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This work describes the design and implementation of the CO2 meter, operated with the PIC18F45K50 microcontroller; which detects the concentration of the gas in parts per thousand (ppm); also, this instrument has an-App downloaded on a mobile device with Android operating system, communicating with the microcontroller via Bluetooth. This to measure the concentration of CO2 which is a colorless gas compound of carbon and oxygen. The measurement of CO2 concentration is a strategy that can warn of the risk of COVID-19 contagion in an enclosed place where a group of people are gathered. In the return to classroom, because the risk of contagion by COVID-19, which is spread through CO2, persists. Also, there are very crowded places due to the daily activities developed by the human being, so now it is not a luxury to take care of the air we breathe to have a healthy life.

In the present report, a two dimensional (2D) model was developed to describe the fluid dynamics, heat and mass transfer of a Chemical Vapor Deposition activated by a Hot Filament (HFCVD) reactor, as well as the chemical generation of the precursor species which are present in the growth of non-stoichiometric silicon rich oxide (SRO) films. The SRO is known for have excellent photo luminescent properties which are useful in optoelectronic applications. This material can be obtained by the HFCVD technique which offers important advantages such as the easily to obtain thin films with diverse structural, compositional and optical characteristics. During deposition is a priority to control key parameters as inlet flow, substrate temperature and pressure so it compels to know previous theoretical information about these parameters which can be obtained by computational simulation. Therefore, by means of commercial Computational Fluid Dynamics (CFD) were solved the continuity, momentum and energy equations in steady state. Also, a thermodynamic equilibrium study of the SiO2(s) + H2 (g) reaction was carried out with the Factsage software. The thermodynamic equilibrium results provide the main chemical species which are present during the deposit process of the SRO films. The 2D model was used to simulate the temperature and velocity distribution of the hydrogen in the deposit process. The theoretical calculated temperatures were compared with those obtained experimentally by thermocouple measurements. From the simulation results, the temperature and gas velocity profiles were obtained at different hydrogen flow levels (50, 75, 100 sccm) and temperature source-substrate distances (5, 6 and 7mm) for a 50 sccm level. SEM micrographs and profilometry measurements disclose that the outlet configuration affects substantially both the thickness and surface uniformity of the SRO films. This parameter was modified to obtain a better quality (thickness and uniformity) and a large deposit area.

In this work, the presence of photoconduction and photovoltaic effects in MOS-type structures manufactured using off-stoichiometric silicon oxide (SiOx) deposited by HFCVD technique is reported. Current-voltage measurements under dark and illumination conditions were carried out. A photoconductive response of 1µA was found under illumination conditions, such current is about 4 orders of magnitude greater than its value in dark condition which was about 100pA. The reported MOS-type structures with SiOx as dielectric layer undergo a change in the charge conduction mechanisms of the injection current, exhibiting a transition from the Hopping to Schottky mechanism, which is dependent on the hydrogen amount and the deposition parameters of SiOx films. A starting charge conduction state identified as the Space Charge Limited Conduction mechanism (SCLC) is found when applying low voltages. Additionally, the photovoltaic effect was obtained and studied for these types of structures, being corroborated by current-time and voltage-time measurements in dark and illuminations conditions without applied bias. The spectral response and quantum efficiencies were also obtained, where the best internal quantum efficiency was 25.59%. The photoconductive effect is present for structures with SiOx films without annealing, while the ones with SiOx films that have thermal annealing exhibit the photovoltaic effect. The studied structures are suitable for photovoltaic applications and they have additional advantages namely: a short time of deposit (3 min) by using the HFCVD technique, and a single MOS-type structure.

This work is focused on making a correlation between results obtained by using spectroscopy and microscopy techniques from single and twofold-layer Silicon-Rich Oxide (SRO) films. SRO films single-layer and twofold-layer characterizations were compared considering the conditions as-grown and with thermal treatment at 1100 &deg, C for 60 min in a nitrogen atmosphere. The thickness of the single-layer film is 324.7 nm while for the twofold-layer film it is 613.2 nm, after heat-treated, both thicknesses decreased until 28.8 nm. X-ray Photoelectron Spectroscopy shows changes in the excess-silicon in single-layer SRO films, with 10% in as-grown films and decreases to 5% for the heat-treated films. Fourier Transform Infrared Spectroscopy (FTIR) exhibits three characteristic vibrational modes of SiO2, as well as, the vibrating modes associated with the Si-H bonds, which disappear after the heat treatment. With UV&ndash, Vis spectroscopy results we obtained the absorbance and the absorption coefficient for the SRO films in order to calculate the optical bandgap energy (Egopt), which increased with heat-treatment. The energy peaks of the photoluminescence spectra were used to calculate the silicon nanocrystal size, obtaining thus an average size of 1.89 &plusmn, 0.32 nm for the as-grown layer, decreasing the size to 1.64 &plusmn, 0.01 nm with the thermal treatment. On the other hand, scanning electron microscopy and high-resolution transmission electron microscopy images confirm the thickness of the twofold-layer SRO films as 628 nm for the as-grown layer and 540 nm for the layer with heat-treatment, and the silicon nanocrystal size of 2.3 &plusmn, 0.6 nm for the films with thermal treatment.

Feature selection has as principal goal to nd a representa- tive space of minimal size from original set of larger size. Several research works have been developed on this problem. This paper presents Support Vector Machine-Recursive Feature Elimination (SVM-RFE), Genetic Al- gorithms (GA), and Dierential Evolution (DE) algorithms for feature selection from a database of an Electric Arc Furnace (EAF) for locating variables related to energy consumption. The proposal suggests merging the coecients generated by LDA and SVM, employing them in RFE to obtain the ranks for each discriminant variables. The measure of accuracy and error rate for each algorithm is presented like a decisive score for choosing the subset obtained by the algorithm with the best performance. The variables selected were adjusted for the EAF control system achieving the reduction of the energy consumption to 3.5% in a steel castings and 1 minute reduction of the connected EAF in a steel casting.