EDP Sciences

With the internet development, querying data on the Web is an attention problem of involving information from distributed, and often dynamically, related Web sources. Basically, some sub-queries can be effectively cached from previous queries or materialized views in order to achieve a better query performance based on the notion of rewriting queries. In this paper, we propose a novel query-rewriting model, called Hierarchical Query Tree, for representing Web queries. Hierarchical Query Tree is a labeled tree that is suitable for representing the inherent hierarchy feature of data on the Web. Based on Hierarchical Query Tree, we use case-based approach to determine what the query results should be. The definitions of queries and query results are both represented as labeled trees. Thus, we can use the same model for representing cases and the medium query results can also be dynamically updated by the user queries. We show that our case-based method can be used to answer a new query based on the combination of previous queries, including changes of requirements and various information sources.

Outlier detection has very important applied value in data mining literature. Different outlier detection algorithms based on distinct theories have different definitions and mining processes. The three-dimensional space graph for constructing applied algorithms and an improved GridOf algorithm were proposed in terms of analyzing the existing outlier detection algorithms from criterion and theory.

In this paper, we propose Term-based Semantic Peerto-Peer Networks (TSPN) to achieve semantic search. For each peer, TSPN builds a full text index of its documents. Through the analysis of resources, TSPN obtains series of terms, and distributes these terms into the network. Thus, TSPN can use query terms to locate appropriate peers to perform semantic search. Moreover, unlike the traditional structured P2P networks, TSPN uses the terms, not the peers, as the logical nodes of DHT. This can withstand the impact of network churn. The experimental results show that TSPN has better performance compared with the existing P2P semantic searching algorithms.

SrTi1−xFexO3−δ ceramics were prepared using a traditional solid-state reaction method. From X-ray diffraction (XRD) result, we found that the doped Fe3+ dissolved in the lattice, and no secondary phase was observed. Cation vacancies in perovskite oxides were identified via positron annihilation lifetime spectroscopy (PALS) measurements. Undoped and Fe-doped SrTiO3 ceramics and single-crystal SrTiO3 were measured by PALS at room temperature. The results show that the main defects in undoped SrTiO3 ceramics are Ti-related defects, and the isolated Ti vacancy lifetime is about 183.4 ps. With the increase of Fe3+, the concentration of the Ti vacancies decreases accompanied by the appearance of the V″Sr − nV o ∙∙ (defect association of Sr vacancies and multiple O vacancies) vacancy defect complexes.

In order to solve security problem of clustering algorithm, we proposed a method to enhance the security of the well-known lowest-ID clustering algorithm. This method is based on the idea of the secret sharing and the (k, n) threshold cryptography. Each node, whether clusterhead or ordinary member, holds a share of the global certificate, and anyk nodes can communicate securely. There is no need for any clusterhead to execute extra functions more than routing. Our scheme needs some prior configuration before deployment, and can be used in critical environment with small scale. The security-enhancement for Lowest-ID algorithm can also be applied into other clustering approaches with minor modification. The feasibility of this method was verified by the simulation results.

Based on the definition of tamper evidence, the authors define a new notion of tamper evidence forward secure signature scheme (TE-FSig), and propose a general method to build a TE-FSig scheme. Based on this method, they also give out a concrete instance. A TE-FSig scheme is constructed by the standard signature scheme, forward secures signature scheme and the aggregate signature scheme. It has an additional property of tamper evidence besides the property of forward secure, which can detect the time period when the key is exposed. In the standard model, the scheme constructed in the paper is proved to satisfy the properties of forward secure, strong forward tamper-evidence secure, and strongly unforgeable under the chosen-message attack.

The chain of trust in bootstrap process is the basis of whole system trust in the trusted computing group (TCG) definition. This paper presents a design and implementation of a bootstrap trust chain in PC based on the Windows and today's commodity hardware, merely depends on availability of an embedded security module (ESM). ESM and security enhanced BIOS is the root of trust, PMBR (Pre-MBR) checks the integrity of boot data and Windows kernel, which is a checking agent stored in ESM. In the end, the paper analyzed the mathematic expression of the chain of trust and the runtime performance compared with the common booting process. The trust chain bootstrap greatly strengthens the security of personal computer system, and affects the runtime performance with only adding about 12% booting time.