Generation of semigroups associated to strongly coupled elliptic operator in Lp(Rd;Rm)L^p(\mathbb R^d;\mathbb R^m)

A class of vector-valued elliptic operators with unbounded coefficients, coupled up to the second-order is investigated in the Lebesgue space $L^p(\mathbb R^d;\mathbb R^m)$ with $p \in (1,\infty)$, providing sufficient conditions for the generation of an analytic $C_0$-semigroup $T(t)$. Under further assumptions, a characterization of the domain of the infinitesimal generator is given

Missing Data and IRT Item Parameter Estimation

Non-randomly missing data has theoretically different implications for item parameter estimation depending on whether joint maximum likelihood or marginal maximum likelihood methods are used in the estimation. The objective of this paper is to illustrate what potentially can happen, under these estimation procedures, when there is an association between ability and the absence of response. In this example, data is missing because some students, particularly low-ability students, did not complete the test

Experimental thermographic investigation for dry finish turning of SAF 2507 steel

The Oil&Gas Industry widely uses Super-Duplex Stainless Steels (S-DSS) since their combination of high mechanical characteristics and corrosion resistance. Among them, the SAF 2507 is one of the renowned. The challenges associated with the machining of these steels are directly related to the high temperature that influences the tool-life and the quality of the finished products. This phenomenon is induced by the low thermal conductivity which leads to a high concentration of heat. In order to properly understand their thermal behavior, the distribution of the temperature varying the cutting parameters should be investigated. During dry finish turning, the evolution of the temperature can be captured through a thermographic test campaign, for instance following a L18 - 2 · 37-5 fractional factorial design with no replications. The data acquired can be deeply studied with a statistical methodology framework, the relationship between the response of the experiment and the machining parameters can be established, and a surrogate model for predicting the temperature can be built and validated. The results show that, for the SAF 2507 steel, the cutting temperature for dry finishing turning is mostly influenced by the deep of cut, the feed rate and slightly by the cutting speed

Generation of semigroups associated to strongly coupled elliptic operators in Lp(Rd;Rm)

A class of vector-valued elliptic operators with unbounded coefficients, coupled up to the second-order is investigated in the Lebesgue space Lp (Rd ; Rm ) with p ∈ (1, ∞), providing sufficient conditions for the generation of an analytic C0-semigroup T (t). Under further assumptions, a characterization of the domain of the infinitesimal generator is given

BV functions and parabolic initial boundary value problems on domains

Il presente lavoro studia il comportamento per tempi piccoli del semigruppo associato ad un operatore ellittico del secondo ordine con coefficienti abbastanza regolari su domini, possibilmente illimitati, regolari. In particolare, considerato il semigruppo associato al problema di co-normale per un operatore ellittico del secondo ordine, viene studiato il comportamento per tempi piccoli del gradiente della soluzione con un certo dato, dimostrando la convergenza alla variazione totale di tale dato, anche in spazi di funzioni con peso continuo. Viene inoltre studiato il comportamento, sempre per tempi piccoli, del semigruppo in un caso di tipo diffusivo, estendendo a semigruppi piu' generici alcuni precedenti lavori di alcuni degli autori. La tecnica utilizzata e' essenzialmente quella degli spazi di interpolazione e della generazione di semigruppi analitici