The long-term durability performance of gypsum-Portland cement-natural pozzolan blends

The density, workability, porosity, strength development, and durability of gypsum-Portland cement-natural pozzolan blends are discussed in this paper. The results indicate that the variation in proportions of the mix constituents causes changes in the density. The effects of adding a superplasticizer depend on the amount of added. The higher dosages of a naphthalene-based superplasticizer permit a much greater increase of workability. This improvement in workability can be used to produce mixes with a lower water/binder ratio while maintaining constant workability. The gypsum-Portland cement-natural pozzolan blend gives lower strength than gypsum at age of 1 day. However, its strength continues to increase from 1 day onward and exceeds that of gypsum at 28 days. The effect of porosity on the strength can be described with a quadratic exponent for gypsum-Portland cement-natural pozzolan blends. The porosity tends to decrease significantly with the curing period. The rate of reduction is high for curing periods up to 28 days. However, above this period, the rate is much reduced. The durability assessments are made by examining the behaviour of gypsum-Portland cement-natural pozzolan blends in water and freezing and thawing cycles. The blends with compositions of 41:41:18 (gypsum/Portland cement/natural pozzolan) and 41:41:18S1 (gypsum/Portland cement/natural pozzolan/1% superplasticizer) give excellent property retention after ageing in water at 20 °C for 95 days. An exponential equation σ=σ₀[1+(1−e^−bt)/a], where σ₀ is the initial strength of gypsum-Portland cement-natural pozzolan blend, σ is the strength of the gypsum-Portland cement-natural pozzolan blend after exposure to the water for time t, t is the duration of exposure to the water, and a and b are the material constants to be determined, is proposed to predict the variation of compressive strength of these blends immersed in water with time. This equation shows excellent agreement with the data on 41:41:18 and 41:41:18S1 in a period of 95 days. These blends perform very well during the freezing and thawing test. They do not show any deterioration up to 20 cycles of freezing and thawing. However, the test results after 30 cycles show that the scaling resistance of 41:41:18S1 is somewhat better than that of 41:41:18.     

A Neurogenetic approach for the resource-constrained project scheduling problem

A variety of metaheuristic approaches have emerged in recent years for solving the resource-constrained project scheduling problem (RCPSP), a well-known NP-hard problem in scheduling. In this paper, we propose a Neurogenetic approach which is a hybrid of genetic algorithms (GA) and neural-network (NN) approaches. In this hybrid approach the search process relies on GA iterations for global search and on NN iterations for local search. The GA and NN search iterations are interleaved in a manner that allows NN to pick the best solution thus far from the GA pool and perform an intensification search in the solution's local neighborhood. Similarly, good solutions obtained by NN search are included in the GA population for further search using the GA iterations. Although both GA and NN approaches, independently give good solutions, we found that the hybrid approach gives better solutions than either approach independently for the same number of shared iterations. We demonstrate the effectiveness of this approach empirically on the standard benchmark problems of size J30, J60, J90 and J120 from PSPLIB.     

An intelligent power factor corrector for power system using artificial neural networks

An intelligent power factor correction approach based on artificial neural networks (ANN) is introduced. Four learning algorithms, backpropagation (BP), delta-bar-delta (DBD), extended delta-bar-delta (EDBD) and directed random search (DRS), were used to train the ANNs. The best test results obtained from the ANN compensators trained with the four learning algorithms were first achieved. The parameters belonging to each neural compensator obtained from an off-line training were then inserted into a microcontroller for on-line usage. The results have shown that the selected intelligent compensators developed in this work might overcome the problems occurred in the literature providing accurate, simple and low-cost solution for compensation.     

Characterization of polyphenoloxidase (PPO) and total phenolic contents in medlar (Mespilus germanica L.) fruit during ripening and over ripening

Characterization of polyphenoloxidase (PPO) enzyme and determination of total phenolic concentrations during fruit ripening and over ripening in medlar (Mespilus germanica L.) were determined. During ripening, PPO substrate specificity, optimum pH and temperature, optimum enzyme and substrate concentrations were determined. Among the five mono- and di-phenolic substrates examined ((p-hydroxyphenyl) propionic acid, l-3,4-dihydroxyphenylalanine, catechol, 4-methylcatechol and tyrosine), 4-methylcatechol was selected as the best substrate for all ripening stages. A range of pH 3.0–9.0 was also tested and the highest enzyme activity was at pH 7.0 throughout ripening. The optimum temperature for each ripening stage was determined by measuring the enzyme activity at various temperatures over the range of 10–70 °C with 10 °C increments. The optimum temperatures were found to be 30, 20 and 30 °C, respectively, for each ripening stage. Optimum enzyme and substrate concentrations were found to be 0.1 mg/ml and 40 mM, respectively. The V_max and K_m value of the reaction were determined during ripening and found to be 476 U/mg protein and 26 mM at 193 DAFB (days after full bloom) – stage 1, 256 U/mg protein and 12 mM at 207 DAFB – stage 2, 222 U/mg protein and 8 mM at 214 DAFB – stage 3. For all ripening stages sodium metabisulfite markedly inhibited PPO activity. For stage 1 of ripening, Cu²⁺, Hg²⁺ and Al³⁺, for stage 2, Cu²⁺ and Hg²⁺, and for stage 3, Cu²⁺, Hg²⁺, Al³⁺ and Ca²⁺ strongly inhibited diphenolase activity. Accordingly, it can be concluded that as medlar fruit ripen there is no significant changes in the optimum values of polyphenoloxidases, although their kinetic parametres change. As the fruit ripening progressed through ripe to over-ripe, in contrary to polyphenoloxidase activity, there was an apparent gradual decrease in total fruit phenolic concentrations, as determined by using the aqueous solvents and water extractions.     

The optimum taper angle for ethanol fermentation in a packed-bed column reactor

In ethanol fermentation, tapered columns facilitate the liberation of CO₂ and, since the bed expands through a larger cross-sectional area, smaller pressure drops occur. In this work, 0°, 2°, and 4° tapered columns, containing Saccharomyces cerevisiae entrapped in beads of K-carrageenan, were operated for continuous production of ethanol from glucose. The column inlet diameters and the bead volume were maintained constant for the three columns. With decreasing taper angle, increasing feed glucose concentration, increasing feed flow rate and increasing bead volume in the reactor, the pressure drop across the bed increased. There was no significant difference between the ethanol productivities obtained in the 0°, 2°, and 4° tapered columns when a packed volume of 52% of the total volume was examined. Increasing the packed volume to 84% of the total caused the cylindrical column to become inoperable due to pressure buildup and bead compression. When the columns were packed to 84% capacity, the productivity and pressure drop values obtained on the 2° and 4° tapered columns did not significantly differ. For a feed concentration of 150 g glucose dm^?3 and a residence time range of 5.4–15.94 h, the pressure drop varied between 4.5 × 10³ and 1.28 × 10⁴ Pa in the 2° and between 4 × 10³ and 7.98 × 10³ Pa in the 4° tapered column. Conversion in the 2° tapered column varied from 94% to 78.8% and in the 4° tapered column from 92.6% to 78.8%. Defining optimum taper angle as the smallest angle which allows for stable operation without any pressure buildup, the taper angle of 2° was selected as nearest to the optimum value.     

Neural network using longitudinal modes of an injection laser withexternal feedback

A new optical neural-network concept using the control of the modes of an injection laser by external feedback is described by a simple laser model. This approach uses the wavelength dispersed longitudinal modes of the laser as neurons and the amount of external feedback as connection weights. The predictions of the simple model are confirmed both with extensive numerical examples using the laser rate equations and also by experiments with GaAlAs injection lasers. The inputs and connection weights to this laser neural network are provided by external masks which control the amount of feedback reaching the laser. Stochastic learning is used to obtain weight masks for a small three-input and four-output neural net for the numerical and experimental examples. Winner-take-all and exclusive-or operations are obtained on the input set with different weight masks. Both of these operations are also obtained in experiments with a three-input/four-output laser neural network operating at an estimated speed greater than 10 GCPS. The eventual speed of this type of neural network hardware is expected to reach well within TCPS range if it is built in an optoelectronic integrated circuit with dimensions in the order of a mm. Different neural-network architectures possible with this approach are discussed.     

Quasioptical multilayered interferometer for gasoline testing

Results of an experimental study and a calculation of the quasi-optical multilayered structure formed by an adjustable dielectric interferometer and a liquid investigated filling its gabs are presented. It is shown that this structure may be used for quality tests of liquid petroleum products, for measurement and investigation of physical parameters of liquid media in the millimeter wavelengths region. This structure is realized practically in the form of uncomplicated adjustable quazi-optical quvette filled with liquid and connected with beam-guiding elements. Comparison of experimental data with theoretical calculations gives us the opportunity to choose a value region of the values for the physical parameters interesting for us for each material under investigation.     

Context matters: The benefits and costs of expressing positive emotion among survivors of childhood sexual abuse.

Positive emotions promote adjustment to aversive life events. However, evolutionary theory and empirical research on trauma disclosure suggest that in the context of stigmatized events, expressing positive emotions might incur social costs. To test this thesis, the authors coded genuine (Duchenne) smiling and laughter and also non-Duchenne smiling from videotapes of late-adolescent and young adult women, approximately half with documented histories of childhood sexual abuse (CSA), as they described the most distressing event of their lives. Consistent with previous studies, genuine positive emotional expression was generally associated with better social adjustment two years later. However, as anticipated, CSA survivors who expressed positive emotion in the context of describing a past CSA experience had poorer long-term social adjustment, whereas CSA survivors who expressed positive emotion while describing a nonabuse experience had improved social adjustment. These findings suggest that the benefits of positive emotional expression may often be context specific. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Performance analysis of drying of green olive in a tray dryer

This paper deals with the performance evaluation of a single layer drying process of green olives in a tray dryer using exergy analysis method. Green olive was used as the test material being dried. Drying process was realized at four different drying air temperatures (40, 50, 60 and 70 °C) and a constant relative humidity of 15%. The effects of temperatures and mass flow rates were investigated. Maximum exergy efficiency of the drying chamber was obtained at a temperature of 70 °C and a drying air mass flow rate of 0.015 kg/s with 0.0004 kg/s of olive. The exergy efficiency values were found to be in the range of 68.65%–91.79% from 40 °C to 70 °C with drying air mass flow rates of 0.01 kg/s–0.015 kg/s.