Showing papers by "Polytechnic University of Valencia published in 2022"

Fundamentals of Wireless Sensor Networks

Abstract: The continuous technological upgradations in the RF (radio frequency), processors, nanotechnology, and microelectromechanical systems (MEMS) domains have fostered the growth of wireless sensor networks (WSN), which in turn allowed to develop a wide range applications based on it, for instance, the technological breakthrough in the semiconductor industry stimulated to produce low-power, low-cost, and small-sized processors with high computational capacities. Speaking in more clear words, the miniaturization of sensing and computing devices enabled the development of tiny, low-cost, and low-power sensors, controllers, and actuators. Basically WSNs consist of a large number of tiny and low-cost sensor nodes that are networked via low-power wireless communication links. These networks allow to closely observe ambient environment of interest at an economical cost much lower than other possible technological solutions. Each sensor node in WSN has sensing, communication, and computation capabilities. By exploiting appropriate advanced mesh networking protocols, these nodes form a sea of connectivity that covers the physical environmental area under observation. In WSN the transmitting node opt out possible communication paths by hopping sensed data of interest from node to node toward its destination. Although the capability of single sensor node is minimal, the composition of hundreds or thousands of such nodes offers very high new technological possibilities for wide variety of applications. The power of WSN lies in the possibility of heavy deployment of large numbers of tiny nodes, which can assemble and configure on their own. Stating in simple words, these nodes have networking capability, which facilitates coordination, cooperation, and collaboration among them to meet the requirements of the underlying application. The WSN can also provide a robust service in hostile or inaccessible environments, wherein human intervention may be too dangerous or almost not possible. This new technology is exciting with unlimited potential for numerous application areas, including environmental, medical, military, transportation, entertainment, crisis management, disaster relief operations, homeland defense, and smart spaces. It is envisioned that in the near future the WSN will be an integral as well as essential aspect of our lives.

Dye removal from aqueous solution using nanocomposite synthesized from oxalic acid-modified agricultural solid waste and ZnFe2O4 nanoparticles

Abstract: Batch adsorption experiments were carried out to eliminating Congo red (CR) and methylene blue (MB) from aqueous solution using oxalic acid-modified jujube shells of Ziziphus lotus (OA-JS)/ZnFe2O4(OA-JS@ZnFe2O4) nanocomposite as a high efficient adsorbent. The Fourier transform infrared (FTIR), Brunauer Emmett Teller, thermogravimetric analysis–differential scanning calorimetry, scanning electron microscope, transition electron microscope, and X-ray diffraction techniques were used to characterize the OA-JS@ZnFe2O4. The equilibrium data fitted to Langmuir isotherm and the maximum adsorption capacities were determined as 980.39 mg g−1 and 476.18 mg g−1 for CR and MB, respectively. The pseudo-second-order model could be best described the sorption kinetics. The calculated thermodynamic suggests that the CR and MB adsorption on OA-JS@ZnFe2O4 is spontaneous and endothermic. The OA-JS@ZnFe2O4 recycled, and the removal CR and MB were 82.08% and 76.59% after seven cycles, respectively. The synthesis of OA-JS@ZnFe2O4 nanocomposite showed excellent potential adsorbent for dye removal from wastewaters.

Cu^II/Cu^I decorated N-doped carbonaceous electrocatalysts for the oxygen reduction reaction

Abstract: Copper- and nitrogen-doped carbonaceous materials, obtained by a simple synthetic procedure are highly efficient and fast catalysts for the oxygen reduction reaction. It is shown, that Cu( i ) containing materials perform with faster reaction kinetics.

Mapping methane plumes at very high spatial resolution with the WorldView-3 satellite

Abstract: Abstract. The detection of methane emissions from industrial activities can help enable effective climate change mitigation strategies. These industrial emissions, such as from oil and gas (O&amp;G) extraction and coal mining, typically occur as large plumes of highly concentrated gas. Different satellite missions have recently shown the potential to map such methane plumes from space. In this work, we report on the promising potential of the WorldView-3 (WV-3) satellite mission for methane mapping. This relies on its unique very high spatial resolution (up to 3.7 m) data in the shortwave infrared part of the spectrum, which is complemented by a good spectral sampling of the methane absorption feature at 2300 nm and a high signal to noise ratio. The proposed retrieval methodology is based on the calculation of methane concentration enhancements from pixel-wise estimates of methane transmittance at WV-3 SWIR band 7 (2235–2285 nm), which is positioned at a highly-sensitive methane absorption region. A sensitivity analysis based on end-to-end simulations has helped to understand retrieval errors and detection limits. The results have shown the good performance of WV-3 for methane mapping, especially over bright and homogeneous areas. The potential of WV-3 for methane mapping has been further tested with real data, which has led to the detection of 26 independent point emissions over different methane hotspot regions, such as O&amp;G extraction fields in Algeria and Turkmenistan, and the Shanxi coal mining region in China. In particular, the detection of very small leaks (< 100 kg h−1) from oil pipelines in Turkmenistan shows the unique capability of WV-3 for mapping industrial methane emissions from space. The mission includes pointing capabilities that allow for a daily revisit over these oil pipelines or other critical infrastructure.

NH3-SCR catalysts for heavy-duty diesel vehicles: Preparation of CHA-type zeolites with low-cost templates

Abstract: Computer-assistance allows selecting the most adequate low-cost organic structure directing agents (OSDAs) for the crystallization of Al-rich CHA-type zeolites. The host-guest stabilization energies of tetraethylammonium (TEA), methyltriethylammonium (MTEA) and dimethyldiethylammonium (DMDEA), in combination with Na, were first theoretically evaluated. This “ab-initio” analysis reveals that two TEA show a serious steric hindrance in a cha cavity, whereas two MTEA would present excellent host-guest confinements. The synthesis of Al-rich CHA-type zeolites has been accomplished using TEA and MTEA. Electron diffraction and high-resolution transmission electron microscopy reveal large CHA-domains with narrow faulted GME-domains in the CHA-type material synthesized with TEA, confirming the better OSDA-directing roles of MTEA cations towards the cha cavity, in good agreement with DFT calculations. Cu-exchanged Al-rich CHA-type samples achieved with MTEA and TEA show excellent catalytic activity and hydrothermal stability for the selective catalytic reduction (SCR) of NOx with ammonia under conditions relevant for future heavy duty diesel conditions.

A tetraazahydroxypyridinone derivative as inhibitor of apple juice enzymatic browning and oxidation

Abstract: Enzymatic browning in fruits and vegetables can produce undesirable colour changes and adversely affect the taste, flavour, and nutritional value. This fact poses a challenge to the food industry to apply appropriate inhibitors to control enzymatic browning to maintain food quality. Accordingly, this study aims to evaluate the effect of small mazamacrocyclic compounds modified with a hydroxypyridinone similar to kojic acid on enzymatic browning, total polyphenols and antioxidant activity in apple juice. The results showed how these compounds interact with the tyrosinase enzyme in a complex interaction inhibiting its activity. The hydroxypyridinone attached to the macrocycle (I1) was crucial to induce the greatest inhibition, being the most powerful inhibitor. The kinetic studies of I1 reveal mixed-type inhibition over tyrosinase with an IC50 of 0.30 mM, which was much higher than the calculated IC50 for I2 and I3. Furthermore, I1 at a concentration of 2.25 mM, significantly reduced the enzymatic browning in fresh apple juice by more than 50% after 1 h under stirring. Also, it completely stops the decrease in the total phenolic content and delays loss of antioxidant capacity during the first 30 min.

A tetraazahydroxypyridinone derivative as inhibitor of apple juice enzymatic browning and oxidation

Abstract: Enzymatic browning in fruits and vegetables can produce undesirable colour changes and adversely affect the taste, flavour, and nutritional value. This fact poses a challenge to the food industry to apply appropriate inhibitors to control enzymatic browning to maintain food quality. Accordingly, this study aims to evaluate the effect of small mazamacrocyclic compounds modified with a hydroxypyridinone similar to kojic acid on enzymatic browning, total polyphenols and antioxidant activity in apple juice. The results showed how these compounds interact with the tyrosinase enzyme in a complex interaction inhibiting its activity. The hydroxypyridinone attached to the macrocycle (I1) was crucial to induce the greatest inhibition, being the most powerful inhibitor. The kinetic studies of I1 reveal mixed-type inhibition over tyrosinase with an IC50 of 0.30 mM, which was much higher than the calculated IC50 for I2 and I3. Furthermore, I1 at a concentration of 2.25 mM, significantly reduced the enzymatic browning in fresh apple juice by more than 50% after 1 h under stirring. Also, it completely stops the decrease in the total phenolic content and delays loss of antioxidant capacity during the first 30 min.