846 research outputs found
AQT - A New Objective Measurement Of The Acoustical Quality Of Sound Reproduction In Small Compartments
No full textHygro-thermo-chemo-mechanical coupled discrete model for the self-healing in Ultra High Performance Concrete
No full textReliable durability predictions and design for advanced cement-based materials cannot disregard the modelling of their inherent self-healing capability. A discrete meso-scale model to simulate the recovery in water tightness, stiffness and strength induced by the (stimulated) autogenous healing of cracks for Ultra High Performance Concrete is presented. In this paper the model is implemented into the numerical framework of the Multiphysics-Lattice Discrete Particle Model (M-LDPM), resulting from the coupling of the Hygro-Thermo-Chemical (HTC) model and Lattice Discrete Particle Model (LDPM). Consistently with experimental evidence, the development of the self-repairing process is modelled as consisting of two independent stages: (a) the healing of matrix cracks, affecting both moisture permeability and fracture strength in the cracked state, and (b) the recovery in terms of fibre bridging action, relying on the adhesion between the healing products and the walls of the tunnel cracks which form during the fibre debonding process. This research activity is framed into the Horizon 2020 project ReSHEALience (GA 760824)
Numerical modelling of the ageing of Ultra High Performance Fibre Reinforced Cementitious Composites
No full textThis paper focuses on the experimental characterisation and numerical modelling of mechanical ageing of UHPC. With reference to a specific UHPC mix, conceived in the framework of the Horizon 2020 project ReSHEALience to be used in extremely aggressive environments, the strength and stiffness build-up have been assessed through two experimental campaigns, for both the plain matrix and the fibre-reinforced composite. Then, the tests have been simulated by means of a discrete numerical model, the Multiphysics—Lattice Discrete Particle Model (M-LDPM), improved for capturing the ma-terial ageing in presence of slag in the mixture. The parameters governing the hydration process have been identified through the ONIX model, equally improved to account for the effect of slag. The com-parison between experimental and numerical results has shown that the model well-captures the mate-rial behaviour at each age. The model capability of capturing the material ageing accurately is necessary to distinguish its effect on the mechanical response from those due to other phenomena such as autog-enous or engineered healing
Corticotropin-releasing factor and vasoactive intestinal polypeptide activate gene transcription through the cAMP signaling pathway in a catecholaminergic immortalized neuron
No full textCorticotropin-releasing factor (CRF) and vasoactive intestinal polypeptide (VIP) are neuropeptides displaying a variety of short-term effects in the nervous system. It is shown here in transfection experiments of an immortalized noradrenergic locus coeruleus-like cell line that both CRF and VIP also trigger a signaling cascade capable of activating gene transcription. To elucidate the signaling pathway leading to transcriptional induction, cells were transfected with an inhibitor for cAMP-dependent protein kinase, targeted to the nucleus via a nuclear-localization signal. Transcriptional induction of a reporter gene by CRF and VIP was blocked in these cells, indicating that the cAMP-dependent protein kinase is required for transducing CRF and VIP generated signals into the nucleus. Additionally, transfection experiments with a reporter gene containing cAMP response elements in its regulatory region demonstrate that CRF and VIP receptor activation induce transcription through this genetic regulatory element. We conclude that long-term effects of CRF and VIP in neurons are likely to be mediated by the transcriptional regulation of CRF and VIP-responsive genes via the cAMP signaling pathway
Sharp Estimates for Fundamental Solutions of some degenerate Kolmogorov equations arising in Finance
No full textThe thesis is devoted to the study of a degenerate parabolic partial differential equation which arises in models for the pricing of Arithmetic Average Asian Options in Finance in the framework introduced by Black, Scholes and Merton.
The aim of the work is to prove optimal estimates for the fundamental solution of the related operator.
The interest in this result is in that an expression of the fundamental solution is not available, whereas explicit information on its asymptotic behaviour are provided in the work.
The problem of proving upper and lower estimates for the fundamental solution of a second order partial evolution operator has long history and it has been considered by many authors in the study of PDE's.
The methodology used involves several techniques belonging to the theory of Partial Differential Equations, Stochastic Processes and Optimal Control Theory, and can be applied to several different problems.
In particular, the proof of the lower bound relies on the repeated application of the Harnack inequality for positive solution of along a suitable chain of points, combined with an optimization procedure. Such procedure lead us to naturally consider an optimal control problem which will be explicitly solved.
For the upper bound, we combine analytical results with elementary tools belonging to Optimal Control Theory. In particular we use an analogous results to the Moser iteration and the Hamilton-Jacobi-Bellman equation for the value function related to a relevant optimal control problem.La tesi è dedicata allo studio di una equazione differenziale alle derivate parziali parabolica degenere che interviene in modelli per il pricing di Opzioni asiatiche a media aritmetica in Finanza nel setting introdotto da Black, Scholes e Merton.
Lo scopo del lavoro è quello di ricavare stime ottimali per la soluzione fondamentale del relativo operatore.
L'interesse in questo risultato risiede nel fatto che un' espressione della soluzione fondamentale non è disponibile, mentre informazioni esplicite sul suo comportamento asintotico sono fornite nel lavoro di Tesi.
Il problema di dimostrare stime ottimali dall'alto e dal basso per la soluzione fondamentale di un operatore di evoluzione del secondo ordine ha lunga storia ed è stato considerato da molti autori nello studio delle PDE's.
La metodologia utilizzata coinvonlge diverse tecniche appartenenti all' Analisi Matematica, Processi stocastici e Teoria del controllo ottimo e può essere applicata a diversi problemi.
In particolare, la prova del limite inferiore si basa sulla ripetuta applicazione della disuguaglianza di Harnack per soluzioni positive lungo un'opportuna catena di punti, combinata con una procedura di ottimizzazione. Tale procedura ci conduce a considerare naturalmente un problema di controllo ottimo che sarà risolto in modo esplicito.
Per il limite superiore, si combinano alcuni risultati di PDE con strumenti elementari appartenenti alla teoria del controllo ottimo. In particolare, si usano risultati analoghi all' iterazione Moser e l'equazione di Hamilton-Jacobi-Bellman per la funzione valore relativo ad un pertinente problema di controllo ottimo
Non-linear Digital Audio Processor for dedicated loudspeaker systems
No full textIn this paper a non-linear loudspeaker
model, which accurately reproduces the low frequency
behavior, is presented. This description, derived from
an extension of the well known Small-Thiele equations,
requires far less computational time and memory space
than generic non linear structures. Moreover a noticeable
further reduction of the number of operations and of
the memory cells required has been achieved by means
of a multirate architecture. Inversion of the proposed
model allows digital prefiltering of the electrical signal in
order to compensate for the non idealities of the electroacoustic
conversion. The above filter structure implemented
on a digital signal processor, placed between the
audio signal source and the power amplifier allows effective
compensation of loudspeaker linear (both magnitude
and phase) and non linear distortion. Measurement
results obtained with a commercial woofer are discussed
Inverse numerical filters for linearisation of loudspeaker's response
No full textIn this paper a non-linear loudspeaker model, which accurately reproduces the low frequency behavior, is presented. This description, derived from an extension of the well known Small-Thiele equations, requires far less computational time and memory space than generic non linear structures. Moreover a noticeable further reduction of the number of operations and of the memory cells required has been achieved by means of a multirate architecture. Inversion of the proposed model allows digital prefiltering of the electrical signal in order to compensate for the nonidealities of the electro-acoustic conversion. The above filter structure implemented on a digital signal processor, placed between the audio signal source and the power amplifier allows effective compensation of loudspeaker linear (both magnitude and phase) and non-linear distortion. Measurement results obtained with a commercial woofer are discussed
RE-1 silencing transcription factor-4 (REST4) is neither a transcriptional repressor nor a de-repressor.
No full textTrait-anxiety negatively correlates to neuroendocrine activity in normal subjects (abstract)
No full textNumerical modelling via a coupled discrete approach of the autogenous healing for Fibre-Reinforced Cementitious Composites (FRCCs)
No full textAiming to predict long-term performance of advanced cement-based materials and design more durable structures, a reliable modelling of the autogenous healing of cementitious materials is crucial. A dis-crete model for the regain in terms of water tightness, stiffness and strength induced by the autogenous and/or “stimulate" autogenous healing was recently proposed for ordinary plain concrete. The modelling proposal stemmed from the coupling of two models, namely the Hygro-Thermo-Chemical (HTC) model, on one side,and the Lattice Discrete Particle Model (LDPM), on the other side, resulting in the Multiphysics-Lattice Discrete Particle Model (M-LDPM). Being this approach not customised only for ordinary concrete, but for the whole broad category of cementitious materials, in this paper, its application to Fibre-Reinforced Cementitious Composites is presented. To accurately simulate what has been experimentally observed so far, the mechanical model is updated to also include the self-healing of the tunnel cracks at the fibre-matrix interfaces. Therefore,the self-repairing process is modelled to develop on two independent stages: (a) matrix cracks healing, and(b) fibre bridging action restoring. This research activity is part of the modelling tasks framed into the project ReSHEALience, funded from the European Union’s Horizon 2020 Research and Innovation Programme
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