Helsinki University of Technology

About: Helsinki University of Technology is a based out in . It is known for research contribution in the topics: Thin film & Vortex. The organization has 8962 authors who have published 20136 publications receiving 723787 citations. The organization is also known as: TKK & Teknillinen korkeakoulu.

The Discrete Basis Problem

Abstract: Matrix decomposition methods represent a data matrix as a product of two factor matrices: one containing basis vectors that represent meaningful concepts in the data, and another describing how the observed data can be expressed as combinations of the basis vectors. Decomposition methods have been studied extensively, but many methods return real-valued matrices. Interpreting real-valued factor matrices is hard if the original data is Boolean. In this paper, we describe a matrix decomposition formulation for Boolean data, the Discrete Basis Problem. The problem seeks for a Boolean decomposition of a binary matrix, thus allowing the user to easily interpret the basis vectors. We also describe a variation of the problem, the Discrete Basis Partitioning Problem. We show that both problems are NP-hard. For the Discrete Basis Problem, we give a simple greedy algorithm for solving it; for the Discrete Basis Partitioning Problem we show how it can be solved using existing methods. We present experimental results for the greedy algorithm and compare it against other, well known methods. Our algorithm gives intuitive basis vectors, but its reconstruction error is usually larger than with the real-valued methods. We discuss about the reasons for this behavior.

Intrinsic n-type behavior in transparent conducting oxides: a comparative hybrid-functional study of In2O3, SnO2, and ZnO.

Abstract: We present a comparative study of oxygen vacancies in In2O3, SnO2, and ZnO based on the hybrid-functional method within the density-functional theory (DFT). For In2O3 and SnO2, our results provide strong evidence of shallow donor states at oxygen vacancies. In comparison with the (semi)local exchange-correlation approximations in DFT, the hybrid-functional method strongly lowers the formation energy of the positive charge state and keeps that of the neutral state nearly intact. The trend is analyzed in terms of changes in lattice relaxation energies and in electron energy levels near the band gap. The existence of shallow donor states at oxygen vacancies and the consequent n-type conductivity are in line with experimental findings. The results invalidate some former theoretical interpretations based on standard DFT calculations.

Becoming an entrepreneurial university? A case study of knowledge exchange relationships and faculty attitudes in a medium-sized, research-oriented university

Abstract: This paper seeks to contribute to the growing literature on the entrepreneurial university by mapping knowledge exchange relationships of entrepreneurial faculty in a comprehensive manner and also capturing faculty attitudes towards measures taken by the university administration to promote entrepreneurship. We report on an exploratory study of Sussex University, a medium-sized, research-oriented university, which launched technology transfer activities in the mid-1990s. Our results show that, in spite of a comparatively late start, a considerable number of researchers engage in knowledge exchange processes with industry and other non-academic partners. We present evidence that suggests faculty in the social sciences and humanities as well as natural sciences and engineering maintain links to industrial partners, including multinational corporations. Furthermore, our observations indicate that schools differ in the way their faculty engage in university–industry collaborations. Further differences can be observed with respect to faculty attitudes towards technology transfer and awareness of the university’s respective codes of practice.