A filter-based evolutionary algorithm for constrained optimization

We introduce a filter-based evolutionary algorithm (FEA) for constrained optimization. The filter used by an FEA explicitly imposes the concept of dominance on a partially ordered solution set. We show that the algorithm is provably robust for both linear and nonlinear problems and constraints. FEAs use a finite pattern of mutation offsets, and our analysis is closely related to recent convergence results for pattern search methods. We discuss how properties of this pattern impact the ability of an FEA to converge to a constrained local optimum.     

Induced mood and the illusion of control.

Examined the directionality of the relationship between realism in judging personal control and depression. Depressed and elated mood states were induced transiently in 40 naturally nondepressed and 40 depressed females (Beck Depression Inventory and the Multiple Affect Adjective Check List), and the impact of these transient mood states on susceptibility to the illusion of control was assessed. Naturally nondepressed Ss gave accurate judgments of control while naturally depressed Ss showed an illusion of control and overestimated their impact on an objectively uncontrollable outcome. Mood induction groups showed predicted changes in self-reported affect and a behavioral measure of depression. These results are in contrast to those of L. B. Alloy and L. Y. Abramson (1979). An implication of the present findings may be that therapeutic interventions for depression that successfully remediate depressive symptoms may also increase depressed individuals' susceptibility to the illusion of control. (39 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Transfer of fluency across repetitions and across texts.

Three experiments examined transfer of reading fluency across repeated readings of the same text and across related but different texts with a total of 102 college students. In Exp 1, it was found that a paraphrase that altered the syntactic structure of sentences but not the lexical identity of main concepts or the unfolding of the message was reprocessed as an unchanged repetition. However, when the paraphrase altered the lexical identity of main concepts, there was a loss in the repetition benefit. In Exps 2 and 3, there was transfer from a representation of 1 text to the reading of a 2nd text only if the messages were continuous. Results are discussed in terms of the influence of episodic text representations on reading fluency. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Development of an optimised papaya pulp nectar using a combination of irradiation and mild heat

Papaya does not sufficiently maintain desired fresh fruit quality when shipped long distances due to an easily bruised soft skin and a short shelf life. This leads to both a large supply of pulp from unsightly fruit that is never shipped and low sales due to blemished fruit. Unfortunately, traditional preservation methods (pasteurisation) negatively alter papaya’s fresh flavour. Thus to effectively utilise available papaya pulp, processing requires an approach that enables retention of papaya’s natural flavours without excessive heat. Papaya fruit (Carica papaya L., var.’s Rainbow (yellow-fleshed) and SunUp (red-fleshed)) were pulped, diluted, and processed with mild heat (80 °C, 5 min), irradiation (5 kGy or 7.5 kGy) or combinations of both. Irradiation resulted in a significant reduction in ascorbic acid content. Mild heat treatment significantly reduced pectinesterase activity and microbiological viability. Irradiation followed by heat further enhanced destruction of Listeria innocua and Clostridium sporogenes and retained the flavour and a nutritional profile closest to untreated controls. The product was microbiologically safe with acceptable enzyme levels and would be shippable under refrigeration.     

An investigation of drum granulation of post-pyrolysis washed biochar

Biochar, unwashed and washed with a solution of Triton and hydrogen peroxide, was wet drum granulated using molasses binder solutions. Unwashed biochar was very hydrophobic and granulation proceeded through forming liquid marbles and layering. Washing reduced the hydrophobicity of the biochar. The effectiveness of the wash depended on the biochar source; it significantly reduced the hydrophobicity of biochar from woodchips and moderately reduced the hydrophobicity of biochar from flower digestate. Therefore, washed biochar from woodchips was granulated using a hydrophilic mechanism, while washed biochar from digestate was granulated according to a combination mechanism of liquid marbles collapsing and then coalescing. The change in granulation mechanism produced stronger and denser granules with higher yields of granules in the 1–4 mm optimal size range. Washing and then granulating biochar created a product that could be further tailored for optimal soil amendment.     

Quantifying health improvements from water quantity enhancement: an engineering perspective applied to rainwater harvesting in West Africa

Knowledge of potential benefits resulting from technological interventions informs decision making and planning of water, sanitation, and hygiene programs. The public health field has built a body of literature showing health benefits from improvements in water quality. However, the connection between improvements in water quantity and health is not well documented. Understanding the connection between technological interventions and water use provides insight into this problem. We present a model predicting reductions in diarrhea disease burden when the water demands from hygiene and sanitation improvements are met by domestic rainwater harvesting (DRWH). The model is applied in a case study of 37 West African cities. For all cities, with a total population of over 10 million, we estimate that DRWH with 400 L storage capacity could result in a 9% reduction in disability-affected life years (DALYs). If DRWH is combined with point of use (POU) treatment, this potential impact is nearly doubled, to a 16% reduction in DALYs. Seasonal variability of diarrheal incidence may have a small to moderate effect on the effectiveness of DRWH, depending on the storage volume used. Similar predictions could be made for other interventions that improve water quantity in other locations where disease burden from diarrhea is known.     

Post-spinning modification of electrospun nanofiber nanocomposite from Bombyx mori silk and carbon nanotubes

Electrospinning is an effective procedure for fabricating submicron to nanoscale fibers from synthetic polymer as well as natural proteins. We successfully electrospun regenerated silk protein from cocoons of Bombyx mori to produce random as well as aligned fibers with diameter less than 100 nm. The fibers were characterized using field emission environmental scanning electron microscope (ESEM), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy and wide angle X-ray diffraction (WAXD) studies. Post-spinning treatment with methanol and/or stretching and co-electrospinning with single walled carbon nanotubes (CNT) were carried out to alter the strength, toughness, crystallinity and conductivity of silk nanofibers. Addition of just 1% CNT along with post-spinning treatments resulted in 7-fold increase in the strength and 35-fold increase in the modulus of silk nanofibers. Raman spectroscopy confirmed that CNTs were incorporated in the silk fibers. FT-IR spectroscopy and WAXD studies proved that silk-CNT nanofibers had more crystallinity compared to silk nanofibers without CNT. Four-probe method demonstrated that silk-CNT nanofibers had 4 times higher electrical conductivity compared to silk nanofibers without CNT.     

Using a new diffusivity model to accelerate the drying of biopolymer films

A model was developed to study the drying rate of biopolymer films. The diffusivity of water in this biopolymer film is an exponential function of the water concentration. This creates a situation where simply increasing gas velocity can decrease the actual drying rate. The model revealed that the main factor limiting the drying of the biopolymer film was a significant and rapid decrease in the diffusivity of water through the film as the film dried. To avoid this a pulsing scheme was proposed where the velocity of the drying gas would be varied during the experiment; this variation allowed for a compromise between a high overall drying rate and maintaining a high diffusivity within the film. It was found that the optimum combination of gas velocities was 0.8 and 0.6 m/s with a duration of 10 min at the high and low gas velocities.     

Reverse osmosis desalination: Water sources, technology, and today's challenges

Reverse osmosis membrane technology has developed over the past 40 years to a 44% share in world desalting production capacity, and an 80% share in the total number of desalination plants installed worldwide. The use of membrane desalination has increased as materials have improved and costs have decreased. Today, reverse osmosis membranes are the leading technology for new desalination installations, and they are applied to a variety of salt water resources using tailored pretreatment and membrane system design. Two distinct branches of reverse osmosis desalination have emerged: seawater reverse osmosis and brackish water reverse osmosis. Differences between the two water sources, including foulants, salinity, waste brine (concentrate) disposal options, and plant location, have created significant differences in process development, implementation, and key technical problems. Pretreatment options are similar for both types of reverse osmosis and depend on the specific components of the water source. Both brackish water and seawater reverse osmosis (RO) will continue to be used worldwide; new technology in energy recovery and renewable energy, as well as innovative plant design, will allow greater use of desalination for inland and rural communities, while providing more affordable water for large coastal cities. A wide variety of research and general information on RO desalination is available; however, a direct comparison of seawater and brackish water RO systems is necessary to highlight similarities and differences in process development. This article brings to light key parameters of an RO process and process modifications due to feed water characteristics.     

Composite double network hydrogels with thermoresponsive colloidal nanoemulsions

We report the formulation and mechanical characterization of double network (DN) composite hydrogels. The first network consists of covalently crosslinked poly(ethylene glycol diacrylate) (PEGDA), which forms a strong, brittle network that provides elasticity to the gel. The second network, sodium alginate, is ionically crosslinked with Ca²⁺ to allow increased dissipation of mechanical energy. The novelty of this system over existing DN hydrogels is the additional incorporation of a third mesoscale network, composed of thermoresponsive poly(dimethyl siloxane) (PDMS) nanoemulsions, which undergo colloidal gelation through the bridging of the PEGDA hydrophobic end groups into the PDMS droplets. The colloidally gelled microstructures are photopolymerized into a solid hydrogel by crosslinking the precursors with ultraviolet (UV) light. Tensile mechanical experiments performed on the crosslinked DN nanoemulsion hydrogels show that their rupture stress (0.17–0.34 MPa), fracture energy (144–421 J/m²), and Young's modulus (1–2.1 MPa) are comparable to similar systems in the literature. These mechanical measurements suggest that the gels may be suitable for manufacturing processes in which large shear rates and deformations are encountered.