148 research outputs found
Relationship between solidification microstructure and hot cracking susceptibility for continuous casting of low-carbon and high-strength low-alloyed steels: A phase-field study
No full text© The Minerals, Metals & Materials Society and ASM International 2013Hot cracking is one of the major defects in continuous casting of steels, frequently limiting the productivity. To understand the factors leading to this defect, microstructure formation is simulated for a low-carbon and two high-strength low-alloyed steels. 2D simulation of the initial stage of solidification is performed in a moving slice of the slab using proprietary multiphase-field software and taking into account all elements which are expected to have a relevant effect on the mechanical properties and structure formation during solidification. To account for the correct thermodynamic and kinetic properties of the multicomponent alloy grades, the simulation software is online coupled to commercial thermodynamic and mobility databases. A moving-frame boundary condition allows traveling through the entire solidification history starting from the slab surface, and tracking the morphology changes during growth of the shell. From the simulation results, significant microstructure differences between the steel grades are quantitatively evaluated and correlated with their hot cracking behavior according to the Rappaz-Drezet-Gremaud (RDG) hot cracking criterion. The possible role of the microalloying elements in hot cracking, in particular of traces of Ti, is analyzed. With the assumption that TiN precipitates trigger coalescence of the primary dendrites, quantitative evaluation of the critical strain rates leads to a full agreement with the observed hot cracking behavior. © 2013 The Minerals, Metals & Materials Society and ASM International
Hydrogenography, a thin film optical combinatorial study of hydrogen storage materials
No full textGriessen, R.P. [Promotor]Dam, B. [Copromotor
Facial Affective Behavior in Borderline Personality Disorder Indicating Two Different Clusters and Their Influence on Inpatient Treatment Outcome : A Preliminary Study
No full textBackground: The purpose of the present study was threefold: first, to investigate the facial affective behavior in patients with a borderline personality disorder (BPD); second, to examine whether these patients could be divided into clusters according to facial affective behavior; and third, to test whether these clusters would influence the inpatient treatment outcome. Methods: Thirty inpatients with BPD were assessed with the Structured Clinical Interviews for DSM-IV Axis I and II Disorders (SCID I, SCID II) and had to complete a series of questionnaires before and directly after the 12-week long inpatient treatment. Facial affective behavior was recorded during the structured interview for personality organization (STIPO) and afterward coded with the emotional facial action coding system (EMFACS). Measures on psychopathology [beck depression inventory (BDI), Spielberger state and trait anxiety inventory (STAI), Spielberger state and trait anger inventory (STAXI), and symptom cheklist-90-revised (SCL-90-R)], interpersonal problems [Inventory of Interpersonal Problems (IIP)], and personality organization [inventory of personality organization (IPO)] were administered. Results: Cluster analysis before the treatment yielded two groups that differed in general facial expressivity, and regarding the display of anger, contempt, and disgust. The effect sizes of the repeated measures ANOVAs showed that persons with higher scores on the affective facial expressions benefitted more from the treatment in terms of STAI state anxiety, STAXI state and trait anger, IIP total, and the two scales primitive defenses and identity diffusion of the IPO, whereas persons with lower scores benefitted more on the scale IPO reality testing. Conclusion: Our results indicated some initial trends for the importance of facial affective behavior in patients with BPD and their treatment outcome. © Copyright © 2020 Dammann, Rudaz, Benecke, Riemenschneider, Walter, Pfaltz, KÌchenhoff, Clarkin and Gremaud-Heitz.</p
O comportamento da relação de troca na suinocultura catarinense no periodo de 2000 a 2012
No full textTCC (Graduação) - Universidade Federal de Santa Catarina. Centro Socioeconômico. Curso de Graduação em Ciências Econômicas.Este trabalho tem o objetivo de analisar o comportamento da suinocultura catarinense de janeiro de 2000 a setembro de 2012, através do índice de paridade com base no número de exclusões de produtores e no índice de concentração da produção em agroindústrias. Para tanto, inicialmente faz-se uma revisão dos principais conceitos relacionados ao sistema agroindustrial do mercado de suínos de Santa Catarina, bem como a adoção de estratégias competitivas, os custos, o comportamento do produtor integrado e do produtor independente. De modo complementar, é apresentada a trajetória do setor suinícola frente às frequentes crises no período de análise devido à forte influencia do mercado externo e interno nos preços dos insumos e da carne suína. Posteriormente, calculou-se o IP (Índice de Paridade) para verificar a relação de trocas entre o preço pago ao produtor pelo kg do suíno vivo e os principais insumos utilizados para sua produção. Portanto, pela grande relevância deste tema no fomento econômico catarinense surge à necessidade em identificar os motivos pelos quais se reduziu significativamente a quantidade de produtores de suínos, bem como verificar a situação econômica deste setor atualmente
Copper-Catalyzed Enantioselective Conjugate Addition to α,β-Unsaturated Aldehydes with Various Organometallic Reagents
No full textβ-Substituted aldehydes constitute a very important class of compounds found in nature. Synthesis of this motif can be envisioned by C–C bond formation on enals. For this purpose, we report herein the development of enantioselective copper-catalyzed conjugate addition of various organometallic reagents to α,β-unsaturated aldehydes with (R)-H8BINAP, (R)-TolBINAP, and (R)-SEGPHOS as chiral ligands. Three sets of conditions were successfully developed and several enals were used. Reactivity and regio- and enantioselectivities were strongly dependent on reaction conditions and substrates. Good to excellent regio- and enantioselectivities were obtained with zinc reagents R2Zn and aluminum reagents R3Al. However, the asymmetric conjugate addition of Grignard reagents afforded only moderate to good regio- and enantioselectivities
A Variable Turbulent Prandtl and Schmidt Number Model Study for Scramjet Applications.
No full textA turbulence model that allows for the calculation of the variable turbulent Prandtl (Prt) and Schmidt (Sct) numbers as part of the solution is presented. The model also accounts for the interactions between turbulence and chemistry by modeling the corresponding terms. Four equations are added to the baseline k-ζ turbulence model: two equations for enthalpy variance and its dissipation rate to calculate the turbulent diffusivity, and two equations for the concentrations variance and its dissipation rate to calculate the turbulent diffusion coefficient. The underlying turbulence model already accounts for compressibility effects. The variable Prt/Sct turbulence model is validated and tuned by simulating a wide variety of experiments. Included in the experiments are two-dimensional, axisymmetric, and three-dimensional mixing and combustion cases. The combustion cases involved either hydrogen and air, or hydrogen, ethylene, and air. Two chemical kinetic models are employed for each of these situations. For the hydrogen and air cases, a seven species/seven reaction model where the reaction rates are temperature dependent and a nine species/nineteen reaction model where the reaction rates are dependent on both pressure and temperature are used. For the cases involving ethylene, a 15 species/44 reaction reduced model that is both pressure and temperature dependent is used, along with a 22 species/18 global reaction reduced model that makes use of the quasi-steady-state approximation.
In general, fair to good agreement is indicated for all simulated experiments. The turbulence/chemistry interaction terms are found to have a significant impact on flame location for the two-dimensional combustion case, with excellent experimental agreement when the terms are included. In most cases, the hydrogen chemical mechanisms behave nearly identically, but for one case, the pressure dependent model would not auto-ignite at the same conditions as the experiment and the other chemical model. The model was artificially ignited in that case. For the cases involving ethylene combustion, the chemical model has a profound impact on the flame size, shape, and ignition location. However, without quantitative experimental data, it is difficult to determine which one is more suitable for this particular application
Computation of Nonclassical Solutions to Hamilton-Jacobi Problems
No full text. This paper is devoted to the construction of numerical methods for the approximation of nonclassical solutions to multidimensional Hamilton-Jacobi equations, for both scalar and vectorial problems. Recent theoretical results have yielded existence of solutions in many cases for which the usual viscosity approach was ill-suited or not applicable. The selection criterion used here is based on a viscoelasticity/capillarity approach, common in Solid Mechanics. Numerical methods adapted to this framework are built. Consistency of the model equation with the given selection criterion is essential. It is achieved here through the use of high order finite difference schemes. By considering applications to potential well problems, the convergence of the methods are investigated. Key words. Hamilton-Jacobi, viscosity solution, nonconvex, systems, numerical viscosity AMS(MOS) subject classifications. 65M60, 65N30, 35L65 1. Introduction. This paper presents some numerical experiments related ..
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