Vienna University of Technology

About: Vienna University of Technology is a education organization based out in Vienna, Austria. It is known for research contribution in the topics: Laser & Context (language use). The organization has 16723 authors who have published 49341 publications receiving 1302168 citations.

Theory of spin-orbit coupling at LaAlO 3 /SrTiO 3 interfaces and SrTiO 3 surfaces

Abstract: The theoretical understanding of the spin-orbit coupling (SOC) effects at LaAlO${}_{3}$/SrTiO${}_{3}$ interfaces and SrTiO${}_{3}$ surfaces is still in its infancy. We perform first-principles density-functional-theory calculations and derive from these a simple tight-binding Hamiltonian, through a Wannier function projection and group theoretical analysis. We find striking differences to the standard Rashba theory for spin-orbit coupling in semiconductor heterostructures due to multiorbital effects: By far the biggest SOC effect is at the crossing point of the $xy$ and $yz$ (or $zx$) orbitals, and around the $\ensuremath{\Gamma}$ point a Rashba spin splitting with a cubic dependence on the wave vector $\stackrel{P\vec}{k}$ is possible.

MINIMOS—A two-dimensional MOS transistor analyzer

Abstract: We describe a user-oriented software tool-MINIMOS-for the two-dimensional numerical simulation of planar MOS transistors. The fundamental semiconductor equations are solved with sophisticated programming techniques to allow very low computer costs. The program is able to calculate the doping profiles from the technological parameters specified by the user. A new mobility model has been implemented which takes into account the dependence on the impurity concentration, electric field, temperature, and especially the distance to the Si-SiO 2 interface. The power of the program is shown by calculating the two-dimensional internal behavior of three MOST's with 1-µm gate length differing in respect to the ion-implantation steps. In this way, the threshold voltage shift by a shallow implantation and the suppression of punchthrough by a deep implantation are demonstrated. By calculating the output characteristics without and with mobility reduction, the essential influence of this effect is shown. From the subthreshold characteristics, the suppression of short-channel effects by ion implantation becomes apparent. The MINIMOS program is available for everyone for just the handling costs.

Guest Editorial: A Review of Worst-Case Execution-TimeAnalysis

Abstract: A development process for safety-critical real-time computer systems has to emphasize the importance of time. On the one hand, such a development process has to be based on hardware and software technology that supports predictability in the time domain. On the other hand, the development process has to provide tools for assessing and verifying the correctness of the timing of both the hardware and the software components of the real-time systems being developed. Together with schedulability analysis, Worst-case execution time analysis (WCET analysis) forms the basis for establishing confidence into the timely operation of a real-time system. WCET analysis does so by computing (upper) bounds for the execution times of the tasks in the system. These bounds are needed for allocating the correct CPU time to the tasks of an application. They form the inputs for schedulability tools, which test whether a given task set is schedulable (and will thus meet the timing requirements of the application) on a given target system. While schedulability analysis is one of the traditional fields of investigation in real-time systems research, WCET analysis caught the attention of the research community only about ten years ago (Kligerman and Stoyenko, 1986; Mok et al., 1989; Puschner and Koza, 1989; Shaw, 1989). In the last decade, however, more and more research groups started to put a focus on WCET analysis. As a result, substantial progress has been made in this area in a relatively short time. After ten years of research in the field, it is appropriate to have a special issue on WCET analysis. It is the goal of this special issue to review the achievements in WCET analysis and to report about the recent advances in this field. In the following section we will define the problem area of WCET analysis and thus clarify the issue WCET analysis is dealing with— still many people mix up execution-time analysis and response-time analysis. We will then summarize the subproblems of WCET analysis and provide an overview of previous contributions to the state of the art in this field. At the end of the introduction we will give an overview to the research papers that have been selected for this special issue.

Approximately self-consistent resummations for the thermodynamics of the quark-gluon plasma: Entropy and density

Abstract: We propose a gauge-invariant and manifestly UV finite resummation of the physics of hard thermal or dense loops (HTL-HDL) in the thermodynamics of the quark-gluon plasma. The starting point is a simple, effectively one-loop expression for the entropy or the quark density which is derived from the fully self-consistent two-loop skeleton approximation to the free energy, but subject to further approximations, whose quality is tested in a scalar toy model. In contrast with the direct HTL-HDL resummation of the one-loop free energy, in our approach both the leading-order (LO) and the next-to-leading order (NLO) effects of interactions are correctly reproduced and arise from kinematical regimes where the HTL-HDL are justifiable approximations. The LO effects are entirely due to the (asymptotic) thermal masses of the hard particles. The NLO ones receive contributions both from soft excitations, as described by the HTL-HDL propagators, and from corrections to the dispersion relation of the hard excitations, as given by HTL-HDL perturbation theory. The numerical evaluations of our final expressions show very good agreement with lattice data for zero-density QCD, for temperatures above twice the transition temperature.

VMF3/GPT3: refined discrete and empirical troposphere mapping functions

Abstract: Incorrect modeling of troposphere delays is one of the major error sources for space geodetic techniques such as Global Navigation Satellite Systems (GNSS) or Very Long Baseline Interferometry (VLBI). Over the years, many approaches have been devised which aim at mapping the delay of radio waves from zenith direction down to the observed elevation angle, so-called mapping functions. This paper contains a new approach intended to refine the currently most important discrete mapping function, the Vienna Mapping Functions 1 (VMF1), which is successively referred to as Vienna Mapping Functions 3 (VMF3). It is designed in such a way as to eliminate shortcomings in the empirical coefficients b and c and in the tuning for the specific elevation angle of $$3^{\circ }$$ . Ray-traced delays of the ray-tracer RADIATE serve as the basis for the calculation of new mapping function coefficients. Comparisons of modeled slant delays demonstrate the ability of VMF3 to approximate the underlying ray-traced delays more accurately than VMF1 does, in particular at low elevation angles. In other words, when requiring highest precision, VMF3 is to be preferable to VMF1. Aside from revising the discrete form of mapping functions, we also present a new empirical model named Global Pressure and Temperature 3 (GPT3) on a $$5^{\circ }\times 5^{\circ }$$ as well as a $$1^{\circ }\times 1^{\circ }$$ global grid, which is generally based on the same data. Its main components are hydrostatic and wet empirical mapping function coefficients derived from special averaging techniques of the respective (discrete) VMF3 data. In addition, GPT3 also contains a set of meteorological quantities which are adopted as they stand from their predecessor, Global Pressure and Temperature 2 wet. Thus, GPT3 represents a very comprehensive troposphere model which can be used for a series of geodetic as well as meteorological and climatological purposes and is fully consistent with VMF3.