Scielo RSS <![CDATA[Journal of applied research and technology]]> vol. 14 num. 1 lang. pt <![CDATA[SciELO Logo]]> <![CDATA[Chemical sensor network for pH monitoring]]> Monitoring of water sources is a major concern worldwide. Wireless sensor networks (WSN) may be used for this monitoring. However, current systems employ mainly physical sensors for variables such as temperature, pressure, humidity and light. Wireless chemical sensors networks (WCSNs) for environmental monitoring are scarce due to the lack of autonomy of conventional sensors. This paper presents results of a WCSN for monitoring pH based on ion selective field effect transistors (ISFETs). Sensing nodes employ a human interface required for in situ calibration of chemical sensors. Unlike most studies, our work evaluates the network employing chemical measurements and wireless network metrics. Results show zero packet losses by using a time division multiple access (TDMA) protocol. The network allows wireless communication within 300 m including attenuation from buildings and trees. Therefore, the system presented in this paper is suitable for long range applications with unobstructed line of sight. pH measurements present a standard deviation below 1%, showing high repeatability. When compared to a commercial pH meter, difference in measurements is below 5%. As a consequence, accuracy is adequate for the application. Measurements also presented high stability during 3 h of continuous measurement. <![CDATA[An integrated study of the workspace and singularity for a Schönflies parallel manipulator]]> This paper presents a simple and systematic approach to formulate the inverse position problem of a Schönflies parallel manipulator. As a result, 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. <![CDATA[2-Imino-(3,4-dimethoxybenzyl) ethanesulfonic acid Schiff base anchored silver nanocomplex mediated by sugarcane juice and their antibacterial activities]]> In this present investigation, 2-imino-(3,4-dimethoxybenzyl)ethane sulphonic acid was anchored on a silver nanoparticle mediated by sugarcane sap. The Schiff base was synthesized from 2-aminoethanesulphonic acid and 3,4-dimethoxybenzaldehyde under lemon juice catalyzed conditions while the nanoparticles were obtained by careful stirring of sugarcane sap and 1 mM AgNO3 in the ratio of 1:10 respectively at room temperature. The resulting nanocomplex was formed by gentle heating and stirring of the silver nanoparticles solution and the ligand at a temperature of about 80 °C for 3 h. The ligand, nanoparticles and nanocomplex were characterized using UV-vis spectrophotometer, scanning electron microscope, FT-IR and XRD machines. From the UV-vis results, surface plasmon bands (SPBs) were observed at 475 nm for the nanoparticle within 1 h of the reaction and 450 nm for the nanocomplex. The ligand exhibited absorption bands at 310 nm, 280 nm and 230 nm which are due to π-electron transitions within the chromophores. The strikingly broad nature of the SPBs especially in the nanoparticles revealed that the particles are kinetically favored, nucleate easily and are polydispersed and the blue shift observed in the nanocomplex suggested further reduction in the particle size therefore giving us a clue on how to tailor the products by tuning the raw materials. From the scanning electron micrographs, the morphologies and growth mechanisms revealed oriented attachment for the nanoparticles onwards digestive ripening for the nanocomplex. All the synthesized materials proved to be potential antibacterial agents as they showed great inhibition to the growth of some bacterial strains with the activity enhanced in the nanocomplex. <![CDATA[Effect of tempering time on the ballistic performance of a high strength armour steel]]> The investigation describes and analyses the effect of tempering time on the mechanical and ballistic performance of a high strength armour steel. 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 in tempering time, whereas ductility and Charpy impact values are found to be decreasing. Ballistic performance of the samples are evaluated by impacting 7.62 mm and 12.7 mm armour piercing projectiles at 0° angle of impact. Results show a small variation in the ballistic performance when impacted with 7.62 mm armour piercing projectile. A decrease in ballistic performance of the material is observed with increasing tempering time when impacted with 12.7 mm armour piercing ammunition. <![CDATA[Microstructure of polyacrylonitrile-based activated carbon fibers prepared from solvent-free coagulation process]]> Polyacrylonitrile precursor fibers prepared using a solvent-free coagulation process were stabilized, carbonized, and physically activated by carbon dioxide into activated carbon fibers (ACFs). The activation temperature varied from 600 to 900 °C while the activation time was 1 h. Atomic force microscopy was used to observe the surface morphology, as well as the surface roughness of the ACFs. Higher pyrolysis temperature formed rougher surfaces, and increased the pore sizes. Meanwhile, Fourier transform infrared spectroscopy revealed more conversion of oxygen containing functional groups to carbonaceous materials as the activation temperature increased. Moreover, the microstructure properties were thoroughly characterized by the X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) studies. XRD analysis showed that the activation of the ACFs shrank the ordered structure, reducing the D-spacing from 0.358 to 0.347 nm for the fibers prepared at activation temperatures of 600 to 900 °C. Meanwhile, XPS analysis concluded that that the oxygen containing functional groups were still retained even at high activation temperatures while the nitrogen containing functional groups were reduced during the high temperature activation in the CO2 atmosphere. <![CDATA[Stability of a ring of coupled van der Pol oscillators with non-uniform distribution of the coupling parameter]]> The stability of a ring of coupled van der Pol oscillators is studied in this work considering a non-uniform distribution of the coupling parameter along the ring. The stability analysis is based on the transformation of the linearized equation of the ring into a canonical Hill equation. A stability condition is derived considering the stability of the non-periodic term of the Hill equation. Stable and unstable dynamic behavior of the ring is studied by means of numerical simulations. <![CDATA[Design partitioning and layer assignment for 3D integrated circuits using tabu search and simulated annealing]]> 3D integrated circuits (3D-ICs) is an emerging technology with lots of potential. 3D-ICs enjoy small footprint area and vertical interconnections between 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 has a significant importance as its outcome will influence the performance of subsequent steps. Like other partitioning problems this one is also an NP-hard. The approach taken to address this critical task is the application of iterative heuristics (Sait &amp; Youssef, 1999), as they have been proven to be of great value when it comes to handling such problems. Many aspects have been taken into consideration when attempting to solve this problem. These factors include layer assignment, location of I/O terminals, TSV minimization, and area balancing. Tabu Search and Simulated Annealing are employed and engineered to tackle this task. Results on well-known benchmarks show that both these techniques produce high quality solutions. The average percentage of the area deviation between layers is around 2.4% and the total number of required TSVs is reduced. <![CDATA[Physico-chemical characterization of collagen scaffolds for tissue engineering]]> The objective was to research the physical and chemical properties of collagen scaffolds (CS) obtained from bone matrix Nukbone(r) subject to a demineralization process using hydrochloric acid. The CS samples were characterized by optical and scanning electron microscopy, elemental chemical analysis, X-ray diffraction, spectroscopy Infrared, thermal analysis, differential scanning calorimetry and nitrogen adsorption. The microanalysis were used to set the macro- and microstructures of CS. They showed that the CS retained the morphology of Nukbone(r) with interconnected pores and their size between 100 and 500 μm, and it is composed of 20% by weight of HA and the rest is collagen type I. By infrared spectroscopy the functional groups of collagen type I (amide A - 3285, B - 2917, I - 1633, II - 1553 and III - 1239 cm−1) were identified. By thermal analysis it was determined that the phenomenon of denaturation of the collagen type I began in the range of 75-85 °C and burned above 200 °C.