Effect of Cu by Co substitution on Ca3Co4O9 thermoelectric ceramics

Ca₃Co_4?xCu_xO₉ polycrystalline thermoelectric ceramics with small amounts of Cu have been synthesized by the classical solid state method. X-ray diffraction data have shown that all the Cu has been incorporated into the Ca₃Co₄O₉ structure and no Cu-containing secondary phases have been produced. Apparent density measurements have shown that all samples are very similar, with densities around 75 % of the theoretical one. Electrical resistivity decreases when Cu content increases until x = 0.03 while Seebeck coefficient remains practically constant for all samples. The improvement in resistivity leads to higher power factor values than the obtained for the undoped samples.     

Enhancement effect on apparent viscosity of aqueous tragacanth gum dispersions promoted by sugars

Flow curves of aqueous dispersions of tragacanth gum (T) with sucrose and glucose at different temperatures were determined using a controlled‐stress rheometer. The effect of sodium chloride without or with sucrose (at the highest content) on the rheology of T dispersions was evaluated. The presence of sucrose and glucose promoted a noticeable enhancement impact on the apparent viscosity of aqueous T dispersions, which depended on sugar type/content, shear rate and temperature. In all cases, the glucose addition led to the largest enhanced viscosities at low shear rates (<10 s^?1) and temperature. The joint action of sugar and salt exhibited a notable effect on apparent viscosity at low shear rates, softening the strong shear‐thinning behaviour of T samples. Flow curves of T in the presence of sugars were satisfactorily described by the Cross‐Williamson model, being semi‐empirical correlations of the model parameters with ingredients content and temperature stablished.     

Thixoforging of 332 aluminum alloy in a mechanical eccentric press

Journal of Materials Science - This study sought to analyze the semi-solid behavior of commercial 332 aluminum alloy during thixoforming in a mechanical eccentric press (thixoforging). The...     

Chromatic interior environments for the elderly: A literature review

The impact of the physical environment on individuals has arisen as a growing body of research in population wellbeing. Yet, most of studies in this area do not focus on elderly even though they are particularly susceptible to the characteristics of their interior spaces. It is a well‐known fact that to be old is to acquire a tolerance of disabilities based on the gradual degeneration. A common problem is a dysfunction in visual sensitivity and accordingly, the alteration of their environmental color perception. That is why these impairments need to be understood in order to minimize the elderly spatial difficulties. To know at what point there is a loss in the ability to perceive color is necessary to understand how should we take these facts into consideration. A state‐of‐the‐art literature review of current studies from the last 20 years is carried out. The aim is to analyze existing practices on Evidence‐Based Research through a multidisciplinary approach in order to create knowledge about chromatic built environments for the elderly. Data are identified and considered together with empirical experience about color, perception, built environment and elderly. Thus, the way in which elderly perceive the space is explored. The adjustments in the formulation of these impairments throughout any design strategy to adapt the environment to their physiological changes are determined. This article aims to determine a design interpretation of the various findings, demonstrating that color, as a parameter of the visual performance, influences visual comfort and helps performance in architecture for old people.     

Processing and characterization of porous titanium for implants by using NaCl as space holder

Porous samples of commercially pure titanium (CP Ti) were fabricated by using sodium chloride (NaCl) as space-holder with percentages between 40 and 70 vol%. The dissolution of NaCl in distilled water, the structural integrity of samples and the reproducibility of the procedure were studied as a step prior to sintering. All these parameters were evaluated in terms of the compaction pressure, temperature and agitation of water, and dissolution time. The characterization of samples included density, porosity and dynamic Young's modulus. The results indicate that the most efficient lixiviation, according to the desired balance of properties, was by immersion in hot water, without agitation and for prolonged cycles of immersion time.     

A graph‐based postoptimization approach for covering arrays

Covering arrays (CAs) are combinatorial objects with interesting features that have practical applications such as experimental design and fault detection in hardware and software. We introduce a graph‐based postoptimization (GBPO) approach to reduce the size of CAs exploiting the redundancy in CAs previously constructed. To evidence the advantages of using GBPO, we have instantiated it with 2 sets of CAs: (1) 560 CAs of strength 2≤t≤6, alphabet 2≤v≤6, and parameters 3≤k≤32 generated by an optimized version of In‐Parameter‐Order‐Generalized (IPOG‐F) and GBPO improved all CAs, and 37 cases matched the best‐known upper bounds; and (2) 32 CAs of strength t=2, alphabet 3≤v≤6, and number of parameters 8≤k≤146; in this set, 16 cases were improved, and 16 cases were matched.     

Influence of the chloride ion concentration on the corrosion of high-purity Mg,ZE41 and AZ91 in buffered Hank’s solution

This research studied the influence of the chloride ion concentration on the corrosion behaviour of high-purity magnesium (Mg) and two Mg alloys in Hank’s solution, using hydrogen evolution and weight loss. A buffer based on CO₂ and NaHCO₃ was used to maintain the pH constant. The corrosion behaviour was governed by a partially protective surface film, and film breakdown by the chloride ions. The carbonated calcium phosphate layer that formed in Hank’s solution was important in determining the protective properties of the surface film.