23 research outputs found
Autonomous energy efficient protocols and strategies for wireless sensor networks
No full textThe aim of this research is to develop a model of a sensor network that will endeavour to monitor a hostile environment (one where communication within the network is difficult and the network entities are under risk due to physical damage). In this context, the study identifies the following key characteristics. A wireless sensor network (WSN) is a wireless network consisting of spatially distributed devices using sensors to monitor physical or environmental conditions at different locations. In addition to one or more sensors, each node in a WSN is typically equipped with a radio transceiver or other wireless communications device, a small micro controller, and an energy source, usually a battery. The size constraints on sensor nodes result in corresponding constraints on resources such as energy, memory, computational speed and bandwidth. Of these, energy is the most important since it is required for everything else. Thus, it directly influences the life-span of the nodes, hence, that of the system as a whole. Furthermore, the environment itself, where these sensor nodes are deployed, plays a big role in influencing the entire architecture of the network hardware platform and protocols that govern its smooth functioning. As a result the protocols required for governing the actions of the sensor nodes need to be designed accordingly.Against this background, this research facilitates the development of an environmental sensor network called GlacsWeb (deployed inside a glacier in Norway) which focuses on providing useful information about sub-glacial dynamics. GlacsWeb nodes are deployed under very hostile conditions. The strain from the moving ice may damage the nodes and the en-glacial water bodies may carry the nodes far out of transmission range from a centrally located base station. For these reasons GlacsWeb nodes have a high rate of failure. In order to effectively tackle this problem, this research develops GW-MAC (a Medium Access Control protocol) which focuses on efficiently connecting GlacsWeb nodes in an ad-hoc manner.Moreover, the poorly understood nature of the glacier imposes further challenges in the area of sensing. Sub-glacial behaviour appears vary across the entire large mass of ice. For this reason, there is a strong need for nodes to make autonomous decisions to adapt their observation patterns and communication patterns accordingly to ensure maximum data is gathered with minimum consumption in energy. The study, therefore, develops USAC (A Utility Based Sensing and Communication Model for an Agent-Based Sensor Network), that provides a measure of utility by combining the task of both sensing and communication by the sensor nodes. The model, at first, develops a sensing protocol in which each agent node locally adjusts its sensing rate based on the value (importance) of the data it believes it will observe. Then, it details a communication protocol that finds optimal routes for relaying this data back the network base station based on the cost of communicating (derived from the opportunity cost of using the battery power for relaying data) it.Both GW-MAC and USAC have been tested in simulation and have shown to perform better than other similar models
GWMAC- A TDMA Based MAC Protocol for a Glacial Sensor Network
No full textWireless sensor networks demand the need to design practical and robust communication protocols to meet the application specifications. Our research focuses on designing and implementing an environmental sensor network to be used for sub-glacial study. The glacier is a very hostile environment presenting severe challenges and complications in the smooth functioning of such a network. In light of these challenges, we present a low power sensor node design and an energy-efficient medium access control protocol called GWMAC developed for a network deployed in a glacier in Norway. The general architecture of GWMAC is based on scheduling and time division multiple accesses (TDMA). We argue that for a highly dynamic network such as ours, GWMAC is more desirable over more widespread protocols such as S-MAC and LMAC. In doing so, we perform extensive series of simulations to empirically evaluate our claim. Our results illustrate that on average GWMAC can increase the network life time by at least 63%. This also has a significant effect on the amount of data that can be collected over network life time
A utility-based adaptive sensing and multi-hop communication protocol for wireless sensor networks
No full textThis article reports on the development of a utility-based mechanism for managing sensing and communication in cooperative multisensor networks. The specific application on which we illustrate our mechanism is that of GlacsWeb. This is a deployed system that uses battery-powered sensors to collect environmental data related to glaciers which it transmits back to a base station so that it can be made available world-wide to researchers. In this context, we first develop a sensing protocol in which each sensor locally adjusts its sensing rate based on the value of the data it believes it will observe. The sensors employ a Bayesian linear model to decide their sampling rate and exploit the properties of the Kullback-Leibler divergence to place an appropriate value on the data. Then, we detail a communication protocol that finds optimal routes for relaying this data back to the base station based on the cost of communicating it (derived from the opportunity cost of using the battery power for relaying data). Finally, we empirically evaluate our protocol by examining the impact on efficiency of a static network topology, a dynamic network topology, the size of the network, the degree of dynamism of the environment, and the mobility of the nodes. In so doing, we demonstrate that the efficiency gains of our new protocol, over the currently implemented method over a 6 month period, are 78%, 133%, 100%, and 93%, respectively. Furthermore, we show that our system performs at 65%, 70%, 63%, and 70% of the theoretical optimal, respectively, despite being a distributed protocol that operates with incomplete knowledge of the environment
A utility-based sensing and communication model for a glacial sensor network
No full textThis paper reports on the development of a utility-based mechanism for managing sensing and communication in cooperative multi-sensor networks. The specific application considered is that of GLACSWEB, a deployed system that uses battery-powered sensors to collect environmental data related to glaciers which it transmits back to a base station so that it can be made available world-wide to researchers. In this context, we first develop a sensing protocol in which each sensor locally adjusts its sensing rate based on the value of the data it believes it will observe. Then, we detail a communication protocol that finds optimal routes for relaying this data back to the base station based on the cost of communicating it (derived from the opportunity cost of using the battery power for relaying data). Finally, we empirically evaluate our protocol by examining the impact on efficiency of the network topology, the size of the network, and the degree of dynamism of the environment. In so doing, we demonstrate that the efficiency gains of our new protocol, over the currently implemented method over a 6 month period, are 470%, 250% and 300% respectively
Glacial Environment Monitoring using Sensor Networks
No full textThis paper reports on the implementation, design and results from GlacsWeb, an environmental sensor network for glaciers installed in Summer 2004 at Briksdalsbreen, Norway. The importance of design factors that influenced the development of the overall system, its general architecture and communication systems are highlighted
Fitness-AQA Dataset
No full textLargest Fine-grained Exercise Action Quality Assessment Dataset.
Dataset available from the following webpage: https://github.com/ParitoshParmar/Fitness-AQA.
If you find our work useful, please consider citing our ECCV 2022 conference paper that can be found at:
https://link.springer.com/chapter/10.1007/978-3-031-19839-7_7
or
https://arxiv.org/abs/2202.14019
Bibtex file:
@article{parmar2022domain,
title={Domain Knowledge-Informed Self-Supervised Representations for Workout Form Assessment},
author={Parmar, Paritosh and Gharat, Amol and Rhodin, Helge},
journal={arXiv preprint arXiv:2202.14019},
year={2022}
}Only available for non-commercial purposes. Users agree to terms and conditions of usage
Dynamic Pile Response During Vibratory Driving and Modal-Based Strain Field Mapping
No full textFor offshore wind turbines (OWTs), the monopile comprises the most common type of foundation and vibratory driving is one of the main techniques for monopile installation (and decommissioning). In practice, prior to pile installation, a pile driving analysis is performed to select the appropriate installation device and the relevant settings. However, pile penetration results from a complicated vibrator-pile-soil interaction and better understanding of the latter is necessary for an efficient installation process. During the course of installation, the interface and boundary conditions of the pile continuously alter due to the soil layering and the non-linearity of the soil reaction. In this paper, a set of experimental data from an onshore experimental campaign are employed in a numerical scheme to identify the pile strain field based on in vacuo modes of simpler yet related systems. By mapping the pile strain field onto physically-based shape functions, the evolution of the soil reaction during pile installation can be studied, in order to facilitate the back-analysis of driving records and, by extension, improve pile drivability and vibro-acoustics predictions.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Dynamics of StructuresOffshore EngineeringEngineering Structure
Dynamic amplication in a periodic structure subject to a moving load passing a transition zone: Hyperloop case study
No full textHyperloop is an emerging high-speed transportation system in which air resistance is minimised by having the vehicle travel inside a de-pressurised tube supported by columns. This design leads to a strong periodic variation of the stiffness (among other parameters) experienced by the vehicle. Also, along its route, the Hyperloop will encounter so-called transition zones (e.g., junctions, bridges, etc.), where the properties (e.g., support stiffness) are different than for the rest of the structure. In railway engineering, increased degradation is seen in the vicinity of these transition zones, leading to increased frequency of maintenance. This work investigates response amplification mechanisms in a Hyperloop system that arise due to the combination of a transition zone and the structure having a periodic nature. The amplification mechanisms investigated here can help prevent degradation of the Hyperloop tube close to transition zones as well as fatigue and wear of the vehicle.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Dynamics of StructuresOffshore EngineeringEngineering Structure
CaptureBias: Supporting Media Scholars with Ambiguity-Aware Bias Representation for News Videos
No full textIn this project we explore the presence of ambiguity in textual and visual media and its influence on accurately understanding andcapturing bias in news. We study this topic in the context of supportingmedia scholars and social scientists in their media analysis. Our focuslies on racial and gender bias as well as framing and the comparisonof their manifestation across modalities, cultures and languages. In thispaper we lay out a human in the loop approach to investigate the role ofambiguity in detection and interpretation of bias.Accepted Author ManuscriptWeb Information System
Characterising and Mitigating Aggregation-Bias in Crowdsourced Toxicity Annotations
No full textTraining machine learning (ML) models for natural language processing usually requires large amount of data, often acquired through crowdsourcing. The way this data is collected and aggregated can have an effect on the outputs of the trained model such as ignoring the labels which differ from the majority. In this paper we investigate how label aggregation can bias the ML results towards certain data samples and propose a methodology to highlight and mitigate this bias. Although our work is applicable to any kind of label aggregation for data subject to multiple interpretations, we focus on the effects of the bias introduced by majority voting on toxicity prediction over sentences. Our preliminary results point out that we can mitigate the majority-bias and get increased prediction accuracy for the minority opinions if we take into account the different labels from annotators when training adapted models, rather than rely on the aggregated labels.Accepted Author ManuscriptWeb Information System
