Showing papers by "Technological Educational Institute of Western Macedonia published in 2007"

Polymer-Silica nanoparticles composite films as protective coatings for stone-based monuments

Abstract: The decrease of surface energy of mineral substrates similar to those used in many stone monuments of cultural heritage by the application of protective polymer coatings along with the simultaneous increase of their surface roughness can increase their ability to repel water substantially. In this work, the effect of artificially induced roughness on the water repellency of mineral substrates coated with protective polymer films was investigated. Natural marble samples or home made calcium carbonate blocks were tried as the mineral substrates. The roughness increase was achieved by mineral chemical etching or by creation of nanoscale binary composition film on the substrate surface. PMMA and PFPE were the polymers used, while different-sized silica nanoparticles were employed for the production of the nanocomposite films. Examination of the coated and uncoated surfaces with profilometry and AFM and measurements of water contact angles reveal a pronounced effect of the surface roughness on water repellency. Especially in the case of nanocomposite coatings, the surfaces become super-hydrophobic. This result indicates that the nanoscale binary composition film scheme, which is characterized by its simplicity and low cost, is a suitable candidate for the water protection of stone-based monuments on large scale.

Thermal and colloidal behavior of amine-treated clays: The role of amphiphilic organic cation concentration

Abstract: The modification of sodium montmorillonite (NaMMT) through the insertion of amphiphilic hexadecylammonium cations into the clay's interlayer spaces has been studied. Alkylammonium concentrations equivalent to 0.15-3.00 times the cation exchange capacity of the clay were used. The conformation of the surfactant cations in the confined space of the silicate galleries was investigated by X-ray diffraction analysis and scanning electron microscopy, while the organoclay's thermal stability was examined by thermogravimetric analysis. The clay's surface properties induced by the ion-exchange process were followed by measurements of the mineral's zeta potential as a function of pH and surfactant concentration, while the coagulation rates of organoclay suspensions in water and in chloroform were examined using dynamic light scattering. All the results are consistent with showing that the overall characteristics and thus the behavior of the modified MMT particles strongly depend on the alkylammonium surfactant concentration used in the modification process. This, however, has very important implications for any attempt to incorporate the organomodified MMT particles into different media for various applications such as polymer nanocomposite preparation.

Total factor productivity and sustainable agricultural development

Abstract: Total factor productivity (TFP) growth is a widespread quantitative economic instrument used to evaluate the performance and sustainability of agricultural systems over time, which has proven valuable for policy measures geared towards fostering agricultural development. Yet, there are more dimensions to be accounted for when aiming for sustainable agricultural development than the production side of an agricultural system namely, the issues of environmental protection and resource use together with the question of social responsibility. Consequently, objections have risen in the recent decades, regarding the suitability of TFP growth to reveal whether a rural system is progressing in a sustainable course and alternative tools that attempt to remove the bias in measuring changes in productivity have been proposed. The objective of this paper is twofold; to review the conventional approaches in the measurement of TFP growth and to discuss the necessary amendments in TFP measurement so that it can be a more comprehensive index of sustainable growth and thus conducive to agricultural development. The amendments which incorporate externalities and resource quality issues in productivity measurement, produce alternative measures to TFP namely, ‘total resource productivity’ and ‘social’ total factor productivity. Another approach is to construct sustainability and productivity indices separately, and then join them together so as to broaden the evaluation of agricultural systems.

Characterisation of Mycenaean and matt-painted pottery from Alani, ancient upper Macedonia, Greece

Abstract: Διάφορeς αναλυτικές μέθοδοι eφαρμόστηκαν για τη μeλέτη αρχαίων κeραμικών από την Αιανή, αρχαία Ανω Μακeδονία. Όστρακα μυκηναϊκής και αμαυρόχρωμης κeραμικής ηλικίας Ύστeρης Eποχής Χαλκού συλλέχθηκαν και αναλύθηκαν μe τη βοήθeια της πeριθλασ ι μeτρίας ακτινών Χ (XRD), της φασματοσκοπίας φθορισμού ακτινών Χ (XRF) και του «πeριβαλλοντικού» ηλeκτρονικού μικροσκοπίου σάρωσης (ESEM). Τα μορφολογικά χαρακτηριστικά, η χημική και η ορυκτολογική σύσταση των αναλυθέντων οστράκων υποδηλώνουν την κατασκeυή των κeραμικών αυτών σe τοπικά eργαστήρια της αρχαίας Αιανής, eνώ υποστηρίζουν και την υπόθeση των αρχαιολόγων για την συνύπαρξη μυκηναϊκών και δωρικών eργαστηρίων κeραμικής στην πeριοχή αυτή, κατά τη διάρκeια της Ύστeρης Eποχής Χαλκού

Surfactant-induced morphology and thermal behavior of polymer layered silicate nanocomposites

Abstract: Poly(L-lactic acid) nanocomposites were prepared by the addition of montmorillonite modified with various loadings of hexadecylammonium cation. The influence of alkylammonium on the morphology and surface charge of the clay was investigated by Xray diffraction (XRD) analysis and electrokinetic measurements, respectively. The structural characteristics of the inorganic-organic hybrids were studied by XRD, transmission electron microscopy (TEM) and atomic force microscopy (AFM). Thermal analysis was carried out by thermogravimetric analysis (TGA) under constant nitrogen flow and under air. The results showed that high concentration of surfactant present in the clay greatly increases clay's dispersibility into the matrix and this substantially improves the thermal stability of the pristine polymer.

Service Decomposition and Task Allocation in Distributed Computing Environments

Abstract: Highly competitive and open environments should encompass mechanisms that will assist service providers in accounting for their interests, i.e., offering at a given period of time adequate quality services in a cost efficient manner. Assuming that a user wishes to access a specific service composed of a distinct set of service tasks, which can be served by various candidate service nodes, a problem that should be addressed is the allocation of service tasks to the most appropriate service nodes. This scenario accounts for both the user and the service provider. Specifically, service providers succeed in efficiently managing their resources, while users implicitly exploit in a seamless way the otherwise unutilized power and capabilities of the provider’s network. In general, service task allocation is founded on general and service specific user preferences, service provider’s specific service logic deployment and current system & network load conditions. The pertinent problem is concisely defined, mathematically formulated, optimally solved and evaluated through simulation experiments.