KEYWORDS: Databases, Data modeling, Data communications, Data conversion, Telecommunications, Computing systems, Artificial intelligence, Network architectures, Computer science, Data integration
In existing peer-to-peer database framework designs, coordination rules are assumed already present and never changed
during the whole course of operation. This paper investigates how coordination rules are created and changed, hence
helping ease the procedure. Local database can be on and off dynamically, but this feature of P2P database is
inconsistent with fixed coordination rules, for dependency path will be broken when an intermediate peer is absent. A
restoration mechanism is designed in this scenario to realize dynamic coordination rule. To achieve this, coordination
rules on the same dependency path have to be available after the path is broken, and combined together to form a new
dependency path and bypass the absent peer. To backup rules before host is down they can be published as resource
advertisement to remote peers by underlying P2P platform facility. Actually since coordination rules are no longer
bounded with their host, they can be viewed independent from the database system to form a coordination rule P2P
network, with some peers having no database and purely as rule cache. The protocols about rule cache, combination and
new rule creation request in such network are discussed. Rules float along dependency paths across network and
combine to form a new rule where necessary. A peer wanting to create new coordination rules can publish query and if
there is a rule on another peer which can be combined with the existing one, a new rule is created and send back. This
dependency path discovery process can be similar to route discovery process.
HASN is a hierarchical routing protocol for heterogeneous sensor networks, optimized via cross-layer designs to save sensor's power and improve reliability. There are two kinds of nodes in heterogeneous sensor networks: normal sensor and header node that has more powerful battery and higher performance antenna. A header and sensors in its radio transmitting range compose a cluster. The header takes charge of data collection and data aggregation in its cluster. In a cluster, the communication is unsymmetrical. From the header to sensors is directly reachable, but from sensors to their header needs multi-hop. In this paper, a new dynamic address assignment method is introduced for large number of sensors automatically. A mathematics model of energy optimum relay tree is designed, which can guarantee the minimum energy cost forwarding and relay load balance. We give an approximation algorithm to resolve the model. A centralized scheduling management is proposed to avoid collisions completely in a cluster. We also introduce a mechanism to depress data redundancy.
KEYWORDS: Systems modeling, Data transmission, Computing systems, Network security, Internet, Data storage, Computer science, Telecommunications, Information security, Performance modeling
P2P systems are usually used for information exchange between peers in recent years. However, the open and anonymous nature of a P2P network makes it an ideal medium for malicious peers. There is a lack of efficient mechanism for existing P2P systems to avoid from free riding, whitewashing, collusion and malicious attackers. In this paper, we describe a novel role-base trust model for P2P file sharing system. First, we give object criteria to track each peer's contribution to the system. Second, according to their contribution we divide all the peers into 2 parts: super peers and normal peers. Each of the 2 roles is bonded with different rights and obligations. Third, we show how to carry out the computation and storage at local and global. Finally, we discuss how our trust model allows peer to revoke relationships with distrusted peers. We present a concrete method to validate the proposed trust model and report sets of simulation-based experiments, showing the feasibility and robustness of this model.
Though controlling the coating reflectivity and intracavity diffraction loss, in the four cavity mirror configuration, a dual-wavelength continuous wave (cw) diode-side-pumped Nd:YAG laser that generates simultaneously at wavelengths of 1064 nm and 1319 nm is demonstrated. The relationship between power ratio of the two wavelengths and cavity length is studied. The cw dual-wavelength output power reaches 85 W when the average pump power is more than 500 W. The output power of respective wavelength exceeds 40 W, which is the best record as we know.
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