2,345 research outputs found
On a general model structure for macroscopic biological reaction rates.
No full textMacroscopic modelling of bioprocesses requires the determination of a biological reaction scheme and a kinetic model. The a priori selection of an appropriate kinetic model structure is usually made difficult by the lack of detailed bioprocess knowledge and the profusion of apparently similar biological kinetic laws. Moreover, parameter identification is made arduous and time-consuming by the strong non-linearities involved in kinetic laws. In most cases, these kinetic structures are non-linearizable and no first parameter estimation can be deduced easily. In order to avoid such identification problems, Bogaerts et al. [Bogaerts, Ph. Castillo, J. Hanus, R. 1999. A general mathematical modelling technique for bioprocesses in engineering applications. Syst. Anal. Model. Simul. 35, 87-113] have developed a general linearizable kinetic structure which allows the representation of activation and/or inhibition effects of each component in the culture. This paper further generalizes this structure in order to improve the way saturation effects are taken into account, and in turn, improve the biological interpretation of the model parameters. The main advantage of the proposed structure lies in an associated systematic estimation procedure. The usefulness of the proposed model is tested with simulated as well as with experimental data.Journal ArticleResearch Support, Non-U.S. Gov'tSCOPUS: ar.jinfo:eu-repo/semantics/publishe
Groundedness in Logics With a Fixpoint Semantics
No full textIn the field of knowledge representation and reasoning, many different logics are
developed. Often, these logics exhibit striking similarities, either because they
emerged from related ideas, or because they use similar underlying fundamental
principles. Approximation fixpoint theory (AFT) is an abstract algebraical
unifying framework that aims at exposing these principles by formalising them
in lattice theory. It has been successfully applied to unify all common semantics
of logic programs, autoepistemic logic, default logic, and more recently Dung’s
argumentation frameworks and abstract dialectical frameworks.
In this dissertation, we extend approximation fixpoint theory to expose more
underlying principles common to the aforementioned logics. In these domains,
researchers have made use of a similar intuition: that facts (or models) can be
derived from the ground up. They typically phrase this intuition by saying, e.g.,
that the facts should be grounded, or that they should not be unfounded, or
that they should be supported by cycle-free arguments. In different domains,
semantics that allow ungrounded models have received a lot of criticism. In logic
programming for example, this was the case for Clark’s completion semantics,
which was later improved by perfect model semantics, stable semantics and
well-founded semantics. In autoepistemic logic, a similar evolution happened:
Moore’s expansion semantics turned out to allow self-supporting models; this
resulted in the development of many different semantics in attempts to get rid
of this erroneous behaviour.
In the first part of this dissertation, we formalise groundedness in approximation
fixpoint theory. We study how groundedness relates to other concepts and
fixpoints studied in AFT. We apply our abstract theory to the aforementioned
domains: we show that our notion of groundedness indeed captures the intuitions
that existed in these domains and study complexity of reasoning with grounded
models. We study which existing semantics are grounded and which are not.
For example, for logic programming, we find that Clark’s completion semantics
(indeed) is not grounded, while stable and well-founded semantics are grounded. We show that the well-founded model is not just any grounded model: it is the
least precise partial grounded model.
In the second part of this thesis we define a class of autoepistemic theories for
which it is informally clear how to construct the intended model. Unfortunately,
despite previous claims that the well-founded semantics captures the meaning
of autoepistemic theories very well (e.g., because of its constructive nature),
the well-founded semantics fails to identify this model. In order to overcome
this limitation, we propose, algebraically, a new constructive semantics based
on the notion of groundedness. Our new construction refines the well-founded
model construction and succeeds in identifying the intended model for the class
of motivating examples. Furthermore, we show that for this class of examples,
our novel construction constructs the unique grounded fixpoint.
Summarised, in this dissertation, we continue the work on approximation fixpoint
theory by identifying novel concepts occurring in all of the application domains
and by refining existing semantics to better capture the intended meaning of a
class of theories
Totally Symmetric Kekule Structures in Fullerene Graphs with Ten or More Symmetries
No full textGraph theoretic fullerenes are designed to model large carbon molecules: each vertex represents a carbon atom and the edges represent chemical bonds. A totally symmetric Kekulé structure in a fullerene is a set of independent edges which is fixed by all symmetries of the fullerene. It was suggested in a paper by S. J. Austin, J. Baker, P. W. Fowler, D. E. Manolopoulos and in a paper by K. M. Rogers and P. W. Fowler that molecules with totally symmetric Kekulé structures could have special physical and chemical properties. Starting from a catalog given by J.E.Graver, we study all graph theoretic fullerenes with at least ten symmetries and we establish exactly which of them have at least one totally symmetric Kekulé structure.SCOPUS: ar.jinfo:eu-repo/semantics/publishe
A logic-based multi-agent system for ethical monitoring and evaluation of dialogues
No full textDialogue Systems are tools designed for various practical purposes concerning human-machine interaction. These systems should be built on ethical foundations because their behavior may heavily influence a user (think especially about children). The primary objective of this paper is to present the architecture and prototype implementation of a Multi Agent System (MAS) designed for ethical monitoring and evaluation of a dialogue system. A prototype application, for monitoring and evaluation of chatting agents' (human/artificial) ethical behavior in an online customer service chat point w.r.t their institution/company's codes of ethics and conduct, is developed and presented. Future work and open issues with this research are discussed
Integrated land delivery: Towards improving land administration in Zambia
No full textCivil Engineering and Geoscience
Totally Symmetric Kekule Structures in Fullerene Graphs with Ten or More Symmetries
No full textGraph theoretic fullerenes are designed to model large carbon molecules: each vertex represents a carbon atom and the edges represent chemical bonds. A totally symmetric Kekulé structure in a fullerene is a set of independent edges which is fixed by all symmetries of the fullerene.
It was suggested in a paper by S. J. Austin, J. Baker, P. W. Fowler, D. E. Manolopoulos and in a paper by K. M. Rogers and P. W. Fowler that molecules with totally symmetric Kekulé structures could have special physical and chemical properties. Starting from a catalog given by J.E.Graver, we study all graph theoretic fullerenes with at least ten symmetries and we establish exactly which of them have
at least one totally symmetric Kekulé structure
Design of silicon Mach-Zehnder interferometer and ring resonator with a free spectral range tolerant against waveguide-width variations
No full textA stoichiometric reaction scheme for Saccharothrix algeriensis growth and thiolutin production
No full textA new bacterial species, Saccharothrix algeriensis NRRL B-24137, was isolated in 1992 in the Sahara desert. This filamentous bacterium is able to produce dithiolopyrrolones, molecules presenting antibacterial, antifungal, and anticancer properties. In this study, a “reaction engineering” approach was adopted to gain more knowledge on the growth of Sa. algeriensis and its dithiolopyrrolone production on a semi-synthetic liquid medium. The objective is to establish a reaction scheme of the bacterium metabolism from extracellular experimental information, relatively easy to obtain. The approach enabled us to show that Sa. algeriensis could grow using several substrates that were sequentially consumed and that substrate limitation may induce a secondary metabolism in antibiotic production. From these qualitative data, a general reaction scheme was extracted consisting of four reactions: growth via amino acids, glucose consumption for maintenance, growth using glucose, and thiolutin production. The stoichiometric coefficients and the reaction extends were identified using a factorial analysis based on the bilinear structure of the component mass balances in a batch reactor. The analysis of the reaction stoichiometry enabled us to draw some conclusions concerning the substrate consumption pathway
De informatievoorziening ten behoeve van de leegstandbestrijding
No full textDeze scriptie betreffende de informatievoorziening ten behoeve van leegstandbestrijding bestaat uit twee delen. Het eerste deel is een algemeen literatuuronderzoek waarin is nagegaan in hoeverre gemeenten aan leegstandbestrijding doen en hoe de informatievoorziening met betrekking tot die bestrijding eruit ziet. Hieruit kwam naar voren dat lang niet elke gemeente leegstand bestrijdt. Het wel of niet bestrijden hangt af van een aantal factoren, waarvan de wel of niet problematische omvang van de leegstand de belangrijkste is. De van kracht zijnde wetgeving schrijft leegstandbestrijding niet voor. Die keuze is aan de gemeente zelf. Verder blijkt dat gemeenten die wel leegstand bestrijden dat op verschillende wijze doen. De rol van de informatievoorziening kan daarbij aanzienlijk verschillen. De voor dit onderzoek meest interessante wijze van leegstandbestrijding is die waarbij een gemeente een leegmeldingsplicht heeft en leegstand in een register bijhoudt. Het tweede deel van de scriptie beschrijft de informatievoorziening tav leegstandbestrijding van de gemeente Rotterdam.Civil Engineering and GeosciencesVastgoedinformatie en kartografi
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