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Open Access
Air flow characteristics in an industrial wood pallet drying kiln
(2010-07-21T09:52:17Z) Tzempelikos, Dimitrios; Filios, Andronikos; Margaris, Dionisios; Τζεμπελίκος, Δημήτριος; Φίλιος, Ανδρόνικος; Μάργαρης, Διονύσιος
Τμήμα Μηχανολόγων και Αεροναυπηγών Μηχαν. (Δημοσ. Π.Π. σε συνέδρια)
The improvement and optimization of air-distribution systems in drying kilns contributes to the preservation of the quality, safety and shelf life of perishable products. The present study reports on the numerical solution of airflow within a two dimensional drying kiln enclosure loaded with wooden pallets. The performance of air flow field is examined with and without supply of wooden pallets. Different arrangements of the supplied wooden pallets are investigated as well as the use of a screen in order to improve the airflow filed. The steady state RANS equations that formulate the flow problem are solved along with a turbulence model that is the standard k-εor the rng k-ε. The effect of the turbulence modeling is distinguished through direct comparisons of the derived airflow patterns. The results obtained show the presence of stagnant zones inside the pallets columns and above of them and the presence of recirculation regions in different zones of the drying kiln with the two turbulence models.
Open Access
Air flow characteristics in an industrial wood pallet drying kiln
(2013-07-30) Tzempelikos, Dimitrios; Filios, Andronikos; Margaris, Dionissios; Τζεμπελίκος, Δημήτριος; Φιλιός, Ανδρόνικος; Μάργαρης, Διονύσιος
Τμήμα Μηχανολόγων και Αεροναυπηγών Μηχαν. (Δημοσ. Π.Π. σε συνέδρια)
The improvement and optimization of air-distribution systems in drying kilns contributes to the preservation of the quality, safety and shelf life of perishable products. The present study reports on the numerical solution of airflow within a two dimensional drying kiln enclosure loaded with wooden pallets. The performance of air flow field is examined with and without supply of wooden pallets. Different arrangements of the supplied wooden pallets are investigated as well as the use of a screen in order to improve the airflow field. The steady state RANS equations that formulate the flow problem are solved along with a turbulence model that is the standard k-ε or the rng k-ε. The effect of the turbulence modeling is distinguished through direct comparisons of the derived airflow patterns. The results obtained show the presence of stagnant zones inside the pallets columns and above of them and the presence of recirculation regions in different zones of the drying kiln with the two turbulence models.
Open Access
Airflow patterns in a laboratory batch-type, tray air dryer
(2013-07-30) Tzempelikos, Dimitrios; Vouros, Alexandros; Bardakas, Achilleas; Filios, Andronikos; Margaris, Dionissios; Τζεμπελίκος, Δημήτριος; Βούρος, Αλέξανδρος; Μπαρδάκας, Αχιλλέας; Φιλιός, Ανδρόνικος; Μάργαρης, Διονύσιος
Τμήμα Μηχανολόγων και Αεροναυπηγών Μηχαν. (Δημοσ. Π.Π. σε συνέδρια)
The batch-type dryer is one of the most popular equipment for fruit drying. However, the optimization of the air distribution inside the drying chamber remains a very important issue, due to its strong impact on efficient drying and uniformity of moisture content of products. A new scale laboratory batch-type, tray air dryer has been designed, constructed and evaluated for drying several horticultural and agricultural products. The flow field inside the dryer is studied through computational fluid dynamics (CFD). A three-dimensional model for laboratory dryer has been created and the steady state incompressible, Reynolds-Averaged Navier-Stokes (RANS) equations that formulate the flow problem are solved, incorporating standard and RNG k-ε turbulence models. The simulations are conducted for testing chamber average velocity of 2,9 m/s at ambient temperature. The CFD models are evaluated by comparing airflow patterns and velocity distributions to measured data. Numerical simulations and measurements convince that the new scale laboratory batch-type dryer is able to produce a sufficiently uniform air distribution throughout the testing chamber of the dryer.
Open Access
An experimental study on convective drying of quince
(2013-08-06) Tzempelikos, Dimitrios; Bardakas, Achilleas; Vouros, Alexandros; Tsepenekas, Dionysios; Filios, Andronikos; Margaris, Dionissios; Τζεμπελίκος, Δημήτριος; Μπαρδάκας, Αχιλλέας; Βούρος, Αλέξανδρος; Τσεπενέκας, Διονύσιος; Φιλιός, Ανδρόνικος; Μάργαρης, Διονύσιος
Τμήμα Μηχανολόγων και Αεροναυπηγών Μηχαν. (Δημοσ. Π.Π. σε συνέδρια)
A laboratory convective drying unit (LCDU) has been designed, constructed and equipped with an integrated measurement and control instrumentation, in order to evaluate the essential drying characteristics of various horticultural and agricultural products. The current paper presents experimental results from tests with quince slices. Drying kinetics was investigated as a function of drying conditions. Experiments were conducted at air flow temperatures of 40, 50 and 60oC and average velocities of 1, 2 and 3 m/s. Temperature changes of the drying quince samples, the relative humidity and the temperature of the drying air were measured during the drying processes and finally the moisture ratio (MR) was calculated. The experimental MR data were fitted with three mathematical models available in the literature and a good agreement was observed. In the ranges measured, Fick’s 2nd law of diffusion was used to fit the experimental data for the determination of the effective moisture diffusivity. The activation energy was determined, assuming an Arrhenius type temperature relationship with moisture diffusivity.
Open Access
Analysis of bone composition with Raman spectroscopy
(2012-05-04) Kontoyannis, Christos; Orkoula, Malvina; Kalonakis, Konstantinos; Κοντογιάννης, Χρήστος; Όρκουλα, Μαλβίνα; Καλονάκης, Κωνσταντίνος
Τμήμα Φαρμακευτικής (Δημοσ. Π.Π. σε συνέδρια)
Bone is a composite material formed by the nucleation and growth of a mineral highly resembling calcium hydroxyapatite, Ca10(PO4)6(OH)2, within an organic matrix consisting mainly of type I collagen. Seventy percent of mature bone consists of the inorganic phase while the organic matrix and water fills the rest. Development of fast and reliable methodologies capable of analyzing chemically the major bone constituents is needed. In the present work, Raman spectroscopy, a non-destructive technique, was applied as such a tool on bovine cortical and trabecular parts of bone. Preliminary results show that their mineral to organic ratio differs at 30%.
Open Access
Can Research-Informed NetLogo Models Promote the Idea of Contingency in Ecosystems' Behaviour?
Ampatzidis, Georgios; Ergazaki, Marida; Αμπατζίδης, Γεώργιος; Εργαζάκη, Μαρίδα
Τμήμα Επιστημών της Εκπαίδευσης και της Αγωγής στην Προσχολική Ηλικία (Δημοσ. Π.Π. σε συνέδρια)
This paper reports on a case study performed in the 3rd cycle of a developmental research, which aims at designing a learning environment with research-informed NetLogo models that could help non-biology major students in challenging the ‘balanced nature’ idea. Our focus is set on whether and how students’ reasoning about ecosystems’ response to human-driven disturbance or protection altered after their engagement with specially designed models of terrestrial or aquatic ecosystems studied by ecologists. Informed by constructivism and problem-posing approach, our CSCL environment highlights ecosystems’ contingent behaviour through the currently valid idea of the ‘resilient nature’. Forty-four, 1st-year educational sciences students were introduced to the assumptions of this idea in five, 2-hour sessions by exploring in triads our NetLogo models aided by worksheets, which asked for predictions/explanations before/after using the model. Each model had two versions showing two different trajectories of an ecosystem, which were linked to differences in initial conditions or human actions for its recovery. The two different trajectories shown in the two versions of each model were discussed in whole class discussions at the end of the sessions. The analysis of students’ responses to certain items of the pre/post-test showed that the ideas of a protected ecosystem’s stability and a disturbed ecosystem’s full recovery retreated in the post-test, while the idea of ecosystems’ contingent behaviour appeared for the first time in high frequencies.
Open Access
Design, construction and performance evaluation of a new laboratory convective dryer
(2013-07-30) Tzempelikos, Dimitrios; Bardakas, Achilleas; Vouros, Alexandros; Tsepenekas, Dionysios; Christoloukas, Dimitrios; Filios, Andronikos; Margaris, Dionissios; Τζεμπελίκος, Δημήτριος; Μπαρδάκας, Αχιλλέας; Βούρος, Αλέξανδρος; Τσεπενέκας, Διονύσιος; Χριστολουκάς, Διονύσιος; Φιλιός, Ανδρόνικος; Μάργαρης, Διονύσιος
Τμήμα Μηχανολόγων και Αεροναυπηγών Μηχαν. (Δημοσ. Π.Π. σε συνέδρια)
Aiming to overcome the lack of experimental data in the open literature and the necessity to validate numerical models which are an essential tool for optimization and increase the efficiency of the drying process, a laboratory convective (LC) dryer has been designed, constructed and equipped with an integrated measurement and control instrumentation. The main sections of the LC dryer, which can be arranged for operation in a closed or open circuit mode through manually controlled dumpers, are the vertical flow drying chamber, the heat exchanger, the boiler and the fan - motor with smooth speed control unit. The experimental facility is under operation for testing and monitoring the hydration of horticultural and agricultural products. The current paper outlines the methodology applied for the design and optimization of the LC dryer which it has been achieved through the analysis of the flow field by means of computational fluid dynamics (CFD). The prediction of the three – dimensional flow problem is accomplished through the solution of the steady-state incompressible, Reynolds-Averaged Navier-Stokes (RANS) equations with the incorporation of standard turbulence model. The measurement and control instrumentation with the inclusion of the innovative, pc-controlled, 3d traverse system that serves detailed surveys of temperature and velocity inside the drying chamber, are discussed. The performance test and evaluation of the LC dryer is conducted using quince as a test material at an average temperature of 60oC and air of 2 m/sec into the drying chamber.
Open Access
Development of methodologies for characterization of calcium phosphates in their mixture
(2012-04-27) Kontoyannis, Christos; Karampas, Ioannis; Κοντογιάννης, Χρήστος
Τμήμα Φαρμακευτικής (Δημοσ. Π.Π. σε συνέδρια)
The characterization of a mixture consisting of four of outmost biologically significance calcium phosphates (hydroxyapatite, octacalcium phosphate, dicalcium phosphate dihydrate and dicalcium phosphate anhydrous) was attempted. The difficulty in this task lies in the similarity of their chemical and crystal structure. For the identification three spectroscopic techniques were applied: Raman spectroscopy, IR spectroscopy and X-ray powder diffraction (XRPD). Based on careful examination of the spectra, three approaches are proposed depending on instrument availability. One requires combination of IR and Raman information, the second IR and XRPD and the third only XRPD patterns before and after the heating the mixture at 850 oC.
Open Access
Distance higher education learning and professional pedagogy : training the trainers
(Academic Conferences International Limited, 2021-10) Fragkaki, Maria; Mystakidis, Stylianos; Φραγκάκη, Μαρία; Μυστακίδης, Στυλιανός
Τμήμα Επιστημών της Εκπαίδευσης και της Αγωγής στην Προσχολική Ηλικία (Δημοσ. Π.Π. σε συνέδρια)
The global disruption of all physical educational activities due the covid-19 pandemic impacted among others also professional development activities of higher educational faculty members and staff. Teaching and learning had to be organized exclusively online. This transition is not straightforward as it often requires a different way of facing new challenges, or even a cultural change in all involved stakeholders. Hence, instructional designers, but also instructors and researchers need to consider multiple factors related to online education instructional design. In this empirical study, we present in detail the views and needs of twenty-three higher education faculty members, on their preferable pedagogy for distance training that had to replace a face-to-face one, in the frame of a multinational capacity building project. The core research question was “what are higher education instructors’ views and educational needs toward meaningful and effective pedagogy of professional development teaching and learning activities both in a face to face and an online training process”. A mixed research method was employed in the form of a 22-item questionnaire (pilot survey) that combined qualitative and quantitative data in the form of open and closed questions, respectively as well as observation. The results are illustrated through graphical representations and analysis comments. Specifically, the examined research indicators were the preferable training form, methodology, assessment, and feedback. Findings suggest that in online training, a flipped learning approach can accommodate the needs of academics where online meetings can be dedicated mainly to critical discussions and practical applications based on prior asynchronous individual study of theoretical material. This knowledge can be useful and support continuous professional development initiatives in the design and implementation of effective e-learning strategies.
Open Access
Effect of dilipidization and deproteination protocols of bone on biological apatite
(2012-05-04) Kontoyannis, Christos; Orkoula, Malvina; Karampas, Ioannis; Κοντογιάννης, Χρήστος; Όρκουλα, Μαλβίνα; Καραμπάς, Ιωάννης
Τμήμα Φαρμακευτικής (Δημοσ. Π.Π. σε συνέδρια)
Delipidization and deproteination methods are essential for the isolation of the mineral phase of bone, the biological apatite. In the present work, the effect of the above methods on the crystal size and crystallinity of bone mineral was studied. Ten bovine bones were subjected to these protocols and their crystal size and crystallinity were determined by X-ray Diffraction. In all cases, the delipidization protocol was found not to affect these parameters. On the other hand, deproteination method induces noteworthy changes. All the results statistically tested for their significance.
Open Access
Enter the serious e-scape room : a cost-effective serious game model for deep and meaningful e-learning
(IEEE, ) Mystakidis, Stylianos; Cachafeiro, Enrique; Hatzilygeroudis, Ioannis; Μυστακίδης, Στυλιανός; Κατσαφέιρο, Ενρίκε; Χατζηλυγερούδης, Ιωάννης
Τμήμα Μηχανικών Η/Υ και Πληροφορικής (Δημοσ. Π.Π. σε συνέδρια)
Escape rooms are a phenomenon that has taken the world by storm in the last decade. Simultaneously Virtual Reality is a promising technology for innovation in education, training and e-learning. Combining these two concepts, this paper outlines a new model for designing serious games in virtual reality environments for high quality, deep and meaningful learning, the Serious E-scape Room. It describes the theoretical grounding, general guidelines and principles of the model. It also presents the case study “Room of Keys”, a serious virtual escape room for biology concepts. To test the assumptions of the model, researchers conducted a mixed research study with 148 students in a US high school. Pre-post test results recorded a 13.8% performance increase and high overall satisfaction. The game has been received enthusiastically by students, it increased their motivation and helped them build a deeper understanding of the learned concepts.
Open Access
Gender and Science: Men and Women in Greek Gymnasium Science Textbooks
(European Science Education Research Association, ) Ampatzidis, Georgios; Armeni, Anastasia; Αμπατζίδης, Γεώργιος; Αρμένη, Αναστασία
Τμήμα Επιστημών της Εκπαίδευσης και της Αγωγής στην Προσχολική Ηλικία (Δημοσ. Π.Π. σε συνέδρια)
Although the gender gap in science related occupations has been considerably reduced during the last 40 years, women still seem to be underrepresented in areas such as physics and technology. Several reasons have been suggested to explain the lack of interest of female students for science classes such as (a) the formation of sex-segregated groups of students especially in early school years, (b) parental attitudes and behaviour and (c) textbooks. Focusing on the latter, it has been argued that the way gender is portrayed in science textbooks may contribute to the sex role socialization of students; gender bias in science textbooks may influence the development of a view that science is a subject addressed more to boys than girls. This article focuses on the frequency of appearance of men/women and male scientists/female scientists in the illustrations of science textbooks of the Greek Gymnasium (students aged 12-15 years old). The analysis of 7 science textbooks shows that men and male scientists appear more frequently than women and female scientists respectively in the illustrations of physics, biology and chemistry textbooks. Relevant limitations and possible implications are discussed.
Open Access
Identification and stability of calcipotriol pseudopolymorphs in pharmaceutical creams
(2012-04-27) Kontoyannis, Christos; Orkoula, Malvina; Κοντογιάννης, Χρήστος; Όρκουλα, Μαλβίνα
Τμήμα Φαρμακευτικής (Δημοσ. Π.Π. σε συνέδρια)
Calcipotriol is a vitamin D analogue and is used as active pharmaceutical ingredient in pharmaceutical formulations against psoriasis. It exists in two pseudopolymorphs, anhydrate and monohydrate, the latter of which, can be found in the commercially available cream Dovonex®. The percentage of the API in the cream is as low as 0.005 wt %. Methodologies were developed for monitoring calcipotriol’s hydrate state in creams exhibiting pharmaceutical strength considerably lower than the detection ability of all commonly used techniques. The methods were based on X-Ray Powder Diffraction and micro-Raman spectroscopy. Transformation of calcipotriol anhydrate crystals to monohydrate was found to take place in the presence of cream’s excipients.
Open Access
Identification of drug polymorphs in tablets
(2012-05-04) Kontoyannis, Christos; Orkoula, Malvina; Karampas, Ioannis; Zissi, Georgia; Skorda, Dimitra; Serpi, E; Κοντογιάννης, Χρήστος; Όρκουλα, Μαλβίνα; Καραμπάς, Ιωάννης; Ζήση, Γεωργία; Σκορδά, Δήμητρα; Σέρπη, Ελευθερία
Τμήμα Φαρμακευτικής (Δημοσ. Π.Π. σε συνέδρια)
Polymorphs of an Active Pharmaceutical Ingredient (API) can have different chemical and physical properties and, thus, a direct impact on the process-ability of the drug substance and the quality/performance of the drug product, such as stability, dissolution, and bioavailability. Therefore, identification of the crystal phase of an API is of outmost importance. In this work methodologies were developed based on X-ray powder diffraction and IR for the identification of the crystal phase of two APIs (Atorvastatin Calcium and Donepezil HCl) in commercial tablets.
Open Access
Industrial drying of wooden pallets - CFD analysis of air flow
(2013-07-30) Ghiaus, Adrian; Filios, Andronikos; Margaris, Dionissios; Tzempelikos, Dimitrios; Φιλιός, Ανδρόνικος; Μάργαρης, Διονύσιος; Τζεμπελίκος, Δημήτριος
Τμήμα Μηχανολόγων και Αεροναυπηγών Μηχαν. (Δημοσ. Π.Π. σε συνέδρια)
This paper presents the results of the airflow 2D numerical simulation inside an industrial unit designed for drying of wooden pallets. The airflow field profile was examined in different operation conditions by plotting velocity vector distribution, path lines and pressure contours for both loaded with the wooden pallets and unloaded drying room. The analysis of the obtained results shows the presence of stagnation zones between and above the pallet columns and recirculation regions in different zones of the drying room. Further work will focus on validation of the predicted CFD results by means of local measurements that will be taken on a full scale dryer.
Open Access
Innovative Retrofitting of RC Structures using Textile- Reinforced Alkali-activated or Cement-based Mortar Overlays: Application in Short Columns
(2023) Azdejkovic, Lazar; Triantafillou, Thanasis; Τριανταφύλλου, Θανάσης
Τμήμα Πολιτικών Μηχανικών (Δημοσ. Π.Π. σε συνέδρια)
The effectiveness of textile reinforced mortars (TRM) in the form of thin overlays applied on reinforced concrete (RC) members is shortly reviewed in the oral presentation of this work, with emphasis on recent findings by the authors, including the development of integrated TRM-thermal insulation systems for the combined seismic and energy retrofitting of existing structures. The possibility of replacing the standard ordinary Portland cement (OPC) matrix with an alternative environmentally friendly mortar based on alkali-activated materials (AAM) is also explored. As a case study, the paper covers the seismic retrofitting of short, shear-critical RC columns using OPC- or AAM-based TRM jackets. A total of seven columns were tested, at a scale of approximately 2/3, with the shear span – to – height ratio of 1.5. Four out of seven specimens were designed to be more ductile with closely spaced shear reinforcement, while the rest had their stirrups positioned at larger spacing. Both series of columns were retrofitted with two and four layers of TRM overlays, made of uncoated carbon textile and AAM or OPC-based mortar, and subjected to cyclic loading combined with a constant vertical load. While control (unretrofitted) specimens exhibited brittle failure, the retrofitted ones performed significantly better in terms of deformation capacity, with a clear shift of the failure mode towards shear-flexure. All experimental findings were verified using analytical modelling, in good agreement with test results. Another interesting result is that AAM-based TRM jacketing is not inferior by any means to its OPC-based counterpart.
Open Access
Interpolation in multispectral data using neural networks
(2011-12-08) Tsagaris, Vassilis; Panagiotopoulou, Antigoni; Anastassopoulos, Vassilis; Τσαγκάρης, Βασίλειος; Παναγιωτοπούλου, Αντιγόνη; Αναστασόπουλος, Βασίλειος
Τμήμα Φυσικής (Δημοσ. Π.Π. σε συνέδρια)
A novel procedure which aims in increasing the spatial resolution of multispectral data and simultaneously creates a high quality RGB fused representation is proposed in this paper. For this purpose, neural networks are employed and a successive training procedure is applied in order to incorporate in the network structure knowledge about recovering lost frequencies and thus giving fine resolution output color images. MERIS multispectral data are employed to demonstrate the performance of the proposed method.
Open Access
Ioannis Sykoutris, «L'Introduction du Mémoire à la Faculté des Lettres de l'Université d'Athènes»
Νιφτανίδου, Θ. Μ.; Niftanidou, Th. M.
Τμήμα Επιστημών της Εκπαίδευσης και Κοινωνικής Εργασίας (Δημοσ. Π.Π. σε συνέδρια)
L’objectif de l’étude est d’illuminer des aspects de la personnalité scientifique de Ioannis Sykoutris (1901-1937), en étudiant l’Introduction du Mémoire qu’il a soumis à la Faculté des Lettres de l’Université d’Athènes en 1933, dans le cadre de sa candidature au poste de Professeur de Lettres Classiques, une synthèse de contenu bio-bibliographique, qui offre au lecteur de son œuvre des éléments d’information précieux concernant les étapes majeures de sa formation et les lignes directrices de son apport intellectuel.
Open Access
Is menopause present in school? An analysis of Greek secondary education biology textbooks
(EMAS, ) Armeni, Anastasia; Ampatzidis, Georgios; Αρμένη, Αναστασία; Αμπατζίδης, Γεώργιος
Τμήμα Επιστημών της Εκπαίδευσης και της Αγωγής στην Προσχολική Ηλικία (Δημοσ. Π.Π. σε συνέδρια)
Menopause is a period of a woman's life that seems to be associated with negative stereotypes. Stereotypes, stigmas and misconceptions linked to menopause can affect women's psychology in several ways. Taking into account that textbooks largely determine the content of biology teaching, this article focuses on the presence of menopause in Greek biology textbooks for secondary education. The analysis of 6 textbooks shows that only in two of them there is information about (a) the nature of menopause and (b) its relation to the occurrence of osteoporosis.
Open Access
La transformación didáctica: de las materias académias a las prácticas escolares
Ravanis, Konstantinos; Ραβάνης, Κωνσταντίνος
Τμήμα Επιστημών της Εκπαίδευσης και της Αγωγής στην Προσχολική Ηλικία (Δημοσ. Π.Π. σε συνέδρια)
Εs necesario que formemos la actividad didáctica en ámbitos que no favorecen simplemente el ocuparse con el contenido dognitivo, sino también el desarrollo de la autonomía, la integración de bienes culturales, la formación de costumbres, actitudes y valores, esdecir, el aportea la creación de la identidad del ciudadano, quien tiene formación académica decierto nivel. Así se plantea el asunto del conocimiento escolar,de la «ciencia escolar» como se ha llamado, en relación al conocimiento por experiencia o al científico.