Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

A low complexity digital hearing aid is designed using a set of subband filters, for various audiograms. It is important for the device to be made of simple hardware, so that the device becomes less bulky. Hence, a low complexity design of reconfigurable filter is proposed in this paper. The tunable filter structure is designed using Farrow based variable bandwidth filter. The coefficients of the filter are expressed in canonic signed digit format. The performance can be enhanced using optimization algorithm. Here, we have explored the strength of hybrid evolutionary algorithms and compared their various combinations to select a proper coefficient representation for the Farrow based filter, which results in low complexity implementation.

The investigation describes and analyses the effect of tempering time on the mechanical and ballistic performance of a high strength armoursteel. The steel is subjected to tempering at 300◦C for 2, 24 and 48 h. A marginal variation in strength and hardness is observed with increase intempering time, whereas ductility and Charpy impact values are found to be decreasing. Ballistic performance of the samples are evaluated byimpacting 7.62 mm and 12.7 mm armour piercing projectiles at 0◦angle of impact. Results show a small variation in the ballistic performancewhen impacted with 7.62 mm armour piercing projectile. A decrease in ballistic performance of the material is observed with increasing temperingtime when impacted with 12.7 mm armour piercing ammunition.

This paper presents a simple and systematic approach to formulate the inverse position problem of a Schönflies parallel manipulator. As aresult, the inverse position problem is solved in closed form and leads directly to the automatic generation of the workspace of the manipulator.Additionally, a systematic velocity analysis is also presented, which allows to detect and characterize all the singularities related to this manipulator.

3D integrated circuits (3D-ICs) is an emerging technology with lots of potential. 3D-ICs enjoy small footprint area and vertical interconnectionsbetween different dies which allow shorter wirelength among gates. Hence, they exhibit both lesser interconnect delays and power consumption.The design flow of 3D integrated circuits consists of many steps, the first of which is the 3D Partitioning and Layer Assignment. This step hasa significant importance as its outcome will influence the performance of subsequent steps. Like other partitioning problems this one is also anNP-hard. The approach taken to address this critical task is the application of iterative heuristics (Sait & Youssef, 1999), as they have been provento be of great value when it comes to handling such problems. Many aspects have been taken into consideration when attempting to solve thisproblem. These factors include layer assignment, location of I/O terminals, TSV minimization, and area balancing. Tabu Search and SimulatedAnnealing are employed and engineered to tackle this task. Results on well-known benchmarks show that both these techniques produce highquality solutions. The average percentage of the area deviation between layers is around 2.4% and the total number of required TSVs is reduced.

Polyacrylonitrile precursor fibers prepared using a solvent-free coagulation process were stabilized, carbonized, and physically activated bycarbon dioxide into activated carbon fibers (ACFs). The activation temperature varied from 600 to 900◦C while the activation time was 1 h. Atomicforce microscopy was used to observe the surface morphology, as well as the surface roughness of the ACFs. Higher pyrolysis temperature formedrougher surfaces, and increased the pore sizes. Meanwhile, Fourier transform infrared spectroscopy revealed more conversion of oxygen containingfunctional groups to carbonaceous materials as the activation temperature increased. Moreover, the microstructure properties were thoroughlycharacterized by the X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) studies. XRD analysis showed that the activationof the ACFs shrank the ordered structure, reducing the D-spacing from 0.358 to 0.347 nm for the fibers prepared at activation temperatures of600 to 900◦C. Meanwhile, XPS analysis concluded that that the oxygen containing functional groups were still retained even at high activationtemperatures while the nitrogen containing functional groups were reduced during the high temperature activation in the CO<sup>2</sup> atmosphere.

The objective was to research the physical and chemical properties of collagen scaffolds (CS) obtained from bone matrix Nukbone® subject toa demineralization process using hydrochloric acid. The CS samples were characterized by optical and scanning electron microscopy, elementalchemical analysis, X-ray diffraction, spectroscopy Infrared, thermal analysis, differential scanning calorimetry and nitrogen adsorption. Themicroanalysis were used to set the macro- and microstructures of CS. They showed that the CS retained the morphology of Nukbone® withinterconnected pores and their size between 100 and 500

The stability of a ring of coupled van der Pol oscillators is studied in this work considering a non-uniform distribution of the coupling parameteralong the ring. The stability analysis is based on the transformation of the linearized equation of the ring into a canonical Hill equation. A stabilitycondition is derived considering the stability of the non-periodic term of the Hill equation. Stable and unstable dynamic behavior of the ring isstudied by means of numerical simulations.

In Cuba, there are 315 species of Orchidaceae family, approximately 32 % of these species are endemic. During 2012 and 2013 an endemic population of Tetramicra malpighiarum (Orchidaceae) was studied at the Desembarco del Granma National Park, Cuba. We determined the abundance of this species, life classes (immature and adult), phorophytes inhabited, vertical distribution (trunk, branches or twigs), solitary or aggregated growing, and its cardinal orientation on phorophytes. We found 254 individuals of T. malpighiarum distributed in 20 phorophytes. For the first time, were found individuals of T. malpighiarum grew on other five species of phorophytes, besides of Malpighia incana (Malpighiaceae) and Erythroxylum havanense (Erythroxylaceae). Of the total of individuals recorded, 69.3 % were adult and 93.7 % were growing on the twigs. The number of solitary individual and aggregated individuals was similar. The population shows a slight tendency to grow toward south and northwest orientations. This is the first study to describe the population ecology of T. malpighiarum, but it is recommended to conduct long-term genetic and demographic studies. These future studies should be explored the reproductive system (e.g., level of endogamy) and population genetic of this species endemic of Cuba in order to evaluate its permanency in the future. 

In Epidendrum, considered a monophyletic genus, diverse groups can be recognized by their similar vegetative and floral characteristics. The revision of one of these groups, the macrostachyum group, recognized by the monopodial habit, with sub-apical branching, apical, erect inflorescence, non-resupinate, fleshy flowers, and entire lip, embracing the column, pubescent at least at the base, has led to the description of several new species, including a new species from Colombia that is here described and illustrated. The species is similar to Epidendrum microrigidiflorum Hágsater, but differs in the inflorescence (distichous, 6 flowered vs. racemose, 8-16 flowered), the shape (trullate vs. widely rhombic) and ornamentation of the lip (sericeous vs. minutely papillose), and the lack of calli on the disc of the lip (ecallose vs. bicallose). In addition, a key to the 41 species of the group is provided. 

Seed morphometric characters of four Colombian Vanilla species (Vanilla odorata, Vanilla calyculata, Vanilla oroana and Vanilla rivasii) were compared by using both light and electron microscopy. Seeds collected from mature fruits were studied by optical microscopy to characterize coat color, length and width of seeds in Vanilla species. Scanning electron microscopy (SEM) was used to characterize the seed surface and cell shape in these species. There were significant differences in length, width and length/width ratio. Vanilla oronana had the largest seeds (431 ± 17 μm long and 312 ± 27 μm wide) and differed from the other species by its dark brown seed coat and the presence of protrusions. Vanilla odorata was the species with smallest seeds (310 ± 15 μm long and 222 ± 18 μm wide) and light brown seed coat. Seeds of all studied species had smooth coat surfaces and were of oval to ellipsoid in shape. The characters evaluated in this work could serve as taxonomic diagnostic markers in Vanilla and these could explain important aspects of the seed biology of this genus.