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Tsai P.-Y.,Taiwan Geographic Information System Center | Lin Y.-T.,National Taiwan Normal University
Lecture Notes in Electrical Engineering | Year: 2014

The alternating group graph, which belongs to the class of Cayley graphs, is one of the most versatile interconnection networks for parallel and distributed computing. Cycle embedding is an important issue in evaluating the efficiency of interconnection networks. In this paper, we show that an n-dimensional alternating group graph AGn has the following results, where F is the set of faulty vertices and/or faulty edges in AGn : (1) For n ≥ 4, AGn-F is edge 4-pancyclic if |F| ≤ n − 4; and (2) For n ≥ 3, AGn-F is vertex-pancyclic if |F| ≤ n − 3. All the results are optimal with respect to the number of faulty elements tolerated, and they are improvements over the cycle embedding properties of alternating group graphs proposed previously in several articles. © Springer Science+Business Media Dordrecht 2014.

Pan T.-Y.,National Taiwan University | Li M.-Y.,Taiwan Geographic Information System Center | Lin Y.-J.,National Taiwan University | Chang T.-J.,National Taiwan University | And 2 more authors.
Hydrological Sciences Journal | Year: 2014

The generation of reliable quantitative precipitation estimations (QPEs) through use of raingauge and radar data is an important issue. This study investigates the impacts of radar QPEs with different densities of raingauge networks on rainfall-runoff processes through a semi-distributed parallel-type linear reservoir rainfall-runoff model. The spatial variation structures of the radar QPE, raingauge QPE and radar-gauge residuals are examined to review the current raingauge network, and a compact raingauge network is identified via the kriging method. An analysis of the large-scale spatial characteristics for use with a hydrological model is applied to investigate the impacts of a raingauge network coupled with radar QPEs on the modelled rainfall-runoff processes. Since the precision in locating the storm centre generally represents how well the large-scale variability is reproduced; the results show not only the contribution of kriging to identify a compact network coupled with radar QPE, but also that spatial characteristics of rainfalls do affect the hydrographs. © 2014 IAHS Press.

Wen T.-H.,National Taiwan University | Jiang J.-A.,National Taiwan University | Sun C.-H.,National Taiwan University | Sun C.-H.,Taiwan Geographic Information System Center | And 2 more authors.
International Journal of Environmental Research and Public Health | Year: 2013

Air pollution has become a severe environmental problem due to urbanization and heavy traffic. Monitoring street-level air quality is an important issue, but most official monitoring stations are installed to monitor large-scale air quality conditions, and their limited spatial resolution cannot reflect the detailed variations in air quality that may be induced by traffic jams. By deploying wireless sensors on crossroads and main roads, this study established a pilot framework for a wireless sensor network (WSN)-based real-time monitoring system to understand street-level spatial-temporal changes of carbon monoxide (CO) in urban settings. The system consists of two major components. The first component is the deployment of wireless sensors. We deployed 44 sensor nodes, 40 transmitter nodes and four gateway nodes in this study. Each sensor node includes a signal processing module, a CO sensor and a wireless communication module. In order to capture realistic human exposure to traffic pollutants, all sensors were deployed at a height of 1.5 m on lampposts and traffic signs. The study area covers a total length of 1.5 km of Keelung Road in Taipei City. The other component is a map-based monitoring platform for sensor data visualization and manipulation in time and space. Using intensive real-time street-level monitoring framework, we compared the spatial-temporal patterns of air pollution in different time periods. Our results capture four CO concentration peaks throughout the day at the location, which was located along an arterial and nearby traffic sign. The hourly average could reach 5.3 ppm from 5:00 pm to 7:00 pm due to the traffic congestion. The proposed WSN-based framework captures detailed ground information and potential risk of human exposure to traffic-related air pollution. It also provides street-level insights into real-time monitoring for further early warning of air pollution and urban environmental management. © 2013 by the authors; licensee MDPI, Basel, Switzerland.

Joe-Air J.,National Taiwan University | Tzu-Shiang L.,National Taiwan University | Cheng-Long C.,National Taiwan University | Chia-Pang C.,National Taiwan University | And 5 more authors.
Sensors | Year: 2011

For mission-critical applications of wireless sensor networks (WSNs) involving extensive battlefield surveillance, medical healthcare, etc., it is crucial to have low-power, new protocols, methodologies and structures for transferring data and information in a network with full sensing coverage capability for an extended working period. The upmost mission is to ensure that the network is fully functional providing reliable transmission of the sensed data without the risk of data loss. WSNs have been applied to various types of mission-critical applications. Coverage preservation is one of the most essential functions to guarantee quality of service (QoS) in WSNs. However, a tradeoff exists between sensing coverage and network lifetime due to the limited energy supplies of sensor nodes. In this study, we propose a routing protocol to accommodate both energy-balance and coverage-preservation for sensor nodes in WSNs. The energy consumption for radio transmissions and the residual energy over the network are taken into account when the proposed protocol determines an energy-efficient route for a packet. The simulation results demonstrate that the proposed protocol is able to increase the duration of the on-dutynetwork and provide up to 98.3% and 85.7% of extra service time with 100% sensing coverage ratio comparing with LEACH and the LEACH-Coverage-U protocols, respectively. © 2011 by the authors; licensee MDPI, Basel, Switzerland.

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