Showing papers by "Technological Educational Institute of Western Macedonia published in 2009"

Fabrication of super-hydrophobic surfaces for enhanced stone protection

Abstract: In the current study, we demonstrate that the modification of a commercial siloxane protective composition by the addition of silica nanoparticles substantially enhances its protective efficiency and renders the treated stone surface super-hydrophobic and self-cleaning. The extent of surface hydrophobization depends on nanoparticle concentration and reaches a maximum value of ~ 160° at 1% w/v of nanoparticles for the case of white Greek marbles (Naxos, Pentelic and Thassos) treated with the modified composition. The investigation of the surface morphology by scanning electron microscopy (SEM) reveals the presence of micron-sized protrusions (10–100 μm in diameter) formed by nanoparticle aggregates consolidated by the siloxane polymer. The diameter and surface density of the protrusions depend on nanoparticle concentration. The developed nanostructure of the protrusions was observed by atomic force microscopy (AFM). The nano-dimensions of the silica particles are essential for the superhydrophobization of the treated marble surfaces. In the case of micron-sized silica particles that were mixed with siloxane and were applied accordingly on similar white Greek marbles, the superhydrophobic effect was not achieved and the observed water contact angles were substantially lower. In the event that hydrophobicity is not the sole parameter of optimal stone and stone-monuments protection, other important parameters, such as water vapor permeability, water capillary absorption and stone color alterations, were also investigated and their dependence on nanoparticle concentration was established.

Superhydrophobic films for the protection of outdoor cultural heritage assets

Abstract: A very simple method that can be used to impart superhydrophobicity to stone surfaces of monuments using common and low-cost materials that are already employed or are easy to be found by conservators is presented. A siloxane-nanoparticle dispersion is sprayed on a stone, and this process can result in the formation of a rough two-length-scale hierarchical structure that exhibits water repellent properties, provided that the nanoparticle concentration in the dispersion is higher than a critical value. Superhydrophobicity (static contact angle >150° and contact angle hysteresis <7°) is achieved, by this simple method (i) on the surfaces of three types of stones, Opuka, Božanovský and Hořický, which have been used for the restoration of the castle of Prague, (ii) using two poly (alkyl siloxane) products such as Rhodorsil 224 and Porosil VV plus, which are utilized by conservators and (iii) using common nanoparticles such as silica (SiO2), alumina (Al2O3), tin oxide (SnO2) and titanium oxide (TiO2). It is shown that the stone substrate and the nanoparticle size (5–50 nm) or type have almost no effect on the wettability of the superhydrophobic surfaces, as comparable contact angles were measured on the three stone substrates, treated with any siloxane-particle composite. Treatments of the stones with pure (hydrophobic) siloxanes and siloxane-SiO2 (superhydrophobic) composites result in comparable reductions of the water vapor permeability and the water amounts absorbed by capillarity. Consequently, the use of nanoparticles in the protective coatings does not have any obvious effect on the results of the aforementioned tests. However, the aesthetic appearance of the three stones, included in this study, is highly affected by the nanoparticles.

A methodological framework for end-of-life management of electronic products

Abstract: A growing number of regulatory interventions such as the European Union's Extended Polluter Responsibility Policy hold manufacturers accountable for the damage inflicted to the natural environment by their products However, not all components of an industrial product have an equitable role regarding their overall burden to the environment In this context, it is of great interest to manufacturers to identify and rank those components with the highest potential value at the end of their useful life, employing an array of economical and environmental criteria In order to assist manufacturers on their decision-making for the optimal end-of-life alternatives for their products, the “Multicriteria Matrix” methodology has been developed The methodology relies on multicriteria analysis and takes into consideration the residual value, environmental burden, weight, quantity and ease of disassembly of each component With the developed methodology only those components that do not have any residual value end up in landfills, while the majority of the components are either reused or recycled The application of the developed methodology is demonstrated employing a real-world case study; that of an ISDN network terminal Finally, the paper is concluded by presenting interesting managerial insights that were obtained

Water quality trends in Polyphytos reservoir, Aliakmon River, Greece

Abstract: A water quality monitoring program was undertaken from June 2004 to May 2005, on a monthly basis, in Polyphytos Reservoir of Aliakmon River. Depth, water temperature, dissolved oxygen, conductivity, pH and transparency (Secchi disk) were measured in situ, while collected water samples were analyzed in the laboratory for the determination of BOD, COD, total phosphorus (TP), ortho-phosphate (OP), chlorophyll-a (Chl-a), ammonium, nitrite and nitrate, total Κjeldahl nitrogen (TKN) and heavy metals (Fe, Mn, Cu, Cr, Pb, Ni and Cd). Measured concentrations were compared to those from two previous studies conducted in July 1987 to June 1988 and January 1991 to February 1993. The following conclusions are drawn: the effect of the watershed on the lake environment, mostly through Aliakmon River, is significant, and it accelerates the eutrophication of the lake. The anoxic zones, which were defined in the lake, reinforce this conclusion. Nitrate, nitrite and ammonia were measured at lower concentrations compared to previous studies, while total phosphorus and chlorophyll-a were found at increased concentrations. The current trophic state of Polyphytos reservoir is eutrophic, based on the OECD method and Carlson’s Trophic State Indices (TSI). The concentration of BOD and COD ranged at low levels. Furthermore, the mean concentrations of metals Fe, Mn, Cu, Cr, Pb, and Cd were below the potable water standards set by WHO and EU. During most part of the study period the ratio N/P for Polyphytos reservoir was higher than 7.2:1, and therefore, phosphorus is the limiting nutrient for algal growth.

Morphological, Thermal, and Mechanical Characteristics of Polymer/Layered Silicate Nanocomposites: The Role of Filler Modification Level

Abstract: Composite materials consisting of poly(L-lactic acid) and montmorillonite modified to a different extent, using various contents of hexadecylammonium cation, were prepared by the solution intercalation method. Investigation of the composites' morphology revealed that a surfactant quantity higher than the mineral's cation exchange capacity (CEC) was necessary for the organomodified clay to be dispersed at nanoscale level into the polymer matrix. The surfactant content in organoclay was found to play a major role in controlling the composite's mechanical properties. Thus, although increase of the alkylammonium concentration initially enhanced these properties, even higher concentrations corresponding to higher modification levels had a negative impact to them causing their dramatic deterioration. Observation of the deformed surfaces showed that the deformation process mechanism of the material is directly related to the degree of clay modification. Thermal degradation studies revealed that the intermediate surfactant excess reinforces the thermal stability of the nanocomposite by increasing the onset decomposition temperature. Additionally, the alkylammonium concentration was found to affect the crystallization temperature and the glass transition temperature of the polymer. In conclusion, an ideal balance between thermal and mechanical properties can be obtained at surfactant quantity equivalent to 1.5 times the clay CEC. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers

Surface Properties of Superhydrophobic Coatings for Stone Protection

Abstract: Superhydrophobic films are produced by a simple and low cost method. Silica (SiO2) nanoparticles are dispersed in solutions of Rhodorsil 224, a commercial poly(alkyl siloxane) which is used for the protection of outdoor cultural heritage objects, and the suspensions are sprayed on glass surfaces. It is shown that the siloxane-nanoparticle composite films prepared from dispersions of high particle concentrations (≥ 0.5% w/v) exhibit superydrophobic properties (high static contact angle and small hysteresis) which can be rationalized by the Cassie-Baxter model, according to quantitative measurements obtained by SEM images. Siloxane-nanoparticle films are then deposited (sprayed) on “Opuka”, a fine-grained argillite which was used for the restoration of the castle of Prague. It is shown that the treated stone surfaces exhibit superydrophobic properties, similar to the treated glass surfaces. The efficacy of the superhydrophobic films to protect Opuka is evaluated by performing water contact angle, water capillary absorption, water vapor permeability and colorimetric measurements. It is shown that the use of nanoparticles in the protective coating has a positive effect on the results of the aforementioned tests, except for the colorimetric measurements.

Ownership Structure in Greece: Determinants and Implications on Corporate Governance

Abstract: The paper analyzes ownership structure in Greece. Greece has the same characteristics as Spain, Italy, Portugal, and other countries that are ranked in the Continental Europe corporate governance system. Two measures of ownership concentration are used. The first is the sum of equity holdings of the five biggest shareholders, while the second is square of the first (Herfindahl Index). Determination of the factors that affect ownership structure is done using Panel Data Regression models. Stratifying variables, like law (before and after the enactment of the corporate governance law), sector (finan 144 cial or not), and index ranking were used. Two main hypotheses were tested: a) ownership structure is affected by quality of corporate governance and its mechanisms, financial performance, board of directors‘ structure and composition and finally firm‘s size, b) the factors that affect ownership concentration in a country like Greece are the same with the ones that literature specifies for the Anglo-Saxon countries. Overall, ownership concentration in Greece has different characteristics than the ownership structure in the Anglo-Saxon countries and creates a very different internal and external environment. Ownership structure is affected by the historical development of the firm, its organizational scheme and even more by the balance of power and control within the firm. Corporate governance quality and mechanisms as well as external factors, like the law, index ranking, and existence of an external market for corporate control do not seem to have any significant effect on ownership structure.

Long-term optimization case studies for combined heat and power system

Abstract: In the next years distributed poly-generation systems are expected to play an increasingly important role in the electricity infrastructure and market. The successful spread of small-scale generation either connected to the distribution network or on the customer side of the meter depends on diverse issues, such as the possibilities of technical implementation, resource availability, environmental aspects, and regulation and market conditions. The aim of this approach is to develop an economic and parametric analysis of a distributed generation system based on gas turbines able to satisfy the energy demand of a typical hotel complex. Here, the economic performance of six cases combining different designs and regimes of operation is shown. The software Turbomatch, the gas turbine performance code of Cranfield University, was used to simulate the off-design performance of the engines in different ambient and load conditions. A clear distinction between cases running at full load and following the load could be observed in the results. Full load regime can give a shorter return on the investment then following the load. In spite combined heat and power systems being currently not economically attractive, this scenario may change in future due to environmental regulations and unavailability of low price fuel for large centralized power stations. Combined heat and power has a significant potential although it requires favorable legislative and fair energy market conditions to successfully increase its share in the power generation market.

Assessing productivity change with SFA in the sheep sector of Greece

Abstract: The objective of this paper is to measure total factor productivity growth in a panel of sheep farms in Greece and assess the relative contribution of technical change, technical efficiency change and scale efficiency change in observed productivity growth. Such decomposition can be useful in planning well defined policies which can support the sector’s sustainable development via the optimization of input/output use. A stochastic frontier production function approach is adopted and maximum likelihood is used to estimate the parameters. The data used for the econometric estimation are obtained from the Greek Farm Accounting Data Network for the period 1997–2002. TFP has been growing in the sector but at a diminishing rate. The major determinant of productivity growth is technical change, which has been shifting the frontier by 2.4% on average during this period, but is counteracted to some extent by technical and scale inefficiency each reducing TFP growth by about 0.3% p.a.

The Banking Network as a Transmission Channel of Migrant Remittances: The Case of Greek and Italian Banks in Albania

Abstract: The paper examines the role of the banking network of foreign banks, namely Greek and Italian banks, on the transfer of remittances of Albanian immigrants. Remittances through the official network that is formed mainly by the banking network, grew much higher in comparison to non-official network during the period 1994–2006. The paper finds that the growth of the amount of remittances conveyed through the official network as part of the total amount of remittances is related to the evolution of branches of Greek and Italian banks in Albania.

Fabrication of ceramic electrolytic films by the method of solution aerosol thermolysis (SAT) for solid oxide fuel cells (SOFC)

Abstract: The technique of solution aerosol thermolysis (SAT) for the production of ceramic electrolytic films suitable for solid oxide fuels cells was investigated. The research has focused on the optimization of process parameters and characterization of the obtained films by means of X-ray diffractometry and scanning electron microscopy/energy-dispersive spectroscopy. Dense films of gadolinia-stabilized ceria of uniform thickness have been successfully produced on substrates consisting of dense disks of yttria-stabilized zirconia by SAT using nitrate salts of the precursors dissolved in an ethanol–water solvent. Substrate temperature is an important parameter and in this system the best initial values identified were of the order of 400–420 °C. The interplay between initial substrate temperature, solution flow rate, and postdeposition temperature is important for a good-quality film.

Macroeconomic Effects on D.J.S.I. - World Returns

Abstract: One of the best known and highly regarded Socially Responsible Investing (SRI) indexes is the Dow Jones Sustainability Index World (D.J.S.I.-World). By using the model of Generalized Autoregressive Conditional Heteroskedasticity (GARCH), the relation between D.J.S.I.-World returns to 10 year bond returns and Yen/U.S. dollar exchange rate is investigated. Research results show that 10 year bond value affects positively the value of D.J.S.I.-World. However, there is a negative relation between Yen/U.S. dollar exchange rate and D.J.S.I.-World with a month delay. According to our results, the total return of D.J.S.I.-World is affected by such macroeconomic factors as the value of 10 year bond, the Yen/U.S. dollar exchange rate and the general economic environment. In this way, investors can understand better the function of SRI market. Additionally, a new channel of information is created and better evaluation of D.J.S.I.-World is enabled.

Trust management framework for intelligent agent negotiations in ubiquitous computing environments

Abstract: In dynamic ubiquitous computing environments, system entities may be classified into two main categories that are, in principle, in conflict. These are the Service Resource Requestors (SRRs) wishing to use services and/or exploit resources offered by the other system entities and the Service Resource Providers (SRPs) that offer the services/resources requested. Seeking for the maximisation of their welfare, while achieving their own goals and aims, entities may misbehave (intentionally or unintentionally), thus, leading to a significant deterioration of system's performance. In this study, a reputation mechanism is proposed which helps estimating SRPs trustworthiness and predicting their future behaviour, taking into account their past performance in consistently satisfying SRRs' expectations. Thereafter, under the assumption that a number of SRPs may handle the SRRs requests, the SRRs may decide on the most appropriate SRP for the service/resource requested on the basis of a weighted combination of the evaluation of the quality of their offer (performance related factor) and of their reputation rating (reliability related factor). The proposed trust management framework is distributed, considers both first-hand information (acquired from the SRR's direct past experiences with the SRPs) and second-hand information (disseminated from other SRRs' past experiences with the SRPs), while it exhibits a robust behaviour against inaccurate reputation ratings. The designed mechanisms have been empirically evaluated simulating interactions among self-interested agents, exhibiting improved performance with respect to random SRP selection.

Corporate Governance and Debt to Equity Ratio

Abstract: Capital structure, especially in the cases of the countries that belong in the Continental Europe system of Corporate Governance has a significant impact on the way that the firm is structured, organizationally, strategically and functionally. The decision to use the capital market or debt in order to obtain the necessary capital to finance firms’ operations is a critical factor for the formulation of corporate environment, because it contributes to the ownership concentration or diffusion and to corporate risk exposure level. Debt aggravation is measured by the ratio “Debt to Equity”. Panel data methodology is used. The hypothesis that are tested: a) is debt aggravation affected by the quality of corporate governance, the structure and composition of the Board of Directors, firm’s size, and other factors, b) are the factors that affect debt aggravation in Greece the same with the ones that are delineate in the literature for the Anglo-Saxon countries. Debt aggravation is statistically affected by performance, organizational structure and firm size. These findings are compatible with the literature. The innovative finding is that variables like Corporate Governance Index (CG), Mergers and Acquisitions (Merger), Major shareholder is the CEO (OWNCEO) and den dismissal or resignation of, executive, non executive (BDIS_P) and independent members of the Board of Directors are not statistical important. Corporate Governance does not seem to have any statistical important impact on capital structure and this conclusion is the opposite of the relevant studies of Shleifer and Vishny (1997) and Vilanova (2007). Greek firms seem to favor debt as a mean of finance, instead of capital-share issues.

Characterisation and treatment of leachates from the municipal sanitary landfill of Thessaloniki, Greece

Abstract: The optimum treatment technologies of leachates produced from a municipal landfill were studied in this work Leachates composition ranged from high-strength acidic down to low-strength stabilised leachates, affecting the applicable treatment process Efficient treatment of fresh leachates was achieved by biological methods, such as the SBR, or the moving bed processes, resulting in increased removal of organic and nitrogen content However, biological methods were not effective for the treatment of stabilised leachates, containing non-biodegradable compound; physical-chemical methods were proved to be more efficient The combination of coagulation/flocculation followed by ozonation was an efficient technique, with low effluent COD values, <180 mg/L

Single and Two Shaft Gas Turbine Configurations Performance Analysis, Using Different Types of Fuels

Abstract: Coal gas and biofuels as alternative fuels have recently become more attractive, because of their benefits, especially in electrical power industry. The major obstruction to their use is the relatively low calorific values. This paper presents a comprehensive simulation method for calculating the adiabatic temperature of various fuels when they are used in combustion chambers under constant pressure. The adiabatic temperature is presented as a function of combustion fuel air ratios and the fuels low calorific values. In addition, the utilization of various gaseous fuels in single shaft and two shaft gas turbine engines is analyzed. This analysis includes the design point (DP) and off-design (OD) performance of the two engines. The calorific values of the four gases investigated correspond to natural gas (NG) and to fuels with significantly lower calorific values than that of NG (coal synthetic gases, biofuels). Two main conclusions are drawn from this analysis. Firstly, for both single shaft and two shaft engines and for a given turbine entry temperature (TET), both power and thermal efficiency are increasing when fuels with decreasing calorific value are burnt. Secondly, for both single shaft and two shaft engines and for a given power, the thermal efficiency is slightly reduced.Copyright © 2009 by ASME

Clusters of Power and Control

Abstract: The corporation environment is a battlefield Key players are competing to gain power and control The paper aims to analyze the power and control function within the firm To do that three basic clusters of people (CEO/Management, Board of Directors, General Shareholders’ Meeting) are recognized and analyzed The analysis takes place using five categories (goal/scope/interest, Strategy, Allies, Foes, Tools, Instruments, Weapons and Preferable Environment) The authors take into account the legal and regulatory framework (corporate law, corporate governance law and codes), the codes of ethics, good practices, principles of corporate governance (OECD, 2004) the market’s needs because they are basic drivers and regulators of how the delegation of power and control takes place and how balance is established The paper shows that power and control is concentrated, legally, at the top of the organizational pyramid, but in reality the only cluster that has the ability (well formulated strategy, tools and allies) to enforce its will on others is the CEO/Management Cluster