Preparation of high pure α-Al2O3 nanoparticles at low temperatures using Pechini method

A Pechini process was successfully used to synthesize alpha-alumina (98.95% mass fraction) at relatively low calcination temperature (925 °C). The synthesis of these nanoparticles was carried out using a polymer prepared from citric acid and ethylene glycol by the melt blending method. This polymer worked as a chelating agent for aluminum cations. The final products were produced after a dual-stages thermal treatment. The resulting α-alumina consisted of nanoparticles of 8–16 nm in diameters with a surface area (～8 m² g^?1). The mass fraction of α-alumina was dependent on the concentration of aluminum salt and polymer precursor's solutions, while the surface area of the final product was dependent on the mass fraction of θ-alumina.     

Service based communication for MPSoC platform-SegBus

MPSoC platforms offer solutions to deal with communication limitations for multiple cores on single chip, but many new issues arise within the context. The SegBus platform is one of the solutions for application deployment on multi-core applications. There are many applications where identical data is transferred from the same source towards different destinations. Multicast services may come as a performance improving factor for the interconnection platform, together with interrupt service.In this paper, the task is to analyze, how different services can be designed for the SegBus platform and observe the improvement in system performance. The designer can select the services according to the requirements. The running example is represented by the H.264 encoder. The SegBus platform architecture, the communication mechanism, the allocation of processing elements on the platform, the communication services and their implementation are the main topics elaborated here.     

Microstructural evolution during friction surfacing of tool steel H13

Coatings of AISI H13 tool steel were made on low carbon steel by friction surfacing. Detailed microstructural studies and microhardness tests were carried out on the coatings. Studies revealed defect-free coatings and sound metallurgical bonding between the coating and the substrate. In addition, mechanical interlocking on a very fine scale was observed to occur between the coating and the substrate. Coatings exhibited martensitic microstructure with fine grain size and with no carbide particles. Coatings in as-deposited condition showed very high hardness (58 HRC) compared to the mechtrode material in annealed condition (20 HRC). Based on these findings, microstructural evolution during friction surfacing of H13 tool steel is discussed. The current work shows that friction surfaced tool steel coatings are suitable for use in as-deposited condition. Further improvements in coating microstructure and properties are possible with appropriate post-surfacing heat treatment.     

Stress Generated on Aluminum During Anodization as a Function of Current Density and pH

Anodic oxidation is accompanied by stressgeneration during the growth of the oxide. The presentstudy focuses on the stress-generation mechanism onaluminum as a function of the applied current density in acidic solutions of sulfuric acid ofdifferent strengths giving variable pH. Abeam-deflection technique was utilized for thedetermination of the magnitude and direction of stressesgenerated during the anodic oxidation process. Generally,thickness of the oxide determines whether the stress iscompressive or tensile in nature. The results have beeninterpreted in terms of the formation and annihilation of anion (O^2-) and cation(Al³⁺) vacancies. A reduction in thealuminum-ion vacancy concentration (V Al ³ ) results in a compressive stressdeflection, whereas tensile-stress deflection isintroduced by an increase in the oxygen vacancy(Vo²⁺) concentration. The mechanism isfurther elucidated by current-density jump/dropexperiments. The results show that stress in this caseis affected by the dissolution of the oxide at the oxide-electrolyteinterface.     

Low-Temperature Preparation and Magnetic Properties of V-Doped SnO2 Nanoparticles

A solid solution of vanadium (V)-doped tin oxide (SnO₂) particles of average diameter 2 nm and V content of 19 at.% was prepared at normal pressure and low temperature (100°C) by mixing wet SnO₂ gel SnO₂· x H₂O with a boiling solution of vanadium oxide (V₂O₅). Experimental characterizations using X-ray, electron diffraction, and transmission electron microscope show evidence of a pure single phase. The nanoparticles exhibit a mixed magnetic behavior, namely paramagnetic and ferromagnetic. Their thermal stability is also investigated. At higher temperature, 850°C, some amount of Fe precipitates from the solid solution.     

Potentiality of daylighting in a maritime desert climate: the Eastern coast of Saudi Arabia

Energy savings from the utilization of daylight will be influenced by the amount of external daylight incident on the external surface of the window plane. Therefore, savings from daylight will vary from a place to another, based on the prevailing sky conditions in the climate concerned. This paper aims to investigate the potentiality of natural light if used a source of internal illuminance in buildings in the Eastern coast of Saudi Arabia. This includes providing information about daylight performance in the area.     

The experience of photologging: global mechanisms and local interactions

This paper describes an in-depth study of the photologging behaviour of a small group of women who are part of an active expatriate community. In addition to sharing with family and friends in their home country, the participants appropriated the photolog as part of local social interactions both with local friends and as part of their role in the local community. The photographs themselves sometimes resemble those of physical albums, but also include more candid, imperfect and apparently trivial topics. The participants report a subtle pattern of prospective anticipation of the impact of postings and retrospective reflection and discussion of others’ postings, linking posters and viewers of photologs in a rich unfolding web of interactions within an extended episodic experience.     

STUDY OF SOME UNIQUE FEATURES OF RATIO-DEPENDENT MODELS FOR PREDATOR-PREY-SUBSTRATE INTERACTIONS IN CONTINUOUS CULTURES

This article studies the dynamics of ratio-dependent models for continuous bioreactors involving interactions between predator, prey, and a limiting substrate. Ratio-dependent models, for which the growth rate of predator is a function of the ratio of prey to predator abundance, have recently received growing attention and were shown to exhibit more interesting behavior than the classical (strictly) prey-dependent models. It is shown that in addition to predicting areas of predator washout and areas of total washout, the studied examples of ratio-dependent models predict areas for which the species coexist either at steady state or in oscillatory mode for any initial population values. The studied models also predict a unique feature for which the interacting species can coexist or wash out depending on their initial values. The objective of this article is to study in some detail this interesting behavior that makes ratio-dependent models better candidates in predicting predator-prey interactions in real biological life.     

Effect of Filler Composition on the Brazing of Alumina to Copper Using Ultrasonic Wave

An ultrasonic wave was applied during brazing of alumina to Cu. First alumina was metallized by applying ultrasonicwave in braze bath. Then the metallized alumina was brazed with Cu using the same filler alloy. The filler used wereZn-Al alloys and Zn-Sn A     

Different starting times of alpha-tocopherol and gamma-tocotrienol supplementation and tumor marker enzyme activities in the rat chemically induced with cancer

1. alpha-Tocopherol (alpha-T) and gamma-tocotrienol (gamma-T) were supplemented continuously for 8 weeks in the diets of normal rats and rats chemically induced with cancer using diethylnitrosamine (DEN), 2-acetylaminofluorene (AAF) and partial hepatectomy. Hepatocarcinogenesis was followed by determining the plasma gamma-glutamyl-transpeptidase (GGT) and alkaline phosphatase (ALP) activities as well as placental glutathione S-transferase (PGST) and GGT activities histochemically, at 4-week intervals. 2. Male Rattus norvegicus were supplemented alpha-T and gamma-T at two different doses of 30 and 300 mg/kg diet. The supplementation was started at three different times: simultaneously with DEN administration; 4 weeks; and 8 weeks after DEN administration. 3. Elevation of plasma GGT activities and formation of PGST and GGT positive foci were attenuated significantly (P < 0.05) when alpha-T and gamma-T were supplemented simultaneously with cancer induction. Supplementation begun 4 and 8 weeks after cancer induction did not affect plasma enzyme activities and formation of enzyme-positive foci. 4. alpha-T was more effective than gamma-T, and a lower dose of 30 mg/kg was found to be more effective in reducing the severity of hepatocarcinogenesis.