6,583 research outputs found
Optimal Time-dependent Sequenced Route Queries in Road Networks
In this paper we present an algorithm for optimal processing of
time-dependent sequenced route queries in road networks, i.e., given a road
network where the travel time over an edge is time-dependent and a given
ordered list of categories of interest, we find the fastest route between an
origin and destination that passes through a sequence of points of interest
belonging to each of the specified categories of interest. For instance,
considering a city road network at a given departure time, one can find the
fastest route between one's work and his/her home, passing through a bank, a
supermarket and a restaurant, in this order. The main contribution of our work
is the consideration of the time dependency of the network, a realistic
characteristic of urban road networks, which has not been considered previously
when addressing the optimal sequenced route query. Our approach uses the A*
search paradigm that is equipped with an admissible heuristic function, thus
guaranteed to yield the optimal solution, along with a pruning scheme for
further reducing the search space. In order to compare our proposal we extended
a previously proposed solution aimed at non-time dependent sequenced route
queries, enabling it to deal with the time-dependency. Our experiments using
real and synthetic data sets have shown our proposed solution to be up to two
orders of magnitude faster than the temporally extended previous solution.Comment: 10 pages, 12 figures To be published as a short paper in the 23rd ACM
SIGSPATIA
Keyword-aware Optimal Route Search
Identifying a preferable route is an important problem that finds
applications in map services. When a user plans a trip within a city, the user
may want to find "a most popular route such that it passes by shopping mall,
restaurant, and pub, and the travel time to and from his hotel is within 4
hours." However, none of the algorithms in the existing work on route planning
can be used to answer such queries. Motivated by this, we define the problem of
keyword-aware optimal route query, denoted by KOR, which is to find an optimal
route such that it covers a set of user-specified keywords, a specified budget
constraint is satisfied, and an objective score of the route is optimal. The
problem of answering KOR queries is NP-hard. We devise an approximation
algorithm OSScaling with provable approximation bounds. Based on this
algorithm, another more efficient approximation algorithm BucketBound is
proposed. We also design a greedy approximation algorithm. Results of empirical
studies show that all the proposed algorithms are capable of answering KOR
queries efficiently, while the BucketBound and Greedy algorithms run faster.
The empirical studies also offer insight into the accuracy of the proposed
algorithms.Comment: VLDB201
An Overview of Mobile Ad Hoc Networks for the Existing Protocols and Applications
Mobile Ad Hoc Network (MANET) is a collection of two or more devices or nodes
or terminals with wireless communications and networking capability that
communicate with each other without the aid of any centralized administrator
also the wireless nodes that can dynamically form a network to exchange
information without using any existing fixed network infrastructure. And it's
an autonomous system in which mobile hosts connected by wireless links are free
to be dynamically and some time act as routers at the same time, and we discuss
in this paper the distinct characteristics of traditional wired networks,
including network configuration may change at any time, there is no direction
or limit the movement and so on, and thus needed a new optional path Agreement
(Routing Protocol) to identify nodes for these actions communicate with each
other path, An ideal choice way the agreement should not only be able to find
the right path, and the Ad Hoc Network must be able to adapt to changing
network of this type at any time. and we talk in details in this paper all the
information of Mobile Ad Hoc Network which include the History of ad hoc,
wireless ad hoc, wireless mobile approaches and types of mobile ad Hoc
networks, and then we present more than 13 types of the routing Ad Hoc Networks
protocols have been proposed. In this paper, the more representative of routing
protocols, analysis of individual characteristics and advantages and
disadvantages to collate and compare, and present the all applications or the
Possible Service of Ad Hoc Networks.Comment: 24 Pages, JGraph-Hoc Journa
Achieving value alignment in project delivery
A study into best practice project delivery and the
development of a suite of products, resources and services
to help guide clients and project teams towards the best
approach for specific projects
The complex hybrid origins of the root knot nematodes revealed through comparative genomics
Meloidogyne root knot nematodes (RKN) can infect most of the world's
agricultural crop species and are among the most important of all plant
pathogens. As yet however we have little understanding of their origins or the
genomic basis of their extreme polyphagy. The most damaging pathogens reproduce
by mitotic parthenogenesis and are suggested to originate by interspecific
hybridizations between unknown parental taxa. We sequenced the genome of the
diploid meiotic parthenogen Meloidogyne floridensis, and use a comparative
genomic approach to test the hypothesis that it was involved in the hybrid
origin of the tropical mitotic parthenogen M. incognita. Phylogenomic analysis
of gene families from M. floridensis, M. incognita and an outgroup species M.
hapla was used to trace the evolutionary history of these species' genomes,
demonstrating that M. floridensis was one of the parental species in the hybrid
origins of M. incognita. Analysis of the M. floridensis genome revealed many
gene loci present in divergent copies, as they are in M. incognita, indicating
that it too had a hybrid origin. The triploid M. incognita is shown to be a
complex double-hybrid between M. floridensis and a third, unidentified parent.
The agriculturally important RKN have very complex origins involving the mixing
of several parental genomes by hybridization and their extreme polyphagy and
agricultural success may be related to this hybridization, producing
transgressive variation on which natural selection acts. Studying RKN variation
via individual marker loci may fail due to the species' convoluted origins, and
multi-species population genomics is essential to understand the hybrid
diversity and adaptive variation of this important species complex. This
comparative genomic analysis provides a compelling example of the importance
and complexity of hybridization in generating animal species diversity more
generally
- …