Modeling the influence of thermal modification on the electrical conductivity of wood

A model has been developed aiming at the description of the effect of thermal modification on the electrical conductivity of wood. The intention was to calculate the moisture content (MC) of thermally modified timber (TMT) through the parameters electrical resistance R, wood temperature T, and CIE Lab color data, which are known to correlate well with the intensity of a heat treatment. Samples of Norway spruce (Picea abies Karst.) and beech (Fagus sylvatica L.) samples were thermally modified in laboratory scale at 11 different heat treatment intensities and the resistance characteristics of the samples were determined. Within the hygroscopic range, a linear relationship between the resistance characteristics and the mass loss (ML) through the heat treatment was established. Based on this, a model was developed to calculate MC from R, T, and ML. To validate this model, color values of 15 different TMTs from industrial production were determined for estimation of their ML and fed into the model. MC of the 15 arbitrarily heat-treated TMTs was calculated with an accuracy of ± 3.5% within the hygroscopic range. The material-specific resistance characteristics based on experimental data led to an accuracy of ± 2.5%. © 2014 Walter de Gruyter GmbH, Berlin/Boston

Ponašanje termički modificiranog drva u vanjskim uvjetima primjene – trajnost, abrazija i izgled

Thermally modified timber (TMT) is increasingly offered in Europe as an alternative to preservative treated timber. TMT durability in field tests as well as its moisture sorption behaviour in façade application was determined so as to consider its suitability for outdoor use. Additionally, abrasion and crack-formation of TMT deckings were examined and the optical appearance of a TMT façade was evaluated after 5 years of service. After 7.5 years exposure in ground contact, the various TMT materials tested were classed as “slightly durable” to “not durable” whereas the classification in above ground exposure was “very durable” to “moderately durable”, which was in line with the reduced moisture sorption of TMT in weathered application. Moreover, the TMT-decking showed less abrasion and crack-formation compared to references, though the TMT façade revealed considerable discoloration by weathering. Hence, the suitability of TMT for above ground use is suggested, but a surface treatment is obligatory if discoloration is objectionable.Termički modificirano drvo (TMT) sve se više nudi u Europi kao alternativa kemijski zaštićenom drvu. Za ocjenu prikladnosti TMT-a za vanjsku upotrebu ispitivana je biološka trajnost u vanjskim uvjetima, kao i sorpcija vode u elementima fasade. Dodatno je ispitivana otpornost na abraziju i nastajanje pukotina u TMT podovima, te je napravljen vizualni pregled TMT fasade nakon petogodišnje upotrebe. Nakon 7,5 godina izloženosti u dodiru s tlom, različiti TMT materijali ocijenjeni su kao "slabo otporni" do "neotporni" dok su ocjene tog istog materijala za izlaganje iznad tla bile "vrlo otporno" do "srednje otporno". Dobivene su ocjene, u skladu sa smanjenom sorpcijom vode TMT materijala u vanjskoj upotrebi. Štoviše, TMT podovi pokazali su manju abraziju i pukotine od referentnog drva, iako su TMT elementi fasade pokazali veću diskoloraciju uzrokovanu abiološkom razgradnjom. Dakle, TMT je u vanjskim uvjetima i iznad tla preporučljiv za upotrebu, ali uz obveznu površinsku obradu ako se želi izbjeći diskoloracija

Performance of thermally modified timber (TMT) in outdoor application - durability, abrasion and optical appearance

Thermally modified timber (TMT) is increasingly offered in Europe as an alternative to preservative treated timber. TMT durability, infield tests as well as its moisture sorption behaviour in facade application was determined so as to consider its suitability for outdoor use. Additionally, abrasion and crack-formation of TMT deckings were examined and the optical appearance of a TMT facade was evaluated after 5 years of service. After 7.5 years exposure in ground contact, the various TMT materials tested were classed as "slightly durable" to "not durable" whereas the classification in above ground exposure was "very durable" to "moderately, durable", which was in line with the reduced moisture sorption of TMT in weathered application. Moreover, the TMT-decking showed less abrasion and crack-formation compared to references, though the TMT facade revealed considerable discoloration by weathering. Hence, the suitability of TMT for above ground use is suggested, but a surface treatment is obligatory if discoloration is objectionable

Ultra Rapid Data Assimilation Based on Ensemble Filters

The goal of this work is to analyse and study an ultra-rapid data assimilation (URDA) method for adapting a given ensemble forecast for some particular variable of a dynamical system to given observation data which become available after the standard data assimilation and forecasting steps. Initial ideas have been suggested and tested by Etherthon 2006 and Madaus and Hakim 2015 in the framework of numerical weather prediction. The methods are, however, much more universally applicable to general non-linear dynamical systems as they arise in neuroscience, biology and medicine as well as numerical weather prediction. Here we provide a full analysis in the linear case, we formulate and analyse an ultra-rapid ensemble smoother and test the ideas on the Lorentz 63 dynamical system. In particular, we study the assimilation and preemptive forecasting step of an ultra-rapid data assimilation in comparison to a full ensemble data assimilation step as calculated by an ensemble Kalman square root filter. We show that for linear systems and observation operators, the ultra-rapid assimilation and forecasting is equivalent to a full ensemble Kalman filter step. For non-linear systems this is no longer the case. However, we show that we obtain good results even when rather strong nonlinearities are part of the time interval [t0, tn] under consideration. Then, an ultra-rapid ensemble Kalman smoother is formulated and numerically tested. We show that when the numerical model under consideration is different from the true model, used to generate the nature run and observations, errors in the correlations will also lead to errors in the smoother analysis. The numerical study is based on the popular Lorenz 1963 model system used in geophysics and life sciences. We investigate both the situation where the full system forecast is calculated and the situation important to practical applications where we study reduced data, when only one or two variables are known to the URDA scheme

Quarks and gluons in the phase diagram of quantum chromodynamics

In this dissertation we study the phase diagram of strongly interacting matter by approaching the theory of quantum chromodynamics in the functional approach of Dyson-Schwinger equations. With these quantum (field) equations of motions we calculate the non-perturbative quark propagator within the Matsubara formalism. We built up on previous works and extend the so-called truncation scheme, which is necessary to render the infinite tower of Dyson-Schwinger equations finite and study phase transitions of chiral symmetry and the confinement/deconfinement transition. In the first part of this thesis we discuss general aspects of quantum chromodynamics and introduce the Dyson-Schwinger equations in general and present the quark Dyson-Schwinger equation together with its counterpart for the gluon. The Bethe-Salpeter equation is introduced which is necessary to perform two-body bound state calculations. A view on the phase diagram of quantum chromodynamics is given, including the discussion of order parameter for chiral symmetry and confinement. Here we also discuss the dependence of the phase structure on the masses of the quarks.In the following we present the truncation and our results for an unquenched Nf=2+1 calculation and compare it to previous studies. We highlight some complementary details for the quark and gluon propagator and discus the resulting phase diagram, which is in agreement with previous work. Results for an equivalent of the Columbia plot and the critical surface are discussed.A systematically improved truncation, where the charm quark as a dynamical quark flavour is added, will be presented in Ch. 4. An important aspect in this investigation is the proper adjustment of the scales. This is done by matching vacuum properties of the relevant pseudoscalar mesons separately for Nf=2+1 and Nf=2+1+1 via a solution of the Bethe-Salpeter equation. A comparison of the resulting Nf=2+1 and Nf=2+1+1 phase diagram indicates that a dynamical charm quark has no influence on the phase structure.An open question about the phase diagram of quantum chromodynamics is the importance of hadronic degrees of freedom. These are subject to an exploratory study in Ch. 5, where we perform a two flavour calculation and include the nucleon as a degree of freedom in the well-known quark-diquark approximation. Due to the lack of explicit knowledge of in-medium properties of the nucleon, we refer to vacuum results and test their influence by variation. The results show that in this truncation baryons have only very little influence on the phase diagram.This is followed by an approach for a systematic investigation of the quark-gluon vertex Dyson-Schwinger equation at finite temperature. The presented work features an internal model vertex. Calculations taking an unquenched gluon as input are presented, where we compare the quark mass function to results from lattice calculations. We give details about the regularised condensate and study the impact of the different quark flavours and the dependence of the calculation on the chosen internal properties.In the last chapter we perform an investigation of the analytical properties of the quark. The Schwinger function, as the Fourier transform of the Euclidean quark propagator with respect to (imaginary) time, is studied in the vacuum as well as the medium. The spectral function, obtained from correlator data by solving an ill-defined inverse problem, is introduced together with the Rothkopf-Burnier Bayesian reconstruction algorithm, which returns the Bayesian answer to the given inverse problem. The status of the reconstruction for test data is presented and an outline given