Climate change: the views of forestry students in a Greek university

The trend to global warming is one of the most important problems of our time. This paper reports the findings of self‐management questionnaires, in regard to views held on the issue of climate change by the students of the Department of Forestry and Management of the Environment and Natural Resources of the Democritus University of Thrace.     

The 2007 forest fires in the prefecture of Ilia: the views of citizens with regard to the actions taken before,during and after the fires

In 2007, the prefecture of Ilia, Peloponnese, Greece, was struck by very serious fires which were not only the result of extreme weather but also of human omissions and mistakes. This paper examines the views of the citizens of Ilia with regard to the actions of the Fire Department, the municipal authorities, the Forest Service, the citizens and the state, before, during and after the fires.     

A New Analog Buffer Using Low-Temperature Polysilicon Thin-Film Transistors for Active-Matrix Displays

In this paper, a new source-follower-type analog buffer for active-matrix displays, designed by using low-temperature polysilicon thin-film transistors (TFTs), is proposed. The buffer, consisting of five n-type polysilicon TFTs, one bias voltage, and an additional control signal, exhibits high immunity to threshold voltage and mobility variations. The functionality of the proposed buffer was verified by HSPICE simulations. In order to obtain realistic simulations, the TFT model parameters used for the simulations were extracted from fabricated TFTs using the Silvaco tools (ATLAS). The proposed buffer has 7-bit output voltage with the dynamic output voltage range of 7.5 V ranging from 2.5 to 10 V and with resolution up to 0.03 V     

Examining the location factors of R&D labor in the regions of Greece

In this paper two models are developed in an attempt to elucidate the factors that influence the regional distribution of R&D labor across the regions of Greece. The first one is based on an adaptation of the [Guerrero and Seró (1997) Regional Studies 31:381–390] model to the Greek context treating the regional distribution of R&D labor as a function of the extent of agglomeration and the prevailing economic conditions. The second model extends the first one by taking into account two additional factors, viz. the production structure and infrastructure. The econometric results indicate the superior performance of the extended model in the context of Greece as well as attribute the location of R&D labor mainly on the diversification of industrial activity and the number of establishments in innovation-intensive sectors. It is therefore suggested that the stimulation of the regional production structure and infrastructure is essential for ‘knowledge-lagging’ regions.

Enhanced reliable reactive routing (ER3) protocol for multimedia applications in 3D wireless sensor networks

Sensor networks designed especially for the multimedia applications require high data rate and better Quality of Service (QoS). Offering a reliable and energy efficient routing technique in a harsh and complex three-dimensional (3-D) environment for multimedia applications is a challenging job. Geo-routing and geometric routing have been efficient routing schemes for two-dimensional (2-D), but are unable to work properly for 3-D sensor networks. In order to enhance the resilience to link the dynamics in the 3-D sensor network, in this research an Enhanced Reliable Reactive Routing (ER3) is proposed. ER3 is an advancement to the existing reactive routing schemes, to provide energy efficient and reliable routing of data packets in the complex 3-D sensor networks for multimedia applications. The major attraction of ER3 is its backoff scheme, which occurs in the route discovery phase. In backoff scheme robust pilot paths formed between the source and destination are calculated to enable cooperative forwarding of the data packets. The data packets in ER3 are forwarded greedily to the destination from the source and doesn’t require any prior location information of the nodes. The encompassing simulations suggest that the ER3 outperforms the existing routing protocols on the basis of energy efficiency, low latency and high packet delivery ratio.

     

Multi-criteria evaluation of hydrogen and natural gas fuelled power plant technologies

This paper evaluates nine types of electrical energy generation options with regard to seven criteria. The options use natural gas or hydrogen as a fuel. The Analytic Hierarchy Process was used to perform the evaluation, which allows decision-making when single or multiple criteria are considered.The options that were evaluated are the hydrogen combustion turbine, the hydrogen internal combustion engine, the hydrogen fuelled phosphoric acid fuel cell, the hydrogen fuelled solid oxide fuel cell, the natural gas fuelled phosphoric acid fuel cell, the natural gas fuelled solid oxide fuel cell, the natural gas turbine, the natural gas combined cycle and the natural gas internal combustion engine.The criteria used for the evaluation are CO₂ emissions, NO_X emissions, efficiency, capital cost, operation and maintenance costs, service life and produced electricity cost.A total of 19 scenarios were studied. In 15 of these scenarios, the hydrogen turbine ranked first and proved to be the most preferred electricity production technology. However since the hydrogen combustion turbine is still under research, the most preferred power generation technology which is available nowadays proved to be the natural gas combined cycle which ranked first in five scenarios and second in eight. The last in ranking electricity production technology proved to be the natural gas fuelled phosphoric acid fuel cell, which ranked in the last position in 13 scenarios.     

Cryopreservation of Mesenchymal Stem Cells Using Medical Grade Ice Nucleation Inducer

Mesenchymal stem cells (MSCs) can differentiate into multiple different tissue lineages and have favourable immunogenic potential making them an attractive prospect for regenerative medicine. As an essential part of the manufacturing process, preservation of these cells whilst maintaining potential is of critical importance. An uncontrolled area of storage remains the rate of change of temperature during freezing and thawing. Controlled-rate freezers attempted to rectify this; however, the change of phase from liquid to solid introduces two extreme phenomena; a rapid rise and a rapid fall in temperature in addition to the intended cooling rate (normally −1 °C/min) as a part of the supercooling event in cryopreservation. Nucleation events are well known to initiate the freezing transition although their active use in the form of ice nucleation devices (IND) are in their infancy in cryopreservation. This study sought to better understand the effects of ice nucleation and its active instigation with the use of an IND in both a standard cryotube with MSCs in suspension and a high-throughput adhered MSC 96-well plate set-up. A potential threshold nucleation temperature for best recovery of dental pulp MSCs may occur around −10 °C and for larger volume cell storage, IND and fast thaw creates the most stable process. For adhered cells, an IND with a slow thaw enables greatest metabolic activity post-thaw. This demonstrates a necessity for a medical grade IND to be used in future regenerative medicine manufacturing with the parameters discussed in this study to create stable products for clinical cellular therapies.     

Transient forces in three phase gas cables

Contents A gas cable for power transmission has been considered. It consists of three infinitely thin, tubular, phase conductors symmetrically arranged in a thin tubular shell which is non magnetic ( _r =1). Transient short circuit currents are imposed through phase conductors corresponding to a three phase fault far from generator. Field and forces are calculated using complex potential and space complex Fourier expansions of currents, i.e. properties of analytical functions are used. Parameters like conductivity, cable dimensions and current asymmetry are varied.

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Transiente Kräfte in dreiphasigen Gasrohrkabeln

Übersicht Es wird ein Gasrohrkabel für Leistungsübertragung betrachtet. Es besteht aus drei unendlich dünnen rohrförmigen Phasenleitern, die symmetrisch in einem unendlich dünnen Mantel angeordnet sind. Der Mantel ist nicht magnetisch ( _r =1). Transiente Kurzschlußströme werden durch die Phasenleiter eingeprägt. Dieser Zustand entspricht einem dreiphasigen generatorfernen Kurzschluß. Feld und Kräfte werden unter Verwendung von raumkomplexen Potentialen und von raumkomplexen Fouriententwicklungen für die Ströme berechnet, d. h., es werden die Eigenschaften von analytischen Funktionen ausgenutzt. Die Berechnung wird für verschiedene Parameterwerte, z. B. Leitfähigkeit, Abmessungen und Stromasymmetrie, durchgeführt.