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With the increasing demand of Medium density polyethylene (MDPE) pipes for gas transmission, the safety concern related with welding defects is becoming a serious matter. In this paper, experimental burst tests and finite element analyses were employed to study butt fusion welded MDPE pipe joints with spherical and planar defects of various sizes. These defects were used to simulate lack of bonding during the welding. Test results showed that in all pipe test cases, the failure location originated from pipe substrates, even though the defect size was increased to 45% of the pipe's wall thickness. The burst pressure could be estimated by the expression employed in the ASME BPVC, and in the burst pressure, the hoop stress was 20.28 MPa. Simulation results showed that the failure position was not only affected by the defect size, but also by the welding bead. It can be argued that a single welding defect whose maximum size is smaller than 15% of the thickness can be used without failure during short-term usage, even when there is no welding bead in the welded joint.

Matching (or mapping) between heterogeneous ontologies becomes crucial for interoperability in distributed and intelligent environments. Although many efforts in ontology mapping have already been conducted, most of them rely heavily on the meaning of entity names rather than the semantics defined in ontologies. In order to deal with semantic heterogeneity, we enrich the semantics of ontologies for content-based matching. In this paper, we propose a semantically-enriched model of ontologies (called MetaOntoModel) where the semantics of concepts are enriched by adding concept-level knowledge (called meta-knowledge) based on three philosophical notions: identity, rigidity, and dependency. Then, we develop a MetaOntoModel-based ontology matching method. Our novel idea is that if two concepts are semantically equivalent, then they have the same metaknowledge. On the contrary, if two concepts possess different kinds of meta-knowledge, then they cannot be matched. We prove that meta-knowledge can determine not only the scope of matches, but also the closest corresponding properties between two similar concepts.

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