Heat Release by Controlled Continuous-Time Markov Jump Processes

We derive the equations governing the protocols minimizing the heat released by a continuous-time Markov jump process on a one-dimensional countable state space during a transition between assigned initial and final probability distributions in a finite time horizon. In particular, we identify the hypotheses on the transition rates under which the optimal control strategy and the probability distribution of the Markov jump problem obey a system of differential equations of Hamilton-Jacobi-Bellman-type. As the state-space mesh tends to zero, these equations converge to those satisfied by the diffusion process minimizing the heat released in the Langevin formulation of the same problem. We also show that in full analogy with the continuum case, heat minimization is equivalent to entropy production minimization. Thus, our results may be interpreted as a refined version of the second law of thermodynamics.     

Improving charge transport in poly(3‐hexylthiophene) transistors via blending with an alkyl‐substituted phenylene–thiophene–thiophene–phenylene molecule

A prototypical semiconducting bicomponent system consisting of a conjugated polymer, that is, poly(3‐hexylthiophene) (P3HT), blended with a small thiophene containing conjugated molecule, that is, an alkyl‐substituted bisphenyl‐bithiophene [phenylene–thiophene–thiophene–phenylene (PTTP)], has been used as an electroactive active layer in field‐effect transistors (FETs). The self‐assembly of this bicomponent system at surfaces has been studied at different length scales, from the nanoscale to the macroscale, and compared with the behavior of monocomponent films of PTTP and P3HT. The correlation between morphology and electric properties of the semiconducting material is explored by fabricating prototypes of FETs varying the relative concentrations of the two‐component blend. The maximum charge carrier mobility value, achieved with a few percent of PTTP component, is not simply due to a uniform dispersion of the molecules in the polymer matrix, but rather to the generation of very long percolation paths, whose composition and electrical properties can be tuned with the PTTP concentration. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Temperature dependence of the time-resolved emissions of CsI:Tl

Abstract

Time-resolved emissions of Csl:T1 are investigated. The system is laser-excited in the A-band at 308 nm and the emissions are observed in the range 370–650 nm, from 30 K to 300 K. Their analysis by means of a deconvolution permits the valuation of decay-times down to 1 ns. At every temperature many bands are observed and some of them show slow and fast components. The decay-times of the fast components are in the range 1–10 ns while the slow ones are even longer than 1 μs. In many cases intermediate decay-times of the order of 100 ns exist. The competition among the bands interests the application of this system as active material for tunable solid-state laser.     

Ionic electroactive polymer metal composites: Fabricating,modeling, and applications of postsilicon smart devices

Smart systems adapt to the surrounding environments in a number of ways. They are capable to scavenge energy from available sources, sense and elaborate external stimuli and adequately react. Electro Active Polymers are playing a main role in the realization of smart systems for applications if fields such as bio inspired and autonomous robotics, medicine, and aerospace. This paper focus on the possibility to use Ionic Polymer Metal Composites as a class of materials relevant to the realization of post silicon smart systems. The three main aspects of this new technology, i.e., fabrication methods, modeling, and applications are described with emphasis to most recent results. Attention is given to main challenges and shortcomings to be solved for technology, modelling, and control of IPMC based devices that need to be solved before this new technology can be fully exploited in real world applications. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013     

Elastic response to temperature variations in granular media: A phenomenological analysis

The purpose of this work is to discuss a methodology for the interpretation of experimental data and its application, in the context of thermo-elasto-dynamics, to the investigation of the time dependence of variables, such as the resonance frequency of a consolidated granular sample, subjected to various protocols of varying temperature. An analytical equation is deduced, which fits extremely well the experimental curves and has the expected asymptotic behavior of the dependent variable. It also predicts the observed asymmetry in the response to the sign of the temperature variation.     

Corrosion on prehistoric Cu–Sn-alloys: the influence of artificial environment and storage

The paper contributes to the identification of different corrosion products detected on the cross-section specimens sampled from Bronze Age swords and one helmet found between 60–160 years ago. The objects are kept in 1889 built oak showcases at the Natural History Museum Vienna, having suffered unknown restoration treatments. The identified corrosion products not only affect further eventual treatment in conservation science of copper base objects but also contribute to identify the often unknown find context, which is meant to facilitate archaeological interpretation of the Bronze Age weapons. The analyses of the samples were carried out using SEM-EDXS-EBSD and optical microscopy.     

The projective dimension of three cubics is at most 5

Let R be a polynomial ring over a field and I an ideal generated by three forms of degree three. Motivated by Stillman's question, Engheta proved that the projective dimension $\mathrm{pd}(R/I)$ of $R/I$ is at most 36, although the example with largest projective dimension he constructed has $\mathrm{pd}(R/I)=5$. Based on computational evidence, it had been conjectured that $\mathrm{pd}(R/I)\le 5$. In the present paper we prove this conjectured sharp bound.     

Coarsening Dynamics in a Simplified DNLS Model

We investigate the coarsening evolution occurring in a simplified stochastic model of the Discrete NonLinear Schrödinger (DNLS) equation in the so-called negative-temperature region. We provide an explanation of the coarsening exponent n=1/3, by invoking an analogy with a suitable exclusion process. In spite of the equivalence with the exponent observed in other known universality classes, this model is certainly different, in that it refers to a dynamics with two conservation laws.