Systematic Methodology for Exploration of Performance – Energy Trade-offs in Network Applications Using Dynamic Data Type Refinement

Modern network applications require high performance and consume a lot of energy. Their inherent dynamic nature makes the dynamic memory subsystem a critical contributing factor to the overall energy consumption and to the execution time performance. This paper presents a novel, systematic methodology for generating performance-energy trade-offs by implementing optimal Dynamic Data Types, finely tuned and refined for network applications. Our systematic methodology is supported by a new, fully automated tool. We assess the effectiveness of the proposed approach in four representative, real-life case studies and provide significant energy savings and performance improvements compared to the original implementations

Dynamic Data Type Refinement Methodology for Systematic Performance-Energy Design Exploration of Network Applications

Network applications are becoming increasingly popular in the embedded systems domain requiring high performance, which leads to high energy consumption. In networks is observed that due to their inherent dynamic nature the dynamic memory subsystem is a main contributor to the overall energy consumption and performance. This paper presents a new systematic methodology, generating performance-energy trade-offs by implementing Dynamic Data Types (DDTs), targeting network applications. The proposed methodology consists of: (i) the application-level DDT exploration, (ii) the network-level DDT exploration and (iii) the Pareto-level DDT exploration. The methodology, supported by an automated tool, offers the designer a set of optimal dynamic data type design solutions. The effectiveness of the proposed methodology is tested on four representative real-life case studies. By applying the second step, it is proved that energy savings up to 80% and performance improvement up to 22% (compared to the original implementations of the benchmarks) can be achieved. Additional energy and performance gains can be achieved and a wide range of possible trade-offs among our Pareto-optimal design choices are obtained, by applying the third step. We achieved up to 93% reduction in energy consumption and up to 48% increase in performance

Design of Energy Efficient Wireless Networks Using Dynamic Data Type Refinement Methodology

This paper presents a new perspective to the design of wireless networks using the proposed dynamic data type refinement methodology. In the forthcoming years, new portable devices will execute wireless network applications with extensive computational demands (2 – 30 GOPS) with low energy consumption demands (0.3 – 2 Watts). Nowadays, in such dynamic applications the dynamic memory subsystem is one of the main sources of energy consumption and it can heavily affect the performance of the whole system, if it is not properly managed. The main objective is to arrive at energy efficient realizations of the dominant dynamic data types of this dynamic memory subsystem. The simulation results in real case studies show that our methodology reduces energy consumption 50% on average

Environmental Risk Assessment in Agriculture: The Example of Pistacia vera L. Cultivation in Greece

In this study, an integrated environmental risk assessment (ERA) study involving frequent monitoring of both water and soil parameters (24 on total), was carried out to assess and compare the environmental risk quality of three pistachio (Pistacia vera L.) fields (two in Aegina island and one in Kilkis) based upon risk categories identified and assessed in terms of quality and quantity. In this context, vertical profiles and risk matrices were created for a 60-month period for the most important soil and water parameters i.e., soil pH, soil organic matter, soil salinity, heavy metals, and irrigation water quality. According to the obtained results, the two pistachio fields in Aegina exhibited reduced overall risk values, i.e., 17% and 27%, respectively after the adoption of sustainable cultivation practices, thus reflecting a transition from “medium to high risk” to “low to medium risk” environmental quality. On the other hand, overall risk values for the pistachio field in Kilkis were reduced by 34% and were lower compared to the ones obtained for the pistachio fields in Aegina. The better environmental profile identified for the entire period in Kilkis ranging from “medium risk” to “low risk” was the result of lower inherent risk associated with irrigation water quality and soil salinity. The proposed methodology can be easily applied in other agricultural areas and for similar cultivations in Greece and other Mediterranean countries

Clean up of leachates generated from mining solid wastes using red mud and fly ash permeable reactive barriers

Inadequate disposal of wastes produced from mining, processing and metallurgical activities causes often severe contamination of soils, surface streams and groundwater, due to oxidation of the residual sulphide phases and the subsequent generation of leachates characterized by high acidity and elevated concentration of hazardous heavy metal ions and sulphates. A relatively low cost alternative to pump and treat approach aiming at prevention of contamination or clean up of contaminated groundwater involves the construction, application and monitoring of in-situ permeable reactive barriers (PRBs). Despite the increasing interest in this research field, the cost of such in-situ systems remains considerable when pure reactive media (e.g activated carbon) are used. The objective of this study is to evaluate “low-cost” media suitable for PRBs and therefore improve the economics of the process. The examined reactive media included wastes or by-products from other mining, metallurgical or chemical processes such as fly ash, red mud and zero-valent iron filings. The experimental investigation involved two main sets of long-term continuous-upflow laboratory column tests: i) single-metal independent tests of Cu2+ aqueous solutions in to elucidate the individual kinetic processes and the effect of initial metal concentration, pH and pore water velocity, and ii) multi-metal component tests of synthetic AMD leachates in order to assess the performance and long term reactivity of the examined PRBs. In addition, tracer tests were carried out to identify transport related issues. Factors such as the hydraulic conductivity of each reactive material and the residence time required for efficient operation over long periods, the quality of the leachates, the loss of reactivity and porosity over time and the main removal mechanisms were also taken into account and discussed. Geochemical modeling of the removal processes, including interactions between reactive materials, heavy metal ions and sulphates, interpretation of the ionic profiles and calculation of porosity loss was also carried out by using the speciation/mass transfer computer code PHREEQC-2 and the WATEQ4F database. The interpretation of the copper breakthrough curves (BTCs) in the first set of column experiments indicates that the removal process was dependent on several operational parameters; higher flow rates, initial pH values and copper concentrations improved PRB performance. The observed copper BTCs in the fly ash and red mud columns are adequately described by the application of the Thomas kinetic model, while kinetic analysis of the zero-valent iron columns suggested that copper removal followed a pseudo first-order reaction.Η ανεξέλεγκτη διάθεση στερεών και υγρών αποβλήτων από μεταλλευτικές και μεταλλουργικές δραστηριότητες συχνά προκαλεί εκτεταμένη ρύπανση εδαφών, επιφανειακών και υπόγειων νερών. Η ρύπανση των υπόγειων νερών προκαλείται από τα εκχυλίσματα που παράγονται λόγω της οξείδωσης των υπολειπόμενων θειούχων φάσεων παρουσία νερού, οξυγόνου και βακτηρίων. Τα εκχυλίσματα αυτά χαρακτηρίζονται σε πολλές περιπτώσεις από χαμηλό pH και υψηλή συγκέντρωση ιόντων βαρέων μετάλλων και θειϊκών. Μια σύγχρονη, υποσχόμενη και σχετικά χαμηλού κόστους εναλλακτική τεχνολογία ως προς την άντληση και επιφανειακή επεξεργασία των υπογείων υδάτων με χρήση χημικών αντιδραστηρίων, περιλαμβάνει την κατασκευή, εγκατάσταση και λειτουργία ενεργών διαπερατών φραγμάτων. Τα τελευταία χρόνια παρά το αυξανόμενο ερευνητικό ενδιαφέρον στην εξέλιξη των ενεργών διαπερατών φραγμάτων, το κόστος ενός τέτοιου επί-τόπου συστήματος παραμένει σημαντικό όταν χρησιμοποιούνται υψηλής καθαρότητας ενεργά υλικά όπως π.χ ο ενεργός άνθρακας. Αντικείμενο της παρούσας διατριβής είναι η διερεύνηση της δυνατότητας χρησιμοποίησης «φθηνών» πληρωτικών υλικών κατάλληλων προς εφαρμογή στα Ενεργά Διαπερατά Φράγματα ώστε να μειωθεί το συνολικό κόστος της μεθόδου επεξεργασίας. Τα πληρωτικά υλικά που μελετήθηκαν περιλαμβάνουν απόβλητα ή παραπροϊόντα άλλων μεταλλευτικών, μεταλλουργικών και χημικών διεργασιών όπως η ιπτάμενη τέφρα, η ερυθρά ιλύς και τα ρινίσματα μεταλλικού σιδήρου. Η πειραματική διαδικασία που ακολουθήθηκε περιελάμβανε δύο κύριες σειρές εργαστηριακών πειραμάτων συνεχούς-ανοδικής ροής σε στήλες: α) μονο-μεταλλικά πειράματα υδατικών διαλυμάτων δισθενούς χαλκού με σκοπό να κατανοηθούν οι κινητικές διεργασίες, η επίδραση της συγκέντρωσης του μετάλλου, το pH και η ταχύτητα ροής, και β) πολυ-μεταλλικά πειράματα συνθετικών διαλυμάτων όξινης απορροής με σκοπό να προσδιοριστεί η απόδοση και η μακροχρόνια αντιδραστικότητα των ΕΔΦ. Επιπλέον, πραγματοποιήθηκαν πειράματα ιχνηθέτησης για να προσδιοριστούν φαινόμενα σχετικά με την υδραυλική μεταφορά των συστημάτων αυτών. Παράγοντες όπως είναι η υδραυλική αγωγιμότητα κάθε πληρωτικού υλικού και ο απαιτούμενος χρόνος παραμονής για μακροχρόνια αποδοτική λειτουργία, η ποιότητα των εκχυλισμάτων, η μείωση της ενεργής δράσης και του πορώδους με την πάροδο του χρόνου καθώς και οι κύριοι μηχανισμοί απορρύπανσης εξετάσθηκαν λεπτομερώς. Γεωχημική μοντελοποίηση των διεργασιών, συμπεριλαμβανομένων των αντιδράσεων μεταξύ των ενεργών υλικών, του ιοντικού φορτίου των βαρέων μετάλλων και των θειϊκών όπως επίσης των ιοντικών μετώπων αντίδρασης και υπολογισμός της μείωσης του πορώδους πραγματοποιήθηκε με χρήση του υπολογιστικού κώδικα προσδιορισμού χημικών μορφών/μεταφοράς μάζας PHREEQC-2 και της βάσης δεδομένων WATEQ4F. Η επεξεργασία των καμπυλών εξόδου της συγκέντρωσης του χαλκού που προέκυψαν από την πρώτη σειρά των πειραμάτων έδειξε ότι η απορρυπαντική διεργασία επηρεάζεται από τους λειτουργικούς παράγοντες που μελετήθηκαν ενώ η απόδοση βελτιώνεται όταν χρησιμοποιούνται μεγαλύτερες ταχύτητες ροής, αρχικές τιμές pH και συγκέντρωσης χαλκού. Τα πειραματικά αποτελέσματα των καμπυλών εξόδου του χαλκού στις στήλες της ιπτάμενης τέφρας και της ερυθράς ιλύος περιγράφονται ικανοποιητικά από την εφαρμογή του κινητικού μοντέλου Thomas, ενώ από την κινητική μελέτη των στηλών του μεταλλικού σιδήρου προέκυψε ότι η απομάκρυνση του χαλκού ακολουθεί ψευδό πρώτης-τάξης αντίδραση

Editorial for Special Issue: Alkali Activated Materials: Advances, Innovations, Future Trends

Alkali activated materials (AAMs), also named geopolymers or inorganic polymers, are materials that are produced when alkaline solutions react with precursors containing aluminosilicate phases [...

Adsorption of Scandium and Neodymium on Biochar Derived after Low-Temperature Pyrolysis of Sawdust

The objective of this study was to investigate the adsorption of two rare earth elements (REEs), namely scandium (Sc) and neodymium (Nd), on biochar produced after low temperature pyrolysis (350 °C) of wood sawdust. The biochar was characterized with the use of several analytical techniques, namely X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and thermogravimetric (TG) analysis, while the pH at point of zero charge (pHPZC) was also determined. The experimental conditions were: absorbent concentration 1–10 g·L−1, REE concentration in solution 20 mg·L−1, contact time for equilibrium 24 h, temperature 25 °C and stirring speed 350 rpm. The efficiency of biochar was compared to that of a commercial activated carbon. Geochemical modelling was carried out to determine speciation of Nd and Sc species in aqueous solutions using PHREEQC-3 equipped with the llnl database. The experimental results indicated the potential of low temperature produced biochar, even though inferior to that of activated carbon, to adsorb efficiently both REEs. The equilibrium adsorption data were very well fitted into the Freundlich isotherm model, while kinetic data suggested that the removal of both REEs follows the pseudo-second order kinetic reaction. Finally, the most probable adsorption mechanisms are discussed

Grinding Behavior and Potential Beneficiation Options of Bauxite Ores

This laboratory study investigates selective grinding and beneficiation options for a Greek bauxite ore. First, a series of batch grinding tests were carried out in order to investigate the grinding behavior of the ore and the effect of the material filling volume (fc) on the distribution of aluminium- and iron-containing phases. Then, the ground ore was subjected to magnetic separation either as received or after reduction roasting in order to further explore potential beneficiation options. The results showed that grinding of the ore exhibits non-first order behavior, while the breakage rate varies with grinding time. Additionally, Al2O3 tends to concentrate in the coarser than 0.300 mm product fraction, while fc 10% and 2 min of grinding time are considered optimum conditions for good distribution of Al2O3 and Fe2O3. When different product fractions were subjected to magnetic separation, it was seen that the non-magnetic product obtained from the 0.300–1.18 mm fraction was more rich in Al2O3. In this fraction, the Al2O3 content increased from 58 wt% in the feed to 67.9 wt%, whereas the Fe2O3 content decreased from 22.4 wt% in the feed to 13.5 wt%. When the ore was subjected to a two-step treatment, involving reduction roasting followed by magnetic separation, the Fe2O3 grade decreased from 20.8 to 5.1 wt%, but in this case the recovery was very low

Quantification of Trace Elements in Surgical and KN95 Face Masks Widely Used During the SARS-COVID-19 Pandemic

During the current coronavirus disease (COVID-19) pandemic, face masks have been the single most important protective equipment against the threat of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). While masks are worn, both the nose and the mouth of the user come in contact with the mask material, and as the latter mediates the inhaled air and may interfere with the swallowed saliva, it is of paramount importance to assure that the mask is free of toxic substances. As there are currently no studies on the total amount of trace elements in masks, the present study fills the void and investigates 24 surgical and KN95 face masks. Specifically, mask samples were analyzed using Inductively Coupled Plasma Mass Spectrometry (ICP-MS) to determine the total concentrations of trace elements as well as to assess the possibility that any detected of the elements present could transfer into the human body, based on saliva leaching and breathing experiments. Accordingly, it is reported herein that although most masks analyzed in this study contain trace elements below their corresponding detection limits, a few masks did contain detectable levels of trace elements. In particular, the maximum values that were determined in certain analyzed samples were: Pb (13.33 μg g−1), Cu (410 μg g−1), Zn (56.80 μg g−1), and Sb (90.18 μg g−1). Finally, in the masks that Pb was present, it easily leached out (58% transfer during a 6-h exposure) during the saliva simulation experiments