Strain-induced kinetics of intergrain defects as the mechanism of slow dynamics in the nonlinear resonant response of humid sandstone bars

A closed-form description is proposed to explain nonlinear and slow dynamics effects exhibited by sandstone bars in longitudinal resonance experiments. Along with the fast subsystem of longitudinal nonlinear displacements we examine the strain-dependent slow subsystem of broken intergrain and interlamina cohesive bonds. We show that even the simplest but phenomenologically correct modelling of their mutual feedback elucidates the main experimental findings typical for forced longitudinal oscillations of sandstone bars, namely, (i) hysteretic behavior of a resonance curve on both its up- and down-slopes, (ii) linear softening of resonant frequency with increase of driving level, and (iii) gradual recovery (increase) of resonant frequency at low dynamical strains after the sample was conditioned by high strains. In order to reproduce the highly nonlinear elastic features of sandstone grained structure a realistic non-perturbative form of strain potential energy was adopted. In our theory slow dynamics associated with the experimentally observed memory of peak strain history is attributed to strain-induced kinetic changes in concentration of ruptured inter-grain and inter-lamina cohesive bonds causing a net hysteretic effect on the elastic Young's modulus. Finally, we explain how enhancement of hysteretic phenomena originates from an increase in equilibrium concentration of ruptured cohesive bonds that are due to water saturation.Comment: 5 pages, 3 figure

Ons Europaplein : ontwerp voor een nieuw Europaplein in Renkum

Het Europaplein in Renkum ligt er triest bij. Er is veel achterstallig onderhoud en het plein wordt als veel te stenig ervaren. Op basis van een gedegen sociaal ruimtelijke analyse en in nauwe samenspraak met de gebruikers van het plein is een schetsontwerp gemaakt voor een nieuw Europaplein: interessant voor iedereen met fijne plekken om te zitten en te spelen met midden op het plein mogelijkheden voor verschillende activiteiten. Het ontwerp is zo opgebouwd dat een gefaseerde realisatie mogelijk is. Afhankelijk van beschikbare financiering kunnen verschillende opties al dan niet worden uitgevoerd. Het ontwerp hoeft niet in één keer uitgevoerd te worden. De aanleg kan gespreid gerealiseerd worden zonder dat de kwaliteit van de uiteindelijke beoogde verbeteringen in het geding komt

Lyndon Interpolation for Modal Logic via Type Elimination Sequences

This note describes a method for constructing Lyndon interpolants based on quasi-models and type elimination sequences.The same method was employed in [2] (using mosaics) to compute optimal-size Lyndon interpolants for formulas in theguarded-fragment and the guarded-negation fragment. This note serves to showcase the method in a simpler setting, namely that of the basic modal language. To provide context, I also briefly survey some other gener

Lyndon Interpolation for Modal Logic via Type Elimination Sequences

This note describes a method for constructing Lyndon interpolants based on quasi-models and type elimination sequences.The same method was employed in [2] (using mosaics) to compute optimal-size Lyndon interpolants for formulas in theguarded-fragment and the guarded-negation fragment. This note serves to showcase the method in a simpler setting, namely that of the basic modal language. To provide context, I also briefly survey some other gener

Characterising Modal Formulas with Examples

We study the existence of finite characterisations for modal formulas. A finite characterisation of a modal formula φ is a finite collection of positive and negative examples that distinguishes φ from every other, non-equivalent modal formula, where an example is a finite pointed Kripke structure. This definition can be restricted to specific frame classes and to fragments of the modal language: a modal fragment Ⅎ admits finite characterisations with respect to a frame class ℱ if every formula φ ∈ Ⅎ has a finite characterisation with respect to Ⅎ consisting of examples that are based on frames in ℱ. Finite characterisations are useful for illustration, interactive specification and debugging of formal specifications, and their existence is a precondition for exact learnability with membership queries. We show that the full modal language admits finite characterisations with respect to a frame class ℱ only when the modal logic of ℱ is locally tabular. We then study which modal fragments, freely generated by some set of connectives, admit finite characterisations. Our main result is that the positive modal language without the truth-constants ⊤ and ⊥ admits finite characterisations w.r.t. the class of all frames. This result is essentially optimal: finite characterisability fails when the language is extended with the truth constant ⊤ or ⊥ or with all but very limited forms of negation.</p

Proving Craig and Lyndon Interpolation Using Labelled Sequent Calculi

We have recently presented a general method of proving the fundamental logical properties of Craig and Lyndon Interpolation (IPs) by induction on derivations in a wide class of internal sequent calculi, including sequents, hypersequents, and nested sequents. Here we adapt the method to a more general external formalism of labelled sequents and provide sufficient criteria on the Kripke-frame characterization of a logic that guarantee the IPs. In particular, we show that classes of frames definable by quantifier-free Horn formulas correspond to logics with the IPs. These criteria capture the modal cube and the infinite family of transitive Geach logics

On the Power and Limitations of Examples for Description Logic Concepts (Extended Abstract)

Labeled examples (i.e., positive and negative examples) are an attractive medium for communicating complex concepts. They are useful for deriving concept expressions (such as in concept learning, interactive concept specification, and concept refinement) as well as for illustrating concept expressions to a user or domain expert. We investigate the power of labeled examples for describing description logic concepts. Specifically, we systematically study the existence and efficient computability of finite characterizations, i.e., finite sets of labeled examples that uniquely characterize a single concept, for a wide variety of description logics between ℰℒ and AℒCQℐ, both without an ontology and in the presence of a DL-Lite ontology. Finite characterizations are relevant for debugging purposes, and their existence is a necessary condition for exact learnability with membership queries.</p

Revisiting vocal perception in non-human animals: a review of vowel discrimination, speaker voice recognition, and speaker normalization

Article / Letter to editorInstituut Biologie LeidenInstituut Biologie Leide