Abatal M.,Autonomous University of Carmen |
Olguin M.T.,Instituto Nacional de Investigaciones Nucleares
Desalination and Water Treatment | Year: 2017
In this paper, the sorption behavior of lead by unmodified and modified natural zeolites is discussed considering, the structural characteristics of each zeolitic material, the contact time, the initial concentration of Pb (II) in solution, the dosage of the adsorbents and the initial pH value. The characterization of all sorbents was performed using X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The surface area (BET) and the pHpzc measurements were also determined. The contact between the Pb(II) solutions and the zeolites were done in a batch system. Mathematical models (pseudo-first and pseudo-second-order) were employed to describe the Pb(II) kinetic adsorption by natural, sodium, and acid-modified clinoptilolite-rich tuffs as well as Langmuir and Freundlich models to analyze the adsorption isotherms. It was found that the percentage of extra red cations from natural zeolite (Nat-CL) changes after contact with NaCl and H2SO4 solutions to obtain the sodium and acid forms (Na-CL and H-CL). The acid treatments of the natural zeolite promote the dealuminization of the material and the pHpzc drastically varied. The pseudo-second-order kinetic model best describes the sorption behavior and the k2 diminished when the concentration of the lead in solution increases from 10 to 100 mg/L. The experimental data of the isotherms fitted to the Langmuir and Freundlich isotherms and the qm and KF are 2.6 and 15.2 times higher for Na-CL than for H-CL, respectively. The variation of kinetic rate constant k2 (g/mg min) as a function of the adsorbent mass presents an exponential behavior for Nat-CL and Na-CL, whereas for H-CL, k2 increase linearly with amount of adsorbent. The initial pH of the Pb solutions affect on the time to reach the Pb2+ sorption equilibrium, the percentage of Pb sorbed in this condition. The mechanism involved on the sorption of Pb(II) by the Nat-CL and Na-CL are ion exchange and precipitation on the surface. In the case of H-CL, only an ion exchange could be possible. © 2017, Desalination Publications. All rights reserved.
Moon I.,Chosun University |
Anand A.,M. S. University of Baroda |
Cruz M.,Autonomous University of Carmen |
Javidi B.,University of Connecticut
IEEE Photonics Journal | Year: 2013
Malaria is one of the most widespread diseases, particularly in Asia and Africa. Correct diagnosis of malaria is necessary for its proper treatment. A compact automated tool for malaria identification will greatly benefit healthcare professionals in these regions. We propose a method that has the potential to automatically detect malaria-infected red blood cells (RBCs). This method combines the simplicity and robustness of lateral shearing interferometry with the flexibility of statistical methods to achieve the classification of diseased RBCs. Shearing interferograms generated using a glass plate in a common path setup were Fourier analyzed to retrieve the gradient phase and amplitude information of the cell. Then, multiple features based on the complex amplitude information of the cells are measured automatically and used to differentiate healthy and malaria-infected cells. Multivariate statistical inference algorithm of the experimental data shows that there is a difference between the populations of healthy and malaria-infected RBCs by using the measured RBC features. © 2009-2012 IEEE.
Moctezuma E.,Autonomous University of San Luis Potosi |
Leyva E.,Autonomous University of San Luis Potosi |
Aguilar C.A.,Autonomous University of Carmen |
Luna R.A.,Autonomous University of San Luis Potosi |
Montalvo C.,Autonomous University of Carmen
Journal of Hazardous Materials | Year: 2012
The advanced oxidation of paracetamol (PAM) promoted by TiO2/UV system in aqueous medium was investigated. Monitoring this reaction by HPLC and TOC, it was demonstrated that while oxidation of paracetamol is quite efficient under these conditions, its mineralization is not complete. HPLC indicated the formation of hydroquinone, benzoquinone, p-aminophenol and p-nitrophenol in the reaction mixtures. Further evidence of p-nitrophenol formation was obtained following the reaction by UV-vis spectroscopy. Continuous monitoring by IR spectroscopy demonstrated the breaking of the aromatic amide present in PAM and subsequent formation of several aromatic intermediate compounds such as p-aminophenol and p-nitrophenol. These aromatic compounds were eventually converted into trans-unsaturated carboxylic acids. Based on these experimental results, an alternative deacylation mechanism for the photocatalytic oxidation of paracetamol is proposed. Our studies also demonstrated IR spectroscopy to be a useful technique to investigate oxidative mechanisms of pharmaceutical compounds. © 2012 Elsevier B.V.
Ruiz-Marin A.,Autonomous University of Carmen |
Mendoza-Espinosa L.G.,Autonomous University of Baja California |
Stephenson T.,Cranfield University
Bioresource Technology | Year: 2010
Two species of microalgae growing as immobilized and free-cells were compared to test its ability to remove N and P in batch cultures of urban wastewater. The best microalgae-cell growth configuration was selected to be tested in bioreactor operated in semi-continuous mode. Scenedesmus obliquus showed a higher N and P uptake rate in urban wastewater than Chlorella vulgaris. When tested in semi-continuous mode and with the re-calcification of beads, S. obliquus was more effective in removing N and P for longer periods (181 h) than batch cultures; fecal coliforms removal was good (95%) although the final concentration was still unsuitable for discharge to natural water bodies. Protein and lipids content analysis suggest that, from a practical point of view, immobilized systems could facilitate the separation of the biomass from the treated wastewater although in terms of nutritional value of the biomass, immobilized systems do not represent an advantage over free-cell systems. © 2009 Elsevier Ltd. All rights reserved.
Abatal M.,Autonomous University of Carmen |
Olguin M.T.,Dep. Quimica
Environmental Earth Sciences | Year: 2013
A comparison of phenol (Phen) and p-nitrophenol (p-NPhen) sorption between sodium (ZCh-Na) and surfactant-modified (ZCh-HDTMA) clinoptilolite-rich tuffs is presented using kinetic and the isotherm parameters to describe the selectivity of the sorption processes. The clinoptilolite-rich tuff (ZCh) used in this work was obtained from a new deposit located in the state of Chihuahua (México). The effective and external cation exchange capacities (EfCEC and ECEC) of the ZCh were evaluated previous surface modification with HDTMA. The clinoptilolite-rich tuff was characterized by X-ray diffraction and electron microscopy. A batch system was used to evaluate the kinetics and the isotherms of Phen and p-NPhen sorption. The results show that EfCEC and ECEC were 112 and 17 meq/100 g, respectively. The clinoptilolite is the major mineral phase although mordenite and quartz are minor components. The pseudo-second order kinetic model better fitted the adsorption data and Langmuir model best describes the isotherms for both Phen and p-NPhen using ZCh-HDTMA. p-NPhen is adsorbed by both ZCh-HDTMA and ZCh-Na; however, ZCh-HDTMA exhibits superior performance which reflex a major selectivity. Therefore, the surfactant-modified clinoptilolite-rich tuff could be used for p-NPhen wastewater treatment. © Springer-Verlag Berlin Heidelberg 2012.
Diaz-Mendez S.E.,Autonomous University of Carmen |
Patino-Carachure C.,Autonomous University of Carmen |
Herrera-Castillo J.A.,Autonomous University of Carmen
Energy Conversion and Management | Year: 2014
Reducing environmental emissions is one of the challenges that human being has to overcome. It can only be reached with a proper energetic efficiency and management of the processes that exist in the society nowadays. Several academic works have mentioned that raising the efficiency of a process it also increases sustainability and in turn decreases the environmental impact. One process that requires much attention is the cooling and heating of buildings; this process contributes to the major part of the electric bill, in particular, if a conventional and old air conditioning is used as commonly occurs in many countries. In recent years there have been developed new alternatives that are used in few countries, such as the earth-air heat exchanger, where air is passed through a heat exchanger buried a few meters below the ground. The heat exchanger takes advantage of the well-known difference between the temperature of the surrounding air and the temperature of the ground for cooling or heating the air that is subsequently injected into the buildings. This process requires less energy, then in the present work is thought that a PID (Proportional, Integral and Derivative) controller can be applied to an earth-air heat exchanger to reduce even more the energy consumption. Therefore, a simulation of a thermodynamic model of an earth-air heat exchanger was done and used along with a PID controller, to estimate savings in energy consumption. The results show that the energy consumption can be reduced up to 87% with the PID control, hence the efficiency of the process is increased as well as the sustainability of the planet and thus the environmental concerns are diminished. © 2013 Elsevier Ltd. All rights reserved.
Rodriguez-Blanco M.A.,Autonomous University of Carmen |
Claudio-Sanchez A.,CENIDET |
Theilliol D.,University of Lorraine |
Vela-Valdes L.G.,CENIDET |
And 3 more authors.
IEEE Transactions on Industrial Electronics | Year: 2011
In this paper, a novel failure-detection technique and its analog circuit for insulated gate bipolar transistors (IGBTs), under open- and short-circuit failures, are proposed. This technique is applied to a three-phase induction-motor (IM) drive system. The detection technique is adapted to detect failures of short-circuit and open-circuit in the IGBT, which is based on gate-signal monitoring. The most important issue of this technique is the reduction of time for fault detection. This is very important in a failure-tolerant IM drive based on the material-redundancy approach or protection systems since the detection must be done before the device is damaged, in approximately less than 10 μ . The experimental test and simulations are presented in order to validate the proposed fault-detection technique, and it is validated, achieving replacement of the damaged element in the most suitable time. © 2010 IEEE.
Benavides O.,Autonomous University of Carmen |
Lebedeva O.,Autonomous University of Carmen |
Golikov V.,Autonomous University of Carmen
Optics Express | Year: 2011
Hemispherical total reflectivity of copper, nickel, and tungsten in ablation by nanosecond Nd:YAG laser pulses in air of atmospheric pressure is experimentally studied as a function of laser fluence in the range of 0.1-100 J/cm2. Our experiment shows that at laser fluences below the plasma formation threshold the reflectivity of mechanically polished metals remains virtually equal to the table room-temperature reflectivity values. The hemispherical total reflectivity of the studied metals begins to drop at a laser fluence of the plasma formation threshold. With increasing laser fluence above the plasma formation threshold the reflectivity sharply decreases to a low value and then remains unchanged with further increasing laser fluence. Computation of the surface temperature at the plasma formation threshold fluence reveals that its value is substantially below the melting point that indicates an important role of the surface nanostructural defects in the plasma formation on a real sample due to their enhanced heating caused by both plasmonic absorption and plasmonic nanofocusing. © 2011 Optical Society of America.
Golikov V.,Autonomous University of Carmen |
Lebedeva O.,Autonomous University of Carmen
IEEE Signal Processing Letters | Year: 2013
We design and assess an adaptive scheme to detect a subpixel target in a sequence of images in the presence of an additive correlated Gaussian background. The presence of the subpixel target decreases the background power that hence may be different under the null and alternative hypotheses. We use the generalized likelihood ratio test (GLRT) to adapt the recently proposed modified matched subspace detector (MMSD) to unknown background variances under the null and alternative hypotheses using the secondary and primary data, respectively. We derive a modified adaptive subspace detector (MASD) that is sensitive to both energy in the target subspace and reduced energy in the orthogonal subspace. We contrast it with the MMSD and the well-known adaptive cosine estimator (ACE). Numerical simulations attest to the validity of the theoretical analysis and show that the proposed detector performance outperforms the ACE, especially in the case of dark subpixel targets. The performance-degrading effects of limited secondary data are presented for the proposed detector. © 1994-2012 IEEE.
Benavides O.,Autonomous University of Carmen |
De La Cruz May L.,Autonomous University of Carmen |
Gil A.F.,Autonomous University of Carmen
Optics Express | Year: 2013
A comparative study on reflection of nanosecond Nd-YAG laser pulses in ablation of aluminum in air and in vacuum under the same other experimental conditions is performed. We find that, hemispherical total reflectivity of aluminum undergoes a sharp drop at the plasma formation threshold both in the air and in vacuum. The initial large value (0.8) of aluminum reflectivity decreases to a level of about 0.14 and 0.24 for ablation in the air and in vacuum, respectively. These decreased reflectivity values remain virtually unchanged with further increasing laser fluence. The reflectivity drop in the air is observed to be sharper than in vacuum. Our study indicates that the reflectivity drop is predominantly caused by absorption of the laser light in plasma. Nano/micro-structural defects present on practical sample surfaces play the important role in the plasma formation, especially for the ablation in the air, where the plasma formation threshold is found to be by a factor of 3 smaller than in vacuum. © 2013 Optical Society of America.