In this article, we address the problem of delayed query processing raised by tree-based index structures in wireless broadcast environments, which increases the access time of mobile clients. We propose a novel distributed index structure and a clustering strategy for streaming XML data that enables energy and latency-efficient broadcasting of XML data. We first define the DIX node structure to implement a fully distributed index structure which contains the tag name, attributes, and text content of an element, as well as its corresponding indices. By exploiting the index information in the DIX node stream, a mobile client can access the stream with shorter latency. We also suggest a method of clustering DIX nodes in the stream, which can further enhance the performance of query processing in the mobile clients. Through extensive experiments, we demonstrate that our approach is effective for wireless broadcasting of XML data and outperforms the previous methods.
In this paper, we propose an energy and latency efficient XML dissemination scheme for the mobile computing. We define a novel unit structure called G-node for streaming XML data in the wireless environment. It exploits the benefits of the structure indexing and attribute summarization that can integrate relevant XML elements into a group. It provides a way for selective access of their attribute values and text content. We also propose a lightweight and effective encoding scheme, called Lineage Encoding, to support evaluation of predicates and twig pattern queries over the stream. The Lineage Encoding scheme represents the parent-child relationships among XML elements as a sequence of bit-strings, called Lineage Code(V, H), and provides basic operators and functions for effective twig pattern query processing at mobile clients. Extensive experiments using real and synthetic data sets demonstrate our scheme outperforms conventional wireless XML broadcasting methods for simple path queries as well as complex twig pattern queries with predicate conditions.
SUMMARYWireless broadcasting of heterogeneous XML data has become popular in many applications, where energy-efficient processing of user queries at the mobile client is a critical issue. This paper proposes a new index structure for wireless stream of heterogeneous XML data to enhance tuning time performance in processing path queries on the stream. The index called PrefixSummary stores for each location path in the XML data the address of a bucket in the stream which contains an XML node satisfying the location path and appearing first in the stream. We present algorithms to generate broadcast stream with the proposed index and to process a path query on the stream efficiently by exploiting the index. We also suggest a replication scheme of PrefixSummary within a broadcast cycle to reduce latency in query processing. By analysis and experiment we show the proposed PrefixSummary approach can reduce tuning time for processing path queries significantly while it can also achieve reasonable access time performance by means of replication of the index over the broadcast stream. key words: wireless broadcast, XML data stream, index, XML path query processing
In this study, a Hydro Co-Extrusion Process of Al-Mn/Al-Si hybrid alloys prepared by electromagnetic duo-casting was investigated. Sleeve of the duo-casted billets is 3003 Al-Mn alloy and core is 4004 Al-Si alloy. It is expected hydrostatic stress during the HCE process enhances formability of materials and minimize any defects in extruded billets due to different material properties between two Al alloys. The duo-casted billet was extruded at temperature of 423K and with extrusion ratio of 5. Finally, the effect of the HCE on microstructure of the billet was investigated by an optical microscope.
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