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Paso de la Mina 3ra. Sección, Mexico

Flores-Garcia E.,CENIDET | Ponce-Silva M.,CENIDET | Vela Luis.G.,CENIDET | Juarez M.A.,CENIDET | Araujo I.,Seccion de Estudios de Posgrado
2010 IEEE Energy Conversion Congress and Exposition, ECCE 2010 - Proceedings | Year: 2010

In this paper a simple method to design and improve the performance of high frequency self-oscillating electronic ballasts is presented. The proposed method is based on the describing function method and allows minimizing the parasitic elements effects presented above 200 kHz by considering the gate-source parasitic capacitance of power Mosfets and the switching delay times. its main advantage is a better operating frequency approximation and hence a better performance of the ballast. Experimental results of the proposed method are compared against a conventional method in a frequency range of 200 kHz to 2 MHz, showing the feasibility of the proposed method. © 2010 IEEE.

Balderas U.,Seccion de Estudios de Posgrado | Falcony C.,CINVESTAV | Moggio I.,Research Center en Quimica Aplicada | Arias E.,Research Center en Quimica Aplicada | Mondragon M.,Seccion de Estudios de Posgrado
Polymer (United Kingdom) | Year: 2013

Flat ribbon-like electrospun fibers of poly(9-vinylcarbazole) (PVK)/Poly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) with thickness ranging from 2 to 6 μm were prepared by electrospinning. The blue emission of the PVK fibers changed to greenish-yellow, with incorporation of MEH-PPV up to 13 wt% content. By analyzing the photoluminescence spectra, we found a significant blue shift of the MEH-PPV emission band in the blend fibers evidencing that PVK prevents aggregation in the MEH-PPV, suppressing the formation of interchain interactions. The morphologies of the blend fibers characterized by TEM, corroborates that multiple coalescing MEH-PPV droplets merge together as PVK content decreases. Compared with PVK/MEH-PPV spin-cast films, blend nanofibers exhibited a more efficient energy transfer due to effective interfacial interactions between PVK and MEH-PPV, at low MEH-PPV content. Our results showed that by using this electrostatic processing method, photophysical properties of light-emitting fibers prepared from polymer blends can be tuned. © 2013 Elsevier Ltd. All rights reserved.

Mondragon M.,Seccion de Estudios de Posgrado | Balderas J.U.,Seccion de Estudios de Posgrado | Jimenez G.L.,Seccion de Estudios de Posgrado | Falcony C.,CINVESTAV
Organic Electronics: physics, materials, applications | Year: 2014

Solution polymer blends of a high molecular weight and a low molecular weight poly(9-vinyl carbazole) PVK with poly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV), at a fixed blend ratio of 95.5:0.5, were processed via electrospraying and electrospinning. SEM studies revealed that electrosprayed particles were produced when low molecular weight PVK was used, while electrospun fibers were successfully obtained from solutions containing high molecular weight PVK, over a concentration range of 4-10% (w/v). From the absorption spectra of the neat polymers it was determined that Urbach energy Euincrease and optical band gap Egdecreases due to the physical defects along the main chain introduced by these electrostatic processing methods. Photoluminescence spectroscopy revealed a particular applied voltage, which depends on concentration and molecular weight, where aggregation of PVK levels off. Luminescence quenching of MEH-PPV is also observed to increase with applied voltage consistent with possible energy transfer from shorter conjugation length segments to nearby longer conjugated segments. The ratio of the intensity of the excitation spectra of the PVK (donor, both PVKLor PVKH) and the MEH-PPV (acceptor), ID/IA, exhibited minima at this particular voltage and then levels off, indicating not only maximum interpenetration and thus compatibility of both polymers but also maximum energy transfer. Hence, we demonstrate that compatibility and energy transfer can be optimized varying concentration and applied voltage during both electrospraying and electrospinning processes. © 2014 Elsevier B.V. All rights reserved.

Balderas J.-U.,CINVESTAV | Falcony C.,CINVESTAV | Jimenez G.-L.,Seccion de Estudios de Posgrado | Garzon A.-S.,Seccion de Estudios de Posgrado | Mondragon M.,Seccion de Estudios de Posgrado
Journal of Electronic Materials | Year: 2015

The morphology and photoluminescence properties of electrospun poly(9-vinylcarbazole) (PVK)/poly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) blend fibers, which were loaded with either halloysite clay nanotubes (HNTs) or an organically modified montmorillonite (OMMT) clay, were studied by scanning electron microscopy, transmission electron microscopy, and fluorescence spectroscopy. A concentration range of 0–30 wt.% was used for the clays, while the MEH-PPV concentration was fixed at 0.5 wt.%. Both clays, especially the OMMT clay, increased the phase separation of the components in the electrospun PVK/MEH-PPV blend fibers. This was attributed to their selective localization on the polymer phases. The HNTs and OMMT clay also increased energy transfer to the lowest energy states of MEH-PPV generated during electrospinning, and modified the amount of the partially overlapping conformation of carbazole groups (p-PVK) that constrained the aggregation of the PVK chains. These changes resulted in an increased emission from p-PVK, which varied depending on the type and concentration of the clay. © 2015, The Minerals, Metals & Materials Society.

Quintanar L.H.,Seccion de Estudios de Posgrado | Isakina S.S.,Seccion de Estudios de Posgrado | de la Rosa Vazquez J.M.,Seccion de Estudios de Posgrado
Revista Facultad de Ingenieria | Year: 2011

Photodynamic Therapy is a well know treatment based on light interaction with a photosensitizing drug, used in the treatment of certain diseases like cancer. In this issue, the development of asystem for superficial irradiation, which allows the application of Photodynamic Therapy at 630nm using a light emitting diode as a radiation source. It is proposed a control for the energy dose delivery in depth, which incorporates the calculations from a radiation distribution model. Also it is reported the construction and characterization of optical phantoms in aqueous suspensions, used for models verification and system performance testing.

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