Theoretical psychology | EPFL Graph Search

Theoretical psychology is concerned with theoretical and philosophical aspects of psychology. It is an interdisciplinary field with a wide scope of study. It focuses on combining and incorporating existing and developing theories of psychology non-experimentally. Theoretical psychology originated from the philosophy of science, with logic and rationality at the base of each new idea. It existed before empirical or experimental psychology. Theoretical psychology is an interdisciplinary field involving psychologists specializing in a wide variety of psychological branches. There have been a few prominent pioneers of theoretical psychology such as Wilhelm Wundt, William James, Sigmund Freud, and John B. Watson. There has also been a number of notable contributors which include Jerome Kagan, Alan E. Kazdin, Robert Sternberg, Kenneth J. Gergen, and Ulric Neisser. These contributors may publish in a variety of journals, including journals for general psychology, like American Psychologist

Finite Element Method on Riemann Surfaces and Applications to the Laplacian Spectrum

Marc Maintrot

The objective of this PhD thesis is the approximate computation of the solutions of the Spectral Problem associated with the Laplace operator on a compact Riemann surface without boundaries. A Riemann surface can be seen as a gluing of portions of the Hyperbolic Plane made with suitable conditions to obtain a 2 dimensional manifold. The solutions of the Spectral Problem associated with the Laplace operator are to be understood as the eigenfunctions defined on the surface and their corresponding eigenvalues. This work is separated into two parts: the first part describes the method used to approximate the eigenvalues and eigenfunctions, the second focuses on the design of a program to compute these approximations. The approximation method is inspired by the Finite Element Method (FEM), in that it relies on the variational expression of the Spectral Problem and the definition of a finite subspace of functions in which the approximated eigenvalues and eigenfunctions are computed. However, it differs from the FEM in that it removes the euclidian basis of the FEM and is invariant under the isometries of the Hyperbolic Plane. To ful fill this objective, we begin by geodesically triangulating the surface as regularly as possible. This hyperbolic triangulation allows us to de ne the finite subspace of functions by using the concept of barycentric coordinates associated with each vertex of the triangulation (idea introduced by Whitney and taken up by Dodziuk). We then prove that the approximated solutions convergence to the exact ones when the diameter of the triangulation decreases, as well as the order of convergence. The program is a practical application of the theoretical work and allows the computation of the approximated eigenfunctions and eigenvalues.

EPFL2012

A theoretical study of disorder and decomposition in multinary nitrides hard coatings materials

Björn Alling

The development of multinary nitrides materials has revolutionised the hard coatings industry over the last 20 years. Especially important materials systems in this matter have been TiAlN and CrAlN which shows higher hardness, better oxidation resistance and can perform at higher temperatures as compared to TiN. When synthesised through physical vapour deposition techniques these system form cubic rock salt structured Ti1-xAlxN and Cr1-xAlxN solid solutions as a metastable phase over a large part of the concentration range. One of the main objectives during the optimisation of the coatings has been to increase the amount of Al in the coating while still keeping the rock salt structure, avoiding phase separation and the formation of hexagonal wurtzite AlN. However, in Al-rich TiAlN coatings it was found that isostructural decomposition within the cubic phase was in fact beneficial for the coatings performance at working temperatures just below 1000 °C. The reason was that the formation of strained coherent c-AlN domains within the grains initiated a age-hardening of the coating. In the CrAlN coatings it is possible to solve a larger amount of Al in the cubic phase. Possibly connected to this fact is that no isostructural decomposition and in principle no age hardening has been observed in rock salt structured Cr1-xAlxN. Although large series of experimental investigations have been performed on these systems, no systematic theoretical study has yet been undertaken. This theoretical work is an attempt by means of first-principles calculations together with thermodynamics considerations within the framework of alloy theory, to close or decrease the knowledge gap between experimental observations of cutting performance of various coatings and the fundamental quantum mechanical and thermodynamics processes that governs it. We first consider the structural properties of the treated mixed nitride systems. The concept of atomic misfit or volume difference, which is well known in the community is studied and the physics that leads to a positive deviation from Vegard's rule is revealed. Then the TiAlN and CrAlN systems are studied in detail. A clear connection between the development of the electronic structure with composition and the mixing enthalpy of the alloys, and thus the tendency for decomposition, is found for TiAlN. The importance of magnetic effects on the thermodynamics of mixing in CrAlN is established leading to a qualitative lower tendency for decomposition. Since the nitrogen composition can deviate substantially from perfect stoichiometry in these systems, a study of the influence of nitrogen vacancies on the decomposition pattern of TiAlN in the cubic phase is performed. The results imply that a presence of nitrogen sub-stoichiometry in Al-rich TiAlN will enhance the tendency for isostructural decomposition. The achieved results including those for the systems ScAlN and HfAlN are compared and discussed especially by considering volume misfit and electronic bandstructure effects as driving forces for coherent and incoherent decomposition.

EPFL2009

Computational Shifts in Theatrical Space

Andrew James Sempere

This dissertation describes a set of research projects that were conducted between 2012 and 2014 in order to answer the question how do computational ideas alter our understanding of place? Each project was produced in the context of the performing arts and included plays, dance performances and film and installation work. For each project new software and hardware systems were created as a means of exploring different types of mediated communication. These systems include a scalable depth-camera based tracking system for performance on stage, a tool for manipulation of live-streamed video incorporated into stage performance, a method of tracking biometric data of performers live during the performance and a game-engine for creating interactive environments. Collectively these experiments establish a framework for the discussion of the nature of the shifts caused by applying computational ideas to space. Finally, the results lay the foundation for further theoretical work concerning the creation of cultural artifacts that exist somewhere between the material and immaterial, the influence of computation on the nature of modeling, and the impact of ubiquitous computing on contemporary notions of performance and play.

EPFL2015