control strategy is utilized to implement the decoupled control of active and reactive power output. In modeling PMSG grid side converter, the grid-voltage-oriented control strategy is applied to realize the control of DC link voltage and the reactive power regulation. Based on the Weibull distribution of wind speed, the Monte Carlo simulation technique based is carried out on the IEEE 16-generator-68-bus test system as benchmark to study the impacts of wind generation uncertainty and volatility on small signal stability. Finally, some preliminary conclusions and comments are given.

• 한국ITS학회 논문지
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• 제13권3호
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• pp.25-37
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• 2014

해외 주요 도시에서 운영되고 있는 트램은 도시부의 교통혼잡과 대중교통의 수송분담율 감소 문제, 환경문제를 해결할 수 있는 대중교통 수단으로 인식되어 우리나라의 각 지방자치 단체에서 시스템 도입을 진행 중에 있다. 본 연구에서는 기존 신호운영 체계에서 트램을 효율적으로 운영하기 위한 능동식 트램 우선신호 전략을 개발하였다. 트램 우선신호를 수행하기 위한 시스템을 구성하고, 트램 정류장의 정차시간을 제어를 통해 트램의 교차로 무정차 통과를 구현하는 알고리즘을 개발하였으며, 대향방향의 트램차량을 고려하여 트램의 신호교차로 연속통행을 구현하였다. 또한 트램의 교차로 도착시간에 따라 정류장의 정차시간을 최소화하기 위한 능동식 우선신호 전략을 선택함으로서 신호제어 효과를 극대화 하였다. 개발된 신호제어전략을 평가하기 위해서 VISSIM 모형의 API 기능을 이용하여 트램 우선신호 제어전략을 구현하여 신호제어 효과를 분석한 결과, 트램차량의 신호교차로 정지수와 통행시간이 감소했음을 확인하였고, 일반차량도 트램 우선신호에 따른 지체증가가 거의 나타나지 않음을 확인하였다.