Technical University Baja California

Mexicali, Mexico

Technical University Baja California

Mexicali, Mexico
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Nesheva D.,Bulgarian Academy of Science | Pantchev B.,Bulgarian Academy of Science | Nedev N.,Autonomous University of Baja California | Valdez B.,Autonomous University of Baja California | And 3 more authors.
Journal of Physics: Conference Series | Year: 2017

First results on resistive switching in SiOx film containing crystalline silicon nanoparticles are reported. SiOx layers (x = 1.15) with thickness of 50 nm were deposited on n-Si crystalline substrates and annealed for 60 min at 1000oC to grow crystalline nanoparticles. Part of the samples were annealed in an inert atmosphere, while the rest were subjected to a two-step (O2+N2/N2) annealing process. Current-voltage (I-V) characteristics were by applying positive or negative voltage to the top contact. For both types of samples the I-V characteristics were asymmetric with lower currents measured at negative voltage, especially in the case of two-step annealed samples. In most of the N2 annealed structures switching behavior high-low/low-high resistance state was observed in both polarities at voltages with amplitudes in the range (2 - 4) V. Uncontrolled switching low/high resistance was also seen, more frequently at positive voltages. In contrast, the two-step annealed samples showed stable behavior. The transition high-low resistance state was achieved by negative voltages in the (-2, -5) V range leading to an increase of the current by more than three orders of magnitude. The structures were reset to the high resistive state, by positive voltage in the range (3 - 4) V. Uncontrolled switching was not observed in the two-step annealed samples for both polarities and they showed higher reliability regarding the number of switching cycles. © Published under licence by IOP Publishing Ltd.


Acuna A.,Autonomous University of Baja California | Lara F.,Technical University Baja California | Rosales P.,Autonomous University of Baja California | Suastegui J.,Autonomous University of Baja California | And 2 more authors.
International Journal of Refrigeration | Year: 2017

This paper presents the influence on the solar fraction of coupling a Solar Cooling System (SCS) with a Geothermal Heat Exchanger (GHX). The SCS analysis was made using a mathematical model and was supported by experimental data of a vertical GHX. First, the cooling capacity of the SCS was calculated, considering the cooling load required for a building of 420 m3. The results show that a 12.30 kW cooling capacity SCS would be necessary to satisfy the maximum cooling load requirement during the summer. A 1 kW PV array was considered to assist the SCS. With the constructed GHX a soil temperature model was validated to estimate the temperature of the output water at different GHX depths. The solar fraction meets between 10 and 23% of the energy demand when the condenser is air cooled. However, when a GHX of 1, 2, 4 and 10 m is implemented the solar fraction increases. © 2017 Elsevier Ltd and IIR


Shapovalova A.I.,Special Astrophysical Observatory of the Russian AS | Popovic L.C.,Astronomical Observatory | Popovic L.C.,Isaac Newton Institute of Chile | Burenkov A.N.,Special Astrophysical Observatory of the Russian AS | And 17 more authors.
Astrophysical Journal, Supplement Series | Year: 2012

We present the results of a long-term (1999-2010) spectral optical monitoring campaign of the active galactic nucleus (AGN) Ark 564, which shows a strong Fe II line emission in the optical. This AGN is a narrow-line Seyfert 1 (NLS1) galaxy, a group of AGNs with specific spectral characteristics. We analyze the light curves of the permitted Hα, Hβ, optical Fe II line fluxes, and the continuum flux in order to search for a time lag between them. Additionally, in order to estimate the contribution of iron lines from different multiplets, we fit the Hβ and Fe II lines with a sum of Gaussian components. We find that during the monitoring period the spectral variation (F max/F min) of Ark 564 is between 1.5 for Hα and 1.8 for the Fe II lines. The correlation between the Fe II and Hβ flux variations is of higher significance than that of Hα and Hβ (whose correlation is almost absent). The permitted-line profiles are Lorentzian-like and do not change shape during the monitoring period. We investigate, in detail, the optical Fe II emission and find different degrees of correlation between the Fe II emission arising from different spectral multiplets and the continuum flux. The relatively weak and different degrees of correlations between permitted lines and continuum fluxes indicate a rather complex source of ionization of the broad-line emission region. © 2012. The American Astronomical Society. All rights reserved.


Shapovalova A.I.,Special Astrophysical Observatory of the Russian AS | Popovic L.C..,Astronomical Observatory | Popovic L.C..,Isaac Newton Institute of Chile | Burenkov A.N.,Special Astrophysical Observatory of the Russian AS | And 13 more authors.
Astronomy and Astrophysics | Year: 2010

Context. We present the results of the long-term (1995-2007) spectral monitoring of the broad-line radio galaxy 3C 390.3, a well known AGN with double-peaked broad emission lines, usually assumed to be emitted from an accretion disk. Aims. To explore dimensions and structure of the BLR, we analyze the light curves of the broad Hα and Hβ line fluxes and the continuum flux. To detect variations in the BLR, we analyze the Hα and Hβ line profiles, as well as the change in the line profiles during the monitoring period. Methods. We attempt first to find a periodicity in the continuum and Hβ light curves, finding that there is a high probability of measuring quasi-periodical oscillations. Using the line shapes and their characteristics (such as e.g., peak separation and their intensity ratio, or FWHM) of broad Hβ and Hα lines, we discuss the structure of the BLR. We also cross-correlate the continuum flux with Hβ and Hα lines to determine the dimensions of the BLR. Results. During the monitoring period, we found that the broad emission component of the Hα and Hβ lines, and the continuum flux varied by a factor of ≈ 4-5. We also detected different structure in the line profiles of Hα and Hβ. An additional central component appears to be present and superimposed on the disk emission. In the period of high activity (after 2002), Hβ became broader than Hα and red wing of Hβ was higher than that of Hα. We detected time lags of ~95 days between the continuum and Hβ flux, and about 120 days between the continuum and Hα flux. Conclusions. Variations in the line profiles, as well as correlation between the line and continuum flux during the monitoring period, are consistent with a disk origin of the broad lines and the possible contribution of some additional region and/or some kind of perturbation in the disk. © 2010 ESO.


Shapovalova A.I.,Special Astrophysical Observatory of the Russian AS | Popovic L.C.,Astronomical Observatory | Popovic L.C.,Isaac Newton Institute of Chile | Burenkov A.N.,Special Astrophysical Observatory of the Russian AS | And 17 more authors.
Astronomy and Astrophysics | Year: 2013

Context. We present results of long-term (1987-2010) optical spectral monitoring of the broad-line radio galaxy Arp 102B, a prototype of an active galactic nucleus with double-peaked broad emission lines that are commonly assumed to be emitted from an accretion disk. Aims. To explore the structure of the broad-line region (BLR), we analyze the light-curves of the broad Hα and Hβ lines and the continuum flux. We aim to estimate the dimensions of the broad-line emitting regions and the mass of the central black hole. Methods. We used the cross correlation function to find lags between the lines and continuum variations. We investigated the correlation between line and continuum fluxes in more detail and explored periodical variations of the red-to-blue line flux ratio using Lomb-Scargle periodograms. Results. The line and continuum light-curves show several flare-like events. The fluxes in lines and in the continuum show no significant change (around 20%) during the monitored period. We found a weak correlation between the line and continuum flux variation that may indicate that the line variation is weakly connected with the variation of the central photoionization source. In spite of this weak line-continuum correlation, we estimated a time lag for Hβ of about 20 days using various methods. The correlation between the Hβ and Hα flux variation is significantly higher than that between the lines and continuum. During the monitored period, the Hβ and Hα lines show double-peaked profiles, and we found an indication for a periodical oscillation in the red-to-blue flux ratio of the Hα line. The estimated mass of the central black hole is ~1.1 × 108 M, which agrees with the mass estimated from the M-σ *-relation. © 2013 ESO.


Acuna A.,Technical University Baja California | Lara F.,Technical University Baja California | Velazquez N.,Autonomous University of Baja California | Cerezo J.,Autonomous University of Baja California
International Journal of Refrigeration | Year: 2014

This paper presents the generator temperatures to achieve the highest efficiency in different solar diffusion absorption cooling systems. Ammonia-lithium nitrate (NH3-LiNO3) and sodium ammonia-thiocyanate (NH3-NaSCN) were examined as the working mixtures, and the flat-plate collector (FPC), the flat-plate collector improved (FPCI), the evacuated-tube collector (ETC) and the compound parabolic concentrator (CPC) were the thermal energy sources. The study was conducted with a simulation in steady-state conditions. The effects of the generator temperature on the global efficiency of each solar cooling system were studied. The results show that the FPC and the FPCI cannot activate the cooling system at evaporator temperatures below 0 °C and the ambient temperature is at 40 °C. At evaporator temperatures above 5 °C with an ambient temperature of 30 °C, all solar collector technologies activated different working mixtures. The optimum coupling temperatures were between 70 and 150 °C. The ETC/NH3-LiNO3 was between 5 and 54% relatively better than other technologies. © 2014 Elsevier Ltd and IIR. All rights reserved.


Rodriguez J.C.,Autonomous University of Baja California | Sergiyenko O.Y.,Autonomous University of Baja California | Tyrsa V.V.,Technical University Baja California | Basaca L.C.,Autonomous University of Baja California | Hipolito J.I.N.,Autonomous University of Baja California
Pan American Health Care Exchanges, PAHCE 2011 - Conference, Workshops, and Exhibits. Cooperation / Linkages: An Independent Forum for Patient Care and Technology Support | Year: 2011

Medical practitioners have traditionally used manual anthropometric meters and X-Ray to monitor the development and treatment of orthopedic diseases as scoliosis. With the disadvantage of generating uncertainty results in the manual methods, also X-Ray radiation can be the cause of several diseases after a long exposure. This is the reason why we developed a new method, noninvasive, without harmful radiation to human beings, assisting in monitoring the treatment of orthopedic diseases such as scoliosis. The following article presents the theoretical performance and experimental results of measurements already made with the new proposed system. © 2011 IEEE.


Burtseva L.,Autonomous University of Baja California | Pestryakov A.,Tomsk Polytechnic University | Romero R.,Technical University Baja California | Valdez B.,Autonomous University of Baja California | Petranovskii V.,National Autonomous University of Mexico
Advanced Materials Research | Year: 2014

This paper summarize idealized theoretical studies of bicomponent particle packing parameters, affecting the phase and pore structure of the obtained materials. Such a kind of analysis can be used both in theoretical consideration of material engineering problems and in the chemical industry. The effects of key variables on the relationship between packing fraction and particle size are re-examined for general application. Potential applications of these results include synthesis of nanomaterials, adsorbents, catalyst carriers and packing for chromatographic columns. Directions for future research are suggested. © (2014) Trans Tech Publications, Switzerland.


Ramos R.,Autonomous University of Baja California | Zlatev R.K.,Autonomous University of Baja California | Stoytcheva M.S.,Autonomous University of Baja California | Valdez B.,Autonomous University of Baja California | And 2 more authors.
ECS Transactions | Year: 2010

A noise suppression approach was developed and applied for pitting corrosion studies of chromatized 6061-T6 airspace aluminum alloy by Scanning Vibrating Electrode Technique (SVET). The proposed approach is based on the power line frequency application as a SVET probe driving frequency combined with a synchronized double integration of the SVET probe signal yielding a free of noise signal product. Noise suppression up to -58 dB was achieved allowing precise measurement of the ionic current above the corroded metal surface proving the opportunity to replace the high cost lock-in amplifier. ©The Electrochemical Society.


Valdez B.,Autonomous University of Baja California | Schorr M.,Autonomous University of Baja California | Quintero M.,Autonomous University of Baja California | Garcia R.,Autonomous University of Baja California | Rosas N.,Technical University Baja California
Corrosion Engineering Science and Technology | Year: 2010

The hydraulic infrastructure is constituted by the assets of two central elements: water supply and energy generation facilities. This study deals with the durability of the structures and their engineering materials. Four vital parts of this infrastructure were selected: dams, canals, aqueducts and hydroelectric stations, which are built of two basic materials; steel and concrete. The global climate change and warming and the greenhouse - gas emissions (all interrelated complex phenomena) affect these construction materials and structures, mainly by their extreme events such as torrential rains and flooding, dry and wet seasons, high and low humidity and solar radiation. This study presents a general global approach to the climate influence on the durability of those materials and structures and concludes with a description of a particular region: a section of the 'Great American Desert' on the Mexico-USA border. © 2010 Institute of Materials, Minerals and Mining.

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