Johannes Kepler University of Linz

About: Johannes Kepler University of Linz is a education organization based out in Linz, Oberösterreich, Austria. It is known for research contribution in the topics: Thin film & Quantum dot. The organization has 6605 authors who have published 19243 publications receiving 385667 citations.

Upper echelons theory in management accounting and control research

Abstract: In recent years, scholars have started to draw on upper echelons theory to analyze the relationship between the characteristics of top managers and management accounting and control systems. This short survey paper aims to give an overview of upper echelons theory and its current applications to management accounting and control research. The paper shows that existing research consistently finds that younger and shorter-tenured CFOs and top managers with business-related backgrounds are associated with more innovative and/or sophisticated management accounting and control systems. In contrast, the (sparse) extant results on CEO characteristics and on characteristics of top management teams are somewhat contradictory. The paper concludes with an outlook on fruitful future research avenues, which include the analysis of additional management accounting and control systems and additional upper echelon characteristics, moderators such as managerial discretion and executive job demands, and the combined effect of upper echelons and management accounting and control systems on organizational performance.

Three real-space discretization techniques in electronic structure calculations

Abstract: A characteristic feature of the state-of-the-art of real-space methods in electronic structure calculations is the diversity of the techniques used in the discretization of the relevant partial differential equations. In this context, the main approaches include finite-difference methods, various types of finite-elements and wavelets. This paper reports on the results of several code development projects that approach problems related to the electronic structure using these three different discretization methods. We review the ideas behind these methods, give examples of their applications, and discuss their similarities and differences.

Direct observation of the LO phonon bottleneck in wide GaAs/AlxGa1-xAs quantum wells

Abstract: We report the direct observation of a bottleneck in electron cooling in wide GaAs quantum wells. Intersubband lifetimes \ensuremath{\tau} and their dependence on intensity, lattice temperature ${\mathrm{T}}_{\mathrm{L}}$ , and well width have been measured using a ps excite-probe technique in wells with subband separation less than the longitudinal optical (LO) phonon energy. Above an electron temperature of about ${\mathrm{T}}_{\mathrm{e}}$ =35 K the lifetime depends on ${\mathrm{T}}_{\mathrm{e}}$ and is determined by LO-phonon emission. Below this bottleneck temperature acoustic phonons dominate the plasma cooling. An energy balance model of these interactions, with no adjustable parameters, gives good agreement with our results. At electron temperatures below 35 K we determine \ensuremath{\tau}=500 and 200 ps for samples of subband energy 19.5 and 26.6 meV, respectively.

On Directional Metric Regularity, Subregularity and Optimality Conditions for Nonsmooth Mathematical Programs

Abstract: This paper mainly deals with the study of directional versions of metric regularity and metric subregularity for general set-valued mappings between infinite-dimensional spaces. Using advanced techniques of variational analysis and generalized differentiation, we derive necessary and sufficient conditions, which extend even the known results for the conventional metric regularity. Finally, these results are applied to non-smooth optimization problems. We show that that at a locally optimal solution M-stationarity conditions are fulfilled if the constraint mapping is subregular with respect to one critical direction and that for every critical direction a M-stationarity condition, possibly with different multipliers, is fulfilled.

Temperature dependence of the charge carrier mobility in disordered organic semiconductors at large carrier concentrations

Abstract: Temperature-activated charge transport in disordered organic semiconductors at large carrier concentrations, especially relevant in organic field-effect transistors OFETs, has been thoroughly considered using a recently developed analytical formalism assuming a Gaussian density-of-states DOS distribution and MillerAbrahams jump rates. We demonstrate that the apparent Meyer-Neldel compensation rule MNR is recovered regarding the temperature dependences of the charge carrier mobility upon varying the carrier concentration but not regarding varying the width of the DOS. We show that establishment of the MNR is a characteristic signature of hopping transport in a random system with variable carrier concentration. The polaron formation was not involved to rationalize this phenomenon. The MNR effect has been studied in a OFET based on C60 films, a material with negligible electron-phonon coupling, and successfully described by the present model. We show that this phenomenon is entirely due to the evolution of the occupational DOS profile upon increasing carrier concentration and this mechanism is specific to materials with Gaussian-shaped DOS. The suggested model provides compact analytical relations which can be readily used for the evaluation of important material parameters from experimentally accessible data on temperature dependence of the mobility in organic electronic devices. Experimental results on temperature-dependent charge mobility reported before for organic semiconductors by other authors can be well interpreted by using the model presented in this paper. In addition, the presented analytical formalism predicts a transition to a Mott-type charge carrier hopping regime at very low temperatures, which also manifests a MNR effect.