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.     

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.     

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...     

Cultural Experience as a (Critical) Factor in Crisis Communication Planning

A key issue in crisis communication is the way people process crisis‐relevant information to minimize danger. This paper discusses the impact of previously experienced crises on the public's interpretation of warning messages. People may not have direct experience of a crisis, but they still have acquired mediated experiences of a variety of crises. The present study introduces the term cultural experience of crisis to label the synthesis of mediated crisis experiences, media and fictional narratives, collective memories of societal disasters, conversations, and immediate crisis experiences of witnesses and victims. The proposed model of cultural experience of crisis is elaborated on the basis of a qualitative text analysis derived from four qualitative interviews 16 focus groups interviews carried out in Estonia from 2008 to 2009.     

A new denoising method for removing salt & pepper noise from image

Multimedia Tools and Applications - Digital image has a significant importance in many fields in human life such as, in medicine, photography, biology, astronomy, industry and defense. Thus, it...     

An adaptive least squares channel estimation based on conjugate gradient approach for multipath fading CDMA systems

Multiple access interference (MAI) is the main factor affecting the performance of channel estimation techniques for code division multiple access (CDMA) systems. Although, several multi-user channel estimation algorithms have been proposed to mitigate MAI, these algorithms require high computational complexities. In this paper, we address the problem of iterative least squares (LS) mobile channel estimation at high channel efficiency that requires a short training sequence along with the spreading sequences. We employ an efficient iterative method based on conjugate gradient (CG) algorithm to reduce the computational complexity of the estimation method. Computer simulations illustrate that the proposed method performs almost identical to the exact LS estimate for reasonable training lengths.     

Optimization of Microchannel Heat Sinks Using Genetic Algorithm

In this study, a genetic algorithm is employed to minimize the entropy generation rate in microchannel heat sinks. The entropy generation rate allows the combined effects of thermal performance and pressure drop to be assessed simultaneously as the heat sink interacts with the surrounding flow field. Previously developed models for the heat transfer, pressure drop and entropy generation rate are used in the optimization procedure. The results of optimization are compared with existing results obtained by the Newton–Raphson method. It is observed that the GA gives better overall performance of the microchannel heat sinks.     

Co-condensates of resorcinols and methylol compounds for adhesive resins

A proton magnetic nuclear resonance study was performed on co-condensation reactions of resorcinol, 5-methylresorcinol and 2,5-dimethylresorcinol with methylol compounds, including ortho- and para-methylolphenol, N-methylol-caprolactam, methylol-N,N-diethylurea, methylolurea and N,N′-dimethylolurea. Spectral assignments, reaction kinetics and composition of products are discussed. The reaction in melt (120°C) with methylolphenols occurs as co-condensation in the presence of all catalysts studied. In resorcinols C4C6 substitution is favored. The rate constants of methylol disappearance clearly indicate the preferable influence of acid and alkaline catalyst (not zinc acetate) on para-methylol. The reaction with N-containing methylol compound does not give any co-condensate in the presence of alkaline catalyst. The optimum conditions for co-condensation mainly depend on reactivity of co-reagents with formaldehyde and stability of methylol compound. The quantitative amount of co-condensate with methylolcaprolactam can be obtained in melt-condensation (70°C) in the presence of acid catalyst. Because of the higher reactivity of urea, the reaction in melt (100°C) in the presence of acid catalyst does not lead to quantitative co-condensation. The condensation of methylol compound or resorcinols with formaldehyde can be avoided substantially by performing the reaction in aqueous solution at lower temperature.