Combustion of Mechanically Alloyed Aluminum‐Magnesium Powders in Steam

Mechanically alloyed Al ⋅ Mg powders with the mole fraction of Al varied from 0.47 to 0.9 were burned at atmospheric pressure in water vapor. The powders were carried by nitrogen through the center of a hydrogen‐oxygen diffusion flame. The particles ignited in the steam at approximately 2500 K, generated as the hydrogen‐oxygen flame product. Filtered photomultiplier tubes were used to capture the optical emission traces of individual particles as they burned. It was assumed that the measured durations of individual emission pulses are representative of individual particle burn times. Distributions of the burn times were obtained for each powder and correlated with respective particle size distributions to relate particle burn times with their sizes. Color temperatures corresponding to the particle emission signals were also obtained. It was observed that the burn times measured for alloys were more close to those of pure Al than Mg; for particles smaller than 2–3 μm, burn times for the alloys were shorter than for pure metal particles. The effect was strongest for the alloy with 50 wt‐% of Mg (Al_0.47Mg_0.54). Approximately, burn times, τ, as a function of particle size, d, could be estimated using a τ∼dⁿ law, where n increased from 0.72 to 1.05 as the mole fraction of Mg increased from 0.1 to 0.53. The particle flame temperatures varied between 2500 and 3100 K for all alloys except for Al_0.7Mg_0.3, for which the temperatures were somewhat lower. The measured flame temperatures were reasonably close to the adiabatic flame temperatures calculated for combustion of mixed elemental Al and Mg in steam.     

Potential of ionic liquids for VOC absorption and biodegradation in multiphase systems

This work aims to evaluate the feasibility of using imidazolium ionic liquids (ILs) in the design of multiphase bioreactors for the removal of volatile organic compounds (VOCs). The IL affinity for three model VOCs (dimethyl sulfide, dimethyl disulfide and toluene) was evaluated by means of the dimensionless partition coefficient (K). It was observed that ILs showed K values comparable to typical liquid solvents used in multiphase bioreactors for VOC biodegradation (K values ranged from 0.009 to 0.011, 0.0012 to 0.0013 and 0.00061 to 0.00096 for dimethyl sulfide, dimethyl disulfide and toluene, respectively). Toxicity tests showed that both ILs at concentrations of 5% and 10% (v/v) inhibited the glucose uptake of an activated sludge during approximately 24 h. After such lag period, the microorganisms were able to recover its metabolic activity. However, VOC biodegradation experiments showed that ILs at 5% (v/v) were toxic for the activated sludge and a toxic synergistic effect of the IL–VOC combination likely occurred. After acclimation to the target VOCs, only the toluene biodegradation capacity was significantly increased in the presence of ILs. These toxic effects represent a key drawback for the potential of IL-based multiphase systems devoted to VOC biodegradation. Therefore, this study suggests that microbial acclimation only to the VOCs is not enough to get an efficient biodegradation in multiphase systems including ILs as non-aqueous phases.     

Volatile compounds of copoazú (Theobroma grandiflorum Schumann) fruit

Volatile compounds were isolated from copoazú (Theobroma grandiflorum Schumann) fruit by liquid–liquid extraction at two different pH values of 3.3 (natural) and 7. The volatile extracts were analyzed by capillary GC–FID and GC–MS. Among the 56 compounds identified at two pH values, many of them were only present in the lower pH extract, confirming the presence of bound compounds in copoazú. Ethyl butanoate, ethyl hexanoate and linalool were the major constituents found in copoazú fruit.     

Honey bee social foraging algorithms for resource allocation: Theory and application

A model of honey bee social foraging is introduced to create an algorithm that solves a class of dynamic resource allocation problems. We prove that if several such algorithms (“hives”) compete in the same problem domain, the strategy they use is a Nash equilibrium and an evolutionarily stable strategy. Moreover, for a single or multiple hives we prove that the allocation strategy is globally optimal. To illustrate the practical utility of the theoretical results and algorithm we show how it can solve a dynamic voltage allocation problem to achieve a maximum uniformly elevated temperature in an interconnected grid of temperature zones.     

Potential for developing small geothermal power stations in peru

Peru is located on the central-western side of South America. Its area is estimated to be 1,200,000 km², between the parallels 0°01′ North 18°20′ South, and the meridians 68°40′ and 81°20′ West, along the Pacific Ocean.The Cordillera de Los Andes is the mountain system which forms the backbone of Peru. It divides the country longitudinally into three sharply contrasted regions, the coastal zone, the sierra and the jungle. The southern zone is characterized by a post-orogenic volcanism which developed along the Cordillera Occidental where the chain of volcanic cones was mainly formed during this volcanic cycle (Upper Tertiary and Quaternary); on the other hand the Central-North zone is characterized by a sedimentary sequence which mainly presents a strong tectonism.Thermal waters can be found in the three natural regions, with temperatures varying from 16 to 92°C, all along the two Cordilleras, Western and Eastern.     

A preliminary study of the fixation mechanism of collagen reaction with a polyepoxy fixative

A new biomaterial has been developed by fixing native collagens with a polyepoxy compound (PC) fixative. Prior studies have shown that this biomaterial has comparable properties as compared to collagen fixed with glutaraldehyde (GA) and thus has a great promise for use as an implantable bioprosthesis. The purpose of this study was to understand the mechanism of the amino acids-PC reactions in the fixation process. Bovine arteries were fixed with PC under various pH, concentration and temperature conditions as a function of fixation time. Individual amino acid components in the fresh and the fixed arteries were assayed using a Beckman amino acid analyzer to determine the degree of tanning. The denaturation temperature (Td) was also measured on each sample. Since the denaturation temperature is a direct indication of cross-linking of individual amino acids with the fixative, the difference in the degree of tanning for the same increase in Td may be indicative of the quantity of the masked, non-cross-linked amino acids. The fixation reaction data indicated that not all amino acids were cross-linked upon contacting the PC fixative. Masking appeared to be more substantial with a fixation at higher pH values.     

Ring-Fluorinated Analog of Methyl Eugenol: Attractiveness to and Metabolism in the Oriental Fruit Fly, <Emphasis Type="Italic">Bactrocera Dorsalis</Emphasis> (Hendel)

Oriental fruit fly, Bactrocera dorsalis (Hendel), males are highly attracted to the natural phenylpropanoid methyl eugenol (ME). They compulsively feed on ME and metabolize it to ring and side-chain hydroxylated compounds that have both pheromonal and allomonal functions. Side-chain metabolic activation of ME leading to (E)-coniferyl alcohol has long been recognized as a primary reason for hepatocarcinogenicity of this compound in rodents. Earlier, we demonstrated that introduction of a fluorine atom at the terminal carbon of the ME side chain significantly depressed metabolism and specifically reduced formation of coniferyl alcohol but had little effect on field attractiveness to B. dorsalis. In the current paper, we demonstrate that fluorination of ME at the 4 position of the aromatic ring blocks metabolic ring-hydroxylation but overall enhances side-chain metabolism by increasing production of fluorinated (E)-coniferyl alcohol. In laboratory experiments, oriental fruit fly males were attracted to and readily consumed 1,2-dimethoxy-4-fluoro-5-(2-propenyl)benzene (I) at rates similar to ME but metabolized it faster. Flies that consumed the fluorine analog were as healthy post feeding as ones fed on methyl eugenol. In field trials, the fluorine analog I was ∼50% less attractive to male B. dorsalis than ME.

Nanostructured quaternary Ni1-xCuxFe2-yCeyO4 complex system: Cerium content and copper substitution dependence of cation distribution and magnetic-electric properties in spinel ferrites

Quaternary Ni_1-xCu_xFe_2-yCe_yO₄ complex nano-ferrites system with different cerium content ratio and copper substitution degree were synthesized via co-precipitation wet chemical technique. The newly obtained nanoparticles, with general formula Ni_1-xCu_xFe_2-yCe_yO₄ (where x = 0.0, 0.3, 0.6 and y = 0.00, 0.03, 0.05, 0.08 and 0.10) were heated up to 600 °C to stabilize the specific crystalline spinel structure. The limit of cerium content was quantitively determined to be around 0.08 and up to 0.10. Furthermore, the powders were pelletized in a 13 mm wide pellets and thermally treated at 950 °C. The thermal treatment affected even more the phases segregation process, as CeO₂ was identified in the sample with lowest degree of cerium insertion – 0.03. Also, a difference in color and size of pelletized samples was noticed after the 950 °C thermal treatment. The Rietveld refinement, crystal structure confirmation, morphology magnetic and electrical properties of samples have been deeply studied. The cation distribution carried out from Rietveld refinement confirms the occupancy of (Fe³⁺) on tetrahedral sites and [Ni²⁺], [Cu²⁺], [Fe³⁺] and [Ce²⁺] on octahedral sites in the crystal lattice. Preliminary information regarding the cation distribution in spinel structures were suggested by FTIR spectral results, precisely in the 650-520 cm^?1 region, as a consequence of peak shape and lack of shiftiness of M^Td – O bond. Spherical-shaped quaternary nano-ferrites of 17–28 nm were determined from FE-SEM analysis and the samples composition was confirmed by EDX analysis. Hysteresis loops shows modifications in coercivity, magnetization and magnetic remanence with Ni²⁺ and Cu²⁺ ions doping in Ni_1-xCu_xFe_2-yCe_yO₄ complex systems with typical ferrimagnetic behavior. Dielectric measurements were employed in order to determine the electrical permittivity, dielectric losses and conductivity values in a 10 Hz – 1 MHz frequency range.     

A centre–free approach for resource allocation with lower bounds

Since complexity and scale of systems are continuously increasing, there is a growing interest in developing distributed algorithms that are capable to address information constraints, specially for solving optimisation and decision-making problems. In this paper, we propose a novel method to solve distributed resource allocation problems that include lower bound constraints. The optimisation process is carried out by a set of agents that use a communication network to coordinate their decisions. Convergence and optimality of the method are guaranteed under some mild assumptions related to the convexity of the problem and the connectivity of the underlying graph. Finally, we compare our approach with other techniques reported in the literature, and we present some engineering applications.