• Journal of Communications and Networks
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• v.18 no.3
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• pp.523-530
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• 2016

We use both theoretical analysis and simulations to study the impact of crosspoint-queued (CQ) buffer size on CQ switch throughput and delay performance under different traffic models, input loads, and scheduling algorithms. In this paper, we present the following. 1) We prove the stability of CQ switch using any work-conserving scheduling algorithm. 2) We present an exact closed-form formula for the CQ switch throughput and a non-closed-form but convergent formula for its delay using static non-work-conserving random scheduling algorithms with any given buffer size under independent Bernoulli traffic. 3) We show that the above results can serve as a conservative guide on deciding the required buffer size in pure CQ switches using work-conserving algorithms such as the random scheduling, under independent Bernoulli traffic. 4) Furthermore, our simulation results under real-trace traffic show that simple round-robin and random work-conserving algorithms can achieve quite good throughput and delay performance with a feasible crosspoint buffer size. Our work reveals the impact of buffer size on the CQ switch performance and provides a theoretical guide on designing the buffer size in pure CQ switch, which is an important step toward building ultra-high-speed switch fabrics.

• Proceedings of the KAIS Fall Conference
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• 2003.11a
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• pp.236-242
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• 2003

ATM ABR service controls network traffic using feedback information on the network congestion situation in order to guarantee the demanded service qualities and the available cell rates. In this paper we apply the control method using queue length prediction to the formation of feedback information for more efficient ABR traffic control. If backward node receive the longer delayed feedback information on the impending congestion, the switch can be already congested from the uncontrolled arriving traffic and the fluctuation of queue length can be inefficiently high in the continuing time intervals. The feedback control method proposed in this paper predicts the queue length in the switch using the slope of queue length prediction function and queue length changes in time-series. The predicted congestion information is backward to the node. NLMS and neural network are used as the predictive control functions, and they are compared from performance on the queue length prediction. Simulation results show the efficiency of the proposed method compared to the feedback control method without the prediction. Therefore, we conclude that the efficient congestion and stability of the queue length controls are possible using the prediction scheme that can resolve the problems caused from the longer delays of the feedback information.

• Tunnel and Underground Space
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• v.33 no.2
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• pp.95-107
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• 2023

In this study, the effect of repeated traffic vibration on the long-term stability of mine openings is analyzed for re-utilization of abandoned mine galleries. The research mine in this study is an underground limestone mine which is developed by room-and-pillar mining method, and a dynamic numerical analysis is performed assuming that the research mine will be utilized as a logistics warehouse. The actual traffic vibration generated by the mining vehicles is measured directly, and its waveform is used as input data for dynamic numerical analysis, As a results of dynamic numerical analysis, after 20,000 repetitions of traffic vibration, the mine openings is analyzed to be stable, but an increase in the maximum principal stress and an additional area of plastic zone are observed in the analysis section. As shown in the changes of displacement, volumetric strain, and maximum principal stress which are measured at the mine opening walls. It is confirmed that if the repeated traffic vibration is continuously applied, the instability of the mine openings can be increased. Authors expect that the results of this study can be used as a reference for basic study on utilization of abandoned mine.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.3
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• pp.1213-1237
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• 2019

Vehicular Ad-hoc Network (VANET) facilities envision future Intelligent Transporting Systems (ITSs) by providing inter-vehicle communication for metrics such as road surveillance, traffic information, and road condition. In recent years, vehicle manufacturers, researchers and academicians have devoted significant attention to vehicular communication technology because of its highly dynamic connectivity and self-organized, decentralized networking characteristics. However, due to VANET's high mobility, dynamic network topology and low communication coverage, dissemination of large data packets (e.g. multimedia content) is challenging. Clustering enhances network performance by maintaining communication link stability, sharing network resources and efficiently using bandwidth among nodes. This paper proposes a mobility-based, multi-hop clustering algorithm, (MBCA) for multimedia content broadcasting over an IEEE 802.11p-LTE-enabled hybrid VANET architecture. The OMNeT++ network simulator and a SUMO traffic generator are used to simulate a network scenario. The simulation results indicate that the proposed clustering algorithm over a hybrid VANET architecture improves the overall network stability and performance, resulting in an overall 20% increased cluster head duration, 20% increased cluster member duration, lower cluster overhead, 15% improved data packet delivery ratio and lower network delay from the referenced schemes [46], [47] and [50] during multimedia content dissemination over VANET.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.29 no.2
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• pp.55-66
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• 2021

ICAO recommended that airspace monitoring and periodic safety assessments in each Contracting State ensure the stability of the airspace, since reducing the aircraft lateral and vertical separation intervals would rather increase the risk of collision. The target level of safety of the AKARA-FUKUE Corridor at the southern end of Jeju was 247×10^-9. In simple comparison, this means that the risk of an aircraft collision in this area (international safety standards, 5.0×10^-9) is about 50 times higher. The scope of this study is to organize the concept of terms, analyze the air traffic volume, the current status of navigational safety facility usage fees, and investigations of an aircraft collision risk in Jeju southern air corridor. Analyzing government policies and overseas evaluations, revising some of the existing contents, presenting some of the additional contents of new routes, and changing the instrument procedure for Korean-Chinese routes, change of arrive/departure route between Incheon Airport and Shanghai Airport, reduce the risk of aircraft collisions. We hope to restore airspace sovereignty, contribute to policies for the government to take the lead in solving this problem, and expect stability and operational efficiency in air traffic.

• Journal of Navigation and Port Research
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• v.46 no.6
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• pp.509-516
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• 2022

Recently, ships have begun using the Asterix CAT 240 format as a method for transmitting radar image data to other devices. However, the Asterix format has a flexible structure that can be defined by the user, and a format structure defined as unsuitable for ship radar operation may undesirably increase navigational equipment network traffic or reduce stability. Therefore, to reduce the traffic of the navigation network and enhance the stability, a method of defining the optimized Asterix CAT 240 format with an appropriate setting value according to the performance of the radar scanner and display device was studied.

• Journal of Korean Society of Transportation
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• v.35 no.4
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• pp.307-320
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• 2017

The objective of this study is to identify the effectiveness of ESC(Electronic Stability Control) based on a meta analysis technique. Accident Rate, Fatal Crash Rate, Loss of Control Crash Rate were set as indexes of traffic safety evaluation. Also, reviews on the effectiveness of ESC were collected using keyword, 'ESC'. As a result, the Effect size of accident rate odd ratio was 0.90. When ESC system was applied on vehicles, accident rate decreased by 10%. Also, the Effect size of fatal crash rate odd ratio was 0.64. When ESC system was applied on vehicles, fatal crash rate decreased by 36%. Lastly, the Effect size of loss of control crash rate odd ratio was 0.73. When ESC system was applied on vehicles, loss of control crash rate decreased by 27%. The outcome of this study would be effectively used for developing polices and regulations for ESC installation obligation of commercial vehicles.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2000.04a
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• pp.261-264
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• 2000

When there ate several classes of customers demanding service times with different distributions at some stations of a queueing network, the stability problem becomes suddenly complicated compared with the single class case. Recently many researchers had tried to find some kind of stability conditions for multiclass queueing networks, but did not get significant results except in very limited 2-station cases. In this study, we try to develop some dynamic control techniques which can guarantee the stability under the nominal traffic condition. Our approach includes the randomization method and the leaky bucket control scheme. Also, we mention other possibilities such as the discrete-review approach and the generalized round-robin technique. Both theoretical and experimental results will be presented.

• Wind and Structures
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• v.7 no.6
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• pp.393-404
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• 2004

The design of truss type sign support structures is based on the guidelines provided by the American Association of State Highway and Transportation Officials Standard Specifications for Highway Signs, Luminaries and Traffic Signals and the American Institute of Steel Construction Design Specifications. Using these specifications, the column design strength is normally determined using the effective length approach. This approach does not always accurately address all issues associated with frame stability, including the actual end conditions of the individual members, variations of the loads in the members, and the resulting sidesway buckling for truss type sign support structures. This paper provides insight into the problems with the simplified design approach for determining the effective lengths and discusses different approaches for overcoming these simplifications. A system buckling approach, also known as a rational buckling analysis, is used in this study to determine improved predictions for design strength of truss type sign support structures.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.12
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• pp.1857-1863
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• 2012

The VDS(Vehicle Detection System) collects and transfers information about traffic situations in real time, therefore it makes the traffic management effective. Recently, the VDSs have provided good stability and accuracy in regard to system reliability and functions but they also have showed problems such as raising costs and consuming times when a new system is installed and/or the environmental requirements for the system are set up. The reason of the problems is that up to now the collection of the data and information about the traffic situations has been achieved by the 1:1 information exchange between the traffic control surveillance center and the each traffic field, between equipments and centers, and among data processing equipments and also centers. The communication systems used in the VDS are generally composed of 1 : 1 connection of the lines because the communication protocols are different in the most of the cases mentioned above. Consequently, this makes the number of communication lines become larger and causes the cost for the whole traffic information systems to increase. In this paper, a development of a controller to unify the communication protocols for the VDS is peformed to solve the problems which were mentioned above. Specially, the controller developed in this paper was applied to a radar vehicle detector and tested to show its usefulness. In addition to that, the developed controller was also designed to include functions to transfer the information about weather conditions on the roads.