Research on Engineering Structures and Materials

89-97

Authors: Filiz Ugur Nigiz, Nilufer Durmaz Hilmioglu

The production of new generation fuels from sustainable resource is prominent issue of the current world. A wide range of feedstock can be used to produce first generation liquid fuel from starch to corn. Besides the first one, second generation fuel is considered as fuel additive for increasing the calorific value of gasoline and limiting the hazardous gas emission. Only small amount usage of lignocellulosic based additives such as ethyl valerate (EV) increases the energy density of fuel. Due to the non-hazardous and less irritant properties of ethyl valerate it is defined as “green fuel”. It was reported that the 10-20% blend ratio of EV with gasoline causes a significant improvement for engine performance. EV is chemically produced by esterification reaction between ethanol and valeric acid. Reaction can be carried out by means of heterogeneous, homogeneous acid catalyst, lipase and ionic liquids and reactive polymers. In this study, a reactive poly (styrene sulfonic acid) (PSSA) catalyst was prepared and used for ethyl valerate synthesis at different temperature conditions. Effect of alcohol:acid feed molar ratio was also investigated as a function of acid conversion. Better results were obtained as 77.9 % acid conversion at 343 K when alcohol:acid feed molar ratio was 4:1.

113-121

Authors: Ioanna Papayianni, Vasiliki Pachta

Earth structures constitute a great part of European Monumental Heritage and are closely related to the wider historic, socio-economic and environmental aspects of each region. In this paper, a methodology is presented regarding the analysis of the constructional materials and techniques of historic earth block structures situated in Northern Greece, as well as the design and testing of compatible repair materials for their restoration. A series of laboratory tests were performed, in order to define the physico-mechanical and chemical characteristics of the historic materials (earth blocks, structural mortars, renders-plasters). After the evaluation of the results compatible repair materials based on earth were designed, manufactured and tested.

135-146

Authors: Erion Bukaçi, Thoma Korini, Erion Periku, Skënder Allkja, Paulin Sheperi

Convergence - confinement method can be used to analyze rock support systems in interaction with rock mass in order to select the appropriate supports system for tunnels in rock. This method enables calculation of the charge applied to the support system and the factor of safety for the tunnel supports. The factor of safety calculated from traditional deterministic analysis methods cannot fully represent tunnel stability. There are many uncertainties in parameters used to calculate the factor of safety, and these uncertainties are not integrated in a deterministic analysis, but can be taken into account using a reliability analysis. Reliability analyses, used to calculate probability of failure for tunnel support system, is a complement of the factor of safety calculated by using deterministic analyses. In this paper, Monte Carlo Simulation is used to calculate probability of failure for tunnel support system. This article shows that significant error may be introduced by accepting a distribution for the performance function, which is obligatory for methods like FOSM, FORM, PEM. It is concluded that in cases when the distribution for the performance factor is not fully known, Monte Carlo analysis may give better results.

155-162

Authors: Müslüm Arıcı, Çağatay Kaptan, Hasan Karabay

In this study, the enhancement introduced by nanoparticles is investigated. Nanosized copper particles are dispersed into water which is confined in a cavity with a trapezoidal cross-section. The bottom and top walls of the cavity are adiabatic while the inclined lateral walls are kept at different constant temperatures. The cavity contains an adiabatic block at its center. The top wall of the cavity slides horizontally with a uniform constant velocity. The effect of adiabatic block size and particle volume fraction on the fluid flow and heat transfer is examined. Grashof number is set to 105 whereas Reynolds number is varied to examine the flow and heat transfer for Richardson numbers of 0.1, 1 and 10. The computational results show that heat transfer rate enhances as Richardson number decreases. It is also observed that large size of adiabatic block impedes the fluid circulation which reduces heat transfer rate.