218 research outputs found
Antonis I
Get PDFA method is proposed to account for asperity interaction and bulk substrate deformation in models that utilize statistical summation of asperity forces to characterize contact between rough surfaces. Interaction deformations of noncontacting asperities are calculated based on the probability that they have taller neighbors in their vicinity, whose deformation upon contact, in turn, induces local substrate deformations. The effect of the order of interaction on the total contact force is explored and a limit is proposed based on asperity density. The updated contact force accounting for asperity interaction is found to tend to a constant fraction of the nominal contact force at the mathematical limit of asperity contact independent of the order of interaction, roughness, or material properties. For contact in the vicinity of zero mean plane separation, rough surfaces are found to exhibit greater asperity interaction resulting in reduced contact forces. A simplified curve-fitted expression is introduced that can be used to account for asperity interaction by adjusting the nominal contact force predicted by other models
Nonlinear control design for wave energy converter
No full textIn this thesis, we study the optimization of a single-piston pump system for use in a new wave
energy converter by using a feedback mechanism.
The first part of the thesis is dedicated to the optimal determination of control variables using the
dynamical model of the single-piston pump system, which is a switched system that is built on first
principles and describes the dynamics of four main important elements of the system: the buoy, the
rod, the piston and the pumped water. Using the Analysis of Variance method, it is found that the
two optimum control variables are the area of the piston, as expected, and the mass of the buoy.
The second part of the thesis deals with the design of optimal feedback control where the area of
the piston is the chosen control variable. The control method is based on the well-known Model
Predictive Control that has been adjusted to our switched system. Our simulation results show that
the proposed control method is able to reach performance close to the optimal one.Outgoin
Dynamical modelling, analysis and optimization of a floater blanket for the Ocean Grazer
No full textThe Ocean Grazer is a novel ocean energy collection and storage device, designed
to extract and store multiple forms of ocean energy.
This work aims to study and model the interaction between sea waves and the Ocean Grazer as well as
to propose a model for its floater blanket. In this line, simulations are performed to gain an
insight into the dynamical behaviour of the whole system and to find out the configuration of the
controllable variable
that enables to harvest the maximum amount of energy
Nonlinear control design for wave energy converter
Get PDFIn this thesis, we study the optimization of a single-piston pump system for use in a new wave
energy converter by using a feedback mechanism.
The first part of the thesis is dedicated to the optimal determination of control variables using the
dynamical model of the single-piston pump system, which is a switched system that is built on first
principles and describes the dynamics of four main important elements of the system: the buoy, the
rod, the piston and the pumped water. Using the Analysis of Variance method, it is found that the
two optimum control variables are the area of the piston, as expected, and the mass of the buoy.
The second part of the thesis deals with the design of optimal feedback control where the area of
the piston is the chosen control variable. The control method is based on the well-known Model
Predictive Control that has been adjusted to our switched system. Our simulation results show that
the proposed control method is able to reach performance close to the optimal one.Outgoin
Analysis and dynamical modeling of a piston valve for a wave energy converter
No full textThe Ocean Grazer, a novel wave energy converter, has been proposed by the University of
Groningen. The system can collect and store multiple forms of ocean energy, with a pistontype
hydraulic pump as its core technology.
In this work, the dynamical behavior of a piston valve for use in the piston pump system is
studied. In order to gain insight into the dynamical behavior of the piston-type hydraulic pump,
a simulation model is developed to describe the movement of the piston valve and the
consequent forces acting on the piston. The model accounts for rigid contacts between the
valve and the piston, as well as hydrodynamic forces created by the pumped fluid
Analysis and dynamical modeling of a piston valve for a wave energy converter
Get PDFThe Ocean Grazer, a novel wave energy converter, has been proposed by the University of
Groningen. The system can collect and store multiple forms of ocean energy, with a pistontype
hydraulic pump as its core technology.
In this work, the dynamical behavior of a piston valve for use in the piston pump system is
studied. In order to gain insight into the dynamical behavior of the piston-type hydraulic pump,
a simulation model is developed to describe the movement of the piston valve and the
consequent forces acting on the piston. The model accounts for rigid contacts between the
valve and the piston, as well as hydrodynamic forces created by the pumped fluid
Analysis and dynamical modeling of a piston valve for a wave energy converter
No full textThe Ocean Grazer, a novel wave energy converter, has been proposed by the University of
Groningen. The system can collect and store multiple forms of ocean energy, with a pistontype
hydraulic pump as its core technology.
In this work, the dynamical behavior of a piston valve for use in the piston pump system is
studied. In order to gain insight into the dynamical behavior of the piston-type hydraulic pump,
a simulation model is developed to describe the movement of the piston valve and the
consequent forces acting on the piston. The model accounts for rigid contacts between the
valve and the piston, as well as hydrodynamic forces created by the pumped fluid
Dynamical modelling, analysis and optimization of a floater blanket for the Ocean Grazer
No full textThe Ocean Grazer is a novel ocean energy collection and storage device, designed
to extract and store multiple forms of ocean energy.
This work aims to study and model the interaction between sea waves and the Ocean Grazer as well as
to propose a model for its floater blanket. In this line, simulations are performed to gain an
insight into the dynamical behaviour of the whole system and to find out the configuration of the
controllable variable
that enables to harvest the maximum amount of energy
Asperity Interaction and Substrate Deformation in Statistical Summation Models of Contact Between Rough Surfaces
No full textA method is proposed to account for asperity interaction and bulk substrate deformation in models that utilize statistical summation of asperity forces to characterize contact between rough surfaces. Interaction deformations of noncontacting asperities are calculated based on the probability that they have taller neighbors in their vicinity, whose deformation upon contact, in turn, induces local substrate deformations. The effect of the order of interaction on the total contact force is explored and a limit is proposed based on asperity density. The updated contact force accounting for asperity interaction is found to tend to a constant fraction of the nominal contact force at the mathematical limit of asperity contact independent of the order of interaction, roughness, or material properties. For contact in the vicinity of zero mean plane separation, rough surfaces are found to exhibit greater asperity interaction resulting in reduced contact forces. A simplified curve-fitted expression is introduced that can be used to account for asperity interaction by adjusting the nominal contact force predicted by other models
Dataset: "I Can't Keep It Up." A Dataset from the Defunct Voat.co News Aggregator
No full textThis is the dataset released with the paper titled: "I Can’t Keep It Up." A Dataset from the Defunct Voat.co News Aggregator.
The dataset consists of 15,133 Newline delimited JSON files (ndjson). More specifically, 7,616 files for submission data, 7,515 for comment data, 1 for user data, and 1 for subverse data. Each line in the ndjson files consists of a JSON object. The JSON objects contain all the key/values we collect through the Voat API and the custom parser of the Internet Archive Wayback Machine Voat snapshot release.
For the detailed description of every key in the JSON structure, along with the type of the value, please read the readme.pdf file provided with this dataset.
If you find our dataset useful, please cite our paper:
@inproceedings{mekacher2022can,
title={"I Can't Keep It Up." A Dataset from the Defunct Voat.co News Aggregator},
author={Mekacher, Amin and Papasavva, Antonis},
booktitle={16th International Conference on Web and Social Media},
year={2022}
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