This paper presents an efficient semantic service discovery scheme called UbiSearch for a large-scale ubiquitous computing environment. A semantic service discovery network in the semantic vector space is proposed where services that are semantically close to each other are mapped to nearby positions so that the similar services are registered in a cluster of resolvers. Using this mapping technique, the search space for a query is efficiently confined within a minimized cluster region while maintaining high accuracy in comparison to the centralized scheme. The proposed semantic service discovery network provides a number of novel features to evenly distribute service indexes to the resolvers and reduce the number of resolvers to visit. Our simulation study shows that UbiSearch provides good semantic searchability as compared to the centralized indexing system. At the same time, it supports scalable semantic queries with low communication overhead, balanced load distribution among resolvers for service registration and query processing, and personalized semantic matching.
Abstract-Exploiting the multirate capability in mobile ad hoc networks (MANETs) is more complex than in single-hop WLANs because of the rate-distance and rate-hop count tradeoffs. This paper proposes Path-centric on-demand Rate Adaptation for MANETs (PRAM) protocol. A unique feature that sets PRAM apart from most of previous studies is its path-centric approach. While others focus on finding the best data rate for each link and offering a routing path as a collection of links at their best rates, PRAM finds the best data rate for a sourcedestination pair and then, dynamically adapts it based on path lifetime and other factors. Another distinctive feature of PRAM is that it can be seamlessly incorporated with an on-demand routing protocol. Extensive performance study based on ns-2 has demonstrated that PRAM achieves as much as 71.7% higher packet delivery ratio than fixed-rate cases (6∼54Mbps) and as much as 43.2% higher than the multihop version of the wellknown ARF mechanism in a wide range of network scenarios. It is also shown that PRAM is capable of using a mixture of data rates in an adaptive manner.
In this study, the length of ITS2 from four species of the Ulvaceae in Jeju Island varied between 167 and 203 bp. The results of this investigation showed that two genus, Ulva and Enteromorpha are grouped in a monophyletic assemblage with 100% bootstrap support in all phylogenetic trees. However, a thorough examination of these characters from representatives does not provided a way to identify any unique morphological features of clades in this tree. This study reveals that Ulva conglobata and Ulva pertusa belong to one clade in the phylogenetic tree with the samples from Jeju Island, Korea.
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