10,177 research outputs found
Succinct Dictionary Matching With No Slowdown
The problem of dictionary matching is a classical problem in string matching:
given a set S of d strings of total length n characters over an (not
necessarily constant) alphabet of size sigma, build a data structure so that we
can match in a any text T all occurrences of strings belonging to S. The
classical solution for this problem is the Aho-Corasick automaton which finds
all occ occurrences in a text T in time O(|T| + occ) using a data structure
that occupies O(m log m) bits of space where m <= n + 1 is the number of states
in the automaton. In this paper we show that the Aho-Corasick automaton can be
represented in just m(log sigma + O(1)) + O(d log(n/d)) bits of space while
still maintaining the ability to answer to queries in O(|T| + occ) time. To the
best of our knowledge, the currently fastest succinct data structure for the
dictionary matching problem uses space O(n log sigma) while answering queries
in O(|T|log log n + occ) time. In this paper we also show how the space
occupancy can be reduced to m(H0 + O(1)) + O(d log(n/d)) where H0 is the
empirical entropy of the characters appearing in the trie representation of the
set S, provided that sigma < m^epsilon for any constant 0 < epsilon < 1. The
query time remains unchanged.Comment: Corrected typos and other minor error
Massless Scalar Field Propagator in a Quantized Space-Time
We consider in detail the analytic behaviour of the non-interacting massless
scalar field two-point function in H.S. Snyder's discretized non-commuting
spacetime. The propagator we find is purely real on the Euclidean side of the
complex plane and goes like as from either the
Euclidean or Minkowski side. The real part of the propagator goes smoothly to
zero as increases to the discretization scale and remains zero
for . This behaviour is consistent with the termination of
single-particle propagation on the ultraviolet side of the discretization
scale. The imaginary part of the propagator, consistent with a
multiparticle-production branch discontinuity, is finite and continuous on the
Minkowski side, slowly falling to zero when . Finally, we
argue that the spectral function for the multiparticle states appears to
saturate as probes just beyond the discretization scale. We
speculate on the cosmological consequences of such a spectral function.Comment: 6 pages, 1 eps figure embedded in manuscrip
Giant Intrinsic Carrier Mobilities in Graphene and Its Bilayer
We have studied temperature dependences of electron transport in graphene and
its bilayer and found extremely low electron-phonon scattering rates that set
the fundamental limit on possible charge carrier mobilities at room
temperature. Our measurements have shown that mobilities significantly higher
than 200,000 cm2/Vs are achievable, if extrinsic disorder is eliminated. A
sharp (threshold-like) increase in resistivity observed above approximately
200K is unexpected but can qualitatively be understood within a model of a
rippled graphene sheet in which scattering occurs on intra-ripple flexural
phonons
Local status and power in area-based health improvement partnerships
This is the authors' PDF version of an article published in Health© 2014. The definitive version is available at http://hea.sagepub.comArea-based initiatives (ABIs) have formed an important part of public policy towards more socio-economically deprived areas in many countries. Co-ordinating service provision within and across sectors has been a common feature of these initiatives. Despite sustained policy interest in ABIs, little empirical work has explored relations between ABI providers and partnership development within this context remains under-theorised. This paper addresses both of these gaps by exploring partnerships as a social and developmental process, drawing on concepts from figurational sociology to explain how provider relations develop within an ABI. Qualitative methods were used to explore, prospectively, the development of an ABI targeted at a town in the north west of England. A central finding was that, although effective delivery of ABIs is premised on a high level of coordination between service providers, the pattern of interdependencies between providers limits the frequency and effectiveness of cooperation. In particular, the interdependency of ABI providers with others in their organisation (what is termed here ‘organisational pull’) constrained the ways in which they worked with providers outside of their own organisations. ‘Local’ status, which could be earned over time, enabled some providers to exert greater control over the way in which provider relations developed during the course of the initiative. These findings demonstrate how historically constituted social networks, within which all providers are embedded, shape partnership development. The theoretical insight developed here suggests a need for more realistic expectations among policy makers about how and to what extent provider partnerships can be managed. Keywords: partnership, collaboration, community services, area-based initiatives, organisational pull, figurational sociologyNational Health Service (NHS
Referral based expertise search system in a time evolving social network
To solve some difficult problems that requires procedural knowledge, people often seek the advice of experts who have got competence in that problem domain. This paper focuses on locating and determining an expert in a particular knowledge domain. In most cases, social network of a user is explored through referrals to locate human experts. Past work in searching for experts through referrals focused primarily on static social network. However, static social network fail to accurately represent the set of experts, as in a knowledge domain as time evolves experts continuously keep changing. This paper focuses on the problem of finding experts through referrals in a time evolving co-author social network. Authors and co-authors of research publication for instance are domain experts. In this paper, we propose a solution where the network is expanded incrementally and the information on domain experts is suitably modified. This will avoid periodic global expertise recomputation and would help to effectively retrieve relevant information on domain experts. A novel data structure is also introduced in our study to effectively track the change in expertise of an author with time. © 2010 ACM
Wood Tracking Information Systems To Confront Illegal Logging
This paper examines the current wood tracking information systems used in international wood trade aiming to prevent and control illegally logged timber and wood products trade. Moreover, innovative log tracking mechanisms and technologies are also described and assessed. Wood tracking can add value to the wood product, by establishing an information system aiming to recognize and locate legal wood and wood products. Apart form the traditional punching and painting log-tracing methods, there are various digital wood traceability information systems for recognition, log tracking and monitoring, including barcodes, QR codes, RFID, microchips etc. Furthermore, various innovative wood tracking systems are also presented and discussed. The aim of the paper is to describe and quote those methods used in wood trade sector, to identify current trends and perspectives and to quote them as to their reliability, practicality, level of information provided and cost. Further it provides insight from log-traceability methods used in Greek Forests.</jats:p
Energy distribution in a BTZ black hole spacetime
We evaluate the energy distribution associated with the (2+1)-dimensional
rotating BTZ black hole. The energy-momentum complexes of Landau-Lifshitz and
Weinberg are employed for this computation. Both prescriptions give exactly the
same form of energy distribution. Therefore, these results provide evidence in
support of the claim that, for a given gravitational background, different
energy-momentum complexes can give identical results in three dimensions, as it
is the case in four dimensions.Comment: 16 pages, LaTeX; v2: comments, clarifications and references added,
version to appear in Int.J.Mod.Phys.
Experimental fully contextual correlations
Quantum correlations are contextual yet, in general, nothing prevents the
existence of even more contextual correlations. We identify and test a
noncontextuality inequality in which the quantum violation cannot be improved
by any hypothetical postquantum theory, and use it to experimentally obtain
correlations in which the fraction of noncontextual correlations is less than
0.06. Our correlations are experimentally generated from the results of
sequential compatible tests on a four-state quantum system encoded in the
polarization and path of a single photon.Comment: REVTeX4, 6 pages, 3 figure
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