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Particular cases of nonlinear systems of delay Volterra integro-differential equations (denoted by DVIDEs) with constant delay
τ > 0, arise in mathematical modelling of ‘predator–prey’ dynamics in Ecology. In this paper, we give an analysis of the global
convergence and local superconvergence properties of piecewise polynomial collocation for systems of this type. Then, from
the perspective of applied mathematics, we consider the Volterra’s integro-differential system of ‘predator–prey’ dynamics
arising in Ecology. We analyze the numerical issues of the introduced collocation method applied to the ‘predator–prey’ system
and confirm that we can achieve the expected theoretical orders of convergence.
相似文献
3.
Institution Morphisms 总被引:1,自引:0,他引:1
Institutions formalise the intuitive notion of logical system, including syntax, semantics, and the relation of satisfaction
between them. Our exposition emphasises the natural way that institutions can support deduction on sentences, and inclusions
of signatures, theories, etc.; it also introduces terminology to clearly distinguish several levels of generality of the institution
concept. A surprising number of different notions of morphism have been suggested for forming categories with institutions
as objects, and an amazing variety of names have been proposed for them. One goal of this paper is to suggest a terminology
that is uniform and informative to replace the current chaotic nomenclature; another goal is to investigate the properties
and interrelations of these notions in a systematic way. Following brief expositions of indexed categories, diagram categories,
twisted relations and Kan extensions, we demonstrate and then exploit the duality between institution morphisms in the original
sense of Goguen and Burstall, and the ‘plain maps’ of Meseguer, obtaining simple uniform proofs of completeness and cocompleteness
for both resulting categories. Because of this duality, we prefer the name ‘comorphism’ over ‘plain map’; moreover, we argue
that morphisms are more natural than comorphisms in many cases. We also consider ‘theoroidal’ morphisms and comorphisms, which
generalise signatures to theories, based on a theoroidal institution construction, finding that the ‘maps’ of Meseguer are
theoroidal comorphisms, while theoroidal morphisms are a new concept. We introduce ‘forward’ and ‘semi-natural’ morphisms,
and develop some of their properties. Appendices discuss institutions for partial algebra, a variant of order sorted algebra,
two versions of hidden algebra, and a generalisation of universal algebra; these illustrate various points in the main text.
A final appendix makes explicit a greater generality for the institution concept, clarifies certain details and proves some
results that lift institution theory to this level.
Received December 2000 / Accepted in revised form January 2002 相似文献
4.
A fast algorithm for computing moments of gray images based on NAM and extended shading approach 总被引:1,自引:0,他引:1
Computing moments on images is very important in the fields of image processing and pattern recognition. The non-symmetry
and anti-packing model (NAM) is a general pattern representation model that has been developed to help design some efficient
image representation methods. In this paper, inspired by the idea of computing moments based on the S-Tree coding (STC) representation
and by using the NAM and extended shading (NAMES) approach, we propose a fast algorithm for computing lower order moments
based on the NAMES representation, which takes O(N) time where N is the number of NAM blocks. By taking three idiomatic standard
gray images ‘Lena’, ‘F16’, and ‘Peppers’ in the field of image processing as typical test objects, and by comparing our proposed
algorithm with the conventional algorithm and the popular STC representation algorithm for computing the lower order moments,
the theoretical and experimental results presented in this paper show that the average execution time improvement ratios of
the proposed NAMES approach over the STC approach, and also the conventional approach are 26.63%, and 82.57% respectively
while maintaining the image quality. 相似文献
5.
David MacQueen 《Formal Aspects of Computing》2002,13(3-5):214-232
At a fundamental level, functional and object-oriented programming languages are all ‘higher-order’, in the sense that they
support computing with values that are themselves pieces of program code encapsulated with a local environment. In functional
languages these ‘active’ values are functions, while in object-oriented languages they are objects. Both styles of higher-order
language claim to provide good support for writing adaptable programs, but functional and object-oriented languages achieve
this adaptability in different ways: functional programs rely on parameterisation at the value, type and module level, while
object-oriented languages rely primarily on subtyping and implementation inheritance. Here we compare these two approaches,
mainly in terms of the features and properties of their type systems, and consider the benefits and disadvantages of unifying
(or merging) the two paradigms by adding object-oriented features to ML as a base language. We argue that while some of the
simpler aspects of object-oriented languages are compatible with ML, adding a full- edged class-based object system to ML
leads to an excessively complex type system and relatively little expressive gain, especially if we aim to preserve that mostly
functional style of programming that is a major advantage of ML.
Received March 2002 / Accepted in revised form April 2002 相似文献
6.
Peter Tolmie Andy Crabtree Stefan Egglestone Jan Humble Chris Greenhalgh Tom Rodden 《Personal and Ubiquitous Computing》2010,14(3):181-196
Deploying UbiComp in real homes is central to realizing Weiser’s grand vision of ‘invisible’ computing. It is essential to
moving design out of the lab and making it into an unremarkable feature of everyday life. Deployment can be problematic, however,
and in ways that a number of researchers have already pointed to. In this paper, we wish to complement the community’s growing
understanding of challenges to deployment. We focus on ‘digital plumbing’—i.e., the mundane work involved in installing ubiquitous
computing in real homes. Digital plumbing characterizes the act of deployment. It draws attention to the work of installation:
to the collaborative effort of co-situating prototypical technologies in real homes, to the competences involved, the practical
troubles encountered, and the demands that real world settings place on the enterprise. We provide an ethnographic study of
the work. It makes visible the unavoidable need for UbiComp researchers to develop new technologies with respect to existing
technological arrangements in the home and to develop methods and tools that support the digital plumber in planning and preparing
for change, in managing the contingencies that inevitably occur in realizing change, and in coordinating digital plumbing
and maintaining awareness of change. 相似文献
7.
DSM as a knowledge capture tool in CODE environment 总被引:1,自引:0,他引:1
A design structure matrix (DSM) provides a simple, compact, and visual representation of a complex system/ process. This paper
shows how DSM, a system engineering tool, is applied as a knowledge capture (acquisition) tool in a generic NPD process. The
acquired knowledge (identified in the DSM) is provided in the form of Questionnaires, which are organized into five performance
indicators of the organization namely ‘Marketing’, ‘Technical’, ‘Financial’, ‘Resource Management’, and ‘Project Management’.
Industrial application is carried out for knowledge validation. It is found form the application that the acquired knowledge
helps NPD teams, managers and stakeholders to benchmark their NPD endeavor and select areas to focus their improvement efforts
(up to 80% valid). 相似文献
8.
K. Bauer R. Gentilini K. Schneider 《International Journal on Software Tools for Technology Transfer (STTT)》2011,13(3):273-287
In this paper, we consider the definition of a three-valued semantics for a μ-calculus on abstractions of hybrid automata. To this end, we first develop a framework that is general in the sense that
it provides a preservation result for several possible semantics of the modal operators. In a second step, we instantiate
our framework to two particular abstractions. To this end, a key issue is the consideration of both over- and underapproximated reachability, while classic simulation-based abstractions rely only on overapproximations, and therefore
limit the preservation to the universal (μ-calculus’) fragment. To specialize our general result, we consider (1) modal abstractions, where the notions of ‘may’ and
‘must’ transitions are extended from the purely discrete to the hybrid time framework, and (2) so-called discrete bounded
bisimulation abstractions. 相似文献
9.
Mark Hogarth 《Natural computing》2009,8(3):493-498
Wittgenstein saw a problem with the idea that ‘rule following’ is a transparent process. Here I present an additional problem,
based on recent ideas about non-Turing computing. I show that even the simplest algorithm—Frege’s successor function, i.e.
counting—cannot by itself determine the ‘output’. Specification of a computing machine is also required. 相似文献
10.
Alastair Butler 《Journal of Logic, Language and Information》2007,16(3):241-264
This paper develops a semantics with control over scope relations using Vermeulen’s stack valued assignments as information
states. This makes available a limited form of scope reuse and name switching. The goal is to have a general system that fixes
available scoping effects to those that are characteristic of natural language. The resulting system is called Scope Control
Theory, since it provides a theory about what scope has to be like in natural language. The theory is shown to replicate a
wide range of grammatical dependencies, including options for, and constraints on, ‘donkey’, ‘binding’, ‘movement’, ‘Control’
and ‘scope marking’ dependencies. 相似文献
11.
Pest Control Expert System for Tomato (PCEST) 总被引:4,自引:0,他引:4
This paper presents a real-life pest control expert system for tomato. The system involves two main subtasks, namely: ‘diagnose’
and ‘treat’. The ‘diagnose’ subtask finds out the causes of the growers' complaints, while the ‘treat’ subtask finds out a
treatment plan for these causes. CommonKADS methodology has been used to develop the system. Dependency network is used as
one of our knowledge representation schemes in both subtasks. An expert system evaluation methodology has been suggested and
applied to the developed system.
Received May 1998 / Revised January 1999 / Accepted in revised form May 1999 相似文献
12.
Market-oriented Grids and Utility Computing: The State-of-the-art and Future Directions 总被引:2,自引:0,他引:2
Traditional resource management techniques (resource allocation, admission control and scheduling) have been found to be inadequate
for many shared Grid and distributed systems, that consist of autonomous and dynamic distributed resources contributed by
multiple organisations. They provide no incentive for users to request resources judiciously and appropriately, and do not
accurately capture the true value, importance and deadline (the utility) of a user’s job. Furthermore, they provide no compensation for resource providers to contribute their computing resources
to shared Grids, as traditional approaches have a user-centric focus on maximising throughput and minimising waiting time
rather than maximising a providers own benefit. Consequently, researchers and practitioners have been examining the appropriateness
of ‘market-inspired’ resource management techniques to address these limitations. Such techniques aim to smooth out access
patterns and reduce the chance of transient overload, by providing a framework for users to be truthful about their resource
requirements and job deadlines, and offering incentives for service providers to prioritise urgent, high utility jobs over
low utility jobs. We examine the recent innovations in these systems (from 2000–2007), looking at the state-of-the-art in
price setting and negotiation, Grid economy management and utility-driven scheduling and resource allocation, and identify
the advantages and limitations of these systems. We then look to the future of these systems, examining the emerging ‘Catallaxy’
market paradigm. Finally we consider the future directions that need to be pursued to address the limitations of the current
generation of market oriented Grids and Utility Computing systems. 相似文献
13.
Summary The informational divergence between stochastic matrices is not a metric. In this paper we show that, however, consistent
definitions can be given of ‘spheres’, ‘segments’ and ‘straight lines’ using the divergence as a sort of ‘distance’ between
stochastic matrices. The geometric nature of many ‘reliability functions’ of Information Theory and Mathematical Statistics
is thus clarified.
This work has been done within the GNIM-CNR research activity. 相似文献
14.
Atsuyoshi Nakamura Jun-ichi Takeuchi Naoki Abe 《Annals of Mathematics and Artificial Intelligence》1998,23(1-2):53-82
We consider a variant of the ‘population learning model’ proposed by Kearns and Seung [8], in which the learner is required
to be ‘distribution-free’ as well as computationally efficient. A population learner receives as input hypotheses from a large
population of agents and produces as output its final hypothesis. Each agent is assumed to independently obtain labeled sample
for the target concept and output a hypothesis. A polynomial time population learner is said to PAC-learn a concept class,
if its hypothesis is probably approximately correct whenever the population size exceeds a certain bound which is polynomial,
even if the sample size for each agent is fixed at some constant. We exhibit some general population learning strategies,
and some simple concept classes that can be learned by them. These strategies include the ‘supremum hypothesis finder’, the
‘minimum superset finder’ (a special case of the ‘supremum hypothesis finder’), and various voting schemes. When coupled with
appropriate agent algorithms, these strategies can learn a variety of simple concept classes, such as the ‘high–low game’,
conjunctions, axis-parallel rectangles and others. We give upper bounds on the required population size for each of these
cases, and show that these systems can be used to obtain a speed up from the ordinary PAC-learning model [11], with appropriate
choices of sample and population sizes. With the population learner restricted to be a voting scheme, what we have is effectively
a model of ‘population prediction’, in which the learner is to predict the value of the target concept at an arbitrarily drawn
point, as a threshold function of the predictions made by its agents on the same point. We show that the population learning
model is strictly more powerful than the population prediction model. Finally, we consider a variant of this model with classification
noise, and exhibit a population learner for the class of conjunctions in this model.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
15.
As part of the Bristol Wearable Computing Initiative, we are exploring location-sensing systems suitable for use with wearable
computing. In this paper we present our findings, and in particular a wearable application — the ‘Shopping Jacket’ — which
relies on a minimal infrastructure to be effective. We use two positioning devices, ‘pingers’ and GPS. The pinger is used
to signal the presence of a shop, and to indicate the type of shop and its website. The GPS is used to disambiguate which
branch of a high street chain is being passed. The wearable uses this information to determine whether the wearer needs to
be alerted that they are passing an interesting shop, or to direct the wearer around a shopping mall. The Shopping Jacket
integrates a wearable CardPC, GPS and pinger receivers, a near-field radio link, hand-held display, GSM data telephone and
a speech interface into a conventional sports blazer. 相似文献
16.
David Smith 《AI & Society》2007,21(4):421-428
This article examines the UNESCO Convention on Intangible Cultural Heritage. It accepts the general case made by UNESCO, but
urges greater attention to the ‘real-world’ knowledge of ordinary people. The paper rejects taxonomies of knowledge based
on metaphysical discussions of knowing. Instead, it argues for an approach to knowledge based on the social production of
‘knowledge acts’. It concludes by asserting that support for the diversity of social enactment of knowledge could have valuable
outcomes in the form of new ways of understanding new and emerging technologies. 相似文献
17.
Sarah Kettley 《AI & Society》2007,22(1):5-14
This paper treats contemporary craft as an under-researched resource for wearable computing, and presents some of the alternative
values and experiences that contemporary craft may be able to contribute to the design of personal technological products.
Through design and implementation of a suite of wirelessly networked ‘Speckled’ jewellery, it considers contemporary craft
for its potential as a critical design resource with especial relevance to wearable computing and the broad development of
this paradigm into the everyday. ‘Critical design’ is given a working definition for the purposes of the argument, and a friendship
group of five women of retirement age introduced as the user group for this research. Current practice in the contemporary
craft genre of jewellery is analysed for its potential as a resource for a critical approach to wearable computing, and based
on a set of semi-structured interviews with contemporary jewellery practitioners, the paper presents a set of propositions
for a critical craft approach to wearables design. 相似文献
18.
We consider the emergence of hybrid ecologies, which marry mixed reality environments and ubiquitous computing environments
together to bridge the physical-digital divide. Hybrid ecologies are new class of digital ecology that merge multiple environments,
physical and digital, together. Collaboration in these emerging environments is characterized by ‘fragmented interaction’
in that it is mediated by interaction mechanisms that are differentially distributed. Unpacking the collaborative nature of
fragmented interaction requires that we uncover the ordinary interactional competences that users exploit to make differentially
distributed mechanisms of interaction work and the distributed practices that articulate ‘seamful’ representations and provide
for awareness and coordination.
相似文献
Tom RoddenEmail: |
19.
Istvan S. N. Berkeley 《Minds and Machines》2008,18(1):93-105
The notion of a ‘symbol’ plays an important role in the disciplines of Philosophy, Psychology, Computer Science, and Cognitive
Science. However, there is comparatively little agreement on how this notion is to be understood, either between disciplines,
or even within particular disciplines. This paper does not attempt to defend some putatively ‘correct’ version of the concept
of a ‘symbol.’ Rather, some terminological conventions are suggested, some constraints are proposed and a taxonomy of the
kinds of issue that give rise to disagreement is articulated. The goal here is to provide something like a ‘geography’ of
the various notions of ‘symbol’ that have appeared in the various literatures, so as to highlight the key issues and to permit
the focusing of attention upon the important dimensions. In particular, the relationship between ‘tokens’ and ‘symbols’ is
addressed. The issue of designation is discussed in some detail. The distinction between simple and complex symbols is clarified
and an apparently necessary condition for a system to be potentially symbol, or token bearing, is introduced. 相似文献
20.
Jaz Hee-jeong Choi 《Multimedia Systems》2010,16(1):75-84
With the rise of ubiquitous computing in recent years, concepts of spatiality have become a significant topic of discussion
in design and development of multimedia systems. This article investigates spatial practices at the intersection of youth,
technology, and urban space in Seoul, and examines what the author calls ‘transyouth’: in the South Korean context, these
people are between the ages of 18 and 24, situated on the delicate border between digital natives and immigrants in Prensky’s
[46] terms. In the first section, the article sets out the technosocial environment of contemporary Seoul. This is followed by
a discussion of social networking processes derived from semi-structured interviews conducted in 2007–2008 with Seoul transyouth
about their ‘lived experiences of the city.’ Interviewees reported how they interact to play, work, and live with and within
the city’s unique environment. The article develops a theme of how technosocial convergence (re)creates urban environments
and argues for a need to consider such user-driven spatial recreation in designing cities as (ubiquitous) urban networks in
recognition of its changing technosocial contours of connections. This is explored in three spaces of different scales: Cyworld as an online social networking space; cocoon housing—a form of individual residential space which is growing rapidly in many Korean cities—as a private living space; and ubiquitous
City as the future macro-space of Seoul. 相似文献