Arbitrary Platform Research Articles

Governance of labour relations in the platform economy. The cooperation between YouTubers Union and IG Metall

AbstractThe article focuses on the factors that explain the emergence and accomplishments of the ‘FairTube’ campaign, which was initiated in 2019 by the YouTubers Union and the German metalworkers' union IG Metall, and was later established as a formalised German association (“Verein”). While the initial focus of the campaign was on changing the monetisation rules, which YouTube had altered very abruptly in 2017, the initiative subsequently focused on improving the working conditions of content creators. Methodologically, we deploy a mixed‐methods design that flanks media discourse network analysis through qualitative content analysis of expert interviews, which helps to identify the interaction between these established and new actors in the governance and interest representation in the digital platform economy. Our findings reveal a ‘hybrid form of governance’ that, by aligning ideologies and combining sources of power, was able to accomplish most of the goals set out by the campaign (avoiding arbitrary platform decisions, increasing transparency and communication, securing creators' income). We conclude that new forms of collective action, i.e. the coalition between “old” and “new” organizations, may mitigate particular negative consequences of the platform economy. The study seeks to contribute to a better understanding of platform work and to the concepts of power, ideas, and interests in industrial relations.

Modelica‐AeroDyn: Development, benchmark, and application of a comprehensive object‐oriented tool for dynamic analysis of non‐conventional horizontal‐axis floating wind turbines

AbstractThe exploitation of offshore wind energy by means of floating wind turbines is gaining traction as a suitable option to produce sustainable energy. Multi‐rotor floating wind turbines have been proposed as an appealing option to reduce the costs associated with manufacturing, logistics, offshore installations, and operation and maintenance of large wind turbine components. The development of such systems is forestalled by the lack of a dedicated tool for dynamics and load analysis. Standard codes, such as FAST by NREL, offer the desired fidelity level but are not able to accommodate multi‐rotor configurations. A few experimental codes have been also proposed, which may accommodate multi‐rotor systems, but low flexibility makes them impractical to study a vast range of innovative multi‐rotor FWTs concepts. To close the gap, this work presents the development and comprehensive benchmark of a fully coupled aero‐hydro‐servo‐elastic tool able to easily accommodate arbitrary platform and tower geometries and the number of wind turbines employed. Development is carried out in Modelica, which allows for the employment of the same code functionality in a virtually unlimited number of physical configurations. Full blade‐element momentum capabilities are achieved by integrating into Modelica the well‐established NREL aerodynamic module AeroDyn v15 within FAST v8. Structural dynamics of tower and blades are implemented through a lumped‐element approach. Hydrodynamic loads are computed by employing the DNV software SESAM WADAM. Thorough benchmark is performed against FAST, and positive results are obtained. The dynamic performance of a two‐rotor floating wind turbine is finally assessed considering different turbulence spectrums.

An object-oriented method for fully coupled analysis of floating offshore wind turbines through mapping of aerodynamic coefficients

This work presents a novel object-oriented approach to model the fully-coupled dynamic response of floating offshore wind turbines (FOWTs). The key features offered by the method are the following: 1) its structure naturally allows for easy implementation of arbitrary platform geometries and platform/rotor configurations, 2) the analysis time is significantly faster than that of standard codes and results are accurate in situations where rotor dynamic contribution is negligible, and 3) an extremely flexible modeling environment is offered by the object-oriented nature of Modelica. Moreover, the current modeling facility used for the code development is open source and is naturally suitable for code sharing. In the present method, the aerodynamic model computes the aerodynamic loads through the mapping of steady-state aerodynamic coefficients. This modeling approach can be placed at the intersection between simplified aerodynamic methods, such as TDHMill, and full beam element/momentum-based aerodynamic methods. Aerodynamic loads obtained from the coefficients mapping are composed of a concentrated thrust and a concentrated torque. The thrust acts at the hub, while the torque is applied at the rotor low-speed shaft of a simplified rigid rotor equation of motion (EoM) used to emulate the rotor response. The aerodynamic coefficients are computed in FAST for a baseline 5 MW wind turbine. A standard rotor-collective blade-pitch control model is implemented. The system is assumed to be rigid. Linear hydrodynamics is employed to compute hydrodynamic loads. The industry-standard numerical-panel code Sesam-Wadam (DNV-GL) is used to preprocess the frequency-domain hydrodynamic problem. Validation of the code considers a standard spar-buoy platform, based on the Offshore Code Comparison Collaboration (OC3-Hywind). The dynamic response is tested in terms of free-decay response, Response Amplitude Operator (RAO), and the time histories and power spectral densities (PSDs) of several load cases including irregular waves and turbulent wind. The resulting model is benchmarked against well-known code-to-code comparisons and a good agreement is obtained.

On-chip trans-dimensional plasmonic router

Abstract Plasmons, as emerging optical diffraction-unlimited information carriers, promise the high-capacity, high-speed, and integrated photonic chips. The on-chip precise manipulations of plasmon in an arbitrary platform, whether two-dimensional (2D) or one-dimensional (1D), appears demanding but non-trivial. Here, we proposed a meta-wall, consisting of specifically designed meta-atoms, that allows the high-efficiency transformation of propagating plasmon polaritons from 2D platforms to 1D plasmonic waveguides, forming the trans-dimensional plasmonic routers. The mechanism to compensate the momentum transformation in the router can be traced via a local dynamic phase gradient of the meta-atom and reciprocal lattice vector. To demonstrate such a scheme, a directional router based on phase-gradient meta-wall is designed to couple 2D SPP to a 1D plasmonic waveguide, while a unidirectional router based on grating metawall is designed to route 2D SPP to the arbitrarily desired direction along the 1D plasmonic waveguide by changing the incident angle of 2D SPP. The on-chip routers of trans-dimensional SPP demonstrated here provide a flexible tool to manipulate propagation of surface plasmon polaritons (SPPs) and may pave the way for designing integrated plasmonic network and devices.

ViDis: A Platform for Constructing and Sharing of Medical Algorithms.

The literature and the Internet provide different sources, in which medical community as well as patients can browse through medical algorithms. These algorithms are dispersed and use different formats of presentation. We present visualized diagnosis (ViDis), a web platform aimed to construction and sharing of graphical representations of medical algorithms in a single place and in a unified format. ViDis is accessible as a web application, which can run on an arbitrary platform with a modern web browser. The platform's user friendly interfaces allow the users with different backgrounds to construct, share, and browse through medical algorithms. Visualization of the algorithms can be created using a flowchart diagram notation that is commonly applied in the design of computer software and is very intuitive to use and understand. Algorithms can be viewed in two different formats, that is, in the format of flowchart diagrams or in the format of sequential steps that guide the user from the beginning to the end of a medical procedure in dependence on his or her decisions made in each step of the process. ViDis enables registered users to create, edit, and share visualized medical algorithms and guest users to view these visualizations. To the best of our knowledge, this is the first platform for efficient sharing of medical algorithms with the community. We believe that ViDis provides an excellent platform for sharing medical knowledge and information among diagnosticians, clinicians, researchers, and patients.

High-efficiency broadband polarization-independent superscatterer using conformal metasurfaces

Safe detection of an arbitrarily shaped platform is critical for survivability, rescue, or navigation safety in a remote region. Metasurfaces afford great potential due to their strong electromagnetic (EM) wave control. However, studies have mainly focused on the physics and design of metasurfaces on planar plates, which does not satisfy the current requirements of aerodynamics and aesthetics. Herein, we propose a sophisticated strategy to design a metasurface that can wrap over arbitrarily shaped objects with moderate curvature on which optical aberrations are commonly introduced. By designing each meta-atom on the basis of the required position and phase compensation, exact EM wavefronts are restored. For verification, several conformal metasurfaces were designed and numerically studied on metallic cylinders at the microwave spectrum. A proof-of-concept device is fabricated and is experimentally characterized. The results demonstrate the availability of the desirable dual-beam superscatterer with strong backscattering enhancement toward two directions, thus indicating that the distortions induced by an arbitrary platform can be efficiently corrected. Our method affords an efficient alternative for designing high-performance multifunctional optoelectronic devices equipped on a moderately curved platform.

Geometrical Variations of Gain Patterns

This paper studies the effect of the altitude and the elliptical nature of the Earth on projected antenna pattern functions (APFs). These variations can play a significant role in spatial filter algorithms, such as the Backus-Gilbert method. In this paper, a solution for projecting an APF from an arbitrary sensor and platform onto an elliptical Earth is presented. A general time integration of this projection is presented, which is important for dynamically generating the effective antenna pattern functions (EAPFs) in cases where the variations are nonnegligible. It is shown that the elliptical nature of the Earth provides a variation of order 1% in the area of the EAPF. These results suggest that approximating the Earth as a sphere is valid. It is also shown that elliptical orbits should consider the implication of the altitude variation before precomputing EAPFs

Synthesis of spatial parallel mechanisms with initial conditions using line geometry

In this paper we describe a coordinate-independent method for synthesis of a spatial parallel mechanism . The mechanism consists of a platform, a base, and five legs connecting the base and platform with spherical joints. The objective is to find the positions of the base anchor points and leg lengths for two arbitrary platform positions and their desired instantaneous motions. A unique solution will be presented that applies the linear line complex, a tool from line geometry. Potential applications that may benefit from this research include a five-link independent suspension system (wheel multilink suspension system for automobiles) and spatial mechanisms used in manufacturing. The algorithm and a numerical example will be discussed.