1,720,959 research outputs found
Automatic Ball Balancer Stability Map Generator
No full textThis is a Pluto.jl Notebook showing an interactive 2D plot generated with Julia.
An instance of the Notebook can be started via binder: start on binder
The figure shows the stable operation condition for automatic ball balancers (ABB) depending on the operating speed and fluid viscosity inside the ABB. It is assumed that the ABB has two identical balls sharing the same orbit
On the dynamic modelling of automatic ball balancers applied to laboratory centrifuges
Full text linkThis thesis deals with the balancing of unbalanced rotor systems and the
resulting reduction of vibration. In particular, calculations and experiments
utilizing so-called automatic balancing units with spherical balancing masses
considering the use case in laboratory centrifuges are described. The specified
modelling approaches for describing the fluid flow and friction effects acting
on the balancing masses aim towards a more differentiated examination of
the influence of geometry and manufacturing tolerances when designing
automatic balancing units. For this purpose, the investigated centrifuges
are modelled by multibody systems in which the kinematic and dynamic
coupling of the balancing masses with the rotor system is realized by a special
force element. In addition to the results on the rotor deflection, which is
relevant from an operational point of view, the comparison of the transient
balancing mass positions relative to the rotor in experiment and simulation is
presented.In der vorliegenden Arbeit wird der Ausgleich von Unwuchten in Rotorsystemen
und der resultierenden Schwingungsreduktion behandelt. Im Speziellen
wird die Verwendung von sogenannten selbsttätigen Auswuchteinheiten mit
kugelförmigen Ausgleichsmassen für Laborzentrifugen beschrieben. Die hierin
dargelegten Modellierungsansätze zur Beschreibung der auf die Ausgleichsmassen
wirkenden Strömungs- und Reibungseinflüsse sollen einen Beitrag
dazu leisten, bei der Gestaltung von selbsttätigen Auswuchteinheiten unter
anderem den Einfluss von Geometrie und Fertigungstoleranzen differenzierter
betrachten zu können. Hierzu werden die untersuchten Zentrifugen durch
Mehrkörpersysteme abgebildet, in denen die kinematische und dynamische
Kopplung der Ausgleichsmassen mit dem Rotorsystem durch ein spezielles
Kraftelement realisiert wird. Neben den Ergebnissen zur betriebstechnisch
äußerst relevanten Rotorauslenkung wird auch der experimentelle Abgleich
der transienten Ausgleichsmassenpositionen relativ zum Rotor dargelegt
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
OpenFOAM case files for drag coefficient determination in automatic ball balancers
No full textThis repository includes
A prototype of an OpenFOAM case file to calculate the drag at low Reynolds numbers on a sphere inside a section of an annular domain representing the geometry of an automatic ball balancer with a radial ball bearing contour on the raceway.
Prerequires:
Linux OS or Windows Subsystem Linux (tested with Ubuntu)
OpenFOAM (tested with OpenFOAM7 Version 20190708)
python3
Usage
create a copy of the OpenFoam case
tar -xf OFcase.tar
mv OFcase case001
modify parameters.py inside the case folder
execute
cd case001
chmod +x Allrun_parallel
./Allrun_parallel
Results gained with this case file, which are presented in the associated publication
Video recording of unstable automatic balancing (Sommerfeld effect) in a centrifuge test rig
No full textThis video material supplements research on the unstable automatic balancing in a centrifuge test rig (see image file).
The motor assembly is of type D25T (LEROY SOMER) mounted on three rubber bushings.
The aluminium discoidal rotor has a transparent lid and the cavity is filled with silicone oil (kinematic viscosity: 0.65 mm²/s) and two and four balancing balls, respectively. The current rotational speed is displayed in the top right corner. The line graph shows the FFT analysis of the measured stator acceleration. The image in the bottom right corner shows the balls position with respect to the rotor. Each frame of the original rotor recording was rotated such that the added rotor unbalance is always located to the right (black marking).
For a detailed description, please refer to the linked publications
TOWARDS LIGHT-WEIGHT AND MECHANICALLY DURABLE PHOTOVOLTAIC MODULES FOR FLOATING APPLICATIONS
No full textWith the increased demand of energy and the scarcity of the conventional energy sources, renewable energy becomes more necessary. Additionally, more renewable energy is required in order to achieve a 55% reduction of CO2 emission by 2030 1. Photovoltaic (PV) generation systems are the biggest contributor to the growth in renewable energy. However, further growth is limited due to the availability of suitable land. Floating PV is an attractive solution for expanding the capacity potential for renewables. Some other advantages of floating PV installations are that they enable dual use of water reservoirs and that the cooling effect on the PV modules increases their efficiency significantly. Within the project Marine Solar POtential and Technology Study (MarineSPOTS), we study the possible deployment of floating PV at the North Sea, by investigating the energy yield production, the integration to the grid, the durability and the environmental impact of such PV plant. One of the major durability concerns of a floating PV installation is the mechanical load that the PV modules undergo, due to strong winds that might occur at open water and the movement induced by the waves. This study focuses on quantifying the impact of the mentioned stressors. For the achievement of this goal, multiple simulations and experiments for validation are conducted. Initially, the effect of configuration of the PV modules (e.g. inclination and orientation) is examined. Additionally, various thicknesses of PV glass are assumed, for the optimization of the mechanical stability and weight/material consumption. Finally, a dynamic mechanical load test is compared to simulations, in order to estimate the influence of the vibration on the stresses developed within a PV module, due to varied wind speed. Preliminary results show that a low-angle east-west configuration is preferable to a high-angle south configuration from the mechanical perspective and that thinner PV glass with 2 mm thickness (glass-glass structure) may be adequate for offshore PV installations, although its durability needs to be evaluated for dynamic mechanical load due to wind and wave speed variation. Furthermore, a method to compare the mechanical stress occurring within a PV module due to varied wind speed and the stress due to dynamic mechanical load testing is being developed and will be extended to include wave induced vibrations.This work is conducted within the project “Marine Solar POtential and Technology Study” (MarineSPOTS) project and funded under with the support of the Belgian Energietransitiefonds
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
TOWARDS LIGHT-WEIGHT AND MECHANICALLY DURABLE PHOTOVOLTAIC MODULES FOR FLOATING APPLICATIONS
No full textWith the increased demand of energy and the scarcity of the conventional energy sources, renewable energy becomes more necessary. Additionally, more renewable energy is required in order to achieve a 55% reduction of CO2 emission by 2030 1. Photovoltaic (PV) generation systems are the biggest contributor to the growth in renewable energy. However, further growth is limited due to the availability of suitable land. Floating PV is an attractive solution for expanding the capacity potential for renewables. Some other advantages of floating PV installations are that they enable dual use of water reservoirs and that the cooling effect on the PV modules increases their efficiency significantly. Within the project Marine Solar POtential and Technology Study (MarineSPOTS), we study the possible deployment of floating PV at the North Sea, by investigating the energy yield production, the integration to the grid, the durability and the environmental impact of such PV plant. One of the major durability concerns of a floating PV installation is the mechanical load that the PV modules undergo, due to strong winds that might occur at open water and the movement induced by the waves. This study focuses on quantifying the impact of the mentioned stressors. For the achievement of this goal, multiple simulations and experiments for validation are conducted. Initially, the effect of configuration of the PV modules (e.g. inclination and orientation) is examined. Additionally, various thicknesses of PV glass are assumed, for the optimization of the mechanical stability and weight/material consumption. Finally, a dynamic mechanical load test is compared to simulations, in order to estimate the influence of the vibration on the stresses developed within a PV module, due to varied wind speed. Preliminary results show that a low-angle east-west configuration is preferable to a high-angle south configuration from the mechanical perspective and that thinner PV glass with 2 mm thickness (glass-glass structure) may be adequate for offshore PV installations, although its durability needs to be evaluated for dynamic mechanical load due to wind and wave speed variation. Furthermore, a method to compare the mechanical stress occurring within a PV module due to varied wind speed and the stress due to dynamic mechanical load testing is being developed and will be extended to include wave induced vibrations.This work is conducted within the project “Marine Solar POtential and Technology Study” (MarineSPOTS) project and funded under with the support of the Belgian Energietransitiefonds
- …
