146 research outputs found
Geometric Separation and Exact Solutions for the Parameterized Independent Set Problem on Disk Graphs (Extended Abstract)
No full textJochen Alber # Universitat Tubingen, Wilhelm-Schickard-Institut fur Informatik, Sand 13, D-72076 Tubingen, Germany
NTMpy: An open source package for solving coupled parabolic differential equations in the framework of the three-temperature model
No full textThe NTMpy code package allows for simulating the one-dimensional thermal response of multilayer samples after optical excitation, as in a typical pump-probe experiment. Several Python routines are combined and optimized to solve coupled heat diffusion equations in one dimension, on arbitrary piecewise homogeneous material stacks, in the framework of the so-called three-temperature model. The energy source deposited in the material is modelled as a light pulse of arbitrary cross-section and temporal profile. A transfer matrix method enables the calculation of realistic light absorption in presence of scattering interfaces as in multilayer samples. The open source code is fully object-oriented to enable a user-friendly and intuitive interface for adjusting the physically relevant input parameters. Here, we describe the mathematical background of the code, we lay out the workflow, and we validate the functionality of our package by comparing it to commercial software, as well as to experimental transient reflectivity data recorded in a pump-probe experiment with femtosecond light pulses.Program summaryProgram title: NTMpy v.0.1.1CPC Library link to program files: https: //doi.org/10.17632/5czr76gmwr.1Developer's repository link: https://github.com/udcm-su/NTMpyCode Ocean capsule: https://codeocean.com/capsule/5661399Licensing provisions: MIT licenseProgramming language: PythonExternal routines: Python 3.5 or higher, numpy, matplotlib, bsplines, tqdmNature of problem: 1-dimensional coupled non linear partial differential equations; diffusion and relaxation dynamics formultiple systems and multiple layers.Solution method: Simulate the diffusion and relaxation dynamics of up to 3 coupled systems via an object oriented user interface. In order to approximate the solution and its derivatives in space B-Spline interpolation is used. The solution is developed in time via the Explicit Euler method.Additional comments including restrictions and unusual features: A routine to automatically select the ideal time step for stability of the algorithm is implemented. Routines for output of raw data in order to post process and pre- made visualization routines are implemented. (C) 2021 The Author(s). Published by Elsevier B.V
Exakte Algorithmen für NP-harte Probleme auf Netzwerken
No full textWir befassen uns in der Arbeit mit dem Entwurf von exakten Algorithmen für verschiedene NP-vollständige Optimierungsprobleme auf Graphen, wie beispielsweise Vertex Cover, Independent Set oder Dominating Set. Im Vordergrund der Arbeit stehen exakte Lösungsverfahren mit beweisbaren Laufzeitschranken. Wir verfolgen dabei den jüngst vorgeschlagenen Ansatz sogenannter “parametrisierter Algorithmen”. Dabei untersuchen wir sowohl von theoretischer, als auch von praktischer Seite unterschiedliche Methoden des Algorithmen-Designs: Datenreduktion, beschränkte Suchbäume, Separation von Graphen und das Konzept von Baumzerlegungen. Schließ- lich stellen wir ein Software-Paket vor, welches im Rahmen dieses Projektes entwickelt wurde und eine Vielzahl der entwickelten Algorithmen implementiert
A General Kernelization Technique for Domination and Independence Problems in Sparse Classes
No full textWe unify and extend previous kernelization techniques in sparse classes [Jochen Alber et al., 2004; Pilipczuk and Siebertz, 2018] by defining water lilies and show how they can be used in bounded expansion classes to construct linear bikernels for (r,c)-Dominating Set, (r,c)-Scattered Set, Total r-Domination, r-Roman Domination, and a problem we call (r,[λ,μ])-Domination (implying a bikernel for r-Perfect Code). At the cost of slightly changing the output graph class our bikernels can be turned into kernels. We also demonstrate how these constructions can be combined to create "multikernels", meaning graphs that represent kernels for multiple problems at once
Age-Inscriptions and Social Change
No full textThis special issue introduces the concept of age-inscription. It accounts for the ways that transitions, expectations and markers around age and life-course stages are modified in interplay with social change. This new concept is necessary, we argue, because age-inscriptions correspond to more indeterminate and transitional levels of changes in aging trajectories and life stages than the concept of norms. Inscriptions lie between rules, laws, and norms on the one hand, and individual feelings, emotions, and actions on the other. They are at least slightly shared between individuals, and, thus, somewhat more standardized than individual behavior, but not as standardized and shared as norms. The introduction to this special issue lays out the reasons why age-inscriptions happen, as well as the primary ways by which they are formed and generated. We conclude by arguing that contemporary age-inscriptions are fashioned in relation to a longer life course encountered by a new generation, an increasing temporalization and institutionalization of the life course, and high levels of mobility and migration.Peer reviewe
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