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Kim  Sehyeong  Jun  Sanghoon  Jung  Donghwi 《Water Resources Management》2022,36(13):5049-5061

Various data-driven anomaly detection methods have been developed for identifying pipe burst events in water distribution systems (WDSs); however, their detection effectiveness varies based on network characteristics (e.g., size and topology) and the magnitude or location of bursts. This study proposes an ensemble convolutional neural network (CNN) model that employs several burst detection tools with different detection mechanisms. The model converts the detection results produced by six different statistical process control (SPC) methods into a single compromise indicator and derives reliable final detection decisions using a CNN. A total of thirty-six binary detection results (i.e., detected or not) for a single event were transformed into a six-by-six grayscale heatmap by considering multiple parameter combinations for each SPC method. Three different heatmap configuration layouts were considered for identifying the best layout that provides higher CNN classification accuracy. The proposed ensemble CNN pipe burst detection approach was applied to a network in Austin, TX and improved the detection probability approximately 2% higher than that of the best SPC method. Results presented in this paper indicate that the proposed ensemble model is more effective than traditional detection tools for WDS burst detection. These results suggest that the ensemble model can be effectively applied to many detection problems with primary binary results in WDSs and pipe burst events.

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In the present study, flow structure around a live rhinoceros beetle in a tethered flight is investigated experimentally using a smoke-wire visualization technique in a wind tunnel with a free-stream velocity of 1.2 m/s, which is close to that of a typical flight speed. While varying the body angle (from 5 to 85°), the flow structures generated by the hindwings, elytra, and body are visualized along the spanwise direction. During the flapping period, the complex flow structures comprised leading-edge, trailing-edge, and tip vortices generated on the hindwing, but the flow structure is quite simple on the elytra (attached flow) and body (separated flow). As the body angle increases, these vortices convect in the downward direction, which matches the observation that the body angle of a hovering flight is larger than that of a forward flight. When the body angle matches the condition of forward flight, it is also found that the Strouhal number of a flapping hindwing is tuned to 0.4, which is known as an optimal value for thrust efficiency. Further, the effect of free-stream velocity (i.e., advance ratio) on the formation and evolution of these coherent vortical structures are investigated.

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This article discusses technical issues related to delivery of multimedia services, such as video-on-demand, over heterogeneous networking environments. In particular, it describes the design and implementation of an experimental system for multimedia service interworking between a DAVIC (Digital Audio Visual Council) domain and an Internet domain. The system, called MIDDLEMEN (middlemen for multimedia environment), consists of the broker and the interworking unit, which work together to provide multimedia services across different types of networks in a seamless manner. The broker acts as a guide to multimedia services, and complements servers or clients that are not equipped with full functionality. The broker also controls the resources in MIDDLEMEN. The interworking unit performs various translation functions under the control of the broker, including stream transport protocol conversion, traffic monitoring and bit-rate control, service gateway conversion, and stream control conversion. Current implementation supports the delivery of a DAVIC-compliant VOD service from an ATM network to an IP network  相似文献   
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