arXiv subjects

Vassilis Kostakos

Publications and source records attributed to Vassilis Kostakos.

32 records · Page 2Linked to original sources

arXiv2021

UbiNIRS: A Software Framework for Miniaturized NIRS-based Applications

We present UbiNIRS, a software framework for rapid development and deployment of applications using miniaturized near-infrared spectroscopy (NIRS). NIRS is an emerging material sensing technology that has shown a great potential in recent work from the HCI community such as in situ pill testing. However, existing methods require significant programming efforts and professional knowledge of NIRS, and hence, challenge the creation of new NIRS based applications. Our system helps to resolve this issue by providing a generic server and a mobile app, using the best practices for NIRS applications in literature. The server creates and manages UbiNIRS instances without the need for any coding or professional knowledge of NIRS. The mobile app can register multiple UbiNIRS instances by communicating with the server for different NIRS based applications. Furthermore, UbiNIRS enables NIRS spectrum crowdsourcing for building a knowledge base.

cs.HC↗

arXiv2021

InfoPrint: Embedding Information into 3D Printed Objects

We present a technique to embed information invisible to the eye inside 3D printed objects. The information is integrated in the object model, and then fabricated using off-the-shelf dual-head FDM (Fused Deposition Modeling) 3D printers. Our process does not require human intervention during or after printing with the integrated model. The information can be arbitrary symbols, such as icons, text,binary, or handwriting. To retrieve the information, we evaluate two different infrared-based imaging devices that are readily available-thermal cameras and near-infrared scanners. Based on our results, we propose design guidelines for a range of use cases to embed and extract hidden information. We demonstrate how our method can be used for different applications, such as interactive thermal displays, hidden board game tokens, tagging functional printed objects, and autographing non-fungible fabrication work.

cs.HC↗

arXiv2021

A Survey on Task Assignment in Crowdsourcing

Quality improvement methods are essential to gathering high-quality crowdsourced data, both for research and industry applications. A popular and broadly applicable method is task assignment that dynamically adjusts crowd workflow parameters. In this survey, we review task assignment methods that address: heterogeneous task assignment, question assignment, and plurality problems in crowdsourcing. We discuss and contrast how these methods estimate worker performance, and highlight potential challenges in their implementation. Finally, we discuss future research directions for task assignment methods, and how crowdsourcing platforms and other stakeholders can benefit from them.

cs.HC↗

arXiv2019

Situationally-Induced Impairments and Disabilities Research

Research has shown that various environmental factors impact smartphone interaction and lead to Situationally-Induced Impairments and Disabilities. In this work we discuss the importance of thoroughly understanding the effects of these situational impairments on smartphone interaction. We argue that systematic investigation of the effects of different situational impairments is quintessential for conducting successful research in the field of SIIDs that might lead to building appropriate sensing, modelling, and adapting techniques. We also provide insights for future work identifying potential directions to conduct research in SIIDs.

cs.HC↗

arXiv2017

Smartphone App Usage Prediction Using Points of Interest

In this paper we present the first population-level, city-scale analysis of application usage on smartphones. Using deep packet inspection at the network operator level, we obtained a geo-tagged dataset with more than 6 million unique devices that launched more than 10,000 unique applications across the city of Shanghai over one week. We develop a technique that leverages transfer learning to predict which applications are most popular and estimate the whole usage distribution based on the Point of Interest (POI) information of that particular location. We demonstrate that our technique has an 83.0% hitrate in successfully identifying the top five popular applications, and a 0.15 RMSE when estimating usage with just 10% sampled sparse data. It outperforms by about 25.7% over the existing state-of-the-art approaches. Our findings pave the way for predicting which apps are relevant to a user given their current location, and which applications are popular where. The implications of our findings are broad: it enables a range of systems to benefit from such timely predictions, including operating systems, network operators, appstores, advertisers, and service providers.

cs.CY↗

arXiv2012

Correlating Pedestrian Flows and Search Engine Queries

An important challenge for ubiquitous computing is the development of techniques that can characterize a location vis-a-vis the richness and diversity of urban settings. In this paper we report our work on correlating urban pedestrian flows with Google search queries. Using longitudinal data we show pedestrian flows at particular locations can be correlated with the frequency of Google search terms that are semantically relevant to those locations. Our approach can identify relevant content, media, and advertisements for particular locations.

cs.HC↗

arXiv2009

Is the crowd's wisdom biased? A quantitative asessment of three online communities

This paper presents a study of user voting on three websites: Imdb, Amazon and BookCrossings. It reports on an expert evaluation of the voting mechanisms of each website and a quantitative data analysis of users' aggregate voting behavior. The results suggest that voting follows different patterns across the websites, with higher barrier to vote introducing a more of one-off voters and attracting mostly experts. The results also show that that one-off voters tend to vote on popular items, while experts mostly vote for obscure, low-rated items. The study concludes with design suggestions to address the "wisdom of the crowd" bias.

cs.HC↗

arXiv2009

An empirical study of spatial and transpatial social networks using Bluetooth and Facebook

This study provides insights into the quantitative similarities, differences and relationships between users' spatial, face-to-face, urban social networks and their transpatial, online counterparts. We explore and map the social ties within a cohort of 2602 users, and how those ties are mediated via physical co-presence and online tools. Our analysis focused on isolating two distinct segments of the social network: one mediated by physical co-presence, and the other mediated by Facebook. Our results suggest that as a whole the networks exhibit homogeneous characteristics, but individuals' involvement in those networks varies considerably. Furthermore this study provides a methodological approach for jointly analysing spatial & transpatial networks utilising pervasive and ubiquitous technology.

cs.CY↗

arXiv2008

Towards sustainable transport: wireless detection of passenger trips on public transport buses

An important problem in creating efficient public transport is obtaining data about the set of trips that passengers make, usually referred to as an Origin/Destination (OD) matrix. Obtaining this data is problematic and expensive in general, especially in the case of buses because on-board ticketing systems do not record where and when passengers get off a bus. In this paper we describe a novel and inexpensive system that uses off-the-shelf Bluetooth hardware to accurately record passenger journeys. Here we show how our system can be used to derive passenger OD matrices, and additionally we show how our data can be used to further improve public transport services.

cs.CY↗

arXiv2008

Temporal Graphs

We introduce the idea of temporal graphs, a representation that encodes temporal data into graphs while fully retaining the temporal information of the original data. This representation lets us explore the dynamic temporal properties of data by using existing graph algorithms (such as shortest-path), with no need for data-driven simulations. We also present a number of metrics that can be used to study and explore temporal graphs. Finally, we use temporal graphs to analyse real-world data and present the results of our analysis.

physics.soc-ph↗

arXiv2008

Intelligence gathering by capturing the social processes within prisons

We present a prototype system that can be used to capture longitudinal socialising processes by recording people's encounters in space. We argue that such a system can usefully be deployed in prisons and other detention facilities in order help intelligence analysts assess the behaviour or terrorist and organised crime groups, and their potential relationships. Here we present the results of a longitudinal study, carried out with civilians, which demonstrates the capabilities of our system.

cs.CY↗

arXiv2008

The privacy implications of Bluetooth

A substantial amount of research, as well as media hype, has surrounded RFID technology and its privacy implications. Currently, researchers and the media focus on the privacy threats posed by RFID, while consumer groups choose to boycott products bearing RFID tags. At the same, however, a very similar technology has quietly become part of our everyday lives: Bluetooth. In this paper we highlight the fact that Bluetooth is a widespread technology that has real privacy implications. Furthermore, we explore the applicability of RFID-based solutions to address these privacy implications.

cs.CR↗

arXiv2008

Size matters: performance declines if your pixels are too big or too small

We present a conceptual model that describes the effect of pixel size on target acquisition. We demonstrate the use of our conceptual model by applying it to predict and explain the results of an experiment to evaluate users' performance in a target acquisition task involving three distinct display sizes: standard desktop, small and large displays. The results indicate that users are fastest on standard desktop displays, undershoots are the most common error on small displays and overshoots are the most common error on large displays. We propose heuristics to maintain usability when changing displays. Finally, we contribute to the growing body of evidence that amplitude does affect performance in a display-based pointing task.

cs.GR↗

arXiv2007

Brief encounter networks

Many complex human and natural phenomena can usefully be represented as networks describing the relationships between individuals. While these relationships are typically intermittent, previous research has used network representations that aggregate the relationships at discrete intervals. However, such an aggregation discards important temporal information, thus inhibiting our understanding of the networks dynamic behaviour and evolution. We have recorded patterns of human urban encounter using Bluetooth technology thus retaining the temporal properties of this network. Here we show how this temporal information influences the structural properties of the network. We show that the temporal properties of human urban encounter are scale-free, leading to an overwhelming proportion of brief encounters between individuals. While previous research has shown preferential attachment to result in scale-free connectivity in aggregated network data, we found that scale-free connectivity results from the temporal properties of the network. In addition, we show that brief encounters act as weak social ties in the diffusion of non-expiring information, yet persistent encounters provide the means for sustaining time-expiring information through a network.

cs.CY↗