A. Vera-Marquina

Annealing effect on structural, morphological, and optical behaviors of CBD-CdS nanostructured films for solar cells

In the current work, the effect of an annealing process on structural, morphological, and optical behaviors of cadmium sulfide thin films is presented. A chemical bath deposition method for cadmium sulfide deposition is based on the use of glycine as a complexing agent. Cadmium sulfide thin films were grown by chemical bath deposition and annealed in a nitrogen atmosphere at 0, 100, 150, 200, and 250 °C for 30 minutes. Crystallographic and morphological studies of CdS thin films were performed by scanning electron microscopy, X-ray photoelectron spectroscopy, atomic force microscopy, and X-ray diffraction. The optical behavior of CdS thin films was evaluated by UV-Visible spectroscopy and band gap values were calculated by approximation using a Tauc plot. After annealing, densified CdS films formed by nanostructured crystallites exhibit suitable band gap values and present relatively high transmittance in the visible region, allowing their application as a window material for solar cells.

Fabrication, characterization, and optimization of an ultraviolet silicon sensor

This work shows the design, fabrication, and optimization of a silicon sensor with an extended sensing range toward the UV region. The main characteristic of this detector is the enlargement of the common silicon detection range to the ultraviolet region (240 to 400 nm). The fabrication process of this detector is compatible with complementary metal oxide semiconductor (CMOS) silicon technology, which makes it cheaper than commercial UV detectors.

Microstructural and Optical Characterization of Single and Multilayers of ZnO for TFTs Active Layer

Polymeric particles loaded with biocompatible magnetic nanoparticles are promising platforms to perform therapy and diagnostic of diseases, acting as the so called theranostic agents. In this work, magnetite nanoparticles were synthesized by coprecipitation method and encapsulated with Polycaprolactone (PCL) and Poloxamer 188 polymers through the innovative Nano Spray Drying technique. X-Ray Diffraction and Infrared Spectroscopy confirmed that the formed particles are composed by PCL, Poloxamer and magnetite, with amount of magnetite determined as 3% by Thermogravimetric Analysis. Particles present a superparamagnetic-like behaviour at 300 K, having negligible coercivity. Dynamic Light Scattering and Scanning Electron Microscopy indicated that the hydrodynamic diameters are of 49 nm for magnetite nanoparticles and of approximately 600 nm for encapsulated particles, with aspect analogous to a “nanocookie” of a PCL/Poloxamer blend with magnetite nanoparticles embedded in it. Cytotoxicity assays presented IC 50 superior to 2.5 mg/mL for healthy cells and a higher viability of cancer cells in comparison to control, suggesting that the particles may have affinity for tumours, which can be useful for the intended biological applications.

Repulsive Function in Potential Field Based Control with Algorithm for Safer Avoidance

In this article, a collision avoidance scheme based on potential functions is proposed. The first part of the paper is intended to establish the equations of the dynamic model of the vehicle, potential attractive functions and nested saturation controller. In the second part, the repulsive scheme is developed. Along with the repulsive scheme, the controller constants are optimized, in order to perform a safer avoidance maneuver. The advantages of the proposed repulsive schemes compared with a conventional repulsive function are demonstrated by simulations.

Microstructural and optical characterizations of highly stable nanospheres of crystalline CdS via selective approach

A novel and selective approach to obtain highly stable and capping nanospheres of crystalline cadmium sulfide (CdS) via solution growth in cadmium nitrate tetrahydrate-thiourea-ligand-pH buffer systems using a Taguchi experimental design is presented. CdS characterization is carried out by laser diffraction particle size analyzer, X-ray diffraction, scanning electron microscope/energy dispersive X-ray spectroscopy, and UV-Vis absorption spectroscopy. Synthesized nanospheres of crystalline CdS with an average crystal particle diameter of 37.5 nm and a capping layer thickness of 17.7–35.7 nm (73 to 115 nm as capped nanoparticles) keep size and form stable in aqueous solution. These crystalline CdS nanospheres exhibit a 2.46 eV band gap, as well as, an optical bandwidth comprises in the visible range with potential applications in solar cells.

An Approach for Optimal Goal Position Assignment in Vehicle Formations

In this paper one methodology to solve the goal position assignment (GPA) problem is developed, this is, to assign the corresponding goal position (desired position) for a group of vehicles, knowing the initial positions and the established formation shape. By using this GPA methodology, it can be guaranteed that the formation will be reached in a minimum period of time and with lower collision risk compared with the other possible combinations of pairs “vehicles-goal position”. Hungarian algorithm was used as combinatorial optimization algorithm, which requires a cost matrix, therefore it is shown the way to compute the cost matrix to obtain the best GPA. In order to show the optimal behavior of the proposed cost matrix, three approaches of cost matrix were evaluated in simulations of quad-rotor formations. Also, the optimal behavior of the proposed GPA is proved with numerical values of some defined parameters to determine optimal performance. The formation control was based on potential functions, while the control law for each vehicle was based on nested saturation.

Synthesis and characterization of CBD-CdS nanospheres

Cadmium sulfide (CdS) nanospheres were successfully synthesized by chemical bath deposition (CBD) in the systems cadmium nitride tetrahydrate (Cd(NO₃)₂.4H₂O) - thiourea (NH₂CSNH₂) - complexing agent - pH buffer. An L₉ Taguchi experimental design was used with the purpose of determines the processing conditions to promote CdS nanospheres formation. For that reason, the processing parameters were varied at three levels, as follows: complexing agent (without complexing agent, glycine (NH₂CH₂COOH) and sodium citrate (Na₃C₆H₅O₇)), pH buffer (4 mL of borate, pH 11; 2 mL of ammonium hydroxide/ ammonium chloride, pH 10; and 2 mL of borate/pH 11), temperature (323.15, 338.15, and 353.15 K) and time (20, 30, and 40 minutes). Microstructural study was performed by SEM/EDS, XRD and laser particle size analyzer. According to characterization results, analysis of variance (ANOVA) and main effects, the processing conditions for CBD-CdS nanospheres synthesis are: cadmium nitride (Cd(NO₃)₂.4H₂O), thiourea (NH₂CSNH₂), glycine as complexing agent, and borate as buffer (2 mL) at 338.15 K for 40 minutes.

Optical NOR gate based on silicon technology

Abstract. An optoelectronic integrated device that carries out digital op-tical functions is designed in silicon technology. The device achieves theNOR gate, which has input and output optical signals, and is designed todetect and emit a 600-nm-wavelength light. The active detection area is1mm 2 , and it can achieve frequencies of the order of megahertz.

Practical application of a bidirectional microwave photonic filter: simultaneous transmission of analog TV signals

Abstract. A practical application of a bidirectional microwave photonic filter (MPF) to transmit simultaneous analog TV signals coded on microwave carriers is experimentally demonstrated. The frequency response of the bidirectional MPF is obtained by the interaction of an externally modulated multimode laser diode emitting at 1.55  μm associated to the free-spectral range of the optical source, the chromatic dispersion parameter of the optical fiber, as well as the length of the optical link. The filtered microwave bandpass window generated around 2 GHz is used as electrical carrier in order to simultaneously transmit TV signals of 67.25 and 61.25 MHz in both directions. The obtained signal-to-noise ratios for the transmitted signals of 67.25 and 61.25 MHz are 37.62 and 44.77 dB, respectively.

Experimental transmission of digital signals in a fiber-radio scheme under external modulation at 2.0 GHz

We report an experimental electro-optical external-modulated system that allow transmission of digital signals at a rate of 40MHz to 70MHz coded on a microwave band-pass window at 2.0GHz over a long-haul optical link using a scheme fiber-radio. Obtained results allow determining the use of this type of telecommunication systems for data distribution in optical links operating at microwave frequencies.