Targeted adjustment of residual stresses in hot-formed components by means of process design based on finite element simulation

The aim of this work is to generate an advantageous compressive residual stress distribution in the surface area of hot-formed components by intelligent process control with tailored cooling. Adapted cooling is achieved by partial or temporal instationary exposure of the specimens to a water–air spray. In this way, macroscopic effects such as local plastification caused by inhomogeneous strains due to thermal and transformation-induced loads can be controlled in order to finally customise the surface-near residual stress distribution. Applications for hot-formed components often require special microstructural properties, which guarantee a certain hardness or ductility. For this reason, the scientific challenge of this work is to generate different residual stress distributions on components surfaces, while the geometric as well as microstructural properties of AISI 52100 alloy stay the same. The changes in the residual stresses should therefore not result from the mentioned changed component properties, but solely from the targeted process control. Within the scope of preliminary experimental studies, tensile residual stresses in a martensitic microstructure were determined on reference components, which had undergone a simple cooling in water (from the forming heat), or low compressive stresses in pearlitic microstructures were determined after simple cooling in atmospheric air. Numerical studies are used to design two tailored cooling strategies capable of generating compressive stresses in the same components. The developed processes with tailored cooling are experimentally realised, and their properties are compared to those of components manufactured involving simple cooling. Based on the numerical and experimental analyses, this work demonstrates that it is possible to influence and even invert the sign of the residual stresses within a component by controlling the macroscopic effects mentioned above

Schonende Bodenbearbeitung – Systemlösungen für Profis

Livro sobre Mobilização de Conservação - Soluções para profissionais (em alemão, está prevista a edição em inglês

Pre-implant right ventricular function might be an important predictor of the response to cardiac resynchronization therapy

<p>Abstract</p> <p>Objective</p> <p>Cardiac resynchronization therapy is proven efficacious in patients with heart failure (HF). Presence of biventricular HF is associated with a worse prognosis than having only left ventricular (LV) HF and pacing might deteriorate heart function. The aim of the study was to assess a possible significance of right ventricular (RV) pre-implant systolic function to predict response to CRT.</p> <p>Design</p> <p>We studied 22 HF-patients aged 72 ± 11 years, QRS-duration 155 ± 20 ms and with an LV ejection fraction (EF) of 26 ± 6% before and four weeks after receiving a CRT-device.</p> <p>Results</p> <p>There were no changes in LV diameters or end systolic volume (ESV) during the study. However, end diastolic volume (EDV) decreased from 226 ± 71 to 211 ± 64 ml (p = 0.02) and systolic maximal velocities (SMV) increased from 2.2 ± 0.4 to 2.6 ± 0.9 cm/s (p = 0.04). Pre-implant RV-SMV (6.2 ± 2.6 cm/s) predicted postoperative increase in LV contractility, p = 0.032.</p> <p>Conclusions</p> <p>Pre-implant decreased RV systolic function might be an important way to predict a poor response to CRT implicating that other treatments should be considered. Furthermore we found that 3D- echocardiography and Tissue Doppler Imaging were feasible to detect short-term changes in LV function.</p

Single polynomials that correspond to pairs of cyclotomic polynomials with interlacing zeros

of cyclotomic polynomials with interlacing zero

Diastolic dysfunction in diabetes and the metabolic syndrome: promising potential for diagnosis and prognosis

Cardiac disease in diabetes mellitus and in the metabolic syndrome consists of both vascular and myocardial abnormalities. The latter are characterised predominantly by diastolic dysfunction, which has been difficult to evaluate in spite of its prevalence. While traditional Doppler echocardiographic parameters enable only semiquantitative assessment of diastolic function and cannot reliably distinguish perturbations in loading conditions from altered diastolic functions, new technologies enable detailed quantification of global and regional diastolic function. The most readily available technique for the quantification of subclinical diastolic dysfunction is tissue Doppler imaging, which has been integrated into routine contemporary clinical practice, whereas cine magnetic resonance imaging (CMR) remains a promising complementary research tool for investigating the molecular mechanisms of the disease. Diastolic function is reported to vary linearly with age in normal persons, decreasing by 0.16 cm/s each year. Diastolic function in diabetes and the metabolic syndrome is determined by cardiovascular risk factors that alter myocardial stiffness and myocardial energy availability/bioenergetics. The latter is corroborated by the improvement in diastolic function with improvement in metabolic control of diabetes by specific medical therapy or lifestyle modification. Accordingly, diastolic dysfunction reflects the structural and metabolic milieu in the myocardium, and may allow targeted therapeutic interventions to modulate cardiac metabolism to prevent heart failure in insulin resistance and diabetes

30 years of collaboration

We highlight some of the most important cornerstones of the long standing and very fruitful collaboration of the Austrian Diophantine Number Theory research group and the Number Theory and Cryptography School of Debrecen. However, we do not plan to be complete in any sense but give some interesting data and selected results that we find particularly nice. At the end we focus on two topics in more details, namely a problem that origins from a conjecture of Rényi and Erdős (on the number of terms of the square of a polynomial) and another one that origins from a question of Zelinsky (on the unit sum number problem). This paper evolved from a plenary invited talk that the authors gaveat the Joint Austrian-Hungarian Mathematical Conference 2015, August 25-27, 2015 in Győr (Hungary)

Determination of nutrient salts by automatic methods both in seawater and brackish water: the phosphate blank

9 páginas, 2 tablas, 2 figurasThe main inconvenience in determining nutrients in seawater by automatic methods is simply solved: the preparation of a suitable blank which corrects the effect of the refractive index change on the recorded signal. Two procedures are proposed, one physical (a simple equation to estimate the effect) and the other chemical (removal of the dissolved phosphorus with ferric hydroxide).Support for this work came from CICYT (MAR88-0245 project) and Conselleria de Pesca de la Xunta de GaliciaPeer reviewe