Market trend, company size and microstructure characteristics of intraday stock price formations

The purpose of this study is to investigate whether there are certain price patterns during the trading session in the Athens Stock Exchange (ASE). We investigate statistically the series of stock returns, the volatility of stock returns and trading volume. In our analysis we use data from two different time periods; a period of rising prices (“bull” market) and a period of declining stock prices (“bear” market). We also use different categories of shares i.e. blue chips, medium capitalization stocks and small capitalization stocks. Our results indicate that there exist specific intraday patterns. The explanation of the revealed patterns can be based on investor sentiment and stock market microstructure characteristics.peer-reviewe

Δομικός χαρακτηρισμός παλυγορσκιτικών αργίλων με φασματοσκοπία μέσου υπερύθρου

65 σ.Ο παλυγορσκίτης είναι φυσική άργιλος με κυψελωτή δομή, που σχηματίζει σωματίδια με μορφολογία πεπλατυσμένης δοκίδας. Η σύσταση του περιγράφεται από τον γενικό τύπο yMg5Si8O20(OH)2 . (1-y)[xMg2Fe2 . (1-x)Mg2Al2]Si8O20(OH)2, όπου 0≤x<0.7 και 0≤y<0.5, με την μεταβλητή x να εκφράζει το ποσοστό του διοκταεδρικού παλυγορσκίτη που είναι σιδηρούχος και την μεταβλητή y το ποσοστό του τριοκταεδρικού παλυγορσκίτη. Στην πρόσφατη βιβλιογραφία, η δομή του παλυγορσκίτη μελετάται αναλυτικά μέσω του φάσματος των δομικών υδροξυλίων (φασματοσκοπία εγγύς υπερύθρου, NIR) που αποκρίνεται στη φύση και τον σχετικό πληθυσμό των οκταεδρικών ιόντων Al, Fe και Mg. Στο μέσο υπέρυθρο οι σχετικές θεμελιώδεις δονήσεις (ιδίως αυτές που αφορούν το πυριτικό πλέγμα) παρουσιάζουν εξαιρετικά υψηλό συντελεστή απορρόφησης και δεν έχει μελετηθεί ακόμα συστηματικά η προσαρμογή τους στις αλλαγές της σύστασης της οκταεδρικής στοιβάδας. Αυτό το κενό έρχεται να καλύψει η παρούσα μελέτη, όπου με χρήση της τεχνικής της αποσβεννύμενης ολικής ανάκλασης (ATR) εξετάζονται δεκαεννέα δείγματα παλυγορσκιτών διαφορετικής χημικής σύστασης και ενίοτε συγκρίνονται με φάσματα συναφών αργίλων όπως ενός σεπιόλιθου και ενός νατριούχου μοντμοριλλονίτη. Βρέθηκε ότι υπάρχει σχέση μεταξύ θέσεων ταινιών απορρόφησης της πυριτικής στοιβάδας με τη χημική σύσταση της οκταεδρικής στοιβάδας, όπως επίσης και μεταξύ της έντασης ταινίας απορρόφησης νερού και της χημικής σύστασης της οκταεδρικής στοιβάδας. Από την ανάλυση των παραπάνω καταλήγουμε σε σημαντικά συμπεράσματα, για τη φύση της δομής του παλυγορσκίτη, τα οποία συνάδουν με αυτά άλλων μελετών που έλαβαν χώρα σε παράλληλο χρόνο με αυτή την εργασία.Palygorskite is a natural hydrous magnesium aluminosilicate mineral with a modular structure and a fibrillar morphology. Palygorskite has a mixed dioctahedral-trioctahedral character described by the general formula yMg5Si8O20(OH)2 . (1-y)[xMg2Fe2 . (1-x)Mg2Al2]Si8O20(OH)2, where x expresses the percentage of dioctahedral palygorskite which is ferric, y refers to the percentage of trioctahedral palygorskite, and 0<x<0.7, 0<y<0.5. Recently, a broad set of palygorskites with variable composition have been investigated by near-infrared spectroscopy, NIR, to reveal correlations between crystal structure and octahedral composition. The present study focuses at the systematic investigation of the mid-infrared spectra of the same samples. Due to the very high absorption coefficient of these minerals, Attenuated Total Reflectance (ATR) is employed for non destructive infrared data acquisition. Results indicate the existence of spectral features that depend exclusively on the trioctahedral content (y), or on the Fe(III) content of the dioctahedral fraction, x. Interestingly, a mode attributed to the linkages between adjacent modules is found to depend on both x and y, in a manner similar to the dependence of the d200 spacing of palygorskite. Further, extrapolations to the spectra of ideal fully trioctahedral palygorskite (y=1) leed to the spectrum of sepiolite, an analogous magnesian trioctahedral mineral with broader modules. In agreement with previous studies, the data suggest that trioctahedral-rich palygorskites are members of a dioctahedral palygorskite – sepiolite polysomatic series.Εμμαμουήλ Α. Αλεξάκη

Theory of Rayleigh–Brillouin optical activity light scattering applicable to chiral liquids

It has long been understood that dilute samples of chiral molecules such as rarefied gases should exhibit Rayleigh optical activity. We extend the existing theory by accounting for molecular dynamics and correlations, thus obtaining a more general theory of Rayleigh–Brillouin optical activity applicable to dense samples such as neat liquids

Διαγνωστική Μελέτη Φθοράς και Χαρακτηρισμός Δομικών Υλικών του Ιερού Κουβουκλίου του Παναγίου Τάφου στα Ιεροσόλυμα

Εθνικό Μετσόβιο Πολυτεχνείο--Μεταπτυχιακή Εργασία. Διεπιστημονικό-Διατμηματικό Πρόγραμμα Μεταπτυχιακών Σπουδών (Δ.Π.Μ.Σ.) “Προστασία των Μνημείων

Market abuse under different close price determination mechanisms: A European case

We examine the presence and the severity of closing price manipulation across two regulatory shifts in the close price determination mechanism in the Athens stock exchange. First, we assess the transition from a value-weighted average price (VWAP) method to a plain-vanilla closing call auction method (CCAM). Second, we examine the effectiveness of additional features of CCAMs in deterring closing price manipulation. We use tick level data with full investor details for a group of highly traded stocks. Our results suggest that the CCAM managed to reduce - but not eliminate - closing price manipulation. CCAMs with additional anti-manipulation features are not effective in eliminating closing price manipulation either. Manipulation is dynamic and investors quickly adapt to new circumstances and opportunities; post-CCAM implementation sell-based closing price manipulation has increased, while part of the manipulation activity has shifted to the reference price formation

Performance of Machine Learning-Based Multi-Model Voting Ensemble Methods for Network Threat Detection in Agriculture 4.0

The upcoming agricultural revolution, known as Agriculture 4.0, integrates cutting-edge Information and Communication Technologies in existing operations. Various cyber threats related to the aforementioned integration have attracted increasing interest from security researchers. Network traffic analysis and classification based on Machine Learning (ML) methodologies can play a vital role in tackling such threats. Towards this direction, this research work presents and evaluates different ML classifiers for network traffic classification, i.e., K-Nearest Neighbors (KNN), Support Vector Classification (SVC), Decision Tree (DT), Random Forest (RF) and Stochastic Gradient Descent (SGD), as well as a hard voting and a soft voting ensemble model of these classifiers. In the context of this research work, three variations of the NSL-KDD dataset were utilized, i.e., initial dataset, undersampled dataset and oversampled dataset. The performance of the individual ML algorithms was evaluated in all three dataset variations and was compared to the performance of the voting ensemble methods. In most cases, both the hard and the soft voting models were found to perform better in terms of accuracy compared to the individual models

Theory of Rayleigh-Brillouin optical activity light scattering applicable to chiral liquids

It has long been understood that dilute samples of chiral molecules such as rarefied gases should exhibit Rayleigh optical activity. We extend the existing theory by accounting for molecular dynamics and correlations, thus obtaining a more general theory of Rayleigh-Brillouin optical activity applicable to dense samples such as neat liquids

A novel application of deep learning approach over IRT images for the automated detection of rising damp on historical masonries

Nowadays, the fusion of Artificial Intelligence (AI) comprises a widespread approach for resolving various types of problems in many scientific domains including Protection of Monuments. Non-Destructive Testing (NDT) approaches and Infra-Red Thermography (IRT) specifically, plays a key role for the diagnosis and the assessment of the monuments’ preservation state. Additionally, IRT comprises a powerful tool for continuous monitoring especially when it concerns the physical and/or chemical processes that take place within or on the material and affect the irradiation of the historical surfaces. This study explores the application of Deep Learning (DL) to IRT images of passive approach, focusing on the automated detection of rising damp in historical masonries. The IRT data were acquired from two monuments, the Holy Aedicule of the Holy Sepulchre and the Historical Building ''Msma’a''. Exploiting the capabilities of AI for enhancing the non-intrusive nature of passive IRT, this research seeks to provide a cost-effective and non-destructive approach for the early identification of rising damp, contributing significantly to the long-term preservation, conservation, and protection of the cultural heritage. To achieve this, the study takes advantage of a combination of the PSPNet image segmentation model with the ResNet-50 backbone, the PSP_R50 model. The mmsegment framework, renowned for its versatility and effectiveness, serves as the ideal platform for training, evaluating, and fine-tuning the proposed segmentation model. Despite having a relatively small dataset, a highly effective segmentation model (0.93 accuracy, 0.89 IoU), has been successfully developed

Multispectral Applications of Infrared Thermography in the Diagnosis and Protection of Built Cultural Heritage

Infrared thermography (IRT) is a powerful non contact imaging technique, appropriate for the protection of cultural heritage. The National Technical University of Athens research team (scientist responsible: A. Moropoulou), started to use this technique in the early 1990s, in all stages of a conservation project, from decay diagnosis to assessment of conservation interventions and monitoring. The monuments investigated with the aid of this technique belonged to different historical periods, dating from antiquity to modern times. The main products of IRT, thermal maps of surfaces, were evaluated and exploited, based on the demands, special needs and requirements of each application. Additionally, in laboratory scale, many IRT measurements were performed in order to investigate the applicability and limitations of this technique for measuring a material’s thermophysical properties. All these data and accumulated knowledge and experience contributed to a set of recommendations, which enabled us to compile a protocol for the application of this technique in a more standardized way. Moreover, the added value of this practice permitted the successful application and integration of this technique in large-scale conservation projects, such as the Pythian Apollo Temple in Acropolis of Rhodes, during the diagnostic study phase, or at the Holy Aedicule, of the Holy Selphuchre in Jerusalem, during the rehabilitation works