Youtube und andere netzmediale visuelle Daten

in Baur, Nina; Blasius, Jörg (Eds.) Methoden der empirischen Sozialforschung (2019)

Fundus omnium communicativum oder Das Al(e)phabet des Kommunikativen Konstruktivismus

Book published by Springer VS (2019)

Visibility and Visual Discourses. Rethinking the Social with the Image

in Qualitative Inquiry (2019), 25(4), 327-338

With this special issue, we aim to address visibility not just as a representation of the social, but as an aspect and element of social and cultural orders and actions sui generis. The texts in this ... [more ▼]

With this special issue, we aim to address visibility not just as a representation of the social, but as an aspect and element of social and cultural orders and actions sui generis. The texts in this volume are dedicated to understanding the practices, power relations and the technological infrastructures in which (audio)-visual practices unfold. To make our proposition clear, we lay out a methodological strategy that we—drawing from French, German and Anglo-Saxon debate—call sociology with the image. Then we provide an overview of the articles in this special issue and point to some ongoing tensions within qualitative inquiry more broadly. [less ▲]

All-Dielectric and Magnetoplasmonic Nanoantenna Surfaces for the Dynamic Chiroptics

in Proceedings 2019 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference (2019)

Optical platforms enabling the dynamic real-time control of the fundamental properties of light at visible and near-infrared wavelengths are the essential components for the future optical devices ... [more ▼]

Optical platforms enabling the dynamic real-time control of the fundamental properties of light at visible and near-infrared wavelengths are the essential components for the future optical devices. Combining magnetic materials with the metallic and all-dielectric nano-optics enables a simultaneous enhancement and mutual control of their magneto-optical and chiro-optical properties. Here we examine hybrid nanoantennas made of Si and ferromagnetic metal developing magnetically-controlled chiroptical surfaces. [less ▲]

Inexact Block Coordinate Descent Algorithms for Nonsmooth Nonconvex Optimization

in IEEE Transactions on Signal Processing (2019)

In this paper, we propose an inexact block coordinate descent algorithm for large-scale nonsmooth nonconvex optimization problems. At each iteration, a particular block variable is selected and updated by ... [more ▼]

In this paper, we propose an inexact block coordinate descent algorithm for large-scale nonsmooth nonconvex optimization problems. At each iteration, a particular block variable is selected and updated by solving the original optimization problem with respect to that block variable inexactly. More precisely, a local approximation of the original optimization problem is solved. The proposed algorithm has several attractive features, namely, i) high flexibility, as the approximation function only needs to be strictly convex and it does not have to be a global upper bound of the original function; ii) fast convergence, as the approximation function can be designed to exploit the problem structure at hand and the stepsize is calculated by the line search; iii) low complexity, as the approximation subproblems are much easier to solve and the line search scheme is carried out over a properly constructed differentiable function; iv) guaranteed convergence of a subsequence to a stationary point, even when the objective function does not have a Lipschitz continuous gradient. Interestingly, when the approximation subproblem is solved by a descent algorithm, convergence of a subsequence to a stationary point is still guaranteed even if the approximation subproblem is solved inexactly by terminating the descent algorithm after a finite number of iterations. These features make the proposed algorithm suitable for large-scale problems where the dimension exceeds the memory and/or the processing capability of the existing hardware. These features are also illustrated by several applications in signal processing and machine learning, for instance, network anomaly detection and phase retrieval. [less ▲]

FPGA Acceleration for Computationally Efficient Symbol-Level Precoding in Multi-User Multi-Antenna Communication Systems

in IEEE Access (2019)

In this paper, we demonstrate an FPGA accelerated design of the computationally efficient Symbol-Level Precoding (SLP) for high-throughput communication systems. The SLP technique recalculates optimal ... [more ▼]

In this paper, we demonstrate an FPGA accelerated design of the computationally efficient Symbol-Level Precoding (SLP) for high-throughput communication systems. The SLP technique recalculates optimal beam-forming vectors by solving a non-negative least squares (NNLS) problem per every set of transmitted symbols. It exploits the advantages of constructive inter-user interference to minimize the total transmitted power and increase service availability. The benefits of using SLP come with a substantially increased computational load at a gateway. The FPGA design enables the SLP technique to perform in realtime operation mode and provide a high symbol throughput for multiple receive terminals. We define the SLP technique in a closed-form algorithmic expression and translate it to Hardware Description Language (HDL) and build an optimized HDL core for an FPGA. We evaluate the FPGA resource occupation, which is required for high throughput multiple-input-multiple-output (MIMO) systems with sizeable dimensions. We describe the algorithmic code, the I/O ports mapping and the functional behavior of the HDL core. We deploy the IP core to an actual FPGA unit and benchmark the energy efficiency performance of SLP. The synthetic tests demonstrate a fair energy efficiency improvement of the proposed closed-form algorithm, also compared to the best results obtained through MATLAB numerical simulations. [less ▲]

Designing MPSK Sequences and Doppler Filter Bank in Cognitive Radar Systems

in International Radar Conference, france, Toulon 23-27 September, 2019 (2019)

In this paper, we propose an attractive method to jointly design discrete phase radar sequence and receive filter bank with the aim of enhancing Signal to Interference and Noise Ratio (SINR) in a ... [more ▼]

In this paper, we propose an attractive method to jointly design discrete phase radar sequence and receive filter bank with the aim of enhancing Signal to Interference and Noise Ratio (SINR) in a cognitive radar system. Towards this, we consider maximizing the worst case SINR at the output of the filter bank when transmitting M-ary Phase Shift Keying (MPSK) sequences, an exercise hitherto not considered. This maximization results in a max-min optimization problem that is multi-variable and non-convex, where we propose an efficient algorithm based on the Coordinate Descent (CD) framework to address it. The gains demonstrated by the proposed algorithm over the state of the art as well as its discrete phase property render the designed sequences attractive for hardware implementation while enabling efficient utilization of transmit power. [less ▲]