Laser sintering of coated polyamide 12: a new way to improve flammability

Journal of Materials Science - In this study coatings of kaolin and talc particles were successfully applied on the surface of polyamide 12 powder intended for laser sintering (LS). Microscopic...     

One-line measurement of the residence time distribution in screw extruders

A fluorescence monitoring device was constructed to measure in real time the residence time distribution (RTD) function in screw extruders. Its centerpiece was an optical fiber probe capable of transmitting optical excitation energy to the processed flow stream and detecting the subsequent fluorescence emission. The source of fluorescence emission was an anthracene-bearing substance that was injected to the flow stream as a pulse (tracer) in very small amounts. This device was validated against an off-line ultraviolet spectrophotometer and self-checked as well. In addition to its great sensitivity to fluorescence emission and ease of implementation on an extrusion line, this device could be used to monitor in real time subtle variations of an extrusion operation. The influence of the nature of anthracene-bearing compounds on the measured distribution and the effects of processing parameters on the RTD function were also investigated.     

Dynamic modelling of consecutive reactions: Application to the acrylonitrile amination

When dealing with optimal control problems to maximize the selectivity of reactions for fine chemical synthesis, representative kinetic and thermodynamic models should be available. While literature appears to be very extensive on theoretical approaches to solve the problem, examples presenting complete models of chemical transformations are scarce. This paper presents the identification of consecutive reactions carried out in a batch reactor. Material and energy balances, satisfying dynamical state evolutions in the temperature range 20-60°C are deduced, for concentrations of acrylonitrile ranging up to 1.6 kmol·m^?3. The stoichiometric network is simplified into two reactions, one reversible and one irreversible. Reaction enthalpies are measured from isothermal runs conducted in the RC1 heat-flow calorimeter from Mettler Toledo.     

Effect of mineral filler type on autogenous shrinkage of self-compacting concrete

Based on an experimental programme, including autogenous shrinkage tests on concrete, ultrasonic monitoring of fresh concrete, and mercury intrusion porosimetry, the influence of the filler type on the autogenous shrinkage of self-compacting concrete has been investigated. The onset of percolating structure formation (time zero) is influenced by the filler type due to a possible accelerating effect of the filler on the cement hydration. Limestone filler accelerates the hydration process, and reduces time zero, while this is not the case when using quartzite filler. Using fly ash, showing only a slight acceleration, a slight reduction of time zero is obtained. A very significant swelling peak is noticed during the first day. This swelling peak is not a measuring artefact, but is caused mainly by water absorption on the filler surface and resulting disjoining pressure. Some part of the swelling peak might also be caused by Ca(OH)₂ crystallisation. The fineness of the filler is an important factor for this swelling behaviour, although also the nature of the filler seems to have an influence. The superplasticiser also interacts with the fillers, influencing the swelling behaviour. The different filler types used in this study did not lead to significant differences in critical pore diameter of the microstructure. This might explain why no significant differences have been found in final autogenous shrinkage values using the different filler types.     

Catalytic coating of virus particles with zinc oxide

We show that the rod-shaped Tobacco mosaic virus (TMV) can be coated with the wide band gap semiconductor zinc oxide by electroless deposition under mild reaction conditions. The process involves pretreatment with aqueous Pd(II), followed by nucleation of ZnO, directed to palladium centers formed on the surface of TMV. The mechanism is based on the local pH change due to the reduction of nitrate by dimethylamine borane at the palladium. Morphology and chemical composition have been analyzed by transmission electron microscopy (TEM) and by energy filtering TEM, respectively. The optical properties were elucidated by cathodoluminescence, which showed the desired near-band edge emission.     

Wood fuel trade in European Union

Wood fuels are the most important alternatives of fossil fuel which is one of the reasons of the climate changes in the world and of global warming. Wood fuels, which have an important role in the cause of both providing energy requirement of production units and heating for household and healing energy deficit, disperse very less CO₂ than fossil fuels to atmosphere. Bio-fuels are used to provide energy requirement among EU countries like using in lots of developed countries. Resources having by lots developed countries and EU countries are not at enough level for bio-fuels. For this reason, trade of bio-fuels has been become in an important situation in recent years. In this study, import and export levels of bio-fuels of EU countries and Turkey, which is a candidate for union, were investigated between 2003 and 2006. The date is obtained from European Forest Institute (EFI) forest products trade flow database. As a result of the study, while rises were determined in years, it is determined that the most important exporters are Germany, Italy, Latvia and Poland and the most important importers are Germany, Italy, Belgium and UK. It is seen that Turkey has a low trade level in selected product groups.     

Efficiency of granulated blast furnace slag replacement of cement according to the equivalent binder concept

The strength development of slag cement has a great consideration for the scheduling of formwork removal, prestressing operations, and other practical aspects of slag cement usage. The prediction of slag concrete strength, using the Feret’s model has been studied by introducing the concept of the equivalent binder. This has led to define an efficiency coefficient of slag which distinguishes the latter with the regard to the cement. Thus, this obtained coefficient characterizes well the slag and lets to predict the slag concrete strength from strength values of a normal concrete made without slag for a given age and replacement rate. At 90 days age, the test results show that for 15% replacement rate, the slag is activated completely and gives 67% of efficiency more than the cement. For higher replacement rate, the efficiency of the slag decreases and becomes similar to that of cement for 50% replacement rate.     

Training Sequence Aided Signature Waveform Estimation

In code division multiple access channels multiuser detection techniques are known to be effective strategies to counter the presence of multiuser interference towards improving spectral efficiency. Generally, multiuser detectors can provide excellent performance only when the signature waveforms of all users are precisely known. Hence, the estimation of signature waveforms is a challenging issue in mobile communication systems. In this paper, we compare the performance of two short training sequence aided signature waveform estimators. One is maximum likelihood type signature waveform estimator that requires the knowledge of spreading sequences and short training sequences. The other estimator is recently proposed based on subspace method and requires the knowledge of training sequences only. Through the simulations, we show the signature waveform estimation performance of both systems and the effect of the estimation error on the performance of a multiuser detector. The complexity comparisons of both systems are also given. We use the term “signature waveform” to refer to the convolution of the channel and the spreading code throughout the paper. Hasan AMCA was born in 1961 in Nicosia-Cyprus. He graduated from the Higher Technological Institute in Magosa – Cyprus (which is renamed later as Eastern Mediterranean University). He joined EMU in 1985 after receiving a M.Sc. (Digital Signal Processing) degree from the University of Essex in England (1985). He took his Ph.D. (Mobile Communications) from the University of Bradford where he was on a Commonwealth scholarship. He has been teaching in the Electrical and Electronic Engineering Department of Eastern Mediterranean University since 1993 where he also served as the Vice Chairman from Spring 1998 to Spring 2000. He has been appointed as the Director of the School of Computing and Technology of the EMU since Spring 2000. His research interests include Multi User Detection of CDMA signals, Adaptive Equalisation, Multi Carrier Systems, Mobile Radio Systems and Networks, Internet and Information Technology Applications in Education. Ahmet Rizaner was born in Larnaca, Cyprus, on January 31, 1974. He received the B.S. and M.S. degrees in Electrical and Electronics Engineering from the Eastern Mediterranean University, Famagusta, North Cyprus, in 1996 and 1998, respectively. He completed his PhD. degree in Electrical and Electronic Engineering in Eastern Mediterranean University and joined Eastern Mediterranean University as a lecturer in 2004. He is lecturing in the School of Computing and Technology. His main research interests include CDMA communications, adaptive channel estimation, and multiuser detection technique. Kadri Hacioğlu was born in Nicosia, Cyprus. He received the B.Sc., M.Sc., and Ph.D. degrees in electrical and electronic engineering from the Middle East Technical University, Ankara, Turkey, in 1980, 1984, and 1990, respectively. After his two-year military service, in 1992, he joined the faculty of Eastern Mediterranean University, Magosa, North Cyprus, as an Assistant Professor, and became an Associate Professor in 1997. While there, he taught several classes on electronics, digital communications, speech processing and neural networks. During this time, he conducted research on applying fuzzy logic, neural networks, and genetic algorithms to signal processing and communications problems. From 1998 to 2000, he was a Visiting Professor in the Department of Computer Science, University of Colorado, Boulder. Here, he taught classes on neural networks and continued his research. Since 2000, he has been a Research Associate at the Center for Spoken Language Research, University of Colorado. He has authored or coauthored numerous papers and supervised a dozen M.Sc./Ph.D. theses. His current research interests are concept-based language modeling, speech understanding, natural language generation, and search methods in speech recognition/understanding. He also does research on multiuser detection and equalization in CDMA systems. Ali Hakan Ulusoy was born in Eskişehir, Turkey, on June 3, 1974. He graduated from the double major program of the department of Electrical and Electronic Engineering and department of Physics in Eastern Mediterranean University as the first rank student of Faculty of Engineering in 1996. He received his M.S. degree in Electrical and Electronic Engineering in Eastern Mediterranean University in 1998. He completed his Ph.D. degree in Electrical and Electronic Engineering in Eastern Mediterranean University and joined Eastern Mediterranean University as a lecturer in 2004. He is lecturing in the School of Computing and Technology. His current research interests include receiver design, multi-user detection techniques, blind and trained channel estimation in Code Division Multiple Access (CDMA).