Distributed Processing of Generalized Graph-Pattern Queries in SPARQL 1.1

We propose an efficient and scalable architecture for processing generalized graph-pattern queries as they are specified by the current W3C recommendation of the SPARQL 1.1 "Query Language" component. Specifically, the class of queries we consider consists of sets of SPARQL triple patterns with labeled property paths. From a relational perspective, this class resolves to conjunctive queries of relational joins with additional graph-reachability predicates. For the scalable, i.e., distributed, processing of this kind of queries over very large RDF collections, we develop a suitable partitioning and indexing scheme, which allows us to shard the RDF triples over an entire cluster of compute nodes and to process an incoming SPARQL query over all of the relevant graph partitions (and thus compute nodes) in parallel. Unlike most prior works in this field, we specifically aim at the unified optimization and distributed processing of queries consisting of both relational joins and graph-reachability predicates. All communication among the compute nodes is established via a proprietary, asynchronous communication protocol based on the Message Passing Interface

Effect of driving cycles on the particulate mass and number emissions from in-use heavy heavy-duty diesel vehicles

This study focused primarily on the particle mass and number emission from various in-use heavy heavy-duty diesel vehicles operating on different driving cycles. Chemical speciation results are also presented to discuss the formation and composition of particles emitted during various cycles. Tests were performed with West Virginia University\u27s Transportable Heavy Duty Vehicle Emissions Testing Laboratory located at Riverside, California. Five vehicles were selected to cover a wide range of model year from 1989 to 2004. All five vehicles were subjected to chemical speciation and analysis conducted by Desert Research Institute. WVU employed the use of the Scanning Mobility Particle Sizer (SMPS) to measure particle size distributions. Regulated gaseous emissions and total particulate matter from the exhaust were sampled from a full-flow CVS dilution tunnel system. A mini-dilution system was dedicated specifically for particle sizing, which samples partially from the raw exhaust. All vehicles were subjected to California\u27s Heavy Heavy-Duty Diesel Truck (HHDDT) schedule which consisted of an idle, creep, transient and cruise mode. Particle size and chemical speciation data are presented only for the idle and cruise modes. (Abstract shortened by UMI.)