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As the most active project in the Hadoop ecosystem these days (Zaharia, 2014), Spark is a fast and general purpose engine for large-scale data processing. Thanks to its advanced Directed Acyclic Graph (DAG) execution engine and in-memory computing mechanism, Spark runs programs up to 100x faster than Hadoop MapReduce in memory, or 10x faster on disk (Apache, 2016). However, Spark performance is impacted...
VF (Variable Frequency) based motor drive, which occupies a large proportion in total power load, is growing up rapidly these years. It shall affect the load model of power system greatly, for their characteristic is quite different from that of traditional asynchronous motor drive. Firstly, both the simulation and physical experiment on VF motor are carried out with voltage drop disturbs, and the...
In order to realize load current imbalance measuring for paralleling IGBT devices, the authors propose a novel method for measuring the imbalances from IGBT gate charge. In the study, an analytical model between gate charge and on-state current has been worked out to find the current differences of IGBT among each paralleled sub-circuits. The results from simulation show that the analytical model...
In the era of big data, Hive has quickly gained popularity for its superior capability to manage and analyze very large datasets, both structured and unstructured, residing in distributed storage systems. However, great opportunity comes with great challenges: Hive query performance is impacted by many factors which makes capacity planning and tuning for Hive cluster extremely difficult. These factors...
Combining condition-based maintenance (CBM) with large-area power-failure, an N-k contingency on-line identification method based on CBM is proposed in this paper. According to real-time data of CBM, a failure possibility model for equipments is built, and the online searching and screening of N-k contingency path are implemented by use of the theory of functional group and modified searching approach;...
The spatial fixed-pattern noise (FPN) compromises severely the quality of the acquired imagery, even makes such images inappropriate for some applications. In order to lower the FPN, some critical nonuniformity correction (NUC) algorithms such as NUC based on linear model, scene-based NUC and so on have been developed. But each algorithm has some drawbacks: restricted application in small dynamic...
Recently, dataspace has been proposed as a new architecture in the evolution of information integration. However, how to fulfill the vision of dataspace, i.e. pay-as-you-go integration, is still a suspensive issue, and the first challenge is data modeling. In this paper, we present a flexible data model called triple model which is similar to RDF but more suitable to dataspace applications. Information...
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