2,008 research outputs found
Max Scheler
No full textL'articolo racconta la vita e le opere di Max Scheler e illustra i contenuti del suo pensiero filosofico in relazione alle diverse fasi attraversate dall'autore nella sua evoluzioneThe paper sketches the life and works of Max Scheler and explains the contents of his philosophical thought in relation to the different stages the author went through in his evolutio
On the behaviour of classes of min-max-plus systems
No full textDiscrete Event Systems are systems, the time evolution of which can be described by the occurence of events. Well-known examples of DESs are manufacturing systems and transportation networks. An important class of DESs can be described by the so-called (max,+) algebra, in which, compared to the usual arithmetic, the operator + is replaced by the operator max and the operator * is replaced by +. In this thesis we model a railroad network by means of the (max,+) algebra. Furthermore, we develop some theory concerning graphs corresponding to the (max,+) matrix. An extension of the (max,+) algebra is considered, that is, bipartite (min,max,+) systems and seperated (min,max,+) systems. Some theory is developed concerning the existence of the eigenvalue for these types of sytems. Furthermore, we have studied whether it is possible to model railroad networks by means of these kind of systems.Information Technology and System
The Göttingen rotating turbulent Rayleigh-Bénard convection facility
No full textThermally driven turbulent convection under the influence of global rotation is ubiquitous in nature. Well known examples are the outer convective shell of our Sun and the outer liquid core of the Earth. Trying to understand the underlying dynamics of such flows is highly challenging, not only because of the enormous range in length- and time-scales that are involved with these geo/astrophysical cases and the complex interaction of hydrodynamics with electromagnetism, but also because direct measurements on these systems are most often impossible to carry out. We gain access to direct measurements by isolating part of the problem: We focus solely on the hydrodynamical aspects of turbulent convection by performing experiments in the lab and making comparisons with direct numerical simulations (DNS). The canonical system that we use to study such flows is Rayleigh-B\'enard convection (RBC), the flow between a warm bottom plate and cold top plate, in a fluid-filled upright cylindrical cell that is rotating around its geometrical axis. This presentation will focus on the newly constructed rotating RBC facility at the Max Planck Institute for Dynamics and Self-Organization (MPIDS) in G\"ottingen
Point contact abrasive wear behavior of MAX phase materials
No full textThe room temperature abrasive wear behavior of three selected MAX phases, Ti3SiC2, solution strengthened Ti2.7Zr0.3SiC2 and Cr2AlC, is investigated by low velocity scratch testing using a diamond conical indentor with a final radius of 100 μm and a cone angle of 120° and applied loads of up to 20 N. All three materials showed a relatively low wear resistance in comparison to most engineering ceramics such as Al2O3, Si3N4 and SiC. For all three materials, the wear rate scaled more or less linearly with the applied load. The softer Ti3SiC2 with a hardness of 2.8 GPa showed the lowest wear resistance with extensive ploughing and grain breakout damage, both within and outside the direct wear track, in particular at the highest load. The hardest material, Ti2.7Zr0.3SiC2, with a hardness of 7.3 GPa, showed a 5 times better wear resistance. The Cr2AlC with a hardness of 4.8 GPa showed a wear resistance equal to or even better than that of the Ti2.7Zr0.3SiC2. The wear mechanism depends on the applied load and the microstructure of the MAX phase materials tested. For the Ti3SiC2 sample, a quasi-plastic deformation behavior occurs below a point load of 10 N, resulting in grain bending, kink band formation and delamination, grain de-cohesion, as well as trans-and intra-granular fracture near the scratch groove. At this load, the Ti2.7Zr0.3SiC2 and Cr2AlC MAX samples display plastic ploughing, grain boundary cracks and material dislodgments.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.(OLD) MSE-1Delft Aerospace Structures and Materials LaboratoryNovel Aerospace Material
Receding-horizon control for max-plus linear systems with discrete actions using optimistic planning
No full textThis paper addresses the infinite-horizon optimal control problem for max-plus linear systems where the considered objective function is a sum of discounted stage costs over an infinite horizon. The minimization problem of the cost function is equivalently transformed into a maximization problem of a reward function. The resulting optimal control problem is solved based on an optimistic planning algorithm. The control variables are the increments of system inputs and the action space is discretized as a finite set. Given a finite computational budget, a control sequence is returned by the optimistic planning algorithm. The first control action or a subsequence of the returned control sequence is applied to the system and then a receding-horizon scheme is adopted. The proposed optimistic planning approach allows us to limit the computational budget and also yields a characterization of the level of near-optimality of the resulting solution. The effectiveness of the approach is illustrated with a numerical example. The results show that the optimistic planning approach results in a lower tracking error compared with a finite-horizon approach when a subsequence of the returned control sequence is applied.Accepted Author ManuscriptTeam Bart De Schutte
Correlated tunneling in intramolecular carbon nanotube quantum dots
No full textWe investigate correlated electronic transport in single-walled carbon nanotubes with two intramolecular tunneling barriers. We suggest that below a characteristic temperature the long-range nature of the Coulomb interaction becomes crucial to determine the temperature dependence of the maximum {\it G} of the conductance peak. Correlated sequential tunneling dominates transport yielding the power law {\it G}–1}$, typical for tunneling between the ends of two Luttinger liquids. Our predictions are in agreement with recent measurements
De Max-Planck medaille
No full textDe Max-Planck-Medaille is een onderscheiding die sinds 1929 jaarlijks wordt uitgereikt door de toentertijd grootste vereniging van natuurkundigen ter wereld: de Deutsche Physikalische Gesellschaft. Het is als het ware de Nobelprijs voor de theoretische natuurkunde, volgens de natuurkundigen zelf. In 1962 werd deze prestigieuze prijs toegekend aan de Delftse hoogleraar in de theoretische natuurkunde, tevens Rector Magnificus van de TH Delft: Ralph Kronig (1904-1995). De medaille is, samen met een klein persoonlijk archief, in 2016 door de familie geschonken aan de TU Delft.Library Research Service
Toughening mechanisms in nanolayered MAX phase ceramics-a review
No full textAdvanced engineering and functional ceramics are sensitive to damage cracks, which delay the wide applications of these materials in various fields. Ceramic composites with enhanced fracture toughness may trigger a paradigm for design and application of the brittle components. This paper reviews the toughening mechanisms for the nanolayered MAX phase ceramics. The main toughening mechanisms for these ternary compounds were controlled by particle toughening, phase-transformation toughening and fiber-reinforced toughening, as well as texture toughening. Based on the various toughening mechanisms in MAX phase, models of SiC particles and fibers toughening Ti3SiC2 are established to predict and explain the toughening mechanisms. The modeling work provides insights and guidance to fabricate MAX phase-related composites with optimized microstructures in order to achieve the desired mechanical properties required for harsh application environments.</p
Synthesis, crystal structure, microstructure and mechanical properties of (Ti1-Zr )3SiC2 MAX phase solid solutions
No full textAlmost pure (Ti1-xZrx)3SiC2 MAX phase solid solutions with x ranging up to 0.17 were synthesized at temperatures in the range of 1450–1750 °C with reactive Spark Plasma Sintering (SPS). The zirconium partially replaces the M-element titanium of the Ti3SiC2 MAX phase up to x equals 0.17. The lattice parameters of the hexagonal (Ti1-xZrx)3SiC2 MAX phase are determined with X-ray diffraction using Rietveld refinement and show an anisotropic lattice expansion upon Zr insertion into Ti3SiC2. This observation is in very good agreement with density functional theory calculations where the deviation between the measured and calculated lattice parameter is less than 1%. The predicted elastic modulus reduction is only 4%. This behavior can be rationalized by considering the electronic structure, where only minute changes are observable as Zr is incorporated into Ti3SiC2. The measured nanohardness of the synthesized (Ti1-xZrx)3SiC2 MAX phase increases from 12.7 ± 1 GPa for Ti3SiC2 to 16.3 ± 1.1 GPa when x is raised from 0 to 0.17 due to an increasing amount of accompanying Ti1-yZryC. The elastic moduli of (Ti1-xZrx)3SiC2 solid solutions measured by an ultrasonic pulse-echo method (325–354 GPa) are in good agreement with the predicted elastic moduli (357–342 GPa).Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.(OLD) MSE-1Novel Aerospace Material
A max-cut approximation using a graph based MBO scheme
No full text© 2019 American Institute of Mathematical Sciences. All rights reserved. The Max-Cut problem is a well known combinatorial optimization problem. In this paper we describe a fast approximation method. Given a graph G, we want to find a cut whose size is maximal among all possible cuts. A cut is a partition of the vertex set of G into two disjoint subsets. For an unweighted graph, the size of the cut is the number of edges that have one vertex on either side of the partition; we also consider a weighted version of the problem where each edge contributes a nonnegative weight to the cut. We introduce the signless Ginzburg–Landau functional and prove that this functional Γ-converges to a Max-Cut objective functional. We approximately minimize this functional using a graph based signless Merriman–Bence–Osher (MBO) scheme, which uses a signless Laplacian. We derive a Lyapunov functional for the iterations of our signless MBO scheme. We show experimentally that on some classes of graphs the resulting algorithm produces more accurate maximum cut approximations than the current state-of-the-art approximation algorithm. One of our methods of minimizing the functional results in an algorithm with a time complexity of O(|E|), where |E| is the total number of edges on G
- …
