Institutional Repository of Academic Research University of Macedonia
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Graph-Based Semi-Supervised Learning with Tensor Embeddings for Hyperspectral Data Classification
No full textHyperspectral data classification is one of the fundamental problems in remote sensing. Several algorithms based on supervised machine learning have been proposed to address it. The performance, however, of the proposed algorithms is inherently dependent on the amount and quality of annotated data. Due to recent advances in hyperspectral imaging and autonomous (unmanned) aerial vehicles collecting new hyperspectral data is an easy task. Annotating those data, however, is a tedious, time-consuming and costly task requiring the in-situ presence of human experts. One way to loosen the requirement of a large number of annotated data is the shift to semi-supervised learning combined with highly sample-efficient tensor-based neural networks. This study provides a comprehensive experimental analysis of the performance of a variety of graph-based semi-supervised learning techniques combined with tensor-based neural network embeddings for the problem of hyperspectral data classification. Experimental results suggest that the combination of tensor-based neural network embeddings with graph-based semi-supervised learning can significantly improve the classification results minimizing human annotation effort.1112481912483
If you play some good music, people immediately understand it: Audience response to busking
No full textBusking is part of the daily urban life of citizens worldwide. Every street music performance can affect buskers or passers-by in different ways because the people, the conditions, the terms and the reasons for music-making is unique every single time. This article aims to deliver social insights from the Greek busking community of Thessaloniki. Specifically, we examine the relationship between street musicians and their audience, according to their attitudes and practices during a street performance. For this study, a mix-methods approach was followed where quantitative and qualitative data was collected from 146 participants (82 were members of the audience and 64 were buskers). Our meth- odology relied on semi-structured interviews to collect buskers’ and audiences’ views on their experiences, as well as field notes and observation to document their relationship and reactions first-hand. The main findings indicate that busk- ers and audiences sustain a healthy relationship between them while buskers are thankful for the audience’s reaction to their performance and tend to make a series of performative choices, according to audience preferences. Furthermore, all audience members actively approve of the existence of street music and show their appreciation of being part of this community, by donating money and participating through various ways (singing, dancing, taking photos).16213515
Identifying the factors to enhance digital competence of students at Vocational Training Institutes
No full textDigital competence is a quite complex and evolving concept, difficult to be defined by using a single definition. The European Digital Competence Framework (DigComp) provides a consistent framework to guide cross-country measurements of digital competence. Even though there are many studies on measuring the digital competence level, there is a limited focus on the factors that may influence each DigComp area. The aim of this study is to examine the factors that affect the different areas of digital competence level of students at Vocational Training Institutes. For the purposes of the study, a set of laboratory tests was developed. The study employs parametric tests – t-test, one-way ANOVA, and Bonferroni correction – to examine those factors. According to the findings: (1) ‘age’ affects the ‘Communication and collaboration’ area of DigComp; (2) ‘educational level’ affects ‘Digital content creation’; (3) ‘specialization’ affects ‘Communication and collaboration’; (4) ‘possession and use of PC’ affects ‘Information and data literacy’, as well as ‘Problem solving’; (5) ‘possession and use of smartphones’ affects ‘Communication and collaboration’; and (6) ‘Internet use’ affects ‘Information and data literacy’. The results suggest that educational institutes should update their curricula to achieve a sufficient level of digital competence for their graduates by developing tailored made courses to reinforce the skills related to those areas separately, and employ educational practices to confront influential factors, such as age and use of technology. Employees’ training processes should also consider updating reskilling and upskilling programs towards improving the five DigComp areas.28161365
Nonparametric estimates of price efficiency for the Greek infant milk market: Curing the curse of dimensionality with shannon entropy
No full textDespite the continuous promotion of breastfeeding by the World Health Organization and national health systems, the consumption of breast milk substitutes (BMS) is increasing. Several BMS brands in the market have varying prices and attributes (i.e., energy, protein, vitamins, minerals, etc.). Using data from Greece, we examine which of these are “value for money” choices and which are overpriced relative to their number of attributes. For this purpose, we estimate their price efficiency using data envelopment analysis, where the discrimination power hinges on the curse of dimensionality. To cope with this, we propose a novel use of Shannon's entropy for pre-aggregating vitamin and mineral items. Our empirical results indicate that most of the considered brands are overpriced relative to their number of attributes. This result is more severe for the infant formulae brands than the follow-on formulae, the growing-up milk brands, and brands with higher prices.12110620
The role of relative income in the share of children born out-of-wedlock in the USA
No full textThis paper investigates the non-marital fertility evolution in the USA for the period between 1976 and 2016. Beyond the well-known determinants in this framework, we add and test for the Easterlin relative income hypothesis. Easterlin stresses the role of the material aspirations formed in childhood (denominator) relative to the current economic perspectives (numerator) of young men. That ratio defines the relative income. We employ panel dynamic techniques at the state level. We find a negative and statistically significant effect of the relative income in the share of children born out-of-wedlock. Most importantly, relative income is robust to the inclusion of marriage. The latter may imply a socio-economic mobility perspective.6431105112
Audit committee characteristics and the audit report lag in Greece
No full textWe review prior empirical studies that investigate the effect of audit committee characteristics on audit report lag and provide insights about this corpus of scholarly literature. We also determine whether these audit committees’ compositional features are associated with audit report lag in the context of an emerging market (Greece). Using a unique set of data hand-collected from the annual reports for 130 firms listed on the Athens Stock Exchange, a multiple regression analysis is conducted to identify and explain this association. This analysis identifies the four audit committee characteristics most frequently mentioned in the literature. By empirically examining these, we demonstrate that audit committee diligence is associated with a shorter audit report lag. The results generally satisfy a number of alternative benchmark tests that control for different types of proxies and transformations of audit report lag. Our results could assist practitioners and/or policy makers in perceiving the efficacy of audit committee diligence as a means to improve the timeliness of financial reporting. This is, to the best of the authors’ knowledge, the first study that provides a synopsis of the prior literature and examines this relationship in the Greek context.181598
Managing the online customer experience and subsequent consumer responses across the customer journey: A review and future research agenda
No full textThe rise of the “post-pandemic new digital consumer” who cherishes personalization, demands trust and expects immersive online experiences has led brands to reexamine their online presence. Brand-driven, experiential and consistent online customer experiences are critical in this context, and it is a brand's website that operates as a hub for its online presence. Understanding how websites can offer online customer experiences that will lead to the desired consumer responses is fundamental. Even though significant research exists regarding online customer experiences on websites, it is highly fragmented across the business and IT literature. Most studies either separately examine the stages of the customer journey or simultaneously examine more than one stages. There have been no attempts to critically review and synthesize the existing body of knowledge regarding how online customer experiences are constructed on websites and their subsequent consumer responses in each separate stage of the customer journey. The purpose of this paper is to fill this gap by synthesizing existing knowledge through a systematic literature review method and providing an overall direction for managing such online customer experiences. The findings indicate under-explored areas and serve as a resource for future studies and practice.5810124
Educators’ views on telepresence robots in teaching
No full textRemote persons can be represented by telepresence robots (TRs) located at another location and be facilitated in their audio-visual communication with other persons and the surroundings at that location. TRs are used in diverse fields including education. However, most of the previous studies have explored particular instances of introducing TRs in education. The present study aims to bring together the viewpoints of educators from different countries and educational institutes. The partners of the Erasmus+ project “TRinE: Telepresence Robots in Education” conducted interviews and focus groups among 46 educators (10 university professors and 36 high school teachers) in Austria, France, Germany, Iceland, and Malta. Findings indicated that educators appreciated that a remote student using a TR can feel and being felt present as well as move around in the class and the school. TRs enhance inclusiveness since the remote user can be an ill student or anyone at a remote location. The educators mentioned TRs’ weaknesses such as their unstable Wi-Fi connectivity and poor audio video quality. They also pointed out challenges concerning privacy issues, loss of Wi-Fi connectivity, noisy environments and obstacles along the way as the TR moves (elevators, doors, stairs, etc.). Finally, the educators recommended that TRs’ manufacturers build more user friendly, visible, and accessible TRs as well as educational institutes apply effective TRs management procedures.122134Πρακτικά του 12ου για την Ανοικτή & εξ Αποστάσεως Εκπαίδευση: Η εξ αποστάσεως και συμβατική εκπαίδευση στην ψηφιακή εποχ
Should stock returns predictability be ‘hooked on’ long‐horizon regressions?
No full textThis paper re-examines stock returns predictability over the business cycle using price-dividend and price-earnings valuation ratios as predictors. Unlike prior studies that habitually implement long-horizon/predictive regressions, we conduct a testing framework in the frequency domain. Predictive regressions support no predictability; in contrast, our results in the frequency domain verify significant predictability at medium and long horizons. To robustify predictability patterns, the analysis is executed repetitively for fixed-length rolling samples of various sizes. Overall, the stock returns are predictable for wavelengths higher than 5 years. This finding is robust and independent of time, window size and predictor.28171873
You Look like You’ll Buy It! Purchase Intent Prediction Based on Facially Detected Emotions in Social Media Campaigns for Food Products
No full textUnderstanding the online behavior and purchase intent of online consumers in socialmedia can bring significant benefits to the ecommerce business and consumer research community.Despite the tight links between consumer emotions and purchase decisions, previous studies focusedprimarily on predicting purchase intent through web analytics and sales historical data. Here, the useof facially expressed emotions is suggested to infer the purchase intent of online consumers whilewatching social media video campaigns for food products (yogurt and nut butters). A FaceReaderOnlineTM multi-stage experiment was set, collecting data from 154 valid sessions of 74 participants.A set of different classification models was deployed, and the performance evaluation metricswere compared. The models included Neural Networks (NNs), Logistic Regression (LR), DecisionTrees (DTs), Random Forest (RF,) and Support Vector Machine (SVM). The NNs proved highlyaccurate (90–91%) in predicting the consumers’ intention to buy or try the product, while RF showedpromising results (75%). The expressions of sadness and surprise indicated the highest levels ofrelative importance in RF and DTs correspondingly. Despite the low activation scores in arousal,micro expressions of emotions proved to be sufficient input in predicting purchase intent based oninstances of facially decoded emotions.1248